The Effects of Defect Type and Depth, and Measurement Direction on the Implant Stability Quotient Value.

The purpose of this study was to evaluate the effect of defect type and depth as well as measurement direction on implant stability in an ex vivo peri-implant bovine rib bone model. Six kinds of defects (3-wall 2.5 mm, 3-wall 5 mm, 1-wall 2.5 mm, 1-wall 5 mm, circumferential 2.5 mm, circumferential 5 mm), and control (no defect) were prepared in 14 bovine rib bones. A total of 84 defects and 14 controls were created. The same type and size of implants (4 × 10 mm) were placed in each group. The thickness of cortical bone and the insertion torque were measured for each defect, and the implant stability quotient (ISQ) value was measured 3 times from 4 different directions. The thickness of cortical bone ranged from 2.71-3.18 mm. Insertion torque decreased as the defect size increased. As the defect size for the same defect depth increased, the ISQ value decreased (P < .001). There were significant differences between the ISQ values obtained with different measurement directions only between the control and 3-wall 5 mm defect (P < .0001). The ISQ value opposite to the defect direction was higher than that in the defect direction in all 3 directions of the 3-wall and 1-wall 5 mm defects. ISQ values were influenced by defect type and depth. Loss of cortical bone reduced the stability of implants and reduced the ISQ value. Measurement direction also influenced ISQ values.

Bone cement grafting increases implant primary stability in circumferential cortical bone defects.

PURPOSE: Implant beds with an insufficient amount of cortical bone or a loss of cortical bone can result in the initial instability of a dental implant. Thus, the objective of this study was to evaluate the effect of bone cement grafting on implant initial stability in areas with insufficient cortical bone. METHODS: Two different circumferential defect depths (2.5 mm and 5 mm) and a control (no defect) were prepared in six bovine rib bones. Fourteen implants of the same type and size (4 mm×10 mm) were placed in each group. The thickness of the cortical bone was measured for each defect. After the implant stability quotient (ISQ) values were measured three times in four different directions, bone cement was grafted to increase the primary stability of the otherwise unstable implant. After grafting, the ISQ values were measured again. RESULTS: As defect depth increased, the ISQ value decreased. In the controls, the ISQ value was 85.45±3.36 (mean±standard deviation). In circumferential 2.5-mm and 5-mm defect groups, the ISQ values were 69.42±7.06 and 57.43±6.87, respectively, before grafting. These three values were significantly different (P<0.001). After grafting the bone cement, the ISQ values significantly increased to 73.72±8.00 and 67.88±10.09 in the 2.5-mm and 5.0-mm defect groups, respectively (P<0.05 and P<0.001). The ISQ value increased to more than double that before grafting in the circumferential 5-mm defect group. The ISQ values did not significantly differ when measured in any of the four directions. CONCLUSIONS: The use of bone cement remarkably increased the stability of the implant that otherwise had an insufficient level of stability at placement, which was caused by insufficient cortical bone volume.

Human gingival fibroblast (HGF-1) attachment and proliferation on several abutment materials with various colors.

PURPOSE: An implant abutment should be soft tissue-compatible and resistant to plaque accumulation, and it is preferable for an implant abutment to have color harmony with the surrounding tissues. This study aimed to compare the in vitro fibroblast cell attachment and proliferation on several abutment materials of different colors. MATERIALS AND METHODS: A total of 240 specimens in 6 experimental groups were used: titanium alloy (SM [smooth machined]; gray), cobalt-chrome-molybdenum alloy (CCM; gray), titanium nitride-coated titanium (TiN; yellow), anodic-oxidized titanium (AO; dark pink), composite resin-coated titanium (R; white), and zirconia (Zr; white). The culture plate surface was employed as a control (C). The surface roughness (Sa), developed interfacial area ratio (Sdr), and water contact angle (WCA) were measured. The human gingival fibroblast (HGF-1) attachment and proliferation at the third and seventh days were observed. RESULTS: Sa values of all experimental groups were < 0.5 µm. Sdr values were between 5% and 8%, except for the Zr group (0.06%). WCA of all groups was greater than 40 degrees. More HGF-1 cells attached on the surfaces of the SM, TiN, and Zr groups than the C group, and the least number of cells were observed on the CCM group (P < .001). On the third day of proliferation, the C group showed significantly greater proliferation than all experimental groups (P < .001). On the seventh day of proliferation, the TiN, AO, Zr, and C groups exhibited twice the number of cells compared to the rest of the groups (P < .001). CONCLUSION: Within the limitations of this study, zirconia abutments would be the best choice in the anterior region. Titanium nitride-coated titanium alloy abutments or anodic-oxidized titanium alloy abutments might also be good choices in areas of esthetic challenge or under high occlusal loads.

