Yang-Jin Yi

Evaluation of peri-implant tissue response according to the presence of keratinized mucosa.

OBJECTIVES The purpose of this study was to evaluate the responses of peri-implant tissue in the presence of keratinized mucosa. STUDY DESIGN A total of 276 implants were placed in 100 patients. From the time of implant placement, the average follow-up observation period was 13 months. The width of keratinized mucosa was compared and evaluated through the gingival inflammation index (GI), plaque index (PI), the pocket depth, mucosal recession, and marginal bone resorption. RESULTS The GI, PI, and pocket depth in the presence or absence of the keratinized gingiva did not show statistically significant differences. However, mucosal recession and marginal bone resorption experienced statistically significant increases in the group of deficient keratinized mucosa. Based on implant surface treatments, the width of keratinized gingiva and crestal bone loss did not show a significant difference. CONCLUSION In cases with insufficient keratinized gingiva in the vicinity of implants, the insufficiency does not necessarily mediate adverse effects on the hygiene management and soft tissue health condition. Nonetheless, the risk of the increase of gingival recession and the crestal bone loss is present. Therefore, it is thought that from the aspect of long-term maintenance and management, as well as for the area requiring esthetics, the presence of an appropriate amount of keratinized gingiva is required.

A randomized controlled clinical trial of two types of tapered implants on immediate loading in the posterior maxilla and mandible.

PURPOSE The aim of this study was to compare clinical outcomes and stability following immediate loading of two types of tapered implants in the partially edentulous posterior maxilla and mandible. MATERIALS AND METHODS A randomized controlled trial with 1 year of follow-up was performed on participants missing two consecutive teeth in a posterior quadrant with tapered implants with a hybrid textured surface. Group 1 received Osstem TSIII HA implants, and group 2 received Zimmer TSV implants. Group 1 implants were 4.5 or 5.0 mm in diameter, and group 2 implants were 4.7 mm in diameter; all implants were 10 mm long. Subjects received provisional restorations within 48 hours. Definitive restorations were provided 3 months (mandible) or 6 months (maxilla) later. Outcome measures were survival and success rates, marginal bone level change, implant stability quotient, and peri-implant soft tissue indices. RESULTS Fifty participants completed the trial (group 1: 52 implants in 26 patients; group 2: 48 implants in 24 patients). The success rates were similar--98.1% in group 1 and 97.9% in group 2--at 12 months after immediate loading, but marginal bone loss was significantly different according to the implant design. Implant stability increased significantly in both arches. There were no significant differences in soft tissue indices between implant systems. CONCLUSION If high primary stability is acquired, tapered implants with hybrid textured surfaces are predictable for immediate loading in the posterior maxilla and mandible. In spite of the influence of implant design on marginal bone loss, all tapered implants showed successful clinical outcomes and stability in immediate loading.

Effect of surface treatment and liner material on the adhesion between veneering ceramic and zirconia

Fully sintered zirconia blocks, each with one polished surface, were treated with one of the followings: 1) no treatment, 2) airborne-particle abrasion with 50μm alumina, and 3) airborne-particle abrasion with 125μm alumina. Before veneering with glass ceramic, either liner Α or liner B were applied on the treated surfaces. All veneered blocks were subjected to shear force in a universal testing machine. For the groups with liner A, irrespective of the particle size, air abrasion on Y-TZP surfaces provided greater bond strength than polishing. Application of liner B on an abraded zirconia surface yielded no significant influence on the adhesion. In addition, specimens with liner A showed higher bond strength than those with liner B, if applied on roughened surfaces. Fractured surfaces were observed as mixed patterns in all groups. For the liner A, surface treatment was helpful in bonding with veneering ceramic, while it was ineffective for the liner B.

Comparison of clinical outcomes of sinus bone graft with simultaneous implant placement: 4-month and 6-month final prosthetic loading

