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.

Effect of ultrasonic and sonic activation of root canal sealers on the push-out bond strength and interfacial adaptation to root canal dentine.

AIM: To evaluate the effect of ultrasonic and sonic activation of two root canal sealers on interfacial adaptation and push-out bond strength (BS) to root canal dentine. METHODOLOGY: The root canals of seventy-eight roots of maxillary canines were prepared with NiTi rotary instruments under irrigation with 2.5% NaOCl and 17% EDTA. Canals were filled by lateral condensation of gutta-percha and AH Plus (n = 39) or MTA Fillapex (n = 39). Three subgroups (n = 13) were formed according to sealer activation: no activation (NA), sonic activation (SA, 20 s) and ultrasonic activation (US, 20 s). In three specimens of each subgroup, 0.1% rhodamine B was added to the sealer. Three 1-mm-thick slices were obtained from each root third. The first and second were used for push-out BS test and the third for a qualitative analysis of interfacial adaptation (gaps) and voids by confocal laser scanning microscopy (CLSM). Intratubular penetration of rhodamine B-labelled sealer was also assessed by CLSM. Data were analysed by two-way anova and Tukey's test (α = 0.05). RESULTS: AH Plus (2.58 ± 1.21) had higher push-out BS than MTA Fillapex (1.45 ± 0.71) (P = 0.000). UA (2.64 ± 1.44) had higher BS (P = 0.000) than NA (1.58 ± 0.73) and SA (1.83 ± 0.85), which did not differ significantly from each other (P = 0.3303). The coronal third had higher BS (2.48 ± 1.49) than the middle (2.08 ± 0.94) (P = 0.0003) and apical (1.48 ± 0.58) (P = 0.00) thirds. For both sealers, UA was associated with a more homogeneous filling material with better interfacial adaptation and greater quantity, density and length of tags in dentinal tubules. When UA was used, the tags had similar quantity, density and length to those formed without activation, but interfacial gaps and voids were observed. CONCLUSION: Ultrasonic activation was associated with higher BS values, deeper intratubular penetration and greater interfacial adaptation to root dentine than sonic activation and no activation techniques, AH Plus had higher BS values than MTA Fillapex irrespective of the type of activation.

Ex vivo evaluation of four final irrigation protocols on the removal of hard-tissue debris from the mesial root canal system of mandibular first molars.

AIM: To evaluate the efficacy of four final irrigation protocols on the reduction of hard-tissue debris accumulated within the mesial root canal system of mandibular first molars using micro-CT analysis. METHODOLOGY: Forty mesial roots of mandibular molars with a single and continuous isthmus connecting the mesiobuccal and mesiolingual canals (Vertucci's Type I configuration) were selected and scanned at a resolution of 8.6 µm. Canals were enlarged sequentially using WaveOne Small and Primary instruments activated in reciprocating motion without intracanal irrigation to allow debris to accumulate within the mesial root canal system. Then, specimens were anatomically matched and distributed into four groups (n = 10), according to the final irrigation protocol: apical positive pressure (APP), passive ultrasonic irrigation (PUI), Self-adjusting File (SAF) and XP-endo Finisher (XPF). The final irrigation procedures were performed over 2 min using a total of 5.5 mL of 2.5% NaOCl per canal. Reconstructed data sets were coregistered, and the mean percentage reduction of accumulated hard-tissue debris after the final irrigation procedures was compared statistically between groups using the anovapost hoc Tukey test with a significance level set at 5%. RESULTS: Reduction of accumulated hard-tissue debris was observed in all groups after the final irrigation protocol. Overall, PUI and XPF groups had higher mean percentage reductions of accumulated hard-tissue debris (94.1% and 89.7%, respectively) than APP and SAF groups (45.7% and 41.3%, respectively) (P < 0.05). No significant differences were found when comparing the results of PUI and XPF groups (P > 0.05) or APP and SAF groups (P > 0.05). CONCLUSIONS: The PUI technique and XP-endo Finisher instrument were associated with significantly lower levels of AHTD compared with conventional irrigation and the modified SAF system protocol in mesial root canals of mandibular molars.

Shaping ability of single-file reciprocating and heat-treated multifile rotary systems: a micro-CT study.

