Access Cavity Design Research Articles

Influence of access cavity design on fracture strength of endodontically treated lower molars.

To assess whether access cavity design influences the fracture strength of endodontically treated and restored molars. Fifty human lower molars with standard crown dimensions were selected and assigned to the following groups: S - positive control (healthy tooth), ET - negative control (conventional endodontic access (CEA) and no restoration), NI - negative control (minimally invasive endodontic access (MEA) and no restoration), ETR (CEA+restoration with Bulkfill flow) and NIR (MEA+restoration with Bulkfill flow). The specimens were subjected to a compression test. The teeth were inspected for the site of fracture: either pulp floor or cusp. ANOVA, followed by Tukey's multiple comparison test (α=5%), was used for statistical analysis. The type of access cavity preparation did not increase the fracture strength of endodontically treated teeth. Even with the restoration, all teeth with endodontic access performed had a higher incidence of fractures at the pulp chamber floor level.

Current status on minimal access cavity preparations: a critical analysis and a proposal for a universal nomenclature.

In the last decade, several access cavity designs involveing minimal removal of tooth tissue have been described for gaining entry to pulp chambers during root canal treatment. The premise behind this concept assumes that maximum preservation of as much of the pulp chamber roof as possible during access preparation would maintain the fracture resistance of teeth following root canal treatment. However, the smaller the access cavity, the more difficult it may be to visualize and debride the pulp chamber as well as locate, shape, clean and fill the canals. At the same time, a small access cavity may increase the risk of iatrogenic complications as a result of poor visibility, which may have an impact on treatment outcome. This study aimed to critically analyse the literature on minimal access cavity preparations, propose new nomenclature based on self-explanatory abbreviations and highlight the areas in which more research is required. The search was conducted without restrictions using specifics terms and descriptors in four databases. A complementary screening of the references within the selected studies, as well as a manual search in the highest impact journals in endodontics, namely International Endodontic Journal and Journal of Endodontics, was also performed. The initial search retrieved 1831 publications. The titles and abstracts of these papers were reviewed, and the full text of 94 studies was assessed. Finally, a total of 28 studies were identified as evaluating the influence of minimally invasive access cavity designs on the fracture resistance of teeth and on the different stages of root canal treatment (orifice location, canal shaping, canal cleaning, canal filling and retreatment). Overall, the studies had major methodological drawbacks and reported inadequate and/or inconclusive results on the utility of minimally invasive access preparations. Furthermore, they offered limited scientific evidence to support the use of minimally invasive access cavities to improve the outcome of root canal treatment and retreatment; they also provided little evidence that they preserved the fracture resistance of root filled teeth to a greater extent than traditional access cavity preparations. It was concluded that at present, there is a lack of supporting evidence for the introduction of minimally invasive access cavity preparation into routine clinical practice and/or training of undergraduate and postgraduate students.

Influence of Endodontic Access Cavity Design on Fracture Strength of Maxillary Incisors and Premolars and on Fatigue Resistance of Reciprocating Instruments

Introduction: The aim of this study was to compare the effect of two different access cavity designs on fracture strength of endodontically treated teeth and on cyclic fatigue resistance of Reciproc blue instruments. Methods: Forty (40) maxillary central incisor teeth and forty (40) upper first premolars were selected and divided into 4 groups (n=20/group): Group 1A, incisors prepared with conservative access cavity (CEC); group 1B, incisors prepared with traditional access cavity (TEC); group 2A, premolars prepared with CEC; group 2B, premolars prepared with TEC. After access cavity preparation, all teeth were endodontically treated, restored and then loaded to fracture. A total of 80 Reciproc blue R25 files were used for root canal shaping and then tested for cyclic fatigue. Normality of data distribution was evaluated by Kolmogorov-Smirnov test. Data were statistically analyzed by Independent T-test and the significance level was set at p<0.05. Results: No statistically significant differences in fracture strength were found between the two tested access cavities both for incisors (P=0.70) and premolars (0.422). Cyclic fatigue resistance of Reciproc blue R25 was significantly reduced in endodontically treated teeth with CEC (P < 0.001). Conclusions: Within the limits of the present in vitro study, CEC does not increase fracture strength of endodontically treated teeth in comparison to TEC. Conservative Endodontic Cavity causes more cyclic fatigue of Reciproc blue R25 than Traditional Endodontic Cavity.

