We have all seen these lesions in clinical practice. What is the first thing that comes to mind? What is the second thing that comes to mind?
A few thoughts to ponder before naming abrasion as the cause of these lesions. You send tell your patient to switch to a soft brush. He tells you he only ever uses soft ones. Maybe he even uses a pressure-sensing battery brush. You suggest maybe he’s scrubbing to hard, or horizontally, so you have him demonstrate his brushing, which he does correctly and very gently. He’s using a gentle gel toothpaste. Yet, he experiences cervical lesoins. Is it still abrasion?2. Is it really plausible that tooth brush bristles are erasing deep wedges of the hardest substance in the human body? We are no longer using crushed bone, sand, and oyster shells in our dentifrice. Is it plausible that today’s toothpastes can be rubbing away the hardest substance in the human body? Historically, research has failed to demonstrate the ability of toothbrushing to cause loss of tooth structure.
When you disclose a patient, what areas usually have the most plaque?
How can we blame maxillary posterior cervical lesions on erosion? Fluids do not “settle” in these areas. Few patients tuch mints, tobacco, etc. into the upper vestibule. Yet, the maxillary teeth are the most frequently affected by these lesions. We have patients who have all the right anwers during the dietary acid assessment. No citric acid, no sugary fluids, no lemon eating, no use of lozenges, etc.
Often, the cervical lesions affect surfaces of the teeth protected by soft tissues. In fact, these lesions have been discovered mid-root on extracted teeth with NO recession. Abrasion and erosion are eliminated as potential causes in these cases.
If grandpa is sitting at this table, and pushes his hands against the table top to help himself stand, is the table going to break? Doubtful. It’s made of very hard wood and is designed to withstand forces. What if Grandpa does this 20 times a day for 20 years? Is the table at risk of eventually breaking from the repeated stress? Probably.
Don’t panic just because I said the word “physics”. It’s simple. Abfraction is a theory of physics and engineering which suggests occlusal forces may concentrate in the cervical area of the tooth. This concentration of force may cause flexure, which may in turn cause microfractures in the cervical enamel.
Three main causes of excessive occlusal force, which we will discuss, are bruxism, misalignment, and believe it or not, tongue thrust.
Forces that are applied laterally, obliquelly, or off-centered may concentrate the stress of the force on the area where the table top (or crown) meets the pedestal (or root), causing it to break there.
The pedestal represents the root, and the table top represents the crown. Tables and teeth are designed to tolerate reasonable, properly applied forces. If forces are applied perfectly vertical, in the center of the table or tooth, along the axis of the pedestal (or root), the force dissipates into the floor (or perdiodontium) 9.
Misaligment contributes to excessive occlusal forces in three main ways. The teeth involved may “hit early”, especially in the case of supraversion.Ideally, the cusp of one tooth will occlude with the cusp tip or the central fossa of the opposing tooth. Finally, points of contact should be small and focused, not widespread or heavy.
While malalignment causes oblique forces, tongue thrust results in lateral force.It’s not the size that matters! It’s the cumulative effects of repeated forces, not necessarily the amount of the force applied. Remember grandpa – he may not be strong or heavy, but he can cause damage over time (if he lives long enough that is).
As you can guess, there are two sides to this issue. Many feel there is not enough definitive evidence to jump in making occlusal adjustments for every patient with cervical lesions. It is very difficult to “prove” a theory like abfraction. How can you truly “prove” repeated forces over a person’s lifetime caused their teeth to break down? In response, many researchers have set out to gather that evidence. Does it matter what causes them? Yes! You can’t treat what you can’t diagnose.
Forces applied to the crown of the tooth are concentrated at the cervical region. Why is this important?Cervical enamel is inherently weaker. Is more brittle, more porous. 9 Cervical enamel has fewer gnarled enamel (interwoven enamel rods which produce higher strength enamel 7. Also, cervical enamel has less compressive strength 8.
Occlusal forces cause tooth flexure. If a tooth is out of alignment, is hitting heavy, or is hitting on a cuspal incline, this flexure will be greater.Researchers have subjected extracted teeth to occlusal loads on various parts of the crown. Cervical fractures were observed after approximately 200,000 chewing cycles, which is 2.5 months worth of chewing for the average person.Forces applied to cuspal inclines, rather than the central fossa or the cusp tips, experience higher stress levels.Teeth with heavy occlusal contacts, as assessed by articulating paper, indicator wax, or computerized occlusion analyzers, experience more cervical lesions.
There have been studies that indicate toothbrushing may cause abrasion. The photo here shows a tooth that was hooked up to a toothbrushing machine in the 1960’s (most likely hard bristles) and was subjected to constant brushing force for hours on end. The lesion created is distinctively different from the typical abfraction lesion, shown on the right.
Start being more observant of patients with cervical lesions. Many of them have heavy wear facets on the affected teeth. Seldomly do you find cervical lesions on mobile teeth.9,12 Why? Imagine the dining table is on a waterbed. Will the forces still concentrate where the pedestal attaches, or will it be absorbed by the water bed?Cervical lesions are seldomly found in patients who are laid back, low-maintenance, with ideal occlusion and straight teeth.
