It is important to evaluate the inhibitory effect on lesion progression of CPP-ACP when delivered in a mousse vehicle, commercially known as MI Paste, and compare it to actual remineralization products already established. SUMMARYThis in-vitro study evaluated the inhibition of demineralization in enamel sections produced by MI paste, fluoride and a combination of both, compared to artificial saliva and NaF 5000 ppm in a caries progression pH-cycling model. Twenty-one teeth were demineralized to create subsurface enamel lesions (approximately 200 microns in depth). The teeth were sectioned and characterized using polarized-light-microscopy (PLM). A single section from each lesion was assigned to a treatment group: Artificial saliva, NaF 5000 ppm (Prevident, Colgate), MI paste (Recaldent, GC America Inc), NaF 1100 ppm (Crest, Procter & Gamble) and NaF 1100 ppm plus MI paste. The sec- tions were covered with varnish except for an exposed window on the external surface of the lesion and placed in a six-day pH-cycling model with two daily treatment applications of two minutes each. The sections were characterized by PLM, and the lesion areas were measured using a digital image analysis system. Based on a pairedsample t-test, significant differences (p<.05) in percentage of change in lesion size were found between the high fluoride group and all the other groups. No significant difference was found between the artificial saliva and MI paste group, neither was there any significant difference between the NaF 1100 ppm, the combined application group or the MI paste group alone. In conclusion, the higher concentration of NaF (5000 ppm) reduced lesion progression to the greatest extent. The MI paste group did not show any effect on the inhibition of lesion progression. Further studies on the preventive effect and longer treatment applications are recommended.

Written and clinical tests compared the change in clinical knowledge and practical clinical skill of irst-year dental students watching a clinical video recording of the three-step etch-and-rinse resin bonding system to those using an interactive dental video game teaching the same procedure. The research design was a randomized controlled trial with eighty irst-year dental students enrolled in the preclinical operative dentistry course. Students' change in knowledge was measured through written examination using a pre-test and a post-test, as well as clinical tests in the form of a benchtop shear bond strength test. There was no statistically signiicant difference between teaching methods in regards to change in either knowledge or clinical skills, with one minor exception relating to the wetness of dentin following etching. Students expressed their preference for an interactive self-paced method of teaching.

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Bleaching with 35 percent hydrogen peroxide causes enamel surface changes, which result in lower bond strengths of composite resin. Although a previous SEM study showed that home bleaching with 10 percent carbamide peroxide does not cause such surface changes, the results of our study indicate that carbamide peroxide bleaching reduces the shear bond strength of composite to etched enamel. Removal of surface enamel, however, restores bond strengths to normal levels.

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