Canal Master Instrumentation: An In Vitro Study of Separation Frequency
Mounce, Nakamuta, and Lovejoy
Apical Sealing Ability of Metal Versus Plastic Carrier Thermafil Obturators
Clark and ElDeeb
Prognosis of Intracoronal Bleaching with Sodium Perborate Preparations In Vitro: 1-Year Study
Rotstein, Mor, and Friedman
Histomorphometric Study of Dental Pulp during Orthodontic Tooth Movement
Nixon, Saviano, King, and Keeling
Chelate Root Filling Cements: Biological Properties
Nielsen, Arenholt-Bindslev, Kilian, and Philipsen
Master Cone Apical Movement during Compaction: Evaluation of Two In Vitro Models
Bou Dagher and Yared
Correlation between Thermal Sensitivity and Microorganisms Isolated from Deep Carious Dentin
Hahn, Falkler, Jr., and Minah
Stereochemical Structure Characterization of Dental Gutta-percha
Marciano, Michailesco, and Abadie
Canal Master Instrumentation: An In Vitro Study of Separation Frequency
Richard E. Mounce, DDS, Hiroyoshi Nakamuta, DDS, DDSc, and Chris Lovejoy
Ninety resin blocks were instrumented by three different operators using the Canal Master Instrumentation system. The frequency of file separation among three operators of varying endodontic experience (novice dental student to endodontist) was compared. Twenty-one of the 87 (24%) of the instruments were separated. The #50 Canal Master file failed most frequently (5 of 21). Three ledges (3 of 90 samples) were created by the novice operator with the Canal Master rotary instruments which could not be bypassed. Separation rates among the operators ranged from 12 of 27 (novice) to 4 of 30 (endodontist). The results suggest that the Canal Master file may be prone to fracture in vitro and that there may be a "learning curve" to proficient Canal Master use.
Apical Sealing Ability of Metal Versus Plastic Carrier Thermafil Obturators
D. Scott Clark, BSc, DDS, MS, and Mahmoud E. ElDeeb, BDS, MS
Sixty straight maxillary canines, 40 straight mandibular incisors, and 40 curved mesial canals of 27 mandibular molars were instrumented and randomly assigned to one of seven groups of 20 canals. Experimental groups were obturated with metal or plastic carrier Thermafil obturators. Control groups were obturated using the lateral condensation technique. An additional group of 20 unobturated curved molar canals served as positive controls. Kerr Pulp Canal Sealer was used in all obturation groups. The presence or absence of apical extrusion of gutta-percha was recorded. Teeth were suspended in black India ink for 2 wk, cleared, and then examined under a dissecting microscope at x20 magnification. No leakage was found in any of the obturated canals, whereas unobturated controls showed total dye penetration. Plastic carrier Thermafil and metal carrier Thermafil groups produced a significantly greater incidence of apical extrusion of gutta-percha compared with lateral condensation groups (p < 0.001). Extrusion for Thermafil groups occurred significantly more frequently in straight compared with curved canals (p = 0.002). The Thermafil groups showed a higher frequency of filled lateral and accessory canals than in the lateral condensation group; however, this was statistically insignificant (p = 0.48).
Prognosis of Intracoronal Bleaching with Sodium Perborate Preparations In Vitro: 1-Year Study
Ilan Rotstein, CD, Chaim Mor, DMD, and Shimon Friedman, DMD
Bleaching materials containing hydrogen peroxide have been used for treating discolored nonvital teeth but their use was occasionally associated with external root resorption. In a previous study it was found that the immediate results of bleaching teeth in vitro were equal for sodium perborate mixed with either water or hydrogen peroxide. The purpose of this study was to compare the bleaching prognosis of sodium perborate mixed with water or hydrogen peroxide over a 1-yr period. Extracted human teeth with intact crowns were discolored with human erythrocytes and bleached by sodium perborate mixed with either 30% hydrogen peroxide (group A), 3% hydrogen peroxide (group B), or water (group C). The bleaching materials were placed in the pulp chambers of the discolored teeth and sealed with IRM. They were replaced with fresh preparations after 3 and 7 days. After 14 days the coronal access cavities were sealed with composite resin and the teeth photographed with a color slide film under standardized conditions. The teeth were stored in artificial saliva for 1 yr and photographed after 3, 6, and 12 months. Two separate evaluators ranked the teeth by comparing them with the shades before and after bleaching. The bleaching success rates of the tested groups at each time interval were compared and analyzed statistically. It was found that after 1 yr all of the teeth in groups A and C maintained their shades. In 20% of the teeth in group B there was color regression. Statistically, these differences were not significant. It was concluded that sodium perborate can be used effectively for bleaching when mixed with water. Therefore, mixing sodium perborate with hydrogen peroxide appears to be unnecessary.
