Update on the Adaptive Immune Responses of the Dental Pulp
Chin-Lo Hahn, MS, PhD, DDS, Frederick R. Liewehr, DDS, MS
Recent advances in immunology have disclosed the enormous complexity of the immune regulatory system. The dental pulp is equipped to mount adaptive immune responses to caries, which include at least antigen-presenting cells, lymphocytes, mast cells and their cytokines, and chemokines. The purpose of this review is to summarize our current understanding of the roles of these cellular and molecular components in the irreversibly inflamed pulp. The immunopathology of abscess formation and the mechanisms for painless pulpitis are also discussed.
The In Vivo Evaluation of Hand/Rotary/Ultrasound Instrumentation in Necrotic, Human Mandibular Molars
Aaron Burleson, DMD, MS, John Nusstein, DDS, MS, Al Reader, DDS, MS, Mike Beck, DDS, MA
This in vivo, prospective, randomized, single-blinded study histologically compared biofilm/necrotic debridement efficiency of a hand/rotary technique versus a hand/rotary/1 min ultrasound technique in the mesial roots of necrotic, human mandibular molars. The hand/rotary group consisted of 20 mesial roots. The hand/rotary/ultrasound group consisted of 20 mesial roots prepared with the same hand/rotary technique followed by 1 min of ultrasonic irrigation, per canal, utilizing an ultrasonic needle in a MiniEndo™ unit. Following extraction, histologic preparation and staining, 0.2 μm cross-sections from the 1- to 3-mm apical levels were evaluated for percentage of biofilm/necrotic debris removal. Cleanliness results at the 1-, 2- and 3-mm levels for the hand/rotary and hand/rotary/ultrasound techniques, respectively, were: Canals, 80% versus 95%, 92% versus 99%, and 95% versus 100%; Isthmuses, 33% versus 83%, 31% versus 86%, 45% versus 91%. Statistical analysis revealed mean percent canal and isthmus cleanliness values to be significantly higher for hand/rotary/ultrasound technique at all levels evaluated.
Antibacterial Efficacy of Chlorhexidine Gluconate Intracanal Medication In Vivo
Lisane Paquette, DMD, MSc, Milos Legner, PhD, Edward D. Fillery, PhD, Shimon Friedman, DMD
The antibacterial efficacy of intracanal medication with 2% chlorhexidine liquid (CHX) was assessed in teeth with apical periodontitis. Canals in 22 teeth were instrumented at the first session, medicated with CHX, and reaccessed after 7 to 15 days. Bacteriological samples were aspirated at the first and second sessions, before (1A, 2A) and after (1B, 2B) canal instrumentation. Viable bacterial counts were obtained by culture (CFU) and microscopy using vital dyes. Microscopic counts were higher than CFU counts. Consistently high CFU counts in 1A samples (mean, 2 × 105 μL−1 canal volume) decreased significantly (p < 0.0001) in 1B samples, increased significantly (p < 0.04) in 2A samples, and decreased in 2B samples to the level of 1B samples. Proportions of negative cultures followed the pattern of CFU counts. Intracanal medication with CHX did not reduce the bacterial concentration. Bacterial counts expressed per microliter canal volume added information beyond the counts per tooth as expressed in previous studies.
Measurement of Mechanical Allodynia and Local Anesthetic Efficacy in Patients With Irreversible Pulpitis and Acute Periradicular Periodontitis
Asma A. Khan, BDS, PhD, Christopher B. Owatz, DMD, William G. Schindler, DDS, MS, Scott A. Schwartz, DDS, Karl Keiser, DDS, MS, Kenneth M. Hargreaves, DDS, PhD
An essential feature of symptomatic periradicular inflammation is mechanical allodynia, defined as reduced mechanical pain thresholds. A previous study evaluating a new digital force transducer showed that it reliably measures mechanical pain thresholds of teeth with normal periradicular tissues. In this study, we tested the hypothesis that the force transducer quantitatively measures mechanical allodynia in teeth with acute periradicular periodontitis (APP) and detects the effects of local anesthetic injection. Mechanical pain thresholds were measured in patients (n = 30) with irreversible pulpitis (IP) and APP and compared with their contralateral teeth. The results show that the mechanical pain thresholds of teeth with IP and APP were reduced by 77% compared with contralateral control teeth. The administration of local anesthesia reversed the mechanical allodynia by 62%, and significant sex-specific effects were observed. In addition, the normal teeth contralateral to the symptomatic teeth had lower mechanical thresholds than those observed in healthy volunteers, suggesting that central sensitization occurs during this type of odontalgia. Thus, we show that the mechanical pain thresholds are significantly reduced in teeth with IP and APP and that the force transducer has potential application as a diagnostic aid in measuring mechanical allodynia and as an outcome measure in endodontic clinical trials such as pharmacologic studies and mechanistic research.
