Jean Camps

Adhesion of endodontic sealers to dentin and gutta-percha.

Adhesion of endodontic sealers to dentin and gutta-percha offers clues into their interaction with the wall of the root canal and the filling material. In this in vitro study, four classes of endodontic sealers (Kerr, a ZOE-based sealer; Sealapex, a calcium hydroxide-based sealer; AH 26, an epoxy resin-based system; and Ketac-Endo, a glass-ionomer based sealer) were compared for their ability to bond to dentin or gutta-percha. Flat coronal dentin or gutta-percha surfaces were created by using a diamond-impregnated saw blade. Aluminum cylinders (ca. 5-mm diameter) were stabilized on the substrates with small amounts of wax and then filled with one of the sealers. After setting in 100% humidity for 24 h, their tensile bond strengths were measured. Controls were the unfilled cylinders stabilized with wax. The bond strengths and modes of failure were measured. The results were statistically analyzed by using a two-way ANOVA (materials versus substrates) and Student-Newman-Keuls test at alpha = 0.05. The results indicated that sealant bond strengths to dentin (from lowest to highest mean +/- SD, n = 10) were: Kerr 0.13 +/- 0.02; Sealapex 0.30 +/- 0.08; Ketac-Endo 0.80 +/- 0.24; AH 26 2.06 +/- 0.53 MPa. The latter two were significantly different (p < 0.05) from the first two sealers and from themselves. The sealant bond strength to gutta-percha (from lowest to highest mean +/- SD, n = 10) were: Ketac-Endo 0.19 +/- 0.01; Sealapex 0.22 +/- 0.01; Kerr 1.07 +/- 0.19; AH 26 2.93 +/- 0.29 MPa. AH 26 gave the significantly highest bonds to gutta-percha.

Reliability of the Dye Penetration Studies

The purpose of this study was to compare the classical dye-penetration method to a dye-extraction method, with a fluid-filtration method as control. Forty teeth were prepared with a ProFile device and divided into four groups (n = 10 per group) according to the sealer used for the lateral condensation: Pulp Canal Sealer, Sealapex, AH Plus, and Ketac-Endo. The apical seal was evaluated on the same teeth with all three methods, successively: a fluid-filtration method, a dye-penetration method with 2% methylene blue, and a new method where the roots were dissolved in 65% nitric acid to extract the methylene blue before reading the absorbance of the solution. The classical dye penetration did not show any difference among the sealers and showed no correlation with the two other techniques. The fluid filtration (p < 0.01) and the dye extraction (p < 0.01) showed that Sealapex displayed the highest apical leakage. The correlation between the results obtained with these two methods was significant (p = 0.001 and r = 0.7). This study showed the limitation of the classical dye-penetration studies and that the dye-extraction, i.e. dissolution, method gave the same results as fluid filtration but saved much laboratory time.

Lack of Correlation among Three Methods for Evaluation of Apical Leakage

The purpose of this study was to compare three methods of evaluation of the apical seal. Thirty-six teeth were prepared with a ProFile device and filled according to three filling methods: Thermafil (n = 12), warm vertical condensation (n = 12), and the single cone technique (n = 2). The apical seal was recorded with three methods, each successively used on the same teeth: a fluid filtration method, an electrochemical method, and a dye penetration study. The three methods of evaluation did not rank the apical leakage of the three filling techniques in the same order. The fluid filtration method showed that the vertical condensation was superior to Thermafil, which was in turn superior to the single cone technique (p = 0.04). The dye penetration study showed that the Thermafil was a better technique than the vertical condensation and the single cone technique (p = 0.005). The electrochemical method showed no statistical difference among the three filling techniques. No correlation was found among the results obtained with the three methods of evaluation. This study shows that several studies are necessary before comparing the apical seal obtained with various filling techniques.

In vitro apical leakage of system B compared with other filling techniques.

