Nociceptive Trigeminal Inhibition Reflex

TMD, Bruxism, chronic tension headaches, migraine, all are controlled and/or moderated by the Trigeminal Nerve System

The trigeminal nerve is the largest of the cranial nerves

Its name derives from the fact that it has three major branches: the ophthalmic nerve (V1), the maxillary nerve V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory. The mandibular nerve has both sensory and motor functions

All three divisions feed into the Trigeminal Sensory Nucleus

The current understanding of the nature of migraine is that it results froma disorder of "sensory modulation", meaning that information received by the Sensory Nucleus is misinterpreted, thereby resulting in either a disproportionate response, or an inappropriate response altogether. For example, during a migraine attack, the simple pressure changes of the fluid that surrounds the brain (resulting from the beatingof the heart), is perceived as "pounding
The therapeutic goal in migraine prevention is to limit the amount of noxious sensory input(that is, to limit your migraine "triggers") to the Trigeminal Sensory Nucleus, so that itis not perceived as nociception. Essentially, the goal is to limit as much negative inputto the Trigeminal Sensory Nucleus as possible

Temporomandibular disorders all have one perpetuating and/or causative factor in common: an excessive motor activity of the mandibular division of the trigeminal nerve, that is, excessive occluding of the teeth

;Four factors dictate the presenting signs and symptoms

Intensity of the occluding

Frequency of the occluding

Duration of the occluding

Degree of condylar translation and direction of the pull on the condyle by the lateral pterygoid during the occluding event

Of those four factors, the most significant is the intensity of the event

The ideal occlusal splint (left) cannot reduce the intensity of nocturnal clenching, in fact, it allows clenching to exceed voluntary maximum
Due to the bilateral intensity of elevation, (that is, clenching), neither lateral pterygoid has the ability to translate its condyle and disclude the teeth. Only until the temporalis' relax do all the teeth disclude.When temporalis relaxation and ipsilateral translation of the condyle occurs unilaterally (right), the remaining scheme of occluding teeth becomes an influential factor in the presenting signs and symptoms, of which, contacting canines during mandibular depression canine rise) is highly desirable, as it minimizes condylar translation and muscle intensity, while directing the vector pull on the condyle more anteriorly than a posterior contact. (The ideal directional pull of the LP's on the condyle is anteriorly, and the more translated the condyle is during parafunctional occluding events, the more pathologic strain on the condyle and shearing load to the disc there is

When lateral pterygoids bilaterally protrude the mandible (left: while teeth are still occluding), or when there is an incisor-to-incisor contact during functional closure, clenching (elevation) intensity is minimized. The force vectors of the pull of the lateral pterygoids on the condyles brace and support the condyle anteriorly against the slope of the eminence

Therefore, the provision of "incisal guidance" is the optimal goal of nocturnal occlusal splint therapy

In July 1998, the U.S. Food and Drug Administration (FDA) granted approval for the "NTI Clenching Suppression System" (now: "Nociceptive Trigeminal Inhibition Tension Suppression System": NTI-tss

According to the manufacturer, the NTI-tss device is indicated for the prevention and treatment of bruxism, temporomandibular disorders (TMDs), occlusal trauma, tension-type headaches and/or migraine

The NTI-tss device is a small pre-fabricated anterior bite stop which covers – in its most widely used form – the two maxillary (or mandibular) central incisors. The fit along the teeth is accomplished at the chair side by filling either an autopolymerizing acrylate or a thermoplastic material into the base of the device, which is subsequently adapted along the central incisors, thereby increasing the vertical dimension between the upper and lower jaw. Adjustments along the outer surface of the bite stop are made by the dentist to ensure that at jaw closure and during excursive movements tooth contacts are present only between the intraoral device and the incisal embrasures of the antagonistic teeth. This "miniature anterior bite appliance" is typically worn during the night, although two variations of the bite stop are offered for daytime use

Rationale

Chronic symptoms of the head and neck can often be attributed to

A) Headache -- the temporalis muscle (it closes and clenches the jaw

B) Sinus pressure and pain -- the lateral pterygoid muscles (it moves the jaw side to side and/or forward

C) Neck stiffness and pain -- trapezius muscle (it stabilizes the skull during jaw clenching and grinding

The NTI device snaps into place and fits comfortably on either the upper or lower front teeth. It is worn during sleep and prevents the intensity of muscular Para function. For migraine sufferers, there is a more discreet version for daytime use, which is usually required (in addition to nighttime device) for 6 to 8 weeks for best results

HOW DOES IT WORK

The Nociceptive Trigeminal Inhibition Tension Suppression System (NTI-tss) takes advantage of a protective reflex which suppresses the temporalis muscles from contracting with their fullest intensity

Here are a couple of examples of this protective reflex. Let's say you've just taken a candy bar out of the freezer. How do you know if it's too hard to eat? Easy, you bite on it with your front teeth. If it's so hard that your lower front teeth can barely make a dent in it without hurting, you know it needs to thaw out a bit. But what if you're really hungry and just can't wait any longer? Simple, just use your back molars and start crushing away! How about when you're eating carrots? You can nibble on the skinny ones with your front teeth, but the big fat ones need to go between your back teeth in order to break off a piece because it would hurt to use your front teeth. Or imagine you're having a bowl of thick'n'chunky beef stew. If you accidentally bite the spoon with your lower front teeth...yeow!You instantly open your mouth. What if there is a piece of bone in the stew? Unfortunately, you may discover it by chewing on it with your back teeth and splitting a molar in half

Here's what's happening. lower incisors are designed to warn you that what you're about to eat may be too hard to chew on. Whenever the lower incisors are put under moderate to severe pressure, they signal the temporalis muscles to relax before pain and damage can happen to them. This is called the jaw-opening-reflex. It is designed to prevent you from putting something too hard into your mouth that may be damaging to your back molar teeth. The back molars, on the other hand, do practically the opposite. Whenever something comes in contact with them (like frozen-solid Snickers Bars, a piece of bone, or TMJ splints), the back molars signal the jaw-closing muscles to bite down hard because they figure, since there's something between them; it must be time to chew

The NTI-tss device takes advantage of the jaw-opening reflex by only allowing contact to be made on only one or two of the lower front teeth (incisors), and never allowing any of the back teeth (or canine teeth) to touch. (The prevention of allowing canine and posterior teeth from contacting is probably just as important as the lone contact on the incisors

The reaserch shows that the contacting of either the canine or posterior teeth instantly allows a significant increase in temporalis contraction. Thus, when the mouth is being closed, a lower incisor will touch the NTI-tss appliance, suppressing the temporalis muscles' ability to contract! Of course, the NTI-tss appliance cannot be worn when actual eating and chewing are taking place

Tension headache and common migraine sufferers develop a habit of pressing some or all of teeth together when concentrating on something. They may squeeze our teeth together just a little bit or go for a full-on clench. Jaw may be lined up in the middle, or they may hold it off to the side a bit, and we have no idea we're doing it. By definition, they usually have absolutely no awareness of their habit. No one else is aware that they are doing anything abnormal because their clenching (whatever the degree) is a silent and motionless act (especially when sleeping, unlike "grinding" of teeth
There are two versions of the NTI-tss appliance, one for sleeping, and one for when awake. Daytime clenching activity by itself really doesn't cause anything, but acts as an irritant to pre-existing condition…one that was developed while asleep. Wearing the daytime appliance for a month or so (except when chewing) allows them to have a more intimate awareness of their habit and most importantly, frequently allows the signal to be sent to suppress the musculature (every time you "tap" on the device). Although clenching activity during sleep is impossible to stop, the nighttime