Effects of Chemomechanical Preparation With 2.5% Sodium Hypochlorite and Intracanal Medication With Calcium Hydroxide on Cultivable Bacteria in Infected Root Canals
José F. Siqueira Jr, PhD, Tatiana Guimarães-Pinto, DDS, Isabela N. Rôças, PhD
This clinical study was conducted to assess the bacterial reduction after chemomechanical preparation with 2.5% NaOCl as an irrigant and the additive antibacterial effect of intracanal dressing with calcium hydroxide. According to stringent inclusion criteria, 11 teeth with primary intraradicular infections and chronic apical periodontitis were selected and monitored in the study. Bacterial samples were taken at the baseline (before treatment) (S1), after chemomechanical preparation with 2.5% NaOCl as an irrigant (S2), and after a 7-day dressing with a calcium hydroxide paste in glycerin (S3). Cultivable bacteria recovered from infected root canals at the 3 stages were counted and identified by means of 16S rRNA gene sequencing analysis. At S1, all canals were positive for bacteria, with the mean number of 2.8 taxa per canal (range, 1–6). At S2, 5 cases (45.5%) still harbored cultivable bacteria, with 1 or 2 species per canal. At S3, bacteria were cultured from 2 cases (18.2%), with 1 species per positive case. There was no indication that any specific bacterial taxon was more resistant to treatment. A significant reduction in bacterial counts was observed between S1 and S2, and S1 and S3. However, no statistically significant difference was observed for comparisons involving S2 and S3 samples with regard to the number of cases yielding negative cultures (P = .18) or quantitative bacterial reduction (P = .19). It was concluded that the whole antibacterial protocol used in this study significantly reduced the number of bacteria in the canal and rendered most canals free of cultivable bacteria.
Identification of C-shaped Canal in Mandibular Second Molars. Part I: Radiographic and Anatomical Features Revealed by Intraradicular Contrast Medium
Wei Fan, DDS, MSc, PhD, Bing Fan, DDS, MSc, PhD, James L. Gutmann, DDS, PhD, FACD, FICD, FADI, Gary S.P. Cheung, BDS, MDS, MSc, PhD
The purpose of this study was to investigate radiographic features of the C-shaped canal system in mandibular second molars and their relationship to the canal anatomy by using intraradicular contrast medium and micro–computed tomography (μCT) scanning. Thirty mandibular second molars with fused roots were collected and stored in 10% formalin solution. After being scanned by μCT and reconstructed with 3-dimensional software, the pulp tissue of each tooth was removed mechanically and chemically. The contrast medium was introduced into the canal by using a specialized device, and the buccal-lingual radiograph was taken for each tooth. The radiographic images were classified into 3 types: Types I (merging type), II (symmetrical type), and III (asymmetrical type). The relationship between the radiographic and anatomic features was analyzed by collating the μCT scanned canal images with the radiographic types. The results were subject to Kruskal-Wallis test. Findings showed that 10 teeth were Type I, 10 teeth Type II, and 10 teeth Type III. Types I and III had more C1, C2 canal shape in their canal orifice, coronal, and middle canal portion than the Type II (P < .05). Types II and III had more C3a, C3b canal shapes in the apical canal portion than Type I (P < .05). On the basis of these results, the radiographic features revealed by the intraradicular contrast medium can help to identify the canal anatomy of C-shaped canal system in mandibular second molars.
