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At least 325 records · Page 18Linked to original sources
PubMed1994

Pulpal response to adhesive resin systems applied to acid-etched vital dentin: damp versus dry primer application.

A number of studies have reported that acid etching of dentin is toxic to the cells of the odontoblastic layer and dental pulp. Other studies report that pulpal inflammation is a consequence of bacterial microleakage. The purpose of this study was to observe the degree of pulpal healing after pretreatment of vital dentin prior to placement of All-Bond and Scotch-bond 2 composite resin adhesives. Zinc oxide-eugenol cement and an acidic cement were employed as controls. One hundred twelve Class V nonexposed cavity preparations were placed throughout the dentitions of five healthy adult rhesus monkeys and observed at 3, 25, and 80 days. Various dentinal pretreatment procedures were employed. The All-Bond Universal primer system was placed on air-dried vital dentin in 23 cavities and on damp vital dentin in 27 cavities. Scotchbond 2 was placed as per manufacturer's instructions. All treatment procedures, materials, and times were represented in all animals. Placement of silicate cement resulted in the most severe pulpal responses at all time periods. Stained bacterial profiles in the remaining dentin on the axial walls of inflamed control pulps were associated with severe pulpal inflammation. These results indicate that acid etching of vital dentin does not impair pulpal healing in deep Class V cavities.

Acid Etching, Dental↗
PubMed1989

Biocompatibility testing of an experimental fluoride releasing resin using human gingival epithelial cells in vitro.

Cell culture is a valuable method of evaluating the biocompatibility of new dental materials. The purpose of this study was to compare the in vitro biocompatibility of an experimental fluoride composite resin with fluoride and non-fluoride-releasing materials currently available. The dental materials tested were: MQ Silicate (silicate cement), KETAC-CEM and FUJI (type II glass ionomer cements), VISIO DISPERS (a light-cured, nonfluoridated, microfilled composite resin), and FR-17 (an experimental fluoride-releasing composite resin). The Smulow-Glickman (S-G) human gingival epithelial cell line, which exhibits semidifferentiated characteristics, was used in the study as a test system. Biocompatibility was quantified by counting the viable cells per unit area remaining after 24 and 48 h at two radial distances from cured specimens immersed in the cell culture medium. The test materials were observed to be most toxic to cells nearest the materials. A Time-Distance Cytotoxicity Index (TDCI) was calculated to relate the percentage of dead cells to viable cells at each diffusion distance for each exposure time compared to a nontoxic control. The relative toxicity ranking of the materials tested based on the TDCI was VISIO DISPERS (91%), FUJI (82%), FR-17 (30%), MQ Silicate (23%), and KETAC-CEM (10%), which exhibited the least toxicity. The cytotoxicity of the experimental resin FR-17 was within the range of cytotoxicity of currently accepted restorative materials.

Cell Survival↗
PubMed1980

The in vitro effect of a glass ionomer cement on dentine and enamel walls. An electron probe and microradiographic study.

Glass ionomer cement (ASPA) was inserted in unconditioned class V cavities or in contact with polished ground surfaces of enamel and dentine in twelve teeth. Ground sections of all teeth were examined by microradiography, and four of the sections submitted to electron probe microanalysis. A narrow outer zone of increased radiopacity in the dentine walls was explained by a 5--10% increase of Ca and P. In some sections this zone covered a partly demineralized subsurface zone. The concentrations of F and Al in enamel and dentine were similar to or approximately 0.3% and 1.5%, respectively, decreasing to less than 0.1% at a distance of 16--80 microns (F) and 8--24 microns (A) from the surface. Both F and Al penetrated deeper into the dentine than into the enamel. Decreased Zn values, sometimes concomitant with increased Ca, P and Mg values, were in some instances observed in an outer narrow zone of the dentine walls. It is assumed that like silicate cement, glass ionomer cement must have anticariogenic properties, due to uptake of F and Al in cavity walls.

Calcium↗
PubMed1978

A method for assessing the clinical solubility and disintegration of luting cements.

