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Biomedical subjects

G Kugel

Publications and source records attributed to G Kugel.

At least 37 records · Page 2Linked to original sources
PubMed1999

One-year clinical evaluation of SureFil packable composite.

The purpose of this trial was to clinically evaluate SureFil high-density posterior composite for Class II restorations of permanent first and second molars. All teeth were restored in occlusion with the natural dentition. After cavity preparation, the enamel was etched for 15 seconds with 34% phosphoric acid. No liner/base material was used for the dentin. Two applications of Prime and Bond 2.1 were placed for adhesion to the exposed dentin and etched enamel. One coat of adhesive was cured for 10 seconds with a curing light, and one thin coat was spread with a gentle jet of air. The cavity was restored in 3-mm to 5-mm increments. Evaluation was assessed immediately after placement (baseline), and at 3 months, 6 months, 9 months, and 1 year for retention, leakage, marginal integrity, color stability, abrasive resistance, surface staining, surface texture, postoperative sensitivity, and secondary caries. The restorations were evaluated indirectly for wear using a modified USPHS and indirect cast comparison method. At baseline, 25 restorations were graded Alfa in all categories. At 3-, 6-, and 9-month recalls (N = 24), all restorations were graded Alfa in all categories. At the 1-year recall (N = 20), there were three Bravos for surface staining.

Adult↗
PubMed1999

In vitro leakage of resin-bonded all-porcelain crowns.

PURPOSE: The purpose of this study was to evaluate the sealing ability of single-unit all-porcelain crowns with margins placed in cementum-dentin and luted with two different cementing materials. MATERIALS AND METHODS: Twenty extracted molars, free of caries and restorations, were selected. The sample abutments were prepared in a standardized manner and then divided in two groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the crowns were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ, and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. IPS-Empress (Ivoclar) crowns were made following manufacturer's instructions. After luting procedures and 2,500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at the cervical site. After scoring dye penetration in group 1 and 2 samples, half of the sections were randomly selected in order to evaluate 1) resin cement thickness and 2) hybrid layer formation at the interface between adhesive material and dental substrate. The leakage data were statistically evaluated with the Kruskal-Wallis non-parametric analysis of variance (ANOVA) by ranks with Bonferroni alpha adjustment (p < 0.05). RESULTS: Sixty percent of the group 1 samples and 80% of group 2 showed leakage. In group 1, the dye penetration was often limited to the cervical margin site, while in group 2, it mainly extended to the axial walls. Statistically significant differences between samples of the two groups were not found. Samples of group 1 showed a cement thickness of 82 microns, while 75 microns was found in group 2. A hybrid layer and resin tag formation were evident in group 1. In group 2 samples, the hybrid layer formation was less evident and thinner than in group 1. CONCLUSIONS: The two adhesive systems performed similarly. The cervical margins of single-unit all-porcelain crowns must be considered as one of the weakest areas of this type of esthetic restoration.

Adult↗
PubMed1999

A prospective clinical evaluation of electronically mixed polyvinyl siloxane impression materials: results from the prosthetic "SuperStudy"--a consumer evaluation.

Polyvinyl siloxane (PVS) impression materials incorporating a polyether carbosilane wetting agent and mixed with an electronic mixing system (Pentamix) were clinically compared with traditionally delivered (i.e., automixed) PVS impression materials during routine use by 1,505 general and specialized dental practitioners evaluating more than 30,000 impressions. Each study participant selected 20 patients and used standard tooth-preparation procedures appropriate to the therapy required, supplied specific data on each case, and ultimately evaluated the marginal detail, fit, and success of the final restorations. The areas requiring evaluation upon completion of the final restorations were ranked between "excellent," "good," "poor," and "remake needed," among users of the PVS materials with the electronic mixing system. About 80% of the respondents rated the Pentamix system as easier to mix and deliver than the gun or hand-mixed systems and two thirds said it was faster to mix. The system also received high scores for hygienic delivery, ease of mixing, and clean-up.

Consumer Behavior↗
PubMed1998

Alterations in catecholamine turnover in specific regions of the rat brain following acute exposure to nitrous oxide.

