Effect of pH and titratable acidity on enamel and dentine erosion.

OBJECTIVES: The relative effect of pH and titratable acidity on tooth erosion remains unclear. We determined the effect of both properties on in vivo salivary pH recovery and on enamel and dentine early erosion in situ. METHODS: Solutions simulating acidic beverages with different pHs (2.5 or 3.5) and titratable acidities (0, 25, or 100 mM citric acid) were tested. In an in vivo study (n = 20 participants), the salivary pH was determined before, during, and up to 2 min after exposure to the tested solutions. In situ, 12 participants exposed enamel and root dentine slabs to the tested solutions simulating a beverage consumption; early erosion was assessed by percentage of surface hardness loss (%SHL). Groups were compared by ANOVA (p < 0.05). RESULTS: Saliva pH was lower after exposure to solutions at pH 2.5, irrespective of titratable acidity; pH recovery took longer for solutions with higher titratable acidities, irrespective of their pHs. In situ, the highest %SHL was observed for the solution with lower pH and higher titratable acidities. The addition of citric acid increased the %SHL by 2.5-3 times in enamel, and at least 5 times in dentine. CONCLUSIONS: Both pH and titratable acidity may play a role on the erosive potential of acidic beverages. CLINICAL RELEVANCE: Acidic beverages with lower pHs promote erosion by an initial acid etching of the surface; those with a higher titratable acidity slow down the salivary pH recovery. Both properties contribute to the overall erosive potential.

Probability of survival and stress distribution of narrow diameter implants with different implant-abutment taper angles.

This study evaluated the probability of survival, failure mode, and stress distribution of narrow diameter implants (NDIs) with internal implant-abutment conical connection comprised of different taper angles and thread designs. Sixty-three NDIs (Ø 3.5 × 8.5 mm) were divided according to the taper angle (TA), internal diameter (ID), and trapezoidal thread design (TD) (n = 21/group), as follows: (a) 11.5°U (11.5° TA; ID: 2.5 mm; TD: dual threaded); (b) 11.5°S (11.5° TA; ID: 2.5 mm; TD: single threaded); (c) 16°S (16° TA; ID: 2.72 mm; TD: single threaded). They were subjected to step-stress accelerated life testing. The reliability and use-level probability Weibull curves were calculated at 50, 100, and 150 N for a mission of 100,000 cycles and the failure mode was analyzed using a scanning electron microscope. For finite element analysis the von-Mises stress (σvM ) was calculated for the abutment and implant. All groups showed high reliability (above 84%) and failures occurred predominantly in the abutment. In the FEA, 11.5°U showed higher σvM for the implant. All NDIs showed high reliability at clinically challenging loads. The system with greater taper angle showed lower σVm in the implant, and dual threaded implants showed a higher stress concentration in the implant and cortical bone.

Accelerated fatigue resistance of endodontically treated incisors without ferrule restored with CAD/CAM endocrowns.

PURPOSE: The present study aimed to investigate the resistance and failure mode of broken-down endodontically treated incisors without ferrule restored with CAD/CAM endocrowns. MATERIALS AND METHODS: Endodontically treated bovine incisors (N = 30) without ferrule were divided into two groups and restored with two types of CAD/CAM endocrowns: lithium disilicate (Eld) or resin nanoceramics (Erc). The preparations included a 4-mm-deep 'internal ferrule' and immediate dentin sealing. The samples were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the incisal edge at a 30-degree angle at a frequency of 5 Hz, beginning with a load of 100 N (5,000 cycles). A 100 N load increase was applied every 15,000 cycles. Specimens were loaded until failure or to a maximum of 140,000 cycles. Previously published data from the same authors regarding lithium disilicate crowns over post-and-core buildups without ferrule (NfPf), core buildups without post without ferrule (NfNpFR), and with a 2-mm ferrule (FNp) using the same experimental setup were included for comparison. Groups were compared using the Kaplan Meier survival analysis for cycles (log rank pairwise post hoc test comparisons at P = 0.05) and Life Table survival analysis for load at failure, followed by the Wilcoxon pairwise comparison at P = 0.05. RESULTS: All specimens failed before 140,000 load cycles. There was no statistically significant difference between the endocrown materials (Eld: 53,448 mean endured cycles; Erc: 52,397 mean endured cycles; P = 0.844). Endocrowns outperformed the group with lithium disilicate crowns on incisors without ferrule and post-and-core buildup (NfPf with mean endured 35,025 cycles), showed no statistical difference compared with the group with no-post fiber-reinforced composite resin core buildup (NfNpFR with 45,557 mean endured cycles), and had a lower survival rate compared with the group with ferrule (FNp with mean endured 73,244 cycles). Endocrowns generated a majority of non-catastrophic failures (with an advantage for Erc), while 100% of catastrophic failures were found in the group with a post. CONCLUSIONS: CAD/CAM endocrowns of nonvital incisors without ferrule improved the resistance and optimized the failure mode when compared with traditional bonded crowns with adhesive post-and-core and no-post buildups.