Effect of access cavity design on gaps and void formation in resin composite restorations following root canal treatment on extracted teeth.

To evaluate the influence of ultraconservative endodontic access cavities (UEC) on gaps and void formation in resin composite restorations in extracted two-rooted maxillary premolars after root canal treatment. Traditional endodontic access cavities (TEC) were used as a reference for comparison. Two-rooted maxillary premolars were scanned in a micro-computed tomographic (micro-CT) device, matched based on similar anatomical features and allocated into two groups (n=10) according to the design of the access cavity: TEC or UEC. Teeth were mounted on a mannequin head and a single operator performed the treatment, including endodontic access cavity preparation, root canal detection, preparation, filling and restoration procedures, under magnification. For restorative procedure, a bulk fill flowable layer was applied initially followed by an overlaying of regular composite. After restoration procedures, a new micro-CT scan was performed to check the quality of the coronal restoration by analysing the percentage volume of empty spaces present in the tooth-restoration interface (gaps) and inside the restoration (voids). Data were analysed statistically using Shapiro-Wilk and Student's t tests with a significance level of 5%. All specimens had gaps and voids. There were significant differences between the access cavity designs regarding the formation of voids with significantly more voids associated with the UEC (P<0.05). Gap formation did not differ between groups (P>0.05). The access cavity design used during root canal treatment interfered with the adaptation of the restorative material. The minimally invasive access cavity design was associated with a significantly greater number of voids within restorations.

The influence of endodontic access cavity design on the efficacy of canal instrumentation, microbial reduction, root canal filling and fracture resistance in mandibular molars.

To assess the impact of conservative endodontic access cavities (CEC) and truss access cavities (TAC) during root canal treatment performed on mandibular molars in terms of: ability to shape and fill root canals, microbial reduction in canals, and cleaning of the pulp chamber. In addition, the fracture resistance of the teeth after coronal restoration was assessed. Traditional endodontic cavities (TEC) were used as a reference technique for comparison. Thirty extracted intact mandibular molars were scanned in a microcomputed tomography device (micro-CT), matched based on similar anatomical features and assigned to TEC, CEC or TAC groups (n=10). The specimens were accessed accordingly, and root canals were contaminated with bacterial suspensions of Enterococcus faecalis (21days). Subsequently, the first microbial sample was collected from root canals (S1). The canals were initially prepared with Reciproc Blue R25 instrument followed by a second instrumentation using Reciproc Blue R40. EightmL of 0.5% NaOCl were used as an irrigant for each instrument. A final irrigation protocol was performed with 2mL of 0.5% NaOCl, 2mL of 17% EDTA and another 2mL of 0.5% NaOCl. Microbial samples were collected from root canals after R25 (S2), R40 (S3) and final irrigation (S4). The teeth were rescanned after S4. Then, root canals were filled, rescanned, restored and the teeth subjected to fracture resistance tests. The statistical analysis was performed with type I negative binomial and beta 0-1 inflation regression models for microbiological analysis. Instrumentation, filling and resistance to fracture results were subjected to anova and Tukey tests (P<0.05). S4 revealed no significant variations in microbial reduction amongst the groups (P>0.05). TEC had a significantly lower percentage of unprepared surface area than CEC (P<0.05). No differences were found regarding the percentage of dentine removed, transportation, centring ability and filling voids amongst the groups (P>0.05). The TEC group had a significantly lower volume of remaining root filling material within the pulp chamber than CEC and TAC groups (P<0.05). There was no difference regarding fracture resistance amongst the groups (P>0.05). Conservative access cavities did not offer any advantage in comparison with the traditional endodontic cavities in any of the parameters considered. Furthermore, conservative methods were associated with larger percentages of unprepared canal surface area and larger volumes of remaining root filling material within the pulp chamber.