A test was designed for evaluating the distintegration of cementing agents in the oral cavity. The cements were placed in small holes located in the proximal surfaces of cast gold restorations so that the materials were not subject to abrasion. Each cement was placed in one hole located occlusally and one located gingivally. Four commercial cements of four different types (zinc phosphate, zinc silicophosphate, polycarboxylate, and EBA-Alumina zinc oxide/eugenol) were tested in 15 patients, and differences were observed in the deterioration rates of the different cements over the 6 month period. The disintegration rate of a given cement was the same in the gingival and occlusal positions. No correlation was observed between the clinical data on loss of material and the solubility of the cements as measured by conventional in vitro tests.

Aluminum↗
PubMed1992

An in vitro comparative analysis: scanning electron microscopy of dentin/restoration interfaces.

One hundred maxillary premolar teeth were randomly allocated to ten groups. Each group was restored with one of ten different restorative techniques. The teeth were stored in deionized water for 7d prior to longitudinal sectioning in a mesio-distal plane. Following sectioning, ten specimens from each group were chosen at random from the 20 available sections. The sectioned surfaces were polished using 600-grit SiC abrasive paper and etched for 10 s with 50% phosphoric acid to remove the smear layer produced by sectioning. Five tooth sections from the dentin bonding resin groups were allowed to dry at 20 degrees C for 24h. The glass ionomer-based groups were reimmersed in deionized water during this period. The remaining five sections from each group were replicated using an addition-cure vinyl polysiloxane impression material and an epoxy resin. A comparison was made of the sections and the replicas. All tooth specimens were sputter-coated with gold for 4 min and examined using a scanning electron microscope. Replicas were gold-coated for 3 min. Different tooth/restoration interfaces, associated with different materials, were observed. A marked difference between the replicas and tooth sections was observed for glass ionomer-based restorations but not for resin-based bonding systems. Representative samples of replicas and specimens are shown, and the significance of the observed differences is discussed.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1990

Load deformation behaviour during a diametral test.

The deformation of a cylinder in the diametral mode proved to be a linear function of the applied load for silicate cements, glass ionomer cements and glass. Two theoretical analyses were investigated, namely, Hertzian indenter theory and integration of the Hondros diametral theory. Whilst both theories predicted the experimentally observed linear behaviour, neither were quantitatively correct. Furthermore, the Hondros theory contained an experimentally inaccessible parameter, the angle subtended by the contact width at the centre.

Dental Cements↗
PubMed1992

A confocal microscopic evaluation of the interface between Syntac adhesive and tooth tissue.

The aim of this study was to microscopically evaluate the effect of dentine smear layer thickness, tubular orientation and immediate stress application on a modern dentine bonding agent. Eighty mesial and distal wedge-shaped cavities were cut into dentine/cementum cervically in 40 extracted human lower third molars. The thickness of the dentine smear layer was reduced by polishing the cavity surface in half the samples. Each component of the bonding agent (Syntac: Ivoclar Vivadent) was labelled with a fluorescent dye, the unfilled resin being light cured for 30 s with the composite restoration placed in one increment and light cured for 40 s. The samples were longitudinally sectioned using a slow speed diamond saw underwater, either immediately or 24 h post placement. The sectioned surfaces were then viewed using a confocal optical microscope. The thickness of the smeared layer only effected the penetration of adhesive in dentine tubules which were separated from the pulp chamber by the cavity design. These areas were well filled with adhesive; however, areas communicating with the pulp chamber showed no penetration differences due to smear layer reduction by polishing. The interdependence of the adhesive components was illustrated by failure to achieve a well-impregnated tooth/adhesive hybrid layer when the materials were incorrectly handled. The Syntac/dentine interface was generally able to withstand the stress of sectioning immediately post placement, but showed signs of failure in the cavity line angle when the applied stresses were greatly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed2005

Effect of water storage, thermocycling, the incorporation and site of placement of glass-fibers on the flexural strength of veneering composite.