The effects of nitrous oxide (N2O) on steady-state concentrations and turnover rates of catecholamines in the olfactory bulb, hypothalamus, brain stem, hippocampus, striatum, thalamus, cerebral cortex, and spinal cord were determined in rats. Animals were exposed for 2 h to either 60% N2O or air. Immediately following exposure, all animals were injected intraperitoneally with alpha-methylparatyrosine (alphaMPT), a competitive inhibitor of tyrosine hydroxylase, and sacrificed at 0, 30, or 90 min postinjection. Brain catecholamine concentrations were determined using high-performance liquid chromatography coupled with electrochemical detection (HPLC-EC). Results indicate that N2O exposure significantly elevates steady-state concentrations of norepinephrine (NE) in the hypothalamus and striatum yet decreases amine levels in the brain stem region. Steady-state levels of dopamine (DA) were not significantly altered in any region of the CNS by N2O exposure. Acute exposure to N2O also resulted in significant decreases in the turnover rate of NE in the brain stem, yet it increased turnover of this amine in the olfactory bulb, hypothalamus, and striatum. Acute exposure to N2O resulted in a decreased turnover rate of DA in the hippocampus and striatum. In contrast, N2O appears to increase DA turnover in the olfactory bulb. These results indicate that acute exposure to N2O in rats causes region-specific alterations in steady-state levels and turnover rates of DA and NE within the central nervous system.

Analysis of Variance↗
PubMed1998

Preliminary report: laboratory-induced stain removal as assessed by environmental scanning electron microscopy.

Environmental scanning electron microscopy (ESEM) was employed to observe stain removal during brushing with Arm & Hammer Dental Care and Crest Regular Toothpaste. ESEM allows serial examinations of the same sample, and does not require a destructive preparative process. Three extracted molars were cleaned, placed into a 96-hour broth culture of Streptococcus mutans, and stain was produced with undiluted chlorhexidine rinse, concentrated coffee and tea for a period of 23 days. After staining, the teeth were examined by ESEM, then brushed using a toothbrushing machine. Imaging was repeated after 5, 10, 15 and 30 seconds of brushing. As seen with ESEM, the Arm & Hammer product had different effects than those from the distilled water control, suggesting something other than that expected from abrasive and mechanical forces alone. There were also differences from the Crest dentifrice removal on this single sample, suggesting a possible difference between the two products. Further studies are needed to confirm and explain these effects.

Chlorhexidine↗
PubMed1998

Handling characteristics of resin composites in posterior teeth.

In the last 10 years, tremendous improvements in strength and shade selection for resin composites have been achieved. Also, a new generation of enamel-dentin bonding systems has been developed, and patient expectations of esthetic treatment have risen. Several techniques are available for restoring posterior teeth. When a caries lesion is limited, a direct esthetic restoration is indicated. Essential elements for obtaining good, long-term clinical results for direct esthetic restorations of posterior teeth are: (1) cavity preparation; (2) knowledge of the characteristics of the three dental substrates; (3) rubber dam use and matrix and wedge placement; (4) correct use of the enamel-dentin bonding system; (5) proper selection of the resin composite material; (6) use of the multilayering technique; (7) finishing and polishing procedures; and (8) maintenance of the restoration.

Acid Etching, Dental↗
PubMed1997

Short-term assessment of leakage of Class V composite restorations placed in vivo.

The purpose of this study was to investigate the effectiveness of two dentin bonding systems, one of which was also in combination with a self-curing resin, when applied in V-shaped circular cavities cut in anterior teeth crossing the cementum-enamel junction. Twenty-seven teeth scheduled for extraction for periodontal reasons were treated in vivo. The sample teeth were divided at random into three groups. Group 1 was treated with All Bond 2 (AB2) + Z-100 composite, group 2 with Scotchbond Multipurpose Plus (SMPP) + Z-100, and group 3 with AB2 in conjunction with Bisfil 2B as liner and Z-100. The in vivo restored teeth were extracted after 2-3 months of clinical service. They were then immersed in a dye solution for 24 h, sectioned, and scored for marginal leakage. Analysis of variance revealed no significant differences between the three groups both at cervical and incisal sites. The enamel sites were free from any leakage. Only two cervical sites of groups 1 and 2 and one of group 3 showed a score 1 for leakage. The results of the short-term clinical performance of the three systems were promising.

Analysis of Variance↗
PubMed1997

Fracture strengths of provisional restorations reinforced with plasma-treated woven polyethylene fiber.