OBJECTIVES The aim of this study was to compare the survival rate and surrounding tissue condition of sinus bone grafts with simultaneous implant placement between 4-month and 6-month occlusal loading after implantation. STUDY DESIGN Twenty-seven patients (61 implants) who were treated with sinus bone grafts (sinus lateral approach) and simultaneous Osstem GS II implant placement from July 2007 to June 2008 were included in this study. Of these patients, 14 (31 implants) were in the 4-month loading group, and 13 (30 implants) were in the 6-month loading group. We investigated the implantation type (submerged or nonsubmerged), sinus membrane perforation, type of prosthesis, opposed tooth type, primary and secondary stability of implants, and crestal bone loss around implant and surrounding tissue conditions. RESULTS The amounts of crestal bone-loss at the final recall time (12.56 ± 5.95 mo after loading) of the 4-month and 6-month loading groups were 0.19 ± 0.33 mm and 0.39 ± 0.86 mm, respectively. However, the difference between groups was not statistically significant (P = .211). The width of keratinized mucosa, gingival index, plaque index, and pocket depth of the 4-month and 6-month loading groups were 2.50 ± 1.69 mm and 1.73 ± 1.40 mm (P = .081), 0.72 ± 0.83 and 0.59 ± 0.69 (P = .671), 1.11 ± 0.96 and 0.76 ± 0.79 (P = .226), 3.56 ± 0.98 mm and 3.65 ± 1.06 mm (P = .758), respectively. The primary stabilities of implants in the 4-month and 6-month loading groups were 61.96 ± 12.84 and 56.06 ± 15.55 (P = .120), and the secondary stabilities were 71.85 ± 6.80 and 66.51 ± 11.28 (P = .026), respectively. The secondary stability of the 4-month group was significantly higher than that of the 6-month group. There was no statistical difference (P > .05) between the 4-month and 6-month loading groups regarding the implantation type (submerged or nonsubmerged), sinus membrane perforation, type of prosthesis, or opposed tooth type. In the 4-month and 6-month groups, all of the implants survived until the final recall time. CONCLUSIONS For the cases in which the residual bone was >3 mm and primary implant stability could be obtained, we conclude that loading is possible 4 months after the sinus bone graft and simultaneous implant placement.

Clinical evaluation of ridge augmentation using autogenous tooth bone graft material: case series study

Objectives Interest in bone graft material has increased with regard to restoration in cases of bone defect around the implant. Autogenous tooth bone graft material was developed and commercialized in 2008. In this study, we evaluated the results of vertical and horizontal ridge augmentation with autogenous tooth bone graft material. Materials and Methods This study targeted patients who had vertical or horizontal ridge augmentation using AutoBT from March 2009 to April 2010. We evaluated the age and gender of the subject patients, implant stability, adjunctive surgery, additional bone graft material and barrier membrane, post-operative complication, implant survival rate, and crestal bone loss. Results We performed vertical and horizontal ridge augmentation using powder- or block-type autogenous tooth bone graft material, and implant placement was performed on nine patients (male: 7, female: 2). The average age of patients was 49.88±12.98 years, and the post-operative follow-up period was 35±5.31 months. Post-operative complications included wound dehiscence (one case), hematoma (one case), and implant osseointegration failure (one case; survival rate: 96%); however, there were no complications related to bone graft material, such as infection. Average marginal bone loss after one-year loading was 0.12±0.19 mm. Therefore, excellent clinical results can be said to have been obtained. Conclusion Excellent clinical results can be said to have been obtained with vertical and horizontal ridge augmentation using autogenous tooth bone graft material.

Effect of loading time on marginal bone loss around hydroxyapatite-coated implants.

Objectives The objective of this study is compare the rate of marginal bone resorption around hydroxyapatite-coated implants given different loading times in order to evaluate their stability. Materials and Methods The study was conducted retrospectively for one year, targeting 41 patients whose treatment areas were the posterior maxilla and the mandible. Osstem TS III HA (Osstem Implant Co., Busan, Korea) and Zimmer TSV-HA (Zimmer Dental, Carlsbad, CA, USA), which employ the new hydroxyapatite coating technique, were used. The patients were divided into two groups - immediate and delayed loading - and the bone level at the time of loading commencement and after one year of loading was measured using periapical radiography. Differences between the groups were evaluated using Mann-Whitney (α=0.05). Results For all patients as a single group, the survival rate of the implants was 100%, and the mean marginal bone loss was 0.26±0.59 mm. In comparison of the differences by loading, mean marginal bone loss of 0.32±0.69 mm was recorded for the immediate loading group whereas the delayed loading group had mean marginal bone loss of 0.16±0.42 mm. However, the difference was not significant (P>0.05). Conclusion Within the limited observation period of one year, predictable survival rates can be expected when using immediately loaded hydroxyapatite-coated implants.

Correlation between interimplant distance and crestal bone loss in internal connection implants with platform switching.

