Canal configuration of the mesiobuccal root of the maxillary first molar: conventional and surgical approaches.

One of the primary causes of endodontic failure is the presence of untreated canals. Although the maxillary first molar has been described as the most endodontically treated tooth, the canal configuration has been the least understood. The purpose of this article is to present, with the aid of several clinical cases, a review of the literature regarding the frequency, the location, and the incidence of the second mesiobuccal canal in relation to the maxillary first molar, both for conventional and surgical approach.

Comparison of two implantation sites for testing intraosseous biocompatibility.

The purpose of this study was to compare two implantation sites--the mandible and the femur of the rabbit--for testing in vivo intraosseous biocompatility. Twenty-two new Zealand rabbits were anesthetized, and the mandibular and femur bones were exposed. A hybrid glass ionomer cement or zinc oxide eugenol cement was loaded into silicone carriers and inserted into the two bones after drilling the two cortical plates. Eleven rabbits were killed 4 wk after implantation, and 11 rabbits were killed after 12 wk. The mandibles and femurs were prepared using standard histological procedures; tissue reactions were graded from none to severe. At 4 wk, no statistically significant difference was found between the two implantation sites. After 12 weeks, bone healing was statistically better in the mandible than in the femur. The mandible seems to be a better implantation site in the case of intraosseous implantation tests. The intraosseous biocompatibility of Vitremer was similar at 4 wk and superior at 12 wk to that of Super-EBA.

Sealing ability of super EBA and Dyract as root-end fillings: a study in vitro.

The purpose of this study was to compare, in vitro, the sealing ability of Super EBA and a compomer, Dyract, as root-end filling materials. Forty-eight single-rooted human teeth were cleaned, shaped and obturated with gutta-percha. The root apices were resected and root-end cavities were prepared. Twenty teeth were retrofilled with Super EBA and Dyract; eight teeth served as positive and negative controls. Half of the teeth in each group were immersed in basic fuschin for 4 weeks, the other half for 12 weeks. The teeth were then embedded in resin, sectioned, and the maximum extent of dye penetration measured. Statistical analysis (ANOVA) did not reveal a significant difference between the two materials at 4 weeks. At 12 weeks, the extent of dye penetration was statistically significant with Super EBA leaking more than Dyract (P = 0.002). Moreover, the extent of the dye penetration was statistically significantly different for Super EBA between the 4- and 12-week groups (P = 0), whereas no such difference was found for Dyract. Thus, the sealing ability of Dyract was found to be better than Super EBA at 12 weeks.

Comparison of the intraosseous biocompatibility of Vitremer and super EBA by implantation into the mandible of rabbits.

OBJECTIVES: This study compared the intraosseous biocompatibility of Vitremer, a new hydrophilic glass-ionomer cement, to that of Super EBA. STUDY DESIGN: Twenty-two New Zealand rabbits were anesthetized, the mandibular bone exposed, and two holes were drilled through the cortical plate. The materials were loaded into silicone carriers and inserted into the mandibles. Eleven rabbits were killed 4 weeks after implantation, 11 animals after 12 weeks. The mandibles were prepared with standard histologic procedures; the tissue reactions were graded from none to very severe. RESULTS: At 4 weeks Vitremer implants showed very slight to slight reactions, and the Super EBA implants showed slight reactions and one moderate reaction with no significant difference between the two materials. At 12 weeks, bone healing had occurred, despite the persistence of some fibrous tissue interposition. The reactions were classified as none to very slight for Vitremer and very slight to slight for EBA. Statistical analysis showed better results for Vitremer at 12 weeks. CONCLUSION: The intraosseous biocompatibility of Vitremer was similar at 4 weeks and superior at 12 weeks to that of Super EBA. Its other properties should be evaluated before considering its use in clinical practice.

Comparison of the intraosseous biocompatibility of Dyract and Super EBA.

The purpose of this study was to compare the intraosseous biocompatibility of Dyract, a new hydrophilic glass-ionomer cement, to that of Super EBA. Twenty-four New Zealand rabbits were anesthetized, one leg was shaved, the femur exposed, and two holes were drilled through the cortical plate. The materials were loaded into silicone carriers and inserted into the femur. Half of the rabbits were killed 4 weeks after implantation and the other half at 12 weeks and the femurs were prepared using standard histological procedures. The tissue reactions were graded from none to severe. At 4 weeks both materials showed slight to moderate reactions, characterized by the presence of fibrous tissue interposition and inflammatory cells. At 12 weeks, bone healing had occurred, despite the persistence of some fibrous tissue interposition, and the reactions were classified as slight. At both observation periods, statistical analysis failed to show any difference between the two materials indicating that Dyract and Super EBA had similar intraosseous biocompatibility.

