Effect of Er:YAG and Nd:YAG lasers on the mineral content of root canal dentin.

The aim of this study was to assess the effect of two different laser systems on the mineral content of root canal dentin. Thirty-six single canal-extracted mandibular premolars were used in this study. The teeth were randomly divided into two groups of 18 teeth each and prepared with a master apical file #50. Dentin chips were obtained by Gates-Glidden burs and saved in Eppendorf tubes to serve as a control. Then, root canals were treated with a erbium:yttrium-aluminum-garnet or neodymium:yttrium-aluminum-garnet laser. Dentin chips were again obtained using Gates-Glidden. The levels of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), and potassium (K) in each specimen were measured by inductively coupled plasma-atomic emission spectrometry. Data were statistically analyzed by a Mann-Whitney U test. The changes in Ca, P, Mg, Ca, and K levels and the Ca/P ratio after laser irradiations were minimal and statistically not significant (p > 0.05). It was determined that the laser systems used in this study did not affect the mineral content of root canal dentin.

The evalution of the effects of different irrigating solutions and laser systems on adhesion of resin-based root canal sealers.

OBJECTIVE AND BACKGROUND DATA: The purpose of this study was to evaluate the effects of different laser systems and different irrigating solutions on the adhesion of AH Plus and EndoREZ root canal sealers to human root canal dentin. Laser irradiation can be used to obtain morphological changes in dentin walls that could influence the adhesion values of endodontic sealers. METHODS: One hundred canine root canals were cleaned and shaped. The specimens were assigned to four groups (n=24). In group I 5% NaOCl (control), in group II 15% ethylenediaminetetraacetic acid (EDTA) followed by 5% NaOCl, in group III Er:YAG laser with 2940 nm wavelength, and in group IV Nd:YAG laser with 1064 nm were used as a final procedure in root canals. In each group, half of the specimens were filled with AH Plus sealer and half with EndoREZ with gutta-percha, using cold lateral compaction. Specimens were sectioned to obtain three slices from each third using a precission saw. The first slice of 1 mm thick dentin disks from each third was subjected to the pushout test (MPa). Results were analyzed by analysis of variance (ANOVA) and Tukey's test (p<0.05). RESULTS: A statistically significant difference (p<0.05) was reported between dentin surface treatments (Er:YAG and control groups). Control (1.60±0.99), EDTA (2.05±1.35), Er:YAG (2.25±1.64), and Nd:YAG (2.13±1.38). AH Plus adhesion values were increased significantly (p<0.05) when the root canal was irradiated with the Er:YAG laser. Nd:YAG laser irradiation increased EndoREZ adhesion values significantly when compared with Er:YAG laser irradiation (p<0.05). In the apical and coronal thirds, AH Plus showed better adhesion than did EndoREZ sealer (p<0.005). In the middle third, there was no statistical difference between AH Plus and EndoREZ. CONCLUSIONS: The use of EDTA and different laser systems influenced the bond strength of resin-based root canal sealers.

Fracture resistance of roots filled with three different obturation techniques.

OBJECTIVES: The aim of this study was to compare in vitro root fracture resistance following root canal filling with AH 26 using lateral condensation, BeeFill, and Thermafil techniques. STUDY DESIGN: Eighty extracted human mandibular premolars with similar dimensions were selected. In order to standardize the roots, measurements were taken in two separate regions of the teeth--at the cemento-enamel junction and 8 mm apically from the junction--buccolingual as well as mesiodistal for every tooth. Teeth were then randomly divided into five groups (n=16). With the exception of the non-prepared group (Group 1), instrumentation was done in all groups. In group 2, instrumentation but no filling was performed; in group 3, the obturation was done with AH 26 + gutta-percha; in group 4, with AH 26 + BeeFill and in group 5, AH 26 + a Thermafil obturator was used. All the roots were mounted vertically in copper rings and filled with acrylic resin, exposing 8 mm of the coronal part. A universal testing machine was used for the strength test. RESULTS: The results were analyzed using the one-way ANOVA test. The significance between the groups was tested with Temhane's T2 test. The results indicate that instrumentation of root canals had a significant effect on fracture resistance (p<0.05). In addition, there were no differences between the root canal obturation techniques; furthermore, these techniques did not create a statistically important resistance to vertical fracture (p>0.05). CONCLUSIONS: The results suggest that instrumentation of root canals significantly weakens the tooth structure to fracture and the root canal obturation techniques that are used are not able to form reinforcement.

Dissolution of root canal sealers in EDTA and NaOCl solutions.

BACKGROUND: Solutions of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) have been used as canal irrigants in endodontic treatment. The authors conducted a study to compare the ability of these solutions to dissolve sealers. METHODS: The authors assessed the solubility of six sealers-calcium hydroxide, polyketone, zinc oxide-eugenol, silicone and two epoxy resins-in EDTA and two concentrations of NaOCl (2.5 percent and 5.0 percent). They immersed standardized samples (n = 5) of each sealer for two minutes and 10 minutes. They obtained the mean values of sealer dissolution in solutions by calculating the difference between the original preimmersion and postimmersion weights to determine the amount of sealer removed. They compared the values via factorial analysis of variance. They analyzed differences between the six sealers with respect to their solubility in EDTA or NaOCl solutions at two minutes and 10 minutes by using a one-way analysis of variance (P < .05). RESULTS: In comparison with NaOCl solutions, EDTA was markedly superior in dissolving root canal sealers (P < .05). There were no significant differences between the two concentrations of NaOCl. The two epoxy resins and the silicone-based sealer were of low solubility. The zinc oxide-eugenol-based sealer was significantly more soluble than were the epoxy resins and the silicone-based sealers. Polyketone and calcium hydroxide-based sealers were the most soluble sealers (P < .05). CONCLUSIONS AND CLINICAL IMPLICATIONS: The results of this study indicate that during nonsurgical endodontic re-treatment, EDTA and NaOCl solutions used for removing smear layer aided in the retreatment by dissolving some root canal sealers.

Nitric oxide levels in serum of patients with symptomatic irreversible pulpitis.

Nitric oxide (NO) affects both pain and inflammation in human tissues. Pharmacotherapy that decreases NO concentrations may have utility in treating inflammatory painful conditions. To determine the types of disorders in which such an approach should be studied, changes in NO serum levels before and after the painful inflammatory condition resolves would be helpful. This study compared the pre-treatment and post-treatment serum nitric oxide (NO) concentrations in irreversible pulpitis (inflammatory toothache). Thirty-two patients (16 males, 16 females) with irreversible pulpitis were included in this study. Before treatment, patients had severe symptoms of inflammation, but at the end of treatment no symptoms of inflammation were observed. NO concentrations were measured in serum of patients with irreversible pulpitis, before and after treatment. Differences in serum NO concentrations were not statistically significantly different before and after treatment.