Clinical Factors Affecting the Accuracy of Guided Implant Surgery-A Systematic Review and Meta-analysis.

OBJECTIVES: To systematically review the current dental literature regarding clinical accuracy of guided implant surgery and to analyze the involved clinical factors. MATERIAL AND METHODS: PubMed and Cochrane Central Register of Controlled Trials were searched. Meta-analysis and meta-regression analysis were performed. Clinical studies with the following outcome measurements were included: (1) angle deviation, (2) deviation at the entry point, and (3) deviation at the apex. The involved clinical factors were further evaluated. RESULTS: Fourteen clinical studies from 1951 articles initially identified met the inclusion criteria. Meta-regression analysis revealed a mean deviation at the entry point of 1.25 mm (95% confidence interval [CI]: 1.22-1.29), 1.57 mm (95% CI: 1.53-1.62) at the apex, and 4.1° in angle (95% CI: 3.97-4.23). A statistically significant difference (P < .001) was observed in angular deviations between the maxilla and mandible. Partially guided surgery showed a statistically significant greater deviation in angle (P < .001), at the entry point (P < .001), and at the apex (P < .001) compared with totally guided surgery. The outcome of guided surgery with flapless approach indicated significantly more accuracy in angle (P < .001), at the entry point (P < .001), and at apex (P < .001). Significant differences were observed in angular deviation based on the use of fixation screw (P < .001). CONCLUSIONS: The position of guide, guide fixation, type of guide, and flap approach could influence the accuracy of computer-aided implant surgery. A totally guided system using fixation screws with a flapless protocol demonstrated the greatest accuracy. Future clinical research should use a standardized measurement technique for improved accuracy.

Tight Placement of Erich Arch Bar While Avoiding Wire Fatigue Failure.

PURPOSE: To determine the number of wire twists needed to acquire ideal Erich arch bar tightness before wire fatigue failure (fracture) in relation to different distances and angles at which different gauge wires are grasped to provide information to improve the efficiency of arch bar application. MATERIALS AND METHODS: This study mimicked surgical placement of arch bars with 24- and 26-gauge wires. The number of twists to tightness and failure was evaluated when the wire distance between the arch bar and wire holder tip changed (5 vs 10 mm) and when the degree at which the wire was held relative to the tooth axis was changed (45° vs 90°). A wire shearing test also was used to investigate the fatigability of wires tightened under these same conditions. Wires twisted to tightness, past tightness, and after shearing test movements were visualized with electron microscopy. RESULTS: For 24-gauge wire held at 5 mm, 2.6 to 2.8 twists were needed for wire tightness, with failure after 1.7 to 1.9 twists past tightness; for 24-gauge wire held at 10 mm, 4.4 to 4.9 twists produced tightness, with failure after 2.3 to 2.9 twists past tightness. For 26-gauge wire held at 5 mm, 3.3 to 3.5 twists provided tightness, with 1.6 to 1.8 twists past tightness causing failure; for 26-gauge wire held at 10 mm, 5.1 to 5.5 twists produced tightness, with 3.1 to 3.7 twists past tightness causing failure. At a 45° angle, the wire tightened with fewer twists and showed more resistance to failure with twists past tightness compared with 90° using 24- and 26-gauge wires. In contrast, 24-gauge wire held at a 5-mm distance showed the opposite result, with decreased resistance to failure at the 45° angle. However, the differences were not statistically meaningful. Scanning election microscopy showed no wire fatigue for either angle for 26-gauge wire held at a 5-mm distance and twisted to tightness. After overtightening and oscillation, the 90° angle trials showed fatigue, whereas the 45° angle trials did not. CONCLUSIONS: Holding a 24-gauge wire at 45° to the tooth axis is recommended owing to fewer twists to tightness and more resistance to failure. A 5-mm grasping distance is recommended for experienced surgeons owing to fewer twists to tightness, whereas a 10-mm grasping distance is recommended for novice surgeons owing to a greater tolerance for over-twisting before failure.

Knot Security- How is it Affected by Suture Technique, Material, Size, and Number of Throws?

