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PubMed2004

The efficiency of different light sources to polymerize resin cement beneath porcelain laminate veneers.

Plasma arc light units for curing resin composites have been introduced with the claim of relatively short curing times. The purpose of this study was to evaluate the efficiency of two different light sources to polymerize dual curing resin cement beneath porcelain laminate veneers. Twenty extracted healthy human maxillary centrals were used. Teeth were sectioned 2 mm below the cemento-enamel junction and crown parts were embedded into self-cure acrylic resin, labial surface facing up. Cavity preparation was carried out on labial surfaces. These teeth were divided into two groups of 10 each. The resin cement/veneer combination was exposed to two different photo polymerization units. A conventional halogen light (Hilux 350, Express Dental Products) and a plasma arc light (Power PAC, ADT) were used to polymerize resin cement. Ten specimens were polymerized conventionally (40 s) and the other specimens by plasma arc curing (PAC) (6 s). Two samples from each tooth measuring 1.2 x 1.2 x 5 mm were prepared. These sections were subjected to microshear testing and failure values were recorded. Statistically significant differences were found between the bond strength of veneers exposed to conventional light and PAC unit (P < 0.001). Samples polymerized with halogen light showed better bond strength. The results of this study suggest that the curing efficiency of PAC through ceramic was lower compared with conventional polymerization for the exposure durations tested in this study.

Adhesiveness↗
PubMed1999

Microleakage of composite resins in cavities of upper primary molars.

OBJECTIVE: To improve the quality of resin restorations, studies are necessary not only of the physical properties of materials but also of the cavity geometry. We have evaluated marginal microleakage for two types of photo-curing composite resin applied to cavities with different marginal structures. SAMPLE AND METHODS: The test materials were 91 extracted upper primary molars. The two composite resins used in this experiment were Liner Bond II (LBII) and Photo Clearfil A (PCA). A class I cavity was created in each tooth; the cavity configuration was a round bevel, a straight bevel and a butt joint. The tooth was then restored with each composite resin. Each tooth was exposed to thermal cycles, followed by immersion in 0.2% basic fuchsin solution. Three sections, through the mesial, central and distal areas of each tooth were taken. The penetration of the dye was examined with a stereoscopic microscope. The sites of observation for examination of microleakage were awarded scores of between 0 and 7. RESULTS: LBII-among the three marginal forms, absence of leakage was observed most frequently in the straight bevel group followed by the round bevel and the butt joint groups, in the mesial and distal sections. In the central section, the straight bevel did not show any scores of 0, 6 or 7. PCA-an absence of leakage in the mesial section occurred most frequently for the round bevel group. However, the absence of leakage in the central and distal sections was most frequent for the straight bevel group. Microleakage of the central section (with scores from 1 to 7) was frequently lower than that for the mesial and distal sections. Scores of 5 and above in the central section were observed only in the butt joint group. The frequency and mean score of leakage were clearly higher in LBII than in PCA, with one significant exception. For both composite resins, the butt joint group showed higher-mean scores of leakage than did either the round or straight bevel group, but for PCA, the mean score of the central section was lower than the other two sections in all groups. CONCLUSION: Our study shows that beveling does reduce marginal leakage. This leakage was more frequently observed with the use of LBII than with PCA. However, the amount of tooth ground away was greater for the bevel-treated cavity. In considering these features, special care is necessary in selecting the bur for treating a bevelled cavity.

Composite Resins↗
PubMed1998

Flexural strength of a provisional resin material with fibre addition.

The effect of fibre addition on the flexural strength of a resin was studied. A provisional material (ALIKE; GC America Inc.) was used as the control and resinous matrix. Silane treated glass fibre was selected for the reinforcing treatment. In order to determine the geometric influence on the strength, ordered fibres (1 w/o) were immersed within a resinous matrix in four different locations. In addition, randomly dispersed fibres, 5 mm in length, were blended at 1 w/o up to 8 w/o with acrylic powder and moulded into rectangular specimens (34 mm x 9 mm x 8 mm) with P:L = 2:1. Ten specimens were prepared for each group. A three-point flexural test was run using a span of 25 mm at a rate of 5 mm/min. The strength values were collected and analysed with ANOVA and Scheffe tests. The strengths of the specimens with orientated fibre addition ranged from 49.4 (s.d. = 5.7) to 64.5 (6.7) MPa and the control was 54.3 (4.0) MPa. In the dispersed groups, the strengths obtained ranged from 55.9 (5.9) to 87.3 (7.9) MPa. The results disclosed that inclusion of orientated fibres horizontally on the tension side of the specimens significantly improved the flexural strength compared with the control (P < 0.05). An optimal strength was obtained in the group of provisional resin containing 5 w/o dispersed fibre. Incorporation of glass fibres significantly improved the flexural strength of the resin and the dispersed method is more efficient than the orientated inclusion method.