Conservative endodontics II: A truss access/ orificeoriented access case series of premolars

Strategic dentin preservation is the prime objective of this case report (i.e. leaving a truss of dentin between the 2 cavities thus prepared). Permanent teeth with an indication for endodontic treatment can be treated via the truss access cavity design rather than traditional access cavity protocol using copious irrigation. The teeth were then given post-endodontic restorations. Endodontically treated teeth did not show any post-operative symptoms or any presence of post-operative periapical radiolucency or flare-up. The main objective of Orifice oriented access/truss access approach mainly stresses on the preservation of the healthy tooth structure with the minimally invasive approach. This minimal invasive approach in truss access designs avoids the need for conventionally placed crowns. Thus, the aim of this case report was to strategically plan truss access cavity designs on premolars.

Conservative endodontics II: A truss access/ orificeoriented access case series of premolars

Strategic dentin preservation is the prime objective of this case report (i.e. leaving a truss of dentin between the 2 cavities thus prepared). Permanent teeth with an indication for endodontic treatment can be treated via the truss access cavity design rather than traditional access cavity protocol using copious irrigation. The teeth were then given post-endodontic restorations. Endodontically treated teeth did not show any post-operative symptoms or any presence of post-operative periapical radiolucency or flare-up. The main objective of Orifice oriented access/truss access approach mainly stresses on the preservation of the healthy tooth structure with the minimally invasive approach. This minimal invasive approach in truss access designs avoids the need for conventionally placed crowns. Thus, the aim of this case report was to strategically plan truss access cavity designs on premolars.

Influence of access cavity design and use of operating microscope and ultrasonic troughing to detect middle mesial canals in extracted mandibular first molars.

To evaluate the influence of various endodontic access cavity designs and the use of an operating microscope (OM) with or without ultrasonic troughing to detect middle mesial canals (MMCs) in extracted mandibular first molars. Sixty extracted mandibular first molars were evaluated by cone beam computed tomography (CBCT) in order to detect the presence of MMCs and then divided into two groups (n=30) with an equal proportion of 1 molar with MMC for each 3 molars. A specific access cavity design was performed for each group, either a conservative access cavity (CAC) or a traditional access cavity (TAC). Root canals were detected in three assessment stages: (i) no magnification, (ii) using an OM and (iii) using an OM together with ultrasonic troughing. Evaluations were performed on a mannequin head in an ergonomic working position. The confidence obtained in the assessment stages was portrayed by sensitivity, specificity and accuracy, calculated by the area under the ROC curve. The difference in the proportion of correct diagnoses in identifying the MMC using either CAC or TAC preparation, at each of the three stages, was checked using Cochran's Q tests. Binomial tests were performed at each stage to investigate whether there was a difference between the types of endodontic access designs to detect MMCs. Significance was set at P<0.05. Accuracy increased at each assessment stage. At the third stage, both groups provided perfect accuracy (1.00). Cochran's Q tests indicated that the confidence of MMC detection for both TAC and CAC groups (P<0.05) increased significantly at each stage. Binomial tests demonstrated that there was no significant difference between the TAC and CAC groups, when evaluation was performed without magnification (P>0.05), with OM (P>0.05), or with OM associated with ultrasonic troughing (P>0.05). The access cavity design did not significantly affect detection of middle mesial canals in extracted mandibular first molars placed in a mannequin. However, the use of OM increased the accuracy of the MMC identification, especially when associated with ultrasonic troughing.

The Effect of Access Cavity Designs and Sizes of Root Canal Preparations on the Biomechanical Behavior of an Endodontically Treated Mandibular First Molar: A Finite Element Analysis

IntroductionThis study aimed to compare the biomechanical properties of a mandibular first molar with different endodontic cavity designs and increasing sizes of root canal preparations using finite element analysis (FEA). MethodsThe experimental finite element models were designed with 3 different endodontic access cavities and 2 sizes of canal preparations: traditional access cavity, conservative access cavity, and truss access cavity and #30/.04 and #40/.04 of root canal preparations. Vertical and oblique loads were applied with a 250-N static force to simulate masticatory forces. Mathematical analysis was performed to evaluate the stress distribution patterns. Maximum von Mises (VM) stresses were assessed at the occlusal surface; cervical line; and 1 , 3, 5, and 7 mm from the root apices. ResultsDecreasing the size of the access cavity was associated with a higher magnitude of cervical stresses. The magnitude of VM stresses was maximum at the 7-mm level and was minimum at the 1-mm level from the root apex. Increasing the size of the access cavity was associated with the transmission of stresses to a further apical direction regardless of the extent of root canal enlargement. The root canal enlargement from #30 to #40 increased radicular VM stresses within all models. ConclusionsWithin the limitations of this study, conservative and truss access designs preserved a significant volume of tooth structure. The extent of root canal enlargement should be as small as practical without jeopardizing the biologic objectives of root canal treatment.

