Non CariousClassVLesions Operatoria
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Non-Carious Class V Lesions: What's Really Going On? By Nichole Dicke, LDH, BS N< I on-carious class V lesions are a familiar yet perplexing patient concern. Dentists frequently encounter such lesions and are faced with the challenge of diagnosing and treating them. How these lesions are diagnosed directly affects their treatment and prognoses. What may come as a surprise to many dental practitioners is that non-carious class V lesions are quite possibly being misdiagnosed, interfering with successful (long-term) treatment and prevention of future lesions. Patients frequently come to the dental office concerned about "notched out" areas near the gumline. In many cases, the first response would be assessing oral hygiene practices for sources of abrasion, including applying too much pressure and/or scrubbing while brushing, using a firm toothbrush, or using too abrasive a dentifrice. If everything in the home care regimen seems correct, the next move is most likely to assess the patient's diet and oral environment for erosive factors, such as a high sugar or acid diet, the chronic use of lozenges, or acidic saliva. The patient is then sent home with a new tooth brushing method, an extra soft toothbrush, a sample of non-abrasive gel toothpaste and dietary recom- mendations. Six months later, the patient returns and the clinician notes two more cervical lesions. Is the patient not complying, or are these lesions being cause by something else altogether? Dentifrices are no longer made from crushed oyster shells, eggshells and bones. Additionally, patients are using soft toothbrushes. Is it really plausible they are still managing to brush away the , hardest substance in the human body? There are patients with these lesions who admittedly hardly ever brush their teeth, thus ruling out toothbrush abrasion. Dentifrices are no longer made from crushed oyster shells, eggshells and bones. Additionally, patients are using soft toothbrushes. Is it really plausible they are still managing to brush away the hardest substance in the human body? Even using firm brushes, is it conceivable that brush- ing back and forth could cause these lesions, which often affect areas of the teeth notoriously missed when patients brush? Would a toothbrush head be able to cause these le- sions, which range from broad and shallow to very narrow, deep and angular? A review of the literature reveals little to no evidence that toothbrushes and dentifrice are capable of causing significant damage to teeth. There are patients with these lesions who have never experienced a cavity and have very low sugar/acid intakes, making diet an unlikely culprit. Finally, these lesions have been found on the roots of extracted teeth with no gingival recession, making abrasion and erosion both virtually impossible. Recent dental research investigating non-carious cervical lesions has resulted in the theory of abfraction, where forces cause flexure and defor- mation of the teeth, usually at the cervical.' Characteristics of Non-Carious Class IV lesions Non-carious class V lesions, or cervical lesions, are losses of tooth structure (enamel and dentin) without the presence of dental caries.^ The exposed dentin is often smooth and shiny. The patient may or may not experience increased sen- sitivity in these areas. There are two morphological types of these defects: concave and wedge-shaped. Concave lesions are smaller and shallower than wedge-shaped lesions, which are deep, with sharp angles, and result in a greater loss of tooth structure. The concave lesions are generally much less severe than wedge-shaped, and it has been hypothesized that wedge-shaped lesions are caused by more stressful, destructive forces than the concave lesions.^ It is this severe and rapid destruction that has caused many researchers to investigate the potential causes and treatments of cervical lesions. Wedge-shaped cervical lesions are often found on teeth with prominent occlusal wear.^ Interestingly, these lesions are most frequently found on surfaces opposite the surface with the most severe wear facet/attrition. Literature as early as the 1977 study by Xhonga documented higher prevalence of cervical lesions in bruxers." In 1987, Lambrechts et al. also concluded bruxism, in addition to malocclusion, were also seemingly associated with abfractive lesions.= In agree- ment was the study by Burke et al. in 1995, in which the authors noted cervical lesions in teeth subjected to lateral forces while the adjacent teeth (not subjected to lateral forces) presented with no lesions.'' Cervical lesions are rarely found on calm, low-stress individuals with ideal (class I) bites. More often, they are found in individuals with maloc- clusions resulting in mal-aligned cusps subject to heavy and/ or oblique occlusal loads.