Assessment of ceramic restorations according to the Cerec method.
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Ceramics↗
Biomedical subjects
K H Kunzelmann
Publications and source records attributed to K H Kunzelmann.
Two-body and three-body wear of glass ionomer cements.
OBJECTIVES: Glass ionomer cements (GIC) have been modified in an attempt to improve their mechanical properties. The objective of the present paper was to compare the two-body and three-body wear of four modified GIC. The tested materials were Fuji IX (GC Corporation), Hi-Fi (Shofu) and Ketac Molar Aplicap (3M/ESPE). The cermet cement Ketac Silver Maxicap (3M/ESPE) was used as reference material. METHODS: Two-body wear tests were carried out in the computer controlled 'artificial mouth' of the Munich Dental School, three-body wear was tested with the ACTA wear machine. RESULTS: The resulting average two-body wear rates (in microm) were: Fuji IX 327 (SD +/- 82) < Ketac Molar 379 (SD +/- 94) < Hi-Fi 376 (SD +/- 90) < Ketac silver 449 (SD +/- 127). The differences between the materials were significant (P < 0.05, ANOVA, modified LSD-test) with the exception of Ketac Molar and Hi-Fi. The average three-body wear rates (in microm) were: Hi-Fi 30 (SD +/- 10) < Ketac Molar +/- 42 (SD +/- 12) < Fuji IX 49 (SD +/- 14) < Ketac silver 73 (SD +/- 23). The difference between Ketac silver and the three other materials was significant (P < 0.05, ANOVA, modified LSD-test). No significant difference was calculated between Hi-Fi, Ketac Molar and Fuji IX. CONCLUSIONS: As Ketac Molar, Hi-Fi and Fuji IX show better wear resistance compared to Ketac silver both in occlusal-contact and contact-free areas, it may be assumed that the wear resistance of a glass ionomer cement may be improved more by changing the powder: liquid ratio than by incorporating silver particles into the glass powder.
Analysis of Variance↗
Simulation of dental microwear: Characteristic traces by opal phytoliths give clues to ancient human dietary behavior.
In order to further evaluate the process of microwear formation on human dental enamel, microwear was experimentally produced by a chewing simulation with an Academic Center for Dentistry Amsterdam (ACTA) device. For this simulation, several cereal species were processed according to historical milling techniques, the experimental results of which were compared with those obtained from cereals processed after modern techniques, and also with natural microwear on early medieval human molars. Comparison of simulated microwear pits with natural microwear pits showed that the simulation led to traces which matched those found on the historical teeth in terms of both size and shape. Experimentally produced microwear pits were especially characteristic for the cereal species used in the simulations, and both pit morphology and enamel loss were a function of cereal phytolith content. Despite the high variability of phytolith size and shape, certain types are characteristic for certain cereals, which in turn are capable of producing cereal-specific microwear. This experimental approach is likely to further define ancient human dietary behavior, including food processing.
Anthropology, Physical↗
Biological clearance of TEGDMA in guinea pigs.
The excretion of the dental composite component triethylene glycol dimethacrylate (TEGDMA) in feces and urine in vivo and, using the pendular perfusion technique with segments of jejunum and colon, the biliary and enteric excretion in situ were investigated in anesthetized guinea pigs. In the in situ experiments guinea pigs (n = 4) received TEGDMA (0.02 mmol/kg body weight labelled with a tracer dose 14C-TEGDMA 0.7 kBq/g body weight) injected into the jugular vein. In the in vivo experiments guinea pigs (n = 4) received TEGDMA (+14C-TEGDMA; same dose as above) via a gastric tube. Urine and feces were collected for 24 h. In the in situ experiments organs were removed from the guinea pigs 60 min after the beginning of the experiment, and the 14C radioactivity measured. During the 60-min perfusion period the calculated amount of 14C radioactivity excreted into the total jejunum and colon was 0.9 +/- 0.2% and 1.9 +/- 0.1% of the dose administered, respectively (means +/- SEM). Of the 14C-TEGDMA dose, 3.7 +/- 0.2% was found in the bile. A significantly (P < 0.05) higher bile/blood concentration ratio was found 10 min after injection of TEGDMA as compared with the ratios at 20 to 60 min. The following 14C activities (percent of the dose) per total organ were found in guinea pigs (in situ experiment; means +/- SEM): 6.9 +/- 1.7 (muscle), 3.9 +/- 0.5 (kidney), 3.3 +/- 0.1 (skin), 1.4 +/- 0.1 (blood), and 1.2 +/- 0.1 (liver). The 14C activity in all other organs was < 0.4%. The total 14C recovery in all organs tested was 17.5 +/- 1.8%. Over 24 h the amounts of 14C activity excreted in the feces and urine were 0.5 +/- 0.1% and 14.7 +/- 1.8% of the dose administered, respectively (means +/- SEM). The following 14C activities (percent of the dose) per total organ or contents of organs were found (means +/- SEM): 1.4 +/- 0.3 (liver), 0.8 +/- 0.3 (muscle), 0.5 +/- 0.1 (skin), and 0.5 +/- 0.1 (contents of cecum). The 14C activity in all other organs was < 0.2%. The total 14C recovery in all organs tested was 3.9 +/- 0.9%. In a second series of in vivo experiments exhaled air from the animals was captured during the 24-h experimental period. Of the administered dose, 61.9 +/- 4.6% of the 14C (means +/- SEM; n = 4) was exhaled as 14C-carbon dioxide. The results indicate a rapid clearance of 14C-TEGDMA and/or 14C-TEGDMA metabolite(s) from the organism and exhalation is the major route of elimination.
