Peter Ottl

TEMPERATURE RESPONSE IN THE PULPAL CHAMBER DURING ULTRAHIGH-SPEED TOOTH PREPARATION WITH DIAMOND BURS OF DIFFERENT GRIT

STATEMENT OF PROBLEM Ultrahigh-speed tooth preparation can traumatize the hard dental tissues and the dental pulp. PURPOSE This in vitro study examined the relationship between different grits of diamond burs on the temperature response within a pulpal chamber during tooth preparation with a turbine. MATERIAL AND METHODS Newly extracted, undamaged third molars were secured by a rapid-tensioning device mounted on an air-supported slide. NiCrNi thermocouples were inserted apically and used to determine the temperature within a pulpal chamber. The grinding tests used cylindrical fine, coarse, and ultracoarse diamond burs. RESULTS The maximal temperature elevation within the pulp was 3.2 degrees C, and the most pronounced rise in temperature occurred with ultracoarse burs. Temperature increases in the pulpal chambers and grinding times or temperatures of the cooling water were approximately proportional. Residual dentinal thickness was inversely proportional to temperature elevation within the pulpal chamber. CONCLUSIONS This study demonstrated that coarse diamond burs resulted in more pronounced temperature increases within the pulpal chamber during tooth preparation. In addition, the benefit of short intervals between grinding steps and a cooling water temperature between 30 degrees C and 32 degrees C was confirmed. A cooling temperature of 38 degrees C to 43 degrees C did not afford actual cooling.

Retrospective Study on the Evaluation of the TMJ by MRI Using a Newly Developed Standardized Evaluation Form

Abstract The objectives of this retrospective study were to systematically assess the temporomandibular joint (TMJ) using a newly developed standardized evaluation form with 16 parameters based on MRI diagnostics and to verify the reliability of the MRI diagnoses. One hundred fifty-four (154) TMJs of 77 patients with arthrogenic complaints were evaluated using MRI on two planes (parasagittal, paracoronal), in both closed-mouth and open-mouth positions. The sequences used were intermediary FLASH and spin echo sequences using T1 or T2 weighting with fat suppression. Examination of the reliability of the MRI evaluations of three independent observers evaluating 60 randomly selected TMJ from among the overall sample using the new evaluation form yielded an average Pearson contingency coefficient of between 0.64 and 0.70 with regard to the 16 parameters studied. In the evaluation of the 77 left (L) and 77 right (R) joints, the biplanar morphology of the disk was the most frequent with 24.7% (L) and 32.5% (R). In paracoronal projection, medial displacement of the disk was seen in 7.9 % (L, R) of the cases and lateral displacement in 6.4% (L) and 3.2% (R). The use of the new evaluation form, in combination with MRI of the TMJ, demonstrated a substantial reliability of the diagnoses. In TMD patients, the biconcave disk shape cannot be considered the sole normal, standard situation. The presence of lateral and medial disk displacement should be given more diagnostic consideration.