NTI-tss device allows for a suppressed or reduced intensity of muscle contraction (which may also by a function of not allowing for canine and posterior teeth to touch). It's important to point out that in the muscular parafunction world, it's the intensity of contraction that creates and perpetuates the symptoms
It's during certain stressful parts of the day (like during scary movies, driving, balancing your checkbook, when the sympathetic nervous system makes its presence felt.) and especially at night, when high intensity temporalis contraction occurs that the NTI-tss appliance is worn

Essentially, the NTI-tss appliance is a simple habit-breaking device for daytime, and prevents the sleep disorder of intense temporalis contraction at night

Contra indications

An anterior midline point stop (as provided by the NTI) has been shown to decrease (suppress) muscle activity, and allow the optimum musculoskeletally stable (anterior-superior) condylar position. In the event the patient’s condylar position is not optimal, the patient’s condyle may re-position more posteriorly/superiorly during resolution of their symptoms. This may result in a change of the patient’s occlusal scheme. Although this is not a result of "supraeruption", it may appear that way, due to the mandible pivoting at the distal most molar, possibly creating a lone contact which may be adjusted through equilibration

In the presense of MINIMAL INCISAL OVERLAP (for example, 1 or 2 mms, which is not uncommon following orthodontic therapy, as the mandibular incisor's brackets limit the degree of overlap), the potential for the development of an Anterior Open Bite is at its greatest
This fact should be pointed out to the patient. If they do not consent to the possibility of a change of occlusal scheme (even though symptoms have improved), this method of therapy is CONTRA-INDICATED

In the presence of advanced periodontal disease, the NTI alone should be used with caution
An opposing device should be considered

Not all occlusal schemes are compatible to the application of an NTI device without significant modifications to the device, such as in the case of severe flaring and/or rotation of the central incisors. A custom device may need to be fabricated instead

Following any apical or alveolar surgery to any of the teeth that support the NTI, discontinue use until completely healed

In the event of severely worn centrals (for example, a loss of 50% of tooth structure) an unaltered typical NTI device is contraindicated, due to lack of available undercut for retention

The device may need to be extended laterally to provide adequate retention

If the patient insists on a "more comfortable" fit, that is, not as snug, confirm that the patient CAN NOT remove the NTI without using their hands. The NTI is contra-indicated if the patient is non-compliant with the appropriate retentive adaptation

Its use is contraindicated if the supporting teeth have provisional restorations. (Use the Thermoplastic Beads instead

An unaltered NTI can not be placed in the presence of orthodontic brackets

Is endodontic treatment passé

It is easy to forget in today’s debate that competently performed endodontic therapy is one of the most predictable dental therapy forms available, with a well documented superb long-term retention of endodontically treated teeth

Dental implants are excellent treatment options in cases when natural teeth have been lost and require replacement
However, the erroneously perceived high rate of treatment success when inserting single tooth implants compared with endodontic treatment has, in recent years, often biased the general dentist’s objectivity when selecting treatment options

Minor concerns about endodontic treatment outcomes often lead to unnecessary tooth extractions and replacement with implants

Many currently published recommendations for extraction of endodontically treated teeth show a stunning ignorance about endodontic treatment outcomes
Surprisingly few official comments have been raised from the organized endodontic community to discuss this dissonance

Instead the American Association of Endodontists has clearly taken a subservient role in this discussion and issued some what ambivalent policy statements
In scientific studies of endodontic treatment outcomes, definitive unambiguous endpoints must be defined to describe treatment results

Such criteria were defined by Strindberg and have become the gold standard for outcome studies

Thus, after sufficient follow-up time, “success" (satisfactory healing) is described as a complete healing of the periradicular bone with a normal periodontal ligament and lamina dura

Teeth with failed endodontic treatment are often candidates for some form of retreatment to achieve complete elimination of periradicular disease
However, a case is often made that these teeth, scheduled for retreatment, are at high risk of repeated failure

This misunderstanding has resulted in an ever-ending large pool of teeth being candidates for single tooth implants identified by uncritical interests
There is ample evidence that in most of these cases, other treatment options are available to maintain a restorable tooth

It is somewhat difficult to understand how we got into this untenable position
Poor communication between various “guilds” of dental specialists and other interest groups is certainly one important factor
The scientific evaluation of successful endodontic treatment requires that the Strindberg criteria of complete bone healing remain the gold standard


For clinical purposes and in the daily assessment of treatment outcome, some “looser” terms, such as “healing" "functional” and “retained” may be more useful descriptions

For implant assessments, however, even the most fastidious evaluator is likely
to use “retained” as a characterization of good outcome

Confusion arises when less than precise clinical criteria of implant treatment are used to compare results when strict scientific endodontic criteria were applied

As a result, it is often wrongly stated that the long-term treatment success rate is equal for endodontic treatment and a single tooth implant

According to many recent reports on the outcomes of endodontic treatment, there are very few teeth that cannot be retained if the full scope of endodontic treatment options issued

Dental implants have been used for many years but not until recently have relatively objective studies of long-term outcomes been available in the literature
The endpoint descriptor in implant studies is often unclear and the desirable result often characterized as a retained implant

It is also rather clear that implants tend to fail in increasing numbers with time
With a 7-year retention rate close to 90% and with more stringent success criteria the rate falls to 83% again

Still, implants with signs of peri-implant infection and maintained by adapted antimicrobial treatment were not considered to be failures in that study
This is a positively biased attitude to peri-implantitis, because it is a difficult to treat chronic pathologic condition with a low rate of long-term success
Similar treatment results have been reported by others

The most convincing value of endodontic treatment is its long-term success and permanence
A periapical lesion that heals after a quality treatment, followed by proper restorative maintenance, will not fail later due to endodontic reasons
Endodontic treatment results are also improving with time
Several studies published during recent years have assessed the retention rate of endodontically treated teeth, those studies show how endodontically treated teeth are retained at

about 95%-97% after 8 years compared with 85%-90% for implant retention during a similar time period

It is also important to notice that implant data available today are from carefully controlled clinical studies with intensive maintenance
No objective long-term data are available on implant survival in a general dental practice setting

On the other hand, endodontic numbers discussed here are retention data from average non specialized dentists

Complications after restorative procedures, such as root fractures, are often mentioned as a strong negative factor against restoring and preserving endodontically treated teeth
However, these treatment complications may be more associated with substandard prosthetic work and poor material choices than with an endodontic complication

In a recent follow-up study of a substantial patient material, the life span of well constructed full crowns on cast posts was equal or higher than full crowns on teeth with vital pulp

Implant is an excellent treatment option for the replacement of a missing tooth However, it should never be an option for the replacement of an existing restorable tooth

A recent literature review and meta-analysis found that natural teeth surrounded by healthy periodontal tissues yield a very high

longevity of up to 99.5% over 50 years

Periodontally compromised teeth that are treated and maintained regularly have a rate of 92%-93 % in survival
That study concluded that oral implants, when evaluated after 10 years of service do not surpass the longevity of even compromised but successfully treated natural teeth

Therefore, an implant should not be a treatment alternative for teeth that a reasonable competent dentist can restore and care for
Endodontic orthograde or retrograde treatment should always be the first treatment choice of a tooth having ongoing endodontic disease

