abfraction

What causes dental abfractions (non-carious cervical lesions) and how should they be managed?

A dental abfraction, also known as an NCCL, is defined as the loss of tooth structure at the cementoenamel junction (CEJ) under pathological conditions. These lesions most frequently occur on the facial surfaces of teeth, but its not entirely impossible to spot them on the lingual or interproximal surface. Epidemiology studies report this phenomenon most frequently occurs in premolars (7, 8, 9). Patients will typically report hypersensitivity as a result of enamel rod corrosion and dentin tubule exposure.

It’s important to note that this loss of tooth structure is not attributed to caries (hence non-carious cervical lesion). There is oftentimes speculation of the cause of NCCLs. I want to thoroughly describe this topic in an effort to present current advances from the last decade that have helped to elucidate the etiology of NCCLs as well as management strategies. I would also like to propose that we as a community should move away from using the term “abfraction” and exclusively use the term “non-carious cervical leasion” (or NCCL). “Abfraction” is a misnomer because this is one of the mechanisms that may cause this lesion, but the lesion may occur from other forces.

Etiology

Today there is extensive evidence that the cause of NCCLs is multifactorial.  The variables involved are biocorrosion (erosion), friction (abrasion), and possibly occlusal stress (abfraction). Below I will delve into those different factors and define what they are.

Biocorrosion

Contemporary literature, such as Grippo’s 2012 article on the topic (“abfraction, abrasion, biocorrosion…”) suggests that the term “biocorrosion” should supplant the term “erosion.” He contends that the term biocorrosion, rather than erosion is a more accurate term to describe the phenomenon. He states that “biocorrosion which is chemical, biochemical or electrochemical action which causes the molecular degradation of the essential properties in a living tissue is more precise than erosion.”

The phenomenon of biocorrosion can be attributed to chemical exogenous and biochemical endogenous acid and biochemical proteolytic enzymes (proteases). Proteases are known to come from plaque microorganisms as well as gingival crevicular fluid. Proteases can also arise from sources such as the stomach and pancreas in individuals that have GERD, bulimia nervosa and hiatal hernias.

Friction (Abrasion)

Abrasion (or friction) occurs when teeth are introduced to a foreign object that introduces a mechanical process. The greatest offenders are excessive force when brushing teeth, abrasive toothpaste and a horizontal brushing technique. Other risk factors include the frequency and duration of the applied force. Interestingly, clinical and lab data contend that there is little evidence that NCCLs are solely caused by abrasion.1

abfraction
All the photos for this article were graciously provided by the very-talented Dr. Alex May. Follow more of his work here: @alexmaydmd

Abfraction (Stress)

The traditional abfraction theory states that the cervical area of the tooth becomes a fulcrum during occlusal loading. This action leads to tensile stress which leads to disruption of the crystalline structure which eventually leads to cracks. This fatigue then causes enamel to break away from the margin.

This theory is one in which most dentists are very familiar with and I myself once subscribed to. While this theory is logical, it is actually quite controversial. Several finite element analysis (FEA) studies have supported this theory while systematic reviews have not.2,3,4,5,6 In Van Meerbeek’s 2020 article he states that there is a weak association between NCCLs and occlusal factors.12 This statement is important because some clinicians treatment plan patients for occlusal adjustments as a way to manage NCCLS. However, several authors would caution dentists against this irreversible treatment strategy. 7, 8, 9

The appearance of NCCLs can provide critical insight into their etiology.10,11 Broad, shallow disk-shaped lesions are typically attributed to erosion. Lesions caused by abrasion from incorrect tooth brushing will exhibit sharply defined margins. NCCLs caused by both abrasion and erosion will appear more U-shaped. Abnormal occlusal loading will lead to wedge-shaped lesions. With that being said, because NCCLs are typically multifactorial, multiple geometric forms are typically present.

Conservative Management Strategies

Preventative intervention for NCCLs should, of course, be the first line of therapy. The patient should be interviewed to identify which habits may be contributing to the formation of these NCCLs. Patients should be monitored for progression of the lesion during 6 month intervals.12

Pecie’s 2011 article and Wood’s 2008 article on the topic both suggest occlusal splint therapy as a treatment strategy to reduce nonaxial forces and manage nocturnal bruxism. This strategy really only applies if abfraction is suspected as the etiology.

In instances when the NCCL is shallow and does not require restorative treatment, hypersensitivity should be managed as noninvasively as possible. Examples of OTC agents include toothpastes  with sodium fluoride, stannous fluoride, strontium chloride, potassium oxalate, etc. These agents work by plugging the dentinal tubules. Per Van Meerbeek’s 2020 article, if at-home desensitizing agents are still ineffective by the 3-4 week mark, in-office therapy should be initiated.12

Personally speaking (I have no financial conflict of interest), I have found 3M’s 5% Sodium Fluoride varnish to be an excellent agent in managing transient sensitivity secondary to NCCLs. A longer lasting, and yet relatively noninvasive, treatment strategy for small NCCLs is to use a resin-based dental adhesive system over the lesion. The adhesive (which some dentists refer to as “bonding agent”) can seal the dentinal tubules and create a hybrid layer which thereby immediately addresses sensitivity. This intervention is effective for about 6 months13, 14

abfraction
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Restoring NCCLs/Abfractions

The decision to intervene should be based on the progression of the lesion and how it impacts esthetics, function and vitality. Proper adhesive techniques are of the upmost importance because these lesions provide poor macroretention (these restorations are effectively shallow saucers).