Tooth Slice–Based Models for the Study of Human Dental Pulp Angiogenesis
Silvana B. Gonçalves, DDS, MS, Zhihong Dong, MD, PhD, Clovis M. Bramante, DDS, MS, Graham R. Holland, BSc, BDS, PhD, Anthony J. Smith, BSc, BDS, PhD, Jacques E. Nör, DDS, MS, PhD
Treatment of avulsed young permanent teeth aims to revascularize the dental pulp. The study of therapeutic strategies for avulsed teeth has been hindered by the scarcity of experimental models. The purpose of this work is to characterize two model systems to study dental pulp revascularization. Tooth slices from human third molars were prepared with a sterile diamond saw. The tooth slices were cultured in vitro for up to 7 days. Immunohistochemical staining with Factor VIII showed an increase in microvascular density in pulps treated with 50 ng/mL rhVEGF165 as compared with untreated controls (p < 0.05). Alternatively, tooth slices were prepared and immediately implanted subcutaneously in immunodeficient mice. Pulp vitality and vascularization were confirmed by histological analysis and terminal deoxynucleotide transferase dUTP nick end labeling assays 7 days after implantation. The models presented here may be valuable in the assessment of angiogenesis-based therapeutic strategies for the dental pulp.
Biofilm Formation of Oral and Endodontic Enterococcus faecalis
Jason M. Duggan, DDS, Christine M. Sedgley, PhD
Biofilms are complex aggregations of microorganisms attached to a surface. The formation of biofilms might facilitate certain survival and virulence characteristics under some situations. This study tested the hypothesis that the ability of Enterococcus faecalis to form biofilms is related to the source of the strains. E. faecalis strains recovered from root canals (n = 33), the oral cavity (n = 21), and non-oral/non-endodontic sources (n = 16) were studied. Biofilms were grown in tryptic soy broth in 96-well plates for 24 hours at 37°C, fixed with Bouin’s fixative, and stained with 1% crystal violet. Optical density at 570 nm (OD570) was measured by using a microtiter plate reader. Experiments were performed in quadruplicate on three occasions and mean OD570 readings determined for each strain. There were no statistically significant differences between groups (p = 0.066, Kruskal-Wallis). Within the root canal and oral isolates there were no significant associations between biofilm formation and the presence of the virulence determinants asa, cylA, esp, and gelE.
Comparison of Growth and Susceptibility to Sodium Hypochlorite of Mono- and Dual-Species Biofilms of Fusobacterium nucleatum and Peptostreptococcus (micromonas) micros
Ahmet Rifat Özok, PhD, Min-Kai Wu, PhD, Suzanne Bernardina Ida Luppens, PhD, Paul Rudolf Wesselink, PhD
This study compared growth and susceptibility to different concentrations of sodium hypochlorite (NaOCl) of mono- and dual-species biofilms of Fusobacterium nucleatum or Peptostreptococcus micros in vitro at 24 hours or 96 hours. A Mann-Whitney U test revealed that although at 24 hours dual-species biofilms had similar viable counts to those of monospecies biofilms (p > 0.001), they were more resistant to NaOCl (p < 0.001). At 96 hours, both microorganisms had higher viable counts and were more resistant to NaOCl in dual-species biofilms than in monospecies biofilms of the same microorganism (p < 0.001). As the age of the biofilms increased, so did their resistance to NaOCl. Mixed-species biofilms of F. nucleatum and P. micros showed a time-dependent synergy in growth and resistance to NaOCl.
The Effect of Mineral Trioxide Aggregate on the Contractility of the Rat Thoracic Aorta
Yasar Meric Tunca, DDS, PhD, Cumhur Aydin, DDS, PhD, Tuncer Ozen, DDS, PhD, Melik Seyrek, MD, PhD, Hasan Basri Ulusoy, MD, PhD, Oguzhan Yildiz, MD, PhD
Mineral trioxide aggregate (MTA) is being advocated for vital pulp therapy. In the case of direct pulp capping, hemorrhage control is an important step on success, but little is known about the effect of MTA on pulpal bleeding. In addition, there has been a lack of information on the effect of MTA on smooth muscle contraction, such as can occur in the blood vessels of dental pulp. The present study assessed the vascular effects of MTA, using the rat aortic ring preparations as a tissue model. MTA (100–500 mg) induced dose–dependent contraction in rat thoracic aorta. The contractile effect of MTA was blocked by calcium channel blocker nifedipine (1 μM). These data suggest that the vasoconstrictor property of MTA is related to calcium influx and it may allow proper control of hemorrhage which is critical for the success of any pulp-capping treatment.