Conclusions of the WHITE PAPER ON THIRD MOLAR DATA of the AAOMS

A Task Force was convened by the American Association of Oral and Maxillofacial Surgeons in March 2007 to review the current literature with regard to selected aspects relating to third molars and their removal

Here are the conclusions of the final report named
WHITE PAPER ON THIRD MOLAR DATA

The Natural History of Third Molars
While it is not possible to predict eruption of third molars in all cases, adequate space
between the anterior border of the mandible and the distal of the mandibular second molar seems to be necessary to allow successful eruption to the occlusal plane Assessment of this space can be determined using a variety of radiographic techniques
However, eruption to the occlusal plane does not imply a good state of health particularly with respect to soft tissue support
Finally, third molars that remain impacted after the age of 25 may still change in position

Periodontal Considerations in Third Molar Removal
The presence of impacted third molars adversely affects the periodontium of adjacent second molars as reflected in disruption of the periodontal ligament, root resorption and pocket depth associated with loss of attachment

The removal of impacted third molars can negatively impact the periodontium of adjacent second molars
The preoperative existence of an intrabony defect, age of the patient, and level of plaque control may serve to predict adverse outcomes

No single surgical approach to the removal of third molars that will minimize loss of
periodontal attachment was identified
GTR and/or DBP may be beneficial in instances where there is evidence of significant
pre-existing attachment loss
Scaling, root planing, and plaque control have the potential to reduce post-operative loss of attachment
Further research is needed to clarify under what conditions GTR and/or DBP can
contribute to minimizing post-operative periodontal defects

The presence of visible third molars is associated with overall elevated levels of
periodontitis and that of immediately adjacent teeth
In the presence of visible third molars, periodontitis involving adjacent teeth is
progressive and only partially responsive to therapy

The evaluation of a visible third molar for removal should include an assessment of the periodontium associated with both the third molar itself and that of adjacent teeth and include anatomical limitations to mechanical removal of plaque
The presence of pocket depths of 4-5 mm and/or bleeding on probing should be recognized as possible predictors of future progression of periodontitis
The association of overall increased disease severity in the presence of visible third
molars, the progressive nature of periodontitis involving non-third molars when third
molars are present, the relationship between visible third molars and bacteria associated with severe and refractory periodontitis, and the negative impact of visible third molars on treatment outcomes all lend support to the hypothesis that third molars should be considered as a possible predictor of periodontitis
Third molars should be included in studies of periodontal disease prevalence and
severity, and in studies assessing factors that may indicate an increased risk for
periodontal disease

The Microflora Around the Second and Third Molars
Data on microflora and asymptomatic disease in the third molar region show
Absence of symptoms does not indicate absence of disease or pathology
Pathogenic bacteria (red and orange complexes) in clinically significant numbers exist in and around asymptomatic third molars
Periodontal disease as indicated by probing depths > 4 mm exists in and around
asymptomatic third molars
Indicators of chronic inflammation exist in periodontal pockets in and around
asymptomatic third molars
Periodontal disease progresses in the absence of symptoms

The Effects of Age on Various Parameters Relating to Third Molars
Periodontal defects, as assessed by pocket depths, deteriorate with increasing age in the presence of retained third molars
Caries in erupted third molars increases in prevalence with increasing age
The incidence of postoperative morbidity following third molar removal is higher in
patients > 25 years
Germectomy may be associated with a lower incidence of postoperative morbidity

Orthodontic and Prosthodontic Considerations in Removal of Third Molars
Despite good intentions, we are not able to explain, predict, or prevent dental crowding, no matter what the cause
While it is likely that third molars play a role in the etiology of crowding, they are only one factor to consider in making a clinical decision about third molar management
Therefore, it is prudent for clinicians to educate patients that the cause of dental crowding is multi-factorial and, while third molars may play a significant role in
some patients, the current state of knowledge does not allow us to identify with accuracy who is at risk
The position and disposition of unerupted teeth has been found to be dynamic and
unpredictable
Therefore, the ultimate decision regarding the management of such teeth is best made by an expert clinician after clinical examination and review of factors such as the
age of the patient, position of the tooth, anticipated difficulty of removal, type of overlying prosthesis, and risks associated with removal

Current Imaging Techniques
The exact role and indications for CT imaging for the management of impacted third molars is unclear and evolving
Additional investigations are warranted to better understand and outline the parameters for effective use of CT imaging in the management of third molars

The Possible Role of Coronectomy (also known as partial tooth removal, partial
odontectomy or intentional root retention) in Third Molar Removal
When imaging suggested an intimate relationship between the roots of the lower third molar and the IAN and the tooth still needs to be removed, consideration should be given to coronectomy with retention of the portion of the roots associated with the IAN
Since there are only five papers in the literature describing more than single cases there is no standard of care with regard to this technique, and until more information is available this technique should be considered as an alternative only

The Role of Lingual Flap Elevation and Lingual Retraction in the Management of
Third Molars
Raising a lingual flap and the use of a lingual retractor for selected indications is felt to bean acceptable technique for removal of lower third molars
The periosteal elevator must remain subperiosteal at all times
A lingual retractor must be broad and without sharp edges so as to protect and not damage the lingual nerve

Should Anything Be Placed in the Socket Following Third Molar Removal
While non-resorbable and resorbable GTR, DBP, and platelet rich plasma (PRP) work in the setting of high-risk or near high-risk third molars, DBP is the simplest to use

Nerve Damage – Prevention, Evaluation and Management in Relation to Third Molars
Occasional damage to the inferior alveolar and lingual nerve occurs following third molar surgery
At least 50 percent of cases recover spontaneously
Attempts to standardize objective evaluation of nerve injuries have been unsuccessful
The results of nerve surgery are variable, but if carried out between 4.5 and 7 months over 50 percent of patients probably show improvement
Later repairs, up to 47 months post injury, can still show some recovery
It is possible that in some cases there may be some recovery of taste in the case of lingual nerve

repair

THE FULL PAPER IS AVAILABLE AT

www.aaoms.org/docs/third_molar_white_paper.pdf

Laser Used To Help Fight Root Canal Bacteria

High-tech dental lasers used mainly to prepare cavities for restoration now can help eliminate bacteria in root canals, according to research published in the July issue of The Journal of the American Dental Association (JADA

The study, conducted by researchers in Austria, credits the development of miniaturized, flexible fiber tips for allowing the laser to be used in endodontic (root canal) treatment

Dr. Ulrich Schoop and a team of researchers in the dental school at the University of Vienna used-60 extracted human teeth with one root each to test the effects of laser irradiation on root canals using an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser.

Dr. Schoop and colleagues inoculated the root canals with one of two types of bacteria Enterococcus faecalis and Escherichia coli and then irradiated the canals using either a 1- or1.5 watt power setting.

The team found that the laser reduced the amount of E-choli at the lower power setting and reduced it to below the detection level at the higher setting. It also was effective in eliminating E. faecalis.

Researchers found, too, that the laser removed the smear layer and debris from the root canal walls and that the temperature rise during irradiation was within safe borders.

The authors concluded that the Er,Cr:YSGG laser may be suitable for cleaning and disinfecting root canals and that it can be used safely if the common precautions for using lasers are observed and the energy levels and irradiation times are within the proposed range.

They also suggested that clinical studies are needed to confirm their laboratory findings.