Effects of Endodontic Access Cavity Design and Thermocycling on Fracture Strength of Endodontically Treated Teeth.

IntroductionThis study aimed to assess the fracture strength of endodontically treated mandibular molars with traditional endodontic access cavity (TEC) and truss endodontic access cavity (TREC) designs that were restored with composite resin and underwent thermocycling.MethodsSixty mandibular first and second molars were randomly divided into 6 groups (n=10) of intact controls without thermocycling (group 1), intact controls with thermocycling (group 2), TEC without thermocycling (group 3), TEC with thermocycling (TEC-TC, group 4), TREC without thermocycling (group 5) and TREC with thermocycling (TREC-TC, group 6). The root canals were then instrumented to #25,7% using nickel-titanium files and were filled with gutta-percha and AH26 sealer with lateral compaction technique. Access cavity was restored with Gradia composite. All teeth were then thermocycled for 480 cycles between 5°C and 55°C for 30 seconds and their fracture strength was measured in a universal testing machine with a round-end piston with 6 mm diameter at a speed of 1 mm/min. Data were analyzed using two-way and one-way ANOVA.ResultsWithout thermocycling, the fracture strength of endodontically treated teeth with TREC designs had no significant difference with the control group (P>0.05). However, both TEC and TREC designs significantly decreased the fracture strength of endodontically treated teeth after thermocycling (P<0.05), such that minimum fracture strength was noted in TEC-TC group.ConclusionUnder the conditions of this ex vivo study, TREC enhances the fracture strength of endodontically treated teeth under thermal stresses.

Effect of Access Cavity Designs On Stress Distribution

The purpose of this study is to analyze the effect of an access cavity design on stress distribution in an endodontically treated maxillary molar using a finite-element method. Two endodontic acces...

Impacts of 3 Different Endodontic Access Cavity Designs on Dentin Removal and Point of Entry in 3-dimensional Digital Models

IntroductionThe purpose of this study was to evaluate the tooth structure theoretically required to be removed in the coronal and cervical regions to accomplish 3 different endodontic access preparations in a novel digital model. The deviation of the center of access cavity from the central fossa will also be measured and compared among the 3 endodontic cavity designs, which in turn may serve as suggested points of entry for different access openings. MethodsTwenty-one maxillary molars and 15 mandibular molars were selected and 3-dimensionally imaged with cone-beam computed tomographic imaging. Three-dimensional (3D) volume reconstructions were made and converted into stereolithography files. Digital access cavity preparation was performed on each 3D reconstruction model with the 3 most commonly used endodontic access preparations: minimally invasive (MI), modified straight-line (MS), and traditional straight-line (TS) techniques. After the access cavity outlines were determined, digital sectioning of each reconstructed 3D tooth model was performed orthogonal to the long axis of the tooth at 3 levels: (1) passing through the central fossa, (2) 1.5 mm apical to the central fossa, and (3) 2 mm apical to the cementoenamel junction. The linear distance from the centroid of the access opening to the central fossa was measured to calculate the point of entry, and the amount of tooth structure removal at the pericervical area was measured to calculate the theoretically minimum amount of linear dentin removal required. Two-way repeated measures analysis of variance was performed for the interactions between different access designs and the amount of cervical dentin removal. Other data were statistically analyzed with 1-way repeated measures analysis of variance. The Tukey post hoc test was used for multiple comparisons. Significance was set at .05. ResultsThe amount of deviation of the center of the access cavity from the central fossa in all test groups was less than 1 mm. The dimensions of access openings differed significantly among the 3 access forms (TS > MS > MI, P < .0001). The amount of required cervical dentin removal was the greatest in the TS method followed by the MS and MI methods (P < .0001). ConclusionsThe central fossa could serve as good starting points in all access preparations in both maxillary and mandibular molars. Dentin removal in the coronal and cervical regions was the greatest in the TS design followed by the MS and MI designs. When comparing different canals in the same access form, less cervical dentin was sacrificed in the palatal canals of maxillary molars and the distal canals of mandibular molars.