Location of maxillary intraosseous vascular anastomosis based on the tooth position and height of the residual alveolar bone: computed tomographic analysis.

PURPOSE: The aims of this study were to measure the distance of the intraosseous vascular anastomosis in the anterolateral wall of the maxillary sinus from different reference points, and to correlate the location of the intraosseous vascular anastomosis with the tooth position and the residual bone height of the maxilla. METHODS: Computed tomography (CT) images were taken from 283 patients undergoing dental implants placement in the posterior maxilla. Three horizontal lines were drawn at the ridge crest, maxillary sinus floor, and the position of the anastomosis. A vertical second line at the center of each tooth was drawn perpendicular to the horizontal lines. The distance from the ridge crest to the maxillary sinus floor and the distance from the maxillary sinus floor to the bony canal were measured from the intersections of the horizontal and vertical lines. The residual alveolar bone height was used to categorize three groups: group 1,<4 mm; group 2, between 4 and 8 mm; and group 3, >8 mm. RESULTS: The residual bone height values of different tooth positions were significantly different (P=0.0002). The distance from the maxillary sinus floor to the intraosseous vascular anastomosis was significantly different between groups 1 and 3 (P=0.0039). At the molar sites, a moderate negative correlation was found between the residual bone height and the distance from the maxillary sinus floor to the intraosseous anastomosis. The distances of the alveolar ridge crest and the maxillary sinus from the intraosseous vascular anastomosis were not significantly different between sexes. CONCLUSIONS: Within the limitations of this study, sites with a higher residual bone height in the molar regions were at a relatively high risk of artery damage during window osteotomy preparation; therefore, we recommend taking more precautions when using a lateral approach for sinus elevation.

The effect of non-resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs.

OBJECTIVE: For successful implant treatment in the esthetic area, stable hard tissue and soft tissue are very important. At the buccal side without buccal bone defects, prophylactic guided bone regeneration (GBR) with bone substitute was frequently used for achieving thick buccal bone. The aim of this study was to evaluate the effect of GBR using a non-resorbable membrane in an immediate implant site without bone defects. MATERIAL AND METHODS: Immediate implants were placed into the mandibles of four mongrel dogs. In the experimental group (TM group), a non-resorbable membrane was placed and fixed onto the buccal bone plate around the implant. In the control group, the implants were placed without membrane coverage. After 12 weeks, the dogs were sacrificed and histological specimens were prepared. The vertical distances from the smooth-rough surface interface (SRI) to the gingiva, the first-bone contact, and the bone crest were measured on the buccal and lingual sides. The horizontal thicknesses of the gingiva and bone at 0, 1, 2, and 3 mm below the SRI were measured. RESULTS: In the TM group, first-bone contact on the buccal side was more coronally positioned approximately 0.8 mm than the control group (P=0.041). The buccal bone thickness of the TM group was well preserved and there was no difference between the buccal and lingual sides. Comparing the control group, implants of the TM group had 1 mm thicker buccal bone (P=0.0051 at bone 1 mm level, P=0.002 at bone 2 mm level). In the control group, buccal bone loss was observed and buccal bone was about 1 mm thinner than the lingual bone (P<0.05). CONCLUSIONS: GBR with a non-resorbable membrane and no bone graft substitute could help to preserve buccal bone thickness on the immediate implant site without defects.

