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Biomedical subjects

E Mizrahi

Publications and source records attributed to E Mizrahi.

At least 19 recordsLinked to original sources
PubMed1998

Electrothermal bonding: shear bond strength of orthodontic brackets after two weeks.

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.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1996

Tooth surface and pulp chamber temperatures developed during electrothermal bonding.

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 degrees C (4 second intervals) to 53.6 degrees C (1 second intervals). By using a 7.5 A current, the temperature ranged from 77.5 degrees C (4 second intervals) to 85.9 degrees 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 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 degree C to 1.6 degrees C. On the basis of current evidence the increase in pulp chamber temperatures during electrothermal bonding may be considered to be clinically safe.

Bicuspid↗
PubMed1995

Shear bond strength of orthodontic brackets treated with Sebond.

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 degrees 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).

Analysis of Variance↗
PubMed1991

The effects of ion implantation on the beaks of orthodontic pliers.

The surface of stainless steel may be hardened by bombarding the material with a stream of nitrogen ions generated by a nuclear accelerator. In the present study this technique was used to determine the hardening effect of ion implantation on the beaks of stainless steel orthodontic pliers. Ten orthodontic pliers (Dentarum 003 094) were divided into two equal groups, designated control and experimental. The beaks of the experimental pliers were subjected to ion implantation, after which the tips of the beaks of all the pliers were stressed in an apparatus attached to an Instron testing machine. A cyclical load of 500 N was applied to the handles of the pliers, while a 0.9 mm (0.036 inch) round, stainless steel wire was held between the tips of the beaks. The effect of the stress was assessed by measurement with a traveling microscope of the gap produced between the tips of the beaks. Measurements were taken before loading and after 20, 40, 60, and 80 cycles. Statistical analysis of variance and the two-sample t tests indicated that there was a significant increase in the size of the gap as the pliers were stressed from 0 to 80 cycles (p less than 0.001). Furthermore, the mean gap was significantly greater in the control group than in the experimental group (p less than 0.001). This study suggests that ion implantation increases the hardness of the tips of the beaks of orthodontic pliers.

Analysis of Variance↗
PubMed1988

Glass ionomer cements in orthodontics--an update.

Because conventional bands continue to be used in clinical orthodontics, it is essential to evaluate new dental cements to establish their suitability as a cementing medium for orthodontic bands. This study was undertaken to determine the failure rate of bands cemented with a glass ionomer cement to premolar and molar teeth. The sample consisted of 100 consecutively completed cases. Stainless steel bands were cemented to premolar and molar teeth (799) with a glass ionomer cement (Ketac-Cem). The failure rate for the bands was 1.9%. This is significantly lower than the 5.1% recorded for bands cemented with a polycarboxylate cement reported in a previous study.

Child↗
PubMed1987

Head holder for panoramic dental radiography.

A radiolucent head holder for the Pancentric Panorex dental x-ray machine is constructed and evaluated. Features include a wooden pointer to orient the head in the midsagittal plane, movable components adjustable into a number of fixed positions and a spirit level on an ear rod fitting.

Equipment Design↗
PubMed1983

Surface distribution of enamel opacities following orthodontic treatment.

A cross-sectional study was carried out to determine the prevalence and severity of enamel opacities occurring on different surfaces of the dentition as well as the distribution of these lesions on individual teeth following orthodontic treatment. The sample consisted of 527 patients examined prior to and 269 other patients examined after completion of multibanded orthodontic treatment. The results showed that following orthodontic treatment there was a significant increase in the prevalence of enamel opacities on the vestibular and lingual surfaces of the dentition. The increase was significantly greater on the cervical and middle thirds of the crown. Among individual teeth, there was a statistically significant increase in the prevalence and severity of enamel opacities on the maxillary and mandibular first molars, the maxillary lateral incisors, and the mandibular lateral incisors and canines. The increase was greatest on the cervical and middle thirds of the vestibular surface of these teeth.

Adolescent↗
PubMed1982

Enamel demineralization following orthodontic treatment.

A cross-sectional study was carried out to determine the prevalence and severity of enamel opacities in patients before and after orthodontic treatment. The sample consisted of 527 patients examined prior to and 269 patients examined after completion of multibanded orthodontic treatment. The results showed that there was a significant increase in both the prevalence (before, 72.3 per cent; after, 84.0 per cent) and severity (Opacity Index: before, 0.125; after, 0.200) following completion of orthodontic treatment. Male patients experienced a significantly higher increase in the severity of enamel opacities following orthodontic treatment. There was no significant sex differential in the prevalence of enamel opacities either before or after orthodontic treatment. This study showed that orthodontic treatment with multibanded appliances contributed to the development of new areas of enamel demineralization and to an increase in the severity of enamel opacities as measured by the Opacity Index.

Adolescent↗
PubMed1982

Success and failure of banding and bonding. A clinical study.

A clinical study on the failure rate of 882 bands and 1194 directly bonded brackets placed on the teeth of 100 consecutively completed orthodontic patients treated with the Begg light wire technique showed an overall adhesion failure rate of 4.7%. This was significantly lower than the 7% recorded in a comparable study by Mizrahi in 1979 using only bands. The reduction was due primarily to a much lower failure rate of directly bonded brackets compared to bands on the maxillary cuspids and incisors. These results indicate that the lowest attachment failure rate during orthodontic treatment can be achieved by using bands on molars and bicuspids, directly bonded brackets on maxillary cuspids and incisors, and either on lower anterior teeth.

Adhesiveness↗
PubMed1981

Effect of surface contamination on band retention.

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 degrees 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 less than 0.01). Only the presence of dry saliva reduced band retention when polycarboxylate (P:L 1:1) was used (P less than 0.05).

Acrylic Resins↗
PubMed1979

The recementation of orthodontic bands using different cements.

A clinical study on band failure rate was carried out on 5949 bands cemented to the teeth of 293 patients drawn from three orthodontic practices. The failure rate ranged from a minimum of 7% in a sample from a practice where bands were cemented with Durelon cement (Group 2) to a maximum of 19% in a sample from a practice where bands were cemented with oxyphosphate cements (Group 3). Comparison between the results of the two controlled prospective studies from one practice (Groups 1 and 2) indicated that the use of a commercially available polycarboxylate cement (Durelon) resulted in a lower failure rate than that experienced with an experimental formulation of polycarboxylate cement. The teeth on which cemented bands failed most frequently were the maxillary central incisors. Comparison of the band failure rates between different practices (Groups 2, 3 and 4) showed that patients in Groups 3 and 4 experienced a higher band failure rate than patients in Group 2, due possibly to different types of bands, cements, and cementing procedures of the different operators.

Adolescent↗