Leakage and sealer penetration in smear-free dentin after a final rinse with 95% ethanol.

Forty extracted maxillary incisors were decoronated, prepared in a crown-down fashion and randomly divided into two groups of 16 roots each. Remaining roots served as controls. Smear layer was removed with 17% EDTA followed by 5.25% NaOCl, the canals in group N were again rinsed with NaOCl before obturation with laterally compacted gutta-percha and Roth's 801 sealer. The roots in group E were rinsed with 95% ethyl alcohol instead of NaOCl for the final rinse. Leakage was determined using a fluid-flow model. Roots were cleared, split, and sealer penetration into the dentinal tubules was measured under light-microscopy. Group E demonstrated significantly greater sealer penetration (p = 0.002) and significantly less leakage (p = 0.040), than group N. Leakage could not be significantly correlated with sealer penetration (p = 0.725). Under the conditions of this study, we found that a final rinse with 95% ethyl alcohol increased sealer penetration and decreased leakage.

Effects of five thermal stressing regimens on the flexural and bond strengths of a hybrid resin composite.

UNLABELLED: Thermocycling is commonly employed in laboratory studies to simulate the in vivo aging of restorative materials. However, there is little consistency in the regimens used, and some researchers have questioned the clinical relevance and, hence, the necessity of including thermal stressing in in vitro protocols. This study examined the effects of five thermal stressing regimens on the flexural and dentin bond strengths of a hybrid resin composite. METHODS: For flexural strength tests, 95 rectangular specimens (15 mm x 2 mm x 2 mm) were fabricated using a stainless steel split mold, then light cured for 60 seconds. For bond strength tests, 75 caries-free molars were flattened occlusally to expose dentin, then polished through 600 grit SiC paper; dentin surfaces were etched, rinsed and blotted dry. A dentin adhesive was applied and light cured for 30 seconds; resin composite was condensed through a stainless steel split mold (4.3 mm diameter x 3.5 mm high), then light cured for 60 seconds. All specimens were stored in deionized water for 24 hours, then stressed for 100 hours according to one of five regimens: 1) cycled between 5 degrees C and 55 degrees C (9000 cycles; 20-second dwell time); 2) held at 5 degrees C constant; 3) held at 22 degrees C constant; 4) held at 55 degrees C constant; 5) held at 5 degrees C for 50 hours, then at 55 degrees C for 50 hours. Flexural strengths were measured using an Instron 5500R and three-point bending apparatus at a crosshead speed of 0.5 mm/minute. Shear bond strengths were measured using an MTS Bionix 200 at a crosshead speed of 0.5 mm/minute. RESULTS: ANOVA revealed no significant differences in either flexural strength or shear bond strength among the five thermal regimens.

Comparison of two different direct digital radiography systems for the ability to detect artificially prepared periapical lesions.

The purpose of this study was to compare Schick CDR and Trophy RVGui direct digital radiography (DDR) systems for the ability to detect periapical lesions in human cadaver mandibles. Digital radiographs were exposed of teeth with normal periapical areas and of teeth with artificially prepared periapical lesions using both DDR systems. Three examiners independently viewed the images at two different time periods and estimated which bony state was present. The resulting data were subjected to statistical analysis using a two-way ANOVA. Interexaminer variability was statistically analyzed using Spearman's rho. There was no significant difference in the level of accuracy between the two different DDR systems at either observation period. There was a statistically significant high level of agreement between examiners (p < 0.01). In conclusion, there was no significant difference in the accuracy of detecting artificially prepared periapical lesions between Schick CDR and Trophy RVGui DDR systems.

Comparison of generated forces and apical microleakage using nickel-titanium and stainless steel finger spreaders in curved canals.

The purpose of this study was to compare (a) forces generated during lateral compaction and (b) apical microleakage for nickel-titanium (NiTi) and stainless steel (SS) finger spreaders. Twenty-eight extracted human teeth were instrumented using a standardized rotary instrumentation technique. NiTi and SS #30 spreaders were used to obturate molar roots while the forces generated during obturation were measured on a Universal testing machine. Apical microleakage was determined using a fluid filtration method. There was no significant difference in microleakage between spreaders. NiTi spreaders produced significantly less force than SS spreaders in all specimens (p < 0.001).

