Biomedical subjects
Publications and source records attributed to R K Ow.
A fractured apical fragment of the resilient intramobile element within the IMZ dental implant cylinder is difficult to remove. The continued usefulness of the implant will be compromised if the fractured intramobile element is not removed. Two methods of retrieving the apical fragment without causing damage to the internal threads of the implant cylinder are described.
A study was made of 28 dentulous Chinese Singaporean adults, using lateral skull radiographs. Various craniofacial reference lines and their relations to the maxillary occlusal line were analyzed. The orientation of the natural occlusal line in Chinese adults differed significantly from Swedish white adults. The Frankfort horizontal line in particular was considered disadvantageous as a clinical reference plane largely because of the acknowledged variation of its inclination between Chinese Singaporean and Swedish white adults. The shallow anatomic cant of the maxillary occlusal line in the Chinese patient could be misrepresented by a steep mechanical inclination on the articulator.
Prosthetic restoration of a facial defect involving the loss of an eye and associated orbital tissues may be restricted by incorrect orientation of the prosthesis if the reconstructed tissue bed is uniform and without distinctive orbital landmarks. A surgically grafted eyelid is useful in this situation. The lower eyelid graft serves to provide an anatomical guide with which to position the ocular component of the orbital prosthesis in relation to its established visual axis. This assists the subsequent orientation of the adjoining tissue portion of the orbital prosthesis, contributing to a well-positioned and cosmetically pleasing result.
A study was made of 28 dentulous Chinese (Singaporean) adults by using lateral skull radiographs. The dimensions of the maxillae and various craniofacial reference lines related to prosthodontic use were analyzed. The craniofacial reference angles that reflect the vertical height and horizontal depth of the maxillae in Chinese adults differed significantly from the norms obtained in a white North American adult population. By comparison, Chinese adults have a vertically high and horizontally receded upper face that could cause planes such as the Frankfort horizontal plane or an arbitrary axis-orbitale plane to assume a steeper anterior inclination, thus modifying the mechanical inclination of the maxillary cast and occlusal plane on the articulator.
Treatment for 10 female patients having craniomandibular disorders of neuromuscular origin showed a reduction in dysfunctional symptoms and improvement in their condition. In response to treatment, a standardized recording method was used to measure alterations to bite force values. In about 60 percent of categories representing various positions in the dental arch from which maximal and submaximal biting forces were measured, there was significant variation between replicate registrations. This persisted after treatment, indicating some loss of sensory acuity for fine bite-force adjustments in these patients. Discriminatory ability for large force adjustments was not, however, observed to be affected. Bite force values showed considerable fluctuation both before and after treatment. The lack of substantial increase in force values after a reduction in muscular dysfunction with treatment appears to suggest that an inhibitory mechanism controlling jaw-closing activity and pressure persists as a protective reflex for these patients.
A case of extensive scarring of the floor of the mouth mucosa is reported. Its unusual position and possible association with keloid formation of the skin is discussed.
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The main purpose of the study was to evaluate the pattern of response of an identified subgroup of patients having clinically diagnosed myofascial pain dysfunction of the stomatognathic system to conservative methods of treatment. 10 affected female adults fulfilling the criterion for selection, were allowed to undergo a closely-monitored treatment regime and evaluated on two occasions, employing accepted clinical indices for gauging the severity of the condition. The patients had clinical features of dysfunction graded as moderately severe to very severe. Evaluation showed that severe symptoms were ameliorated for 4 subjects thus affected. Moderate to marked improvement in condition was observed in 6 cases out of the 10 subjects investigated over the 5 to 8 weeks of therapy. The patients showed an encouraging interim response to treatment and their prognosis in general appeared fairly good.
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Different quantities and sizes of peanuts were offered to six human subjects for mastication at two or three experimental sessions during which jaw movements and chewing cycle duration were measured. The amplitude of vertical movement and cycle duration depended on the position of a chew in a sequence of chews (masticatory sequence). Cycle duration also depended on the position of a given masticatory sequence during the first experimental session, the earlier sequences tending to be longer. Lateral jaw movements fluctuated about a reasonably constant value during a sequence and were unaffected by different food inputs. The amplitude of vertical movements increased markedly with an increase in food weight but was unaffected by change in the initial food particle size. These results were analyzed in the light of previous reports on the comminution of peanuts. It is hypothesized that observed jaw movements were unrelated to food particle size but that the amplitude of each vertical movement depended on the volume of food that was broken by the teeth during the next closing stroke. This food volume was provided and selected by bulk movements of the tongue during the preceding jaw opening.
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The purpose of constructing prosthesis to restore post-surgical deformities of the jaws and the face is to enable such patients to cope better with the difficult process of rehabilitation. Patients with post-surgical maxillofacial defects are presented in this article to illustrate how prosthodontic restoration could improve their functional or cosmetic disability.