Proliferation of Epithelial Cell Rests, Formation of Apical Cysts, and Regression of Apical Cysts after Periapical Wound Healing
Louis M. Lin, BDS, DMD, PhD⁎, George T.-J. Huang, DDS, MDS, DSc, Paul A. Rosenberg, DDS
There is continuing controversy regarding the potential for inflammatory apical cysts to heal after nonsurgical endodontic therapy. Molecular cell biology may provide answers to a series of related questions. How are the epithelial cell rests of Malassez stimulated to proliferate? How are the apical cysts formed? How does the lining epithelium of apical cysts regress after endodontic therapy? Epithelial cell rests are induced to divide and proliferate by inflammatory mediators, proinflammatory cytokines, and growth factors released from host cells during periradicular inflammation. Quiescent epithelial cell rests can behave like restricted-potential stem cells if stimulated to proliferate. Formation of apical cysts is most likely caused by the merging of proliferating epithelial strands from all directions to form a three-dimensional ball mass. After endodontic therapy, epithelial cells in epithelial strands of periapical granulomas and the lining epithelium of apical cysts may stop proliferating because of a reduction in inflammatory mediators, proinflammatory cytokines, and growth factors. Epithelial cells will also regress because of activation of apoptosis or programmed cell death through deprivation of survival factors or by receiving death signals during periapical wound healing.
Effects of Dentin on the Antimicrobial Properties of Endodontic Medicaments
Markus Haapasalo, DDS, PhD, Wei Qian, DDS, PhD, Isabelle Portenier, DDS, PhD†, Tuomas Wal
Successful treatment of apical periodontitis is dependent on the elimination of the infective microflora from the necrotic root canal system.
Antimicrobial irrigating solutions and other locally used disinfecting agents and medicaments have a key role in the eradication of the microbes.
While most if not all presently used disinfecting agents rapidly kill even the resistant microbes when tested in vitro in a test tube, the effectiveness of the same agents is clearly weaker in the in vivo conditions. Recent studies have given valuable information about the interaction of endodontic disinfecting agents with dentin and other compounds present in the necrotic root canal. As a result of such interactions the antimicrobial effectiveness of several of our key disinfectants may be weakened, or even eliminated under certain circumstances. Different disinfectants show different sensitivity to the action by the various potential inactivators, such as dentin, serum proteins, hydroxyapatite, collagen derived from different sources, and microbial biomass. This review is a summary of our present knowledge of the mostly negative interactions between endodontic disinfecting agents and the various compounds present in the root canal environment.
Adenovirus-mediated Recombinant Human Bone Morphogenetic Protein-7 Expression Promotes Differentiation of Human Dental Pulp Cells
Zheng-Mei Lin, MD⁎, Wei Qin, MS, Nian-Hua Zhang, MS†, Lin Xiao, MS†, Jun-Qi Ling, MD
Recombinant human bone morphogenetic protein-7 (BMP-7) has been shown to stimulate new reparative dentin formation in animal models. However, little is known about whether BMP-7 could promote the odontoblast-like differentiation and the formation of mineralized nodules in human dental pulp cells. Here, we reported that the infection with adenovirus-BMP-7 (Ad-BMP-7), a BMP-7–expressing adenoviral vector, induced the expression of BMP-7 in primarily cultured human dental pulp cells in the long term with little effect on their proliferation and viability. Importantly, BMP-7 expression significantly increased alkaline phosphatase activity and induced the dentin sialophosphoprotein expression in a dose- and time-dependent manner, suggesting that BMP-7 promoted the odontoblast differentiation. Furthermore, BMP-7 expression stimulated the formation of many mineralized dentin-like calcified nodules. Our data suggest that Ad-BMP-7–mediated BMP-7 expression can promote the differentiation of human pulp cells into odontoblast-like cells and mineralization in vitro, which may provide insight for the design of new gene therapy for the pulp capping in the clinic.