AIM: To investigate changes in three-dimensional geometry, in various cross-sectional morphological parameters and in the centring ability of root canals prepared with different preparation systems using microcomputed tomographic imaging technology. METHODOLOGY: Sixty-four mesial canals of mandibular molars were matched based on similar morphological dimensions using micro-CT evaluation and assigned to four experimental groups (n = 16), according to the canal preparation technique: Reciproc, WaveOne, Twisted File and HyFlex CM systems. Changes in several 2D (area, perimeter, form factor, roundness, minor and major diameter) and 3D [volume, surface area, structure model index (SMI)] morphological parameters, as well as canal transportation, were compared with preoperative values using Kruskal-Wallis and anovapost hoc Tukey's tests with the significance level set at 5%. RESULTS: Preparation significantly increased all tested parameters in the experimental groups. No significant differences were observed between groups regarding changes in volume, surface area, SMI, form factor and roundness of the root canal after preparation (P > 0.05). In the apical third, the Reciproc group had significantly greater changes in canal area, perimeter, major and minor diameters than the other groups (P < 0.05). Overall, the Twisted File and HyFlex CM systems were associated with significantly less transportation than the reciprocating instruments, Reciproc and WaveOne (P < 0.05). CONCLUSIONS: Shaping procedures led to the enlargement of the root canal space with no evidence of significant preparation errors. Changes in 3D parameters were not different between groups whilst, in the apical third, Reciproc was associated with significantly greater changes in several 2D parameters compared to the other groups. Twisted File and HyFlex CM systems were able to maintain the original canal anatomy with less canal transportation than Reciproc and WaveOne; however, these differences are unlikely to be of clinical significance.

Use of a dissolved oxygen microsensor for assessing the viability and thickness of microbial biofilm on root surfaces.

AIM: To evaluate the use of a dissolved oxygen microsensor (DOMS) for assessing the viability and thickness of microbial biofilms on the apical external surface of contaminated human tooth roots. METHODOLOGY: Apical biofilm formation was evaluated in 15 roots contaminated in vitro with a polymicrobial mixture of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans for 7, 21 and 60 days and in three freshly extracted roots with associated radiographically visible periapical lesions. In each root, the thickness and viability (measured by the amount of dissolved oxygen) of biofilm formed on the apical 2 mm were examined with the DOMS. Scanning electron microscopy (SEM) was used as an auxiliary analysis to confirm the existence of the biofilms detected by the DOMS. RESULTS: The DOMS detected dissolved oxygen on the biofilms formed on the three residual roots up to thickness of 375 µm, 480 µm and 1650 µm. In the 15 roots contaminated in vitro, the DOMS detected dissolved oxygen in six specimens up to thicknesses from 75 to 250 µm, and the intensity of the metabolic activity (biofilm thickness) was directly proportional to the contamination time. SEM confirmed the presence of biofilm in all roots. CONCLUSION: The dissolved oxygen microsensor allowed the measurement of the amount of dissolved oxygen in the biofilm, which is indicative of the intensity of the microbial metabolic activity (viability), correlating the results with biofilm thickness. The DOMS was effective in freshly extracted roots, but had limitations in roots contaminated in vitro after short periods (7 and 21 days) of contamination.

Microcomputed tomography analysis of the root canal morphology of single-rooted mandibular canines.

AIM: To investigate the anatomy of single-rooted mandibular canine teeth using microcomputed tomography (µCT). METHODOLOGY: One hundred straight single-rooted human mandibular canines were selected from a pool of extracted teeth and evaluated using µCT. The anatomy of each tooth (length of the roots, presence of accessory canals and apical deltas, position and major diameter of the apical foramen and distance between anatomical landmarks) as well as the two- and three-dimensional morphological aspects of the canal (area, perimeter, form factor, roundness, major and minor diameter, volume, surface area and structure model index) were evaluated. The results of the morphological analysis in each canal third were compared statistically using Friedman's test (α = 0.05). RESULTS: The length of the roots ranged from 12.53 to 18.08 mm. Thirty-one specimens had no accessory canals. The location of the apical foramen varied considerably. The mean distance from the root apex to the major apical foramen was 0.27 ± 0.25 mm, and the major diameter of the major apical foramen ranged from 0.16 to 0.72 mm. Mean major and minor diameters of the canal 1 mm short of the foramen were 0.43 and 0.31 mm, respectively. Overall, the mean area, perimeter, form factor, roundness, major and minor diameters, volume, surface area and structure model index (SMI) were 0.85 ± 0.31 mm(2) , 3.69 ± 0.88 mm, 0.70 ± 0.09, 0.59 ± 0.11, 1.36 ± 0.36 mm and 0.72 ± 0.14 mm, 13.33 ± 4.98 mm(3) , 63.5 ± 16.4 mm(2) and 3.35 ± 0.64, respectively, with significant statistical difference between thirds (P < 0.05). CONCLUSIONS: The anatomy and morphology of the root canal of single-rooted canines varied widely in different levels of the root.