A fluid filtration system was used to compare the apical microleakage of roots filled with the system B (Analytic Technology), single-cone technique, lateral condensation, vertical condensation, and Thermafil (Caulk-Dentsply). After preparation of the canal system with a Profile (Caulk-Dentsply) five groups of 10 single-rooted teeth were randomly filled according to 1 of the 5 techniques. Phosphate-buffered saline was forced under a 15 cm H2O pressure, through the apex, toward the coronal part of the root. The filtration rate in L s(-1) Kpa(-1) was recorded 24 h after filling and after 1-month storage in phosphate-buffered saline. The 24 h results showed that the single cone technique provided the highest leakage (p = 0.001). At 1-month system B, Thermafil and vertical condensation had less leakage than the two other techniques (p = 0.0001): lateral condensation produced moderate apical leakage, whereas the single cone technique showed the highest leakage. Regardless of the technique the apical leakage increased after 1-month storage (p = 0.001 or p = 0.0001, depending on the technique).

Apical leakage of four endodontic sealers.

The purpose of this study was to evaluate the sealing properties of four root canal sealers. Forty-eight maxillary central incisors were instrumented with Profile rotary instruments. They were randomly divided into four groups (n = 12) and filled using lateral condensation with one of the four sealers: Sealapex, Pulp Canal Sealer, AH 26, and Ketac-Endo. The apical leakage was measured with a fluid filtration method and expressed as L s(-1) KPa(-1). The teeth filled with Sealapex displayed a higher apical leakage (8.42 +/- 4.2 10(-11) L s(-1) KPa(-1)) than those filled with AH 26 (2.10 +/- 1.39 10(-11) L s(-1) KPa(-1)), Pulp Canal Sealer (0.17 +/- 0.09 10(-11) L s(-1) KPa(-1)) or Ketac-Endo (0.32 +/- 0.24 10(-1) L s(-1) KPa(-1)) (p < 0.01). No statistically significant difference was found among AH 26, Pulp Canal Sealer, and Ketac-Endo. No correlation was found between the sealing efficiency of the four sealers and their adhesive properties recorded in a previous study.

Factors influencing pulpal response to cavity restorations.

OBJECTIVES The purposes of this retrospective work were: (1) to determine the relative importance of bacteria on cavity walls, remaining dentin thickness and post-operative time on pulpal inflammation after cavity restoration; (2) to compare the respective influences of bacterial microleakage and the restorative material itself on pulp reaction severity. METHODS 317 class V cavities, in human bicuspids scheduled for extraction for orthodontic reasons were used for this study. Nine different materials were included. The severity of the pulpal reaction was ranked on hematoxylin/eosin stained sections according to FDI standards. The further parameters recorded were: (1) the presence or absence of bacteria on the cavity walls was noted on Brown and Brenn stained sections; (2) the remaining dentin thickness was measured and the teeth classified into three groups (< 500, 500-1000, > 1000 microns); and (3) the post-operative delay before extraction was recorded and classified as short time (< 5 weeks) or long time (> 5 weeks). Three two-way analyses of variance (ANOVA) followed by Kruskall and Wallis tests evaluated the influence of the three parameters on pulpal reaction severity. The third ANOVA also compared pulpal reactions under the different materials when the teeth were pooled, on bacteria free teeth and on bacteria contaminated teeth. RESULTS The first ANOVA ranked by decreasing order of importance: the presence of bacteria (p < 0.0001), the remaining dentin thickness (p = 0.02) and the post-operative delay (p = 0.04). The second ANOVA showed no difference among the restorative materials when bacteria were present on the cavity walls. SIGNIFICANCE The presence of bacteria on the cavity walls is the main factor influencing pulpal reaction under restorative materials, but does not account for 100% of the cases.

