IN VITRO INCIDENCE of ROOT CANAL BIFURCATION IN MANDIBULAR INCISORS BY RADIOVISIOGRAPHY

Objective: The aim of this study was to verify, in vivo and in vitro, the prevalence of root canal bifurcation in mandibular incisors by digital radiography. Material and Methods: Four hundred teeth were analyzed for the in vivo study. Digital radiographs were taken in an orthoradial direction from the mandibular incisor and canine regions. The digital radiographs of the canine region allowed visualizing the incisors in a distoradial direction using 20 degrees deviation. All individuals agreed to participate by signing an informed consent form. The in vitro study was conducted on 200 mandibular incisors positioned on a model, simulating the mandibular dental arch. Digital radiographs were taken from the mandibular incisors in both buccolingual and mesiodistal directions. Results: The digital radiography showed presence of bifurcation in 20% of teeth evaluated in vitro in the mesiodistal direction. In the buccolingual direction, 17.5% of teeth evaluated in vivo and 15% evaluated in vitro presented bifurcation or characteristics indicating bifurcation. Conclusions: Digital radiography associated with X-ray beam distally allowed detection of a larger number of cases of bifurcated root canals or characteristics of bifurcation.

Action of propolis and medications against Escherichia coli and endotoxin in root canals

This study evaluated the action of propolis and intracanal medications against Escherichia coli and endotoxin. Forty-eight dental roots were contaminated with E. coli. The root canals were instrumented with propolis and divided into groups according to the type of intracanal medication: Ca(OH)(2), polymyxin B, or Ca(OH)(2) + 2% chlorhexidine gel. In the control group, saline solution was used without application of intracanal medication. Counts of colony-forming units were carried out and the endotoxin was quantified by the chromogenic Limulus amobocyte lysate assay. The results were evaluated by analysis of variance and the Dunn test (5%). Root canal irrigation with propolis was effective to completely eliminate E. coli and reduce the amount of endotoxins. All intracanal medications contributed to the significant decrease in endotoxins. Only intracanal medications may reduce the amount of endotoxins in the root canals. The greatest efficacy was observed for medications containing Ca(OH)(2). (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:e70-e74)

Peroxide penetration from the pulp chamber to the external root surface after internal bleaching

Purpose: To quantify the amount of peroxide penetration from the pulp chamber to the external surface of teeth during the walking bleaching technique. Methods: Seventy-two bovine lateral incisors were randomly divided over five experimental groups and one control (n = 12 per group): (1) 35% hydrogen peroxide (HP); (2) 35% carbamide peroxide (CP); (3) sodium perborate (SP); (4) (HP+SP); (5) (CP+SP) and (6) Control (CG), deionized water. All groups were treated according to the walking bleach technique. After 7 days at 37 degrees C in an acetate buffer solution, 100 mu l violet leukocrystal coloring and 50 mu l peroxidase was added, producing a blue stain that could be measured in a spectrophotometer and then converted into peroxide mu g/ml. Results: G5 exhibited the greatest penetration, while G2 and G3 produced the lowest values. All bleaching agents penetrated from the pulp chamber to the external root surface. There was a direct correlation between the presence of oxidative agents and penetration potential. Sodium perborate in distilled water was less oxidative and appeared to be the least aggressive bleaching agent. (Am J Dent 2010;23:171-174).

Effects of mechanical cycling on the bonding of zirconia and fiber posts to human root dentin

