Estudo ex vivo da elevação do pH em superfície radicular externa após agitação ultrassônica de diferentes pastas de hidróxido de cálcio / Assessment of pH increase in the external root surface after ultrasonic agitation of different calcium hydroxide pastes: Ex vivo study

Objetivo: O presente estudo teve por objetivo avaliar, ex vivo, a capacidade de elevação do pH da superfície radicular externa de diferentes pastas de hidróxido de cálcio (HC) utilizadas como medicação intracanal, além da influência da ativação ultrassônica (AUS) durante aplicação no interior do canal radicular. Métodos: Foram utilizados 100 incisivos humanos superiores unirradiculares, que tiveram os canais radiculares modelados e divididos aleatoriamente em seis grupos experimentais (n=15), de acordo com a pasta de HC, tendo como variáveis as medicações utilizadas e a ativação da pasta com AUS no momento da aplicação, além de um grupo controle (n=10): Pasta Calen; HC+clorexidina 2% gel (CX2%); e HC + água destilada. Os dentes foram mantidos imersos em água deionizada e as medidas do pH, verificadas nos períodos de 7, 14, 21 e 28 dias, com auxílio de pHmetro. Resultados: De acordo com os dados obtidos, verificou-se elevação do pH nos períodos de 7 e 14 dias em todos os grupos. Apenas os grupos em que foi utilizada a associação do HC com CX2% apresentou evolução com aumento significativo do pH ao longo dos períodos analisados (p<0,05). A ativação das pastas com AUS proporcionou incremento significativo dos valores de pH (p<0,05). Conclusão: De acordo com a metodologia empregada, pode-se concluir que todas as pastas utilizadas promovem elevação do pH no tecido dentinário, e a ativação das pastas com AUS influencia significativamente na elevação do pH no tecido dentinário (AU).

Objective: The aim of the present study was to evaluate, ex-vivo, the pH elevation capacity on the external root surface of different calcium hydroxide (HC) pastes, utilized as intracanal medication, it was also evaluated the influence of the ultrasonic activation at the application within the root canal. Methods: 100 human single root superior incisors were used, which had their root canals shaped and randomly divided into 6 experimental groups (n=15) according to the following HC pastes: Calen; HC + Chlorhex- idine 2% gel (CX2%); HC + distilled water, utilizing the medications and the ultrasonic activation of the paste at the time of the application as variables and 1 control group (n=10). The teeth were kept immersed in deionized water and the pH parameters were verified in 7, 14, 21 and 28 days with a pH measurement machine. Results: According to the data obtained, pH was elevated in the first week in all groups. Only the groups which the association of HC with CX2% was made, did show a significant increase in the pH level over the analyzed periods (p < 0,05). The activation of the pastes with US provided a significant increase in pH values (p < 0,05). Conclusion: According to the methodology used, we can conclude that all the HC pastes used, promote pH elevation in dentin tissue. And the acti- vation of the pastes with US significantly influences the pH increase in dentin tissue

12-Year Follow-Up of Regenerative Endodontic Treatment of Immature Permanent Upper Incisors with Acute Abscess.

This case report discusses the endodontic treatment of a 7-year-old girl who suffered trauma (intrusion) to the immature upper central incisors secondary to a fall from a bicycle. Thirty days after the accident the patient was brought by her mother for clinical and radiographic assessment with a chief complaint of swelling and tenderness to percussion and palpation. Acute apical abscess associated with immature teeth were diagnosed. A decision was made to perform regenerative endodontic treatment. Access cavities were made and the root canals were disinfected by irrigation with 2.5% sodium hypochlorite. Final irrigation was performed with 17% EDTA. Due to pain and presence of secretions, 2% chlorhexidine gel was applied as an intracanal medicament. Seven days later, at the second visit, the root canals were once again disinfected and the canals of the right and left permanent upper central incisors were filled with double antibiotic paste (metronidazole/ciprofloxacin) and calcium hydroxide paste, respectively. Zinc oxide was mixed in both pastes. At the third visit, after 21 more days, the pastes were removed and the periapical areas were stimulated with a #80 K-file to encourage clot formation within the pulp cavities. A mineral trioxide aggregate (MTA) paste cervical plug was placed and the teeth were restored with glass ionomer cement. Radiographs and CBCT scans demonstrated complete root formations. The patient has been followed for 12 years, with evidence of clinical success throughout.