Model for quantitative immunohistochemical assessment of pulpal response to biomaterials.

The purpose of this study was to propose a new method for quantitative evaluation of the pulpal inflammation to restorative materials using immunohistochemistry and image analysis. Class V cavities were prepared and filled with different restorative materials in 20 healthy premolars to be extracted for orthodontic reasons. Teeth were extracted at different time intervals, fixed, demineralized, and embedded in paraffin. Six-micrometer-thick sections were cut serially and mounted on slides and every fifth section was stained using hematoxylin and eosin or Masson's trichrome, and served to localize the inflammatory reaction. The slides corresponding to the bulk of the inflammatory reaction were then used for immunohistochemical detection of the inflammatory cells using monoclonal antibodies: CD15 (granulocytes and histiocytes), CD45RO (T lymphocytes and monocytes), Pan-B cell (B lymphocytes, macrophages, and a subpopulation of T lymphocytes), CD45RA (B lymphocytes and monocytes), and EMA (plasma cells). The slides were observed and submitted to computerized image analysis using a SAMBA 2000 system for counting of the cells. The CD15, CD45RO, Pan-B-cell, and CD45RA antibodies positively stained the target cells, which could be counted with the computer. The EMA antibody did not permit staining of cells. These results indicate that polymorphonuclears, T lymphocytes, and B lymphocytes are present in inflamed human dental pulp. The immunologic detection of inflammatory cells followed by computerized image analysis allows an accurate characterization of pulpal pathology, and could be useful for the study of pulp reactions to restorative biomaterials.

Young's modulus of warm and cold gutta-percha.

The purpose of this study was to evaluate the Young's modulus of cold and warm gutta-percha. Rods of gutta-percha. Specially designed by three companies were tested at 20 degrees C and 55 degrees C with a tensile testing machine. The Young's modulus, the yield strength and the percentage of deformation were automatically recorded. There was a statistically significant difference, for the three criteria, between the cold and warm gutta-percha. Warm gutta-percha presented a Young's modulus 100 times smaller, a yield strength 2 times smaller but a percentage of permanent deformation 10 times higher than cold gutta-percha. Gutta-percha Hygenic presented the best characteristics.

Relationship between file size and stiffness of nickel titanium instruments.

The purpose of this study was to evaluate the relationship existing between file size and stiffness for 3 endodontic files made of nickel titanium. Three groups of instruments with different cross-sections were tested: a triangular cross-section, a square cross-section and a modified triangular cross-section. The instruments were tested from size 15 to size 40 or 60 according to ANSI/ADA specification no. 28 for binding moment evaluation. There was a statistically significant difference between the 3 groups: the square cross-section K files presented a larger bending moment than the triangular cross-section K files, which presented a larger bending moment than the modified cross-section K files. Like the stainless steel instruments, there was an exponential relationship between file size and bending moment for triangular and square cross-section K files, but a linear relationship between file size and bending moment for the files with a modified triangular cross-section.

Machining efficiency of nickel-titanium K-type files in a linear motion.

The purpose of this study was to compare, in vitro, the machining efficiency of four brands of nickel-titanium files and two brands of stainless steel K-type files. Instruments sizes 15 to 40 were tested in a linear motion simulating the clinical motion used to remove a file from the canal. The tips of the loaded files were in contact with a resin block. The load applied increased with file size. An indentation varnish caliper was used to measure the depth of the groove after 100 back-and-forward motions. The stainless steel instruments with a triangular cross-section were more efficient than the stainless steel instruments with a square cross-section. There was a significant discrepancy between the machining ability of the nickel-titanium K files. The Maillefer instruments were the most efficient.

Torsional and stiffness properties of nickel-titanium K files.

The purpose of this study was to compare stiffness and resistance to fracture of four brands of nickel titanium K files. Instruments of sizes 15 to 40 were tested according to ANSI/ADA Specification No. 28. Resistance to fracture was determined by twisting and measuring the maximum torque and angular deflection at failure. Stiffness was determined by measuring the moment required to bend the instrument 45 degrees. The permanent deformation angle remaining between the tip and the flutes of the instruments after bending ceased was also recorded. Nickel titanium K files satisfied and far exceeded specification standards for stiffness. They also satisfied and exceeded the standards for angular deflection at failure. They met or exceeded the maximum torque at failure standards in all sizes except for the size 40 of the Maillefer Niti, and the size 30 of the MacSpadden Niti. Nickel titanium K files presented a null permanent deformation angle. Clinical studies are required to evaluate the influence of low bending moment on other properties such as breakage and canal transportation.

