Evaluation of Candida Albicans biofilm formation on various parts of implant material surfaces.

AIMS: Candida albicans adhesion to any oral substrata is the first and essential stage in forming a pathogenic fungal biofilm. In general, yeast cells have remarkable potential to adhere to host surfaces, such as teeth or mucosa, and to artificial, non-biological surfaces, such as dental materials. C. albicans adhesion to denture materials is widely recognized as the main reason for the development of stomatitis. This study compared the susceptibility of different parts of the implant system with C. albicans adhesion. MATERIAL AND METHODS: Each material maintained contact with C. albicans suspension, and biofilm formations around the implant materials were evaluated. To evaluate the biofilm formation, the XTT technique and scanning electron microscopy (SEM) were used. RESULTS: In general, a fine biofilm layer of C. albicans species was found on the surface of all examined materials. However, when examining the SEM images, candidal growth was significantly lower on the surfaces of the gingival former, abutment, and machined surface implant samples. According to the colorimetric assay (XTT), the gingival former samples revealed the lowest quantity of biofilms formed (median XTT value, 0.0891) (P < 0.001). The abutment and machined surface implant samples had low XTT values with similar values. The highest median colorimetric XTT values (0.1741), significantly higher than those of the other materials (P < 0.001), were for the bone level implant samples. CONCLUSIONS: This finding emphasizes implant treatment would be chosen complacency in patients who are prone to oral candidosis, medically compromised patients under immunosuppression, and patients with tumor who are being treated with chemotherapy or radiation.

Onset, progression and resolution of experimental peri-implant mucositis at different abutment surfaces: A randomized controlled two-centre study.

OBJECTIVES: To assess the onset, progression and resolution of experimentally induced peri-implant mucositis lesions at abutments with different microstructures in humans. MATERIAL & METHODS: In a randomized, controlled, interventional two-centre study, a total of 28 patients had received 28 target implants and were randomly allocated to either partially microgrooved (test) or machined (control) healing abutments. The study was accomplished in three phases, including a wound healing period (WH) following implant placement (12 weeks), a plaque exposure phase (EP-21 days) and a resolution phase (RP-16 weeks). Clinical (e.g. bleeding on probing-BOP), immunological (MMP-8) and microbiological (DNA counts for 11 species) parameters were evaluated. RESULTS: The incidence of peri-implant mucositis at EPd21 was comparable in both test and control groups (60.0% versus 61.5%), but markedly lower at control abutments after a nonsurgical treatment and reconstitution of oral hygiene measures at RPw16 (46.7% versus 15.4%). At any follow-up visit (i.e. EP and RP), clinical parameters, MMP-8 levels and DNA counts of major bacterial species were not significantly different between both groups. CONCLUSION: The onset, progression and resolution of experimental peri-implant mucositis lesions were comparable in both groups.

Evaluation of resistance against bacterial microleakage of a new conical implant-abutment connection versus conventional connections: an in vitro study.

The aim of the present in vitro study was to evaluate bacterial microleakage from inside to outside the implant-abutment assembly in a new design of internal conical connection compared to eight different internal connections. The design of this connection should prevent or limit microbiologic leakage into the surrounding implant tissue, that could contribute to infections without bone loss (mucositis) or with bone loss (peri-implantits). In order to investigate bacterial microleakage, the inner part of each system was inoculated with an Escherichia coli suspension. Eight different groups were considered; each group was composed of 10 dental implants, for a total of 80 implants. Groups 1-7 were considered controls, while group 8 was the test connection (an internal connection characterized by a double taper principle). Results showed that in control implants (Group 1 to 7), little microleakage was observed after the first 6 hours (500 CFU/ µl) and, after 24 hours of incubation, they showed a significant bacterial contamination in all samples (>100.000 CFU/ µl). In group 8 (test connection) no contamination was found in the first 6 hours, with 7 out of 10 implants showing no contamination even after 96 hours. Statistically significant differences were found between Group 8 and the other groups (p<0.05), whereas no significant differences were found among implants of the control groups (from group 1 to 7). Within the limits of the present study, the new connection studied presented significantly less microleakage at 96 h in comparison with the other control internal connections.

