In-vitro polymicrobial oral biofilm model represents clinical microbial profile and disease progression during implant-related infections.

AIM: Clinically relevant in-vitro biofilm models are essential and valuable tools for mechanistically dissecting the etiopathogenesis of infectious diseases and test new antimicrobial therapies. Thus, the aim of this study was to develop and test a clinically relevant in-vitro oral polymicrobial biofilm model that mimics implant-related infections in terms of microbial profile. METHODS AND RESULTS: For this purpose, 24-well plate system was used to model oral biofilms, using three different microbial inoculums to grow in-vitro biofilms: (1) human saliva from periodontally healthy patients; (2) saliva as in inoculum 1 + Porphyromonas gingivalis strain; and (3) supra and subgingival biofilm collected from peri-implant sites of patients diagnosed with peri-implantitis. Biofilms were grown to represent the dynamic transition from an aerobic to anaerobic community profile. Subsequently, biofilms were collected after each phase and evaluated for microbiological composition, microbial counts, biofilm biomass, structure, and susceptibility to chlorhexidine (CHX). Results showed higher live cell count (P < .05) for biofilms developed from patients' biofilm inoculum, but biomass volume, dry weight, and microbiological composition were similar among groups (P > .05). Interestingly, according to the checkerboard DNA-DNA hybridization results, the biofilm developed from stimulated human saliva exhibited a microbial composition more similar to the clinical subgingival biofilm of patients with peri-implantitis, with proportions of the main pathogens closer to those found in the disease. In addition, biofilm developed using saliva as inoculum was shown to be susceptible to CHX with significant reduction in bacteria compared with biofilms without exposure to CHX (P < .05). CONCLUSION: The findings suggested that the in-vitro polymicrobial biofilm developed from human saliva as inoculum is a suitable model and clinically relevant tool for mimicking the microbial composition of implant-related infections.

Funding assistance and global productivity in the field of implant overdentures: A bibliometric analysis of 35 years.

STATEMENT OF PROBLEM: Implant overdentures have been widely used as a treatment option for edentulous patients. However, the development of implants, aside from commercial growth, requires funding assistance to determine scientific reliability and clinical applications. Nonetheless, bibliometric studies in the implant overdenture field are lacking. PURPOSE: The purpose of this bibliometric analysis was to evaluate the prevalence of funding and its bibliometric associated parameters according to the financial assistance granted and the implant overdenture documentation over time. MATERIAL AND METHODS: Six databases were assessed, and 12 bibliometric parameters related to the economy, geographical origin, publication details, and corresponding author metrics were recorded. An incidence rate ratio was applied by using a multiple Poisson regression model (α=.05) to assess the association between funding and each bibliometric parameter. RESULTS: In total, 1369 studies published between 1986 and 2021 were assessed bibliometrically. The prevalence of funded studies was 34.8% (n=477). The parameter associated with the presence of funding was country income (P<.01), with those having a high and upper-middle income being more funded than those with a lower-middle and low income. Oceania and South America were the continents more frequently funded (P<.05), with Africa being the least frequent. Randomized and nonrandomized controlled trials, in vitro studies, and in silico studies were more funded (P<.001) than case reports and series. Stud and ball attachment systems were more funded (P<.01) than studies with more than 1 retention system. Funding increased over time (P<.01), and corresponding authors with a higher h-index had more studies funded (P<.05). CONCLUSIONS: The number of funded studies on implant overdentures increased over the years. Other bibliometric parameters such as country income, continent, study design, retention system, and corresponding author h-index were associated with the frequency of funded studies published.

Factors and clinical outcomes for standard and mini-implants retaining mandibular overdentures: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Standard-diameter dental implants are not always applicable because of anatomic limitations of the residual ridge. Thus, mini-implants have been increasingly used and offer an alternative. However, data regarding prosthetic complications, maintenance factors, and clinical outcomes are limited. PURPOSE: The purpose of this systematic review and meta-analysis was to compare prosthetic complications and maintenance events and clinical outcomes in residual ridges rehabilitated with mandibular implant overdentures (IODs) by using standard implants or mini-implants. MATERIAL AND METHODS: Nine electronic databases were searched. Quantitative analyses to measure the risk ratio (RR) and standardized mean difference (SMD) were applied. Those methods were used to assess prosthetic complications and maintenance events (abutment adjustments, replacement of retentive element, occlusal adjustment, and overdenture fracture) and clinical outcomes related to postoperative pain, probing depth (PD), plaque index (PI), marginal bone loss (MBL), and implant survival rate. RESULTS: Altogether, 7 publications were selected. Mini-implants presented reduced abutment adjustments (RR 0.23 [0.07, 0.73], P=.01), replacement of retentive element (RR 0.41 [0.31, 0.54], P<.001), occlusal adjustment (RR 0.53 [0.31, 0.91], P=.02), and overdenture fracture (RR 0.46 [0.23, 0.94], P=.03) compared with standard implants. Additionally, mini-implants presented lower values for PI at 6 months (SMD -0.27 [-0.47, -0.08], P=.006) and 12 months (SMD -0.25 [-0.46, -0.05], P=.01). No additional tangible differences were noted. CONCLUSIONS: Mini-implants might be an alternative choice based on the number of prosthetic complications and maintenance events. This was also confirmed by the comparable clinical data between standard implants and mini-implants.

