Post retention strength of apical and conventional coating obturation methods using bioceramic sealer: a laboratory investigation.

BACKGROUND: Once bioceramic sealer (BCS) enters the dentinal tubules, it cannot be reliably removed. BCS-occupied dentinal tubules reduce fibre post retention strength. Coating gutta-percha with BCS only on the apical portion may improve post retention strength due to increased retention strength between the dentin and resin cement interface. The aim of the study was to test this hypothesis. METHODS: Root canals of 27 extracted human mandibular premolars were instrumented and randomly assigned to three obturation methods: conventional coating (CC), non-coating (NC), and apical coating (AC). The root canals were obturated with gutta-percha to 4 mm from the working length under an operating microscope. After the BCS was completely set, post spaces were prepared, and quartz fibre posts were cemented. The apical 4.5 mm of the roots were removed. Two samples were prepared at the apical, middle, and coronal root levels (one for scanning electron microscope (SEM) study and another for the push out bond strength (PBS) test). After the PBS test, the samples were examined with a stereo microscope to determine the failure mode: dentine-cement (DC), post-cement (PC) and mixed. The PBS data were analysed by One way ANOVA for the specific obturation method effects. Repeated ANOVA was used for the specific effects of the root levels on PBS in different obturation methods. RESULTS: At all three root levels, more continuous hybrid layers and denser resin tags were found in the NC and AC than the CC group. The AC and NC groups' PBS was significantly higher than the CC group at the apical 1/3 (p = 0.002 and p = 0.001) and coronal 1/3 (p = 0.016 and p = 0.041). The PBS in the CC group at the middle 1/3 was significantly higher than the apical 1/3 (p = 0.022). DC failure mode was most commonly found in the CC group, while PC failure mode was found most frequently in the NC and AC groups. CONCLUSIONS: The apical coating obturation method significantly increased PBS over the conventional coating method, potentially reducing fiber post dislodgement. However, this study was only preliminary. Clinical studies are required to confirm the results.

Evaluation of the chemical, physical, and biological properties of a newly developed bioceramic cement derived from cockle shells: an in vitro study.

BACKGROUND: Tricalcium silicate is the main component of commercial bioceramic cements that are widely used in endodontic treatment. Calcium carbonate, which is manufactured from limestone, is one of the substrates of tricalcium silicate. To avoid the environmental impact of mining, calcium carbonate can be obtained from biological sources, such as shelled mollusks, one of which is cockle shell. The aim of this study was to evaluate and compare the chemical, physical, and biological properties of a newly developed bioceramic cement derived from cockle shell (BioCement) with those of a commercial tricalcium silicate cement (Biodentine). METHODS: BioCement was prepared from cockle shells and rice husk ash and its chemical composition was determined by X-ray diffraction and X-ray fluorescence spectroscopy. The physical properties were evaluated following the International Organization for Standardization (ISO) 9917-1;2007 and 6876;2012. The pH was tested after 3 h to 8 weeks. The biological properties were assessed using extraction medium from BioCement and Biodentine on human dental pulp cells (hDPCs) in vitro. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5[(phenylamino)carbonyl]-2 H-tetrazolium hydroxide assay was used to evaluate cell cytotoxicity following ISO 10993-5;2009. Cell migration was examined using a wound healing assay. Alizarin red staining was performed to detect osteogenic differentiation. The data were tested for a normal distribution. Once confirmed, the physical properties and pH data were analyzed using the independent t-test, and the biological property data were analyzed using one way ANOVA and Tukey's multiple comparisons test at a 5% significance level. RESULTS: The main components of BioCement and Biodentine were calcium and silicon. BioCement's and Biodentine's setting time and compressive strength were not different. The radiopacity of BioCement and Biodentine was 5.00 and 3.92 mmAl, respectively (p < 0.05). BioCement's solubility was significantly higher than Biodentine. Both materials exhibited alkalinity (pH ranged from 9 to 12) and demonstrated > 90% cell viability with cell proliferation. The highest mineralization was found in the BioCement group at 7 days (p < 0.05). CONCLUSIONS: BioCement exhibited acceptable chemical and physical properties and was biocompatible to human dental pulp cells. BioCement promotes pulp cell migration and osteogenic differentiation.

