Investigation of the change in the degree of Frankfort mandibular plane angle after levelling the curve of spee in different malocclusion groups

BACKGROUND AND OBJECTIVES

The curve of Spee is a naturally occurring phenomenon in the human dentition. Leveling the curve of Spee can affect the Frankfort-mandibular plane (FMP) Angle and thus the lower anterior facial height. This study examined the degree of change in FMP angle after leveling the curve of Spee in different malocclusion groups.

METHODS

In this study, 75 patients who were aged >14 years and had undergone fixed appliance therapy using a 0.022-slot MBT bracket system were included. The pre- and post-treatment casts and lateral cephalograms of the patients were divided into three groups, namely Class I, II, and III malocclusions, with 25 patients in each group. The curve of Spee and FMP angle were measured before and after orthodontic treatment, and their correlation was evaluated.

RESULTS

After leveling the curve of Spee, the FMP angle decreased in Class I and II groups and increased in Class III group. These results were statistically significant except in Class I malocclusion group. A mild positive correlation was observed between the curve of Spee and FMP angle in Class I and III malocclusion groups and a negative correlation in Class II malocclusion group.

CONCLUSION

The change in FMP angle, following the leveling of the curve of Spee, in Class II and III malocclusion group, is attributed to alterations in lower anterior facial height. The study observed a mild positive correlation between the curve of Spee and FMP angle in Class I and III malocclusion groups and a negative correlation in Class II malocclusion group.

Assessment of curve of spee in different malocclusions

Purpose

The aim of this study was to compare the depth of curve of Spee (COS) in Angle Class I, Angle Class II and Angle Class III malocclusions.

Materials and methods

The Samples were chosen among the diagnostic materials in İstanbul Medipol University Department of Orthodontics. Ninety plaster models were chosen, and were divided into 3 groups (n=30) according to Angle dental malocclusion classification. The depth of curve of Spee was measured on left and right sides of mandibular dental models and mean values were used as depth of curve of Spee. ANOVA test was used to evaluate normally distributed data. Comparison of the sides were performed by using paired sample t test. Significance level was set to p<0.05.

Results

The depth of COS was found as deepest in Class II malocclusion (2.9±0.8 mm) and was relative flat in Class III malocclusion (2.1±0.9 mm) and the difference was statistically significant (p<0.05). No significant difference was found between Angle Class I and Class III malocclusions.

Conclusion

Since the depth of curve of Spee is increased in Class II malocclusions, this factor should be considered in treatment planning.