On the release of fluoride from biofilm reservoirs during a cariogenic challenge: an in situ study.

Biofilm fluoride reservoirs may be a source of fluoride to the fluid phase during a sugar challenge reducing tooth mineral loss. However, the evidence for that is conflicting and has not been studied in biofilms containing different fluoride levels. In order to test fluoride release from biofilms with distinct fluoride concentrations, biofilms were grown in situ exposed to a combination of placebo, calcium and fluoride rinses forming biofilms with no (fluoride-free rinses), low (fluoride-only rinses) or high (calcium followed by fluoride rinses) fluoride concentrations, and collected before and 5 min after a sucrose challenge. Rinsing with fluoride increased fluoride concentration in the biofilm (p < 0.05), mainly when a calcium pre-rinse was used before the fluoride (p < 0.05). However, after a sugar challenge, no significant increase in the biofilm fluid fluoride concentration was observed, even in the fluoride-rich biofilms (p > 0.05). Fluoride-rich biofilms do not release fluoride to the fluid phase during a sugar challenge.

Zirconia-reinforced lithium silicate crowns: Effect of thickness on survival and failure mode.

OBJECTIVE: To evaluate the reliability and failure mode of zirconia-reinforced lithium silicate (ZLS) molar crowns of different thicknesses. METHODS: Monolithic ZLS molar crowns (0.5mm, 1.0mm, and 1.5 mm thickness) were modeled and milled using a CAD/CAM system (n = 21/group). Crowns were cemented on dentin-like epoxy resin replicas with a resin cement. The specimens were subjected to single load-to-failure test for step-stress profiles designing. Mouth-motion step-stress accelerated-life test was performed under water by sliding an indenter 0.7 mm lingually down on the distobuccal cusp until specimen fracture or suspension. Use level probability Weibull curves and reliability were calculated and plotted. Polarized-light optical microscope and scanning electron microscope (SEM) were used to characterize fracture patterns. RESULTS: Irrespective of crown thickness, beta (ß) values were higher than 1 and fatigue accelerated failures. While 0.5 mm ZLS crowns exhibited a significant reduction in the probability of survival at 200N, 300N and 400 N mission loads (69%, 41% and 19%, respectively), no significant difference was observed between 1.0 mm and 1.5 mm crowns. Both thicknesses have maintained the survivability at approximately 90%. Failure primarily comprised bulk fracture where radial cracks originated from the cementation surface beneath the indenter loading trail and propagated towards the cervical margin. SIGNIFICANCE: 1.5 mm- and 1.0 mm-thickness monolithic ZLS crowns presented higher probability of survival compared to 0.5 mm crowns. Bulk fracture was the chief failure mode, regardless of thickness.

Candida albicans Increases Dentine Demineralization Provoked by Streptococcus mutans Biofilm.

