Showing papers in "Journal of Prosthodontics in 2015"

Intraoral Digital Impression Technique: A Review

Abstract: With the techniques of computer-aided design and computer-aided manufacturing (CAD/CAM) being applied in the field of prosthodontics, a concept of intraoral digital impressions was put forward in the early 1980s. It has drawn comprehensive attention from dentists and has been used for dental prosthesis fabrication in a number of cases. This new digital impression technique is expected to bring about absolute digitization to the mode of prosthodontics. A few published articles have indicated that dental prostheses fabricated from intraoral digital impressions have exhibited remarkable advantages over those from conventional impressions in several respects. The present review discusses intraoral digital impression techniques in terms of the following aspects: (1) categories and principles of intraoral digital impression devices currently available; (2) operating characteristics of the devices; and (3) comparison of the manipulation, accuracy, and repeatability between intraoral digital impression and conventional impression.

Selective Laser Melting Technique of Co-Cr Dental Alloys: A Review of Structure and Properties and Comparative Analysis with Other Available Techniques

Abstract: Purpose The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co-Cr alloys and to evaluate its quality and compare it to those produced by conventional casting and milling fabrication techniques. Materials and Methods A computerized database search using PubMed and Scopus was conducted for peer-reviewed scientific research studies regarding the use of SLM in Co-Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review. Results The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single-metal ceramic crowns is comparable to Au-Pt dental alloy. Conclusion The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques. Clinical significance: The current SLM devices provide metallic restorations made of Co-Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community.

A multispecies probiotic reduces oral Candida colonization in denture wearers.

Abstract: Purpose: The prevalence ofCandida infections has been rising with an increasingly aging population and a larger population of immunocompromised individuals. The use of probiotics may be an alternative approach to antifungal agents in the prevention and treatment of oral candidiasis. This study aimed to evaluate the short-term effect of probioticsin reducingtheinfection leveloforalCandidaincandidiasis-asymptomatic elderly denture wearers. Materials and Methods: In a double-blind randomized study, 59 denture wearers harboringCandidaspp.intheoralcavitywithnoclinicalsymptomswereallocatedinto two groups: probiotic and placebo. All patients were instructed to clean the denture daily. The probiotic group poured a capsule containing lyophilized Lactobacillus rhamnosus HS111, Lactobacillus acidophillus HS101, and Bifidobacterium bifidum daily on the palatal surface of the maxillary denture, whereas the placebo group was submitted to the same regimen using placebo capsules. Candida spp. infection levels were evaluated in palate mucosa samples obtained before and after a 5-week experimental period. Results: All patients harbored Candida in the palate mucosa at baseline. Fifty-five individuals completed the experimental period. The detection rate of Candida spp. was 92.0% in the placebo group after the experimental period, whereas it was reduced to 16.7% in the probiotic group. The reduction promoted by the probiotic regimen was independentofbaseline characteristics suchasCandidainfection levelandcolonizing species, age of denture, and other variables. Conclusion: The probiotic product was effective in reducing the colonization of the oral cavity with Candida in candidiasis-asymptomatic elderly denture wearers, suggesting that this multispecies probiotic could be used to prevent oral candidiasis. Clinical implications: Colonization of oral surfaces by Candida is considered a risk factor for invasive fungal infections. The use of a product with L. rhamnosus, L. acidophilus ,a ndB. bifidum may represent an alternative treatment for reduction of Candida infections in elderly denture wearers.

Fabricating Complete Dentures with CAD/CAM and RP Technologies.

Abstract: Two techological approaches for fabricating dentures; computer-aided design and computer-aided manufacturing (CAD/CAM) and rapid prototyping (RP), are combined with the conventional techniques of impression and jaw relation recording to determine their feasibility and applicability. Maxillary and mandibular edentulous jaw models were produced using silicone molds. After obtaining a gypsum working model, acrylic bases were crafted, and occlusal rims for each model were fabricated with previously determined standard vertical and centric relationships. The maxillary and mandibular relationships were recorded with guides. The occlusal rims were then scanned with a digital scanner. The alignment of the maxillary and mandibular teeth was verified. The teeth in each arch were fabricated in one piece, or set, either by CAM or RP. Conventional waxing and flasking was then performed for both methods. These techniques obviate a practitioner's need for technicians during design and provide the patient with an opportunity to participate in esthetic design with the dentist. In addition, CAD/CAM and RP reduce chair time; however, the materials and techniques need further improvements. Both CAD/CAM and RP techniques seem promising for reducing chair time and allowing the patient to participate in esthetics design. Furthermore, the one-set aligned artificial tooth design may increase the acrylic's durability.

Assessment of the Internal Fit of Lithium Disilicate Crowns Using Micro-CT.

Abstract: Purpose The aim of this study was to compare the internal fit of lithium disilicate crowns fabricated using digital technology with those fabricated by conventional means. Materials and Methods Forty-five lithium disilicate crowns were fabricated: 15 using digital impression and computer-aided design/computer-aided machining technique (group 1), 15 from the same digital impressions, but using a conventional die and laboratory fabrication process (group 2), and 15 using a conventional poly (vinyl siloxane) (PVS) impression and laboratory fabrication process (group 3). Tooth #15 was prepared for all-ceramic restoration on an ivorine typodont, which was digitized and a replica milled in zirconia to serve as master model. The master zirconia model was used for the impression procedures. Duplicate dies of the master zirconia die were made in polyurethane, enabling the internal fit of each crown to be evaluated using X-ray microcomputed tomography. The total volume of the internal space between the crown and die, the mean and maximum thickness of this space, and the percentage of the space that was at or below 120 μm thickness was calculated for each group and statistically tested for significant difference using one-way ANOVA, with post hoc Scheffe analysis. Results Group 1 crowns resulted in a smaller volume of internal space (12.49 ± 1.50 mm3) compared to group 2 (15.40 ± 2.59 mm3) and to those of group 3 (18.01 ± 2.44 mm3). The mean thickness of the internal space for group 1 (0.16 ± 0.01 mm) and for group 2 (0.17 ± 0.03 mm) was significantly lower than that of group 3 (0.21 ± 0.03 mm). The average percentage of the internal space of a thickness of 120 μm and below was different between the three groups: 46.73 ± 5.66% for group 1, 37.08 ± 17.69% for group 2, and 22.89 ± 9.72% for group 3. Three-dimensional renderings of the internal space were also created. Conclusions The results of this study suggested that pressed and milled IPS e. max crowns from LAVA COS digital impressions had a better internal fit to the prepared tooth than pressed IPS e.max crowns from PVS impressions in terms of total volume of internal space, average thickness of internal space, and percentage of internal space at or below 120 μm.

