PubMed Health⌕ Search

Biomedical subjects

Samir E Bishara

Publications and source records attributed to Samir E Bishara.

34 records · Page 2Linked to original sources
PubMed2004

Factors that influence the proclination or retroclination of the lower incisors in children with prolonged thumb-sucking habits.

In some children with a prolonged finger-sucking habit, the lower incisors are retroclined, however, proclination of the lower incisors has been frequently observed. The purpose of this study was to determine how such differences develop in the child with a digit-sucking habit. Children with a prolonged thumb-sucking habit and proclination of the lower incisors (Ili/ML > 97 degrees) were cephalometrically and clinically compared to persistent thumb-suckers with retroclined lower incisors (Ili/ML < 89 degrees). In the group with retroclined lower incisors the angle between the thumb and the lower incisors was significantly smaller and the thickness of the lower lip significantly thinner than in the group with proclined incisors. A higher frequency of early loss of deciduous molars was also observed in the group with retroclined incisors. The tightness of the lower lip, early loss of deciduous molars and the angle between the teeth and the thumb are factors which have been identified to influence the inclination of the lower incisors in persistent digit suckers. The majority of children with prolonged thumb-sucking have proclined lower incisors rather than retroclined lower incisors.

Adolescent↗
PubMed2004

Effect of water storage on the shear bond strength of a cyanoacrylate adhesive: clinical implications.

AIM: To compare the effects of water storage on the shear bond strength of a cyanoacrylate adhesive system at three time intervals: (1) within 30 minutes after bonding the bracket to the tooth; (2) 24 hours from the time of bonding; and (3) after 30 days of storage in water at 37 degrees C. METHODS: Sixty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleansed and polished, then randomly separated into three groups: group 1, cyanoacrylate adhesive debonded within 30 minutes from initial bonding; group 2, cyanoacrylate adhesive debonded after 24 hours immersion in deionized water at 37 degrees C; group 3, cyanoacrylate adhesive debonded after 30 days immersion in deionized water at 37 degrees C. RESULTS: Analysis of variance (F = 11.94) comparing the experimental groups indicated the presence of significant differences between the three groups (P = .0001). The shear bond strengths were significantly greater in the two groups debonded after 30 minutes (mean = 5.8+/-2.4 MPa) and 24 hours (mean = 7.1+/-3.3 MPa) than the group debonded after 30 days of water storage (mean = 2.7+/-2.0 MPa). CONCLUSION: The present findings indicate that the cyanoacrylate adhesive has clinically adequate shear bond strengths at 30 minutes and 24 hours after initial bonding, but that the bond strength decreases by 50% within 30 days. The clinician needs to carefully take the overall properties of the adhesive into consideration.

Analysis of Variance↗
PubMed2003

Tooth size-arch length relationships in the deciduous dentition: a comparison between contemporary and historical samples.

In a recent study, it was reported that maxillary and mandibular arch lengths were significantly shorter in a sample of contemporary children in the deciduous dentition compared with a historical sample from about 50 years earlier. The purpose of this study was to describe secular changes that might have occurred in tooth sizes and tooth size-arch length relationships in the same cohorts of contemporary and historical North American white children in the deciduous dentition. The 2 samples were similar in terms of geographic location, racial and ethnic backgrounds, and socioeconomic status. Both samples were restricted to white children with a normal overjet (<4 mm) and a normal anteroposterior molar relationship, no anterior open bite, and no crossbite. In addition, subjects were excluded if any permanent teeth were erupted. Measurements of mesiodistal tooth sizes and arch lengths of maxillary and mandibular arches were made, and tooth size-arch length discrepancies (TSALD) were determined. The results indicated that tooth sizes were generally similar in the 2 cohorts but slightly larger in contemporary children. Crowding, as measured by TSALD, was found to be common in the mandibular arch for contemporary children in the deciduous dentition of both boys and girls. Moreover, crowding was much more common and severe in contemporary children compared with children in the historical cohort. Further research is needed to determine whether the increase in mandibular crowding in the deciduous dentition will continue to be observed in the mixed and permanent dentitions and to further establish these possible secular trends.