Gene Profiles during Root Canal Treatment in Experimental Rat Periapical Lesions
Zulema Rosalia Arias Martinez, DDS, Koji Naruishi, DDS, PhD, Keisuke Yamashiro, DDS, PhD, Fumio Myokai, DDS, PhD, Teruo Yamada, PhD, Kaori Matsuura, DDS, PhD, Naoko Namba, DDS, Hideo Arai, DDS, PhD, Junzo Sasaki, MD, PhD, Yoshimitsu Abiko, DDS, PhD, Shogo Takashiba, DDS, PhD
The purpose of this study was to profile gene expression in periapical lesions during root canal treatment (RCT). Periapical lesions were induced experimentally by exposing the pulp in Sprague-Dawley rats. After 3 wk, the animals received root canal filling (RCF) and were sacrificed 1 or 4 wk later. From the periapical tissues, total RNA was extracted and processed for cDNA-microarray analysis. The lesions were histologically and radiographically confirmed to expand 4 wk after pulp exposure (inflammation phase) and to stabilize 4 wk after RCF (healing phase). In approximately 30,000 genes on the microarray, 203 genes were up-regulated to more than 5-fold (e.g., IL-1β), and 864 genes were down-regulated to less than 20% of baseline level (e.g., caspase 8) in inflammation phase. Compared with inflammation phase, we found that 133 genes were up-regulated (e.g., IL-1α) and 50 genes were down-regulated (e.g., defensin α5) in healing phase. Corresponding to the gene expression profiles, accumulation of IL-1α and IL-1β was observed in the periapical lesions by immunohistochemistry. These gene profiles might be useful in diagnosing the healing process of periapical lesions.
Evaluation of the Quality of the Apical Seal in Resilon/Epiphany and Gutta-Percha/AH Plus–filled Root Canals by Using a Fluid Filtration Approach
Rakesh Raina, DDS, Robert J. Loushine, DDS, R. Norman Weller, DMD, MS, Franklin R. Tay, BDSC (Hons), PhD, David H. Pashley, DMD, PhD
This in vitro fluid filtration study compared the apical leakage of root canals that were obturated with Resilon/Epiphany (Resilon Research LLC, Madison, CT) or gutta-percha/AH Plus (GP/AH; DENTSPLY Tulsa, Tulsa, OK) sealer using warm vertical condensation. Fluid flow rate through the filled roots was measured 7 days after the obturations by using a fluid filtration device. Measurements were made before root resection and after 3 to 11 mm of resections. Before any removal of root length, there were no significant differences between the roots filled with Resilon/Epiphany or GP/AH. Analysis of individual root resection results revealed that differences in the fluid flow rate of the two systems occurred only when 9 or 10 mm of the roots were resected with more than half the root length resected when GP/AH Plus leaked more than Resilon/Epiphany. There were no significant differences in the fluid flow rate up to and including 8 mm of root resection. It is concluded Resilon/Epiphany sealed 17-mm root canals as well as gutta-percha and AH Plus sealer and that it does not create a monoblock root filling that does not leak.
Residual Effects and Surface Alterations in Disinfected Gutta-Percha and Resilon Cones
Brenda P.F.A. Gomes, PhD, Vanessa B. Berber, MSc, Francisco Montagner, DDS, Neylla T. Sena, MSc, Alexandre A. Zaia, PhD, Caio C.R. Ferraz, PhD, Francisco J. Souza-Filho, PhD
The aim of this study was to evaluate alterations on the surface of gutta-percha and Resilon cones when exposed to 2% chlorhexidine gel (CHX) and 5.25% sodium hypochlorite (NaOCl) and to evaluate their possible antibacterial residual effects against Enterococcus faecalis and Porphyromonas gingivalis.
A total of 270 medium tapered cones (135 gutta-percha and 135 Resilon) were selected and divided into three groups, according to the substance (NaOCl, CHX, and sterile saline solution). The cones were immersed in each substance (for 1, 5, 10, 20, and 30 min), rinsed in saline solution, and dried. They were placed onto inoculated agar plates and incubated under specific conditions. Scanning electron microscopy analysis was performed on additional 270 disinfected cones. Another 18 cones were used as controls. Based on the results, it was concluded that Resilon cones exposed to CHX for 10, 20, and 30 min demonstrated residual antibacterial action and that substances did not cause alterations to the cones’ surface.
Susceptibility of a Polycaprolactone-based Root Canal–filling Material to Degradation. III. Turbidimetric Evaluation of Enzymatic Hydrolysis
Noriko Hiraishi, DDS, PhD, Joyce Y.Y. Yau, BSc, MSc, Robert J. Loushine, DDS, Steven R. Armstrong, DDS, MS, R. Norman Weller, DMD, MS, Nigel M. King, BDS, MSc, PhD, David H. Pashley, DMD, PhD, Franklin R. Tay, BDSc (Hons), PhD
The susceptibility of Resilon (Pentron Clinical Technologies, Wallingford, CT) to biotic biodegradation by two hydrolases, lipase PS and cholesterol esterase, was investigated with a turbidimetric approach by measuring the optical density reductions in aqueous emulsions containing dissolved, filtered, surfactant-stabilized polymeric components of Resilon. Polycaprolactone, the major polymeric component of Resilon, was also examined in a similar manner using equivalent or a four-fold increase in enzyme concentration. Optical density time plots were characterized by an initially linear steep reduction in optical density, from which the reaction rates were derived. For both enzymes, the rates of hydrolysis for Resilon were much faster than those of polycaprolactone at 1× or even 4× enzyme concentration. Field-emission scanning electron microscopy of air-dried Resilon and polycaprolactone emulsions revealed the presence of spherical polymer droplets that appeared deformed, pitted, or much reduced in dimensions after enzymatic hydrolysis.
