Predictors of variation in mandibular incisor enamel thickness

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ABSTRACT

Background

Interproximal reduction of mandibular incisor enamel often is performed as an adjunct to orthodontic alignment. The authors conducted a study to determine factors contributing to variations in incisor enamel thickness.

Methods

The authors compared enamel thickness between mandibular central and lateral incisors, between mesial and distal surfaces, between male and female subjects (N = 40 each) and between African-American and white subjects (N = 40 each). The authors also evaluated correlations between overall tooth width and enamel thickness.

Results

The authors found significantly greater enamel thickness in lateral incisors, on distal tooth surfaces and in black subjects (P < .0001 for each); they found no differences between male and female subjects. They found that wider teeth were associated with greater enamel thickness (P < .01) but that the amount of thickness varied greatly among subjects (range: 0.44–1.28 millimeters).

Conclusions

Thicker enamel was found on the distal aspect of lateral incisors, in black subjects and in wider teeth. The authors observed, however, that the variations in thickness are not fully explained by these factors alone.

Clinical Implications

If substantial enamel reduction is planned as part of dental treatment, the authors recommend that clinicians use calibrated radiographs to measure the thickness of their patients' enamel surfaces because of the extensive variation in enamel thickness among and within people.

Section snippets

SUBJECTS, MATERIALS AND METHODS

We evaluated 80 subjects at Virginia Commonwealth University School of Dentistry who agreed to participate in the study. We obtained approval from the university's institutional review board and received informed consent from each subject or his or her parent or guardian. Our eligibility criteria were that subjects have no history of IPR and that they have well-aligned permanent mandibular incisors; we required the latter so that we could obtain radiographs with no overlap of adjacent teeth. We

RESULTS

We detected no statistically significant differences between the repeated sets of measurements for 10 subjects. The correlation between the sets was high for tooth thickness (r = .99), enamel thickness on the mesial surface (r = .95) and enamel thickness on the distal surface (r = .98). Average differences between repeated measures were less than 0.01 mm.

Table 1 shows the mean values for incisor width and enamel thickness for all subjects. We detected no significant differences between the

DISCUSSION

IPR is a technique that many practitioners use to reduce incisor crowding, resolve anterior tooth size discrepancies and improve the stability of tooth alignment. It is believed that the thickness of an incisor's enamel at the contact point is related to the amount of enamel that can be removed safely without deleterious sequelae.4, 5, 6, 7, 8, 9, 10, 11, 12, 13 We conducted this study to determine factors that can be used to help predict the amount of enamel at the contact points on the

CONCLUSIONS

Our study examined the relationship between mandibular incisor proximal enamel thickness and tooth type, tooth surface, race, sex and overall tooth width. We found significant differences in enamel thickness related to tooth type and surface, as well as race. Lateral incisors had a greater proximal enamel thickness than did central incisors. Enamel thickness on distal surfaces was greater than that on mesial surfaces. Black subjects had thicker enamel on average than did white subjects. Overall

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    1

    Dr. Hall is in private practice in orthodontics, Iowa City, Iowa.

    2

    Dr. Lindauer is the Norborne Muir professor and the chair, Department of Orthodontics, Virginia Commonwealth University, School of Dentistry, 520 N. 12th St., Richmond, Va. 23298-0566

    3

    Dr. Tüfekçi is an assistant professor, Department of Orthodontics, Virginia Commonwealth University, School of Dentistry, Richmond.

    4

    Dr. Shroff is a professor, Department of Orthodontics, Virginia Commonwealth University, School of Dentistry, Richmond.

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