Clinical efficacy of triclosan-containing toothpaste in peri-implant health: A systematic review and meta-analysis of randomized clinical trials.

STATEMENT OF PROBLEM: Recent evidence suggests that toothpaste containing 0.3% triclosan (TCS) is more effective than regular toothpaste in improving clinical periodontal conditions. However, a consensus on whether TCS favors a healthy peri-implant environment is limited. PURPOSE: The purpose of this systematic review and meta-analysis of randomized clinical trials was to determine the effects of TCS-containing toothpaste on dental implant health based on clinical, immunological, and microbiological parameters, as well as on reported adverse events. MATERIAL AND METHODS: Clinical studies comparing peri-implant conditions in participants by using TCS toothpaste versus conventional fluoride toothpaste (control) were extracted from 9 databases. The studies were assessed with the Cochrane risk-of-bias tool for randomized clinical trials (RoB 2). Datasets for bleeding on probing (BOP), probing depth (PD), clinical attachment level (CAL), gingival index (GI), plaque index (PI), osteo-immunoinflammatory mediators, and bacterial load were plotted, and the standard mean difference (SMD) quantitative analysis was applied by using the Rev Man 5.3 software program. Adverse effects reported by the studies were also tabulated. The certainty of evidence was assessed by using the grading of recommendations assessment, development, and evaluation approach. RESULTS: Six studies were included in the meta-analyses. BOP was higher in the control group than in the TCS toothpaste group at 3 months (SMD -0.59 [-1.11, -.07] P=.002, I2=77%) and 6 months (SMD -0.59 [-0.83, -0.34] P=.009, I2=79%). PD (SMD -0.04 [-0.08, -0.00] P=.04, I2=0%) was also deeper in the control group versus TCS toothpaste at 6 months (SMD -0.41 [-0.73, -0.10] P=.04, I2=77%). CAL, GI, and PI did not differ between groups (P>.05). Among the osteo-immunoinflammatory mediators, IL-10 levels increased, and IL-1ß and osteoprotegerin levels decreased in the TCS toothpaste group (P<.05). Microbiological findings found that TCS toothpaste prevented the growth of periodontal pathogens, specifically in up to approximately 20% of the Prevotella intermedia. Adverse effects were not reported after toothbrushing in either group. However, most studies had "some" or "high" risk of bias, and the certainty of the evidence was considered to be "very low." CONCLUSIONS: Most studies were short-term (3 and 6 months) analyses, and the results found that, although TCS-containing toothpaste had positive osteo-immunoinflammatory and microbiologic results, clinical parameters, including CAL, GI, and PI, were not influenced.

Bibliometric assessment in implant-retained overdenture articles: Mapping citation and journal impact factor trends.

STATEMENT OF PROBLEM: Implant-retained overdentures are a recognized treatment option. However, a comprehensive assessment of all articles on implant-retained overdentures to identify publication standards such as mean citation and the Journal Citation Reports (JCR) impact factor is lacking. PURPOSE: The purpose of this bibliometric assessment was to evaluate the association of mean citation and JCR impact factor with bibliometric parameters in articles on implant-retained overdentures. MATERIAL AND METHODS: Articles reporting randomized controlled clinical trials (RCTs) and nonrandomized controlled clinical trials (N-RCTs); case reports and series; retrospective studies; and in silico, in vitro, or systematic reviews in 6 databases were included. Data were extracted, and 2 multiple Poisson regressions analyses were applied (α=.05). The dependent variables were mean citation and JCR impact factor, which were evaluated to identify their association with bibliometric parameters by using prevalence ratio (PR) values. RESULTS: A total of 1369 articles published from 1986 to 2021 were included. The data revealed a high mean citation and high JCR impact factor for RCT, N-RCT, retrospective, and in vitro studies (P<.05). In silico studies presented a high mean citation (P<.001). Senior researchers with a high h-index were more likely to have a high mean citation and publications with a high JCR impact factor (P<.001). Also, senior authors associated with an international network were more likely to have a high mean citation (P=.001). High-income countries had more studies with a high mean citation and JCR impact factor (P<.05). Higher JCR impact factors were associated with articles evaluating only the maxilla or mandible (P<.05). The topics "implant setting" and "macrodesign" were associated with a high mean citation (P<.05). CONCLUSIONS: The publication trends suggest a high mean citation and a high JCR impact factor for clinical designs (RCT, N-RCT, retrospective) and in vitro studies. The same pattern was also displayed for researchers with a high h-index and located in high-income countries.