Effect of ultrasonication on physical properties of mineral trioxide aggregate.

AIM: To evaluate the effect on physical properties of Mineral Trioxide Aggregate (MTA) of using direct hand compaction during placement and when using hand compaction with indirect ultrasonic activation with different application times. METHODS: One hundred acrylic canals were obturated in 3 increments with MTA in sample sizes of 10. One group was obturated by hand with an endodontic plugger and the remainder obturated with indirect ultrasonic application, with times ranging from 2 seconds to 18 seconds per increment. Microhardness values, dye penetration depths, and radiographs of the samples were evaluated. RESULTS: As ultrasonic application time per increment increased, microhardness values fell significantly (P < 0.001) while dye penetration values increased (P < 0.001). Microhardness of MTA ultrasonicated for 2 seconds was significantly higher than hand compaction (P = 0.03). Most radiographic voids were visible in the hand-compacted group (P < 0.001), which also had higher dye penetration depths than the 2-second ultrasonicated samples. Ultrasonication of MTA for 10-18 seconds resulted in significantly more voids than 2-8 seconds of ultrasonication (P = 0.02). CONCLUSION: The use of ultrasonics with MTA improved the compaction and flow of MTA, but excessive ultrasonication adversely affected MTA properties. A time of 2 seconds of ultrasonication per increment presented the best compromise between microhardness values, dye penetration depths, and lack of radiographic voids.

A comparative investigation of cone-beam computed tomography and periapical radiography in the diagnosis of a healthy periapex.

INTRODUCTION: This research aimed to compare the appearance of healthy periapical tissues on cone-beam computed tomography (CBCT) with periapical radiography and to measure the periodontal ligament (PDL) space on CBCT for teeth with healthy and necrotic pulps. METHODS: Patient records from specialist endodontic practices were examined for teeth that had a high-resolution (0.08-mm voxel) and small field-of-view CBCT scan, a periapical radiograph, and clinical pulp tests (CO2 and electric pulp testing). The periapical regions of the CBCT scans and radiographs were scored individually by 2 calibrated, blinded examiners by using a modified CBCT-periapical index (CBCT-PAI) for both and represented as CBCT-PAI and PAI, respectively. The Fisher exact and χ(2) statistics tested the relationships between CBCT-PAI, PAI, and pulp status. RESULTS: Of 200 teeth included in the study, 166 showed clinical signs of pulpal health, and the CBCT-PAI score was greater than the PAI in 72% (119 of 166), with a vital pulp likely to have a radiographic PDL space widening of 0-1 mm (P < .001). Although 2 healthy teeth showed radiolucencies 2-4 mm on CBCT scan when the periapical radiograph showed none, a PDL space of greater than 1-2 mm was indicative of a necrotic pulp (P < .001). CONCLUSIONS: Teeth with necrotic pulps were more likely to have PDL widening, but the PDL space of a healthy tooth demonstrated significant variation when examined by CBCT. The radiographic interpretation of health and disease on CBCT must be further investigated before usage in outcome or epidemiologic investigations. This research questions the traditional radiographic interpretation of the PDL space.

In vitro assessment of mineral trioxide aggregate setting in the presence of interstitial fluid alone.

INTRODUCTION: The aim of this study was to determine the ability of white mineral trioxide aggregate (MTA) Angelus (Solucoes Odontologicas, Londrina, Brazil) to set in 24 hours within the root canal in the presence of an intrinsic moisture source (interstitial fluid) alone without the need for moist cotton pellet placement. METHODS: Extracted teeth were used to simulate the open apex situation. MTA was placed to a depth of 4 mm and allowed to set for 24 hours in the following test groups: a current protocol group with a moist cotton pellet, a test group with no moist cotton pellet placement, and positive and negative control groups with varnished roots. The teeth were embedded in florist sponges immersed in fetal bovine serum at 13.3-kPa pressure. The MTA set was tested using the Vickers hardness test, and the data were analyzed using analysis of variance. RESULTS: The greatest mean surface hardness values were observed in the current protocol group (80.7 ± 35.6), but this was not statistically different when compared with the test group without a moist cotton pellet (78.3 ± 53.7) or the control groups. CONCLUSIONS: Moist cotton pellet placement may not be essential for MTA setting in apexification procedures or situations in which the apical surface of the MTA is against a moist opening of greater than 1 mm.

