Rubens Ferreira de Albuquerque Junior

Influence of repeated screw tightening on bacterial leakage along the implant-abutment interface

OBJECTIVES Bacterial penetration along the implant-abutment interface as a consequence of abutment screw loosening has been reported in a number of recent studies. The aim of this in vitro study was to investigate the influence of repeated tightening of the abutment screw on leakage of Streptococcus mutans along the interface between implants and pre-machined abutments. MATERIALS AND METHODS Twenty pre-machined abutments with a plastic sleeve were used. The abutment screws were tightened to 32 N cm in group 1 (n=10 - control) and to 32 N cm, loosened and re-tightened with the same torque twice in group 2 (n=10). The assemblies were completely immersed in 5 ml of Tryptic Soy Broth medium inoculated with S. mutans and incubated for 14 days. After this period, contamination of the implant internal threaded chamber was evaluated using the DNA Checkerboard method. RESULTS Microorganisms were found on the internal surfaces of both groups evaluated. However, bacterial counts in group 2 were significantly higher than that in the control group (P<0.05). CONCLUSION These results suggest that bacterial leakage between implants and abutments occurs even under unloaded conditions and at a higher intensity when the abutment screw is tightened and loosened repeatedly.

Use of checkerboard DNA-DNA hybridization to evaluate the internal contamination of dental implants and comparison of bacterial leakage with cast or pre-machined abutments.

AIMS To evaluate the checkerboard DNA-DNA hybridization method for detection and quantitation of bacteria from the internal parts of dental implants and to compare bacterial leakage from implants connected either to cast or to pre-machined abutments. MATERIALS AND METHODS Nine plastic abutments cast in a Ni-Cr alloy and nine pre-machined Co-Cr alloy abutments with plastic sleeves cast in Ni-Cr were connected to Branemark-compatible implants. A group of nine implants was used as control. The implants were inoculated with 3 microl of a solution containing 10(8) cells/ml of Streptococcus sobrinus. Bacterial samples were immediately collected from the control implants while assemblies were completely immersed in 5 ml of sterile Tripty Soy Broth (TSB) medium. After 14 days of anaerobic incubation, occurrence of leakage at the implant-abutment interface was evaluated by assessing contamination of the TSB medium. Internal contamination of the implants was evaluated with the checkerboard DNA-DNA hybridization method. RESULTS DNA-DNA hybridization was sensitive enough to detect and quantify the microorganism from the internal parts of the implants. No differences in leakage and in internal contamination were found between cast and pre-machined abutments. Bacterial scores in the control group were significantly higher than in the other groups (P<0.05). CONCLUSION Bacterial leakage through the implant-abutment interface does not significantly differ when cast or pre-machined abutments are used. The checkerboard DNA-DNA hybridization technique is suitable for the evaluation of the internal contamination of dental implants although further studies are necessary to validate the use of computational methods for the improvement of the test accuracy.

Bacterial survival rate on toothbrushes and their decontamination with antimicrobial solutions

The purpose of this study was to evaluate bacterial survival rate on toothbrushes after brushing and the efficacy of their decontamination by spraying antimicrobial solutions. Thirty subjects were instructed to spray the solutions on toothbrush bristles after brushing. Each volunteer tested three sprays, one solution per week; the sprays were labeled spray 1 (cetylpyridinium chloride - CPC - and basic formulation), 2 (basic formulation only) and 3 (control - sterile tap water). At the end of each week, the brushes were collected and sonicated in Letheen Broth®; the suspensions were ten-fold diluted and the dilutions were plated on various culture media. Anaerobic bacteria, evaluated by colony count of black pigment producing organisms on Ask medium, were recovered from 83.3% of the samples, Streptococci from 80% and aerobic Gram-negative bacilli from 46.7% of them in the control tests. There was a significant decrease in toothbrush contamination with antimicrobial sprays 1 and 2, the first showing the greatest decrease on bacterial counts.

Bacterial Culture and DNA Checkerboard for the Detection of Internal Contamination in Dental Implants

PURPOSE The aim of this in vitro study was to evaluate the bacterial leakage along the implant-abutment interface by the conventional bacterial culture and DNA Checkerboard hybridization method. MATERIALS AND METHODS Twenty Branemark-compatible implants with a 3.75-mm diameter and external hexagonal platform were randomly placed in two groups of ten implant-abutment assemblies each. One group was used to analyze bacterial counts by DNA Checkerboard hybridization and the other by a conventional bacterial culture. Suspensions of Fusobacterium nucleatum (3 microl) were injected into the grooved internal cylinders of each implant assembly, and the abutment was connected by a 32 Ncm torque. The combined implant-abutments were individually placed in tubes containing the CaSaB culture medium and incubated in a bacteriological constant temperature oven for 14 days. The samples were observed daily as to the presence of turbidity, and after the designated time the microorganisms were collected from the implant interiors and analyzed by the two methods. RESULTS After 14 days, six implant-abutment assemblies showed turbidity. Both methods indicated reduced microorganism counts in samples from the interior of the implant-abutment assemblies after incubation in the culture medium; however, the number of counts of F. nucleatum was higher by the DNA Checkerboard method when compared to the group analyzed by conventional bacterial cultures (p < 0.05). CONCLUSION The DNA Checkerboard method was shown to be more sensitive than conventional cultures in the detection of microorganisms.

