Ju-Hui Wu

Stress Analysis of Different Angulations of Implant Installation: The Finite Element Method

Clinically, many implant cases with different angulation over the lower posterior area have been found. The purpose of this study was to analyze the bony stress with different implant tilting during normal masticatory load using the finite element method (FEM), with the hope of discovering a desirable installation of implant. Athree‐dimensional finite element method was employed to analyze the bony stress generated by different angulation designs (15°) of implant bodies. Eight solid models of the mandibular first and second molars were built up and then transferred to a mesh model in FEM (ANSYS) to perform a stress analysis. A simulated load (400N) was applied to the splinted crowns with vertical and horizontal forces. The loading sites were on the central fossa of the splinted crowns. For stress distribution, some designs will be better than a parallel installation. The results suggested that not all implant bodies tilting with the splinted crowns lead to stress concentration.

Effects of denture maintenance on satisfaction levels of Taiwanese elderly using removable partial dentures: a pilot study

OBJECTIVE The aim of this study was to evaluate the correlation between patient satisfaction with removable partial dentures and denture maintenance by patients, including regular application of denture adhesives and cleansers. BACKGROUND The success of removable partial dentures depends on patient satisfaction with dentures and their regular denture maintenance. MATERIALS AND METHODS Demographic information, the Oral Impacts on Daily Performance (OIDP) indicator and details of denture maintenance (including the use of denture cleansers and adhesives) were collected from 193 (41.5% men and 58.5% women) participants by using questionnaires. A dentist performed oral examinations to evaluate denture function according to the OIDP items photographically and recorded the number of remaining teeth and Kennedys classification. RESULTS Most participants were satisfied with their removable partial dentures and tended to have higher satisfaction levels than the dentists estimation. Further, those using denture adhesives and cleansers had higher satisfaction levels than those not using such denture maintenance. CONCLUSIONS Appropriate education regarding denture use is important because regular denture maintenance by patients affects their degree of satisfaction with dentures, as well as the dentists skill and the patients oral condition. Dentists could use this information to predict the potential success of dentures.

Correlation between the change of gonial region and skeletal relapse after intraoral vertical ramus osteotomy for correction of mandibular prognathism.

Background: The gonial region is coincided with harmonious face and masticatory function. The aims of the present study were to assess changes in the gonial region in patients who had mandibular setback surgery by intraoral vertical ramus osteotomy (IVRO) and to investigate the contributing factors in relation to skeletal relapse. Methods: Twenty-one patients with mandibular prognathism were corrected by IVRO. Three cephalometric radiographs were collected from preoperative orthodontic treatment (T1), immediately after surgery (T2), and at 2-year postoperative follow-up (T3). Relapse was defined as forward movement of menton (Me) after the 2-year follow-up. Three angular (SN-Go angle, mandibular plane angle, and gonial angle) and 2 linear (horizontal-Me and vertical-Me) measurements were compared after immediate operation and at the 2-year follow-up. Spearman rank correlation and Student t tests were used for statistical analysis. Results: The mean setback of the Me was 12.7 mm, and the mean relapse was 1.5 mm. The magnitude of setback was not significant for relapse. There were weak correlations between relapse and factors concerned with the gonial region (SN-Go angle, mandibular plane angle, and gonial angle). Conclusions: Surgical correction of mandibular prognathism using IVRO can lead to an increase in the angle changes of gonial region but not correlate to skeletal relapse in long-term follow-up.

Horizontal pull-out strength of orthodontic infrazygomatic mini-implant: an in vitro study.

Purpose:New modified mini-implants have recently come into use for reinforcing skeletal anchorage in orthodontic application. The aim of this study was to investigate the influence of the design of a mini-implant on its mechanical strength. Materials and Methods:We measured the insertion torques and horizontal pull-out strengths of 3 brands of infrazygomatic mini-implants (AbsoAnchor, Bioray, and Lomas; 2 mm for all). Five implants of each brand were manually driven 6 mm into the artificial bone. Significant differences in various parameters among the brands were investigated with the Kruskal–Wallis test. Results:There was no significant relationship between insertion torque and horizontal pull-out strength. The Bioray mini-implants had significantly greater horizontal pull-out strength than the AbsoAnchor mini-implants. Conclusions:The design of the mini-implant can influence its insertion torque and horizontal pull-out strength. In our findings, the horizontal pull-out strength of all mini-implants placed in the infrazygomatic crest was significantly greater than the orthodontic force applied.

