Effect of DBM on the healing of intramembranous bone graft

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Surgical reconstruction of the jaws after ablative surgery

Ablative surgery of the jaws may be necessary when malignant disease or destructive benign disease occurs. Surgical reconstruction needs to include the restoration of masticatory function so that the quality of life after operation is optimal. This paper describes some current concepts in functional reconstruction after mandibulectomy and maxillectomy and includes case examples that illustrate bone-grafting procedures and occlusal rehabilitation by implant-borne restorations.published_or_final_versio

Are hearing and middle ear statuses at risk in Chinese patients undergoing orthognathic surgery?

Orthognathic surgery, which is performed to correct dentofacial abnormalities, has been associated with postoperative reduction in hearing sensitivity and middle ear dysfunction. In this study, the pre- and postoperative hearing status and middle ear function of 37 Chinese subjects who underwent orthognathic surgery, as well as subjective reports of aural symptoms, particularly hearing loss, tinnitus, fullness and otalgia, were investigated. There was a significant increase in the number of subjects with measured loss, perceived loss and aural fullness from pre-surgery to 1 week post surgery. However, the percentage of increase was small compared with previous findings. This difference in findings was attributed to the type of surgical techniques used, and to the fact that the Chinese population appears to be less susceptible to middle ear effusion. Subjective complaints of aural symptoms may not be accompanied by measured loss.postprin

Cephalometric norms for the upper airway in a healthy Hong Kong Chinese population

Objective. To obtain normative data for cephalometric measurements of the upper airway in the local Chinese population. Design. Observational study. Setting. University department and teaching hospital out-patient clinic. Subjects and methods. Subjects included 74 healthy patients, 29 males (age range, 18-35 years) and 45 females (age range, 16-42 years), with normal skeletal facial profile, no history of snoring, sleep apnoea, upper airway disease, tonsillectomy or adenoidectomy, obesity, of pathology in the pharynx. Twenty cephalometric airway measurements, including size of the tongue, soft palate, nasopharynx, oropharynx, hypopharynx, and relative position of the hyoid bone and valleculae were obtained. Landmarks on cephalometric radiographs were digitised and measurements were made using a specially designed computer programme. Error analysis of measurements was performed and comparison of measurements according to sex was made. Results. Significant sex dimorphism was seen for the majority of measurements, with the exception of minimal depth of the airway, oropharyngeal depth of the airway, and the soft palate angle with the hard palate. Conclusion. A minimum sagittal dimension of the upper airway was evident despite differences in measurements between sexes. Findings from this study should be a useful reference for the assessment of sleep apnoea in the local population.published_or_final_versio

Asymptotic behavior of the average local ionization energy in finite basis sets

The average local ionization energy (ALIE) has important applications in several areas of electronic structure theory. Theoretically, the ALIE should asymptotically approach the first vertical ionization energy (IE) of the system, as implied by the rate of exponential decay of the electron density; for one-determinantal wavefunctions, this IE is the negative of the highest-occupied orbital energy. In practice, finite-basis-set representations of the ALIE exhibit seemingly irregular and sometimes dramatic deviations from the expected asymptotic behavior. We analyze the long-range behavior of the ALIE in finite basis sets and explain the puzzling observations. The findings have implications for practical calculations of the ALIE, the construction of Kohn–Sham potentials from wavefunctions and electron densities, and basis-set development

Patulous Eustachian tube after Le Fort I osteotomy in a cleft palate patient

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Experimentally induced unilateral tooth loss: Histochemical studies of the temporomandibular joint

Occlusal abnormality may contribute to osteoarthrosis of the temporomandibular joint (TMJ). Since mechanical force may induce changes in the extracellular matrix, we tested the hypothesis that unilateral removal of teeth and the resulting unilateral mastication change the content of glycosaminoglycans (GAGs) in the TMJ condyle and disc. Lower-right-side teeth were extracted from 12 adult male rabbits, which were killed 3 or 6 weeks later. Three normal rabbits served as controls. Sections were analyzed for morphological changes and levels of sulfated GAGs in the condyle and disc. Unilateral removal of teeth led to thickening of the condylar cartilage, alterations in the morphology of chondrocyte nuclei in the condylar cartilage and disc, and increases in levels of negatively charged ions in the hypertrophic layer of condylar cartilage. Small differences were observed, after unilateral removal of teeth, between the functional and non-functional sides of the TMJ. The results suggest that in response to mechanical stress, chondrocytes alter sulfated glycosaminoglycan (GAGs) synthesis and degradation rates, resulting in an elevated level of sulfated GAGs in the condylar cartilage.published_or_final_versio

The effect of demineralized bone matrix on the healing of intramembranous bone grafts in rabbit skull defects

A clinical dilemma exists regarding the type of bone that should be used to replace diseased or traumatized osseous tissue. Oral, plastic, and orthopedic surgeons normally implant viable mineralized endochondral (EC) autografts or demineralized EC allografts. A few clinicians have recognized the disadvantages of using EC bone in craniofacial surgery and advocated the replacement of intramembranous (IM) bone with healthy IM bone. However, controversy and uncertainty surround our understanding of these matrices to induce bone formation. Recent studies have advocated the use of other materials with osteoinductive properties, such as demineralized bone matrix (DBM). The proposed delivery system used in this study included IM bone grafts, DBM, and fixation of the IM bone graft. The purpose of this work was to gain further insights into the mechanism of healing of IM bone, in both the presence and the absence of DBM, and to compare the healing of IM bone grafts with that of DBM alone. Critical-sized (10 × 5 mm), full-thickness bony defects in rabbit parietal bone, devoid of periosteum, were filled with IM bone graft (mandible) alone, demineralized cortical bone matrix (DBM) alone, or combined DBM-IM bone graft, or were left unfilled. Histologic changes were examined 14 days later. The IM bone graft healed through IM ossification with no intermediate cartilage stage. DBM and composite DBM-IM healed through an EC ossification with an intermediate cartilage stage. It is hypothesized that the role of the IM graft is to induce neovascularization into the defect site, and that the undifferentiated mesenchymal cells in the perivascular region of the new blood vessels are induced by the bone morphogenetic protein(s) in the DBM into bone-forming cells.published_or_final_versio