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The phenomenon of orthodontic anchorage miniscrews loosening after being implanted several times happens in daily clinical practice, and the reasons need to be traced. This study aimed to investigate the underlying risk factors influencing the progressive susceptibility of orthodontic miniscrews to failure.Overall, 889 miniscrews were successively inserted into 347 patients because some loosened or fell off once, twice, or more before achieving their purposes. The number of miniscrew failures (ie, once, twice, or more) was defined as progressive susceptibility to failure. The clinical indicators were assessed via univariate analysis, multicollinearity diagnosis, and Poisson log-linear regression model with stepwise calculation to screen out.The progressive susceptibility of miniscrews to failure was proved to be affected by the age of patients, the onset of force application, site of placement, and appliance type. Age and onset of force application presented a negative relationship with susceptibility. Miniscrews inserted in the palatal region appeared to be more stable than the forepart of the arch. In contrast, the retromaxillary and retromandibular areas obtained the lowest stability. The patients with fixed appliances were more unlikely to suffer progressive failure than removable appliances. In addition, the larger number of screws inserted in each patient, the greater probability of failure.Younger people with removable appliances that miniscrews inserted in the retromaxillary or retromandibular regions and earlier onsets of loading had a higher progressive susceptibility to loosening. Meanwhile, the failure rate was elevated with the increasing number of screws per patient received.

INTRODUCTION: This retrospective study aimed to quantify the impact of coronavirus disease 2019 (COVID-19) on the orthodontic appointment and make an analysis of orthodontic emergencies (OEs) that occurred during the pandemic. METHODS: A total of 628 patients were randomly sampled from 3489 subjects who were undergoing active orthodontic treatment with fixed appliances, and the medical records were reviewed. OE occurrence was analyzed from 617 patients who had explicit return-visit records after the COVID-19 outbreak. Wilcoxon signed rank tests, chi-square tests, and a binary logistic regression were performed. RESULTS: The return-visit of 98.6% of the patients was delayed significantly with an increase over 8.98 ± 4.76 weeks (P

Objective: To determine whether temporary anchorage devices (TADs) could enhance the mandibular effects of Forsus Fatigue Resistant Devices (FFRD) in growing patients presenting with a Class II malocclusion. Materials and methods: Without language restriction, electronic and manual searches were conducted through databases and relevant journals until the 20th February, 2020. Studies comparing the therapeutic effects in Class II patients treated with TA-anchored FFRD and patients receiving conventional FFRD were considered eligible. Two reviewers independently conducted the study inclusion, data extraction and risk of bias assessment following Cochrane guidelines. The outcomes were qualitatively synthesised and the level of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) tool. Results: Six studies meeting the selection criteria were identified. All except one reported that a greater reduction in the proclination of the mandibular incisors was achieved in TAD-anchored groups compared with the conventionally-treated groups. Controversial results were found in the skeletal and soft tissue descriptions of positional change. The evidence quality varied from very low to moderate. Conclusion: Moderate-quality evidence suggests that TADs are beneficial in reducing the proclination of the mandibular incisors caused by FFRD in Class II patients. Controversies related to the effects on mandibular growth and soft tissue positional change remain. There is a trend that miniplates may enhance the mandibular skeletal effects of FFRD better than miniscrews but further investigation is indicated.

Introduction The aim of this study was to evaluate the impact of the placement angle on the stability of loaded microscrews. Methods Forty-eight microscrews were placed at 4 angles ( 30°, 50°, 70°, and 90°) into the tibiae of 12 beagles, loaded with a force of 2 N immediately, and maintained for 8 weeks. Microcomputed tomography and pullout tests were used for morphometric and biomechanical analyses, respectively. Results All microcomputed tomography parameters and the peak loads at extraction of the microscrews were influenced by the placement angles of the microscrews. The higher microcomputed tomography parameters and the peak load at extraction were measured at angles from 50° to 70°. Oblique and vertical placement angles resulted in reduced stability of the loaded microscrews ( P Conclusions To achieve the best stability of microscrews, a placement angle of 50° to 70° is advisable.

