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Compomers--a new bracket bonding generation in orthodontics?

Compomers are a new class of materials. With the compomer Dyract Ortho., specifically for bracket bonding, and with Prime & Bond 2.0, a one-component primer for enamel and dentin, DeTrey/Dentsply has developed alternative new materials. The aim of this in vitro study was to test the tensile bonding strength of these materials with different kinds of brackets. Twelve test groups, each with 30 prepared bovine incisors, were formed. Two primers, Prime & Bond 2.0 and PSA, were used. 50% of all teeth were first etched will 36% phosphoric acid. Three types of brackets--metal, ceramic and silan ceramic--were bonded with the compomer Dyract Ortho. For 90 teeth forming a control group, the composite Concise was used. When conditioning the enamel with 36% phosphoric acid, the compomer Dyract Ortho showed a similar tensile bonding strength to the composite Concise. This was not the case if metal brackets were used. Metal brackets had significantly less tensile bonding strength (p < 0.001). The interface of the compomer with the bracket was the main failure site. There was insufficient retention between the compomer and the foil mesh of the bracket base because of the strong consistency of the compomer. Without enamel etching, Dyract Ortho produced an acceptable result only in combination with the primer Prime & Bond 2.0 and silan ceramic brackets. As insufficient data are available to date, the use of compomers in clinical practice cannot yet be recommended.

Animals

Fluoride release from glass-ionomer and compomer restorative materials: 6-month data.

OBJECTIVES: To investigate the daily fluoride release of two glass ionomers (Ketac-Fil and ChemFil Superior) and two compomers (Compoglass and Dyract Restorative) over 6 months. METHODS: A pilot study evaluated the time taken for sample solutions to equilibrate to establish an appropriate time period for sample solution storage between fluoride ion measurements. In the main study storage water replacement and fluoride ion determination was made daily using a specific ion electrode, TISAB buffer and standard solutions for calibration. RESULTS: Equilibration of fluoride concentration in aqueous solution occurred in under 48 h for all materials. Total fluoride released (microgram mm-2) after 6 months by Ketac-Fil (30.6, s.d. 4.9) was significantly greater than ChemFil Superior (12.7, s.d. 2.5), Compoglass (10.4, s.d. 1.0) and Dyract Restorative (7.7, s.d. 1.7) (P < 0.05). Daily fluoride release at 24 h and 10 days was significantly higher for the glass ionomers than the compomers (P < 0.05). After 40 days the daily fluoride release (microgram mm-2) from ChemFil Superior (0.05, s.d. 0.01) was not significantly different from Compoglass (0.04, s.d. 0.01) and Dyract Restorative (0.03, s.d. 0.00) (P > 0.05). Daily fluoride release from Ketac-Fil remains significantly higher than the compomers at 3 and 6 months (P < 0.05). CONCLUSIONS: Specimens stored in water equilibrate rapidly, suggesting the rate at which storage water is changed may alter the relative fluoride release rates of materials. This important fact is often overlooked. Fluoride release from the glass ionomers is initially higher than for the compomers. Fluoride release from glass ionomers falls rapidly to approach levels released by compomers. Compomers produce no initial burst of fluoride and levels of release remain relatively constant.

Aluminum Silicates

Biocompatability of compomer restorative systems on nonexposed dental pulps of primate teeth.

This study evaluated the histologic response of total-etched and nonetched compomer restored cavity preparations. One hundred fifteen class 5 cavity preparations were placed in the teeth of four healthy adult monkeys at 7, 27, and 90 days. A 37% H3PO4 was applied for 10 seconds and rinsed in total-etched preparations. No statistical differences were seen in inflammatory reactions among total-etched or nonetched compomers at 7, 27, and 90 days. There were no statistical differences in inflammatory cell responses among all compomer systems in regard to time intervals. Pulpal responses of compomers were greater than IRM at each time period. Pulp responses were associated with stained bacteria in 32 of 89 compomer teeth. No necrotic pulps were seen in any teeth. Statistical data show a positive correlation (P < 0.05) between bacterial presence and pulpal inflammation. IRM pulps showed no inflammation or bacterial staining. Compomers are biologically compatible with pulp tissues when bacteria are excluded.