Streptococcus mutans are considered the most cariogenic bacteria, but it has been suggested that Candida albicans could increase their cariogenicity. However, the effect of this dual-species microorganisms' combination on dentine caries has not been experimentally evaluated. Biofilms of C. albicans, S. mutans and C. albicans + S. mutans (n = 12/biofilm) were grown in ultra-filtered tryptone yeast extract broth culture medium for 96 h on root dentine slabs of known surface hardness and exposed 8 times per day for 3 min to 10% sucrose. The medium was changed 2 times per day (after the 8 cariogenic challenges and after the overnight period of famine), and aliquots were analyzed to determinate the pH (indicator of biofilm acidogenicity). After 96 h, the biofilms were collected to determine the wet weight, colony-forming units, and the amounts of extracellular polysaccharides (soluble and insoluble). Dentine demineralization was assessed by surface hardness loss (% SHL). The architecture of the biofilms was analyzed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Data were analyzed by ANOVA followed by Tukey's test (α = 0.05). The dual-species C. albicans + S. mutans biofilm provoked higher % SHL on dentine (p < 0.05) than the S. mutans and C. albicans biofilm. This was supported by the results of biofilm acidogenicity and the amounts of soluble (6.4 ± 2.14 vs. 4.0 ± 0.94 and 1.9 ± 0.97, respectively) and insoluble extracellular polysaccharides (24.9 ± 9.22 vs. 18.9 ± 5.92 and 0.7 ± 0.48, respectively) (p < 0.05). The C. albicans biofilm alone presented low cariogenicity. The images by CLSM and TEM, respectively, suggest that the C. albicans + S. mutans biofilm is more voluminous than the S. mutans biofilm, and S. mutans cells interact with C. albicans throughout polysaccharides from the biofilm matrix. These findings show that C. albicans enhances the cariogenic potential of the S. mutans biofilm, increasing dentine demineralization.

The effect of DLC-coating deposition method on the reliability and mechanical properties of abutment's screws.

OBJECTIVE: To characterize the mechanical properties of different coating methods of DLC (diamond-like carbon) onto dental implant abutment screws, and their effect on the probability of survival (reliability). METHODS: Seventy-five abutment screws were allocated into three groups according to the coating method: control (no coating); UMS - DLC applied through unbalanced magnetron sputtering; RFPA-DLC applied through radio frequency plasma-activated (n=25/group). Twelve screws (n=4) were used to determine the hardness and Young's modulus (YM). A 3D finite element model composed of titanium substrate, DLC-layer and a counterpart were constructed. The deformation (µm) and shear stress (MPa) were calculated. The remaining screws of each group were torqued into external hexagon abutments and subjected to step-stress accelerated life-testing (SSALT) (n=21/group). The probability Weibull curves and reliability (probability survival) were calculated considering the mission of 100, 150 and 200N at 50,000 and 100,000 cycles. RESULTS: DLC-coated experimental groups evidenced higher hardness than control (p<0.05). In silico analysis depicted that the higher the surface Young's modulus, the higher the shear stress. Control and RFPA showed ß<1, indicating that failures were attributed to materials strength; UMS showed ß>1 indicating that fatigue contributed to failure. High reliability was depicted at a mission of 100N. At 200N a significant decrease in reliability was detected for all groups (ranging from 39% to 66%). No significant difference was observed among groups regardless of mission. Screw fracture was the chief failure mode. SIGNIFICANCE: DLC-coating have been used to improve titanium's mechanical properties and increase the reliability of dental implant-supported restorations.

Survival of extensively damaged endodontically treated incisors restored with different types of posts-and-core foundation restoration material.

