James C. Kulild

The mental forman: Part I. Size, orientation, and positional relationship to the mandibular second premolar

Seventy-five adult human mandibles were examined to determine the size, orientation, and position of the mental foramen. The average size of the foramen was found to be larger on the left side of the mandible and its usual direction of exit was in a posterior-superior direction. The most common location of the mental foramen was inferior to the crown of the second premolar and approximately 60% of the distance from the buccal cusp tip of that tooth to the inferior border of the mandible.

Root canal configuration of the mandibular first premolar

One hundred six human mandibular left and right first premolars, previously extracted due to nonrestorable caries, periodontal disease, or orthodontic reasons, were sectioned perpendicular to the long axis of the root starting at the cementoenamel junction. Three-millimeter sections were made with an ultrathin separating disc to the level of the anatomical apex. After 1 day in 5.25% NaOCl, each section was rinsed in phosphate-buffered saline, evaluated with a stereomicroscope, and photographed. The slides were projected and the shape of the canal, incidence of multiple canals, level of bifurcation, and any other variant anatomy were recorded. Seventy-six percent of the premolars demonstrated Type I canals and 24% contained Type IV. The shape of the canals was predominantly oval or round. An interesting finding was the number of C-shaped canals which were associated predominantly with Type IV canal systems. This occurred in 14% of the roots.

A comparison of thermoplasticized injectable gutta-percha obturation techniques

This study compared the quality of obturation of high- and low-temperature thermoplasticized injectable gutta-percha techniques and standard lateral condensation. A new model system was developed to more closely simulate the clinical environment. All obturations were performed in this same model which allowed direct comparisons between the different techniques. The resultant mass of gutta-percha was visually examined and graded for each obturation. Statistical analysis of the results indicated that both thermoplasticized injectable techniques were significantly better than lateral condensation. There was no significant difference between either of the thermoplastic obturation techniques.

Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin

Forty single-rooted teeth were sectioned transversely through the cementoenamel junction and instrumented to a size #50 K-Flex file at the working length by saline irrigation. Each root was placed in a dilution vial containing 10 ml of normal saline, and the pH and Ca2+ levels were recorded after 24 h. The roots in group 1 then received a final irrigation with 20 ml of normal saline. Group 2 received a final irrigation with 10 ml of 17% ethylenediaminetetraacetic acid followed by 10 ml of 5.25% NaOCl to remove the smear layer. Group 3 was irrigated in the same manner as group 2, but calcium hydroxide (CH) was placed into the root canal. Group 4 was irrigated with 20 ml of NaOCl, and CH was placed into the root canal. The pH and Ca2+ levels were recorded at 1, 3, 5, and 7 days. After 7 days a 3- x 3- x 1-mm external defect was created in the coronal one third of the root surface. The pH and Ca2+ levels were subsequently recorded at 1, 3, and 7 days. Groups 3 and 4 demonstrated significantly higher H+ and Ca2+ levels than did groups 1 and 2 three days after CH placement and at all subsequent intervals. Group 3 demonstrated significantly higher H+ and Ca2+ readings at some but not all intervals. The results demonstrated that CH diffuses from the root canal to the exterior surface of the root and that the removal of the smear layer may facilitate this diffusion.

The mental foramen: Part II. Radiographic position in relation to the mandibular second premolar

Seventy-five adult human mandibles were radiographed with a paralleling technique to determine the ability to visualize the mental foramen as well as its size and position. The foramen was seen on 75% of the horizontal periapical radiographs examined. When the foramen was not visualized, is was usually below the inferior edge of the film. The radiographic size of the foramen was smaller than the anatomical size previously reported. The position of the mental foramen was usually mesial and below the radiographic apex of the second premolar.

The mental foramen: Part III. Size and position on panoramic radiographs

Panoramic radiographs were made of 75 dry, adult human mandibles. The size and position of the mental foramen in relation to the second premolar was determined. The mental foramen on panographic radiographs was slightly larger than reported on periapical radiographs. The average position of the foramen was mesial and below the radiographic apex of the tooth. Panoramic radiography may account for a distal shift of the foramen and a 23% increase in size of the mandibles examined.

Treatment considerations in dens invaginatus.

Dens invaginatus has numerous and complex forms. Nonsurgical and surgical root canal therapy was performed on a permanent maxillary lateral incisor with this condition. Satisfactory radiographic healing was evident at the 2-yr recall appointment. Suggestions are made for future treatment of cases of this type.

Effect of smear layer removal on the diffusion permeability of human roots

Ten human maxillary incisors, extracted because of periodontal disease or nonrestorable caries, were obtained and instrumented to a size #70 K-Flex file at the working length using a standard stepback technique. Tritiated water (3H2O) was placed in the root canals and allowed to diffuse to the external surface of the roots until it reached a constant rate. The smear layer in each of the experimental roots was then removed using 0.5 M EDTA followed by 5.25% sodium hypochlorite (NaOCI). The constant rate diffusion of 3H2O was remeasured. The roots were then stored in deionized H2O for 2 months and the constant rate diffusion of 3H2O was remeasured. A statistically significant difference was noted between all three groups. A decrease in the diffusion permeability of the root to 3H2O was noted immediately after smear layer removal and the highest permeability was recorded after storage in the deionized water for 2 months.

An evaluation of the apical seal produced by lateral and warm lateral condensation techniques

The apical sealing ability of a standard lateral condensation technique was compared with that of two different warm lateral condensation techniques. Sixty extracted human teeth with single canals were instrumented and randomly placed into three groups. Four additional teeth were used as controls. Each group of 20 teeth was obturated with gutta-percha and sealer using one of the three techniques. After 7 days in India ink, the teeth were cleared and the linear extent of ink penetration was measured with a stereomicroscope. No leakage was evident in the two negative controls whereas complete leakage was present in the two positive control teeth. Statistical analysis of the results showed no significant difference in leakage between the experimental groups.

Effect of mechanical versus thermal removal of gutta-percha on the quality of the apical seal following post space preparation*

The objective of this study was to compare the effects of a flame-heated endodontic plugger, an electrically-heated endodontic spreader, Peeso reamers, and GPX burs on the apical seal when gutta-percha was removed from the root canal for post space preparation. Eighty-nine human canines were instrumented and obturated with gutta-percha and sealer to a standardized working length of 15 mm. An 11-mm segment of gutta-percha was removed from the roots in each of the four experimental groups of 20 teeth to simulate post space preparation. The teeth were immersed in India ink for 7 days and rendered transparent. The extent of linear dye leakage was measured with a stereomicroscope. There was no statistically significant difference in linear dye leakage among any of the experimental groups when 4 mm of gutta-percha remained.