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Biomedical subjects

J P Coffey

Publications and source records attributed to J P Coffey.

7 recordsLinked to original sources
PubMed1989

A preliminary study of the effects of tooth guidance on working-side condylar movement.

Clinical observations have indicated that lateral working-side tooth contacts can produce a posterior shift of the working-side condyle, resulting in pain in the temporomandibular joint. This study examined the influence of lateral retrusive and lateral protrusive tooth guidance on the movements of working condyles of the lateral pole. Four patients with lateral retrusive natural tooth contacts and four patients with lateral protrusive natural tooth contacts were studied. Movement of the lateral pole of the working condyle was recorded under the following conditions: (1) natural teeth in contact, (2) wearing of a mandibular acrylic resin splint that created lateral protrusive or lateral retrusive tooth guidance, and (3) a central bearing screw and bearing plate separating the teeth. The results indicated that the condition of the patient's temporomandibular joints was a crucial factor in consistency of condylar tracings. Condylar tracings from patients with temporomandibular joint condyle-disk lacking coordination were inconsistent and unreproducible. Consistent, reproducible tracings for patients without condyle-disk disorders indicated that lateral retrusive guidance can cause a more posterior pathway of the lateral pole of the working condyle than lateral protrusive guidance. Future studies are necessary to establish the relationship between lateral tooth guidance and temporomandibular disorders.

Adult↗
PubMed1989

Human bite force discrimination using specific maxillary and mandibular teeth.

The purpose of this study was to determine whether performance differences existed in subjects' self-generated bite force discrimination ability using maxillary and mandibular central incisors, canines, premolars and first molars. Two separate studies were conducted: (i) to assess whether performance differences existed in subjects' bite force discrimination ability using central incisors and premolars; (ii) to compare subjects' performance on bite force discrimination using central incisors, canines and first molars. Assessment of bite force was measured using a specially designed strain gauge scale allowing subjects to visually monitor when their biting force equalled a preset resistance. Resistance forces of 500, 1000 and 3000 g were selected as standards. Subjects were presented with a series of paired resistance settings, one at a time, the first of each pair being the standard and the second being the comparator setting of a predetermined amount. This paired-comparisons procedure was continued until the subjects' difference limen (DL) value (the threshold of discrimination between two forces) could be established. The first study revealed no significant (P greater than 0.05) overall difference in subjects' bite force discrimination ability relative to specific teeth. In contrast, in the second study a significant difference (P less than 0.05) was identified in subjects' performance relative to specific teeth; subjects' performed better using central incisors compared to first molars. In both studies, subjects' performance was significantly better (P less than 0.05) using the 500 g standard compared to the 3000 g standard in the first study, and compared to the 1000 g standard in the second study. No significant differences (P greater than 0.05) were observed between the performance of males and females in either study.

Adult↗
PubMedDate not supplied

Elongation and preload stress in dental implant abutment screws.

A common problem associated with dental implant restorations is loosening of screws that retain the prosthesis to the implant. A method was developed to determine initial preload on UCLA-type abutment screws by measuring elongation after applying known tightening torques with a digital torque gauge. Loosening torque was also measured after tightening to 32 N-cm torque for gold alloy abutment screws and 20 N-cm for titanium abutment screws. Gold alloy and titanium abutment screws were each used to secure a gold UCLA hexed abutment to a titanium implant. Stresses and forces were calculated from the elongation measurements for three regions of each screw. Elongation of the screws after applying the manufacturer's recommended tightening torques were within the elastic range. Induced stresses were 57.5% and 56% of the yield strengths for gold alloy and titanium, respectively. Tightening of screws beyond recommended levels may be possible without producing plastic deformation. At manufacturer's recommended torques, mean preload was 468.2 (+/- 57.9) N using gold alloy screws and 381.5 (+/- 72.9) N with titanium screws.

Dental Abutments↗