Long-term evaluation of masseter muscle activity, dimensions, and elasticity after orthognathic surgery in skeletal class III patients.

OBJECTIVE: To evaluate changes in the masseter muscle after orthognathic surgery using electromyography (EMG), ultrasonography (US), and ultrasound elastography (USE) in individuals with skeletal class III anomaly over long-term follow-up and compare with a control group. MATERIALS AND METHODS: The study group included 29 patients with class III dentofacial deformities scheduled to undergo orthodontic treatment and orthognathic surgery. The control group included 20 individuals with dental class I occlusion. Assessment of the masseter muscles using EMG, US, and USE was performed before orthognathic surgery (T1) and at postoperative 3 months (T2) and 1 year (T3) in the study group, and at a single time point in the control group. All assessments were performed at rest and during maximum clenching. Masseter muscle activity, dimension, and hardness were analyzed. RESULTS: Electromyographic activity of the masseter muscle during maximum clenching was increased at postoperative 1 year but did not reach control group values. On ultrasonography, the masseter muscle showed minimal changes in dimension at postoperative 1 year compared to preoperative values and remained below control group values. The postoperative increase in masseter muscle hardness at rest and during maximum clenching persisted at postoperative 1 year. CONCLUSION: The results of this study suggest that after orthognathic surgery, additional interventions and much longer follow-up are needed to ensure better muscle adaptation to the new occlusion and skeletal morphology. CLINICAL RELEVANCE: All assessment methods are useful for comprehensively evaluating changes in the masticatory muscles after orthognathic surgery.

Ultrasonographic and electromyographic evaluation of three types of occlusal splints on masticatory muscle activity, thickness, and length in patients with bruxism.

OBJECTIVE: To evaluate occlusal splint type differences in patients with bruxism. METHODS: Seventeen controls and 51 patients were divided into three subgroups, each assigned to use a different occlusal splint (hard, soft, or semi-soft) for 3 months and assessed by ultrasonography and electromyography (EMG) before (BT) and 3 months after treatment (AT). RESULTS: EMG values in all of the occlusal splint groups were significantly lower AT than BT (p < 0.05). BT and AT EMG values in the control group did not differ. Mean muscle thicknesses in bruxism patients was greater than in controls, and the greatest muscle thickness changes occurred with the hard occlusal splint (p < 0.05). DISCUSSION: A decrease in EMG activity occurred with all three splint types and was most prominent in the hard occlusal splint group. Ultrasonographic measurements of muscle length and thickness should be used alongside EMG to measure muscle activity in bruxism patients.

Does cad software affect the marginal and internal fit of milled full ceramic crowns?

Although the effects of different intraoral scanners, model scanners, and CAM units on the marginal and internal fitting of restorations have been investigated, the effects of CAD software in particular has not been evaluated. The marginal and internal fit of indirect restorations may vary according to the CAD software used, even when using the same intraoral scanner and milling machine. The purpose of this study was to evaluate the marginal and internal fit of milled full ceramic crowns designed with three different CAD systems. Eleven typodont maxillary first premolar teeth were prepared and scanned using a 3Shape TRIOS Intraoral Dental Scanner. The obtained STL scan data were exported and used to design a full crown using three different CAD systems (CEREC, KaVo, and Planmeca). An independent milling unit was used to manufacture the crowns for each group (n = 11). The marginal and internal fit were evaluated for each restoration using 2D and 3D micro-CT analysis. For 2D analysis, 18 measurements for each sample were made, covering the marginal (Marginal Gap Buccal (MG-A), Marginal Gap Palatinal (MG-B), Finish Line Buccal (FL-A), Finish Line Palatinal (FA-B)) and internal fit locations (Axial Wall Buccal (AW-A), Axial Wall Palatinal (AW-B), Lingual Cusp (LC), Buccal Cusp (BC), and Occlusal Central Fossa (OCF)). Statistical analyses were performed using Open Source R Statistical Software (α = 0.05) The results of Duncan's multiple range test showed that the values for the marginal measurement points MG-A, MG-B, FL-A, and FL-B in the Planmeca group were significantly higher than the values obtained in the CEREC and KaVo groups (p < 0.05). In AW1, values of the CEREC group were found to be higher than those of the KaVo and Planmeca groups (p < 0.05). CAD software showed an effect on the marginal fit values of crowns whereas no significant difference was observed in terms of the internal fit, except for a single measurement point made from the buccal direction.

Does cad software affect the marginal and internal fit of milled full ceramic crowns?