Acrylic Resins↗
PubMed1999

The stress reducing capacity of unfilled resin in a Class V cavity.

This study examined the stress reducing capacity of varying thicknesses of unfilled resin in a Class V cavity. A two dimensional plane strain mesh of a Class V cavity, 3 mm in diameter and 2 mm deep, was produced and the thickness of the unfilled resin layer was varied from 0 to 80 microm. A polymerization shrinkage of 1.5% was applied to the composite resin and the interfacial forces examined. The maximum shear stresses were found to occur along the pulpal floor of the restoration at the unfilled resin-dentine interface. The maximum shear stress values varied from 11.1 to 22.4 MPa and the shear stresses decreased by up to 38% as the thickness of the unfilled resin increased to 80 microm.

Composite Resins↗
PubMed2000

Effects of aging on repair of resin-modified glass-ionomer cements.

The effects of aging on the repair bond strengths of resin-modified glass-ionomer cements after different methods of surface conditioning were studied. Surface conditioning methods included the following: maleic acid; maleic acid with resin application; polyacrylic acid; polyacrylic acid with resin application. Shear bond testing between the aged and new material was carried out with an Instron Universal testing machine. Surface conditioning with maleic acid and resin application gave the highest repair bond strengths at 3 and 6 months. There was, however, no statistically significant difference in bond strengths between the different treatment groups after both 3 and 6 months storage. Intergroup comparisons revealed no significant difference in failure modes after both storage periods. For all treatment groups, no significant difference in repair bond strengths was noted between storage after 1 week, 3 and 6 months. There appears to be a general decrease in repair bond strengths for all treatment groups after 3 months storage. The clinical repair of resin-modified glass-ionomer cements after this period of time is therefore not recommended.

Acid Etching, Dental↗
PubMed2001

Influence of thermal cycles in water on flexural strength of laboratory-processed composite resin.

Recently a new generation of laboratory-processed composite resins containing submicron glass fillers was introduced, with claims of high strength. The purpose of this study was to evaluate the effect of thermal cycling in water on the flexural strength and hardness of several laboratory composite systems. The flexural strength of the new laboratory processed composite resins (Artglass [AG], Targis [TR] and Estenia [ES]) was significantly higher than that of conventional resins (Dentacolor [DC] and Cesead II [CS]). Thermocycling caused a reduction of the flexural strength but not a reduction of the hardness for most of materials tested. It was concluded that thermocycling affected the properties of the laboratory-processed hybrid type composite resin, ES, AG and TR. However, the changes of these properties were smaller than those of microfine type composite resin DC. Thus, ES, AG and TR may maintain better properties during service compared with DC.

Analysis of Variance↗
PubMed2003

The effect of home-use fluoride gels on glass-ionomer, compomer and composite resin restorations.

The purpose of this study was to investigate the resistance to dissolution by two home-use fluoride gels on the surface integrity of glass-ionomer, resin modified glass-ionomer, compomer and composite resin restorations. Class V cavities prepared in extracted teeth were restored with a glass-ionomer (Fuji II), a resin modified glass-ionomer (Vitremenr), two compomers (Dyract and F-2000) and a composite resin (Z-100). Groups of five specimens of each material were treated for 24 h with one of the following: (i). distilled water, (ii). neutral fluoride gel and (iii). acidulated phosphate fluoride (APF) gel. Surface degradation of the restorations was studied using standard electron microscopy (SEM), rated according to specific criteria and statistically analysed by the Wilcoxon test (rank sums). Acidulated phosphate fluoride was found to have a significant effect on all examined materials, while minimal effects resulted from the neutral fluoride gel compared with the control group. The effect of home-use fluoride gels on glass-ionomer, compomer and composite resin restorations.

Acidulated Phosphate Fluoride↗
PubMed2002

Candida albicans adherence to resin-composite restorative dental material: influence of whole human saliva.

