Effect of miniscrew-assisted rapid palatal expansion on mandibular position / 口腔医学

Objective@#To explore the effect of miniscrew-assisted rapid palatal expansion (MARPE) on mandible position in the treatment of adult skeletal Class Ⅰ malocclusion with maxillary transverse deficiency. @*Methods@#In this retrospective study, 20 cases of adult skeletal Class Ⅰ malocclusion with maxillary transverse deficiency treated with MARPE in our hospital from July 2019 to March 2022 were selected as research objects. CBCT data of three time points before treatment (T0), immediately after expansion (T1) and six months after retention (T2) were collected. The head position was standardized and calibrated by Dolphin software, and then mandible landmarks (left and right Condylion, left and right Gonion, Menton) were positioned. The linear distance changes of each landmark relative to the reference plane of coronal plane, axial plane and sagittal plane were measured, which represented the sagittal, vertical and horizontal displacement of mandible respectively. Repeated measurement ANOVA and LSD multiple comparison were used to evaluate the position change of each landmark.@*Results @#The Menton and right Gonion rotated clockwise at T1, and relapsed to the initial position at T2. No lateral displacement of Menton was found.@*Conclusion@#When MARPE is used to treat skeletal Class Ⅰ malocclusion with maxillary transverse deficiency, it causes a transient clockwise rotation of the mandiblar. The mandible does not show sagittal, vertical and horizontal position changes in long-term evaluation.

Clinical application and research progress of digital complete denture / 华西口腔医学杂志

Digital technologies use high-precision three-dimensional scanning, intelligence-aided design software, and multi-axis numerical control milling or 3D printing, which can produce restorations with reliable precision and suitable function. However, the development of digital technologies in the field of complete denture restoration has been slow due to the complexity of prosthesis. This review article introduces the current research status and clinical applications of digital complete dentures in prosthodontic clinics and dental laboratories to provide beneficial references to prosthodontists and dental technicians.

Design of points, lines and planes in the reconstruction of occlusion and the risk control in implantation / 中华口腔医学杂志

Occlusion reconstruction involves various factors, such as joints, muscles, teeth and mental states. The relationship between implantation complications and occlusion, especially in the method of reducing the risk of implantation during occlusal reconstruction, is more and more emphasized by clinicians. This article mainly summarized the essentials of occlusal factors, such as mandibular position, cusp inclination and occlusal contacts, Spee's curve, Wilson curve and occlusal plane, in clinical treatment from the perspective of static geometry, dynamic functional movement in points, lines and planes, in order to accomplish precise occlusion reconstruction to achieve a stable and functional occlusion reconstruction, i.e. comfortable mandibular position, reasonable protrusive and lateral guidance, firm retrusive control and stable posterior supports, and to maintain the stability of implant.

The influence of horizontal cephalic rotation on the deviation of mandibular position

PURPOSE: When performing an occlusal procedure, it is recommended that the patient should be sitting straight with the head in a natural position. An inappropriate mandibular position caused by an incorrect occlusal record registration or occlusal adjustment can result in damaged teeth and cause functional disorders in muscles and temporomandibular joints. The purpose of this study was to clarify the influence of horizontal cephalic rotation on mandibular position by investigating the three-dimensional positions of condylar and incisal points. MATERIALS AND METHODS: A three-dimensional jaw movement measurement device with six degrees of freedom (the WinJaw System) was used to measure condylar and incisal points. The subjects were asked to sit straight with the head in a natural position. The subjects were then instructed to rotate their head horizontally 0°, 10°, 20°, 30°, 40°, 50°and 60° in the right or left direction. RESULTS: The results indicated that horizontal cephalic rotation made the condyle on the rotating side shift forward, downward, and toward the inside, and the condyle on the counter rotating side shift backward, upward, and toward the outside. Significant differences in deviations were found for angles of rotation higher than 20°. The incisal point shifted in the forward and counterrotating directions, and significant differences were found for angles of rotation higher than 20°. CONCLUSION: The mandibular position was altered by horizontal cephalic rotations of more than 20°. It is essential to consider the possibility of deviation of the mandibular position during occlusal procedures.

