Dazhang Wang

Effects of mandibular setback on the temporomandibular joint: A comparison of oblique and sagittal split ramus osteotomy

PURPOSE This investigation studied the changes in temporomandibular joint function and condylar position after mandibular setback using different ramus osteotomies. PATIENTS AND METHODS The sample consisted of 50 Chinese adults with mandibular prognathism. Twenty-eight of the patients underwent intraoral oblique ramus osteotomy (IORO), and 22 received sagittal split ramus osteotomy (SSRO) with rigid internal fixation (RIF). TMJ symptoms and radiographic findings were evaluated preoperatively and postoperatively. RESULTS After surgery in the IORO group, the TMJ radiographs showed a significant anterior-inferior displacement of the condyle. Seventy-five percent of the preoperatively symptomatic patients reported fewer or no TMJ symptoms and no preoperatively asymptomatic patients developed new TMJ symptoms. In the SSRO group, the TMJ radiographs showed a posterior displacement of the condyle. Sixty percent of the preoperatively symptomatic patients had no improved TMJ function and 8% of asymptomatic patients developed TMJ symptoms after surgery. CONCLUSION The results of this study show that IORO with MMF appears to be more favorable to the TMJ than the SSRO with RIF; IORO is particularly good in orthognathic surgery patients with preoperative TMJ symptoms.

The effect of hydrofluoric acid treatment on titanium implant osseointegration in ovariectomized rats

This study aimed to investigate the effects of hydrofluoric acid (HF) treatment of grit-blasted Ti implants on osseointegration in ovariectomized (OVX) rats. After blasting with aluminium oxide particles, half implants were treated with 0.2 vol.% HF, and the other half were kept non-modified as control. The topographical and chemical changes of implant surface were determined by Scanning Electron Microscope, Atomic Force Microscope, and X-ray Photoemission Spectroscopy. 12 Weeks after bilateral ovariectomy, each rat accepted two implants in distal femora, with the control implant on the left and the fluoride-modified on the right. As a result, fluoride modification induced markedly changed surface topography and chemical composition. 12 Weeks after implant insertion, the fluoride-modified implants showed improved osseointegration compared to control, with the bone area ratio and bone-to-implant contact increased by 0.9- and 1.4-fold in histomorphometry, the bone volume ratio and percent osseointegration by 0.8- and 1.3-fold in micro-CT evaluation, and the maximal push-out force and ultimate shear strength by 1.2- and 2.0-fold in biomechanical test. These promising results indicated that HF treatment of Ti surface improved implant osseointegration in OVX rats, and suggested the feasibility of using fluoride modification to improve Ti implant osseointegration in osteoporotic bone.

Temporospatial expression of vascular endothelial growth factor and basic fibroblast growth factor during mandibular distraction osteogenesis

OBJECTIVE Distraction osteogenesis is a vascular-dependent process. This study investigated expression patterns of two major angiogenic factors, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), in the distracted calluses following mandibular lengthening in a goat model. MATERIAL AND METHODS Bilateral mandibular osteotomies were performed in 15 young adult goats. After a latency of 7 days, the mandibles were elongated using custom-made distractors with a rate of 1 mm/day for 10 days. Three animals each were sacrificed at the end of the delay phase, at 0, 7, 14, and 28 days after completion of distraction, respectively. The lengthened mandibles were harvested and processed for histological and immunohistochemical examinations. RESULTS Elevated cellular expression of VEGF and bFGF, with neovascularization in the distraction gap, was observed following mandibular lengthening. VEGF staining was noted in the endothelial cells and osteoblasts. bFGF staining was seen in the fibroblast-like cells, osteoblasts and immature osteocytes. Their strongest expression was found 0-7 days after the end of distraction, and declined with maturation of the newly formed bone. CONCLUSION A temporal and spatial expression pattern of VEGF and bFGF was found during distraction osteogenesis in goat mandibles. It suggests that distraction forces can stimulate the production of VEGF and bFGF, which contribute to neovascularization and new bone formation during gradual distraction of the mandible. Application of angiogenic factors may be considered as a potential method to enhance angiogenesis and osteogenesis in osteodistraction, especially in sites without enough vascularization.

