Claudia Reis

The Self-Adjusting File Optimizes Debridement Quality in Oval-shaped Root Canals

INTRODUCTION Oval-shaped canals represent a challenge for rotary nickel-titanium (NiTi) files because buccal and/or lingual recesses are commonly left uninstrumented. The aim of the present study was to evaluate the debridement quality of the Self-Adjusting File (SAF) system in oval canals and compare it with the debridement achieved by a commonly used NiTi rotary system. METHODS A careful specimen selection resulted in two equal groups each consisting of 12 extracted mandibular canines with oval canals that had vital pulps before extraction. All canals had a buccolingual diameter that was at least 2.5 times larger than that of the mesiodistal one as defined from radiographs. One group was subjected to the SAF protocol, whereas the other group underwent conventional protocol; the ProTaper system up to the F2 instrument was used with syringe and open end needle irrigation. Sodium hypochlorite (5.25%) was used as an irrigant for both groups. The roots were then histologically processed and 0.6-μm-thick cross-sections were obtained every 0.5 mm from the 1- to 5-mm apical levels. Morphometric evaluation was performed on cross-sections to determine the amount of remaining pulp tissue as a percent of the root canal area. RESULTS The group-by-location interaction was not significant (P > .05), which means that the group comparisons were not dependent on the cross-sectional level. There was significantly greater residual pulp tissue left after ProTaper system instrumentation versus SAF instrumentation (21.4% vs 9.3%, P < .05). CONCLUSIONS The SAF protocol was significantly more efficient for debridement of oval root canals than the rotary ProTaper protocol.

Limited ability of three commonly used thermoplasticized gutta-percha techniques in filling oval-shaped canals.

The present study was designed to compare the percentage of gutta-percha-filled area (PGFA) achieved in oval-shaped canals after filling by 3 thermoplasticized techniques. Eighty-seven oval-shaped root canals were prepared and root-filled as follows: lateral condensation (n = 20), thermomechanical compaction (n = 20), wave of condensation (n = 20), and Thermafil system (n = 20). A cross section of each tooth was made 5 mm from the apex, and the samples were prepared for microscopic analysis. Digital image measurements of the cross-sectioned area of the canal and the gutta-percha were performed, and the PGFA was calculated. Nonparametric statistical analysis was performed with the Kruskal-Wallis H test and post hoc Dunn test. Overall, PGFAs were variable among the experimental groups, ranging from 37.1%-98.5%, and the pooled data from all techniques had a general mean of 69.6% +/- 18%. Thermafil system, wave of condensation, and thermomechanical compaction produced significantly higher PGFAs than lateral condensation (P < .05); however, no significant differences among these techniques were detected (P > .05). Therefore, a limited ability to fill oval-shaped canals was achieved in the 3 thermoplasticized techniques tested.

Lack of correlation between sealer penetration into dentinal tubules and sealability in nonbonded root fillings

AIM To determine the correlation between leakage and sealer penetration into dentinal tubule. METHODOLOGY The root canal of 60 mandibular central incisor teeth were prepared and filled under standardized conditions. Teeth were placed into a device to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured using an enzymatic reaction. Each specimen was then sectioned horizontally at 3, 6 and 8 mm from the apex, and a standard metallographic preparation was performed. The coronally facing surface of each slice was examined in a high-resolution stereomicroscope and under Confocal Laser Scanning Microscope. For each slice, the external outline of the root canal, the internal circumference of the root canal walls and the areas along the canal walls where the sealer had penetrated into the dentinal tubules (sealer tags) were outlined and measured. Afterwards, the percentage of the sealer penetration in each section was calculated. The Spearman correlation test was used to verify the correlation between the variables studied (glucose leakage and sealer penetration into dentinal tubules). RESULTS The means and standard deviations of glucose leakage were 0.744 g L(-1) (±0.5), and the percentage of the dentinal tubule sealer penetration varied between teeth from 5.6% to 42.21%, with an average of 13.7 ± 17.2%. The Spearman correlation test revealed no significant correlation between the two factors analysed (P = 0.082). The r(2) value was equal to 0.12. CONCLUSIONS There was no significant correlation between sealability sealer penetration into dentinal tubules. The lack of correlation reported is of relevance as sealer penetration into dentinal tubules has been used as an advantageous property during the launch of new root filling materials and techniques.