Animals↗
Class V lesions restored with four different tooth-colored materials--3-year results.
The aim of this study was to compare the treatment results using four different types of tooth colored materials for restoring class V lesions. A total of 197 class V restorations (n = 197) were placed by one dentist in 37 patients on incisors, canines and premolars. The fillings were placed due to different indications: erosion/non-carious cervical defects (n = 69), primary carious lesions (n = 57), and for replacing defective existing fillings (n = 71). The teeth were assigned on a random basis to four groups for restoration with either a composite (group 1: n = 36; Tetric, Vivadent), or a polyacid-modified resin composite (group 2: n = 79; Dyract, Dentsply), or one of two different resin-modified glass ionomer cements (group 3: n = 51, Fuji II LC,GC; group 4: n = 31, Photac-Fil, Espe). The restorations were evaluated by a single-blind design, according to a modified USPHS system 36 months following placement. Statistical analysis was completed with the Pearson Chi-square test for comparing the results of the four groups (P < 0.05). Additionally, the survival rates were analyzed with the Kaplan-Meier estimator and the Log-rank test (P < 0.05). The Alpha ratings were as follows (Tetric/Dyract/Fuji II LC/Photac Fil): shade match (86%/77%/58%/40%), surface texture (81%/83%/16%/9%), marginal integrity (enamel) (73%/67%/61%/61%), marginal integrity (dentin) (86%/70%/55%/61%), marginal discoloration (enamel) (59%/44%/58%/52%), marginal discoloration (dentin) (82%/84%/71%/48%), anatomic contours (91%/83%/39%/35%). One Tetric restoration, five Dyract restorations, two Fuji II LC restorations and three Photac restorations were dislodged within the study period. The retention of the restorations showed no significant difference among the four materials. However, the clinical performance of the restorations retained over the 3-year period showed distinct differences for the four materials. The best clinical performance was observed for the resin composite, whereas the quality of the Dyract restorations without enamel etching was worse. The poorest results were obtained for the restorations with the resin-modified glass ionomers.
Adult↗
Cytotoxicity of dental composite components and mercury compounds in lung cells.
OBJECTIVE: The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA), as well as mercuric chloride (HgCl2) and methylmercury chloride (MeHgCl) was investigated on the release of lactatedehydrogenase (LDH) from alveolar epithelial lung cell lines in vitro. METHODS: The confluent cell layers from the A549 (human, malignant) and the L2 cells (rat) were incubated with various concentrations of HEMA, TEGDMA, MeHgCl and HgCl2 at 37 degrees C in 2% (v/v) CO2 atmosphere for 8h. In further experiments the L2 cells were incubated with the same compounds for 6-48 h. LDH release was measured and the values were expressed as percentage of the LDH content. The values were plotted on a concentration log-scale and the substance concentration at the maximum slope was assessed as effective concentration (EC50). RESULTS: A significant (p<0.05) increase in the LDH release was found in the L2 cells after 8-h incubation with HEMA (4 mmol/l), TEGDMA (2 mmol/l), MeHgCl (0.01 mmol/l) and HgCl2 (0.015 mmol/l), and in A549 cells with HEMA (14 mmol/l), TEGDMA (15 mmol/l), MeHgCl (0.15 mmol/l) and HgCl2 (0.05 mmol/l), compared to controls. The EC50 values from compounds in the L2 cells are shown in the following table (mean; sem in parentheses; n=3-6; #n=1): [see text]. SIGNIFICANCE: The toxic effect of HgCl2 and MeHgCl from the L2 cells was about 100-700-fold higher than of the dental composite components. A significant (p<0.05) time dependent increase of toxicity was observed with TEGDMA, HEMA and MeHgCl.