Patient-reported outcome measures and clinical assessment of implant-supported overdentures and fixed prostheses in mandibular edentulous patients: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: A consensus based on patients' perceptions as to whether to use overdentures or fixed prostheses to rehabilitate mandibular edentulous arches is limited. PURPOSE: The purpose of this systematic review and meta-analysis was to compare the patient-reported outcome measures (PROMs) and clinical outcomes associated with implant-supported overdentures and fixed prostheses in edentulous mandibles. MATERIAL AND METHODS: Nine electronic databases were searched for randomized clinical trials (RCTs) and nonrandomized clinical trials (N-RCTs). The risk of bias was assessed by the revised Cochrane risk of bias tool for RCTs (RoB 2) and N-RCT (ROBINS-I). Data sets for oral health-related quality of life (OHRQoL), satisfaction, survival rate, implant probing depth, and marginal bone loss were plotted, and the appropriate analyses were applied by using the Rev Man 5.3 software program. Certainty of evidence was also evaluated by means of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: Ten eligible trials were included and evaluated quantitatively. For 3 domains of OHRQoL, fixed prostheses showed significantly higher quality of life when compared with overdentures regarding functional limitation (P<.001), physical disability (P=.001), and physical pain (P=.003). Fixed prostheses also improved satisfaction, when compared with overdentures for comfort (P=.02), ease of mastication (P<.001), retention (P<.001), and stability (P<.001). The same pattern was observed for overall OHRQoL (P=.01) and satisfaction (P=.01) in which fixed prostheses improved patient satisfaction. Only ease of cleaning presented greater satisfaction for the overdenture group. Clinical parameters did not differ statistically (P>.05) between both types of prosthesis. CONCLUSIONS: Fixed rehabilitations for mandibular edentulous patients seem to be a well-accepted treatment from the patients' oral health perspective. However, mandibular overdentures are no less efficient than fixed prostheses in terms of clinical outcomes.

Peri-implant and esthetic outcomes of cemented and screw-retained crowns using zirconia abutments in single implant-supported restorations-A systematic review and meta-analysis.

OBJECTIVES: To evaluate the peri-implant tissue changes and esthetic outcomes of cemented and screw-retained crowns of single-tooth implants in the esthetic zone using zirconia abutments. MATERIAL AND METHODS: An electronic search was performed on nine databases. The risk-of-bias was assessed by the revised Cochrane risk-of-bias tool for randomized (RoB 2) and non-randomized (ROBINS-I) clinical trials. Marginal bone level change, soft tissue thickness, bleeding on probing, probing depth, survival rates of implants and crowns, complications, plaque and papilla indexes, and pink esthetic score data were extracted and analyzed. The certainty of evidence was accessed through the GRADE approach. RESULTS: Nine records were included and 7 were used in the meta-analyses. Screw-retained crowns presented greater marginal bone level change (MD -0.04 [-0.08, -0.00] p = 0.04, I2  = 0%) compared to cemented crowns up to 1-year. At 3 and 4 years no significant differences (p > 0.05) were observed. Soft tissue thickness did not differ between groups (p > 0.05). The bleeding on probing was higher in cemented group than in screw-retained crowns at 1-year (MD 0.17 [0.08, 0.27] p = 0.0005, I2  = 0%), at medium-term periods (3 and 4 years) no statistically significant differences (p > 0.05) were observed for this outcome. Probing depth, survival rates of implants and crowns, complications, and plaque index, as well as esthetic analysis using the papilla index and pink esthetic score did not differ statistically (p > 0.05) between both retention systems at short and medium-term periods. CONCLUSION: The connection system considering zirconia abutments presented no influence on peri-implant parameters and esthetics evaluation for medium-term periods (3 and 4 years).

Clinical efficacy of anodized dental implants for implant-supported prostheses after different loading protocols: A systematic review and meta-analysis.

