Lim Kwong Cheung

Meta-Analysis of Mandibular Distraction Osteogenesis : Clinical Applications and Functional Outcomes

Background: Mandibular distraction osteogenesis has been used effectively to treat syndromic craniofacial deformities. In recent years, its scope of application has widened to include treatment of airway obstruction in adults and children and nonsyndromic class II mandibular hypoplasia. So far, there has been no evidence-based review of mandibular distraction osteogenesis for mandibular lengthening. Methods: Two rounds of searches were performed by two independent assessors. The first-round PubMed search used the keywords “mandible” and “distraction osteogenesis.” In the second-round search, the reference lists of the articles were retrieved. For both rounds, abstracts and then full articles were reviewed and selected on the basis of a set of inclusion and exclusion criteria. Results: The 178 retrieved articles yielded 1185 mandibular distraction osteogenesis patients: 539 received unilateral mandibular distraction osteogenesis and 646 received bilateral mandibular distraction osteogenesis. Mandibular distraction osteogenesis was reported to improve facial asymmetry and retrognathia (50.1 percent), correct the slanted lip commissure (24.7 percent), and improve or level the mandibular occlusal plane (11.1 percent) in unilateral asymmetry cases, whereas bilateral mandibular distraction osteogenesis was shown to be effective in preventing tracheostomies for 91.3 percent of neonates or infants with respiratory distress, and in relieving symptoms of obstructive sleep apnea for 97.0 percent of children and 100 percent of adult patients. Conclusions: Mandibular distraction osteogenesis is effective in treating craniofacial deformities, but further clinical trials are required to assess the long-term stability and to compare the treatment with conventional treatment methods, especially in cases of obstructive sleep apnea or class II mandibular hypoplasia.

Safety of coronectomy versus excision of wisdom teeth: A randomized controlled trial

OBJECTIVE The objective of this study was to compare the surgical complications and neurosensory disturbances of coronectomy and total excision of lower wisdom teeth with roots in close proximity to the inferior dental nerve (IDN). STUDY DESIGN A randomized controlled trial was conducted to compare the surgical complications and IDN deficit of coronectomy and total removal of wisdom teeth. Patients with specific radiographic signs of close proximity of wisdom teeth roots to the IDN were randomized. RESULTS A total of 231 patients underwent surgery for 349 lower wisdom teeth (171 coronectomies, 178 controls); 16 coronectomies failed and were removed in total. Nine patients in the control group presented with IDN deficit, compared with 1 in coronectomy group (P = .023). Pain and dry socket incidence was significantly lower in the coronectomy group, and there were no statistical differences in infection rate between the 2 groups. Reoperation of one coronectomy case was performed owing to persistent root exposure. CONCLUSION There are fewer complications in terms of IDN deficit, pain, and dry socket after coronectomy, but the infection rate is similar to that of total excision.

Changes in blood perfusion and bone healing induced by nicotine during distraction osteogenesis

Nicotine is the main chemical in cigarettes responsible for the tobaccos pathological effects. The influence of nicotine on bone healing remains controversial. Distraction osteogenesis provides an ideal model to study bone healing and regeneration. The present study aims to evaluate the effects of nicotine on blood perfusion, angiogenesis and bone formation using a rabbit model of mandibular lengthening. Twenty adult New Zealand white rabbits were randomly assigned to the control group and nicotine group. The total nicotine or placebo exposure time for all animals was 7 weeks. After 2- or 4-week of consolidation following osteotomy, 3-day of latency and 11-day of active distraction, the animals were sacrificed and the mandibles were harvested. Blood perfusion and vascularization were evaluated by Laser Doppler monitoring and Collagen IV immunohistochemistry staining respectively. Bone formation was assessed by radiological, histological and immunohistochemical examination. Results showed that nicotine exposure increased microvessel density, whereas inhibited blood flow and bone formation. The expression of bone morphogenetic protein (BMP)-2 in osteoblasts was also decreased. Frequent appearance of cartilage islands suggested ischemia and low oxygen tension in the distraction regenerate. We concluded that nicotine compromises bone regeneration possibly by causing ischemia and directly inhibitory effect on osteoblastic cells. Nicotine exposure enhances angiogenesis but cannot compensate for the adverse effect of vasoconstriction.

