Effect of polymerization temperature on the properties of autopolymerizing resin.

STATEMENT OF PROBLEM: The polymerization conditions of an autopolymerizing resin affect its physical properties, and at chairside, 3 different methods are commonly used: cooling in cold water, warming in warm water, and heating in hot water. However, the effects of polymerization temperature on the physicomechanical properties of autopolymerizing resin are unclear. PURPOSE: The purpose of this in vitro study was to determine the effect of polymerization temperature on the physicomechanical properties of autopolymerizing resin, including shrinkage, water absorption, surface roughness, amount of residual monomer, and flexural strength. MATERIAL AND METHODS: The experiment was designed to simulate a direct technique commonly used for the fabrication of interim crowns. Autopolymerizing resin specimens were made according to the powder-to-liquid ratio recommended by the manufacturer and soaked in water at 13°C, 37°C, or 60°C for 2 minutes to mold the resin until polymerization was completed 4 minutes after mixing. Shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength were measured immediately after polymerization and after 1, 3, and 7 days in distilled water at 37°C. Differences among these properties among the 3 different temperatures groups were statistically analyzed by using 1-way ANOVA and the Tukey honest significant difference test (α=.05). RESULTS: Shrinkage tests showed that the 13°C group had significantly lower shrinkage (P=.004 for 37°C and P<.001 for 60°C) than the other groups immediately after specimen preparation. The 13°C group had significantly higher surface roughness after 0 (P<.001 for 37°C and P<.001 for 60°C), 1 (P=.025 for 37°C and P=.012 for 60°C), 3 (P<.001 for 37°C and P<.001 for 60°C), and 7 days (P<.001 for 37°C and P<.001 for 60°C) than those in the other groups and significantly higher water absorption rates (P=.033 for 37°C and P<.001 for 60°C) than the other groups during the 7 days after fabrication. However, the 13°C group showed significantly higher weight percentage of residual monomers than the 60°C group at 0 (P<.001) and 1 day (P<.001). Finally, 3-point bend tests showed that the 13°C group had significantly lower flexural strength at 0 (P<.001), 1 (P<.001), 3 (P<.001), and 7 days (P<.001) than the other groups. CONCLUSIONS: The temperature environment during dental chairside polymerization of the autopolymerizing resin affected the physicomechanical properties of shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength.

Prevalence of Torus Mandibularis in Young Healthy Dentate Adults.

PURPOSE: There have been only a few reports on the prevalence of torus mandibularis (TM) in young adult patients, and TM can have various adverse effects on oral and occlusal states in middle-age patients. This study was designed to determine the association between TM status and oral and occlusal states in young healthy dentate adults. MATERIALS AND METHODS: This was a cross-sectional study; the sample population included students at Hiroshima University (Hiroshima, Japan) who participated for practical education. The predictor variables in this study included oral symptoms (temporomandibular joint noise, tooth clenching and grinding, buccal mucosa ridging, dental attrition, and tongue habit), oral anatomy (occlusal vertical dimension), and oral function (average occlusal pressure, occlusal contact area, and maximum voluntary tongue pressure). The outcome variable was TM status (present or absent). Additional variables were demographic in nature and included age, number of residual teeth, body weight, and gender. These variables were compared among participants with and without TM using univariate analysis and multiple logistic regression analysis. Statistical analyses were carried out using SPSS Statistics 19 for Windows (IBM Corp, Armonk, NY); a P value less than .05 was considered significant. RESULTS: Of 204 participants included in the study, 50% were men and 50% were women. The mean age was 22.4 ± 2.7 years. TM was present in 119 (58.3%). Multiple logistic regression analysis showed that TM status was associated with dental attrition and occlusal contact area (P < .05). CONCLUSIONS: This study showed that TM was present in more than half the young healthy dentate participants and was closely associated with dental attrition and occlusal contact area. This study will provide readers with useful information to help prevent the development of TM before middle age.

Nd:YVO4 laser groove treatment can improve the shear bond strength between dental PEEK and adhesive resin cement with an adhesive system.

