Gerard Kugel

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.

Clinical Trial Assessing Light Enhancement of In-office Tooth Whitening

OBJECTIVE Evaluate a light-enhanced in-office tooth whitening system in order to assess tooth color and safety. METHODS Thirty-three adults were randomly assigned to one of three treatment groups. Professional treatment involved application of a 25% H(2)O(2) gel (Discus Dental ZOOM!) with light enhancement, H(2)O(2) gel alone, or the light alone with no peroxide. The 12 anterior teeth were treated three times for 20 minutes each. Efficacy was measured objectively as L*a*b* color change using digital images, tooth shade was measured, and safety was evaluated immediately after treatment and at posttreatment days 7 and 30. RESULTS After adjusting for baseline and age, immediate (end-of-treatment) means (SE) for Deltab* (yellowness) were -3.1 (0.25) for the gel + light, -2.0 (0.25) for the gel-only group, and -2.4 (0.25) for the light-only group. Significant (p < 0.05) color rebound was evident at posttreatment day 7. By day 30, adjusted means (SE)for Deltab* were -1.7 (0.20) for the gel + light group, -1.1 (0.20) for the gel-only group, and -0.5 (0.20) for the light-only group. Both peroxide groups differed significantly (p < 0.05) from light alone on Deltab* and DeltaL*. In the gel + light group, 91% of subjects experienced tooth sensitivity, the majority of which was moderate or severe. Adverse events were low in the light-only group. CONCLUSION Use of light enhancement for in-office whitening leads to immediate color change, after which there was significant color and shade rebound within 7 days as well as moderate-to-severe tooth sensitivity during and after treatment. CLINICAL SIGNIFICANCE Increased tooth sensitivity during treatment and appreciable short-term color rebound after treatment may impact the utility of in-office tooth whitening with peroxide and light as a stand-alone esthetic procedure. (J Esthet Restor Dent 21:336-347, 2009).

The influence of laser-textured dentinal surface on bond strength

OBJECTIVE To assess the influence of laser-textured surfaces on the adhesion of composite to dentin after being rotary prepared. METHODS Thirty healthy teeth were kept in 0.1% thymol solution prior to being ground down to dentin to create a 4 × 4 mm² flat surface. Teeth were divided into 3 groups (n=10). Groups 1 and 2 utilized the prototype Erbium doped, Yttrium-Aluminum-Garnet Er:YAG laser by Dental Photonics, Inc. A single pulse was delivered to each spot to create an equally spaced square 4 × 4 mm² matrix of micro craters. All craters had 100 μm diameter/45 μm depth; two different spacing patterns were prepared in Groups 1 and 2. In Group 1, distance between crater centers was 50 μm; Group 2 had 100 μm. In Group 3 (control), 10 samples were prepared without laser texturing. G-bond (GC America) was applied to testing area of all samples in all groups according to manufacturers instructions. Bonding resin was applied and shear-bond strength tests were employed using an Instron machine to measure adhesive strength. RESULTS One-way analysis of variance (ANOVA) was used to compare the 3 groups. Pair wise t-tests implementing the Bonferroni correction for multiple comparisons found a statistically significant difference between Group 3 and Group 2 (p=0.019) but no statistically significant difference between Group 3 and Group 1 (p=0.263) or Group 1 and Group 2 (p=0.743). SIGNIFICANCE The bond strengths between bonded composite to laser-textured dentinal surfaces with larger spacing patterns are greater than that of non-textured surfaces.

Shear bond strength of techniques for bonding esthetic veneers to metal

STATEMENT OF PROBLEM New composites with improved qualities have been introduced to the dental profession as alternatives to porcelain. There is concern about the strength and reliability of new metal-resin bonding systems when these composites are used as esthetic veneers over metal frameworks. PURPOSE This in vitro study compared the shear bond strength of 2 metal-resin bonding techniques with the bond strength of conventional porcelain fused-to-metal (PFM). Effects of water storage and thermocycling were also evaluated. MATERIAL AND METHODS Ninety disks, cast in a medium gold, high noble PFM alloy, were divided equally into 6 groups, and received 3 treatments for veneering: conventional feldspathic porcelain on 1 group, and a composite (Artglass) bonded to the metal, using 2 metal-resin bonding techniques. Specimens were tested in shear, half of them after a 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37 degrees C and thermocycling. Fractured specimens were evaluated under x10 magnification to determine the nature of failure. Statistical analysis was performed with 2-factor analysis of variance (ANOVA). RESULTS Mean shear bond strength values before and after wet storage and thermocycling were 29.66 and 22.91 MPa for the PFM group; 21.43 and 17.92 MPa for the Siloc group; and 19.34 and 15.64 for the etched group, respectively. The PFM group exhibited significantly higher bond strength values compared with the other 2 groups (P<.001). All groups showed a significant decrease in bond strength values after wet storage and thermocycling (P<.001). CONCLUSION Wet storage and thermocycling caused a significant decrease in shear bond strength of all specimens. Shear bond strength of conventional feldspathic PFM was significantly higher than that of the 2 metal-resin bonding techniques tested. The 2 latter techniques did not reveal any statistically significant differences.