Association between Oral Mucosal Lesions and Hygiene Habits in a Population of Removable Prosthesis Wearers.

Abstract: PURPOSE: This prospective study evaluated the influence of self-reported prosthesis hygiene regimens and prosthesis usage habits on the presence of oral mucosal lesions (OMLs) in complete removable and/or partial removable dental (CRDP/PRDP) prosthesis wearers (PWs). MATERIALS AND METHODS: Between January 2009 and January 2011, the conventional oral mucosa of 400 consecutive PWs (252 women; 148 men), aged between 29 and 86 years, were examined clinically. Information was derived considering the type and age of the prosthesis, hygiene level, frequency and style of prosthesis cleaning, overnight prosthesis use, storage conditions, and systemic diseases. Non-prosthesis- and prosthesis-related OMLs were identified. The data were analyzed using univariate (Chi-square) and multivariate (logistic regression) tests to assess the development of OMLs as a function of the selected variables. Odds ratios (OR) were calculated at 95% confidence intervals (CI; α = 0.05). RESULTS: Of the 400 PWs, 21.5% had CRDP, 52.5% PRDP, and 25.8% CRD/PRD prostheses. Thirty-two percent of the PWs cleaned their prosthesis once a day. Brushing the prosthesis with toothbrush and soap/toothpaste was the most commonly practiced cleaning regimen (85.8%). More than half (64.5%) of the PWs used their prosthesis overnight. Among all PWs, 37.8% had a prosthesis-related OML. Stomatitis Newton Type II (46%) and Type III (38%) were the most common OMLs. OML frequency was higher in PWs having CRDPs than those having PRDPs (p < 0.05). Overnight prosthesis use (p = 0.003, OR: 13.65; 95% CI: 1.7-109.3), denture age ≥11 years (p = 0.017, OR: 1.72; 95% CI: 1.1-2.7), and immersion in water and solution (p = 0.023, OR: 1.13; 95% CI: 0.02-1.02) affected the incidence of OML significantly. Hypertension was the most common systemic disease (31.5%). CONCLUSION: Overnight use, denture age, and storage conditions of CRDP or PRDPs demonstrated a more significant impact on OML incidence than frequency of cleaning. Oral healthcare programs for removable PWs should specifically provide education on prosthesis usage instructions. © 2014 by the American College of Prosthodontists

Self-adhesive resin cements: a clinical review.

Abstract: Purpose To review the performance of self-adhesive luting agents to determine their clinical evidence. Materials and Methods In March 2013, we conducted a literature search by means of PubMed and manually searched German and English medical journals using general search terms (e.g., “self-adhesive resin cements”), detailed search terms (e.g., clinical study “self-adhesive resin cement”), and brand name search terms (clinical study AND “brand name of the cement”). The resulting lists of articles were manually searched for clinical studies. Because of the low number of relevant articles, we decided to broaden our search by including in vitro studies based on a thermal cycling and mechanical loading (TCML) design. Results The search using the six general search terms yielded a list with over 100 studies with only 13 in vivo studies and 6 in vitro studies based on a TCML design. The other studies either did not comply with the requirements or were not in vitro studies based on a TCML design. Two more in vivo studies could be added after the brand name search. Altogether, 15 in vivo studies and 6 in vitro studies were included in our analysis. Conclusion Because of the low number of studies available, the clinical evidence of self-adhesive luting agents cannot be assessed in a sufficient manner.

Clinical Marginal and Internal Fit of Crowns Fabricated Using Different CAD/CAM Technologies.

Abstract: Purpose The aims of this in vivo investigation were to compare the marginal and internal fit of single-unit crowns fabricated using a selective laser melting (SLM) procedure with two CAD/CAM grinding procedures, and to evaluate the influence of tooth type on the parameters measured. Materials and Methods A total of 270 crowns were evaluated, including 90 SLM metal-ceramic crowns (group B), 90 zirconium-oxide-based ceramic crowns (group L), and 90 lithium disilicate ceramic crowns (group C). The marginal and internal gaps of the crowns were recorded using a replica technique with a silicone indicator paste stabilized with a light-body silicone. The gap replica specimen were sectioned buccolingually and mesiodistally and then examined using a stereomicroscope at 30× magnification. Ten reference points were measured on each anterior and premolar specimen, and 20 reference points were measured on each molar specimen. Two-way ANOVA was performed to identify the significant differences between the groups. Results The mean marginal fit of group B was significantly better than those of group C and group L (p 0.05). The mean axial gap of group B was significantly smaller than those of group C and group L (p 0.05). The mean occlusal gap of group B was significantly higher than those of group C and group L (p 0.05). The marginal and internal gaps of crowns varying according to tooth type were not significantly different (p > 0.05). Conclusion The SLM system demonstrated better marginal and internal fit compared to the two CAD/CAM grinding systems examined. Tooth type did not significantly influence the marginal or internal fit.

