Wear profile of canal wall surfaces and bond strength of endodontic sealers after in situ acid challenge

AIM

To evaluate the wear of root wall surfaces, the bond strength of sealers to dentine and the demineralization around root filling materials after canals were exposed to acid challenge in situ.

METHODOLOGY

Eighty-seven roots of mandibular incisors were selected. Thirty-two were used in the laboratory bond strength study (n = 8), and 55 in the in situ study (n = 11). Root canals were prepared biomechanically and then filled with gutta-percha and AH Plus, MTA Fillapex, Sealapex or Endofill. For 14 days, 11 participants used intra-oral devices with five sterilized roots (four experimental and one control - only canal prepared). Drops of sucrose were dripped onto roots allowing the accumulation of biofilm on canal surfaces. Roots were removed, sectioned and analysed for the following: bond strength of filling material using a push-out test and also wear profile and dentine demineralization using confocal microscopy. Bond strength (MPa) was evaluated by two-way anova and Tukey test (α = 0.05), and wear profile was assessed by Kruskal-Wallis and t-tests (α = 0.05).

RESULTS

AH Plus had the highest bond strength values. Intermediate results were found in roots with MTA Fillapex and Endofill, whilst Sealapex had inferior results (P < 0.05). No significant differences were found amongst root thirds (P > 0.05). For wear profile, samples were associated with degradation of the filling materials after exposure to the oral environment (P < 0.05). Roots had signs of demineralization around the filling material when Sealapex and Endofill were used.

CONCLUSIONS

Sealers were not able to prevent degradation of the adhesive interface and dentine. AH Plus and MTA Fillapex had superior bond strength to dentine and less intense demineralization around the root filling.

Enamel pearls in permanent dentition: case report and micro-CT evaluation

OBJECTIVES

To investigate the frequency, position, number and morphology of enamel pearls (EPs) using micro-CT (µCT) and to report a case of an EP mimicking an endodontic-periodontic lesion.

METHODS

Cone beam CT (CBCT) was performed in a patient to evaluate a radio-opaque nodule observed on the left maxillary first molar during the radiographic examination. Additionally, 23 EPs were evaluated regarding frequency, position, number and morphology by means of µCT. The results were statistically compared using the Student's t-test for independent samples.

RESULTS

1 pearl was presented in 13 specimens, while 5 specimens presented 2 pearls. The most frequent location of the EPs was the furcation between the disto-buccal and the palatal roots of the maxillary molars. Overall, the mean major diameter, volume and surface area were 1.98 ± 0.85 mm, 1.76 ± 1.36 mm³ and 11.40 ± 7.59 mm², respectively, with no statistical difference between maxillary second and third molars (p > 0.05). In the case report, CBCT revealed an EP between the disto-buccal and the palatal roots of the maxillary first left molar associated with advanced localized periodontitis. The tooth was referred for extraction.

CONCLUSIONS

EPs, located generally in the furcation area, were observed in 0.74% of the sample. The majority was an enamel-dentin pearl type and no difference was found in maxillary second and third molars regarding diameter, volume and surface area of the pearls. In this report, the EP mimicked an endodontic-periodontic lesion and was a secondary aetiological factor in the periodontal breakdown.

Chitosan: a new solution for removal of smear layer after root canal instrumentation

AIM

To evaluate, by scanning electron microscopy (SEM), the efficacy of smear layer removal using chitosan compared with different chelating agents, and to quantify, by atomic absorption spectrophotometry with flame (AASF), the concentration of calcium ions in these solutions after irrigation.

METHODOLOGY

The root canals of twenty-five canines were prepared using a crown-down technique and irrigated with 1% sodium hypochlorite. The teeth were randomly divided into groups (n = 5), according to the type of final irrigation: 15% EDTA, 0.2% chitosan, 10% citric acid, 1% acetic acid and control (without final irrigation). The total volume of each chelating solution was collected from the canals and analysed by AASF for quantification of calcium ions in the solutions. Then, the roots were split longitudinally and examined by SEM for evaluation of smear layer removal in the middle and apical thirds. Cleaning scores were attributed and analysed statistically using the Kruskal-Wallis and Dunn tests. The AASF data were analysed by one-way anova and Tukey-Kramer test. A significant level of α = 0.05 was adopted.