Cyclic fatigue resistance of different continuous rotation and reciprocating endodontic systems.

OBJECTIVE: The objective of this study is to compare the cyclic fatigue resistance of nine types of endodontic instruments of nickel-titanium. MATERIALS AND METHODS: Five files of 25 mm of length of each group: Reciproc (RC) R25; WaveOne (WO) Primary; Unicone (UC) L25 25/0.06; K3XF 25/0.06; ProTaper Universal F2 (PTF2); ProTaper Next X2 (PTX2); Mtwo 25/0.06; BioRaCe 25/0.06; One Shape L25 25/0.06 were subjected to a cyclic fatigue resistance test on a mechanical apparatus. The mean fracture time was analyzed statistically by one-way analysis of variance and Tukey's honest significant difference post hoc test, with significance set at P< 0.05. CONCLUSION: It was observed that the groups PTX2, RC, R25, UC L25 25/0.06, and WO Primary presented greater cyclic fracture resistance than the other groups (P< 0.001).

Push-out bond strength of a self-adhesive resin cement used as endodontic sealer.

OBJECTIVES: The aim of the present study was to investigate the bond strength of RelyX Unicem (3M) to root canal dentin when used as an endodontic sealer. MATERIALS AND METHODS: Samples of 24 single-rooted teeth were prepared with Gates Glidden drills and K3 files. After that, the roots were randomly assigned to three experimental groups (n = 8) according to the filling material, (1) AH Plus (Dentsply De Trey GmbH)/Gutta-Percha cone; (2) Epiphany SE (Pentron)/Resilon cone; (3) RelyX Unicem/Gutta-Percha cone. All roots were filled using a single cone technique associated to vertical condensation. After the filling procedures, each tooth was prepared for a push-out bond strenght test by cutting 1 mm-thick root slices. Loading was performed on a universal testing machine at a speed of 0.5 mm/min. One-way analysis of variance and Tukey test for multiple comparisons were used to compare the results among the experimental groups. RESULTS: Epiphany SE/Resilon showed significantly lower push-out bond strength than both AH Plus/Gutta-Percha and RelyX Unicem/Gutta-Percha (p < 0.05). There was no significant difference in bond strength between AH Plus/Gutta-Percha and RelyX Unicem/Gutta-Percha (p > 0.05). CONCLUSIONS: Under the present in vitro conditions, bond strength to root dentin promoted by RelyX Unicem was similar to AH Plus. Epiphany SE/Resilon resulted in lower bond strength values when compared to both materials.

Comparative evaluation of push-out bond strength of a MTA-based root canal sealer

AIM: To evaluate the bond strength to root dentin of three root canal sealers: a mineral trioxide aggregate (MTA)-based sealer (MTA Fillapex(r)), an epoxy resin-based sealer (AH Plus(r)), and a zinc oxide eugenol-based sealer (EndoFill(r)). METHODS: Thirty extracted single-root human teeth of similar sizes and circular canals were prepared using #3 and #2 Gates Glidden drills in the cervical portion of the canal and K3(r) rotary instruments to a size #25/0.06 to working length. Irrigation with 0.5 mL 2% chlorhexidine gel was used before and 1 mL saline after each instrument.The smear layer was removed with 3 mL 17% EDTA for 3 min. The samples were sectioned horizontally into eight 1±0.1 mm-thick serial slices and then the push-out test was carried out. Two-way analysis of variance (ANOVA) and the post-hoc Tukey test were used for the analysis of the data with a significance level of 5%. RESULTS: AH Plus presented significantly higher bond strengths (p<0.05) than the other sealers, while MTA Fillapex showed the lowest bond strengths (p<0.05). CONCLUSIONS: The present study concluded that EndoFill(r) sealer and MTA FillApex(r) core combination were not superior to AH Plus(r) sealer and gutta-percha core combination...

Response of mice connective tissue to three different endodontic materials.

