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ABSTRACT: We present a new method for replicating the skull and occlusal surface with an accurate physical model that could be used for planning orthognathic surgery. The investigation was made on 6 human skulls, and a polyvinyl splint was fabricated on the dental cast of the maxillary dentition in each case. A cone beam computed tomogram (CBCT) was taken of each skull and a three-dimensional replica produced. The distorted dentition (as a result of magnification errors and streak artefacts) was removed from the three-dimensional model and replaced by new plaster dentition that was fabricated using the polyvinyl splint and a transfer jig replication technique. To verify the accuracy of the method the human skulls and the three dimensional replica model, with the new plaster dentition in situ, were scanned using a laser scanner. The three-dimensional images produced were superimposed to identify the errors associated with the replacement of the distorted occlusal surface with the new plaster dentition. The overall mean error was 0.72 and SD was (0.26)mm. The accuracy of the method encouraged us to use it clinically in a case of pronounced facial asymmetry.
British Journal of Oral and Maxillofacial Surgery 12/2010; 50(1):49-54. · 1.95 Impact Factor
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ABSTRACT: Osteoinductive bone morphogenetic proteins (BMPs) have been used extensively in experimental and clinical orthopaedic research. It is a natural progression for these growth regulators to be tested in the craniofacial region. The aim of this investigation was to analyse the mechanical properties of the sheep mandibles reconstructed using recombinant human osteogenic protein type 1 (rhOP-1). A unilateral 35 mm osteoperiosteal continuity defect was created at the parasymphyseal region of the mandible in six adult sheep. The animals were sacrificed 3 months after surgery and mechanical properties of the regenerated bone at the operated sides (OS) were compared to the corresponding bone at the non-operated side (NOS). The regenerated tissue at the OS were then submitted for histological and histomorphometric analysis. Although all the animals achieved complete bony union, a wide range of mechanical properties was found. The rhOP-1-induced bone achieved a mean of 36% of the strength of the bone at the NOS (P < 0.05). The mean value of the stiffness of the OS was 24% of the NOS (P < 0.05). While half of the samples of the OS had 'weak' mechanical properties (9-25% strength compared to NOS) and a low stiffness (6-18%), the rest showed relatively higher strength (47-63%) and were stiffer (35-47%). Unlike the NOS, the operated sides failed under tensile stresses and cracks initiated at the superior border of the mandible. The wide mechanical variations suggest that further basic bone biology research is needed to provide better understanding of the cellular and molecular events which take place during the process of osteoinduction.
International Journal of Oral and Maxillofacial Surgery 06/2005; 34(3):287-93. · 1.51 Impact Factor
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ABSTRACT: Pressure sore prevalence and incidence were assessed in 275 patients who were admitted to a well-staffed internal medicine ward during a 12-month study period or who were present on day 1. Pressure sore risk was assessed by use of the Braden scale and patients scoring 16 or less were provided with intensive preventive care. During the study period 5.1% (95% confidence interval 2.7-7.8) of 275 patients had pressure sores (prevalence) and 4.4% (1.9-6.9) developed sores (incidence). None of the 239 patients who were assessed as not being at risk developed a sore. 36 patients were assessed as being at risk at some time during the study and 12 of these developed sores despite receiving high-quality preventive care. The results suggest that not all pressure sores can be prevented in severely ill patients. We believe that the 4.4% incidence of sores in this study approaches the current limit of prevention.
Journal of the Royal Society of Medicine 12/1999; 92(11):576-8. · 1.41 Impact Factor
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ABSTRACT: The active and passive behaviour of the extraocular muscles can be investigated by measuring the force that must be applied to rotate the eyeball when the muscles are relaxed (the forced duction test) or the force required to maintain the eyeball stationary while the contralateral eye follows a moving target (the force generation test). Apparatus and test procedures for carrying out both tests are described. Normal values and confidence intervals for the tests have been obtained and the results of muscle entrapment and palsy illustrated.
Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 02/1991; 205(2):101-8. · 1.21 Impact Factor
