Larz S.W. Spångberg

Biologic effects of dental materials

Abstract Twelve different root canal filling materials were tested regarding cytotoxicity in vitro with a new method which allowed complete material-cell contact throughout the entire setting time. Quantitation of toxicity was possible. All materials tested were highly toxic when freshly prepared, although an experimental cement was remarkably less toxic than other materials. Chloropercha, after chloroform evaporation , had the lowest toxic effect of all set materials. A correlation of in vitro and in vivo methods for evaluation of root canal filling materials was made.

Adhesion of human osteoblasts on root-end filling materials

Adhesion of human osteoblasts to root-end filling materials (mineral trioxide aggregate (MTA), IRM, composite, and amalgam) was observed by scanning electron microscopy. Root-end filling materials were inserted into 96-well flat-bottomed plates and condensed to disks of approximately 1 mm thick and the same diameter as the wells. After the disks were set, they were placed in the bottom of Nunc four-well culture plates at one disk per well. Then human osteoblasts were seeded into the wells at 1.5 x 10(5) cells per well. After 1 day in culture the disks of root-end filling materials along with cells grown on their surface were examined with a scanning electron microscopy. Results showed that osteoblasts attached and spread on MTA and composite by forming a monolayer. Osteoblasts also attached on amalgam, but with few cells spreading. In the presence of IRM, osteoblasts appeared rounded with no spreading. These results indicate that osteoblasts have a favorable response to MTA and composite resin compared with IRM and amalgam.

Endodontic infection: some biologic and treatment factors associated with outcome☆

OBJECTIVE We sought to investigate the simultaneous effect of apical periodontitis, instrumentation level, and density of root canal filling on endodontic treatment outcome. METHODS For this study, 200 endodontically treated teeth with 441 roots were used. A follow-up examination was conducted 4 +/- 0.5 years postoperatively. Data were subjected to univariate and multivariate analysis. RESULTS Periapical pathosis had the strongest effect on treatment outcome (P <.0001). The instrumentation level (mean +/- SEM of the working length) for successfully treated teeth/roots with normal preoperative pulp and periapex was farther away from the radiographic apex (1.23 +/- 0.13 mm) than for teeth/roots with an unsuccessful outcome (0.20 +/- 0.09 mm; P <.005). However, successfully treated teeth/roots with pulp necrosis and apical periodontitis had working length levels closer to the radiographic apex (0.55 +/- 0.12 mm) than did teeth/roots with unsuccessful outcomes (1.73 +/- 0.30 mm; P<.001). In teeth/roots with apical periodontitis, a millimeter loss in working length increased the chance of treatment failure by 14%. The risk of failure was higher for a fair/poor density of obturation than for a good density for all diagnoses of periradicular status. CONCLUSION Diseased periapex, level of working length relative to the radiographic apex, and fair/poor density all affect the outcome of endodontic treatment.

Kinetic and quantitative evaluation of material cytotoxicity in vitro

Abstract A new method of evaluating cytotoxicity of materials on the basis of cell damage is described. This method, whereby the release of radioactive chromium from target cells is measured, is rapid and highly sensitive, allows adequate cell-material contact, and permits objective quantitation of cell damage with good accuracy.

Endodontic anesthesia in mandibular molars: A clinical study

Sixty-one mandibular molar teeth with clinically manifest pulpitis, which required endodontic therapy, were studied. Twenty-seven subjects received standard inferior alveolar nerve block (IANB) with 2% lidocaine HCI with 1:100,000 epinephrine and 34 subjects received IANB with 3% mepivacaine with no vasoconstrictor. Pulpal anesthesia was assessed with dichlorodifluormethane (DDM). Subjects who gave a positive response to DDM were given a periodontal ligament injection with 2% lidocaine with 1:100,000 epinephrine. This study showed that 3% mepivacaine HCI is as effective as 2% lidocaine HCI in achieving pulpal anesthesia in mandibular molars with IANB. Of a total 61 IANB with lip anesthesia, 23 subjects required periodontal ligament injection to achieve a negative response to DDM. It was concluded that lip anesthesia is not a reliable indicator of pulpal anesthesia. The use of DDM is a reliable method of determining true pulpal anesthesia.

