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PubMed2003

A comparative study of root canal preparation using FlexMaster and HERO 642 rotary Ni-Ti instruments.

AIM: To compare several parameters of root canal preparation using two different rotary nickel-titanium (Ni-Ti) instruments: FlexMaster (VDW, Munich, Germany) and HERO 642 (Micro-Mega, Besançon, France). METHODOLOGY: Fifty extracted human mandibular molars with root canal curvatures between 20 and 40 degrees were embedded into a muffle system. All root canals were prepared to size 45 using a high-torque motor with two different Ni-Ti instruments, FlexMaster and HERO 642. In both groups, irrigation was performed with 2 mL NaOCl (3%) after each instrument size. RC-Prep (Premier, Philadelphia, USA) was used as a chelating agent with each instrument. The following parameters were evaluated: straightening of curved root canals, postoperative root canal diameter, working safety (file fractures, perforations, apical blockages, loss of working length), cleaning ability and working time. Statistical analysis was performed using the Wilcoxon's test (P < 0.05) for straightening and Fishers's exact test (P < 0.05) for comparison of cross-sections, contact between pre- and postoperative diameter, root canal cleanliness and working time. RESULTS: Both Ni-Ti systems maintained the curvature well: the mean degree of straightening was 0.6 degrees for FlexMaster and 0.5 degrees for HERO 642. One file was fractured with the FlexMaster system, but further procedural incidents were not recorded. Following preparation with FlexMaster, 18% of the root canals had a round diameter, 53% an oval diameter and 29% an irregular diameter; HERO 642 preparations resulted in a round diameter in 25%, oval shape in 47% and irregular cross-sections in 28% of the cases. Mean working time was shorter for HERO 642 (66.0 s) than for FlexMaster (71.1 s). Cleanliness of the root canal walls was investigated under the SEM using 5-score indices for debris and smear layer. For debris, HERO 642 and FlexMaster achieved 73 and 70% scores of 1 and 2, respectively. The results for smear layer were similar: HERO 642 and FlexMaster achieved 33 and 26% scores of 1 and 2, respectively. Significant differences between the two systems were not detected for any of the parameters evaluated. CONCLUSIONS: Both systems respected original root canal curvature well and were safe. Both systems failed to remove debris and smear layer in the majority of the cases.

Chelating Agents↗
PubMed2006

Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth.

AIM: To compare the cleaning effectiveness and shaping ability of Mtwo, K3, and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 60 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into three groups of 20 canals. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared using a low-torque control motor. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. The amount of debris and smear layer was quantified on the basis of a numerical evaluation scale. The data established for scoring the debris and the smear layer was separately recorded and analysed statistically using the Kruskal-Wallis test. RESULTS: During preparation no instrument separated. Completely clean root canals were never observed. For debris removal Mtwo instruments achieved significantly better results (P < 0.001) than K3 and RaCe instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). Mtwo instruments maintained the original canal curvature significantly better (P < 0.05) than the other instruments. Instrumentation with Mtwo files was significantly faster than with K3 or RaCe instruments (P < 0.05). CONCLUSIONS: Under the conditions of this study, Mtwo instruments resulted in good cleaning and maintained the original curvature significantly better than K3 or RaCe files.

Analysis of Variance↗
PubMed1999

Morphological and atomic analytical changes of root canal wall dentin after treatment with thirty-eight percent Ag(NH3)2F solution and CO2 laser.

OBJECTIVE: The morphological and atomic analytical changes of the root canal wall dentin, treated with 38% diamine silver fluoride [Ag(NH3)2F] solution and irradiated by carbon dioxide (CO2) laser at the continuous wave mode were evaluated in vitro. SUMMARY BACKGROUND DATA: There has been no report on the morphological or atomic analytical changes of the effect of Ag(NH3)2F solution and CO2 laser on root canal walls. METHODS: Eighty extracted human single-rooted teeth were instrumented using a conventional technique and randomly divided into 8 groups of 10 teeth each. The teeth in group 1 were neither treated with Ag(NH3)2F solution nor lased. Groups 2, 3, and 4 were irradiated by laser at the parameters of 1, 2, and 3 W for 10 seconds, respectively. Group 5 was treated with Ag(NH3)2F solution only. The other 3 groups were treated with Ag(NH3)2F solution and then lased by the same method as groups 2, 3, and 4. After this treatment, 4 specimens each from group 1, 5, and 6 were analyzed by scanning electron microscope-energy dispersive x-ray spectroscopy (SEM-EDX) and other specimens in all groups were examined by scanning electron microscopy (SEM). RESULTS: The smear layer and debris of the control and lased specimens were not completely removed, but the areas of carbonization of evaporation of smear layer and open dentinal tubules were observed on the specimens treated with Ag(NH3)2F and lased at 1 W (group 6). After laser irradiation, the amount of silver on the root canal surfaces was significantly reduced to approximately one-third level on the measurement of SEM-EDX (p < 0.01). CONCLUSION: These results suggest that CO2 laser is an effective method to remove or melt smear layer of root canal walls after treatment with 38% Ag(NH3)2F solution if an appropriate parameter is selected.