Critical appraisal of published smear layer-removal studies: methodological issues

The smear layer phenomenon has been extensively addressed over the past 3 decades. However, there still are unanswered questions on this issue and the main responsible factor is the qualitative and nonreproducible character of most in vitro smear layer removal studies. The methodological reasons that led to the current lack of reliable conclusions on procedures aiming to remove the smear layer are comprehensively addressed. The limitations and outcomes related to different assessment methods are discussed as well. General speaking, the results by score-based conventional SEM studies are not trustworthy and reproducible. Computational routines able to automatically extract quantitative data of dentin morphology are necessary to minimize the human bias. An ideal experimental model should have a longitudinal observational character, in which a given dentin area can be observed at different times. The use of flat dentin samples should be avoided because of the influence of gravity as well as root canal anatomy on the final result of the chelating process. The experimental model also needs to take into consideration the amount and distribution of sclerotic dentin and irregular secondary dentin, otherwise the final results can be compromised. Inasmuch as there is a clear lack of scientific standard, simple comparative SEM evaluations are pointless at the present moment. The ideal experimental model to assess smear layer removal is not currently available. Therefore, further research efforts should be directed to the development of and testing of new methodological approaches to be used in the smear layer removal studies. The improvement of the experimental models is a requirement to draw up optimized clinical guidelines for the chemical treatment of the root dentin.

Accumulated hard tissue debris produced during reciprocating and rotary nickel-titanium canal preparation.

INTRODUCTION This study compared the amount of hard tissue debris produced after different apical enlargement with single-file reciprocating systems (WaveOne [Dentsply Maillefer, Baillaigues, Switzerland] and Reciproc [VDW, Munich, Germany]) and a conventional multifile rotary system (BioRaCe [FKG Dentaire, La-Chaux-de-Fonds, Switzerland]) using micro-computed tomographic imaging. METHODS Thirty moderately curved mesial roots of mandibular molars presenting 2 independent root canals were selected and scanned at an isotropic resolution of 14.16 μm. The sample was assigned to 3 groups (n = 10) with respect to the root length and degree of curvature of the mesial root according to the system used for the root canal preparation: Reciproc, WaveOne, and BioRaCe. Second and third scans were taken after the root canals were prepared up to ISO sizes 25 and 40, respectively. The matched images of the mesial canals, before and after preparation, were examined from the furcation level to the apex to evaluate the amount of hard tissue debris (%). Data were statistically compared using a general linear model for repeated-measures with a significance level set at 5%. RESULTS Instrumentation systems per se did not influence the amount of hard tissue accumulation (P > .05), whereas a significant reduction in the percentage of hard tissue debris was observed after sequential enlargement in all groups (P < .05). CONCLUSIONS None of the systems yielded root canals completely free from packed hard tissue debris. The increased final apical size resulted in significantly less debris accumulation for both reciprocating and rotary systems.

Assessing accumulated hard-tissue debris using micro-computed tomography and free software for image processing and analysis.

INTRODUCTION The accumulation of debris occurs after root canal preparation procedures specifically in fins, isthmus, irregularities, and ramifications. The aim of this study was to present a step-by-step description of a new method used to longitudinally identify, measure, and 3-dimensionally map the accumulation of hard-tissue debris inside the root canal after biomechanical preparation using free software for image processing and analysis. METHODS Three mandibular molars presenting the mesial root with a large isthmus width and a type II Vertuccis canal configuration were selected and scanned. The specimens were assigned to 1 of 3 experimental approaches: (1) 5.25% sodium hypochlorite + 17% EDTA, (2) bidistilled water, and (3) no irrigation. After root canal preparation, high-resolution scans of the teeth were accomplished, and free software packages were used to register and quantify the amount of accumulated hard-tissue debris in either canal space or isthmus areas. RESULTS Canal preparation without irrigation resulted in 34.6% of its volume filled with hard-tissue debris, whereas the use of bidistilled water or NaOCl followed by EDTA showed a reduction in the percentage volume of debris to 16% and 11.3%, respectively. The closer the distance to the isthmus area was the larger the amount of accumulated debris regardless of the irrigating protocol used. CONCLUSIONS Through the present method, it was possible to calculate the volume of hard-tissue debris in the isthmuses and in the root canal space. Free-software packages used for image reconstruction, registering, and analysis have shown to be promising for end-user application.