The aim of this study was to evaluate the biocompatibility of mineral trioxide aggregate (MTA) Bio and Portland cement (PC) and compare with those of ProRoot MTA. Polyethylene tubes were filled with materials and placed into dorsal subcutaneous connective tissue of Wistar albino rats. After 7, 30, and 60 days after the surgical procedure, the implants with the surrounding tissue were removed. Tissue samples were subjected to histological processing, and sections were stained with hematoxylin and eosin. Sections were evaluated for the intensity of inflammation, predominant cell type, presence of fibrous capsule and granulation tissue. Data were submitted to Kruskal-Wallis test at a significant level of P ≤ 0.05. No statistical differences were observed at any evaluated condition among tested materials (P > 0.05). Statistically significant differences were observed between mean inflammatory scores, cell types and granulation tissue of the same material in different experimental periods (P < 0.05). Can be concluded that biocompatibility of MTA bio and PC were comparable with that of ProRoot MTA.

Chemical composition and thermal behavior of five brands of thermoplasticized gutta-percha.

OBJECTIVE: The aim of this study was determine the chemical composition and thermal behavior of Thermafil (TH), Microseal Cone (MC), Microseal Microflow (MF), Obtura (OB) and Obtura Flow (OF). In addition, their thermal behavior in response to temperature variations was studied by differential scanning calorimetry (DSC) to determine the temperature at which gutta-percha switches from the beta to alpha form, and from the alpha to the amorphous phase. MATERIALS AND METHODS: The organic and inorganic fractions were separated by dissolution in chloroform. Gutta-percha (GP) was precipitated with acetone. The inorganic fraction was analyzed via Elemental Microanalysis. Energy Dispersive X-ray Microanalysis and X-ray Diffraction were used to identify the chemical elements and compounds (BaSO4 and ZnO). Thermal analysis was conducted using DSC. RESULTS: The organic and inorganic fractions ranged from 21.3% and 26.9% of weights, respectively. MC and MF showed the highest percentages of organic compounds (P = 0.0125). All specimens exhibited two crystalline transformations when heated from ambient temperature to 130°C. MC presented the highest percentage of GP. CONCLUSIONS: No correlation was observed between chemical composition and thermal behavior. Each of the products showed thermal behavior that is typical of beta-phase gutta-percha.

Preliminary investigation to achieve patency of MB2 canal in maxillary molars

Aim: To establish a preliminary investigation about the possibility to achieve patency of second mesiobuccal canal (MB2) in mesiobuccal roots of maxillary molars. Methods: Three hundred and five first maxillary molars were examined with direct vision and with magnification. The root canal configurations were classified according to the possibility to achieve patency in MB2 canals. Clearing technique was also performed to illustrate root canal anatomy and verify the presence of extra canals not identified with magnification. Results: The prevalence of MB2 canals detected only with direct vision was 53.4% and the use of the surgical operating microscope increased rate detection to 90.7%. The clearing technique revealed the presence of MB2 canal in 12 more teeth (94.7%). In 49.1% of the localized MB2 canals, it was not possible to achieve patency. Conclusions: The findings of the presented study revealed that it was only possible to achieve patency in 50.9% of the MB2 canals, showing that achieve patency in the MB2 canal is much more challenging than locating them.

In vitro penetration of two cements into artificially created lateral canals / Análise in vitro da obturação de canais laterais simulados utilizando dois tipos de cimentos

Objective: The aim of this study was to assess the penetration of two obturation materials, Guta-percha (Konne Ind. e Com. Ltda., Belo Horizonte, Brazil) / Pulp Canal Sealer (Kerr Sybron, Romulus, USA) and Resilon (Resilon Research LLC, Madison, CT, USA) / Epiphany (Pentron Clinical Technologies, Wallingford, CT, USA), into artificially created lateral canals. Methods: Twenty upper, single-rooted human teeth with full or partial crown, straight root and radiograph suggesting one root canal were selected. Six lateral canals were created on each root, two on each third. The teeth were then divided randomly into 2 groups of 10 teeth each. The continuous wave of condensation technique was used to obturate all canals. After obturation, the roots were sectioned cross-sectionally into 3 segments with a diamond disc to expose the lateral canals. The segments were fixed in a fast curing epoxy resin and micrographs of the lateral canals magnified 20 times were taken. The software Carnoy 2.0 was then used to measure obturation material penetration into each lateral canal. The data were treated by the non-parametric Kruskal-Wallis test. Results: The extent of the lateral canals penetrated by the two obturation materials did not differ significantly in any of the root thirds (p>0.05). Conclusion: Both obturation materials, Guta-percha (Konne Ind. e Com. Ltda., Belo Horizonte, Brazil) / Pulp Canal Sealer (Kerr Sybron, Romulus, USA) and Resilon (Resilon Research LLC, Madison, CT, USA) / Epiphany (Pentron Clinical Technologies, Wallingford, CT, USA), presented good penetration, which did not differ significantly.

