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PubMed1989

Repair of glass ionomer restorative materials: flexure strength of specimens repaired by two methods.

This study evaluated the adhesion of newly mixed glass ionomer restorative materials to set materials. The flexure strength of specimens formed by the addition of new material to week-old material by using two different surface treatments was compared with the flexure strength of solid specimens that were 1 week old. All repaired specimens attained at least 44% of the average strength of unrepaired specimens of the same material. Repairs made with a combination of unlike materials were not significantly different from most repairs with like materials. For all materials collectively, repairs made with a 37% phosphoric acid pretreatment were significantly stronger than repairs made with a 40% polyacrylic acid pretreatment.

Acid Etching, Dental↗
PubMed2000

Analysis of composite type and different sources of polymerization light on in vitro toothbrush/dentifrice abrasion resistance.

OBJECTIVES: This study examined toothbrush/dentifrice abrasion of a photo-activated prosthetic composite (dentin and enamel variations) for the purpose of evaluating the influence of polymerization sources on abrasive wear. METHODS: A photo-activated prosthetic composite material (Artglass) was assessed. Dentin and enamel variations were polymerized using a proprietary photo-curing unit with two xenon stroboscopic lamps (UniXS), and other enamel specimens were polymerized either with a laboratory photo-curing unit with three fluorescent tubes or with a high intensity unit with two metal halide lamps. All specimens were stored in water for 14days and subjected to toothbrush/dentifrice abrasion (350g vertical load) using an abrasive slurry (Colgate Fluoriguard) and a toothbrush (Oral-B 40). The amount of vertical loss and the surface roughness of the specimens after 20,000 strokes were determined by profilometer. Average values of groups of five specimens were compared using analysis of variance (ANOVA) and Sheffe's S intervals (p<0.05). RESULTS: When polymerizing with the proprietary unit, the abrasion and surface roughness of the enamel material required respective means of 34.08microm (+/-3.66) and 1.00microm (+/-0.08), and the those of the dentin material required means of 42.02microm (+/-5.62) and 1.23microm (+/-0.20). Both abrasion and surface roughness after toothbrushing of the enamel material were significantly smaller than were those of the dentin material. The abrasion of specimens polymerized with the metal halide unit required a mean of 23.89microm (+/-6.17) and demonstrated minimal wear. CONCLUSIONS: The use of a high intensity metal halide photo-curing unit effectively enhanced the abrasion resistance of the composite. Surfaces of restorations should be covered with the enamel material in order to achieve smoothness and wear resistance.

Analysis of Variance↗
PubMed2001

A comparison of the wear resistance and hardness of indirect composite resins.

STATEMENT OF PROBLEM: Various new, second-generation indirect composites have been developed with claimed advantages over existing tooth-colored restorative materials. To date, little independent research has been published on these materials, and the properties specified in the advertising materials are largely derived from in-house or contracted testing. PURPOSE: Four second-generation indirect composites (Artglass, belleGlass, Sculpture, and Targis) were tested for wear resistance and hardness against 2 control materials with well-documented clinical application. Human enamel was also tested for comparison. MATERIAL AND METHODS: Twelve specimens of each material were fabricated according to the manufacturers' directions and subjected to accelerated wear in a 3-body abrasion, toothbrushing apparatus. Vickers hardness was measured for each of the tested materials, and energy dispersive x-ray (EDX) spectroscopy was performed to determine the elemental composition of the composite fillers. The statistical tests used for wear and hardness were the Kruskal-Wallis 1-way ANOVA test with Mann-Whitney tests and 1-way ANOVA with multiple comparisons (Tukey HSD). The Pearson correlation coefficient was used to determine the existence of a relationship between the hardness of the materials and the degree to which they had worn. The level of statistical significance chosen was alpha=.05. RESULTS: The control material Concept was superior to the other composites in wear resistance and hardness and had the lowest surface roughness. Significant relationships were observed between depth of wear and hardness and between depth of wear and average surface roughness. Enamel specimens were harder and more wear resistant than any of the composites. EDX spectroscopy revealed that the elemental composition of the fillers of the 4 new composites was almost identical, as was the composition of the 2 control composites. CONCLUSION: The differences in wear, hardness, and average surface roughness may have been due to differences in the chemistry or method of polymerization of the composites. Further research in this area should be encouraged. It was also apparent that the filler present in the tested composites did not exactly fit the manufacturers' descriptions.

