ABRASION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Abrasion is the pathological loss of tooth substance resulting from biomechanical wear. It can occur at the cervical region of teeth as a result of improper or excessive toothbrushing (Figures 1 and 2). Abraded surfaces of enamel have a smooth, glazed appearance. Affected dentin has a similar surface, resulting from sclerosis of dentinal canals and surface calcification.^1,2 Abrasion lesions seldom have any plaque accumulation or caries in them, are linear in outline and follow the path of the etiologic agent. They appear initially as a small, horizontal groove across the facial (or rarely lingual) surface of the natural crown, near the cementoenamel junction. In later stages, the surrounding walls of the abrasive lesion make a V-shape by meeting at an acute angle axially.³ Finally, the peripheries of the lesion are angularly demarcated from the adjacent tooth surface.³ Incorrect toothbrushing technique, in addition to causing tooth abrasion, can simultaneously cause gingival recession, resulting in root surface exposure.⁴

View larger version (86K): [in this window] [in a new window]   Figure 1. Noncarious cervical lesions caused by abrasion in a subject with a history of traumatic toothbrushing.

View larger version (87K): [in this window] [in a new window]   Figure 2. Localized wedge-shaped cervical destruction associated with the facial aspect of the teeth in a subject with a history of traumatic toothbrushing.

	EROSION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

View larger version (101K): [in this window] [in a new window]   Figure 3. Dish-shaped erosive lesions affecting the facial aspect of the subject’s teeth. This patient had a history of severe gastric acid reflux disorder.

	ABFRACTION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

Grippo and Masi⁹ are credited with describing the process of stress-corrosion in teeth. This process involves the combined physicochemical activity occurring in a tooth being stressed by occlusal load in the presence of acid. It has been suggested that cervical defects with sharp, wedge-shaped features are associated with the effect of occlusal stress.¹⁰ Finite element stress analysis supports the stress theory of occlusal loading that results in localized stress concentrations with subsequent loss of tooth structure.¹¹ Ott and Proschel¹² found highly significant relationships between heavy occlusal working contacts and cervical wedge-shaped defects in posterior teeth. However, a recent investigation failed to demonstrate a relationship between abnormal occlusal stresses and cervical defects.¹³

	ATTRITION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Some investigators have defined attrition to include only physiological wear.^1,2 This type of mechanical wear usually affects incisal or occlusal surfaces.^14,15 Depending on the occlusion, lingual surfaces also may be affected. In Western civilizations, bruxism is a common cause of attritionlike wear.¹⁴ Bruxism is the habitual grinding of teeth that takes place during sleep or subconsciously while awake. Wear facets appear first on cusps and marginal, oblique and transverse ridges.¹⁴ A highly polished surface is formed.¹⁶

Clinicians must be able to distinguish between the causes of noncarious cervical wear to effectively treat patients and prevent more advanced tooth destruction. If it truly exists, abfraction warrants careful occlusal evaluation with treatment (such as occlusal adjustments, bitesplint therapy and cervical restorations). Without proper diagnosis and treatment, restorations likely will fail as a result of the high degree of stress being applied to them.

We sought to investigate the presence, characteristics and prevalence of abfractionlike lesions in the teeth of a population of U.S. veterans. We hypothesized that a history of repeated lateral forces on teeth may produce lesions with the following characteristics:

– present at the cervical region of affected teeth;

– a wedge-shaped appearance;

– a width that is greater than height and size directly related to the size of occlusal facets.

	SUBJECTS, MATERIALS AND METHODS

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Subjects. The study protocol was approved by the local Institutional Review Board and the Veterans Affairs Research Committee. From September through November 1998, 32 men who received routine dental treatment at the Roudebush Veterans Affairs Medical Center, Indianapolis, were evaluated. Their ages ranged from 38 to 80 years (mean age, 60.4 years). Informed consent was obtained from eligible subjects before we proceeded with any further clinical evaluation.

Identification of samples. One of us (B.P.) served as the evaluating dentist, examining characteristics of the noncarious affected teeth, including lesion size, shape, contour, evidence of occlusal wear, region of the mouth, tooth surface, surface texture of the lesion and distribution of bacterial plaque. The teeth selected for evaluation were molars, premolars, canines and incisors. In addition, we selected control teeth, preferably adjacent to the affected teeth; these teeth did not exhibit evidence of cervical lesions or have restorations. If an adjacent tooth was not available to serve as a control, the nearest acceptable tooth was selected.