Objetivo: Avaliar a capacidade de selamento de canais laterais simulados frente a dois sistemas obturadores: Guta-percha (Konne Ind. e Com. Ltda., Belo Horizonte, Brasil) e cimento Pulp Canal Sealer (Kerr Sybron, Romulus, USA) e Resilon (Resilon Research LLC, Madison, CT, USA) com Epiphany (Pentron Clinical Technologies, Wallingford, CT, USA). Métodos: Foram selecionados 20 dentes humanos unirradiculares superiores, com coroas totais ou parcialmente íntegras, raízes retas e imagem radiográfica sugestiva de um canal. Foram confeccionados seis canais laterais, com a utilização de uma broca Long Neck ½ (Dentsply-Maillefer, Ballaigues, Suíça), em cada espécime, sendo igualmente distribuído nos 3 terços radiculares. Posteriormente, os dentes foram divididos aleatoriamente em 2 grupos de 10 dentes. A técnica de obturação utilizada foi a Onda Contínua de Condensação. Após as obturações, as raízes foram seccionadas transversalmente com um disco de diamante em 3 segmentos, que possibilitou a visualização dos canais laterais. Os segmentos foram incluídos em uma resina epóxica de presa rápida. As imagens dos terços radiculares inseridos em resina epóxica foram capturadas em lupa estereomicroscópica, com aumento de 20 vezes. Foram realizadas medições lineares das obturações em cada um dos canais dos diferentes segmentos dos dentes de cada grupo através do programa Carnoy 2.0. Os dados foram submetidos à análise estatística utilizando o teste não paramétrico de Kruskall-Wallis. Resultados: A análise dos resultados demonstrou não haver diferença estatística no escoamento entre os materiais obturadores e seus terços apicais, médios e cervicais (p > 0,05). Conclusão: Concluiu-se que os dois materiais obturadores, apresentaram um bom escoamento nos canais laterais, não havendo diferença estatística entre eles.

Evaluation of the dentin remaining after flaring using Gates Glidden drills and Protaper rotary files

INTRODUCTION: The application of rotary instruments for root canal preparation requires a safe, not harming procedure to the root structure remaining. OBJECTIVES: The purpose of this study was to analyze the root thickness in 28 mesial canals of lower permanent first molars before and after flaring using two rotary instruments: Gates-Glidden drills and ProTaper rotary files. MATERIAL AND METHODS: Teeth were embedded into a muffle system. Samples were obtained by cutting 2mm below the furcation. The images were captured by a digital video system (8X and 12X magnification). For image analysis and processing, Pro-Image Plus 4.1 software was used. Each image captured by the computer was gauged, eliminating any possible distortion. Gates-Glidden drills were used in decreasing order of size (GG#4, GG#3, GG#2). ProTaper was used according to the manufacturer's recommendations, with hand-piece powered by an electric motor with low torque. 5.25 percent sodium hypochlorite was utilized as irrigant. RESULTS: The average thickness between the canal and furcation before and after use of rotary instruments were: 0.857 mm and 0.561 mm for Gates-Glidden drills, and 0.858 mm and 0.486 mm for ProTaper, respectively. No statistical differences were found in the root thickness of specimens shaped with ProTaper rotary files and Gates Glidden drills. CONCLUSION: The use of Gates-Glidden drills is as safe as ProTaper rotary files with respect to danger of perforation on the distal side of the mesial roots of lower molars.

Avaliação in vivo da dor pós-operatória em dentes vitais após o alargamento do forame apical / In vivo evaluation of post operative pain in vital pulps after the foramen enlargement

Objetivo: O objetivo do presente trabalho foi avaliar a dor pós-operatória em dentes vitais uni ou birradicularessubmetidos ou não ao alargamento foraminal até a lima # 30. Métodos: Quarenta dentes foram selecionados e divididos randomicamente em dois grupos. No Grupo I (experimental) foi preconizada ampliação foraminal até a lima # 30 e comprimento de trabalho 1 a2 mm aquém do forame. No Grupo II (de controle) foi preconizado limite de trabalho de 1 a 2 mm aquém do ápice e manutenção do remanescente pulpar. Todos os procedimentos foram realizados pelo mesmo operador. A vitalidade foi analisada com base em aspectos clínicos e radiográficos. Todos os dentes foram tratados em sessão única e o localizador apical Root ZX® foi utilizado para a determinação do comprimento de trabalho, conjuntamente com a comprovação radiográfica. A dor foi avaliada por um período de 24 e 48h. Resultados e Conclusão: Com base nos resultados relatados pelos pacientes, não foi observada diferença estatística entreos dois grupos, ou seja, o alargamento do forame apical não aumentou a incidência de dor

Filling lateral canals: evaluation of different filling techniques.

