Comparison of dentin root canal permeability and morphology after irradiation with Nd:YAG, Er:YAG, and diode lasers

The aim of this study was to compare the effects of Nd:YAG, Er:YAG, and diode lasers on the morphology and permeability of root canal walls. The three laser wavelengths mentioned interact differently with dentin and therefore it is possible that the permeability changes caused will determine different indications during endodontic treatment. Twenty-eight human single-rooted teeth were instrumented up to ISO 40 and divided into four groups: group C, control (GC), non-laser irradiated; group N (GN), irradiated with Nd:YAG laser; group E (GE), with Er:YAG laser and group D (GD) with diode laser. After that, the roots were filled with a 2% methylene blue dye, divided into two halves and then photographed. The images were analyzed using Image J software and the percentage of dye penetration in the cervical, middle, and apical root thirds were calculated. Additional scanning electron microscopy (SEM) analyses were also performed. The analysis of variance (ANOVA) showed significant permeability differences between all groups in the middle and cervical thirds (p < 0.05). The Tukey test showed that in the cervical third, GN presented means of dye penetration statistically significantly lower than all of the other groups. In the middle third, GE and GD showed statistically higher dye penetration means than GC and GN. SEM analysis showed melted surfaces for GN, clean wall surfaces with open dentinal tubules for GE, and mostly obliterated dentinal tubules for GD. Er:YAG (2,094 nm) laser and diode laser (808 nm) root canal irradiation increase dentinal permeability and Nd:YAG (1,064 nm) laser decreases dentin permeability, within the studied parameters.

Effect of ion-exchange temperature on mechanical properties of a dental porcelain

The objective of this study was to determine the influence of different ion-exchange temperatures on the biaxial flexural strength (sigma(f)), hardness (HV) and indentation fracture resistance (K(IF)) of a dental porcelain. Disk-shaped specimens were divided into five groups (n = 10) and submitted to an ion-exchange procedure using KNO(3) paste for 15 min in the following temperatures (degrees C); (I) 430; (II) 450; (III) 470; (IV) 490; (V) 510; and control (no ion exchange). The value of sigma(f) was determined in artificial saliva at 37 degrees C. The values of HV and K(IF) were obtained using 3 Vickers indentations in each specimen (19.6 N). Results showed that ion exchange increases significantly the properties of the material as compared to the control and no significant differences were found among the temperatures tested for any of the properties studied. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Effect of processing induced particle alignment on the fracture toughness and fracture behavior of multiphase dental ceramics

Objective. To investigate the processing induced particle alignment on fracture behavior of four multiphase dental ceramics (one porcelain, two glass-ceramics and a glass-infiltrated-alumina composite). Methods. Disks (empty set12mm x 1.1 mm-thick) and bars (3 mm x 4 mm x 20 mm) of each material were processed according to manufacturer instructions, machined and polished. Fracture toughness (K(IC)) was determined by the indentation strength method using 3-point bending and biaxial flexure fixtures for the fracture of bars and disks, respectively. Microstructural and fractographic analyses were performed with scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Results. The isotropic microstructure of the porcelain and the leucite-based glass-ceramic resulted in similar fracture toughness values regardless of the specimen geometry. On the other hand, materials containing second-phase particles with high aspect ratio (lithium disilicate glass-ceramic and glass-infiltrated-alumina composite) showed lower fracture toughness for disk specimens compared to bars. For the lithium disilicate glass-ceramic disks, it was demonstrated that the occurrence of particle alignment during the heat-pressing procedure resulted in an unfavorable pattern that created weak microstructural paths during the biaxial test. For the glass-infiltrated-alumina composite, the microstructural analysis showed that the large alumina platelets tended to align their large surfaces perpendicularly to the direction of particle deposition during slip casting of green preforms. Significance. The fracture toughness of dental ceramics with anisotropic microstructure should be determined by means of biaxial testing, since it results in lower values. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Subcritical crack growth in porcelains, glass-ceramics, and glass-infiltrated alumina composite for dental restorations

