Yu-Chuan Tseng

Intraoral vertical ramus osteotomy for correction of mandibular prognathism: long-term stability.

Various techniques and modifications have been introduced in the treatment of mandibular prognathism. However, there are still few reports concerning long-term stability, especially using the intraoral vertical ramus osteotomy (IVRO) method. The purpose of this study was to investigate the long-term stability for correction of mandibular prognathism using IVRO. Twenty-five mandibular prognathism patients were treated by bilateral IVRO, and were evaluated cephalometrically by reference to the menton. A set of 3 standardized lateral cephalograms were obtained from each subject preoperatively (T1), immediately postoperatively (T2), and after 2 years postoperatively (T3). Relapse was defined as forward movement of menton after the 2-year follow-up. The mean setback of the menton was 12.8 mm in horizontal direction and 0.9 mm downward in vertical direction. The average follow-up was 33.9 months. The mean relapse was 1.3 mm (10.2% = 1.3 of 12.8) in forward direction and 0.6 mm in upward direction. There was no significant movement in the vertical direction. However, significant relapse was shown in the horizontal direction, even though the amount was small. The long-term stability of our present study suggested that IVRO is useful for correction of mandibular prognathism.

The use of miniplate osteosynthesis for skeletal anchorage.

Background: The purpose of this study was to explore the use of miniplates as skeletal anchorages for orthodontic treatment and to investigate the stability of miniplates and the causes of failure. Methods: Forty-four miniplates were applied in the maxilla or mandible as skeletal anchorages in orthodontic treatment. Two weeks later, a force of 100 to 200 g was applied by an elastometric chain or nickel-titanium coil spring to move the teeth. To compare nominal variables related to miniplate failure, the chi-square or Fishers exact test was used. Results: The average insertion time of a miniplate was approximately 25 to 30 minutes. One miniplate loosened before orthodontic force loading. The other miniplate was removed after orthodontic force loading. The overall success rate was 95.5 percent. The authors found no significant differences in the risk factors for failure of miniplates. Conclusions: Miniplates are easy to insert for skeletal anchorage, simplify treatment mechanics, and shorten the orthodontic treatment period.

Simple technique to achieve a natural head position for cephalography.

The cephalometric measurement of the face in terms of aesthetics can be difficult and misleading due to the variability of the intra-cranial reference lines according to diversity of head posture. Natural head position (NHP) has been proposed as a preferred reference position for assessing facial morphology. Even though natural head position is more proper and valid, it is still abandoned by reasons of time-consumption and additional and necessary complex equipment. Hence, we developed a modified level laser approach to acquire the natural head position. This method was a simple and straightforward technique which may be of value as and adjunct to routine orthognathic planning.

Cranial-Base Morphology in Children with Class III Malocclusion

The association between cranial‐base morphology and Class III malocclusion is not fully understood. The purpose of this study was to investigate the morphologic characteristics of the cranial base in children with Class III malocclusion. Lateral cephalograms from 100 children with Class III malocclusion were compared with those from 100 subjects with normal occlusion. Ten landmarks on the cranial base were identified and digitized. Cephalometric assessment using seven angular and 18 linear measurements was performed by univariate and multivariate analyses. The results revealed that the greatest between‐group differences occurred in the posterior cranial‐base region. It was concluded that shortening and angular bending of the cranial base, and a diminished angle between the cranial base and mandibular ramus, may lead to Class III malocclusion associated with Class III facial morphology. The association between cranialbase morphology and other types of malocclusion needs clarification. Further study of regional changes in the cranial base, with geometric morphometric analysis, is warranted.

The perception of pain following interdental microimplant treatment for skeletal anchorage: a retrospective study

During orthodontic therapy, patients frequently complain about pain and discomfort, especially during insertion of fixed appliances. Skeletal anchorage using an interdental microimplant is a new concept in orthodontic treatment. The purpose of this study was to investigate differences and changes in the level of pain among patients in relation to orthodontic microimplant treatments. Forty microimplants were applied to the maxilla as skeletal anchors in the orthodontic treatment. The visual analog scale (VAS) was used to evaluate the patients’ perception of pain during this new modality treatment. The premolar extraction VAS core was used as a baseline for the complete orthodontic procedure. The mean VAS score was 35.8 mm at 24 h after premolar extraction. The mean VAS score for insertion and removal of the microimplant 24 h after the operation was 12.3 and 7.8 mm, respectively. Three months after removal of the skeletal anchors, the VAS score had decreased to 3.2 mm and was the same as with the traditional orthodontic treatment. By using the repeated-measure general linear model (GLM), we found that the score 1 day after microimplant placement was significantly less than that 1 day after first premolar extraction or that 1 day after fixed appliance insertion. This result indicates that interdental microimplant did not generate any greater pain than other orthodontic procedures. Therefore, patients were willing to adopt the new orthodontic treatment.