STATEMENT OF PROBLEM: Fracture strength of interim fixed partial prosthesis is of great concern, especially in long-span restorations or areas of heavy occlusal stress. PURPOSE: Effects of a plasma-treated woven polyethylene fiber (Ribbond) on the fracture strength of polymethyl methacrylate (Coldpac) and a resin-based two-phase curing provisional restorative material (Provipont DC) were evaluated. MATERIAL AND METHODS: A polyvinyl siloxane template was used to fabricate three-unit posterior provisional prostheses on a stainless steel die with two abutments 22 mm apart. The reinforced groups were fabricated by affixing 3 mm wide pieces of fiber treated with methyl methacrylate monomer or polyisocyanate (activator part of Provipont DC) on the occlusal surfaces of abutments. The interim materials were mixed, according to the manufacturers' specifications, and placed in the template. The template was pressed on the die and held secure until complete setting of the material occurred by light curing (Provipont DC) or autopolymerization (PMMA). The specimens were divided into 4 groups of 10 each (A, reinforced Provipont DC; B, unreinforced Provipont DC; C, reinforced PMMA; and D, unreinforced PMMA). A central compressive load force was exerted on the specimen to determine the fracture load of the restorations. RESULTS: The data revealed mean fracture loads of A, 65.59 +/- 11.27 kg; B, 46.59 +/- 14.84 kg; C, 53.46 +/- 7.76 kg; and D, 49.86 +/- 14.44 kg. CONCLUSION: Plasma-treated polyethylene reinforced PMMA restorations showed no significant increase in fracture loads when compared with unreinforced restorations (p > 0.10), whereas reinforced resin-based restorations revealed significantly higher fracture loads (p < 0.01) than the unreinforced resin-based and PMMA provisional restorations.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1997

Effective tooth bleaching in 5 days: using a combined in-office and at-home bleaching system.

This article compares the bleaching efficacy of a combined at-home and in-office system with that of an in-office system alone. Twenty people participated in the study. Ten of these participants were treated with an in-office 35% carbamide peroxide bleaching product in 2 visits of 15 minutes each. The remaining participants were treated with a combination at-home and in-office system that included a 15% carbamide peroxide at-home bleaching agent. After 5 days of treatment, the participants using the combination system demonstrated increased tooth whitening compared to those using the in-office system alone. Based on the sample size (20 patients), statistical significance was achieved.

Adolescent↗
PubMed1997

Use of environmental scanning electron microscopy to evaluate dental stain removal.

The purpose of the study was to assess the usefulness of environmental scanning electron microscopy (ESEM) to evaluate stain removal from extracted teeth. The ESEM differs from conventional SEM in that no sample preparation is needed, eliminating artifactual changes. Furthermore, the same sample can be viewed on multiple occasions, allowing "before" and "after" pictures of the same tooth. As a model stain removal device, we tested the Sonicare sonic toothbrush, which has previously been shown to remove dental stain in vivo. Twelve freshly extracted teeth with extrinsic coffee, tea or tobacco stain were obtained for the study. Nine of these had heavy stain (stain covering more than one-third buccal or lingual surface) and were used without further modification. Three teeth were treated in vitro with chlorhexidine and a mixture of coffee and tea to enhance staining. All teeth were examined by ESEM at three times: prior to brushing, after 15-30 seconds of brushing, and after 60-80 seconds of brushing. Light microscopy and 35 mm photography was also done to correlate the ultrastructural changes with those visible at low magnification. Water, mouthwash and 30% slurry of toothpaste were used as fluid vehicles during brushing, but little difference in stain removal was noted among these three fluids. Approximately half the stain was removed within 15-30 seconds, and most visible stain was removed in 60-80 seconds of brushing. Pits and crevices of tooth enamel that were smaller than the bristle diameter, and thus would be inaccessible to abrasive cleaning by direct bristle contact, were generally found to be stain-free. These findings confirm previous reports of the stain removal effectiveness of the Sonicare, and demonstrate the usefulness of ESEM for stain removal studies.

Chlorhexidine↗
PubMed1997

In vitro comparison of restoration wear and tensile strength following extended brushing with Sonicare and a manual toothbrush.