Points of contact may be assessed using occlusal indicator was, articulating paper, pressure detecting sheets, or computerized occlusal analyzers such as the T-Scan by a company called Tekscan.
A healthy swallow begins with the tip of the tongue on the palate. The tongue uses a peristaltic motion to force to food bolus down the throat. In a tongue thrust swallow, the sides of the tongue press against the lingual surfaces of the teeth. The average person swallows hundreds, even thousands of times per day. That’s a lot of flexing!Some conditions such as congested airways and large tongues may contribute to tongue thrust activity. For many patients, it is a habit developed during infanthood or childhood.
** *Think of Partial denture clasps. Occlusal forces cause a concentration of stress where? Yes, the cervical region, where denture clasps rest. This could an abrasion-abfraction lesion.
Many practitioners do not restore cervical lesions unless there is severe sensitivity, problems with catching food, etc.If the cause of the lesion is not addressed, what makes us think the restoration will last? When we restore caries, do we not at least attempt to identify the source of the caries to prevent recurrence?If a composite restoration is going to be placed, the dentist should consider fine tuning the patient’s occlusion to increase the chances of retention.Gingival clefting may be a precursor to abfraction and warrants an occlusal evaluation in patients. In fact, research has demonstrated the ability to reduce/correct clefts simply by adjusting the contact points!
You can see the heavy markings on tooth #21, which was the opposing tooth to the sensitive #12. The contact point was refined, and sensitivity was completely eliminated. Also, these adjustments restored canine guidance – the patient had bicuspid guidance before. End of case.
Class V Lesions
NON-CARIOUS CLASS V LESIONS: ASSESSING THE CAUSE Nichole Dicke, LDH, BGS
OBJECTIVES Identify the clinical characteristics of non-carious class V lesions Discuss the traditional suspected causes of these lesions Describe the theory of abfraction Compare the various types/sources of abfractive forces Identify potential co-contributers to class V lesionsDescribe patient evaluation procedures for diagnosing the cause of the lesions Describe the management and treatment of these lesions and their causes
A FAMILIAR SIGHTThese lesions are typically diagnosed as abrasion or erosion .
ABRASION: THOUGHTS TO CONSIDER * Home self-care….what if they’re doing it right?* Are we giving toothbrushes and toothpastes too much credit? Researchers think so. 1,2,3,4,5,6
ABRASION: THOUGHTS TO CONSIDER How can oral hygienetechnique, which all too often results in this…. ….also result in this?
EROSION: THOUGHTS TO CONSIDER* Location, location, location. * Where’s the acid source?
ABRASION AND EROSION: A FINAL THOUGHTHow could abrasion and/or erosion cause this?
SO WHAT’S REALLY GOING ON?Imagine Grandpa at the dining table.
ABFRACTION = PHYSICS Misallignment may cause teeth to: * “Hit early”* Occlude with the opposing tooth on a cuspal incline * Have heavy contact with opposing teeth
ABFRACTION = PHYSICS* Tongue thrust applies lateral pressure to the crown. * Remember: it’s the cumulative effect of repeated forces, not necessarily the amount of force applied.* And remember grandpa! He may not be very strong or heavy, but he can still cause damage over time.
ABFRACTION: THE RESEARCH * Controversial* Burden of Proof* Does it matter? Innocent until proven guilty!
ABFRACTION: THE RESEARCH Research tells us that:* Occlusal forces are concentrated at the cervical region.7,8,9 * Cervical enamel is inherently weak. 10,11,12
ABFRACTION: THE RESEARCH *Occlusal forces cause teeth to flex. *Cycles of occlusal loads on extracted teeth have causedcervical fractures after 2.5 months worth of “chewing”. 8,9 *Forces applied to cuspal inclines = more stress. 13*Heavy occlusal contact areas are directly associated with cervical lesions.14
ABFRACTION: THE RESEARCHResearch that DOES suggest toothbrush abrasion (suchas the 1960’s study pictured below) resulted in distinctive lesions. Abrasion from toothbrushing machine abfraction
ABFRACTION: OBSERVATIONAL EVIDENCE* Cervical lesions are frequently found on teeth with heavy wear facets.15 * Cervical lesions not commonly found on mobile teeth.12,16 Why? * Patient profiling15
ASSESSING FOR ABFRACTION: CONTACT POINTS*Occlusal indicator wax*Articulating paper*Pressure detecting sheets*Computerized assessment T-Scan II by Tekscan
ASSESSING FOR ABFRACTION: CONTACT POINTSHeavy contact markings Heavy markings on cuspal inclines
ASSESSING FOR ABFRACTION: CANINE GUIDANCE Canine Guidance Illustration
ASSESSING FOR ABFRACTION: TONGUE THRUST*A healthy swallow involves the tongue and the palate.17*A tongue thrust swallow involves the tongue, palate, and the teeth.17*Some patients are at risk of developing a tongue thrust swallow. 17
ASSESSING FOR ABFRACTION: TONGUE THRUST *With the patient in centricocclusion, ask him to swallow, watch the tongue. *Watch for bubbles and saliva. *Tongue thrust may easily be corrected through therapy. Tongue thrust with abfraction
ASSESSING FOR ABFRACTION: MULTIFACTORIAL CONSIDERATIONS ? * The questionremains…..erosion, abrasion, or abfraction? * Why Does it have to beeither-or? Why not both, or even all?