OBJECTIVES: To summarize the clinical performance of anodized implants connected to different prostheses design after immediate/early (IL) or conventional loading (CL) protocols. MATERIALS AND METHODS: Seven databases were surveyed for randomized (RCTs) and non-randomized controlled clinical trials (CCTs). Studies comparing IL vs. CL protocol of anodized implants supporting single crown, fixed partial denture (FPD), full-arch fixed dental prosthesis (FDP), or overdenture were included. Risk-of-bias was evaluated using Cochrane Collaboration tools. Meta-analyses for different follow-up were analyzed, followed by heterogeneity source assessment and GRADE approach. The outcomes included implant survival rate, marginal bone loss (MBL), implant stability quotient (ISQ), probing depth (PD), plaque index (PI), and peri-implantitis prevalence. RESULTS: From 24 eligible studies, 22 were included for quantitative evaluation. Most RCTs (58%, n = 11) and all the 5 CCTs had high and serious risk-of-bias, respectively. Overall, pooling all prosthesis design, no difference between IL vs. CL protocols was observed for all outcomes (p > .05). However, according to prosthesis type subgroups, CL reduced MBL for full-arch FDP (p < .05). In a point-in-time assessment, with overdenture, although IL presented higher PI (12 months), it showed lower MBL (≥24 months), higher ISQ (3 months), and lower PD (6 and 12 months) (p < .05). Conversely, PD was higher for IL in single crown (3 and 6 months) (p < .05). Regarding MBL, IL demonstrated higher mean difference for full-arch FDP (36 months) and FPD (12 and 36 months) (p < .05). CONCLUSION: Within the limitations of this study, overall, there is no significant difference in the outcomes between IL and CL loading protocols.

Biofilm Interactions of Candida albicans and Mitis Group Streptococci in a Titanium-Mucosal Interface Model.

Streptococci from the mitis group (represented mainly by Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii) form robust biofilms with Candida albicans in different experimental models. These microorganisms have been found in polymicrobial biofilms forming on titanium biomaterial surfaces in humans with peri-implant disease. The purpose of this work was to study mutualistic interactions in biofilms forming on titanium and their effect on the adjacent mucosa, using a relevant infection model. Single and mixed biofilms of C. albicans and each Streptococcus species were grown on titanium disks. Bacterial and fungal biovolume and biomass were quantified in these biofilms. Organotypic mucosal constructs were exposed to preformed titanium surface biofilms to test their effect on secretion of proinflammatory cytokines and cell damage. C. albicans promoted bacterial biofilms of all mitis Streptococcus species on titanium surfaces. This relationship was mutualistic since all bacterial species upregulated the efg1 hypha-associated gene in C. albicans Mixed biofilms caused increased tissue damage but did not increase proinflammatory cytokine responses compared to biofilms comprising Candida alone. Interestingly, spent culture medium from tissues exposed to titanium biofilms suppressed Candida growth on titanium surfaces.IMPORTANCE Our findings provide new insights into the cross-kingdom interaction between C. albicans and Streptococcus species representative of the mitis group. These microorganisms colonize titanium-based dental implant materials, but little is known about their ability to cause inflammation and damage of the adjacent mucosal tissues. Using an in vitro biomaterial-mucosal interface infection model, we showed that mixed biofilms of each species with C. albicans enhance tissue damage. One possible mechanism for this effect is the increased fungal hypha-associated virulence gene expression we observed in mixed biofilms with these species. Interestingly, we also found that the interaction of multispecies biofilms with organotypic mucosal surfaces led to the release of growth-suppressing mediators of Candida, which may represent a homeostatic defense mechanism of the oral mucosa against fungal overgrowth. Thus, our findings provide novel insights into biofilms on biomaterials that may play an important role in the pathogenesis of mucosal infections around titanium implants.

Photofunctionalization as a suitable approach to improve the osseointegration of implants in animal models-A systematic review and meta-analysis.

OBJECTIVES: To determine whether photofunctionalization influences dental implant osseointegration. MATERIAL AND METHODS: Data on osseointegration rates were extracted from 8 databases, based on bone-to-implant contact (BIC) and pushout tests. Internal validity was accessed through the SYRCLE risk of bias tool for animal experimental studies. Meta-analyses were performed for investigation of the influence of photofunctionalization on implant osseointegration, with a random effect and a confidence interval of 95%. The certainty of evidence was accessed through the GRADE approach. RESULTS: Thirty-four records were identified, and 10 were included in the meta-analysis. Photofunctionalized implants showed higher mean values for BIC in rabbits (MD 6.92 [1.01, 12.82], p = .02), dogs (MD 23.70 [10.23, 37.16], p = .001), rats (MD 20.93 [12.91, 28.95], p < .0001), and in the pooled BIC analyses (MD 14.23 [7.80, 20.66], p < .0001) compared to those in control implants in the overall assay. Conversely, at late healing periods, the pooled BIC meta-analyses showed no statistically significant differences (p > .05) for photofunctionalized and control implants at 12 weeks of follow-up. For pushout analysis, photofunctionalized implants presented greater bone strength integration (MD 19.92 [13.88, 25.96], p < .0001) compared to that of control implants. The heterogeneity between studies ranged from "not important" to "moderate" for rabbits I2  = 24%, dogs I2  = 0%, rats I2  = 0%, and pooled BIC (I2  = 49%), while considerable heterogeneity was observed for pushouts (I2  = 90%). CONCLUSION: Photofunctionalization improves osseointegration in the initial healing period of implants, as summarized from available data from rabbit, dog, and rat in vivo models.

