Root Surface Temperature Rises In Vitro During Root Canal Obturation Using Hybrid and Microseal Techniques
Mariusz Lipski, DDS, PhD
The aim of this in vitro study was to measure the temperature rise on the outer surface of roots during filling with hybrid technique and Microseal. Twenty extracted human maxillary and mandibular premolars with a single canal were randomly divided into two groups of 10 teeth each. In the first group, the teeth were filled with hybrid technique (thermomechanical compaction with Engine Plugger used following lateral condensation of the apical part of the canal), the second group was filled using Microseal. After root canal obturation the filling material was removed and the obturation procedure was repeated. A total of 20 obturations in each group were performed. Temperature changes were measured using a thermal imaging camera. The temperature of certain regions of the mesial surface was analyzed and the highest temperature values were recorded. Statistical analysis was performed using the Mann-Whitney U test. The mean increase of temperature during the hybrid technique with Engine Plugger was 23.8°C, while during Microseal it was significantly lower (p = 0.000001) at 5.5°C. The temperature rise generated by Microseal was below the critical level and should not damage supporting structures, however, the hybrid technique generated a relatively high temperature rise that may cause periodontal tissue damage.
Comparison of Two Different Direct Digital Radiography Systems for the Ability to Detect Artificially Prepared Periapical Lesions
Robert B. Folk DDS, MS, Jeffery R. Thorpe, DDS, Scott B. McClanahan DDS, MS, James D. Johnson DDS, MS, and James M. Strother, DDS, MS
The purpose of this study was to compare Schick CDR and Trophy RVGui direct digital radiography (DDR) systems for the ability to detect periapical lesions in human cadaver mandibles. Digital radiographs were exposed of teeth with normal periapical areas and ofteeth with artificially prepared periapical lesions using both DDR systems. Three examiners independently viewed the images at two different time periods and estimated which bony state was present. The resulting data were subjected to statistical analysis using a twoway ANOVA. Interexaminer variability was statistically analyzed using Spearman’s rho. There was no significant difference in the level of accuracy between the two different DDR systems at either observation period. There was a statistically significant high level of agreement between examiners (p < 0.01). In conclusion, there was no significant difference in the accuracy of detecting artificially prepared periapical lesions between Schick CDR and Trophy RVGui DDR systems.
Analysis of Heat Generation Using Ultrasonic Vibration for Post Removal
John T. Dominici, DDS, MS, Stephen Clark, DMD, James Scheetz, PhD, and Paul D. Eleazer, DDS, MS
This study measured the temperature of the root surface and post during the application of ultrasonic vibration to cemented posts to simulate post removal procedure. Root canal therapy was performed on ten extracted maxillary incisors. A stainless steel Parapost was cemented into each prepared post space. Ultrasonic vibration was applied to the post and temperatures were recorded at the coronal post and the cervical root surface. Data were analyzed with ANOVA using the independent variables of (a) time of ultrasonic application (15, 30, 45 and 60 s) and 2) location (post and root surface). Greater temperature increase was observed at the post (52.6°C, SD 11.1; 82.6°C, SD 20.1; 111.0°C, SD 29.1; 125.3°C, SD 33.2) compared to the root surface (9.5°C, SD 4.6; 17.5°C, SD 4.8; 25.4°C, SD 7.3; 32.2°C, SD 8.1) for each time period, P < 0.001. Ultrasonic application to the post for longer than 15 s generates high temperature on the root surface.
A Comparison of the Effects of Two Canal Preparation Techniques on Root Fracture Susceptibility and Fracture Pattern
Chankhrit Sathorn, DDS, Joseph E.A. Palamara, PhD, and Harold H. Messer, DDS, PhD
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.
Shear Bond Strength of Three Resin Based Sealers to Dentin With and Without the Smear Layer
Ayce Unverdi Eldeniz, DDS, PhD, Ali Erdemir, DDS, PhD, and Sema Belli, DDS, PhD
Bond strength of root canal sealers to dentin is an important property for the integrity of the sealings of root-canals. The purpose of this study was to test shear bond strength of three endodontic sealers (Diaket, AH Plus and Endo-REZ). The coronal two thirds of ninety extracted human third molars were removed. The smear layer of the exposed dentin surfaces were removed using 17% EDTA followed by 5.25% NaOCl and the teeth were randomly divided into two groups ( n= 45). Group 1 was kept as control and in group 2, uniform smear layer was created using waterproof polishing papers. Three-mm long sections of polyethylene tubing were filled with freshly mixed sealer and placed on the dentin surfaces for conducting a shear bond strength test. The data was calculated as MPa and was statistically analyzed using a two way ANOVA, Kruskal-Wallis and Mann-Whitney U tests. A significant difference was found among the bond strength of the sealers, smear layer, and control groups. AH Plus sealer showed the highest bond strength in smear layer removed surfaces (p < 0.05). Pretreatment with EDTA/NaOCl affected bond strength of AH Plus. AH Plus had the highest bond to dentin with or without smear layer.
