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The purpose of this study was to investigate the effects of various titanium and zirconia polishing protocols on the colonization of oral bacteria. Titanium and zirconia discs were divided into five groups: unpolished (control, UNP) and polished with Brownie only (BRO), Brownie plus Greenie (BPG), Brownie plus Greenie plus Supergreenie (BGS), and CeraMaster Coarse plus CeraMaster polishing tips (CER). The samples were sterilized and immersed in unstimulated saliva, then incubated in a liquid suspension of Streptococcus gordonii (S gordonii). The number of attached bacteria were counted 48 hours after the diluted suspensions were inoculated. Data were analyzed with ANOVA and Tukey test (P < .05). For titanium discs, the average number of bacteria from each group (CFU/mm²) was 1.51 x 10³ for UNP; 3.71 x 10³ for BRO; 5.65 x 10³ for BPG; 8.99 x 10² for BGS; and 8.49 x 10² for CER. For zirconia, the averages were 2.87 x 10² for UNP; 3.16 x 10² for BRO; 3.50 x 10² for BPG; 1.83 x 10² for BGS; and 8.73 x 10¹ for CER. Inadequate polishing roughens surfaces and promotes microbial adhesion to titanium and zirconia. Sequential polishing to the finest-finish polishing tips minimizes bacterial adherence to abutment surfaces. Zirconia exhibited less bacterial adhesion than titanium.

Purpose: The aim of this study was to analyze and compare the stress distribution patterns of different implant and restorative materials in the supporting tissue and implants. Materials and Methods: Twelve different implant/bone models were created using SolidWorks 2015 software (SolidWorks Corp) and analyzed using the finite element method. Straumann Bone Level implants with zirconia abutments and single-piece Straumann PURE Ceramic implants (Institute Straumann) restored with lithium disilicate glass-ceramic and zirconia ceramic cement-retained crowns were evaluated. A 118.2-N load was applied to the coronal aspect of the buccal cusp at a 75.8-degree angle in relation to the occlusal plane. Principal stress values for cortical and trabecular bone and the equivalent von Mises stress values for implants and frameworks were calculated. Results: Zirconia (ZrO₂) implant models showed lower principal stress values than the commercially pure titanium (cpTi) and titanium-zirconium (TiZr) implant models in cortical bone. All models showed similar principal stress values in trabecular bone. Von Mises stress values at the cpTi and TiZr implants were similar; however, values observed of ZrO₂ implants were higher. TiZr implants of 3.3 mm diameter showed similar strength to 4.1-mm-diameter cpTi implants. Both zirconia and lithium disilicate glass-ceramic frameworks transferred similar von Mises stress values in the supporting tissue of implant-supported prostheses. Conclusion: Narrow-diameter TiZr implants may be preferred for patients who have insufficient bone volume without bone augmentation procedures due to the material's enhanced biomechanical properties. ZrO₂ implants may be a suitable alternative for esthetic regions. Further clinical studies are recommended to investigate the long-term performance of TiZr and ZrO₂ implants. Keywords: lithium disilicate glass-ceramic, three-dimensional finite element analysis, TiZr implants, zirconia, zirconia implants

Objectives: To evaluate the effect of different abutment-framework designs and different layering materials on the fracture strength of implant-supported zirconia-based single crowns following artificial aging. Materials and methods: Seventy ti-base abutments (Conelog 4.3-0.8mm, C2242.4308, Camlog® Implant, Basel, Switzerland) were screwed onto dental implants (Conelog 4.3-11mm, C1062.4311, Camlog® Implant, Basel, Switzerland). Abutment-implant complexes were randomly divided into seven groups (n = 10) according to the design of the zirconia abutment and framework (VITA YZ T, VITA Zahnfabrik, Germany) as follows: uniform-thickness zirconia abutment and uniform-thickness zirconia framework layered with feldspathic porcelain (Group 1); layered with indirect composite material (Group 2); uniform-thickness zirconia abutment and anatomic design zirconia framework layered with feldspathic porcelain (Group 3); layered with indirect composite material (Group 4); anatomic design zirconia abutment and anatomic design zirconia framework layered with feldspathic porcelain (Group 5); layered with indirect composite material (Group 6); uniform-thickness zirconia abutment and monolithic zirconia crown (Group 7). All fabricated zirconia abutments were cemented on ti-base abutments, and then all crowns were cemented on ti-base-zirconia abutment complexes. All specimens were exposed to 10,000 thermal cycles between 5°C and 55°C and then tested for fracture strength. The data were statistically analysed using 3-way ANOVA and Bonferroni-corrected t tests (p≤0.05). Results: The mean fracture strength values of groups were found to be statistically different with a ranking from highest to lowest as follows: Group 7 > Group 5 > Group 3 > Group 1 > Group 6 > Group 4 > Group 2 (p0.05). Anatomical abutment and framework designs showed significantly higher strength compared to uniform abutment and framework designs regardless of layering material (p0.05). Porcelain-layered groups had significantly higher fracture strength values in comparison to the groups layered with indirect composite (p0.05). Conclusions: A framework design with anatomical form supported by an anatomical abutment design increases fracture resistance in implant-supported zirconia-based restorations. Indirect composite material and porcelain perform similarly to layering materials on zirconia frameworks. Fabricating monolithic zirconia crown onto zirconia abutment may be recommended for higher strength. Keywords: ti-base, zirconia, implant-supported, layering material, framework

Objective: To evaluate the clinical effectiveness of the Vector system (Dürr Dental) in excess cement removal from subgingival margins during fixed prosthodontic treatment. Method and Materials: A total of 41 subjects, each in need of a minimum of 2 metal-ceramic crowns in different quadrants, took part in this study. Altogether, 156 abutment teeth were randomly assigned into 2 groups: In one group, excess cement was removed with the Vector system after cementation of provisional and permanent restorations, while in the other group, handheld instruments were used for this procedure. The clinical parameters Plaque Index (PI), Gingival Index (GI), and probing pocket depth (PPD) were recorded at baseline, at the same appointment after cementation of provisional restorations, 2 weeks later after cementation of permanent restorations, and 3 weeks after final cementation. Results: Both the Vector system and the handheld instruments were able to reduce PPD and PI significantly at 2 and 5 weeks, but no significant differences could be demonstrated between the groups. Regarding GI, significant reductions were found at 2 and 5 weeks for the Vector group (P .001), whereas for the handheld instrument group, the only significant difference could be demonstrated at 5 weeks (P = .001). Significant differences between the groups occurred at 2 weeks (P = .003) and 5 weeks (P = .002), with the Vector group having the greatest reduction in GI. Conclusion: Although similar reductions in Plaque Index and probing pocket depths were observed with both the Vector system and handheld instruments, the Vector system produced a significantly greater benefit in reducing Gingival Index. Keywords: excess cement removal, gingival health, Vector system