The Effects of Different Endodontic Access Cavity Design and Using XP-endo Finisher on the Reduction of Enterococcus faecalis in the Root Canal System

IntroductionThe aim of this study was to evaluate the effect of using the XP-endo Finisher (XPF; FKG Dentaire, La Chaux de Fonds, Switzerland) in teeth that have a traditional access cavity (TEC) and a contracted access cavity (CEC) design on the amount of decrease in the number of Enterococcus faecalis bacteria within the root canal system. MethodsEighty mandibular first molar teeth were selected and randomly divided into 2 groups: TEC and CEC (n = 40/group). After access cavity preparation in the 2 groups, 80 mesiobuccal root canals were contaminated with Enterococcus faecalis for 4 weeks. After the first sampling (S1), in order to perform root canal instrumentation, the TEC and CEC groups were further divided into 4 subgroups (10 teeth/group): Reciproc (VDW GmbH, Munich, Germany) and ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) with or without XPF. Bacterial sampling from the root canals was performed with sterile paper points before (S1) and after (S2) instrumentation to determine the bacterial load. The bacterial reduction was counted as colony-forming units/mL and analyzed statistically by 3-factor repeated measures analysis of variance. Multiple comparisons of the main factor effect were performed using the Bonferroni correction (α < .05), all at 5% significance. ResultsThe number of E. faecalis bacteria in all the samples with different cavity designs were significantly reduced after instrumentation. The lowest value of bacterial decrease percentage was observed in the CEC-Reciproc-XPF (82.8%) group. ConclusionsThe bacterial reduction counts of E. faecalis were a similar level in the TEC and CEC cavities, and the use of XPF did not show significant differences between groups.

A comparative evaluation of the effect of different access cavity designs on root canal instrumentation efficacy and resistance to fracture assessed on maxillary central incisors: An in vitro study.

Aim:The purpose of this study is to evaluate and compare the effect of different access cavity designs on root canal instrumentation efficacy using micro-computed tomography (CT) scan and resistance to fracture evaluated using the universal testing machine on maxillary central incisor.Materials and Methodology:Forty extracted human permanent maxillary central incisors were divided into four groups for each access cavity. The access cavities were prepared according to predefined criteria and were further assessed under Micro-CT to evaluate pre and postoperative instrumentation efficacy. After biomechanical preparation and obturation, the teeth were wrapped with tin foil to maintain a thickness of 0.2–0.3 mm as periodontal ligament. Then, the silicon impression material was applied in the acrylic alveolus, to maintain and simulate the thickness of periodontal ligament and fracture resistance was checked using the universal testing machine.Statistical Analysis:Data were analyzed using one-way analysis of variance test. Pair-wise comparison was made using post hoc multiple comparison (Tukey) test.Results:Fracture resistance was highest (1272 N) for the control group followed by the Lingual Conventional Access Group (1153.90 N). Fracture resistance for Lingual Cingulum Access Group was 1130.70 N and least for the Lingual Incisal Straight-Line Access Group (1022.80 N). This difference in fracture resistance among all the groups was significant (P = 0.001). Overall comparison showed that dentin volume reduction (DVR) for Group II was 22.45 mm3, for Group III was 17.37 mm3 and for Group IV was 28. 41 mm3. This difference in DVR among the three groups was significant (P = 0.001).Conclusion:The most effective instrumentation efficacy was obtained in lingual incisal straight-line access group, followed by lingual cingulum access group, followed by lingual conventional access group. The most effective fracture resistance was obtained in the lingual conventional access group, followed by the lingual cingulum access group, followed by the lingual incisal straight-line access group.