RESULTS

15% EDTA, 0.2% chitosan and 10% citric acid had similar smear layer removal capacity with a significant difference (P < 0.05) from 1% acetic acid and the control group. There was no significant difference (P > 0.05) between the smear layer remaining in the middle and apical thirds. The highest calcium ion concentration was observed with 15% EDTA (121.80 ± 5.13) and 0.2% chitosan (104.13 ± 19.23), with no significant difference. The lowest calcium ion concentration was obtained with 1% acetic acid (25.62 ± 7.68), whilst 10% citric acid (70.38 ± 11.15) had intermediate results, differing significantly from the other solutions (P < 0.01).

CONCLUSIONS

15% EDTA, 0.2% chitosan and 10% citric acid effectively removed smear layer from the middle and apical thirds of the root canal. 15% EDTA and 0.2% chitosan were associated with the greatest effect on root dentine demineralization, followed by 10% citric acid and 1% acetic acid.

Changes in the surface of four calcium silicate-containing endodontic materials and an epoxy resin-based sealer after a solubility test

AIM

To compare the changes in the surface structure and elemental distribution, as well as the percentage of ion release, of four calcium silicate-containing endodontic materials with a well-established epoxy resin-based sealer, submitted to a solubility test.

METHODOLOGY

Solubility of AH Plus, iRoot SP, MTA Fillapex, Sealapex and MTA-Angelus (MTA-A) was tested according to ANSI/ADA Specification 57. The deionized water used in the solubility test was submitted to atomic absorption spectrophotometry to determine and quantify Ca(2+), Na(+), K(+), Zn(2+), Ni(2+) and Pb(2+) ions release. In addition, the outer and inner surfaces of nonsubmitted and submitted samples of each material to the solubility test were analysed by means of scanning electron microscopy and energy-dispersive spectroscopy (SEM/EDX). Statistical analysis was performed by using one-way anova and Tukey's post hoc tests (α = 0.05).

RESULTS

Solubility results, in percentage, sorted in an increasing order were -1.24 ± 0.19 (MTA-A), 0.28 ± 0.08 (AH Plus), 5.65 ± 0.80 (Sealapex), 14.89 ± 0.73 (MTA Fillapex) and 20.64 ± 1.42 (iRoot SP). AH Plus and MTA-A were statistically similar (P > 0.05), but different from the other materials (P < 0.05). High levels of Ca(2+) ion release were observed in all groups except AH Plus sealer. MTA-A also had the highest release of Na(2+) and K(+) ions. Zn(+2) ion release was observed only with AH Plus and Sealapex sealers. After the solubility test, all surfaces had morphological changes. The loss of matrix was evident and the filler particles were more distinguishable. EDX analysis displayed high levels of calcium and carbon at the surface of Sealapex, MTA Fillapex and iRoot SP.

CONCLUSIONS

AH Plus and MTA-A were in accordance with ANSI/ADA's requirements regarding solubility whilst iRoot SP, MTA Fillapex and Sealapex did not fulfil ANSI/ADA's protocols. High levels of Ca(2+) ion release were observed in all materials except AH Plus. SEM/EDX analysis revealed that all samples had morphological changes in both outer and inner surfaces after the solubility test. High levels of calcium and carbon were also observed at the surface of all materials except AH Plus and MTA-A.

SEM analysis of enamel surface treated by Er:YAG laser: influence of irradiation distance

BACKGROUND

Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology.

PURPOSE

To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM).

METHODS

Sixty human third molars were employed to obtain discs (approximately =1 mm thick) that were randomly assigned to six groups (n=10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm and the control group was treated with 37% phosphoric acid for 15 s. The laser-irradiated discs were bisected. One hemi-disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM.

RESULTS

Laser irradiation at 11 and 12 mm provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased-surface partially removed the disorganized tissue.