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.

Pulp pathosis in inlayed teeth of the ancient Mayas: a microcomputed tomography study.

AIM: To evaluate three-dimensionally, using microcomputed tomography (µCT), the anatomical relationship between the cavity prepared to hold the inlay stone and the pulp chamber in the teeth of the ancient Maya. METHODOLOGY: Six well-preserved teeth from Maya corpses found in an archaeological site in Guatemala (approximately 1600 year old) were selected and scanned using a high-resolution µCT system (SkyScan 1174v2; SkyScan N.V., Kontich, Belgium). The sample comprised six maxillary teeth: two canines, one premolar, two central incisors and one lateral incisor. All teeth had one or two inlay stones on the buccal surface of the crown. Each specimen was scanned at an isotropic resolution of 22.5 µm, a rotational step of 0.70°, a rotational angle of 180° and a 3.1-s exposure time, using a 1-mm-thick aluminium filter. Images of each specimen were reconstructed from apex to the crown with dedicated software (NRecon v1.6.1.5) in approximately 450 slices. CTan v1.11 and CTVol v2.1 were used for three-dimensional visualization and qualitative analysis of the external and internal anatomy of the teeth. RESULTS: The tooth modification in all samples was classified as type E1 (one stone on the buccal surface of the crown) or E2 (two stones on the buccal surface of the crown). In the canine teeth, the cavities created to insert the inlay stone did not reach the pulp chamber. Conversely, in the maxillary incisors, the cavities clearly perforated the pulp chamber resulting in massive internal inflammatory resorption or partial calcification of the pulp cavity. In the premolar tooth, a small perforation of the pulp chamber under the buccal cusp, without morphological alteration of the intraradicular dentine, was observed. CONCLUSIONS: Microcomputed tomography analysis of teeth of the ancient Maya civilization showed that the inlay cavities cut reached the pulp chamber in the maxillary incisors and premolar teeth, with the potential to cause pulp and periapical disease.

The anatomy of two-rooted mandibular canines determined using micro-computed tomography.

AIM: To investigate the internal and external anatomy of extracted human mandibular canines with two roots and two distinct canals using micro-computed tomography (µCT). METHODOLOGY: Fourteen two-rooted human mandibular canines were scanned using a high-resolution µCT system (SkyScan 1174v2; SkyScan N.V., Kontich, Belgium). The images were processed to evaluate the size of the roots, the furcation regions, the presence of accessory canals, the mean distances between several anatomical landmarks, the position of the apical foramina, the direction of root curvatures, the cross-sectional appearances (SMI index), the volume and surface areas of the root canals. RESULTS: Root bifurcation was located in both apical (44%, n = 6) and middle (58%, n = 8) thirds of the root. The size of the buccal and lingual roots was similar in 29% of the sample. From a buccal view, no curvature towards the lingual or buccal direction occurred in either roots. From a proximal view, no straight lingual root occurred. In both views, S-shaped roots were found in 21% of the specimens. Location of the apical foramen varied considerably, tending to the mesio-buccal aspect of both roots. Lateral and furcation canals were observed mostly in the cervical third in 29% and 65% of the sample, respectively. The structure model index (SMI) index ranged from 1.87 to 3.86, with a mean value of 2.93 ± 0.46. Mean volume and area of the root canals were 11.52 ± 3.44 mm(3) and 71.16 ± 11.83 mm(2), respectively. CONCLUSIONS: The evaluation of two-rooted mandibular canines revealed that bifurcations occurred in the apical and middle third. S-shaped roots were found in 21% of the specimens. Mean volume, surface area and SMI index of the root canals were 11.52 mm(3), 71.16 mm(2) and 2.93, respectively.

Evaluation of physicochemical properties of four root canal sealers.