Effect of different cleaning regimens on the adhesion of resin to saliva-contaminated ceramics

Abstract: Purpose The aim of this study was to evaluate the influence of different cleaning regimens on the microshear bond strength (μSBS) of three different all-ceramic surfaces after saliva contamination. Material and Methods Cubic ceramic specimens (3 × 3 × 3 mm3) were prepared from three types of ceramics: zirconium dioxide (Z), leucite-reinforced glass ceramic (E), lithium disilicate glass ceramic (EX; n = 12/subgroup). A total of 144 composite resin cylinders (diameter: 1 mm, height: 3 mm) were prepared. Three human-saliva–contaminated surfaces of ceramic specimens were cleaned with either water spray (WS), with 0.5% sodium hypochlorite solution (HC), or with a cleaning paste (CP). Control surface (C) was not contaminated or cleaned. Composite cylinders were bonded to each surface with a resin luting cement. All specimens were stored at 37°C in deionized water until fracture testing. μSBS tests were performed in a universal testing machine (0.5 mm/min), and the results (MPa ± SD) were statistically analyzed (two-way ANOVA, Bonferroni a = 0.05). Fractured surfaces were analyzed to identify the failure types using an optical microscope at 50× magnification. Two representative specimens from all groups were examined with scanning electron microscopy. Results μSBS test results were significantly affected by the saliva cleaning regimens (p = 0.01) and the ceramic types (p = 0.03). The interaction terms between the ceramic type and saliva cleaning regimen were also significant (p 0.05). In the EX group, C resulted in significantly higher μSBS values (32.6 ± 7.4) than CP (17.4 ± 8.9), WS (15.6 ± 7.3), and HC (14.3 ± 4.5) (p < 0.05); however, C (20.4 ± 7.1) and HC (19.2 ± 7.5) showed higher μSBS values than CP (13.8 ± 4.8) and WS (10.9 ± 5.7) in the E group. Some cohesive failures within the luting resin were observed in the E and EX groups, whereas only adhesive failures were seen in zirconia groups for all surface treatments. Conclusions Different ceramic surface cleaning regimens after saliva contamination of the zirconium dioxide revealed μSBS similar to the control group, whereas all surface cleaning regimens tested significantly decreased the bond strength values in the lithium disilicate glass ceramic. The leucite-reinforced glass-ceramic group benefited from 0.5% sodium hypochlorite solution cleaning with increased bond strengths. Clinical significance: Adhesive cementation of zirconia presents a clinically challenging protocol, and the cementation surface contamination of the zirconia restorations and the inadequate removal of the contaminants increase the risk of failure, as for all ceramic types. This study demonstrated that surface cleaning regimens should be applied according to different ceramic properties.

Clinical Marginal and Internal Adaptation of Maxillary Anterior Single All-Ceramic Crowns and 2-year Randomized Controlled Clinical Trial.

Abstract: Purpose The aims of this randomized-controlled clinical trial were to compare marginal and internal adaptation of all-ceramic crowns fabricated with CAD/CAM and heat-pressed (HP) techniques before luting and to evaluate the clinical outcomes at baseline and at 6, 12, and 24 months after luting. Materials and Methods Fifteen CAD/CAM (CC) and 15 HP all-ceramic crowns were placed in 15 patients. A silicone replica was obtained to measure marginal and internal adaptation of each all-ceramic crown before luting, and they were sectioned buccolingually and mesiodistally. Marginal and internal adaptations were measured using computerized light microscope at 40× magnification. Clinical evaluations took place at baseline (2 days after luting) and at 6, 12, and 24 months after luting. Replica scores were analyzed with Mann-Whitney U and Student's t-test (α = 0.05). Survival rate of crowns was determined using Kaplan-Meier statistical analysis. Results The median marginal gap for the CC group was 132.2 μm and was 130.2 μm for the HP group. The mean internal adaptation for the CC group was 220.3 ± 51.3 μm and 210.5 ± 31 μm for the HP group. There were no statistically significant differences with respect to marginal opening (Mann-Whitney U test; p = 0.95) and internal adaptation (Student's t-test; p = 0.535) between the 2 groups. Based on modified Ryge criteria, 100% of the crowns were rated satisfactory during the 2-year period. Conclusion In this in vivo study, CAD/CAM and HP all-ceramic crowns exhibited similar marginal and internal adaptations. A 100% success rate was recorded for the 15 CAD/CAM and for the 15 HP all-ceramic crowns during the 2-year period.

Antifungal Activity of Apple Cider Vinegar on Candida Species Involved in Denture Stomatitis

Abstract: Purpose To evaluate the in vitro antifungal activity of apple cider vinegar on Candida spp. involved in denture stomatitis. Material and Methods The microdilution technique was used to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of apple cider vinegar containing 4% maleic acid, and nystatin (control). Further tests of microbial kinetics and inhibition of adherence to acrylic resin were performed testing different concentrations (MIC, MICx2, MICx4) of the products at time intervals of 0, 30, 60, 120 and 180 minutes. A roughness meter was used to measure the changes in surface roughness; color change of the acrylic resin specimens exposed to the test products in different concentrations and time intervals were also evaluated. Results Apple cider vinegar (4%) showed MIC of 2500 μg/ml and MFC of 2500, 5000, and 10,000 μg/ml depending on the strain tested. Nystatin showed MIC of 3.125 μg/ml and strain-dependent MFC values ranging from 3.125 to 12.5 μg/ml. The microbial kinetic assay showed a statistical difference between apple cider vinegar and nystatin (p 0.05), and both had no influence on their color. Conclusion Apple cider vinegar showed antifungal properties against Candida spp., thus representing a possible therapeutic alternative for patients with denture stomatitis.

Double Full-Arch Versus Single Full-Arch, Four Implant-Supported Rehabilitations: A Retrospective, 5-Year Cohort Study.