Contouring of a square jaw on a short face by narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy in orientals.

Background: A square face is considered unattractive in Orientals; thus, it has become a frequently encountered reason for patients undergoing face contouring surgery. While reviewing the unsatisfactory cases of mandibular reduction, the authors discovered that some failed cases were related to a square jaw on a short face. The conventional procedures fix only the posterior region of the mandible, resulting in increased prominence of the stunted or square chin and short face. Thus, the authors applied a narrowing and sliding genioplasty procedure combined with a mandibular outer cortex ostectomy technique to reshape a wide, weak chin, and a square jaw on a short lower facial contour into a slender and attractive oval face. Methods: From July of 2005 to October of 2009, there were a total of 57 patients in this study who underwent a narrowing and sliding genioplasty combined with a mandibular outer cortex ostectomy procedure to correct a square jaw on a short face. Results: The postoperative appearance of all 57 cases showed that the lower face had narrowed and had become softer, slender, and oval, with a slick mental region. Conclusion: Narrowing and sliding genioplasty combined with a mandibular outer cortex ostectomy procedure could efficiently adjust the shape and position of the chin to obtain a good proportion of the lower face and change a square, short face to a slender, oval one in a single operation in accordance with fashionable aesthetics in Orientals.

Treatment guidelines for temporomandibular joint ankylosis with secondary dentofacial deformities in adults

Temporomandibular joint (TMJ) ankylosis with secondary dentofacial deformities in adult patients is a severely disfiguring condition and surgical treatment of this disease remains a great clinical challenge. Treatment goals are to restore the joint function, to improve facial appearances and to correct malocclusion, as well as to re-establishing harmony among them. Currently, various surgical techniques, such as arthroplasty with or without interpositional material, orthognathic surgery, distraction osteogenesis, autologous bone or bone replacement materials graft and plastic surgery, have been described in the literature. In most cases these techniques should be used in combination to achieve satisfactory outcomes. The biggest difficulty for most clinicians is to determine the proper sequence of these procedures because no uniform treatment protocol has been established. Based on the published literature and our own clinical experiences, we have prepared this review article to provide some guidelines for the surgical management of TMJ ankylosis with dentofacial deformities in adults, which will be modified and updated periodically to provide the best treatment options to benefit our patients.

Correction of zygoma and zygomatic arch protrusion in East Asian individuals

OBJECTIVE Prominent zygoma is commonly seen in the East Asian population with the clinical characteristics of anteriorly and/or laterally projected zygoma and zygomatic arch resulting in an increased midfacial width. The esthetic surgical modification of zygoma is one of the major aspects of facial-contouring surgery in certain parts of the world. This article aims to evaluate the effectiveness of various surgical methods for reducing the prominent zygoma so as to obtain a harmonious and natural facial contour. METHODS Surgical approaches, such as zygomatic complex shaving, I-shaped osteotomy, L-shaped osteotomy, and C-shaped osteotomy were used according to the clinical characteristics of zygoma and zygomatic arch protrusion. The corrective effectiveness was then evaluated through cephalometric radiographs, 3D-CT, and pre- and postsurgical standard facial photographs. RESULTS The zygoma and zygomatic arch protrusion was effectively corrected resulting in improved facial contours in all cases postoperatively. The postoperative period was uneventful except for the slight limitation in mouth opening, which recovered fully after mouth-opening exercises. Serious complications, such as facial nerve injury, were not witnessed in our study. CONCLUSIONS Malar reduction is an effective and a safe method for the treatment of prominent zygoma. The selection of surgical procedure should be based on different presenting characteristics of zygoma and zygomatic arch protrusion. The correction of prominent zygoma should be designed well, performed precisely, and observed carefully to avoid severe complications so as to achieve a harmonious facial contour.

