Sung-Am Cho

The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching

Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H(2)SO(4) dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H(2)SO(4), group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) (p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1-2 microm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. There is less correlation between removal torque and the difference in HF volume%.

A removal torque of the laser-treated titanium implants in rabbit tibia

The purpose of the present study is to evaluate the significance of different surface textures by comparison of the removal forces for laser-treated and machined titanium screw 8 weeks after the installation in rabbit tibia. A total of 14 screw shaped, commercially pure titanium implants with a length of 5 mm, a diameter of 3.75 mm were grouped as follows: Group A: seven implants left as-machined; Group B: seven implants treated with laser method (CSM implant, CSM company, Daegu, Korea) Topographic evaluation was performed with scanning electron microscope (Hitachi S-4200, Japan) to compare the surface structure of laser-treated and machined ones. Installation procedures were done according to Branemark protocol after pre-threading, machined implants were inserted in right tibia metaphysics and laser-treated surface implants were inserted in left ones. Eight weeks post surgically seven rabbits were sacrificed. The implant sites were exposed, and the bone and soft tissues that had formed on top of the implants were carefully removed. Subsequently, the force needed to unscrew the implants (n=14) was measured using a digital torque gauge (Mark-10 corporation, USA). Scanning electron micrographs of the laser-treated and machined control groups demonstrated created a deep and regular honey-comb pattern with small pore, while machined treatment created the typical microscopically grooved and relatively smooth surface characteristic. Eight weeks after implant placement, the average removal torque was 23.58+/-3.71 N cm for the machined implants, 62.57+/-10.44 N cm for the laser-treated implants. The torque measurements yielded statistically significant differences between the machined group and the laser-etched group (p=0.00055) (Wilcoxons signed-rank test). The laser-treated group achieved higher removal torque values compared to the machined control group.

The effects of laser etching on shear bond strength at the titanium ceramic interface

STATEMENT OF PROBLEM The use of titanium has increased for metal ceramic restorations, as well as for use in titanium implants, with developments in CAD/CAM technology. Some surface treatments of titanium have been introduced to enhance the titanium bond strength to low-fusing porcelains; however, a more reliable, easily used dental laboratory method has not been established. PURPOSE The purpose of this study was to compare the effect of laser etching as a titanium surface treatment with 3 other surface treatments (machining, airborne-particle abrasion, and acid etching), evaluating their ability to enhance the bond strength between a titanium substrate and porcelain. MATERIAL AND METHODS A total of 64 specimen rods of commercially pure titanium (ASTM grade 2, 20 mm in length and 5.7 mm in diameter) were divided into 4 experimental groups (n=16) to receive different surface treatments: machined with no treatment (MS), airborne-particle abraded with alumina particles (250 microm) (APAS), acid etched with 10% HCl (AES), and laser etched (LES) using a neodymium-doped yttrium aluminum garnet laser (Nd:Y(3)AL(5)O(12), or Nd/YAG). Low-fusing porcelain (Triceram) was applied (4-mm thickness) to the treated titanium surfaces and fired. Shear bond strength testing was performed in a universal testing machine. All of the data were compared using 1-way ANOVA and the post hoc multiple range Tukey test (alpha=.05). Measurement of roughness (Ra value) and SEM analysis were also performed for 1 specimen of each group before and after the shear bond strength test to evaluate the nature of the fracture surface. RESULTS Shear bond strength values for the APAS group (22.22 (4.04) MPa) and the LES group (21.22 (3.41) MPa) were significantly greater (P<.05) than for the MS group (13.76 (3.16) MPa) and the AES group (14.98 (3.26) MPa). The SEM image after debonding of MS and AES showed porcelain retained on the surface. However, there was no difference in appearance between the APAS and LES before and after debonding. CONCLUSIONS Laser etching of titanium surfaces using an Nd/YAG laser was effective in improving bond strength with low-fusing porcelain, as compared to the acid-etching method. However, there was no significant difference between laser etching and airborne-particle-abrasion surface treatment.

Two-body wear comparison of zirconia crown, gold crown, and enamel against zirconia.