Animals↗
Polymerization contraction stress in light-cured packable composite resins.
OBJECTIVE: Determination of the polymerization contraction stress of packable composites (ALERT, Surefil, Solitaire, Solitaire 2) and a packable ORMOCER material (Definite) in comparison with a conventional hybrid composite (Tetric Ceram). METHODS: Contraction force generated by the test materials (10 replications each) was measured by polymerizing the composites filled in a plastic tray between two aluminum attachments mounted in a Stress-Strain-Analyzer testing machine (specimen size: 4x4x2 mm, C-factor=0.33). Contraction force was recorded for 300s under a standard exposure condition (40s, 800mW/cm(2)). Maximum contraction stress (MPa), force rate (N/s), relative force rate (%/s) of each material were statistically analyzed by ANOVA (alpha=0.05) and post-hoc Tukey's test. RESULTS: Maximum contraction stresses of the packable materials were 4.60 +/- 0.32MPa (ALERT), 4.16 +/- 0.18MPa (Definite), 3.36 +/- 0.08MPa (Solitaire 2), 3.33 +/- 0.23MPa (Solitaire) and 3.13 +/- 0.18MPa (Surefil), which were significantly higher than that of Tetric Ceram (2.51 +/- 0.14MPa). Tetric Ceram exhibited the significantly lowest force rate. Force/time curves were S-shaped. Solitaire especially showed a longer pre-gelation phase before contraction force was recorded. SIGNIFICANCE: High contraction stress and rapid contraction force development can lead to failure of bond to tooth structure. This study suggested that, packable composite resins are less capable of reducing the contraction stress during the early setting stage, thus not superior in maintaining the bond with cavity walls to conventional hybrid composite Tetric Ceram.
Analysis of Variance↗
Distribution and excretion of TEGDMA in guinea pigs and mice.
The monomer triethyleneglycoldimethacrylate (TEGDMA) is used as a diluent in many resin-based dental materials. It was previously shown in vitro that TEGDMA was released into the adjacent biophase from such materials during the first days after placement. In this study, the uptake, distribution, and excretion of 14C-TEGDMA applied via gastric, intradermal, and intravenous administration at dose levels well above those encountered in dental care were examined in vivo in guinea pigs and mice as a test of the hypothesis that TEGDMA reaches cytotoxic levels in mammalian tissues. 14C-TEGDMA was taken up rapidly from the stomach and small intestine after gastric administration in both species and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as 14CO2. The peak equivalent TEGDMA levels in all mouse and guinea pig tissues examined were at least 1000-fold less than known toxic levels. The study therefore did not support the hypothesis.
Animals↗
Clinical performance of a resin-modified glass-ionomer and a compomer in restoring non-carious cervical lesions. 5-year results.
PURPOSE: To evaluate the 5-yr clinical performance of a resin-modified glass-ionomer cement and a polyacid-modified resin composite in restoring non-carious cervical lesions. MATERIALS AND METHODS: Non-carious cervical lesions in 46 incisors, canines, and premolars were restored either with Fuji II LC (n=18) or with Dyract (n=28) in 16 healthy patients. The lesions were restored without cavity preparation strictly according to the manufacturer's instructions. The restorations were clinically evaluated single blind after 5 yrs using modified USPHS criteria. RESULTS: The percentage of Alfa ratings were as follows (Dyract/Fuji II LC): color match 81.3%/28.6%, surface texture 93.8%/21.4%, anatomic form 75.0%/28.6%, marginal integrity (enamel) 62.5%/42.9%, marginal integrity (dentin) 68.8%/28.6%, marginal discoloration (enamel) 56.3%/42.9%, marginal discoloration (dentin) 68.8%/21.5%. Five-yr data revealed a significant difference between the clinical ratings of Dyract and Fuji II LC for all criteria except marginal integrity and marginal discoloration in enamel. A total of five Dyract restorations and four Fuji II LC restorations failed within the study period. CLINICAL SIGNIFICANCE: A considerably high and almost similar overall failure rate was found for both restorative materials in restoring non-carious cervical lesions. However, retained Dyract restorations presented superior clinical performance compared to Fuji II LC restorations.