Histomorphometric Study of Dental Pulp during Orthodontic Tooth Movement
Craig E. Nixon, DMD, MS, Julie A. Saviano, DMD, Gregory J. King, DMD, DMSc, and Stephen D. Keeling, DDS, MS
Orthodontic tooth movement has been implicated in secondary changes to the dental pulp. The purpose of this study was to correlate the effects of orthodontic tooth movement on the dental pulp by histomorphometric parameters. Four groups, each consisting of 36 male adult Sprague-Dawley strain rats, were studied with differing force magnitudes. These included a sham group in addition to groups with bilaterally placed appliances activated to 20, 40, and 60 g of initial force designed to mesially tip the maxillary first molars. Six rats were killed at 1, 3, 5, 7, 10, and 14 days. Specimens were fixed, embedded, and stained with tetrachrome. Pulpal measurements were made with an image analyzer and included changes in predentin and vascularity. Findings indicated a significant increase (p < 0.05) relative to time and force magnitude in capillary number. An initial pulpal hyperemia was observed following activation of orthodontic force which was unrelated to force magnitude. A force-dependent increase in predentin width was measured at the peak of the tooth movement cycle.
Chelate Root Filling Cements: Biological Properties
T. Halfdan Nielsen, DDS, Dorthe Arenholt-Bindslev, DDS, PhD, Mogens Kilian, DDS, Dr. Odont, and Hans P. Philipsen, DDS, Dr. Odont
The purpose of this study was to test in vivo and in vitro the toxicity and the antibacterial activity of an experimental chelate cement (HN cement) using zinc oxide-eugenol cement as a reference. After subcutaneous injection of the spatulated HN cement paste in rats, it induced markedly less tissue injuries than did the zinc oxide-eugenol cement. In toxicity tests using cultures of human fibroblasts, the HN cement was found to be less toxic than the reference cement. Bacteriologically, blood agar plates inoculated with Streptococcus sanguis, Staphylococcus aureus, and the anaerobic Prevotella intermedia developed inhibition zones between 3 and 12 mm upon application of both cements. Both demonstrated marked bacteriostatic and bactericidal properties.
Master Cone Apical Movement during Compaction: Evaluation of Two In Vitro Models
Fadia E. Bou Dagher, DDS, and Ghassan M. Yared, DDS
This study evaluated two in vitro models (a split hard metal model and a split natural tooth model) for the assessment of master cone apical movement. Gutta-percha cones were fitted 0.5 and 1.0 mm short of the apical ends of the artificial canals. Photographs were taken before and after vertical or lateral compaction and measurements were made. The results demonstrated no significant difference between the two models.
Correlation between Thermal Sensitivity and Microorganisms Isolated from Deep Carious Dentin
Chin-Lo Hahn, DDS, PhD, William A. Falkler, Jr., MS, PhD, and Glenn E. Minah, DDS, PhD
The correlation between thermal sensitivity and the microorganisms present in 29 deep carious lesions was studied. The numbers of lactobacilli and total Gram-positive rods in the carious lesions were found to be negatively related to the length of pain triggered by cold and heat stimulants. The presence of Gram-positive cocci and non-black-pigmented Bacteroides were positively associated with both cold and heat sensitivities. Black-pigmented Bacteroides, Streptococcus mutans, and total anaerobic colony counts were positively related to the heat sensitivity. Recovery of Fusobacterium nucleatum, Actinomyces viscosus, and enterics on the selective plates was associated with cold sensitivity. Total counts of Gram-positive cocci and Gram-negative rods on the anaerobic nonselective medium were positively related to the cold sensitivity. It appeared that teeth with low numbers of lactobacilli in the carious lesions usually responded to thermal tests with longer duration of pain. Conversely, teeth with high numbers of lactobacilli in the carious lesions usually responded with shorter duration of pain.
Stereochemical Structure Characterization of Dental Gutta-percha
Joseph Marciano, DCD, DSO, Pierre Michailesco, DCD, DSO, MCU, and Marc J.M. Abadie, PhD
Natural gutta-percha is well known for its mechanical properties which derive from its particular stereochemical 1-4 trans structure. The gutta-percha contained in the various commercially available points is made of natural gutta-percha which has undergone a heating process to allow inclusion of the other elements found in its composition, especially a nonspecified coloring agent.
The purpose of this study was to confirm that the stereochemical 1-4 trans structure contained in commercial points is identical to that of natural gutta-percha and that it has not been altered by the heating process inherent to its fabrication. Furthermore, we wanted to identify the coloring agent also included in its composition.
Samples of commercial gutta-percha points were studied using nuclear magnetic resonance spectral analysis and compared with that of natural gutta-percha
Our results show that both natural and commercial gutta-percha mainly have a 1-4 trans stereochemical structure and that the coloring agent is erythrosin.