Comparison of CAD/CAM abutment and prefabricated abutment in Morse taper internal type implant after cyclic loading: Axial displacement, removal torque, and tensile removal force

PURPOSE: The purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading.MATERIALS AND METHODS: The study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (10⁶ cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces.RESULTS: There was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant.CONCLUSION: The use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

Digital evaluation of axial displacement by implant-abutment connection type: An in vitro study

PURPOSE: To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS: Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at 10 N·cm, simulating hand tightening, and then at the manufacturers' recommended torque (30 N·cm) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS: Significant differences were observed in axial displacement according to the type of implant-abutment connection (P < .001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P < .05). CONCLUSION: Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

Effect of cyclic loading on axial displacement of abutment into implant with internal tapered connection: a pilot study / 대한치과보철학회지

PURPOSE: To evaluate the axial displacement of implant-abutment assembly after cyclic loading in internal tapered connection system. MATERIALS AND METHODS: External butt-joint connection implant and internal tapered connection implant were connected with three types of abutment for cement-retained prostheses, i.e. external type abutment (Ext group), internal tapered 1-piece abutment (Int-1 group), and internal tapered 2-piece abutment (Int-2 group). For each group, 7 implants and abutments were used. The implantabutments assemblies were clamped into the implant holder for vertical loads. A dynamic cyclic loading was applied for 150 +/- 10 N at a frequency of 4 Hz. The amount of axial displacement of the abutment into the implant was calculated at each cycle of 0, 5, 10, 50, 100, 1,000, 5,000, and 10,000. A repeated measures analysis of variance (ANOVA) for the overall effect of cyclic loading and the pattern analysis by linear mixed model were used for statistical analysis. Differences at P<.05 were considered statistically significant. RESULTS: The mean axial displacement after 10,000 cycles were 0.714 +/- 0.488 microm in Ext group, 5.286 +/- 1.604 microm in Int-1 group, and 11.429 +/- 1.902 microm in Int-2 group. In the pattern analysis, Int-1 and Int-2 group showed continuous axial displacement at 10,000 cycles. There was no declining pattern of axial displacement in the Ext group. CONCLUSION: The pattern of linear mixed model in Ext group showed no axial displacement. There were continuous axial displacements in abutment-implant assemblies in the Int-1 and Int-2 group at 10,000 cycles. More axial displacement was found in Int-2 group than in Int-1 group.

Comparison of Long-Term Results between One-piece and Three-piece Acrylate Intraocular Lens

PURPOSE: To compare the long-term clinical results of one-piece Acrysof(R) (SA60AT) hydrophobic acrylic intraocular lens (IOL) implantation compared with implantation of three-piece Acrysof(R) (MA60BM) hydrophobic acrylic IOL. METHODS: We retrospectively analyzed each 50 eyes of 50 patients underwent MA60BM or SA60AT IOL implantation and followed for at least 6 months. RESULTS: Final visual acuity of 0.5 or better was 38 eyes (76%) and 0.8 or better was 20 eyes (40%) in the SA60AT group. In the MA60BM group, it was 41 eyes (82%) and 23 eyes (46%) respectively. There were no significantly differences in predictability, intraocular pressure, endothelial cell density, astigmatism, and incidence of posterior capsule opacification between the two groups. Spherical equivalent at postoperative 1 week was -0.50+/-0.95D in SA60AT group and was -0.31+/-0.88D in MA60BM group (P=0.04). However, there was no significant difference between the two groups during follow up period. In MA60BM group, anterior chamber depth (P=0.02) and distance between iris and IOL (P=0.04) reduced significantly during the first postoperative month. CONCLUSIONS: Early postoperative axial displacement and changes in spherical equivalent can be occurred in MA60BM group. However there was no difference in long-term clinical results between SA60AT and MA60BM groups.