Carbon Dioxide↗
PubMed2004

The effect of MTAD on the coronal leakage of obturated root canals.

The purpose of this study was to evaluate the effect of smear-layer removal using MTAD on coronal leakage of obturated root canals using a dye-leakage test. Fifty, extracted, single-rooted, human teeth were cleaned and shaped and divided into 5 equal groups of 10 each. The smear layer in groups 1 to 3 was left intact. The smear layer in groups 4 and 5 was removed using 17% EDTA or MTAD, respectively. After obturation of root canals, the access opening to each canal was filled with India ink for 48 h. The depth of coronal-dye penetration was measured using the Sigmascan software. ANOVA showed statistically significant differences among the groups (p < 0.05). Samples treated with MTAD yielded significantly less leakage than samples treated with sodium hypochlorite. The amount of dye penetration was not statistically different between teeth treated with MTAD or EDTA (p = 0.062).

Analysis of Variance↗
PubMedDate not supplied

Permeability effects of two dentin adhesive systems.

This in vitro study evaluated the effects of two dentin adhesive systems on dentin permeability. The XR-Bonding System modifies the smear layer but does not open dentinal tubules. The Kanca or "total-etch" technique (phosphoric acid, Tenure A and B, Scotchbond 2 Adhesive) removes the smear layer and opens dentinal tubules. Despite these differences, both systems reduced dentin permeability in a similar manner. XR-Bond decreased permeability to 52% of the smear layer value, while total etching reduced permeability to 66% of that value.

Acid Etching, Dental↗
PubMed2003

Efficiency of rotary nickel-titanium K3 instruments compared with stainless steel hand K-Flexofile. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth.

AIM: To determine the cleaning effectiveness and the shaping ability of K3 nickel-titanium rotary instruments and stainless steel hand K-Flexofiles during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 60 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 30 canals. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared by K3 instruments using a crown-down preparation technique or by K-Flexofiles using a reaming motion up to size 35. After each instrument, the root canals were flushed with 5 mL of a 2.5% NaOCl solution and at the end of instrumentation with 5 mL of saline. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale, using a scanning electron microscope. The data established for scoring the debris and the smear layer were separately recorded and analysed statistically using the Wilcox-on's test. RESULTS: None of the stainless steel K-Flexofiles but 5 K3 nickel-titanium instruments separated. Completely clean root canals were never observed. For debris removal, K-Flexofiles achieved significantly better results (P < 0.001) than K3 instruments. The results for remaining smear layer were similar (P > 0.05). K3 instruments maintained the original canal curvature significantly better (P < 0.0001) than K-Flexofiles. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals. CONCLUSIONS: Under the conditions of this study, K-Flexofiles allowed significantly better removal of debris than K3 instruments. K3 files maintained the original curvature significantly better. A number of K3 instruments fractured.

Dental Alloys↗
PubMed2002

Characterization of sound human dentin particles of sub-millimeter size.

OBJECTIVES: To obtain small dentin particles to provide material for the characterization of dentin. To study the interaction of etchants with dentin not covered by a smear layer and bonding agents. METHODS: Sound human dentin particles of sub-millimeter sizes were obtained by room temperature high-pressure fragmentation. Smear-layer free particles of three different average sizes were obtained by sieving. Surface areas were measured by the BET method. Simultaneous thermogravimetric and differential thermal analysis was carried out on all specimens and etched samples. Densities were measured by helium pycnometry. RESULTS: On average, the water, organic and mineral contents show the expected proportions. The more dense particles tend to be in the smaller sized fractions. Thus dentin particles of average size 100 microm have a density of 2.482(0.002) g/ml which is statistically different from the 300 microm average sized particles with 2.306(0.002) g/ml. However, the respective measured specific surface areas of 2.54(0.01) and 2.50(0.02) m(2)/g are not found to be statistically different. The specific surface areas of dentin particles increase upon etching, the increase being related to acid strength. Thermal analysis of acid-etched 200 microm diameter particles shows up to 75% loss of carbonate and only 30% loss of phosphate. SIGNIFICANCE: Smear-layer free dentin particles which have not been exposed to heat by grinding can be obtained by room temperature high-pressure fragmentation. Such sub-millimeter sized dentin particles can be acid-etched to significantly increase their specific surface area. Thermogravimetry used to analyze carbonate and phosphate contents gives new insight to the buffering action of human dentin.