In Van Meerbeek’s 2020 article he provides 6 indications for restoring NCCLs. They are as follows:

  1. The NCCL also has active cavitated caries
  2. The NCCL lesion margins are subgingival and therefore preclude plaque control in such a way that the dentition may succumb to caries or periodontal disease
  3. Tooth structure loss is so extensive, there is a heightened risk of pulpal exposure
  4. Dentinal hypersensitivity and noninvasive therapeutic options have failed
  5. The tooth is a prosthetic abutment for a removable prosthesis
  6. The patient is displeased with the esthetics of the NCCL

Which material should be used to restore NCCLs/Abfractions?

Clinicians usually have the choice between glass-ionomer, resin-modified glass-ionomer and resin composite. A systematic review conducted by Peumans in 2014 compared the efficacy of these three materials for restoring NCCLs. The material with the lowest annual failure rate was glass ionomer followed closely by a three-step etch and rinse adhesive (specifically Kerr Optibond FL), a two-step self-etching adhesive (specifically Kuraray’s Clearfil SE) and also a one-step self-etching adhesive (GC’s G-Bond).

Despite GI’s performance with retention, it must be considered that GI has poor wear resistance, poor esthetic characteristics and it readily solubilizes in the presence of acid. For the aforementioned reasons, GI may be an inferior choice when repairing NCCLs.   

You may have noticed that NCCLs are oftentimes sclerotic and therefore particularly difficult to bond to. Tay and Pashley’s 2004 article explains that sclerotic dentin becomes occluded with minerals that are more obstinate toward acid dissolution.15 The remedy to this conundrum is to roughen the superficial layer of dentin with a coarse diamond bur. This step will generate a thick smear layer which can then be thinned with air abrasion. The smear layer can be a very useful component of bonding. If properly thinned, the calcium and phosphate within the smear layer can be used for ionic bonding.16

Workflow for restoring a NCCL/Abfraction

Personally speaking (again, I have no financial conflicts of interest), I use the gold-standard dentin adhesive Clearfil SE (Kuraray). Here are the steps I would implement to restore an NCCL. In this approach I’m assuming the dentin is not sclerotic and free of caries. If the dentin were sclerotic, I would not use a rough diamond.

  1. Place isolation with an inverted rubber dam 
  2. Conservatively bevel the incisal enamel
    1. I would implement this step not only for esthetics but also to give the enamel rods a more favorable orientation for bonding
  3. Air abrade the lesion
  4. Scrub with primer for 60 seconds and air dry
  5. Apply the dentin adhesive
  6. Apply a thin layer (500 microns or less) of a flowable composite
  7. Refine the enamel margins
  8. Selectively etch the enamel margins
    1. You may notice that I’m selectively etching the enamel margins once the dentin is sealed. This is because a 35-40% Phosphoric acid can collapse the collagen framework. I’ve waited until the dentin is protected to apply the etch.
  9. Apply adhesive throughout the cavity
  10. Incrementally buildup the restoration beginning with the gingival wall and then working to the surrounding enamel
    1. Although this type of prep has a low C-factor configuration I would still not restore the restoration in a single increment unless its small.
  11. Polish
  12. Follow up on restoration at bi-annual exam and polish as needed.(43 and 78)
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Periodontal Considerations for NCCLs/Abfractions

Oftentimes NCCLs can be associated with gingival recession. Although a composite restoration can be placed in these instances, if the patient is esthetically-conscious, the outcome may be disappointing. In instances when recession occurs in the presence of NCCLs, root coverage periodontal surgery should be considered. Periodontal systematic reviews suggest that a connective tissue graft and a coronally advanced flap achieves the best outcome. 17, 18

P.S. I hope this article is of service to you. As a dentist myself, I want to be apart of creating value for our community. Did you know you can earn CE through the Dental Digest dental podcast? Click here to get started. You’re busy. Earning CE through the dental podcast makes it possible to stay at the forefront of dentistry while you multitask. Good luck, my friend!

Dr. Melissa Seibert

This article was written by proud dental nerd,

Dr. Melissa Seibert. Click here to learn more.

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  14. Lehman ML, Meyer ML. Relationship of dental caries and stress concentrations in teeth as revealed by photoelastic tests. J Dent Res 1966;45:706–14.
  15. Spranger H, Weber G, Kung YS. Untersuchungern die Atitologie, Pathogeneses un therapiekonsequenzen der zervialaen Zahnartsubstanzdefekte. Der Hessiche Zahnartz Separatum Otto-Loos Preis 1973;328–41.
  16. Goel VK, Khera SC, Ralston JL, Chang KH. Stresses at the dentino enamel junction of human teeth. A finite element investigation. J Prosthet Dent 1991;66(4):451–9.
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