A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Purpose: This study will evaluate the influence of different convergence angles and tooth preparation heights on the marginal adaptation and retention of allceramic CAD/CAM crowns. Materials & Methods: Seventy two typodont teeth (Ivorine teeth; Columbia Dentoform Corp, Long Island City, NY) were prepared using milling burs (Brasseler, USA) and a parallometer (PFG 100, Cendres and Metaux, Switzerland) with 1.0 mm rounded shoulder finish lines. Specimens were divided into 3 groups (n=24) according to 3, 4.5 and 6mm occluso-gingival (O-G) heights. The teeth within each group were then subdivided into 3 subgroups (8 in each sub-group) according to total occlusal convergence (TOC) of 8,16 and 22 degrees. Using the intra-oral camera wand of the Cerec AC machine (Sirona, Germany), optical impressions were made of each tooth. This data was then transferred to the Cerec MC XL milling unit for fabrication of all-ceramic crowns using IPS Empress II (Ivoclar Vivadent, US). The crowns were cemented on typodont teeth with glass ionomer cement. The marginal discrepancy was measured at 6 points with optical microscopy. Retention was evaluated by measuring the tensile force required to dislodge or break the crown from the corresponding tooth preparation in a universal testing machine. Data were analysed using Shapiro-Wilke tests for normality and Leven's tests for equal variances. To look for differences between groups, analysis of variance (ANOVA) with Tukey's HSD test was performed. Results: Mean marginal gap was 35.9 ± 18.4ìm to 81.4 ± 61.3ìm. 2- way ANOVA shows no significant difference in marginal gap among the groups (P< 0.05). The height mean retentive force 183.84 ± 27.0 N, was measured for 6mm height and 8° group and lowest force 86.01±10.75 N, was measured for 3 mm and 22° group. 2- way ANOVA with turkey's HSD test shows significant difference among the groups (P > 0.05). Conclusion: Marginal adaptation of the CAD/CAM all-ceramic crowns is comparable to conventional cast crowns. The preparation recommendation for conventional porcelain fused to metal crowns can be applied to CAD/CAM crown restorations. Retention of cemented CAD/CAM crowns is comparable to conventional cast crowns

Background. There are many polishing systems available on the market have been used by many clinicians to improve the color stability, wear resistance and surface smoothness of composite restorations. Several changes have been made in the fabrication of dental resin composites to improve their mechanical strength and esthetic properties. Previous studies have shown that composite resins are susceptible to color instability because of surface roughness and exposure to various staining media, especially red wine, coffee, soda and tea. The purpose of this study was to evaluate the average surface roughness (Ra) and color stability of two direct resin compositespolished with four different polishing systems. Methods. Two resin composites (nanohybrid and nanofill) were evaluated using four polishing systems (Four versus three steps; diamond versus fluted burs). A disk-like specimen of each composite material was fabricated (10 mm in diameter and 2 mm thick). Ten specimens of each composite were randomly assigned to one of four polishing systems. The surface roughness values were measured using the profilometer. In addition, discoloration of the polished composites was evaluated after immersion into different solutions, namely coffee and red wine. The staining of the materials was evaluated using the spectrophotometer. Results. No difference was noted between any of the four different polishing techniques, type of composite and surface roughness (Ra). A one way ANOVA showed that there was a statistical significant difference between color change (ΔE) and polishing techniques, p