Acid Etching, Dental↗
PubMed2004

Comparative investigation of two rotary nickel-titanium instruments: ProTaper versus RaCe. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth.

AIM: To determine the cleaning effectiveness and shaping ability of ProTaper and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 48 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 24 canals each. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared using a crown-down preparation technique. After each instrument, the root canals were flushed with a 2.5% NaOCl solution and at the end of instrumentation with NaCl. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer was quantified on the basis of a numerical evaluation scale, using a scanning electron microscope (SEM). The data established for scoring the debris and the smear layer were separately recorded and analysed statistically using the Wilcoxon test. RESULTS: Two ProTaper and three RaCe instruments fractured; there was no significant difference between instrument types (P > 0.05). Completely clean root canals were never observed. For debris removal, RaCe files achieved significantly better results (P < 0.001) than ProTaper instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). RaCe instruments maintained the original canal curvature significantly better (P < 0.05) than ProTaper instruments. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals. CONCLUSIONS: Under the conditions of this study, RaCe instruments resulted in relatively good cleaning and maintained the original curvature significantly better than ProTaper did.

Chelating Agents↗
PubMed1992

Endodontic dowel retention with resinous cements.

This study compared the capability of three composite resin cements to sustain a standard endodontic dowel. All of the systems incorporated some form of smear layer removal on the dentin of the endodontic channel. One system that used a methyl ethyl ketone drying agent provided inadequate clinical resistance to dislodgment of 5.4 DaN. A second cementing system that used only smear layer removal resisted loads at 54.7 DaN. The third cementing regimen that included a surface-initiated dentinal adhesive and smear layer removal recorded retention of 77.4 DaN. This study supported the concept that passively cemented dowels with composite resin can be as effective as actively seated dowels.

Acrylic Resins↗
PubMed1992

Effects of aluminum oxalate/glycine pretreatment solutions on dentin permeability.

Aluminum oxalate buffered with glycine to pH 0.5-2.5 has been proposed as a dentin pretreatment for the Gluma bonding system. In this experiment, the effects of 1-minute treatments of smear layers with these aluminum oxalates on the permeability of human dentin were determined in vitro. The aluminum oxalate solutions at pH 0.5-1.5 removed most of the original smear layer but occluded the tubules with crystalline deposits which decreased dentin permeability. Those solutions used at pH 2.0 and 2.5 increased dentin permeability. All dentin pretreatments increased dentin permeability when measured after a 24-hour storage period, especially the solutions at pH 2.0 and 2.5. The SEM correlates of these permeability changes indicated that these solutions remove the smear layer but reocclude the tubules with precipitates which are probably different forms of calcium oxalate, aluminum phosphate and calcium phosphates.

Adult↗
PubMed2002

A comparative study of root canal preparation using Profile .04 and Lightspeed rotary Ni-Ti instruments.

