John F. Corcoran

Anatomy of the root apex and its histologic changes with age

There were 87 vital and 24 nonvital teeth for a total of 111 specimens from 47 patients. The specimens were prepared to a thickness of 500 microns with a Buehler Isomet Bone Saw. Distances were measured and recorded with a Bioquant II Image Analysis System. The mean age of the patients was 48.9 years. The median age was 52 years. The range was 51 years, with a maximum of 77 years and a minimum of 26 years. There is a positive correlation, which could not have occurred by chance, that as age increases the deviation and the width of the foramen opening both increase. This increase appears to be a result of apical cemental thickening that occurs as the patient ages. The tissue in the apical area seems to be capable of generating additional cementum as the tooth ages. The cementodentinal junction width, or most apical extent of the dentin, remains constant.

The influence of the major and minor foramen diameters on apical electronic probe measurements

There have been conflicting reports on the accuracy of electronic devices used for determining working length. The influence of the major and minor diameters on electronic probe measurements were evaluated to ascertain whether anatomical features of the apical portion of the canal might be responsible for these discrepancies. Forty-seven nonrestorable teeth selected from 22 patients were studied. Conventional access was made. A Kerr file was placed to a position 0.5 mm from the major foramen as registered by the Neosono-D apex locator. The electronic probe length was then measured. After the tooth was extracted, the file was fixed with autopolymerizing composite in the canal. A Buehler Isomet lapadary saw was used to prepare specimens to a thickness of 500 microns. A Bioquant II Image Analysis System was used to measure and record distances. It was found that as the width of the major foramen increased, the discrepancy between the electronic probe tip length induction and the actual position of the major foramen increased.

Average maximum post lengths in endodontically treated teeth

T here is a controversy in regard to recommended post lengths for endodontically treated teeth. Varying lengths have been advocated without comparing them with limits set by root canal therapy or anatomic lengths. A comparison of advocated post length with tooth length and the obturated root canal allows the establishment of broad clinical guidelines for the dentist. Paladino’ suggests that a post longer than 5 mm may be adequate to reduce dentinal stresses. Other authors suggest post lengths that are (1) equal to or greater than the length of the clinical crown,2-4 (2) equal to the length of the anatomic crown,’ (3) half to two thirds of

Pararadicular cementum deposition as a criterion for age estimation in human beings

The purpose of this article is to ascertain if pararadicular cementum can be used as a reliable criterion for age estimation in human beings. Fifty-two nonrestorable teeth were extracted from 42 patients at the Veterans Administration Medical Center at Ann Arbor, Mich. The specimens were prepared to a thickness of 500 microns with a Buehler Isomet bone saw (Bronwell Scientific, Inc., Rochester, N.Y.). Longitudinal sections were cleaned of artifacts in an ultrasonic cleaner and stained with 1% alizarin red. Photomicrographs were taken of each prepared section. The cementum was composed of multiple light and dark bands that were counted on the photograph and added to the average eruption time of the individual tooth. There was an overall Pearsons product-moment correlation coefficient of r = 0.93 between the patients predicted age with the use of cementum annulations as compared with the actual chronologic age of the person. Predicted age counts showed greater divergence from actual age in persons older than 55 years. A formula is presented to adjust for this discrepancy. The data indicate that quantitation of cementum annuli is a moderately reliable means for age estimation in humans.

Cutting ability of square versus rhombus cross-sectional endodontic files

The cutting ability on the “pull” stroke of square and rhombus cross-sectional endodontic files was measured and compared using a custom designed apparatus that controlled the force on the files and the length and number of strokes. The cutting efficiency was determined by measuring the depth of cut in poly(methyl methacrylate) wafers. A statistically significant increase in cutting ability was achieved with rhombus instruments in sizes 30, 35, and 40 whereas in sizes 20 and 25 there was no significant difference.