^ A Theory of Physics and Engineering What if repeated forces, namely lateral and oblique forces, could cause stress points on teeth that eventually break loose? These forces could be due to malocclusion or tongue thrust. At first, the idea of a tongue movement caus- ing tooth breakage may seem unrealistic. An analogy would be a new dining room table with a pedestal base, made of solid and very strong maple wood. Imagine the person sit- ting at the "head" of the table pushes his hands against the table top to help him stand up from sitting in a chair. This action alone is not likely to break the table. However, if this person does this repeatedly, hundreds or even thousands of times per day (as often as humans swallow), it is plausible this force could cause such stress on the table that it breaks. The table top is analogous to the crown of a tooth, and the pedestal base is analogous to the root. Repeated pressure on the crown, albeit slight and undamaging as a single incident, may accumulate as chronic stress that eventually manifests as fractures. Abfraction is based on principals in physics and engineer- ing. Ideally, occlusal forces are transmitted vertically along the axis of the tooth and absorbed by the periodontium. In the table analogy, this would be similar to a person push- 16 NOV 2012 access
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Transcript of Non CariousClassVLesions Operatoria
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Non-Carious Class V Lesions:What's Really Going On?By Nichole Dicke, LDH, BS
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ing their bodyweight perfectly downward on the very middle of thedining table where the pedestal base attaches beneath - the forcewould pass through the pedestal to the floor beneath with no dam-age done. If forces are applied in a non-axial direction as lateral oroblique pressure, or if the forces are repeated excessively, they mayconcentrate in the cervical area of the tooth and cause enamel anddentin destruction (Figure 1).
Strains on teeth are concentrated into the cervical region,particuiarly forces not directed onto the occiusal surface along theaxis of the tooth.' Cervical enamel is inherently weaker, with poorerstructure and greater pore volume, and with fewer areas of gnarledenamel (interwoven enamel rods that produce stronger enamel).^Cervical enamel also has less compressive strength than enamelfound on cusps' and is considerably thinner and more brittle."
Occiusal loads, particularly lateral forces, may cause the teeth toflex. This flexure may in turn break the bonds in the hydroxyapatite,which leads to cracks and fractures in the enamei and underlyingstructures. Oblique stresses applied to the cuspal inclines, ratherthan cusp tips, put more stress on the tooth structure (Figure 2).^Teeth are better able to withstand direct vertical pressure than lat-eral or oblique pressures. Heavy occiusal contact areas, determinedby heavy markings using pressure-detecting sheets, have beensignificantly linked to the occurrence of cervical lesions (Figure 3).^
Several studies have revealed the impact chewing has on cervicalenamel. Extracted teeth subjected to cycles of occiusal loading be-gan to suffer fractures in the cervical enamel after only 2.5 months'worth of chewing (200,000 cycles)." These fractures worsened asmore cycles were applied. Networks of microcracks have been notednear the CEJ when on teeth subjected to cyclic occiusal pressures.'^Occiusal forces pass through the teeth into the periodontium, wherethe supporting structures help to absorb the forces and provide acushion. Mobile teeth are less prone to cervical concentration ofthese forces." A relationship between mobility and cervical lesionswas discovered where less mobile teeth (with more rigid support)exhibited higher rates of cervical lesions."
If no heavy attrition, wear facets, or markings on cuspal inclina-tions are present, pressure from tongue movements may be the cul-prit (Figures 4 and 5). An ideal swallow involves placing the tip of thetongue on the palate, behind the anterior teeth. As the swallow pro-ceeds, the body of the tongue continues to press upward against thepalate, pushing the food towards the throat in a peristaltic manner."The tongue should not press against any teeth during the swallowingaction. A tongue-thrust swallow, one where the tongue pushes theteeth in order to force the food towards the throat, may be the resultof habit, an abnormally large tongue or a congested airway." It hasbeen theorized that abnormal swallows in infants may actually causemalocclusions such as narrow arches, crowding and overjets.'^Therepeated pressing of the tongue against the tooth acts as a personpushing against the edge of a table when standing up; over time, itmay cause enough stress for a fracture to occur. These lesions aremost common on anteriors and premolars, the teeth most affectedby abnormal tongue movements."
