Determination and comparison of the bone mineral density of different skeletal regions of female Wistar rats at different ages / 中国比较医学杂志

Objective To provide reference values for bone mineral density(BMD)in different skeletal regions of female Wistar rats at different ages. Methods Thirty SPF female Wistar rats were selected. The BMD of different skeletal regions(skull,upper limbs,thighs,trunk,ribs,pelvis,spine and the whole body)was measured by dual energy X-ray absorptiometry(DXA)at 6,10,12,24 and 30 months of age. The bone mineral densities between different age groups and that of different skeletal regions in the same age groups were compared. Results The BMD of the skull,upper limbs,thighs,trunk,ribs,pelvis, spine and the whole body was increased rapidly with age, and reached a peak at 10 months of age. The BMD of the skull,upper limbs,thighs,trunk,ribs were significantly higher than the whole body BMD in the same month-age group(P< 0.05 or P< 0.01). However,there was no significant difference between the pelvic, spine and the whole body BMD(P> 0.05). There was a significant positive correlation among the three correlations(P<0.01). Conclusions Some background data are provided for the bone biology studies of female Wistar rats, and provide useful supplementary reference for the studies of bone metabolism in rats and their application in biomedicine.

On the osseointegration of zirconia and titanium implants installed at defect site filled with xenograft material / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare zirconia implants with titanium implants from the view point of biomechanical stability and histologic response on osseointegration when those were placed with xenograft materials. MATERIALS AND METHODS: Specimens were divided into two groups; the control group was experimented with eighteen titanium implants which had anodized surface and the experimental group was experimented with eighteen sandblasted zirconia (Y-TZP) implants. At the tibias of six pigs, implants were installed into bone defect sites prepared surgically and treated with resorbable membranes and bovine bone. Two pigs were sacrificed after 1, 4 and 12 weeks respectively. Each implant site was sampled and processed for histologic and histomorphometric analysis. The stability of implants was evaluated with a Periotes(R). And the interfaces between bone and the implant were observed with a scanning electron microscope. RESULTS: In stability analysis there was no significant difference between Periotest values of the control group and the experimental group. In histologic analysis with a light microscope after 4 weeks, there was new bone formation with the resorption of bovine bone and the active synthesis of osteoblasts in both groups. In bone-implant contact percentage there was significant difference between both groups (P<.05). In bone area percentage there was no significant difference between both groups. In analysis of both groups with a scanning electron microscope there was a gap between bone and a surface at 4 weeks and it was filled up with bone formed newly at 12 weeks. CONCLUSION: When accompanied by xenograft using membrane, bone to implant contact percentage of zirconia implants used in this experiment was significantly less than that of the titanium implants by surface treatment of anodic oxidation. So, it is considered that the improvement of zirconia implant is needed through ongoing research on surface treatment methods for its practical use.

Osseointegration of zirconia implant in the tibia of pigs / 대한치과보철학회지

PURPOSE: The purposes of this study were to investigate osseointegration around zirconia implants which had machined or alumina sandblasted surface, and to compare the results with titanium implants. MATERIALS AND METHODS: The study was performed on the tibia of 6 pigs. Three types of implants were investigated: group T-titanium implant, group Z-machined zirconia implant, group ZS-alumina sandblasting treated zirconia implant. Zirconia implants were manufactured from yttria-stabilized tetragonal zirconia polycrystalline (Acucera Inc., Pocheon, Korea). A total of 36 implants were installed in pigs' tibias. After 1, 4 and 12 weeks of healing period, the periotest and the histomorphometric analysis were performed. The data were analyzed using one-way ANOVA and significance was assessed by the Scheffe test (alpha=.05). RESULTS: In the measurement of surface roughness, highest Ra value was measured in group T with significant difference. No significant differences were found among groups regarding Periotest values. After 1 week, in comparison of bone to implant contact (BIC), group Z showed higher value with significant difference. In comparison of bone area (BA), group T and group Z showed higher value with significant difference than group ZS. After 4 weeks, in comparison of BIC, group T showed higher value with significant difference. Comparison of BA showed no significant difference among each implant. After 12 weeks, the highest mean BIC values were found in group T with significant difference. Group ZS showed higher BIC value with significant difference than group Z. In comparison of BA, group T and group ZS showed higher value with significant difference than group Z. CONCLUSION: Zirconia implant showed low levels of osseointegration in this experiment. Modification of surface structure should be taken into consideration in designing zirconia implants to improve the success rate.