In a related article in July JADA, Dr. Roy H. Stevens and colleagues at the Kornberg School of Dentistry, Temple University, describe their study of an Er,Cr:YSGG laser with a new tip that emits radiation radially.Dr. Stevens and colleagues examined the efficiency of this new laser tip in disinfecting root canal dentin walls infected with E. faecalis.

They found that it significantly reduced the amount of E. faecalis in contaminated root canals

More researches will be conducted in this field, it may become the future treatment option in endodontics.

Differnt Designs of Dental Clinics

Treatment Strategies for Teeth Hypersensitivity

Clinical significance of hypersensitivity

Dentinal hypersensitivity, while neither life threatening nor a serious dental problem, can be a particularly
uncomfortable and unpleasant sensation for patients and can dictate types of foods and drinks ingested.
Patients may describe the condition as dull or sharp, vague or specific and intermittent or constant. Teet causing such symptoms are rarely considered to be as seriously affected as those affected by caries, endodontic problems or periodontal disease, however, the condition is nonetheless of sufficient concern to warrant appropriate and proper management. In most instances the condition can be managed by patients through appropriate home care using properly prescribed over the- counter products. These features of the condition negate, in the majority of cases, the need for expensive and lengthy professional care. Notwithstanding the above, the condition still requires an appropriate differential diagnosis since carious exposure of dentine surfaces, inflamed pulps or cracked cusps can produce symptoms similar to cervical dentinal hypersensitivity.

Treatment for hypersensitivity

There is a surprisingly large number of treatment options for managing dentinal hypersensitivity. Chemical or physical agents are used to either desensitize the nerve or cover the exposed dentinal tubules. The most common form of management is the placement of a topically applied agent applied either by a dental professional or by the patient at home. All currently available treatments appear to work.
Several criteria are recognized as constituting an ideal desensitizing agent. These include not irritating the pulp, being relatively painless to apply, easily applied, rapid action, permanently effective and should not discolour the teeth.20 Overall, patient responses are very subjective and thus treatment results are largely dependent upon the individual’s pain threshold.

Role of dental plaque

While there are many factors which can contribute to dentine hypersensitivity, plaque accumulation has often been cited as an important factor.23 Plaque accumulation on root surfaces may lead to demineralization of tooth structures which could be associated with patency of dentinal tubule orifices.23 It has been reported that patients who maintain good levels of plaque control are less likely to report dentine hypersensitivity.24 On the other hand, patients who have significant proportions of their root surfaces covered with dental plaque report more problems with dentine hypersensitivity.
Despite these findings, the influence of plaque on dentine hypersensitivity remains controversial. Interestingly, many patients with gingival recession have minimal plaque deposits yet still complain of sensitivity.

Nerve desensitization

Potassium nitrate

A number of studies have reported the efficacy of potassium nitrate for managing dentinal hypersensitivity.
While the Hodosh study was the first to report that potassium nitrate was a “superior desensitizer” this study was not well controlled and it was not until the studies of Tarbet et al that good evidence for the efficacy of potassium nitrate in managing dentinal hypersensitivity was demonstrated.
These controlled studies demonstrated that potassium nitrate at a concentration of 5% in a low abrasive toothpaste was able to desensitize dentine for up to four weeks compared to a control paste. Potassium nitrate in bioadhesive gels at 5% and 10% has also been shown to be effective in reducing dentinal hypersensitivity. Importantly, it has been shown that potassium nitrate does not induce any pulpal changes.
Despite these encouraging findings it is interesting to note that a recent Cochrane Database Systematic
Review failed to find strong evidence supporting the efficacy of potassium nitrate toothpaste for dentine
hypersensitivity.34 Nonetheless, this review did report that the differences which were noted were statistically significant in favour of treatment with potassium nitrate toothpaste.
The mechanism of action of potassium nitrate is largely unknown, although an oxidizing effect or blocking of tubules by crystallization has been proposed28 but not proven. The effect of potassium nitrate on dentinal fluid flow has been reported to be minimal even at a 30% concentration.35 A more likely explanation is that the potassium ions are the active component and that potassium nitrate reduces dentinal sensory nerve activity due to the depolarizing activity of the K+ ion,36 although this proposal has never been confirmed in intact human teeth

Anti-inflammatory agents

Corticosteroids

Anti-inflammatory agents such as corticosteroids have been proposed for use to manage dentine hypersensitivity. However, trials have not found them to be particularly useful.22 While it is presumed that these agents may induce mineralization leading to tubule occlusion, this view has yet to be validated38 and the validity of using such agents has been questioned.

Covering or plugging dentinal tubules

Calcium hydroxide

Several studies have reported on the effectiveness of calcium hydroxide in managing dentinal hypersensitivity. Its mode of action has been proposed to be via occlusion of dentinal tubules through the binding of loose protein radicals by calcium ions42 and increasing mineralization of the exposed dentine. Although immediately effective, the action of calcium hydroxide diminishes rapidly requiring multiple applications to maintain its effect.19 A negative feature of calcium hydroxide is its reported irritation of gingival tissues.

Casein phosphopeptides

A relatively new product on the market composed of casein phosphopeptides has been used for the management of dentinal hyperersensitivity. Despite a number of anecdotal case reports on various websites, to date there are no published studies reporting the efficacy of this material for dentinal hyperersensitivity.

Sodium fluoride

Many clinical studies have shown that treatment of exposed root surfaces with fluoride toothpaste and concentrated fluoride solutions is very efficient in managing dentinal hypersensitivity.43-45 The improvement
appears to be due to an increase in the resistance of dentine to acid decalcification as well as to precipitations in the exposed dentinal tubules. Tal et al.46 suggested that the probable desensitizing effects of fluoride are related to precipitated fluoride compounds mechanically blocking exposed dentinal tubules or fluoride within the tubules blocking transmission of stimuli.

Sodium monofluorophosphate

Toothpastes containing sodium monofluorophosphate have been shown to be effective in managing dentinal hypersensitivity.47,48 The mechanism of action of sodium monofluorophosphate is unclear.21 It does not appear to act by occluding dentinal tubules since scanning electronmicroscopic studies have failed to demonstrate any visual changes to the dentine surface treated with sodium monofluorophosphate.21 Any tubule occlusion which might occur does not appear to be permanent.

Stannous fluoride

Stannous fluoride in either an aqueous solution or in glycerine gelled with carboxymethyl cellulose is
effective in controlling dentinal hypersensitivity.50 The mode of action appears to be through the induction of a high mineral content which creates a calcific barrier blocking the tubular openings on the dentine surface.Alternatively, stannous fluoride may precipitate on the
dentine surface leading to occlusion of the exposed dentinal tubules.

Fluoride iontophoresis

Iontophoresis is the process of influencing ionic motion by an electric current and has been used as a desensitizing procedure in conjunction with sodium fluoride.42 Studies report that there is an immediate reduction in sensitivity after treatment with iontophoresis, but the symptoms gradually return over the ensuing six months.52 This method has enjoyed some popularity but more controlled studies are required.

Formaldehyde or glutaraldehyde

Claims have been made that formaldehyde and glutaraldehyde, through their ability to precipitate salivary proteins in dentinal tubules, can be used to manage dentinal

hypersensitivity. However, this effect
has been questioned since various formulations have been found to have little or no effect on dentinal hypersensitivity.Given that these agents are very strong tissue fixatives, they should be used with extreme
caution to ensure they do not come in contact with the vital gingival tissues.

