James H.S. Simon

Incidence of periapical cysts in relation to the root canal

Summary The study shows the occurrence of two types of epithelial-lined cavities related to the apical foramen. The incidence of true cysts is low, in our study 8.6%. As our sample size is small, this figure is probably an approximation. From the potential of healing, the true cyst may not heal with nonsurgical endodontic therapy. The bay cysts may heal with nonsurgical endodontic therapy, as they may be extensions of epithelial granulomas and statistically should be listed with them.

Evaluation of the apical seal produced by injected thermoplasticized gutta-percha in the absence of smear layer and root canal sealer

The apical seal produced by injected thermoplasticized gutta-percha with and without root canal sealer and smear layer was evaluated by ink penetration. Sixty-four extracted human teeth were divided into eight groups with and without the smear layer removed. They were filled with injected thermoplasticized gutta-percha or lateral condensation using Procosol sealer or with no sealer. The results showed that injected thermoplasticized gutta-percha does not provide an apical seal to ink penetration when used without a root canal sealer, even with the smear layer removed. Sealer was the only significant variable responsible for apical seal when conditions of gutta-percha delivery, smear layer presence or absence, and use or deletion of sealer were evaluated. The use of injected thermplasticized gutta-percha should be accompanied by a sealer whether or not the snear layer has been removed.

A Comparison of the Effect of Modified and Nonmodified Instrument Tips on Apical Canal Configuration. Part II

Forty canals in plastic blocks were prepared by two instrumentation techniques, each with or without instrument tip modification. Modified instruments used in this study were commercially prepared (Union Broach, New York, NY), unlike those used in the previous study which were a hand-modified prototype. The canals were photographed before and after preparation. A composite print was made by superimposition, and the deviation from the original canal form was measured. Statistical analysis revealed the modified (R-type) file provided the closest to ideal instrumentation regardless of technique used.

Herpesviruses in periapical pathosis: an etiopathogenic relationship?

BACKGROUND Much remains to be learned about the etiopathogenesis of periapical pathosis, especially about the molecular events preceding and causing disease onset. Human cytomegalovirus and Epstein-Barr virus, 2 herpesviruses, are discussed in this review as they relate to apical periodontitis in humans. RESULTS Cytomegalovirus or Epstein-Barr virus active infections are detected in more than 90% of granulomas of symptomatic and large periapical lesions. Dual infection with cytomegalovirus and Epstein-Barr virus is closely associated with symptomatic lesions. Herpes simplex virus active infection has no apparent relationship to periapical disease. DISCUSSION The available evidence suggests the involvement of active cytomegalovirus and Epstein-Barr infections in the etiopathogenesis of apical periodontitis. In periapical pathosis, herpesviruses may cause the release of tissue-destructive cytokines, the overgrowth of pathogenic bacteria, and the initiation of cytotoxic or immunopathologic events. Immune impairment resulting from herpesvirus infection may aid bacteria at several stages of the pathogenesis of periapical lesions, including growth in the periapical environment, possible invasion of tissue, and direct damage to tissue. Unraveling the etiology and pathogenesis of periapical pathosis may require a broadening of our experimental approaches to include studies on interactions among herpesviruses, bacteria, and host immune reactions. Understanding the significance of herpesviruses in the development of periapical lesions may aid in the diagnosis, prevention, and treatment of the diseases.

In vivo measurement accuracy in vital and necrotic canals with the endex apex locator

Currently apex locators are being used to determine working length. This study was undertaken to see what is actually being measured and if the pulp status, i.e. vital or necrotic, makes a difference in the determination. In this in vivo study, 33 teeth, both vital and necrotic, were measured by the Endex apex locator and then radiographed. After the length determination, the file was cemented to place, the tooth extracted, and then shaved back until the file and the apex were exposed. The position of the file was measured in relation to the apical foramen. Results indicate that all measurements were within a narrow range (-0.86 mm to 0.50 mm). There was no statistical difference in measurements between vital and necrotic canals.

Predictable endodontic and periodontic failures as a result of radicular anomalies

Abstract A pathosis that is associated with developmental radicular anomalies is described. Such conditions are easy to diagnose only when the diagnostician is aware of their existence. At present, since these anomalies constitute unresolvable periodontal problems, extraction of the involved teeth is the treatment of choice.

Endotoxic activity in periapical lesions

Thirty tissue samples were examined histologically and classified as being inflamed (apical granulomas) or noninflamed (scars or noninflamed cysts). The samples were then homogenized in pyrogen-free water and treated to remove interfering substances. The presence of endotoxin was then determined by means of the limulus assay; 75 percent of the inflamed tissues were positive for endotoxin, while only 20 percent of the noninflamed tissues contained endotoxin. The presence of endotoxin was thus highly correlated (p = 0.015) with the presence of inflammation in these tissues.

Cytomegalovirus and Epstein-Barr Virus Active Infection in Periapical Lesions of Teeth with Intact Crowns

Herpesviruses seem to play an important role in the pathogenesis of aggressive periodontitis and may also contribute to periapical pathosis. This study determined the presence of human cytomegalovirus, Epstein-Barr virus, and herpes simplex virus productive infection in five symptomatic periapical lesions of teeth having intact crowns and calcified necrotic pulps. Periapical samples were collected in conjunction with periapical surgery and kept frozen until virological examination. Reverse transcription-polymerase chain reaction was used in herpesviral identification. RNA was isolated from periapical tissue by a guanidinium isothiocyanate-acid phenol procedure. cDNAs were generated from highly conserved regions of the test viruses using a preamplification kit. Sensitivity and validity of the PCR-primers were determined according to established methods. Amplification products were identified using gel electrophoresis. Human cytomegalovirus and Epstein-Barr virus dual transcription was detected in all five periapical lesions studied. Herpes simplex virus transcript was not identified in any lesion. The present data suggest that human cytomegalovirus or Epstein-Barr virus activation participate in the pathogenesis of symptomatic periapical lesions. We hypothesize that periapical active herpesvirus infection impairs local defenses, thereby inducing overgrowth of endodontopathic bacteria and the clinical flare-up of inflammation.

Recall Evaluation of latrogenic Root Perforations Repaired with Amalgam and Gutta-percha

Fifty-seven endodontic cases involving iatrogenic perforations were obtained from the student clinic at the University of Oklahoma College of Dentistry. The perforations had been repaired with internally placed amalgam (24) or gutta-percha (33). Five cases that were determined to be failing upon recall evaluation were subsequently treated surgically. Recall periods ranged from 3 months to 6 yr. Gutta-percha repairs had a 57.6% failure rate and accounted for 73% of all failures, while 26% of amalgam repairs failed. Seventy percent of all failures involved extruded material and 83% of these were gutta-percha repairs. Successes outnumbered failures with both materials, even when the repair was delayed up to 60 days. Amalgam was found to be superior to gutta-percha when used under the conditions of this study. Repairs involving extrusion of gutta-percha were most likely to fail. The rate of success of perforation repair was not adversely affected by a treatment delay (p>0.05). Of the five failing cases that were surgically treated, all demonstrated evidence of healing during subsequent evaluations.

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.