PURPOSE To evaluate resin bond strength to enamel contaminated with handpiece oil. MATERIALS AND METHODS Bovine teeth were randomly assigned to six groups of 20 teeth each for treatment with one of six different bonding systems (five one-bottle and one multibottle). For each system, 10 enamel specimens were contaminated with handpiece oil before acid-etching and 10 were contaminated after acid-etching. The enamel was etched for 15 seconds using 35% phosphoric acid. Following adhesive application, composite resin was bonded using a gelatin capsule technique. Shear bond strengths from the two contaminated groups were compared to bond strengths to uncontaminated enamel obtained from a previous study that was performed by the same group of investigators, using the same facility, materials, and methods. RESULTS Two-way analysis of variance (ANOVA) showed that the factor "surface contamination" did not have a significant effect on bond strength (p > .542). The type of adhesive and the interaction of adhesive and surface contamination were significant (p < .0001 and p < .003, respectively). When oil was applied before etching, mean bond strengths ranged from 18.0 +/- 4.8 MPa for OptiBond SOLO (Kerr Corp., Orange, California) to 25.3 +/- 5.6 MPa for Tenure Quik with Fluoride (Den-Mat Corp., Santa Maria, California). With oil applied after etching, bond strengths ranged from 18.4 +/- 8.0 MPa for Tenure Quik with Fluoride to 27.4 +/- 5.4 MPa for Single Bond (3M Dental Products, St. Paul, Minnesota). For the same adhesive, comparing uncontaminated and "oil-before-etch" contaminated groups, the only statistically significant difference in bond strengths was for OptiBond SOLO: 21.8 +/- 4.0 MPa (uncontaminated) versus 18.0 +/- 4.8 MPa (oil before etch). Comparing uncontaminated and "oil-after-etch" groups, the only statistically significant difference was for Tenure: 24.5 +/- 5.7 MPa (uncontaminated) and 18.4 +/- 8.0 MPa (oil after etch).
PURPOSE:To evaluate in vitro any increase in size of Class V resin-based composite (RBC) restorations as a result of replacement.MATERIALS AND METHODS:For group 1, 20 Class V cavity preparations were prepared in extracted incisor and canine teeth. The cavosurface margin was prepared as a butt joint 90-degree angle toward the occlusal wall. Impressions were made of all preparations with a polyvinyl siloxane material. The cavities then received a 1.5-mm 45-degree bevel at the cavosurface margin of the occlusal wall. Impressions were again made of the preparations. The cavities were then restored with a conventional multistep bonding system (Scotchbond Multi-Purpose, 3M Dental Products, St. Paul, Minnesota) and a microfilled RBC (Silux Plus, 3M Dental Products). As a second part of the study (group 2), another 20 Class V cavity preparations were prepared. Half of the cavities received a bevel at the cavosurface margin of the occlusal wall, and half were finished with a butt joint. Impressions were made from all 20 specimens followed by resin-based composite restoration in the same manner as previously described. All the restorations from both group 1 and group 2 were then removed with carbide burs. New impressions were made, and 100 stone models were fabricated. The perimeter and area of the cavity preparations, including the beveled area, were recorded using a video-based imaging system equipped with macro lens, at 10 to 15 times magnification. Both perimeter and area of the postoperative cavity preparation were compared to the initial cavity size for both butt joint and bevel finishing.RESULTS:Intraclass correlation coefficient and paired t-test showed no significant difference between the preoperative bevel type of cavity preparation and its postoperative counterparts for both group 1 and group 2 (p > .05). However, a significant increase in the size of the cavity preparation was found preoperatively when a bevel was placed at the cavosurface margin. Postoperatively, a significant increase in size of the cavities was found for butt joint type finishing for both area (p = .0001) and perimeter (p = .0001), compared to initial cavity size.