Proteomic profile of the saliva and plasma protein layer adsorbed on Ti-Zr alloy: the effect of sandblasted and acid-etched surface treatment.

Titanium-zirconium (Ti-Zr) alloy has been widely used as a biomaterial for implant devices, and it is commonly treated by sandblasting followed by acid etching (SLA) to improve biological responses. Although protein adsorption is the first biological response, the effect of this SLA treatment on the proteomic profile of proteins adsorbed from saliva and blood plasma has not been tested. In this study, the proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Streptococcus sanguinis was used to test whether the protein layer affects bacterial adhesion. SLA treatment affected the proteomic profile, showing exclusive proteins adsorbed from saliva (14) and plasma (3). However, both groups exhibited close patterns of intensity for common proteins, molecular functions and biological processes mediated by proteins. Interestingly, Ti-ZrSLA showed higher bacterial adhesion (∼1.9 fold over) for the surface coated with plasma proteins. Therefore, SLA treatment of Ti-Zr alloy changed the proteomic profile, which may affect bacterial adhesion.

Dimensional precision of implant-supported frameworks fabricated by 3D printing.

STATEMENT OF PROBLEM: Selective laser melting (SLM) is a promising additive technology for clinical practice, but data on dimensional precision assessed by marginal fit combined with stress and strain investigations of implant-supported fixed partial dentures (FPDs) are lacking. PURPOSE: The purpose of this in vitro study was to verify whether the SLM additive manufacturing technology provides better dimensional precision for 3-unit FPD frameworks than subtractive manufacturing with soft metal block (SMB) milling and the standard casting technique. MATERIAL AND METHODS: Thirty 3-unit implant-supported FPDs with Co-Cr frameworks were made by the casting, SMB milling, and SLM methods (n=10). The marginal fit between the framework and the implant abutment was evaluated with photoelastic (PH) and strain gauge (SG) models. Stress and strain in the implant-supported system were measured by quantitative PH and SG analyses after prosthetic screw tightening. Data were subjected to the Kruskal-Wallis test, Mann-Whitney U test, and Spearman correlation test (α=.05). RESULTS: The framework manufacturing method affected the marginal fit (P<.001), stress, and strain values (P<.05). The SLM group showed the best mean ±standard deviation marginal fit (µm) (PH model: 8.4 ±3.2; SG model: 6.9 ±2.1) in comparison with SMB milling (PH model: 42.3 ±15.7; SG model: 41.3 ±15.3) and casting (PH model: 43.5 ±27.8; SG model: 41.3 ±24.6) (P<.05). SLM showed lower mean ±standard deviation stress and strain values (60.3 ±11.6 MPa; 91.4 ±11.1 µstrain) than casting (225.5 ±142.8 MPa; 226.95 ±55.4 µstrain) and SMB milling (218.6 ±101.7 MPa; 289.7 ±89.3 µstrain) (P<.05). A positive correlation was observed between fit and stress or strain for all groups (P<.05). CONCLUSIONS: Three-unit FPD frameworks made using the SLM technology showed better dimensional precision than those obtained with the casting or SMB milling methods.

Dose-response effect of chlorhexidine on a multispecies oral biofilm formed on pure titanium and on a titanium-zirconium alloy.

This study aimed to test the dose-response effect of chlorhexidine on multispecies biofilms formed on commercially pure titanium (cpTi) and titanium-zirconium (TiZr) alloy. Biofilms were formed on cpTi and TiZr discs and treated two times per day with five different chlorhexidine concentrations (0.12, 0.20, 0.50, 1, 2%). The biofilms were collected for microbiological, biochemical and microscopic analyses. The significance of differences among groups was evaluated by linear regression, ANOVA, Bonferroni and Tukey tests. The mean number of colony-forming units decreased as the chlorhexidine concentration increased for both cpTi and TiZr (p < 0.05). The maximum effect was observed with the 0.5% concentration. Confocal microscopy images suggested an increase in the number of dead bacterial cells with increased chlorhexidine concentration. The biofilm pH increased after chlorhexidine exposure (p < 0.05). Chlorhexidine showed an antimicrobial dose-response effect in controlling biofilm on cpTi and TiZr. 0.5% chlorhexidine can be used to achieve the maximum antimicrobial effect on both materials.