STATEMENT OF PROBLEM: Which post-and-core combination will best improve the performance of extensively damaged endodontically treated incisors without a ferrule is still unclear. PURPOSE: The purpose of this in vitro study was to investigate the restoration of extensively damaged endodontically treated incisors without a ferrule using glass-ceramic crowns bonded to various composite resin foundation restorations and 2 types of posts. MATERIAL AND METHODS: Sixty decoronated endodontically treated bovine incisors without a ferrule were divided into 4 groups and restored with various post-and-core foundation restorations. NfPfB=no-ferrule (Nf) with glass-fiber post (Pf) and bulk-fill resin foundation restoration (B); NfPfP=no-ferrule (Nf) with glass-fiber post (Pf) and dual-polymerized composite resin core foundation restoration (P); NfPt=no-ferrule (Nf) with titanium post (Pt) and resin core foundation restoration; and NfPtB=no-ferrule (Nf) with titanium post (Pt) and bulk-fill resin core foundation restoration (B). Two additional groups from previously published data from the same authors (FPf=2mm of ferrule (F) and glass-fiber post (Pf) and composite resin core foundation restoration; and NfPf=no-ferrule (Nf) with glass-fiber post (Pf) and composite resin core foundation restoration), which were tested concomitantly and using the same experimental arrangement, were included for comparison. All teeth were prepared to receive bonded glass-ceramic crowns luted with dual-polymerized resin cement and were subjected to accelerated fatigue testing under submerged conditions at room temperature. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees with a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied every 15000 cycles. The specimens were loaded until failure or to a maximum of 1000 N (140000 cycles). The 6 groups (4 groups from the present study and 2 groups from the previously published study) were compared using the Kaplan-Meier survival analysis (log-rank post hoc test at α=.05 for pairwise comparisons). RESULTS: None of the tested specimen withstood all 140 000 cycles. All specimens without a ferrule were affected by an initial failure phenomenon (wide gap at the lingual margin between the core foundation restoration/crown assembly and the root). NfPfP, NfPt, and NfPtB had similar survival (29649 to 30987 mean cycles until initial failure). NfPfB outperformed NfPt and NfPtB. None of the post-and-core foundation restoration materials were able to match the performance of the ferrule group FPf (72667 cycles). In all groups, 100% of failures were catastrophic. CONCLUSIONS: The survival of extensively damaged endodontically treated incisors without a ferrule was slightly improved by the use of a fiber post with a bulk-fill composite resin core foundation restoration. However, none of the post-and-core techniques was able to compensate for the absence of a ferrule. The presence of the posts always adversely affected the failure mode.

Stress distribution of single-implant-retained overdenture reinforced with a framework: A finite element analysis study.

STATEMENT OF PROBLEM: Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture. PURPOSE: The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture. MATERIAL AND METHODS: Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone. RESULTS: In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone. CONCLUSIONS: A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the prosthesis and could minimize the incidence of fracture.

The role of prosthetic abutment material on the stress distribution in a maxillary single implant-supported fixed prosthesis.

PURPOSE: Evaluate the influence of abutment's material and geometry on stress distribution in a single implant-supported prosthesis. MATERIALS AND METHODS: Three-dimensional models were made based on tomographic slices of the upper middle incisor area, in which a morse taper implant was positioned and a titanium (Ti) or zirconia (ZrN) universal abutments was installed. The commercially available geometry of titanium (T) and zirconia (Z) abutments were used to draw two models, TM1 and ZM1 respectively, which served as control groups. These models were compared with 2 experimental groups were the mechanical properties of Z were applied to the titanium abutment (TM2) and vice versa for the zirconia abutment (ZM2). Subsequently, loading was simulated in two steps, starting with a preload phase, calculated with the respective friction coefficients of each materials, followed by a combined preload and chewing force. The maximum von Mises stress was described. Data were analyzed by two-way ANOVA that considered material composition, geometry and loading (p<0.05). RESULTS: Titanium and zirconia abutments showed similar von Mises stresses in the mechanical part of the four models. The area with the highest concentration of stress was the screw thread, following by the screw body. The highest stress levels occurred in screw thread was observed during the preloading phase in the ZM1 model (931MPa); and during the combined loading in the TM1 model (965MPa). Statistically significant differences were observed for loading, the material×loading interaction, and the loading×geometry interaction (p<0.05). Preloading contributed for 77.89% of the stress (p<0.05). There were no statistically significant differences to the other factors (p>0.05). CONCLUSION: The screw was the piece most intensely affected, mainly through the preload force, independent of the abutment's material.

Interkingdom cooperation between Candida albicans, Streptococcus oralis and Actinomyces oris modulates early biofilm development on denture material.