Pattern-related visual stress (PRVS) refers to the perceptual difficulties experienced by some individuals when exposed to high contrast striped patterns. People with PRVS were reported to have reduced sensitivity to global motion at baseline testing and the difference disappears at a second estimate. The present study was to investigate the effect of practice on global motion threshold in adults with and without PRVS. Methods: A total of 101 subjects were recruited and the Wilkins & Evans Pattern Glare Test was used to determine if a subject had PRVS. The threshold to detect global motion was measured with a random dot kinematogram. Each subject was measured 5 times at the first visit and again a month later. Receiver operating characteristic (ROC) curve analysis was applied to show the agreement between the two tests. Results: Twenty-nine subjects were classified as having PRVS and 72 were classified as normal. At baseline, the threshold to detect global motion was significantly higher in subjects with PRVS (0.832 ± 0.098 vs. 0.618 ± 0.228, p < 0.001). After 5 sessions, the difference between the normal and subjects with PRVS increased (0.767 ± 0.170 vs. 0.291 ± 0.149, p < 0.001). In ROC analysis, the area under the curve (AUC) improved from 0.792 at baseline to 0.964 at the fifth session. After a one-month break, the difference between normal and subjects with PRVS was still significant (0.843 ± 0.169 vs. 0.407 ± 0.216, p < 0.001) and the AUC was 0.875. Conclusion: The ability to detect global motion is impaired in persons with PRVS and the difference increased after additional sessions of practice.

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Background. Earlier research evaluated the 3D internal fit of CAD/CAM crowns after direct versus indirect laser scanning. To date, no study has evaluated the marginal integrity of all-ceramic crowns milled with different type of scanning systems via different methods of scanning. The purpose of This study was conducted to assess the marginal integrity of all-ceramic crowns milled with the E4D CAD/CAM system (D4D, Richardson, Texas) using three different scanning methods of a prepared model (direct scanning and indirect scanning of a cast, and scanning of an impression material). Methods. A metal die model of a prepared mandibular first molar was fabricated according to specifications for tooth preparation for the E4D CAD/CAM system. Fifty five all-ceramic crowns were milled using this system: 5 crowns were made from scanning of the metal die; 25 crowns were made from scanning of 5 PVS impressions of the metal die, with each impression scanned 5 times; and 25 crowns were made from scanning stone dies poured from the same previous 5 PVS impressions. Each stone die was scanned 5 times. An internal gap to provide space for cement was kept constant at 25 microns. Marginal integrity of the crowns was assessed using optical microscopy. Results. The overall mean marginal gap and standard deviation for crowns was 78.1&mgr;m (18.9) for scanning the metal dies, 148.9&mgr;m (25.4) for scanning impressions and 126.2&mgr;m (28.2) for scanning the stone casts. ANOVA revealed significant differences in marginal gap between the three different groups. Conclusions. The direct scanning of a metal die produced crowns with significantly smaller marginal gaps than the marginal gap seen from scanning a PVS impression or a stone cast (P<.05). Additionally, it was found that scanning PVS impressions or stone casts, produced crowns with unacceptable mean marginal gaps (over 120&mgr;m). It was also observed that difficulty of scanning PVS impressions and tracing the finish line lead to overhanging margins and larger marginal gaps for both crowns produced via that method.

Pain is one of the cardinal signs of inflammation, but its production during the inflammatory process has been poorly delineated. While analgesic and antiedema activities have been well studied in the literature, neurogram studies of nerves directly involved with local inflammation have not been reported to date. One purpose of this investigation was to determine if differences in neurogram patterns were apparent using different phlogistic agents and electrophysical recording of the inflammation-induced “pain.”

The purpose of this study was to determine changes induced by cisplatin on hair cell (HC) morphology, compound action potential (CAP), Preyer reflex (PR), and Na,K-ATPase activity in the cochlear lateral wall. Guinea pigs were treated with either 0.42, 0.83, 1.17, 1.50 mg/kg cisplatin, i.p. or sterile water for 12 consecutive days and tested on day 13. HC condition was visualized with scanning electron microscopy (SEM), CAP was initiated with a 1 volt click, and Na,K-ATPase activity was measured by the method of Fiske and SubbaRow. HC damage was linear with dose and occurred throughout the turns of the cochlea with greatest predominance in the basal turn. Degrees of HC distortion were represented by separation of stereocilia, formation of blebs, and expulsion of HC contents. Complete suppression of CAP and PR occurred in all 1.5 mg/kg treated animals and 50% of the 1.17 mg/kg dose group. A 60% depression of CAP occurred in 50% of the 0.83 dose group. Na,K-ATPase activity was not significantly different between treatment groups. These results indicated that cisplatin ototoxicity appeared to be dose-dependent for measurements of CAP, PR and HC damage but was not related to Na,K-ATPase activity in cochlear lateral wall.

