Torque removal force for osseointegrated implants--two experimental studies.

OBJECTIVE: To introduce a rabbit-based model for testing the torque removal force (TRF) of implants and to compare the TRF of a series of titanium implants. METHODS: Two experiments were performed at the University of the Witwatersrand. In the first, a Swedish- (SSM-N) or a South African-manufactured (SSM-S) implant was implanted into the tibiae of 12 rabbits and the TRF measured at 1, 3 and 6 months. In the second experiment, the TRF of 4 South African-manufactured titanium implants in the tibia or femur of 32 rabbits were compared at 3 and 6 weeks. The implants were: 1 threaded machined (SSM-S), and 3 surface-enhanced--1 threaded (SLA), 1 threaded tapered (MTT) and 1 pitted (RI). RESULTS: In experiment 1, TRF increased significantly with time (p<0.05) but there was no significant difference between TRF for the South African and Swedish machined-surface implant types. In experiment 2, the TRF of the MTT implant was significantly greater (p<0.0001) than the other 3 types, which did not differ significantly from each other. Time had no significant effect. CONCLUSION: In an internationally used rabbit-based model, South African and Swedish machined-surface titanium implants were equivalent; surface-enhanced implants produced higher TRF, and a tapered implant showed the highest TRF.

Postoperative skeletal stability following clockwise and counter-clockwise rotation of the maxillomandibular complex compared to conventional orthognathic treatment.

Rotation of the maxillomandibular complex (MMC) and the consequent alteration of the occlusal plane (OP) angulation is a well documented orthognathic surgical design. This study presents a comparison of the long-term postoperative skeletal stability following clockwise rotation (CR), and counter-clockwise rotation (CCR) of the MMC with the skeletal stability of patients treated according to conventional treatment planning principles. The long-term postoperative skeletal stability of the (CR) group and the (CCR) group of patients were found to compare favorably with the group of patients treated by conventional treatment (CT) planning. The long-term postoperative stability of all three groups also compared well with skeletal stability reported in the literature following double jaw surgery.

Combined treatment of arteriovenous malformations by transarterial microembolization and surgery.

An arteriovenous malformation is defined as a congenital lesion of dysplastic vascular origin with large feeding arteries causing decreased vascular resistance. Previously, initial attempts toward treatment by complete excision of the vascular mass were complicated by hemorrhage and infection. Cardiac failure and abnormal growth may result from the shunted blood flow. With the advancement of angiography, more defined study of the arteriovenous anomaly can be identified and a reduction of risk during treatment can be promised. Three cases of extensive arteriovenous malformations are presented. Each has been successfully treated by combining radiologic microembolization followed by surgical extirpation of the vascular mass, without complication.

The effect of burn wound size on resting energy expenditure.

Numerous formulas have been used to estimate the calorie requirements of hypermetabolic burned patients. With the recent development of instrumentation for indirect calorimetric measurements, questions have been raised concerning the validity and accuracy of the early equations. Because metabolic rate decreases during the course of wound healing, we attempted to determine the magnitude of hypermetabolism and the accuracy of the Curreri formula in patients with various wound sizes. Twenty-eight patients with a mean initial burn size of 29% body surface area (BSA) had measurements of resting energy expenditure (REE) at regular intervals during their postburn course. Concomitantly, basal energy expenditure (BEE) was calculated from the Harris-Benedict equation; and the predicted energy needs were calculated using the Curreri formula adjusted for current wound size (ACEE). Three significantly different burn size (%BSA) groups were identified: Group 1, 1-10%; Group 2, 11-30%; and Group 3, 31-60% BSA. The measured REE was 27, 35, and 50% greater than the BEE in Groups 1, 2, and 3, respectively (p less than 0.001). The ACEE underestimated REE by 7% in Group 1, and overestimated REE by 13 and 35% in Groups 2 and 3, respectively (p less than 0.001). Resting energy expenditure should be measured at regular intervals in individuals with open burn wounds greater than 10% BSA in order to adjust nutritional support appropriately.