A total of 103 teeth exhibiting noncarious cervical lesions qualified for the study (29 incisors, 65 premolars and nine molars). An additional 63 teeth were selected as controls (34 incisors, 23 premolars and six molars). The evaluating dentist recorded the surface on which the lesion was located as buccal or lingual. The lesion was recorded as saucer- or wedge-shaped. The dentist used a probe (Marquis Perio Probe, Marquis Dental Mfg. Co., Aurora, Colo.) to measure recession, which was recorded to the nearest millimeter for all affected teeth and control teeth.

Subject evaluation. The dentist evaluated evidence of prematurity in patients’ centric occlusion, as well as interference in balancing, working or protrusive excursive movements on all affected and control teeth. The presence or absence of wear facets was recorded for all teeth. The subject then rinsed with an antimicrobial solution (Perio-Guard chlorhexidine gluconate oral rinse, 0.12 percent, Colgate-Palmolive Co., New York) for 30 seconds to remove loose debris from the teeth. We used Bismarck Brown disclosing solution to determine the presence or absence of plaque on experimental and control teeth.¹⁷ The dentist evaluated the same surfaces on control teeth as those on the adjacent experimental teeth. Plaque was scored as present or absent on the lesion. He also noted if the nonlesion portion of the affected tooth surface had plaque. Impressions then were taken of both arches and casts were made. From these models, the evaluating dentist measured the lesions and facets.

He evaluated each tooth lesion using artificial light and by rubbing a standard new cowhorn explorer (number 3CH DE, Hu-Friedy Mfg. Co. Inc., Chicago) gently across the surface to determine its texture. We earlier performed a pilot study to establish a standard scale for evaluating surface roughness. The surface texture was recorded as being one of the following: very smooth, smooth, medium, rough or very rough.

Subject questionnaire. In an attempt to establish the role of systemic conditions, traumatic toothbrushing, patients’ other oral hygiene habits, parafunctional activity and diet, we requested that each subject complete a questionnaire. In addition, they were asked to demonstrate, using a toothbrush, their brushing technique in the affected areas. We noted if they were right- or left-handed. Toothbrushing techniques were scored as back and forth, up and down, roll, circular or other. Finally, we determined if the tooth was subjected to unusually high stress (such as serving as an abutment for a removable partial denture) or if it was oriented prominently in the arch, rendering it susceptible to heavy toothbrushing forces.

Wedge-shaped lesions had a significantly higher percentage of plaque and significantly lower levels of recession than did saucer-shaped lesions.

Measurement of samples. The evaluating dentist measured the depth of the lesions to the nearest 0.5 millimeter using an automated periodontal probe. Lesion and wear-facet outlines were demarcated on the models with a sharp pencil. He measured the lesion or facet size to the nearest 0.01 mm using 10x magnification and a digital caliper. From the values obtained for each facet, we calculated the area using the two-dimensional measurements as the axes of an oval. An appropriate formula for measuring this shape then was used to provide an estimated mean surface area for each facet (measured in square millimeters).

Statistical analysis. We used ² tests to make comparisons between categorical outcomes. Correlation coefficients were computed to examine the linear associations between all cervical lesion dimensions and facet area and between wedge-shaped lesion dimensions and facet area.

	RESULTS

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
We used a P value of .05 in comparing experimental teeth with control teeth. When considering the entire tooth surface, we found that experimental teeth had a significantly higher percentage of surfaces with plaque (P = .04) than did control teeth. Experimental teeth also had significantly higher levels of gingival recession (P = .001). However, there was no significant difference in wear-facet dimensions (P 1.0) or in occlusal contacts (P = .41) between experimental and control teeth.

Wedge-shaped lesions had a significantly higher percentage of plaque (P = .01) and significantly lower levels of recession (P = .02) than did saucer-shaped lesions. As demonstrated in Table 1, wedge- and saucer-shaped lesions did not have significantly different opposing contacts (P = .67). In addition, they did not have significantly different surface texture (P = .46) or facets (P = .10).

When taking the whole tooth surface into consideration, we found that 61 (59 percent) of 103 experimental teeth were plaque-free compared with 52 (84 percent) of 62 control teeth. Sixteen (84 percent) of 19 saucer-shaped lesions were plaque-free, while only 42 (53 percent) of 79 wedge-shaped lesions were plaque-free. A history of using a firm toothbrush did not correspond to the presence of either saucer- or wedge-shaped lesions.