ASSESSING FOR ABFRACTION: MULTIFACTORIAL CONSIDERATIONS * Erosion-Abfraction: Erosive agents seep into microfractures, undermining and the enamel. Even GCF may be errosive. 12,15,18 * Abrasion-Abfraction occurs when occlusal forces cause stress concentration in areas with external friction sources. 12 * Erosion-Abrasion, likewise, combines corrosive chemical exposures with external friction sources.12* Caries can also combine with erosion, abrasion, and abfraction. 12
TREATING ABFRACTIONS * Many practitioners do not restore cervical lesions unless necessary. * If the occlusal forces are not corrected, a cervical lesion will likely fail.* It is recommended that dentists consider making fine adjustments to the occlusion prior to placing composite restorations. 17* It has been speculated that isolated areas of recession, or clefting, is a precursor to abfraction and warrants an occlusal assessment. 17,19
TREATING ABFRACTIONS Occlusal adjustment exampleClassic abfraction affecting Canines and premolars. Heavy contacts on cuspal Contact points reduced.Patient experiences severe inclines. sensitivity tooth #12.
TREATMENT OF ABFRACTION Example continuedHeavy markings on opposing Contact point reduced. Canine guidance restored. tooth #21 Sensitivity on tooth End of case. #12 eliminated!
REMEMBER…The treatment isonly as good as the diagnosis.
REFERENCES1. Radentz WH, Barnes GP, Cutright DE. A survey of factors possibly associated with cervical abrasion of tooth surfaces. J Periodontol. 1976; 47: 148-542. Sangnes G, Gjermo P. Prevalence of oral soft and hard tissue lesions related to mechanical toothcleansing proceedures. Community Dent Oral Epidemiol. 1976;4:77-833. Saxton CA, Cowell CR. Clinical investigation of the effects of dentifrices on dentin wear at the cementoenamel junction. J Am Dent Assoc. 1981; 10:, 38-43.4. Sognnaes R, Wolcott R, Xhonga F. Dental erosion: erosion-like patterns occurring in association with other dental conditions. J Am Dent Assoc. 1972; 84: 571-82.5. Volpe A, Mooney R, Zumbrunnen C, et al. A longterm clinical study evaluating the effect of two dentifrices on oral tissue. J Periodont. 1975; 46: 113-8.6. Joiner A, Pickles MJ, Tanner C, et al. An in situ model to study the toothpaste abrasion of enamel. J Clin Periodontol. 2004; 31: 434-8.7. Nohl FS, McCabe JF, Walls AWG. The Effect of Load Angle on Strains Induced in Maxillary Premolars in vitro. British Society of Dental Research Meeting. University of Leeds. April 12-15 1999; Abstract no. 200.
8. Palamara D, Palamara JE, Tyas MJ, et al. Effect of stress on acid dissolution of enamel. Dent Mater. 2001; 17(2):109-15.9. Hanaoka K, Magao D, Mitusi K, et al. A biomechanical approach to the etiology and treatment of non-carious dental cervical lesions. Bull Kanagawa Dent Coll. 1998; 26(2) 103-11.10. Scott JH, Symons NBB. Introduction to Dental Anatomy, 9 th ed. 1982. Churchill Livingstone, Edinburgh, UK.11. Stanford JW, Paffenbarger GC, Kampula JW. Determination of some compressive properties of human enamel and dentine. J Am Dent Assoc. 1958; 57: 487-95.12. Grippo JO, Simring M, Schreiner S. Attrition, abrasion, corrosion, and abfraction revisited. J Am Dent Assoc 2004; 135: 1109-18.13. Rees J. The effect of variation in occlusal loading on the development of abfraction lesions: a finite element study. J Oral Rehabil. 2002; 29: 188-93.14. Takehara J, Tomotsugu T, Akhter R, et al. Correlations of noncarious cervical lesions and occlusal factors determined by using pressure-detecting sheet. J Dent. 2008; 36: 774-9.
15. Rees J, Hammadeh M. Undermining of enamel as a mechanism of abfraction lesion formation: a finite element study. Eur J Oral Sci. 2004; 112: 347-52.16. Kuroe T, Itoh H, Caputo AA, et al. Potential for load-induced cervical stress concentration as a function of periodontal support. J Esthet Dent. 1999; 11: 215- 22.17. Palmer B. The significance of lateral forces to the development of dental abfractions. Available at http://www.brianpalmerdds.com/lateralforce_abfract.htm. Accessed Jan 27, 2011.18. Bodecker CF. Local acidity: a cause of dental erosion-abrasion. Ann Dent. 1945; 4(1): 50-55.19. Solnit A, Stambaugh R. Treatment of gingival clefts by occlusal therapy. Int J Periodont Rest. March 1983:38-55. Intra-oral images used with explicit permission from Dr. Brian Palmer, DDS.