Effect of brushing and thermocycling on the shade and surface roughness of CAD-CAM ceramic restorations.

STATEMENT OF PROBLEM: The effects of toothbrushing (B) and thermocycling (TC) on the surface texture of different materials with various fabrication processes have been investigated. However, studies of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations are limited. PURPOSE: The purpose of this in vitro study was to evaluate the effect of B and TC on the color stability and surface roughness of extrinsically characterized and glazed CAD-CAM ceramic restorations. MATERIAL AND METHODS: Lithium disilicate CAD ceramic (n=90) and zirconia ceramic (n=90) were studied. All specimens were crystallized/sintered, characterized, and glazed following the manufacturer's recommendation. The specimens were divided into 9 different groups: B, TC, and a combination of B plus TC (B+TC). Brushing was performed at 50 000, 100 000, and 150 000 cycles, simulating an oral environment of 5, 10, and 15 years. Thermocycling was performed at 6000, 12 000, and 18 000 cycles, simulating an oral environment of 5, 10, and 15 years. Brushing plus TC was performed with the combination of the 50 000 cycles of B, then 6000 cycles of TC, and 10 000 cycles of B, then 12 000 cycles of TC, and 15 000 cycles of B, then 18 000 cycles of TC. The color and surface roughness of each specimen were measured before and after all interventions with simulated cycles. Color differences (ΔE) and surface roughness (ΔRa) data were analyzed using 2-way ANOVA, followed by the least significant difference test (α=.05). The correlation between ΔE and ΔRa was statistically analyzed using the Pearson correlation analysis. RESULTS: Within the lithium disilicate CAD groups, intervention did not result in any significant differences in color change (P>.05). Within the zirconia groups, a 15-year clinical simulation revealed significantly higher ΔE values than a simulated 5-year exposure (P=.017). Increased simulated cycles showed significantly higher Ra values for all groups. Within the zirconia groups, B revealed significantly smoother surfaces than TC (P<.001) and B+TC interventions (P<.001). For the zirconia, simulating B+TC for15 years revealed significantly higher Ra values than the groups of B+TC for 5 years (P<.001) and B+TC for 10 years (P=.003). No correlation (lithium disilicate CAD, r=.079; P=.462; zirconia, r=.001; P=.989) was found between the color change and surface roughness. CONCLUSIONS: For both lithium disilicate CAD and zirconia, color changes were below the selected clinical perceptible threshold (ΔE=2.6) after all intervention and simulated cycles. All mean surface roughness measurements were below 0.2 µm. Generally, the surface of both lithium disilicate CAD and zirconia became rougher. No correlation was found between color difference and surface roughness for either material.

Influence of spark erosion on the fit of screw-retained Co-Cr fixed complete denture frameworks veneered with different materials.

STATEMENT OF PROBLEM: Spark erosion is a fit corrective technology that can be used even after the veneering material has been applied. The framework does not require sectioning, thus preserving its mechanical resistance. However, the spark erosion effect on veneered Co-Cr fixed complete denture (FCD) frameworks has not been investigated. PURPOSE: The purpose of this in vitro study was to evaluate whether spark erosion is effective in improving marginal fit on screw-retained Co-Cr FCD frameworks veneered with different materials. A comparison between ceramic applications and simulated ceramic firing cycles was also investigated. MATERIAL AND METHODS: Forty FCD frameworks were fabricated with a Co-Cr alloy. Four groups (n=10) were obtained according to the veneer material used on frameworks: HR (heat-polymerized resin); LR (light-polymerized resin); C (ceramic); and SC (simulated ceramic firing cycle). The spark erosion process was conducted for all groups. The marginal fit was analyzed according to the single-screw test protocol, and the measurements were performed at 3 evaluation times: initial, after veneer material application, and after spark erosion process. The results were submitted to a 2-way repeated measures ANOVA and the Tukey honest significant differences test (α=.05). RESULTS: Poorer marginal fit (in micrometers) was noted after veneer material application, where the HR and C groups presented the worst values (HR: 170; LR: 72; C: 165; SC: 86; P<.05). The spark erosion process was effective in improving the fit for all groups (HR: 109; LR: 52; C: 110; SC: 60; P<.05). CONCLUSIONS: Spark erosion improved the fit of Co-Cr FCD frameworks veneered with different materials. An actual ceramic application should be used to assess distortions generated by veneer material application instead of using only simulated ceramic firing cycles.