Acrylic Resins↗
PubMed1991

In vitro antibacterial effect of chlorhexidine added to glass-ionomer cements.

The aims of the present study were to investigate the antibacterial properties of glass-ionomer cements containing different concentrations of chlorhexidine and the possible release of chlorhexidine from the compound. Chlorhexidine gluconate or diacetate was mixed with glass-ionomer cements and tested in vitro against strains of Lactobacillus casei and mutans streptococci. A spectrophotometric test was used to monitor the release of chlorhexidine from the mixture. In a broth culture test, the higher the concentrations of chlorhexidine in the mixture, the longer the time of antibacterial effect on Streptococcus mutans and the greater the tendency of the material to deteriorate. Agar diffusion tests revealed bacterial inhibition in a dose-response manner. The tested bacterial strains were similarly inhibited and the antibacterial properties decreased with time. A minor portion of added chlorhexidine was released from the cement. The deterioration of the cements indicates that the material could be useful as a varnish-like chlorhexidine carrier.

Acrylic Resins↗
PubMed1999

A bad fit?

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Composite Resins↗
PubMed2000

Bonding the gap between petralit and ceromers: with case reviews.

The search for a metal-free, aesthetic restoration with optimal strength, longevity, and comfort easily dates back to the 19th century. However, the popularity of adhesively retained restorations has reached an all-time high due to improvements in wear, post-op sensitivity, bond material and strength, and aesthetic quality. Targis/Vectris, a ceromer restorative material introduced in 1997 by Ivoclar-Williams, is a ceramic optimized polymer that produces a strong fiber-reinforced tooth-colored restoration. It allows the clinician to fabricate metal-free restorations without the fracture potential seen with ceramic materials. Long-term longitudinal studies of this restorative material will be the litmus test, but we now have 10-year studies that show very promising results.

Adhesives↗
PubMed2000

Creating esthetic composite restorations.

The purpose of this article is to describe a fabrication technique to assist dental technicians creating esthetic indirect composite restorations. After the teeth have been prepared and the models completed, the technician can begin the fabrication process. Translucent dentin is selected to reduce opacity and enhance the blend with the remaining dentition. High chroma modifiers can then be placed into the fossa area to replicate dentin seen in natural dentition. Different incisal materials can then be layered into the build-up to regulate the value of the restoration. Special effects such as hypocalcification are placed internally to mimic naturally occurring esthetics. Realistic anatomy is created using a small-tipped instrument directly into the final layer of uncured enamel material. Fissure characterization is placed in the restoration to match existing dentition. Fit and margins are verified on separate dies to minimize discrepancies. Path of insertion and proximal contacts are established on a solid model to minimize chairside adjustments.

Color↗
PubMed2002

Resin/Resin bonding: a new adhesive technology.