Dentine sealers

Resins and adhesives

Sealing of dentinal tubules with resins and adhesives has been advocated for many years as a means of managing dentinal hypersensitivity.55 In general, results have been good but problems arise when the adhesive breaks away resulting in exposure of the tubules. This technique is generally reserved for cases of specific and localized dentinal hypersensitivity rather than generalized
dentinal pain.

Lasers

Both the Nd:YAG and CO2 lasers have been studied for their use in managing dentinal hypersensitivity. Both applications rely on their ability to occlude the dentinal tubules. The Nd:YAG laser has been used in conjunction with sodium fluoride varnish with encouraging results showing up to 90 per cent of the dentinal tubules being occluded through use of this combined therapy.56 CO2 laser irradiation and stannous fluoride gel has also been shown to be effective for inducing tubule occlusion for up to six months after treatment.57,58 While still largely experimental, this technique requires further scientific investigation before it becomes a clinically acceptable means of treatment.

Combination of desensitizing agents and fluoride

Because some effective desensitizing dentifrices (such as those containing potassium nitrate) were not fluoridated, people requiring relief from dentinal sensitivity and protection against dental caries needed to use both desensitizing and fluoridated dentifrices. As a result a number of well-controlled clinical studies have been carried out to determine the efficacy of potassium nitrate as a desensitizing agent in dentifrices containing fluoride.As early as 1992, the United States Food and Drug Administration granted Category 1 status to combination 5% potassium nitrate:fluoride dentifrices, indicating they were not only safe but also effective.

Restorative materials

The use of restorative materials is generally an invasive solution to the problem of hypersensitivity. Commonly used materials include composite resins and glass ionomer restorations. Generally this approach is reserved for situations where there has been significant prior loss of cervical tooth structure or as a last resort for a tooth which does not respond to other less invasive desensitizing protocols.

Periodontal surgery

There are numerous soft tissue grafting procedures which can be carried out to cover exposed root surfaces including lateral sliding grafts, free gingival grafts, connective tissue grafts and coronally repositioned flaps. While these procedures may cover exposed dentinal tubules, some are not very predictable in terms of their efficacy in root surface coverage. Soft tissue grafting for localized recession defects requires careful planning and an understanding of the anatomical defect to be treated. In general, soft tissue grafting for the management of sensitivity is not regarded as a very predictable treatment strategy.

Safety of commonly used at home desensitizing agents

Most “at home” desensitizing agents are generally restricted to dentifrices and mouthrinses containing one or a combination of the agents discussed above. Of these, the most common “active ingredients” are potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride.For all products which are currently on the market as over-the-counter products extensive toxicity testing has already been carried out by the manufacturers and has been reviewed by various regulatory bodies to ensure both safety and efficacy. Although there is only minimal evidence to demonstrate superiority of one desensitizing agent over another, there is ample evidence that desensitizing toothpastes do provide benefit to the patients suffering from dentinal hypersensitivity. As a general rule, all well performed clinical studies published in the literature report safety assessments of the products under study.60 Moreover, in recent times, studies carried out within universities require the approval of a human ethics committee prior to commencement. All such committees require safety issues of products under investigation to be reported as part of the routine experimental protocol. Safety measures for toothpastes generally include adverse event data to elicit complaints/symptoms of the subjects at each examination time point and by evaluating changes in medical history and concomitant medications. All adverse reactions are recorded, listing the date of onset, duration, frequency, maximum intensity, seriousness, action taken and outcome. In addition, the oral soft tissues and perioral area should always be visually examined to evaluate effects that could be manifested as a tissue response to an irritant, soft tissue pathology or other clinically meaningful deviations from the normal. It is of particular note here that there are very few (if any) reports of adverse reactions to dentifrices containing the desensitizing agents listed above (Table 2). A Medline search (concluded December 2005) failed to find any citations regarding adverse reactions, toxicity or safety problems with strontium chloride or potassium nitrate. Only a few citations were found for fluoride formulations and these involved predominantly children. Since dentinal hypersensitivity is considered to be a response to a localized condition within individual teeth and is not indicative of, or related to, any known
systemic condition, management of dentinal hypersensitivity is not considered to mask or impact on any other systemic conditions which a patient might have.

There is no literature to support the concept that dentinal hypersensitivity is anything other than a well-localized dental problem. Finally, one of the most effective treatments for the majority of patients is simple daily plaque removal. Daily plaque removal over time allows demineralization of the dentinal tubules from salivary minerals and can alleviate much of the discomfort caused by exposed dentine. The use of an additional aid, such as a dentifrice containing additional agents which might expedite (or at least encourage) improved oral hygiene and daily plaque removal, is not considered harmful to either the tooth, the surrounding soft tissues, or the whole body.

CONCLUSION

Dentinal hypersensitivity is a relatively common and significant dental problem which can be successfully managed by a very wide variety of procedures, agents and formulations applied locally, either “in office” or “at home”. It is clear that some products appear to be more effective than others. For those products developed for self application at home, potassium nitrate, stannous fluoride, sodium fluoride, sodium monofluorophosphate and strontium chloride have all been extensively studied and shown to be not only safe to use but of benefit to individuals suffering from dentinal hypersensitivity.

Brushing Dentures Might Be Best Cleaning Method

Brushing dentures with a paste product might be the best way to keep them clean, better than soaking in effervescent or enzyme cleaning solutions, suggests a new review of what little dental literature exists on the topic. Keeping dentures clean and free from plaque buildup can help prevent oral infections and gingivitis; however, few clinical studies focus on the best way to clean partial or complete dentures.This scarcity of studies on real-life patients was surprising, said lead review author Raphael Freitas de Souza, D.D.S.

Studies compared different denture cleaning methods to one another or to a placebo.

Cleaning methods included soaking dentures in enzyme solutions, soaking in effervescent solutions, routine brushing with a paste product and a combination of brushing and soaking.

The studies examined the effects of each method on outcomes such as irritation in the mouth or inflammation of the gums and other oral tissue, the presence of bad breath and how much plaque was on the dentures.

Although it is not possible to draw a strong conclusion on what method works best, de Souza said, there was weak evidence that among chemical cleaners, enzyme-cleaning products were more effective than a placebo."We cannot be pretty sure what the most effective methods for denture cleaning are. But we can infer possibly that brushing can give better results," he said.

A patient with poor manual dexterity who cannot brush well might be better off using chemical cleaners and soaks, he added.

Systematic reviews such as this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.The results of the review are interesting, but might have little effect from a practical standpoint, said Susan Brackett, D.D.S, director of public and professional relations for the American College of Prosthodontists. She is in private practice as a prosthodontist in Oklahoma City."We give our patients a sheet of instructions and recommend that they mechanically clean the dentures by brushing with dishwashing soap to get the major debris off," she said.

All dentures should be stored in water or a cleaning solution overnight because dentures should not dry out, she added. "If they like, patients can soak the dentures in an effervescent solution overnight. You can do both mechanical and chemical, but it is not absolutely necessary."

De Souza said that professionals usually do not recommend boiling dentures because it can cause them to deform. Similarly, heating dentures in water or another solution in a microwave oven can cause damage to the dentures, Brackett said.

