Effect of multiple consecutive adhesive coatings on microleakage of class v cavities.

OBJECTIVES: The purpose of this in vitro study was to evaluate the effect of multiple consecutive adhesive coatings of a one-step self-etch adhesive on microleakage of Class V cavities. METHODS: Standardized box shaped Class V cavities were prepared onto the buccal side of forty five non-carious human premolar teeth. The teeth were randomly divided into three groups of fifteen teeth in each and restored as: Group I- one-step self-etch adhesive resin (Clearfil S3, Kuraray Co. Ltd., Osaka, Japan) was applied according to the manufacturer's instructions, Group II- two consecutive same one-step self-etch adhesive application was performed, and Group III- three consecutive same one-step self-etch adhesive application was performed. After the adhesive applications light curing unit was activated for 20 seconds and the cavities were restored with a composite resin. The restorations were finished with aluminum oxide discs and the specimens were stored in water at room temperature for 24 hours before they were immersed in 2% methylene blue for 48 hours. The dye penetration was examined under a stereomicroscope and the asymtotic significance were analysed with Kruskall Wallis and Mann Whitney U tests and dentin-enamel margins were compared with each other with Wilcoxon Signed Rank test. RESULTS: The microleakage at the dentinal margins of Class V cavities were significantly decreased with two (Group II) and three (Group III) consecutive adhesive applications (P<.05). There was no significant difference between Group I, Group II and Group III at the enamel margins (P<.05). The microleakage at the dentinal margins were significantly higher than the enamel margins in Group I and Group II but in Group III there was no statistically significant difference (P<.05). CONCLUSIONS: Within the limitations of this in vitro study, it may be concluded that three consecutive applications of the one-step self-etch adhesive resin provided better sealing than the one coat of adhesive resin at the dentinal margins of Class V cavities.

Computer-assisted evaluation of microleakage after apical resection with laser and conventional techniques.

The purpose of this in vitro study was to observe the morphological changes and apical dye penetration at apical dentin surfaces after apicoectomy with conventional techniques and laser beam. Sixty single-rooted extracted teeth were selected for the study. The crowns were resected below the cemento-enamel junction. Then, these teeth were treated endodontically and filled with gutta-percha using AH-26 root canal sealer. The teeth were randomly divided into four groups of 15 teeth in each. The roots were resected perpendicular to its long axis 3 mm from the apex using Er: yttrium-aluminium-garnet (YAG) laser irradiation in groups 1 and 2, and the resected root surfaces were lased with Nd:YAG laser in group 2. The apexes were resected by a high-speed handpiece in groups 3 and 4, and the resected root surfaces were lased with Nd:YAG laser in group 4. Ten teeth in each group were used for leakage studies, and the other five teeth were used for scanning electron microscopic examinations. Seven sections were obtained from each root to assess the microleakage, and the sections were analyzed in a computer-assisted manner. No statistically significant differences were observed between the leakage percentage of groups 1 and 3 and groups 2 and 4 (p>0.05). Morphological differences were observed between apical dentin surfaces resected with conventional techniques and laser beam.

Effects of Nd:Yag laser irradiation on osteoblast cell cultures.

The application of Nd:YAG lasers in endodontics has been explored by many investigators for different purposes. The aim of this in vitro study is to evaluate the effects of Nd:YAG laser on osteoblast cell cultures. A 1,064 nm Nd:YAG laser was used to irradiate human osteoblast-like cells (Saos-2) in noncontact mode for 10 s with different energy settings. The settings varied were pulse energy (20-120 mJ), pulse repetition rate (10-30 Hz), and power output (0.2-3.6 W). He-Ne, the aiming beam of Nd:YAG laser, was used in noncontact mode for 10 s. After 7-, 14-, and 21-day incubation period, cell viability and proliferation were evaluated with methylthiazoletetrazolium (MTT) colorometric method. The comparison of average MTT values gave no statistically significant difference between 20 mJ, 10 Hz, He-Ne, and control (p < 0.05). The differences between all other groups were significant (p < 0.05). Increase in the pulse energy, pulse repetition rate, and power output has a negative effect on the cell viability and proliferation.

The effects of water and acetone-based dentin adhesives on apical microleakage.

