Objectives
This controlled study aimed to evaluate the effects of Herbst therapy on the trabecular structure of the condyle and angulus mandible using fractal dimension analysis (FD-A) accompanied by skeletal cephalometric changes.
Material and method
The panoramic and cephalometric radiographs of 30 patients with skeletal Class II malocclusion treated with the Herbst appliance (C II-H group, mean age: 15.23 ± 1.08), 30 patients with skeletal Class II malocclusion that received fixed orthodontic treatment (C II-C group, mean age: 15.73 ± 1.38), and 30 patients with skeletal Class I malocclusion (C I-C group, mean age: 15.90 ± 1.30) were selected. FD-A was performed on the superoposterior region (C-SP) and centre of the condyles (C-C) and the mandibular angulus (Ang) on the panoramic radiographs taken at the pretreatment (T0), intermediate stage of treatment (T1), and posttreatment (T2) timepoints just like cephalometric analysis.
Results
Herbst therapy provided a statistically significant increase in SNB, ANS-Me, Na-Me, S-Go, Co-Gn and a decrease in ANB and overjet (P < 0.05). All skeletal changes remained stable during the fixed appliance treatment after Herbst. The FD values in C-C increased (P < 0.05), and C-SP values decreased (P < 0.05) during Herbst therapy, while after removal of the Herbst appliance, no significant change was observed despite an increase in C-SP. The Ang value did not change during Herbst treatment, but then increased significantly (P < 0.05). There was no significant change in the FD values of the C I-C and C II-C groups at any stage of treatment. The C-C and C-SP changes at T1–T0 period, C-SP and Ang changes at T2–T1 period, and C-C, C-SP, and Ang values at T2–T0 period were found higher in C II-H group compared with the C II-C group significantly (P < 0.05).
Conclusion
Herbst therapy changed the trabecular structure of the condyles in different directions at the superoposterior and central regions of the condyles, while the structural complexity of the angulus mandible, which did not change during the Herbst treatment, increased during the fixed orthodontic treatment after Herbst.
The effects of different desensitizer agents on shear bond strength of orthodontic brackets after home bleaching: an in vitro study
PurposeThe aim of this study was to test the null hypothesis that no difference exists between shear bond strength values of control and bleaching plus desensitizer applied groups.
Materials and methodsA hundred freshly extracted human premolar teeth were randomly divided into five groups. Group I served as the control group with no bleaching application, while only bleaching was achieved in Group II. Desensitizer containing potassium nitrate-fluoride and casein phosphopeptide amorphous calcium phosphate were applied in Groups III and IV, after bleaching respectively. A bleaching agent containing amorphous calcium phosphate was used in Group V. Shear bond strength tests were carried out using a universal testing machine (Instron Corp., Norwood, MA, USA). Remnant adhesive on the teeth and brackets was examined to score the adhesive remnant index. Kruskal-Wallis and Chi-Square tests were used for statistical analysis of the data.
ResultsStatistically significant differences were found among the groups for shear bond strength values (p<.001). The shear bond strength of Group III (8.0±2.2 MPa) was significantly lower than the other groups (p<.05). The highest shear bond strength values were found for Group I (13.6±3.7 MPa) and Group IV (12.8±4.0 MPa). No statistically significant difference was observed between Group II (10.0±2.7 MPa) and Group V (10.8±2.9 MPa). The differences between adhesive remnant index scores of the groups were not statistically significant.
ConclusionCasein phosphopeptide amorphous calcium phosphate gel application showed a similar shear bond strength value to the control group, while shear bond strength values decreased after using other desensitizers.
Summary
Objectives
The aim was to evaluate the effects of mesenchymal stem cell (MSC) transfer to periodontal ligament (PDL) on the inhibition and/or repair of orthodontically induced root resorption (OIRR) during and after arch expansion and on the orthodontic tooth movement (OTM) rate of the maxillary first molar teeth of rats.
Material and methods
Sixty Wistar rats were divided into three groups as the untreated group, MSC and control injections during the expansion period group (EMSC-EC), and MSC and control injections at the retention period group (RMSC-RC). Fifty grams of orthodontic force was applied to the maxillary first molar teeth of the rats for 14 days in the vestibular direction, and then, 20 days of retention was carried out. MSCs and control injections were performed every 3 days in the EC, RC, EMSC, and RMSC groups. At the end of the experiment, samples were prepared for OTM evaluation, mRNA expression analysis, micro-computed tomography measurements, cementum thickness calculations, and structural examinations.
Results
The amount of OTM in EMSC group was significantly higher than in EC group (P < 0.001). MSC transfer during the expansion and retention periods reduced the number of resorption lacunae, volumetric and linear resorptive measurements, and cyclooxygenase-2 and receptor activator of nuclear factor kappa B ligand (RANKL) mRNA expression levels, and increased the osteoprotegerin (OPG) expression levels, OPG/RANKL ratio, and cementum thickness in the EMSC and RMSC groups.
Conclusions
MSC transfer to PDL during expansion increased the amount of OTM. Injection of MSC during the retention period was found to be slightly more effective in prevention and/or repair of OIRR than MSC transfer during the expansion period.
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