If using household bleach do so carefully, because it can cause discoloration in gum-colored portions of dentures, she added. "We do recommend a solution of water, bleach and Calgon to treat a yeast infection, but that is not something for routine basis," she said.Another cleaning method is an ultrasound device that vibrates the water the dentures are in. Brackett said that battery-operated ultrasound cleaners are available for about $10, but that the professional models used by prosthodontists' offices to clean dentures are better. In her office, dentures undergo ultrasonic cleaning when the patient comes in for an annual check-up, which is advisable both to check for fit and wear and tear on the dentures and to screen for head and neck cancer.

Resorption of Byond Apex Calcium Hydroxid Paste in RCT

Calcium Hydroxide is widely used in endodontics for a number of purposes. Its antimicrobial properties are attributed to its high pH (basic), destructive effects on bacterial cell walls and ability to dissolve organic tissue. It is used routinely as an intracanal medicament. It is also used for apexification, apexigenesis, treatment of root resorption.

Ca(OH)2 used in endodontics is made with Ca(OH)2 powder, a vehicle and a radiopacifier. Most common radiopacifiers are barium sulfate, bismuth or compounds containing iodine or bromine. While radiopacifiers make the calcium hydroxide more visible radiographically, some radiopacifiers are known to resorb at a slower pace, sometimes making it difficult to see the subtle changes.

While the control of a paste material at the apex of a canal can be very difficult, the resorptive properties of calcium hydroxide make it a very forgiving material. Extrusion of calcium hydroxide past the apex of a tooth is not uncommon. In fact, there are some who would recommend deliberate extrusion in the case of a large, chronic periapical lesion to help in the healing of such a lesion.

Calcium hydroxide (Ultracal - Ultradent - 35% Ca(OH)2 with barium sulfate) was used during treatment of this tooth to control exudate prior to obturation. A significant amount was extruded past the apex in close approximation to the maxillary sinuses during the endodontic treatment.




14 months later, the patient returned for treatment of #14. Our recall radiograph of #15 shows complete resorption of Ca(OH)2. The patient had no complaints and is in full function.



Sources:

Hasan Orucoglu, Funda Kont Cobankara, "Effect of Unintentionally Extruded Calcium Hydroxide Paste Including Barium Sulfate as a Radiopaquing Agent in Treatment of Teeth with Periapical Lesions: Report of a Case", Journal of Endodontics, July 2008 (Vol. 34, Issue 7, Pages 888-891)

Periodontitis Must be Prevented to Cut Head and Neck Cancer Risk

There is an urgent need for increased efforts to prevent and treat chronic periodontitis to reduce the risk for head and neck cancer, according to researchers at the University of Buffalo. Led by Dr. Mine Tezal at Buffalo, periodontitis is an independent risk factor for head and neck squamous cell carcinoma

Prevent periodontitis; if you have it already, get treatment and maintain good oral hygiene," said Tezal

Chronic periodontitis is characterized by progressive loss of the bone and soft tissue attachment that surround the teeth

Researchers assessed the role of chronic periodontitis on head and neck squamous cell carcinoma, as well as individual roles on three subsites: oral cavity, oropharyngeal and laryngeal

They used radiographic measurement of bone loss to measure periodontitis among 463 patients, of whom 207 were controls. The results of the study revealed that chronic periodontitis might represent a clinical high-risk profile for head and neck squamous cell carcinoma. The strength of the association was greatest in the oral cavity, followed by the oropharynx and larynx, according to Tezal. When they stratified the relationship by tobacco use, they found that association persisted in those patients who never used tobacco

They did not expect the periodontitis-head and neck squamous cell carcinoma association to be weaker in current smokers compared to former and never smokers, according to Tezal

However, this interaction, although statistically significant, was not very strong. "Confirmatory studies with more comprehensive assessment of smoking, such as duration, quantity and patterns of use, as well as smokeless tobacco history are needed," said Tezal

"Our study also suggests that chronic periodontitis may be associated with poorly differentiated tumor status in the oral cavity. Continuous stimulation of cellular proliferation by chronic inflammation may be responsible for this histological type. However, grading is subjective and we only observed this association in the oral cavity. Therefore, this association may be due to chance and needs further exploration," she added

Andrew Olshan, Ph.D., said these results lend further support to the potential importance of poor oral health in this form of cancer. Olshan said, "Although the study is comparatively small, the researchers were able to also see an association between bone loss and the risk of head and neck cancer

The results of the study have been published in Cancer Epidemiology, Biomarkers and Prevention, a journal of the American Association for Cancer Research

THE REMOVAL OF RADICULAR FILLING
MATERIAL OR OBSTRUCTIONS

The following basic principles must be considered as
radicular filling materials are removed:

1. The hardness or consistency of a nonmetallic filling Or the ability to remove an intracanal material cannot be determined radiographically

2. Removal of a previous filling material is usually easier if the root canal treatment is failing because of recurrent
leakage.

3. No canal space is naturally round.

4. Access to the apex and patency are necessary to achieve the root goals of cleaning and shaping the
canal system.

5. The philosophy behind the "crown-down" approach' is most applicable to the removal of radicular
filling materials or obstructions.

6. All preparations increase in size during retreatment. Usually the coronal third demonstrates the greatest
enlargement.9

7. Canals that initially deviate from their natural centerline tend to continue to deviate in the same direction during retreatment. Areas not instrumented during initial treatment are more difficult to contact
during retreatment.

8. Irrigation and disinfection must be emphasized because all canals that are retreated should be considered contaminated with microorganisms.

9. Solvents, while useful, can interfere with debridement.
10. All methods of instrumentation and removal leave debris remaining in the canals.

11. Open canals not being treated should be protected or covered.

12. Patience is a virtue.

The three categories of materials most commonly considered during retreatment are pastes, semisolids with sealers, and solids placed with or without sealers


Removing Gutta-Percha Core Materials

Mechanical and/or solvent dissolution techniques can be used to remove gutta-percha and sealer. The preferred technique is mechanical because it allows for better debris removal. The use of solvents substantially complicates
debridement. When solvents are used to remove gutta-percha or pastes, the dissolved infected debris from these materials is more likely to flow into and coat inaccessible canal irregularities and/or penetrate into the periradicular tissues.


The decision to use one or both techniques hinges on
three factors:

1. The existing condensation quality-Densely filled canals may require a solvent to facilitate penetration.
Poorly condensed fillings can usually be removed mechanically. Usually the coronal aspect of any canal is most densely compacted.

2. The length o f the existing filling material-The use of solvents to dissolve filling materials in the apical third of the canal system risks pushing these materials into
the periradicular tissues. The use of solvents in the apical third with an overextended cone all but ensures that the overextended segment will be severed and remain in the periradicular tissues.

3. The tooth's root morphology, canal shape, size, and curvature-Mechanical techniques remove more dentin than solvent approaches. With a comparatively
straight and substantial root, the clinician may be able to remove all of the gutta-percha using rotary instrumentation. In contrast, a densely filled curved
canal such as the mesiobuccal root of a maxillary first molar may require solvents to reduce the risk of apical transportation or furcal strip perforation.

A mechanical removal technique usually begins with rotary instrumentation (using Gates Glidden drills or nickel-titanium files) to rapidly remove the coronal portion of the gutta-percha. The canal is larger coronally and straight enough to tolerate these procedures.

Minimal pressure is exerted as smaller sizes are used to progress apically in a crown-down manner. The clinician should promptly remove any material adherent to the rotary instrument and carefully cut away from furcal concavities. Alternatively, a heat source with diminishing sizes of heat carriers may be used to remove the gutta-percha.

