Alex Jacobson

Psychological Aspects of Dentofacial Esthetics and Orthognathic Surgery

The literature and the results of the survey clearly confirm that physical attractiveness plays a major role in the social life and interaction among individuals. Cosmetic improvement is a powerful motivating factor leading people to seek treatment. Those who believe that the rewards of facial improvement will enable them to lead more satisfying and comfortable lives should be encouraged to proceed with the treatment. However, it is absolutely essential that those contemplating treatment be counseled before-hand and fully informed on the prognosis, risks and hazards, advantages and disadvantages of such procedures before embarking on treatment.

Orthodontic In Vivo Bond Strength: Comparison with In Vitro Results

The purpose of the present study was to test a new in vivo debonding device and compare in vivo bond strengths recorded by this device with in vitro bond strengths recorded by a universal testing machine such as the Instron. For the in vitro part of the study, 60 extracted premolar teeth were divided into 2 groups of 30 each. Both groups of 30 teeth had 3M Unitek Victory Twin brackets, precoated with Transbond XT composite resin, bonded to them. Shear bond strength tests were carried out in vitro using the universal testing machine on one group of 30 teeth while the debonding device was used on the other group of 30 teeth. The mean shear bond strength of the group debonded using the universal machine was 11.02 MPa and that of the group debonded with the debonding device was 12.82 MPa. For the in vivo part of the study, 8 patients randomly assigned to the research clinician from patients in The University of Alabama School of Dentistry, Department of Orthodontics, had a total of 60 premolar teeth bonded with 3M Unitek Victory Twin brackets. Following comprehensive orthodontic treatment (average time of 23 months), shear bond strength tests were carried out using the debonding device, which can measure debonding forces in vivo. The mean shear bond strength recorded in vivo was 5.47 MPa. Statistically significant differences were found between all 3 groups tested. The results appear to indicate that mean bond strengths recorded in vivo following comprehensive orthodontic treatment are significantly lower than bond strengths recorded in vitro.

An Evaluation of the Use of Digital Study Models in Orthodontic Diagnosis and Treatment Planning

The purpose of the present study was to determine the diagnostic and treatment planning value of digital models when compared with plaster study casts. In addition, the level of orthodontic experience of the examiner was assessed to determine whether this would have an influence on the decision-making process. Thirty randomly selected orthodontic patients from the Department of Orthodontics at the University of Alabama were selected for the study. From the 30 record sets, seven were selected attempting to mirror cases required for presentation to the American Board of Orthodontics. The seven evaluators were divided into two groups on the basis of their level of orthodontic experience. Initially, each evaluator assessed each patient record. Each evaluator was given a standardized questionnaire which recorded the evaluators diagnosis based on use of the digital study models (T1). Regardless of whether the evaluator requested a review of the plaster study casts, the evaluator was given the plaster study casts. The evaluator then, using the plaster casts, filled out another identical questionnaire (T2). A chi-square test was used to determine any group differences in the frequency of changed diagnostic characteristics, treatment mechanical procedures, or proposed treatment plans after evaluating plaster study models. The statistical significance selected was P = .05 level of significance. The results showed that 12.8% of diagnostic characteristics, 12% of treatment mechanic procedures, and 6% of proposed treatment plans changed after T2. The results of the present study indicate that in the vast majority of situations digital models can be successfully used for orthodontic records.

Update on the Wits appraisal.

A review of various aspects of the application of the Wits appraisal of anteroposterior apical base relationships since its introduction in 1975.

A key to the understanding of extraoral forces.

By following certain basic principles, the effects, advantages, and disadvantages of the wide assortment of extraoral assemblies marketed are easily understood. The key to this understanding is the appreciation of the relationship of the line of action of the force application to the center of resistance of the tooth. These principles are discussed in three planes of space: sagittal, coronal, and transverse. Because of the many variables and complexity of mathematically computing the force effects of unilateral or asymmetric extraoral assemblies on molar teeth, a mechanical testing apparatus was designed to accommodate the various face-bows. Not all the designs proved effective, and many of the clinical side effects of the respective face-bow designs became manifest on mechanical testing.

