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Biomedical subjects

L G Watanabe

Publications and source records attributed to L G Watanabe.

25 records · Page 2Linked to original sources
PubMed1988

Bond strength of 4-META acrylic resin denture base to cobalt chromium alloy.

This study was designed to compare the bond strength of a conventional poly(methyl methacrylate) acrylic resin denture base (Lucitone 199) with a recently developed acrylic resin base containing 4-META (Meta-Dent) to CoCr metal alloy by using various designs representative of clinical situations. The mechanical bond strength of Lucitone 199 resin was compared with the chemical and combination chemical and mechanical bond strength of Meta-Dent resin. The following conclusions may be extrapolated from the results. 1. The highest bond strength was observed between Meta-Dent resin and the plain flat metal plate. 2. The second highest bond strength was observed between Meta-Dent resin and the flat metal plate with two posts. 3. The lowest bond strengths were observed between Meta-Dent resin and the samples containing mesh retentive mechanisms. 4. The mean bond strength of Lucitone 199 resin was highest for the flat metal plate with two posts, followed by the large mesh. Bond strength with the small-mesh samples was lowest. These differences were not statistically significant. 5. The mean bond strengths of Meta-Dent resin to flat metal plates with or without posts was significantly higher than any of the Lucitone 199 resin metal bond strengths, to the 99% confidence level. Additional studies will be necessary to confirm the validity of these conclusions with respect to clinical removable partial dentures. Longitudinal investigations will be required to reveal clinical performance of these resin systems.

Acrylic Resins↗
PubMed1988

Xeroradiography in root fracture diagnosis.

Root fracture is a clinical problem that often is difficult to diagnose. The purpose of this study was to compare diagnostic value of conventional radiographic and xeroradiographic images of experimentally fractured teeth. Forty-five extracted human single-rooted teeth were used. The roots of the teeth were coated with wax to simulate periodontal ligament and invested in acrylic to the cementoenamel junction. An access cavity was prepared and para-post, size 4 to 12 mm, was placed into the root canal. Each tooth with post was placed on the load cell table of an Instron testing machine. The Instron continuously recorded load on a moving graph paper. The load was increased until the tooth fractured. Determination of fracture was made by the sound of a sharp "crack" and by a sudden release of load on the post, as seen on the Instron recording graph. After fracture, conventional radiograph and xeroradiograph were obtained for each tooth by use of the paralleling technique. The x-ray beam angle, film distance, and tooth placement were held constant in both techniques by use of a Rinn instrument. All films were evaluated by use of light from a masked viewbox, while all of the xeroradiographs were viewed in reflected light. A magnifying glass was used to aid in the examination process. The samples were examined and categorized for root fracture by the examiners with the use of the following scores: 0 = unacceptably poor, 1 = poor but diagnostic, 2 = adequate for diagnostic information, and 3 = optimal for diagnostic information.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Stress Analysis↗
PubMed1988

Cyanoacrylate as a retrofilling material.

The sealing ability of cyanoacrylate as a retrograde root canal filling material was evaluated in vitro. Fifty roots were cleansed, shaped, and assigned to five groups of ten roots each. The root canals were obturated with gutta-percha and Grossman's sealer. The apical 2 mm of each root in the five groups was resected. In groups I, II, and III, retrofilling preparation was made and filled with amalgam, varnish and then amalgam, and cyanoacrylate, respectively. In group IV, a hot instrument was used to seal the gutta-percha, and in group V, a cold burnisher was used for the same purpose. All of the teeth were immersed in 1% methylene blue dye for 24 hours and sectional longitudinally; dye penetration was then measured. One-way analysis of variance performed on the means of the groups indicated that group III had the least amount of leakage (p less than 0.05). This study indicates that cyanocrylate may have potential as a retrograde filling material.

Apicoectomy↗
PubMedDate not supplied

Microhardness of carious deciduous dentin.

The purpose of this study was to measure the microhardness values of deciduous dentin and to compare the values as a function of position in the caries-affected layers of dentin including transparent, adjacent sound dentin, and dentin regions far from and not related to caries. Seven extracted or exfoliated deciduous anterior teeth that had dentin caries on a proximal surface were sectioned parallel to the long axis of the tooth. Ten sectioned and polished specimens were dehydrated and dried. Microhardness was measured with a Knoop indenter and correlated with wet-SEM micrographs. All data were statistically analyzed using a two-way ANOVA with subsequent Tukey-Kramer multiple comparison tests at p < 0.05. The hardness decreased from the dentinoenamel junction to the pulp chamber wall, except for the region under the caries. The hardness values of the region under the caries were significantly lower than those of other regions except for the inner region. For both the carious and sound sides, the hardness values of the inner region were significantly lower than those of the outer and middle regions. In comparing the hardness among regions in the carious and sound sides, the hardness of the outer, middle, and inner regions on the carious side was significantly lower than those in the sound side.

Analysis of Variance↗
PubMedDate not supplied

Adhesive monomers for porcelain repair.

The purpose of this investigation was to test the bond strengths of several adhesive systems intended for intraoral resin-to-porcelain and resin-to-metal bonding. All measurements were compared with resin bonding to etched bovine enamel. Based on these data and the authors' own clinical experiences, protocols for intraoral porcelain repair are presented for fractures in porcelain only, fractures with both porcelain and metal exposed, and fractures with all metal exposure.

Dental Bonding↗