Effect of thermal cycling on microleakage between hard chairside relines and denture base acrylic resins

Objectives:Microleakage is a pre-stage of debonding between hard chairside relines and denture base acrylic resins. Therefore, it is important to assess them with regard to the longevity of the relined denture. This study investigated the effect of thermal cycling on the microleakage at the interface of three hard chairside reline resins and three denture base resins.Material and methods:Rectangular bars (12 mm x 3 mm x 3 mm) of Lucitone 550, Acron MC and QC 20 were made and relined with Kooliner, Tokuyama Rebase Fast II and Ufi Gel Hard, Lucitone 550, Acron MC and QC 20 resins. Specimens were divided into one control and two test groups (n = 10). In specimens of the control group, the microleakage was performed after the reline procedure. In Test Group 1, the specimens were stored for 24 h in distilled water at room temperature and in Test Group 2; the specimens were thermal cycled from 5 to 55 degrees C for 5000 cycles with a 30-s dwell time. Subsequently, all specimens were immersed in 50% silver nitrate solutions for 24 h. All specimens were sectioned longitudinally into three fractions and the lateral sections were examined (n = 20). Silver nitrate stain penetration was examined under a stereoscopic lens with x30 magnification, and the images were captured. Leica Qwin image analysis software was used to determine microleakage at the interface of the materials. Data were analysed using the Kruskal-Wallis test at a 95% level of significance.Results:For all cycles, there were no statistically significant differences between thermal cycled and non-thermal cycled groups (p > 0.05).Conclusion:It can be concluded that thermal cycling had no effect on the microleakage.

Influence of Microwave Disinfection on the Dimensional Stability of Denture Reline Polymers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

HARDNESS and SURFACE ROUGHNESS of RELINE and DENTURE BASE ACRYLIC RESINS AFTER REPEATED DISINFECTION PROCEDURES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of microwave irradiation and water storage on the viscoelastic properties of denture base and reline acrylic resins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Flexural strength and hardness of reline and denture base acrylic resins after different exposure times of microwave disinfection

Objectives: To evaluate the effect of microwave disinfection on the flexural strength and Vickers hardness of 4 autopolymerized resins (Kooliner [K], Tokuso Rebase Fast [T], Ufi Gel Hard [U], and New Truliner [N]) and 1 denture base resin (Lucitone 550 [L]). Method and Materials: For each material, 48 specimens (64 x 10 x 3.3 mm) were made and divided into 6 equal groups (n = 8). In the control group, specimens were untreated. Before testing, specimens were immersed in 200 mL of distilled water and submitted to disinfection for 1 of the following irradiation times: 1, 2, 3, 4, or 5 minutes. The irradiation procedure was performed twice. The flexural strength was determined using a testing machine MTS-810 and measurements of Vickers hardness were made on Micromet 2100. The values were submitted to ANOVA and Tukey's test (P = .05). Results: The K material showed a significant increase (P = .0010) in flexural strength following 5 minutes of disinfection compared to control specimens. The flexural strength mean values of materials T, U, and N were not significantly affected (P > .05) by disinfection. Compared to the control group, the K material showed a significant increase in hardness (P < .001) following disinfection for 3, 4, and 5 minutes. For material U, disinfection for 4 and 5 minutes produced specimens with significantly increased hardness values (P < .001) compared to the control group. For material N, disinfection for 5 minutes resulted in significantly higher hardness values (P < .001) than the control group. Conclusion: Regardless of the irradiation time, the flexural strength and hardness of the materials evaluated were not detrimentally affected by microwave disinfection. (Quintessence Int 2008;39:833-840)

Measurement of Interfacial Porosity at the Acrylic Resin/Denture Tooth Interface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of water storage on the shear strength and fatigue limit of the reline resin bond to denture base resins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Weight loss and changes in surface roughness of denture base and reline materials after simulated toothbrushing in vitro

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of long-term water immersion on the fracture toughness of denture base and reline resins

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of Candida albicans adhesion and biofilm formation on a denture base acrylic resin containing silver nanoparticles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

CORRELATING THE CURVE DISTANCE BETWEEN THE DISTAL of THE CANINES TO THE COMBINED WIDTH of THE SIX ANTERIOR TEETH WHEN SELECTING DENTURE TEETH FOR DIFFERENT ETHNIC GROUPS