Paraquat was administered to male, Sprague-Dawley rats via continous infusion, at dosage rates of 250 (LoPQ) or 500 (HiPQ) nmoles/hr for seven days. The purpose was to characterize the effects of prolonged, low blood levels of the herbicide on selected lung biochemical parameters. The efficacy of putrescine as an inhibitor of pulmonary paraquat accumulation, in vivo, was assessed in these animals by I.V. coinfusion of 2500 or 5000 nmoles putrescine/hr. Dose-dependent levels of both paraquat and putrescine were achieved by 18 hours and were maintained throughout the exposure period. Terminal lung paraquat content was also dose-dependent and up to 18-fold greater than corresponding blood levels, indicative of pulmonary accumulation of the herbicide. Despite relatively high putrescine dosage rates, resulting blood levels of this diamine were low and did not significantly alter terminal lung paraquat content. No evidence of paraquat toxicity was seen in LoPQ animals while frank toxicity was observed in the HiPQ animals beginning between the fourth and fifth day. Qualitative histopathological examination of the lungs revealed changes typical of paraquat toxicity (e.g., interstitial edema, increase in type II cells) resulting from HiPQ. Significant increases were found in levels of lung glutathione and activities of the GSH peroxidase system enzymes, glucose-6-phosphate dehydrogenase and GSSG reductase. These changes were probably the result of paraquat-induced oxidant stress and increased NADPH requirements. Elevations in lung putrescine, spermidine, and ornithine decarboxylase activity were detected in HiPQ animals only, and reflected the observed lung damage and/or resulting "proliferative" state of the tissue rather than a direct response to paraquat. As in the case of pulmonary oxygen toxicity, the increased levels of lung polyamines may serve to mediate a reparative response to paraquat-induced lung damage. The results demonstrate only a narrow difference between a paraquat dose which produces no apparent lung damage but stimulates components of the GSH peroxidase antioxidant system and one which causes characteristic, paraquat-induced lung damage. The experimental model employed here represents a useful means to study subtle, paraquat-induced biochemical and morphological alterations in lung by avoiding paraquat doses which rapidly produce lung damage or are directly toxic to extrapulmonary tissues.

Dopamine (DA) agonist-induced behavioral supersensitivity in the adult rat has served as the standard model for certain of the motor and behavioral side effects associated with long-term exposure to DA agonists in humans. The mechanisms relating receptor events with behavior mediation, however, remain unclear. The striatum of rats progresses through a prolonged and varied postnatal developmental period. In order to examine the relative contribution of D1 and D2 receptor-mediated mechanisms to behavioral changes which follow chronic dopamine agonist exposure, developing rats were treated daily from birth with a D1 agonist, SKF 38393 hydrochloride (3.0 mg/kg $\times$ 32d, i.p.), or a D2 agonist, LY 171555 hydrochloride (3.0 mg/kg $\times$ 32d, i.p.), and/or 6-OHDA (134 $\mu$g, i.c.v., at 3 d after birth). Following a drug-free interval, behavioral responses to selective DA agonists were evaluated. The results indicate that (1) prolonged LY 171555 treatments in development produced a supersensitive animal model for yawning and eating behaviors. (2) Perioral movements of high frequency could be produced by a very low dose of the DA D2 antagonist spiroperidol in rats treated neonatally with 6-OHDA, thereby providing a useful animal model to study tardive dyskinesia. (3) The "priming" phenomenon described by Breese and co-workers which was thought to be produced by D1 agonists only has been found in this study to be produced by a D2 agonist as well. This model provides a means for studying specific stereotypic behaviors in animals. (4) (3H) SCH 23390 and (3H) spiroperidol binding to striatal tissue was not altered in rats treated in development with specific agonists or antagonists for the D1 and D2 receptors. A neonatal 6-OHDA lesion did not modify binding in any of the agonist- or antagonist-treated groups. In conclusion, DA D1 and D2 agonist treatments during postnatal development are effective means of producing new animal models that are potentially useful for studying clinical disorders in man.

