Biomedical subjects

Jason A Griggs

Publications and source records attributed to Jason A Griggs.

9 recordsLinked to original sources

PubMed2006

Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth.

STATEMENT OF PROBLEM: A restored endodontically treated tooth is less likely to fracture when there is axial tooth structure between the core base and preparation finish line. However, an accurate prognosis requires knowing whether fracture resistance depends on a complete circumferential distribution of tooth structure or tooth structure in a specific location related to the applied force. PURPOSE: This in vitro study investigated the fracture resistance of restored endodontically treated teeth when residual axial tooth structure was limited to one half the circumference of the crown preparation. MATERIAL AND METHODS: Fifty extracted maxillary anterior teeth were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. Four groups were prepared with full shoulder crown preparations having axial wall heights of 2 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, one half of the axial tooth structure was removed, palatally, labially, or proximally, and groups were identified according to the site of retained coronal tooth structure. For the fifth group, all axial tooth structure was removed to the level of the preparation shoulder. Thus, in 1 group the axial walls were circumferential, 360 degrees around the preparations (Complete group), in 3 groups the axial walls were continuous for 180 degrees (Palatal, Labial, and Proximal groups), and the last group had no retained coronal tooth structure incisal to the finish line (Level group). All 50 prepared teeth were then restored with quartz fiber posts (Bisco), composite resin (Bisco) cores, and metal crowns. A universal testing machine compressively loaded the tooth specimens from the palatal at a crosshead speed of 0.5 cm/min at an angle of 135 degrees to the long axis of teeth until failure occurred. A survival analysis was conducted using a log-rank test followed by Holm-Sidak pairwise tests (alpha=.05) to detect significant differences in median failure load between groups. The mode of failure was determined by visual inspection of all specimens. RESULTS: The median failure load (P<.001) was 607 N, 782 N, 358 N, 375 N, and 172 N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. The predominant mode of failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. CONCLUSION: For restored endodontically treated teeth that do not have complete circumferential tooth structure between the core and preparation finish line, the location of the remaining coronal tooth structure may affect their fracture resistance.

Dental Restoration Failure↗

PubMed2004

Influence of powder/liquid mixing ratio on porosity and translucency of dental porcelains.

STATEMENT OF PROBLEM: Dental technicians use a variety of techniques when condensing dental porcelains. It is unclear whether these techniques affect the total porosity and translucency of dental porcelains. PURPOSE: The objective of this study was to determine whether varying the powder/liquid ratio during condensation affects porosity and translucency of porcelains. Material and methods Duceram LFC dentin, Duceram LFC incisal, IPS Eris dentin, and IPS Eris incisal porcelains were studied. For each specimen, 1.0 g of porcelain powder was mixed with 1 of 3 different volumes of deionized water to form a slurry with a thin, medium, or thick consistency. The slurries were condensed in a plastic syringe mold, fired, and polished to a 3-microm finish to form 12 groups of 4 specimens each (14-mm diameter, 1.10-mm thickness). The apparent density (g/mL) of each specimen was measured using Archimedes method, and the porosity (%) calculated. Each specimen was coupled to standard ceramic tiles using an immersion liquid, and the color shade was measured in CIE Yxy coordinates using a tristimulus colorimeter. Translucency was assessed by calculating the contrast ratio of shade value (Y) in front of black versus white backgrounds. Two-way analysis of variance and Tukey's multiple comparison tests (alpha = .05) were used to test for significant effects of factors. RESULTS: Porcelain type and powder/liquid ratio had a significant interactive effect on the apparent density (P < .001) and on total porosity (P = .003); however, there was no consistent trend. The powder/liquid ratio did not significantly affect translucency (P = .28), but porcelain type had a significant effect on translucency (P < .001). CONCLUSION: In this in vitro study, total porosity of specimens prepared using 4 porcelains was found to be sensitive to powder/liquid ratio; whereas translucency was found to be insensitive to powder/liquid ratio.

Analysis of Variance↗

PubMed2004

Fracture resistance of three all-ceramic restorative systems for posterior applications.