A Confocal Laser Scanning Microscope Investigation of the Epiphany Obturation System
Saman R. Gharib, DMD, MS, Patricia A. Tordik, DMD, Glen M. Imamura, DDS, MS, Thomas A. Baginski, MS, Gary G. Goodell, DDS, MS, MA
The purpose of this study was to assess the sealer-dentin interface and compare the percentage and average depth of dentinal tubule sealer penetration in the coronal, middle and apical thirds of teeth obturated with the Epiphany Obturation System using 10x and 40x confocal laser scanning microscopy. Ten anterior teeth were instrumented and obturated with Resilon points and Epiphany sealer labeled with fluorescent Rhodamine B isothiocyanate dye. Two-millimeter sections cut from the coronal, middle and apical thirds of each root were viewed using 10x and 40x confocal laser scanning microscopy. A consistent fluorescent sealer ring was seen around the canal wall in all sections. No gaps or definitive hybrid layer were observed in the sealer-dentin interface, however a 1–1.5 μm wide high fluorescence zone was detected. One-way ANOVA and post-hoc tests showed significantly less percentage of sealer penetration in apical sections than middle or coronal sections (p < 0.05). The Kruskal-Wallis test and post-hoc tests found significantly lower average depth of sealer penetration in apical sections than middle or coronal sections (p < 0.05).
Canal Transportation after Root Canal Instrumentation: A Comparative Study with Computed Tomography
Mateus Silveira Martins Hartmann, MSc, Fernando Branco Barletta, DDS, MSc, PhD, Vânia Regina Camargo Fontanella, DDS, MSc, PhD, José Roberto Vanni, DDS, MSc, PhD
This in vitro study used computed tomography (CT) to compare the occurrence of canal transportation in the apical third of mesiobuccal canals in maxillary molars instrumented with 3 techniques. Sixty teeth were assigned to 3 groups (n = 20), and the root canals were instrumented as follows: Group 1, hand instrumentation with K-files; Group 2, K-files coupled to an oscillatory system powered by an electric engine; Group 3, ProTaper NiTi rotary system powered by an electric engine. To compare the canal transportation produced by the different techniques, preinstrumentation and postinstrumentation 3-dimensional CT images were obtained from root cross-sections of the region located 3 mm short of the apical foramen of each root canal. The CT scans were exported to Adobe Photoshop software, and the initial and final images were superimposed to detect the root canal wall differences between them. Canal transportation was measured by the distance between the prepared canal center and the anatomic canal center. The manual technique produced lesser canal transportation (0.10 mm) than the oscillatory and rotary techniques (0.37 and 0.22 mm, respectively); this difference was statistically significant (P = .021). All studied techniques produced canal transportation.
Interaction between Sodium Hypochlorite and Chlorhexidine Gluconate
Bettina R. Basrani, DDS, Sheela Manek, BSc, Rana N.S. Sodhi, PhD, Edward Fillery, BSc, PhD, Aldo Manzur, DDS, MSc
The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCl required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023 % and 0.19 % NaOCl, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCl before placing CHX into the canal.
Interaction between Sodium Hypochlorite and Chlorhexidine Gluconate
Bettina R. Basrani, DDS, Sheela Manek, BSc, Rana N.S. Sodhi, PhD, Edward Fillery, BSc, PhD†, Aldo Manzur, DDS, MSc
The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCl required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023 % and 0.19 % NaOCl, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCl before placing CHX into the canal.
Effects of pH and Mixing Agents on the Temporal Setting of Tooth-colored and Gray Mineral Trioxide Aggregate
J. Dustin Watts, DMD, Dennis M. Holt, DMD, Thomas J. Beeson, DDS, Timothy C. Kirkpatrick, DDS, Richard E. Rutledge, DDS
The purpose of this study was to test the compressive strength of white mineral trioxide aggregate (WMTA) and gray mineral trioxide aggregate (GMTA) when mixed with sterile water or local anesthetic and exposed to an acidic environment. A total of 248 samples of WMTA and GMTA were mixed and placed in phosphate-buffered saline (PBS), at pH 5.0 or 7.4, for a period of 7 or 28 days. When WMTA and GMTA were mixed with local anesthetic, the following were observed: 1) pH 5.0 caused a significant decrease in compressive strength (p < 0.0001); 2) WMTA was significantly stronger than GMTA (p < 0.0001); and 3) more time in PBS (total 28 days) caused a significant decrease in compressive strength (p < 0.001). There were no consistent differences in compressive strength for WMTA or GMTA when mixed with sterile water. Variability of results suggests both types of MTA be mixed with sterile water in acidic and neutral environments.