Acid Etching, Dental

Shear bond strengths produced by composite and compomer light cured orthodontic adhesives.

OBJECTIVES: To test the shear bond strengths obtained when orthodontic brackets were bonded ex vivo using a composite resin and a compomer orthodontic adhesive. METHODS: Specimens were tested in a special jig made to fit an Instron testing machine. After debonding, the adhesive remaining on bracket bases and enamel surfaces was mapped. RESULTS: Bond strengths ranged from 8 to 23 MPa with the composite resin producing higher strengths than the compomer for similar combinations of variables. Bond strength was increased by longer curing and a longer debond interval and was higher for brackets with mesh bases than undercut bases. More compomer remained on the enamel surface after debonding than did the composite resin. CONCLUSION: The compomer produced bond strengths within the range considered to be clinically acceptable in other studies. If it was clinically successful as an orthodontic adhesive a compomer would confer the advantage that fluoride release would help to minimize the onset of early caries around bonded brackets.

Acrylic Resins

Marginal adaptation of commercial compomers in dentin cavity.

The dentin cavity adaptation and setting characteristics of four commercial compomers were evaluated by measuring the wall-to-wall contraction gap width in the cylindrical dentin cavity and measuring the compressive strength for a maximum of 14 days after setting. The dentin cavity wall was pretreated by the dentin adhesives according to each manufacturer's instructions or the experimental contraction gap-free dentin bonding system. Complete marginal integrity was obtained in only one compomer and two resin composites which were combined with the experimental dentin bonding system. The compressive strength of two resin composites and two compomers ten minutes after setting was comparable to that after 14 days which indicated that the compomers exhibited setting characteristics as rapidly as the resin composite. It was concluded that a high efficacy dentin bonding system is required for commercial compomers to prevent gap formation during irradiation caused by the rapid setting shrinkage.

Analysis of Variance

Laboratory evaluation of a compomer and a resin-modified glass ionomer cement for orthodontic bonding.

The mean shear debonding force of stainless steel orthodontic brackets with microetched bases bonded with either a compomer or a resin-modified glass ionomer cement was assessed. In addition, the amount of cement remaining on the enamel surface following bracket removal was evaluated. Finally, survival time of orthodontic brackets bonded with these materials was assessed following simulated mechanical stress in a ball mill. Debonding force and survival time data were compared with those obtained for brackets bonded with a chemically cured resin adhesive, a light-cured resin adhesive, and a conventional glass ionomer cement. There were no significant differences in mean shear debonding force of brackets bonded with the compomer, resin-modified glass ionomer, chemically cured resin adhesive, or the light-cured resin adhesive. Brackets bonded with a conventional glass ionomer cement had a significantly lower mean shear debonding force than that recorded for the other materials. The Adhesive Remnant Index (ARI) mode score indicated that significantly less cement remained on the enamel following debonding of brackets cemented with resin-modified or conventional glass ionomers compared with other adhesives. The median survival time for brackets cemented with the compomer, resin-modified glass ionomer, chemically cured resin, or light-cured resin were significantly longer than for brackets cemented with conventional glass ionomer. The compomer and the resin-modified glass ionomer adhesive appear to offer viable alternatives to the more commonly used resin adhesives for bracket bonding.

Acid Etching, Dental

Residual monomer/additive release and variability in cytotoxicity of light-curing glass-ionomer cements and compomers.

