Exploring access cavity through non-carious cervical lesions: Impacts on instrumentation, obturation, and fracture resistance in mandibular incisors.

AIM: To compare the effects of Cervical Access Cavity (CervAC) and Traditional Access Cavity (TradAC) on root canal preparation, root canal filling, and fracture resistance in mandibular incisors. METHODOLOGY: Twenty recently extracted and intact mandibular incisors were initially scanned using a micro-CT device. The specimens were anatomically matched to create two groups (n = 10). A wedge-shaped non-carious cervical lesion (NCCL) was created on the buccal aspect of all teeth using a double-faced segmented diamond disc. In group 1, a TradAC was prepared, whilst in group 2, access was created through the simulated NCCL using a round diamond bur 1012. After root canal preparation with Rotate instruments sizes 15/0.04, 20/0.04, and 25/0.04, the teeth were scanned again and evaluated for root canal volume and surface area, static voxels, volume of removed dental tissue, and dentine thickness. After that, the root canals were filled using the single-cone technique, teeth were restored with composite resin, and subsequently rescanned to calculate the volume of filling materials and voids. Then, the restored teeth were subjected to fracture resistance tests using a universal testing machine. Statistical comparisons between groups were performed with the Mann-Whitney test or the Student's t-test, with a statistical significance level of 5%. RESULTS: Statistical comparisons indicated no significant differences between groups in terms of root canal volume, surface area, static voxels, removed root dentine, root canal filling volume, percentage of voids, or fracture resistance load (p > .05). Conversely, teeth prepared with TradAC showed a significantly higher percentage of dental tissue removed from the crown (p = .001) and a greater volume of filling material remnants in the pulp chamber (p < .001) compared to the CervAC group. A significantly lower percentage reduction in dentine thickness was observed only on the mesial aspect of root at Level 1 in TradAC group (p = .008). CONCLUSIONS: CervAC can be considered a viable alternative approach in the presence of NCCL in mandibular incisors.

Influence of the use of chelating agents as final irrigant on the push-out bond strength of epoxy resin-based root canal sealers: A systematic review.

This systematic review (PROSPERO - CRD42020150722) was performed to answer the following question: Does the use of chelating agents affect the dislodgment resistance of epoxy resin-based root canal sealers? A search was conducted in PubMed, EMBASE, Scopus, LILACS and Web of Science, hand searching of two endodontic journals and grey literature until September 2020. Extracted data included: teeth used, sample size, root canal preparation, irrigant, chelating solution, neutralisation solution, type of resin-based sealer and obturation approach, storage method and duration, root third and slice thickness, plunger dimension and loading direction and the push-out testing parameters and values. The search retrieved a total of 2.389 studies. After analysis, 12 studies fulfilled the eligibility criteria and were included. Most of the final irrigation protocols with chelating agents had a positive impact and promoted an improvement in the dislodgment resistance of epoxy resin-based sealers to the root dentin.

Influence of access cavity preparation on the dentine thickness of mesial canals of mandibular molars prepared with reciprocating instruments.

AIM: To evaluate the influence of traditional and conservative access cavity preparations on the remaining dentine thickness in the coronal third of mesial canals of extracted mandibular molars prepared with reciprocating instruments using micro-computed tomography as the analytical tool. METHODOLOGY: Seventy extracted mandibular molars were scanned at a pixel size of 19 µm. From this initial sample, 20 teeth were selected, pair-matched and distributed into two groups (n = 10) according to the access cavity preparation: traditional (TradAC) or conservative (ConsAC). The root canals were sequentially enlarged with Reciproc Blue R25 (size 25, 0.08v taper) and R40 (size 40, 0.06v taper) instruments. A new scan was performed and the postoperative stacks were coregistered with their respective preoperative datasets. A colour-coded cross sections of the roots were created and used to identify and measure the smallest dentine thickness related to both MB and ML canals at 1.0-mm intervals from the furcation level of up to 5 mm in the apical direction, in both mesial and distal aspects of the roots, before and after preparation. The statistical analyses were performed with paired-samples t-test, independent-samples Student T-test and Chi-Square test with a significance level of 5%. RESULTS: At all levels of both groups, dentine thickness before preparation was greater than after preparation (p < .05). No difference in the percentage of dentine reduction was observed between TradAC and ConsAC groups (p > .05), but a significantly greater reduction was observed to the distal aspect of the roots (p < .05). After root canal preparation, dentine thinner than 0.5 mm was observed mostly along the distal aspect of the root (10% to 15%) of the MB and ML canals, with no influence of the access cavity type on its incidence to either mesial (X2  = 1.66; p = .2) or distal (X2  = 0.40; p = .5) directions. In the TradAC group, dentine thickness in most slices was greater than 1.0 mm after preparation (n = 124) whilst, in the ConsAC, it ranged from 0.5 to 1.0 mm (n = 136). CONCLUSION: Traditional or conservative access cavity preparation in extracted mandibular molars did not influence the remaining dentine thickness in the coronal third of mesial canals enlarged with thermomechanically treated nickel-titanium reciprocating instruments.

Confocal laser scanning microscopy evaluation of roots subjected to activation protocol in endodontic microsurgery.

This study evaluated the penetration of the irrigant subject to activation after performing retro-preparation in endodontic microsurgery. Forty mandibular premolars were prepared and filled. Subsequently, 1 mm from the root apex was cut using a multi-blade bur and the retro-preparation was performed. In group 1, the retro-cavity was cleaned with 2 mL of saline and then with 2 mL of 5.25% NaOCl gel mixed with 0.1% Rhodamine B. In group 2, the retro-cavity was cleaned with 2 mL of saline, 17% EDTA gel was activated ultrasonically for 30 s and 5.25% NaOCl gel was mixed with 0.1% Rhodamine B and activated for 30 s. After 7 days, the roots were cut at 1mm from the apex and the slices were evaluated with confocal laser scanning microscopy. The samples of group 2 showed statistically better results. The activation protocol proposed resulted in enhanced irrigant penetration when compared to the traditional.