Statement of problem. To select the width of denture teeth, the distance between the marks indicating the location of the canines is usually measured around the curvature of the wax occlusal rim; however, most manufacturers' mold charts provide the measurements of the artificial 6 anterior teeth as if they were on a straight line.Purpose. The purpose of this study was to investigate whether the curve distance between the distal surfaces of the maxillary canines can be related to the combined width (straight measurement) of the 6 anterior teeth in 4 ethnic groups.Material and methods. Maxillary stone casts were obtained for 160 dentate subjects of 4 ethnic groups (40 whites, 40 blacks, 40 multiracial - descendants of white and black parents, and 40 Asians). The width of each maxillary anterior tooth was measured on the casts with sliding calipers. The combined width of the 6 anterior teeth (CW) corresponded to the sum of the width of each anterior tooth. The curve distance between the distal surfaces of the canines (CD) was measured by using dental tape and sliding calipers. The Pearson correlation coefficient and regression analysis were used to evaluate the relationship between CD and CW in each ethnic group (alpha=.05).Results. The mean CD and CW values (in mm) obtained were: whites (CD=52.12; CW=45.65); blacks (CD=56.10; CW=48.13); multiracial (CD=53.58; CW=46.54); and Asians (CD=53.29; CW=46.60). Significant (P<.001) correlations between CD and CW measurements were observed for all ethnic groups studied (whites, r=0.957; blacks, r=0.803; multiracial, r=0.917; and Asians, r=0.881). The following linear regression equations were obtained: whites [CD=1.1(CW)+0.3]; blacks [CD=0.95(CW)+9.3]; multiracial [CD=1.2(CW)-1.1]; and Asians [CD=1.0(CW)+5].Conclusions. The curve distance between the distal surfaces of the maxillary canines can be accurately related to the combined width of the 6 anterior teeth in the selection of denture teeth for the studied ethnic groups. (J Prosthet Dent 2012;107:400-404)

Maxillary complete denture movement during chewing in mandibular removable partial denture wearers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The center of the incisive papilla for the selection of complete denture maxillary anterior teeth in 4 racial groups

Objectives: To evaluate the use of the center of the incisive papilla as a guide for the selection of the proper width of maxillary dentures in 4 racial groups. Method and Materials: One hundred sixty stone casts were obtained from impressions of the maxillary arch of white, black, mixed, and Asian subjects. The occlusal surfaces of the casts were photocopied and the images placed on a digitizer. The most anterior and posterior points of the papilla and cusp tips of the canines were digitized. Dentofacial Planner Plus software was used to calculate the distance from a line passing through the cusp tips of the canines to the center of the papilla, defined as the midpoint of the anterior and posterior points of the papilla. The selection error (in millimeters) due to the clinical application of the method of the incisive papilla was calculated and analyzed. Results: In all studied racial groups, there was no coincidence between the center of the incisive papilla and the canine line. The utilization of the center of the papilla would lead to the selection of wider artificial teeth. In 24.9% of the white, 19.3% of the mixed, 32.9% of the black, and 15.5% of the Asian populations, errors greater than 4 mm would be present with the utilization of the papilla. Conclusion: The method of the center of the incisive papilla is not accurate, but may aid in initial artificial teeth selection for the racial groups studied. (Quintessence Int 2008;39:841-845)

Cytotoxicity of denture base and hard chairside reline materials: a systematic review

Statement of problem. Adverse reactions to the materials used for the fabrication and reline of removable denture bases have been observed.Purpose. The purpose of this study was to systematically review the published literature on the cytotoxicity of denture base and hard reline materials.Material and methods. MEDLINE via PubMed, Google Scholar, and Scopus databases for the period January 1979 to December 2009 were searched with the following key words: (biocompatibility OR cytotoxic* OR allergy OR burning mouth OR cell culture techniques) and (acrylic resins OR denture OR monomer OR relin* OR denture liners). The inclusion criteria included in vitro studies using either animal or human cells, in which the cytotoxicity of the denture base and hard chairside reline resins was tested. Studies of resilient lining materials and those that evaluated other parameters such as genotoxicity and mutagenicity were excluded. Articles published in the English language and in peer-reviewed journals focusing on the cytotoxicity of these materials were reviewed.Results. A total of 1443 articles were identified through the search. From these, 20 studies were judged to meet the selection criteria and were included in the review. In the majority of the studies, continuous cell lines were exposed to eluates of specimens made from the materials, and mitochondrial activity was used to estimate cell viability. The tested acrylic resins were grouped according to 5 major categories: (1) heat-polymerized; (2) microwave-polymerized; (3) autopolymerizing; (4) light-polymerized; and (5) hard chairside reliners.Conclusions. This review provided some evidence that the heat-polymerized resins showed lower cytotoxic effects than autopolymerizing denture base acrylic resins and light or dual polymerized reline resins. However, because of the large number of variables in the reviewed literature, a definitive conclusion could not be drawn. (J Prosthet Dent 2012;107:114-127)

Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)