In previous studies, light-cured glass-ionomer cements have been shown to evoke cytotoxic reactions. It was the purpose of this investigation (a) to determine the nature of the ingredients released into an aqueous medium from 2 light-cured glass-ionomer cements (GICs) and 3 compomers; (b) to evaluate the cytotoxicity of these extracts; and (c) to correlate the extent of the cytotoxic effects with eluted substances. Specimens of 2 light-cured GICs and 3 compomers were prepared and extracted in distilled water or cell culture medium for 24 hrs (surface-liquid ratio 42.4 mm2/mL). The aqueous eluates were analyzed by gas chromatography/mass spectrometry (GC/MS). The relative amounts of the components released from various products were compared by means of an internal caffeine standard [%CF]. For evaluation of cytotoxic effects, permanent 3T3 fibroblasts were incubated with medium extracts for 24 hrs. In addition, the ED50 concentration of the photoinitiator diphenyliodoniumchloride (DPICl) was determined. In all extracts, several water-elutable organic substances were found: (Co)monomers (especially HEMA and ethylene glycol compounds), additives (e.g., camphorquinone and diphenyliodoniumchloride), and decomposition products. The extracts of 3 products inhibited cell growth only moderately, whereas the light-cured GIC Vitrebond and the compomer Dyract Cem revealed severe cytotoxic effects. Vitrebond liberated the initiator DPICl, whereas Dyract Cem segregated a relatively high quantity [2966 %CF] of the comonomer TEGDMA in comparison with the other products. The present data show that TEGDMA and DPICl may be regarded as the prime causes for cytotoxic reactions evoked by the investigated light-cured glass-ionomer cements or compomers. Therefore, leaching of these substances should be minimized or prevented.

3T3 Cells

Flexural properties and swelling after storage in water of polyacid-modified composite resin (compomer).

The flexural properties, flexural strength, flexural modulus and modulus of resilience, of four commercially available compomers, and one resin-modified glass ionomer cement and one microfilled resin comosite (as controls) immediately after light-activation and after 1 week of water storage were tested to assess the mechanical properties. The water swelling after storage in water was also tested to assess the characteristics in water of compomers. The flexural test showed compomers to be statistically stronger and more resilient than the resin-modified glass ionomer cement or the microfilled composite, when tested immediately after light-activation and after 1 week of water storage. Water swelling of compomers was statistically less than the resin-modified glass ionomer cement after 1 week of water storage.

Analysis of Variance

Surface hardness and wear of glass ionomers and compomers.

PURPOSE: To determine the surface hardness and in vitro wear of glass ionomer cements (GIC) and compomers in comparison with a resin composite and to test for a possible correlation between the determined hardness and wear values. MATERIALS AND METHODS: Samples were made of conventional GIC (Ketac-Fil, Fuji II, Fuji IX, Ketac-Prototype = Ketac-Molar), resin-modified GIC (Photac-Fil, Fuji II LC, Vitremer), compomers (Dyract, Compoglass) and resin composite (Z100) for the hardness test (n = 10) and for the wear test (n = 3). The materials were handled according to the manufacturers' instructions. The samples were stored in deionized water for 48 hours at 37 degrees C prior to the determination of Rockwell hardness and three-body in vitro wear. RESULTS: Hardness could not be measured on Ketac-Fil and Fuji II as the samples fractured before a reading was obtainable. Statistically significant differences were found in hardness and wear between brands and between the four types of material. Surface hardness: resin-modified GIC < conventional GIC = compomers < resin composite. In vitro wear: resin-modified GIC > compomers > conventional GIC > resin composite. A negative correlation between hardness and wear was recorded.

Analysis of Variance

Compomers and glass ionomers: bond strength to dentin and mechanical properties.

PURPOSE: To compare compomers and conventional and resin-modified glass ionomer cements (GIC) with respect to bond strength to dentin and mechanical properties. MATERIALS AND METHODS: Seven conventional GICs (BaseLine, ChemFil Superior, Fuji II, Fuji IX, Ketac-Fil, Ketac-Silver, and Miracle Mix), three resin-modified GICs (Fuji II LC, Photac-Fil, and Vitremer), and two compomers (Dyract and Compoglass) were investigated. Bond strength was determined to untreated as well as pre-treated human dentin. The mechanical properties tested were flexural strength and flexural modulus. RESULTS: Mean bond strengths to untreated dentin ranged from 0.0 MPa (Photac-Fil) to 8.5 MPa (Fuji IX). Generally, the bond strengths of the compomers and resin-modified GICs were lower than those of the conventional GICs. Mean bond strengths to pre-treated dentin ranged from 0.5 MPa (Photac-Fil) to 13.7 MPa (Compoglass). No clear-cut bond strength pattern was observed for the three types of materials. Pretreatment improved the bond strength of nine out of 12 materials. Flexural strengths ranged from 13 MPa (Miracle Mix) to 180 MPa (Dyract). Generally, the compomers were stronger than the resin-modified GICs, which were much stronger than the conventional GICs. Flexural moduli ranged from 4.0 GPa (Miracle Mix) to 7.2 GPa (Fuji IX and Dyract) with no typical variations between the three categories of materials.

