Biomedical subjects

G Kugel

Publications and source records attributed to G Kugel.

49 records · Page 3Linked to original sources

PubMed1996

Class II composite resin restorations using glass-ionomer liners: microleakage studies.

Microleakage studies were undertaken for Class II composite resin restorations that had been lined with glass-ionomer cement using the 'sandwich' technique. Thirty freshly extracted permanent molars and premolars were mounted in polymethylmethacrylate blocks. Class II cavities were prepared using carbide burs No. 245 in a water cooled dental handpiece, (cavity box 5 x 3 x 2 mm). Specimens were divided into three groups of 10 each. Group A was restored with hybrid composite resin only, Group B with hybrid composite using a light-cured glass-ionomer liner applied to dentin only, and Group C with hybrid composite using light-cured glass-ionomer liner carried out to the cavosurface margin, (beyond the DEJ). All the specimens were thermocycled between 5 degrees C and 55 degrees C for 250 cycles for 3 hours, followed by placement in 0.5% aqueous basic fuchsin dye for 24 hours at 37 degrees C. Specimens were sectioned mesio-distally through the restorations using an Isomet apparatus. The extent of dye penetration was scored under a stereomicroscope with reference to the DEJ, (0 = no penetration, 1 = penetration to the enamel, 2 = penetration beyond the DEJ). Statistical analysis of the data showed significant differences among the means of the groups at p < 0.001. The results of this study indicate that the application of a light-cured glass-ionomer up to the cavosurface margin inhibits the microleakage of Class II restorations in vitro.

Bicuspid↗

PubMed1996

Dentin infiltration by three adhesive systems in clinical and laboratory conditions.

PURPOSE: To evaluate in vivo and in vitro the formation of hybrid layer, resin tags and adhesive lateral branches, by use of three different enamel dentin bonding systems. MATERIALS AND METHODS: The dentin adhesives were tested on flat dentin preparations made on buccal surfaces of vital, periodontally compromised teeth. The samples were randomly divided in four groups: Group 1: Prime & Bond 2.0; Group 2: Scotchbond Multi-Purpose Plus; Group 3: Clearfil Liner Bond 2 (the self-etching primer was applied for 30 seconds on the enamel and dentin); Group 4: Clearfil Liner Bond 2 (the self-etching primer was applied for 60 seconds on the enamel and dentin). The sample teeth were extracted immediately after the bonding was cured. The same procedure described for the in vivo samples was performed in vitro on extracted molars. All the samples were split-fractured along their long axis. Half of the samples were used to visualize the hybrid layer and the other half to observe the morphology of resin tags by use of scanning electron microscopy. RESULTS: All the tested products formed a hybrid layer, both in vivo and in vitro. In many areas of the samples of Groups 1, 2 and 4, characteristic reverse cone-shaped tags with their corresponding adhesive lateral branches were evident. In contrast to this, resin tags found in samples of Group 3 were narrower at the tubule orifices, and adhesive lateral branches were scarce. The length of the resin tags observed in the samples of Groups 1 and 2 were longer than those found in Groups 3 and 4. The morphology of the hybrid layer of the in vivo samples was similar to that of the in vitro samples.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1994

An evaluation of the effect of the adhesive luting on microleakage of the IPS empress crowns.

In an ongoing search for improved aesthetics, new materials and techniques are being developed and evaluated for clinical application; all-ceramic crown systems are among them. This paper presents an in vitro evaluation of the effect of dentin and porcelain bonding, with luting resin, on microleakage of porcelain crowns. Clinical application is discussed, and three cases are used to illustrate the procedure. The learning objective of this article is to enhance the knowledge of the more recent developments in dental materials and application techniques.

Aluminum Silicates↗

PubMed1992

The motivational benefits of a dentifrice containing baking soda and hydrogen peroxide.

Twenty-two family practice dentists, in a large metropolitan area, were recruited to act as independent examiners in a study to evaluate the compliance of their patients to accept a good oral hygiene regimen with the use of a fluoride dentifrice, containing hydrogen peroxide and baking soda, dispensed from a dual dispensing package. To evaluate compliance, the dentists attended an orientation seminar and were trained to assess gingival health using the CPITN periodontal probe. Each dentist evaluated the gingival health status of five to seven of his own patients, initially and after one and three months of product use following hygiene instruction and product assignment. One-hundred and thirty-one patients successfully completed the study. After one month of using the hydrogen peroxide/baking soda toothpaste, the mean reduction in bleeding sites was 53%; at three months the reduction was 62%. The hydrogen peroxide/baking soda dentifrice was well accepted by dentist and patient, and a discernible improvement in oral health of the patients was achieved when the product was used in a conscientious oral hygiene program.

Adult↗

PubMed1990

Nitrous oxide and infertility.