Electrochemical behavior of titanium exposed to a biofilm supplemented with different sucrose concentrations.

STATEMENT OF PROBLEM: Biofilms can reduce the corrosion resistance of titanium because of the bacterial metabolism of fermentable carbohydrates, including sucrose. However, studies evaluating whether biofilms exposed to higher sucrose concentrations can affect the electrochemical behavior of titanium are lacking. PURPOSE: The purpose of this in vitro study was to test the electrochemical behavior of titanium previously exposed to biofilm supplemented with different sucrose concentrations. MATERIAL AND METHODS: Streptococcus mutans UA159 biofilms were formed on commercially pure titanium (cpTi) surfaces and supplemented constantly with different sucrose concentrations (0%, 1%, 10%, and 40%) for 7 days (experimental groups) (n=12 per group). CpTi disks without biofilm were used as a control (n=12). The standard electrochemical tests open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic curve were performed. Data were submitted to ANOVA and the Tukey honestly significant difference (HSD) tests (α=.05). RESULTS: The biofilm exposed to sucrose had an increased biofilm dry weight (P<.05). The polysaccharide amount and the pH drop were higher in the groups exposed to sucrose (P<.05). No difference was noted between the control and experimental groups for the electrochemical properties of cpTi (P>.05). CONCLUSIONS: Biofilms exposed to greater carbohydrate concentration did not alter the corrosive behavior of titanium.

Initial investigation of the corrosion stability of craniofacial implants.

STATEMENT OF PROBLEM: Although craniofacial implants have been used for retention of facial prostheses, failures are common. Titanium undergoes corrosion in the oral cavity, but the corrosion of craniofacial implants requires evaluation. PURPOSE: The purpose of this in vitro study was to investigate the corrosion stability of commercially pure titanium (CP Ti) exposed to simulated human perspiration at 2 different pH levels (5.5 and 8). MATERIAL AND METHODS: Fifteen titanium disks were divided into 3 groups (n=5 per group). The control group was subjected to simulated body fluid (SBF) (control). Disks from the 2 experimental groups were immersed in simulated alkaline perspiration (SAKP) and simulated acidic perspiration (SACP). Electrochemical tests, including open circuit potential (3600 seconds), electrochemical impedance spectroscopy, and potentiodynamic tests were performed according to the standardized method of 3-cell electrodes. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference tests (α=.05). RESULTS: Simulated human perspiration reduced the corrosion stability of CP Ti (P<.05). The SBF group presented the lowest capacitance values (P<.05). SAKP and SACP groups showed increased values of capacitance and showed no statistically significant differences (P>.05) from each other. The increase in capacitance suggests that the acceleration of the ionic exchanges between the CP Ti and the electrolyte leads to a lower corrosion resistance. SAKP reduced the oxide layer resistance of CP Ti (P<.05), and an increased corrosion rate was noted in both simulated human perspiration groups. CONCLUSIONS: Craniofacial implants can corrode when in contact with simulated human perspiration, whereas alkaline perspiration shows a more deleterious effect. Perspiration induces a more corrosive effect than simulated body fluid.

Biomechanical behavior of 2-implant- and single-implant-retained mandibular overdentures with conventional or mini implants.

STATEMENT OF PROBLEM: The use of single or mini dental implants to retain mandibular overdentures is still questionable. PURPOSE: The purpose of this finite element analysis (FEA) study was to investigate the biomechanical behavior of 2- and single-implant-retained mandibular overdentures with conventional or mini implants. MATERIAL AND METHODS: Four 3-dimensional (3D) finite element models were constructed with the following designs of mandibular overdentures: 2 (group 2-C) and single (group 1-C) conventional external hexagon implants with ball or O-ring attachment and 2 (group 2-M) and single (group 1-M) 1-piece mini implants. A 150-N axial load was applied bilaterally and simultaneously on the first molar. Overdenture displacement, von Mises equivalent stress (implants and/or prosthetic components), and maximum principal stresses (peri-implant bone) were recorded numerically and then color-coded and compared among the groups. RESULTS: The overdenture displacement (in mm) was higher for the 1-M (0.16) and 2-M (0.17) groups when compared with 1-C (0.09) and 2-C (0.08). Irrespective of the type of implant, the single-implant groups presented higher values of stress (in MPa) on the implants than did the 2-implant groups (1-C=52.53; 1-M=2.95; 2-C=34.66; 2-M=2.37), ball attachment (1-C=201.33; 2-C=159.06), housing or O-ring (1-C=125.01; 1-M=1.96; 2-C=88.84; 2-M=1.27), and peri-implant cortical bone (1-C=19.37; 1-M=1.47; 2-C=15.70; 2-M=1.06). The mini implant overdentures presented lower stress values on the implants, housing or O-ring, and peri-implant bone than did the conventional implant overdentures, regardless of the number of implants. CONCLUSIONS: The 2-implant-retained overdentures exhibited lower stresses than the single- implant-retained overdentures, irrespective of the type of implant. The mini implants demonstrated higher overdenture displacement and lower stresses than did conventional implant overdentures for single- and 2-implant-retained overdentures.

