An In Vitro Evaluation of the Loosening of Different Interchangeable Abutments in Internal-Connection-Type Implants.

PURPOSE: The aim of this study was to compare the loosening of interchangeable one-piece abutments connected to internal-connection-type implants after cyclic loading. MATERIALS AND METHODS: Four implant abutment groups (n = 7 in each group) with Straumann tissue-level implants were assessed: Straumann solid abutment (group S), Southern Implants solid abutment (group SI), Implant Direct straight abutment (group ID), and Blue Sky Bio regular platform abutment (group BSB). The implant was firmly held in a special jig to ensure fixation. Abutment screws were tightened to manufacturers' recommended torque with a digital torque gauge. The hemispherical loading members were fabricated for the load cell of a universal testing machine to evenly distribute the force on the specimens and to fulfill the ISO 14801:2007 standard. A cyclic loading of 25 N at 30 degrees to the implant's long axis was applied for a duty of a half million cycles. Tightening torques were measured prior to the loading. Removal torques were measured after cyclic loading. The data were analyzed with one-way analysis of variance (ANOVA), and the significance level was set at P < .05. RESULTS: The mean removal torques after cyclic loading were 34.0 ± 1.1 Ncm (group S), 25.0 ± 1.5 Ncm (group SI), 23.9 ± 2.1 Ncm (group ID), and 27.9 ± 1.3 Ncm (group BSB). Removal torques of each group were statistically different in the order of group S > group BSB > groups SI and ID (P < .05). The mean reduction rates were -2.9% ± 3.2% (group S), -21.9% ± 4.8% (group SI), -20.2% ± 7.2% (group ID), and -6.9% ± 4.3% (group BSB) after a half million cycles, respectively. Reduction rates of groups S and BSB were statistically lower than those of groups SI and ID (P < .01). The standard deviation of group S was lower than group BSB. CONCLUSION: The removal torque of the original Straumann abutment was significantly higher than those of the copy abutments. The reduction rate of the groups S and BSB abutments was lower than those of the other copy abutments.

Axial displacement of external and internal implant-abutment connection evaluated by linear mixed model analysis.

PURPOSE: To analyze the axial displacement of external and internal implant-abutment connection after cyclic loading. MATERIALS AND METHODS: Three groups of external abutments (Ext group), an internal tapered one-piece-type abutment (Int-1 group), and an internal tapered two-piece-type abutment (Int-2 group) were prepared. Cyclic loading was applied to implant-abutment assemblies at 150 N with a frequency of 3 Hz. The amount of axial displacement, the Periotest values (PTVs), and the removal torque values(RTVs) were measured. Both a repeated measures analysis of variance and pattern analysis based on the linear mixed model were used for statistical analysis. Scanning electron microscopy (SEM) was used to evaluate the surface of the implant-abutment connection. RESULTS: The mean axial displacements after 1,000,000 cycles were 0.6 µm in the Ext group, 3.7 µm in the Int-1 group, and 9.0 µm in the Int-2 group. Pattern analysis revealed a breakpoint at 171 cycles. The Ext group showed no declining pattern, and the Int-1 group showed no declining pattern after the breakpoint (171 cycles). However, the Int-2 group experienced continuous axial displacement. After cyclic loading, the PTV decreased in the Int-2 group, and the RTV decreased in all groups. SEM imaging revealed surface wear in all groups. CONCLUSION: Axial displacement and surface wear occurred in all groups. The PTVs remained stable, but the RTVs decreased after cyclic loading. Based on linear mixed model analysis, the Ext and Int-1 groups' axial displacements plateaued after little cyclic loading. The Int-2 group's rate of axial displacement slowed after 100,000 cycles.

Effects of anodized oxidation or turned implants on bone healing after using conventional drilling or trabecular compaction technique: histomorphometric analysis and RFA.

OBJECTIVES: The aim of this study was to compare the bone healing characteristics adjacent to anodic oxidation and turned surfaces after implant installation using the trabecular compaction technique or the conventional drilling technique in the soft bone area. MATERIAL AND METHODS: A total of 72 implants (36 anodic oxidation surface and 36 turned surface implants) were inserted into the distal end of the femur head of 12 dogs by two different surgical techniques. There were four experimental groups: (1) DT group; drilling+turned, (2) DO group; drilling+oxidation, (3) CT group; compaction+turned, and (4) CO group; compaction+oxidation. The resonance frequency was measured and six specimens/treatment group were obtained at 0, 3 and 8 weeks, postoperatively. Undecalcified ground sections were prepared for histologic and histomorphometric examinations. RESULTS: At week 0, the trabecular compaction groups showed a higher bone to implant contact ratio (BIC) than the conventional drilling groups, regardless of surface types. The CT group showed a higher implant stability quotient (ISQ) than the DT group. At week 3, the oxidation groups showed a higher BIC than the turned groups regardless of the surgical technique used. The CO group showed higher ISQ than the CT group. At week 8, there was no statistically significant difference in BIC and ISQ between the groups. CONCLUSIONS: Surgical technique and implant surface state have an effect on the initial bone response to two-stage implants inserted into trabecular bone regions.