How to predict the timing of eruption of mandibular second premolars

Correlation coefficients for predicting canine diameters from premolar and molar sizes

BACKGROUND/PURPOSE

The permanent canine is the most widely used tooth for sex estimation because it is the tooth with the highest degree of sexual dimorphism; however, there are several factors that can limit the analysis (e.g., pathologies, postmortem loss). The aim of this work was to analyse the correlation between the dimensions of the canines and those of the premolars and molars, and evaluate the correspondence of real and predicted canine dimensions by applying the equations developed.

MATERIALS AND METHODS

The sample was composed of digital models of 80 adult individuals from Temuco, Chile. The buccolingual and mesiodistal diameters of the canine, premolar and molar dental crowns were measured and Pearson's linear regression analysis was performed in order to determine the correlation between the diameters. The equations obtained from the reference subsample were applied to a validation subsample to predict canine dimensions from the dimensions of the postcanine teeth.

RESULTS

Four regression equations were obtained, all for prediction of the size of the lower canines, whose correlation coefficient ranged from 0.701 to 0.738. The regression equations developed with the reference sample were tested on the validation sample using a Student's t-test for paired samples and the intraclass correlation coefficient. The differences between actual dental size and that predicted by the equations were not significantly different, and concordance analysis showed a moderate degree (0.485-0.585).

CONCLUSION

There is a limited correlation of canine dimensions with respect to premolars and molars. The correspondence between the actual and predicted canines dimensions is moderate.

Histological Evaluation and Management of Rare Case of Supernumerary “Ghost” Teeth

Supernumerary teeth are teeth that exceed the normal dental formula. Their prevalence in the permanent dentition is 1–14% and they occur more frequently in maxilla with a sex ratio of 2 : 1 in favor of males. They are often associated with syndromes but there are examples of nonsyndromic multiple supernumerary teeth reported in the literature. CBCT is usually the best exam for radiographic diagnosis and treatment planning, because it provides 3D information about location and morphology of supernumerary teeth. This paper reports a rare case of four supernumerary teeth in a nonsyndromic 9-year-old boy. The peculiarity of this case is that two more exceeding teeth were found during surgical procedure. After extraction, all the teeth underwent a histological undecalcified processing for light microscopical examination. The two “ghost” supernumerary teeth seemed to be primordial dental germs, possibly resulting from an altered odontogenic process. After supernumerary teeth extraction, X-rays and exfoliation monitoring are recommended, since permanent retained teeth often erupt naturally or, at least, improve their condition. Radiographic follow-up is also useful in order to assess the formation of further teeth due to the hyperactivity of the dental lamina.

Eruption rates of lower second premolars at different development stages evaluated with cone-beam computed tomography

OBJECTIVE

To evaluate and compare the eruption rates of lower second premolars (LPm2) at different developmental stages using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Retrospectively, 31 individuals (9.77 ± 1.25 years) had their LPm2 scored according to the Demirjian method, and afterwards they were split into three groups according to developmental stage, as follows: D = complete-formed crowns; E = root length less than crown height; and F = root length greater than or equal to crown height. Linear distances from the LPm2 crown tip to the anatomical reference line (ARL) and to the occlusal plane line (OPL) were measured in paired CBCT scans (T1, T2), taken with an average interval of 8.6 months between them. Eruption rates (mm/y) were calculated and then compared between groups.

RESULTS

Eruption rates were greater for LPm2 at stage F than at stages D or E (P < .01) regardless of whether they were measured from the ARL (D = 2.84 mm/y; E = 2.55 mm/y; F = 5.38 mm/y) or from the OPL (D = 1.82 mm/y; E = 2.02 mm/y; F = 5.26 mm/y). Eruption rates evaluated from the ARL and the OPL had no statistically significant differences (P = .052), and a positive correlation (r = .79, P < .001) between them was observed.

CONCLUSIONS

LPm2 at Demirjian stage F showed greater eruption rates than at stages D or E, regardless of whether rates were measured from the ARL or the OPL. Faster eruption is expected for LPm2 at stage F. Evaluation of the LPm2's developmental stage using CBCT can aid in clinical decision making regarding the correct timing for intervention.