Study of the re-osseointegration of implant fixture after mechanical unscrewing / 대한치과보철학회지

PURPOSE: The purpose of this study was to investigate whether the re-osseointegration of the implants that had mechanical unscrewing possibly occurred or not. Furthermore, if it happened, the degree of re-osseointegration was evaluated by comparing with previous osseointegration. MATERIALS AND METHODS: The smooth implant (commercial pure titanium 99%) specimens, whose diameter and length was 3.75 mm, 4 mm, respectively were produced. Two implants were inserted into each tibia of 7 New Zealand female white rabbits weighing at least 3.0 kg. The torque removal force for each implant after 6 weeks of implants placement was measured and included in group I . The torque removal forces were assessed after the fixtures were re-screwed to original position and the subjects were allowed to have 4 more weeks for healing and included in group II. One rabbit was sacrificed after first measurement and produced 4 slide specimens in group I, and two rabbits were sacrificed after 2nd measurement, 7 slide specimens, in group II for histomorphologic investigations. All slide specimens were assessed based on the proportion of BIC (bone-implant contact) as well as CBa (Bone area in the cortical passage) value produced by counting the screw threads embedded in the compact bones under the optical microscopic analysis (x20). Statistical analysis was conducted to evaluate the torque removal force, BIC and CBa between group I and II. RESULTS: As for the torque removal force, the result was 10.8 +/- 3.6 Ncm for group I and 20.2 +/- 9.7 Ncm for group II. Furthermore, the torque removal force of group II increased by 98.1% in average compared to group I (P .05), and RT/BIC and RT/CBa between group I and group II were statistically significant (P < .05). CONCLUSION: It is possible to obtain more substantial re-osseointegration within shorter periods than the period needed for the initial osseointegration in case of iatrogenically unscrewed implants.

Clinical, histologic, and histometric evaluation of implants with microthreaded crest module and SLA surface / 대한치주과학회지

BACKGROUND: Crestal bone loss known as saucerization is a frequently observed phenomenon. Recent studies have shown that implants with micothreaded crest module reduced the force concentration in the crestal region thus resulting in no or reduced crestal bone loss. This study presents a clinical, histologic, and histometric evaluation of implants with microthreaded crest module and SLA surface. METHODS: The implants were placed in the mandible of 5 beagle dogs weighing 10-15kg. Four premolars were bilaterally extracted 8 weeks prior to implant placement. Mucoperiosteal flap was elevated and drilling with increasing diameter was performed under saline irrigation. After countersinking 2 implants were placed in each side resulting in 4 implants per dog. Healing period of 8 weeks was allowed before sacrificing the animals. Histologic preparation was performed for histologic and histometric analysis. Bone to implant contact as well as percentage of bone area inside threads were measured. T-test was used for statistical analysis with pvalue p<0.05. RESULTS: 1. Healing was uneventful without any cover screw exposure. New bone formation around the implants was observed without any inflammatory infiltration. 2. Bone to implant contact in the microthread and thread were 43.90 +/- 20.30 %, and 53.19 +/- 20.97 % respectively. The overall bone to implant contact was 48.54 +/- 20.95 %. 3. Percentage of bone area inside threads were 54.43 +/- 10.39 %, and 38.44 +/- 16.44 % for the microthread and thread respectively. There was statistically significant difference(p<0.05). The overall percentage of bone area inside threads was 46.67 +/- 15.68 %.

Removal Torque and Histometric Evaluations of Implants with Various Area of Hydroxyapatite Coating Placed in the Rabbit Tibia / 대한치주과학회지

BACKGROUND: This study presents a biomechanical and histometric comparison of bone response to implants with various area of hydroxyapatite(HA) coating. METHODS: The implants were placed in the tibia of 10 rabbits weighing 2.5-3.5kg. The control group had a machined surface, the experimental group 1 had 50micrometer thick HA coated in a band form, and the experimental group 2 had 50micrometer thick HA coated on the entire surface. 8 weeks after implantation, the animals were sacrificed. Removal torque was measured and histologic preparation was also performed for histologic and histometric analysis. Bone to implant contact as well as percentage of bone area inside threads were measured. ANOVA post hoc, and t-test were used for statistical analysis with p-value p<0.05. RESULTS: 1. The removal torques were 9.36 +/- 5.64 Ncm, 48.40 +/- 16.66 Ncm, and 82.37 +/- 22.56 Ncm for the control, exp. 1, and exp. 2 group respectively. Statistically significant difference were found among all the groups(p<0.05). 2. Bone to implant contact in the cortical bone were 38.94 +/- 10.9 %, 66.90 +/- 14.1 %, 73.00 +/- 19.4 %, in the marrow bone, 8.30 +/- 5.4 %, 14.59 +/- 5.9 %, 18.54 +/- 11.8 %, and in total, 22.40 +/- 10.1 %, 31.19 +/- 7.5 %, 41.41 +/- 12.2 % for the control, exp.1, and exp. 2 group respectively . In the cortical bone, exp. 1, and exp. 2 group showed statistically significantly higher contact compared to control group. Total contact and in the marrow bone, only exp. 2 group showed statistically significantly higher contact compared to control group(p<0.05). In all the groups significantly higher contact were observed in the cortical bone compared to the marrow bone(p<0.05). 3. Percentage of bone area inside threads in the cortical bone were 55.68 +/- 7.25 %, 55.19 +/- 13.19 %, 57.04 +/- 13.33 %, in the marrow bone, 12.34 +/- 14.61 %, 17.56 +/- 20.04 %, 20.26 +/- 12.83 %, and in total, 30.30 +/- 12.46 %, 31.57 +/- 15.15 %, 34.25 +/- 12.56 % for the control, exp.1, and exp. 2 group respectively. There was no statistical difference among the groups. In all the groups significantly higher bone area were observed in the cortical bone compared to the marrow bone(p<0.05)