Changes in mandibular third molar angle and position after unilateral mandibular first molar extraction.

INTRODUCTION: Third molars often become impacted because of lack of space for their eruption. Because the third molars play an important role occlusally, premolars or second molars are sometimes extracted to create space. First molars are seldom extracted to create space, but they are occasionally extracted for other reasons, especially caries. The aim of this study was to investigate the spontaneous angular and positional changes in mandibular third molars when mandibular first molars are extracted. METHODS: The sample consisted of panoramic radiographs of 107 patients (age, 18-40 years; mean, 25.69 years) who had unilateral mandibular first-molar extractions (because of caries) before age 16. Ramus relationship, impaction depth, and angulation of third molars on the extraction and nonextraction sides were assessed. A chi-square test was performed to compare the differences. RESULTS: The prevalence of third molars at the anterior border of the mandibular ramus was significantly greater on the extraction side than on the nonextraction side (P < .001). Third molars were positioned more occlusally in the mandible on the nonextraction side than on the extraction side (P < .001). The prevalence of vertically angulated third molars was greater on the extraction side than on the nonextraction side (P < .001). CONCLUSIONS: Mandibular first-molar extraction increases the space for mandibular third-molar eruption and helps the third molars move into better positions. But early extraction can lead to uncontrolled tipping of adjacent teeth into the extraction space. Only third-molar angle and position were evaluated in this study; problems such as dental asymmetry, premature contacts, and uncontrolled tipping should be assessed in the future.

The role of psycho-social factors in headgear compliance.

The aim of this study was to identify the role of psycho-social factors in headgear compliance. Fifty-one patients, with an Angle Class II division 1 malocclusion comprised the study sample. The treatment plan aimed to correct the malocclusion using cervical pull headgear. An electronic module timer was attached to the neckstrap to evaluate the number of hours the patients wore the headgear. One of their parents was asked to answer the Child Behaviour Checklist (CBCL), which defines a patient's behaviour. The patients were monitored for 6 months and the modules were measured at the end of each 2 month period. Mann-Whitney U and Chi square tests were used to analyse the data. The patients were separated into groups according to their compliance. The results showed that although there were significant differences in the use of headgear between the groups (P < or = 0.001), age, gender, and CBCL subgroup scores were not statistically significant (P > 0.05).

Nasal airway changes due to rapid maxillary expansion timing.

The purpose of this study was to evaluate the effect of rapid maxillary expansion (RME) on nasal minimum cross-sectional area (MCA) using acoustic rhinometry (AR) in two groups of subjects who were treated before and after the pubertal growth spurt. The sample consisted of 29 patients with maxillary constriction and a control sample of 15 subjects. Both samples were divided into two groups according to individual skeletal maturation as assessed by the cervical vertebral maturation (CVM) method. Group I T (early-treated) consisted of 16 patients (eight girls and eight boys). Group I C (early-control) consisted of eight patients, and both groups had not reached the pubertal peak (CVM Stage 1-3). Group II T (late-treated) consisted of 13 patients (eight girls and five boys). Group II C (late-control) consisted of seven patients, and both groups were at a stage during or after the pubertal peak (CVM Stage 4-6). AR records were obtained for each treated subject before treatment (T1), after expansion (T2), and immediately after a three-month retention period (T3); only T1 and T3 records were obtained for controls. The overall increase in MCA was significantly greater in the early- and late-treated groups (group I T, group II T) as compared with the early and late controls. (group I C, group II C) (P < .05). The results of the present study suggest that even the overall (T1-T3) increase for MCA in group I T is greater (0.34 mm) than the increase for MCA in group II T (0.19 mm), but the difference was not significant (P > .05).

The role of the headgear timer in extraoral co-operation.

The aim of this research was to study headgear co-operation using an objective measuring instrument, the Compliance Science System (CSS). Forty-six patients were included in the investigation, 32 girls and 14 boys (10-15 years of age; mean 13 years). The patients, who were not informed that they were being monitored, were instructed to wear the headgear, with an electronic module timer attached to the neckstrap, for 16 hours per day. At the end of 2 months (T1), the time for which the headgear was worn was measured. At this stage the patients were divided into two groups: group 1 (unco-operative patients) who wore the headgear for less than 16 hours per day, and group 2 (co-operative patients) who wore the headgear for at least 16 hours per day. Only the unco-operative patients were informed that they had been monitored, and a subsequent 4 month treatment period was initiated for both groups. The time was also measured at the end of the second (T2) and third (T3) 2 month treatment periods. The unco-operative patients increased their use of the headgear to approximately 4.5 to 6 hours per day (P < 0.05). All of the co-operative patients also used their headgear as recommended during the 4 month period.

A comparison of the effects of rapid maxillary expansion and fan-type rapid maxillary expansion on dentofacial structures.

The aim of this study was to evaluate and compare the sagittal, transverse, and vertical effects of rapid maxillary expansion (RME) and fan-type RME on dentofacial structures. The study group consisted of 34 patients, 14 boys and 20 girls (average age 12.5 years), selected without considering their skeletal class and sex. The fan-type RME group comprised 17 subjects, who had an anterior constricted maxilla with a normal intermolar width. The RME group comprised 17 other subjects, who had a maxillary transverse discrepancy with a posterior crossbite. The records obtained for each patient included a lateral and a frontal cephalometric film, upper plaster models, and occlusal radiograph obtained before treatment (T1), after expansion (T2), and immediately after a three-month retention period (T3). The data obtained from the evaluation of the records before and after treatment, after treatment and after retention, and before treatment and after retention were compared using paired t-test. Further comparisons between the groups were made using Student's t-test. There was significantly greater expansion in the intercanine than in the intermolar width in the fan-type RME group as compared with the RME group. Downward and forward movement of the maxilla was observed in both groups. The upper incisors were tipped palatally in the RME group, but they were tipped labially in the fan-type RME group. There was significantly greater expansion in the nasal cavity and maxillary width in the RME group as opposed to the fan-type RME group.