Evaluation of mandibular motion in adolescents with skeletal class II division 1 malocclusion during mandibular advancement using clear functional aligners: a prospective study

BACKGROUND

This study aimed to evaluate the characteristics of mandibular protrusive condylar trajectory in adolescents with skeletal Class II Division 1 malocclusion and the changes of condylar trajectory during mandibular advancement (MA) treatment using clear functional aligners.

METHODS

This prospective study consisted of a cross-sectional study and a longitudinal study. In cross-sectional study, sixty-one adolescents were divided into two groups: Class I (n = 30) and Class II Division 1 (n = 31). The condylar trajectory was measured and compared using the Mann-Whitney U test. The longitudinal study was the MA treatment group using clear functional aligner and consisted of 16 participants from Class II Division 1group. The condylar trajectory was collected at three-time points: pre-treatment (T1), during MA treatment at approximately 3 months (T2, 105.6 days average), and at the end of MA treatment (T3, 237.6 days average). The changes at T1, T2, and T3, as well as the symmetry between the left and right condyles across all groups, were examined using the Wilcoxon paired test.

RESULTS

A greater increase in the anteroposterior displacement and space displacement during protrusive movements was observed in the Class II Division 1 group compared with that in the Class I group, with a large difference being observed in the left and right condylar movements. The condylar anteroposterior displacement and space displacement decreased significantly at T2 and increased significantly at T3; however, no significant difference was observed between T1 and T3. A significant difference was observed between the condylar movement on the left and right sides at T1; however, no significant difference was observed at T2 and T3.

CONCLUSIONS

Adolescents with Class II Division 1 malocclusion had higher protrusive capacity than those with Class I. Moreover, their left and right condylar motion was more asymmetric. The range of condyle motion decreased first and then increased during MA therapy, and the left and right condyle movement became more symmetrical, which may be the adaptive response of neuromuscular function to the changes in jaw position.

Accuracy of the maxillomandibular relationship at centric relation position recorded by using 3 different intraoral scanners with or without an optical jaw tracking system: An in vivo pilot study

PURPOSE

To measure the accuracy (trueness and precision) of the maxillomandibular relationship at centric relation position recorded by using 3 different intraoral scanners with or without an optical jaw tracking system.

MATERIAL AND METHODS

A completely dentate volunteer was selected. Seven groups were generated: conventional procedure (control group), 3 IOSs: Trios4 (Trios4 group), Itero Element 5D Plus (Itero group), i700 (i700 group), and 3 groups with a jaw tracking system for each corresponding IOS system (Modjaw-Trios4, Modjaw-iTero, and Modjaw-i700 groups) (n = 10). In the control group, casts were mounted on an articulator (Panadent) using a face bow and a CR record captured with the Kois deprogrammer (KD). The casts were digitized by using a scanner (T710) (control files). In the Trios4 group, intraoral scans were obtained by using the corresponding IOS and duplicated 10 times. The KD was used to obtain a bilateral occlusal record at CR position. These same procedures were followed for the Itero and i700 groups. In the Modjaw-Trios 4 group, the intraoral scans acquired by using the corresponding IOS at MIP were imported into the jaw tracking program. The KD was used to record the CR relationship. For acquiring the specimens in the Modjaw-Itero and Modjaw-i700 groups, the same procedures were followed as in the Modjaw-Trios4 group, with the scans obtained with the Itero and i700 scanners respectively. The articulated virtual casts of each group were exported. Thirty-six inter-landmark linear measurements were used to calculate the discrepancies between the control and experimental scans. The data were analyzed by using 2-way ANOVA followed the pairwise comparison Tukey tests (α=0.05).

RESULTS

Significant trueness and precision discrepancies were found among the groups tested (P<.001). The Modjaw-i700, Modjaw-iTero, Modjaw-Trios4, and i700 groups obtained the best trueness and precision among the groups tested, and the iTero and Trios4 groups obtained the worst trueness. The iTero group obtained the worst precision among the groups tested (P>.05).

CONCLUSIONS

The maxillomandibular relationship recorded was influenced by the technique selected. Except for the i700 IOS system, the optical jaw tracking system tested improved the trueness value of the maxillomandibular relationship recorded at CR position when compared with the corresponding IOS.

Therapeutic effect of pregabalin on radiotherapy-induced trismus in nasopharyngeal carcinoma patients

AIMS

To evaluate the effect of pregabalin on radiotherapy-induced trismus in patients with nasopharyngeal carcinoma, a hospital-based, clinical retrospective cohort study was conducted.

MATERIALS AND METHODS

Data were collected on patients diagnosed with radiotherapy-induced trismus from March 2014 and March 2016 in the department of neurology in our hospital. Patients in the treatment group were administrated pregabalin for 8 weeks combined with rehabilitation, while the control group only received rehabilitation. The clinical therapeutic effects were observed and evaluated by mandibular motion, severity of trismus measured by late effects of normal tissues/subjective and objective medical analysis (LENT/SOMA) scales, and quality of life (QOL) assessed using the World Health Organization QOL instrument (WHOQOL-BREF) at baseline, week 4 and week 8 during treatment in these two groups, respectively.

RESULTS

In the treatment group, the number of patients with improvement on maximal vertical dimension (MVD) was significantly more than controls at week 4 and week 8 (P=0.013, P=0.004, respectively). Moreover, at week 4 and week 8, the severity of trismus was both significantly improved on LENT/SOMA grade in treatment group (P=0.047, P=0.032, respectively). And at week 8, the physical health and the whole life domain of the WHOQOL-BREF score were significantly increased (P=0.037, P=0.034, respectively). In the treatment group, 11 patients (36.7%) presented dizziness, and 7 patients (23.3%) presented somnolence.

CONCLUSIONS

Administration of pregabalin, in adjunct to rehabilitation, might provide a better outcome in patients with radiotherapy-induced trismus.