Kv1.4 Subunit Expression is Decreased in Neurons of Painful Human Pulp
Jason E. Wells, PhD, Edward T. Rose, DMD, MS, Kevin C. Rowland, PhD, John F. Hatton, DMD
Kv1.4, a subunit of voltage-gated K+ channels, plays a large role in regulating neuronal excitability. The level of Kv1.4 expression is unknown in human sensory neurons innervating healthy or painful tissue. Therefore, we examined Kv1.4 immunoreactivity in axons innervating both clinically diagnosed asymptomatic and painful symptomatic human tooth pulp. Antibodies directed against Kv1.4 and PGP9.5, a protein marker for axons, was used to determine the proportion of PGP9.5 immunopositive tissue that was also immunopositive for Kv1.4. We report that on pulpal axons innervating symptomatic teeth Kv1.4 immunoreactivity, a correlate of decreased Kv1.4 expression, is significantly decreased (p < 0.0001), suggestive of a factor responsible for facilitating chronic dental pain and decreases in currents produced, such as IA, in neurons innervating painful pulp.
Evaluation of the Bactericidal Effect of Er,Cr:YSGG, and Nd:YAG Lasers in Experimentally Infected Root Canals
Qian-qian Wang, DDS, Cheng-fei Zhang, DDS, PhD, Xing-zhe Yin, DDS
The aim of this study was to evaluate the bactericidal effect of the Er,Cr:YSGG laser and the Nd:YAG laser in experimentally infected root canals. Sixty single-rooted teeth with straight canals were selected. After preparation and sterilization, the specimens were inoculated with Enterococcus faecalis for 3 weeks. After irradiation by lasers, the number of bacteria in each root canal was examined. The Er,Cr:YSGG laser gave a reduction of 77% after irradiation at 1 W and 96% at 1.5 W, but there was no significant difference (p > 0.05). The Nd:YAG laser gave a reduction of 97% at 1 W and 98% at 1.5 W, and there was no significant difference (p > 0.05). Compared with the Er,Cr:YSGG laser, the Nd:YAG laser is more effective (p < 0.05). In conclusion, both lasers systems have a significant bactericidal effect in infected root canals, and the Nd:YAG laser is more effective than the Er,Cr:YSGG laser.
Behavior of Human Dental Pulp Cells Exposed to Transforming Growth Factor-Beta1 and Acidic Fibroblast Growth Factor in Culture
Simone B. Luisi, DDS, MSc, PhD, João Jorge D. Barbachan, DDS, PhD, José Artur B. Chies, MSc, PhD, Manoel Sant’Ana Filho, DDS, PhD
The development of methods for regenerative endodontic procedures requires an understanding of the factors regulating the development of odontoblasts from adult cell populations such as pulpal cell lines. In this study, we exposed cultures of human pulp cells (7th passage) to growth factors including transforming growth factor–β1 (TGF-β1, at 1 or 5 ng/mL), acidic fibroblast growth factor (aFGF, 5 ng/mL), or a combination of the 2 growth factors and evaluated cellular morphology and markers of cell phenotype including alkaline phosphatase activity, osteocalcin, bone sialoprotein (BSP), and dentin sialophosprotein (DSPP). The mean number of nucleoli in the 1 ng/mL TGF-β1 group was significantly higher than with 5 ng/mL aFGF. Alkaline phosphatase activity was significantly greater with 1 ng/mL TGF-β1 versus 5 ng/mL TGF-β1 + 5 ng/mL aFGF (P < .05). Osteocalcin mRNA was expressed in all samples. The cells exposed to 1 ng/mL TGF-β1 were stimulated; however, exposure to growth factors for 8 days was not sufficient for expression of BSP and DSPP mRNA. Cells treated with 1 ng/mL TGF-β1 exhibited higher activity, whereas 5 ng/mL aFGF–treated cells were inhibited. Although osteocalcin was observed in all cultures, suggestive of the potential for odontoblast formation, under the present conditions, the exposure to TGF-β1 and aFGF was not sufficient to induce expression of the dentin matrix components BSP and DSPP.