Surface Characterization of a Glass Fiber Post after Nonthermal Plasma Treatment with Hexamethyldisiloxane.

PURPOSE: To characterize the surface of glass fiber posts (GFP) after different surface treatments and evaluate which method incorporates higher amounts of silicon (Si) particles, as well as to evaluate the bond strength at the post/ composite-cement interface with four different surface treatments of glass fiber posts luted with composite cement. MATERIALS AND METHODS: Twelve glass fiber posts were obtained from the manufacturer. The posts were randomly distributed into four groups (n = 3): Co (control), no surface treatment; S, 70% alcohol and silane (60 s); HF + S, 10% hydrofluoric acid gel (60 s) and silane (60 s); NTP, nonthermal plasma of hexamethyldisiloxane (HMDSO) associated with argon (30 min). The surface of each GFP was characterized through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Forty GFPs were randomly divided into 4 groups according the surface treatments (n = 10) and cemented with one composite cement (Rely X U200) into artificial canine teeth. The specimens were placed in a universal testing machine and subjected to tensile testing until failure occurred. Statistical analysis of the atomic percentage and bond strength was performed using ANOVA, followed by the post-hoc Tukey test (p = 0.05). RESULTS: EDS graphics showed that the NTP group had a higher Si atomic percentage (at%) than the other groups (p < 0.001). The HF + S group had a higher Si at% than did the Co and S groups. SEM images illustrated that the surfaces of the GFPs were variously modified after different treatments. The NTP group incorporated higher Si levels on the GFP surface and yielded the highest bond strengths (p < 0.005) compared to the other tested groups. CONCLUSION: Treatment with HMDSO + Ar plasma (NTP) incorporated higher Si levels on the surface of the GFPs without inducing critical defects. NTP treatment promoted better bond strength results when compared to the other tested group when GFPs were cemented with composite cement.

Marginal fit and photoelastic stress analysis of CAD-CAM and overcast 3-unit implant-supported frameworks.

STATEMENT OF PROBLEM: Several studies have shown the superiority of computer-assisted design and computer-assisted manufacturing (CAD-CAM) technology compared with conventional casting. However, an advanced technology exists for casting procedures (the overcasting technique), which may serve as an acceptable and affordable alternative to CAD-CAM technology for fabricating 3-unit implant-supported fixed dental prostheses (FDPs). PURPOSE: The purpose of this in vitro study was to evaluate, using quantitative photoelastic analysis, the effect of the prosthetic framework fabrication method (CAD-CAM and overcasting) on the marginal fit and stress transmitted to implants. The correlation between marginal fit and stress was also investigated. MATERIAL AND METHODS: Three-unit implant-supported FDP frameworks were made using the CAD-CAM (n=10) and overcasting (n=10) methods. The frameworks were waxed to simulate a mandibular first premolar (PM region) to first molar (M region) FDP using overcast mini-abutment cylinders. The wax patterns were overcast (overcast experimental group) or scanned to obtain the frameworks (CAD-CAM control group). All frameworks were fabricated from cobalt-chromium (CoCr) alloy. The marginal fit was analyzed according to the single-screw test protocol, obtaining an average value for each region (M and PM) and each framework. The frameworks were tightened for the photoelastic model with standardized 10-Ncm torque. Stress was measured by quantitative photoelastic analysis. The results were submitted to the Student t test, 2-way ANOVA, and Pearson correlation test (α=.05). RESULTS: The framework fabrication method (FM) and evaluation site (ES; M and PM regions) did not affect the marginal fit values (P=.559 for FM and P=.065 for ES) and stress (P=.685 for FM and P=.468 for ES) in the implant-supported system. Positive correlations between marginal fit and stress were observed (CAD-CAM: r=0.922; P<.001; overcast: r=0.908; P<.001). CONCLUSIONS: CAD-CAM and overcasting methods present similar marginal fit and stress values for 3-unit FDP frameworks. The decreased marginal fit of frameworks induces greater stress in the implant-supported system.