PURPOSE: To measure knot security in relation to different surgical knotting techniques, suture materials, suture sizes, and number of throws commonly used in oral and maxillofacial surgery. MATERIALS AND METHODS: Three surgical tying techniques were tested: square, surgeon's, and sliding knots. Suture materials included chromic gut, nylon, silk, and Vicryl (polyglycolic acid). Suture diameter sizes 3-0, 4-0, and 5-0 were tested. Ten trials were undertaken for each combination of material, size, and technique using 2, 3, 4, 5, and 6 throws (ties). Suture materials were presoaked in 0.9% saline solution for 15 minutes to simulate the environment of the oral cavity. A standard knot-tying force for each throw was applied to each combination. Knot security satisfaction was set from pilot experimental trials at less than 1.8-mm slippage from the center of the knot while testing. The dichotomous outcome of knot slippage (stable or unstable) was analyzed using logistic regression analysis and odds ratios with Tukey-adjusted 95% confidence intervals. RESULTS: Knot security depended on suture technique, material, and number of throws but did not depend on suture size. In general, 4 throws were required for surgeon's and square knots, whereas 5 throws were required for sliding knots. After 5 throws, tying an additional throw did not contribute to knot security. Surgeon's knots were stronger than square knots and sliding knots (P < .0001 and P < .0001). Square knots were stronger than sliding knots (P = .01). Vicryl had the greatest knot security, followed by chromic gut, nylon, and silk. CONCLUSION: This study showed that knot security depends on suture material, tying technique, and number of throws, but is independent of suture size. Surgeon's knot security was greater than that for square and sliding knots when using sutures commonly used in the oral cavity. Vicryl had the greatest knot security and silk had the least. For surgeon's and square knots, at least 4 throws were generally indicated to achieve knot security; for sliding knots, at least 5 throws were generally indicated. Knot security did not increase after 5 throws and 2 throws are never indicated.

A 1-year study of osteoinduction in hydroxyapatite-derived biomaterials in an adult sheep model: part I.

The study presented here investigated hydroxyapatite biomaterials implanted in soft-tissue sites in adult sheep to determine whether these materials are osteoinductive and whether the rate of osteoinduction can be increased by manipulating the composition and porosity of the implants. For the study, 16.8-mm x 5-mm discs were prepared from mixtures of hydroxyapatite and beta-tricalcium phosphate. Five mixtures of hydroxyapatite-ceramic and hydroxyapatite-cement paste forms were studied: 100 percent hydroxyapatite-ceramic (Interpore), 60 percent hydroxyapatite-ceramic, 100 percent hydroxyapatite-cement paste, 60 percent hydroxyapatite-cement paste, and 20 percent hydroxyapatite-cement paste. Biomaterials were implanted in subcutaneous and intramuscular soft-tissue pockets in 10 adult sheep. Cranial bone grafts of equal dimension were implanted as controls. One year after implantation, the volume of all biomaterials and bone grafts was determined from a computed tomographic scan, and porosity and bone formation were determined using backscatter electron microscopy. Cranial bone and the 20 percent hydroxyapatite-cement paste implants demonstrated significant volume reduction in all sites after 1 year (p < 0.001). No significant difference in volume of the remaining four biomaterials was found. There was no significant change in pore size in the ceramic implants (range, 200 to 300 micro) and in the cement-paste implants containing 60 percent hydroxyapatite or more (range, 3 to 5 nm). Pore size in the cement-paste implants containing 20 percent hydroxyapatite increased significantly with resorption of the tricalcium-phosphate component, reaching a maximum of 200 to 300 micro in the periphery, where the greatest tricalcium-phosphate resorption had occurred. Both ceramic biomaterials demonstrated lamellar bone deposition within well-formed haversian systems through the entire depth of the implants, ranging from a mean of 6.6 percent to 11.7 percent. There was minimal bone formation in the cement-paste implants containing 60 percent hydroxyapatite or more. In contrast, cement-paste implants containing 20 percent hydroxyapatite demonstrated up to 10 percent bone replacement, which was greatest in the periphery of the implants where the greatest tricalcium-phosphate resorption had occurred. This study confirms the occurrence of true osteoinduction within hydroxyapatite-derived biomaterials, when examined using backscatter techniques. In this study, the rate of osteoinduction was greatest when a porous architecture was maintained, which was best achieved in ceramic rather than cement-paste forms of hydroxyapatite. Porosity and resultant bone formation in cement-paste implants can be improved by combining hydroxyapatite with a rapidly resorbing component, such as tricalcium phosphate.

Osteogenesis in calvarial defects: contribution of the dura, the pericranium, and the surrounding bone in adult versus infant animals.