Abfraction may also serve as a co-contributor to cervical lesions.One possible hypothesis is that non-carious class V lesions couldoccur when erosive dietary fluids (which affect buccal surfacesmore than lingual surfaces) leak into the microscopic cracks in thehydroxyapatite that resulted from occiusal loads concentrated intothe cervical areas. A 2004 study examined abfraction in teeth withcervical enamel that has been undermined (the dentine beneath hasbegun to erode).'"^ The researchers applied 100 Newtons of obliqueload pressure (bruxers may apply as much as 500 Newtons) tointact teeth and teeth with varying degrees of undermined enameland measured the resulting levels of stress on the buccal enamelnear the amelo-dentine junction. Teeth with cervical enamel defectsexhibited much higher stress values; the larger the enamel defect,the higher the stress value. Enamel defects as small as 0.34 mm inlength resulted in stress values above the known fracture limit. Gin-gival crevicular fluid has been shown to be acidic and may contributeto enamel undermining."
Figure 1. Oblique occiusal forces may cause concentrated stress in thecervical area, resulting in microfractures and eventual ioss of enameland dentin.
Figures 2 and 3. Abfraction lesions present on teeth with heavy indica-tor maridngs. The mari
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Figure 6. Heavy indicatormarkings on cuspal inclinestooth #12 (slightly rotated).Note gingival cleft and begin-ning of abfractlon lesion. Pa-tient was experiencing sensi-tivity. Reprinted with permissionfrom Dr. Robert Palmer, DDS.
Figure 7. Selective minoradjustment to contactpoints reduced the side ofthe contact area removingthe oblique occlusal forces.Patient reported relief ofsensitivity. Reprinted witlipermission from Dr. RobertPalmer, DOS.
Patient Assessment
As stated earlier, a tongue-thrust swallow results in tiie tonguepressing against the lingual surfaces of the teeth rather than againsttiie palate. Assessing patients for tongue-thrust is quite simpie.Wiiile retracting the patient's cheeks, tiie clinician should ask tiiepatient to swallow. If any teeth are missing, or if large interproximalspaces are present, the clinician can watch for tiie tongue to pusiiinto tiiese gaps while the patient swallows. If dentition is full andcontacts are closed, a tongue-tiirust swallow will usually result insaiiva and/or bubbles being forced through the interdentai spaces."Tine patient may need to swailow more than once for this to be seenand/or ineard by the clinician.
The typical occlusai assessment during office exams consists ofnoting Class I, II and II I malocclusions, over/underbite, overjet,crossbite, openbite and end-to-end reiationships. Tinese indeed areimportant factors for many aspects of dental health. However, winenevaluating for the potential of abfractive lesions, more detectivework is necessary. Articuiating paper, occiusal indicator wax, pres-sure detecting sheets and otiner occlusal pressure analyzers areuseful tools for assessing the risk of abfraction. A inealthy occlusionsinould resuit in small areas of contact on cusp tips or in occiusalfossae. The clinician should look for large areas of contact, par-ticulariy on cuspal inclinations and on buccal and lingual surfaces.Canine guidance is anotiner key element of the occlusal exam. Whiletiie patient is in centric occiusion, ask him to very siowly slide theirmandible to the right (and then left), until tiie buccal surfaces of themandibular and maxiilary molars are flush with one another At thispoint, only the patient's canines should be in contact. Similarly, whenthe patient extrudes their mandible forward, the incisors shouldfirst guide the movement, followed by the canines alone being incontact with one anotiner. If non-canine teeth are guiding occlusionmovement, they are experiencing more occlusal load than tiiey aredesigned to handle and therefore may be at risk for periodontaldamage, excessive wear and abfraction.
Assessing tiie patient's diet and oral environment for sources oferosive elements is aiso necessary, as erosion and occlusal/tongueforces may serve as co-contributors to cervical lesions. Saliva pHand salivary flow rates can be tested in the office. Interviewing thepatient can reveal dietary sources, such as carbonated beverages,fruit juices and alcohol. Foods and beverages high in sugars alsoneed to be identified as contributors to erosion due to tiie well-known oral "acid attack" that occurs after consuming fermentablecarboinydrates. Frequency of consumption will be the key to deter-mining which dietary factors are likely to be contributors. In addition
to assessing for corrosion-abfraction, other possible co-contributorssiiould be identified. Areas of severe attrition also need to be noted,as well as abrasion from partial denture clasps, habits such as exces-sive tootiipick use, parafunctionai habits or any other finding thatmay weaken the tootii structure.
