Factors related to microimplant-assisted rapid palatal expansion in teenagers and young adults: A cone-beam computed tomography study.

INTRODUCTION: For patients with maxillary transverse deficiency, selecting an appropriate therapeutic method is important for the treatment effect and prognosis. Our study aimed to explore factors related to microimplant-assisted rapid palatal expansion (MARPE) in teenagers and young adults using cone-beam computed tomography. METHODS: Twenty-five patients who underwent MARPE were included in this retrospective study from February 2014 to June 2019. Midpalatal suture density (MPSD) ratio, midpalatal suture maturation (MPSM), bone effect, dentoalveolar effect, and dental effect in maxillary first molar were evaluated using cone-beam computed tomography. Spearman correlation analysis was used to analyze the correlation between the MPSD ratio, MPSM, age, and the expansion amount generated by MARPE. RESULTS: Twenty-five patients (mean age, 19.84 ± 3.96 years; range, 15-29 years) with maxillary transverse deficiency were analyzed. Age was negatively correlated with bone expansion, alveolar expansion, and alveolar change (all P <0.05). There was a negative correlation between MPSM and nasal cavity variation, bone expansion, and alveolar change (all P <0.05). The bone expansion was negatively correlated with MPSD ratio 3 (r = -0.417; P <0.05) and MPSD ratio 4 (all P <0.05). CONCLUSIONS: Age, MPSM, and MPSD ratio were significantly related to the MARPE effect. Age, MPSM, and MPSD ratio should be considered when choosing MARPE.

Treatment effects after maxillary expansion using invisalign first system vs. acrylic splint expander in mixed dentition: a prospective cohort study.

BACKGROUND: Invisalign First System (First) is a new type of orthodontic appliance for maxillary arch expansion in mixed dentition children. Till now, few studies have evaluated the expansion effects of First versus other appliances. What's more, most studies of arch expansion did not include a natural group to rule out growth effects. This prospective cohort study aimed to evaluate the dental and dentoalveolar effects using First or acrylic splint rapid maxillary expander (RME) in adolescents excluding growth factors. MATERIALS AND METHODS: After screening by strict inclusion criteria and propensity score matching (PSM), fifty-one patients were included: First group (n = 17), RME group (n = 17), and natural growth (NG) group (n = 17). Nine indicators including dental arch width, dentoalveolar arch width, and inclination of the molars were measured on digital dental casts at baseline (T0) and six-month follow-up (T1). Paired t-tests were used for intra-group results, and two-sample independent t-tests were used for inter-group comparisons. RESULTS: There was no significant increase in all indicators within six months in the NG group (p > 0.05). In the First group and RME group, all width indicators were significantly increased after treatment (p < 0.05). The RME group exhibited greater expansion than the First group in intercanine width, first interpremolar width, second interdeciduous molar width, first intermolar width, arch perimeter, intercanine dentoalveolar width, intermolar dentoalveolar width, and inclination of the molars (p < 0.05). Whereas, there was no significant difference in arch depth between the two treated groups. CONCLUSIONS: Both First and RME can expand the maxillary arch in mixed dentition. In case of mild to moderate maxillary transverse deficiency (MTD), Invisalign First System could be a reasonable option. RME shows significant better efficiency of dental arch expansion than First, recommended for patients with severe MTD. TRIAL REGISTRATION: This prospective study was registered on ClinicalTrials.gov (01/02/2022, registration number: ChiCTR2200056220). The trial was approved by the Ethical Committee of the Hunan Xiangya Stomatological Hospital Central South University (20,200,088), and informed consent was obtained from all subjects and their legal guardian(s).

Morphological changes in alveolar bone thickness and height after orthodontic proclination or labial movement combined with autogenous soft tissue grafting: a CBCT evaluation.

BACKGROUND: Autogenous soft tissue grafting is indicated in thin gingival biotypes before orthodontic proclination or labial movements to increase the keratinized gingiva and prevent gingival recession. However, its effect on local alveolar bone remodeling is unclear. The aim of this study was to investigate the effects of autogenous soft tissue grafting on local alveolar bone after orthodontic proclination or labial movements. METHODS: Sixteen patients with a thin scalloped gingival biotype, narrow keratinized gingiva, or thin cortical bone requiring orthodontic proclination or labial movement of teeth were included. Cone-beam computed tomography (CBCT) images were obtained before grafting and at least 6 months after surgery. Sixty mandibular teeth were included, and the vertical bone level and horizontal labial bone thickness were measured. The results were compared using paired t-tests or Wilcoxon signed-rank test. RESULTS: The horizontal labial bone thickness increased, especially at 6 mm below the cementoenamel junction (CEJ) in the mandibular central and lateral incisors (P < 0.05). The total alveolar bone area of the canines, first premolars, and second premolars increased at 3, 6, and 9 mm below the CEJ, respectively, and the differences were statistically significant (P < 0.05). Additionally, vertical bone height increased minimally on the labial side, but the differences were not statistically significant (P > 0.05). CONCLUSIONS: New bone regeneration was observed on the labial (pressure) side after autogenous soft tissue grafting, which may represent a mechanism to effectively prevent gingival recession and maintain periodontal health. IRB APPROVAL: All the experimental procedures involving humans in this study were approved by the Medical Ethics Committee of Xiangya Stomatological Hospital, Central South University ( No. 20190048).

Displacement and stress distribution of the craniomaxillofacial complex under different surgical conditions: a three-dimensional finite element analysis of fracture mechanics.

