Larry Z. Koren

Effect of different endodontic treatment protocols on periodontal repair and root resorption of replanted dog teeth

This study examined, histologically, the healing of intentionally damaged root surfaces of replanted teeth with either uninfected or infected root canals treated with short- and long-term calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1, uninfected obturated incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as described in group 1. Fourteen days after replantation, the root canals were fully instrumented and medicated with intracanal calcium hydroxide. One week later the root canals were permanently obturated with gutta-percha and sealer. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. After 8 wk, sacrifice and histological preparation were carried out. In group 1 complete cemental repair was seen in all teeth. In groups 2 and 3, complete and incomplete cemental repair was seen in seven and two teeth, respectively. An ankylotic area was present in one tooth in group 3. None of the teeth in group 4 showed cemental repair. It was concluded that short- and long-term calcium hydroxide treatment resulted in similar healing patterns when endodontic treatment is initiated 14 days after replantation of teeth.

A comparative tissue toxicity evaluation of established and newer root canal sealers

Grossmans sealer, eucapercha, Endo-Fill, CRCS, Sealapex, Hypocal, and sterile saline solution (0.3 ml of each) were injected into specific dorsal subdermal tissue sites of 12 guinea pigs. The animals were killed after 6 days, 15 days, and 80 days (four per time period). Analysis of tissue response showed that, overall, Sealapex and Endo-Fill had less severe inflammatory reactions than any of the other test materials. Grossmans sealer, CRCS, and Hypocal showed principally severe inflammatory responses at both 6 and 15 days, but mild reactions at 80 days. Overall, eucapercha showed less severe inflammatory responses than Grossmans sealer, CRCS, and Hypocal. Diffuse calcification was induced by the three calcium hydroxide preparations (CRCS, Sealapex, and Hypocal). Eucapercha and Endo-Fill had minute local areas of calcification. Both Grossmans sealer and CRCS did not have overall favorable histologic reactions; however, Grossmans sealer and CRCS have been used successfully clinically. Further clinical studies are needed.

Prophylactic use of penicillin V in teeth with necrotic pulps and asymptomatic periapical radiolucencies

As a result of (1) clinical experience with flare-ups occurring in teeth with necrotic pulps and asymptomatic periapical radiolucencies and (2) on apparent reduction to the incidence of such flare-ups by the administration of penicillin V at the first sign of swelling, this study on the prophylactic administration of penicillin V in similar cases was undertaken. The subjects were 100 consecutive clinic patients whose teeth had necrotic pulps and asymptomatic periapical radiolucencies. At the initial visit, all teeth were instrumented completely to the radiographic apex, with 0.5% to 2.54% sodium hypochlorite as the irrigant. Sterile, dry cotton pellets and ZOE restorations were used. Alternate patients were given 250 mg of penicillin V and an identical-appearing placebo with instructions to take two tablets every 6 hours for the first 24 hours, followed by one tablet every 6 hours until all tablets were taken. Pain and swelling were graded by the patients on five-point scales, and flare-ups were scored when either pain and/or swelling necessitated an unscheduled emergency visit. Fifteen patients developed flare-ups, with significantly more flare-ups in the placebo group (p less than 0.05). The findings indicate that, in selected cases, prophylactic penicillin can be used to prevent flare-ups.

Dye leakage in retrofilled dog teeth and its correlation with radiographic healing

In a previous study in beagle dogs, statistically significant differences in healing were observed radiographically 6 months after apicoectomy and retrofilling with amalgam and varnish, glass ionomer cement, or a composite resin. The purpose of this study was to compare the leakage of these retrofilling materials and to correlate leakage data with healing. After the dogs were sacrificed, 48 roots were extracted. Half of the roots had been irradiated with a CO2 laser on the bevelled root surface after retrofilling. The roots were coated with nail polish, except for their bevelled surface, and were suspended together with positive and negative controls in 2% methylene blue for 8 h. After the specimens were longitudinally split, they were ranked according to the severity of dye penetration, as observed with a dissecting microscope. The differences in dye leakage among the three retrofilling materials were not statistically significant. Consequently, dye leakage did not correlate with the previously assessed healing. Dye penetrated into the root through the bevelled root surface, regardless of CO2 laser exposure of that surface.

A scanning electron microscopic examination of surface changes obtained from two variable methods of precurving files: A clinical observation

This clinical observational study compared finger-bending and cotton pliers-bending methods of precurving endodontic files. Changes to the surface appearance of the flutes of the files were examined with the scanning electron microscope. Thirty-six files (#15 and 25) were used in two groups of 16 each: group A, finger bending and group B, cotton-pliers bending. A control group had four files. In each group, one-half were bent at approximately 20 degrees and the other one-half at approximately 30 degrees. The files were examined by scanning electron microscopic observation. No differences were found relative to instrument size or degree of bending. In general, the cotton plier-bent files gave the appearance of flattening of the flutes. Flattening of the finger-bent files was not observed. However, more debris accumulated on the finger-bent files. Hence, from this study it appears that finger bending is preferable to cotton pliers bending as a method for precurving of endodontic files. However, a controlled study is necessary to determine which are the preferred bending sites, degrees, and methods.

Endodontic flare-ups: The tape

A discussion is given of the pros and cons of the recently distributed audio tape on endodontic flare-ups. Highlighted is the relationship of endodontic flare-ups to infection and how specific antibiotics and certain intracanal medicaments can reduce flace-ups and non-flare-up-associated pain and swelling.

A detailed analysis of four long-term silver cone root canal fillings

Because many failures in root canal therapy have been attributed to the use of silver cones as a filling material, it was decided to examine four roots of three teeth, each of which had been successfully treated endodontically with silver cones ranging from 24 to 34 years previously. These roots, which were resected for periodontal reasons, were examined both under the scanning electron microscope and histologically. Examination with the scanning electron microscope revealed that all four cones were moderately to severely corroded. Histologic examination of two teeth disclosed corrosion products along the entire wall and, in one instance, within the dentinal tubules and apical tissue. The corrosion products, however, were most extensive in the cone that appeared to be loose fitting within the canal. The results indicated that corrosion products occurred in all of the teeth examined. Therefore, corrosion may not be the primary factor accounting for failure in teeth endodontically treated with silver cones.