Sliding reconstruction of the condyle using posterior border of mandibular ramus in patients with temporomandibular joint ankylosis

The traditional approach for ankylosis is gap arthroplasty or interpositional arthroplasty followed by reconstruction of the condyle using, for example, costochondral grafts. As these are non-pedicled grafts, there is eventual resorption with subsequent decrease in height of the ramus, facial asymmetry and deviated mouth opening. The authors have applied the method of total and partial sliding vertical osteotomy on the posterior border of the mandibular ramus for reconstruction of the mandible condyle as a pedicled graft for the correction of temporomandibular joint (TMJ) ankylosis. From 2004 to 2008, 18 patients who were diagnosed with TMJ ankylosis underwent operations for resection of the ankylosed condyle. Two methods were performed depending on the level of osteotomy on the posterior part of the mandibular ramus. All patients were followed-up for an average of 36 months (range 24-48 months). All patients showed apparent improved joint function with no cases of re-ankylosis. The results showed that sliding vertical osteotomy on the posterior border of the mandibular ramus seems to be an alternative and promising method for condylar reconstruction in patients with TMJ bony ankylosis.

Total or partial inferior border ostectomy for mandibular contouring: indications and outcomes.

Among the East Asian population, a long or square face produces a characteristic coarse and masculine appearance and is therefore considered undesirable and unattractive. Because of this many Orientals seek to achieve a harmonious contour of their face by undergoing various cosmetic surgical procedures. Mandibular contouring for a long or asymmetrical face with/without square jaw is rarely reported in the literature and the objective of this study was to investigate the effectiveness of total or partial inferior border ostectomy for mandibular contouring and to discuss its indications. From July 2005 to November 2009, 74 patients in this study received mandibular contouring by total or partial inferior border ostectomy procedure to correct a disharmonious facial contour. Postoperatively the appearance of all 74 cases showed that the length of the lower 3rd of the face and the width of the mandible were decreased effectively, and the mandibular contour was improved. The final aesthetic outcomes were satisfactory for both the surgeons and the patients. The results suggest that facial contour could be improved by using total or partial inferior border ostectomy of the mandible thus achieving a harmonious facial outline based on East Asian aesthetics.

A new method to induce multi-drug resistance to carboplatin in a mouse model of human tongue squamous cell carcinoma

Multi-drug resistance (MDR) in human head and neck squamous cell carcinoma (HNSCC) constitutes a major obstacle to the effectiveness of chemotherapy. In previous studies, MDR was mainly induced in vitro. The authors report a novel in vivo method of inducing MDR in nude mice with xenotransplanted Tca8113 cells. Carboplatin, a chemotherapeutic agent used to treat HNSCC, was injected around the tumors for 10 weeks. A subsequent cell survival assay of dissociated tumor cells suggested that MDR had been induced successfully. Immunocytochemistry, reverse transcription polymerase chain reaction and Western blot analysis showed that the expression levels of MDR-related proteins, including topoisomerase II, MRP and glutathione transferase, were elevated in the induction group. The authors conclude that in vivo induction of MDR provides a useful method for establishing animal models of MDR.

Correction of midface hypoplasia using a novel trapezoidal osteotomy.

Background Currently, investigating an optimal method to deal with midface hypoplasia has become a significant issue in the field of facial aesthetic surgery. Traditional ways to address this problem primarily include segmental osteotomies and using autogenous bone or cartilage grafts or synthetic implants. For the patients with paranasal hypoplasia but without malocclusion, autogenous bone grafts or implants are recommended. However, some of these patients have a flattened nose and protrusive malar, especially in the Eastern Asian; the nose will seem more flattened after augmentation the paranasal area. Hence, osteotomy is necessary in these patients to bring the flattened nose forward to get a more satisfying contour of the midface. Methods We propose a novel osteotomy through the application of model surgery to solve the problem of midface hypoplasia combined with flattened nose but without malocclusion. When compared with other techniques, this novel method not only allows the augmentation to be performed on a broader scale composed of different segments of the midface skeleton, but also results in a lower surgical risk and maintenance of the stability of occlusion. Results This novel osteotomy can bring the premaxilla in combination with the nasal bone forward to solve the problem of midface hypoplasia combined with flattened nose in patients with normal occlusion. Conclusions Through simultaneous augmentation of the different segments of the midface through this novel osteotomy, a more pleasing contour of the midface in all 3 dimensions can be achieved.