OBJECTIVES: To evaluate the effects of water storage, thermocycling, and the incorporation of glass-fibers, on the flexural strength of veneering composites. METHODS: Veneering composites with different fillers, matrices and polymerization methods (Belleglass Kerr Inc., Orange, CA, USA; Sculpture, Pentron Inc. Wallingford CT, USA; Sinfony, 3M Espe, Seefeld, Germany; SR Adoro LC and HP, Targis, Ivoclar Vivadent, Schaan, Liechtenstein), a glass-fiber framework material (Vectris Pontic VP, Ivoclar Vivadent) and a direct restorative composite control (Tetric Ceram, Ivoclar Vivadent) were selected. For the first part of the study, 30 bar specimens (25 x 2 x 2 mm3) per material were fabricated. Ten were stored for 24 h and 10 for 14 days in water at 37 degrees C. Ten were thermocycled (3000 x; 5-50-5 degrees C). Three-point bending tests (crosshead speed: 0.5 mm/min) were performed. For the second part of the study, all veneering materials were combined with a glass-fiber framework (VP). Sixty specimens were produced for each material (25 x 4 x 2 mm3) and treated as in the first part. Three-point bend tests were performed with the reinforcing glass-fiber framework either on the tension or the compression side. Data was evaluated by ANOVA and Weibull analysis. RESULTS: A decrease in flexural strength was observed after water storage or thermocycling for all veneering materials tested. None of the tested materials exhibited significant advantages compared to the control. The flexural strength of glass-fiber reinforced frameworks was ten times higher and not influenced by water storage or thermocycling. A significant reinforcing effect from glass fibers was observed when they were placed on the tension but not when placed on the compression side. SIGNIFICANCE: A glass-fiber framework on the tension side significantly improved the flexural strength of veneering composites. There was less deterioration due to water storage and thermocycling with the glass-fiber reinforced veneering composite compared to the non-reinforced materials.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2004

Effect of finish line variants on marginal accuracy and fracture strength of ceramic optimized polymer/fiber-reinforced composite crowns.

STATEMENT OF PROBLEM: Ceramic optimized polymer (Ceromer)/fiber-reinforced composite (FRC) crowns have been promoted as alternatives to conventional crowns. However, little is known regarding the ideal tooth preparation for this type of crown. PURPOSE: This in vitro study evaluated the marginal adaptation and fracture strength of ceromer/FRC crowns with respect to the various types of finish lines. MATERIAL AND METHODS: Four metal dies with different finish lines (0.9-mm chamfer, 1.2-mm chamfer, 1.2-mm rounded shoulder, and 1.2-mm shoulder) were prepared. Forty (10 for each finish line) Targis/Vectris crowns were fabricated on duplicated base metal alloy dies. The restorations were stereoscopically evaluated at 56 points along the entire circumferential margin for measuring the margin adaptation before and after cementation with a resin luting agent. The specimens were then compressively loaded to failure using a universal testing machine. The marginal adaptation (microm) was analyzed with the Kruskal-Wallis test and post-hoc Dunnett test (alpha=.05). The fracture load (N) was analyzed with a 1-way analysis of the variance and the Scheffe adjustment (alpha=.05). The fractured surfaces of the crowns were examined with a scanning electron microscope to determine the mode of fracture. RESULTS: The marginal adaptation of crowns with a shoulder finish line was significantly better than crowns with a chamfer finish line before and after cementation (P<.001). The increased marginal gap after cementation was the lowest in the 1.2-mm rounded shoulder group. The fracture strength of the crowns with the 0.9-mm chamfer and crowns with 1.2-mm chamfer was significantly greater than those of the crowns with the 1.2-mm shoulder or rounded shoulder (P=.011, P=.049, respectively). The mean fracture load of all crowns, regardless of the finish line design, was 1646 N. The fractured surface of the crown revealed adhesive failure and 3 types of cohesive failure (fracture of the Targis and Vectris, Targis fracture with a crack in the Vectris layer, and crushing without fracture). CONCLUSION: The marginal gaps were greater for the chamfer finish line specimens than in the shoulder finish line specimens. However, the fracture strength of the chamfer finish line specimens was greater than that of the shoulder finish line specimens.

Analysis of Variance↗
PubMed2005

In vitro evaluation of microleakage of indirect composite inlays cemented with four luting agents.