The introduction of many new packable composites suggests that these products are rapidly gaining popularity. The purpose of this study was to evaluate the in vitro properties of a variety of packable composites and to determine if significant enhancements in physical and mechanical properties have been achieved for these materials compared with two popular nonpackable posterior composites. For the five packable and two regular composites tested (ALERT, Pyramid-Dentin, Pyramid-Enamel, Solitaire, SureFil, Heliomolar, and Z100), the values for fracture toughness, flexure strength, flexure modulus, hardness, and volumetric polymerization shrinkage were determined. In general, although the packable composites were of heavier consistency, they had mechanical properties that were intermediate to (ALERT, Pyramid, and SureFil) or lower than (Solitaire) those of the nonpackable materials. These results could have been predicted based on the similar methacrylate resin chemistry and filler volumes of the various composites. No composite had adequate depth-of-cure when tested in increments greater than 2 mm thick. Polymerization contraction of the packable composites was similar to or higher than that of the nonpackable composites. In addition, the radiopacity of at least one material, Solitaire, was not considered to be adequate (less than 2 mm of aluminum). The results of this study suggest that these packable composites are unlikely to offer improved clinical performance over well-placed nonpackable composites.
PURPOSE:The purpose of this study was to assess noncarious cervical lesions in young patients and to establish a possible relation with occlusal aspects.MATERIALS AND METHODS:Forty-eight dental students (28 males; 20 females) between the ages of 16 and 24 years, were investigated to verify the presence of noncarious cervical lesions and their relation to some occlusal aspects. The assessment involved a questionnaire, clinical examinations, and model analysis.RESULTS:The results indicated that the lower first molars (21.3%), the upper first molars (16.0%), the upper first premolars (12.8%), the lower first premolars (11.7%), and the lower second premolars (11.7%) were the teeth most affected by the lesions. Age was a significant factor with respect to the presence of lesions; the students with noncarious cervical lesions were older than the students who showed no lesions. Among the 79 teeth exhibiting lesions, 62 (78.5%) showed wear facets. In the group with lesions, the mean, per subject, was 15.0 teeth with wear facets, whereas in the group without lesions the mean was 10.8 teeth with wear facets per subject, suggesting that occlusal stress has some effect on lesion development.
PURPOSE:Quality standards for restorations recently have been defined in Switzerland. Amalgam substitutes must meet restoration Grade 2 requirements (i.e., pulp and dental hard substance must be preserved, and both form and function of the tooth have to be reconstituted). The pertinent operative technique has to be simple and amalgam-like. A minimum service life of 8 years is required. This in vitro study investigated the clinical potential of several amalgam substitutes, taking into account the operative requirements, the defined restorative guidelines, and the required service life.MATERIALS AND METHODS:Potential amalgam substitutes evaluated in this study included compomers (Compoglass, Dyract, Dyract AP, Elan, F 2000) and resin-based composites (Alert, Ariston, Definite, Nulite, Solitaire, Surefil). The composites Adaptic and Tetric Cream, using a simplified placement technique, were tested as negative and positive controls, respectively. Marginal adaptation and wear properties were measured in vitro in mixed Class II cavities. Relative radiopacity was measured in terms of millimeters of equivalent aluminum.RESULTS:All compomers showed a radiopacity of 2.5 mm or more aluminum. Only Dyract AP and Elan were more wear resistant than amalgam. After stressing, the percentage of continuous margin was at best 31% overall and 17% in dentin only. Among resin-based composites, the minimum requirements of radiopacity were fulfilled only by Alert, Surefil, and Tetric. Only Definite, Surefil, Solitaire, and Tetric exhibited wear resistance greater than amalgam. After stressing, the best marginal qualities were 41% continuous margin overall, and 8% in dentin only.
Many contemporary restorative procedures are primarily esthetically driven, and patients have high expectations. It is imperative for the restorative dentist to understand patients' desires and expectations prior to initiating irreversible therapy. It is equally important for patients to understand the anatomic and technical limitations inherent with restorative therapy.
