Douglas J. McKendry

Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys

Mineral Trioxide Aggregate (MTA) has been shown in a number of experiments to be a potential root-end filling material. The purpose of this study was to examine the periradicular tissue response of monkeys to MTA and amalgam as root-end fillings. The pulps were removed from all the maxillary incisors of three monkeys. The root canals were prepared and filled with laterally condensed guttapercha and sealer, and the access cavities were restored with amalgam. Buccal mucoperiosteal flaps were raised, and root-end resections were performed before root-end cavity preparation with burs. The root-end cavities in half of the teeth were filled with MTA, while amalgam was placed in the other cavities. After 5 months the periradicular tissue response was evaluated histologically. The results showed no periradicular inflammation adjacent to five of six root ends filled with MTA; also five of six root ends filled with MTA had a complete layer of cementum over the filling. In contrast, all root ends filled with amalgam showed periradicular inflammation, and cementum had not formed over the root-end filling material, although it was present over the cut root end. Based on these results and previous investigations, MTA is recommended as a root-end filling material in man.

Dye leakage of four root end filling materials: Effects of blood contamination

The purpose of this study was to compare the amount of dye leakage (in the presence versus absence of blood) in root end cavities filled with amalgam, Super EBA, IRM, and a mineral trioxide aggregate. After removing the anatomical crowns of 90 extracted human teeth, their roots were instrumented and obturated. Except for their apical 2 mm, the root surfaces were sealed with nail polish. After removal of the apical 2 to 3 mm of each root, a standardized root end cavity was prepared. Five root ends were filled with gutta-percha and no sealer, and another five root ends were filled with sticky wax. These served as positive and negative controls, respectively. The remaining 80 roots were divided into four equal groups and filled with the test materials. For each material, half of the root end cavities were dried prior to placing the filling material. The remaining half were filled after they were contaminated with blood. All 90 roots were then immediately placed in 1% methylene blue dye for 72 h. Finally, the roots were split and linear dye penetration was measured and statistically analyzed (analysis of variance). Presence or absence of blood had no significant effect on the amount of dye leakage. However, the results showed that there was a significant leakage difference between the root end filling materials (p < 0.0001). Mineral trioxide aggregate leaked significantly less than other materials tested with or without blood contamination of the root end cavities.

Use of mineral trioxide aggregate for repair of furcal perforations

The histologic response to intentional perforation in the furcations of 28 mandibular premolars in seven dogs was investigated. In half the teeth, the perforations were repaired immediately with either amalgam or mineral trioxide aggregate; in the rest the perforations were left open to salivary contamination before repair. All repaired perforations were left for 4 months before histologic examination of vertical sections through the site. In the immediately repaired group, all the amalgam specimens were associated with inflammation, whereas only one of six with mineral trioxide aggregate was; further, the five noninflamed mineral trioxide aggregate specimens had some cementum over the repair material. In the delayed group, all the amalgam specimens were associated with inflammation; in contrast only four of seven filled with the aggregate were inflamed. On the basis of these results, it appears that mineral trioxide aggregate is a far more suitable material than amalgam for perforation repair, particularly when used immediately after perforation.

Comparison of Balanced Forces, Endosonic, and Step-back Filing Instrumentation Techniques: Quantification of Extruded Apical Debris

Randomly assigned groups of 15 single-canal, extracted human teeth were instrumented by one of three techniques: balanced forces, endosonic, or step-back filing. Debris extruded from the apical foramen during instrumentation was collected onto preweighed filters using a suction filtration apparatus. Following desiccation, weight determinations were made on an analytical electrobalance. A one-factor analysis of variance was performed on the debris weight data revealing that the endosonic technique apically extruded significantly more debris than the balanced forces technique (p less than 0.05). Further analysis of the data, excluding debris weights greater than 1 SD from the mean, using a one-factor analysis of variance revealed the balanced forces technique apically extruded significantly less debris than either endosonic or step-back filing techniques (p less than 0.05). No significant difference was demonstrated between endosonic and step-back filing techniques.

Effects of resorbable membrane placement and human osteogenic protein-1 on hard tissue healing after periradicular surgery in cats*

Periradicular surgeries were performed on the maxillary cuspid teeth of twelve cats. Before reapproximation of the surgical flaps, eight of the osteotomies were covered with a resorbable membrane and eight were filled with human osteogenic protein-1 (hOP-1) on a collagen carrier. The remaining eight sites received no further treatment and served as controls. The animals were euthanized after 12 wk, and the specimens were examined histomorphometrically for the presence or absence of osseous regeneration, inflammation, and cementum formation on the root ends. The results showed that the sites treated with the membrane exhibited significantly more inflammation adjacent to the resected root ends (p < 0.05), and that the use of the membrane had no statistically significant effect on osseous healing or new cementum formation. The use of hOP-1 was associated with a significant decrease in the thickness of new cementum formed on the resected root ends (p < 0.05), but had no statistically significant effect on osseous healing or degree of inflammation. Based on these results, it seems that neither the use of hOP-1 nor resorbable membranes have a positive effect on periradicular tissue healing in endodontic surgery.