CONCLUSIONS

Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

Microscopic characterization of teeth of pacas bred in captivity (Agouti paca, Linnaeus, 1766)

The microscopic description of the teeth of pacas (Agouti paca) bred in captivity was developed for providing biological data on one of the largest American wild rodents, as not many references exist in the literature about this species. Two newborn males, two adult males (9 and 72 months old), one newborn female and two adult females (30 and 54 months old) were used after death due to fights, neonatal cannibalism or unknown causes. Animals were radiographed, and their teeth were extracted and put on an acrylic resin block, cut on a diamond-like disc microtome and diaphanized. It was noted that enamel surrounds the coronary dentine and projects to the root region, besides being present as internal laminae, arranged in a parallel way and in the vestibulolingual direction. The dentine is located between the enamel laminae and surrounds the pulp horns. The cementum is located internal to the enamel laminae. From scanning electronic microscopy, we find that the enamel is the outer element on the vestibular surface, and it is in direct contact with the dentine. On the lingual surface, the cementum and dentine are the outer elements.

Efficacy of intracoronal bleaching techniques with different light activation sources

AIM

To evaluate ex vivo the efficacy of 35% hydrogen peroxide for intracoronal bleaching when activated by LEDs, halogen lamp or by the walking bleach technique.

METHODOLOGY

Forty extracted human maxillary central incisors had their crowns resected 1 mm below the amelo-cemental junction and were submitted to artificial staining in centrifuged rat haemolysed blood. A 2-mm thick glass ionomer cervical plug was placed inside the canal, at the level of the amelo-cemental junction. Samples were divided randomly into five groups: group I received 35% hydrogen peroxide gel activated by LEDs. Group II received 35% hydrogen peroxide gel activated by a halogen lamp-based light curing unit. Group III received 35% hydrogen peroxide gel followed by the walking bleach technique. Group IV was neither artificially stained nor bleached (positive control) and group V was stained, but not bleached (negative control). The shade of the teeth was assessed visually by three independent and calibrated evaluators, before and after bleaching. The results were analysed using Kruskal-Wallis one-way analysis of variance and Dunn's post-test.

RESULTS

No statistical differences regarding sample shades were found amongst groups for the tested internal bleaching techniques (P > 0.05).

CONCLUSIONS

Hydrogen peroxide for intracoronal bleaching when activated either by LEDs, halogen lamp or by the walking bleach technique presented similar efficacy.

Anatomoradiographic Description of the Teeth of Pacas Bred in Captivity (Agouti paca, Linnaeus, 1766)

Two newborn males, two adult males 9 and 72 months old, one newborn female and two adult females of 30 and 54 months old pacas were used. Animals were radiographed on lateral recumbency, teeth were extracted and the vestibulolingual and mesiodistal lengths were achieved at the occlusal surface, besides the longitudinal length. The lower incisors presented greater length in relation to the other ones and sinuous shape; the upper incisors, relatively smaller, are practically straight. There is no canine tooth, and after a great diastema there is one premolar and three molars in each hemiarcade. In adult pacas, the enamel of incisors presents yellowish colour, mainly in the labial surface; in the premolars and molars, the enamel is present as internal sheets disposed nearly in a parallel way and in vestibulolingual direction, through practically all the dental length, which provides several joined teeth aspect.

Er:YAG Laser: Antimicrobial Effects in the Root Canals of Dogs' Teeth with Pulp Necrosis and Chronic Periapical Lesions

OBJECTIVE

Our goal in this study was to evaluate the antimicrobial effect of Er:YAG laser applied after biomechanical preparation of the root canals of dog's teeth with apical periodontitis.

BACKGROUND DATA

Various in vitro studies have reported effective bacterial reduction in infected root canals using Er:YAG laser. However, there is no in vivo research to support these results.

METHODS

Forty root canals of dogs' premolar teeth with pulp necrosis and chronic periapical lesions were used. An initial microbiological sample was taken, and after biomechanical preparation was carried out, a second microbiological sample was taken. The teeth were divided into two groups: Group I-biomechanical preparation was taken of root canals without Er:YAG laser application; Group II-biomechanical preparation was taken of root canals with Er:YAG laser application using 140-mJ input, 63-mJ output/15 Hz. After coronal sealing, the root canals were left empty for 7 days at which time a third microbiological sample was taken. The collected material was removed from the root canal with a #40 K file and placed in transport media. It was serially diluted and seeded on culture dishes selective for anaerobes, aerobes, and total streptococci. Colony-forming units per milliliter (CFU/mL) were counted.