AIM: The purpose of this Study was to compare several parameters of root canal preparation using two different rotary nickel-titanium instruments: ProFile .04 (Dentsply/ Maillefer, Ballaigues, Switzerland) and Lightspeed (Lightspeed Technology Inc., San Antonio, TX, USA). METHODOLOGY: Fifty extracted mandibular molars with root canal curvatures between 20 degrees and 40 degrees were divided into two similar groups having equal mean curvatures. The teeth were then embedded into a muffle system as described by Bramante et al. (1987) and modified by Hülsmann et al. (1999b). All root canals were prepared using ProFile .04 or Lightspeed Ni-Ti instruments to size 45 following the manufacturers' instructions. The Lightspeed system was used in a step-back technique: ProFile .04 instruments were used in a crown-down technique. The following parameters were evaluated: straightening of curved root canals (superimposition of pre- and postoperative radiographs), postoperative root canal diameter (superimposition of pre- and postoperative photographs of root canal cross-sections), safety issues (file fractures. perforations, apical blockages, loss of working length) (protocol), cleaning ability (SEM-evaluation of root canal walls using a five-score system for debris and smear layer), and working time (protocol). Statistical analysis was performed using the Wilcoxon test (P < 0.05) for straightening, and Fisher's exact-test (P < 0.05) for comparison of cross-sections, for comparison of contact between pre- and postoperative diameter, root canal cleanliness and working time. RESULTS: Both Ni-Ti systems maintained curvature well; the mean degree of straightening was less than 1 degrees for both ProFile .04 and for Lightspeed with no statistical significance between the groups. Most procedural incidents occurred with Profile .04 instruments (three fractures), Lightspeed preparation was completed without instrument fractures. Loss of working length, perforations or apical blockage did not occur with either instrument. Following preparation with Profile.04. 64.0% of the root canals had a round, 30.7% an oval, and 5.3% an irregular cross-section, Lightspeed preparation resulted in a round cross-section in 41.3% of cases, an oval shape in 45.3% of cases: 13.3% of cases had an irregular cross-section. No significant differences were found between the two systems. Lightspeed instruments enlarged the root canal more uniformly with no specimen showing 50% or more contact between pre- and postoperative diameter. The difference was statistically significant only for the coronal third of the root canals (P = 0.032). Mean working time was significantly shorter for Profile .04 (105 s) than for Lightspeed (140 s) (P = 0.02). For debris removal Lightspeed achieved the best results (68% scores 1 and 2), followed by Profile .04 (48.4%) with no significant differences between the systems. The results for remaining smear layer were similar: the lowest amount of smear layer on the root canal walls was found after preparation with Lightspeed (30.7% scores 1 and 2). followed by Profile.04 (23.1%). In the coronal third of the root canals Lightspeed performed significantly better than Profile .04 (P = 0.029): in the middle and apical third the differences were not significant. CONCLUSIONS: Both systems under investigation respected original root canal curvature and were safe to use. Both systems can be recommended for clinical use.

Dental Alloys↗
PubMed1991

The effect of dentin pre-treatment and heat-augmented cure on marginal gap formation of a dentin bonding agent.

This study evaluated the effect of enhancing the cure of a DBA and the effect of dentin surface pre-treatment on marginal gap formation. Dentin cavities were prepared on extracted teeth and were pre-treated either with EDTA or phosphoric acid. Marginal leakage was expressed as percent length of margins with gaps. The mean percent length of margins with gaps for the chemically cured groups ranged from a maximum of 97% to a minimum of 85%. For the chemical/thermal-cured group, the mean percent length of margins with gaps was 95%, 95%, 73%, 35%, and 65%, corresponding to the following: pretreatment, no pre-treatment, EDTA, and phosphoric acid for 60, 15, or five s, respectively. SEM micrographs showed partial removal of one smear layer with EDTA and total removal of the smear layers with phosphoric acid. It is concluded that dentin pre-treatment methods have an effect on the percent length of margins with gaps when the DBA used had its cure supplemented with heat.

Acid Etching, Dental↗
PubMed1992

Relationship between bond strength and microleakage measured in the same Class I restorations.

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Adhesives↗
PubMed2005

Influence of Er:YAG laser irradiation on apical sealing of four different sealers.

The sealing of the root canal system is of fundamental importance for successful endodontic treatment. To obtain an adequate apical seal, many factors must be considered such as the presence of smear layer and the sealer applied. After canal preparation, this layer must be removed because it prevents close contact between the dentinal walls and the sealing material. The goal of this study was to evaluate the sealing ability of four different sealers after smear layer removal with either 17% EDTA-T irrigation or Er:YAG laser irradiation of 46 teeth. The canals were sealed with four different sealers: Sealapex, Ketac Endo, AH Plus and N-Rickert. The method for smear layer removal did not influence apical sealing. AH Plus and N-Rickert allowed less dye leakage when compared to Sealapex and Ketac Endo.

Calcium Hydroxide↗
PubMed2005

Application of biologically-oriented dentin bonding principles to the use of endodontic irrigants.