The purpose of this study was to investigate the effect of various surface treatments on the shear bond strength between dental polyetheretherketone (PEEK) and adhesive resin cement. Two hundred and forty specimens were randomly classified into four groups: no treatment, sandblasted, sulfuric-acid-etched, and laser-grooved treatment. Each group was classified into two adhesive resin cement subgroups. Surface roughness, water contact angle, shear bond strength, and failure mode were measured; SEM and XPS results were obtained. The data were statistically analyzed using one-way or two-way analysis of variance and Tukey's honest significant difference test (α=0.05). Laser-grooved PEEK surface showed regular grooves and carbonization by thermal degradation; the surface roughness as well as water contact angle of were the highest in all groups. Shear bond strength values were significantly higher in the laser-groove-treated and sulfuric-acid-etched groups. Laser-groove-treated specimens showed cohesive failure. Laser-grooved treatment can improve shear bond strength between PEEK and adhesive resin cement.

Association between buccal mucosa ridging and oral feature/symptom and its effects on occlusal function among dentate young adults in a cross-sectional study of Japan.

Objective: The purpose of this study was to assess the distinction in oral features/symptoms and occlusal function between young dentate individuals with and without buccal mucosa ridging (BMR). Methods: This cross-sectional study included 200 young adults. The outcome variable was BMR state. The predictor variables were oral features/symptoms (torus palatinus, torus mandibularis, temporomandibular joint noise, bruxism, tongue thrusting habit, number of teeth present, and occlusal vertical dimension) and oral function (occlusal force, occlusal contact area, occlusal pressure, tongue pressure). These variables were compared among participants with and without BMR using univariate and multiple logistic regression analysis. Results: There were 119 participants with BMR and 81 without BMR. Multiple logistic regression analysis revealed that BMR was closely associated with bruxism, occlusal vertical dimension, and occlusal pressure. Discussion: Oral/occlusal changes of increased bruxism, lower occlusal vertical dimension, and lower occlusal pressure constitute the major causes of BMR.

Oral Implant Treatment for a Patient Undergoing Molecularly Targeted Drug Therapy for Chronic Myelocytic Leukemia: A Case Report.

The primary concern in carrying out dental implant treatment in patients with chronic myelogenous leukemia is the development of peri-implantitis. However, currently, the advent of molecular-targeted drugs such as nilotinib markedly improves the survival rates in such patients, and it is reported that remission status can be maintained for a long time without abnormalities such as a decrease in white blood cell count. This case history report discusses an 8-year follow-up of implant treatment administered during the remission phase of chronic myelogenous leukemia maintained using nilotinib. A 56-year-old male patient who was undergoing treatment for chronic myelogenous leukemia at the Department of Hematology requested a dental consultation for the treatment of a mastication disorder due to loss of mandibular left molars. After confirming via oral and radiographic examination that there were no abnormalities such as periodontal disease, temporomandibular joint symptoms, or metal allergy, two Brånemark System Mk III implants with diameters of 3.75 and 5 mm and lengths of 10 and 8.5 mm, respectively, were embedded in the defect. Following this, no problems were observed in the general condition, esthetics, or oral function around the implant. Further, symptoms such as mobility of the implant body or inflammation of the surrounding tissue have not appeared to this day, as the molecular-targeted drug decreases the occurrence of immunosuppression, which could not be achieved conventionally. Although this is only one instance, the possibility of implant treatment for chronic myelogenous leukemia patients in the remission phase has been presented in this case.

Association between salivary alpha-amylase and subjective and objective oral parafunctions in community-dwelling elderly individuals.

BACKGROUND/PURPOSE: Stress in the elderly is caused by loss of physical and psychological health. Although there have been many reports on the intraoral environment affecting physical health, few reports exist on stress and the intraoral environment in the elderly. The aim of this study was to investigate the relationship between salivary α-amylase as an index of stress value and the intraoral environment. MATERIALS AND METHODS: Three hundred and nineteen participants were community-dwelling independent individuals over 65 years old. The outcome variable was salivary α-amylase. After measurement, salivary α-amylase was classified into four groups (0 = 0-30, 1 = 31-45, 2 = 46-60, 3 = 61-200). The predictor variables were physical status (which includes age and male body-mass index) and subjective and objective symptoms (which include present teeth, torus palatinus, torus mandibularis, temporomandibular joint noise, bruxism, and dental attrition). These variables were compared among participants using univariate analysis and multiple logistic regression analysis. RESULTS: The participants included 77 men and 242 women, with a mean age of 75.8 ±â€¯5.4 years (65-94 years). Although temporomandibular joint noise and dental attrition were significantly positively correlated with salivary α-amylase, bruxism was significantly negatively correlated with salivary α-amylase (p < 0.05). Stepwise regression analysis revealed a significant relationship between salivary α-amylase and temporomandibular joint noise, bruxism, and dental attrition. CONCLUSION: High salivary α-amylase is associated with a high rate of temporomandibular joint noise and dental attrition, and a low rate of bruxism among elderly participants.

