Biomedical subjects

Tatsuo Endo

Publications and source records attributed to Tatsuo Endo.

5 recordsLinked to original sources

PubMed2006

Dimensional accuracy of a new polyether impression material.

OBJECTIVES: The purpose of this study was to evaluate the dimensional accuracy of stone dies produced from standardized impressions with 1 new and 1 conventional polyether impression material and a polyvinyl siloxane reference material. METHODS AND MATERIALS: Impressions with the polyether materials P2 and Impregum and with the polyvinyl siloxane Flexitime were produced at 23 degrees C or 37 degrees C from a truncated steel cone in cylindrical steel trays giving 4-mm impression layer thickness at the prominence line. Stone dies were poured after 1 or 24 hours of storage at ambient atmosphere. Additional impressions were stored at different relative humidity levels (0%, 33%, 50%, 75%, or 100%) for 24 hours prior to die pouring. The accuracy of the stone dies was determined as axial discrepancy between a steel ring, which fit perfectly on the steel die and the occlusal die surface. The base-diameter deviation (deltad) was calculated. RESULTS: After 1 hour, a similar increase in deltad was noticed for impression materials when dies were poured at impression temperature. Impressions made at 37 degrees C exhibited significantly higher deltad than at 23 degrees C. Light-bodied P2 showed the highest deltad increase when dies were poured after 24 hours. Flexitime showed moderate deltad differences at the 2 pouring times. The deltad of dies made from polyether materials decreased significantly with increasing humidity, whereas polyvinyl siloxane was not adversely affected. CONCLUSION: The dimensional accuracy of P2 is comparable to that of the conventional polyether impression material after short-term storage. Polyethers may absorb water, significantly compromising die accuracy upon storage at high humidity.

Absorption↗

PubMed2006

Relationship between degree of polymerization and enamel bonding strength with self-etching adhesives.

PURPOSE: To investigate the relationship between the degree of conversion of double bonds of all-in-one adhesives and their shear bond strength on ground human enamel. MATERIALS AND METHODS: Six commercially available systems and one experimental adhesive were tested: Absolute (ABS; Dentsply-Sankin), Clearfil S3 Bond (CSB; Kuraray), G-Bond (GBO; GC), Hybrid Bond (HYB; Sun Medical), iBond (IBO; Heraeus Kulzer), Xeno IV (XEN; Dentsply Caulk), and experimental iBond NG (ING; Heraeus Kulzer). Conventional shear bond strengths (SBS, n=8) of adhesive-coated enamel specimens bonded to Venus composite (Heraeus Kulzer) and degrees of conversion (DC) (FTIR, n=5) were determined after 1 and 10 min, 1, 2, and 24 h of storage. Data were statistically analyzed using ANOVA and Duncan's post hoc test (0 < 0.05). RESULTS: The adhesives' SBS (MPa) and DC (%) by testing time followed logarithmic regression lines established by the least square method. Mean shear bond strengths after 1 min/24 h were: ABS 9.8/14.9; CSB 14.7/23.4; GBO 14.8/22.0; HYB 9.7/17.0; IBO 11.3/22.3; XEN 9.1/17.3; ING 9.7/25.6. The corresponding mean DC values were: ABS 51.3/66.2; CSB 83.1/90.8; GBO 75.8/87.7; HYB 49.6/67.2; IBO 72.6/93.7; XEN 61.6/74.1; ING 64.9/89.1. Linear regressions for the relationship DC vs. SBS were significant with coefficients of determination (r2) between 0.72 and 0.97. CONCLUSION: Despite similar acidity, the adhesives showed different SBSs on enamel. Based on the relationships between DC and SBS, the cohesive failure patterns observed, and the composition-property relations discussed, it is concluded that the percentage DC is the main parameter influencing an adhesive's bonding efficacy to ground enamel.

Analysis of Variance↗

PubMed2005

Compatibility between self-etching adhesive and self-curing resin by addition of anion exchange resin.

OBJECTIVE: The aim was to investigate whether anion exchange resin powder in the OH(-) form, added to the amine component of self-cured resin can deprotonize acid groups of a self-etching adhesive and thus eliminate incompatibility caused by amine neutralization. METHODS: Shear bond strength (SBS) of a self-cured CorePaste (COP), bonded either with all-in-one adhesive iBond (IBO) or with IBO coated with a self-cured experimental resin (SCR), loaded with 0, 8, 16, or 32 wt% of anion exchange resin powder (AER) in OH- form, were determined on 80 enamel and dentin surfaces each after 24 h water storage. IBO specimens were either light-activated or not. Flexural modulus and strength of the four SCR resins were determined by three-point bending. Data was analyzed by one-way ANOVA and Duncan's post hoc test (p<0.05). RESULTS: Enamel SBSs of COP on IBO were 20-25 MPa, in combination with SCR (0 up to 32%) >25 MPa for activated or non-activated IBO. COP on IBO produced no bond on dentin, with the non-loaded SCR 5-10 MPa SBS was achieved, and 15 and 21 MPa were measured with the three AER-loaded SCRs on activated and non-activated IBO, respectively. Flexural moduli of SCR with 0 and 8% AER were higher than with 16 and 32%. Flexural strengths were not significantly different. SIGNIFICANCE: Addition of anion exchange resin to the amine component of self-cured resin is an effective means of enhancing the bond strength on dentin and to prevent amine neutralization through the acid groups of self-etching primer adhesives.

Acid Etching, Dental↗

PubMed2005

Evaluation of the elastic recovery of polyether impression materials.

PURPOSE: To evaluate and compare the effects of induced strain, time of straining, and loading time on the elastic recovery of two polyether impression materials and a vinyl polysiloxane reference material. METHODS: Specimens of the light and heavy-bodied types of the polyether materials P2 (P2L/H) and Impregum (IML/H) and of the vinyl polysiloxane impression material Flexitime (FLC/H) were loaded in a cone-plate rheometer with tensile strains between 16.4 and 60%, at different times after mixing, and at loading times between 1 and 10 seconds. The resulting permanent deformation was determined from creep curves. For each material and each variable condition six specimens were tested at ambient laboratory atmosphere. Regression analyses and ANOVA were used for statistical data analysis. RESULTS: Both induced strain, time of straining, and straining rate were significantly associated with the resulting permanent deformation of all materials, except FLC when loaded in the well-set stage between 1 and 10 seconds loading time at 37.4% induced tensile strain (P< 0.001). Apart from P2 the heavy-bodied impression materials showed significantly higher secondary creep (P < 0.05) than their corresponding light-bodied versions.

Dental Impression Materials↗

PubMed2002

High oleic acid oil suppresses lung tumorigenesis in mice through the modulation of extracellular signal-regulated kinase cascade.

This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30 after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E2 (PGE2) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk) cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses lung tumorigenesis and that this suppression is correlated with the inhibition of PGE2 production and inactivation of the Erk cascade.

Animals↗