The effect of chlorhexidine as an endodontic disinfectant

OBJECTIVE The purpose of this study was to establish whether addition of a 2% chlorhexidine rinse to a conventional treatment protocol enhances the rate of the successful disinfection of the root canal system in vivo. STUDY DESIGN Twenty-four teeth with infected necrotic pulps and resorbing apical periodontitis were treated with a conventional technique in which 1% NaOCl as irrigant was used. Half of the cases received an additional rinse with 2% chlorhexidine. Prereduced thioglycollate medium was used to take cultures that were incubated for 4 weeks. RESULTS Cultivable bacteria were retrieved at the conclusion of the first visit in 1 out of 12 chlorhexidine cases whereas in the control group 7 out of 12 cases showed growth. This difference was significant (P < .05). CONCLUSION The findings are clinically important.

Shaping Ability of Three ProFile Rotary Instrumentation Techniques in Simulated Resin Root Canals

The aim of this study was to compare the shaping ability of three ProFile rotary instrumentation techniques and a conventional step-back method in simulated root canals. Prevalence of canal aberrations, change in working length, and preparation time were measured. A total of 48 composite images were made from pre- and postcanal scanned images using Corel Photopaint 8.0 and then the amount of coronal substance the instruments removed was also calculated two-dimensionally on digitized images with the Brain C software to compare the enlarging efficiency. There were no significant differences between the three rotary groups in preparation time, change in working length, and the incidence of aberrations (p > 0.05). The amount of coronal substance the instruments removed in the ProFile .04 taper group was significantly smaller than the other three groups (p < 0.05).

Antifungal effects of sodium hypochlorite and chlorhexidine in root canals.

The purpose of this study was to evaluate the antifungal properties of 0.12% chlorhexidine, 1% NaOCl, and 5% NaOCl. Root sections were enlarged and the smear layer was removed in half of the specimens. The specimens were fixed in the wells of tissue culture plates. Each root canal was dispensed with an inoculum of Candida albicans. After 10 days, the root sections were treated with 3 ml of either disinfectant solution for 1 min, 5 min, 30 min, and 1 h. Then, root sections were incubated in test tubes having Sabourauds Dextrose Broth at 37 degrees C for 24 h. In the presence of the smear layer, antifungal activity was observed only in 1-h treatment groups for all solutions. However, in the absence of the smear layer, 5% NaOCl alone started to show antifungal activity after 30 min. The antimicrobial effectiveness of irrigating solutions should be re-evaluated, particularly in patients predisposed to oral candidiasis.

A prospective cohort study of endodontic treatments of 1,369 root canals: results after 5 years

OBJECTIVE The purpose of this prospective study was: 1) to follow-up a large number of endodontic treatments performed by a single operator, periodically checked over a 5-year period; and 2) to correlate outcome to a number of clinical variables. STUDY DESIGN This prospective study included all consecutive cases during the selected time period. All cases were followed regularly for a 5-year period. At the 5-year end point of the study, 470 patients with 816 treated teeth and with 1,369 treated root canals were available for evaluation. RESULTS The overall rate of success among the 816 teeth/1,369 root canals available for evaluation was 88.6%/90.3%. The success rate for 435 teeth/793 root canals undergoing vital pulp therapy was 91.5%/93.1%. Teeth/root canals with necrotic pulp but without detectable periapical bone lesion were successfully treated in 89.5%/92.3%. If the pulp necrosis was complicated by apical periodontitis, the success rate fell to 82.7% for the teeth and 84.1% for the root canals (P = .037). Teeth with periapical lesion <5 mm had a success rate of 86.6%, and in cases where the lesion was ≥ 5 mm the rate of success was 78.2%. CONCLUSIONS More severe disease conditions negatively affects outcome. An optimal working length was identified. Excess of root canal filling material decreases success. Infected pulp space should be treated with an effective intracanal dressing. The quality of the coronal restoration or the placement of intracanal post retentions does not affect treatment outcome.

Dimensional changes of endodontic sealers

The purpose of this study was a long-term comparison of the dimensional changes of endodontic sealers of diverse properties. The sealers were injected as thin layers on the internal walls of glass pipettes 1 mm in diameter. The pipettes were filled with deionized water, and the water meniscus levels were recorded periodically up to 180 days. The water was removed from the pipettes, samples were allowed to dry, and the mass and the volume of the sealers were measured. AH26 and Endo-Fill had an initial expansion followed by a volumetric loss. The two zinc oxide eugenol-based sealers studied started to shrink within hours after mixing; the first volumetric loss for AH26 was recorded during the first 30 days and for Endo-Fill after 30 days. The least dimensional change at any time was observed for Endo-Fill. It was concluded that a significant dimensional change and continued volume loss can occur in some endodontic sealers.