As the coronal bulk of material is removed, penetration of the apical radicular filling becomes possible. Using an appropriately curved, short ( 21 mm) size 15 or 20 K-file with a repeated reaming action, the clinician should be able to instrument next to the previous filling material.

He or she should not file, force, or push instruments apically. Frequently, the operator will sense that it is possible to almost "screw the file in." If this is feasible, the operator should be careful that the file is not placed so aggressively as to demonstrate "spring-back" when the handle is released. Ideally the entire gutta-percha filling will be bypassed with size 20 or larger K-files. The clinician can use an apex locator to estimate the file position if necessary. Frequent and generous irrigation with NaOCI is indicated.

Old gutta-percha fillings are likely to be brittle. In such situations the gutta-percha will seem to shred and break into small pieces as the path alongside it is created and debris is removed.

After establishing a path, the clinician chooses the next larger Hedstrom file (at least a size 20) and rotates it clockwise alongside the filling material, avoiding springback. Although this file will engage dentin, it will preferentially embed its flutes in the softer gutta-percha.

With controlled force, the clinician removes the Hedstrom file as though it were a corkscrew, turning counterclockwise as necessary if too much resistance is encountered. The entire gutta-percha mass may release, but more often small fragments will be removed each time this process is repeated. The clinician may consider a larger file size if the canal anatomy permits but should be careful not to sever overextended segments. When working close to the estimated working distance, the clinician can take a radiograph with the file in place. Ideally, all apical filling materials should be removed. The value of removing materials that remain in the middle and coronal thirds must be carefully weighed against concerns for
preservation of tooth structure.

Many solvents have been proposed to aid in retreatment of gutta-percha fillings. The authors of this chapter prefer chloroform, but less volatile solvents such as d-limonene (a xylene substitute)" are being investigated and may prove safer.

A solvent dissolution approach usually begins, as does the mechanical approach, with the bulk of materials being removed by rotary instrumentation. This action creates a coronal space or reservoir where the solvent can be deposited. Initially, a 21- mm 15 or 20 K-file can be used to penetrate and remove the dissolving mass of filling material. The instrument flutes should be cleaned after each pass, with the solvent being replenished as it evaporates. As the material further softens, Hedstrom files may be used to expedite removal.

Slowly and without forcing, the clinician can use precurved files to work through the previous filling. Unless it is necessary for visualization, irrigation is not indicated because it will dilute and diminish the solvent's effectiveness. As the apical extent of the filling is approached, the clinician may attempt to complete the process mechanically. If this is not possible, he or she may continue with the solvent while using files with a reaming action to minimize pushing debris apically.

After the file has bypassed or is completely alongside the filling material, he or she can begin irrigating with NaOCI and follow the steps of mechanical removal

REGAINING ACCESS TO THE APEX:
REINSTRUMENTATION, IRRIGATION,
DEBRIDEMENT, AND DISINFECTION

After removing previous filling materials and obstructions, the clinician must re-establish access to the apex along the path of the original canal. It is unusual to find a readily patent and negotiable canal "on the other side."


If this were the case, the operator could proceed with the usual techniques of cleaning and shaping, while placing particular emphasis on irrigation to debride and disinfect. Working length radiographs are essential to evaluate length and preparation. Information provided by electronic measuring devices is complementary to these radiographs.

As the final cleaning and apical shaping continues, the operator must recall that continued preparation naturally tends to deviate from the original centerline of the canal, especially in the coronal third.

If the previous filling materials were under-extended, the goal of apical instrumentation may be complicated by the following canal abnormalities:
1. Blockages with dentinal and/or pulpal debris
2. Dentistogenic complications such as ledges and transportation
3. Calcifications
4. Anatomic complexities

In the worst case scenario, a canal will feel solidly blocked and impenetrable. Recalling basic principles of endodontic instrumentation, the operator should choose a short (21-mm, size .08, .10, or .15) file size, irrigate, and gently feel for a "catch." Usually a small J hook is placed at the instrument's tip and a gradual bend is placed throughout the instrument's length. While exploring the canal, the clinician should resist the natural tendency to push more aggressively, which will only complicate a blockage or ledge.

Frequent irrigation should be employed to remove debris. If no catch is detected, the canal should be dried and irrigated with a chelating agent such as 17% ethylenediaminetetraacetic acid (EDTA) in aqueous solution. As gentle exploration continues, the clinician should curve and recurve the file, while ascertaining that no coronal or radicular access restrictions impede the motion of the file. Irrigation should not be performed with NaOCI because it will neutralize the effect of the chelating agent.

If several canals are being re-entered and the first yields no initial signs of progress, the clinician should leave EDTA in place and proceed to work on another canal. Without rushing, the clinician continues to explore each canal for even the slightest catch and gently pursues it with the smallest file sizes when a catch manifests. This gentle but persistent effort rarely results in perforation, even with EDTA. The clinician should conscientiously discard worn instruments while replenishing the EDTA. After the estimated distance has been achieved, it can be enlarged to a size 15 file and a working radiograph can be taken to confirm length and file position.

If a previously blocked canal continues to resist apical instrumentation, a clipped file approach may carefully be attempted.10 Typically about 1 to 2 mm are clipped from the tip of a 21- mm size 15 file. This procedure leaves the tip with sharp cutting edges that can be used with a back-and-forth, auger-like motion. 13 With this technique the clinician may be able to work through the resistant blockage. Discretion normally dictates that only 1 to 2 mm of length should be attempted in this manner before the clinician gently feels for the natural canal again with a small, unclipped, curved file. Radiographs are essential to monitor the files' progress, especially around curves.

After the original canal has been re-established, hand or rotary instrumentation techniques can be used to finish shaping the preparation.

Considerable emphasis must be placed on debridement, irrigation, and finally disinfection. The retreating dentist must remove as much of the contaminated previous materials as possible, as well as debris created by new instrumentation. Any motion that might push this debris apically should be avoided. As the preparation nears completion, the clinician must undertake a focused search for any additional untreated canals.

The operating microscope offers ideal illumination and v1sibility to accomplish all of these goals. Anatomic grooves and dentin coloration can also guide the operator in locating additional canals. In the apical area, bubble trails and careful tactile exploration with appropriately curved small files may reveal patent apical ramifications. The radiographic file position (centered or not) within the root is also an excellent indicator of
additional canals.

All authors concede that complete debridement of the root canal system is impossible. During retreatment, remnants of previous filling materials will always remain out of reach of reasonable instrumentation.

The operator must assume that these uninstrumented areas and their adjacent dentinal tubules are contaminated with microorganisms. To date, the consensus of most authors suggests that a conscious effort at further canal disinfection must follow cleaning and shaping and precede the filling appointment. At this time, placement of an intracanal dressing such as calcium hydroxide (CaOH)14 or an antibiotic-containing fiber 15 for a period of at least 1 week seems most appropriate. A temporary restoration at least 4 to 5 mm thick is then placed against the sound walls of the access preparation.

FILLING, PROGNOSIS
AND POSTTREATMENT RESPONSIBILITIES

All filling techniques attempt to prevent recurrent leakage and seal in or entomb debris that cannot be removed from the root canal system. The clinical conceptualization of a root canal filling should be that of a maze on a micrometer scale. No ionic or covalent bonds come into play, only physical interfaces among dentin, sealer, and gutta-percha.