Guided bone regeneration is a promising means for reconstructing bone defects in the cranium. The present study was performed to better define those factors that affect osteogenesis in the cranium. The authors studied a single animal model, investigating the contribution of the dura, the pericranium, and the adjacent calvarial bone in the process of calvarial regeneration in both mature and immature animals. Bilateral, 100-mm2, parietal calvariectomies were performed in immature (n = 16) and mature (n = 16) rabbits. Parietal defects were randomized to one of four groups depending on the differential blockade of the dura and/or the pericranium by expanded polytetrafluoroethylene membranes. Animals were humanely killed after 12 weeks, and histometric analysis was performed to quantitate the area of the original bone defect, new bone formation, and new bone density. Bone formation was quantified separately both at the periphery and in the center of the defects. Extrasite bone formation was also quantified both on the dural and on the pericranial sides of the barriers. Bone regeneration was incomplete in all groups over the 12-week study period, indicating that complete bone healing was not observed in any group. The dura was more osteogenic than the pericranium in mature and immature animals, as there was significantly more extrasite bone formed on the dural side in the double expanded polytetrafluoroethylene barrier groups. In both the dural and the double expanded polytetrafluoroethylene barrier groups, dural bone production was significantly greater in immature compared with mature animals. The dura appeared to be the source of central new bone, because dural blockade in the dural and double expanded polytetrafluoroethylene groups resulted in a significant decrease in central bone density in both mature and immature animals. Paradoxically, isolation of the pericranium in mature animals resulted in a significant reduction in total new bone area, whereas pericranial contact appeared to enhance peripheral new bone formation, with the control group having the greatest total new bone area. The present study establishes a model to quantitatively study the process of bone regeneration in calvarial defects and highlights differences in the contribution of the dura and pericranium to calvarial bone regeneration between infant and adult animals. On the basis of these findings, the authors propose that subsequent studies in which permeability of the expanded polytetrafluoroethylene membranes is altered to permit migration of osteoinductive proteins into the defect while blocking prolapse of adjacent soft tissues may help to make guided bone regeneration a realistic alternative for the repair of cranial defects.

Regulation of osteogenesis and survival within bone grafts to the calvaria: the effect of the dura versus the pericranium.

BACKGROUND: The present study evaluates the isolated role of dura and pericranium in the survival of fresh (osteoblasts viable) and frozen (osteoblasts nonviable) bone grafts. METHODS: Bilateral craniectomies were performed in 48 mature rabbits. On one side, bone was replaced immediately; on the contralateral side, it was flash-frozen before replacement. Animals were randomized into four groups by placement of Silastic barriers adjacent to bone grafts, as follows: (1) control (no barriers); (2) dural barrier; (3) pericranial barrier; and (4) double (dural and pericranial) barriers. Fluorescein labels were injected at specified intervals, with animals euthanized after 1 or 10 weeks. RESULTS: After 1 week, fresh grafts without dural barriers demonstrated greater fluorescein labeling on the dural than on the pericranial surface (p < 0.05); in contrast, fresh grafts without pericranial barriers had no statistical difference in fluorescein labeling between pericranial and dural surfaces. After 10 weeks, the new bone area was greater in fresh than in frozen grafts (p < 0.05). Total new bone area and dural-side new bone were greater in grafts without dural barriers (p < 0.001); this was not seen in grafts without pericranial barriers. Pericranial new bone was greatest in fresh grafts without a pericranial barrier (p < 0.001); this was not seen in frozen grafts. CONCLUSIONS: The dura and pericranium each contributed to osteogenesis, although dural contact was more effective. Maintenance of dural contact enhanced osteogenesis through the entire graft, whereas pericranial contact enhanced osteogenesis only on the pericranial surface of fresh grafts. These data suggest dura is largely responsible for cranial graft survival.

Synthesis and biological evaluation of decavanadate Na4Co(H2O)6V10O28.18H2O.

We have reported the synthesis and biological evaluation of a decavanadate Na(4)Co(H(2)O)(6)V(10)O(28).18H(2)O (CoV(10)) designed as a potential antitumoral agent. The human cancer cell lines SMMC-7721 (liver cancer) and SK-OV-3 (ovary cancer) were tested for their viability by the MTT method in vitro, which showed that the compound exhibited a remarkable activity against two cell lines with IC(50) values smaller than 0.24 microg/mL, 0.32 microg/mL, respectively. CoV(10) showed the tumor growth suppression for Hep-A-22 (mice liver cancer) in tumor bearing mice in vivo. In addition, using flow cytometry analysis, the ratio of apoptotic cells was up to 8.33% with treatment of CoV(10) at 1.56 microg/mL after 30 min, suggesting that the antitumoral activity of CoV(10) comes from the activation of the apoptotic pathway.

A 1-year study of hydroxyapatite-derived biomaterials in an adult sheep model: III. Comparison with autogenous bone graft for facial augmentation.

