RESUMEN
BACKGROUND: The present study was conducted to quantify the relationships between bone drilling process parameters (i.e., feed rate, resting time, exit rate, and drill bit diameter) and drilling outcome parameters (i.e., thrust force and maximum temperature). METHODS: This study utilized 10-cm cortical bovine samples to evaluate the effects of four independent parameters, including drill bit diameters, six different feed rates, three various resting times, and three different exit rates on thrust force and maximum temperature (MT). A total of 28 stainless steel orthopedic drill bits with a diameter of 2.5 and 3.2 mm, as well as an orthopedic handpiece were attached to the 500N load cell and an accurate linear variable differential transformer to obtain forces. Moreover, two k-type thermocouples were utilized to record the temperature-time curve near the drilling site. The data were analyzed using the two-way analysis of variance and post hoc Tukey-Kramer Honest test. RESULTS: Maximum thrust force (MTF) decreased by almost 230% as the drill bit diameter increased from 2.5 to 3.2 mm in the lowest feed rate. The MTF showed a 335% increase, whereas a decrease of 69% was observed as the feed rates rose from 0.5 to 3 mm/sec. Moreover, the MT decreased to 67% with an increasing exit rate from 1 to 3 mm/sec. Furthermore, a slight increase was observed in MT when the resting time increased from 0 to 2 seconds (P>0.05). CONCLUSION: The desired drilling is drilling with lower thrust force and lower final temperature of bone. Increasing feed rate can cause an increase and decline in thrust force and final temperature, respectively. The highest rates of MT were 0.5 and 1 mm/min, and the optimum feed rate would be 1.5 mm/min due to the averaged thrust force. Moreover, the resting time had no significant effects on the final temperature. Attentions to resting time would be useful to provide a more accurate, efficient, and uniform drill hole.
RESUMEN
PURPOSE: In addition to lipid-lowering properties, statins have been suggested to affect bone turnover by increasing the osteoblastic bone formation and blocking the osteoclastogenesis. However, there are many controversial reports regarding the beneficial effect of statins on osteoporosis. In this study, we investigated the therapeutic effects of the most important lipophilic statins administered orally for 60 days to the ovariectomized (OVX) female Sprague-Dawley rats and compared the effects on different harvested trabecular and compact bones. METHODS: Thirty female rats were divided into five equal groups including the normal rats, untreated OVX rats (negative control), and the OVX rats treated with atorvastatin (20 mg/kg/day), simvastatin (25 mg/kg/day), and lovastatin (20 mg/kg/day). The osteoporotic animals were treated daily for 60 days and euthanized at the end of experiments. The effectiveness of these treatments was evaluated by biomechanical testing, histopathologic, histomorphometric, micro-CT scan, real-time PCR, and serum biochemical analysis. Moreover, the hepatotoxicity and rhabdomyolysis related with these treatments were assessed by biochemistry analysis and histopathological evaluation. RESULTS: The results and statistical analysis showed that systemic delivery of simvastatin and lovastatin significantly increased serum calcium level, expression of osteogenic genes, bone mineral density (BMD), and biomechanical properties in comparison to the untreated OVX rats, especially in trabecular bones (P < 0.05). The results of different analysis also indicated that there was no statistical difference between the atorvastatin-treated animals and the negative control. Among all treatments, only atorvastatin showed an evident hepatotoxicity and myopathy. CONCLUSIONS: It was concluded that the lovastatin and simvastatin efficiently ameliorated the OVX-induced osteoporosis. Moreover, the simvastatin-treated animals showed more resemblance to the normal group in terms of BMD, expression of osteogenic genes, serum biochemical parameters, histomorphometric findings, and biomechanical performance with no significant side-effects.
