Factors associated with spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction

Alveolar bone changes after molar protraction in young adults with missing mandibular second premolars or first molars

OBJECTIVES

To assess the changes in alveolar bone of the mandibular second molars following molar protraction and investigate the factors associated with the alveolar bone changes.

MATERIALS AND METHODS

Cone-beam computed tomography of 29 patients (mean age 22.0 ± 4.2 years) who had missing mandibular premolars or first molars and underwent molar protraction were reviewed. Alveolar bone level was measured as the distance from the cementoenamel junction at six points, buccal, lingual, mesiobuccal (MB), mesiolingual (ML), distobuccal (DB), and distolingual (DL), of the second molars at pretreatment (T0) and after molar protraction (T1). Factors associated with alveolar bone changes at the distal and mesial of the second molars were assessed.

RESULTS

Mean alveolar bone changes ranged from -1.2 mm (bone apposition) to 0.8 mm (bone resorption). The presence of a third molar impaction at T0 (P < .001), third molar angulation at T0 (P < .001), and Nolla's stage of third molar at T0 (P = .005) were significantly associated with alveolar bone level changes distal to the second molars. Treatment duration (P = .028) was significantly associated with alveolar bone level changes mesial to the second molar.

CONCLUSIONS

Patients with impacted third molars, third molars at an earlier stage of development, and mesially angulated third molars at pretreatment may have less alveolar bone resorption distal to the second molars following protraction. Patients with increased treatment time may have reduced alveolar bone resorption mesial to the second molars.

Effects of Angle class II correction with the Forsus fatigue resistant device on mandibular third molars : A retrospective study

PURPOSE

The goal was to evaluate the effects of Angle class II malocclusion treatment using the Forsus fatigue resistant device (FRD, 3M, St. Paul, MN, USA) on the position and angulation of mandibular third molars and retromolar space.

PATIENTS AND METHODS

In all, 58 class II patients (mean age 13.6 ± 1.8 years) treated with the FRD (FRD group) were compared with 51 class I patients (mean age 13.5 ± 1.6 years) who underwent orthodontic treatment (control group). A total of 109 mandibular third molars in the FRD group and 91 in the control group were evaluated. Changes in the retromolar space, angulation of the second (ɣ) and third molars (β), and the angle between these teeth (α) were assessed with panoramic radiographs taken at the beginning and the end of the treatment. Data were statistically analyzed.

RESULTS

At the end of the treatment, there were significant increases in ɣ and β in the FRD group and ɣ in the control group (p < 0.05). The decrease in α in the FRD group and increase in the control group were not significant (p > 0.05); however, this change led to a small significant change between the groups (p < 0.05). The retromolar space significantly increased in the FRD group compared to the control group (p < 0.05). No significant correlation was found between retromolar space and third molar uprighting in any of the groups (p > 0.05).

CONCLUSION

Class II correction with FRD led to mesialization of the lower arch which provided an increase in the retromolar space. Little improvement in the uprighting of the third molars occurred.

Factors associated with the maxillary third molar position after total arch distalization using a modified C-palatal plate in adolescents

INTRODUCTION

The purpose of this study was to evaluate the long-term position of erupted third molars after maxillary total arch distalization using modified C-palatal plates (MCPPs) in adolescents and to identify factors associated with these positions.

SETTING AND SAMPLE POPULATION

Sixty-two third molars (male: 20, female: 42) in Class II patients treated with MCPPs and thirty-nine teeth for the Control group (male: 22, female: 17).

MATERIALS AND METHODS

Samples were analyzed using panoramic radiographs taken initially (T0), after treatment (T1) and after >3 years retention (T2). Third molars were classified as downward (Group A, N = 31; males: 12, females: 19) and upward (Group B, N = 31; males: 8, females: 23) based on their vertical position after treatment. Analysis of variance and multiple logistic regression analysis were performed.

RESULTS

The vertical position of the third molars of Group A, Group B, and the Control showed a 2.2, 3.5 and 2.7 mm downward movement at T2. However, there was no difference in the amount of third molar eruption among the groups. Regarding factors affecting the vertical distance of the third molar, Age, C8-OP, ∠8-OP and D7-T at the initial affected vertical position of the third molars after molar distalization (P < .05).

CONCLUSIONS

Group A and B showed no difference in the third molar eruption during retention after total arch distalization. This study suggests that it might be unnecessary to extract the developing third molar before molar distalization in Class II adolescents.

Factors associated with spontaneous mesialization of impacted mandibular third molars after second molar protraction

OBJECTIVES

To investigate factors associated with spontaneous mesialization of impacted third molars after second molar protraction to close the space caused by a missing mandibular first molar (L-6) or retained deciduous mandibular second molars with a missing succedaneous premolar (L-E).

MATERIALS AND METHODS

Panoramic radiographs of patients treated with mandibular second molar protraction to close the space due to missing L-6 or L-E (14 males, 36 females, mean age = 18.6 ± 4.4 years) were analyzed before treatment (T1) and after second molar protraction (T2). Factors associated with the amount of third molar mesialization were investigated using regression analyses.

RESULTS

Mandibular second molars were protracted by 5.1 ± 2.1 mm and 5.8 ± 2.7 mm, measured at the crown and root furcation, respectively. After second molar protraction, third molars showed spontaneous mesialization by 4.3 ± 1.6 mm and 3.8 ± 2.6 mm, measured at the crown and root furcation, respectively. Nolla's stage of the third molar at T1 (B = 0.20, P = .026) and second molar protraction time (B = 0.04, P = .042) were significantly associated with the amount of third molar mesialization.

CONCLUSIONS

Greater third molar mesialization was observed when Nolla's stage of the third molar was higher before treatment and when the second molar protraction time was longer.