The effects of electrostimulation on parotid saliva flow: a pilot study.

OBJECTIVE: Saliva is a critical fluid necessary for oral health. Medications, radiation therapy, and systemic conditions can decrease salivary function and increase a patient's risk for caries and other oral infections. Palliative management of xerostomia includes wetting agents such as ice chips and saliva substitutes. Systemic agents stimulate salivary flow but often have unfavorable side effects. All have met with limited success. The purpose of this study is to assess the effectiveness of transcutaneous electric nerve stimulation (TENS) as a means of stimulating salivary function in healthy adult subjects. STUDY DESIGN: Twenty-two healthy, adult subjects with no history of salivary gland disorder enrolled in the protocol. The TENS electrode pads were placed externally on the skin overlying the parotid glands. Unstimulated saliva was collected for 5 minutes via the Carlson-Crittenden cup into preweighed vials using standardized collection techniques. The TENS unit was then activated and stimulated saliva collected for an additional 5 minutes. RESULTS: Fifteen of 22 subjects demonstrated increased parotid salivary flow when stimulated via the TENS unit. Five experienced no increase and 2 experienced a decrease. The mean unstimulated salivary flow rate was 0.02418 mL/min (SD 0.03432) and mean stimulated salivary flow rate was 0.04946 mL/min (SD 0.04328). Statistical analysis of flow rates utilizing the paired t test demonstrated the difference to be statistically significant, P < .001. In 7 subjects with 0 baseline flow, 5 continued to have no flow. CONCLUSIONS: The TENS unit was effective in increasing parotid gland salivary flow in two-thirds of healthy adult subjects. A further study in a cohort of patients with salivary gland disorders is warranted.

Comparative study of white and gray mineral trioxide aggregate (MTA) simulating a one- or two-step apical barrier technique.

This study investigated the use of Mineral Trioxide Aggregate (MTA) as an apical barrier by comparing the sealing ability and set hardness of white and gray MTA. Forty-four root segments were prepared to simulate an open apex. Apical barriers of white and gray MTA were placed to a thickness of 2 mm or 5 mm. The samples were obturated immediately (one-step) or after the MTA set for 24 h (two-steps). After placement in methylene blue dye for 48 h, the samples were sectioned for leakage analysis and microhardness testing of the barrier. Gray MTA demonstrated significantly less leakage than white MTA (p < 0.001), and the two-step technique showed significantly less leakage than one-step (p < 0.006). The 5-mm thick barrier was significantly harder than the 2 mm barrier, regardless of the type of MTA or number of steps (p < 0.01). Results suggested that a 5 mm apical barrier of gray MTA, using two-steps, provided the best apical barrier.

Cold testing through full-coverage restorations.

Endodontic diagnosis often requires thermal testing through porcelain fused-to-metal (PFM) and all-ceramic restorations. The purpose of this study was to measure and compare the temperature change during thermal testing by three commonly used methods occurring at the pulp-dentin junction (PDJ) of nonrestored teeth and teeth restored with full coverage restorations made of PFM, all-porcelain, or gold. The methods used to produce a thermal change were (a) an ice stick, (b) 1,1,1,2-tetrafluoroethane (TFE), and (c) carbon dioxide snow. A thermocouple measured temperature changes occurring at the PDJ in 10 extracted premolars when thermal tested by each method over a period of 30 seconds. Temperature reduction was also measured for the same samples restored with full gold crowns, PFM, and Empress crowns. Results showed intact premolars and those restored with PFM or all-ceramic restorations to respond similarly to thermal testing. In these teeth, TFE produced a significantly greater temperature decrease than carbon dioxide snow between 10 and 25 seconds (p < 0.05). In conclusion, application of TFE on a saturated #2 cotton pellet was the most effective method for producing a temperature reduction at the PDJ of intact teeth and those restored with gold, PFM, and all-porcelain when testing for less than 15 seconds.