Expression of Bone Extracellular Matrix Proteins on Osteoblast Cells in the Presence of Mineral Trioxide
Nobuyuki Tani-Ishii, DDS, PhD, Nobushiro Hamada, DDS, PhD, Kiyoko Watanabe, PhD, Yasuhisa Tujimoto, DDS, PhD, Toshio Teranaka, DDS, PhD, Toshio Umemoto, DDS, PhD
The biocompatibility of periapical tissue with mineral trioxide aggregate (MTA) affects its ability to repair and regenerate itself. Here we report the cytotoxicity of MTA and how it affects the expression of bone extracellular matrix protein in MC3T3-E1 osteoblast cells. We quantified the cytotoxicity of MTA, amalgam, and Dycal (Dentsply/Caulk, Milford, DE) on MC3T3-E1 cells by measuring the ability of cells to cleave a tetrazolium salt to produce formazan dye during a period of 24, 48, or 96 hours. We used reverse-transcriptase polymerase chain reaction with primer sets for type I collagen, osteocalcin, and bone sialoprotein to measure the gene-expression response of MC3T3-E1 cells treated with MTA. MTA, amalgam, and Dycal were less toxic after 48 hours. MC3T3-E1 cell growth with MTA and Dycal was greater than nonstimulated controls. MTA caused an upregulation of type I collagen and osteocalcin messenger RNA expression after 24 hours. These results showed that, in the presence of MTA, cells grow faster and produce more mineralized matrix gene expression in osteoblasts.
Effect of Adhesive Resin Cements and Post Surface Silanization on the Bond Strengths of Adhesively Inserted Fiber Posts
Karl-Thomas Wrbas, DDS, Markus Jörg Altenburger, DDS, Jörg Fabian Schirrmeister, DDS, Kerstin Bitter, DDS, Andrej Michael Kielbassa, PhD
This study evaluated the tensile bond strengths and the effect of silanization of fiber posts inserted with different adhesive systems. Sixty DT Light Posts (size 1) were used. Thirty posts were pretreated with silane. The posts were cemented into form-congruent artificial root canals (12 mm) of bovine dentine. Six groups were formed: G1, Prime&Bond NT/Calibra; G2, Monobond-S+Prime&Bond NT/Calibra; G3, ED Primer/Panavia 21ex; G4, Monobond-S+ED Primer/Panavia 21ex; G5, RelyX Unicem; and G6, Monobond-S+RelyX Unicem. The mean (standard deviation) tensile bond strengths (megapascals) were 7.69 (0.85) for G1, 7.15 (1.01) for G2, 6.73 (0.85) for G3, 6.78 (0.97) for G4, 4.79 (0.58) for G5, and 4.74 (0.88) for G6. G1 achieved significantly higher bond strengths than G3 and G5; G3 had significantly higher values than G5 (P < .05; Scheffé procedure). Silanization had no significant effect (P > .05, one-way analysis of variance). Tensile bond strengths were significantly influenced by the type of resin cement. Silanization of fiber post surfaces seems to have no clinical relevance.
The Anti-microbial Effect Against Enterococcus faecalis and the Compressive Strength of Two Types of Mineral Trioxide Aggregate Mixed With Sterile Water or 2% Chlorhexidine Liquid
Dennis M. Holt, DMD⁎, J. Dustin Watts, DMD⁎, Thomas J. Beeson, DDS†, Timothy C. Kirkpatrick, DDS⁎, Richard E. Rutledge, DDS⁎
The purpose of this in vitro study was 2-fold: First, to compare the antimicrobial effect of gray and tooth-colored mineral trioxide aggregate (MTA) when mixed with sterile water or 2% chlorhexidine. Second, to compare the compressive strengths of the MTA/chlorhexidine versus MTA/sterile water samples. The antimicrobial effect test was accomplished by placing freshly mixed MTA samples on agar plates inoculated with Enterococcus faecalis and comparing the zones of inhibition at 24 hours. In the compressive strength test, MTA pellets were allowed to set for 72 hours and then compressed to fracture by using an Instron testing machine. Values were recorded and compared. In the antimicrobial effect experiment, the zones of inhibition were significantly larger for samples mixed with 2% chlorhexidine. In the compressive strength study, statistical evaluation showed no significance due to variability. However, data revealed that MTA mixed with sterile water always had higher compressive strengths than MTA mixed with chlorhexidine.