Cephalometry↗
PubMed2003

Evaluation of a new curing light on the shear bond strength of orthodontic brackets.

With the introduction of photosensitive (light-cured) restorative materials in dentistry, various methods were suggested to enhance their polymerization and to shorten the curing time including layering and the use of more powerful light-curing devices. The purpose of this study was to determine the effect of using a new light-curing apparatus that uses a light-emitting diode (LED) on the shear bond strength of an orthodontic adhesive. The new light-curing apparatus used in the study was UltraLume 2 (Ultradent USA, South Jordan, Utah) that has an 8-mm footprint and can simultaneously cure two orthodontic brackets. Forty teeth were etched with 37% phosphoric acid, washed and dried, and sealant applied, and then precoated brackets with the Transbond adhesive (APC II, 3M Unitek, Monrovia, Calif) were placed. The teeth were randomly divided into two groups according to the curing light used. In group I (control), 20 brackets were cured using an Ortholux (3M Unitek) halogen curing light for 20 seconds. In group II, 20 brackets were cured using the new LED light for 20 seconds. The findings indicated no significant (P = .343) differences in the shear bond strength between the Ortholux halogen light (5.1 +/- 2.5 MPa) and the UltraLume 2 LED light when the two groups were compared using Student's t-test (t = -0.961). In conclusion, the advantages of the new unit include the ability to cure two brackets at a time and a smaller light-emitting apparatus for the clinician to handle.

Acid Etching, Dental↗
PubMed2003

Rapid maxillary expansion and conductive hearing loss.

The purpose of this study was to evaluate the effects of rapid maxillary expansion (RME) on conductive hearing loss in 35 subjects (21 girls and 14 boys) with an average age of 14 years 6 months. All patients had maxillary constriction with a high palatal vault and a conductive hearing loss. Pure-tone audiometric records were used to determine the hearing levels at four time intervals, namely, before RME, after sufficient midpalatal suture opening was obtained (mean: 18 days), after the retention period (mean: six months), and a final set two years after the retention period. Records were evaluated by the same otolaryngologist. Analysis of variance was used to assess the changes in the hearing level and the air-bone gap. Descriptive statistics were calculated for each subject at each period. The results indicated that significant changes occurred in both the hearing levels and air-bone gaps in both timing and frequency after the active treatment period (P < .001). For most patients (74%), these improvements were maintained two years after active treatment.

Adolescent↗
PubMed2003

Effect of thermocycling on the shear bond strength of a cyanoacrylate orthodontic adhesive.

The purpose of this study was to evaluate the effects of thermocycling on the shear bond strength of a cyanoacrylate adhesive system, specifically 24 hours after bonding when the adhesive has achieved most of its bond strength and after thermocycling. Forty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned, polished, and randomly separated into 2 groups: group I, cyanoacrylate adhesive debonded after 24 hours immersion in deionized water at 37 degrees C; and group II, cyanoacrylate adhesive debonded after thermocycling at 5 degrees C and 55 degrees C. The results of the t test comparing the 2 groups (t = 6.84) indicated significant differences between them (P =.0001). The cyanoacrylate adhesive at 24 hours had significantly greater shear bond strength (macro x = 7.1 +/- 3.3 MPa) than after thermocycling 500 times between 5 degrees C and 55 degrees C (macro x = 1.5 +/- 1.4 MPa). The findings indicated that the cyanoacrylate adhesive tested has clinically adequate shear bond strength at 24 hours after initial bonding but loses about 80% of its strength after thermocycling. The clinician should consider all properties of the adhesive, including no need for a curing light, working time of 5 seconds before the adhesive starts to set, and the significant decrease in bond strength after thermocycling.

