Aim The aim of the present study was to investigate the effectiveness of one total-etch self-priming adhesive and two one-step self-etching adhesive systems on the adhesion of a resin composite to both dentin and enamel. The effect of thermocycling on the adhesion was also investigated. The null hypothesis tested was thermocycling would not affect bond strengths to enamel and dentin treated with self-etching adhesives or a total-etch adhesive. Methods and Materials Two single-step self-etching adhesives [Xeno III (XE3) and Prompt L-Pop (PP)] and one two-step total-etch adhesive system (Prime & Bond NT) (P&B NT) were used in this study. Thirty cariesfree unrestored human third molars were used to make specimens of enamel and dentin. Different adhesives were applied on enamel and dentin surfaces according to the manufacturer's instructions then hybrid composite restorative material was condensed on the surface using a mold. The bonded specimens were stored in distilled water at 37°C for 24 hours before being tested. Half of the bonded specimens were tested for shear bond strength without thermocycling. The other half of the test specimens were thermocycled using a thermocycling apparatus in water baths held at 5°C and 55°C with a dwell time of one minute each for 10,000 cycles prior to shear testing. The mean shear bond strength before and after thermocycling was calculated, and the results were subjected to two-way analysis of variance (ANOVA) and repeated measure design to show the interaction between different materials and different times. Results The results showed shear bond strength on both enamel and dentin of the total-etch adhesive and the self-etching adhesives decreased after the specimens were subjected to thermocycling. Conclusions The null hypothesis tested “thermocycling would not affect bond strengths treated with selfetching adhesives” was rejected. Furthermore, the study revealed the following: The shear bond strength to both enamel and dentin of the total-etch adhesive and the self-etching adhesives decreased after the specimens were subjected to thermocycling. XE3 achieved the highest bond strength to both enamel and dentin (26.994±1.17 and 25.22±1.26, respectively). XE3 showed even better bonding after thermocycling to enamel and dentin than the total-etching system or PP. Although PP bonded to enamel showed lower shear bond strength value than XE3, it has durable bond strength even after thermocycling. Citation El Araby AM, Talic YF. The Effect of Thermocycling on the Adhesion of Self-etching Adhesives on Dental Enamel and Dentin. J Contemp Dent Pract 2007 February;(8)2:017-024.

Dentin primer is applied as a routine procedure prior to bonding to improve the sealing properties of direct polymerizing resins. Some primers contain acetone or alcohol that may affect the properties of calcium hydroxide liner which is placed as a direct or indirect pulp cap. If calcium hydroxide is softened or smeared over the cavity walls, the bonding will be impaired. Therefore, if this occurs, the cement must be removed, the walls must be cleansed, and the procedure must be repeated with careful application of dentin primer. Objective The purpose of this study was to determine the wear and compressive strength of a calcium hydroxide liner after exposure to different kinds of dentin primers for different periods of time. Methods The calcium hydroxide used in this study was Dycal™. It was mixed according to the manufacturer's instructions and placed in plastic rings of 0.5 mm x 5 mm and allowed to set at 37°C for 15 min under 500 gm load. To determine erosion, the height for each sample before and after application of primers was recorded using a Digital Height Measuring Instrument “Digmar” 817. Compressive strength specimens were also prepared. Results Calcium hydroxide treated with Optibond (alcohol based) or Syntac (acetone based) for 1 min or 5 min had the highest erosion values and the lowest compressive strength values. Gluma CPs (water based primer) had the least effect on calcium hydroxide values. Citation El-Araby A, Al-Jabab A. The Influence of Some Dentin Primers on Calcium Hydroxide Lining Cement. J Contemp Dent Pract 2005 May;(6)2:001-009.

The electrical resistivity measurement to determine a critical temperature (Tc) in a stoichiometric CuAu alloy is discussed on the dependence of the current used. The tempetrature was measured on two ways: With the thermocouple connected to the specimen by spot-welding, and with them separated. In the latter case, the greater the current, the lower the apparent Tc because of the generation of Joule heat. To obtain a more precise Tc, the current should be as small as possible or the thermocouple should be located as close as possible to the specimen. It is highly desirable for the thermocouple and the specimen to be welded together, if the effects of some contamination can be ignored in measuring system.

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