Sunjai Kim

Systematic review of the survival rate and incidence of biologic, technical, and esthetic complications of single implant abutments supporting fixed prostheses.

PURPOSE To assess the 5-year survival rate and number of technical, biologic, and esthetic complications involving implant abutments. MATERIALS AND METHODS Electronic (Medline) and hand searches were performed to assess studies on metal and ceramic implant abutments. Relevant data from a previous review were included. Two reviewers independently extracted the data. Failure and complication rates were analyzed, and estimates of 5-year survival proportions were calculated from the relationship between event rate and survival function. Multivariable robust Poisson regression was used to compare abutment characteristics. RESULTS The search yielded 1,558 titles and 274 abstracts. Twenty-four studies were selected for data analysis. The survival rate for ceramic abutments was 97.5% (95% confidence interval [CI]): 89.6% to 99.4%) and 97.6% (95% CI: 96.2% to 98.5%) for metal abutments. The overall 5-year rate for technical complications was 11.8% (95% CI: 8.5% to 16.3%), 8.9% (95% CI: 4.3% to 17.7%) for ceramic and 12.0% (95% CI: 8.5% to 16.8%) for metal abutments. Biologic complications occurred with an overall rate of 6.4% (95% CI: 3.3% to 12.0%), 10.4% (95% CI: 1.9% to 46.7%) for ceramic, and 6.1% (95% CI: 3.1% to 12.0%) for metal abutments. CONCLUSIONS The present meta-analysis on single-implant prostheses presents high survival rates of single implants, abutments, and prostheses after 5 years of function. No differences were found for the survival and failure rates of ceramic and metal abutments. No significant differences were found for technical, biologic, and esthetic complications of internally and externally connected abutments.

Accuracy of implant impressions without impression copings: a three-dimensional analysis.

STATEMENT OF PROBLEM Implant impressions without impression copings can be used for cement-retained implant restorations. A comparison of the accuracy of implant impressions with and without impression copings is needed. PURPOSE The purpose of this study was to evaluate and compare the dimensional accuracy of implant definitive casts that are fabricated by implant impressions with and without impression copings. MATERIAL AND METHODS An acrylic resin maxillary model was fabricated, and 3 implant replicas were secured in the right second premolar, first, and second molars. Two impression techniques were used to fabricate definitive casts (n=10). For the coping group (Group C), open tray impression copings were used for the final impressions. For the no-coping group (Group NC), cementable abutments were connected to the implant replicas, and final impressions were made assuming the abutments were prepared teeth. Computerized calculation of the centroids and long axes of the implant or stone abutment replicas was performed. The Mann-Whitney U test analyzed the amount of linear and rotational distortion between groups (α =.05). RESULTS At the first molar site, Group NC showed significantly greater linear distortion along the Y-axis, with a small difference between the groups (Group C, 7.8 ± 7.4 μm; Group NC, 19.5 ± 12.2). At the second molar site, increased distortion was noted in Group NC for every linear and rotational variable, except for linear distortion along the Z-axis. CONCLUSIONS Implant impression with open tray impression copings produced more accurate definitive casts than those fabricated without impression copings, especially those with greater inter-abutment distance.

Influence of internal-gap width and cement type on the retentive force of zirconia copings in pullout testing

OBJECTIVES The purpose of this study was to evaluate the influence of internal-gap width and cement type on the retentive force of zirconia copings. METHODS A CAD/CAM system was used to mill 48 identical abutments on extracted human molars and fabricate 48 zirconia copings. The internal-gap width for cement was set to 40 μm or 160 μm (n=24 each). Three cement types (Panavia F, RelyX Unicem, and RelyX Luting) were used with each internal-gap width (n=8/cement type). The intaglio surfaces of the copings were airborne-particle abraded, and each coping was cemented onto the corresponding abutment using the indicated luting agent. After 10,000 cycles of thermocycling, the retentive force was evaluated by pullout tests. Kruskal-Wallis and Wilcoxon Rank Sum tests were used for data analysis (α=0.05). RESULTS In the 40-μm gap groups, Panavia F had the highest mean retentive force compared to RelyX Unicem and RelyX Luting (P<0.000). In 160-μm gap groups, RelyX Unicem had the highest mean retentive force compared to Panavia F and RelyX Luting (P<0.000). CONCLUSIONS With the increase in internal gap width, a resin cement with self-etching agents as a co-initiator for autopolymerization resulted in significantly decreased retentive force, whereas a resin-modified glass ionomer cement or a self-adhesive resin cement did not. Use of resin cements rather than resin-modified glass ionomer cements improved the retentive force of zirconia copings regardless of the amount of internal gap width.