Effect of Different All-Ceramic Crown System on Fracture Resistance and Failure Pattern of Endodontically Treated Maxillary Premolars Restored With and Without Glass Fiber Posts
Ziad Salameh, DCD, MS, Roberto Sorrentino, DDS, MS, Hani F. Ounsi, DCD, DESE, DEA, FICD, Cecilia Goracci, DDS, MS, PhD, Esam Tashkandi, DDS, MS, PhD, Franklin R. Tay, DDS, PhD, Marco Ferrari, DDS, MS, PhD
Endodontically treated teeth are traditionally restored with a crown to prevent fracture. The aim of this study was to compare the fracture resistance and failure modes of endodontically treated maxillary premolars treated with or without a fiber post and restored with different types of crowns. Eighty human maxillary premolars were selected. After root canal treatment, the teeth were embedded in resin blocks and divided into four groups. Samples received MOD cavity preparations and were divided into two subgroups: with and without fiber posts and restored using porcelain fused to metal, lithium disilicate, fiber-reinforced composite, or zirconia crowns. The specimens were vertically loaded in the central fossa using a universal loading machine until failure, and the maximum breaking loads were recorded. Samples were perfused with Indian ink to highlight the fracture lines and the mode of failure that was classified as restorable or nonrestorable. Even without post, all crown designs resisted vertically applied forces beyond those that may be encountered in the mouth. Two-way analysis of variance revealed the use of a fiber post (p = 0.007) and the type of crown (p < 0.001) significantly affected the restorability of fractured teeth. The relationship between placing or not placing the post and the type of failure (restorable/nonrestorable) was found to be significant (χ2 test, p = 0.002). Although post placement resulted in higher fracture resistance values, these were significant for Empress II crowns only. The results suggest that the posts could contribute to the reinforcement and strengthening of pulpless maxillary premolars. With respect to failure modes, placement of fiber posts improved the fracture from nonrestorable to restorable patterns. This study suggests that the placement of fiber posts is necessary to improve fracture resistance even under full-coverage crowns.
Comparative Evaluation of Antimicrobial Efficacy of Sodium Hypochlorite, MTAD, and Tetraclean Against Enterococcus faecalis Biofilm
Luciano Giardino, MD, DDS, Emanule Ambu, MD, DDS†, Enrico Savoldi, MD, DDS, Roberto Rimondini, PhD, MS, Clara Cassanelli, MD, Eugenio A. Debbia, MD
The aim of this study was to compare the antimicrobial efficacy of 5.25% NaOCl, BioPure MTAD (Dentsply Tulsa Dental, Johnson City, TN), and Tetraclean (Ogna Laboratori Farmaceutici, Milano, Italy) against Enterococcus faecalis biofilm generated on cellulose nitrate membrane filters. After incubation, the membrane filters were transferred into tubes containing 5 mL of the selected antimicrobial solution test agent or NaCl 0.9% (positive control) and incubated for 5, 30, and 60 minutes at 20°C. After each period of time, the test agents were vortexed for 60 seconds to resuspend the microorganisms. Ten-fold serial dilutions were generated in reduced transport fluid. Each dilution was plated onto a brain heart infusion plates. The plates were then incubated for 48 hours in an aerobic atmosphere at 37°C and colony-forming units per membrane was calculated. Statistical analysis showed that only 5.25% NaOCl can disgregate and remove the biofilm at every time; however, treatment with Tetraclean caused a high degree of biofilm disgregation in every considered time intervals as compared with MTAD (T5 p < 0.05, T30 p < 0.01, and T60 p < 0.001).
An In Vitro Comparison of Bond Strength of Various Obturation Materials to Root Canal Dentin Using a Push-Out Test Design
Matthew A. Fisher, DDS, David W. Berzins, PhD, James K. Bahcall, DMD, MS
The purpose of this in vitro study was to compare the bond strength of various obturation materials to root canal dentin by using a push-out test design. Twenty-five single-rooted extracted human teeth were used in this study. The crowns were removed, and root canal instrumentation was completed by using Endogel-coated 0.06 EndoSequence rotary files (Brasseler, Savannah, GA) and appropriate irrigation with 5.25% NaOCl and a final rinse with 17% EDTA. After instrumentation, the roots were randomly divided into five single-matched cone obturation groups (n = 5 roots/group), as follows: group 1, gutta percha with Kerr EWT (Kerr Corp, Romulus, MI); group 2, gutta percha with AH Plus (Dentsply, DeTrey, Germany); group 3, Resilon (Pentron Clinical Technologies, Wallingford, CT) and Epiphany (Pentron); group 4, Activ GP (Brasseler) obturation system; and group 5, EndoREZ obturation system (Ultradent, South Jordan, UT). The obturated roots were cut perpendicular to the long access to create 1-mm thick slices from the apical, middle, and coronal thirds. The bond strength was measured for each test slice with a push-out testing machine. Statistical analysis was completed by using a two-way analysis of variance and the post hoc Tukeys test with significance set at p < 0.05. Group 2 showed a significantly (p < 0.05) greater bond strength compared with all other groups. Also, groups 1 and 4 had significantly (p < 0.05) higher bond strengths compared with groups 3 and 5.