Influence of access cavity design on the fracture resistance and root canal filling efficacy in simulated young permanent molars using cone-beam computed tomography: An in vitro study

Aims: The aim of this study is to evaluate the influence of access cavity designs on the fracture resistance and root canal filling efficacy of simulated young permanent molars.Methodology: A total of seventy human unerupted impacted mandibular third molar teeth were collected. Ten were allocated as control; the remaining were designated as experimental, which were divided into three groups (20 each) based on access cavity design. All the samples were exposed to cone-beam computed tomography (CBCT) scanner before the access cavity preparation. Group I-The control group. Group IIa-traditional endodontic cavity (TEC), Group IIb-conservative endodontic cavity (CEC), Group IIc-ninja endodontic cavity (NEC). Endodontic access cavities were prepared and exposed to CBCT. Pre- and post-treatment percentage volumes of lost pericervical dentin were evaluated. Then the root canals were filled with calcium hydroxide and subjected to CBCT imaging for the evaluation of root canal filling efficacy. Evaluation of fracture resistance was carried out using a universal testing machine.Results: On observation, the volume of lost pericervical dentin was (14.8%) in TEC, (8.3%) in CEC and (6.8%) in NEC. There was no statistically significant difference (P > 0.05) between all the groups on root canal filling efficacy and the number of voids. Fracture resistance of the NEC and control group (P > 0.05) was greater compared to CEC and TEC.Conclusion: NEC is the accepted method that had better fracture resistance, with a minimum number of voids in the coronal and middle third of the root and had adequate apical seal compared to conservative and TECs.

Effect of Truss Access and Artificial Truss Restoration on the Fracture Resistance of Endodontically Treated Mandibular First Molars

IntroductionThis study evaluated the effects of traditional and truss access cavity preparations in addition to artificial truss restoration on the fracture resistance of endodontically treated mandibular molars. MethodsA total of 66 recently extracted, intact mandibular first molars were collected from patients between 20 and 45 years of age. After the preparation of a mesio-occluso-distal cavity in all teeth, the teeth were randomly grouped into the following 4 groups according to the access cavity design: traditional access cavity, artificial truss restoration, truss access cavity, and control groups. Endodontic access cavities were performed in the experimental groups according to each treatment modality followed by instrumentation, irrigation, and obturation. After composite restoration, the teeth were subjected to a vertical occlusal force until fracture occurred. The data were statistically analyzed, and the fracture patterns were evaluated. ResultsFirst, a 1-way analysis of variance test analysis of the fracture resistance of the experimental groups showed nonsignificant differences among groups (P > .05). Second, the data were statistically analyzed using the Student t test to compare the fracture resistance of each experimental group with that in the control group. The control group had statistically significantly higher mean values for fracture resistance than the traditional access group and the artificial truss restoration group (P < .05). No statistically significant difference was recorded in the fracture resistance between the control group and the truss access cavity group (P > .05). ConclusionsThe truss access cavity preparation improved the fracture resistance of endodontically treated teeth with mesio-occluso-distal cavities, whereas the artificial truss restoration did not improve it.

Endodontic guided treatment using augmented reality on a head‐mounted display system

Endodontic treatment is performed to treat inflamed or infected root canal system of any involved teeth. It is estimated that 22.3 million endodontic procedures are performed annually in the USA. Preparing a proper access cavity before cleaning/shaping (instrumentation) of the root canal system is among the most important steps to achieve a successful treatment outcome. However, accidents such as perforation, gouging, ledge and canal transportation may occur during the procedure because of an improper or incomplete access cavity design. To reduce or prevent these errors in root canal treatments, this Letter introduces an assistive augmented reality (AR) technology on the head-mounted display (HMD). The proposed system provides audiovisual warning and correction in situ on the optical see-through HMD to assist the dentists to prepare access cavity. Interaction of the clinician with the system is via voice commands allowing the bi-manual operation. Also, dentist is able to review tooth radiographs during the procedure without the need to divert attention away from the patient and look at a separate monitor. Experiments are performed to evaluate the accuracy of the measurements. To the best of the authors’ knowledge, this is the first time that an HMD-based AR prototype is introduced for an endodontic procedure.

Impact of Access Cavity Design and Root Canal Taper on Fracture Resistance of Endodontically Treated Teeth: An Ex Vivo Investigation