Acrylic Resins↗
Wear evaluation of MZ100 compared to ceramic CAD/CAM materials.
The material and antagonist wear of two CAD/CAM ceramic materials, the laboratory-processed IPS Empress ceramic, and the composite mill block material MZ100 were tested in an artificial wear simulator with human enamel as the antagonistic material. The material samples underwent 50,000 test cycles (1 cycle per second, 50 N) in distilled water. The wear of the material samples and of the opposing enamel was documented after 30,000 and 50,000 cycles with replicas, digitized, and evaluated with a 3D evaluation system. The loss of volume and height caused by wear was calculated. No significant difference between the ceramic materials could be found either in the amount of material or in the amount of antagonist wear. The material wear of MZ100 differed significantly from Vita Mark II only in terms of volume loss. Regarding height loss, MZ100 exhibited a significantly higher wear than all ceramic materials. The wear of the enamel antagonists does not differ significantly between the ceramic materials. With MZ100, however, a significantly smaller amount of enamel wear was found when compared with Empress and Vita Mark II. Despite the highest material wear, MZ100 had the lowest material wear rate, the lowest enamel wear rate, and the lowest total wear rate. The laboratory-processed IPS Empress material had a clearly higher material wear rate than the CAD/CAM materials.
Aluminum Silicates↗
Mechanical properties of new composite restorative materials.
OBJECTIVE: Determination of flexural strength, flexural modulus, fracture toughness, Vickers hardness, and wear resistance of condensable composites (Solitaire, Surefil, Alert) and an ormocer (Definite) in comparison with a hybrid composite (Tetric Ceram) and an ion-releasing composite (Ariston pHc). METHODS: Flexural strength, flexural modulus, and fracture toughness were determined in 3-point bending. Single-edge notched-bend specimens were used to evaluate fracture toughness. Microhardness was measured with a Vickers indenter. Wear was determined in a pin-on-block-design with a Degusit antagonist at 50 N load and quantified by a replica technique after 6000, 10000, 30000, and 50000 load cycles using a 3D-laser scanner. All results were statistically analyzed with ANOVA and post hoc Tukey HSD tests. RESULTS: Alert exhibited the highest flexural modulus, K(IC), and hardness, but lowest wear resistance. Solitaire presented the highest wear resistance, but significantly lower flexural strength, flexural modulus, K(IC), and hardness than all other materials. No significant correlation could be detected between hardness and wear of the tested composites with Pearson's correlation coefficient. SIGNIFICANCE: The condensable composites differed significantly in their mechanical properties. This study suggested that, besides the filler content level and filler size, other factors like matrix-filler interactions highly influence the fracture and wear behavior of the materials.
Composite Resins↗
Influence of a high-speed polymerization method on the marginal integrity of composite fillings in Class-II cavities.
The aim of this study was to evaluate the effect of a rapid photopolymerization method on the marginal integrity of composite fillings. Ninety two-surface cavities were prepared in extracted human molars using the SonicSys preparation system. All cavities were bonded with one bonding agent (Syntac) and filled with a microfilled composite (Herculite XRV), a heavy filled composite (Z100 MP), and an Ormocer (Definite) in two increments. Each increment had a thickness of approximately 1.5 mm and was polymerized using either halogen light or the plasma light of Apollo 95 E. In this process, six trial groups each containing 15 fillings were created. After replicas were made, the test teeth were subjected to a thermocycling process of 2000 temperature cycles (5 degrees C/55 degrees C) followed by a wear simulation of 50,000 stress cycles each with 50 N. This was followed by the creation of a second set of replicas, quantitative margin analysis, and dye penetration. A significant (P < 0.05) influence of the thermomechanical stress and a significant (P < 0.05) influence of the factor "material" were shown for the margin criterion "continuous margin" using MANOVA. The factor "light source" produced no significant influence (P = 0.57) on the amount of continuous margin. During the dye penetration, no significant differences between the polymerization methods could be established with the materials Herculite XRV and Z100 MP (H-test according to Kruskall and Wallis). Only with the material Definite was a significantly higher dye penetration observed at the occlusal measuring point in the plasma light group. A rapid polymerization with high light intensity had no adverse effects on the margin quality within the limitations of this in vitro study. However the marginal integrity might have been influenced by the chosen adhesive system/composite resin combination, which does not represent the respective product line. Additionally, further studies ought to show which exposure time is necessary for a sufficient degree of conversion.
Acrylates↗
Mechanical properties and wear behavior of light-cured packable composite resins.