Antibacterial effect of doxycycline-coated dental abutment surfaces.

Biofilm formation on dental abutment may lead to peri-implant mucositis and subsequent peri-implantitis. These cases are clinically treated with antibiotics such as doxycycline (Doxy). Here we used an electrochemical method of cathodic polarization to coat Doxy onto the outer surface of a dental abutment material. The Doxy-coated surface showed a burst release in phosphate-buffered saline during the first 24 h. However, a significant amount of Doxy remained on the surface for at least 2 weeks especially on a 5 mA-3 h sample with a higher Doxy amount, suggesting both an initial and a long-term bacteriostatic potential of the coated surface. Surface chemistry was analyzed by x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Surface topography was evaluated by field emission scanning electron microscopy and blue-light profilometry. Longer polarization time from 1 h to 5 h and higher current density from 1 to 15 mA cm(-2) resulted in a higher amount of Doxy on the surface. The surface was covered by a layer of Doxy less than 100 nm without significant changes in surface topography. The antibacterial property of the Doxy-coated surface was analyzed by biofilm and planktonic growth assays using Staphylococcus epidermidis. Doxy-coated samples reduced both biofilm accumulation and planktonic growth in broth culture, and also inhibited bacterial growth on agar plates. The antibacterial effect was stronger for samples of 5 mA-3 h coated with a higher amount of Doxy compared to that of 1 mA-1 h. Accordingly, an abutment surface coated with Doxy has potential for preventing bacterial colonization when exposed to the oral cavity. Doxy-coating could be a viable way to control peri-implant mucositis and prevent its progression into peri-implantitis.

Bacterial microleakage at the implant-abutment interface in Morse taper implants

AIM: To evaluate the microleakage at the implant-abutment (I-A) interface of Morse tapered implants inoculated with different volumes of bacterial suspension. METHODS: Morse tapered I-A sets were selected and divided in two groups depending on the type of abutment: passing screw (PS) and solid (S), and then subdivided into four subgroups (n=6) according to the suspension volume: PS1: 0.1 µL; PS3: 0.3 µL; PS5: 0.5 µL; PS7: 0.7 µL; S1: 0.1 µL; S3: 0.>3 µL; S5: 0.5 µL and S7: 0.7 µL. A control test was performed to verify the presence of external contamination during the inoculation and the implants were incubated for microbiological analysis. The microleakage was evaluated every 24 h for 7 days by the clarity of solution. After this period, the implants were disassembled for confirmation of bacterial viability. RESULTS: All the specimens with 0.7 µL and one sample of S5 presented turbidity in the control test indicating external contamination, and were excluded from the study. After 7 days of observation, none of the specimens presented positive results for microleakage and the bacterial viability was confirmed in all specimens. The 0.1 µL and 0.3 µL volumes did not present bacterial microleakage, meaning that these volumes may be inadequate for analysis. CONCLUSIONS: None of the sets evaluated showed bacterial microleakage at the I-A interface and the volume of 0.7 µL exceeded the internal capacity of the implants...

Analysis of the bacterial seal at the implant-abutment interface in external-hexagon and Morse taper-connection implants: an in vitro study using a new methodology.

PURPOSE: The aim of this study was to compare, in vitro, external-hexagon and Morse taper implant systems with respect to bacterial sealing between implants and abutments using a new methodology. MATERIALS AND METHODS: Two groups of implants were tested. Group 1 implants had an external-hexagon implant-abutment interface (Neodent) and group 2 implants featured a Morse taper (Neodent) interface. The implants were perforated apically with a 1-mm bur until the bur reached the internal chamber. Prosthetic components were adapted with the recommended torque (32 and 10 Ncm, respectively) for each group. The implants were attached to an assay vial, with the abutment end positioned into the tube. With a sterilized syringe, the assay vials were filled with liquid culture medium (brain heart infusion broth). All the specimens were sterilized by gamma radiation. After the efficacy of sterilization had been confirmed using control samples, the apical hole was carefully opened and inoculated with Escherichia coli. RESULTS: Samples were examined daily for evidence of contamination. Within a 14-day period, 60% of the samples of group 1 were contaminated and 30% of group 2 samples were contaminated. After this period there was no further contamination in either group. CONCLUSION: Although both systems exhibited bacterial contamination, the Morse taper implants of the system used in this study provided a better bacterial seal than external-hexagon implants of the same system.