Objective The aim of this study was to evaluate the influence of different healing times before loading on the stability of implanted titanium mini-implant. Study design Forty mini-implants were implanted in bilateral maxilla in 10 beagles, loaded with a force of 0.98 N after a delay of 0 day (immediately activated) and 1, 3, 5, and 7 weeks. Microscopic computerized tomography (μCT) and pullout test were used for morphometric and biomechanical analyses, respectively. Results All μCT parameters and the Fmax of mini-implants were stimulated with the prolongation of healing time before loading. Between the group of 1 week and 3 weeks, a more obvious rising tendency of both μCT parameters and the Fmax of implants was observed. After 3 weeks, the tendency of increase tapered off. Conclusion The results indicated that early loading may decrease osseointegration of mini-implants.

Introduction This study was designed to investigate how the factors including the healing time, implantation location, inserting method and bone density play the important roles in the stability of mini-implant anchorage (MIA), and to evaluate the effects of using the mini-implants in the dental clinic. Materials and Methods Eighteen adult Beagle dogs implanted Aarhus MIAs were chosen to establish the animal experimental model and four vital factors including the healing time, implantation location, inserting method and bone density were considered. The stability of MIAs in different groups was evaluated by super sclerous tissues slice technique, pull-out test and immunohistochemistry. Meanwhile, MIAs were used in clinical therapy for closing extraction space and intruding lower incisors, compared with conventional anchorage methods. Results and Discussion All the MIAs with different healing time (immediate, 2 weeks or 4 weeks loading) provided sufficient anchorage for tooth movement, while the 2- week-loading group showed a relatively better performance. MIAs implanted in the mandible expressed a significantly higher osseointegration ratio and pull-out strength than those in the maxilla. The MIAs implanted close to an extraction wound had more active bone remodeling than the control group. In both self-tapping and pilot-drilling ways, the MIAs showed enough stability though their osseointegration ratio were obviously different. The clinical application of MIA took a distinctive advantage over the conventional methods in such occasions as extraction space closing and tooth intruding. The healing time, implantation location, inserting method and bone density have significant effects on the osseointegration ratio at the interface between MIA and bone, thus the stability of MIA. However, application of MIA as a powerful tool in orthodontic treatment, especially in some complicated cases, widens the scope of the treatment and brings a new prospect of the orthodontic therapy.

Objective: To evaluate the effect of insertion angle on stability of loaded titanium microscrews in beagle jaws. Materials and Methods: Forty-eight microscrews were inserted at four different angles (30°, 50°, 70°, and 90°) into the intraradicular zones of the mandibular first molars and third premolars of 12 beagles and immediately loaded with a force of 2 N for 8 weeks. Microcomputed tomography (micro-CT) and biomechanical pull-out tests were used to assess osseointegration of the interface. Results: All micro-CT parameters and maximum pull-out force (FMAX) of the microscrews were affected by insertion angles of microscrews. Higher micro-CT parameters and FMAX were seen for implants inserted at angles between 50° and 70° (P < .05). Excessive oblique and vertical insertion angles resulted in reduced stability (P < .05). Conclusion: An insertion angle of 50° to 70° is more favorable than excessive oblique or vertical angles to achieve stability of microscrews.

Objective: To compare the effects of different cortical bone thicknesses on the stability of microscrews at different healing times. Materials: Sixty-four microscrews were inserted into the femurs of eight beagles, with four microscrews for one femur of one beagle dog. The dogs were sacrificed at 0, 3, 6, and 9 weeks after microscrew placement, respectively. All specimens were prepared for pullout testing. Cortical bone thickness was measured. Statistical analyses were conducted with analysis of variance (ANOVA) and Student-Neuman-Keuls (SNK) tests. Results: Pullout forces in thick cortical bone sites are significantly higher than those in thin sites at 0 week and 3 weeks. For both thick and thin cortical bone thickness sites, the highest pullout forces were seen in the 0 week group and the lowest in the 3 week group. In the thin cortical bone thickness sites, the pullout force of the 3 week group was statistically different from those of the 6 week group and the 9 week group; however, no such differences were noted in thick cortical bone thickness sites. Conclusion: Microscrews inserted into thick cortical bone thickness sites had better stability than those inserted into thin cortical bone thickness sites at early healing time. The difference diminished and became insignificant as healing time got longer. Longer healing time may be necessary if microscrews are inserted into thin cortical bone thickness sites.