OBJECTIVES: The purpose of this in vitro quantitative laboratorial study is to compare the ability of three filling techniques to fill simulated lateral canals. METHODS: Thirty extracted, single-rooted human teeth were used. After cleaning and shaping, three lateral canals were created, one in each third. The teeth were randomly separated into three groups: continuous wave of condensation (Group 1); thermomechanical compaction (Group 2); and lateral condensation (Group 3). The teeth were cross-sectioned, making the cut through points over the lateral canals; thus, 90 specimens were obtained. Each specimen was immersed in a polyester resin, and the blocks were polished. Images were obtained using a stereoscopic lens (40x). Radiographic analysis was performed, followed by a filling linear measure using the Image Tool 3.0 program (University of Texas). Data were statistically analyzed using SPSS 12.0 for Windows (Kruskal-Wallis test). RESULTS: A greater number of simulated lateral canals were obturated in Groups 1 and 2. Group 2 presented the largest percentage of linear measure of lateral canals filling with gutta-percha and sealer. No statistical differences were found between Group 1 and Group 2 when we analyzed the filling with gutta-percha and sealer or just sealer (P>.05). CONCLUSIONS: Thermoplasticized gutta-percha filling techniques (Groups 1 and 2) are better for filling lateral canal with gutta-percha and sealer or with just sealer than lateral condensation (Group 3).

Coronal leakage of four intracanal medications after exposure to human saliva in the presence of a temporary filling material.

AIM: To determine the time required for the recontamination of root canals medicated with four different materials. MATERIALS AND METHODS: A total of 60 intact, caries-free, human single-rooted teeth with straight roots were selected for this study. After chemo-mechanical preparation they must be changed in the specimens into seven groups: 10 teeth medicated with calcium hydroxide (Ca(OH) 2) + Camphorated paramonochlorophanol (CPMC) (G.1); 10 medicated with 2.5% Sodium hypochlorite (NaOCL) (G.2); 10 medicated with 2% Chlorhexidine gluconate (CHX) in gel (G.3); 10 medicated with 2% CHX in gel + Ca(OH) 2 (G.4); 10 without intracanal medicament and sealed with a coronal temporary filling (G.5). Five teeth were without intracanal medicament and coronally unsealed, used as the positive control group (PC) (G.6) and 5 teeth with intact crowns used as the negative control group (NC) (G.7). Glass vials with rubber stoppers were adjusted for use. The medicaments were prepared and injected into the root canals using sterile plastic syringes. An apparatus was used to evaluate for 30 days leakage. The chamber was filled with 3 ml of human saliva and Brain Heart Infusion (BHI) broth, incubated at 37 degrees C and checked daily for the appearance of turbidity in the BHI broth. RESULTS: Recontamination was detected after an average time of 2.6 days in group 2, 15.9 days in group 3, 30 days in group 1, 27.6 days in group 4, 2.9 days in group 5, 1 day in the positive control, and there was no contamination in the negative control group. CONCLUSION: The NaOCl group showed the highest worst average of recontamination; on the other hand, high averages were also shown by Ca(OH) 2 + CPMC and Ca(OH) 2 + 2% CHX in gel.

Ex vivo evaluation of coronal and apical microbial leakage of root canal--filled with gutta-percha or Resilon/Epiphany root canal filling material.