STATEMENT OF PROBLEM: Microleakage around dental restorations is implicated in the occurrence of secondary carious lesions, adverse pulpal response, and reduced restoration longevity. PURPOSE: The aim of this in vitro study was to evaluate the microleakage of indirect resin composite inlays cemented with 4 luting agents. MATERIAL AND METHODS: Standardized Class V inlay preparations overlapping the cemento-enamel junction were prepared on the buccal and lingual surfaces of 40 extracted human mandibular third molars. Eighty postpolymerized, heat-treated resin composite inlays (Targis, 72 specimens, 8 controls) were processed in stone replicas and cemented into the preparations using 4 luting agents (n = 18 + 2 controls for each cement group): a resin composite used with a bonding agent (Variolink II/Excite), a resin composite used with a self-etching primer, but without bonding agent (Panavia F/ED Primer), a modified resin composite used with a bonding agent (Resinomer/One Step), and a resin-modified glass-ionomer cement (Fuji Plus). Thirty-six inlays (n = 9 + 1 control) were subjected to thermal cycling (2000 cycles, 5 degrees C/55 degrees C), whereas the other 36 were not. All the teeth were then immersed in 1% methylene blue dye solution for 48 hours. Microleakage score, margin location (enamel/cementum), thermal cycling history, and preparation location (buccal/lingual) were analyzed using a multivariate model (alpha = .05). Multivariate analysis was performed using a polychotomous logistic regression. RESULTS: The preparation location had no significant effect on dye penetration. The margin location (enamel or cementum) and the thermal cycling had a significant effect on microleakage (odds ratios [ORs] = 17.6 and 8.04, respectively). In comparing the 3 resin-based luting agents (Variolink II, Panavia F, and Resinomer) to Fuji Plus, Panavia F exhibited the lowest significant overall microleakage (OR = 0.09), followed by Variolink II (significant OR equal to 0.43), whereas Resinomer demonstrated the greatest significant overall microleakage (OR = 1.35). CONCLUSION: Within the experimental conditions of this in vitro study, thermal cycling significantly increased microleakage (OR = 8.04). The overall microleakage at the enamel margins was significantly lower than the overall microleakage at the cementum margins for the 4 luting agents tested (OR = 17.6).

Acid Etching, Dental↗
PubMed2000

Color stability of new-generation indirect resins for prosthodontic application.

STATEMENT OF PROBLEM: Several new-generation indirect resins are being advocated for full contour restoration of teeth. Previous indirect resin systems have failed in this application, due in part to color instability. PURPOSE: This study evaluated and characterized the color stability of various new-generation indirect resins (ceramic-polymers) when subjected to accelerated aging. MATERIAL AND METHODS: Four new-generation indirect resin systems, 1 direct resin system, and 1 dental porcelain control were subjected to accelerated aging for a period of 300 hours. Initial specimen color parameters were determined in the Commission International de l'Eclairage Lab (CIELAB) color order system with a colorimeter. Color changes (DeltaE) were calculated between baseline color measurements and measurements made after 150 and 300 hours of accelerated aging. Color difference data were subjected to a 1-way analysis of variance to examine the interaction between material and time interval of aging. Where significant interactions occurred, a least-squared means test was performed to identify differences in the color stability between the materials (P </=.05). RESULTS: After 300 hours of accelerated aging, color changes of the indirect resins ranged between 0.62 and 3.40 DeltaE units. Two of the products tested demonstrated color stability that was not significantly different from the porcelain control. CONCLUSION: All the indirect resins tested demonstrated color stability at or below a quantitative level that would be considered clinically acceptable. Color changes of ceramic-polymers occurred because of changes in chroma, rather than alterations in lightness.

Analysis of Variance↗
PubMed2003

Effects of two preparation designs and pontic distance on bending and fracture strength of fiber-reinforced composite inlay fixed partial dentures.