Critical appraisal of implant impression accuracies: A systematic review

STATEMENT OF PROBLEM Different assessment methods have been used to measure the accuracy of implant impression techniques; therefore, the readers should understand the benefits and limitations of each assessment method used. PURPOSE The purpose of this systematic review was to classify the implant impression studies by the assessment methods and techniques used and to understand the characteristics of each assessment method. The results of published studies were also analyzed to draw meaningful conclusions about the accuracy of the implant impressions. MATERIAL AND METHODS An electronic search of the MEDLINE/PubMed database was performed in February 2013 using specific search terms and predetermined criteria to identify and assess laboratory studies of the accuracy of implant impression techniques. A final list of articles deemed to be of interest was comprehensively reviewed by 2 reviewers to ensure that these were suitable for the purpose of this review. The results of the current review were also compared with results from a previous systematic review. RESULTS A total of 56 studies met the inclusion criteria for this review. Thirty-seven studies measured the amount of linear distortion, and 17 studies compared the angular change to assess the accuracy. Most linear or angular distortions were only measured in 2 dimensions, and 3-dimensional analysis was rare. More than 80% of the studies compared nonsplinting versus splinting, direct versus indirect techniques, and different impression materials. CONCLUSIONS In recent publications, the direct or splint technique showed more accurate results than the indirect or nonsplinted technique. In contrast to external connection implants, inconsistent results were reported for internal connection implants.

The change of rotational freedom following different insertion torques in three implant systems with implant driver.

STATEMENT OF PROBLEM Implant drivers are getting popular in clinical dentistry. Unlike to implant systems with external hex connection, implant drivers directly engage the implant/abutment interface. The deformation of the implant/abutment interface can be introduced while placing an implant with its implant driver in clinical situations. PURPOSE This study evaluated the change of rotational freedom between an implant and its abutment after application of different insertion torques. MATERIAL AND METHODS Three kinds of internal connection implants were utilized for the current study (4.5 × 12 mm Xive, 4.3 × 11.5 mm Inplant Magicgrip, 4.3 × 12 mm Implantium MF). An EstheticBase, a 2-piece top, a Dual abutment was used for its corresponding implant system. The rotational freedom between an implant and its abutment were measured before and after applying 45, 100 Ncm insertion torque. Repeated measures ANOVA was used for statistical analysis. RESULTS Under 45 Ncm insertion torque, the rotational freedom between an implant and its abutment was significantly increased in Xive (P = .003). However, no significant change was noted in Inplant Magicgrip and Implantium MF. Under 100 Ncm torque, both in Xive (P = .0005) and Implatium MF (P = .03) resulted in significantly increased rotational freedom between the implant and its abutment. DISCUSSION The design of the implant/implant driver interface effectively prevented the deformation of implant/abutment interface. Little change was noted in the rotational freedom between an implant and its abutment, even though the insertion torque was far beyond clinical application. CONCLUSIONS The implant/abutment joint of internally connecting implants were quite stable under insertion torque in clinical situation.

Effect of number of pontics and impression technique on the accuracy of four-unit monolithic zirconia fixed dental prostheses

