Yasuhiko Kawai

Efficient Resource Use in Simplified Complete Denture Fabrication

PURPOSE Conventional dentures will remain the only treatment available to most edentulous people for the foreseeable future. In this study, we compared the efficiency of two methods of making complete conventional dentures-the traditional academic standard (T) and a simplified technique (S) used in private practice. We have previously shown that they produce similar levels of patient satisfaction and denture quality. MATERIALS AND METHODS Data were gathered during a randomized controlled clinical trial of 122 subjects from initial examination until 6-month follow-up. For this report, the direct costs of providing one set of conventional complete dentures by T or S techniques were estimated. All materials used were recorded and their cost was calculated in Canadian dollars (CAN

Clinical application of removable partial dentures using thermoplastic resin. Part II: Material properties and clinical features of non-metal clasp dentures

). The costs of fabrication in an outside laboratory were added. Clinicians labor time was recorded for every procedure. Between-group comparisons for each clinical procedure were carried out with independent t-tests. The number of patients in each group who needed postdelivery treatment was compared with Chi-square tests. The effect of group assignment and of treatment difficulty on outcomes was analyzed with multiple regression analysis. RESULTS The mean total cost of the T method was significantly greater than S (CAN

The combination of a nylon and traditional partial removable dental prosthesis for improved esthetics: A clinical report

166.3; p < 0.001), and clinicians spent 90 minutes longer (p < 0.001) on clinical care. The difficulty of the case had no significant influence on outcomes. CONCLUSIONS The results indicate that the S method is the more cost-efficient method and that there are no negative consequences that detract from the cost savings.

Randomized controlled trial to investigate how acrylic-based resilient liner affects on masticatory ability of complete denture wearers

This position paper reviews physical and mechanical properties of thermoplastic resin used for non-metal clasp dentures, and describes feature of each thermoplastic resin in clinical application of non-metal clasp dentures and complications based on clinical experience of expert panels. Since products of thermoplastic resin have great variability in physical and mechanical properties, clinicians should utilize them with careful consideration of the specific properties of each product. In general, thermoplastic resin has lower color-stability and higher risk for fracture than polymethyl methacrylate. Additionally, the surface of thermoplastic resin becomes roughened more easily than polymethyl methacrylate. Studies related to material properties of thermoplastic resin, treatment efficacy and follow-up are insufficient to provide definitive conclusions at this time. Therefore, this position paper should be revised based on future studies and a clinical guideline should be provided.

Survival analysis of mandibular complete dentures with acrylic-based resilient liners.

A benefit of a nylon partial removable dental prosthesis (PRDP) is the absence of a metal framework, providing improved esthetics. Unfortunately, the lack of a traditional framework reduces rigidity and the support of occlusal rests. This clinical report describes a combination of a nylon PRDP (polyamide denture base resin) and a traditional PRDP (framework/resin) for a Kennedy Class II, Modification 1, partially edentulous mandible.

The use of existing denture-satisfaction ratings for a diagnostic test to indicate prognosis with newly delivered complete dentures

The aim of this study was to determine the effects of an acrylic-based resilient liner (ARL) on masticatory ability by verifying the null hypothesis that masticatory performance and mandibular movements do not differ between people who wear mandibular complete dentures with ARL and those who wear complete dentures with conventional acrylic resin (CAR). From April 2004 to July 2006, we conducted a randomized controlled trial study at two centres. After written informed consent was obtained from 74 edentulous patients, they were randomly allocated to either the ARL group or CAR group. Masticatory performance and mandibular movement at the lower incisal point during chewing were measured as the outcomes. We did not observe significant differences in both outcomes between the groups. The chewing cycles were significantly different during the initial, middle, and final phases of mastication. Within the limitations of the current study, the results indicate that the acrylic-based resilient denture liners used have no clinical impact on the masticatory ability of complete denture wearers.

Effects of home and office care denture reliners on maxillary complete dentures.

OBJECTIVE The purpose of this long-term randomised controlled trial was to compare the longevity of dentures constructed using a conventional acrylic resin (CAR) to that of dentures constructed using an acrylic-based resilient liner (ARL). MATERIALS AND METHODS The follow-up study was essentially carried out by annual telephone calls to each of the 67 participants. The Kaplan-Meier method and life-table analysis were used for univariate analyses. The Cox proportional-hazards test was used as a final model for statistically adjusting predictor variables such as sex, clinician type, mandibular denture type and age at denture delivery. RESULTS The denture type was likely to affect the survival time of the dentures, while the sex and clinician type were not. The group using acrylic-based resilient denture liners had twice the risk of having shorter denture-survival times than those using conventional acrylic resin dentures. Younger participants were likely to have a reduced risk of having shorter denture-survival times than older participants. CONCLUSION We conclude that mandibular complete dentures constructed using ARL are twice as likely as dentures constructed using CAR to have shorter denture survival times, mainly because of material deterioration.

