Fluoride release process of (resin-modified) glass-ionomer cements versus (polyacid-modified) composite resins.

The fluoride release of conventional and resin-modified glass-ionomers is reviewed and compared to that of fluoride-releasing (polyacid-modified) composite resins. Each formulation displays a typical fluoride release profile. The cumulative amount of fluoride released is described by [F]c = [F](I)t/(t + t1/2) + beta square root t for glass ionomers whether resin-modified or not, whereas for composite resins this quantity is given by [F]c = [F](I)t/(t + t1/2) + alpha t. Both equations indicate that two kinetic processes are responsible for the fluoride release profiles. The kinetic parameters [F](I), t1/2, beta and alpha depend on the formulation. On the basis of the exchange characteristics for fluoride, an attempt is made to explain the mechanisms responsible for these fluoride release processes.

Long-term fluoride release of some orthodontic bonding resins: a laboratory study.

OBJECTIVES: The present study compared the amounts and profiles of long term fluoride release from four commercial direct bonding resins (Light-Bond, Reliance Orthodontic Products; Rely.a. Bond, Reliance Orthodontic Products; Orthon, Orthon Dental Inc.; Fluor Ever, Macro-Chem Corporation) and one glass ionomer cement (Ketac-Cem, Espe). METHODS: The specimens were equilibrated in double-deionized water at 37 degrees C. At predetermined intervals, and up to 560 days, the fluoride concentration of the equilibrated solution was determined with a fluoride ion selective electrode. For Light-Bond and Rely.a. Bond two batches were studied and the amount of fluoride released in a 0.1 mol/L NaCl solution was also determined. Differences in the fluoride release profiles due to batch, type of solution and time were determined with a three-factor mixed design ANOVA with repeated measures on one factor. RESULTS: The fluoride release profiles of the orthodontic adhesives studied differ markedly. Initially, Fluor Ever and Ketac-Cem release comparable amounts of fluoride which are greater than those released by Orthon. After a few weeks the amounts of fluoride released by Ketac-Cem and Orthon become comparable, but are considerably higher than those released by Fluor Ever. During the first days of the elution, the amount of fluoride released by Light-Bond equals that of Orthon, but then decreases below the determination limit of the analytical method within half a year. No difference was found between the fluoride release profiles in water and the NaCl solution. However, the fluoride release profiles apparently depend on the batch. For Rely.a. Bond, the amount of fluoride released is smaller than the detection limit for the fluoride analysis. SIGNIFICANCE: The fluoride release of the orthodontic adhesives investigated markedly depends on the mechanisms responsible for the fluoride release process.

Effect of electric toothbrushes versus manual toothbrushes on removal of plaque and periodontal status during orthodontic treatment.

This study compared the effectiveness of three different types of electric toothbrushes, i.e., Interplak, Philips, and Rotadent, with a manual multitufted toothbrush (Blend-a-Med), in removing supragingival plaque and in preventing the development of gingivitis in adolescent patients with fixed orthodontic appliances. A single blind, cross-over, clinical trial was carried out in 36 adolescent patients, randomly divided into four equal groups. Every group tested each type of toothbrush, in a different sequence. Plaque and gingival scores were recorded at baseline and after 1 and 2 months of the test period. All patients received a professional prophylaxis after each clinical evaluation, except during the test period. The analysis of the data was performed with the nonparametric Friedman test. The results demonstrated, in essence, for all parameters that the manual toothbrush was the most effective. Of the three electric toothbrushes tested, the Philips toothbrush seemed to give slightly better results than the Interplak toothbrush, whereas Rotadent very clearly gave results inferior to all others. Personal preference on the four toothbrushes used revealed that the group as a whole least preferred a manual brush. However, the answers on the questionnaire did not always show a logical consistency. Therefore it should be interpreted with some caution.

A clinical trial comparing the failure rates of two orthodontic bonding systems.

A clinical trial was carried out to compare the failure rates of a visible light-cured fluoride-releasing material with a chemically cured adhesive. Fifty patients were used for the trial and 762 brackets were bonded in a split-mouth experimental design. Bracket failures were reported over the full period of orthodontic treatment. Statistical data analysis was carried out by means of chi 2 tests. The results of this study indicate that brackets, bonded with a chemically cured material (Lee Insta-bond, Lee Pharmaceuticals, EI Monte, Calif.), showed significantly fewer failures than brackets bonded with the light-cured material (Orthon, Orthon Dental Inc., Victoria, Canada). When the site of bond failure was evaluated in an overall manner, there were significantly more lower than upper, and more posterior than anterior bond failures.

A clinical evaluation of the effectiveness of a fluoride-releasing visible light-activated bonding system to reduce demineralization around orthodontic brackets.

The presence of decalcification (white spots) after the removal of orthodontic appliances still remains a problem. A method to deliver fluoride to the area beneath and around the bonded attachments, independent of patient compliance, could be very helpful. Therefore special attention is being currently directed to the so-called "fluoride releasing bonding adhesives." A clinical trial was carried out to compare the effect of a visible light-cured fluoride-releasing (F-releasing) material with a chemically cured nonfluoride resin on white spot formation during fixed orthodontic therapy. Fifty patients entered the trial, and 762 brackets were bonded in a crossover design. Intraoral slides were taken before and after treatment and were evaluated for white spot formation. Statistical data analysis was carried out by means of a chi-square test. The results of this clinical study indicate that there was no significant difference between the decalcification rates for both types of adhesives. When the appearance of white spots was evaluated in an overall manner, there was significantly more upper than lower decalcification.

Comparative shear bond strength of some orthodontic bonding resins to enamel.

The aim of this study was to compare the in vitro bond strength, to bovine enamel measured in shear, of the orthodontic adhesives Lee Insta-bond (LiB), Rely-a-Bond (RaB), Right-on (Ro), Concise precoating method (Cc), Concise mixed method (CaB), Super-C (Sc), and Orthon (Or), and of the glass ionomer cement Ketac-Cem (KC). The fracture surfaces after debonding were also examined in order to determine the sites of failure. The results indicate that there is a significant difference between the shear bond strength obtained with the different adhesives so that the mean shear bond strength decreases in the order [Ro approximately Cab approximately Sc] > [LiB approximately RaB approximately Cc] > Or > KC. Moreover, for Cab and Sc it was found that the shear bond strength varies depending on the location on the bovine tooth. The failure site was essentially at the resin-bracket interface, except for Concise, where only 50 per cent of the cases failed at the resin-bracket interface.