Biomedical subjects

S E Bishara

Publications and source records attributed to S E Bishara.

At least 19 recordsLinked to original sources

PubMed1992

Laser-aided debonding of orthodontic ceramic brackets.

The removal of ceramic brackets from the enamel surface by means of laser heating was investigated with the use of CO2 and YAG lasers. The two bracket types investigated were polycrystalline alumina and monocrystalline alumina. The average torque force necessary to break the adhesive between the polycrystalline ceramic brackets and the tooth was lowered by a factor of 25 when the brackets were illuminated with a CO2 laser beam of 14 watts for 2 seconds. All polycrystalline brackets debonded with the CO2 laser resulted in a complete bracket detachment without bracket failure. The average torque force needed to debond monocrystalline brackets was lowered by a factor of 5.2 when illuminated with a laser setting of 7 watts. Monocrystalline brackets cracked along the bracket slot in 2 of 10 cases. Debracketing without laser heating resulted in a slightly higher incidence of bracket failure (12 of 50). Nevertheless, no visible damage to the enamel surface was observed. Advantages of the laser-aided bracket-removal techniques include the following: The heat produced is localized and controlled; the debracketing tool is essentially "cold"; and the method can be used for removal of various types of ceramic brackets, regardless of their design.

Acrylic Resins↗

PubMed1992

Impacted maxillary canines: a review.

An overview of the incidence and sequelae, as well as the surgical, periodontal, and orthodontic considerations in the management, of impacted canines is presented. The clinician needs to be familiar with the differences in the surgical management of the labially and palatally impacted canines, the best method of attachment to the canine for orthodontic force application, the advantages of one-arch versus two-arch treatment, and the implications of canine extraction. The various factors that influence all these decisions are discussed.

Adolescent↗

PubMed1992

Comparisons of postsurgical stability of the LeFort I maxillary impaction and maxillary advancement.

The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. Descriptive statistics for the absolute and the relative changes of the various linear and angular parameters were calculated for the different stages. The analysis of variance general linear models procedure was used to compare the impaction group (n = 23) with the advancement group (n = 8). The findings indicated that the two groups could be studied independent of age, sex, surgeon, the presence of pretreatment open bite, and the length of the postsurgical fixation. The findings further indicated the presence of significant differences in the postsurgical changes between the maxillary impaction and the maxillary advancement groups. As an example, during fixation, the maxilla moved superiorly more at point A in the advancement group (mean = 1.89 mm) than in the impaction group (mean = 0.67 mm). The upper incisor movements showed a similar pattern, moving more superiorly for the advancement group (mean = 2.30 mm) than for the impaction group (mean = 0.96 mm). Therefore care should be taken to avoid "burying" the incisors beneath the lip in patients undergoing maxillary advancement, who have minimal exposure of the maxillary incisors before surgery.

Adolescent↗

PubMed1992

Patient discomfort levels at the time of debonding: a pilot study.

Several investigations have evaluated the degree of discomfort that patients experience during orthodontic treatment, but most of the research centered on tactile sensory (touch) threshold, reaction to spacers used to separate the teeth or reaction to the initial leveling wires, and the periodic adjustment of the appliances. The purpose of this investigation is to determine the discomfort threshold for patients undergoing orthodontic treatment at the time immediately before appliance removal. Such information will be useful in determining the force levels that patients can tolerate during debonding. From the findings in this study the following can be concluded: (1) The threshold of patient discomfort, at the time of debonding, is significantly influenced by two factors: the mobility of the tooth and the direction of force application. Sex and tooth type differences also influence the discomfort threshold but to a lesser degree. (2) At the time of debonding, patients can withstand intrusive forces significantly more than forces applied in a mesial, distal, facial, lingual, or an extrusive direction. The clinical implications of these findings are discussed.

Analysis of Variance↗

PubMed1992

Craniofacial development in myotonic dystrophy.

Anthropometric, cephalometric, and dental data from 23 subjects (12 males and 11 females) afflicted with myotonic dystrophy were compared to similar data from normal subjects who participated in the Iowa Facial Growth Study. A two by two analysis of variance showed that myotonic subjects differed from normal subjects in headlength, head breadth, cephalic index, bizygomatic face width, nosebreadth, maxillary arch widths, palatal depth, anterior and posterior face heights, cranial base lengths, cranial base angles, and other cephalometric measures. Sex differences were observed for many of the variables. It is hoped that these findings will assist clinicians who treat patients having this disorder.

Adolescent↗

PubMed1991

Profiling providers of orthodontic services in general dental practice.

