RESUMEN
PURPOSE: This study aims to assess the impact of different surgical techniques and three expansion appliances on maxillary expansion in adults using finite element analysis (FEA), with a focus on maxillary displacement and stress on surrounding structures. METHODS: Seven different FEA models were created to compare different surgical techniques and three different expansion appliances. Model I represented a bone-supported appliance without surgical assistance. Model II, Model III, and Model IV were surgically assisted rapid palatal expansion (SARPE) models without pterygomaxillary suture disjunction (PMD). Model V, Model VI, and Model VII were SARPE models with PMD. RESULTS: The largest displacement at the anterior nasal spine (ANS) was recorded for Model II (2.95 mm). For the posterior nasal spine (PNS), the highest displacement was observed in Models V, VI, VII (2.50 mm), with the lowest in Model III (0.79 mm). Stress analysis revealed the highest stress in Model I, with models featuring PMD displaying nearly zero stress at all anatomical points, highlighting distinct expansion patterns and stress distributions between models with and without PMD. CONCLUSION: SARPE models with PMD demonstrated a parallel expansion of the maxilla with minimal stress, while the miniscrew assisted rapid maxillary expansion (MARPE) model displayed transverse rotation. SARPE models without PMD exhibited a V-shaped expansion pattern. SARPE models with PMD represent an optimal approach for achieving uniform expansion and minimizing stress, with stress levels nearly negligible at all anatomical points in models with PMD.
RESUMEN
PURPOSE: The purpose of this study was to compare the color changes of two different nanocomposites used for two different designs of clear aligner attachments. METHODS: In all, 120 human premolars were embedded in 12 upper dental models with 10 premolars in each model. Models were scanned and attachments were digitally designed. Conventional attachments (CA) were prepared for the first six models and optimized multiplane attachments (OA) were prepared for the other six models with packable composite (PC) on the right quadrant and flowable composite (FC) on the left quadrant of each model. The models were subjected to 2000 thermal cycles at 5⯰C/55⯰C and then consecutively immersed in the five different staining solutions each for 48â¯h to simulate external discoloration. Color measurements were taken with a spectrophotometer. Color changes (∆E*ab) of the attachments before and after immersion were compared with the Commission Internationale de l'Éclairage L*a*b* (CIELAB) color space approach. RESULTS: When ∆E*ab values were examined, no significant difference was observed between the groups according to the attachment type (Pâ¯> 0.05). After the coloration process, the flowable composite group showed less coloration than the packable composite group for both attachment designs (Pâ¯< 0.05). Color difference values after the staining procedure were significantly higher in the CA-PC and OA-PC groups compared to the CA-FC and OA-FC groups (Pâ¯< 0.05). CONCLUSION: Color change of the packable nanocomposite was more pronounced than that of the flowable nanocomposite for both attachment designs. Therefore, clear aligner attachments created using flowable nanocomposite can be recommended, especially in the anterior region where esthetics are important for the patient.