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Previous studies have shown that due to poor adhesion between bonding resins and stainless steel orthodontic brackets, this interface remains a weak link in clinical orthodontic practice. A paste-like substance, Sebond®, has been developed in order to strengthen the weak link between metal and resin. The present study was carried out to determine the effect on the shear bond strength, of pretreating the bracket base with Sebond®. Two composite resins, Concise® Orthodontic Bonding System and Nimetic-Grip® were tested, using 40 orthodontic brackets for each resin; 20 brackets were pretreated with Sebond® and the remaining 20 acted as controls. Of the Sebond® brackets 10 were sandblasted prior to Sebond® application. The bonded brackets were stored in water at 37°C for 14 days after which they were tested to failure in the shear mode. Analysis of the results, using a general linear models analysis, showed that pretreating the brackets with Sebond® significantly reduced shear bond strength (P<0.001).

Anterior open bite malocclusion is reviewed under the headings of aetiology, morphology and treatment. The aetiology is discussed within the classification originally described by Dockrell in 1952. The morphological differences between skeletal and dental open bite together with the extra oral, intra oral, and cephalometric characteristics are described. Recognition is given to the recent developments in maxillo facial surgery and the importance of a combined surgical and orthodontic approach to the treatment of skeletal open bite. The merits of the palatal crib either on a fixed or removable appliance to break a thumb sucking habit are discussed in relation to the dental open bite. The relationship of post treatment stability to the adequate removal or modification of the aetiological factor is stressed.

In this study 1,976 bands were cemented onto the teeth of 102 patients. The mean duration of active treatment for a case was 702 (± 182) days, during which time 419 bands, i.e. 21·2 per cent were recemented. Bands which required most frequent recementing were those affixed to the upper central incisor teeth. Of the 102 bands cemented on the upper central incisors 28·4 per cent remained intact, while 71·6 per cent required recementing. The possible causes for the high incidence of recementation of the incisor bands are discussed. The performance of the direct attachment technique in relation to the conventional orthodontic band is reviewed in the light of the data presented in this survey.

Electrothermal bonding is based on acceleration of the setting reaction of a bonding: resin by the selective application of heat to the orthodontic bracket through the passage of a low voltage electric current. The purpose of this study was to compare the shear bond strength of nine resins comprising chemically-cured, light-cured, and glass ionomer types, 14 days after electrothermal and conventional bonding. Mean shear and bond strengths ranged from a low of 7.4 MPa for Sequence (electrothermally bonded) to a high of 15.4 MPa Concise (control). There was no statistically significant difference between the electrothermal and conventional bonding methods. All the resins produced bond strengths adequate for clinical orthodontics at 14 days.

Laboratory investigations on the retention of orthodontic bands have been concerned with testing the retentive strength of different cements. This study reported here was designed to evaluate the effect of tooth-surface contamination on band retention. Zinc phosphate, silicophosphate, and polycarboxylate (powder:liquid ratio 1.5:1 and 1:1) cements were each tested on different groups of ten teeth. Preformed bands were selected, prepared, and cemented under controlled conditions. Specially designed jigs were used for cementing and for testing. For each cement, the tooth surfaces were pretreated prior to cementing as follows: (1) cleaned with pumice, (2) covered with wet saliva, (3) covered with saliva which was allowed to dry, and (4) covered with liquid paraffin. All specimens were stored in water at 37 °C. for 1 week prior to testing. Retention values were established by determining the tensile load required to dislodge the band divided by the surface area of the band. The retention of bands cemented with zinc phosphate and silicophosphate cements was unaffected by contamination of the enamel. The presence of dry saliva and of liquid paraffin significantly reduced the retention of bands cemented with polycarboxylate (P:L 1.5:1) (P < 0.01). Only the presence of dry saliva reduced band retention when polycarboxylate (P:L 1:1) was used (P < 0.05).

The rationale of electrothermal bonding is based on the premise that when an electric current is passed across the beaks of tweezers holding a stainless steel orthodontic bracket, heat will be generated by virtue of the electrical resistance of the steel bracket. This study was carried out to evaluate the temperatures generated on the tooth surface at the bracket/tooth interface and within the pulp chamber during electrothermal bonding. Temperatures were recorded with 5 and 7.5 A current levels applied as a 1 second pulse with time intervals between pulses of 1, 2, 3, and 4 seconds. The data showed that after three pulses with a 5 A current, the temperature on the tooth surface ranged between 43.3^o C (4 second intervals) to 53.6^o C (1 second intervals). By using a 7.5 A current, the temperature ranged from 77.5^o C (4 second intervals) to 85.9^o C (1 second intervals). The pulp chamber temperatures were evaluated in vitro for a mandibular incisor, the maxillary central and lateral incisors, a canine, a premolar, and a molar. The pulp chamber temperature of a mandibular incisor responded 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^o C for 5 A and 2.8^o C for 7.5 A current while for a premolar the increase ranged from 0.9^o C to 1.6^o C. On the basis of current evidence the increase in pulp chamber temperatures during electrothermal bonding may be considered to be clinically safe. (Am J Orthod Dentofac Orthop 1996;109:506-14.)