This study was designed to ascertain whether general practitioners who provide some orthodontic treatment to a relatively large proportion of their patients tend to limit themselves to the treatment of simple cases while they continue to refer more difficult cases or whether a high volume of orthodontic treatment is linked to an expanded scope of treatment and fewer referrals. Data pertaining to volume, scope, and other correlates of orthodontic services in general practice were obtained through a survey of dentists currently in general practice in Iowa. Of 1159 questionnaires mailed out, 728 (62.8%) were returned. To determine how the values of recorded variables differ among the providers of high and low volumes of orthodontic services and to determine whether these differences are significant, chi 2 tests of independence were calculated. The results obtained were used to generate descriptive measures of the profiles of providers of a high volume of orthodontic services in general practice. These profiles indicated that providers of a high volume of orthodontic treatment (1) performed the same amount of limited orthodontic treatment as providers of a low volume of orthodontic treatment; (2) performed significantly more major orthodontic treatment; (3) used significantly more fixed appliances, functional appliances, and headgears, but not removable appliances; (4) took significantly more hours of continuing education in orthodontics; and (5) referred significantly fewer patients to orthodontic specialists. In view of the projected increase in the amount of orthodontics performed in general practice, these findings suggest that, in the future, relatively more major orthodontic treatment is likely to be provided by general practitioners.

Education, Dental, Continuing↗

PubMed1991

Evaluation of fluoride release from an orthodontic bonding system.

Decalcification around brackets is sometimes observed after orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed in an attempt to reduce the frequency and severity of decalcification. This study evaluated, in vitro, a light-activated, fluoride-releasing composite resin adhesive, FluorEver OBA. The findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. A mean of 2.6 ppm was released on day 1, decreasing to a mean of 0.42 ppm by day 2 and to 0.04 ppm by day 43. The clinical implications of these findings are discussed.

Acrylic Resins↗

PubMed1990

Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Part I. Background and methods.

Techniques for removing metal orthodontic attachments are, for the most part, not as effective with ceramic brackets because the properties of ceramic brackets differ greatly from those of the conventional metal orthodontic brackets. Currently available ceramic brackets are composed of aluminum oxide crystals in either a polycrystalline or monocrystalline form that has a low fracture toughness compared with that of stainless steel. Metal brackets will deform 20% under stress before fracturing, whereas ceramic brackets will deform less than 1% before failing. The purpose of this study was (1) to evaluate the debonding characteristics of three different types of ceramic brackets when removed by techniques recommended by the manufacturers; (2) to evaluate and compare the conventional, ultrasonic, and electrothermal bracket-removal techniques, and (3) to evaluate and compare the mean enamel loss from removal by high-speed bur, by slow-speed bur, and by the ultrasonic method. In the first phase of the investigation, 140 teeth (70 maxillary central incisors and 70 third molars) were bonded with one of three types of ceramic brackets. Three different debonding methods were tested--(1) the conventional method recommended by the manufacturer (either pliers or wrench), (2) an ultrasonic method that employed specially designed tips, and (3) an electrothermal method involving an apparatus that transmits heat to the bracket. In each of the test groups, five variables were evaluated during and after bracket removal: (1) the incidence of bracket failure, (2) the amount of adhesive remaining after bracket removal, (3) the site of bond failure, (4) the debonding time for each technique, and (5) enamel damage resulting from bracket removal.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗

PubMed1990

Cephalometric comparisons of dentofacial parameters between Egyptian and North American adolescents.

The purpose of this study was to develop cephalometric standards for the Egyptian adolescent boys and girls and to compare them to a matched Iowa adolescent sample. The Egyptian sample consisted of 39 boys and 51 girls with a mean age of 12.5 years. The Iowa sample consisted of 33 boys and 22 girls with a mean age of 13.0 years. Basic descriptive statistics were calculated for 35 cephalometric dentofacial parameters. The general linear models procedure, analysis of variance, was used for the comparisons between the groups. F values were calculated for the overall group comparisons, and the statistical significance was predetermined at the 0.05 level of confidence. Comparisons between the boys and girls in both populations indicated that the boys were larger in the linear dimensions of the cranial base and face heights than the girls. Comparisons between the Egyptians and the Iowans indicated that Egyptian boys have a tendency toward bimaxillary dental protrusion and a decreased overbite as compared with Iowa boys. Egyptian girls have a relatively more convex profile and a tendency toward mandibular dental protrusion. When the overall findings are evaluated, it could be concluded that, in general, there is a great similarity in the overall facial morphology between the Egyptian and Iowa populations.