BACKGROUND: The present study investigates onlay bone grafts and implants in a large-animal (sheep) model to determine whether there are composite biomaterials that can maximize long-term facial augmentation when compared with conventional bone grafts. METHODS: Facial augmentation was performed in 10 adult sheep. First, 16.8 x 5-mm disks were prepared from autogenous calvarial bone, hydroxyapatite ceramic, ceramic composite of 60 percent hydroxyapatite and 40 percent beta-tricalcium phosphate (60 percent hydroxyapatite ceramic), and hydroxyapatite cement paste. Facial recipient sites were the body of the mandible (depository), the maxillary region (resorptive), and the frontal bone (depository). The volume of all bone grafts and implants was determined using computed tomographic scans, and the amount of bone formation was measured by means of backscatter electron microscopy 1 year postimplantation. RESULTS: Cranial bone graft demonstrated a highly significant reduction in volume in all sites studied. Other than a slight decrease in volume of hydroxyapatite cement paste disks applied to the maxillary region, there was no significant change in volume of the biomaterials implanted in any of the remaining recipient sites. Bone replacement was greatest in hydroxyapatite ceramic (23.9 percent) followed by 60 percent hydroxyapatite ceramic (16.4 percent) and least with hydroxyapatite cement paste (4.2 percent). Minimal differences in bone replacement were noted between recipient sites. CONCLUSIONS: This study demonstrates that the volume maintenance of onlay hydroxyapatite composites is highly predictable, whereas that of cranial bone graft is unpredictable. Minimal differences were seen in bone replacement within biomaterials between "depository" and "resorptive" facial recipient sites. Ceramic forms of onlay hydroxyapatite implants demonstrated significantly greater bone replacement than did the cement paste forms of hydroxyapatite.

A 1-year study of osteoinduction in hydroxyapatite-derived biomaterials in an adult sheep model: part II. Bioengineering implants to optimize bone replacement in reconstruction of cranial defects.

The present study investigated hydroxyapatite biomaterials implanted in critical-size defects in the calvaria of adult sheep to determine the optimal bioengineering of hydroxyapatite composites to facilitate bone ingrowth into these materials. Five calvarial defects measuring 16.8 mm in diameter were made in each of 10 adult sheep. Three defects were filled with cement paste composites of hydroxyapatite and beta-tricalcium phosphate as follows: (1) 100 percent hydroxyapatite-cement paste, (2) 60 percent hydroxyapatite-cement paste, and (3) 20 percent hydroxyapatite-cement paste. One defect was filled with a ceramic composite containing 60 percent hydroxyapatite-ceramic, and the fifth defect remained unfilled. One year after implantation, the volume of all biomaterials was determined by computed tomography, and porosity and bone replacement were determined using backscatter electron microscopy. Computed tomography-based volumetric assessment 1 year after implantation demonstrated that none of the unfilled cranial defects closed over the 1-year period, confirming that these were critical-size defects. There was a significant increase in volume in both the cement paste and ceramic implants containing 60 percent hydroxyapatite (p < 0.01). There was no significant change in volume of the remaining cement paste biomaterials. Analysis of specimens by backscatter electron microscopy demonstrated mean bone replacement of 4.8 +/- 1.4 percent (mean +/- SEM) in 100 percent hydroxyapatite-cement paste, 11.2 +/- 2.3 percent in 60 percent hydroxyapatite-cement paste, and 28.5 +/- 4.5 percent in 20 percent hydroxyapatite-cement paste. There was an inverse correlation between the concentration of hydroxyapatite and the amount of bone replacement in the cement paste for each composite tested (p < 0.01). Bone replacement in 60 percent hydroxyapatite-ceramic composite (13.6 +/- 2.0 percent) was not significantly different from that in 60 percent hydroxyapatite-cement paste. Of note is that the ceramic composite contained macropores (200 to 300 microm) that did not change in size over the 1-year period. All cement paste composites initially contained micropores (3 to 5 nm), which remained unchanged in 100 percent hydroxyapatite-cement paste. Cement paste implants containing increased tricalcium phosphate demonstrated a corresponding increase in macropores following resorption of the tricalcium phosphate component. Bone replacement occurred within the macropores of these implants. In conclusion, there was no significant bone ingrowth into pure hydroxyapatite-cement paste (Bone Source, Stryker-Leibinger Inc., Dallas, Texas) in the present study. The introduction of macropores in a biomaterial can optimize bone ingrowth for reconstruction of critical-size defects in calvaria. This was demonstrated in both the ceramic composite of hydroxyapatite tested and the cement paste composites of hydroxyapatite by increasing the composition of a rapidly resorbing component such as beta-tricalcium phosphate.