Effect of laser groove treatment on shear bond strength of resin-based luting agent to polyetheretherketone (PEEK).

PURPOSE: The mechanical properties of polyetheretherketone (PEEK) are ideally suited for fixed dental prostheses. However, PEEK typically has low adhesion strength to resin-based luting agent. This study assessed the shear bond strength between laser groove treated PEEK and resin-based luting agent. METHODS: A total of 230 specimens were randomly divided into five groups (n=46): no-treatment, air abrasion treatment, 100µm-deep, 150µm-deep, and 200µm-deep laser groove treatments. The surface roughness was measured, scanning electron microscopy was used to observe the specimen surfaces, and X-ray photoelectron spectroscopy (XPS) was used to analyze the surfaces. Each group was divided into four resin-based luting agent subgroups: Panavia V5, RelyX Ultimate Resin Cement, G-CEM Link Force, and Super-Bond C&B. After the resin-based luting agent was bonded to the specimens, the bond strength was measured using shear tests and the failure modes were assessed by stereomicroscopy. The surfaces were also observed by scanning electron microscopy (SEM) after the shear bond strength measurements. The data were statistically analyzed using a two-way analysis of variance and Tukey's honest significant difference test (α=0.05). RESULTS: The PEEK surface after laser groove treatment groups exhibited the highest mean Ra values. In the XPS analysis, the laser treated PEEK surface exhibited an effective surface composition for bonding with resin-based luting agent. The shear bond strengths for the laser groove treated samples were significantly higher (p<0.05) than those of the no-treatment and air abrasion treatment groups. CONCLUSIONS: The shear bond strength between PEEK and resin-based luting agent was substantially improved by laser groove treatment.

Factors related to masticatory performance in healthy elderly individuals.

PURPOSE: Maintenance of natural dentition and/or prosthodontic rehabilitation is necessary for good masticatory function. Although other factors such as physical and oral functions are also important for masticatory performance, only a few studies have evaluated their roles. The aim of the current study was to assess factors associated with masticatory performance among elderly individuals, while maintaining and/or reconstructing all occlusal support areas. METHODS: The present study was designed and implemented as a cross-sectional study, involving a total of 262 participants (mean age: 74.2±5.9years) who participated in the Kyoto Elders Physical Fitness Measurement Research Project. Individuals with partial or complete edentulousness who did not use dentures were excluded from the study. The predictor variables included physical status (i.e., age, gender, body-mass index, and grip strength), oral conditions (i.e., number of present teeth, temporomandibular joint noise, and denture wearer), and oral functions (i.e., maximum voluntary occlusal force; occlusal contact area; cheek pressure; oral diadochokinesis test /pa/, /ta/, /ka/; and maximum voluntary tongue pressure). The variable outcome was masticatory performance. These variables among the participants using univariate and multivariate analyses were compared. RESULTS: Grip strength, number of present teeth, maximum voluntary occlusal force, occlusal contact area, oral diadochokinesis /ka/ /ta/, and maximum voluntary tongue pressure were significant factors for masticatory performance. Stepwise regression analysis showed that grip strength, maximum voluntary occlusal force, and diadochokinesis /ta/ significantly affected masticatory performance. CONCLUSIONS: Masticatory performance was closely associated with grip strength, maximum voluntary occlusal force, and diadochokinesis /ta/ among healthy elderly participants.

The dynamic viscoelasticity and water absorption characteristics of soft acrylic resin materials containing adipates and a maleate plasticizer.

The purpose of this study was to investigate the use of different plasticizers in soft acrylic resin materials to reduce leaching of the plasticizer and thus increase the durability of tissue conditioners. Samples were prepared containing different combinations of three types of polymer/copolymer powder and four types of plasticizer liquid (DEHM, DIBA, DAA and DINA). The dynamic viscoelasticity of each sample was measured after water immersion using a dynamic mechanical analyzer. Water absorption, solubility and weight change were also measured. A significant difference was found among the materials regarding dynamic viscoelasticity, water absorption and solubility. The samples containing P-n-BMA had the most stable G' and G'' scores throughout the immersion. P-n-BMA is the most suitable powder together with DEHM as the most suitable liquid component for a tissue conditioner. These results suggest that it is possible to improve the durability of tissue conditioners by combining different polymers and plasticizers.