Analysis of Variance

Sealing ability of two "compomers" applied with and without phosphoric acid treatment for Class V restorations in vivo.

STATEMENT OF PROBLEM: "Compomers" are being used with increasing frequency in Europe and North America. PURPOSE: This study evaluated the marginal seal of two compomers in vivo. MATERIAL AND METHODS: Periodontally involved teeth, scheduled for extraction, were selected. Four groups of a combination of materials were used (Dyract with Dyract-PSA primer, group 1; Dyract with Prime and Bond 2.0, group 2; Compoglass with SCA primer, group 3; and Compoglass with Syntac Single Component, group 4). The restorations were made in a standardized shaped cavity, across the cementoenamel junction, and the teeth were extracted after 2 to 3 months of clinical service. The specimens were kept in a solution of 2% methylene blue for 24 hours. After being embedded in epoxy resin, sections were made with a low speed saw along the longitudinal axis of the teeth. The examination of dye penetration was made with a microscope at a magnification of x20 and scoring was done at both coronal and apical sites. Kruskal-Wallis statistical analysis was performed at 5% significance level. RESULTS: Groups 2 and 4 scored significantly less than groups 1 and 3 and for groups 2 and 4, 30% of the restorations exhibited leakage. CONCLUSION: These restoration systems did not completely prevent leakage either at the incisal or the cervical margins. Therefore the use of an enamel-dentin bonding system in combination with the proprietary compomer is recommended.

Acid Etching, Dental

Microleakage of Class V compomer and light-cured glass ionomer restorations.

STATEMENT OF PROBLEM: Resin-modified (light-cured) glass ionomer and polyacid-modified composite resin (compomer) restorations are popular choices for the restoration of root caries and cervical abrasion/erosion lesions, but clinical studies are relatively few and have been published primarily as abstracts. PURPOSE: In the absence of adequate clinical data, the marginal integrity of restorations of the above two types of material was compared in vitro. The microleakage of restorations of two light-cured glass ionomer restorative materials and of one compomer material was evaluated. METHODS AND MATERIAL: Restorations of the three materials were placed in facial and lingual Class V cavity preparations in bovine incisors. All preparations were centered on the cementoenamel junction and were prepared with 45-degree enamel bevels. After thermal cycling, teeth were immersed in methylene blue dye, then sections of the restorations (n = 16) were visually evaluated. RESULTS: Dye penetration was observed at approximately 20% of restoration margins for all three materials, with the greatest incidence of severe leakage in the compomer restorations. CONCLUSION: No significant difference in microleakage among the three materials (ANOVA; p > 0.05) was found.

Animals

Compomers: between glass-ionomer cements and composites.

The term 'compomer' was crafted by the producers of the first commercial material of this kind: a polyacid-modified composite resin, sold as a filling material for some specific applications. This term should recall the composite resins and glass-ionomer cements, since some features of these two generic materials are found in the compomers. Compomers contain a bifunctional monomer, which should be able to react with the pendant methacrylate groups of other monomers, as well as with the cations liberated by the glass particles. Several products of this kind are now available, and the purpose of this paper is to describe some of their specificities and to compare their influence on the mechanical properties, water uptake and fluoride release.

Biocompatible Materials

Clinical evaluation of compomer in primary teeth: 1-year results.

The clinical performance of the compomer Dyract (L.D. Caulk, Dentsply) was evaluated and compared with that of the hybrid composite resin Prisma TPH (L.D. Caulk, Dentsply) in restorations of 60 bilateral matched pairs of primary teeth. After 1 year, the overall failure rate for both restorative materials was 1.7 percent. There were no statistically significant differences in recurrence of caries, color matching, marginal integrity or anatomic form. The only statistically significant differences were in marginal discoloration and wear, where the compomer was inferior to the hybrid composite resin. The authors conclude that compomer is a suitable alternative to amalgam for restoring primary teeth.