Emergence Angles of the Cementoenamel Junction in Natural Maxillary Anterior Teeth

STATEMENT OF THE PROBLEM   Fabrication of normal crown contour to maintain gingival health is difficult in the absence of emergence angle data. PURPOSE   The aim of this study was to measure the geometric values of the emergence angles on the cementoenamel junction (CEJ) for natural maxillary anterior teeth. MATERIAL AND METHODS   This study collected 148 natural permanent maxillary anterior teeth (74 central incisors, 59 lateral incisors, and 15 canines) with intact cervixes for this study. The teeth were scanned with a three-dimensional (3D) scanner to construct 3D models. This study measured the emergence angles of the cervical CEJ on the zenith of labial, palatal, mesial, and distal, for each tooth. RESULTS   Measurements made on 148 maxillary anterior teeth showed the emergence angle to be within a narrow range from 11.30° to 15.26°, irrespective of the tooth location. There were no statistically significant differences between any two groups (p > 0.05). CONCLUSIONS   On the basis of measurements taken from natural teeth, we conclude that the emergence angles of the CEJ in natural maxillary anterior teeth should be 15° from the root surface. CLINICAL SIGNIFICANCE The information presented in this article may be useful in helping to create dental restorations with optional emergence angles over the CEJ in natural maxillary anterior teeth. Prior to the treatment the dentist should consider not only the fit of the crown, but also the emergence angles and contours of the soft tissues surrounding the involved teeth.

Interdisciplinary management of mandibular intraosseous haemagioma.

Intraosseous haemagiomas usually occur in the vertebral column, and are rare in the facial bones. Mandibular intraosseous haemangioma makes up less than 1% of all intraosseous tumours. We describe here the presentation, diagnosis, treatment, and outcome in a 15-year-old boy who presented with a mandibular intraosseous haemangioma. He was treated by embolisation, en bloc resection, and immediate replacement of the mandibular segment. We also harvested the proximal tibia bone grafts and inserted four dental implants. He is well 3 years later.

Reconstruction of the Soft Palate In Oral Cancer to Repair an Operative Defect with Speech Aid Prosthesis: A Case Report

A soft palate defect may result from surgical resection, and its consequences could include hypernasal speech and nasal regurgitation of food and liquids. A speech aid prosthesis fabricated for patients can improve nasal emission during speech, and assist in preventing nasal regurgitation of food. This article presents a case of the reconstruction of a soft palate defect by prosthetic obturation.

Horizontal and vertical resistance strength of infrazygomatic mini-implants

This study assessed the adequacy of anchorage strength of infrazygomatic mini-implants in vertical and horizontal directions. Each brand of infrazygomatic mini-implant tested provided acceptable skeletal anchorage.

Mechanical strength of orthodontic infrazygomatic mini-implants

Orthodontic anchorages have recently been reinforced by newly developed mini-implants. The aim of the present study was to investigate the mechanical strengths of infrazygomatic mini-implants. We measured the insertion torque and pull-out strength of three brands of infrazygomatic mini-implants (AbsoAnchors, Bioray, and Lomas). All three mini-implants were 2 mm in diameter, and five of each brand were manually driven 6 mm into artificial bone. Significant differences among the brands were investigated with Kruskal-Wallis tests. We found no significant relationship between insertion torque and pull-out strength in any individual brand. Among the three brands of infrazygomatic mini-implants, we found no significant difference in mechanical strength. The design of an infrazygomatic mini-implant may be the most important factor determining its mechanical strength.

Biomechanical Analysis of Distal Extension Removable Partial Dentures with Different Retainers

The purposes of this study were to compare various retainer designs with different design philosophies based on stress breakers and rigid support. The technique of quasi-3-dimensional photoelastic stress analysis was used for this investigation. A photoelastic model was made with individual simulative materials for tooth structure and alveolar bone. The model was fabricated to simulate a mandibular Kennedy class Ⅱ modification 1 edentulous state with the right 1st premolar as the terminal abutment Six types of retainers were fabricated for the analysis: a wrought wire clasp; rest, proximal plate, Ⅰ-bar (RPI) system; conical crown telescopic retainer; rest, bi-proximal plate, Ⅰ-bar (RPPI) system; ring clasp, and cast circumferential clasp. For each experimental removable partial denture (RPD), a micro-load cell transducer was placed under the denture base to measure the denture base shearing load of the occlusal force. After 18 kg was loaded vertically on the occlusal table of the RPD, photoelastic stress distribution isochromatics and the denture base shearing load were obtained. Results indicated that an unfavorable stress gradient was found with the wrought wire clasp design, with the maximum stress (5.59 kg) being concentrated at the residual ridge while the minimum stress occurred at the abutment. A favorable stress gradient was found with the conical crown telescopic retainer design, with the stress (1.05 kg) being concentrated at the residual ridge. Within the limitations of this experiment, different retainer designs had different effects on the abutment and residual ridge. The retainers designed based on a rigid support philosophy concentrated more stress at the abutment and generated less stress at the residual ridge than those retainers designed with a flexible support.