Benzodiazepine receptor mediation of behavioral effects of nitrous oxide in mice.

Nitrous oxide produces behavioral effects, the underlying mechanism of which is not known. In the mouse staircase test, exposure to nitrous oxide caused a reduction in rearing activity, an effect similar to that produced by benzodiazepines in this paradigm, when its opioid action on locomotion is blocked by naloxone. In this study, we tested whether effects of nitrous oxide might be mediated by benzodiazepine receptors, using chlordiazepoxide as a control. The abilities of nitrous oxide and chlordiazepoxide to reduce rearing were significantly attenuated in mice pretreated with the benzodiazepine receptor blocker flumazenil or rendered tolerant to benzodiazepines. These findings suggest an involvement of benzodiazepine receptors in mediation of certain behavioral effects of nitrous oxide.

Strain-dependent variability in nitrous oxide withdrawal seizure frequency.

Exposure to nitrous oxide produces handling induced convulsions following withdrawal in mice. Since strain differences in responsiveness to the antinociceptive potency of N2O have been found, we examined whether there were differences in susceptibility to N2O withdrawal seizures. Significant differences were found between mouse strains, varying between 100% and 0% of mice exhibiting withdrawal seizures. There was a lack of correlation between the sensitivity of the mouse strains to N2O-induced analgesia and N2O withdrawal seizures, suggesting different mechanisms of action.

Management of the nonerupted maxillary anterior tooth.

The noneruption of maxillary anterior teeth, particularly the canine, is a common problem. The cause of the noneruption is multifactorial but almost always involves a lack of space. The literature presents an active and a passive form of orthodontic treatment and has recently stressed the periodontal management of these teeth. Two cases are presented. In both cases the orthodontic techniques of regaining space and providing traction on the unerupted tooth are described. A free gingival graft is used in one case and an apically repositioned flap in the other to achieve a healthy periodontium. The advantages and disadvantages of the techniques used as well as their rationale are discussed.

Odontodysplasia.

Results of a comprehensive dental examination, including a histologic evaluation, of a patient showing unilateral odontodysplasia revealed no hint as to the origin of the abnormality. A complete medical examination also resulted in negative findings, with the excetion of congenital bilateral talipes equinovarus. The genetic history was negative, and results of chromosomal studies of the child and her mother revealed no abnormalities. Neither had an anatomic or a functional abnormality, with the exception of the odontodysplasia in the child. Results of laboratory studies including complete blood counts, urinalyses, ferric chloride tests of the urine, and electrolyte tests also were negative. The special considerations given in this case in an attempt to establish a possible causation of the abnormality were inconclusive. We think, however, that the management of the patient was successful in regard to the prosthetic appliance, and every attempt will be made to follow up the patient to ensure a good prognosis of the remaining developing dentition.

Relationship between formocresol pulpotomies on primary teeth and enamel defects on their permanent successors.

Twenty-five permanent premolars were evaluated for enamel defects. The primary molars that they succeeded had been successfully treated with a formocresol pulpotomy. A relationship between the enamel defects and the pulpotomy procedures has been found.

Rechargeability of fluoride releasing pit and fissure sealants and restorative resin composites.

PURPOSE: To evaluate the effect of exposure of 1.23% acidulated phosphate fluoride gel on fluoride release from fluoride releasing pit and fissure sealants and restorative resin composites. MATERIALS AND METHODS: Specimens of four fluoride releasing pit and fissure sealants (Helioseal F, Ultraseal XT, Seal Rite-Low Viscosity and Seal Rite-Regular Viscosity) and two fluoride releasing restorative resin composites (Tetric and Heliomolar Radiopaque) were prepared using a Teflon mold. The specimens were divided into two groups. The experimental group was exposed to 1.23% acidulated phosphate fluoride gel and the control group was exposed to 1.23% acidulated phosphate gel without fluoride. The specimens were stored in deionized water and the fluoride concentration of the solution was measured every 24 hours. On day 7, the discs were exposed to the respective gel for 4 minutes and then rinsed in a continuous stream of deionized water for 30 seconds. The fluoride concentration was then measured for another 7 days. RESULTS: There was a significant increase after the fluoride gel treatment in the amount of fluoride released from all of the materials studied. When the cumulative amount of fluoride released was evaluated, Tetric, Heliomolar radiopaque, Helioseal F, and Ultraseal XT released significantly (P < 0.01) more fluoride than the respective control groups. There was no significant difference between groups from day 8 to day 14 for Seal Rite-Regular Viscosity and Seal Rite-Low Viscosity.

Combination effects of chloral hydrate and nitrous oxide/oxygen in the mouse staircase test.

The effects of chloral hydrate and/or nitrous oxide were assessed in the mouse staircase test. In this paradigm, the number of steps ascended is thought to reflect locomotor activity, whereas the number of rears is an index of anxiety. Chloral hydrate alone produced a dose-dependent decrease in the number of rears but no change in the number of steps ascended except at the highest dose. Nitrous oxide alone produced a concentration-related increase in the number of steps ascended but no change in rearing. When the two drugs were combined, nitrous oxide appeared to potentiate the rearing suppressant activity of chloral hydrate. Analysis of our experimental findings suggests that chloral hydrate exerts a specific anxiolytic drug effect that can be potentiated by concurrent treatment with nitrous oxide.

Interaction between nitrous oxide and diazepam in the mouse staircase test.