Influence of Different Root Canal–Filling Materials on the Mechanical Properties of Root Canal Dentin
Nicola M. Grande, DDS, Gianluca Plotino, DDS, Luca Lavorgna, DDS, Pietro Ioppolo, Rossella Bedini, Cornelis H. Pameijer, DMD, DSc, PhD, Francesco Somma, MD, DDS
The aims of this study were to compare Resilon (Resilon Research LLC, Madison, CT) in conjunction with either a bonding (Epiphany; Pentron Clinical Technologies, Wallingford, CT) or a nonbonding endodontic sealer (Pulp Canal Sealer; Kerr Corporation, Orange, CA) to EndoRez (Ultradent Products Inc, South Jordan, UT) and gutta-percha with regards to the physical properties and flexural stress in standardized dentin cylinders and the flexural stress of Resilon and gutta-percha. The external surface of 50 maxillary central incisors was reduced by means of mechanical milling to obtain dentin cylinders with an external diameter of 3 mm and minimum length of 12 mm. Root canals were prepared to obtain a standardized cylindrical preparation of 1.3 mm in diameter at the center of the root. The cylinders were randomly divided into five groups (n = 10): group 1: obturation with gutta-percha and Pulp Canal Sealer; group 2: obturation with Resilon, Epiphany primer, and Epiphany; group 3: obturation with Resilon and Pulp Canal Sealer; group 4: obturation with EndoRez methacrylate-based endodontic sealer; and group 5: dentin cylinders were not obturated. Ten gutta-percha (group 6) and Resilon (group 7) pellets for the Obtura gun were also tested. A three-point bending test was used to measure the maximum load values of specimens from groups 1 to 5 and the flexural strength and flexural modulus values for specimens from groups 6 and 7. Statistical analysis was performed to determine significance differences (p < 0.05). An analysis of variance test showed no significant difference among groups 1 to 5 (p = 0.697; F = 0.60). An independent sample t test showed statistically significant differences between groups 6 and 7 in flexural strength (p = 0.000) and flexural modulus (p = 0.000). Within the limits of this study, it may be concluded that the currently available endodontic-filling materials and their recommended adhesive procedures are not able to influence the mechanical properties of root canal dentin and that the flexural properties of Resilon and gutta-percha are too low to reinforce roots.
Influence of Surface Treatments on the Flexural Properties of Fiber Posts
Camillo D’Arcangelo, DDS, Maurizio D’Amario, DDS, Mirco Vadini, DDS, Francesco De Angelis, DDS, Sergio Caputi, MD, DDS
The aim of this study was to evaluate the effect of three post-surface treatments on flexural properties of fiber posts. Three types of posts were selected (n = 88 per post type). Four groups of specimens were prepared for each different post (n = 22). For the control group, posts were used as supplied by the manufacturers. Silanization, hydrofluoric etching, and sandblasting with 50 μm Al2O3 were performed on post surfaces for each of the other groups. Two posts of each group were submitted to a qualitative scanning electron microscopy (SEM) analysis. Remaining specimens were positioned in a universal testing machine and a three-point bending test was conducted (n = 20) until fracturing of the posts. Flexural strengths and flexural modules were calculated and recorded. None of the surface pretreatments had a significant influence on the tested properties of the posts (p > 0.05). Visual analysis of SEM micrographs showed significant changes of post surfaces determined by each conditioning treatment, which could increase post-retentive properties.
Shaping Abilities of Two Different Engine-Driven Rotary Nickel Titanium Systems or Stainless Steel Balanced-Force Technique in Mandibular Molars
Michael J. Matwychuk, DMD, MS, Walter R. Bowles, DDS, MS, Scott B. McClanahan, DDS, MS, Jim S. Hodges, PhD, Igor J. Pesun, MS, DDS
The purpose of this study was to compare apical transportation, working-length changes, and instrumentation time by using nickel-titanium (Ni-Ti) rotary file systems (crown-down method) or stainless steel hand files (balanced-force technique) in mesiobuccal canals of extracted mandibular molars. The curvature of each canal was determined and teeth placed into three equivalent groups. Group 1 was instrumented with Sequence (Brasseler USA, Savannah, GA) rotary files, group 2 with Liberator (Miltex Inc, York, PA) rotary files, and group 3 with Flex-R (Union Broach, New York, NY) files. Pre- and postoperative radiographs were superimposed to measure loss of working length and apical transportation as shown by changes in radius of curvature and the long-axis canal angle. Sequence rotary files, Liberator rotary files, and Flex-R hand files had similar effects on apical canal transportation and changes in working length, with no significant differences detected among the 3 groups. Hand instrumentation times were longer than with either Ni-Ti rotary group, whereas the rotary NiTi groups had a higher incidence of fracture.