The data support the premise that noncarious cervical lesions most often are multifactorial in origin.

Sixty-five (66 percent) of 99 experimental teeth had 2 mm or more of recession, while only 10 (16 percent) of 62 control teeth did. (Although there were 103 experimental teeth, a few did not meet the criteria for certain measurements and were excluded from those analyses.) Zero lesions (0 percent), four lesions (4 percent), 29 lesions (29 percent), 66 lesions (67 percent) and zero lesions (0 percent) were very rough, rough, medium, smooth and very smooth in texture, respectively.

Nine (45 percent) of the 20 teeth with saucer-shaped lesions had clinically observable occlusal contacts, while 63 (80 percent) of the 79 teeth with wedge-shaped lesions had clinically observable occlusal contacts. The various combinations of occlusal contacts did not relate in any way to the degree of recession. The various combinations of occlusal contacts also did not relate in any way to the distribution of facets. However, all 10 experimental teeth with premature contacts had wedge-shaped lesions.

We found 60 teeth in the maxilla with lesions and 43 teeth in the mandible with lesions. In evaluating the teeth with only wedge-shaped lesions, we found that 53 teeth were in the maxilla and 31 teeth were in the mandible. Of the teeth with wedge-shaped lesions, six were molars, 54 were premolars and 21 were incisors. It was common to encounter teeth with lesions opposing one another.

Tables 3 and 4 summarize the measurements of the lesions. In general, saucer-shaped lesions had a greater mean height, a greater mean width and a smaller mean depth than wedge-shaped lesions. Repeated measurements showed excellent intraexaminer reproducibility, with intraclass correlation coefficients of 0.98 for the lesion height, 0.98 for lesion width, 0.87 for lesion depth and 0.98 for the facet measurements.

	DISCUSSION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

Multifactorial nature of lesions. The data from our study support the premise that these lesions most often are multifactorial in origin and are not due to a single mechanism. Even the level of scrutiny with which we used to investigate the lesions did not allow us to effectively categorize them. This is because it is difficult and perhaps impossible to separate clinically an abfraction lesion from an abrasion lesion. It would be necessary to evaluate the patient carefully to determine if adequate etiologic occlusal conditions, such as excessive lateral or oblique occlusal forces, were present that would enable a tooth to form an abfraction lesion. An abrasion lesion would have to be suspected if the affected tooth surface is situated in a prominent position in the arch that leaves it prone to excessive forces from toothbrushing, if adjacent teeth are affected similarly, or both conditions are present. Other components that may need to be taken into consideration include stress-corrosion and corrosion-fatigue.

The authors found a strong abrasion component in the investigation of the data.

Abrasion component. We found a strong abrasion component in our investigation of the data. Twenty-four (75 percent) of the 32 subjects reported a history of having used a firm or hard toothbrush. Twenty-five (78 percent) of the subjects used a back-and-forth brushing technique. This pattern of brushing is most commonly associated with causing abrasion.^3,18 Fifteen patients (47 percent) reported currently using a specific brand of toothpaste that is considered to be moderately or more abrasive. Twenty patients (62.5 percent) reported using a tartar control toothpaste, pure baking soda or a pure salt extensively in the past to clean their teeth.

In addition, we found that the distribution of lesions was weakly associated with right-handed brushers, since 64 percent of wedge-shaped lesions in right-handed brushers were located on the left side of the mouth. This agrees with the findings of other investigators^3,19 who suspected that right-handed brushers are more prone to experience tooth wear on the left side of the mouth.

Presence of plaque. The clinical examinations demonstrated that the cervical region of 85 percent of the control teeth was plaque-free. By comparison, the cervical portion of only 60 percent of the teeth with lesions was plaque-free. This suggests that the mere shape of cervical lesions presents a more difficult challenge to subjects trying to maintain plaque-free surfaces when compared with corresponding control surfaces. If the lesions were caused by toothbrushing, one would expect them to be plaque-free unless the toothbrushing method had changed since the lesions formed.