Impact of a retained instrument on treatment outcome: a systematic review and meta-analysis.

INTRODUCTION: Fracture of root canal instruments is one of the most troublesome incidents in endodontic therapy. This systematic review and meta-analysis aim to determine the outcome difference between retained fractured instrument cases and matched conventional treated cases. METHODS: The MEDLINE database, EMBASE, Web of Science, and the Cochrane Database were searched. Reference lists were scanned. A forward search was undertaken on identified articles. Papers citing these articles were identified through Science Citation Index to identify potentially relevant subsequent primary research. A systematic data extraction sheet was constructed. Data in these studies were independently extracted. Risk differences of included studies were combined by using the generic inverse variance data and fixed effects method. A 2-stage analysis was conducted. The first was limited to case-control studies, and the second included case series in which data were available for teeth with and without periradicular lesions. RESULTS: Two case-control studies were identified and included, covering 199 cases. Weighted mean healing for teeth with a retained instrument fragment was 91%. The 2 studies were homogeneous. Risk difference of the combined data was 0.01, indicating that a retained fragment did not significantly influence healing. Overall, 80.7% of lesions healed when a periapical lesion was present, compared with 92.4% remaining healthy when no lesion was present initially (P < .02). CONCLUSIONS: On the basis of the current best available evidence, the prognosis for endodontic treatment when a fractured instrument fragment is left within a root canal is not significantly reduced.

How useful is root canal culturing in predicting treatment outcome?

Microbial control--fundamental to healing of apical periodontitis--is central to endodontic practice. The effectiveness of antibacterial measures is generally monitored (in clinical research studies) by microbiological root canal sampling (MRS), which is often used as a predictor for healing. This article addresses the question of the extent to which positive or negative cultures at time of obturation are able to predict treatment outcome. To date only one small clinical study has attempted to relate the treatment outcome to intraradicular bacterial status (p = 0.025, Fisher's exact test): the strength of the association was not great, with a wide confidence interval (odds ratio = 6.8; 95% CI: 1.5 to 32). The extent to which current canal sampling techniques accurately reflect the bacterial status of the canal space must also be taken into account. False positive and negative cultures may adversely affect the performance of MRS. These conditions emphasize how potentially error-prone MRS can be. As currently practiced, intracanal sampling techniques suffer from deficiencies that limit their predictive value. This article in no way questions the role of intracanal bacteria in causing apical periodontitis, nor the central role of bacterial control in endodontic treatment. Rather, it emphasizes the need for more detailed clinical studies of bacterial status and healing, as well as refinement of techniques for microbial sampling of canals.

A comparison of the effects of two canal preparation techniques on root fracture susceptibility and fracture pattern.

The purpose of the study was to determine whether rotary nickel-titanium (NiTi) canal preparation strengthens roots, and whether the fracture pattern can be predicted by finite element analysis (FEA) models. From a fracture mechanics viewpoint, structural defects, cracks or canal irregularities are likely to play a major role in fracture susceptibility of the roots, because stresses can be exponentially amplified at these sites. By incorporating defects into a smooth round canal using rotary NiTi, theoretically the roots could be strengthened. 25 teeth were prepared using hand files and another 25 using rotary NiTi. After obturation, all teeth were subject to loading until fracture; load and patterns were recorded. Four FEA models were created from fractured roots. No significant difference of fracture load between the two techniques was found. Mesio-distal fracture occurred more often in the rotary NiTi group. Stress patterns in three of the four FEA models correlated well with the observed fracture patterns.

Effect of root canal size and external root surface morphology on fracture susceptibility and pattern: a finite element analysis.

The aim of the study was to determine the extent to which canal size, radius of curvature and proximal root concavity influence fracture susceptibility and pattern. A standardized cross-section of the mid-root region of a mandibular incisor was created by averaging the dimensions of 10 extracted teeth, and then the basic finite element analysis (FEA) model was created. By varying canal diameter, shape, and proximal concavity, these factors could be examined for roles in fracture susceptibility and pattern. The factors all interact in influencing fracture susceptibility and pattern, with dentin thickness not the only determining factor. The removal of dentin does not always result in an increased fracture susceptibility.