Effects of pH on the microhardness of resin-based restorative materials.

This study determined the effect of pH on the microhardness of commonly used resin-based restorative materials which included a resin composite (Esthet-X, Dentsply), a new generation compomer (Dyract Extra, Dentsply) and a giomer (Beautifil, Shofu). Fifty-four specimens (3-mm wide x 3-mm long x 2-mm deep) were made for each material. The specimens were divided into six equal groups and conditioned in the following solutions at 37 degrees C for one week: 0.3% citric acid at pH 2.5, sodium hydroxide-buffered citric acid at pH 3, 4, 5, 6 and 7. After conditioning, the specimens were subjected to hardness testing using a digital microhardness tester (load 500gf; dwell time 15 seconds). Data was analyzed using one-way ANOVA and Scheffe's test at a significance level of 0.05. The effects of pH on the microhardness of resin-based restoratives were material dependent. The compomer and giomer materials were more affected by acids of low pH than the composite material that was evaluated.

Effects of pH on the surface texture of glass ionomer based/containing restorative materials.

This study determined the effect of pH on the surface texture of commonly used posterior glass-ionomer based/containing restorative materials. The materials evaluated included a compomer (Dyract AP), a giomer (Beautifil) and two highly viscous glass ionomer cements (Fuji IX and Ketac Molar). A resin composite (Esthet-X) was used for comparison. Forty-two specimens (3-mm wide x 3-mm long x 2-mm deep) were made for each material. The specimens were divided into six groups and conditioned in the following solutions at 37 degrees C for one week: Citric acid (pH 2, 3, 4, 5 and 6) and distilled water (pH 7). After conditioning, the surface roughness (Ra, microm) of each specimen was measured using a surface profilometer (Surftest, Mitutoyo Corp, Tokyo, Japan). Data was analyzed using one-way ANOVA and Scheffe's test at a significance level of 0.05. The effects of pH on the surface texture of glass-ionomer based/containing restoratives were material dependent. Ra values ranged from 0.02 microm to 0.15 microm and 0.03 microm to 4.40 microm for pH 7 and 2, respectively. With the exception of the composite, the surface roughness of all materials evaluated was significantly affected by acids of low pH. The surface texture of highly viscous glass ionomer cements deteriorated significantly when conditioned in solutions of low pH, which makes them more susceptible to clinical failure.

Informed consent: optimism versus reality.

OBJECTIVE: To determine whether parents of children attending the outpatient general anaesthesia (OPGA) session at the Eastman Dental Hospital, London fully understand the proposed treatment. DESIGN: Observational study supported by structured questionnaires and interviews. SETTING: Casualty service in the Department of Paediatric Dentistry and the Victor Goldman Unit (a day-stay general anaesthetic unit) of the Eastman Dental Hospital. MAIN OUTCOME MEASURES: The parents' understanding of the consent was assessed based on their knowledge of the actual treatment procedure, the type of anaesthesia to be used and the number and type of teeth that would be extracted. RESULTS: Fifty-two of the 70 subjects (74%) approached completed both parts of the survey (interviews one and two). Results showed that 40% of the written consent obtained from the parents were not valid. The subjects' knowledge of the proposed treatment improved on the day of the actual treatment although 19% of them still did not fully understand the procedure. There was a statistically significant increase in the proportion of valid consent on the day of the actual treatment. Many of the subjects had no knowledge of the type of anaesthesia that would be used for their children but were more aware of the number and type of teeth that were going to be extracted. The time interval between the consent process and the actual treatment did not have any significant effect on the subjects' understanding of the consent, but it implied that with time the subjects' knowledge improved. CONCLUSION: A proportion of subjects did not fully understand the proposed treatment procedure even after being adequately informed. Appropriate measures should be taken to ensure that the patients or their guardians truly understand the proposed treatment.