Our laboratory has reported changes in luteinizing hormone releasing hormone (LHRH) from the hypothalamus following nitrous oxide (N2O) exposure. LHRH augments LH release, which in turn causes ovulation. This study evaluated how N2O disrupts ovulation and the possible resulting infertility. Adult virgin female rats (N = 64) were housed with a 12 h:12 h light cycle. Daily vaginal smears were taken and only rats exhibiting two consecutive normal 4-day ovulatory cycles were used. Thirty-two rats were placed in an environmental chamber and exposed to a mix of hydrated 30% N2O and compressed air delivered at 1.6 L/min for 8 h/day for 4 days (one cycle); controls received compressed air. All rats exposed to N2O exhibited disrupted cycles following the first day of the 4-day exposure. From a group of 12 N2O-exposed rats, 11 went into constant proestrus (day of ovulatory surge) for up to 3 weeks. Control rats cycled normally. Following each exposure, eight rats were perfused, brains sectioned, and LHRH cells identified by immunocytochemistry. Eight control rats also underwent this procedure. A threefold increase in LHRH cells was noted in N2O rats. In addition, 12 rats received 30% N2O for 4 days, followed by mating with proven male breeders for 4 days, as were controls. Six of 12 N2O rats and 12 of 12 control rats gave birth. Contrary to previous reports, no significant difference was noted in litter size or weight. The constant proestrus seen after N2O exposure is due to disruption of LHRH cells in the hypothalamus (blocked LHRH release). It is this disruption of LHRH, and therefore ovulation, which results in infertility.

Animals↗

PubMed1983

Acrolein: a fixative for immunocytochemical localization of peptides in the central nervous system.

Acrolein was examined as an alternative fixative to formaldehyde for immunocytochemical localization of neuropeptides in the rat brain. A brief (5 min) vascular perfusion with a 5% acrolein solution allowed the identification of thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide (VIP), somatostatin (SRIF), neurotensin (NT), methionine enkephalin (Menk), adrenocorticotropic hormone (ACTH), tyrosine hydroxylase (TH), and luteinizing hormone-releasing hormone (LHRH) in fibers and perikarya within the central nervous system of the rat using the peroxidase-antiperoxidase (PAP) technique. Acrolein appears to be particularly valuable for immunocytochemistry, as it 1) stabilizes heterogeneous peptides and proteins rapidly and effectively, 2) retains antigenicity, and 3) preserves morphological detail.

Acrolein↗

PubMedDate not supplied

Changes in populations of LHRH-immunopositive cell bodies following gonadectomy.

One day after castration of male rats, plasma LH rose and the number of LHRH immunopositive neuronal perikarya decreased. As plasma LH continued to rise six days and three weeks post-castration, the number of LHRH immunopositive neurons also increased. The largest population of LHRH immunopositive neurons was detected three weeks post-castration and the cell group that showed the greatest increase was in the rostral preoptic area. In females, the largest population of LHRH immunopositive neurons was observed one day post-ovariectomy; at this time plasma LH levels were not significantly elevated above diestrous levels. Six days post-ovariectomy, LH levels were elevated and the number of LHRH immunopositive cells decreased. As LH levels continued to rise three weeks post-ovariectomy, the population increased in size. In males, primarily LHRH cells of the rostral preoptic area increased in in number; in females, the cell groups that increased were scattered over the diagonal band of Broca, preoptic and anterior hypothalamic areas. Although LHRH neurons demonstrated these variations following gonadectomy, there was no evidence of alteration(s) in molecular processing of precursor hormone.

Animals↗

PubMedDate not supplied

Dyract compomer: comparison of total etch vs. no etch technique.

Different dental materials and methods can influence the integrity of the marginal seal of restorations. To evaluate the microleakage of Dyract AP Light Cured Compomer, a polyacid modified resin (Caulk), using etched and unetched techniques, standardized trapezoidal Class V restorations were placed on facial or lingual surfaces of 20 human molars with the gingival margin in the cementum. Each restoration was scored at the cervical by two independent, double blinded operators, with reference to the DEJ, for dye penetration on a ranking system of: 0 = no evidence of dye penetration; 1 = dye penetration up to one-half the distance to the axial wall; 2 = dye penetration beyond one-half the distance to the axial wall but short of the axial wall; 3 = dye penetration to the axial wall or beyond. Statistical analysis (Fisher Exact Test) indicated that the etched compomer demonstrated significantly less microleakage when compared to the unetched compomer (p < 0.05).

Acid Etching, Dental↗

PubMedDate not supplied

Effect of nitrous oxide on the concentrations of opioid peptides, substance P, and LHRH in the brain and beta-endorphin in the pituitary.