Abstract: Purpose To report the 5-year outcome of the All-on-4 treatment concept comparing double full-arch (G1) and single-arch (G2) groups. Materials and Methods This retrospective cohort study included 110 patients (68 women and 42 men, average age of 55.5 years) with 440 NobelSpeedy groovy implants. One hundred sixty-five full-arch, fixed, immediately loaded prostheses in both jaws were followed for 5 years. G1 consisted of 55 patients with double-arch rehabilitations occluded with implant-supported fixed prostheses, and G2 consisted of 55 patients with maxillary single-arch rehabilitations or mandibular single-arch rehabilitations occluded with natural teeth or removable prostheses. The groups were matched for age (±6 years) and gender. Primary outcome measures were cumulative prosthetic (both interim and definitive) and implant survival (Kaplan-Meier product limit estimator). Secondary outcome measures were marginal bone levels at 5 years (through periapical radiographs and using the patient as unit of analysis) and the incidence of mechanical and biological complications. Differences in survival curves (log-rank test), marginal bone level (Mann-Whitney U test), and complications (chi-square test) were compared inferentially between the two groups using the patient as unit of analysis with significance level set at p ≤ 0.05. Results No dropouts occurred. Prosthetic survival was 100%. Five patients lost 5 implants (G1: n = 3; G2: n = 2) before 1 year, rendering an estimated cumulative survival rate of 95.5% (G1: 94.5%; G2: 96.4%; Kaplan-Meier, p = 0.645, nonsignificant). The average (SD) marginal bone level was 1.56 mm (0.89) at 5 years [G1: 1.45 mm (0.77); G2: 1.67 mm (0.99); p = 0.414]. The incidence rate of mechanical complications (in both interim and definitive prostheses) was 0.16 and 0.13 for G1 and G2, respectively (p = 0.032). The incidence rate of biological complications was 0.06 and 0.05 for G1 and G2, respectively (p = 0.669). Conclusions Based on the results, rehabilitating double- or single-arch edentulous patients did not yield significant differences on survival curves. The incidence of mechanical complications was significantly higher for double-arch rehabilitated patients but nevertheless, these mechanical complications did not affect the long-term survival of either the prostheses or the implants.

Effect of the addition of antimicrobial agents on Shore A hardness and roughness of soft lining materials.

Abstract: Purpose While the incorporation of antimicrobial agents into soft denture liners has been suggested as a reliable alternative treatment for denture stomatitis, it may affect the liner's properties. The effect of addition of antimicrobial agents for the treatment of denture stomatitis on the surface roughness and Shore A hardness of soft lining materials was evaluated. Materials and Methods The test groups comprised specimens (36 × 7 × 6 mm3) of soft materials (Softone and Trusoft) without (control) or with incorporation of drugs (nystatin, miconazole, ketoconazole, chlorhexidine diacetate, and itraconazole). Hardness (Shore A) and roughness (Ra) were evaluated after immersion of specimens (n = 10) in distilled water at 37°C for 24 hours, 7 and 14 days. Data were analyzed by 3-way ANOVA/Tukey's test (α = 0.05). Results After 14 days, an increase (p < 0.05) was observed in the hardness of soft materials with time for the modified specimens, except for itraconazole. Addition of drugs increased the Softone roughness only for the addition of miconazole and chlorhexidine (p < 0.05), and did not increase the roughness of Trusoft with time. Only chlorhexidine and itraconazole altered the roughness compared to the control for each material (p < 0.05). Conclusions The smallest changes of hardness and roughness with time in the modified groups compared to controls were observed for itraconazole groups for both materials.

Effect of Veneering Methods on Zirconia Framework-Veneer Ceramic Adhesion and Fracture Resistance of Single Crowns.

Abstract: Purpose The aim of this study was to evaluate the fracture resistance (FR) and shear bond strength (SBS) via finite element analysis (FEA) of zirconia framework veneered with different methods. Materials and Methods Zirconia frameworks were prepared as crowns for FR and cubic blocks for SBS (N = 60, n = 10). The specimens were veneered with one of the following veneering methods: (a) overcemented file-splitting (OCF), (b) layering (L), or (c) overpressing (P). For crowns, stainless steel dies (N = 30; chamfer: 1 mm) were scanned using a contrast spray. Bilayered design for OCF and reduced design (1 mm) for both L and P were performed by computer-aided design and manufacturing. For the SBS test, zirconia blocks were sectioned (4 × 4 × 4 mm3) under water cooling and sintered. Frameworks were veneered with compatible ceramics for each veneering method and subjected to mechanical tests. The milled suprastructures were bonded to zirconia frameworks using a resin composite in Group OCF and photopolymerized. Crowns were cemented to the metal dies with resin modified glass-ionomer cement. All specimens were stored at 37°C, 100% humidity for 48 hours prior to mechanical tests. Data were statistically analyzed (ANOVA, Bonferroni tests, α = 0.05). Fractured specimens were examined under scanning electron microscopy (SEM), and FEA modeling of the crowns was performed. Results Mean FR values (N) were significantly higher with L (6102 ± 1519) and P (4117 ± 1083) than with of OCF (1900 ± 254) (p = 0.01). The mean SBS (MPa) in OCF (24 ± 4) was significantly lower (p 0.05). For crown restorations, while only adhesive failures were found in OCF, cohesive failures within veneering ceramic were more frequent in P and L. FEA verified these findings. Conclusion Veneering methods based on layering or pressing may reduce ceramic chipping but the overcemented file-splitting method does not seem to prevent this failure. Clinical Significance Layering and overpressing veneering methods on zirconia frameworks with reduced design might decrease chipping compared to overcemented file-splitting, where in the latter, zirconia framework and feldspathic suprastructure are combined using a resin cement.

Changes in Oral Health-Related Quality of Life in Elderly Edentulous Patients after Complete Denture Therapy and Possible Role of their Initial Expectation: A Follow-Up Study.