PROBLEM STATEMENT Full zirconia crowns have recently been used for dental restorations because of their mechanical properties. However, there is little information about their wear characteristics against enamel, gold, and full zirconia crowns. PURPOSE The purpose of this study was to compare the wear rate of enamel, gold crowns, and zirconia crowns against zirconia blocks using an in vitro wear test. MATERIALS AND METHODS Upper specimens were divided into three groups: 10 enamels (group 1), 10 gold crowns (group 2, Type III gold), and 10 zirconia crowns (group 3, Prettau(®)Zirkon 9H, Zirkonzahn, Italy). Each of these specimens was wear tested against a zirconia block (40×30×3mm(3)) as a lower specimen (30 total zirconia blocks). Each specimen of the groups was abraded against the zirconia block for 600 cycles at 1Hz with 15mm front-to-back movement on an abrading machine. Moreover, the load applied during the abrading test was 50N, and the test was performed in a normal saline emulsion for 10min. Three-dimensional images were taken before and after the test, and the statistical analysis was performed using the Krushal-Wallis test and Mann-Whitney test (p=0.05). RESULTS The mean volume loss of group 1 was 0.47mm(3), while that of group 2 and group 3 was 0.01mm(3). CONCLUSION The wear volume loss of enamels against zirconia was higher than that of gold and zirconia crowns. Moreover, according to this result, zirconia crowns are not recommended for heavy bruxers.

Biomechanical evaluation of laser-etched Ti implant surfaces vs. chemically modified SLA Ti implant surfaces: Removal torque and resonance frequency analysis in rabbit tibias.

PURPOSE To compare osseointegration and implant stability of two types of laser-etched (LE) Ti implants with a chemically-modified, sandblasted, large-grit and acid-etched (SLA) Ti implant (SLActive(®), Straumann, Basel, Switzerland), by evaluating removal torque and resonance frequency between the implant surface and rabbit tibia bones. We used conventional LE Ti implants (conventional LE implant, CSM implant, Daegu, Korea) and LE Ti implants that had been chemically activated with 0.9% NaCl solution (LE active implant) for comparison with SLActive(®) implants MATERIALS AND METHODS Two types of 3.3×8mm laser-etched Ti implants - conventional LE implants and LE active implants were prepared. LE implants and SLActive(®) implants were installed on the left and right tibias of 10 adult rabbits weighing approximately 3.0kg LE active implants and SLActive(®) implants were installed on the left and right tibias of 11 adult rabbits. After installation, we measured insertion torque (ITQ) and resonance frequency (ISQ). Three weeks (LE active) or 4 weeks (conventional LE) after installation, we measured removal torque (RTQ) and ISQ. RESULTS In the conventional LE experiment, the mean ITQ was 16.99±6.35Ncm for conventional LE implants and 16.11±7.36Ncm for SLActive(®) implants (p=0.778>0.05). After 4 weeks, the mean of RTQ was 39.49±17.3Ncm for LE and 42.27±20.5Ncm for SLActive(®) (p=0.747>0.05). Right after insertion of the implants, the mean ISQ was 74.8±4.98 for conventional LE and 70.1±9.15 for SLActive(®) implants (p=0.169>0.05). After 4 weeks, the mean ISQ was 64.40±6.95 for LE and 67.70±9.83 for SLActive(®) (p=0.397>0.05). In the LE active experiment, the mean ITQ was 16.24±7.49Ncm for LE active implants and 14.33±5.06Ncm for SLActive(®) implants (p=0.491>0.05). After 3 weeks, the mean RTQ was 39.25±16.41Ncm for LE active and 41.56±10.41Ncm for SLActive(®) implants (p=0.698>0.05). Right after insertion of the implants, the mean ISQ was 58.64±10.51 for LE active implants and 53.82±15.36 for SLActive(®) implants (p=0.401>0.05). After 3 weeks, the mean ISQ was 63.82±5.88 for LE active and 66.27±6.53 for SLActive(®) (p=0.365>0.05). CONCLUSION We observed no significant differences in biomechanical bond strength to bone or implant stability in bone between the conventional LE Ti implant surface and the surface of the SLActive(®) implant or between the chemically activated LE Ti implant surface and the surface of the SLActive(®) implant during the early stage of osseointegration.

Comparison of removal torques between laser-treated and SLA-treated implant surfaces in rabbit tibiae

PURPOSE The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ×25, ×150 and ×1,000 magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS In the experimental group, the surface analysis showed uniform porous structures under ×25, ×150 and ×1,000 magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants.

The Use of Telescopic Crowns in Removable Partial Denture Treatment for Patients with Severe Periodontal Disease: Two Patient Case History Reports

Two patient case histories are described as examples of treatment of severe periodontitis in severely compromised partial dentitions. Management consisted of periodontal treatment and telescopic crown support for removable partial dentures with friction pin retention.