AIM: To assess the physicochemical properties and the surface morphology of AH Plus, GuttaFlow, RoekoSeal and Activ GP root canal sealers. METHODOLOGY: Five samples of each material were evaluated for setting time, dimensional alteration, solubility and radiopacity tests, according to ANSI/ADA Specification 57. A total of 50 mL of deionized distilled water from the solubility tests were used to measure the metal solubility by atomic absorption spectrometry. The morphologies of the external surface and the cross-section of the samples were analysed by means of a scanning electron microscope (SEM). Statistical analysis was performed by using one-way anova and post hoc Tukey-Kramer tests with the null hypothesis set as 5%. RESULTS: AH Plus had the longest setting time (580.6 ± 3.05 min) (P<0.05). Activ GP did not have a mean value on the radiopacity and solubility tests (1.31 ± 0.35 mm and 11.8 ± 0.43%, respectively) in accordance with ANSI/ADA, being significantly different from the other materials (P<0.05), which had mean values for these tests in accordance with the ADA's requirements. GuttaFlow was the only sealer that conformed to the Specification 57 concerning the dimensional alteration test (0.44 ± 0.16%) (P<0.05). The spectrometry test revealed significant Ca(2+), K(+), Zn(2+) ion release from Activ GP sealer (32.57 ± 5.0, 1.57 ± 0.22 and 8.20 ± 1.74 µg mL(-1), respectively). In SEM analysis, the loss of matrix was evident and the filler particles were more distinguishable in all groups. CONCLUSIONS: The setting time of all sealers was in accordance with ANSI/ADA's requirements. Activ GP did not fulfill ANSI/ADA's protocols regarding radiopacity, dimensional alteration and solubility. GuttaFlow was the only sealer that conformed to the Specification 57 in all tests. SEM analysis revealed that the surfaces of all sealers had micromorphological changes after the solubility test.

Histological evaluation of the effectiveness of increased apical enlargement for cleaning the apical third of curved canals.

OBJECTIVE: To evaluate the influence of apical size on cleaning of the apical third of curved canals prepared with rotary instruments. METHODOLOGY: Forty-four mesiobuccal canals of maxillary molars teeth were instrumented to different apical sizes (30, 0.02; 35, 0.02; 40, 0.02; 45, 0.02) using a crown-down technique. After canal preparation, the apical thirds of the roots were submitted to histological processing and examination. The specimens were analysed at 40× magnification and the images were submitted to morphometric analysis with an integration grid to evaluate the percentage of debris and uninstrumented root canal walls. The action of the instruments on the root canal walls was assessed based on the surface regularity, abrupt change on the continuity of root canal walls, and partial or total pre-dentine removal. The results were statistically compared using one-way anova with post hoc Tukey test. Pearson's correlation was performed to identify potential correlations between values. RESULTS: The percentage of uninstrumented root canal dentine was higher when apical enlargement was performed with instruments 30, 0.02 taper (55.64 ± 4.62%) and 35, 0.02 taper (49.03 ± 5.70%) than with instruments 40, 0.02 taper (38.08 ± 10.44%) and 45, 0.02 taper (32.65 ± 8.51%) (P < 0.05). More debris were observed when apical enlargement was performed with instruments 30, 0.02 taper (34.62 ± 9.49%) and 35, 0.02 taper (25.33 ± 7.37%) (P < 0.05). There was a significant correlation between the amount of remaining debris and the perimeter of uninstrumented root canal dentine (r = 0.9130, P < 0.001). CONCLUSION: No apical enlargement size allowed the root canal walls to be prepared completely. Apical third cleanliness could be predicted by instrument diameter.

Nitric oxide detection in cell culture exposed to LPS after Er:YAG laser irradiation.