Candida-associated stomatitis affects up to 60% of denture wearers, and Candida albicans remains the most commonly isolated fungal species. The oral bacteria Actinomyces oris and Streptococcus oralis are abundant in early dental plaque. The aims of this study were to determine the effects of S. oralis and A. oris on the development of C. albicans biofilms on denture material. Resin discs were coated with saliva and at early (1.5 h) or later (24 h) stages of biofilm development, cell numbers of each species were determined. Spatial distribution of microorganisms was visualized by confocal scanning laser microscopy of biofilms labelled by differential fluorescence or by fluorescence in situ hybridization. Interkingdom interactions underpinning biofilm development were also evaluated planktonically utilizing fluorescence microscopy. Synergistic interactions between all three species occurred within biofilms and planktonically. Bacterial cells coaggregated with each other and adhered singly or in coaggregates to C. albicans hyphal filaments. Streptococcus oralis appeared to enhance hyphal filament production and C. albicans biovolume was increased 2-fold. Concomitantly, cell numbers of S. oralis and A. oris were enhanced by C. albicans. Thus, cooperative physical and metabolic processes occurring between these three microbial species intensify pathogenic plaque communities on denture surfaces.

The role of nicotine, cotinine and caffeine on the electrochemical behavior and bacterial colonization to cp-Ti.

Although smoking promotes deleterious effect to bone healing, there is a lack of study investigating its role on the implant structure and biofilm growth. We hypothesized that nicotine, cotinine and caffeine would impair the corrosion resistance of commercially-pure titanium (cp-Ti) and would enhance Streptococcus sanguinis biofilm growth. Neither the smoking products nor the caffeine affected the corrosion tendency (P>.05) and the oxide layer resistance (P=.762) of cp-Ti. Lower capacitance values were noted in the presence of nicotine (P=.001) and cotinine (P=.0006). SEM showed no pitting corrosion, and the EDS spectra did not differ among groups. Nicotine (300µg/mL) induced higher surface roughness (P=.03) and greater surface change of cp-Ti. Nicotine at 3µg/mL, and cotinine at 0.3 and 3µg/mL increased the number of viable cells (P<.05). Biofilm exposed to nicotine (0.3, 3 and 30µg/mL) (P=.025, .030, .040, respectively) and cotinine (3 and 30µg/mL) (P=.027, .049, respectively) enhanced carbohydrate content. Biofilm biomass and protein content were similar among groups (P>.05). These findings suggest a greater biofilm accumulation in smokers, a risk factor that may lead to peri-implantitis.

Biofilm and saliva affect the biomechanical behavior of dental implants.

Friction coefficient (FC) was quantified between titanium-titanium (Ti-Ti) and titanium-zirconia (Ti-Zr), materials commonly used as abutment and implants, in the presence of a multispecies biofilm (Bf) or salivary pellicle (Pel). Furthermore, FC was used as a parameter to evaluate the biomechanical behavior of a single implant-supported restoration. Interface between Ti-Ti and Ti-Zr without Pel or Bf was used as control (Ctrl). FC was recorded using tribometer and analyzed by two-way Anova and Tukey test (p<0.05). Data were transposed to a finite element model of a dental implant-supported restoration. Models were obtained varying abutment material (Ti and Zr) and FCs recorded (Bf, Pel, and Ctrl). Maximum and shear stress were calculated for bone and equivalent von Misses for prosthetic components. Data were analyzed using two-way ANOVA (p<0.05) and percentage of contribution for each condition (material and FC) was calculated. FC significant differences were observed between Ti-Ti and Ti-Zr for Ctrl and Bf groups, with lower values for Ti-Zr (p<0.05). Within each material group, Ti-Ti differed between all treatments (p<0.05) and for Ti-Zr, only Pel showed higher values compared with Ctrl and Bf (p<0.05). FC contributed to 89.83% (p<0.05) of the stress in the screw, decreasing the stress when the FC was lower. FC resulted in an increase of 59.78% of maximum stress in cortical bone (p=0.05). It can be concluded that the shift of the FC due to the presence of Pel or Bf is able to jeopardize the biomechanical behavior of a single implant-supported restoration.

Confocal analysis of the exopolysaccharide matrix of Candida albicans biofilms.