Abstract: Purpose An edentulous patient's psychosocial attributes that may have influence on the oral health-related quality of life (OHRQoL) are given little consideration in therapeutic care. The aim of this study was to assess the impact of complete denture therapy on overall OHRQoL in elderly edentulous patients. The possible role of the patient's initial expectation toward OHRQoL was also evaluated. Methods and Materials OHRQoL was assessed using the OHIP-EDENT psychometric instrument, and 56 patients participated in the study. The assessment was done at three time points including pretreatment, after 1 month, and after 6 months. Significant differences in the OHIP-EDENT scores between pretreatment to after 1 month and pretreatment to after 6 months were calculated using Wilcoxon Signed Rank test (p < 0.05). Mann-Whitney test was used to analyze the association of patient expectations with OHIP-EDENT scores. Result Statistically significant improvement in OHRQoL after complete denture therapy at both 1 and 6 months postinsertion was evident. Statistically significant difference in the mean scores between the genders was observed after 6 months. There was no statistically significant difference in the levels of dysfunction, discomfort, and disability associated with oral problems between moderate and high expectation group at any time point. Conclusion Elderly edentulous patients had an improved overall OHRQoL after complete denture therapy, and female patients had appreciably better OHRQoL than their male counterparts. A patient's initial expectation did not have significant influence on overall OHRQoL.

Surface Detail Reproduction and Effect of Disinfectant and Long‐Term Storage on the Dimensional Stability of a Novel Vinyl Polyether Silicone Impression Material

Abstract: Purpose This study investigated the surface detail reproduction and dimensional stability of a vinyl polyether silicone (VPES) in comparison to a vinylpolysiloxane (VPS) material as a function of prolonged storage for up to 2 weeks. Materials and Methods Heavy-body VPES (EXA'lenceTM Fast Set) and VPS (ImprintTM 3 Quick Step) were compared. Forty impression ingots of each material were made using a stainless steel die as described by ANSI/ADA specification No. 19. Twenty impressions of each material were disinfected by immersion in a 2.5% buffered glutaraldehyde solution. Surface quality was assessed and scored immediately after making the ingots. Dimensional stability measurements were made immediately and repeated on the same ingots after 7 and 14 days storage in ambient laboratory conditions. Data were analyzed using the D'Agostino and Pearson omnibus normality test followed by two-way repeated measures ANOVA with post hoc Bonferroni tests. Values of p < 0.01 were deemed to be significant. Results Disinfected VPES and VPS specimens had significantly reduced dimensional changes at 7 and 14 days when compared with the nondisinfected ones (p < 0.0001). The dimensional stability of both materials was within ANSI/ADA specification No. 19's acceptable limit throughout the 2-week test period, regardless of whether they were disinfected. Out of the initial 80 ingots, 8 VPES and 1 VPS ingot scored a 2 on the surface detail test, while the remaining 71 ingots scored 1. Conclusions Heavy-body fast-set VPES experienced minimal contraction in vitro after prolonged storage, though surface detail scores were not as consistent as those of the VPS tested. The least contraction occurred when the material was examined immediately after ingot production.

Effect of Incorporation of Nano-Oxides on Color Stability of Maxillofacial Silicone Elastomer Subjected to Outdoor Weathering

Abstract: Purpose The aim of this study was to evaluate the effect of incorporation of two compositions of nano-oxides on color stability of intrinsically colored maxillofacial silicone elastomer subjected to outdoor weathering. Materials and Methods Ninety Cosmesil M511 silicone elastomer specimens were fabricated. The control group was incorporated with intrinsic coloring agents (umber, brown, yellow), group A was incorporated with intrinsic coloring agents and nanosized titanium oxide (TiO2), and group B was incorporated with intrinsic coloring agents and nanosized zinc oxide (ZnO). For outdoor weathering, specimens were mounted on a treated plywood rack, and the assembly was weathered for 6 months. A GretagMacbeth Spectrolino spectrophotometer was used to determine the CIELAB (L*a*b*) parameter before and after weathering of each specimen, and the values were noted. The color change (∆E) values were analyzed by one-way ANOVA, Tukey's post hoc test, and paired t-test. Results The color change (ΔE*) for groups were control group > group A > group B. The control group (0.76 ± 0.32) and group A (0.47 ± 0.19) showed significant difference in the color change before and after weathering (p < 0.00001). Group B (0.03 ± 0.05) showed no significant difference in color change before and after weathering (p = 0.08). Conclusions The present findings suggest that incorporation of nano-oxides improved the color stability of Cosmesil M511 silicone elastomer and also acted as an opacifier. ZnO-incorporated Cosmesil M511 specimens showed minimal or no color change and proved to be most color stable after being subjected to outdoor weathering.

Clinical Outcome of Double Crown-Retained Mandibular Removable Dentures Supported by a Combination of Residual Teeth and Strategic Implants.

Abstract: Purpose There is a lack of data regarding the clinical outcome of removable partial dentures (RPDs) supported by a combination of residual natural teeth and implants placed in strategic positions. The aim of the present case series was to conduct a retrospective investigation of the clinical outcome of mandibular tooth-implant-retained partial dentures (TIRPD) rigidly retained via telescopic double crowns. Material and Methods Between 1999 and 2010, 18 patients with reduced residual dentition (1 to 3 natural abutment teeth) and in need of an RPD received 1 to 3 implants in strategic positions for support of the removable prostheses. All TIRPDs were rigidly retained by telescopic crowns according to the Marburg Double Crown (MDC) technique; all prostheses were placed in a private practice. Tooth/implant survival and success rates, prosthetic maintenance requirements, and peri-implant parameters were analyzed retrospectively using patient records and clinical examinations during the final recall appointments. Only patients attending at least annual supportive post-implant hygiene therapy visits (SIT) were included. Results After a mean functional period of 5.84 ± 3 years (range: 3.01–12.21), 14 patients with 14 dentures supported by 24 implants and 27 teeth (mean number of abutments: 3.6) were available for assessment. Four teeth (survival rate: 85.19%) and no implants (survival rate: 100%) were lost. Peri-implantitis was observed around one implant (4.17%). All 14 dentures were functional (survival rate: 100%) and required only limited maintenance (i.e., screw loosening, acrylic resin fracture repairs, relining) amounting to 0.086 treatments per patient per year (T/P/Y). Conclusions Within the limitations of this case series, it can be concluded that TIRPDs retained via MDCs might represent a viable treatment option in mandibles with few remaining abutment teeth. Further long-term clinical evaluations with a greater sample size are needed for a more detailed evaluation of this treatment concept.