OBJECTIVES: Determination of flexural strength, flexural modulus, fracture toughness and wear resistance of three packable composites (Solitaire, Surefil, ALERT) and a packable ormocer (Definite) in comparison with an advanced hybrid composite (Tetric Ceram) and an ion-releasing composite (Ariston pHc). METHODS: Flexural strength, flexural modulus and fracture toughness of each material were determined in three-point bending (each test n = 10). Single-edge notched-bend specimens were used to evaluate the fracture toughness (K1C). Wear of the materials (n = 8) was determined in a pin-on-block-design with a spherical Degusit antagonist at 50 N vertical load and quantified by a replica technique using a 3D-laser scanner. Replicas were made after 6000, 10,000, 30,000 and 50,000 load cycles. The mean wear rate (MWR (micron 3 cycle-1)) was obtained by a linear regression analysis in the steady-state of the time-wear-curve. All results were statistically analyzed with ANOVA and post hoc Tukey HSD tests (p < 0.05). RESULTS: ALERT exhibited the highest flexural modulus (12.5 +/- 2.1 GPa) and K1C (2.3 +/- 0.2 MN m-3/2), but the lowest wear resistance (8275 micron 3 cycle-1). Solitaire presented the highest wear resistance (1591 micron 3 cycle-1), but significantly lower flexural strength (81.6 +/- 10.0 MPa), flexural modulus (4.4 +/- 0.3 GPa), and K1C (1.4 +/- 0.2 MN m-3/2) than all other materials. Surefil revealed a significantly higher flexural modulus (9.3 +/- 0.9 GPa) and wear resistance (3028 micron 3 cycle-1) than Tetric Ceram (6.8 +/- 0.5 GPa; 5417 micron 3 cycle-1) and Ariston pHc (7.3 +/- 0.8 GPa; 7194 micron 3 cycle-1). SIGNIFICANCE: The tested packable composite resins differed significantly in their mechanical properties. This study suggested that fracture and wear behavior of the composite resins are highly influenced by the filler system. Overall, Surefil demonstrated good fracture mechanics parameters and a low wear rate.
Analysis of Variance↗
Determination of changes on tooth-colored cervical restorations in vivo using a three-dimensional laser scanning device.
The present study aimed at the determination of changes of tooth-colored cervical restorations in vivo using an optical 3-dimensional laser scanning device. The study was performed on 197 cervical restorations placed on incisors, canines, and premolars. Four different tooth-colored restoration materials, a composite, a polyacid-modified resin composite, and two resin-modified glass ionomer cements, were used for the restoration of the lesions. For the determination of changes, images were taken at baseline and 15, 24 and 36 months after the placement of the fillings using a 3D-laser scanning device. The images were superimposed automatically, and digital subtraction was made by a specially developed image analysis software. The total substance loss on the entire filling surface at 36 months for the resin-modified glass ionomer Photac-Fil was 44 (+/-23) microm, for Fuji II LC 45 (+/-26) microm, for Dyract 71 (+/-47) microm and for Tetric 18 (+/-12) microm. Differentiating between the class of lesion, a higher wear rate was observed at 36 months on restorations which had been placed in erosion/non-carious cervical cavities (66 (+/-33) microm). In conclusion, the composite material demonstrated a distinctly lower surface wear rate over time in comparison to the resin-modified glass ionomer cements and the polyacid-modified resin composite.
Adult↗
Composite restoration wear analysis: conventional methods vs. three-dimensional laser digitizer.
UNLABELLED: The purpose of this study was to compare three-dimensional laser digitizing with subjective evaluations of wear in posterior resin-based composite restorations during a 24-month period. BACKGROUND: The authors describe an indirect method of analyzing wear in resin-based composite restorations. A computer-driven laser was used to scan stone casts of restorations and create three-dimensional computerized surface models of the teeth. A standard computer algorithm was used to superimpose the follow-up model images over the baseline model images and to calculate the amount of wear within 10 micrometers. METHODS: Patients were selected whose treatment plans required a Class II restoration. A total of 100 restorations were inserted at baseline and evaluated at six months, 12 months and 24 months. Polyether quadrant impressions were taken and casts were made. Twenty-one casts were selected for the three-dimensional laser digitizing technique. The same casts were evaluated via subjective evaluations using sets of 18 calibrated standard models, following the method developed by Leinfelder. RESULTS: Statistical analysis using the Wilcoxon test revealed significant differences (P < .01) between subjective wear evaluation and the three-dimensional laser digitizing wear analysis. CONCLUSION: The normalized three-dimensional laser digitizing technique is significantly more effective than subjective evaluations in establishing restoration wear rates.