PURPOSE The aim of this study was to investigate the influence of interimplant distance of internal connection implants with platform switching on crestal bone loss using radiographic evaluation. MATERIALS AND METHODS The present study included patients missing two consecutive teeth in the posterior quadrant and receiving internal connection implants. Digital periapical radiographs were taken at the time of superstructure connection and at the time of more than 1 year of loading. Bone level change was measured on the modified image using a digital subtraction program. The crestal bone loss between implants and the horizontal and vertical loss of peri-implant marginal bone were evaluated, and the influence of interimplant distance on crestal bone loss was analyzed at α = .05. RESULTS A total of 10 pairs of implants having ≤ 3 mm of interimplant distance was included in this study (group 1). The other 15 pairs of implants having > 3 mm of interimplant distance were selected as a control group (group 2). After the mean 19.3 months of observation, the mean crestal bone loss between implants was -0.26 ± 0.14 mm in group 1 and -0.23 ± 0.29 mm in group 2 (P > .05). There was no significant difference between the interimplant distance and the crestal bone loss according to the regression analysis (P = .765). The mean horizontal and vertical marginal bone loss was -0.18 ± 0.25 mm and -0.15 ± 0.18 mm, respectively, in group 1 and -0.17 ± 0.31 mm and -0.11 ± 0.33 mm, respectively, in group 2. There were no significant differences between outside and inside bone loss of implants in horizontal and vertical change (P > .05). CONCLUSIONS Within the limitations of the short-term study, the interimplant distance did not affect the crestal bone loss with internal connection implants with platform switching. The horizontal and vertical marginal bone loss was found to be too small to result in overlapping loss of the interimplant crestal bone.

Effects of Computer-Aided Manufacturing Technology on Precision of Clinical Metal-Free Restorations

Purpose. The purpose of this study was to investigate the marginal fit of metal-free crowns made by three different computer-aided design/computer-aided manufacturing (CAD/CAM) systems. Materials and Methods. The maxillary left first premolar of a dentiform was prepared for all-ceramic crown restoration. Thirty all-ceramic premolar crowns were made, ten each manufactured by the Lava system, Cercon, and Cerec. Ten metal ceramic gold (MCG) crowns served as control. The marginal gap of each sample was measured under a stereoscopic microscope at 75x magnification after cementation. One-way ANOVA and the Duncans post hoc test were used for data analysis at the significance level of 0.05. Results. The mean (standard deviation) marginal gaps were 70.5 (34.4) μm for the MCG crowns, 87.2 (22.8) μm for Lava, 58.5 (17.6) μm for Cercon, and 72.3 (30.8) μm for Cerec. There were no significant differences in the marginal fit among the groups except that the Cercon crowns had significantly smaller marginal gaps than the Lava crowns (P < 0.001).  Conclusions. Within the limitation of this study, all the metal-free restorations made by the digital CAD/CAM systems had clinically acceptable marginal accuracy.

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

Abstract Objectives. The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. Materials and methods. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. Results. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface. Conclusions: A glass–ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

Comparative clinical study of three-unit fixed partial prostheses supported by two or three implants.

PURPOSE To compare clinical outcomes of three-unit fixed prostheses supported by two or three implants in the posterior region. MATERIALS AND METHODS Patients in this retrospective study were restored with three-unit fixed partial prostheses supported by two (group 1) or three (group 2) implants in the partially edentulous posterior maxilla and mandible. Outcome measures were survival and success rate, marginal bone loss, complication rate, and peri-implant soft tissue indices. Two-way ANOVA and an independent t test were performed at a significance level of P < .05. RESULT A total of 48 implants placed in 23 patients (group 1) and 132 implants placed in 40 patients (group 2) were observed for 52.9 ± 19.7 months and 58.5 ± 22.0 months, respectively. Both groups showed a 100% survival rate. The success rate, considering marginal bone loss, was 82% (group 1) and 86% (group 2). Marginal bone loss was greater in group 1 every year during 3 years of measurement, but the difference was not statistically significant (P > .05). Differences of marginal bone loss according to sex, anatomical location (maxilla vs mandible), and connection type (external vs internal) also were not significant (P > .05). Complication rates were similar, but Plaque Index was significantly greater in group 2 (P < .05). CONCLUSION Within the limitations of this study, three-unit fixed partial prostheses supported by two implants showed comparable clinical outcomes with those supported by three implants in the partially edentulous posterior maxilla and mandible during the short- to medium-term.