Influence of implant angulation on the fracture resistance of zirconia abutments.

Abstract: Purpose To investigate the effects of abutment design to correct for implant angulation and aging on the fracture resistance of zirconia abutments. Greater understanding of the fracture strength of the zirconia abutments under various clinical conditions may lead to improvement of clinical protocols and possibly limit potential failures of implant prosthetics. Materials and Methods Test specimens consisted of an implant-zirconia abutment-zirconia crown assembly with implant apex positioned at 0°, 20° to the facial (20F), and 20° to the lingual (20L) with respect to a constant crown contour. To keep the abutment design as the only variable, CAD/CAM technology was used to generate monolithic zirconia crowns identical both in external and internal dimensions and marginal contours to precisely fit all the abutments in an identical fashion. The monolithic zirconia abutments were designed to fit the constant crown contours and the internal connection of the implant at the three angulations. The customized abutments for the three implant angulations varied in emergence profile, screw hole location, and material thickness around the screw hole. Half the specimens from each group were subjected to steam autoclaving and thermocycling to simulate aging of the restorations in vivo. To mimic the off-axis loading of the central incisor, the specimens were loaded at the recommended cephalometric interincisal relationship of 135° between the long axis of the crown supported by the implant and the Instron force applicator simulating the mandibular incisor. The force applicator was positioned 2 mm from the incisal edge and loaded at a 1 mm/min crosshead speed. Data were evaluated by 2-way ANOVA (α = 0.05) and Tukey's HSD. Results The 20F group had the highest fracture values followed by the 0° group, and the 20L group had the lowest fracture values. Aging did not yield any significant difference in fracture force magnitudes. Conclusion Within the limitations of this study, tilting the implant apex to the lingual significantly reduced the fracture strength of angle-corrected zirconia abutments. Accordingly, while the angle between the occlusal force application and the long axis of the implant decreases, the resistance (force) to fracture decreases.

In Vitro Comparison of the Cytotoxicity and Water Sorption of Two Different Denture Base Systems

Abstract: Purpose Denture base resins have the potential to cause cytotoxicity in vivo, and the mechanical properties of resins are affected by water sorption. There is a correlation between residual monomer and water sorption. Thus, the purpose of this study was to evaluate water sorption and cytotoxicity of light-activated urethane dimethacrylate (UDMA) denture base resin compared to a conventional heat-activated polymethyl methacrylate (PMMA) resin. Materials and Methods Two denture base resins, heat-activated PMMA (Meliodent) and light-activated UDMA (Eclipse), were used in this study. Cytotoxicity (5 × 1 mm2) and water sorption (1 × 1 mm2) specimens were made following the manufacturers’ instructions (n = 10). Cytotoxicity tests of denture base resins were performed according to ISO10993–5:1999, and water sorption was evaluated according to ISO 1567:1997. ANOVA tests were employed for evaluating data (α = 0.05). Results There was no cytotoxic effect in either the PMMA or UDMA group. In addition, contrary to short-term water storage, a significantly lower water sorption value was shown for UDMA resins compared to PMMA resins in both 3- and 6-month storage periods (p = 0.043 and p = 0.002, respectively). Conclusion The tested denture base materials adhered to the ISO standards for both cytotoxicity and water sorption. The cytotoxicity of the light-activated UDMA resin tested was statistically similar to that of the heat-activated PMMA resin; however, the UDMA resin exhibited decreased water sorption in long-term water storage.

Patients' Evaluations of Complete Denture Therapy and Their Association with Related Variables: A Pilot Study.

Abstract: Purpose Patient satisfaction is an important goal in complete denture therapy, and many factors influence this parameter. This study aimed to evaluate expectations before and satisfaction after therapy with complete dentures. As a secondary objective, other variables that may interfere with patient satisfaction were also evaluated. Material and Methods A representative sample of 99 patients assigned visual analog scale (VAS) scores to their expectations before and satisfaction after therapy regarding chewing, esthetics, comfort, and phonetics. Demographic data and answers to a questionnaire concerning the dentists’ conduct were recorded. Multiple linear regression was used to evaluate the association among studied variables and patients’ expectation and satisfaction with their dentures. Results The average VAS scores were high for both expectations and satisfaction, and satisfaction exceeded expectations. Patients’ expectations about esthetics and comfort were associated with age and self-reported time of using complete dentures. Patient satisfaction regarding chewing was associated with the number of postdelivery adjustments. Also, patient satisfaction regarding esthetics was associated with gender and esthetic expectations. In regard to phonetic satisfaction, associations were verified among self-reported time of using complete dentures, comfort and phonetics expectations, and dentists’ explanations. Comfort satisfaction was associated only with educational level. Conclusions Patient satisfaction regarding complete dentures exceeded expectations and an expressive majority of positive evaluations of the dentists was noticed. Many patient-related variables seemed to influence their evaluations of their dentures.

Microtensile bond strength of lithium disilicate to zirconia with the CAD-on technique.

