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PubMed1990

The effects of dentine bonding agents on marginal leakage of composite restorations.

The aim of this study was to compare the effects upon marginal leakage of a number of dentine bonding agents: Gluma, Scotchbond, Topaz and an experimental material when used with a posterior composite resin, Occlusin. The results were also compared with composite used without a dentine bonding agent and with a glass ionomer, Chemfil II. Class V cavities with or without a bevelled cavo-surface margin were prepared in the buccal surfaces of extracted premolar teeth. Following restoration, the teeth were stored for periods of up to 3 months and then thermally cycled. Marginal leakage was subsequently determined using a radioactive isotope containing 45Ca, and an autoradiographic technique. Image analysis was used to determine the total amount of linear leakage for each specimen. The results showed that some leakage occurred for all materials at each time interval. The bevelled design of cavity allowed significantly less leakage than the non-bevelled type. The use of dentine bonding agents did not improve the marginal seal of the composite restorations, and the glass ionomer restorations showed significantly less leakage than the composite resin and dentine bonding agent combinations.

Adhesives↗
PubMed1993

The effects of dentine bonding agents on marginal leakage of composite restorations--long-term studies.

The aim of this study was to compare the effects upon marginal leakage of a number of dentine bonding agents when used with a posterior composite resin, Occlusin, after storage for periods of up to 2 years. The bonding agents used were Gluma, Scotchbond, Topaz and an experimental material. The results were compared with a glass ionomer, Chemfil II. Class V cavities with or without a bevelled cavo-surface margin were prepared in the buccal surfaces of extracted premolar teeth. Following restoration, the teeth were stored for periods of up to 2 years and then thermally cycled. Marginal leakage was subsequently demonstrated using a radioactive isotope containing 45Ca, and an auto-radiographic technique. Image analysis was used to determine the total amount of linear leakage for each specimen. The results showed that some leakage occurred for all materials at each time interval. The bevelled design of cavity allowed significantly less leakage than the unbevelled cavity. Overall, there was little difference between the various dentine bonding agents. The glass ionomer restorations showed significantly less leakage than the composite resin and dentine bonding agent combinations in unbevelled cavities.

Composite Resins↗
PubMed1977

Toxicity of some dental cements in a cell culture system.

A cell culture method has been used to study the effect of zinc phosphate cement (De Trey's Zinc Zement Improved), zinc silicophosphate cement (Fluoro-Thin) and polycarboxylate cement (Durelon) on animal cells. Disks (20 x 1 mm) of the materials were placed in the center of plastic Petri dishes and subsequently incubated with human epithelial cells. Cell multiplication, medium pH and the release of cement constituents were measured. All three cements exhibited a cytotoxic effect, which was most pronounced in the cultures with zinc silicophosphate cement and polycarboxylate cement. The results also indicated that cell growth on the surface of the disks is a more sensitive indicator of cytotoxicity than cell growth around the disks. pH of the medium was only slightly affected in cultures with polycarboxylate cement, whereas a decrease was found in cultures with zinc phosphate cement and especially with zinc silicophosphate cement. A rapid release of phosphate was found in cultures with zinc silicophosphate cement. Zinc was released into the medium from disks of zinc phosphate cement, zinc silicophosphate cement and polycarboxylate cement--exceeding the toxicity level for the present cell line after 24 h. In cultures with zinc silicophosphate cement and polycarboxylate cement the release of fluoride reached toxic levels within the same time interval.

Cell Division↗
PubMedDate not supplied

Development of an adhesive system for bonding to hard tooth tissues.

The development of an adhesion system for bonding dental composites to dentin and enamel is reviewed. Building on findings concerning adhesion to enamel, a field pioneered by Dr. Michael Buonocore and others, Dr. R.L. Bowen and his colleagues at the Paffenbarger Research Center, National Institute of Standards and Technology, began addressing and solving problems associated with (1) silicate cements and unfilled resins, (2) bonding in an aqueous environment, and (3) the development of an adhesion system for both dentin and enamel that could withstand various stresses. Although commercial products based on this adhesion system are currently available in the dental materials marketplace, experimentation continues, focusing on the synthesis of potentially better component analogs, the optimization of the individual components, and on improved storage stability and ease of synthesis.

Benzoates↗
PubMed2000

Bond strength of dual-cured resin cements to human teeth.

PURPOSE: This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second-generation laboratory composite. MATERIALS AND METHODS: Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2-bond-2, and Permalute System, using an inverted, truncated cone of pre-cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37 degrees C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two-way analysis of variance. Tukey-Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level. RESULTS: Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement-dentin interface. Permalute System had higher bond strengths than 2-bond-2 and Dual Cement when bonded to enamel. CONCLUSIONS: Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements.

Acrylates↗
PubMed1979

A new type of hydraulic dental cement.

A new type of hydraulic cement has been developed. This cement consists of a mixture of cement powder and setting agent powder and therefore has only to be kneaded with a little amount of water when being used.

