TOOTH SURFACE AND PULP CHAMBER TEMPERATURES DEVELOPED DURING ELECTROTHERMAL BONDING

The rationale of electrothermal bonding is based on the premise that w hen an electric current is passed across the beaks of tweezers holding a stainless steel orthodontic bracket, heat will be generated by virt ue of the electrical resistance of the steel bracket. This study was c arried out to evaluate the temperatures generated on the tooth surface at the bracket/tooth interface and within the pulp chamber during ele ctrothermal bonding. Temperatures were recorded with 5 and 7.5 A curre nt levels applied as al second pulse with time intervals between pulse s of 1, 2, 3, and 4 seconds. The data showed that after three pulses w ith a 5 A current, the temperature on the tooth surface ranged between 43.3 degrees C (4 second intervals) to 53.6 degrees C (1 second inter vals). By using a 7.5 A current, the temperature ranged from 77.5 degr ees C (4 second intervals) to 85.9 degrees C (1 second intervals). The pulp chamber temperatures were evaluated in vitro for a mandibular in cisor, the maxillary central and lateral incisors, a canine, a premola r, and a molar. The pulp chamber temperature of a mandibular incisor r esponded most, whereas that of premolars and molars responded least to temperature changes on the labial surface. The increase in mandibular incisor pulp chamber temperature after three pulses was 2.1 degrees C for 5 A and 2.8 degrees C for 7.5 A current while for a premolar the increase ranged from 0.9 degrees C to 1.6 degrees C. On the basis of c urrent evidence the increase in pulp chamber temperatures during elect rothermal bonding may be considered to be clinically safe.