Micro-computed tomography study of the internal anatomy of mesial root canals of mandibular molars

Introduction

The aim of this study was to determine the mesiodistal and buccolingual diameter, apical volume, and the presence of isthmuses at the apical level of mesial root canals of mandibular molars.

Methods

Sixty extracted first and second mandibular molars were scanned by using a SkyScan 1076 micro-computed tomography system with a voxel size of 18 μm. The apical thirds of the samples were reconstructed to allow a perpendicular section of the apical third by using the multiplanar reconstruction tool of the OsiriX software. The mesiodistal and the buccolingual distances of root canals were measured between the 1- to 4-mm levels. The type of root canal isthmuses present at these levels was classified by using modified criteria of Hsu and Kim. The volume of the root canal anatomy between the 1- to 3-mm apical levels was obtained by using the CTAN-CTVOL software.

Results

The medians of the mesiodistal diameter at the 1-, 2-, 3-, and 4-mm levels in the mesiobuccal and mesiolingual canals were 0.22 and 0.23 mm, 0.27 and 0.27 mm, 0.30 and 0.30 mm, and 0.36 and 0.35 mm, respectively. The buccolingual lengths at the 1-, 2-, 3-, and 4-mm levels were 0.37-0.35 mm, 0.55-0.41 mm, 0.54-0.49 mm, and 0.54 and 0.60 mm, respectively. The presence of isthmuses was more prevalent at the 3- to 4-mm level. However, 27 cases presented complete or incomplete isthmuses at the 1-mm apical level. The mean of the volume of the apical third was 0.83 mm³, with a minimum value of 0.02 and a maximum value of 2.4 mm³.

Conclusions

Mesial root canals of mandibular molars do not present a consistent pattern. A high variability of apical diameters exists. The presence of isthmuses at the apical third was not uncommon even at the 1-mm apical level.     

Finishing of glass ionomer retroseals.

Various techniques have been suggested for the finishing of retrosealing materials. By measuring marginal leakage and by the use of scanning electronic microscopy, this study evaluated the use of bone files, burnishers, and Shofu points for the finishing of 60 retrosealings done with glass ionomer. With each of the three finishing agents, one group of teeth was polished with movements directed from the palatal toward the buccal, and in another group it was done from the center of the retroseal toward the margins of the cavity. ANOVA showed significant differences among the groups according to the way the finishing was done. The use of instruments from the center to the margins of the cavity rather than in just one direction always caused less leakage. The Shofu stone and the burnisher caused equivalent leakage which was significantly less than that caused by bone files. Scanning electron microscopic photos show that the use of the instrument in only one direction caused the material to shift away from the palatal side. This shift always led to greater leakage of dyes on that side.     

Malignant parotid tumors. Diagnostic considerations and therapeutic suggestions

This paper presents our experience of the problem of diagnosis and surgical treatment of malignant parotid tumors, based on a retrospective evaluation of a series of 478 parotid tumors, of which 100 were malignant. Out of 75 primaris malignant tumors of epithelial origin, 35 belonged to the "epidermoid" group (adenocarcinomas, undifferentiated carcinomas, malignant mixed tumors, squamous cell carcinoma), 20 were mucoepidermoid carcinomas, 15 adenoid cystic carcinomas and 5 were acinic cell carcinoma. Altogether, 58.7% of the treated patients do not at the moment present evidence of disease; 33.3% are dead from the disease or are alive with active disease; 5.3% are dead from other causes and 2.7% are lost to follow-up. Underlining the importance of histologic examination of the swelling by intraoperative biopsy, the authors propose a diagnostic and therapeutic protocol.     

Evaluation of the temperature of different refrigerant sprays used as a pulpal test

The temperature of different refrigerant sprays (Endo‐Ice, Endo‐Frost, Coolermatic and Sprayon Contact and Tuner Cleaner) used as pulpal tests were evaluated in vitro. A thermocouple placed inside the pulp chamber of a maxillary central incisor was used to register the temperature changes when the refrigerant sprays were applied with a cotton swab, for 10 s. Results indicate that Endo‐Ice and Endo‐Frost presented the lowest temperatures among the refrigerant sprays tested. Temperatures measured inside the pulp chamber, however, were statistically similar in all groups.     

EVALUATION OF THE EFFECTS OF PROCESSING DELAYS AND PROTECTIVE PLASTIC CASES ON IMAGE QUALITY OF A PHOTOSTIMULABLE PHOSPHOR PLATE SYSTEM

This ex vivo study evaluated the quality of digital radiographic images obtained with the photostimulable phosphor plate system (Digora) according to the processing delay and maintenance of optical plates in either opaque (supplied with the system) or transparent protective plastic cases during this period. Five radiographs were obtained from the mandibular molar region of a dry human mandible using optical plates. These plates were placed in the protective plastic cases before obtaining the radiographs and were processed immediately or after processing delays of 5, 60 and 120 min, when the case was removed. The results revealed a reduction in image quality when processing was delay 120 min compared to the other times. The opaque case provided better protection to the sensor than the transparent case. In conclusion, a 120-min processing delay for the Digora system caused a reduction in image quality, yet without interfering with the quality of diagnosis. The opaque case supplied by the system''s manufacturer provided better protection to the optical plate than the transparent case.