Abstract: Purpose Recently, a novel technique was introduced to combine lithium disilicate and zirconia into one restoration. The purpose of this study was to compare the microtensile bond strength of veneering ceramic to a zirconia core in two techniques: the e.max® CAD-on technique and the Press-on technique. Materials and Methods Group A was prepared by veneering sintered zirconia blocks (e.max® ZirCAD) with lithium disilicate blocks (e.max® CAD) using the CAD-on technique according to manufacturer's instructions. Group B was prepared by taking sintered e.max® ZirCAD blocks and veneering them with fluorapatite glass-ceramic (e.max® ZirPress) using the Press-on technique according to manufacturer's instructions. Each block was loaded in a dynamic cyclic loading machine. The blocks were then sectioned into 1 × 1 mm2 beams (n = 43) using a precision saw, thermocycled, and loaded in tension until failure on a universal testing machine. A mean and standard deviation were determined per group. Data were analyzed using an unpaired t-test (α = 0.05). Results The mean microtensile bond strengths were 44.0 ± 13.8 MPa for the CAD-on technique and 14.9 ± 8.8 MPa for the Press-on technique. Significant differences were found between the two groups (p = 2.7E−19). Conclusions The CAD-on technique (lithium disilicate/zirconia) resulted in greater microtensile bond strength than the Press-on technique (fluorapatite glass-ceramic/zirconia).

Micro‐CT Detection and Characterization of Porosity in Luting Cements

Abstract: Purpose To evaluate porosity volume and localization in luting cements under fixed dental prostheses after cementation using micro-computed tomography (CT). Materials and Methods Seventy-seven sound molars were circumferentially prepared to receive all-ceramic crowns, and IPS e.max ceramic copings were fabricated according to the manufacturer's instructions. For this study, different dental luting cements were used: eight resin-based cements (Variolink II, RelyX ARC, Clearfil Esthetic, BisCem, RelyX U100, Panavia EX, Super Bond C&B, and Multilink Automix), one resin-modified glass ionomer (Ketac Cem Plus), one glass ionomer (Ketac Cem), and one polycarboxylate (Durelon). Specimens were scanned with a micro-CT (SkyScan) for detection and comparison of the cements’ porosities. Statistical analyses were performed using Kruskal-Wallis one-way ANOVA and Bonferroni's adjusted Mann-Whitney U tests. Results Multilink Automix (Volume = 0.11 ± 0.08 mm3; Surface Area = 1.63 ± 1.31 mm2), Ketac Cem Plus (Volume = 0.22 ± 0.21 mm3; Surface Area = 4.32 ± 3.71 mm2), and Variolink II (Volume = 0.34 ± 0.38 mm3; Surface Area = 6.47 ± 5.10 mm2) contained less porosity (p 0.05); however, the volume and surface area of the porosity found in the other tested luting cements were significantly greater than those of the Multilink Automix, Ketac Cem Plus, and Variolink II (p 0.05). Conclusion The liquid and powder forms prepared by manually mixing the cements were found to cause greater porosity.

A Newly Proposed Method to Predict Optimum Occlusal Vertical Dimension.

Abstract: Purpose Establishing the optimum occlusal vertical dimension (OVD) in prosthetic treatment is an important clinical procedure. No methods are considered to be scientifically accurate in determining the reduced OVD in patients with missing posterior teeth. The purpose of this study was to derive a new formula to predict the lower facial height (LFH) using cephalometric analysis. Materials and Methods Fifty-eight lateral cephalometric radiographs of Japanese clinical residents (mean age, 28.6 years) with complete natural dentition were used for this study. Conventional skeletal landmarks were traced. Not only the LFH, but six angular parameters and four linear parameters, which did not vary with reduced OVD, were selected. Multiple linear regression analysis with a stepwise forward approach was used to develop a prediction formula for the LFH using other measured parameters as independent variables. Results The LFH was significantly correlated with Gonial angle, SNA, N-S, Go-Me, Nasal floor to FH, Nasal floor to SN, and FH to SN. By stepwise multiple linear regression analysis, the following formula was obtained: LFH (degree) = 65.38 + 0.30* (Gonial angle; degree) – 0.49* (SNA; degree) – 0.41* (N-S; mm) + 0.21* (Go-Me; mm) – 15.45* (Nasal floor to FH; degree) + 15.22* (Nasal floor to SN; degree) – 15.40* (FH to SN; degree). Conclusions Within the limitations of this study for one racial group, our prediction formula is valid in every LFH range (37 to 59°), and it may also be applicable to patients in whom the LFH deviated greatly from the average.

Impact of Loss of Removable Dentures on Oral Health after the Great East Japan Earthquake: A Retrospective Cohort Study

Abstract: Purpose The Great East Japan Earthquake in March 2011 destroyed many communities, and as a result many older victims lost their removable dentures. No previous studies have documented the prevalence of denture loss after a natural disaster or examined its negative impact. Therefore, investigation of the consequences of such a disaster on oral health is of major importance from a public health viewpoint. Materials and Methods Three to five months after the disaster, questionnaire surveys were conducted in two coastal towns, Ogatu and Oshika, located in the area of Ishinomaki city, Miyagi prefecture. Among the survey participants, 715 individuals had used one or more removable dentures before the disaster, and these comprised the population analyzed. The effect of denture loss on oral health-related quality life (OHRQoL) was examined by a modified Poisson regression approach with adjustment for sex, age, subjective household economic status, dental caries, tooth mobility, psychological distress (K6), access to a dental clinic, physical activity, and town of residence. Results There were 123 (17.2%) participants who had lost their dentures. In comparison with participants who had not lost their dentures, those lacking dentures showed a significantly higher relative risk for eating difficulties (RR = 2.65, 95%CI = 1.90–3.69), speech problems (RR = 4.37, 95%CI = 2.46–7.76), embarrassment upon smiling, laughing, or showing their teeth (RR = 5.32, 95%CI = 2.34–12.1), emotional distress (RR = 2.38, 95%CI = 1.41–4.03), and problems related to social interaction (RR = 6.97, 95%CI = 1.75–27.7). Conclusions Denture loss appeared to impair eating and speaking ability, thus discouraging communication with others. Public health intervention after major natural disasters should include dental care.