Blood loss and transfusion requirements in orthognathic surgery

Abstract Purpose: This study quantified the blood loss and transfusion requirements in orthognathic surgery. Patients and Methods: Three hundred sixty consecutive healthy orthognathic surgery patients were included in this retrospective study. The female:male ratio was 1.8:1, and the age range was 8 to 49 years (mean, 24). Estimated blood volume (EBV), estimated blood loss (EBL), and transfused blood were calculated. Results: EBL ranged from 50 to 5,000 mL (mean, 600) representing up to 73% of EBV (mean, 16%). In total, 24% (84 patients) were transfused, 8.7% (6 patients) after single-jaw surgery and iliac bone harvest and 26.7% (78 patients) after bimaxillary osteotomies. Forty-seven patients received 1 unit of transfused blood, 25 patients had 2 units, and 12 patients had more than 2 units. Most transfused patients lost 11% to 40% of EBV. Conclusions: Transfusion is not necessary for single-jaw surgery unless a bicoronal flap or iliac bone harvest are required. Although only 27% of bimaxillary osteotomy patients required transfusion of 1 to 2 units, this group was not predictable based on the type of procedure involved, and a further subgroup (4% of the 291 patients) required a larger transfusion.

Dental implants in reconstructed jaws: implant longevity and peri-implant tissue outcomes

PURPOSE The study aimed to evaluate the clinical status and survival of dental implants inserted in reconstructed jaws, with particular reference to the peri-implant tissues. MATERIALS AND METHODS We conducted a clinical follow-up study based on 29 rehabilitated patients after oral tumor surgery, who received autogenous bone grafts from the ilium and endosseous implants (14 maxillary and 15 mandibular cases; 140 implants) for functional jaw reconstruction between 1988 and 1999. Clinical records of the patients were reviewed retrospectively. Clinical parameters of plaque index, probing pocket depth, and bleeding on probing were assessed around the implants and control teeth at 4 locations (mesiobuccal, distobuccal, mesiolingual, and distolingual). Implant mobility was assessed clinically and objectively using a Periotest (Gulden; Siemens, Bensheim, Germany) equipment for those implants supporting removable prostheses. Radiographically, the proportion of implant length remained osseointegrated was measured. RESULTS With a mean follow-up time of 50 months, 90.7% of the 140 implants placed were functional in supporting dental prostheses; 4.3% of implants failed in osseointegration and the remaining 5.0% implants were osseointegrated but nonfunctional. A total of 493 sites of 127 functional implants and 392 sites of 98 control teeth were assessed. No significant difference was found between the implants and control teeth parameters, except on the probing pocket depth. The mean peri-implant probing depth was 3.5 mm, and 52.7% of the measured sites were 3 mm or less. More than one third of the implants (35.9%) presented with increased probing depth (> or =4 mm), and this was significantly higher than in the control teeth (P <.001, chi(2) test). Bleeding on probing was found in 19.3% of the measured peri-implant sites, corresponding to 42.2% of the dental implants. Of the implants, 28.9% were completely free from plaque and 9.4% show visible plaque accumulation. Mobility assessment was feasible on 32 implants and no mobility was detected. Radiographically, the mean implant length remained in bone was 81.1%, with 82.6% in the maxilla and 79.4% in the mandible. Implant survival rate calculated using the Kaplan-Meier method was 86.9% for 5 years. Based on the defined criteria, the success rate of implants placed in reconstructed jaws in this study was 90.7%. CONCLUSION Endosseous implants can be successfully placed in reconstructed jaws for oral rehabilitation with maintenance of reasonable health status of the peri-implant tissues in the long-term.

Posterior maxillary anatomy: implications for Le Fort I osteotomy

The most common site of haemorrhage in maxillary osteotomies is the posterior maxilla. Better understanding of the anatomy in this region may minimize possible vascular complications. The aim of the study was to study the osteology of the posterior maxillary region and establish clinical safety guidelines for the Le Fort I osteotomy Thirty human dry skulls were selected and assessed by a combination of direct inspection, computerized imaging and computed tomography (CT) scan analysis. Results showed that the presence of maxillary third molars influenced the transverse angulation of the posterior vertical cut. Synostosis of the pterygomaxillary junction was noted in 12% of samples. The mean length of the medial sinus wall from the piriform rim to the descending palatine canal at the Le Fort I level was 34 mm. The three-dimensional CT-reconstructed descending palatine canal ran at 60 degrees anteroinferiorly to the palatine plane and slightly medially to the exit through the greater palatine foramen.