Treatment of Abfractions
There are mixed viewpoints about restoring these lesions.Resin-based composites are frequently used to reduce sensitiv-ity and improve esthetics. Many dental practitioners do not restoreabfractions for two main reasons: the lesions are non-carious, andthey are likely to return if the cause of abfraction has not been ad-dressed. The longevity of resin class V restorations is questionablein patients who experience tinese lesions due to occiusal stresses.In 2009, Friscisconi et al. investigated tiie effects of occlusal pres-sure on resin Class V restorations." The researciiers created class Vlesions in 40 extracted teeth, restored them witin resin composites,and tinen subjected tine teeth to 150 Newtons of occiusal pressure onthe buccal cusps, lingual cusps and central fossae. The restorationmargins were inspected using fluorescein to evaiuate defects. Oc-ciusal pressure, regardiess of location, contributed to tine formationof margin gaps. This occurred on resins of varying sizes and depths.The researciners concluded tinat occlusal loading must be addressedin patients being treated for abfraction lesions to ensure that resinmargin integrity is maintained.
Treating the cause of abfraction may require retraining theindividual to swallow correctly. Patients may be referred to speechtinerapists for help in breaking the tongue tiirust habit. Bruxersshould be fitted witii splints or guards. Tiie clinical work of RobertPaimer, DDS, iias demonstrated success witii creating equiiibrium.Palmer performs fine modification of the contact areas, reducingtiieir size (Figures 6 and 7). Palmer's patients reported immediatereiief of sensitivity, indicating that tine sensitivity may be caused byflexure resulting from occlusai load." Occlusal therapy may be usefulin treating gingival clefts, whicii Palmer identified as a precursor toabfraction."'" In 1983, Solnit and Stambaugii reported tinat refiningcontact points on teeth with gingival ciefts actually resulted in a par-tiai to complete reversal of tiie clefts in all 25 cases studied." It isPaimer's standard to refine occlusion for teeth witii abfractions thatare being restored with resin-based composites to prevent recur-rence."
If co-contributors are identified, tiiey wiil also need to be ad-dressed as part of the treatment plan. Sources of erosion need tobe reduced or eliminated. Salivary replacement products siiouldbe recommended for those with xerostomia. Fiuoride rinses, gelsor varnishes are appropriate for patients wino are at high risk forerosion, tinougin researcin has produced mixed results regardingfluoride's ability to prevent erosion in inighiy acidic environments."""Products that contain the casein pinospinopeptide-amorphous calciumpinospinate (CPP-ACP) complex have been sinown to reduce acid-ity and strengthen the tooth surface."-^^ Xyiitoi products, such aschewing gums and mints, inhibit microbial metabolism, thus loweringoral acidity; research suggests this effect may persist after using theproducts."'^^ Ortinodontia may be recommended to reduce end-to-end occlusion areas or other maiocclusion. If abrasion is beingcaused by partial denture clasps, the dentist may need to makeadjustments to the partial or consider recontouring and/or restoringthe abutment tooth.
Conclusion
As with any tineory, tinere are conflicting viewpoints tinat mustbe considered. Abfraction is a theory based on engineering princi-pals of occlusal stress being concentrated at the cervical portions ofteeth. While the evidence is compelling, tinere is limited conclusiveresearch on occlusal forces causing cervicai lesions, indicating a need
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for further research,^^ Rees' 2002 studies demonstrated occlusalloads cause stress on the lingual cervical areas also, yet lesions arerarely found here, suggesting a multifactorial nature,' It is difficultto "prove" abfraction, as the lesions resemble those thought to becaused by toothbrush abrasion and erosion, though research hashistorically failed to prove toothbrushing and dentifrice are causes ofsignificant cervical wear.'"'= Many practitioners feel more definitivedata is needed to attribute these lesions solely to abfraction andcaution against making permanent changes to patients' teeth basedon abfraction theory alone. When patients present with non-cariousclass V lesions, the clinician may be faced with a complex mystery tosolve, one with a multifactorial answer. It is in patients' best interestfor the clinician to be open-minded and thoroughly investigate allpossible causes, as a treatment is only as good as the diagnosis.
References
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Nichoie Dicke, LDH, BS, works part time as adentai hygienist in private practice in Indiana.She graduated with her associate's degree in2003 and completed her bachelor degree in2008 from Indiana University - Purdue Univer-sity in Fort Wayne, Ind., where she currentlyalso works as a clinicai instructor. She is finish-ing her thesis research through Idaho StateUniversity and wiil earn a Master of Science indental hygiene with an emphasis in education.
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