Case-Control Studies

Evaluation of the handling of a new compomer and novel dispensing system in general dental practice.

OBJECTIVE: Easy handling of materials is essential to the production of good clinical results. The handling properties of a new compomer material and its novel primer/adhesive-dispensing system were tested in clinical use. METHOD AND MATERIALS: Ten general dental practitioners used the new material and dispenser for 3 weeks and completed a questionnaire regarding the handling, esthetics, and ease of use. They were asked to compare the new material to the compomer, resin composite, and glass-ionomer materials normally used in their own practice. RESULTS: The material scored a mean of 4.4 for dispensing convenience on a linear scale of 1 (inconvenient) to 5 (convenient) and 4.6 for ease of use (5 = easy to use, and 1 = difficult to use). The dispensing system achieved a high rating of 4.9 for convenience (5 = convenient, and 1 = inconvenient). CONCLUSION: The new material received ratings that were superior to those of the glass-ionomer and compomer materials normally used by the evaluators and similar to ratings of the resin composite normally used.

Adult

Dyract compomer: comparison of total etch vs. no etch technique.

Different dental materials and methods can influence the integrity of the marginal seal of restorations. To evaluate the microleakage of Dyract AP Light Cured Compomer, a polyacid modified resin (Caulk), using etched and unetched techniques, standardized trapezoidal Class V restorations were placed on facial or lingual surfaces of 20 human molars with the gingival margin in the cementum. Each restoration was scored at the cervical by two independent, double blinded operators, with reference to the DEJ, for dye penetration on a ranking system of: 0 = no evidence of dye penetration; 1 = dye penetration up to one-half the distance to the axial wall; 2 = dye penetration beyond one-half the distance to the axial wall but short of the axial wall; 3 = dye penetration to the axial wall or beyond. Statistical analysis (Fisher Exact Test) indicated that the etched compomer demonstrated significantly less microleakage when compared to the unetched compomer (p < 0.05).

Acid Etching, Dental

Adhesion of a compomer to dental structures.

The objective of this study was to evaluate the bond strength of a compomer to dental enamel, dentin, and cementum. Flat surfaces of these tissues were obtained from recently extracted human teeth. The different substrates were either treated with PSA (a primer and adhesive) or acid etched (35% phosphoric acid gel) and treated with PSA. Cylindrical specimens of compomer were then bonded to the substrates. Shear bond strength was determined after a 24-hour immersion in 37 degrees C water. Significant differences were found between both treatments on enamel, while none were found on dentin or cementum. The use of acid etchant on enamel as a surface-conditioning step previous to priming with PSA allowed a better bond between Dyract compomer and that substrate; acid etching was not particularly needed on dentin and cementum.

Acid Etching, Dental

Component release from light-activated glass ionomer and compomer cements.

The purpose of this study was to identify and quantify any component released from seven commercially available light-cured or resin-modified glass ionomer and compomer cements. Twenty-one separate cylindrical stainless steel moulds 6 mm in diameter and 1.0 mm deep were filled with one of seven glass ionomer or compomer cements, light activated and then immediately immersed in separate containers of distilled water. Water samples were retrieved over a time period of up to 30 days and retained for analysis. An occlusal cavity 6 mm in diameter was prepared in extracted human third molar teeth with a remaining dentin thickness of 1.6-2.0 mm. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Ten teeth were each filled with one of three cements and light activated. Water samples (eluates) were retrieved over a period of time. All samples were analysed by high performance liquid chromatography. Only one component, hydroxyethyl methacrylate (HEMA), was detected in the eluates from both tooth and mould samples. Analysis of diffusion of the HEMA through dentin showed a relatively sustained movement into the pulp space during the first day, with exponential decline thereafter. Our data show that HEMA was released from all of the light activated glass ionomer cements studied and from the compomer, both directly into water and through dentin. This release may be relevant both to the risk of adverse pulpal responses in patients and to the risk of allergy in patients and dental personnel.

Chromatography, High Pressure Liquid