Buccal cortical bone thickness at miniscrew placement sites in patients with different vertical skeletal patterns

OBJECTIVE

Cortical bone thickness plays an important role in the primary stability of miniscrews. The purpose of this study was to evaluate the buccal cortical bone thickness in adolescent subjects with different vertical skeletal patterns using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

We examined the CBCT images of 75 patients (30 males, 45 females; mean age 16.5 years; range 15.3-17.7 years) in the present study. High-, average- and low-angle subgroups were generated according to SN-GoMe angle. On volumetric images, we measured the buccal cortical bone thickness from canine to the second molar teeth at heights of 5, 7 and 9 mm from cemento-enamel junction (CEJ). For statistical evaluation, the Wilcoxon signed rank, Kruskal-Wallis and Tukey HSD tests were applied at the p < 0.05 level.

RESULTS

Buccal cortical bone was thickest in the low-angle group. We observed statistically significant differences in the maxilla between the high- and low-angle groups at all levels. In the mandible, we noted statistically significant differences between high-angle and low-angle groups in the canine-first premolar regions at heights of 5 and 7 mm, and in the second premolar-first molar region at 7 mm height from CEJ. Significant differences were also present between the first and second premolars at heights of 7 and 9 mm. Average cortical bone thickness ranged from 1.10-1.37 mm in the maxilla and 1.20-3.28 mm in the mandible for all groups.

CONCLUSION

Buccal cortical bone thickness in adolescents varied in different vertical skeletal patterns and was greater in the mandible than in the maxilla, with the distance increasing from the CEJ to the apex. As the buccal cortical bone is thinner in high-angle patients, patient-specific measures should be taken when performing miniscrew treatment.

Evaluation of alveolar bone loss following rapid maxillary expansion using cone-beam computed tomography

Objective

To evaluate the changes in cortical bone thickness, alveolar bone height, and the incidence of dehiscence and fenestration in the surrounding alveolar bone of posterior teeth after rapid maxillary expansion (RME) treatment using cone-beam computed tomography (CBCT).

Methods

The CBCT records of 20 subjects (9 boys, mean age: 13.97 ± 1.17 years; 11 girls, mean age: 13.53 ± 2.12 year) that underwent RME were selected from the archives. CBCT scans had been taken before (T1) and after (T2) the RME. Moreover, 10 of the subjects had 6-month retention (T3) records. We used the CBCT data to evaluate the buccal and palatal aspects of the canines, first and second premolars, and the first molars at 3 vertical levels. The cortical bone thickness and alveolar bone height at T1 and T2 were evaluated with the paired-samples t-test or the Wilcoxon signed-rank test. Repeated measure ANOVA or the Friedman test was used to evaluate the statistical significance at T1, T2, and T3. Statistical significance was set at p < 0.05.

Results

The buccal cortical bone thickness decreased gradually from baseline to the end of the retention period. After expansion, the buccal alveolar bone height was reduced significantly; however, this change was not statistically significant after the 6-month retention period. During the course of the treatment, the incidence of dehiscence and fenestration increased and decreased, respectively.

Conclusions

RME may have detrimental effects on the supporting alveolar bone, since the thickness and height of the buccal alveolar bone decreased during the retention period.

Evaluation of root resorption following rapid maxillary expansion using cone-beam computed tomography

OBJECTIVE

To evaluate the root resorption after rapid maxillary expansion (RME) via cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Records of 25 patients who had undergone RME with tooth-borne banded expander were obtained from the archive of the orthodontic department. CBCT data were reconstructed with surface and volume rendering, and the volumetric images were manipulated to display the root surfaces from various orientations. On these three-dimensional images, permanent first molars and first and second premolars were segmented, and their roots were isolated. Volumes of roots were calculated. The difference between pre-expansion and postexpansion root volumes was statistically evaluated with a paired-samples t-test. Also, the percentage of root volume loss was calculated for each root and statistically compared with each other with one-way analysis of variance at the P < .05 level.

RESULTS

The difference between the pre-expansion and postexpansion root volumes was statistically significant for all roots investigated. Maximum volume decrease was observed for the mesiobuccal root of first molar teeth (18.60 mm(3)). It was determined that the distobuccal root of first molar teeth was less affected from the expansion procedure (9.47 mm(3)). No statistically significant difference was found for the percentage of root volume loss.

CONCLUSION

Following RME treatment, significant root volume loss was observed for all investigated posterior teeth. However, the percentage of volume loss was not statistically different among roots.

The influence of the masticatory hypofunction on the craniofacial growth and development in rats

In the present study, one masticatory hypofunction group and one normal function group were comprised of growing Wistar albino rats. The influence of the masticatory hypofunction on the growth and development of the craniofacial skeleton in rats was examined. The normal function group received the diet in the form of hard pellets, but the hypofunction group was fed powdered food. To avoid growth reduction because of nutritional deficiency, the animals were fed ad libitum, diet and water. At the end of the experimental period, the 90-day-old adult animals were killed and the direct anthropometric cranial, maxillary, and mandibular measurements were made on the skulls. The significant results can be summarized as follows: Total skull length, total anterior face height, lower anterior face height, ramus mandibula height, corpus mandibula height, premaxillary length, and maxillary width have been reduced but foramen incisivum width has been increased. This study showed that there is no significant effect of the masticatory hypofunction on the cranial growth and development in the growing rats, but that masticatory hypofunction affected the growth and development of the maxillofacial skeleton.