Effect of Root Canal Size and External Root Surface Morphology on Fracture Susceptibility and Pattern: A Finite Element Analysis
Chankhrit Sathorn, DDS, Joseph E.A. Palamara, PhD, Darunee Palamara, DDS, PhD, and Harold H. Messer, DDS, PhD
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.
Coronal Leakage of Sealer-Only Backfill: An In Vitro Evaluation
John Martin Whitworth, PhD, and Lina Baco, MSc
We tested the hypothesis that AH Plus and Roeko Seal Automix (RSA) sealers alone are no less effective in preventing coronal microleakage than gutta-percha compacted with sealer. Freshly prepared sheep incisor root canals were obturated with warm gutta-percha alone, AHPlus or RSA alone, or warm gutta-percha with AH Plus or RSA ( n = 20 each group). Coronal leakage was assessed under vacuum conditions with Indian ink and tooth clearing. Sealer-only backfills with AH Plus and RSA yielded significantly more dye-free canals than backfills of gutta-percha alone or with sealer (p < 0.001). Warm gutta-percha with or without sealer kept no more canals sealer free than the positive control. Mean dye penetration was 0.92% of canal length for AH Plus and RSA backfills, 27.42% for gutta-percha only backfills, 26.47% for gutta-percha with RSA and 13.92% for gutta-percha with AH Plus. Sealer only backfills allowed significantly less leakage than those including warm gutta-percha (p < 0.001). Sealer-only backfills may be a viable alternative to traditional gutta-percha and sealer compaction methods.
Root Canal Treatment in a Mandibular Second Premolar with Three Root Canals
Roeland J.G. De Moor, DDS, PhD, MSc, and Filip L.G. Calberson, DDS
According to the endodontic literature, the possibility of three canals in mandibular second premolars is quite small. When three or more canals are present separation of the root canals has only been described at mid-root level. The present case describes root canal treatment of a root canal aberration at the level of the apical third (apical root canal separation starting at a length of 20 mm) where a combined use of the fiberoptic endoscope and the operating microscope was necessary to locate the canal orifices and to enter these orifices. The present report emphasizes the need of color contrast to enhance visualization.
The Cytotoxicity of RoekoSeal and AH Plus Compared during Different Setting Periods
Ivana Miletić, DDS, PhD, Nevena Devčić, DDS, Ivica Anić, DDS, PhD, Josipa Borčić, DDS, MS, Zoran Karlović, DDS, PhD, and Maja Osmak, PhD
The aim of this study was to evaluate the cytotoxicity of the root canal sealers RoekoSeal Automix (RSA) and AH Plus in vitro on human cervical carcinoma (HeLa) cells and mouse skin fibroblasts (L929). The sealers were covered with a 3 × 10⁴ cell suspension 1 h, 24 h, 48 h, 7 days and 1 month after mixing. Four samples and respective controls without sealer were prepared. After 5 days of incubation, the number of cells was determined using an electronic counter; the number of viable cells was determined under light microscopy following the addition of nigrosin dye. The experiment was repeated twice for each sealer and each period. AH Plus was significantly more cytotoxic after 1 h, 24 h, and 48 h, compared to the 7 day and 1 month setting period on both cell lines. RoekoSeal had no cytotoxic effect on either cell line at any setting time.
Determining the Optimal Obturation Length: A Meta-Analysis of Literature
Michelle A. Schaeffer, DDS, MPH, Robert R. White, DMD, and Richard E. Walton, DMD, MS
The purpose was to aid in determining termination of instrumentation and obturation. A meta-analysis was conducted as to success/failure of different obturation lengths. Inclusion criteria were (a) minimum follow-up of 2 yr, (b) data on obturation length, (c) definition of success/failure, (d) available data on success/failure, (e) radiographic evaluation. Correlations were made as to success/failure as related to length of obturation from the apex. When comparing group A (obturated 0–1 mm from apex) versus group C (obturated past apex) using the DerSimonian and Laird estimates, group A showed a marginally better (p < 0.10) success rate than group C by 28.8%. Group A had better success than group B (obturated >1 mm short); the difference was insignificant. The results were similar after controlling for study quality using a single random effects regression model. In conclusion, the meta-analysis indicated that a better success rate is achieved when treatment includes obturation short of the apex.