Provisional restorations fulfill many functions in restorative dentistry. Quality provisional restorations can provide the clinician, the patient, and the laboratory technician much valuable information prior to fabrication of the definitive restoration. Such diagnostic provisional restorations fabricated with acrylic resin are easily adjusted and modified until both esthetic and functional results are approved by the patient. Once this approval has been obtained, the definitive restorations can be fabricated with confidence, using the esthetic form of the provisional restorations as a blueprint.
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.
UNLABELLED:The development and continued evolution of photopolymerizable dental materials, particularly dental composite restoratives, represent a significant, practical advance for dentistry. The highly successful integration of the light-activated curing process for dental applications is described in this review. The basic mechanisms by which the photoinitiators efficiently convert monomers into polymers are discussed along with the variety of factors that influence the photopolymerization process. The conventional camphorquinone-amine visible light photoinitiator system used in most dental restorative materials is illustrated in addition to some alternative initiator systems that have been studied for dental materials applications.CLINICAL SIGNIFICANCE:Photopolymerization has become an integral component of the practice of dentistry. A better appreciation of the photopolymerization process as well as its potential and limitations may aid the dentist in the delivery of both esthetic and restorative dental care.
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.
Enamel microabrasion is a proven method of removing superficial intrinsic enamel discoloration defects. The method is safe, easily performed, and causes no discomfort for the patient. A new commercially available microabrasion system has been introduced by Ultradent Products Inc. In addition, a new tooth isolation material is available, along with a visible light-activated in-office hydrogen peroxide solution. This article describes these new products and documents tooth-color correction for two young patients using this new tooth-color correction approach.
The choice of implant diameter depends on the type of edentulousness, the volume of the residual bone, the amount of space available for the prosthetic reconstruction, the emergence profile, and the type of occlusion. Small-diameter implants are indicated in specific clinical situations, for example, where there is reduced interradicular bone or a thin alveolar crest, and for the replacement of teeth with small cervical diameter. Before using a small-diameter implant, the biomechanical risk factors must be carefully analyzed. Preliminary reports of this type of implant show good short- and medium-term results.
The desire to place esthetically pleasing, conservative, functionally stable, posterior restorative materials has steadily increased over the past 20 years. The creation of successful dentin bonding adhesives and appropriate resin luting cements has paved the way for the development of a myriad of indirect resin-based restorative materials. These materials have been specifically designed to overcome the negative attributes of their porcelain counterparts, and to simplify fabrication, insertion, and post-delivery adjustments. Possibly like no other product before, these restorative materials have met with instant clinical acceptance by many practitioners, and concern exists that these materials have not been sufficiently studied to warrant such widespread acceptance. This article presents an overview of the history and development of resin-based, esthetic, indirect systems, and offers the clinician a review of the literature supporting their role in posterior restorative dentistry. Additionally, a scientifically based protocol for preparation, impressing, provisionalization, and subsequent cementation and adjustment of indirect laboratory-processed resin inlays and onlays is presented.
PURPOSE:This study determined the color stability of a compomer, hybrid ionomer, and composite after staining with three fluoride varnishes.MATERIALS AND METHODS:Five disks (10 mm in diameter, 2 mm thick) of each material were prepared in a mold and incubated at 100% relative humidity at 37 degrees C for 24 hours. Duraphat, Duraflor, FluorProtector, and water (control) were applied to the disks, which were subsequently brushed with a soft toothbrush and dentifrice. Color was measured at baseline, after staining, and after brushing using CIE L*a*b* (source C) against white background on a reflection spectrophotometer, and color change (delta E*) was calculated. Means (n = 5) and standard deviations were calculated and compared using a repeated-measures analysis of variance (ANOVA). Tukey-Kramer intervals (p = .05) were calculated to compare means.RESULTS:Varnishes Duraflor and Duraphat caused perceptible color changes (delta E* > 3.3) in compomer, hybrid ionomer, and composite after application; however, FluorProtector did not affect the color of the materials. After brushing, none of the materials exhibited perceptible values of delta E*, except the composite with Duraflor (delta E* = 5.4).