Acrylic Resins↗
PubMed1995

Model investigations of caries inhibition by fluoride-releasing dental materials.

Fluoride-releasing dental materials are generally believed to reduce or prevent secondary caries. The evidence for this is largely anecdotal and centers on clinical experience with silicate cements and, more recently, with glass-ionomer cements. Unfortunately, corroborating evidence from controlled clinical trials is inadequate to establish precisely how effective these materials are or under what conditions they might be effective. Even less is known about the clinical effectiveness of newer materials that, often, release less fluoride. In vitro model systems have been used to study the effects of dental materials on de/remineralization of surrounding tooth structure. Fluoride-releasing materials have been shown in these models to reduce demineralization of both enamel and dentin compared with a material that does not release fluoride. This is useful from a mechanistic standpoint, but without clinical "standards" to guide model results, it is not possible to define an acceptable level of fluoride release or the length of time such release is required. A limited number of in situ model studies has been conducted, and some fluoride dose-response information has been obtained. These models are closer to the real situation and perhaps provide the best means to define required levels of fluoride release from materials in the absence of adequate clinical information.

Cariostatic Agents↗
PubMed1975

Cements for permanent luting: a summarizing review.

Three cement systems are favored for permanent luting of cast restorations. These include zinc phosphate, reinforced zinc oxide-eugenol, and polycarboxylate cements. Although others have been used in the past and new luting media are anticipated for the future, the status of currently used cement for luting is based mainly on the results of laboratory research and on clinical experience. Zinc phosphate cement, with an impressive 100-year history, currently holds the advantage. Future comprehensive clinical studies, correlated with results of physical and biological testing, may eventually direct the clinican's preference to another, newer material. It is hoped that properties and strength values that are clinically significant also will be identified, so that laboratory tests can be more predictive of clinical success.

Animals↗
PubMed1987

In vivo disintegration of luting cements.

The in vivo disintegration of luting cements was determined at 6- and 12-month intervals in two test series of 20 participants each. Four cements were inserted in the wells located in the mesial and distal surfaces of cast crowns. Glass ionomer, silicophosphate, polycarboxylate, and zinc phosphate cements prepared with recommended powder/liquid ratios are discussed, and are ranked with respect to disintegration at 6 and 12 months.

Chemical Phenomena↗
PubMed1988

Posterior composite resins.

A quarter of a century ago, composite resin was introduced and quickly outmoded silicate cement and acrylic resin as a restorative material. Although composite resin cannot replace amalgam, it has a strong foothold in dentistry, most notably for its superior color-matching ability. This article contrasts many properties of composite resin to amalgam, and takes a look at new developments in posterior esthetic materials.

Chemical Phenomena↗
PubMed1982

Tooth colored dental restorative materials: porosities and surface topography in relation to bacterial adhesion.

The present investigation was carried out to determine whether differences in initial bacterial accumulation on dental restorations could be explained by differences in surface topography, particularly porosities, of the materials. A point counting method was used to determine the number and the size of the porosities in 15 materials. The results demonstrated great variation among the materials in the number of porosities. However, in vitro bacterial adhesion tests failed to show any relationship between porosities in the materials and the number of bacteria adhering to them. Nor were differences in surface topography, as measured profilometrically, associated with differences in bacterial adhesion. It is concluded that variations in surface topography including porosities do not suffice to explain differences in initial bacterial accumulation on silicate cements and composite dental restoratives.

Adhesiveness↗
PubMedDate not supplied

Two-body wear resistance and degree of conversion of laboratory-processed composite materials.

PURPOSE: The purpose of this investigation was to evaluate the relative 2-body abrasive wear and degree of conversion of 4 laboratory-processed composites (Targis, Concept, belleGlass, and Artglass) and 2 direct placement composites (Herculite and Heliomolar) after 7 days of storage. MATERIALS AND METHODS: Human enamel was used as a positive control for 2-body abrasive wear, and 10 cylindric specimens (3.5-mm diameter, 8-mm height) of each material were prepared and stored in distilled water at 37 +/- 2 degrees C for wear testing. Relative 2-body abrasive wear rates were determined using a 30-micron diamond disk and a 2-body pin-on-disk apparatus. Subsequently, 3 polymerized specimens that had been stored in sealed polyethylene vials for 7 days were prepared for degree of conversion testing. The degree of conversion was determined on an infrared spectrometer using standard baseline techniques and various internal standards. RESULTS: Statistical analysis using analysis of variance and the Tukey-Kramer multiple range test indicated significant differences between several of the materials tested for both 2-body abrasive wear and degree of conversion. CONCLUSION: Concept exhibited significantly less 2-body abrasive wear compared to the direct and indirect composites (P < 0.01). Concept and belleGlass exhibited a mean degree of conversion that was significantly higher than any of the other composites tested (P < 0.01).

Acrylic Resins↗