Purpose: To evaluate the effect of cyclical mechanical loading on the bond strength of a fiber and a zirconia post bonded to root dentin.Materials and Methods: Forty single-rooted human teeth (maxillary incisors and canines) were sectioned, and the root canals were prepared at 12 mm. Twenty randomly seleced specimens received a quartz fiber post (FRC) (D.T. Light-Post) and 20 others received a zirconia post (ZR) (Cosmopost). The posts were resin luted (All Bond 2 + resin cement Duo-link) and each specimen was embedded in epoxy resin inside a PVC cylinder. Ten specimens with FRC post and 10 specimens with ZR post were submitted to fatigue testing (2,000,000 cycles; load: 50 N; angle of 45 degrees; frequency: 8 Hz), while the other 20 specimens were not fatigued. Thus, 4 groups were formed: G1: FRC+O cycles; G2: FRC+2,000,000 cycles; G3: ZR+O cycles; G4: ZR+2,000,000 cycles. Later, the specimens were cut perpendicular to their long axis to form 2-mm-thick disk-shaped samples (4 sections/specimen), which were submitted to the push-out test (1 mm/min). The mean bond strength values (MPa) were calculated for each tooth (n = 10) and data were submitted to statistical analysis (alpha = 0.05).Results: Two-way ANOVA revealed that the bond strength was significantly affected by mechanical cycling (p = 0.0014) and root post (p = 0.0325). The interaction was also statistically significant (p = 0.0010). Tukey's test showed that the mechanical cycling did not affect the bonding of FRC to root dentin, while fatigue impaired the bonding of zirconium to root dentin.Conclusion: (1) the bond strength of the FRC post to root dentin was not reduced after fatigue testing, whereas the bonding of the zirconia post was significantly affected by the fatigue. (2) Cyclical mechanical loading appears to damage the bond strength of the rigid post only.

The Disk-Specimen Thickness Does Not Influence the Push-Out Bond Strength Results Between Fiber Post and Root Dentin

This study evaluated the effect of different thickness of disk-shaped specimens on the push-out bond strength test. Eighteen lower bovine teeth were sectioned (20mm) and prepared (15mm) with the same post system drill (Light Post (R) #1, Schaumburg, IL, Bisco, USA). The apical third of each specimen was embedded in a plastic matrix filled with an acrylic resin (Dencrilay (TM), Dencril, São Paulo, Brazil). The posts were cleaned with alcohol, silanated (ProSil (R), FGM, Joenville, SC, Brazil) and cemented with the RelyX (TM) U100 (3M ESPE, St. Paul, MN, USA). Each specimen was sectioned into three pieces of differing thicknesses (1, 2, and 4 mm). These disk-samples were allocated into 3 groups (n=18) and subjected to push-out testing. One-way ANOVA showed no influence of the specimen thickness on the results (p=0.842). No correlation was observed between thickness and push-out bond strength (Pearson Correlation, r(2)=0.0688; P=0.6209). The push-out bond strength test was not affected by the thickness of the disk-specimens.

The adhesive system and root canal region do not influence the degree of conversion of dual resin cement

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of Nd : YAG and Er : YAG lasers on the sealing of root canal fillings

Objective: the ability of the laser irradiation to promote the cleaning and disinfection of the radicular canal system has become this type of treatment in a viable and real alternative in endodontics. The purpose of this study was to evaluate the apical marginal sealing of root canal fillings after the irradiation with the laser of Nd:YAG or of Er:YAG. Materials and Methods: Forty-two human, extracted single-rooted teeth had their crowns sectioned and the root canals prepared with a no. 70 K-file. Then, they were dried and divided into three groups according to canal wall treatment: group 1: the canals were filled with EDTA for 3 min, followed by irrigation with 1% sodium hypochlorite solution; group 2: the canal walls were irradiated with Nd:YAG laser; and group 3: the canal walls were irradiated with Er:YAG laser. Afterwards, the root canals were obturated by the lateral condensation technique. The roots were externally waterproof, except in the apical foramen and immerged in 2% methylene blue aqueous solution during 48 hours. Results: the results showed that the largest infiltrations happened in the group 3-Er:YAG (7.3 mm), proceeded by the group 1-EDTA (1.6 mm) and by the group 2-Nd:YAG (0.6 mm). The group Er:YAG differed statistically of the others (p < 0.05). Conclusion: It was concluded that the Er:YAG laser intracanal irradiation previously to the root canal filling must be used with caution until future research is define the best parameters for it's use.

In vitro evaluation of the effectiveness of irrigants and intracanal medicaments on microorganisms within root canals