The objective was to compare fracture toughness (K(Ic)), stress corrosion susceptibility coefficient (n), and stress intensity factor threshold for crack propagation (K(I0)) of two porcelains [VM7/Vita (V) and d.Sign/Ivoclar (D)], two glass-ceramics [Empress/Ivolcar (E1) and Empress2/Ivlocar (E2)] and a glass-infiltrated alumina composite [In-Ceram Alumina/Vita (IC)]. Disks were constructed according to each manufacturer`s processing method, and polished before induction of cracks by a Vickers indenter. Crack lengths were measured under optical microscopy at times between 0.1 and 100 h. Specimens were stored in artificial saliva at 37A degrees C during the whole experiment. K(Ic) and n were determined using indentation fracture method. K(I0) was determined by plotting log crack velocity versus log K(I). Microstructure characterization was carried out under SEM, EDS, X-ray diffraction and X-ray fluorescence. IC and E2 presented higher K(Ic) and K(I0) compared to E1, V, and D. IC presented the highest n value, followed by E2, D, E1, and V in a decreasing order. V and D presented similar K(Ic), but porcelain V showed higher K(I0) and lower n compared to D. Microstructure features (volume fraction, size, aspect ratio of crystalline phases and chemical composition of glassy matrix) determined K(Ic). The increase of K(Ic) value favored the increases of n and K(I0).

Tooth Replantation After Use of Euro-Coffins Solution or Bovine Milk as Storage Medium: A Histomorphometric Analysis in Dogs

Purpose: Euro-Collins solution was developed for the preservation of organs for transplantation, whose characteristics have raised interest for its use as a storage medium for avulsed teeth before replantation. This study evaluated histologically and morphometrically the healing process of dog teeth replanted after storage in Euro-Collins solution or bovine milk. Materials and Methods: Eighty roots of 4 young adult mongrel clogs were randomly assigned to 4 groups (n = 20) and the root canals were instrumented and obturated with gutta-percha and a calcium hydroxide-based sealer. After 2 weeks, the teeth were extracted and subjected to the following protocols: GI (negative control), replantation immediately after extraction; GII (positive control), bench-drying for 2 hours before replantation; GIII and GIV, immersion in 10 mL of whole bovine milk and Euro-Collins solution at 4 C, respectively, for 8 hours before replantation. The animals were sacrificed 90 days postoperatively. The pieces containing the replanted teeth were subjected to routine processing for histologic and histometric analyses under light microscopy and polarized light microscopy. Results: Root resorption was observed in all groups. GII exhibited the greatest loss of dental structure (P < .01), and inflammatory resorption was predominant in this group. Storage in milk showed poorer results than immediate replantation and storage in Euro-Collins solution (P < .01). The teeth stored in Euro-Collins solution presented similar extension of root resorption and periodontal ligament reorganization to those of immediately replanted teeth. Conclusions: The findings of this study suggest that the Euro-Collins solution is an adequate storage medium for keeping avulsed teeth for up to 8 hours before replantation. Crown Copyright (C) 2010 Published by Elsevier Inc on behalf of American Association of Oral and Maxillofacial Surgeons. All rights reserved. Oral Maxillofac Surg 68:111-119, 2010

Comparison of GPX with or without solvent and hand files in removing filling materials from root canals-An ex vivo study

Objective. The aim of this study was to compare GPX instruments and hand files for gutta-percha removal. Study design. Fifty maxillary central incisors with a single straight canal were instrumented and filled. The teeth were divided into 5 groups of 10 specimens each, according to the gutta-percha removal techniques: group 1: GPX (21-mm-long teeth); group 2: GPX and xylol as solvent (21-mm-long teeth); group 3: GPX (25-mm-long teeth); group 4: GPX and xylol as solvent (25-mm-long teeth); and group 5: hand files and xylol as solvent. The amount of time for gutta-percha removal and the number of fractured instruments were evaluated. Radiographs were taken, and the teeth were grooved longitudinally and split. The area of residual debris was measured using Sigma Scan software. Results. The time for filling material removal was significantly shorter when GPX was used (P < .05). Overall, hand files and solvent produced fewer remnants of filling materials (P < .05). In the GPX 25 mm-long teeth group, the filling material was not removed in the apical third. Conclusions. Under the experimental conditions, the GPX instruments proved to be faster than hand instruments in removing root filling materials; however, hand instruments left a smaller amount of residual filling materials on the canal walls. The GPX instruments did not pull the gutta-percha beyond its tip. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110: 675-680)

Root Canal Area Increase Promoted by the EndoSequence and ProTaper Systems: Comparison by Computed Tomography