Long-term efficacy of reverse-pull headgear therapy

OBJECTIVE To add to the data for long-term reverse pull headgear (RPHG) outcomes and further explore possible variables that could be predictors of long-term failure. MATERIALS AND METHODS Cephalometric radiographs of 41 Class III malocclusion children treated with RPHG (face mask) were evaluated before and immediately after treatment; at 5 years posttreatment; and, for 18 patients, at 10 years posttreatment. Patients were assigned to success or failure groups according to positive or negative overjet at the longest available recall. RESULTS Seventy-five percent of the patients maintained positive overjet, whereas 25% outgrew the correction. In a stepwise discriminant analysis, a large mandible and vertical positioning of the maxilla and mandible so that mandibular growth would be projected more horizontally were the major indicators of unfavorable later mandibular growth. Patients who experienced downward-backward rotation of the mandible during RPHG treatment were more likely to be categorized in the failure group. The age at which treatment began had no effect on long-term success and failure for patients younger than 10 years, but the percentage of successful treatment decreased after that age. CONCLUSIONS When RPHG treatment is used for all but the most obviously prognathic children to correct anterior cross-bite in the early mixed dentition, positive overjet is maintained long-term in 70%-75% of cases, whereas 25%-30% of cases relapse into reverse overjet mainly because of increased horizontally directed and often late mandibular growth. Up to age 10, the time at which RPHG treatment began does not appear to be a major factor in long-term success in maintaining positive overjet.

An in vivo comparison between a visible light-cured bonding system and a chemically cured bonding system

Direct bonding of brackets has become a routine procedure in clinical orthodontics. Many techniques and materials are currently advocated and used, the most recent being light-cured composites. Advantages of the light-cured systems are their relative ease of use, improved bracket placement, and more rapid set of the composite. For a new system to be clinically viable, it must possess properties that are at least as reliable as existing systems. The purpose of this longitudinal clinical study was to evaluate and compare the rate of success and/or failure between a visible light-cured bonding material (Sequence) and a chemically cured bonding material (System 1+), using both systems in every patient. Contralateral quadrants were bonded with each system respectively. A total of 32 patients were followed for a mean period of 11 months (range of 3 to 21 months), with a total of 531 brackets bonded, 265 with visible light-cured and 266 with chemically cured resins. Failures for each system were recorded and failure rates calculated. The failure rate of the visible light-cured composite was 11.3% and that of the chemically cured composite was 12%. A Chi-squared (chi2) test did not reveal any statistically significant differences between the failure rates of the two systems, (chi2 = 0.014, df-1, P > 0.9).

Air-rotor stripping and enamel demineralization in vitro

This investigation sought to evaluate the effects of air-rotor stripping on the susceptibility of human enamel to demineralization using an in vitro caries model. Crowns of extracted premolar teeth were abraded (0.5 mm) on one proximal surface by air-rotor stripping. The teeth were placed in a demineralizing gel and removed at various intervals up to 336 hours. Lesion depth and mineral content on the abraded and intact surfaces was measured with contact microradiography and computerized image analysis (double window technique). For each time interval measured, lesion depth was greater (p < 0.05) on the abraded surfaces and mineral density was significantly less (p < 0.05). In a second experiment, the effect of fluoride supplements (dentifrice or topical gel) were examined on abraded and intact enamel surfaces that were exposed to the acid gel for 192 hours. The data showed that fluoride treatments significantly reduced lesion penetration on intact and abraded surfaces compared with a no fluoride group. Lesion depth on the abraded, fluoride treated surfaces was significantly greater (p < 0.05) than on the intact untreated surfaces. No significant differences (p < 0.05) were apparent between the fluoride treatment groups with respect to lesion depth and mineral density within the lesion. These results suggest that air-rotor stripping significantly increases the susceptibility of proximal enamel surfaces to demineralization. As a result, the clinician should use caution in the application of this technique until the long-term effects on caries susceptibility have been determined.

Vertical changes in high-angle class II, division 1 patients treated with cervical or occipital pull headgear

Before, after, and 2 years after treatment serial radiographs of two samples of patients with high mandibular plane angle Class II, Division 1 nonextraction who were treated were evaluated retrospectively. One sample comprised patients treated with cervical headgear (CHG), and the other was treated with occipital headgear (OPHG). No significant differences were found when mandibular plane angle or facial height changes, anterior or posterior, were compared. Regarding vertical changes, only maxillary molar height, relative to both sella-nasion and palatal plane, and occlusal plane angle changes were significantly different when cervical and occipital-pull headgear were compared. In both groups of patients, responses to treatment were highly variable and only subtle vertical differences were apparent between mean changes in the cervical and occipital-pull samples.

The proportionate template as a diagnostic aid

Many traditional cephalometric analyses used do not consistently reflect the extent of anteroposterior or vertical jaw dysplasias. Nor do such analyses give accurate information as to which jaw(s) is at fault. The proportionate template is designed as a diagnostic aid which enables the clinician to identify and determine rapidly the extent of craniofacial skeletal jaw discrepancies in adults. The template is found to be particularly useful for orthodontists and surgeons engaged in orthognathic surgery. (Proportionate templates are available upon request from the author).