Factors influencing the outcome of root-resection therapy in molars: a 10-year retrospective study.

BACKGROUND: Root resection is one treatment option for preserving molars with furcation involvement. This study evaluated the prognosis of root-resection therapy retrospectively and examined the factors influencing the survival rate of resected molars. METHODS: Root-resection therapy was performed on 691 molars in 579 patients. The associated factors were examined from 342 of 402 molars that had been followed up for >1 year. Survival analysis was used to statistically analyze the factors. RESULTS: Over the past 10 years, 102 of 342 cases (29.8%) failed. The factors were classified into four groups and analyzed to determine their influence on the survival rate of the resected molars. Regarding the resection-related factors, the molars resected because of periodontal problems had a higher survival rate than those resected because of non-periodontal problems (tooth fracture, dental caries, and endodontic problems; P = 0.0097). Patient- and tooth-related factors had no effect on the survival rates. Among the site-related factors, only the amount of bone support of the remaining roots at the time of surgery had a significant effect on the survival rate in the group of molars with periodontal problems (P = 0.0269). CONCLUSIONS: Root resection to treat periodontal problems had a better prognosis than for non-periodontal problems. To achieve a good result, it was important that the remaining roots had >50% bone support. This guideline may help to improve the predictability of root-resection therapy.

Immediate implant placement into infected and noninfected extraction sockets: a pilot study.

OBJECTIVE: This study compared the osseointegration of immediate implants in dogs in infection-free sites and in sites with periradicular lesions which were removed by simulated periradicular surgery. STUDY DESIGN: Periradicular surgeries were performed to remove intentionally induced periradicular lesions, followed by teeth extraction and immediate implant placement with (experimental group 1) or without (experimental group 2) membranes. In the control group, implants were placed at healthy extraction sockets. After 12 weeks, the animals were killed and the results of histomorphometric study were analyzed by Kruskal-Wallis test. RESULTS: Both the control and the experimental implants were clinically acceptable. The control group showed significantly higher bone-implant contact (BIC; 76.03 +/- 7.98%) than the experimental groups 1 (59.55 +/- 14.21%) and 2 (48.62 +/- 20.22%) (P < .05). CONCLUSIONS: Despite the lower BIC of the experimental groups, this pilot study showed the possibility that immediate implant placement might be successful in extraction sockets with periradicular lesions. Further studies with larger sample sizes are required.

Relationship between implant stability measured by resonance frequency analysis (RFA) and bone loss during early healing period.

OBJECTIVE: The aim of this study was to monitor the changes in the stability-related bone loss during the early healing period. STUDY DESIGN: A total of 43 implants were installed in 19 patients, and their stability was measured by resonance frequency analysis (RFA) at the time of surgery and once per week for 12 weeks. A total of 32 implants had radiographs taken at the placement of implant and 4, 8, and 12 weeks postoperatively. The data for gender, bone density, different surgery protocols, and bone loss around implant were analyzed. RESULTS: The mean implant stability quotient values were not changed during the healing period. The marginal bone losses at 12 weeks were 1.28 +/- 0.51 mm and 1.32 +/- 0.57 mm on the mesial and distal sides, respectively. CONCLUSIONS: The implant stability in normal and hard bone density did not change with time, and there was no correlation between the marginal bone loss and the change of implant stability.

Bone reaction to bovine hydroxyapatite for maxillary sinus floor augmentation: histologic results in humans.

This study was designed to examine the sequential progress of healing, at two different time intervals, following delayed sinus augmentation using bovine hydroxyapatite (BHA) as the sole grafting material. Fourteen pairs of bone biopsies were taken from 10 patients after 6 and 12 months of healing, respectively. The biopsy specimens were examined histologically and histomorphometrically. The bone that was formed following sinus augmentation with BHA increased and matured over time up to 12 months after grafting; meanwhile, no overt signs of resorption of BHA were visible within the study period.