Abstract: Although the effects of different intraoral scanners, model scanners, and CAM units on the marginal and internal fitting of restorations have been investigated, the effects of CAD software in particular has not been evaluated. The marginal and internal fit of indirect restorations may vary according to the CAD software used, even when using the same intraoral scanner and milling machine. The purpose of this study was to evaluate the marginal and internal fit of milled full ceramic crowns designed with three different CAD systems. Eleven typodont maxillary first premolar teeth were prepared and scanned using a 3Shape TRIOS Intraoral Dental Scanner. The obtained STL scan data were exported and used to design a full crown using three different CAD systems (CEREC, KaVo, and Planmeca). An independent milling unit was used to manufacture the crowns for each group (n = 11). The marginal and internal fit were evaluated for each restoration using 2D and 3D micro-CT analysis. For 2D analysis, 18 measurements for each sample were made, covering the marginal (Marginal Gap Buccal (MG-A), Marginal Gap Palatinal (MG-B), Finish Line Buccal (FL-A), Finish Line Palatinal (FA-B)) and internal fit locations (Axial Wall Buccal (AW-A), Axial Wall Palatinal (AW-B), Lingual Cusp (LC), Buccal Cusp (BC), and Occlusal Central Fossa (OCF)). Statistical analyses were performed using Open Source R Statistical Software (α = 0.05) The results of Duncan's multiple range test showed that the values for the marginal measurement points MG-A, MG-B, FL-A, and FL-B in the Planmeca group were significantly higher than the values obtained in the CEREC and KaVo groups (p < 0.05). In AW1, values of the CEREC group were found to be higher than those of the KaVo and Planmeca groups (p < 0.05). CAD software showed an effect on the marginal fit values of crowns whereas no significant difference was observed in terms of the internal fit, except for a single measurement point made from the buccal direction.

Electromyographic, Ultrasonographic, and Ultrasound Elastographic Evaluation of the Masseter Muscle in Class III Patients Before and After Orthognathic Surgery.

PURPOSE: The aim of this study was to examine changes in the electromyographic activity, thickness, width, and hardness of the masseter muscle from before to after orthognathic surgery. MATERIAL AND METHODS: The study included 15 patients with Class III dentofacial deformities who were treated with combined orthodontic and orthognathic surgery. Fifteen individuals with normal occlusion and no signs or symptoms of temporomandibular joint dysfunction were used as controls. All records were obtained bilaterally in the study group before surgery (T1), at 3 months after surgery (T2), and in the control group (CG) while at rest and in maximum voluntary contraction (MVC). RESULTS: There was no difference in resting masseter muscle activity between T1, T2, and CG. Resting thickness and width of the masseter muscle did not differ significantly between T1 and T2. MVC masseter muscle activity and thickness increased significantly and width decreased significantly from T1 to T2 but did not reach CG values. Muscle hardness increased from T1 to T2. CONCLUSIONS: The authors' findings indicate that despite improved muscle activity and dimensions, postoperative 3 months is still early period for adaptation of the masseter muscles to the new occlusion and skeletal morphology.

Biomechanical Comparison of a New Triple Cylindrical Implant Design and a Conventional Cylindrical Implant Design on the Mandible by Three-Dimensional Finite Element Analysis.

PURPOSE: The aim of this study was to evaluate the effect of implant designs with different lengths and diameters on the stress distribution in abutments, implants, and cortical and trabecular bone of the edentulous mandible via three-dimensional finite element analysis. MATERIALS AND METHODS: Eight different finite models (cylindrical 3.5 × 6; cylindrical 3.5 × 10.5; cylindrical 4.5 × 6; cylindrical 4.5 × 10.5; triple cylindrical 3.5 × 6; triple cylindrical 3.5 × 10.5; triple cylindrical 4.5 × 6; and triple cylindrical 4.5 × 10.5) were created. Abutments, abutment screws, and metal-retained porcelain crowns were modeled on the implants. A 200-N oblique load was applied on the buccal cusp of the crown. The highest maximum principal (Pmax) and minimum principal (Pmin) stresses were calculated for trabecular and cortical bone, and von Mises stress values were calculated for the implant and abutment. RESULTS: The triple cylindrical implant abutments showed lower stress values than cylindrical implant abutments. The highest von Mises stress values were observed in the cervical third of the abutments. The stress values on implants were found at the neck of the implants, and cylindrical implants showed higher stress values than triple cylindrical implants. The peak Pmax and Pmin values in cortical bone were detected around the implant neck. For implants with a 3.5-mm diameter, the triple cylindrical implant design showed lower stresses in cortical bone than the cylindrical implant design; however, similar stresses were observed in 4.5-mm implants for both designs. Implant length did not affect the stresses in cortical bone. Implants with a 10.5-mm length showed lower Pmax values than implants with a 6-mm length in trabecular bone. For Pmin values in trabecular bone, the triple cylindrical implant design had lower values than did the cylindrical implant design. CONCLUSION: Within the limitations of this study, the triple cylindrical implants, with a new implant design, showed appropriate results in terms of abutment, implant, and bone tissue stress.