Cyanoacrylates↗
PubMed2003

The effect of blood contamination on the shear bond strength of orthodontic brackets with the use of a new self-etch primer.

The success of bonding brackets to enamel with resin bonding systems is negatively affected by contamination with oral fluids such as blood and saliva. The new self-etch primer systems combine conditioning and priming agents into a single application, making the procedure more cost-effective. The purpose of this study was to assess the effect of blood contamination on the shear bond strength of orthodontic brackets with a new self-etch primer. The brackets (precoated brackets APC II, 3M Unitek, Monrovia, Calif) were bonded to 52 extracted human molars according to 1 of 4 protocols. Group I: A self-etch acidic primer, Angel I (3M/ESPE, St. Paul, Minn), was placed on the enamel for 15 seconds, gently dried with air, and light cured for 10 seconds. Brackets were bonded and light cured for 20 seconds. Group II: The enamel surface was contaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. Angel I was applied on the contaminated surface; the brackets were then bonded and light cured as in group I. Group III: Angel I was applied as described in group I. The surface was then contaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. Precoated brackets were then bonded as in groups I and II. Group IV: The enamel surface was contaminated with human blood for 10 seconds and blown off with an air syringe for 5 seconds. The self-etch primer, Angel I, was applied as described earlier, and the surface was recontaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. The brackets were then bonded as in groups I, II, and III. The results of the analysis of variance (F = 13.31) indicated that the shear bond strengths of the 4 groups were significantly different (P =.001). Tukey HSD posterior tests indicated that the uncontaminated control group had a significantly stronger (mean = 6.0 +/- 3.5 megapascal [MPa]) shear bond strength than the groups that had blood contamination, regardless of whether this occurred before (mean = 2.7 +/- 2.4 MPa), after (mean = 1.1 +/- 0.6 MPa), or before and after (mean = 0.5 +/- 0.2 MPa) the application of the self-etch primer. Blood contamination at any stage of the bonding procedure results in a significant and drastic drop in the shear bond strength of orthodontic brackets.

Acid Etching, Dental↗
PubMed2002

Effect of a fluoride-releasing self-etch acidic primer on the shear bond strength of orthodontic brackets.

Conventional adhesive systems use three different agents--an enamel conditioner, a primer solution, and an adhesive resin--during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single application. Combining conditioning and priming saves time and should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to assess and compare the effects of self-etching primers, including a fluoride-releasing primer, on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human teeth according to one of four protocols. In group 1 (control), teeth were etched with 37% phosphoric acid; after the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In group 2, a self-etch acidic primer (3M ESPE, St Paul, Minn) was applied as suggested by the manufacturer, and the brackets were then bonded with Transbond XT as in the first group. In group 3, an experimental self-etch primer EXL #547 (3M ESPE) was applied to the teeth as suggested by the manufacturer, and the brackets were then bonded as in groups 1 and 2. In group 4, a fluoride-releasing self-etch primer, One-Up Bond F (J. Mortia, USA Inc. Irvine, Calif) that also has a novel dye-sensitized photo polymerization initiator system was applied as suggested by the manufacturer, and the brackets were then bonded as in the other groups. The present in vitro findings indicated that the shear bond strengths of the four groups were significantly different (P = .001). Duncan multiple range tests indicated that One-Up Bond F (mean +/- SD strength, 5.1+/-2.5 MPa) and Prompt L-Pop (strength, 7.1+/-4.4 MPa) had significantly lower shear bond strengths than both the EXL #547 self-etch primer (strength, 9.7+/-3.7 MPa) or the phosphoric acid etch and the conventional adhesive system (strength, 10.4+/-2.8 MPa).

Acid Etching, Dental↗
PubMed2002

Effects of modifying the adhesive composition on the bond strength of orthodontic brackets.