Osseous healing kinetics after apicoectomy in monkeys: II. A quantitative histological appraisal

A study was conducted on four 8- to 12-kg adult monkeys ( Macaca mulatta ). Mandibular lateral incisor, first premolar, second premolar, and first molar teeth were involved. Each tooth was subjected to conventional root canal treatment followed by a standardized apicoectomy procedure. The standardized surgical defects were allowed to heal 2, 4, 8, or 16 wk after apicoectomy. The animals were killed and histological material was processed. A representative histological section containing the tooth root and the mid-portion of each surgical defect was analyzed. Surface area of newly formed bone was quantified for each defect site using a microscope grid and subjective scoring criteria. Proportions of regenerated bone tissue were localized to cortical plate or trabecular bone regions. Bony regeneration initiated from trabecular bone regions and progressed as a generalized chronological remodeling pattern toward complete repair of cortical plate and periodontium.

Maxillary lateral incisor with two roots and dens formation: a case report.

Summary A case report is given to increase the practitioners awareness of aberrations in tooth morphology of maxillary lateral incisors.

A spectrophotometric analysis of dentinal leakage in the resected root

The purpose of this study was to compare dye leakage in the dentin of resected and nonresected roots. Fifty-four single rooted extracted teeth were used. The two groups were subdivided into young, middle age, and old age samples. Each sample was biomechanically prepared in a standard fashion and obturated using lateral condensation with sealer and gutta-percha. All root surfaces were sealed with nail polish, leaving the apical portion exposed. The apical portion of the roots were placed in 2% methylene blue dye for 72 h, rinsed, and placed in 15 ml of 35% HNO3 for 72 h. The supernatant was analyzed at 640 nm using a visible light spectrophotometer. The amount of leakage was extrapolated from a standard linear regression curve constructed from the stock 2% methylene blue dye solution. The percentage of concentration leakage in all samples ranged from less than 0.0600 to 0.1658. It was concluded that there is a greater amount of leakage in resected versus nonresected extracted teeth. The data also suggest that older teeth exhibit less leakage than younger teeth.

Langerhans Cells in Apical Periodontal Cysts: An Immunohistochemical Study

The purpose of this study was to evaluate the epithelium of apical periodontal cysts for the presence of Langerhans cells using immunohistochemical techniques. Antisera to S-100 protein, muramidase, and monoclonal antibody to HLA-DR antigens were tested on formalin fixed, paraffin-embedded tissue from 60 apical periodontal cysts. S-100-positive dendritic intraepithelial cells (Langerhans cells) were found in 51 apical periodontal cysts. In 55 cases, S-100-positive cells were found in the supporting connective tissue (indeterminate cells). HLA-DR-positive intraepithelial dendritic cells were noted in 34 cases. HLA-DR also stained connective tissue macrophages. Muramidase-positive cells were found predominantly in connective tissue. Muramidase did not stain dendritic cells in the epithelium. It is concluded that Langerhans cells are present in the epithelium of apical periodontal cysts. Their function in this pathological condition is likely one of antigen processing and presentation, analogous to their role in normal epithelium. These findings provide additional support for the importance of the cell-mediated immune response in periapical disease.

Nonionizing method of locating the apical constriction (minor foramen) in root canals

The electronic method was evaluated as to its accuracy when used to determine the position of the apical constriction (minor foramen) in root canals. There were 39 vital and 8 nonvital teeth for a total of 47 specimens from 22 patients. The specimens were prepared with a Buehler Isomet bone saw to a thickness of 500 microns. Distances were measured and recorded with the use of a Bioquant II image analysis system. The electronic method appeared to measure a mean value of 0.2 mm coronal to the cemetodentinal junction in 47 canals where the apex locator was set at a reference setting of 40. When a frequency curve was plotted, it showed that the probability of being within 0.76 mm (1 SD) of the cementodentinal junction was 68%. This appears to correlate to where Kuttler indicated the minor constriction to be located. These devices seem to offer a unique method to locate the apical constriction and thus to ensure proper working length while reducing ionizing radiation.