The purpose of this study was to compare the wear, cement margin breakdown and bond strength of restorations following 6 to 12 months of simulated use in vitro of the Sonicare and a manual toothbrush. Extracted molar teeth with Class V hybrid composite resin restorations (n = 21) or with Class V gold inlays cemented with zinc phosphate cement were tested for wear and marginal integrity following brushing for a period that simulated 6 months of typical use. One-third of the molars in each group were brushed with the Sonicare and one-third were brushed with the manual brush. The remaining third served as non-treated controls. Toothbrushing was performed under a standardized load using a piston-action brushing machine. After brushing, the enamel, dentin/cementum and restorations were examined by light and scanning electron microscopy. There was no apparent wear of tooth structure or of restorative materials with either the Sonicare or the manual brush. There was a small loss of cement from the margins of the gold inlays following toothbrushing, which was similar and not significantly different between the sonic and manual brush. To test brushing effects on crown retention, four identical metal dies were prepared to simulate premolar crown preparations. Thirty cast copings, prepared to fit the dies, were cemented with zinc phosphate cement. Toothbrushing with Sonicare or the manual toothbrush was performed as before (n = 15 for each brush), but the simulated time was extended to the equivalent of 1 year of brushing. The dislodgement force of cemented crowns was not significantly different (t-test, p > 0.10) between the manual (207 +/- 69 N) and Sonicare (221 +/- 61 N) groups. These results demonstrate that despite its high frequency bristle motion, Sonicare exerts no detrimental effects on cement margin integrity, crown bond strength or surface wear of dental and restorative materials.

Analysis of Variance↗
PubMed1997

Buying right.

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Dental Materials↗
PubMed1997

Classification and application of cementation alternatives.

More important than any resin cement is the marginal fit and retentive nature of the ceramic restoration to be bonded. Cementation should not be intended to compensate for poor dentistry, but to assist in producing superior aesthetic results. Responding to the demand for all-ceramic restorations, dental manufacturers continue to refine the resin cements used in luting for this modality. The ideal resin cement for ceramic restorations must demonstrate low viscosity; easy loading; a film thickness which facilitates complete seating high strength; and excellent wear resistance. This article reviews the available resin cements, with particular focus on a new type of initiator and stabilizer for light- and dual-cured resin cements.

Cementation↗
PubMed1996

Effect of low and high doses of nitrous oxide on preproenkephalin mRNA and its peptide methionine enkephalin levels in the hypothalamus.

The effect of exposure to nitrous oxide (N2O) on the levels of preproenkephalin mRNA in the hypothalamus of rats was examined. In the first experiment, rats were exposed to 1000 ppm N2O for 8 h a day over 4 days. Compared with controls (which were exposed to air over the same duration), the N2O exposed animals exhibited significant elevations in preproenkephalin mRNA levels in the hypothalamus. In a second experiment, rats were exposed to 60% N2O or air for 12, 24 and 48 h duration, and hypothalamic levels of preproenkephalin mRNA as well as methionine enkephalin were analyzed. Compared with controls, N2O exposed rats exhibited significant elevations in preproenkephalin mRNA levels. The levels on preproenkephalin mRNA were significantly higher after 48 h of N2O exposure than after 12 h of N2O exposure. Similarly, the concentration of methionine enkephalin was significantly higher after 24 and 48 h of exposure of N2O than after exposure to 12 h of N2O or air. These results indicate that (a) exposure to N2O results in significant elevations in preproenkephalin mRNA levels, (b) the increased preproenkephalin mRNA levels appear to be proportional to the concentration of N2O exposure as well as the duration of N2O exposure, and (c) N2O-induced elevation in preproenkephalin mRNA levels is associated with corresponding increase in tissue concentrations of methionine enkephalin. In total, these results suggest that N2O selectively stimulates synthesis of methionine enkephalin in the diencephalic region of the brain.

Animals↗
PubMed1996

Teaching the use of bases and liners: a survey of North American dental schools.

The authors surveyed 64 dental schools in North America about their instruction on the use of bases and liners. Respondents cited the materials being taught at the time of the survey, two years before the survey and four years before the survey. There was no consensus as to the materials being used. Copal varnishes and dentin bonding agents, or DBAs, were used most often in Class II preparations more than 2 millimeters from the pulp, and glass ionomers and DBAs were equally popular for Class II preparations within 1 mm of the pulp. Most schools were pleased with the materials they are currently teaching but continue to review material selection annually.

Calcium Hydroxide↗