Smear layer dissolution by peracetic acid of low concentration

AIM To test the effect of a noncaustic concentration of peracetic acid (PAA) in a standardized smear layer model. METHODOLOGY The smear layer dissolution kinetics of 0.5% PAA on human dentine were compared to those of 2.25% PAA and 17% ethylenediaminetetraacetic acid (EDTA) solutions. Coronal dentine discs were prepared from six human maxillary molars. A standardized smear layer was produced on the pulpal side of each disc. The smear layer-covered surface was divided into three similar areas and then exposed to one of the three solutions tested. Co-site image sequences (around 40, 500 ×) of the specific areas were obtained after four cumulative demineralisation times (15, 30, 60 and 180 s). An image processing and analysis sequence measured sets of images, providing data of area fraction (AF, dentine-free area in % of total analysis area). A general linear model for repeated measures was used to verify the influence of time and solution type over the change in AF from baseline (ΔAF). RESULTS Overall, EDTA and 2.25% PAA produced higher ΔAF values than the 0.5% PAA solution (P < 0.05). No significant difference was observed in ΔAF between 15 s and 30 s (P > 0.05). After 60 s of etching, all tested solutions produced similar ΔAF (P > 0.05), whereas at 180 s, ΔAF of both EDTA and 2.25% PAA continued to increase (P > 0.05). CONCLUSIONS After 60 s of contact, the 0.5% PAA solution dissolved smear layer as well as 2.25% PAA and 17% EDTA.

Interfacial adaptation of the Epiphany self-adhesive sealer to root dentin

OBJECTIVE The present study was designed to investigate interfacial quality between both Epiphany and Epiphany SE and the surrounding dentin having conventional gutta-percha/AH plus root filling as reference for comparison. STUDY DESIGN A sample of 36 human maxillary canines was prepared and assigned to experimental groups of 12 teeth each, designated as G1, Resilon/Epiphany; G2, Resilon/Epiphany SE; and G3, gutta-percha/AH Plus. After the filling procedures, each specimen was horizontally sectioned at 3, 6, and 8 mm from the apex and a metallographic preparation was performed to enable the evaluation under Confocal Laser Scanning Microscopy (CLSM). The integrity of the interface was determined by calculating the ratio between the total sealer/dentin interface and the sealer/dentin interface that presented gap-containing regions. Additionally, the width of each gap was measured and pooled per each specimen for comparison. Statistical analysis was performed using nonparametric methods. RESULTS Nonbonding AH Plus/gutta-percha root fillings showed a significantly higher amount of gap-free regions (P < .05). In the same way, nonbonding AH plus root fillings displayed significantly narrower gaps compared with the 2 adhesive root-filling groups (P < .05). CONCLUSIONS Under the present in vitro conditions, the quality of the interfacial adaptation of the current adhesive root fillings is compromised even when teeth with simple anatomic features were obturated under well-monitored laboratory conditions.

Analysis of the sealing ability of different obturation techniques in oval-shaped canals: a study using a bacterial leakage model

The aim of this study was to evaluate the sealing ability of 3 obturation techniques in oval canals using a bacterial leakage model. Seventy mandibular incisors with oval canals were selected after buccolingual and mesiodistal radiographs, and divided into three groups. After instrumentation, the canals were obturated respectively by lateral condensation (G1), warm vertical condensation (G2) and Thermafil (G3). Five root canals were not obturated and served as positive controls; five teeth with intact crowns served as negative controls. All teeth were mounted on a 2 chamber apparatus and then exposed to human saliva. The number of days required for the entire contamination of the root canals was recorded, observing the turbidity of the BHI broth, for a period of 100 days. 84.21% of the samples from the lateral condensation group (G1); 84.21% of the samples from the warm vertical condensation group (G2); and 89.47% of the samples from the Thermafil System group (G3) showed no contamination at the end of the study. No statistical significant difference was found among the three techniques. The quality of the apical seal in the three techniques tested was similar.

Dentine demineralization when subjected to EDTA with or without various wetting agents: a co-site digital optical microscopy study

AIM To analyse quantitatively the chelating ability of ethylenediaminetetraacetic acid (EDTA) and three common EDTA-based associations with wetting agents. METHODOLOGY Twelve maxillary human molars were selected, from which 3 mm thick discs were obtained from the cervical third of the root. Following the creation of standardized smear layer co-site microscopy image sequences of the dentine surface submitted to EDTA, EDTA plus 0.1% cetavlon (Sigma Chemical Co., St Louis, MO, USA), EDTA plus 1.25% sodium lauryl ether sulphate and SmearClear (Sybron Endo, Orange, CA, USA) were obtained after several cumulative demineralization times. Sixteen images were obtained of each dentine sample for each experimental time, at 1000 x magnification. An image processing and analysis sequence was used to measure the area of open tubules for each experimental time. Thus, it was possible to follow the demineralization process and quantitatively analyse the effect of the various substances. The Students t-test was used to assess differences between experimental groups. Results EDTA solution had the strongest effect at all experimental times whilst the association of EDTA with wetting agents showed a weaker chelating effect and this difference was statistically significant (P < 0.05). CONCLUSIONS (i) The EDTA solution had the strongest effect at all experimental times (P < 0.05); (ii) the association of EDTA with wetting agents did not improve the chelating power of the solution; (iii) co-site optical microscopy represents a powerful approach to compare directly, longitudinally and quantitatively the ability of the chelating solutions.