In Vivo Evaluation of ProPex Electronic Apex Locator
Ebru Özsezer, DDS, PhD, Uǧur İnan, DDS, PhD, Uǧur Aydın, DDS
The aim of this in vivo study was to evaluate the performance of ProPex apex locator after extirpation and in presence of different irrigation solutions: 2.5% NaOCl, 0.9% NaCl, and 0.2% chlorhexidine gluconate solutions. Twenty-seven single-rooted human teeth scheduled for extraction with mature apices were selected for this study. Measurements were performed by using ProPex after extirpation and in presence of the irrigation solutions. After extraction of the teeth, a stereomicroscope was used to confirm visually the relationship of the tip of the endodontic file to the apical foramen, and actual lengths (ALs) were determined by reducing 0.5 mm from these lengths. The data were statistically analyzed with cluster analysis. The results of this study showed that measurements after extirpation had the smallest distance to the ALs. Among the irrigation solution groups, chlorhexidine gluconate group had the smallest distance to the ALs, whereas saline group had the greatest. Most accurate measurements were obtained after extirpation.
In Vitro Evaluation of the Sealing Ability of Newly Developed Calcium Phosphate–based Root Canal Sealer
Sung-Eun Yang, DDS, MSD, Seung-Ho Baek, DDS, MSD, PhD, WooCheol Lee, DDS, MSD, PhD, Kee-Yeon Kum, DDS, MSD, PhD, Kwang-Shik Bae, DDS, MSD, PhD
This study compared the sealing ability of newly developed calcium phosphate–based root canal sealers (CAPSEAL I, CAPSEAL II) with other calcium phosphate–based sealer (Sankin Apatite Root Canal Sealer: SARCS I, SARCS III), a resin-based sealer (AH Plus), a ZOE-based sealer (Pulp Canal Sealer EWT), and a calcium hydroxide–based sealer (Sealapex) by using an anaerobic bacterial leakage model with Prevotella nigrescens during a 90-day observation period (n = 15/group). SARCS I and III had significantly greater leakage with P. nigrescens than all other groups (P < .05). There was no other statistical difference between the sealers. Field emission–scanning electron microscope observations showed that both CAPSEAL I and II sealers were well-adapted to the canal wall and infiltrated into the dentinal tubules.
Influence of Sodium Hypochlorite on Mechanical Properties of K3 Nickel-Titanium Rotary Instruments
Fabiola Ormiga Galvão Barbosa, José Antônio da Cunha Ponciano Gomes, Marcos Cesar Pimenta de Araújo
Several studies have evaluated the influence of various factors on the fracture of nickel-titanium endodontic rotary instruments. The present study analyzed the influence of sodium hypochlorite on flexural fatigue and torsional properties of nickel-titanium endodontic rotary instruments. New files and files previously exposed to sodium hypochlorite were tested for flexural fatigue and for resistance to fracture by twisting. The t test was used to compare the groups for number of cycles, angle of rotation, and maximum torque required to fracture. No statistical difference existed between these groups. Scanning electron microscopy analysis showed no evidence of localized corrosion in files exposed to sodium hypochlorite solution. These results suggest that the exposure to sodium hypochlorite has no influence on resistance to fracture of K3 rotary instruments.
Study of the Progressive Changes in Canal Shape After Using Different Instruments by Hand in Simulated S-Shaped Canals
Huang Ding-ming, DDS, PhD, Luo Hong-xia, DDS, MD, Gary S.-P. Cheung, MDS, MSc, Zhang Lan, MD, Tan Hong, DDS, Zhou Xue-dong, DDS, PhD
This study analyzed the progressive changes in canal shape after the use of different instruments by hand in simulated S-shaped canals.
Forty simulated canals with double curvatures, 30° coronally and 20° apically, were randomly divided into four groups and prepared with stainless steel K-files, the ProTaper for hand use (PHU) system, NiTi K-files, and the combination of PHU and NiTi K-files, respectively, by hand. All canals were scanned pre-and postoperatively. Each postinstrumentation image was superimposed with the preoperative one in a computer. The amount of material removed after every instrument was measured at 14 points. Statistical analysis was performed using an analysis of variance (ANOVA) test at α = 0.05.