OBJECTIVE: Attachment of Candida albicans to oral surfaces is believed to be a critical event in the colonization of the oral cavity and in the development of oral diseases such as Candida-associated denture stomatitis. Although there is considerable information about the adhesion of C albicans to buccal epithelial cells and prosthetic materials, there is very little information about the adhesion of C albicans to composite restorative materials. The purpose of this study was to investigate the degree of adhesion of C albicans to a resin-composite restorative material (Herculite). METHODS: The adhesion of 2 strains of C albicans, a germinative and a germ tube-deficient mutant, was studied by a visual method after incubating the fungus and the resin with and without human whole saliva. RESULTS: In absence of saliva, the adhesion of the C albicans germinative isolate to the resin showed an increase in parallel with the germination, reaching a maximum at the end of the experiment (120 minutes). However, no significant differences were observed in the adhesion of the agerminative mutant during the period of time studied. In the presence of saliva, the adhesion of both isolates to the resin was significantly lowered. CONCLUSION: Germination and the presence of human whole saliva are important factors in the adhesion of C albicans to the resin-composite restorative material Herculite.

Analysis of Variance↗
PubMed2002

Comparison of microleakage of three acid-base luting cements versus one resin-bonded cement for Class V direct composite inlays.

STATEMENT OF PROBLEM: Demineralized dentin beneath set cement may adversely affect microleakage under fixed restorations. PURPOSE: Microleakage of direct composite inlays cemented with acid-base cements and a methyl methacrylate resin cement were evaluated to determine their effect on the integrity of the underlying hybridized dentin. MATERIALS AND METHODS: Sixty Class V box preparations (3 mm x 3 mm x 1.5 mm) were precisely prepared in previously frozen bovine teeth with one margin in enamel and another margin in dentin. Direct composite inlays (EPIC-TMPT) for each preparation were divided into 4 groups of 15 specimens each and cemented with 3 acid-base cements (control group): Elite, Ketac-Cem, Hy-Bond Carbo-Cem, and 1 adhesive resin cement: C&B Metabond. All specimens were stored in distilled water for 24 hours at 37 degrees C before immersion in 0.5% basic fuchsin for 24 hours. The dye penetration was measured on the sectioned specimens at the tooth-cement interface of enamel and cementum margins and recorded with graded criteria under light microscopy (Olympus Vanox-T) at original magnification x 50, 100, and 200. A Kruskal-Wallis and the Mann-Whitney test at P<.05 were used to analyze leakage score. RESULTS: All cementum margins of the 3 acid-base cements tested demonstrated significantly higher leakage scores than cementum margins for inlays cemented with the resin cement tested(P<.01). No leakage along the tooth-cement interface was found for inlays retained with the adhesive resin cement. CONCLUSIONS: Within the limitations of this study, the 3 acid-base cements tested exhibited greater microleakage at the cementum margins than did the adhesive resin cement that was tested.

Animals↗
PubMed2003

Antibacterial effects of resinous retrograde root filling materials.

The effect of three resinous retrograde root filling materials on the growth of four obligate anaerobic bacteria associated with endodontic infections was determined by using the agar diffusion inhibitory test. Samples of the following resinous materials (resin-modified, glass-ionomer cement, Fuji II LC; compomer, Dyract; and composite resin, Spectrum) were incubated for 1 week with the following anaerobic bacteria: Fusobacterium nucleatum, Porphyromonas gingivalis, P. endodontalis, and Prevotella intermedia. The freshly mixed and set resinous materials were placed into the prepared wells of agar plates inoculated with the test microorganisms for 1 week. After the end of the incubation period, the zone of growth inhibition was observed and measured. Analysis of variance of the mean diameter of the zone of inhibition indicated no statistically significant overall differences in the response of the black-pigmented Bacteroides species (p > 0.05). For F. nucleatum, Spectrum had more antibacterial effect against this bacteria than Dyract (p < 0.05). Additionally, Fuji II LC was ineffective against F. nucleatum (p < 0.05). However, positive control plates showed bacterial growth in all cases. Our data suggest that the antibacterial potency of polymerized materials varied considerably, depending on the type and the product tested.

Analysis of Variance↗
PubMed2004

Shear bond strength of microwaveable acrylic resin for denture repair.