The Crisis in Endodontic Education: Current Perspectives and Strategies for Change
Gerald N. Glickman, DDS, MS, Alan H. Gluskin, DDS, William T. Johnson, DDS, MS, and Jarshen Lin, DDS, MS
The current status of dental education in the United States and Canada with respect to faculty recruitment and retention is reviewed; poor salaries and lack of interest are major reasons for dwindling numbers. The pros and cons of an academic career and what the American Association of Endodontists’ (AAE) and other constituencies have done to help alleviate the problem are presented. The results of an on-line survey to fulltime endodontic educators on their perspectives on education are presented; personal fulfillment, sharing knowledge, giving back to the profession, and passion for teaching were reasons for teaching whereas income disparity, lack of mentoring, and high demands of the job were reasons against an academic career. The final phase of the paper proposes various strategies on how the AAE and its membership, dental schools, and the American Board of Endodontics (ABE) can further work together to alleviate the critical problems facing endodontic education.
Preliminary Evaluation of BMP-2 Expression and Histological Characteristics During Apexification with Calcium Hydroxide and Mineral Trioxide Aggregate
Karla A. Ham, DDS, David E. Witherspoon, BDS, MS, James L. Gutmann, DDS, S. Ravindranath, BDS, MDS, Toh Chooi Gait, BDS Hons, MSc, FDSRCPS, DRDRCS, FDSRCS, Lynne A. Opperman, PhD
Histological characteristics and bone morphogenetic protein-2 (BMP-2) expression were evaluated in apexification procedures using calcium hydroxide [Ca (OH)₂] and mineral trioxide aggregate (MTA). In three of four quadrants of the mouth, monkey ( Macaca fascicularis) teeth were infected by pulpal exposure to saliva. After 90 days, each group was treated with Ca (OH)₂ or MTA. Infected, untreated teeth were used as negative controls and normally developing teeth were used as positive controls. Areas within the apical region of each sample were scored based upon histological findings and BMP-2 expression. Overall, BMP-2 expression in all areas was similar in the Ca (OH)₂, MTA, and infection/no treatment groups, which tended to be more immunoreactive for BMP-2 than the untreated group. Use of MTA in combination with Ca (OH)₂ may initiate regeneration of the periodontium more quickly than either material used alone, but further studies involving MTA use in apical closure are indicated.
A Comparison of Articaine and Lidocaine for Inferior Alveolar Nerve Blocks
Philip Mikesell, DDS, MS, John Nusstein, DDS, MS, Al Reader, DDS, MS, Mike Beck, DDS, MA, and Joel Weaver, DDS, PhD
The purpose of this prospective, randomized, doubleblind study was to compare the degree of pulpal anesthesia obtained with 4% articaine with 1:100,000 epinephrine and 2% lidocaine with 1:100,000 epinephrine in inferior alveolar nerve blocks. Using a crossover design, inferior alveolar nerve blocks were randomly administered, in a double-blind manner, using 4% articaine with 1:100,000 epinephrine and 2% lidocaine with 1:100,000 epinephrine, at two separate appointments, to 57 subjects. A pulp tester was used to test for anesthesia, in 4-min cycles for 60 min, of the molars, premolars, central, and lateral incisors. Anesthesia was considered successful when two consecutive 80 readings were obtained within 15 min and the 80 reading was continuously sustained for 60 min. Using the articaine solution, successful pulpal anesthesia ranged from 4 to 54% from the central incisor to the second molar. Using the lidocaine solution, successful pulpal anesthesia ranged from 2 to 48%. There was no significant difference (p > 0.05) between the articaine and lidocaine solutions. We concluded that 4% articaine with 1:100,000 epinephrine was similar to 2% lidocaine with 1:100,000 epinephrine in inferior alveolar nerve blocks.
A 5 Yr Clinical Investigation of Second Mesiobuccal Canals in Endodontically Treated and Retreated Maxillary Molars
James Wolcott, DDS, Dave Ishley, DDS, MS, Wade Kennedy, DMD, Scott Johnson, DMD, MS, Scott Minnich, DDS, and John Meyers, DDS
An examination of 5616 endodontically treated and retreated maxillary first and second molars was made in an attempt to determine the percentage of MB2 canals that could be located routinely, and evaluate if there were any significant differences between initial treatments and retreatments. The teeth examined were 3578 first molars and 2038 second molars treated consecutively over a 5-yr period by six endodontists. Overall the MB2 canal was found in 2133 (60%) first molars, and 712 (35%) second molars. The incidence of a MB2 canal in first molar retreatments was 66% compared to a 58% incidence in initial treatments. Whereas in second molars the retreatment incidence was 40% compared to 34% in initial treatments. The significant difference in the incidence of a MB2 canal between initial treatments and retreatments suggests that failure to find and treat existing MB2 canals will decrease the long-term prognosis.