Comparative Evaluation of the Bonding Efficacy of Multimode Adhesive, Two-Step Self-Etch Adhesive, and a Total-Etch System to Pulpal Floor Dentin - An In vitro Study.

Background: Postendodontic restoration with composite resins has gained popularity due to the development of more reliable adhesives with simplified bonding procedures and less technique sensitivity. Pulpal floor dentin is a complex biological structure and a more challenging bonding substrate. Hence, appropriate selection of the bonding agent for these regions of the tooth is important. Aims: To compare the shear bond strength of a new generation of dental adhesives referred to as multimode adhesives, two-step self-etch adhesive, and a total-etch system to pulpal floor dentin. Materials and Methods: Sixty human mandibular molars were sectioned with a slow speed diamond disc to expose the pulp chamber and divided into four groups of 15 teeth each, based on the bonding agent used. Group A: Single bond universal (self-etch); Group B: Single Bond Universal (etch-and-rinse), Group C: Clearfil SE Bond, Group D: Adper Single Bond 2. Using a split Teflon mold, composite cylinders were built on the prepared dentinal surfaces. The shear bond strength was then evaluated with the universal testing machine. Results: Two step self-etch adhesives recorded higher shear bond strength than total-etch and multimode/universal adhesives applied in both self-etch and etch-and-rinse techniques. Conclusion: The self-etching/priming system bonded more strongly to the pulpal floor dentin than multimode adhesive and total-etch system.

Effect of pulpal floor perforation repair on biomechanical response of mandibular molar: A finite element analysis.

Background: Evaluation of the biomechanical response of tooth with perforation repair is important to attain predictable prognosis. It may remain altered even after perforation repair due to the loss of tooth structure. Aim: The aim of this study is to assess and compare the effect of pulpal floor perforation repair of different sites with biodentine, on the biomechanical response of mandibular molar through 3-dimensional (3D) finite element analysis (FEA). Materials and Methods: Five different 3D models were constructed based on the site of perforation on the pulpal floor using cone-beam computed tomographic images of an extracted mandibular molar. Perforation size was standardized and simulated to be repaired with calcium silicate-based cement. A force of 200 N was applied simulating normal occlusal loads. Static linear FEA was performed using the Ansys FEA software. Tensile stresses were evaluated (Pmax). Statistical Analysis Used: The data were evaluated using the independent t-test (P = 0.05). Results: All the simulated models with perforation repair exhibited higher stress values than their equivalent sites in the control group. The Pmax values of the repaired models were highest in central furcal perforation, followed by buccal furcal perforation. However, there was no statistically significant difference in the stress accumulation among the different repaired perforation sites. Conclusion: The site of the pulpal floor perforation affected the stress distribution and accumulation. Central and buccal furcal perforation repairs on the pulpal floor with calcium silicate-based cement in mandibular molar are likely to have an increased risk of fracture.

Evaluation of Composite Adaptation to Pulpal Chamber Floor Using Optical Coherence Tomography.

INTRODUCTION: A coronal seal is fundamental for a positive outcome to endodontic therapy. In this in vitro study, we evaluated the adaptation of composite resins in postendodontic restorations using optical coherence tomographic (OCT) imaging. Our null hypothesis was that there would be no difference in marginal adaptation to the pulp chamber floor between resin composites of different viscosities. METHODS: Thirty intact upper molars extracted for periodontal reasons were selected, endodontically treated, and filled with gutta-percha. The excess gutta-percha was entirely removed from the pulp chamber floor, and teeth were randomly divided into 3 groups (n = 10) according to the material used for the restoration: group 1: 0.5-mm horizontal layer of flowable composite followed by nanohybrid composite, group 2: bulk layering of bulk fill flowable composite; and group 3: oblique layering of nanohybrid composite. The degree of adaptation to the cavity floor was assessed using OCT imaging, and images were analyzed with the software program ImageJ (National Institutes of Health, Bethesda, MD) to assess the marginal gap between the composite and the pulp chamber floor. Collected data were statistically analyzed using analysis of variance testing, and statistical significance was set at P < .05. RESULTS: Flowable composites showed significantly better adaptation than traditional packable nanohybrid composites (P < .05). All significant differences were found between groups 1 and 2. CONCLUSIONS: Within the limitations of this OCT imaging-based in vitro study, it was concluded that the flowable composite (flow + nanofilled; flow bulk fill composite) adapted better to the pulp chamber floor than the packable nanohybrid composite resin. Further studies are necessary to confirm these results.