AIM: Confocal laser-scanning microscopy (CLSM) was carried out to investigate the exopolysaccharide matrix of Candida albicans (C. albicans) biofilms developed on denture material under dietary carbohydrate exposure. METHODS: Biofilms were developed on poly(methyl methacrylate) discs in culture media without (control) or with supplementation by glucose or sucrose for 72 h. For the CLSM analysis, biofilms were labeled with concanavalin A (ConA) during its development. Afterwards, biofilms were also labeled with SYTO-9. To confirm the results, the matrix was investigated by the phenol-sulfuric method. Data were analyzed by anova, followed by Tukey's test, with the level of significance set at 5%. RESULTS: The use of ConA during biofilm development provided effective labeling of the exopolysaccharide matrix. The exposure to sucrose resulted in biofilms with the highest exopolysaccharide matrix biovolume (P < 0.05). The characterization obtained by CLSM was confirmed by the phenol-sulfuric method. CONCLUSION: Confocal laser-scanning microscopy was found to be an effective tool for investigating the exopolysaccharide matrix of C. albicans biofilms, and exposure to sucrose resulted in increased matrix production.

Influence of surface free energy of denture base and liner materials on Candida albicans biofilms.

AIM: This study aimed to evaluate the influence of surface free energy (SFE) of denture base and liner materials on Candida albicans biofilm development. METHODS: Discs were fabricated using poly(methyl methacrylate) acrylic resin and poly(ethyl methacrylate) denture liner, according to the manufacturers' instructions. For SFE test, discs were pellicle-coated with saliva alone, saliva + blood plasma, or blood plasma alone. Candida albicans biofilms were allowed to form on pellicle-coated discs for 48 h. Biofilms were evaluated for cell counts, metabolic activity, and structural characteristics at adhesion phase (after 1.5 h of development) and at biofilm maturity (after 48 h of development). Data were analyzed by anova and Tukey tests using a significance level of 5%. RESULTS: Saliva + blood plasma pellicles had a higher SFE compared to pellicles of saliva or blood plasma alone (P < 0.001). Differences in SFE by pellicle-coating did not affect the cell counts, metabolic activity, or structure at the adhesion phase (P > 0.05). In contrast, the presence of blood plasma resulted in higher cell counts, biovolume, and thickness of mature biofilms on both materials (P < 0.001). CONCLUSIONS: Increases in SFE from pellicle-coating leads to robust mature C. albicans biofilms on both denture materials.

Plasma proteins in the acquired denture pellicle enhance substrate surface free energy and Candida albicans phospholipase and proteinase activities.

AIM: The objective of the present study was to determine if blood plasma proteins could change the proteome of the acquired denture pellicle by label-free quantitative proteomics. As pellicle proteome modulates the interaction between substrates and Candida cells, we investigated its effect on the surface free energy (SFE) of the coated resin and on Candida albicans phospholipase and aspartyl proteinase activities. METHODS: Poly(methylmethacrylate) discs were exposed to saliva (control) or saliva enriched with blood plasma (experimental group). The pellicle proteome was analyzed by mass spectrometry coupled with liquid chromatography. SFE was determined by acid-base technique. After biofilm formation, phospholipase and proteinase activities were determined accordingly to classic plate methods. Data were analyzed by two-way anova and Tukey test (P < 0.05). RESULTS: α-Amylase, cystatins, mucins, and host-immune system proteins were the main proteins identified in the control group. Fibrinogen and albumin were observed only in the experimental group. Coated discs of the experimental group presented an increased SFE (P < 0.05). For both enzymes tested, the experimental group showed higher proteolytic activity (P < 0.001). CONCLUSION: Blood plasma changes the proteome of the acquired denture pellicle, increasing surface free energy and the activity of Candida albicans phospholipase and aspartyl proteinase.

The Use of Implants to Improve Removable Partial Denture Function.

The oral rehabilitation with conventional removable partial dentures in Kennedy class I patients allows continuous bone resorption, dislodgment of the prosthesis during the mastication caused by the resilience of the mucosa, and rotation of the prosthesis. Thus, the associations of distal implants become an attractive modality of treatment for these patients. This case report presented an association of removable partial dentures, milled crowns and osseointegrated implants to rehabilitate a partial edentulous patient. A removable partial denture associated with implants and metal-ceramic milled crowns can offer excellent esthetics, and will improve function and biomechanics, at a reduced cost.

Adding denture cleanser to microwave disinfection regimen to reduce the irradiation time and the exposure of dentures to high temperatures.