In an attempt to save chair time during bonding, metal brackets have been precoated with the adhesive material. Although the adhesive used on the precoated brackets is basically similar in composition to that used for bonding uncoated brackets, there are differences in the percentages of the various ingredients incorporated in the material. These changes are intended to enhance specific clinical properties. The purpose of this study was to determine whether modifications in the composition of the adhesives, used on precoated and uncoated metal brackets, affect their shear bond strengths during the first half hour after bonding. This is the time span when the initial arch wires are ligated. Sixty freshly extracted human molars were bonded with three different compositions of the same basic adhesive. The teeth were mounted in phenolic rings. An occlusogingival load was applied to the brackets producing a shear force at the bracket-tooth interface utilizing a Zwick Universal Test Machine. Analysis of variance was used to compare the three adhesives. Significance was predetermined at < or =.05 level of confidence. The present findings indicated that the shear bond strengths of the various modifications of the adhesive used on two different precoated metal brackets were not significantly different (F-ratio = .729 and P = .407) from those obtained with the conventional adhesive used on uncoated brackets. The mean values for the shear bond strengths of the two precoated brackets were: APC = 5.1+/-1.7 MPa and APC II = 4.9+/-2.1 MPa. The shear bond strength for the conventional adhesive used on the uncoated brackets was = 5.7+/-2.4 MPa. All bracket/adhesive combinations tested provided clinically acceptable shear bond forces within the first 30 minutes after initial bonding.

Acid Etching, Dental↗
PubMed2002

The effect of saliva contamination on shear bond strength of orthodontic brackets when using a self-etch primer.

The purpose of this study was to assess the effect of saliva contamination on the shear bond strength of orthodontic brackets, at various stages of the bonding procedure using a new self-etch primer. Brackets were bonded to 52 extracted human molars according to one of the following four protocols. Group I (uncontaminated control): A self-etch acidic primer, Angel I (3M/ESPE Minneapolis, Minn) was placed on the enamel for 15 seconds, gently dried with air, and light cured for 10 seconds. Precoated brackets APC II (3M Unitek, Monrovia, Calif) were then placed on the teeth and light cured for 20 seconds. Group II: The enamel surface was first contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The bonding procedure was then repeated as in group I. Group III: The self-etch primer was applied for 15 seconds, gently dried with air, and light cured for 10 seconds. The surface was then contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The precoated brackets were then bonded as in groups I and II. Group IV: The enamel surface was contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The self-etch primer was applied. The surface was then re-contaminated with human saliva for 10 seconds, blown off with an air-syringe for five seconds. The precoated brackets were then bonded as in groups I, II, and III. The results of the analysis of variance (F = 4.79) indicated that the shear bond strengths of the four groups were significantly different (P = .005). Tukey HSD tests indicated that contamination both before and after the application of the acid-etch primer resulted in a significantly lower (=1.7+/-1.4 MPa) shear bond strength than either the control group (=6.0+/-3.5 MPa) or the groups where contamination occurred either before (=4.8+/-3.3 MPa) or after (=4.8+/-3.3 MPa) the application of the primer. The new acid-etch primer can maintain adequate shear bond strength if contamination occurs either before or after the application of the primer. On the other hand, contamination both before and after the application of the primer significantly reduced the shear bond strength of orthodontic brackets.

Acid Etching, Dental↗
PubMed2002

Effect of time on the shear bond strength of cyanoacrylate and composite orthodontic adhesives.