PAIN PERCEPTION DURING MINIPLATE-ASSISTED ORTHODONTIC THERAPY

Miniplate and screw devices are widely used for fracture repair and fixation of osteotomies. Currently, these miniplate systems are being used as orthodontic treatments for skeletal anchorage. However, despite the widespread use of these treatments, patients are apprehensive when they need to undergo miniplate procedures. Recently, we assessed pain perception using the visual analog scale (VAS) score (0–100 mm) in patients who had undergone miniplate procedures. Thirty miniplates were positioned in the maxilla as skeletal anchors for orthodontic treatment. On the first day after insertion of the fixed orthodontic appliances, the mean VAS score was 36.3 mm. The mean VAS score at 24 hours after insertion of the miniplate was 58 mm. Three months after orthodontic force was applied to the miniplate, the mean VAS scores during eating and speaking gradually decreased to 20 mm and 15 mm, respectively. The mean VAS score at 24 hours after removal of the miniplate was 41.3 mm. Three months after removal of the skeletal anchors, the VAS score decreased to 5 mm. Eighty‐eight percent of patients stated that they would be prepared to undergo these new and more efficient treatment modalities in the future. The miniplate system was successfully used in this study as a skeletal anchor, and the patients could endure the pain and discomfort of this orthodontic treatment.

Interdisciplinary management of unfavorable posterior intermaxillary space

The patient was a case of severe dentoalveolar extrusion of the right maxillary posterior segment due to early loss of mandibular molars. Therefore, it is difficult to replace the missing teeth with either fixed or removable prostheses. Her occlusion was Angle Class II malocclusion and no mandibular molars for anchorage on the right side. A posterior maxillary subapical osteotomy was utilized for reestablishing the intermaxillary space. A titanium alloy miniplate placed in the right mandible provide skeletal anchorage to distalize the anterior mandibular teeth. Dental implants were placed to restore masticatory function.

Interdisciplinary Management of Dental Implant Patient: A Case Report

Maxillary molars can over‐erupt when their antagonists are lost and there are no replacements. When the opposing molars severely extrude into the edentulous space, it is difficult to replace the missing teeth with either fixed or removable prostheses. We present the following case report, providing a solution for this type of problem. A two‐stage posterior subapical osteotomy was used to reestablish the intermaxillary space. Following orthodontic treatment and implant placement, the patient regained occlusal harmony and normal masticatory function.

Are Hyoid Bone and Tongue the Risk Factors Contributing to Postoperative Relapse for Mandibular Prognathism

Objective. The purpose of this study was to investigate postoperative stability and the correlation between hyoid, tongue, and mandible position following surgery for mandibular prognathism. Materials and Methods. Thirty-seven patients, treated for mandibular prognathism using intraoral vertical ramus osteotomy (IVRO), were evaluated cephalometrically. A set of four standardized lateral cephalograms were obtained from each subject preoperatively (T1), immediately postoperatively (T2), six weeks to three months postoperatively (T3), and more than one year postoperatively (T4). The Student t-tests, the Pearson correlation coefficient, and the multiple linear regression were used for statistical analysis. Results. Immediately after surgery, menton (Me) setback was 12.8u2009mm, hyoid (H) setback was 4.9u2009mm, and vallecula epiglottica (V) setback was 5.8u2009mm. The postoperative stability significantly correlated (r = −0.512, p < 0.01) with the amount of setback. The hyoid bone and tongue did not have significant effects on postoperative stability. Multiple linear regression model (R 2 = 0.2658, p < 0.05) showed predictability: Horizontal Relapse Me (T4-T2) = −6.406 − 0.488Me (T2-T1) + 0.069H (T2-T1) − 0.0619V (T2-T1). Conclusion. Mandibular setback surgery may push the hyoid and tongue significantly backward, but this did not correlate with mandibular relapse. Postoperative stability significantly correlated with the amount of mandibular setback.

Tooth morphometry in lingual orthodontics.

Lingual orthodontics is used clinically. This study investigated the lingual crown angulation and inclination of optimal occlusion in Taiwanese people. The sample included 45 sets of dental study casts from 28 males and 17 females with optimal occlusion selected from approximately 5,000 young adults. Mesial tipping occurred in all teeth except the upper second molars, the lower central incisors, and the lower lateral incisors. The greatest mesial tipping was observed in the lower second molars. The greatest distal tipping was observed in the lower lateral incisors. Labial (buccal) inclination was observed in all teeth except the lower first molars and the lower second molars. Maximum labial inclination occurred in the upper central incisors. Maximum lingual inclination was observed in the lower first molars.