Microbiome of titanium and zirconia dental implants abutments

OBJECTIVES This study employed culture-independent molecular techniques to extend the characterization of the microbial diversity of biofilm associated with either titanium or zirconia implant-abutments, including not-yet-cultivated bacteria species, and to identify and quantify species recovered from peri-implantar/periodontal sulci, supragingival biofilm and the internal parts of implants. Probing depth, clinical attachment level, bleeding on probing, and marginal bone level were also evaluated over time and correlated with biofilm formation. METHODS Twenty healthy participants were analyzed. DNA-Checkerboard and 16S-rDNA-Pyrosequencing were used to quantify and determine species identity. RESULTS 161 bacterial taxa representing 12 different phylotypes were found, of which 25% were non-cultivable. Species common to all sites belonged to genera Fusobacterium, Prevotella, Actinomyces, Porphyromonas, Veillonella and Streptococcus. While some species were subject-specific and detected in most sites, other species were site-specific. Moderate to higher levels of unclassified species were found colonizing titanium-related sites. Pathogenic and non-pathogenic species were detected colonizing oral sites in both materials. Titanium-related sites presented the highest total microbial count and higher counts of pathogenic species. CONCLUSIONS Our results revealed differences regarding microbial diversity and microorganisms counts in oral biofilm associated with titanium or zirconia. The obtained data suggests a possible relation between microbiological findings and clinical outcomes. SIGNIFICANCE Next-generation methods of detection have provided new insights on complex microbiota colonizing different sites of oral cavity. The present study demonstrates relevant differences in the communities and microbial counts colonizing different tested substrates with consequent significant differences in the clinical-outcomes, suggesting a probably different mechanism for specific bacterial adhesion.

Effect of Implant Angulation on Attachment Retention in Mandibular Two-Implant Overdentures: A Clinical Study

PURPOSE Attachment wear can affect the performance of mandibular two-implant overdentures (IODs). This prospective clinical study aimed to investigate the effect of interimplant angulation on the retention achieved by two attachment systems at different time points within 1 year of wearing IODs. MATERIALS AND METHODS Twenty-four patients (mean age = 73.2 years; standard deviation (SD) = 3.1) wearing IODs opposed by conventional maxillary complete dentures were randomly assigned to two groups in two-by-two crossover design. Retentive Anchor (RA) and Locator (LA) were installed in the IODs of both groups for 1 year, sequentially. Coronal and sagittal interimplant angulation were measured on posterior-anterior and lateral cephalometric radiographs. Retention was measured at baseline, 1 week, 3, 6, and 12 months postattachment installation. Data were analyzed using mixed models with α = 0.05. RESULTS Mean coronal and sagittal interimplant angulations were 4.6 (SD = 2.9) and 3.5 (SD = 2.6) degrees, respectively. Only with LAs a statistically significant decrease was found in retention (average 1.1 Newton; standard error = 0.38; p = .007) per 1 degree increased sagittal interimplant angulation. CONCLUSIONS Increased interimplant angulation appears to have higher impact on the retention of LA than of RA attachments. The effect of larger interimplant angulation on the loss of attachment retention and its clinical implications should be further assessed.

In vivo evaluation of Candida spp. adhesion on titanium or zirconia abutment surfaces

OBJECTIVE Candida spp. have been found colonising implant sites in healthy or diseased subjects. The aim of this in vivo study was to evaluate the Candida spp. adhesion on machined or cast titanium and zirconia (Zc) abutment substrates. DESIGN Six healthy subjects were enrolled in this randomised crossover clinical investigation. The study was conducted in three phases according to evaluated substratum. Participants were advised to use an intraoral splint containing four discs of the same tested substrate for 24h. Two discs were located in the anterior region and two in the posterior region. DNA checkerboard hybridisation method was used to detect and quantify five different Candida species. Data on the surface roughness and the total area of discs covered by formed biofilm were also provided to correlate the species and biofilm found between different substrates. RESULTS Zc presented the highest means of surface roughness. Total area of the biofilm covering was not different in the tested groups. Moderate to high levels of target microorganisms were recorded for all the tested substrates. Zc showed the lowest indices, followed by machined pure titanium (MPT) and cast and polished titanium (CPT). Candida albicans and Candida krusei were not detected in the Zc group. The region of disc placement did not show differences in relation to Candida adhesion. CONCLUSIONS There was a significant difference in the total cell count between the three groups. CPT presented the higher mean counts, followed by MPT and Zc. There was no positive correlation between the cell counts recorded and the surface roughness or total area of formed biofilm.