Electrodeposited silk coatings for bone implants

The aim of this study was to characterize the mechanical properties and drug elution features of silk protein-based electrodeposited dental implant coatings. Silk processing conditions were modified to obtain coatings with a range of mechanical properties on titanium studs. These coatings were assessed for adhesive strength and dissolution, with properties tuned using water vapor annealing or glycerol incorporation to modulate crystalline content. Coating reproducibility was demonstrated over a range of silk concentrations from 1% to 10%. Surface roughness of titanium substrates was altered using industry relevant acid etching and grit blasting, and the effect of surface topography on silk coating adhesion was assessed. Florescent compounds were incorporated into the silk coatings, which were modulated for crystalline content, to achieve four days of sustained release of the compounds. This silk electrogelation technique offers a safe and relatively simple approach to generate mechanically robust, biocompatible, and degradable implant coatings that can also be functionalized with bioactive compounds to modulate the local regenerative tissue environment.

Lead-induced cell signaling cascades in GT1-7 cells.

The effects of lead on the signal transduction pathways that may be involved in the release of gonadotropin-releasing hormone (GnRH) from neurons in the hypothalamus have not been well defined. Using the GT1-7 cell line, an in vitro model for GnRH-secreting neurons, we examined signal transduction pathways directly affected by lead. We found that lead-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1 and ERK2), as well as p90RSK and cAMP response element-binding protein (CREB), but did not induce IkappaB degradation. MEK1/2 inhibitor (PD98059) suppressed lead-induced ERK and p90RSK activation. Neither PKC inhibitors (Go6983, Go6976) nor CaMKII inhibitor (KN-62) had a pronounced effect on lead-induced ERK1 and ERK2 phosphorylation. However, MEK1/2 inhibitor, CaMKII inhibitor, and PKC inhibitor significantly suppressed lead-induced CREB phosphorylation. These results indicate that lead-activated PKC, CaMKII and MEK/ERK/p90RSK pathways simultaneously, all of which contributed to CREB phosphorylation. Our results also indicate that lead-induced p90RSK and CREB activation does not alter expression of early response genes like c-fos. We conclude that lead activates PKC, CaMKII or MEK-ERK-p90RSK pathways in GT1-7 cells, leading to CREB phosphorylation and modulation of gene expression.

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.

Placebo-Controlled Clinical Trial of Use of 10% Hydrogen Peroxide Whitening Strips for Medication-Induced Xerostomia

Objective: A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the effectiveness and safety of peroxide-containing strip-based tooth whitening among subjects with medication-induced hyposalivation. Methods: Eligibility for this tooth whitening study was limited to dentate adults taking xerogenic medications with an unstimulated salivary flow ≤0.2 ml/min. After giving informed consent, 42 subjects were randomized using a 2:1 ratio to 10% hydrogen peroxide whitening strips (Crest® Whitestrips® Premium) or placebo strips without peroxide. Strips were used for 30 min twice daily for a 14-day period. Usage was unsupervised, and only the maxillary arch was treated. On days 8 and 15, efficacy was assessed from standard digital images of the anterior dentition and quantified using the Cielab color system, while safety was assessed from interviews and clinical examinations. Results: At day 8, the peroxide group experienced significant (p < 0.001) color improvement relative to baseline and placebo. Adjusted means ± standard errors for yellowness reduction were –1.65 ± 0.115 units for the peroxide group and –0.32 ± 0.170 units for the placebo group. For the increase in lightness, adjusted means ± standard errors on day 8 were 1.53 ± 0.130 units for the peroxide group and 0.37 ± 0.191 units for the controls. Continued strip use through day 15 yielded incremental color improvement for the peroxide group. Mild and transient tooth sensitivity represented the most common adverse events. No subject discontinued treatment due to a product-related adverse event. Conclusion: Twice daily use of 10% hydrogen peroxide whitening strips by adults with medication-induced xerostomia was well tolerated, with significant tooth color improvement evident within 7 days.

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

Abstract 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.

Silk electrogel coatings for titanium dental implants

The aim of this study was to develop biocompatible, biodegradable dental implant coatings capable of withstanding the mechanical stresses imparted during implant placement. Two techniques were developed to deposit uniform silk fibroin protein coatings onto dental implants. Two novel coating techniques were implemented to coat titanium shims, studs, and implants. One technique involved electrodeposition of the silk directly onto the titanium substrates. The second technique consisted of melting electrogels and dispensing the melted gels onto the titanium to form the coatings. Both techniques were tested for coating reproducibility using a stylus profilometer and a dial thickness gauge. The mechanical strength of adhered titanium studs was assessed using a universal mechanical testing machine. Uniform, controllable coatings were obtained from both the electrodeposition and melted electrogel coating techniques, tunable from 35 to 1654 µm thick under the conditions studied, and able to withstand delamination during implantation into implant socket mimics. Mechanical testing revealed that the adhesive strength of electrogel coatings, 0.369 ± 0.09 MPa, rivaled other biologically derived coating systems such as collagen, hydroxyapatite, and chitosan (0.07–4.83 MPa). These novel silk-based techniques offer a unique approach to the deposition of safe, simple, mechanically robust, biocompatible, and degradable implant coatings.