Effect of different final irrigation protocols on pulp tissue dissolution from an isthmus model.

This study assessed the pulp tissue dissolution from isthmus of a two-rooted maxillary premolar using different final irrigation protocols. After root canal preparation, the surface of the tooth was reduced to an extent that the isthmus could be observed, and 1 mg of pulp tissue was introduced into the isthmus which was covered with a glass slide. Following six groups were tested: syringe and needle; subsonic activation; sonic activation; ultrasonic activation; heating followed by sonic activation; and heating followed by ultrasonic activation. Before and after each experiment a photograph of the isthmus was taken at 30× to register the area of the pulp tissue. Statistical analysis was performed with Kruskal-Wallis and Mann-Whitney tests (P < 0.05). Syringe and needle group showed the lower value of pulp tissue dissolution followed by subsonic irrigation procedures. Pulp tissue dissolution was significantly higher when heating was followed by sonic or ultrasonic activation.

Shaping ability of reciprocating and rotary systems in oval-shaped root canals: a microcomputed tomography study.

This study compared the shaping ability of single-file reciprocating (WaveOne Gold) and multifile rotary (Mtwo) systems on mandibular oval-shaped canine root canals, using microcomputed tomography (micro-CT). Thirty mandibular canines were scanned by micro-CT and assigned to one of two groups (n=15) according to the system used for root canal preparation: WaveOne Gold or Mtwo. After preparation, the teeth were rescanned, and the percentage of untouched canal area, apical transportation and centering ability were analyzed. The data was evaluated using Kruskal and Mann- Whitney tests (p<0.05). No difference was found in percentage of unprepared canal area between groups in the entire root canal or the apical third, or in centering ability (p>0.05). WaveOne gold had less canal transportation than MTwo at the 5 mm section (p<0.05). WOG and Mtwo systems presented similar shaping ability and centering ability in oval-shaped canals. However, WOG presented less transportation than Mtwo at 5 mm from the apex.

Este estudo comparou a capacidade de modelagem dos sistemas reciprocante de lima única (WaveOne Gold) e rotatórios com múltiplas limas (Mtwo) em caninos ovais inferiores, usando microtomografia computadorizada (micro-CT). Trinta caninos inferiores foram escaneados por micro-CT e divididos em dois grupos (n = 15) de acordo com o sistema usado durante o preparo do canal radicular: WaveOne Gold (WOG) e Mtwo. Os dentes foram reeescaneados e a porcentagem de área do canal não preparada, transporte apical e capacidade de centralização foram analisados. Os dados foram avaliados pelos testes de Kruskal Wallis e Mann-Whitney (p<0,05). Nenhuma diferença foi encontrada na porcentagem de área não preparada entre os grupos em todo o canal radicular e no terço apical e na capacidade de centralização (p>0,05). O sistema WOG promoveu menor transporte do canal do que o sistema Mtwo na região de 5mm aquém do ápice (p<0,05). Os sistemas WOG e Mtwo apresentaram capacidade de modelagem e capacidade de centralização semelhantes em canais ovais. No entanto, WOG promoveu menor transporte do que Mtwo a 5 mm do ápice.

Shaping ability of reciprocating and rotary systems in oval-shaped root canals: a microcomputed tomography study / Capacidade de modelagem dos sistemas reciprocante e rotatório em canais radiculares ovais: um estudo de microtomografia computadorizada

ABSTRACT This study compared the shaping ability of single-file reciprocating (WaveOne Gold) and multifile rotary (Mtwo) systems on mandibular oval-shaped canine root canals, using microcomputed tomography (micro-CT). Thirty mandibular canines were scanned by micro-CT and assigned to one of two groups (n=15) according to the system used for root canal preparation: WaveOne Gold or Mtwo. After preparation, the teeth were rescanned, and the percentage of untouched canal area, apical transportation and centering ability were analyzed. The data was evaluated using Kruskal and Mann- Whitney tests (p<0.05). No difference was found in percentage of unprepared canal area between groups in the entire root canal or the apical third, or in centering ability (p>0.05). WaveOne gold had less canal transportation than MTwo at the 5 mm section (p<0.05). WOG and Mtwo systems presented similar shaping ability and centering ability in oval-shaped canals. However, WOG presented less transportation than Mtwo at 5 mm from the apex.

RESUMO Este estudo comparou a capacidade de modelagem dos sistemas reciprocante de lima única (WaveOne Gold) e rotatórios com múltiplas limas (Mtwo) em caninos ovais inferiores, usando microtomografia computadorizada (micro-CT). Trinta caninos inferiores foram escaneados por micro-CT e divididos em dois grupos (n = 15) de acordo com o sistema usado durante o preparo do canal radicular: WaveOne Gold (WOG) e Mtwo. Os dentes foram reeescaneados e a porcentagem de área do canal não preparada, transporte apical e capacidade de centralização foram analisados. Os dados foram avaliados pelos testes de Kruskal Wallis e Mann-Whitney (p<0,05). Nenhuma diferença foi encontrada na porcentagem de área não preparada entre os grupos em todo o canal radicular e no terço apical e na capacidade de centralização (p>0,05). O sistema WOG promoveu menor transporte do canal do que o sistema Mtwo na região de 5mm aquém do ápice (p<0,05). Os sistemas WOG e Mtwo apresentaram capacidade de modelagem e capacidade de centralização semelhantes em canais ovais. No entanto, WOG promoveu menor transporte do que Mtwo a 5 mm do ápice.