Aim To evaluate in vitro the effectiveness of sodium hypochlorite (NaOCl). chlorhexidine (CHX) and live intracanal medicaments on microorganisms within root canals.Methodology Ninety-six human single-rooted extracted teeth were used. After removing the crowns, canal preparation was completed and the external root Surfaces were coated with epoxy resin. Following sterilization. The teeth were contaminated with Candida albicans and enterococcus faecalis. and were incubated at 37 +/- 1 degreesC for 7 days. The teeth were divided according to the irrigant solution or intracanal medicament: group 1. sterile physiologic solution (SPS) and calcium hydroxide (Ca(OH)(2)) paste: group 2. SPS and camphorated paramonochlorophenol (CPMC): group 3.SPS and tricresol formalin: group 4, SPS and CaOH2 + CPMC paste: group 5, SPS and PMC furacin; group 6.2.5%, NaOCl without intracanal medication: group 7, 2.0% CHX without intracanal medication and group 8, SPS Without intracanal medication (control group). Microbiological samples were collected with sterile paper points, and bacterial growth was determined. The data were submitted to the analysis of variance (ANOVA. P = 0.05).Results For C. albicans, groups 3 and S were statistically less effective than groups 1, 2. 4 and 5 (Kruskal-Wallis (K-W) = 65.241; gl = 7; P = 0.001). For E. faecalis, groups 6 and 8 were statistically less effective than groups 1-4 and 7 (K-W = 61.048; gl = 7; P = 0.001).Conclusions Ca(OH)(2) + CPMC paste was the most effective intracanal medicament for the elimination of the two microorganisms; 2.0% CHX solution was more effective than 2.5% NaOCl against E. faecalis.

In vitro evaluation of apical sealing in root apex treated with demineralization agents and retrofiled with mineral trioxide aggregate through marginal dye leakage

O objetivo deste estudo foi avaliar o selamento de ápices radiculares tratados com diferentes agentes desmineralizantes e retrobturados com agregado de trióxido mineral (MTA), mediante infiltração marginal por corante. Cinqüenta e seis dentes unirradiculares humanos extraídos foram instrumentados, obturados e seccionados apicalmente. Os preparos cavitários apicais foram confeccionados com pontas ultra-sônicas e os agentes desmineralizantes foram aplicados previamente à retrobturação com Pro Root MTA. Os espécimes foram divididos aleatoriamente em 4 grupos (n=14): grupo 1 (sem agente desmineralizante); grupo 2 (ácido fosfórico 35% durante 15 s); grupo 3 (solução de EDTA 17%, pH 7, durante 3 min); grupo 4 (gel de EDTA 24%, pH 7, durante 4 min). A extensão da infiltração de corante (rodamina B 2% a 37°C, por 24 h) foi avaliada em milímetros utilizando-se um estereomicroscópio. Os resultados foram analisados estatisticamente por meio de análise de variância a um critério e do teste Tukey com nível de significância de 5%. Dentre os grupos experimentais, a menor extensão de infiltração do corante foi verificada no grupo 1 (1,89 mm), seguido pelos grupos 2 (2,18 mm), 4 (2,54 mm) e 3 (2,64 mm). Não houve diferenças estatisticamente significante (p>0.05) na infiltração marginal pelo corante entre os grupos 1, 2 e 4 e os grupos 2, 3 e 4. Com base nos resultados obtidos, pode-se concluir que a aplicação de agentes desmineralizantes não pode ser recomendada quando da utilização do MTA em cirurgias parendodônticas.

ANTIMICROBIAL ACTIVITY of SODIUM HYPOCHLORITE ASSOCIATED WITH INTRACANAL MEDICATION FOR Candida albicans and Enterococcus faecalis INOCULATED IN ROOT CANALS

Objective: The purpose of this study was to evaluate the action of sodium hypochlorite (NaOCl) associated with an intracanal medication against Candida albicans and Enterococcus faecalis inoculated in root canals. Material and Methods: Thirty-six human single-rooted teeth with single root canals were used. The canals were contaminated with C. albicans and E. faecalis for 21 days and were then instrumented with 1% NaOCl. The roots were divided into 3 groups (n=12) according to the intracanal medication applied: calcium hydroxide paste, 2% chlorhexidine (CHX) gel, and 2% CHX gel associated with calcium hydroxide. The following collections were made from the root canals: a) initial sample (IS): 21 days after contamination (control), b) S1: after instrumentation, c) S2: 14 days after intracanal medication placement; S3: 7 days after intracanal medication removal. The results were analyzed statistically by the Kruskal-Wallis test at 5% significance level. Results and Conclusions: Both 1% NaOCl irrigation and the intracanal medications were effective in eliminating E. faecalis and C. albicans inoculated in root canals.

Cytotoxicity and Genotoxicity of Root Canal Sealers Based on Mineral Trioxide Aggregate

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)