The interaction between nitrous oxide and diazepam was assessed in the mouse staircase test. In this paradigm, the numbers of rears (NR) (simultaneous standing on hindlegs and sniffing the air) and steps ascended (NSA) reflect anxiety and locomotor activity, respectively. Antianxiety drugs characteristically reduce NR but not NSA, while sedative drugs reduce both NR and NSA in generally parallel fashion. In this study, increasing concentrations of nitrous oxide alone produced progressively greater and statistically significant increases in NSA. Nitrous oxide alone had no significant effect on NR until, at a concentration of 75%, it decreased NR. Diazepam alone decreased NR equally and significantly at all doses. With certain combinations of concentration and dose, nitrous oxide enhanced the effect of diazepam on NR without altering NSA. These findings suggest that nitrous oxide can increase the antianxiety effect of diazepam without increasing its sedative effect in the mouse staircase paradigm.

A psychological rationale for the use of nitrous oxide psychosedation for children.

N2O is, perhaps, the best adjunct, available today, in the management of emotional factors which influence problem behavior. It is not panacea, however, and should be used only in conjunction with sound psychological methods. The use of N2O must not be thought of as a method by which dentists can elude their responsibility to deal logically with the fears and anxieties of the patient. The fears and anxieties are frequently the result of rational mental functions flowing logically from the individual's previous dental history and learning experience. Viewed thusly, patients can be assisted to overcome the problems at a logical level, and N2O or other sedatives may be mere tools to assist the patient in overcoming the emotional elements of the situation. The real worth of N2O can only be evaluated intelligently by those who learn to "demand and to expect rational explanation in addition to empirical discovery".

Modification of an infant incubator for exposure of experimental animals to nitrous oxide.

Research with N2O is hampered because it is a gas and must be inhaled by the test subject rather than injected. Described herein is the development of a practical and efficient exposure chamber for such research. A Model C-35 Isolette infant incubator was modified by installation of a manifold system for distribution and opposed-suction fans for a circulation of the gas mixture (N2O in oxygen). An exponential model was developed, predicated on gas concentration uniformity, to track the increasing concentration of N2O during chamber filling and to predict the time required for the chamber to assume a steady-state level of N2O. This model requires that three things be known: the volumetric flow rate of administered gas mixture, the concentration of N2O in that mixture, and the volume of the chamber. The model predicts that X(t)/X infinity = 1 - exp(-t/tau), where X(t) is the concentration of N2O of an instant t; X infinity, the concentration of N2O administered; and tau, the time constant--the ratio of chamber volume to volumetric flow rate. This model was confirmed via mass spectroscopy analysis of gas from the chamber during filling.

Hand-over-mouth behavior management technique in a solo pedodontic practice: a study.

The hand-over-the-mouth technique (HOM) was studied in a single-dentist pedodontic practice. The study included the frequency of its use relative to the patient's age, sex, previous dental experience and history of a significant medical experience. Observations were also made of the nature of subsequent appointments. HOM was used for almost 10 percent of the patients studied in less than 2 percent of the total number of dental appointments. It was used most often for three-year-old patients, especially female. In the majority of cases (89 percent), it was used on a single occasion and that incident was followed by appointments of a positive nature.

Sealant status and factors associated with sealant presence among children in Milwaukee, WI.

To determine the percent of school-children aged 6-14 years with sealants placed in their permanent molars in the City of Milwaukee. 2) To describe factors associated with sealant presence among these children. 3) To describe differences, if any, among ethnic majority and minority groups. Twelve public schools agreed to participate in this project. After consent forms were obtained, 1,234 dental exams were performed. A 15-item pretested questionnaire was given to each child to take home for the parent(s) to complete. Response rate was 60 percent (N = 742). Data were analyzed using frequencies and Chi-Square tests (P-value < 0.05). Only 9.6 percent of the sample had sealants on their permanent molars. Variables that were found associated with children more likely to have sealants included: gender (female children more likely than males); children with a recent dental exam; children having a regular dentist; parents having heard about sealants before this study; parents' correct knowledge regarding the purpose of sealants; higher level of parents' education; higher parents' total annual income; ethnicity (Caucasian children more likely than Hispanic, African American, American Indian, or Asian children); and age (children in the older group, 10-14 years, more likely than children in the younger group, 6-9 years). Percent of school-children with sealants on their permanent molars in the city of Milwaukee is low. Efforts are needed to increase the knowledge of sealants by the general public as well as to promote sealant use by dentists in both private practice and public health programs, especially for minority children.

Effects of appliance size, arch wire diameter, and alloy composition on the in vitro force delivery of the quad-helix appliance.

The quad-helix appliance is a fixed lingual arch wire appliance that produces slow maxillary expansion for the treatment of maxillary constriction or crossbite in the primary and mixed dentitions. Despite considerable success in the clinical treatment of patients, there is little quantitative information about the force delivery of this appliance. The purpose of this investigation was to characterize the in vitro force delivery of the quad-helix appliance. Appliances of four sizes were fabricated from Elgiloy blue and stainless steel wires with diameters of 0.032, 0.036, and 0.038 inch. The force delivery in grams for 8-mm activation was determined from the force-extension characteristics using an Instron mechanical testing machine. The results show that the force delivery of the quad-helix appliance is affected significantly by changes in the appliance size and arch wire diameter, but is independent of alloy type (stainless steel or Elgiloy blue). The quantitative results from this investigation should provide worthwhile information for clinical appliance selection and treatment of patients with varying arch dimensions.