RESULTS

Groups I and II showed an increase of CFU/mL for all microorganisms 7 days after treatment, being statistically significant for anaerobes in Group I and for anaerobes and total streptococci in Group II. When comparing CFU/mL of Groups I and II, there was a statistically significant increase after 7 d for total streptococci in Group II.

CONCLUSION

Er:YAG laser applied after biomechanical preparation did not reduce microorganisms in the root canal system.

Clinical aspects of pulpal-periodontal lesions

It is well known that the main purpose of dentistry is to keep teeth in the oral cavity so that they may fulfill their various roles. This case report demonstrates a method to treat a situation involving a pulpal-periodontal lesion, by using a simple and efficient combined therapy. The clinician can thereby determine the cause of the lesion (pulpal and/or periodontal) and subsequently establish the correct treatment, thus improving the prognosis of the case.

Solvent action of sodium hypochlorite on bovine pulp and physico-chemical properties of resulting liquid

The solvent effect of 4 concentrations of sodium hypochlorite (0.5, 1.0, 2.5, and 5.0%) on bovine pulp tissue and the level of residual chlorine, pH and surface tension before and after dissolution were studied in vitro. A fragment of bovine pulp was submersed in sodium hypochlorite that circulated in an apparatus with a peristaltic pump and Luer Lok syringe. The higher the concentration of sodium hypochlorite the faster the dissolution of the pulp tissue. All concentrations of sodium hypochlorite reduced the pH and the surface tension and the higher concentrations of the solution had the least consumption of chlorine during tissue dissolution. Thus this study indicated that residual chlorine was directly proportional to concentration in the process of pulp tissue dissolution and that there was residual chlorine at all concentrations used.

Microleakage of class V resin composite restorations after bur, air-abrasion or Er:YAG laser preparation

This in vitro study compared the microleakage of Class V resin composite restorations placed in cavities prepared with a high-speed dental bur, air-abrasion or Er:YAG laser. Twenty sound extracted human third molars were selected and randomly assigned to four equal Groups (n=10): Group I, cavities were cut by dental drill at high-speed; Group II, aluminum oxide air-abrasion was used for cavity preparation, and in Groups III and IV, cavities were prepared by Er:YAG laser. Following cavity preparation, Groups I and II were acid-etched, Group III was treated only by Er:YAG laser and Group IV was conditioned by Er:YAG laser followed by acid-etching. Cavities were restored (Single Bond + Z-100) and the teeth stored for seven days in distilled water. Then, the restorations were polished and the specimens thermocycled, immersed in a 0.2% Rhodamine solution, sectioned and analyzed for leakage at the occlusal (enamel) and cervical (dentin/cementum) interfaces using an optical microscope connected to a video camera. The images were digitized and software was utilized for microleakage assessment. Upon analyzing the results, statistically significant differences (p<0.01) between the occlusal and cervical regions for all groups was observed, and, as a rule, there was better marginal sealing at the enamel margins. The highest degree of infiltration was observed for cavities prepared and treated exclusively by Er:YAG (Group III). The other experimental groups showed statistical similarities in the amount of marginal leakage at the enamel margins. However, at the cervical margins, there was a significant difference (p<0.05) between Group I and the remaining groups. None of the techniques completely eliminated marginal microleakage at the dentin/ cementum margins.

Dental anomaly: dens evaginatus (talon cusp)

Dens evaginatus is a developmental anomaly characterized by the occurrence of an extra cusp shaped as a tubercle projecting from the palatal or buccal surfaces (talon cusp). In the anterior dentition, dens evaginatus is more commonly found in the maxilla and on the palatal surface of the tooth. The authors present a case of dens evaginatus in a maxillary central incisor, in which the evagination was removed and routine endodontic treatment was performed.

Control of microorganisms in vitro by calcium hydroxide pastes

AIM

The aim of this study was to determine the influence of vehicles on the antimicrobial efficiency of calcium hydroxide.