Micro-leakage at the implant-abutment interface with different tightening torques in vitro

OBJECTIVES: This study evaluated the microleakage at the implant/abutment interface of external hexagon (eH) implants and abutments with different amounts of bacteria and tightening torques. MATERIAL AND METHODS: A bacterial suspension was prepared to inoculate the implants. The first phase of this study used nine EH implants and abutments that were divided into three groups with different amounts of bacterial suspension (n=3): V0.5: 0.5 µL; V1.0: 1.0 µL e V1.5: 1.5 µL, and tightened to the manufacturer's recommended torque. The second phase of this experiment used 27 assemblies that were similar to those used in the first phase. These samples were inoculated with 0.5 µL of bacterial suspension and divided into three groups (n=9). T10: 10 Ncm; T20: 20 Ncm and T32: 32 Ncm. The samples were evaluated according to the turbidity of the broth every 24 hours for 14 days, and the bacteria viability was tested after that period. The statistical evaluation was conducted by Kruskal-Wallis testing (p<.05). RESULTS: During the first phase, groups V1.0 and V1.5 was presented with bacterial contamination in all samples after 24 h. During the second phase, two samples from group T10 and one from T20 presented positive results for bacterial contamination. Different amounts of bacterial solution led to overflow and contamination during the first 24 h of the experiment. The tightening torques did not statistically affect the microleakage in the assemblies. However, the group that was tightened to 32 Ncm torque did not show any bacterial contamination. CONCLUSION: After 14 days of experimentation, the bacteria were proven to remain viable inside the implant internal cavity.

Bacterial adhesion and colonization differences between zirconium oxide and titanium alloys: an in vivo human study.

PURPOSE: The purpose of this study was to compare zirconium oxide and titanium alloys with respect to their tendency to adhesion and colonization of two periodontal pathogens on both hard surfaces and on soft tissues in vivo. MATERIALS AND METHODS: The present study was designed as a prospective stratified randomized controlled clinical trial. Patients were scheduled to receive two implants with different types of abutments in the posterior mandible. Three months after implant placement, titanium and zirconium abutments were connected. Five weeks after abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsy samples were obtained. Abutments and biopsy specimens were analyzed by reverse-transcriptase polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated by sesile water drop before replacement. RESULTS: No statistically significant differences were found between probing depths or DNA copy numbers of A actinomycetemcomitans, P gingivalis, and total bacteria both for both titanium alloys and zirconium oxide surfaces and the biops specimens obtained from their buccal gingival. With respect to the surface free energy of zirconium and titanium abutments, zirconium abutments showed lower surface free energy than titanium abutments. CONCLUSION: The results of this study showed that zirconium oxide surfaces have comparable properties to titanium alloy surfaces in their tendency to adhesion and colonization of two periodontal pathogens on both hard surfaces and in soft tissues.

Early bacterial colonization and soft tissue health around zirconia and titanium abutments: an in vivo study in man.