STATEMENT OF PROBLEM: The failure loads of all-ceramic crowns are influenced not only by the fracture resistance of the component materials but also by prosthesis geometry and size and location of flaws, thus there is a need for a study that compares the fracture resistance of all-ceramic systems using a simple and reproducible specimen geometry that includes flaws occurring at material interfaces. PURPOSE: The research aim was to compare the in vitro fracture resistance and origin of failure of simulated first molar crowns fabricated using 3 all-ceramic systems, IPS Empress 2, Procera AllCeram, and In-Ceram Zirconia. MATERIAL AND METHODS: Twenty axisymmetric crowns of each system were fabricated to fit a preparation with 1.5- to 2.0-mm occlusal reduction. The center of the occlusal surface on each of 15 specimens per ceramic system was axially loaded to fracture in a universal testing machine, and the maximum load (N) was recorded. Fractured surfaces were examined using optical and electron microscopy to determine the most prevalent origin of failure in each ceramic system. Five crowns per system were sectioned, and thickness of the luting agent, core material, and veneer porcelain layers were measured. The 95% confidence intervals of the Weibull modulus and characteristic failure load were compared between the 3 systems. Two-way multivariate analysis of variance was used to analyze the thickness of the luting agent, ceramic core, and veneer porcelain layers (alpha=.05). RESULTS: The 95% confidence intervals for Weibull modulus were 1.8 to 2.3 (IPS Empress 2), 2.8 to 3.6 (Procera AllCeram), and 3.9 to 4.9 (In-Ceram Zirconia). The 95% confidence intervals for characteristic failure load were 771 to 1115 N (IPS Empress 2), 859 to 1086 N (Procera AllCeram), and 998 to 1183 (In-Ceram Zirconia). The origin of failure was most commonly found at the interface between the ceramic core and veneer porcelain for IPS Empress 2 and between the ceramic core and luting agent layer for the other systems. CONCLUSIONS: There was no significant difference in fracture resistance; however, there was a significant difference in failure origin between the all-ceramic systems studied.

Aluminum Oxide↗

PubMed2003

Effects of bur abrasive particle size and abutment composition on preparation of ceramic implant abutments.

STATEMENT OF PROBLEM: Amid increasing use of preparable ceramic implant abutments, there is a lack of quantitative data to show which abrasive particle size of diamond bur yields the fastest reduction and provides the smoothest surface. PURPOSE: The research aim was to determine the effects of diamond bur abrasive particle size and abutment material composition on preparation efficiency, prepared surface roughness, and surface deterioration of diamond burs. MATERIAL AND METHODS: Fifteen alumina (Cera Base) and 15 zirconia (ZiReal) implant abutments were each machined using a high-speed hand piece with a diamond bur having 1 of 3 abrasive particle sizes (150, 100, or 30 microm) (n=5). Control abutments (n=5) were analyzed without machining. Abutments were weighed before starting and between machining cycles. Three profilometry measurements (root mean square surface roughness) were made for each abutment. Scanning electron micrographs were made of each bur. Lost abrasive particles were then counted on each micrograph through a randomly placed template. Two-way analysis of variance (alpha=0.05) was used to test for significant effects. RESULTS: Bur abrasive particle size and ceramic type had a significant interactive effect on the amount of material removed (P<.001). Super coarse (150 microm) burs yielded the roughest surfaces for each abutment material (P<.001), and prepared alumina surfaces were rougher than zirconia surfaces (P<.001). Super coarse burs showed the highest proportion of lost particles (P<.001). Abutment composition did not significantly affect bur wear. CONCLUSION: Super coarse burs yielded the most efficient material removal for alumina abutments. All abrasive particle sizes removed a similar amount of material from zirconia abutments. Fine-grained alumina abutments experienced greater material removal and rougher prepared surfaces compared with zirconia abutments. Material was removed by an intergranular fracture mechanism for alumina abutments, in contrast to transgranular fracture for zirconia abutments.

Aluminum Oxide↗

PubMed2003

Effect of hydrolyzed surface layer on the cytotoxicity and chemical resistance of a low fusing porcelain.