METHODOLOGY

A total of 588 size 50 sterile absorbent paper points, were immersed in various microbial suspensions for 3 min. The points were then placed on Petri dishes and covered with intracanal dressings containing calcium hydroxide: Ca(OH)2 + saline; Ca(OH)2 + camphorated paramonochlorophenol; Ca(OH)2 + 1% chlorhexidine solution: Ca(OH)2 + 3% sodium lauryl sulphate; Ca(OH)2 + Otosporin. After 1 min, 48 and 72 h and 7 days, 147 absorbent paper cones were removed from contact with the intracanal dressings and individually transported and immersed in 5 mL of Letheen Broth, followed by incubation at 37 degrees C for 48 h. Microbial growth was evaluated by turbidity of the culture medium. A 0.1-mL inoculum obtained from the Letheen Broth was transferred to 5 mL of BHI, and incubated at 37 degrees C for 48 h. Bacterial growth was again evaluated by turbidity of the culture medium. Positive BHI tubes were selected and inocula were spread on the surface of BHI agar and incubated at 37 degrees C for 48 h. Gram staining of the BHI growth and from colonies growing on BHI agar was carried out.

RESULTS

An antimicrobial effect occurred after 48 h on the cultures of S. mutans, E. faecalis, S. aureus, P aeruginosa, B. subtilis, C. albicans and a mixed culture, irrespective of the intracanal dressing.

CONCLUSIONS

Under the conditions of this study, the various vehicles associated with calcium hydroxide pastes did not influence the time required for microbial inactivation.

Microleakage of a resin sealant after acid-etching, Er:YAG laser irradiation and air-abrasion of pits and fissures

OBJECTIVE

The aim of this in vitro study was to assess microleakage underneath a filled pit-and-fissure sealant bonded to occlusal surfaces treated by four enamel etching techniques.

SUMMARY BACKGROUND DATA

There has been no report of a study assessing microleakage of a pit-and-fissure sealant, comparing acid-etching, Er:YAG laser and air-abrasion for treating enamel surface.

METHODS

Forty extracted human third molars were selected and randomly assigned into four groups of ten teeth: group I, the occlusal surfaces were acid-etched; group II, a very short pulsed Er:YAG laser was used to treat the surfaces; group III, aluminum oxide air-abrasion was associated with acid-etching; group IV, Er:YAG laser was associated with acid-conditioning. The surfaces were sealed and the teeth were stored for 7 days in distilled water. Then, specimens were thermocycled, immersed in a 0.2% rhodamine solution, sectioned, and analyzed for leakage using an optical microscope connected to a video camera. The images were digitized and analyzed by software that allowed microleakage assessment in millimeters.

RESULTS

Statistical analysis showed that occlusal surfaces treated exclusively by the Er:YAG laser (group II) provided the poorest marginal sealing and that acid-etching (group I) was statistically similar to aluminum oxide air-abrasion + acid etching (group III) and to Er:YAG laser + acid-etching (group IV).

CONCLUSIONS

The results suggest that complementing either air-abrasion or Er:YAG laser irradiation with a subsequent acid-conditioning did not lessen microleakage at the enamel-sealant interface when compared with an acid-etched group. It was also observed that treating the enamel surface exclusively by Er:YAG laser resulted in the highest degree of leakage.

Antimicrobial and chemical study of MTA, Portland cement, calcium hydroxide paste, Sealapex and Dycal

The objective of this study was to investigate the antimicrobial action of mineral trioxide aggregate (MTA), Portland cement, calcium hydroxide paste (CHP), Sealapex and Dycal. The chemical elements of MTA and two Portland cements were also analyzed. Four standard bacterial strains: Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), Bacillus subtilis (ATCC 6633), one wild fungus, Candida albicans (ICB/USP-562), and one mixture of these were used. Thirty Petri plates with 20 ml of BHI agar were inoculated with 0.1 ml of the experimental suspensions. Three cavities, each one measuring 4 mm in depth and 4 mm in diameter, were made in each agar plate using a copper coil and then completely filled with the product to be tested. The plates were pre-incubated for 1 h at environmental temperature followed by incubation at 37 degrees C for 48 h. The diameters of the zones of microbial inhibition were then measured. Samples from diffusion and inhibition halos were extracted from each plate and immersed in 7 ml BHI broth and incubated at 37 degrees C for 48 h. Analyses of chemical elements present in MTA and in two samples of Portland cement were performed with a fluorescence spectrometer Rx. The results showed that the antimicrobial activity of CHP was superior to those of MTA, Portland cement, Sealapex and Dycal, for all microorganisms tested, presenting inhibition zones of 6-9.5 mm and diffusion zones of 10-18 mm. MTA, Portland cement, and Sealapex presented only diffusion zones and among these, Sealapex produced the largest zone. Dycal did not show inhibition or diffusion zones. Portland cements contain the same chemical elements as MTA except that MTA also contains bismuth.