AIM: To compare the early bacterial colonization and soft tissue health of mucosa adjacent to zirconia (ZrO(2)) and titanium (Ti) abutment surfaces in vivo. MATERIALS AND METHODS: Twenty edentulous subjects received two endosseous mandibular implants. The implants were fitted with either a ZrO(2) or a Ti abutment (non-submerged implant placement, within-subject comparison, left-right randomization). Sulcular bacterial sampling and the assessment of probing pocket depth, recession and bleeding on probing were performed at 2 weeks and 3 months post-surgery. Wilcoxon matched-pairs, sign-rank tests were applied to test differences in the counts of seven marker bacteria and the clinical parameters that were associated with the ZrO(2) and Ti abutments, at the two observation time points. RESULTS: ZrO(2) and Ti abutments harboured similar counts of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Peptostreptococcus micros, Fusobacterium nucleatum and Treponema denticola at 2 weeks and 3 months. Healthy clinical conditions were seen around both ZrO(2) and Ti abutments at all times, without significant differences in most clinical parameters of peri-implant soft tissue health. Mean probing depths around Ti abutments were slightly deeper than around ZrO(2) abutments after 3 months (2.2 SD 0.8 mm vs. 1.7 SD 0.7 mm, P=0.03). CONCLUSIONS: No difference in health of the soft tissues adjacent to ZrO(2) and Ti abutment surfaces or in early bacterial colonization could be demonstrated, although somewhat shallower probing depths were observed around ZrO(2) abutments after 3 month.

Preload loss and bacterial penetration on different implant-abutment connection systems

Preload loss can favor the occurrence of implant-abutment interface misfit, and bacterial colonization at this interface may lead to implant failure. The aim of this study was to evaluate the preload loss and bacterial penetration through the implant-abutment interface of conical and external hexagon connection systems subjected to thermal cycling and mechanical fatigue (TM). Four different implant-abutment connection systems were evaluated (n=6): external hexagon with universal post, Morse taper with universal post, Morse taper with universal post through bolt, and locking taper with standard abutment. The assemblies (implant-abutment) were subjected to a thermal cycling regimen (1,000 cycles of 5°C and 55°C) and to mechanical fatigue (1.0 million cycles, 1.0 Hz, 120 N). The assemblies were immersed in Tryptic Soy + Yeast Extract broth containing Streptococcus sanguinis and incubated at 37°C and 10 percent CO2 for 72 h. Detorque values were recorded. The bacterial penetration was assessed and the abutments were observed by scanning electron microscopy. The preload data were analyzed statistically by two-way ANOVA and Tukey’s test at 5 percent significance level. All screw abutment systems showed significantly higher (p<0.05) detorque values when subjected to TM and all conical systems presented bacterial penetration. The results show no relationship between the preload loss and the bacterial penetration.

A perda da pré-carga pode favorecer o desajuste da interface implante-pilar e a colonização bacteriana nesta interface pode levar a perda de implantes. O objetivo deste estudo foi avaliar a perda de pré-carga e a infiltração bacteriana através da interface implante-pilar de sistemas de conexão cônica e hexágono externo, submetidos à ciclagem térmica e fadiga mecânica (CF). Quatro diferentes sistemas de conexão implante-pilar foram avaliados (n=6): hexágono externo com munhão universal, cone Morse com munhão universal, cone Morse com munhão universal parafuso passante e cônica justaposição com pilar padrão. Os espécimes (implante-pilar) foram submetidos à ciclagem térmica (1000 ciclos a 5°C e 55°C) e à fadiga mecânica (1,0 milhão de ciclos, 1,0 Hz, 120 N). Os espécimes foram imersos em caldo Tryptic Soy + Yeast Extract contendo Streptococcus sanguinis e incubados a 37°C e 10 por cento de CO2 por 72 h. Os valores de destorque foram registrados. A infiltração bacteriana foi avaliada e os pilares foram observados por microscopia eletrônica de varredura. Os dados de pré-carga foram analisados estatisticamente por ANOVA a dois critérios e teste de Tukey, com nível de significância de 5 por cento. Todos os sistemas de pilares parafusados apresentaram maiores valores de destorque quando submetidos à CF (p<0,05) e todos os sistemas cônicos apresentaram infiltração bacteriana. Os resultados mostram que não houve relação entre a perda da pré-carga e a infiltração bacteriana.

Association between transmucosal depth of osseointegrated implants and malodor production.