Transportation of curved canals prepared with canal master U, canal master U niti, and stainless steel K-type files.

The purpose of this study was to evaluate and to compare root canal configuration after preparation with three different hand instruments and techniques: the canal master U preparation technique (Brasseler, Savannah, GA.), using stainless steel or nickel-titanium canal master U instruments, and the step-back technique using precurved conventional stainless steel K-type files. Sixty-three simulated curved canals were divided in three groups of 21 each. Each group was prepared using one of the three instruments. Comparison of root canal configuration was evaluated with pre- and postoperative photographs that measured the difference in canal diameter and the mesial and distal transportation of the canal walls at the canal length and at levels 1, 2, 3, 4, 5, 6, 7, and 8 mm coronal to the canal length. Data obtained were analyzed statistically using an analysis of variance. Instrument breakage was also recorded. Results showed that the final diameter of the prepared canals as well as canal transportation were significantly different between both canal master U instruments and the stainless steel K file. Three stainless steel canal master U instruments separated during instrumentation whereas none in the nickel-titanium canal master U and stainless steel K-type file groups separated. The results of this study show that the canal master U instruments and technique provide a better canal configuration than K files using the step-back technique and that the nickel-titanium canal master U and stainless steel K-type file offers a greater safety factor against breakage than the stainless steel canal master U.

Relationship between file size and stiffness of stainless steel instruments.

The purpose of this study was to evaluate the relationship existing between file size and stiffness for three endodontic files of different cross-sections. Three groups of instruments were tested: Flexofiles from the Maillefer company, K Files and K-Flex from the Kerr company. Flexofiles have a triangular cross-section, K Files a square cross-section, and K-Flex instruments a rhombus cross-section from size 15 to size 40. For each group, 10 files from size 15 to size 40 were compared according to ANSI/ADA specification N degrees 28 for bending moment evaluation. There was a statistical difference between the three groups: the square cross-section K files presented a larger bending moment than the rhombus cross-section K Flex, which presented a higher bending moment than the triangular cross-section Flexofiles. There was an exponential relationship between file size and bending moment.

Torsional properties of stainless steel Canal Master U and Flexogates.

The purpose of this study was to evaluate and compare the torsional properties of Flexogates and Canal Master U instruments. Torsion and bending tests were performed on both designs of instrument according to ANSI/ADA specification number 28 criteria and standards. Ten instruments of each size, sizes 25 to 50 were used for each test. Four parameters were measured: the moment at failure, the rotation at failure, the separation point at failure and the bending moment at a 45 degrees angle. Both instruments satisfied ANSI/ADA standards for rotation at failure and bending moment. Canal Master U satisfied ANSI/ADA standards for moment at failure in all sizes except 45 and 50. Flexogates did not satisfy these standards in all sizes except 50. Flexogates separated at the end of the shaft whereas Canal master U separated just behind the cutting head. Both instruments showed favourable physical properties for preparing root canals.

Torsional and stiffness properties of Canal Master U stainless steel and nitinol instruments.

The purpose of this study was to compare stiffness and resistance to fracture of stainless steel and nickel titanium Canal Master U instruments. Instruments sizes 20 through 50 were tested according to ANSI/ADA Specification No. 28. Resistance to fracture was determined by twisting and measuring the maximum torque and angular deflection (rotation) at the failure point. Stiffness was determined by measuring the moment required to bend the instrument 45 degrees. Stainless steel and nickel titanium Canal Master U instruments satisfied and far exceeded specification standards for stiffness. They also satisfied and far exceeded the standards for angular deflection at the failure point. Stainless steel Canal Master U met or exceeded the maximum torque at failure standards in all sizes except 50, whereas the nickel titanium instruments met the standards in all sizes except 45 and 50. The mechanical properties of nickel titanium, especially its low bending moment and high angular rotation at failure, encourage further evaluation with clinical studies.

Effects of the Flexogates and Canal Master U on root canal configuration in simulated curved canals.

The purpose of this study was to compare the Canal Master U (CMU) instrumentation technique with that of a similar instrument, the Flexogates (FG). Forty simulated curved canals were divided in two groups of 20 each. One group was prepared using the CMU instrumentation technique and the other using the FG technique. Comparison was made by measuring the diameter of the prepared canals and transportation that occurred at the canal length and at levels 1, 3 and 5 mm coronal to the canal length. Data obtained were analysed statistically. Results showed that the final diameter of the prepared canals was not significantly different between the CMU or the FG. However, the FG transported the outer wall of the curvature more than the CMU at the canal length and at 1 mm from the CL. Although the difference in the canal transportation was statistically significant it may not be of clinical importance.