Comparative Evaluation of Microshear Bond Strength of 5(th), 6(th) and 7(th) Generation Bonding Agents to Coronal Dentin Versus Dentin at Floor of Pulp Chamber: An In vitro Study.

BACKGROUND: Lack of seal and adhesion between the final restoration and tooth structure adversely affects the results of root canal treatment. Lots of adhesive bonding agents are marketed to overcome this deficiency and achieve successful restoration. So the study compares and evaluates the micro shear bond strength of coronal dentin and pulp chamber dentin using three different generation dentin bonding systems and to know clinical efficiency for clinical use. MATERIALS AND METHODS: DIFFERENT GENERATION DENTIN BONDING SYSTEMS USED WERE: (1) One bottle total etch system (XP Bond-5(th) generation), (2) Two-step self-etch system (Clearfil SE Bond-6(th) generation) and (3) All-in-one system (G Bond-7(th) generation). Thirty human mandibular molars were collected out of which sixty samples were prepared by sectioning each tooth into coronal dentin and pulpal floor dentin. They were divided into two major groups. Group I: 30 Coronal dentin samples. Group II:30 Pulpal floor dentin samples. Both the groups were further subdivided depending on the bonding agent used. Subgroup Ia:XP Bond, Subgroup Ib:Clearfil SE Bond, Subgroup Ic:G Bond, Subgroup IIa:XP Bond, Subgroup IIb:Clearfil SE Bond, Subgroup IIc:G Bond. Resin composite was bonded to these samples and tested for micro-shear bond strength. The mean bond strengths and standard deviations were calculated and analyzed using one-way ANOVA test and Student's t-test (unpaired) and honestly significant difference post-hoc tests. RESULTS: Coronal dentin showed higher values of micro shear bond strength than the pulpal floor dentin. All-in-one system (G Bond) showed least bond strength values to both the regions coronal dentin and pulpal floor dentin. CONCLUSION: Factors affecting the shear bond strength are dependent on material (adhesive system), substrate depth and adhesive/depth interaction. Hence composition and substrate treatment should be considered for good adhesive. Chemical composition of adhesive system determines clinical successes.

A study on the C-shaped root canal system of mandibular second molar / 대한치과보존학회지

C-shaped canals are known to present a complex canal anatomy with numerous fins connecting individual canals, thus requiring supplementary effort to accomplish a successful root canal treatment. This study examined the frequency of the C-shaped mandibular second molars and interrelation between the clinical records and radiographs to recognize them treated in the Department of Conservative Dentistry of the Chosun University Dental Hospital during a six-year period (1998 - 2004). This study reviewed the clinical records of 227 patients who underwent root canal treatment of the mandibular second molars. After opening the chamber, those cases with C-shaped orifices in the pulpal floor were selected, and the C-shaped root canal types were classified according to Melton's criteria. Three experienced dentists evaluated the radiographs of the C-shaped mandibular second molar on a viewer using a magnifying glass in order to determine if the root apex was fused or separated, the distal root canal was either centered or mesial shifted in the distal root, and if there was bilateral symmetry in a panorama. In conclusion, there is a high frequency of C-shaped mandibular second molars in Koreans. Simultaneous interpretation of the root shape and distal root canal using the preoperative, working length and post-treatment radiographs is important for diagnosing a C-shaped mandibular second molar.