Adult↗
Marginal characteristics of different filling materials and filling methods with standardized cavity preparation.
PURPOSE: The aim of the present study was to investigate the influence of different filling materials and methods on marginal integrity in Black Class I fillings. MATERIALS AND METHODS: Standardized occlusal cavities were prepared in 80 extracted human molars. The preparations were filled with composite resin (1), with composite resin using the incremental technique (2), an experimental glass-fiber-reinforced (3) and polyester-reinforced (4) composite resin, a direct composite inlay (5), a ceramic insert (6), a Cerafil inlay (7), and with an experimental direct filling using Dyract AP compomer (8). Allocation of the teeth to the test groups was randomized; further processing was done on a blind basis. After the preparation of replicas, the teeth were subjected to a thermomechanical cycling process of 2,000 temperature cycles (5 degrees C/55 degrees C) and 50,000 stress cycles (50 N). This was followed by production of a second set of replicas and quantitative margin analysis by SEM (200X). A dye penetration test was then performed on the mesiodistal section. RESULTS: Groups 1, 2, 5, 6 and 7 displayed a good primary marginal quality, with the proportion of continuous margins reaching more than 85%. Significantly poorer results were recorded for the experimental glass-fiber-reinforced composite resins and Dyract compomer, where the proportion of perfect margins was only between 36% and 73%. In groups 1, 2, 5, 6 and 7, marginal integrity remained stable after the thermomechanical stress cycles, with the Cerafil inlays recording the best values: 89% perfect margins and 3% marginal gaps. In contrast, the experimental composite resins and the compomer underwent a significant (p < 0.05) increase in the proportion of marginal gaps and a significant (p < 0.05) reduction in the proportion of continuous margin. CONCLUSION: The results of this study show that neither Dyract compomer nor the glass-fiber-reinforced composite resins tested can be recommended for use in the occlusally stressed posterior region, whereas the other filling materials and methods were sufficiently stress resistant.
Acid Etching, Dental↗
Effect of dental materials on gluconeogenesis in rat kidney tubules.
The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl(2)) and methylmercury chloride (MeHgCl) on gluconeogenesis was investigated in isolated rat kidney tubules. From starved rats kidney tubules were prepared and isolated by digestion with collagenase. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.3 +/- 0.2 nmol/mg. per min (mean +/- SEM, n=21). Relative rates of glucose formation were obtained by expressing individual rates as a percentage of the corresponding control. X-Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90 to approx. 80% (controls), <25 (HEMA), <20 (TEGDMA), <10 (MeHgCl), and <10% (HgCl(2)). Values of 50% effective concentration (EC(50)) were calculated from fitted curves. EC(50) values were (mmol; mean +/- SEM; n=4): HEMA, 17.7 +/- 2.9; TEGDMA, 1.8 +/- 0.2; MeHgCl, 0.018 +/- 0.0005; and HgCl(2), 0. 0016 +/- 0.0005. The toxic effect of HgCl(2) was approximately 1000 or 10 000 higher than that of the dental composite components TEGDMA or HEMA, respectively.
Animals↗
Bond strength of a compomer to dentin under various surface conditions.
This study determined the influence of different dentin pretreatments on the shear bond strength of an adhesive system and corresponding compomer material. One hundred and twenty freshly extracted human molars were ground with wet SiC paper to expose flat oral/buccal surfaces of superficial dentin. The teeth were assigned to 12 treatment groups (n = 10) based on dentin surface finish (600-grit SiC vs. air abrasion vs. 40 microns diamond bur), surface conditioning (acid etching vs. no etching), and moisture content of the dentin (moist vs. dry). Cylinders of Compoglass F compomer were bonded to the dentin with Syntac Single-Component. After 24-h storage in distilled water, the specimens were debonded in shear mode. Bond strengths in MPa (SD) were calculated and bonding sites were analyzed for the mode of failure. Three-way ANOVA revealed significantly higher bond strength values for acid etched specimens (P = 0.001). Moisture content of the dentin surface (P = 0.614) and mechanical surface finish (P = 0.367) had no significant influence on the results. Debonding in unetched groups ranged from 94 to 100% adhesively. Acid etched groups showed adhesive failures ranging from 56 to 100%. To obtain a more reliable bond it is recommended that dentin is acid etched prior to the bonding of a compomer.
Acid Etching, Dental↗