Chong-Hyun Han

Biological performance of calcium phosphate films formed on commercially pure Ti by electron-beam evaporation

Thin and defect-free calcium phosphate films with a Ca/P ratio of 1.62 were formed by electron-beam evaporation. The as-deposited films had average bonding strengths to the metal implants of 64.8 MPa and the dissolution rates of 47.5 nm/h in isotonic saline solutions. The interface mechanical characteristics and histology of the as-machined, as-blasted, and calcium phosphate coating on the machined surfaces of commercially pure titanium were investigated. After a healing period of 12 weeks, the implants were unscrewed with a torque gauge instrument at the day of sacrifice. The coated sample showed a removal torque of 48.5 Ncm (SD 5.4) compared to 32.3 Ncm (SD 2.91) for the uncoated implant with the same surface roughness, and 47.3 Ncm (SD 5.8) for the grit blasted screw. The histomorphometric analyses of the calcium-phosphate-coated implants revealed a mean of 52.4% (SD 6.3) as the highest bone to implant contact.

Marginal bone loss around three different implant systems: radiographic evaluation after 1 year

This study was designed to radiographically evaluate the effect of surface macro-and microstructures within the coronal portion of the external hex implant at the marginal bone change after loading. The fifty-four patients included in the study were randomly assigned to treatment groups with rough-surface implants (TiUnite, n = 45), a hybrid of smooth and rough surface implants (Restore, n = 45) or rough-surface with microthreads implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline) and at 1-year post-loading. A three-level mixed-effect ancova was used to test the significance of the mean marginal bone change of the three implant groups from baseline to 1-year follow-up. At 1-year, significant differences were noted in marginal bone loss recorded for the three groups (P < 0.0001). The rough surface with microthread implants had a mean crestal bone loss of 0.42 +/- 0.27 mm; the rough surface implants, 0.81 +/- 0.27 mm; and the hybrid surface implants, 0.89 +/- 0.41 mm. Within the limitations of this study, a rough surface with microthreads at the coronal part of implant maintained the marginal bone level against functional loading better than implants without these two features.

A 3-year prospective radiographic evaluation of marginal bone level around different implant systems

The aim of this study was to evaluate the change of marginal bone level radiographically around three different implant systems after 3 years in function. Fifty-four patients were included and randomly assigned to three treatment groups of rough-surface implants (TiUnite, n = 37), hybrid of smooth and rough-surface implants (Restore, n = 38) and rough surface with microthread implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline), 1 and 3 years after loading. A three-level mixed-effect analysis of covariance (ancova) was used to test the significance of the mean marginal bone change of the three implant groups. A total 120 of 135 implants completed the study. None of the implants failed to integrate. Significant differences were noted in the marginal bone loss recorded for the three groups (P < 0.0001). At 3 years, the rough surface with microthread implants had a mean crestal bone loss of 0.59 +/- 0.30 mm; the rough-surface implants, 0.95 +/- 0.27 mm; and the hybrid surface implants, 1.05 +/- 0.34 mm. Within the limitations of this study, rough-surface implants with microthread at the coronal part might have a long-term positive effect in maintaining the marginal bone level against functional loading in comparison with implants without these two features.

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.

The effect of ultraviolet-C irradiation via a bactericidal ultraviolet sterilizer on an anodized titanium implant: a study in rabbits.

PURPOSE After placement, titanium dental implants are conditioned by blood and tissue fluid. These initial processes are affected by the hydrophilicity of the implant. The hydrophilicity of titanium dioxide (TiO2) can be increased by ultraviolet (UV)-C irradiation. Anodic oxidation is an electrochemical treatment used to form TiO2 layers that are characterized by their thickness, roughness, and porosity on the surface of titanium implants. These oxide layers increase implant durability and performance. Therefore, the aim of this study was to investigate the effect of UV-C irradiation on the anodized titanium surface and the resultant tissue response. MATERIALS AND METHODS Twenty-five titanium disks and 56 screw-type implants were fabricated of commercially pure titanium and anodized. The samples were divided into a control group (anodized) and a test group (anodized and UV-C irradiated with a bactericidal UV sterilizer for 24 hours just prior to experimentation). The surface characteristics of the disks, including roughness, crystal phase of the oxide layer, chemical composition, and water contact angle, were then evaluated. Implants were placed into rabbit tibiae, and histomorphometric analysis was performed after healing periods of 4 and 12 weeks. The results were compared between groups. RESULTS The surface topography and phase of the oxide layer were not significantly different between test and control groups. Carbon surface impurities were noticeably decreased after UV-C irradiation, and water contact angle measurements were significantly lower (P < .001). After a healing period of 4 weeks, test implants showed higher values for both bone-to-implant contact and the amount of bone in the thread area of the implant (P < .01). No significant differences between groups were found for either histomorphometric measurement after 12 weeks. CONCLUSIONS UV-C irradiation of an anodized titanium implant, accomplished via a bactericidal UV sterilizer, promoted an early bone response in rabbit tibiae.

The Microtomographic Evaluation of Marginal Bone Resorption of Immediately Loaded Scalloped Design Implant With Various Microthread Configurations in Canine Mandible: Pilot Study

This study was undertaken to evaluate the effect of microthread geometry of scalloped design implant on marginal bone resorption. Four types of scalloped design titanium implant specimens were prepared. The type 1 implant had a machined scalloped collar, type 2 had a sandblasted and acid-etched scalloped collar, type 3 had horizontal microthreads, and type 4 had parabolic microthreads, which are parallel with the scalloped conical margin. Two implants of a type were randomly installed immediately after extraction in the mandible of a beagle dog. Definitive prostheses were delivered immediately after surgery. After 12 weeks of healing, the dog was sacrificed and microtomography was performed. Type 4 specimens showed a marginal bone loss pattern definitively analogous to the scalloped margin. In this preliminary study, microthread geometry affected the marginal bone resorption pattern of scalloped design implants. However, additional specimens and more controlled conditions should be applied in future studies to confirm these results.

A Long-Term Prospective Evaluation of Marginal Bone Level Change Around Different Implant Systems.

PURPOSE The purpose of this prospective study was to assess the change of marginal bone level around three different types of external-hex implants after 5 years using radiography. MATERIALS AND METHODS Included in this study were 54 patients randomly put into three different groups; rough-surface implants (Brånemark), machined coronal aspect implants (Restore), and microthreaded coronal aspect implants (Hexplant). Clinical and radiographic assessments were performed contemporaneously with implant loading (baseline) and at 1, 3, and 5 years post-functional loading. A mixed-model analysis was employed to examine mean marginal bone change significance in the three treatment groups. RESULTS In a total of 31 out of 54 patients, 81 of 135 implants remained to the end of the study. At 5 years, the microthreaded coronal aspect implants had 0.61 ± 0.32 mm mean crestal bone loss; the rough-surface implants without microthread, 0.99 ± 0.38 mm; and the machined coronal aspect implants, 1.06 ± 0.39 mm. The rough-surface implants and the machined coronal aspect implants did not exhibit statistically significantly different marginal bone loss, whereas the microthreaded coronal aspect implants exhibited significantly less marginal bone loss (P = .0015). CONCLUSION In this research, rough-surface implants with microthreads showed positive long-term effects in preserving peri-implant bone level against functional loads when compared with implants lacking these aspects at the coronal part. Most of the bone loss was shown within 1 year of loading, and all types of implants stabilized after 1 year.

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.

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.