Microwaveable acrylic denture resins are believed to provide an effective means of repairing fractured dentures. This in vitro investigation compared the bond strength of a microwaveable acrylic resin as a denture repair material to two established auto-polymerized resins. Fifty-one specimens were made using Lucitone 199 as a simulated denture base, and were then divided into three groups of 17 samples each. Each test group was bonded with the following acrylic resins: Acron Mc, Rapid Repair and Palapress. A shear bond strength test was carried out 24 h after the samples were bonded. Fracture analysis showed that bond failure was adhesive for all groups. Shear bond values showed a statistically significant difference at P < 0.05 level between Acron Mc and Rapid Repair; Palapress and Rapid Repair, and indicated that Acron Mc and Palapress were superior to Rapid Repair as a repair material. However, there was no statistical difference found between Acron Mc and Palapress. Microwaveable acrylic resins produce repaired junctions of adequate strength.

Acrylic Resins↗
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↗
PubMed2000

Polymerization contraction stress of resin composite restorations in a model Class I cavity configuration using photoelastic analysis.

PURPOSE: An important factor that contributes to deterioration of resin composite restorations is contraction stress that occurs during polymerization. The purpose of this article is to familiarize the clinician with the characteristics of contraction stress by visualizing the stresses associated with this invisible and complex phenomenon. MATERIALS AND METHODS: Internal residual stresses generated during polymerization of resin composite restorations were determined using micro-photoelastic analysis. Butt-joint preparations simulating Class I restorations (2.0 mm x 5.0 mm, 2.0 mm in depth) were prepared in three types of substrates (bovine teeth, posterior composite resin, and transparent composite resin) and were used to examine contraction stress in and around the preparations. Three types of composite materials (a posterior composite, a self-cured transparent composite, and a light-cured transparent composite) were used as the restorative materials. The self-cured composite is an experimental material, and the others are commercial products. After treatment of the preparation walls with a bonding system, the preparations were bulk-filled with composite. Specimens for photoelastic analysis were prepared by cutting sections perpendicular to the long axis of the preparation. Fringe patterns for directions and magnitudes of stresses were obtained using transmitted and reflected polarized light with polarizing microscopes. Then, the photoelastic analysis was performed to examine stresses in and around the preparations. RESULTS: When cavity preparations in bovine teeth were filled with light-cured composite, a gap was formed between the dentinal wall and the composite restorative material, resulting in very low stress within the restoration. When cavity preparations in the posterior composite models were filled with either self-cured or light-cured composite, the stress distribution in the two composites was similar, but the magnitude of the stress was greater in the light-cured material. When preparations in the transparent composite models were filled with posterior composite and light-cured transparent composite material, significant stress was generated in the preparation models simulating tooth structure, owing to the contraction of both restorative materials. CLINICAL SIGNIFICANCE: Polymerization contraction stress is an undesirable and inevitable characteristic of adhesive restorations encountered in clinical dentistry that may compromise restoration success. Clinicians must understand the concept of polymerization contraction stress and realize that the quality of composite resin restorations depends on successful management of these stresses.

Animals↗
PubMed2003

Long-term resin bond to densely sintered aluminum oxide ceramic.

BACKGROUND: Densely sintered aluminium oxide ceramic is a popular material for ceramic copings and all-ceramic restorations. A strong, predictable, and long-term durable resin bond is key for long-term clinical success of bonded alumina-based restorations. PURPOSE: The purpose of this study was to measure and compare in vitro shear bond strengths of three resin cements with and without their corresponding silane coupling/bonding agent to air particle- abraded densely sintered aluminum oxide ceramic after long-term water storage and thermocycling. MATERIALS AND METHODS: Composite resin cylinders were bonded to air particle-abraded samples of densely sintered aluminum oxide ceramic with Noribond DC (Noritake Dental Supply, Inc., Aichi, Japan), Panavia 21 EX (Kuraray, Osaka, Japan), and Variolink II (Ivoclar Vivadent, Schaan, Liechtenstein), which were used with and without their corresponding silane coupling and bonding agents (n = 15). All specimens (N = 90) were stored for 180 days in water and subjected to repeated thermocycling for a total of 12,000 cycles before shear bond strength was tested. Data were analyzed with the Kruskal-Wallis test and the Wilcoxon two-sample rank sum test at the 5% level of significance. RESULTS: Most groups had no or only minimal bond strength to densely sintered alumina after simulated aging. Panavia had the highest bond strength without silane/bonding agent application. Noribond with its silane/bonding agent revealed the highest overall bond strength, which was significantly greater than that of either Variolink or Panavia after silanization. CONCLUSIONS: Resin cements revealed significantly different bond strengths, and the use of silane coupling and bonding agents had various effects on the resin bond to pure densely sintered alumina. CLINICAL SIGNIFICANCE: Selection of the proper cement/bonding system is fundamental to clinical long-term success of bonded alumina-based restorations. Noribond with its bonding agent and ceramic primer seem to fulfill these requirements under clinically relevant testing conditions.