Introduction: The aim of this study was to compare the increase of the root canal area after instrumentation with EndoSequence or ProTaper rotary systems. Methods: Twenty-two mesial root canals from mandibular molars were instrumented. Teeth were mounted on a base, numbered, and divided into 2 groups; teeth from 1-11 (PT group) were instrumented by using the ProTaper system, and teeth from 12-22 (ES group) were instrumented by using the EndoSequence system. Cone beam computed tomography was performed on all teeth before and after instrumentation. Measurements at 3,5, and 7 mm as well as differences in instrument performance were statistically compared by the Student t test at 5% significance level. Results: Both systems increased significantly the root canal area (P < .05) at all levels. Comparison between the rotary systems showed significantly greater increase (P < .05) for EndoSequence at 3 mm, with no statistically significant difference (P < .05) at the other levels. Conclusions: Both rotary systems increased significantly the root canal area. (J Endod 2010;36:1179-1182)

Bacterial leakage in obturated root canals-part 2: a comparative histologic and microbiologic analyses

Objective. In this study, presence of dentin infection in root canals, obturated with 4 techniques submitted to the bacterial leakage test, was evaluated using histologic methods. Study design. The canals of palatal roots of 160 molars were instrumented and divided into different groups, according to the obturation technique used (lateral condensation, MicroSeal system, Touch `n Heat + Ultrafil, and Tagger`s hybrid technique) and extent of the remaining obturation material (5 mm and 10 mm). Ten additional roots were used as control samples. The roots were sterilized in ethylene oxide and mounted on a device for evaluation of bacterial leakage using the bacteria Enterococcus faecalis for 120 days. After the leakage test, roots were microscopically analyzed for the presence of dentin infection in the root canals and dentinal tubules. Results. A total of 154 specimens were analyzed using both methodologies in the experimental groups; 50 root canals (32.4%) showed bacterial leakage at the end of the experimental period, and 118 (76.6%) showed the presence of bacteria in the root canals using the histologic criteria. The lateral condensation technique allowed lower penetration of bacteria in the root canals and dentinal tubules, followed by Touch `n Heat + Ultrafil, MicroSeal, and Tagger`s hybrid technique, which allowed significantly greater penetration of bacteria. Root canals with 10 mm of remaining obturation material presented similar bacterial penetration as root canals with 5 mm. Conclusions. Even when an adequate seal of the apical foramen was shown by the absence of turbidity in the bacterial leakage test, E. faecalis dentin infection was present in a high percentage of the root canals after 120 days of root filling exposure to the bacteria. Tagger`s hybrid technique presented greater quantity of bacteria in histologic sections than root canals obturated with the other techniques. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: 788-794)

Efficacy of Profile .04 taper series 29 in removing filling materials during root canal retreatment-an in vitro study

Objective. The aim of this study was to compare Profile .04 taper series 29 instruments and hand files for gutta-percha removal. Study design. Twenty maxillary central incisors with a single straight canal were instrumented and filled. The teeth were divided into 2 groups of 10 specimens each, according to gutta-percha removal techniques: Group 1- Profile series 29 and Group 2- hand files and solvent. The amount of time for gutta-percha removal and the number of fractured instruments were evaluated. Radiographs were taken and the teeth were grooved longitudinally and split. The area of residual debris was measured using computer software. Results. The time for filling material removal was significantly shorter when Profile series 29 was used (P = .00). Regarding cleanliness, there were no statistical differences in the teeth halves evaluations (P = .05). Hand instruments cleaned the canals significantly better than Profiles, in the radiographic analysis considering the whole canal. Overall, the radiographic analysis showed a smaller percentage of residual debris than the teeth halves analysis. Conclusion. The Profile series 29 instruments proved to be faster than hand instruments in removing root filling materials; however, hand instruments yielded better root canal cleanliness. Some residual debris was not visualized by radiographs. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: e46-e50)

Ultrasonic Chemical Vapor Deposition-coated Tip versus High- and Low-speed Carbide Burs for Apicoectomy: Time Required for Resection and Scanning Electron Microscopy Analysis of the Root-end Surfaces