OBJECTIVE: This ex vivo study compared coronal and apical microleakage of root canals filled with Resilon/Epiphany (RE) or gutta-percha/Grossman sealer (GP), using either lateral condensation (LC) or System B (SB) technique. MATERIALS AND METHODS: Specimens in eight experimental groups were obturated using the following materials and techniques: Groups 1 and 3--GP and LC; groups 2 and 4--GP and SB; groups 5 and 7--RE and LC; groups 6 and 8--RE and SB. Apical and coronal leakages were tested using bacterial methods. For coronal analysis, the number of days required for complete contamination of the root canals was recorded according to observation of the brain heart infusion broth turbidity for 15 weeks. For apical analysis, the teeth were cleaved and the leakage was measured at 30 days. Data were collected for each sample and analyzed statistically with the Chi-square and ANOVA tests. RESULTS: Leakage was found in all groups. The difference between filling materials, obturation techniques, and median time of leakage was not statistically significant for coronal ( P=0.847) and apical ( P=0.5789) leakages. CONCLUSION: There were no differences between the different filling materials (gutta-percha/Grossman sealer and Resilon/Epiphany) and obturation techniques (lateral condensation and system B technique) in coronal or apical leakages.

Radiopacity and histological assessment of Portland cement plus bismuth oxide.

OBJECTIVE: The present study evaluated the subcutaneous connective tissue reactions and the radiopacity of MTA, Portland cement (PC), and Portland cement plus bismuth oxide (BO). STUDY DESIGN: Forty rats were divided into 5 groups (n = 8 per group): A1: Control (empty capsule); A2: Pro-Root MTA; A3: PC; A4: PC + BO 1:1; and A5: PC + BO 2:1. Polyethylene tubes were filled with the test materials and standardized radiographic images were taken. Histological evaluation was done after 7 and 60 days. Student t test and Fisher's test were used in the statistical analysis (P < .05). RESULTS: The radiopacity of the materials were in decreasing order: A2 > A4 > A5 > A3. No differences were found for the tissue response in the 2 experimental periods. A positive correlation between BO concentration and radiopacity of PC was determined. CONCLUSION: The histological evaluation suggests that all studied materials were biocompatible at 7 and 60 days.

Evaluation of the risk of a stripping perforation with Gates-Glidden drills: serial versus crown-down sequences.

The aim of this study was to evaluate the remaining dentine/cementum thickness using Gates-Glidden burs in serial and crown-down sequences and to observe which of the two sequences is the safest for preparing mesial roots of molars. Thirty-six left and right human mandibular first molars were selected. Standard access cavities were made and initially explored with Flexofiles sizes 10 and 15 until the tip was visible at the apex. The teeth were embedded in a muffle specially developed for this study using a PVC tube with two parallel metal rods in its lid. Each tooth-block was sectioned 3 mm apically to the furcation using a low-speed saw with a diamond disc. The tooth-block was examined under a microscope and an initial image was captured by a digital video system with 8 X and 12 X magnifications. Finally, the tooth-blocks were reassembled in the muffle so that the canals could be instrumented. After instrumentation the area of each mesial canal as well as the smallest distance to the root furcation were measured again. The mesio-buccal canals (crown-down order) and the mesio-lingual canals (serial sequence) presented an average area of 0.46 +/- 0.16 mm(2) and 0.88 +/- 0.27 mm(2) (P < 0.01), respectively. The mean values of the smallest distance to the furcation for the mesio-buccal and mesio-lingual canals were 0.66 +/- 0.19 mm and 0.39 +/- 0.13 mm (P < 0.01), respectively. The remaining dentine/cementum thickness using Gates-Glidden burs was greater in the crown-down sequence than in the serial sequence.

Evaluation of the risk of a stripping perforation with gates-glidden drills: serial versus crown-down sequences

The aim of this study was to evaluate the remaining dentine/cementum thickness using Gates-Glidden burs in serial and crown-down sequences and to observe which of the two sequences is the safest for preparing mesial roots of molars. Thirty-six left and right human mandibular first molars were selected. Standard access cavities were made and initially explored with Flexofiles sizes 10 and 15 until the tip was visible at the apex. The teeth were embedded in a muffle specially developed for this study using a PVC tube with two parallel metal rods in its lid. Each tooth-block was sectioned 3 mm apically to the furcation using a low-speed saw with a diamond disc. The tooth-block was examined under a microscope and an initial image was captured by a digital video system with 8 X and 12 X magnifications. Finally, the tooth-blocks were reassembled in the muffle so that the canals could be instrumented. After instrumentation the area of each mesial canal as well as the smallest distance to the root furcation were measured again. The mesio-buccal canals (crown-down order) and the mesio-lingual canals (serial sequence) presented an average area of 0.46 ± 0.16 mm² and 0.88 ± 0.27 mm² (P < 0.01), respectively. The mean values of the smallest distance to the furcation for the mesio-buccal and mesio-lingual canals were 0.66 ± 0.19 mm and 0.39 ± 0.13 mm (P < 0.01), respectively. The remaining dentine/cementum thickness using Gates-Glidden burs was greater in the crown-down sequence than in the serial sequence.