OBJECTIVE: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC and to determine its effect on the cytotoxicity of the porcelain as measured by cellular activity and concentrations of leached ionic species. METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique. Half of the specimens underwent accelerated aging by subjecting them to the standard test for hydrolytic resistance (ISO 6872). Fibroblast cell cultures were placed in direct contact with specimens. Cell viability was assessed using succinic dehydrogenase activity. Chemical resistance was determined by leaching specimens with a continuous flow of deionized water and measuring the concentrations of soluble ions in the leachates. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to detect the composition of the surface layer. RESULTS: Hydrolyzation treatment created a smooth texture on the porcelain surfaces but did not result in a hydrolyzed surface layer with increased hydroxyl content. There was a decreased alkali ion content in the surface layer of hydrolyzed specimens. Mean cellular SDH activities for non-hydrolyzed and hydrolyzed porcelain were 75+/-7 and 80+/-5% of Teflon controls, respectively. Only sodium ions were present in significant concentrations in collected leachates. The sodium concentration decreased over the initial 4.5h of leaching. SIGNIFICANCE: The changes in surface layer texture and composition as the result of the aging treatment had little effect on the cytotoxicity and chemical resistance of Duceram LFC. The results suggest that Duceram LFC would pose no biocompatibility risk even after extended exposure to the oral environment. These data also provide baseline material properties to be used in future studies of the effects of porcelain additives.

3T3 Cells↗

PubMed2003

Mechanism of strength increase for a hydrothermal porcelain.

OBJECTIVES: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC, to determine the effects of such a layer on mechanical material properties, and to identify a specific mechanism responsible for any strength increase observed. METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique and were prepared to have either blunt or sharp surface flaws. Half of the specimens underwent accelerated aging. Specimens were fractured in three-point flexure to measure their strength, and fractographic analysis was used to determine fracture toughness and residual surface stress. Surface hardness and elastic modulus were measured using a microindentation method. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to determine the composition of the surface layer. RESULTS: The aging treatment modified the porcelain surface topography but did not create a layer with increased hydroxyl ion content. Porcelain strength increased upon aging, and the increase was proportional to initial flaw severity. The apparent fracture toughness of sharp flaw specimens increased to match that for specimens containing blunt flaws upon aging. Surface hardness and elastic modulus decreased upon aging. SIGNIFICANCE: Previous studies on the strength increase of hydrothermal porcelain were contradictory because a variety of specimen preparation procedures were used. This study resolves the apparent contradiction by determining the effect of specimen preparation on material strength.

Analysis of Variance↗

PubMedDate not supplied

Immediate bonding to bleached enamel.

This research sought to determine the shear bond strength, degree of resin infiltration and failure mode when organic solvent-based adhesives (acetone or ethanol) were used in immediate bonding to enamel bleached with 10% carbamide peroxide or 38% hydrogen peroxide systems. Seventy-two non-carious bovine incisors were randomly assigned to three groups of 24 specimens each-control group (deionized water), 38% hydrogen peroxide bleach group and 10% carbamide peroxide bleach group. Each group was further subdivided into two subgroups of 12 specimens each according to the adhesive system used to bond the resin composite to enamel surfaces. The two adhesive systems used were Single Bond, an ethanol-based adhesive, and One Step, an acetone-based adhesive. The shear bond strengths of 38% hydrogen peroxide and 10% carbamide peroxide were significantly lower compared to the non-bleached controls. Fractography revealed an adhesive failure mode in all specimens. Qualitative comparisons of resin tags present in the bleached and unbleached specimens using scanning electron microscopy (SEM) revealed few, thin and fragmented resin tags when 38% hydrogen peroxide and 10% carbamide peroxide were used.

Acetone↗

PubMedDate not supplied

Effect of no ferrule on failure of teeth restored with bonded posts and cores.

This study investigated how the absence of a ferrule affected the failure load of teeth that had been restored with bonded fiber posts and resin cores. There was a significant difference (p < 0.001) between the ferrule and nonferrule groups' load to failure. For the ferrule group, root fracture was the predominant mode of failure; in the nonferrule group, debonding failures were predominant.

Acid Etching, Dental↗

PubMedDate not supplied

Resin bonding to sclerotic, noncarious, cervical lesions.

Noncarious, cervical, wedge-shaped, sclerotic lesions are commonly encountered in clinical practice. In such lesions, dentin has been pathologically altered, often resulting in partial or complete obliteration of the dentinal tubules. These lesions are known to respond to etching and bonding differently from normal dentin, leading to complications during clinical treatment. A search of the literature was performed to obtain background information on the most commonly cited etiologic factors, clinical diagnoses, and morphologic and chemical characterizations along with an extensive review of all potential obstacles to bonding the most recent adhesives to such a dentinal substrate. Recent progress in adaptive strategies to render dentin more receptive to resin bonding is emphasized in this article, and the major drawbacks of these strategies are discussed.

Acid Etching, Dental↗