The purpose of this study was to compare the effects of time on the shear bond strength of a cyanoacrylate system and a composite adhesive system (1) within half an hour after bonding the bracket to the tooth, and (2) after 24 hours from the time of bonding when the adhesive had achieved most of its bond strength. Eighty freshly extracted molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleansed, polished, and randomly separated into 4 groups: (I), cyanoacrylate adhesive debonded within one-half hour from initial bonding; (II), cyanoacrylate adhesive debonded after 24 hours immersion in deionized water at 37 degrees C; (III), composite adhesive debonded within one-half hour from initial bonding; (IV), composite adhesive debonded after 24 hours immersion in deionized water at 37 degrees C. The results of the analysis of variance comparing the 4 experimental groups (F = 12.68) indicated significant differences between them (P =.0001). The composite adhesive at 24 hours had significantly greater shear bond strength than did the other 3 groups. In general, the shear bond strengths were greater in the 2 groups debonded after 24 hours. This was true for both the cyanoacrylate ((-)x 7.1 +/- 3.3 megaPascals [MPa]) and the composite ((-)x 10.4 +/- 2.8 MPa) adhesives. On the other hand, the shear bond strength was significantly lower in the 2 groups debonded within one-half hour of their initial bonding. The bond strength of the cyanoacrylate adhesive ((-)x 5.8 +/- 2.4 MPa) was not significantly different from that of the composite ((-)x 5.2 +/- 2.9 MPa) adhesive. Our findings indicated that the cyanoacrylate and the composite adhesives tested have clinically adequate shear bond strengths at half an hour and at 24 hours after initial bonding. The clinician needs to consider the properties of each adhesive: eg, the need to use a curing light and the ability to have more working time with the composite adhesive versus no light but only a 5-second working time before the cyanoacrylate adhesive starts to set.

Analysis of Variance↗
PubMed2002

Duration of nutritive and nonnutritive sucking behaviors and their effects on the dental arches in the primary dentition.

The purpose of this study was to determine the association between the duration of nutritive and nonnutritive sucking behaviors and various occlusal characteristics in the primary dentition. Sucking behavior data were collected on 372 children followed longitudinally from birth by using periodic questionnaires completed by parents. Study models were obtained from the children at 4 to 5 years of age and assessed for posterior crossbite, anterior open bite, and overjet. Dental arch parameters including arch widths, arch lengths, and arch depths were measured directly from the models. The subjects were grouped according to type of habit (pacifier or digit) and duration of nonnutritive sucking behaviors (less than 12, 12 to 24, 24 to 36, 36 to 48, and more than 48 months). Children with nonnutritive sucking of less than 12 months were further grouped according to the duration of breast-feeding. The dental arch and the occlusal characteristics were then compared among these groups. The results indicated no relationship between duration of breast-feeding during the first year of life and any dental arch or occlusal parameters. The study found that prolonged pacifier habits resulted in changes to the dental arches and the occlusal parameters that were different from the effects of digit sucking. In addition, some changes in the dental arch parameters and occlusal characteristics (eg, prevalence of posterior crossbite and increased amount of overjet) persisted well beyond the cessation of the pacifier or digit habit. Although further study is needed to determine the effects of nonnutritive sucking behavior in the mixed dentition, the results suggest that current recommendations for discontinuing these habits may not be optimal in preventing habit-related malocclusions.

Analysis of Variance↗
PubMed2002

The effect of repeated bonding on the shear bond strength of different orthodontic adhesives.

One problem clinicians face during treatment is bracket failure. In a busy orthodontic practice, a significant number of teeth will need to be rebonded. The purpose of this study was to evaluate the effect of repeated bonding with 2 different adhesives, a composite and a cyanoacrylate, on the shear bond strength of orthodontic brackets. Thirty-one freshly extracted human molars were collected. Brackets were bonded with 1 of the orthodontic adhesives according to the manufacturer's instructions. In group I, the teeth were etched with 37% phosphoric acid, a sealant was applied, and the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In group II, the teeth were etched with 35% phosphoric acid, and the brackets were bonded with SmartBond (Gestenco International, Göthenburg, Sweden). In each group, the teeth were bonded and debonded 3 times with the same adhesive. At each sequence, the brackets were removed within 30 minutes after bonding to simulate the clinical condition at which a newly bonded bracket is tied to the archwire. Student t tests and the analysis of variance repeated measure were used to compare the shear bond strength between adhesives and within each adhesive at different debonding sequences. The results indicated that, at the first debonding sequence, the 2 adhesives did not have significantly different shear bond strengths. Between debonding sequence 1 and 2, there was a significant (P <or=.05) decrease in the shear bond strength of both adhesives. SmartBond decreased from x = 5.7 +/- 3.8 MPa to x = 2.2 +/- 2.6 MPa, and Transbond decreased from x = 6.1 +/- 3.4 to x = 4.1 +/- 2.3 MPa. When the 2 adhesives were compared at the second debonding sequence, the shear bond strength of Transbond was significantly greater than that of SmartBond (P =.046). Between debonding sequences 2 and 3, there were no significant differences either between the adhesives or in the change within each adhesive. The highest values for shear bond strength were obtained after the initial bonding. Rebonded teeth had significantly lower shear bond strength. The composite adhesive had a higher shear bond strength than the cyanoacrylate adhesive at the second bonding/debonding sequence but not at the third. The changes in bond strength after repeated bonding may be related to changes in the morphologic characteristics of the tooth surface caused by adhesive remnants.