Many studies have indicated that nitrous oxide (N2O) exposure results in specific effects on the reproductive system, some of which are antigonadotropic. The neurochemical events regulating the pituitary-gonadal axis are probably influenced by N2O, but precise documentation is lacking. The effects of exposure to 30% N2O in air on the brain tissue concentrations of luteinizing hormone releasing hormone (LHRH), substance P (SP), met-enkephalin, and beta-endorphin and on beta-endorphin concentrations of the pituitary gland are described in this study. Female rats were exposed to either N2O or air for 8 hr a day over one estrous cycle, and the brain and pituitary tissues were collected and processed. Neuropeptide concentrations were measured by specific radioimmunoassays. Exposure to N2O resulted in significant elevation of LHRH in the preoptic area, with a concomitant decrease in SP. The SP concentration of the medial basal hypothalamus was significantly elevated in N2O-exposed animals. Exposure to N2O resulted in significant increases in met-enkephalin in the brainstem area and beta-endorphin in the pituitary. These results suggest that exposure to N2O alters the interactive neural system activity regulating gonadotropin secretion from the pituitary. The significance of increased met-enkephalin in the brainstem of N2O-exposed animals is not known.

Animals↗

PubMedDate not supplied

Evaluation of a new intraoral isolation device.

Control of moisture is critical in the oral cavity to obtain the optimal properties of dental materials and thus increase their longevity. The conventional rubber dam is a 6" x 6" latex sheet held in place with a separate frame. This study evaluated a new moisture control device that is self-supported by a rolled spring border. Twenty-four patients seen by 24 different dental operators and six dental assistants, with previous experience using the conventional rubber dam, participated. The study concluded that there was significant improvement in user acceptance and patient comfort with the use of this isolation device and, from the compilation of remarks from questionnaires, it was concluded that it was most effective for completion of anterior teeth restorations.

Evaluation Studies as Topic↗

PubMedDate not supplied

Nitrous oxide and occupational exposure: it's time to stop laughing.

Although nitrous oxide (N(2)O) has been widely used since 1844, in recent years it has been implicated in a number of serious health hazards such as reproductive, nerve, liver, and kidney disorders. The National Institute of Safety and Health (NIOSH) recommends a limit of 25 ppm for chronic exposure to N(2)O in the dental office. Our study monitored ambient N(2)O levels in the dental office. N(2)O levels were compared for procedures performed in open clinics and private operatories as well as with and without a gas-scavenging system. Measurements were taken in the Dental Breathing Zone (DBZ) and Dental Chair Foot (DCF) at regular intervals. A four- to eightfold increase in average N(2)O levels was noted in the DBZ for unscavenged versus scavenged procedures. A three- to fourfold increase for unscavenged versus scavenged procedures was similarly noted in the DCF. N(2)O were significantly higher in private operatories than in open clinics, due to limited room volumes and in the DBZ over the DCF, due to mask leakage and increased oral exhalation. Scavenged N(2)O levels for both operatory types did not meet NIOSH guidelines. In contrast to previous studies using any form of gas removal, our study shows a significant decrease in N(2)O level achieved with an adequate scavenger system. With only four states regulating the use of N(2)O, and with concern over its deleterious effects growing, additional states and the federal government are expected to enact legislation regulating the use of N(2)O in the near future.

Air Pollutants, Occupational↗

PubMedDate not supplied

All-ceramic fixed restorations: a preliminary clinical evaluation.

This article is a preliminary evaluation of a limited size clinical trial of all-ceramic fixed restorations. The maxillary anterior region in each of eight patients was restored with single-unit and three-unit fixed restorations, using a particular all-ceramic system. Patient selection, laboratory procedures, clinical techniques, patient follow-up, and the interim clinical results of the restorations, are presented and evaluated. The learning objective of this article is to review and update the knowledge of all-ceramic restorative materials and clinical procedures. Two of the eight cases in the study are presented to illustrate the clinical results.

Aluminum Oxide↗

PubMedDate not supplied

A two-year clinical evaluation of TPH for restoration of Class II carious lesions in permanent teeth.

To evaluate the clinical suitability of a barium silicate-filled composite (TPH) for restoration of posterior teeth, 50 Class II restorations were restored in 36 patients. Restorations included 22 molars and 32 premolars. Cavity preparations were protected with calcium hydroxide or a resin-modified glass ionomer cement, or both. Enamel was etched for 30 seconds with 37 percent H3PO4. All dentin surfaces were treated with a dentin bonding system that was placed, cured, and restored in 2 microns increments. The restorations were finished using diamond burs, polishing points, and paste. Evaluation periods were at zero (50 restorations), 6 months (35 restorations), 1 year (31 restorations), and 2 years (29 restorations), using the USPHS System and M-L indirect scale. At zero time, 50 restorations were scored "a" in all categories by using two independent evaluators. After 6 months, 35 restorations were graded with one "a" in postoperative sensitivity. After 1 year, 31 restorations were evaluated with one additional "b" for marginal integrity. After 2 years, 2 additional "b" for marginal integrity and 1 "b" for surface staining were noted. No "c" was observed in any categories throughout this study. Wear analysis revealed, on average, 2 microns of wear after 6 months, 7.8 microns of wear after one year, and 10.3 microns of wear after 2 years.

Adult↗