OBJECTIVE: To provide a simplified treatment strategy for patients with maxillary transverse deficiency. We investigated and compared the fracture mechanics and stress distribution of a midline palatal suture under dynamic loads during surgically-assisted rapid palatal expansion. METHODS: Based on the cone-beam computed tomography (CBCT) data of a 21-year-old female volunteer, a three-dimensional model of the cranio-maxillofacial complex (including the palatal suture) was constructed. A finite element analysis model was constructed based on meshwork. After the yield strength of the palatal suture was set, an increasing expansion force (0-500 N) was applied within 140 ms to calculate the time-load curve, which mimicked nonsurgical bone expansion (model A). The same method was used to evaluate the fracture process, time and stress distribution of the palatal suture in maxillary lateral osteotomy-assisted (model B) and LeFort osteomy I (LFIO)-assisted expansion of the maxillary arch (model C). RESULTS: Compared with model A, the palatal suture of model B and model C showed a faster stress accumulation rate and shorter fracture time, and the fracture time of model B and model C was almost identical. Compared with model A, we discovered that model B and model C showed greater lateral extension of the maxilla, and the difference was reflected mainly in the lower part of the maxilla, and there was no difference between model B and model C in lateral extension of the maxilla. CONCLUSIONS: Compared with arch expansion using nonsurgical assistance (model A), arch expansion using maxillary lateral wall-osteotomy (model B) or LFIO had a faster rate of stress accumulation, shorter time of fracture of the palatal suture and increased lateral displacement of the maxilla. Compared with arch expansion using LFIO (model C), arch expansion using lateral osteotomy (model B) had a similar duration of palatal suture rupture and lateral maxillary extension. In view of the trauma and serious complications associated with LFIO, maxillary lateral wall-osteotomy could be considered a substitute for LFIO.

Local injection of RANKL facilitates tooth movement and alveolar bone remodelling.

OBJECTIVES: To investigate the effect of local injection of receptor activator of nuclear factor kappa B ligand (RANKL) on experimental tooth movement and subsequent alveolar bone remodelling in mice. MATERIALS AND METHODS: Sixty mice were randomised to receive daily local RANKL or phosphate-buffered saline injections in the buccal premaxillary bone for 14 of 21 days of incisor movement, followed by a 21-day retention period. Five mice from each group were euthanised on days 0, 3, 7, 14, 21 and 42, and specimens were prepared for haematoxylin and eosin, tartrate-resistant acid phosphatase and immunohistochemical staining. Five mice from each group were subjected to serial microcomputed tomography until day 42 for tooth movement and bone volume quantification. RESULTS: The experimental group showed significantly greater tooth movement and bone volume reduction on days 14 and 21; an increased osteoclast number on days 3, 7, 14 and 21; and no difference on day 42. Higher RANKL expression was observed on days 7 and 14, with remarkable alkaline phosphatase activity. No significant systemic changes were observed. CONCLUSION: Local RANKL injection leads to increased osteoclastic activity and facilitates tooth movement, followed by subsequent alveolar bone formation; this implies a reversible transitional acceleration of bone resorption.

[Efficiency of clear aligners in extrusion of posterior teeth evaluated by 3-dimensional model superimposition].

PURPOSE: To explore the efficiency of posterior teeth extrusion with clear aligners by 3-dimensional model superimposition, which provides a reference for the design of clinical programs. METHODS: We selected 24 patients with clear aligners whose posterior teeth were designed to extend more than 0.5 mm, and a total of 126 teeth were included. Digital models were obtained before and after treatment by intraoral scanning with iTero, named as "actual initial" and "achieved" digital models. Initial and final models from the ClinCheck, labeled as "virtual initial" and "predicted" models respectively. Initial, predicted, and achieved digital dental models were exported as stereolithography files and subsequently imported into Geomagic Studio. Extrusive measurements were made from the superimposition of the initial and predicted models (predicted movement) and from the superimposed initial and achieved models (achieved movement). Statistical analysis was performed with SPSS 23.0 and GraphPad Prism 5.0 software package. The extrusion efficiency of the posterior teeth was calculated, at the meanwhile the influencing factors were analyzed. RESULTS: The mean extrusion efficiency of posterior teeth during clear aligners treatment was 30.2%. The actual extrusion was linearly related to the expected(P<0.05), and the linear regression equation was y=0.305x-0.010. The difference between the actual and the predicted extrusion was positively correlated with the number of appliances(P<0.05), and also positively correlated with the predicted extrusion value(P<0.001). This difference was larger in low-angle patients than in patients with average angle (P<0.05). CONCLUSIONS: The extrusion rate of posterior teeth is relatively low during clear aligners treatment, and the average efficiency is 30.2%. Vertical growth pattern affects the extrusion efficiency. So more overcorrections can be designed for average angle patients.

Mitofusin-2 Expression Is Implicated in Cervical Cancer Pathogenesis.

BACKGROUND/AIM: It remains unclear whether mitofusin-2 (MFN2) functions as a tumour suppressor or oncogene in cancer progression. In this study we, therefore, aimed to investigate the effect of MFN2 on the pathogenesis of cervical cancer. MATERIALS AND METHODS: MFN2 expression was detected in seven healthy cervical, 64 cervical intraepithelial neoplasia (CIN), and 120 cervical squamous cell carcinoma (SCC) tissues by immunohistochemistry. Moreover, biological function of MFN2 in cervical cancer was investigated in vitro. RESULTS: MFN2 levels exhibited a tendency to gradually increase from healthy cervical tissue to CIN to SCC. Moreover, MFN2 expression was significantly associated with higher T-stage (p=0.008) and lymph node metastasis (p<0.001). The proliferative, migratory, and invasive abilities of MFN2-knockdown cells were significantly lower (p<0.001, p<0.001, and p<0.001, respectively) than control cells. CONCLUSION: MFN2 may be involved in cervical cancer pathogenesis as an oncogene and might serve as a biomarker of cervical SCC.