Durability and Weibull Characteristics of Lithium Disilicate Crowns Bonded on Abutments with Knife-Edge and Large Chamfer Finish Lines after Cyclic Loading.

Abstract: PURPOSE The aim of this study was to evaluate the durability of lithium disilicate crowns bonded on abutments prepared with two types of finish lines after long-term cyclic loading. MATERIALS AND METHODS Pressed lithium disilicate all-ceramic molar crowns were bonded (Variolink II) to epoxy abutments (height: 5.5 mm, O: 7.5 mm, conicity: 6°) (N = 20) with either knife-edge (KE) or large chamfer (LC) finish lines. Each assembly was submitted to cyclic loading (1,200,000×; 200 N; 1 Hz) in water and then tested until fracture in a universal testing machine (1 mm/min). Failure types were classified and further evaluated under stereomicroscope and SEM. The data (N) were analyzed using one-way ANOVA. Weibull distribution values including the Weibull modulus (m), characteristic strength (0), probability of failure at 5% (0.05), 1% (0.01), and correlation coefficient were calculated. RESULTS Type of finish line did not significantly influence the mean fracture strength of pressed ceramic crowns (KE: 1655 ± 353 N; LC: 1618 ± 263 N) (p = 0.7898). Weibull distribution presented lower shape value (m) of KE (m = 5.48; CI: 3.5 to 8.6) compared to LC (m = 7.68; CI: 5.2 to 11.3). Characteristic strengths (0) (KE: 1784.9 N; LC: 1712.1 N) were higher than probability of failure at 5% (0.05) (KE: 1038.1 N; LC: 1163.4 N) followed by 1% (0.01) (KE: 771 N; LC: 941.1 N), with a correlation coefficient of 0.966 for KE and 0.924 for LC. Type V failures (severe fracture of the crown and/or tooth) were more common in both groups. SEM findings showed that fractures occurred mainly from the cement/ceramic interface at the occlusal side of the crowns. CONCLUSION Lithium disilicate ceramic crowns bonded onto abutment teeth with KE preparation resulted in similar fracture strength to those bonded on abutments with LC finish line. CLINICAL SIGNIFICANCE Pressed lithium disilicate ceramic crowns may not require invasive finish line preparations since finish line type did not impair the strength after aging conditions.

The effect of offset implant configuration on bone stress distribution: a systematic review.

Abstract: Purpose: The aim of this systematic review was to compare straight-line and offsetimplant configurations for three-element implant-retained prostheses. Materials and Methods: Two independent reviewers conducted a review onPubMed/Medline, EMBASE, and Cochrane Library for studies published in En-glish, from January 1, 1995 to January 17, 2014. A systematic review was conductedfollowingthePRISMAstatement.Allrelevanttitleswereselectedaccordingtoinclu-sion/exclusioncriteria.Fromthispooloftitles,abstractsandfulltextswerereviewed. Results: Atotalof6080titleswereidentifiedwiththeinitialsearch.Twenty-onewereselected based on title and abstract. Of these, after discussion and complete reading,12studieswereselectedaccordingtotheinclusionandexclusioncriteria,allofwhichwere in vitro studies. Conclusions: A systematic review of the current literature showed only in vitroevidence that there is no consensus on the advantage of using an offset configurationimplant compared to those in straight-line configuration, even though some studiespresent a slight improvement of bone stress distribution when an offset implant isunder oblique loading (PICO).At present, the use of dental implants to rehabilitate patientswith tooth loss has become a clinical reality.

The Digital One-Abutment/One-Time Concept. A Clinical Report.

Abstract: The digital fabrication of dental restorations on implants has become a standard procedure during the last decade. Avoiding changing abutments during prosthetic treatment has been shown to be superior to the traditional protocol. The presented concept for implant-supported single crowns describes a digital approach without a physical model from implant placement to final delivery in two appointments. A 54-year-old man was provided with a single-tooth implant on his left mandibular first molar. Before wound closure, the implant position was captured digitally with an intraoral scanning device. After bone healing at the time of second-stage surgery the final screw-retained crown fabricated without a physical model was inserted. Soft tissue healing took place at the definitive restoration, avoiding abutment changes or changes of the healing cap. These led to stable soft tissues with a minimum of surgery. The benefits of digital fabrication and the unique way to scan the implant right after placement give an additional value that would not be achieved by analog techniques. In addition to financial benefits it represents a biologically advantageous, one-abutment/one-time approach with customized screw-retained, full-contour crowns or cemented crowns on custom abutments.

Finite element analysis of the influence of geometry and design of zirconia crowns on stress distribution.

Abstract: Purpose: To evaluate the influence of the geometry and design of prosthetic crown preparations on stress distribution in compression tests, using finite element analysis (FEA). Materials and Methods: Six combinations of 3D drawings of all-ceramic crowns (yttria-stabilized zirconia framework and porcelain veneer) were evaluated: F, flat preparation and simplified crown; FC, flat preparation and crown with contact point; FCM, flat preparation and modified crown; A, anatomical preparation and simplified anatomical crown framework; AC, anatomical preparation and crown with contact point; and ACM, anatomical preparation and modified crown. Bonded contact types atallinterfaceswiththemeshwereassigned,andthematerialpropertiesusedwereaccordingtotheliterature.A200Nverticalloadwasappliedatthecenterofeachmodel. The maximum principal stresses were quantitatively and qualitatively analyzed. Results: The highest values of tensile stress were observed at the interface between the ceramics in the region under the load application for the simplified models (F and A). Reductions in stress values were observed for the model with the anatomical preparation and modified infrastructure (ACM). The stress distribution in the flat models was similar to that of their respective anatomical models. Conclusions: The modified design of the zirconia coping reduces the stress concentration at the interface with the veneer ceramic, and the simplified preparation can exert a stress distribution similar to that of the anatomical preparation at and near the load point, when load is applied to the center of the crown.