IntroductionThe susceptibility of endodontically treated teeth (ETT) to fracture is mainly associated with the loss of tooth structure. This study evaluated the effect of the access cavity design and taper preparation of root canals on ETT fracture resistance of maxillary molars. MethodsFor tapering assessment, 30 sound distobuccal roots of maxillary molars were randomly assigned to 1 of 3 groups (n = 10): a .04 taper, a .06 taper, or a .08 taper. Endodontic canal preparations were performed using the Twisted Files rotary system (Kerr Co, Glendora, CA). In addition, 48 intact maxillary first and second molars were randomly assigned to 1 of 3 groups (n = 16) for cavity preparation approaches: intact teeth, traditional access cavity (TAC), or conservative access cavity (CAC). Fracture resistance was tested using a universal testing machine. For statistical analysis, the level of significance was P ≤ .05. ResultsThe .04 taper instrumentation had the highest fracture resistance (259.61 ± 52.06), and the .08 taper had the lowest (168.43 ± 59.63). The .04 and .06 groups did not differ significantly (P > .05); however, these groups differed significantly from the .08 group (P ≤ .05). Regarding the cavity preparation approaches, the 3 groups of intact teeth, CAC, and TAC showed fracture resistance mean values of 2118.85 ± 336.97, 1705.69 ± 591.51, and 1471.11 ± 435.34, respectively, with no significant difference between the CAC and TAC groups (P > .05). ConclusionsIncreasing the taper of the root canal preparation can reduce fracture resistance. Moreover, access cavity preparation can reduce resistance; however, CAC in comparison with TAC had no significant impact.

Does the Orifice-directed Dentin Conservation Access Design Debride Pulp Chamber and Mesial Root Canal Systems of Mandibular Molars Similar to a Traditional Access Design?

IntroductionDespite the increasing reports on mechanical aspects of contracted endodontic access cavities (CECs), we believe that the biological aspects (debridement) have not been adequately investigated. This study examined if 1 type of CEC (orifice-directed dentin conservation [DDC] access) was able to debride the pulp chamber, root canals, and isthmus of mesial roots of mandibular molars similar to a traditional endodontic access cavity (TEC). MethodsMandibular molars (N = 32) were selected and divided randomly into 2 experimental groups (n = 12) after micro–computed tomographic scanning (group 1: TEC and group 2: DDC) and histologic controls (n = 8). After instrumentation to a size 30/0.06 taper using 3% sodium hypochlorite as irrigant, specimens were processed for histologic evaluation, and the remaining pulp tissue (RPT) was measured from the pulp chamber, root canal, and isthmus at all root thirds. Data were analyzed using 1-way analysis of variance, Kruskal-Wallis, and appropriate post hoc tests (P = .05). ResultsThe RPT in the pulp chamber was significantly higher in DDC compared with TEC (P < .05). Comparing the root thirds in each group, there was no significant difference in the RPT within the root canals or the isthmus (P > .05). The RPT within the root canals and isthmus was not significantly different between the 2 access cavity designs at any root third (P > .05). ConclusionsDebridement of the pulp chamber was significantly compromised in DDC. The type of access cavity did not influence the amount of RPT in the root canals and isthmus.

Impact of contracted endodontic cavities on fracture resistance of endodontically treated teeth: a systematic review of in vitro studies.

This systematic review was performed to answer the following question: do contracted endodontic cavities (CECs) increase resistance to fracture in extracted human teeth compared to traditional endodontic cavities (TECs)? A literature search without restrictions was carried out in PubMed, Science Direct, Scopus, Web of Science, and Open Grey databases. Articles were selected by two independent reviewers. In addition, a reference and hand search was also fulfilled. All included in vitro studies evaluated the influence of CECs on strength to fracture in extracted human teeth and compared to TECs. The quality of the selected studies was evaluated and they were classified as having a low, moderate or high risk of bias. A total of 810 articles were obtained in the electronic search. After the application of the eligibility criteria, reference and hand search, and duplicate removal, six studies were included in this systematic review. All included studies evaluated the influence of CECs on strength to fracture in extracted human teeth and compared to TECs. Characteristics investigated in the selected articles included the sample size and tooth type, access cavity design, filling and restoration procedures, load at fracture test characteristics, and results. The studies demonstrated large variability among the fracture resistance values and standard deviations and low power. Three of the reviewed studies presented low risk of bias and the other three showed medium risk of bias. Overall, this systematic review of in vitro studies showed that there is no evidence that supports the use of CECs over TECs for the increase of fracture resistance in human teeth. Recently, CECs have gained attention in endodontics due to maximum tooth structure preservation including the pericervical dentin, which could improve the strength to fracture of endodontically treated teeth. However, the influence of access cavity design on fracture resistance remains limited and controversial.