Evaluation of Er:YAG laser and EDTAC on dentin adhesion of six endodontic sealers

The effect of Er:YAG laser application and EDTAC on the adhesion of epoxy resin-based endodontic sealers to human dentin was evaluated in vitro. A total of 99 extracted human maxillary molars with their crowns worn flat were used. The teeth were divided into 3 groups: group 1, the dentin surface received no treatment; group 2, EDTAC was applied to the dentin surface for 5 min; group 3, the dentin surface received Er:YAG laser application (2.25 W potency; 11 mm focal distance; 4 Hz frequency; 200 mJ energy; 62 J total energy; 313 mean impulse). Three teeth from each group were analyzed by scanning electron microscopy for changes in dentin surface. The epoxy resin root canal sealers used were: AH Plus, Topseal, Sealer 26, AH 26, and Sealer Plus. The zinc oxide eugenol-based sealer Fillcanal was used as control. Adhesion was measured with a Universal testing machine. The results showed a statistically significant difference at the level of 1% among the dentin treatments. The dentin treated with Er:YAG laser showed greater adhesion with the sealers than dentin treated with EDTAC which was greater than dentin that received no treatment. The Tukey test showed the formation of 5 groups in decreasing order of adhesion: AH Plus, Topseal and Sealer 26, AH 26, Sealer Plus, and Fillcanal (Grossman cement).

Modeling capacity of ENDOflash files in simulated root canals

With the development of rotary nickel-titanium files and their applications in Endodontics, the concepts of root canal preparation have changed. The objective of this research is to evaluate the transportation of simulated root canals caused by stainless steel ENDOflash rotary files compared to nickel-titanium ProFile files (.04, .06 and Orifice Shapers). Twenty-four simulated root canals with a 30 degrees curvature were randomly divided into 2 groups and prepared with ENDOflash or ProFile files according to manufacturers' instructions. Comparison between the simulated root canals before and after instrumentation showed significant differences (p < 0.001) between the groups, with greater transportation observed with ENDOflash files. One case of deformation was observed with a ProFile instrument (#20/.04) and there were no fractures.

In vitro study of the effect of aged eugenol on the flow, setting time and adhesion of Grossman root canal sealer

In the present study, the effect of aged eugenol (up to 180 days) on the flow, setting time and adhesion of Grossman root canal sealer was evaluated, following the American Dental Association specification number 57 for root canal sealers. An Instron Universal testing machine 4444 was used for testing adhesion. There were statistically significant differences between groups, with a higher flow, lower setting time and adhesion for aged eugenol. It can be concluded that time affects eugenol, with consequent effects on Grossman sealer.

Evaluation of the effect of EDTAC, CDTA, and EGTA on radicular dentin microhardness

The effect of EDTAC (ethylenediamine tetra-acetic acid plus Cetavion, an ammonium surfactant), CDTA (cyclohexane-1,2-diaminetetra-acetic acid), and EGTA (ethylene glycol-bis-(beta-amino-ethyl ether) N,N,N',N'-tetra-acetic acid) on the microhardness of radicular dentin of the cervical third of human teeth was studied. Five newly extracted maxillary incisors were sectioned transversely at the cementoenamel junction, and the crowns were discarded. The roots were embedded in blocks of high-speed polymerized acrylic resin and cut transversely into 1-mm sections. The second slice of the cervical third of the root of each tooth was sectioned and divided into four parts. Each part was placed on an acrylic disc that was used as a base for microhardness measurement. Fifty microliters of 15% EDTAC, 1% CDTA, or 1% EGTA were applied to the dentin surface. Deionized and distilled water was used as control. Dentin microhardness was then measured with a Vicker's microhardness apparatus with a load of 50 g for 15 s. Statistical analysis showed that the three chelating solutions significantly reduced dentin microhardness when compared with water; however, there was no statistically significant difference among the three solutions.