PURPOSE: To compare the removal of smear layer and the structure of the hybrid layer formed after the use of EDTA or MTAD solutions when used as a final flush. METHODS: Single-rooted extracted premolars (n=18) were collected and treated for root canal therapy using NaOCl irrigation followed by a final rinse of 17% EDTA, Biopure MTAD, or saline (negative control). The roots were obturated with gutta-percha and a hydrophilic HEMA-containing root canal sealer. The TEM specimens were impregnated with 50% silver nitrate to visualize sealing imperfections and nanoleakage. The structure of the coronal, middle and apical parts of root canal walls was examined using transmission electron microscopy. RESULTS: After NaOCl irrigation, a final rinse with BioPure MTAD or 17% EDTA completely removed the 2 microm-thick smear layer on mechanically instrumented root canal walls. The BioPure MTAD hybrid layer was thicker than the 17% EDTA hybrid layer. Both the BioPure MTAD and EDTA caused a collapse of the dentin matrix structure which impeded sealer infiltration and the formation of high quality hybrid layer bonding. The hybrid layers created in smear layer-covered dentin exhibited less potential for nanoleakage than the MTAD or EDTA hybrid layers.

Bicuspid↗
PubMed2004

Effect of sodium hypochlorite treatment on the molecular composition and morphology of human coronal dentin.

PURPOSE: The aim of the present study was to evaluate the deproteination potential of 5% aqueous NaOCl solution applied by rubbing action on the molecular composition and morphology of smear-layer covered and acid-etched human coronal dentin surfaces. MATERIALS AND METHODS: Paired specimens (n = 4 x 2 per group) of acid-etched (Group A) and smear-layer covered (Group B) human coronal dentin surfaces were sequentially treated with the NaOCl solution for time intervals ranging from 5 s to 120 s and analyzed by reflectance FTIR microspectroscopy and tapping mode atomic force microscopy. The changes in the mineral (v4 P-O stretching vibrations) to matrix (C = O stretching vibrations of amide I) peak area ratios and in the Ra roughness parameter were used to quantify the effect of treatment. Two-way ANOVA and Dunn's tests were used to assess the differences within each group and between groups (a = 0.05). RESULTS: In both groups, NaOCl treatment reduced organic matrix (amide I, II, III peaks), but did not affect carbonates and phosphates. In group A, the rate of deproteination was slow, and reached a peak value after 120 s. Tubule orifices became visible after 40 s of treatment; after 120 s, excessive porosity was detected, with Ra values presenting no statistically significant difference from group B. In group B after 10 s, the extent of deproteination was enhanced, reaching a plateau between 30 s and 60 s, and attaining a maximum after 120 s. Tubule diameter, intertubular porosity, and Ra were increased; intertubular dentin area was reduced. For both groups after 40 s of treatment, the mineral to matrix ratio recorded was similar to smear-layer-free sectioned dentin. CONCLUSION: The results of the present study imply that deproteination of mineralized or acid-etched dentin surfaces within a clinically relevant time frame may provide methods for bonding to dentin alternative to conventional technique-sensitive dentin hybridization.

Acid Etching, Dental↗
PubMed1995

Dentin wall adaptation of multiphase versus temperature thermoplasticized gutta-percha. A scanning electron microscopic study.

An in-vitro study was designed to compare dentin wall adaptation of Multiphase gutta-percha root canal obturation technique versus high temperature thermoplasticized gutta-percha (Obtura) in the presence and absence of smear layer. Forty single rooted teeth with straight canals were used. After decapitation roots were divided into two equal groups. Group (I) received final irrigation with EDTA and Sodium hypochlorite (NaOCI) to remove the smear layer, while roots in Group (II) were irrigated with NaOCI alone. Each group was then subdivided into two subgroups to represent the two filling techniques. Teeth were sectioned longitudinally and viewed under scanning electron microscope. Multiphase gutta-percha showed excellent adaptation to canal wall, specially in the absence of smear layer and displayed a homogeneous mass with little amount of voids than the Obtura system.

Dental Marginal Adaptation↗
PubMed2005

Effect of MTAD on postoperative discomfort: a randomized clinical trial.

The purpose of this study was to compare levels of postoperative discomfort after cleaning and shaping of root canals using two protocols for removal of smear layer. Seventy-three consecutive patients requiring root canal treatment were included. At random, canals were cleaned and shaped with one of the following protocols. In group 1, 5.25% sodium hypochlorite was used as the root canal irrigant. The smear layer was removed by placing 17% EDTA in the canal(s) for 1 min followed by a 5-ml rinse with 5.25% NaOCl. In group 2, canals were irrigated with 1.3% NaOCl; the smear layer was removed by placing MTAD in the canal(s) for 5 min. Access cavities were closed with a sterile cotton pellet and Cavit. The patients recorded degree of discomfort at various time intervals after cleaning and shaping on a visual analogue scale for 1 wk. No significant statistical difference was found in the degree of discomfort between the two groups (p = 0.58).

Adult↗