In this study, the aim was to assess the in vitro apical microleakage of a resin-based sealer used with two different adhesives. Thirty nine freshly extracted maxillary incisors were used. The teeth were decoronated at the cemento-enamel junction with a water-cooled fissure bur. Chemo-mechanical debridement of the root canals was accomplished with the step-back technique. The smear layer was removed by 19% ethylenediamine tetra acetic acid (EDTA). The roots were then divided into three experimental groups of thirteen teeth in each. Specimens in group 1 were filled with gutta-percha, AH Plus sealer, and water-based adhesive system (Syntac Single Component). Group 2 specimens were filled with gutta-percha, AH Plus sealer, and acetone-based dentin adhesive (Prime & Bond NT ). Specimens of group 3 were filled with only gutta-percha and AH Plus sealer (no adhesive was applied). The teeth were immersed into 2% methylene blue solution. Apical sealing qualities were assessed by measuring the linear dye penetration with a stereomicroscope. Dentin tubule penetration was observed under scanning electron microscopy (SEM). Results showed no statistically significant difference between the materials used, however, the leakage in group 2 was less than group 1 and 3.

Assessment of morphological changes and permeability of apical dentin surfaces induced by Nd:Yag laser irradiation through retrograde cavity surfaces.

The purpose of this in vitro study was to observe the morphological changes and apical dye penetration at apical dentin surfaces induced by Nd:YAG laser irradiation at different power settings with and without a laser initiator. Seventy five single rooted human maxillary anterior teeth were used. Following the establishment of the working lengths, the root canals were enlarged with step-back technique. The apex of each root was resected 3 mm perpendicular to its long axis. Standard Class I cavities of 2 mm depth and 2 mm width were prepared. The teeth were randomly divided into five groups with fifteen teeth in each. In Group 1, the retrograde cavity preparations were lased with Nd:YAG laser at 2 W and those in Group 2 preparations were lased with Nd:YAG laser at 3.2 W. In Group 3, the retrograde cavity surfaces were lased with Nd:YAG laser at 2 W following the application of India ink. Group 4 was lased with the same settings of Group 2 after an absorbent cotton point soaked with India ink was inserted into the cut dentinal surfaces and the inner walls of the apical preparations. Group 5 served as control. Five teeth from each group were examined using scanning electron microscopy (SEM). The amounts of smear layer, debris, and recrystalized dentin present were assessed and scored. Retrograde cavities of ten teeth from each group were filled with amalgam to examine apical dye penetration. The teeth were immersed in 2% basic fuscin and kept for 48 hours. Dye penetration was evaluated by stereomicroscope at a magnification of X10. The results showed the usage of India ink with Nd:YAG laser enhanced the amount of melting and recrystalization of dentin and the radiation and initiator increased the leakage.

The accuracy of three different electronic root canal measuring devices: an in vitro evaluation.

The main objective of this in vitro study was to evaluate the effects of the operator's experience level and pre-flaring on the accuracy of the results of three different brands of a new generation of root canal measuring devices, as well as the comparison among them. Extracted human teeth were prepared and then actual length and electronic length measurements were made by three different operators according to a double-blind technique. Three different operators performed electronic measurements on each specimen separately with three different electronic root canal measuring devices using in vitro models. Measurements were repeated by all operators after the pre-flaring. Taking the clinical tolerance of +/- 0.5 mm into account, there was no statistically significant difference between the accuracy of the instruments (P > 0.01). However, the results obtained from the Bingo electronic apex locator in pre-flared canals by the beginner operator were statistically significant (P < 0.01). All of the instruments had a clinically acceptable result at the tolerance of +/- 0.5 mm. If the instruments are used in accordance with the manufacturer's instructions, experience with electronic root canal measurement is not essential. However, the operator has to be more careful when working on pre-flared canals.

The effects of sodium hypochlorite concentrations on the accuracy of an apex locating device.

This study aimed to evaluate Root ZX accuracy with different NaOCl concentrations and to observe effects of the alginate model when NaOCl was used in the canal during electronic measurements. Fifty extracted single-rooted, single-canal human teeth were used in five experimental groups. NaOCl concentrations of 5.25%, 2.65%, 1.00%, and 0.50%, respectively, were injected into the root canals of teeth in four groups and distilled water in control group 5. After measuring root lengths with Root ZX, the files were locked in place. There were no statistically significant differences among all the groups (p > 0.95) when evaluating the distance of the file tips and apical constriction or for the distance from file tip to apical foramen. Root ZX could be used in root canal length measurements with various NaOCl concentrations. Designation of apical constriction needs more care. The alginate model could be used for in vitro electronic measurements with various NaOCl concentrations.