Cytotoxicity Testing of Endodontic Sealers: A New Method

The purpose of this study was to compare ISO standards versus a new technique for in vitro evaluation of cytotoxicity of root canal sealers. The cytotoxicity of AH Plus, Cortisomol, and Sealapex was first recorded according to ISO standards on L 929 fibroblasts by the MTT assay. In parallel, 30 single-rooted teeth were cut at the cementum enamel junction (CEJ), and the roots were prepared and sterilized before filling with the lateral condensation using one of three sealers (n = 10). The apexes of the roots were dipped into 1 ml of minimum essential medium for 1, 2, and 30 days renewing the medium every other day. After 24-h contact between the medium and the filled roots, the medium was used to measure the cytotoxicity on L 929 with the MTT assay. ISO standards always gave a statistically higher cytotoxicity than the root-dipping technique (p < 0.0001), whatever the sealer and the exposure time. The ISO standards showed statistically significant differences among the sealers (p < 0.0001). AH Plus was noncytotoxic, Cortisomol showed a high cytotoxicity decreasing over time (p < 0.001), and Sealapex displayed a high cytotoxicity that did not decrease over time (NS). The new technique showed statistically significant differences among the sealers (p = 0.001), but the differences were so small that they were likely not clinically relevant. The high cytotoxicity of Sealapex decreased over time but the cytotoxicity of AH Plus and Cortisomol did not. The results show that the ISO standards may strongly over-evaluate the cytotoxicity of the endodontic sealers, emphasize the difference among the sealers, and may clinically correspond to a large overfilling. The new technique reduces the discrimination of the test and may clinically correspond to a classical filling. Therefore, both methods might be considered as clinically relevant, corresponding to classical and overfilling conditions.

Effects of Pressure and Measurement Time on the Fluid Filtration Method in Endodontics

The purpose of this study was to evaluate the influence of the measurement time and the pressure on the outcome of a fluid filtration test. Thirty-six roots were prepared with a Profile device and filled with Thermafil. The leakage along the filling material was recorded under a 15 cm H2O pressure (n = 18) or a 150 cm H2O pressure (n = 18) at 3 min, 1 h, and 24 h. The fluid flow expressed as microl min(-1) decreased with an increased measurement time (p = 0.001) and was higher in the high pressure group (p = 0.001). The fluid flow of this study, where all of the teeth were filled with the same technique, ranged from 3.8 x 10(-5) microl min(-1) cm H2O(-1) to 43 x 10(-5) microl min(-1) cm H2O(-1), depending on the pressure and measurement time. This shows the need for standardization to compare the results from various studies.

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.

Influence of criteria on the results ofin vitro evaluation of microleakage

OBJECTIVES The aim of this study was to compare and explain the statistical methods employed to evaluate the in vitro sealing efficiency of adhesive restorative systems. METHODS Two hundred and sixty sound freshly extracted human premolars were randomly divided into 13 groups. Standardized cavities were prepared, and the teeth were restored with 13 restorative systems. The teeth were thermocycled, immersed in dye, embedded in resin and sectioned. Five evaluation criteria were recorded: mean, median and mode of the data measured on each tooth, maximum dye penetration measurements on each tooth, and percentage of teeth in each group without any dye penetration. For each parameter, one-way ANOVAs and Duncan a posteriori tests were used to compare the 13 systems. RESULTS The number of non-statistically different subgroups, pointed out by Duncan tests, was greater when the selected criterion was the maximum dye penetration (6 subgroups) or the percentage of teeth without any penetration (5 subgroups) than when the criterion was the median (3 subgroups), the mode or the mean (4 subgroups). The positioning of the 13 adhesive restorative systems established from the five criteria was different. Equivalent adhesion strategies revealing different experimental results indicate that other factors contribute to the final effectiveness of a particular system: clinical approach with respect to the formation of an elastic bonding layer, and shrinkage, physical and rheological properties of resin composite. SIGNIFICANCE The results of these in vitro studies of dye penetration must be considered as comparisons and not as absolute conclusions. The maximum dye penetration measured on each tooth, which complies with the aim of the in vitro evaluation of sealing efficiency defined by Pashley (1990) and allows powerful statistical analysis of results, seems to be the best evaluation criterion.