AIM: To evaluate in vitro the effect of calcium hydroxide [Ca(OH)(2)] and Er:YAG laser on bacterial endotoxin [also known as lipopolysaccharide (LPS)] as determined by nitric oxide (NO) detection in J774 murine macrophage cell line culture. METHODOLOGY: Samples of LPS solution (50 microg mL(-1)), Ca(OH)(2) suspension (25 mg mL(-1)) and LPS suspension with Ca(OH)(2) were prepared. The studied groups were: I - LPS (control); II - LPS + Ca(OH)(2); III - LPS + Er:YAG laser (15 Hz 140 mJ); IV - LPS + Er:YAG laser (15 Hz 200 mJ); V - LPS + Er:YAG laser (15 Hz 250 mJ), VI - Pyrogen-free water; VII - Ca(OH)(2). Murine macrophage J774 cells were plated and 10 microL of the samples were added to each well. The supernatants were collected for NO detection by the Griess reaction. Data were analysed statistically by one-way anova and Tukey's test at 5% significance level. RESULTS: The mean and SE (in micromol L(-1)) values of NO release were: I - 10.48 +/- 0.58, II - 6.41 +/- 0.90, III - 10.2 +/- 0.60, IV - 8.35 +/- 0.40, V - 10.40 +/- 0.53, VI - 3.75 +/- 0.70, VII - 6.44 +/- 0.60; and the values for the same experiment repeated after 1 week were: I - 21.20 +/- 1.50, II - 9.10 +/- 0.60, III - 19.50 +/- 1.00, IV - 18.50 +/- 0.60, V - 21.30 +/- 0.90, VI - 2.00+/- 0.20, VII - 6.80 +/- 1.70. There was no significant difference (P > 0.05) between the control and the laser-treated groups (III, IV and V), or comparing groups II, VI and VII to each other (P > 0.05). Group I had significantly higher NO release than group II (P < 0.05). Groups II and VI had similar NO release (P > 0.05). CONCLUSIONS: Calcium hydroxide inactivated the bacterial endotoxin (LPS) whereas none of the Er:YAG laser parameter settings had the same effectiveness.

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.

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.

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.

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.

A comparison of techniques for cleaning endodontic files after usage: a quantitative scanning electron microscopic study.

One-hundred ten new endodontic files were used to prepare canals and were then cleaned using three different techniques: (a) gauze soaked with alcohol, (b) sponge soaked with alcohol, and (c) ultrasonic bath. The cleaning ability of each of these techniques immediately after use and after 1 h of delay were compared. Identical areas on each file were examined by using a custom-made jig. Morphometric analysis of debris was carried out using a Bioquant image analysis system. Sponge/alcohol was the worst cleaning method; this was significantly different from the other two techniques. The gauze/alcohol and ultrasonic bath were similar. The 1-h delay before instrument cleaning did not affect the ability of any of the techniques tested. None of the methods tested were able to totally clean the files.

Two methods to evaluate the antimicrobial action of calcium hydroxide paste.

The objective of this study was to analyze two methods for determining the antimicrobial effectiveness of (i) calcium hydroxide plus saline, (ii) calcium hydroxide plus polyethylene glycol, and (iii) calcium hydroxide plus camphorated paramonochlorophenol. Four microorganisms (Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), and Bacillus subtilis (ATCC 6633)), one yeast (Candida albicans (ICB/USP-562)), and one mixture of these organisms were used. The strains were inoculated in Brain Heart Infusion (BHI) and incubated at 37 degrees C for 24 h. Two methods, the direct exposure test and the agar diffusion test were used to evaluate antimicrobial effects. For the direct exposure test (DET) 288 paper points were contaminated with the standard microbial suspensions and exposed to the intracanal dressings for 1, 24, 48, and 72 h. The points were immersed in Letheen Broth, followed by incubation at 37 degrees C for 48 h. An inoculum of 0.1 ml obtained from Letheen Broth was then transferred to 7 ml of BHI under identical incubation conditions, and microbial growth was evaluated. Pastes showed activity between 1 and 72 h, depending on the microorganism/mixture tested. For the agar diffusion test 36 Petri plates with 20 ml of BHI agar were inoculated with 0.1 ml of the same microbial suspension used for the DET, using sterile swabs that were spread on the medium. Five cavities were made in each of two agar plates (total = 10) and completely filled with one of the calcium hydroxide pastes. The plates were preincubated for 1 h at environmental temperature and then incubated at 37 degrees C for 24 to 48 h. The inhibition zone around each well was recorded in millimeters, and the results were submitted to ANOVA and Tukey test (alpha = 0.05). All intracanal dressings induced inhibition zones (range 5.0-10.0 mm). Data obtained showed that both the DET and agar diffusion test are useful in establishing the calcium hydroxide antimicrobial spectrum, thus improving infection control protocols. The direct exposure method is independent of other variables and is a practical laboratory procedure. A complete antimicrobial effect was observed after 48 h on indicator microorganisms, in both tests, irrespective of the calcium hydroxide paste vehicle.

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.