Qualitative correlation between postoperatively increased vertical dimension and mandibular position in skeletal class III using partial-least-square path modeling / 대한악안면성형재건외과학회지

BACKGROUND: This study constructed a partial-least-square path-modeling (PLS-PM) model and found the pathway by which the postsurgical vertical dimension (VD) affects the extent of the final mandibular setback on the B point at the posttreatment stage for the skeletal class III surgery-first approach (SFA). METHODS: This study re-analyzed the data from the retrospective study by Lee et al. on 40 patients with skeletal class III bimaxillary SFA. Variables were obtained from cone beam computed tomography (CBCT)-generated cephalograms. Authors investigated all variables at each time point to build a PLS-PM model to verify the effect of the VD on the final setback of the mandible. RESULTS: From PLS-PM, an increase in VD10 was found to decrease the absolute value of the final setback amount of the mandible, which reflects the postsurgical physiological responses to both surgery and orthodontic treatment, which, in turn, can be interpreted as an increase in postoperative mandibular changes. CONCLUSIONS: To resolve the issue of collinear cephalometric data, the present study adopted PLS-PM to assess the orthodontic treatment. From PLS-PM, it was able to summarize the effect of increased postsurgery occlusal vertical dimension on the increased changeability of the B point position at the posttreatment stage.

Evaluation of hyoid bone position and airway size in Class III malocclusion / 대한치과교정학회지

This study was performed to evaluate the hyoid bone position and airway in skeletal class III malocclusion and to prove the correlation between airway, hyoid bone position and mandibular position. The sample, considered of 47 class III malocclusion patients for experimental group and 52 class I malocclusion students for control group. Twenty three linear and angular measurements about hyoid bone position, airway size, mandibular position were taken from the lateral cephalograms. The differences between skeletal class III malocclusion group and normal occlusion group were compared and the correlation were evaluated statistically. The results obtained were as follows, 1. There were significant difference in S-APH, A-APH, N-APH, LAH-PBR, AA-PNS, PNS-ad between class I and class III malocclusion groups. 2. The hyoid bone was more anteriorly positioned in class III malocclusion group than class I malocclusion group and skeletal airway size in class III malocclusion group was smaller than class I malocclusion group. 3. There were significant difference in several measurements especially vertical and angular measurements of hyoid bone position and airway size between male and female. Usually the measurements in male were larger than female. 4. There were no significant correlation between hyoid bone position and airway size also airway size, and didn't showed significant correlation with mandibular position. 5. S-APH showed negative correlation with Wits appraisal and A-APH, N-APH showed positive correlation with Wits appraisal. On the contrary vertical measurements of hyoid bone position showed positive correlation with lower facial height.

A clinical study on the centric discrepancy in postorthodontic patients / 대한치과교정학회지

If the centric prematurity occurs after orthodontic treatment, it creates centric slide regarded as a possible factor in the cause of temporomandibular disorder and/or postorthodontic relapse. The purpose of this study was to investigate the manner of centric prematurity and centric slide in postorthodontic patients. The 36 orthodontic patients who had been treated with edgewise appliance at least 3 months previously were used in this study. After recording centric relation by the leaf gauge technique, the centric prematurity and centric slide were studied using SAM2 articulator and mandibular position indicator. The results were as follows: 1. The highest percentage of centric prematurities were found on the second molars. 2. The buceal incline of the palatal cusp was the most frequent area of centric prematurities in the maxilla, while the lingual incline of the buccal cusp was the most frequent area in the mandible. 3. There were no trends in the direction of centric slide on the mandibular position indicator. 4. There were no significant differences in centric discrepancies between the premolar extraction and nonextraction group.