We found that 65 (66 percent) of 99 affected teeth had 2 mm or more of recession, while only 10 (16 percent) of 62 control teeth had 2 mm or more of recession on the corresponding surfaces. A strong abrasion component should be suspected for the teeth with lesions since a history of heavy toothbrush forces is associated with causing recession.²⁰

We did not find an erosive component in our review of subjects’ responses on the questionnaires. The medical or diet histories of 28 (87.5 percent) of 32 subjects did not reveal any obvious erosive contribution. Saucer-shaped lesions traditionally have been associated with erosion, but only 20 (20 percent) of 99 lesions were saucer-shaped. We can conclude that factors other than erosion may produce saucer-shaped lesions, or other unidentified chemically related erosive elements existed. We found it interesting that 16 (84 percent) of 19 saucer-shaped lesions were plaque-free, while only 42 (53 percent) of 79 wedge-shaped lesions were plaque-free. Perhaps a saucer-shaped lesion lends itself to being more easily cleaned with a toothbrush. It also is possible that a saucer-shaped lesion, resulting from toothbrush abrasion, is the early form of tooth wear that later gives way to a more advanced, wedge-shaped lesion as a result of long-term abrasion.

We speculated that a lesion caused by toothbrush abrasion would likely have a clinically smooth and polished surface. In the teeth examined in this study, however, a spectrum of surfaces was found. Wedge- and saucer-shaped lesions did not have significantly different surface textures (P = .46). In addition, lesions with plaque did not have significantly different surface textures than plaque-free lesions (P = .85). Thus, it is possible that abrasion could be ruled out as the sole cause of many of these lesions. We can only speculate that other causes, such as abfraction, may be a factor in the formation of some of these lesions. More rigorous statistical analysis was limited by the relatively small sample size. Finally, a limitation of this study is that only men were included. Although women demonstrate the same types of lesions, we cannot generalize our findings to include both sexes.

Toothbrush abrasion was believed to play a major etiologic role in the lesions in 19 subjects. Two other subjects had severe and less-severe saucer-shaped lesions with indistinct margins, so they were nonmeasurable. Both patients had a history of severe gastric reflux so these lesions were attributed largely to the effects of acid erosion. The teeth in these 21 subjects accounted for 84 of the 103 total experimental teeth in this study.

The remaining 11 patients (with 19 lesions) had at least one affected tooth whose features were such that the major or sole cause of the lesions could not be attributed easily to the effects of abrasion or erosion (because these subjects did not have a history of using a firm toothbrush or abrasive paste). The lesions in four teeth could be explained by abrasion as a result of their obvious prominence or the presence of similarly affected adjacent teeth. However, since the remaining lesions did not fit the criteria set for abrasion or erosion, we suspect that the lesions in these remaining 15 teeth were caused predominantly by a phenomenon other than abrasion or erosion (Figure 4).

View larger version (84K): [in this window] [in a new window]   Figure 4. A class V noncarious lesion in a lower premolar. Etiologic factors such as abrasion and erosion associated with the subject’s history were ruled out. Despite some gingival recession in adjacent teeth, the adjacent teeth do not exhibit similar lesions.

	CONCLUSION

TOP ABSTRACT ABRASION EROSION ABFRACTION ATTRITION SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Most of the noncarious cervical lesions in this study had the clinical appearance and features commonly associated with facial toothbrush abrasion or chemical erosion. However, of the 103 lesions, 15 did not have this type of clinical appearance and features. It may be that these lesions represent abfraction, although we could not prove it with the methods used in this study. It does seem clear that most cervical lesions are not the result of abfraction alone, and the study could not rule out a multifactorial etiology to cervical lesions.

Although the presence of wedge-shaped non-carious lesions did not correspond with the dimensions of occlusal wear facets, many subjects did relate a history of bruxism; their dentitions frequently contained prematurities in centric occlusion, interferences in lateral excursions, or both. Clinically, the inherent shape of cervical lesions, possibly resulting from abfraction, leaves a tooth prone to simultaneous caries infection. Before restoring any teeth with cervical lesions, dentists should correct the occlusion to remove functional interferences that might lead to restoration failure as a result of tooth flexion.

View larger version (94K): [in this window] [in a new window]   Dr. Piotrowski is in private practice, 201 Eighth St. S., Suite 309, Naples, Fla. 34102, e-mail "mbpiotr{at}msn.com". Address reprint requests to Dr. Piotrowski.

View larger version (145K): [in this window] [in a new window]   Dr. Gillette is the former program director of periodontics, Dental Service, Veterans Affairs Medical Center, Indianapolis. He now is a consultant in periodontics.

View larger version (138K): [in this window] [in a new window]   Dr. Hancock is a professor and chairman, Periodontics Department, Indiana University School of Dentistry, Indianapolis.