Air Abrasion, Dental↗
PubMed1995

Dimensional changes of relined denture bases with heat-cured, microwave-activated, autopolymerizing, and visible light-cured resins. A laboratory study.

The dimensional changes of relined denture bases were evaluated in a laboratory study. Heat-cured resin, two autopolymerizing resins, microwave-activated resin and a new visible light-cured resin were used as relining materials in this study. The gaps between the metal die and the relined denture bases were measured immediately after the relining procedure and subsequently on the first day, first week, fourth week, and eight week. The relined denture bases were stored in distilled water at 37 degrees C between measurements. It was shown that dimensional changes in relined denture bases were influenced by the relining materials and procedures, and that heat-cured resin proved to have the smallest dimensional change as well as the greatest dimensional stability in comparison with the other relining materials and procedures.

Acrylic Resins↗
PubMed2000

Bond strength of resin to acid-etched dentin studied by 13C NMR: interaction between N-methacryloyl-omega-amino acid primer and dentinal collagen.

The application of the hydrophilic methacrylate primer to acid-etched dentin increases the bond strength of the resin to the acid-etched dentin. However, the mechanism for the bonding of the resin to dentinal collagen through the primer remains to be determined. Before a more effective adhesive primer can be developed, we must understand the adsorption behavior of the primer to the dentinal collagen. The purpose of this study was to determine how 5 derivatives of N-methacryloyl-omega-amino acid (NMomegaA) primers enhance the bonding of the resin to acid-etched dentin. The interaction between the NMomegaA primers and dentinal collagen was studied by the 13C NMR technique, including the observation of spin-lattice relaxation times, T1. When the dentinal collagen was dispersed into the NMomegaA solution, the T1 values of the two carbonyl carbons attributed to the amide and the carboxylic acid in the NMomegaA molecule decreased dramatically. This result was due to the interaction between the amide group and the carboxylic acid group in the NMomegaA molecule and the dentinal collagen molecule. The T1 values of these carbonyl carbons decreased when the number of methylene groups in the NMomegaA molecule increased. The interaction became stronger as the number of methylene groups in the NMomegaA molecule was increased. Further, the bond strength of the resin to the acid-etched dentin primed with NMomegaA increased with a decrease in the T1 value of the amide carbonyl carbon. The strength of the interaction of the NMomegaA primer to the dentinal collagen molecule, determined by the 13C NMR technique, showed a direct correlation with the bond strength of the resin to acid-etched dentin that was treated with the NMomegaA primer.

Acid Etching, Dental↗
PubMed2002

The extent to which resin can infiltrate dentin by acetone-based adhesives.

The combined methodologies of fractography and laser-Raman spectroscopic analysis were used for evaluation of the resin-dentin bonds made with wet and dry bonding. Resin-dentin-bonded beams were produced by means of 2 acetone-based adhesives (One-Step and Prime & Bond NT). The micro-tensile bond test was conducted, and the fractured surfaces of all specimens were examined by SEM and an image analyzer. The amount of resin infiltration within the hybrid layer was quantified by means of a laser-Raman spectroscope. In Raman analysis, the amount of resin impregnation within the hybrid layer of the dry bonding was found to be significantly lower (approximately 50%) than that in the wet one. Under fractographic analysis, a correlation was found between the bond strength and the failure mode. Based on those findings, it was suggested that the integrity between the bonding resin and the top of the hybrid layer played a major role in bond strength.

Acetone↗
PubMed1982

Pulpal response to a new adhesive restorative resin.

The pulpal response to a new adhesive restorative resin was histopathologically investigated using dogs, and was compared with a representative conventional resin. When filled without etching and cavity wall lining, bacterial penetration and pulpal response were less with the new resin. Lining of dentin walls and total etching of cavity walls, including dentin, caused less pulpal response under the new resin. Cavities which were totally etched and filled with the new resin showed only a slight pulpal response and no bacterial penetration.

Acid Etching, Dental↗