PURPOSE: The aim of the present study was to test the association between transmucosal depth of 2-stage dental implants and malodor production. MATERIALS AND METHODS: Fifty-nine 2-stage implants were tested in 14 patients. Measurements were conducted 3 to 4 weeks following second-stage surgery. Measurements included healing abutment malodor scored using a subjective scale, volatile sulfide compounds levels measured using a sulfide monitor (Halimeter), and microbial sampling for anaerobic growth and malodor production. RESULTS: All the malodor-related parameters measured in this study were significantly associated with the transmucosal depth. A significant increase in severity was observed concomitant with the increase in transmucosal depth. CONCLUSION: Based upon the data from this study of 59 two-stage implants in 14 patients, it appears that transmucosal depth of 2-stage dental implants may be an important factor affecting the presence of anaerobic bacterial population and resulting malodor production within the implant-abutment interface.

Bacterial leakage along the implant-abutment interface of premachined or cast components.

In recent clinical studies, contamination of the inner parts of dental implants through bacterial penetration along the implant components has been observed. The aim of the present in-vitro study was to investigate leakage of Fusobacterium nucleatum through the interface between implants and premachined or cast abutments. Both premachined (n=10) and cast (n=10) implant-abutment assemblies were inoculated with 3.0 microL of microbial inoculum. The assemblies were completely immersed in 5.0 mL of tryptic soy broth culture medium to observe leakage at the implant-abutment interface after 14 days of anaerobic incubation. Bacterial growth in the medium, indicative of microbial leakage, was found only in 1 out of 9 samples (11.1%) in each group. Both premachined and cast abutments connected to external hexagonal implants provide low percentages of bacterial leakage through the interface in in vitro unloaded conditions if the manufacturer's instructions and casting procedures are properly followed.

Evaluation of surface characteristics of Ti-6Al-4V and Tilite alloys used for implant abutments

The aim of this study was to evaluate surface free energy (SFE), surface roughness (SR) and surface hardness (SH) of two commercially available materials for fabricating dental implant abutments. In addition, the specimens were investigated by scanning electron microscopy (SEM) to determine the surface morphology. Twenty five discs (5 x 2 mm) of Ti-6Al-4V and Tilite (Ni-Cr-Ti) alloys were used in this study. Surface free energy was determined by the contact angle formed between a drop of distilled, deionized water and the surface of the specimen of each material. The surface roughness was measured with a mechanical profilometer and the surface hardness was evaluated by means of the Vickers hardness micro indentation test. SFE, SR and SH data were analyzed using one-way ANOVA (p < 0.05). Statistical differences (p < 0.05) were found between Ti-6Al-4V (36.2 erg.cm-2; 0.2 æm) and Tilite (30.9 erg.cm-2; 0.16 æm) for SFE and SR. However, the differences between the surface hardness values of Ti-6Al-4V (325.0 kg/mm²) and Tilite (324.3 kg/mm²) were not statistically significant (p > 0.05). Evaluations by SEM revealed different surface morphology. Within the limits of this study, it can be concluded that the Ti-6Al-4V and Tilite alloys showed differences in surface properties, except for surface hardness, suggesting that both alloys may be considered appropriate for producing abutments. Further studies are, however, necessary to elucidate the biological responses to implant abutments made with these alloys.