Statement of problem. Because of their relatively small scanning area, intraoral scanners may result in less accurate fixed dental prostheses (FDPs) than do laboratory scanners. Purpose. The purpose of this in vitro study was to evaluate the accuracy of monolithic zirconia FDPs with different numbers of pontics fabricated with different impression techniques. Material and methods. The mandibular right premolars and molars of an acrylic resin model were prepared to receive 4‐unit FDPs. Three master models were fabricated with epoxy resin: model NP, no pontic; model 1P, 1 pontic; and model 2P, 2 pontics. Each master model was scanned by using direct (DD) and indirect digitalization (ID). Four‐unit monolithic zirconia FDPs were fabricated and divided into 3 groups (groups NP, 1P, and 2P) and then subdivided according to the digitalization technique (group DD and ID; n=10). The FDPs were also evaluated based on the presence (Po) or absence (NPo) of an adjacent pontic. The marginal, axial, and occlusal gap widths of each FDP were measured, and statistical analyses were performed to evaluate and compare the amount of gap present (&agr;=.05). Results. For direct digitalization, group 2P had significantly greater marginal (69.4 &mgr;m versus 60.9 &mgr;m or 62.3 &mgr;m; P<.001) and axial gap widths (127.1 &mgr;m versus 108.9 &mgr;m or 110.4 &mgr;m; P<.001) than group NP or 1P. Group DD resulted in significantly smaller gaps compared with group ID at marginal (64.8 &mgr;m versus 73.6 &mgr;m), axial (114.8 &mgr;m versus 124.3 &mgr;m), and occlusal (172.6 &mgr;m versus 184.1 &mgr;m) measurement locations (P<.001). Greater marginal and axial gaps were noted in group Po than NPo (P<.001). Conclusions. The length of the edentulous area significantly influenced the extent of the marginal and internal gap with the use of direct digitalization. Direct digitalization resulted in significantly smaller gap widths in all measurement areas than indirect digitalization; however, the mean differences were less than 12 &mgr;m, which is considered clinically insignificant. The presence of an adjacent pontic had a significant effect on the adjacent marginal and axial gap widths.

The effect of different cooling rates and coping thicknesses on the failure load of zirconia-ceramic crowns after fatigue loading

PURPOSE The purpose of this study was to evaluate the influence of different coping thicknesses and veneer ceramic cooling rates on the failure load of zirconia-ceramic crowns. MATERIALS AND METHODS Zirconia copings of two different thicknesses (0.5 mm or 1.5 mm; n=20 each) were fabricated from scanning 40 identical abutment models using a dental computer-aided design and computer-aided manufacturing system. Zirconia-ceramic crowns were completed by veneering feldspathic ceramics under different cooling rates (conventional or slow, n=20 each), resulting in 4 different groups (CONV05, SLOW05, CONV15, SLOW15; n=10 per group). Each crown was cemented on the abutment. 300,000 cycles of a 50-N load and thermocycling were applied on the crown, and then, a monotonic load was applied on each crown until failure. The mean failure loads were evaluated with two-way analysis of variance (P=.05). RESULTS No cohesive or adhesive failure was observed after fatigue loading with thermocycling. Among the 4 groups, SLOW15 group (slow cooling and 1.5 mm chipping thickness) resulted in a significantly greater mean failure load than the other groups (P<.001). Coping fractures were only observed in SLOW15 group. CONCLUSION The failure load of zirconia-ceramic crowns was significantly influenced by cooling rate as well as coping thickness. Under conventional cooling conditions, the mean failure load was not influenced by the coping thickness; however, under slow cooling conditions, the mean failure load was significantly influenced by the coping thickness.

The level of buccal gingival margin around single and two adjacent implant restorations: a preliminary result.

STATEMENT OF PROBLEM Little information is available about the buccal gingival level of multiple implant restorations. PURPOSE This study was aimed to evaluate the relationship between width and height of buccal soft tissue around single and 2 adjacent implant restorations. MATERIAL AND METHODS Four implant restoration groups (first and second molars, single second molars, posterior single restorations between teeth, and anterior single restorations between teeth) were randomly chosen from one dental institute. Each group comprised of 6 patients. After 6 months of function, silicone impressions were taken and stone models were fabricated for each restoration group. The stone models were cut in bucco-lingual direction at the most apical point of buccal gingival margin. The height and width of buccal supra-implant soft tissue were measured. One way ANOVA and Tukey HSD post hoc tests were performed to analyze the data obtained (P < .05). RESULTS The most unfavorable width-height ratio was noted for the group, which was comprised of the second molar in the multiple adjacent (first and second molar) implant-supported restorations. The group also resulted in the shorter height of buccal supra-implant mucosa rather than that of anterior single implant restorations between natural teeth. CONCLUSION To achieve a favorable level of buccal gingival margin, greater thickness of buccal supra-implant mucosa is required for the implant restorations without a neighboring natural tooth compared to the implant restorations next to a natural tooth.