All obturation techniques leak. 17 As long as clinicians continue to fill canals in a manner that facilitates nonsurgical retreatment, they will never measurably improve on existing obturation techniques.

The time-honored adage, "It's what you take out, not what you put in," is as true today as it was 100 years ago (see Chapter 7). The reader is left to choose an appropriate filling technique.

The completion of canal obturation leaves the clinician with a sense of prognosis. As part of the ongoing process of consent, treatment outcomes must be conveyed
to the patient. Additional referrals for periodontal or related procedures must be arranged if they were not anticipated preoperatively. For the patient, filling is usually perceived as completion, the end of the root canal treatment. They have survived, and usually their worst fears have passed uneventfully. They are also comfortable and all too frequently complacent, wishing to take a break from treatment. Beyond providing any required postoperative management (e.g., pain and/or infection control), the clinician also has a responsibility to ensure that the patient returns promptly for definitive restorative procedures

. When a specialist provides treatment, this process may begin as a phone call and/or a referral
acknowledgment and a radiograph.

Posttreatment follow-up is as essential as retreatment planning. If any delays in the restorative process are anticipated, a more definitive temporary restoration such as reinforced zinc oxide and eugenol or a light-cured intermediate composite should be placed. Application of an orthodontic band to reduce the possibility of fracture or placement of the core build-up and a temporary crown is frequently indicated. Loss of a temporary restoration requires immediate replacement. Treatment must never be considered complete until the tooth is restored to function.

Endodontic recall examinations should be scheduled at any time if signs or symptoms develop and planned routinely at 1 and 2 or more years.

Soundwaves may find early dental decay

Soundwaves could soon be used to identify the early stages of decay, a process that often relies on the use of painful and damaging probes, say Australian researchers.
PhD researcher, David Hsiao-Chuan Wang from the University of Sydney and colleagues, report their findings in the most recent issue of the journal Optics Express .
"We want to be able to be able to quantify mineral content of the dental enamel," says Wang, whose research was supervised by Professor Simon Fleming.
Tooth decay begins by acid-forming bacteria eating away at the enamel, causing minerals to leach from it, softening and weakening the tooth.
Dentists can sometimes identify this demineralisation by seeing a change in the colour of the tooth, or by looking at x-rays.
Other times, they use sharp probes that test the hardness of the enamel and find where the rot has set in.
Unfortunately these probes can be painful and cause unnecessary damage to the teeth.

Less invasive
Wang and colleagues are developing a less invasive new technique to measure mineral content of teeth, using sound waves generated by laser pulses.
"We can keep the laser power below a damaging threshold," says Wang.
Laser pulses aimed at the tooth set up a series of high frequency sound waves (ultrasound) that travel through the enamel surface, penetrating it to different depths.
As a soundwave moves through a demineralised part of the tooth, it changes its speed, and this can be detected.
Each soundwave penetrates to different depths of the enamel, depending on its wavelength, enabling a profile of the tooth to be built up, showing where decay has begun.
Wang and colleagues first tested the system on different known materials before testing it on extracted human teeth.
They have yet to test the system on teeth in patients. They first need to develop a convenient handheld device and obtain ethics permission to trial it in humans.
Wang says a prototype of the hand-held device could be ready in two years.
Professor Ian Meyers of the Australian Dental Association says testing the technique in the mouth is important, as saliva affects the property of teeth enamel.
Meyers, who is based at the University of Queensland in Brisbane, says when decay is detected early, fillings can be avoided by either stopping the demineralisation through better oral care.
Alternatively, he says, the tooth can be re-mineralised using products specifically designed for this purpose.

Other methods
Meyers says the new research shows scientific evidence that sound waves can be used to detect mineral change in teeth.
Mineral content can already be measured using a different method, called quantitative light fluorescence. Another method called laser fluorescence can be used to detect bacteria in the teeth, says Meyers.
wang says the new technique could add to the range of tools available for dentists to identify early stages of decay, as long as it is affordable.
He says the ultrasound technique will be particularly useful in research, especially in evaluating the effectiveness of remineralisation treatments.

Worm-Like Structures Linked to Tooth Decay

For years, scientists have debated the exact nature of the worm like structures inside a human tooth. The structures are not worms, but what they are is still in question. Micro-images in a dissected molar suggest they caused tooth decay

Studies by University of Maryland (U-M) Dental School researchers' revealed that cylindrical objects extending or 'growing' out of the natural pores or tubules of teeth

Inside a human tooth, more than 50,000 such tubules per square mm act as channels running from the nerve up through the tooth. They are associated with transporting hot or cold sensitivity to the tooth

The worm-like-structures were photographed in clear detail by Ru-Ching Hsia, director of the electron microscope core facility at the school

"Most (dentists) say 'I have no idea'. Others say they are made of bacteria, or minerals, or hyphal branches of yeast cells (C. albicans) which have infected the tooth structure," said co-presenter Gary Hack, associate professor at the Dental School

For the sake of humouring his students, Hack said: "I call them tooth worms and I'm sticking to it." The aim of the Maryland study was to investigate the structures with scanning electron imagery and different specimen preparation techniques

The researchers' observations raised new questions in the controversy over nature of the strange structures. For example, they found two of the cylinder structures within a single tubule, a discovery that challenges the hypothesis that the structures are cellular extensions

Whereas the majority of the structures appear to be hollow and devoid of any content, a number of these structures appear to be solid, said an U-M release

These findings were presented at the annual meeting of the Microscopy Society of America in Richmond

Cryosurgery

Cryosurgery

Cryosurgery (cryotherapy) is the application of extreme cold to destroy abnormal or diseased tissue The term comes from the Greek words cryo ("icy cold") and surgery (cheirourgiki) meaning "hand work" or "handiwork".Cryosurgery is used to treat a number of diseases and disorders, especially a variety of benign and malignant skin & oral conditions. Warts, moles, skin tags, solar keratoses, and small skin cancers are candidates for cryosurgical treatment. Several internal disorders are also treated with cryosurgery, including liver cancer, prostate cancer, cervical disorders and, more commonly in the past, hemorrhoids. Although found to be effective, this method of treatment is only appropriate for use against localized disease with no metastasis.Cryosurgery works by taking advantage of the destructive force of freezing temperatures on cells. At low temperatures, ice crystals form inside the cells, which can tear them apart. More damage occurs when blood vessels supplying the diseased tissue freeze.The most common method of freezing lesions is using liquid nitrogen as the cooling solution. The super-cooled liquid may be sprayed on the diseased tissue, circulated through a tube called a cryoprobe, or simply dabbed on with a cotton or foam swab. Less frequently, doctors use carbon dioxide "snow" formed into a cylinder or mixed with acetone to form a slush that is applied directly to the treated tissue. Recent advances in technology have allowed for the use of argon gas to drive ice formation using a principle known as the Joule-Thomson effect. This gives physicians excellent control of the ice, and minimizing complications using ultra-thin 17 gauge cryoneedles.Cryosurgery is a minimally invasive procedure, and is often preferred to more traditional kinds of surgery because of its minimal pain, scarring, and cost; however, as with any medical treatment, there are risks involved, primarily that of damage to nearby healthy tissue. Damage to nerve tissue is of particular concern.Patients undergoing cryosurgery usually experience minor-to-moderate localized pain and redness, which can be alleviated by oral administration of an analgesic such as aspirin, ibuprofen or acetaminophen (paracetamol). Blisters may form, but these usually scab over and peel away within several days.