This study compared ultrasonic chemical vapor deposition (CVD)-coated tip (CVDentus #8.1117-1; Clorovale Diamantes Ind. e Com. Ltda Epp, Sao Jose dos Campos, SP, Brazil) versus high-speed (#FG700L) and low-speed (#699) carbide burs for apicoectomy, evaluating the time required for resection and analyzing the root-end surfaces by scanning electron microscopy. Thirty extracted human premolars had the canals instrumented and obturated and were randomly assigned to 3 groups (n = 10), according to the instrument used for root-end resection. The time required for resection of the apical 2 mm of each root was recorded. The resected apical segments were dried, sputter coated with gold, and examined with a scanning electron microscope at X 350 magnification. A four-point (0-3) scoring system was used to evaluate the apical surface smoothness. The results were analyzed statistically by the Kruskal-Wallis test and two-by-two comparisons analyses were performed using the Miller test. The significance level was set at 5%. Root-end resection with the high-speed bur was significantly faster (p < 0.05) compared with the low-speed bur and CVD tip. The carbide burs produced significantly smoother root-end surfaces than the CVD tip (p < 0.05). The low-speed bur produced the smoothest root-end surfaces, whereas the roughest and most irregular root ends (p < 0.05) were obtained with the CVD tip. However, no statistically significant difference (p > 0.05) was found between the high- and low-speed burs regarding the surface roughness of the resected root ends (p > 0.05). In conclusion, under the tested conditions, ultrasonic root-end resection took a longer time and resulted in rougher surfaces compared with the use of carbide burs at both high and low speed. (J Endod 2009;35:265-268)

Bacterial leakage in root canals obturated by different techniques. Part 1: microbiologic evaluation

Objective. This study compared the coronal bacterial leakage of root canals obturated by different techniques and with different lengths of obturation. Study design. The canals of palatal roots of 160 maxillary molars were instrumented and divided into different groups according to the obturation technique used (lateral condensation, Microseal system, Touch `n Heat + Ultrafil system, or Tagger`s hybrid technique) and the length of obturation (5 mm or 10 mm). The roots were impermeabilized, sterilized in ethylene oxide, and mounted on a device for evaluation of the bacterial leakage. Results. Tagger`s hybrid technique produced a statistically greater number of specimens with coronal leakage than the other techniques. There was no statistically significant difference between the lateral condensation, Touch `n Heat + Ultrafil, and Microseal groups. Root canals with 10 mm of obturation produced a statistically significantly smaller number of specimens with leakage than root canals with 5 mm of obturation. Conclusion. Tagger`s hybrid technique produced a greater number of specimens with coronal leakage than the other techniques, and a greater number of root canals with 5 mm of obturation leaked than root canals with 10 mm of obturation.

Post space cleaning using a new nickel titanium endodontic drill combined with different cleaning regimens

This study compared the effect of two drills and five cleaning regimens on post space debridement. One hundred extracted premolars were instrumented and obturated with warm vertical compaction of gutta percha. The teeth were divided into two groups according to the drill used to remove gutta percha/sealer and for post space preparation: a Largo drill (Largo; Dentsply, St Quentin en Yvelines, France) or a MTwo-PF drill (Sweden&Martina, Due Carrare, Padova, Italy). The following cleaning regimens were used: EDTA, ultrasonics, ultrasonics + EDTA, phosphoric acid, and distilled water. Scanning electron microscopic images of the post spaces were taken, and the presence of debris and of open dentin tubules were evaluated. The ultrasonics + EDTA, phosphoric acid, and EDTA groups were comparable in open tubules scores for both drills and in debris scores after the use of MTwo-PF (p > 0.05). The ultrasonics and control groups performed significantly worse (p < 0.05). The MTwo-PF drill resulted as effective as the Largo drill in obtaining a good post space cleaning, especially when followed by ultrasonics + EDTA irrigant regimen.

Reliability of Metalloceramic and Zirconia-based Ceramic Crowns

Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing.

High frequency of low-level microsatellite instability in early colorectal cancer

Molecular events in early colorectal cancers (CRCs) have not been well elucidated because of the low incidence of early CRCs in clinical practice. Therefore, we studied 104 sporadic early CRCs with invasion limited to submucosa compared with 116 advanced CRCs. Loss of heterozygosity as well as microsatellite instability (MSI) status was examined. A significantly high frequency of low-level MSI (MSI-L) phenotype was detected in early CRCs (51.0%) compared with advanced CRCs (25.9%; P = 0.0001). In early and advanced CRCs, samples with MSI-L phenotype differed from microsatellite stable (MSS) phenotype with respect to loss of heterozygosity at 1p32 and 8p12-22. MSI-L is a frequent genetic event in early CRCs and may be a novel pathway in colorectal carcinogenesis distinct from both MSI-H and MSS.

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

P>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 40x 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.