O objetivo deste estudo foi avaliar a energia livre de superfície (ELS), rugosidade superficial (RS) e dureza de superfície (DS) de dois materiais disponíveis comercialmente para fabricação de "abutments" de implante. Em acréscimo, os espécimes foram investigados por microscopia eletrônica de varredura (MEV) para determinar a morfologia de superfície. Vinte e cinco discos de ligas de Ti-6Al-4V e Tilite (Ni-Cr-Ti) (5 x 2 mm) foram usados neste estudo. A energia livre de superfície foi determinada pela mensuração do ângulo de contato formado entre uma gota de água destilada e deionizada e a superfície do espécime para cada material. A rugosidade superficial foi mensurada com uso de um rugosímetro e a dureza de superfície foi avaliada por meio do teste de microdureza Vickers. Os dados foram analisados usando Análise de variância (P < 0,05). Foram encontradas diferenças significantes (P < 0,05) para os valores de ELS e RS entre Ti-6Al-4V (36,2 erg.cm-2; 0,2 æm) e Tilite (30,9 erg.cm-2; 0,16 æm). Entretanto, os valores de dureza de superfície não foram diferentes para ambos os materiais (Ti-6Al-4V - 325,0 kg/mm² e Tilite - 324,3 kg/mm²) (P > 0,05). A análise topográfica dos materiais pela MEV revelou superfícies diferentes. Dentro das limitações deste estudo, concluiu-se que as ligas de Ti-6Al-4V e Tilite mostraram diferenças nas propriedades de superfícies, exceto dureza, sugerindo que ambas as ligas são adequadas para a confecção de "abutments". Entretanto, estudos são necessários para evidenciar as respostas biológicas aos "abutments" de implantes confeccionados com essas ligas.

Soft tissue response to clinically contaminated and thereafter cleaned titanium surfaces. An experimental study in the rat.

The aim of the present study was to evaluate the soft tissue response to intra-orally exposed and contaminated titanium surfaces (machined, blasted or polished) after being chemically and/or mechanically cleaned. Eight adult Sprague-Dawley rats were used for histomorphometrical and histological analyses. A total of 44 experimental abutments (26 tests and 18 controls) were inserted into abdominal skinpockets of the rats for 6 weeks. No differences regarding the soft tissue response between the different surface characteristics analysed and between test and control could be observed.

Design features that may influence bacterial plaque retention: a retrospective analysis of failed implants.

OBJECTIVE: The purpose of this study was to conduct a postmortem examination of retrieved failed dental implants to identify design characteristics that may have contributed to premature loss. METHOD AND MATERIALS: Forty-five failed implants retrieved from 40 patients with no significant risk factors for implant failure (e.g., history of smoking or diabetes) were examined by scanning electron microscopy. All implants were placed by general dentists or periodontists in private practice and had functioned for an average of 4 years. RESULTS: Several design features of currently used implants present plaque-retentive areas. Plaque accumulation occurred along the implant-transmucosal abutment interfaces, transmucosal abutment-prosthesis interfaces, implant-prosthesis interfaces, and on surfaces of the abutment, the implant, and the prosthesis. The size of the microgap between the various components, the degree of surface roughness of the restorations and abutments, the exposure of plasma-sprayed coatings and threaded surfaces of implants, and overcontouring of implant restorations contributed to plaque accumulation and provided an ideal environment for bacterial colonization. CONCLUSION: These implant features may be key precipitating or exacerbating factors in the development of peri-implant inflammation, predisposing patients to implant failure.

In vivo early plaque formation on pure titanium and ceramic abutments: a comparative microbiological and SEM analysis.

A lack of information exists about the influence of different implant abutment materials on bacterial colonization and its role in the development of perimplantar infections. In order to study these aspects, removable acrylic devices, harboring samples of titanium and novel ceramic abutments (Nobel Biocare) were adapted to the molar-premolar region in 2 mandibular quadrants of 4 volunteers. Samples of each material were collected at 6 and 24 h, 7 and 14 days. Samples were observed by scanning electron microscopy and bacterial counts were made by means of ATP detection and direct plate count. The electron micrographs demonstrated that the bacteria colonization was already present after 6 h of presence in the oral cavity. After 24 h, both the materials were covered by several layers of bacterial cells. No differences in microbial colonization were observed between titanium and ceramic samples. The microbiological analysis confirmed the presence of relevant amounts of microbial cells on the tested samples. The maximum of colonization was achieved after 24 h in the oral cavity and the bacterial counts remained constant over the 14 day period. No significant differences were observed between the two materials analyzed in this study. In addition, ATP-bioluminescence technology was demonstrated to be a suitable system to evaluate bacterial colonization in the oral cavity.