PURPOSE: Evaluation of a new surface treatment method to obtain a good bond strength between a luting composite and (1) a light-cured, (2) a heat-cured and (3) a thermoplastic resin. MATERIALS AND METHODS: Specimens were prepared and tests conducted according to ISO 10477, Amend. 1. The surfaces of Targis (light cured), SR Isosit (heat cured), and Dental D (thermoplastic) were ground under water cooling with 400-grit grinding paper, polished with 800-grit paper and air dried. Each resin material was divided into 3 groups of 10 specimens each. Group 1 was flame treated with a PyrosilPen for 5 s/2 cm2, group 2 for 10 s/2 cm2, and group 3 for 20 s/2 cm2. Subsequently, a methacryl silane was applied, followed by a luting composite. Prior to measuring shear bond strength, the specimens were thermocycled 5000 times in a water bath between 5 degrees C and 55 degrees C. SEM, FTIR investigations, and fracture analysis were also done. Etched and silanized Empress II - the gold standard - was used as a control. RESULTS: The following shear bond strengths were found: treatment time 5 s/2 cm2, Targis 25 (+/- 12) MPa, SR Isosit 17 (+/- 11) MPa; treatment time 10 s/2 cm2, Targis 23 (+/- 12) MPa, SR Isosit 26 (+/- 8) MPa; treatment time 20 s/2 cm2, Targis 29 (+/- 5) MPa, SR Isosit 26 (+/- 9) MPa. All Dental D specimens failed completely so that shear bond strength could not be measured. The control achieved 27 (+/- 6) MPa. No significant differences were found between the materials or the flaming times. On all flamed surfaces, Si was detected by FTIR. SEM showed that no heat destruction occurred at a flaming time of 5 s/2 cm2, a slight change at 10 s/2 cm2, and a significant change at 20 s/2 cm2. CONCLUSION: This new bonding technology is an effective method for surface-treating polymerized composite resin materials to obtain good bonding to luting composites. The method fails on thermoplastic resins.

Acrylic Resins↗
PubMed1997

Ceramic optimized polymer: the next generation of esthetic restorations--Part 1.

An abundance of new materials and techniques that challenge the clinician to recommend and provide the appropriate restoration for each clinical situation have been developed in the last decade. A new generation of materials, described by manufacturers as ceramic optimized polymers, have been recommended for a wide variety of restorations including inlays/onlays, crowns and bridges, and direct restorations. In this article, the appropriate preparation and luting technique for inlays/onlays are delineated. The use of ceromer inlays/onlays for teeth exhibiting symptoms of the partially fractured tooth is demonstrated.

Ceramics↗
PubMed2005

Strength and fracture pattern of monolithic CAD/CAM-generated posterior crowns.

OBJECTIVES: This study evaluated the strength and fracture pattern of monolithic posterior CAD/CAM crowns hypothesizing that zinc-phosphate cemented lithium disilicate crowns might show the same fracture strength as adhesively cemented crowns. METHODS: Two sets of monolithic posterior crowns each with uniform occlusal and lateral wall thickness of 1.5mm were fabricated from three types of block ceramic (1) lithium disilicate glass, (2) leucite glass and (3) feldspathic ceramic using CEREC 3 CAD/CAM. Crowns (n = 15) of ceramics (1), (2) and (3) each were (A) zinc-phosphate cemented, (B) adhesively cemented on resin-based composite dies and loaded until fracture. Load data was analyzed using ANOVA and Scheffé tests. Crack pattern was evaluated on an additional three sample cross-sections for each group at start of fracture. RESULTS: Radial cracks originated early at the cementation interfaces and cone cracks were observed finally at the loading sites. Mean load values (SD) of A-crowns at fracture start/end (1) 807 (91) N/2082 (192) N; (2) 915 (193) N/1130 (166) N; (3) 985 (199) N/1270 (301) N were all significantly (P < 0.001) lower when compared to their B-crown analogs (1) 1456 (205) N/2389 (84) N; (2) 1684 (395) N/2469 (171) N; (3) 1548 (304) N/2392 (75) N, rejecting the authors hypothesis. A-1 crowns had significantly (P < 0.001) higher fracture load than A-2 and A-3 crowns. The A-1 crown fracture load data, even if significantly (P < 0.001) lower, came close to the B-1 values. SIGNIFICANCE: Adhesive cementation balanced the strength of weak ceramics with that of strong ceramic and recommended itself for leucite glass ceramic and feldspathic ceramic crowns. Zinc-phosphate cementation appeared feasible for lithium disilicate crowns.

Aluminum Silicates↗