Coronectomy of the Lower Third Molar Is Safe Within the First 3 Years

PURPOSE There is no long-term evaluation on the safety of coronectomy of the lower third molar. The aim of this study was to investigate the 3-year morbidity of coronectomy of the lower third molars and to monitor the behavior and migration pattern of the retained roots after coronectomy. MATERIALS AND METHODS This was a prospective cohort study. Patients with lower third molars with specific radiographic sign(s) showing proximity of the roots to the inferior alveolar nerve who underwent coronectomy in a previous randomized clinical trial were reviewed postoperatively in the first week and the third, sixth, 12th, 24th, and 36th months. The morbidities of infection, pain, root eruption, reoperation to remove the root, and the development of any pathology were recorded. The pattern of any root migration was analyzed. RESULTS Ninety-eight patients (35 men and 63 women; mean age, 25.7 yrs; standard deviation, 7.9 yrs) with 135 coronectomies completed the 36-month review. None presented with infection or pain from the postoperative third month onward. Root eruption causing sensitivity occurred in 3% (4/135) of the sample and the erupted roots were removed. None of the reoperated cases presented with a postoperative inferior alveolar nerve deficit. No pathology developed in any of the retained roots after coronectomy. Root migration was noted in most cases in the first 12 months, and all roots stopped migrating from the 24th month onward. The mean root migration at 36 months was 2.8 mm (standard deviation, 1.4 mm). CONCLUSIONS This study confirms that retained roots after coronectomy in the lower third molars produce no complications in terms of infection, pain, or the development of pathologies within the first 3 years. Root eruption can occur in a very small percentage of patients and may require reoperation to remove the root.

Immediate reconstruction following maxillectomy: A new method

A new method for immediate reconstruction of the maxilla after resection is described. The ipsilateral pedicled temporalis muscle is tunneled into the defect and sagittaly split into two layers. The inner layer is used to line the nasal side. An individually shaped titanium mesh, tightly filled with free autogenous corticocancellous bone, is fixed by titanium screws to the remnant of the zygoma and contralateral maxilla. The outer layer of the split muscle covers the reconstruction, the temporalis fascia forming the oral side. The method resulted in good cosmetic appearance and permitted the re-creation of a maxillary alveolar ridge suitable for endosseous implants or a simple prosthesis.

Uncoupled Angiogenesis and Osteogenesis in Nicotine-Compromised Bone Healing

Nicotine is the main chemical component responsible for tobacco addiction. This study aimed to evaluate the influence of nicotine on angiogenesis and osteogenesis and the associated expression of angiogenic and osteogenic mediators during bone healing. Forty‐eight adult New Zealand White rabbits were randomly assigned to a nicotine group and a control group. Nicotine pellets (1.5 g, 60‐day time release) or placebo pellets were implanted in the neck subcutaneous tissue. The nicotine or placebo exposure time for all the animals was 7 weeks. Unilateral mandibular distraction osteogenesis was performed. Eight animals in each group were euthanized on day 5, day 11 of active distraction, and week 1 of consolidation, respectively. The mandibular samples were subjected to radiographic, histologic, immunohistochemical, and real‐time reverse‐transcriptase polymerase chain reaction examinations. Nicotine exposure upregulated the expression of hypoxia inducible factor 1α and vascular endothelial growth factor and enhanced angiogenesis but inhibited the expression of bone morphogenetic protein 2 and impaired bone healing. The results indicate that nicotine decouples angiogenesis and osteogenesis in this rabbit model of distraction osteogenesis, and the enhanced angiogenesis cannot compensate for the adverse effects of nicotine on bone healing.

Mandibular reconstruction with the Dacron urethane tray: A radiologic assessment of bone remodeling

A retrospective study was made of 22 consecutive patients who underwent mandibular reconstruction with a Dacron (Osteo-mesh, Xomed Inc, Jacksonville, FL) tray technique from September 1988 to April 1992. Free autogenous iliac bone, in the form of particulate cancellous chips and marrow, was densely packed into the Dacron tray, that was adapted to bridge the mandibular segmental defect. Sixteen cases underwent uneventful healing with the formation of a continuous bony bridge and union with the remaining mandible. The pattern of bone remodeling and rate of resorption in these cases were assessed by sequential panoramic radiographs taken up to 3 years postoperatively. The mean horizontal dimension of the mandibular defects was 75 mm and the mean vertical reconstructed height was 25 mm. When the grafted bone was radiographically of uniform density, it progressed into a mature trabecular pattern matching that of the normal mandible. However, when there were areas of radiolucency, most likely from inadequate condensation of the graft, such areas were not replaced by bone in the long term. The bony height at both ends and the middle of the reconstructed segment underwent reasonably even resorption and retained about 80% of the bony height over a 3-year period. The rate of resorption was highest in the first 6 months and stabilized at about 2 years. There were six failures, all showing significant irregular bony resorption prior to tray removal.