Dopamine (DA) agonist-induced behavioral supersensitivity in the adult rat has served as the standard model for certain of the motor and behavioral side effects associated with long-term exposure to DA agonists in humans. The mechanisms relating receptor events with behavior mediation, however, remain unclear. The striatum of rats progresses through a prolonged and varied postnatal developmental period. In order to examine the relative contribution of D1 and D2 receptor-mediated mechanisms to behavioral changes which follow chronic dopamine agonist exposure, developing rats were treated daily from birth with a D1 agonist, SKF 38393 hydrochloride (3.0 mg/kg $\times$ 32d, i.p.), or a D2 agonist, LY 171555 hydrochloride (3.0 mg/kg $\times$ 32d, i.p.), and/or 6-OHDA (134 $\mu$g, i.c.v., at 3 d after birth). Following a drug-free interval, behavioral responses to selective DA agonists were evaluated. The results indicate that (1) prolonged LY 171555 treatments in development produced a supersensitive animal model for yawning and eating behaviors. (2) Perioral movements of high frequency could be produced by a very low dose of the DA D2 antagonist spiroperidol in rats treated neonatally with 6-OHDA, thereby providing a useful animal model to study tardive dyskinesia. (3) The "priming" phenomenon described by Breese and co-workers which was thought to be produced by D1 agonists only has been found in this study to be produced by a D2 agonist as well. This model provides a means for studying specific stereotypic behaviors in animals. (4) (3H) SCH 23390 and (3H) spiroperidol binding to striatal tissue was not altered in rats treated in development with specific agonists or antagonists for the D1 and D2 receptors. A neonatal 6-OHDA lesion did not modify binding in any of the agonist- or antagonist-treated groups. In conclusion, DA D1 and D2 agonist treatments during postnatal development are effective means of producing new animal models that are potentially useful for studying clinical disorders in man.

Morphine and exogenous opioid peptides alter the development of central noradrenergic neurons damaged by neonatal treatment with the neurotoxin 6-hydroxydopa. Transection of the dorsal noradrenergic bundle (DNB) in neonatal rats produces nearly the same alteration in the developmental pattern. It was of interest to determine whether morphine or an exogenous opioid peptide (metenkephalin) was able to modify the recovery of noradrenergic neurons after neonatal surgical transection of the DNB. Neonatal rats were divided into two groups. Both groups received saline (0.85%) or naloxone (2.0 mg/kg) by the intraperitoneal (i.p.) route. In the first group the animals received an additional i.p. injection of either saline or morphine sulfate (3.33 mg/kg). The second group received an intraventricular injection of either saline, morphine (10 (mu)g/5 (mu)l), or methionine-enkephalin (25 (mu)g/5 (mu)l) ten minutes after the i.p. injection. Half the animals in these groups then received a DNB lesion, made with a blade 3mm (depth) by 5mm (width) at the level of the colliculi. At 6 weeks brains were removed for assay of norepinephrine (NE) content by a fluorometric method, and for determination of the rate of ('3)H-NE uptake, in order to assess noradrenergic fiber number. It was found that in the cerebellum both the ('3)H-NE uptake rate and NE content were significantly elevated by approximately 75% in the animals that received the lesion. The recovery in the anterior cortex (39%) was significantly greater than in the posterior cortex (27%), while recovery in the hippocampus (21%) was the least. This indicates a regional difference in recovery in the more distal projections of the DNB. Within the lesion group, however, there was no alteration in ('3)H-NE uptake rate nor NE content in any of the above regions with any of the drug treatments. Therefore, none of the drug treatments effectively altered the recovery from surgical transection of the DNB. It is suggested that opioids are capable of modifying neurotoxin damage per se, but not capable of modifying regeneration of noradrenergic neurons.