Effect of vehicle on antimicrobial properties of calcium hydroxide pastes

The current discussion about the importance of intracanal dressings and the effect of vehicles on calcium hydroxide pastes is justified by controversy concerning the achievement of complete disinfection after preparation of infected root canals and the real antimicrobial effect of these vehicles. The aim of this study is to investigate the role of vehicles in the antimicrobial effect of calcium hydroxide pastes. Well-conducted research about the characteristics of calcium hydroxide, such as antimicrobial potential, physico-chemical aspects and histocompatibility, gives credibility to the choice of this medication in several clinical situations. Different vehicles have been added to calcium hydroxide in an attempt to enhance its properties. Scientific reasoning indicates the use of hydrosoluble vehicles (distilled water, saline) associated with calcium hydroxide because of their chemical characteristics of dissociation, diffusibility and filling capability which are decisive for the biological behavior, i.e., antimicrobial qualities and induction of tissue repair.

Treatment Of Middle-Apical Level Root Fracture In Necrotic Teeth

The purpose of this paper is to present two case reports of dental trauma with middle-apical level root fractures and pulp necrosis. The treatment consisted of programmed applications of calcium hydroxide until a calcified barrier was formed at the fracture level. The technique presented here proved efficient in treating horizontal fractures at the middle and apical thirds of the root.

Effect of different grades of gum rosins and hydrogenated resins on the solubility, disintegration, and dimensional alterations of Grossman cement

In the present study, we investigated the effect of the addition of different grades of gum rosins and hydrogenated resins to Grossman cement on dimensional stability, solubility and disintegration. pH and conductivity, which may affect these properties, were also determined. The experiments were performed according to Specification 57 of the American Dental Association for root canal cements using Grossman cements containing three gum rosins (grades X, WW, and WG) and two hydrogenated resins (Staybelite and Staybelite ester 10). The results showed that the solubility, disintegration, and dimensional stability of Grossman cement containing Staybelite and Staybelite ester 10 were inferior to the values considered acceptable by the American Dental Association Specification 57.

External and internal anatomy of third molars

The external and internal anatomy of 269 third molars (155 maxillary and 114 mandibular) were studied. The teeth were measured, classified according to their root number and shape and the internal anatomy was observed by the use of diaphanization. A great anatomical variability was found, with the presence of up to 5 roots in maxillary third molars and 3 roots in mandibular third molars. The number of root canals followed the same pattern.

The influence of different grades of rosins and hydrogenated resins on the powder-liquid ratio of Grossman cements

In this study, the effect of different grades of rosin and hydrogenated resin on the setting time of Grossman cement was evaluated. The experiments were carried following the American Dental Association Specification number 57 for root canal sealers. For this analysis, different Grossman cement powders were prepared using different grades of rosin (X,WW and WG) and hydrogenated resin (Staybelite and Staybelite ester 10). The pH and electrical conductance of the different grades of rosin and hydrogenated resin were evaluated. The physicochemical properties of the Grossman cements obtained with the different grades of rosin and hydrogenated resins interfere in the powder-liquid ratio of the cements. The sealers obtained with the hydrogenated resin showed a higher powder-liquid ratio.

Treatment of dens invaginatus in supernumerary teeth

The endodontic treatment and aesthetic restoration of a case of Oehlers Type I dens invaginatus in supernumerary teeth is presented.

Comparative in vitro study of apically extruded material after four different root canal Instrumentation techniques

Forty newly extracted human upper central incisors were submitted to root canal instrumentation 1 mm from the apex using four different techniques: standard, step-preparation, crown-down, and ultrasound, with distilled and deionized water as the irrigating solution. The extrusion product was collected into a collecting device constructed for this purpose. Extrusion was calculated by the determination of the mass of extruded material. The step-preparation technique caused a larger amount of extrusion than the standard technique, which in turn caused greater extrusion than the crown-down and ultrasound techniques. All techniques used caused extrusion of material beyond the apical foramen.