STATEMENT OF PROBLEM: Joint fractures observed in Targis/Vectris inlay adhesive fixed restorations may be related to the preparation design. PURPOSE: This in vitro study investigated the effects of the proximal tooth preparation design and the pontic distance on the fracture strength and the amount of bending of fiber-reinforced inlay adhesive fixed partial dentures. MATERIALS AND METHODS: Forty extracted premolars and 40 molars were embedded in a PMMA resin to represent a premolar and molar mesiodistal separation distance of 7 mm and 11 mm, respectively. Two preparation designs were used (proximal box and tub-shaped). The sample size was 10 for each group. Fiber-reinforced inlay adhesive fixed partial dentures were fabricated by use of the Targis/Vectris system and luted adhesively to the teeth with Variolink luting agent. A vertical force was loaded to the center of the fixed partial dentures at a crosshead speed of 1 mm/min. The initial bending (mm) prior to fracture was evaluated by measuring the distance the test rod moved from a 10 N preload to fracture. The differences in the mean fracture strength and the average amount of bending as a function of the preparation designs and pontic distances were compared by use of a 2-way analysis of variance (alpha=.05). The specimens were examined optically for the type of failure with a stereomicroscope. The fracture surface of the specimens was examined by scanning electron microscopy, and radiography was used to investigate the surface morphological features at the failure sites and to determine the fracture mode. A chi-square test was used to identify the differences in the debonding rates between the types of preparation designs and the pontic distance (alpha=.05). RESULTS: The mean fracture strength and the standard deviation of the fiber-reinforced inlay retained adhesive fixed partial denture group was 1368+/-212 N for the 7-mm tub group, 885+/-109 N for the 11-mm tub group, 1779+/-317 N for the 7-mm box group, and 1336+/-281 N for the 11-mm box group. The fracture strength was significantly higher in the 7-mm pontic distance (P<.001) and for the box-shaped tooth preparation (P<.001). The amount of bending was significantly greater in the 7-mm pontic distance (P=.025) and the box-shaped tooth preparation (P=.002). Debonding was observed only in premolar teeth and tub-shaped design groups. CONCLUSION: The box-shaped tooth preparation may be considered for restoration of a missing single posterior tooth with fiber-reinforced inlay adhesive fixed partial dentures.

Adhesiveness↗
PubMed1978

Film thickness of cements beneath complete crowns.

The results showed that Durelon, EBAC, zinc phosphate, Epoxylite CBA, and Fynal had thinner film thicknesses than EBA and Fluro-Thin. In addition, venting of a crown resulted in lower film thicknesses with all cements except Fynal and EBAC. No significant differences occurred with these two cements whether the crown was vented or not. Obviously many other factors besides film thickness, such as toxicity, strength, and solubility, have to be considered before selecting a cement for clinical use. When only film thickness is to be considered, all of the cements in the study could be recommended for the cementation of crowns with the exception of EBA and Fluoro-Thin.

Cementation↗
PubMed2003

Effect of different luting materials on the marginal adaptation of Class I ceramic inlay restorations in vitro.

OBJECTIVES: The aim of this in vitro study was to assess the marginal adaptation of prefabricated Class I ceramic inlay restorations placed with various luting materials. METHODS: Forty-two standardized occlusal cavities were prepared in extracted human molars with diamond burs exactly corresponding to the dimensions of prefabricated glass ceramic inlays. The prepared teeth were randomly assigned to seven groups of six teeth each and restored using (1). the composite resin Tetric Ceram in increment technique [Group I] or (2). ceramic inlays (Cerana) luted with: the composite based materials Dual Cement [Gr. II] and Panavia 21 [Gr. III], the compomer material Dyract Cem [Gr. IV], Dyract Cem with additional use of Prime & Bond 2.1 [Gr. V], the silicophosphate cement Trans-Lit [Gr. VI], or the ethylcyanoacrylate Cyano-Veneer [Gr. VII]. Marginal adaptation was evaluated by SEM-analyses before and after thermal cycling (2500 cycles; 5-55 degrees C) and mechanical loading (100N; 500000 cycles) using replica models. Kruskal-Wallis H-test and Mann-Whitney U-test were used for statistical analyses. RESULTS: Group I (increment technique) as well as Groups II-V (inlay technique) revealed high percentages of perfect marginal adaptation in over 95% of the analyzed margins, both before and after thermo-mechanical loading. Statistical significant differences could not be detected within these groups. All inlays luted with silicophosphate cement (Group VI) and four of six inlays applied with Cyano-Veneer (Group VII) fractured under occlusal load. SIGNIFICANCE: A stable bonding to the enamel and to the ceramic inlay was achievable with the composite luting resins Dual Cement and Panavia 21 as well as with the compomer based luting material Dyract Cem but not with the use of the silicophosphate cement Trans-Lit or the ethylcyanoacrylate Cyano-Veneer.

Compomers↗