Analysis of Variance↗
PubMed2002

Tooth wear patterns in the deciduous dentition.

Tooth wear is common in the deciduous dentition. A recent study suggests that tooth wear in the deciduous dentition is related to subsequent tooth wear in adults, so that early identification of factors related to tooth wear could be of long-term benefit. The purposes of this study were to describe patterns of tooth wear in the deciduous dentition and to relate tooth wear to occlusal characteristics and longitudinal dietary patterns. Data were collected as part of a longitudinal study of a cohort of children recruited at birth from Iowa hospitals. Stone casts were obtained in the deciduous dentition stage, and 355 children, 4 to 5 years old, met the selection criteria. Tooth wear was categorized for each tooth as none, mild, moderate, or severe, and related to occlusal characteristics and longitudinal data on fruit juice and soft drink consumption. All children exhibited some tooth wear on at least 1 tooth, and nearly 16% of them had at least 1 tooth with severe wear. Tooth wear was generally more severe in the maxillary arch and the anterior teeth. Severe tooth wear on the molars was significantly related to posterior crossbites, but severe tooth wear on the incisors was related to Class III canine relationships. There were no statistically significant relationships between tooth wear and soft drink or fruit juice consumption. Based on our results, we concluded that mild tooth wear is universal in the deciduous dentition, but only a few occlusal factors are related to severe tooth wear. Tooth wear was not related to any dietary patterns we investigated.

Analysis of Variance↗
PubMedDate not supplied

Effects of nonnutritive sucking habits on occlusal characteristics in the mixed dentition.

PURPOSE: Little is known about the extent to which nonnutritive sucking habits contribute to malocclusion in the mixed dentition. The purpose of this study was to report on the relationship between certain occlusal traits in the mixed dentition and longitudinal sucking behaviors. METHODS: Dental examinations were conducted on 630 children in the mixed dentition who participated in a large, ongoing longitudinal study. Five hundred eighty consented to impressions, and 524 adequate study models were obtained. Of these, 444 also had adequate longitudinal nonnutritive sucking data obtained via mailed questionnaires to parents at 3- to 6-month intervals from birth to 8 years. Sucking behaviors were grouped by predominant type and duration. Study models were hand articulated using wax bites to evaluate the occlusion for the presence of open bite, crossbite, molar relationship, and excessive overjet. Bivariate statistical analyses related presence of these malocclusions to sucking duration and type. RESULTS: Fifty-five percent of the children had malocclusions (anterior open bite, posterior crossbite, bilateral Class II molar relationship, or overjet >4 mm). Class II molar relationship was most common (30%). Overall, anterior open bite and posterior crossbite was associated with habits of 36 months or more. Sustained pacifier habits, including those of 24 to 47 months, were associated with anterior open bite and Class II molar relationships, while digit habits were associated with anterior open bite when sustained for 60 months or longer. CONCLUSIONS: Malocclusions are quite prevalent in the mixed dentition, and anterior open bite and posterior crossbite may be preventable by modifying nonnutritive sucking behaviors.

Chi-Square Distribution↗