The external and internal anatomy of human mandibular canine teeth with two roots

This study investigated the internal anatomy of 65 human mandibular canines with two well-defined roots. The teeth were decalcified and injected with gelatin coloured with india ink. Diaphanization was carried out using clear resin to allow permanent preservation. It was found that all mandibular canines with two roots had two root canals. Lateral canals were found in 68.9% of teeth and 19.7% had lateral canals at the bifurcation. The results of the external measurements (cusp tip to root apex) showed that the average buccal root length was 23.0 mm and the average lingual root length was 22.7 mm. The maximum and minimum buccal lengths were 26.7 mm and 17.9 mm respectively and the maximum and minimum lingual lengths were 27.2 mm and 17.1 mm respectively. The buccal root was the larger of the two in 47.7% of teeth and 43.1% had roots of equal size. The lingual root was larger than the buccal root in 9.2% of cases. Clinicians should be aware of the anatomical variation that exists for mandibular canines.

Surface tension of different dentin bonding resin systems

Surface tension together with the hybridization process is one of the factors required to attain hybrid layer formation in dentinal tissue when bonding resin systems are used. The objective of the present study was to determine the surface tension of primers and fluid resins of 4 fourth generation bonding systems (All Bond 2, Denthesive Bond, Scotchbond Multi-Purpose and Optibond) and of one resin cement with metal affinity (Panavia Ex), all of them commonly used by Brazilian dentists. All primer solutions presented a lower surface tension than dentin, suggesting that all bonding systems are capable of wetting the tissue and probably cause tissue hybridization. The resin cement demonstrated the highest value, about 2 times that of dentin, which leads us to suppose that it is inefficient in deeply wetting the dentinal structure, without implying inefficient bonding since its analysis is multi-factorial.

External and internal anatomy of mandibular molars

The external and internal anatomy of 628 extracted, mandibular first and second molars was studied. The external anatomy was studied by measuring each tooth and by observing the direction of the root curvatures from the facial surface. The internal anatomy of the pulp cavity was studied by a method of making the teeth translucent.

In vitro action of various carbamide peroxide gel bleaching agents on the microhardness of human enamel

The authors verified a decrease in human enamel microhardness after application of the following carbamide peroxide gel bleaching agents for 8 hours daily for 1 week: 10% Nite White, 16% Nite White, Opalescence, Karisma Alpha and Perfect Smile. Statistical analysis showed that these agents caused a decrease in enamel microhardness. Nite White (16%) was the most effective in reducing enamel microhardness and Opalescente the least effective. Nite White (10%), Karisma Alpha and Perfect Smile fell into a statistically intermediate position.

Root canal therapy of an anomalous maxillary central incisor: a case report

A case of endodontic conservative treatment of a maxillary central incisor with an atypical crown and Type III dens invaginatus is presented. The greatest difficulty was to locate the root canals due to the atypical internal anatomy. There were not two clear canals, but the coronal pulp chamber showed two entrances to the root canal. The tooth presented a distal periodontal pocket and various lingual radicular grooves. The appearance of the crown was improved by alteration of its dimension using diamond rotary instruments and correction with photopolymerized resin.

[Dimensional instability of zinc oxide-eugenol based temporary sealing materials used in endodontics]

The dimensional instability of temporary sealing materials based on zinc oxide-eugenol was studied in vitro by chemical reaction between an indicator solution (5% nickel sulfate) and a developing solution (1% alcohol dimethylglixime). Thermal cycling was performed (5, 37 and 60 degrees C). Zinc acetate was added to zinc oxide to test its action on dimensional instability. The materials were divided into two groups. 1) group with double sealing (gutta-percha + sealing material), and 2) group without double sealing. It was concluded that none of the temporary sealing materials tested, with or without double sealing, prevented marginal infiltration when submitted to thermal cycling. The addition of zinc acetate to zinc oxide was not effective in preventing marginal infiltration.

["In vitro" evaluation of the action of various cavity varnishes]

The authors studied in vitro the capacity of FORP-USP cavity varnishes, COPALAINE (Prodonto), COPALITE (H. J. Bosworth Co.), CAVITINE (SS WHITE) and UNIVERSAL (SS WHITE) to promote impermeabilization. The tests were done by the use of filter paper and the impermeabilization was measured by the Rhodamine B stain infiltration. The FORP-USP cavity varnishes Copalaine and Copalite were more effective in promoting impermeabilization.

[Absorption capacity of different brands of paper points]

The absorption ability of paper points of different brands was assessed "in vitro". All points showed absorbing ability higher than 100 per center their own weight, but differences in moistening rate were detected among brands.