Adolescent↗

PubMed1990

Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Part II. Findings and clinical implications.

A series of tests of three different debonding techniques applied to three different types of ceramic brackets revealed the following: (1) The incidence of bracket failure during debonding was significantly greater with conventional debonding recommended by the manufacturer (10-35%), as compared with the incidence associated with either the ultrasonic or the electrothermal methods (0%). (2) Bond failure at the bracket-adhesive interface occurred with significantly greater frequency for the Starfire brackets when debonding was performed with the electrothermal instrument and with significantly less frequency when the debonding pliers were used. Combination bond failures, in which part of the adhesive stayed on the enamel and part stayed on the bracket, occurred with significantly greater frequency when Transcend and Starfire brackets were debonded with debonding wrenches than when other methods were used. Combination-bond failures occurred with significantly less frequency when the brackets were removed with ultrasonic tips or with the electrothermal instrument. (3) The debonding times for the ultrasonic method were significantly greater than the times for either the conventional or the electrothermal methods. There were no significant differences among the debonding times for the three bracket types. There were no significant differences in the debonding times between the electrothermal method (means = 3.0 seconds) and the conventional bracket-removal method (means = 1.0 seconds). (4) Enamel loss as a result of adhesive removal was not significantly different among the three adhesive-removal techniques tested. Post-treatment roughness of the enamel surface was greater for the high-speed adhesive-removal technique than for either the low-speed or ultrasonic adhesive-removal methods.

Ceramics↗

PubMed1990

In vitro evaluation of a fluoride-releasing orthodontic resin.

Decalcification around brackets is sometimes observed following orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed and used for reduction of the frequency and severity of decalcification. This study evaluated a light-activated, fluoride-releasing resin composite adhesive, FluorEver OBA. Our findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. However, the adhesive had significantly lower tensile bond strengths than a conventional composite cement. Microhardness testing indicated that the resin underneath metal orthodontic brackets was not thoroughly polymerized, which may have contributed to cohesive failures of the resin composite. Despite its lower tensile bond strength, FluorEver OBA may be indicated for cases where decalcification is expected.

Analysis of Variance↗

PubMed1989

Functional appliances: a review.

The purpose of this review was to evaluate the scientific studies that describe the effects of functional appliances on the dentofacial structures in the treatment of Class II malocclusions. The review is limited to two appliances: the activator and the functional regulator.

Activator Appliances↗

PubMed1989

The effect on the bonding strength of orthodontic brackets of fluoride application after etching.

Etching of the enamel surface in preparation for bonding orthodontic brackets is an essential part of the bonding procedure. In an attempt to alleviate concerns regarding the decalcified enamel, it has been suggested that a fluoride solution be applied to the etched surface before placing the bonding material. The purpose of this study is to test the tensile bonding strength of the composite to fluoride-treated enamel. Four groups of 10 teeth each were compared. Group I received a solution of 2% NaF in 0.1 M H3PO4 after etching; groups II and III received a solution of 4% NaF in 0.1 M H3PO4 after etching; and group IV served as the control--that is, no fluoride solution was applied to the enamel after etching. The orthodontic brackets were bonded to the teeth in the four groups with the same procedure. The 40 teeth were then placed in synthetic saliva. Groups I, II, and IV were debonded after 24 hours; group III was debonded after 7 days. The Instron Universal testing machine was used to determine the tensile bonding strength of the adhesive to the teeth. The basic statistics for the tensile strength were calculated and the analysis of variance, general linear models procedure, was used to determine whether significant differences were present among the groups. The findings indicate that the application of either 2% or 4% NaF in a 0.1 M H3PO4 solution does not significantly influence the tensile bonding strength of the adhesive material to the enamel surface.

Acid Etching, Dental↗

PubMed1989

Changes in the maxillary and mandibular tooth size-arch length relationship from early adolescence to early adulthood. A longitudinal study.

