Genomic Evaluation of Formed Biofilm on Dental Implants with Different Surface Treatments Associated with Zirconia or Titanium Abutments: An In Vitro Study.

PURPOSE: The aim of this study was to evaluate the formed biofilm on two types of implant surfaces (hydrophilic or hydrophobic) associated with titanium (Ti) or zirconia (Zn) abutments. MATERIALS AND METHODS: Samples were separated into four groups according to type of surface and abutment used (n = 10): (1) hydrophobic/Ti abutment, (2) hydrophilic/Ti abutment, (3) hydrophobic/Zn abutment, and (4) hydrophilic/Zn abutment. Implant-abutment assemblies were incubated with human saliva and supragingival biofilm. Samples of biofilm were evaluated by DNA Checkerboard hybridization, identifying up to 41 species. Scanning electron microscopy (SEM) images were obtained from the implants and abutments. RESULTS: The microbial count was higher for samples from groups with the hydrophilic/Ti abutment, followed by hydrophobic/Zn abutment, hydrophilic/Ti abutment, and hydrophobic/Zn abutment (P < .05). Hydrophilic surfaces and Zn abutments showed the highest counts of microorganisms. Individual bacterial counts were variable between groups; the hydrophilic/Zn abutment group had the highest microbial diversity, including T forsythia, P nigrescens, S oralis, S sanguinis, L casei, M orale, P aeruginosa, P endodontalis, S aureus, S gallolyticus, S mutans, S parasanguinis, S pneumoniae, and C albicans. The hydrophilic/Ti abutment group had the highest count of T forsythia and T denticola, microorganisms of Socransky red complex. The SEM images showed the bacterial colonization in both surfaces of the implant and abutment. CONCLUSION: Different surfaces of implants and abutments showed significant differences in the count and diversity of species. The hydrophilic/Zn abutment group presented the highest count and diversity of target species.

Different sealing materials preventing the microbial leakage into the screw-retained implant restorations: an in vitro analysis by DNA checkerboard hybridization.

OBJECTIVES: The aim of this controlled in vitro study was to identify and quantify up to 38 microbial species penetrating through the screw-retained implant prostheses with different sealing materials. MATERIAL AND METHODS: Sixty morse cone implants were restored with single-unit screw-retained prostheses. All the components were randomly divided into five groups (n = 12) according to the proposed materials: (1) polytetrafluoroethylene tape+composite resin; (2) polytetrafluoroethylene tape+gutta-percha; (3) polytetrafluoroethylene tape+light-polymerized provisional composite; (4) cotton pellet+gutta-percha; and (5) cotton pellet+light-polymerized provisional composite. Human saliva was used as contaminant media, and DNA checkerboard hybridization was used to identify and quantify microbial species. RESULTS: Microbial leakage was observed in all groups: M. salivarium, S. pasteuri, P. nigrescens, and P. melaninogenica were the species presenting the highest values of genome count, prevalence, and proportion within the groups. The total microbial mean counts (×105 , ±SD) were as follows: Group 1 (2.81 ± 0.38), Group 2 (3.41 ± 0.38), Group 3 (6.02 ± 1.48), Group 4 (6.40 ± 1.42), and Group 5 (17.45 ± 1.67). Group 5 showed the higher microbial counts (P < 0.001). CONCLUSIONS: Moderate to high counts of pathogenic/nonpathogenic species were detected in the inner parts of implants from all groups. The lowest values of microbial counts were recorded for polytetrafluoroethylene tape associated with composite resin or gutta-percha; cotton pellet associated with light-polymerized provisional composite presented the highest microbial counts.

Effect of internal hexagonal index on removal torque and tensile removal force of different Morse taper connection abutments.

STATEMENT OF PROBLEM: The maintenance of the mechanical stability of implant-abutment connections is relevant to the clinical success of implant-supported restorations. However, the reduction in the conical area of abutments with an internal hexagonal index may result in a biomechanical disadvantage in Morse taper connections. PURPOSE: The purpose of this in vitro study was to evaluate the influence of an internal hexagonal index on the removal torque and tensile removal force of different Morse taper connection abutments submitted to thermomechanical cycling. MATERIAL AND METHODS: Forty Morse taper implants with their respective abutments were divided into 4 groups (n=10): straight abutment without index (PRNI); straight abutment with index (PRI); angled abutment without index (PANI); and angled abutment with index (PAI). Each abutment received an insertion torque of 15 Ncm, and the removal torque was recorded before and after thermomechanical cycling (106 cycles, 2 Hz, load of 130 N). After cycling, the groups were submitted to tensile testing at 0.5 mm/min under a load of 500 N until displacement of the abutment. A paired t test was performed for the intragroup analysis of removal torque before and after cycling and 2-way ANOVA followed by the Tukey Honestly Significant Difference (HSD) test was used for intergroup comparison (α=.05). RESULTS: Statistical analysis showed significant differences in intragroup removal torque values before compared with after thermomechanical cycling (P<.05). No statistically significant differences were found between the experimental groups in the removal torque of the prosthetic screw after cycling. The index factor (P=.028) was significant for tensile removal force. CONCLUSIONS: The type of abutment did not significantly influence the removal torque or tensile removal force after cycling. However, the presence of the internal hexagonal index significantly reduced the force necessary to dislodge the abutment from the implant.