[The coherence between 3 evaluation methods of biocompatibility]. / Etude de la coherence entre trois modes d'évaluation de la biocompatibilité.

Three successive series of tests (the primary including cytocompatibility tests and the secondary in vivo and usage tests) can be used to evaluate the biocompatibility of dental materials. The products are only submitted to secondary tests in case of satisfactory results obtained with primary tests. A coherence between the results of primary and secondary tests is necessary before performing in vivo tests. The aim of this paper is to study the coherence between two primary tests and a secondary test. The biocompatibility of Sealite and a pulp canal sealer was studied 4 and 12 weeks after mixing, according to two primary models (cell culture on agarose and a toxicity study of the extraction products) and a secondary model (intrabony implantation in the rabbit). The two primary tests gave different results for Sealite and the pulp canal sealer. Only the agarose cell culture and the intrabony implantation in the rabbit have given similar statistical results. The biological evaluation of biomaterials should begin with a study of the mechanism of action of the cytotoxic products using several in vitro tests. These latter are unable to predict the behaviour of a biomaterial in an in vivo test.

Bone and root resorption. Effects of the force developed during periodontal ligament injections in dogs.

The purpose of this study was to determine the role of the pressure generated during the intraligamentary injection technique on the occurrence of root and bone resorptions in dogs. Five beagles were used in the study, and interventions were scheduled to provide observation periods at 7, 25, and 45 days. One hundred five sites on the dogs were divided into three groups: (1) those subjected to needle penetration; (2) those subjected to saline solution injection; and (3) the control sites. Injections were made with a specially designed syringe equipped with a miniaturized force transducer. The dogs were then killed, and block sections of the sites were made and treated in accord with standard histologic procedures. The mean number of osteoclasts and odontoclasts was calculated for each group, and the mean value of bone and tooth resorption angle was measured. Data were then analyzed statistically. Results showed that, at 7 days, needle penetration and saline solution injection caused osteoclastic activity and bone resorption; the number of osteoclasts and the extent bone resorption were greater in the group that received the injection of saline solution. No difference was found for the odontoclastic activity and tooth resorption. A correlation was found between the force developed during injection, the mean number of osteoclasts, and the mean angle of bone and tooth resorption. At 25 and 45 days, healing had occurred. These findings suggest that fluid pressure within the periodontal ligament is sufficient to initiate osteoclastic, reversible bone resorption.

In vivo comparison of the biocompatibility of two root canal sealers implanted into the mandibular bone of rabbits.

The purpose of this study was to evaluate the in vivo biocompatibility of two zinc oxide-eugenol-based sealers, Sealite and Pulp Canal Sealer, after implantation into the mandibular bone of rabbits. Thirty female New-Zealand rabbits were randomly divided into three groups on the basis of the material to be implanted in each side of the mandible: six rabbits received a positive control implant (silicone tubes filled with asbestos) in both sides of the mandible; 12 rabbits received a Sealite implant in the left side and a negative control implant (silicone tubes filled with silicone adhesive) in the right side of the mandible; and 12 rabbits received a silicone tube filled with Pulp Canal Sealer in the left side and a negative control implant in the right side of the mandible. The sealers were implanted in a freshly mixed, unset state. The rabbits were killed 4 or 12 weeks after implantation and the implants and surrounding bone were sectioned and treated in accord with standard histologic procedures. The tissue reactions were scored and rated as none, very slight, slight, moderate, severe, and very severe. The statistical analysis of the data showed that the two sealers had similar, good biocompatibility, and that the reactions observed at the 12-week period were better than those observed at the 4-week period. Both sealers may be used indifferently in routine endodontic practice.

Ex vivo evaluation of side-perforated needles by injection of anesthetic solutions into the mandibular bone and the periodontal ligament of pigs.

New 27-gauge side-perforated needles were compared with conventional needles during injection in dense tissues on the basis of (a) the force to be applied on the syringe plunger and (b) the frequency of complete needle clogging. A miniaturized force transducer was used to measure the forces applied to the syringe plunger. One hundred intraosseous injections and one hundred intraligamentary injections were performed in fresh pig mandibles, using both types of needles. Results showed that (a) less force was required when performing injections with the side-perforated needles and (b) side-perforated needles got clogged less frequently than conventional ones. This result is of special interest for routine dental practice.

[Intraligamentary anesthesia: review of the literature]. / L'anesthésie intraligamentaire: revue de la littérature.

Intraligamentary anesthesia is widely used both as a primary and a supplemental injection technique. The purpose of this review of the literature is to answer questions one may ask about the technique, its efficacy, anesthetic solutions, postinjection discomfort, distribution of the injected solutions, systemic effects and pulpal and periodontal tissue response.