American Journal of Orthodontics and Dentofacial Orthopedics最新文献

Introduction: In recent times, noncoding RNAs have received increasing interest for their potential role in the molecular pathways of orthodontic tooth movement. This study was designed to evaluate microRNA (miRNA)181a, 181b, 181c, and 181d as potential biomarkers by measuring their expression in gingival crevicular fluid (GCF) during different phases of tooth movement.

Methods: GCF was collected from patients undergoing fixed appliance treatment at 4 time points: T0: Baseline (pretreatment), T1: 24 hours after force application (initial phase), T2: 7-14 days after force application (lag phase), and T3: 14-21 days after force application (log phase). Total RNA was isolated using the Qiagen miRNeasy kit (Qiagen, Hilden, Germany), quantified using NanoDrop (NanoDrop, Wilmington, Del), and converted to complementary DNA using the miScript Reverse Transcription kit (Qiagen). Quantitative real-time polymerase chain reaction was performed to assess the expression of miRNA-181a, 181b, 181c, and 181d. Statistical analyses included the Shapiro-Wilk test, the Friedman test, and Dunn's multiple comparison test.

Results: All 4 miRNA-181 subtypes were expressed at baseline (T0) in GCF. After orthodontic force application, their expression progressively increased in subsequent phases. MiRNA-181b showed a significant rise at T1 (P = 0.013), and miRNA-181a showed a significant increase at T2 (P = 0.035). By T3, all 4 subtypes showed significantly increased expression compared with T0 (P <0.0001).

Conclusions: All 4 miRNAs were expressed throughout the study period from T0-T3 with progressive increase in expression from T0-T3. However, at each given time point (T0, T1, T2, and T3), there was no statistically significant difference among the subtypes. This study provides evidence that miRNA-181 subtypes function as potential biomarkers of orthodontic tooth movement.

Introduction: This study aimed to compare the accuracy of a novel 3-dimensional (3D)-printed attachment transfer technique with conventional composite-based methods, evaluating the effect of template material and thickness.

Methods: Three transfer methods were investigated: nonflowable composite resin, flowable composite resin, and 3D-printed attachments with a transfer carrier. In the conventional attachment transfer method, 4 different thermoplastic template sheet thicknesses were used: 0.3, 0.5, 0.75, and 0.8 mm. A standardized reference model with 6 digitally planned attachments was used for all groups. Using each method, attachments were transferred to 3D-printed dental models, which were then scanned and superimposed with the reference model. Root mean square and mean distance values were calculated using CloudCompare software (version 2.14; www.danielgm.net/cc/) for surface deviation analysis.

Results: Statistically significant differences were observed among the attachment transfer methods (P <0.001, Kruskal-Wallis test). The 3D-printed attachment group exhibited the highest geometric accuracy across all evaluated sites. Pairwise comparisons showed that the 3D-printed group performed significantly better than both composite-based groups (P <0.001, Dunn's test). Composite viscosity showed no significant effect on transfer accuracy, except for attachments 16 and 23 in mean distance values (P = 0.023-0.031) and attachment 16 in root mean square values (P = 0.043). Template thickness significantly influenced transfer accuracy, with thicker aligners generally producing lower deviation values, particularly between Tristar (0.3 mm) and Track A (0.8 mm) (P <0.05 to P <0.001).

Conclusions: The 3D-printed attachment transfer method demonstrated superior accuracy than conventional composite-based methods. Although the thinnest template exhibited greater deviations, accuracy varied among the different templates, suggesting that both material thickness and composition may influence transfer performance. Composite viscosity did not substantially affect transfer accuracy, as both flowable and nonflowable composite resins produced comparable results in most attachment sites.

Introduction: Bite-raising posterior occlusal attachments are integrated into clear aligner treatments to prevent posterior extrusion and promote intrusion by enhancing masticatory muscle activity (MMA) and occlusal forces. However, their effect remains anecdotal. The study aimed to (1) investigate the effect of passive aligners with posterior occlusal attachments on daily MMA compared with control aligners, and (2) determine if bite raising induces transient temporomandibular disorder (TMD); explore whether any early intrusive effects on teeth could be detected.

Methods: Twelve volunteers participated in a randomized, crossover experiment. MMA recordings (amplitude, duration, frequency, and duty time) were collected using a wearable electromyography device over 5-hour sessions in natural settings while wearing (1) no aligners, (2) passive aligners for 8 days, and (3) aligners with occlusal attachments for 8 days. Participants' freeway space (FWS), occlusal discomfort, perceived stress levels, TMD symptoms, and intraoral scans were monitored. Data were analyzed with linear mixed modeling.

Results: Bite-raising attachments increased contraction episodes per hour by 55% (95% confidence interval, 12%-67%) from days 1 to 8, but not compared with baseline. Both aligners significantly increased FWS, with bite-raising aligners showing a 114% increase (95% confidence interval, 85%-144%). Significant occlusal discomfort was reported in the first 3 days for both aligner types. No participants were diagnosed with TMD. No discernible intrusion was detected on serial intraoral scans.

Conclusions: Aligners encroaching into the FWS transiently increase MMA in healthy young adults, despite adaptation and diminishing discomfort. However, we found no convincing evidence to support the hypothesis that occlusal attachments contribute to vertical control or enable intrusion in the short term. More research is needed to assess long-term effects and determine whether intrusions become clinically relevant.