Comparison of alkaline phosphatase activity of MC3T3-E1 cells cultured on different Ti surfaces: modified sandblasted with large grit and acid-etched (MSLA), laser-treated, and laser and acid-treated Ti surfaces.

PURPOSE In this study, the aim of this study was to evaluate the effect of implant surface treatment on cell differentiation of osteoblast cells. For this purpose, three surfaces were compared: (1) a modified SLA (MSLA: sand-blasted with large grit, acid-etched, and immersed in 0.9% NaCl), (2) a laser treatment (LT: laser treatment) titanium surface and (3) a laser and acid-treated (LAT: laser treatment, acid-etched) titanium surface. MATERIALS AND METHODS The MSLA surfaces were considered as the control group, and LT and LAT surfaces as test groups. Alkaline phosphatase expression (ALP) was used to quantify osteoblastic differentiation of MC3T3-E1 cell. Surface roughness was evaluated by a contact profilometer (URFPAK-SV; Mitutoyo, Kawasaki, Japan) and characterized by two parameters: mean roughness (Ra) and maximum peak-to-valley height (Rt). RESULTS Scanning electron microscope revealed that MSLA (control group) surface was not as rough as LT, LAT surface (test groups). Alkaline phosphatase expression, the measure of osteoblastic differentiation, and total ALP expression by surface-adherent cells were found to be highest at 21 days for all three surfaces tested (P<.05). Furthermore, ALP expression levels of MSLA and LAT surfaces were significantly higher than expression levels of LT surface-adherent cells at 7, 14, and 21 days, respectively (P<.05). However, ALP expression levels between MSLA and LAT surface were equal at 7, 14, and 21 days (P>.05). CONCLUSION This study suggested that MSLA and LAT surfaces exhibited more favorable environment for osteoblast differentiation when compared with LT surface, the results that are important for implant surface modification studies.

Precision of the milled full-arch framework fabricated using pre-sintered soft alloy: A pilot study

PURPOSE This study aimed to evaluate the marginal discrepancy of full-arch frameworks in implant-supported prostheses fabricated using pre-sintered soft alloy (PSA). MATERIALS AND METHODS Full-arch metal frameworks were fabricated on the edentulous implant model using casting alloy (CA), fully-sintered hard alloy (FHA), and PSA (n = 4 in each group). To evaluate the misfit of the framework to the abutments, the absolute marginal discrepancy (AMD) values of the frameworks were measured in cross-sectional images that had been drawn as part of the triple-scan protocol. The AMD values were compared among the tested alloy groups using the Kruskal-Wallis test, with a post hoc Mann-Whitney U test (α=.05). RESULTS The FHA and PSA groups showed lower marginal discrepancies than the CA group (P<.001). However, the FHA group did not differ significantly from the PSA group. CONCLUSION Soft alloy milling is comparable to hard alloy milling, and it is more precise than casting in terms of the marginal fit of implant-supported, full-arch prostheses.

Comparison of removal torques between laser-etched and modified sandblasted acid-etched Ti implant surfaces in rabbit tibias

PURPOSE The purpose of this study was to analyze the effects of two different implant surface treatments on initial bone connection by comparing the Removal Torque Values (RTQs) at 7 and 10 days after chemically modified, sandblasted, large-grit and acid-etched (modSLA), and Laser-etched (LE) Ti implant placements. MATERIALS AND METHODS Twenty modSLA and 20 LE implants were installed on the left and right tibias of 20 adult rabbits. RTQs were measured after 7 and 10 days in 10 rabbits each. Scanning electron microscope (SEM) photographs of the two implants were observed by using Quanta FEG 650 from the FEI company (Hillsboro, OR, USA). Analyses of surface elements and components were conducted using energy dispersive spectroscopy (EDS, Horiba, Kyoto, Japan). RESULTS The mean RTQs were 12.29 ± 0.830 and 12.19 ± 0.713 Ncm after 7 days (P=.928) and 16.47 ± 1.324 and 16.17 ± 1.165 Ncm after 10 days (P=.867) for LE and modSLA, respectively, indicating no significant inter-group differences. Pore sizes in the LE were 40 µm and consisted of numerous small pores, whereas pore sizes in the modSLA were 5 µm. In the EDS analysis, Ti, O, and C were the only three elements found in the LE surfaces. Na, Ca, Cl, and K were also observed in modSLA, in addition to Ti, O, and C. CONCLUSION The implants showed no significant difference in biomechanical bond strength to bone in early-stage osseointegration. LE implant can be considered an excellent surface treatment method in addition to the modSLA implant and can be applied to the early loading of the prosthesis clinically.