In vitro evaluation of the effectiveness of the chemomechanical preparation against Enterococcus faecalis after single- or multiple-visit root canal treatment.

The purpose was to assess the elimination of Enterococcus faecalis in vitro in human mandibular premolars after chemomechanical preparation with or without the use of a calcium hydroxide dressing. After 60 days of contamination with E. faecalis, the root canals were prepared using the Crown-Down technique combined with 2% chlorhexidine gel irrigation. Then, the specimens were divided into two experimental groups, treated in a single visit or in multiple visits, and two control groups. The multiple-visit group received a dressing with calcium hydroxide for 14 days (Calen) and the single-visit group did not receive any medication. In the two control groups, the canals were filled with BHI after chemomechanical preparation with 2% chlorhexidine gel or distilled water. Microbial samples were taken from the root canals for colony forming unit count for each phase of the treatment using sterile paper points inside the root canal lumen. Data were ranked and analyzed by the Kruskal-Wallis statistical test. The residual microbial colonies were then assessed. The results showed that chemomechanical preparation using 2% chlorhexidine gel with no intra-canal dressing reduced by 100% the E. faecalis contamination of the root canal lumen. The calcium-hydroxide group that received the 14-day intra-canal dressing allowed a small number of bacteria to grow between visits, but without statistical differences between groups.

Cleaning ability of chlorhexidine gel and sodium hypochlorite associated or not with EDTA as root canal irrigants: a scanning electron microscopy study

The aim of this study was to evaluate the cleaning efficacy of 2 percent chlorhexidine gluconate gel (CHX) compared to 2.5 percent sodium hypochlorite solution (NaOCl) associated or not with 17 percent EDTA used as irrigants during the biomechanical preparation. Fifty freshly extracted single-rooted human teeth with complete apex formation were randomly divided into five groups: G1 - sterile saline, G2 - 2.5 percent NaOCl, G3 - 2 percent CHX, G4 - 2.5 percent NaOCl + EDTA and G5 - 2 percent CHX + EDTA. The specimens of G1 were subdivided into two control groups. The teeth were decoronated and the coronal and middle root thirds were prepared with Gates-Glidden burs, and the apical third was reserved to manual instrumentation. All procedures were performed by a single operator. In all groups, 2 mL of irrigant was delivered between each file change. The teeth were sectioned and prepared for analyses under scanning electron microscopy (SEM). SEM micrographs were graded according to a score scale by two examiners. Data were analyzed statistically by Kruskal-Wallis and Dunn tests at 1 percent significance level. The best results were obtained in the groups in which the irrigant was used followed by the chelating agent. No statistically significant difference was observed among G4, G5 and the positive control group (p<0.01). The groups G2 and G3 were significantly different from the others, presenting the worst cleaning capacity. In conclusion, the use of the chelating agent is necessary to obtain clean canal walls, with open tubules and no heavy debris. The use of 2 percent chlorhexidine gluconate gel alone is not able to remove the smear layer.

Brazilian gutta-percha points. Part II: thermal properties.

This study was undertaken to explore the effect of heating on gutta-percha, analyzing the occurrence of endothermic peaks corresponding to the transformation that occurs in the crystalline structure of the polymer during thermal manipulation. This study also sought to determine the temperature at which these peaks occur, causing a transformation from the beta- to the alpha-form, and from the alpha- to the amorphous phase. Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP, Dentsply FM) and pure gutta-percha (control) were analysed using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The transition temperatures were determined and analysed. With the exception of Dentsply 0.04 and Dentsply 0.06, the majority of the products showed thermal behaviour typical of beta-gutta-percha, with two endothermic peaks, exhibiting two crystalline transformations upon heating from ambient temperature to 130 degrees. Upon cooling and reheating, few samples presented two endothermic peaks. It was concluded that heating dental gutta-percha to 130 degrees C causes changes to its chemical structure which permanently alter its physical properties.