BACKGROUND: The microwave energy is an efficient disinfection method; however, it can generate high temperatures that can result in distortion of the dentures. OBJECTIVES: To evaluate whether the addition of an enzymatic cleanser to microwave disinfection regimen would disinfect dentures with shorter irradiation time. MATERIALS AND METHODS: Seven resin discs colonized with Candida albicans biofilm were placed on the palatal surface of sterile dentures to be randomly assigned to the following treatments: immersion in distilled water for 3 min with 0 (DW), 1 (DW + M1), 2 (DW + M2), or 3 min (DW + M3) of microwave irradiation; or immersion in denture cleanser for 3 min with 0 (DC), 1 (DC + M1), 2 (DC + M2) or 3 min (DC + M3) of irradiation. After the treatments, the viable cells were counted by a blinded examiner. The temperature was measured immediately after irradiation. The data were analyzed by ANOVA and Tukey post hoc tests (α = 0.05). RESULTS: No viable cells were found after DC + M2, DC + M3, and DW + M3 treatments, of which DC + M2 achieved the lowest temperature. No significant difference was found between the effectiveness of DW, DW + M1 and DC treatments (p > 0.05). CONCLUSION: Within the limits of this study, the association of a denture cleanser and microwave energy is efficient to disinfect dentures in lower irradiation time and temperature.

Influence of immersion time of denture cleansers on the surface roughness of resilient denture liners / Influência do tempo de imersão de limpadores químicos sobre a rugosidade de superfície de reembasadores resilientes para próteses removíveis

PURPOSE: The objective of this study was to evaluate the effect of different immersion times in denture cleansers on surface roughness (SR) of two resilient denture liners (RDL) after the cleanliness of Candida albicans biofilm. METHODS: Poly(methyl methacrylate) (PMMA) resin discs (10x1.5 mm) were relined with a 1.5 mm layer of RDL (PMMA or silicone-based). The initial SR of each specimen was measured and C. albicans biofilm was developed for 48 h. Subsequently, the discs were randomly assigned for one of four cleansing treatments (n=8): two alkaline peroxide (soaking for 3 or 15 min), 0.5 percent sodium hypochlorite (10 min) or distilled water as control (15 min). After the treatments, the SR was measured again. Data were analyzed by ANOVA and the Tukey post-hoc test (α=0.05) RESULTS: No differences were found between the cleansing treatments evaluated (P>0.05). The PMMA-based liner exhibited higher SR than silicon-based (P<0.001); however, both liners showed higher SR after the reatments compared with the baseline values (P<0.001). CONCLUSION: Within limitations of this study, it can be concluded that the surface roughness of RDL increased after the immersion in denture cleansers, independently of the time of immersion.

OBJETIVO: O objetivo deste estudo foi avaliar o efeito de diferentes tempos de imersão em limpadores químicos sobre a rugosidade de superfície ( RS)de reembasadores resilientes após a simulação da limpeza de biofilmes de Candida albicans. METODOLOGIA: Discos (10x1,5 mm) de poli(metilmetacrilato) (PMMA) foram cobertos com uma camada de 1,5 mm de reembasador resiliente (a base de PMMA ou silicone). A RS inicial de cada espécime foi mensurada e biofilmes de C. albicans desenvolvidos por 48 h. Em seguida, os espécimes foram submetidos aleatoriamente a um dos tratamentos (n=8): duas soluções alcalinas a base de peróxido (imersão por 3 ou 15 min), hipoclorito de sódio a 0.5 por cento (10 min) ou água destilada como grupo controle (15 min). Após o tratamento, a RS foi mensurada novamente. Os resultados foram analisados por ANOVA e teste Tukey (α=0,05). RESULTADOS: Não houve diferença estatística entre os tratamentos (P>0,05). O reembasador a base de PMMA apresentou maior RS que os de silicone (P<0,001); entretanto, ambos apresentaram um aumento da RS após os tratamentos (P<0,001). CONCLUSÃO: Dentro das limitações deste estudo, conclui-se que a RS dos reembasadores resilientes aumenta após a imersão em limpadores químicos, independentemente do tempo de imersão.