All four instruments straightened the S-shaped canals, except the combination of PHU (S1, Sx, and S2) and NiTi K-files, which created a continuous funnel shape. There was a significant difference in the amount of material removed between S2 and F1 of the PHU system (p < 0.05), and the finishing files of PHU created the same transportation as the stainless steel instruments with the same tip size (p > 0.05).
Water Sorption and Solubility of Methacrylate Resin–based Root Canal Sealers
Adam Donnelly, BS, Jeremy Sword, BS, Yoshihiro Nishitani, DDS, PhD, Masahiro Yoshiyama, DDS, PhD, Kelli Agee, BS, Franklin R. Tay, BDS, PhD, David H. Pashley, DMD, PhD
The water sorption and solubility characteristics of three contemporary methacrylate resin-based endodontic sealers, EndoREZ, Epiphany, and InnoEndo, were compared with those obtained from Kerr EWT, Ketac-Endo (positive control), GuttaFlow, and AH Plus (both negative controls). Ten disks of each material were dehydrated in Drierite for 24 h and weighed to constant dry mass. They were placed in water and weighed periodically until maximum water sorption was obtained. The disks were dehydrated again to determine their mass loss (solubility) at equilibrium. Epiphany exhibited the highest apparent water sorption (8%) followed by Ketac-Endo (6.2%), InnoEndo (3.4%), EndoREZ (3.0%), AH Plus (1.1%), GuttaFlow (0.4%), and Kerr EWT (0.3%). Significantly higher solubility (3.5-4%) were observed for all three methacrylate resin-based sealers and Kerr EWT (3.95%), compared with Ketac-Endo (1.6%), AH Plus (0.16%), and GuttaFlow (0.13%). American Dental Association specifications require <3% solubility for endodontic sealers. Only Ketac-Endo, AH Plus, and GuttaFlow met that criterion.
Influence of Apical Constriction Diameter on Root ZX Apex Locator Precision
Manuela Herrera, DDS, MD, PhD, Camilo Ábalos, DDS, MD, PhD, Amparo Jimenez Planas, DDS, MD, PhD, Rafael Llamas, DDS, MD, PhD
Small-diameter hand files are systematically used to determine the initial working length and to establish patency of the root canal. In wide canals, electronic apex locator accuracy might be influenced by file size. This article reports on a study to assess the influence of apical constriction diameter on the precision of the Root ZX apex locator by using files of varying diameter on teeth with 3 different degrees of apical widening: 0.37, 0.62, and 1.02 mm. Ten extracted single-root teeth, stored in saline solution at 37°C, were sectioned at the enamel-cement junction and embedded in an alginate mold. Initial working length (L0) was determined with a #10 Kerr file, and canals were irrigated with either 50% citric acid or 5.25% sodium hypochlorite. To assess the ability of the locator to identify the narrowest area of the root canal as constriction diameter increased, the canal was progressively widened by insertion of files of increasing diameter (10–100) at a point L0 + 1 mm. After each enlargement, the working length (L) was redetermined, with files from #10 (L10) up to the file used for widening. Comparison of statistical results was based on the difference between final working length and initial length (L10) for each apical width. Statistical analysis was carried out with analysis of variance test for comparison of means. Results showed that at apical constriction widths of 0.37 and 0.62 mm, there was no significant difference between initial working lengths as determined by a Kerr #10 file and final working lengths after widening with files of up to #60. In those teeth whose apical width had been increased to 1.02 mm, there was no statistically significant difference between initial and final working lengths as measured by files from #10–#25; however, significant differences were apparent between #10 and #30, #35, or #40 (P < .05), and the degree of significance increased considerably (P < .001) for files #45 or greater. These results suggest that Root ZX apex locator precision varies as a function of apical constriction diameter.
Invasive Cervical Resorption: A Case Report
Hemalatha Hiremath, Postgraduate student, Shoeb Sheikh Yakub, MDS, Sandeep Metgud, MDS, S.V. Bhagwat, MDS, Sadanand Kulkarni, MDS
Invasive cervical resorption (ICR) is a relatively uncommon form of external resorption, which may occur in any tooth in the permanent dentition. Characterized by its cervical location and invasive nature, this resorptive process leads to progressive and usually destructive loss of the tooth structure, the clinical features of which often resemble internal resorption (“pink tooth”). This article describes a case report of ICR and its management. The salient features were a large resorptive defect and localized fibrous in-growth located almost wholly on the cervicolabial aspect of the maxillary incisor crown involving the enamel and dentin.