An In Vitro Comparison of Bacterial Leakage of Three Common Restorative Materials Used as an Intracoronal Barrier
Bahareh Fathi, DDS, James Bahcall, DMD, MS, James S. Maki, PhD
The purpose of this in vitro study was to evaluate quantitatively the effectiveness of three different restorative materials used as an intracoronal barrier to prevent microleakage of endodontically treated teeth. Fifty-five extracted human single-canal teeth were used in this study. The teeth were endodontically prepared and obturated. Forty-five teeth were randomly assigned to three experimental groups: group 1: sealed with Ketac-Cem (3M ESPE, St Paul, MN) (n = 15), group 2: sealed with Clearfil Protect Bond/Clearfil AP-X (Kuraray, New York, NY) (n = 15), and group 3: sealed with Maxcem (Kerr, Orange, CA) (n = 15). Ten teeth were also randomly assigned to a negative control group (n = 5) and a positive control group (n = 5). Microleakage was tested by using a sterile two-chamber bacterial method and Enterococcus faecalis was used as a microbial marker. Samples were incubated aerobically at 37 °C for 120 days. Bacterial leakage was determined by change in turbidity in the medium. Statistical analysis was performed using a Wald chi-square test. No significant difference (p > 0.05) in bacterial leakage was found between the three experimental groups tested. All positive controls leaked within 60 days and broth of the negative control group remained clear throughout the entire experimental period.
Marginal Leakage of Different Temporary Restorations in Standardized Complex Endodontic Access Preparations
Yi-Yin Lai, DDS, MSD, Lu Pai, PhD, Chin-Ping Chen, DDS, CAGS, DSc
This study compared the marginal leakage of temporary restorations using Cavit, IRM, zinc phosphate cement (ZPC), and copper bands cemented with ZPC. Standardized complex endodontic access preparations were made in 176 extracted human molars. The teeth were divided into six groups, including positive and negative controls. A Universal matrix system was placed over each tooth before restoration, except in the copper band group, in which teeth were restored with ZPC after copper band cementation. Marginal leakage was evaluated with a binocular microscope after the teeth were immersed in artificial saliva, colored with 2% methylene blue and buffered to neutral pH, at 37 °C for various time intervals after thermal cycling. In the experimental groups, the differences in the leakage scores of the Cavit group and the other groups were very marked. The Cavit group presented the least marginal leakage, irrespective of time, whereas more than half the specimens from the IRM, ZPC, and copper band groups displayed severe leakage from day 1.
Effects of Time and Concentration of Sodium Ascorbate on Reversal of NaOCl-Induced Reduction in Bond Strengths
Charles H. Weston, DMD⁎, Shuichi Ito, DDS, PhD†, Bakul Wadgaonkar, BS, MS†, David H. Pashley, DMD, PhD†
The use of NaOCl as an endodontic irrigant lowers the bond strength of resin cements but this can be reversed by the use of 10% sodium ascorbate for 10 min. The objective of this study was to evaluate the effect of time and concentration of ascorbate at restoring the bond strength. Group 1 roots were prepared using 0.9% NaCl as an irrigant; group 2 roots were irrigated with 5.25% NaOCl; group 3 roots were irrigated with 5.25% NaOCl followed by 10% ascorbate for 10 min; group 4 roots were irrigated with 5.25% NaOCl followed by 10% ascorbate for 3 min; group 5 roots were irrigated with 5.25% NaOCl followed by 10% ascorbate for 1 min; and group 6 roots were irrigated with 5.25% NaOCl followed by 20% ascorbate for 1 min. All roots were then filled with C&B Metabond, stored 1 day in water, and then cross-sectioned into 6 slabs, 1 mm thick, that were trimmed and tested for tensile bond strength. The results demonstrated that 5.25% NaOCl irrigation produced (p < 0.05) significant reduction in resin–dentin bond strengths, but this can be reversed by 10% ascorbate treatment for 1 min.