R. Norman Weller

Efficacy of ultrasonic cleaning.

Resin blocks containing simulated root canal spaces were compared with extracted teeth as models for measuring the efficiency of endodontic debridement with hand instrumentation, ultrasonication, or a combination of both techniques. Canal spaces were filled with radioisotope-laden gelatin, and the loss of radioactivity was measured after treatment. No significant differences in efficiency of debridement were observed in teeth prepared with hand instruments or ultrasonics alone; both techniques reduced radioactivity by between 77% and 79%. Ultrasonication after hand instrumentation was the most efficient method; it reduced radioactivity in the teeth and blocks by 88% and 92%, respectively.

The mental forman: Part I. Size, orientation, and positional relationship to the mandibular second premolar

Seventy-five adult human mandibles were examined to determine the size, orientation, and position of the mental foramen. The average size of the foramen was found to be larger on the left side of the mandible and its usual direction of exit was in a posterior-superior direction. The most common location of the mental foramen was inferior to the crown of the second premolar and approximately 60% of the distance from the buccal cusp tip of that tooth to the inferior border of the mandible.

Root canal configuration of the mandibular first premolar

One hundred six human mandibular left and right first premolars, previously extracted due to nonrestorable caries, periodontal disease, or orthodontic reasons, were sectioned perpendicular to the long axis of the root starting at the cementoenamel junction. Three-millimeter sections were made with an ultrathin separating disc to the level of the anatomical apex. After 1 day in 5.25% NaOCl, each section was rinsed in phosphate-buffered saline, evaluated with a stereomicroscope, and photographed. The slides were projected and the shape of the canal, incidence of multiple canals, level of bifurcation, and any other variant anatomy were recorded. Seventy-six percent of the premolars demonstrated Type I canals and 24% contained Type IV. The shape of the canals was predominantly oval or round. An interesting finding was the number of C-shaped canals which were associated predominantly with Type IV canal systems. This occurred in 14% of the roots.

Incidence and position of the canal isthmus. Part 1. Mesiobuccal root of the maxillary first molar

The mesiobuccal roots of 50 randomly selected maxillary first molars were examined to assess the incidence and position of the canal isthmus. Transverse serial sections of the apical 6 mm of each root were prepared in 1-mm increments. The apical side of each section was stained with methylene blue dye, viewed with a surgical operating microscope, and videotaped. Forty percent of the roots had one canal, whereas 60% had two canals. None of the sections had more than two main canals. The incidence of an isthmus was highest in the apical 3- to 5-mm levels. In teeth that had two canals, the 4-mm sections contained a complete or partial isthmus 100% of the time. The concept of a partial isthmus was presented. Failure to deal with the isthmus may explain why some posterior teeth do not heal completely following endodontic surgery.

A comparison of thermoplasticized injectable gutta-percha obturation techniques

This study compared the quality of obturation of high- and low-temperature thermoplasticized injectable gutta-percha techniques and standard lateral condensation. A new model system was developed to more closely simulate the clinical environment. All obturations were performed in this same model which allowed direct comparisons between the different techniques. The resultant mass of gutta-percha was visually examined and graded for each obturation. Statistical analysis of the results indicated that both thermoplasticized injectable techniques were significantly better than lateral condensation. There was no significant difference between either of the thermoplastic obturation techniques.

Setting Properties and Cytotoxicity Evaluation of a Premixed Bioceramic Root Canal Sealer

INTRODUCTION This study investigated the setting time and micohardness of a premixed calcium phosphate silicate-based sealer (EndoSequence BC Sealer; Brasseler USA, Savannah, GA) in the presence of different moisture contents (0-9 wt%). The moisture content that produced the most optimal setting properties was used to prepare set EndoSequence BC Sealer for cytotoxicity comparison with an epoxy resin-based sealer (AH Plus; Dentsply Caulk, Milford, DE). METHODS Standardized disks were created with BC Sealer, AH Plus, Pulp Canal Sealer EWT (positive control) (SybronEndo, Orange CA), and Teflon (Small Parts Inc., Miami Lakes, FL; negative control). Disks were placed in Transwell Inserts, providing indirect contact with MC3T3-E1 cells. Succinate dehydrogenase activity of the cells was evaluated over a 6-week period using MTT ((3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cytotoxicity profiles of BC Sealer and AH Plus were fitted with polynomial regression models. The time for 50% of the cells to survive (T(0.5)) was analyzed using the Wald statistic with a two-tailed significance level of 0.05. RESULTS BC Sealer required at least 168 hours to reach the final setting using the Gilmore needle method, and its microhardeness significantly declined when water was included in the sealer (P = .004). All set sealers exhibited severe cytotoxicity at 24 hours. The cytotoxicity of AH Plus gradually decreased and became noncytotoxic, whereas BC Sealer remained moderately cytotoxic over the 6-week period. A significant difference (P < .001) was detected between T(0.5) of BC Sealer (5.10 weeks; 95% confidence interval [CI], 4.69-5.42, standard error [SE] = 0.09) and T(0.5) of AH Plus (0.86 weeks; 95% CI, 0.68-1.05; SE = 0.18). CONCLUSIONS Further studies are required to evaluate the correlation between the length of setting time of BC Sealer and its degree of cytotoxicity.

Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin

Forty single-rooted teeth were sectioned transversely through the cementoenamel junction and instrumented to a size #50 K-Flex file at the working length by saline irrigation. Each root was placed in a dilution vial containing 10 ml of normal saline, and the pH and Ca2+ levels were recorded after 24 h. The roots in group 1 then received a final irrigation with 20 ml of normal saline. Group 2 received a final irrigation with 10 ml of 17% ethylenediaminetetraacetic acid followed by 10 ml of 5.25% NaOCl to remove the smear layer. Group 3 was irrigated in the same manner as group 2, but calcium hydroxide (CH) was placed into the root canal. Group 4 was irrigated with 20 ml of NaOCl, and CH was placed into the root canal. The pH and Ca2+ levels were recorded at 1, 3, 5, and 7 days. After 7 days a 3- x 3- x 1-mm external defect was created in the coronal one third of the root surface. The pH and Ca2+ levels were subsequently recorded at 1, 3, and 7 days. Groups 3 and 4 demonstrated significantly higher H+ and Ca2+ levels than did groups 1 and 2 three days after CH placement and at all subsequent intervals. Group 3 demonstrated significantly higher H+ and Ca2+ readings at some but not all intervals. The results demonstrated that CH diffuses from the root canal to the exterior surface of the root and that the removal of the smear layer may facilitate this diffusion.

Sealing Ability of Mineral Trioxide Aggregate and Super-EBA When Used as Furcation Repair Materials: A Longitudinal Study

Immediate sealing of furcation perforations enhances the repair process. The purpose of this study was to longitudinally compare the ability of mineral trioxide aggregate (MTA) and Super-EBA to seal furcation perforations. Fifty-one extracted human maxillary molars were decoronated 3 mm above the CEJ, and the roots were amputated 3 mm below the furcation. A #2 high-speed round bur was used to perforate the center of the furcations. The canals were obturated with gutta-percha, and the root ends were sealed with C&B Metabond. Three experimental groups of 15 teeth each were restored with MTA, Super-EBA, or a combination of MTA in the perforation and a Super-EBA dome on the pulpal floor. Six teeth served as controls. Each tooth was affixed to a fluid filtration device and subjected to a pressure of 20 cm H2O. The integrity of the perforation seal was evaluated initially at 30 min for the Super-EBA and the combination groups and at 4 h for the MTA group. Additional measurements were then made at 24 h, 1 week, and 1 month. The controls behaved as expected. A two-way ANOVA revealed a significant difference (p = 0.01) between materials. Tukeys test isolated the difference to Super EBA as producing a superior seal but only at 24 h. There was no significant effect with time (p = 0.57) or the interaction of the materials with time (p = 0.66). All materials sealed the perforations very well. The maximum leakage of all materials was <0.007 microL min(-1) cm H2O(-1).

Anesthetic efficacy of the supplemental intraosseous injection for teeth with irreversible pulpitis.

The purpose of this study was to determine the efficacy of a supplemental intraosseous injection (IOI) of 2% lidocaine with 1:100,000 epinephrine using the Stabident device, after conventional anesthetic methods had failed. Patients who experienced pain during endodontic access and required a supplemental IOI using 0.45 to 0.90 ml of the local anesthetic were identified. All 37 of the patients treated had teeth diagnosed with irreversible pulpitis. Thirty-four of the teeth were mandibular posterior teeth, 2 were maxillary posterior teeth, and 1 was a maxillary anterior tooth. Patients with maxillary teeth had received infiltration anesthesia, and those with mandibular teeth had received an inferior alveolar nerve block in conjunction with long buccal infiltration. A minimum of 3.6 ml of local anesthetic was used with the conventional techniques. Modified visual analogue scales, coupled with operator evaluations, were used to measure success. The Stabident IOI was an effective supplemental anesthetic technique in 89% (+/- 5.1) or 33/37 patients evaluated. The 95% confidence interval was 74 to 97%. The IOI was successful in 91% (+/- 4.9) of the mandibular posterior teeth (31/34), and 67% of the maxillary teeth (2/3).

A comparison of thermoplastic obturation techniques: adaptation to the canal walls.

The purpose of this study was to directly compare the ability of the three types of Thermafil obturators, the Obtura II thermoplasticized injectable technique, and the lateral condensation technique to obturate a standardized root canal. A split-tooth model was constructed and the root canal was obturated 20 times with each technique. The quality of each obturation was graded according to established criteria of adaptation. Statistical analysis of the results indicated that all the techniques were significantly different from each other (p < 0.0001) except for the plastic and titanium Thermafil groups (p > 0.05), which were similar. Based on the evaluated criteria, the Obtura II injectable technique demonstrated the best adaptation to the prepared root canal. This group was followed in order by the plastic and titanium Thermafil obturators, the stainless steel Thermafil obturators, and finally by the lateral condensation technique.