Basic investigation of the laminated alginate impression technique: Setting time, permanent deformation, elastic deformation, consistency, and tensile bond strength tests

PURPOSE The study investigated the relation between subjective satisfaction ratings of existing dentures and outcomes of newly delivered dentures, and the ability of the diagnostic test, using existing ratings, to indicate prognosis with newly delivered dentures. METHODS Consecutive 165 edentulous patients were recruited from November 2001 to August 2006 at a university-affiliated hospital. Dentures were fabricated with an acrylic base with full-balanced occlusion using hard resin artificial teeth by multiple prosthodontists. At the baseline and 3-month after delivery, patients rate their overall, maxillary, and mandibular satisfaction for existing and replaced dentures on a 100-mm visual analogue scale (VAS). The association between baseline ratings and newly delivered dentures was analyzed by regression analysis. The tests performance was measured by constructing a two-by-two table; patients with the following cutoff values on the VAS (overall: <or=31; maxillary: <or=47; mandibular: <or=36) were considered unsatisfied with existing or new dentures. Relative validity of the diagnostic tests was assessed by means of sensitivity, specificity, and likelihood ratios. RESULTS Mandibular dentures showed a significant association between baseline and new dentures (coefficient=0.27, p=0.01). Results of test measures for overall, maxillary, and mandibular existing dentures were 71%, 38%, and 87% (sensitivity); 62%, 66%, and 49% (specificity); and 1.1, 1.9, and 1.7 (positive likelihood), and 0.5, 1.0, and 0.2 (negative likelihood). CONCLUSIONS Test performance indicates that the negative (satisfied) result for mandibular existing dentures may be useful to rule out the unsatisfied patients with new mandibular dentures.

Assessment of the Quality of Newly Formed Bone around Titanium Alloy Implants by Using X-Ray Photoelectron Spectroscopy

OBJECTIVES The aim of this study was to evaluate the effects of office (OR) and home (HR) care temporary denture reliners on satisfaction and functional outcomes in maxillary complete denture wearers. METHODS Thirty-four maxillary edentulous patients received application of either OR or HR to their maxillary complete dentures. Patients ratings on satisfaction and functional aspects were measured on a 100-mm visual analogue scale at 4 days post-application. Associations between baseline ratings and improvement were also assessed. RESULTS There were no significant differences between the two groups in satisfaction ratings or in the functional outcomes. The OR group showed a significant improvement in mastication and retention, whereas the HR group exhibited a significant improvement in general satisfaction and mastication. Improvement was negatively associated with baseline ratings of speech, ease of cleaning, stability and retention in the OR groups and across all variables, except ease of cleaning, in the HR group. CONCLUSION When used correctly, home care denture therapy can be as effective as office applied temporary liner in improving satisfaction with problematic maxillary dentures.

A double blind randomized clinical trial comparing lingualized and fully bilateral balanced posterior occlusion for conventional complete dentures

PURPOSE Laminated alginate impression for edentulous is simple and time efficient compared to border molding technique. The purpose of this study was to examine clinical applicability of the laminated alginate impression, by measuring the effects of different Water/Powder (W/P) and mixing methods, and different bonding methods in the secondary impression of alginate impression. METHODS Three W/P: manufacturer-designated mixing water amount (standard), 1.5-fold (1.5×) and 1.75-fold (1.75×) water amount were mixed by manual and automatic mixing methods. Initial and complete setting time, permanent and elastic deformation, and consistency of the secondary impression were investigated (n=10). Additionally, tensile bond strength between the primary and secondary impression were measured in the following surface treatment; air blow only (A), surface baking (B), and alginate impression material bonding agent (ALGI-BOND: AB) (n=12). RESULTS Initial setting times significantly shortened with automatic mixing for all W/P (p<0.05). The permanent deformation decreased and elastic deformation increased as high W/P, regardless of the mixing method. Elastic deformation significantly reduced in 1.5× and 1.75× with automatic mixing (p<0.05). All of these properties resulted within JIS standards. For all W/P, AB showed a significantly high bonding strength as compared to A and B (p<0.01). CONCLUSIONS The increase of mixing water, 1.5× and 1.75×, resulted within JIS standards in setting time, suggesting its applicability in clinical setting. The use of automatic mixing device decreased elastic strain and shortening of the curing time. For the secondary impression application of adhesives on the primary impression gives secure adhesion.