Marginal fit and microbial leakage along the implant-abutment interface of fixed partial prostheses: An in vitro analysis using Checkerboard DNA-DNA hybridization

STATEMENT OF PROBLEM Bidirectional leakage through the implant-abutment interface still constitutes a major concern in implant-supported restorations. PURPOSE The purpose of this in vitro study was to evaluate the marginal fit, before and after loading simulation, of 3-unit fixed partial prostheses supported by external hexagon or Morse cone implants and to identify and quantify up to 43 microbial species penetrating through the implant-abutment interface after loading. MATERIAL AND METHODS Forty-eight dental implants with external hexagon (EH; n=24) or Morse cone (MC; n=24) connections were investigated. Experimental specimens were made from 2 implants restored with a 3-unit fixed partial prosthesis and divided into 2 groups (n=12) according to platform connection EH or MC. Vertical misfit at the implant-abutment interface was measured before and after loading (150 Ncm during 500,000 cycles at 1.8 Hz). checkerboard DNA-DNA hybridization was used to identify and quantify up to 38 bacterial and 5 Candida species colonizing the internal parts of the implants after loading. Generalized estimating equations were used for statistical analysis (α=.05). RESULTS The mean values (mm, ±SD) of vertical misfit for EH were 0.0131 ±0.002 before loading and 0.0138 ±0.002 after loading and for MC were 0.0132 ±0.003 before loading and 0.0137 ±0.001 after loading. Twenty-one bacterial species, including periodontal pathogens and C. albicans, were found colonizing the inner surfaces of EH implants after loading. None of the target species were detected in the internal parts of MC implants. CONCLUSIONS EH implants showed higher microbial counts than MC implants, in which microbial colonization was not found after loading. Detected species included nonpathogens and microorganisms related to periodontal/periimplant diseases. Further studies are needed to evaluate the effect of loading simulation on the marginal misfit of 3-unit fixed partial prostheses supported by EH or MC implants, because no significant differences could be found either before or after loading.

Effect of electromagnetic field on bone regeneration around dental implants after immediate placement in the dog mandible: a pilot study.

BACKGROUND Accelerating bone healing around dental implants can reduce the long-term period between the insertion of implants and functional rehabilitation. OBJECTIVE This in vivo study evaluated the effect of a constant electromagnetic field (CEF) on bone healing around dental implants in dogs. MATERIALS AND METHODS Eight dental implants were placed immediately after extraction of the first pre-molar and molar teeth on the mandible of two male dogs and divided into experimental (CEF) and control groups. A CEF at magnetic intensity of 0.8 mT with a pulse width of 25 μs and frequency of 1.5 MHz was applied on the implants for 20 min per day for 2 weeks. RESULT AND CONCLUSION After qualitative histological analysis, a small quantity of newly formed bone was observed in the gap between the implant surface and alveolar bone in both groups.

Shear bond strength between Ni-Cr alloy bonded to a ceramic substrate

INTRODUCTION The aim of this study was to evaluate the shear bond strength between a Ni-Cr alloy and a ceramic system submitted or not to thermocycling. MATERIALS AND METHODS Forty-eight cylinder blocks of Ni-Cr with 3.0 mm diameter by 4.0 mm hight and 48 disc-shaped specimens (7.0 mm in diameter by 2.0 mm thick) composed of ceramic were prepared. The Ni-Cr cylinder blocks were randomised in two groups of 24 specimens each. One group was submitted to air-particle abrasion (sandblasting) with 50 μm Al(2)O(3) (0.4-0.7 MPa) during 20 s, and the other group was submitted to mechanical retentions with carbide burrs. Each group was subdivided into other two groups (n = 12), submitted or not to thermocycling (500 cycles, 5-55°C). The cylinder blocks were bonded to the disc-shaped ceramic specimens under 10 N of load. The shear bond strengths (MPa) were measured using a universal testing machine at a cross head speed of 0.5 mm/min and 200 kgf of load. The data were submitted to statistical analysis (anova and Tukeys test). RESULTS The air-particle abrasion group exhibited significantly higher shear bond strength when compared to drilled group (p < 0.05). CONCLUSIONS Thermocycling decreased significantly the bond strengths for all groups tested.