PURPOSE:The purpose of this study was to evaluate the effect of various media on the color stability of compomer and to compare these results to those of other materials that could be used in similar clinical circumstances.MATERIALS AND METHODS:In this test, six materials (shade A2) were used: four compomers (Dyract, Compoglass F, Xeno, F2000), one composite resin (Clearfil AP-X), and one resin-modified glass ionomer cement (Fuji II LC). There were four test solutions: one alcoholic (whiskey), two low pH soft drinks (Coca Cola, orange juice), and deionized water as a control. A plastic ring mold (9-mm diameter x 1-mm height) was used to prepare 120 disk specimens. For 60 days, the test specimens were immersed in the various media daily for 3 hours then transferred to the deionized water. Color was measured by CIE L* a* b* relative to CIE source against a white background, using a colorimeter. Color change (delta E*) was calculated as delta E* = [(delta L*)2 + (delta a*)2 + (delta b*)2]1/2. Color changes (delta E*) were recorded after 1, 7, 30, and 60 days.RESULTS:The results indicated that compomer and resin-modified glass ionomer were susceptible to discoloration in various solutions over an extended period of time. Composite resin showed minimal perceptible color change. Specimens immersed in whiskey showed a significantly high perceptible color change (p < .0001). Water caused no perceptible color changes.
PURPOSE:This study determined the effect of distance on the power density from standard and Turbo light guides (Demetron/Kerr, Danbury, Connecticut).MATERIALS AND METHODS:Power density was measured from 0 to 10 mm away from the tip of standard 8-mm curved light guides and 13/8-mm Turbo curved light guides. To determine the effect of distance on power density, a polynomial regression line was fitted. The Kolmogorov-Smirnov (K-S) statistic and the Wilcoxon rank sum (WR) tests were used to determine if there was a difference in the rate at which the power density decreased for the standard and Turbo light guides as the distance from the tip increased. Photographs of the light dispersion from each tip were also taken.RESULTS:At 0 mm, the mean (+/- SD) power density from the two standard light guides was 743 +/- 6.1 mW/cm2 and from the four Turbo light guides was 1128 +/- 22.1 mW/cm2. As the distance from the tip of the light-guide tip increased, the power density decreased, but the rate of decrease was greater from the Turbo light guides than from the standard light guides. At 6 mm the power density from the standard light guides fell to 372 mW/cm2 (50% of the original value) and the power density from the Turbo light guides fell to 263 mW/cm2 (23% of the original value). Both the K-S statistic and the WR sum test indicated that the distribution of light intensities was significantly different from the two light guides (WR p-value = .0246, K-S p-value < .0001). The two estimated polynomials intersected at 3.66 mm, and the 95% prediction intervals intersected at about 2.8 and 4.8 mm. Therefore, beyond 5 mm away from the tip of the light guide, the standard light guides gave higher power density readings than the Turbo light guides. Photographs showed that the light dispersed at a wider angle from the Turbo light guides than from the standard light guide.CLINICAL SIGNIFICANCE:The design of the light guide of a light curing unit affects light dispersion, power density, and ultimately the dentist's ability to properly cure composite. For these reasons, manufacturers should report the power density at the tip of the light guide and 6 mm from the tip of the light guide, since significant differences exist between light guide designs.
PURPOSE:This article reviews material properties and application techniques important in minimizing effects of polymerization shrinkage during the curing reaction of resin composite restorative materials used in adhesive dentistry.MATERIALS AND METHODS:Relevant scientific publications were critically reviewed.RESULTS:Since it was recognized that shrinkage, which takes place during the curing reaction of resin composite restorative materials, may cause severe problems in adhesive dentistry, considerable effort has been put into reducing the negative effects. The most important problem is the debonding of the restoration-tooth interface, resulting in increased microleakage and, ultimately, in secondary caries. Despite all efforts, there is still no material or general application method that guarantees a leak-proof and durable restoration.CLINICAL SIGNIFICANCE:It is of the utmost importance that dental practitioners know how to deal with the problems related to resin composite shrinkage, so that they can choose the material and procedure most likely to produce a leak-proof and durable restoration, maximizing the potential for clinical success.