The purpose of this study was to determine the association between the changes in maxillary and mandibular tooth size-arch length discrepancies (TSALD) and various dentofacial variables for 18 male and 14 female subjects with normal occlusion. All subjects were participants in the Iowa Longitudinal Growth Study and records were evaluated at two stages of dental development: stage I, when the permanent second molars initially erupted into occlusion (X age = 13.3 years); and stage II, at early adulthood (X age = 26.0 years). The following sets of variables were evaluated: mesiodistal crown diameters of single and groups of permanent teeth, dental arch widths and lengths, curve of Spee, maxillary and mandibular anterior and total crowding or spacing, anterior tooth rotations, and various cephalometric dentofacial parameters. Student's t test were used to compare subjects with the most and least changes. Regression analyses also were used to assess the relationships between these parameters and the changes in the maxillary and mandibular tooth size-arch length relationship. The most consistent finding from the t test comparisons is the significantly greater reduction in the available arch length in the group with the most TSALD at early adulthood. No other variables were found to be consistently different in the comparisons between the two groups. The results of the regression analysis indicated that a number of dentofacial variables are associated with the changes in the maxillary and mandibular TSALD--for example, the mesiodistal diameter of different teeth and the changes in anterior and posterior facial heights. The clinical implications of the present findings are discussed.

Adolescent↗

PubMed1989

Comparisons of mesiodistal and buccolingual crown dimensions of the permanent teeth in three populations from Egypt, Mexico, and the United States.

The purpose of this study is to examine the mesiodistal and buccolingual crown dimensions in three populations--57 subjects (35 boys and 22 girls) from Iowa City, Iowa; 54 subjects (30 boys and 24 girls) from Alexandria, Egypt; and 60 subjects (26 boys and 34 girls) from Chihuahua, Mexico. All subjects had normal Class I occlusion, with no history of orthodontic treatment. Comparisons of single teeth as well as sums of groups of teeth were performed between boys and girls within and between the two populations. The analysis of variance general linear models procedure was used for statistical comparisons. The findings from this investigation indicated that (1) differences between antimeres are of small magnitude and of no statistical significance; (2) all populations have significant differences in tooth dimensions between the sexes with boys having larger canines and first molars; (3) there is greater variation in the buccolingual than in the mesiodistal dimensions among the three populations; (4) there is a greater similarity in tooth dimensions among the boys from the three populations than among the girls, but the magnitude of these differences is considered to be of little clinical significance; and (5) standards for the buccolingual diameters were developed for the three populations. As a result, it was concluded that prediction equations used for space analysis in the mixed dentition to determine tooth size-arch length discrepancies in the Iowa population can also be used for persons from Egypt and from the northern part of the Mexican Republic, with some suggested modifications.

Adolescent↗

PubMed1989

Compensatory developmental interactions in the size of permanent teeth in three contemporary populations.

The purpose of this study was to determine whether developmental interactions exist between the mesio-distal diameters of the first and second developing teeth in each of two morphologic tooth classes. The interactions were evaluated for the maxillary and mandibular incisors and premolars. Measurements were obtained on the dentitions of three contemporary samples from Iowa, Egypt and Northern Mexico. The findings from this study indicate that developmental interactions are present in the mesio-distal diameters between the first and second developing teeth within the two morphologic tooth classes evaluated, namely incisors and premolars. In other words, the mesiodistal diameter of the first developing tooth significantly influences the size of the second developing tooth within the same morphologic class.

Adolescent↗

PubMed1988

Stability of the LeFort I one-piece maxillary osteotomy.

The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after one-piece maxillary impaction and wire fixation. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and postfixation. All subjects had characteristics of excessive vertical maxillary growth. Descriptive statistics for the absolute and relative changes of the various linear and angular parameters were calculated for the different stages. The analysis of variance general linear models procedure was used to compare the repeated measures of the total sample. From the present findings, it was concluded that (1) after the initial surgical superior repositioning, the maxilla continued to move superiorly and most of the upward movement occurred during fixation, (2) the anterior part of the maxilla moved superiorly more than twice that of the posterior part of the maxilla, (3) maxillary superior dental movement exceeded maxillary superior skeletal movement, and (4) maxillary horizontal skeletal movement exceeded maxillary horizontal dental movement. The clinical significance of the findings are discussed.

Adolescent↗

PubMed1988

The effect of temperature change of composites on the bonding strength of orthodontic brackets.

In an orthodontic office, the bonding system is subjected to certain temperature variation that ranges between 5 degrees C (refrigeration) and 25 degrees C (room temperature). The purpose of this study was to determine whether such temperature variation has any effects on tensile and shear bond strengths and the type of bracket failure. Two groups of 20 teeth each were compared; in one group the temperature of the composite during bonding was 5 degrees C and in the other group the temperature was 25 degrees C. Student's t test was used to determine whether significant differences were present between the two groups. The results of the present findings indicate that the variation in the temperature of the composite, within the limits tested, does not seem to adversely affect the bonding strength of the bracket to the enamel. In addition there was no difference between the two groups in the type of interface bond failure among the enamel, composite, and bracket.

Acrylic Resins↗