Analysis of the "shear" bond strength of pretreated aged composites used in some indirect bonding techniques.

Investigations of the repair of composites have shown that bond strengths can be significantly reduced at an interface involving an aged composite. Brackets placed by some indirect bonding techniques also have an interface involving an aged composite. This study investigated some of the properties of sealant-composite interfaces and parameters affecting these properties independent of other regions and interfaces found in the total enamel-sealant-composite-bracket system using a shear bond-strength test and fractographic analysis. The effects of various pretreatments of 7-day-old composite surfaces on the bond strength and contact angle of a mixed sealant on these pretreated surfaces were determined. Fractured specimens with adhesive failure closest to the point of force application had low bond strengths (17.62 MPa), which could be correlated with surface pretreatment. Preliminary tests showed that acetone pretreatment produced the most consistently strong interfaces with the fewest adhesive failures of this type. Specimens with adhesive failure only in other regions had higher bond strengths (23.41 MPa), which showed no dependence on pretreatment. There was no statistical relationship between contact angle and bond strength. The data coupled with fracture path analysis suggest that: first, the critical region for fracture analysis is that part of the adhesive interface which is closest to the point of force application; second, failure during some dental shear bond strength tests probably occurs as a consequence of tensile stress induced by a bending moment rather than by shear stress; and third, specifying bond strength as breaking load/area may be incorrect.

Case report BC: extraction decisions based on treatment responses.

We have all been into treatment and lost sight of the "plan" we were so familiar with at the treatment planning stage. Eighteen to 21 months into treatment, we are faced with extraction decisions or surgical planning that should have been addressed at 9 or 12 months. This case report illustrates a treatment plan with several variables that were dependent upon treatment responses. It also illustrates planning a gingival graft to increase the crown length of a first premolar after the canine was substituted as the lateral incisor.

Case report TM: early intervention makes nonextraction, nonsurgical treatment possible.

An early phase of treatment limited to orthopedic change as well as the elimination of injurious oral habits makes possible a nonextraction, nonsurgical approach to treatment. Although careful timing and excellent cooperation are essential, it is hard to fault the long-term results of this treatment plan.

Case report RW: correction of a mandibular transverse discrepancy resulting from anteroposterior skeletal disharmony.

Patients with severe Class II malocclusion commonly have transverse problems upon advancement of the mandible. These problems are due to maxillary transverse deficiency and need to be addressed by archwires, maxillary expansion, or mandibular constriction. This report illustrates management of a transverse problem opposite in nature where the mandibular dentition is too narrow upon advancement of the mandible. A removable bite plane to help correct the dental compensations, headgear with Class III elastics to prevent additional incisor proclination, and post-orthodontic restoration to enhance the stability are demonstrated.

Bond strength of aged composites found in brackets placed by an indirect technique.

The "Thomas" indirect technique for bracket attachment produces an interface not present in direct techniques, that is, an aged composite-sealant interface. Our primary goal was to determine if a weakened interface was produced by a modified (sealant was mixed prior to placement of brackets) Thomas indirect technique when the composite was aged for 7 days. The enamel-bracket system was investigated in vitro by comparison of shear bond strengths for metal and ceramic brackets bonded to bovine teeth by a direct and indirect method. Nearly all specimens failed at the bracket-composite interface and, subsequently, no difference was found between specimens placed by direct or indirect methods. No evidence was found to suggest that an aged composite would predispose the enamel-bracket system to fail at the sealant-composite interface. The ceramic brackets used in this investigation had lower bond strengths then metal ones, but the breaking loads were similar.

Cephalometric evaluation of two treatment strategies for deep overbite correction.

This study compared the cephalometric changes achieved using fixed versus removable appliances to correct deep overbite in growing patients. Forty-five patients treated with cervical headgear/tandem mechanics and 50 patients treated with a bionator appliance were compared with 95 control subjects from the Bolton Study. Treatment differences were determined using a cephalometric analysis that isolated vertical changes in overbite as the composite result of 6 variables: maxillary skeletal change, tipping of the upper incisors, bodily movement of the upper incisors, mandibular skeletal change, lower incisor tipping, and bodily movement of the lower incisors. The interaction of treatment type with facial type was also examined. In the headgear/tandem group, overbite was corrected by a combination of intrusion of the upper incisors and increases in mandibular skeletal change. Treatment with the bionator resulted in correction of the overbite by relative intrusion of the upper and lower incisors and increases in mandibular skeletal change. There were no significant interactions with facial type in the headgear group. Gonial angle and lower tipping were influenced by facial type in the bionator group. These results demonstrate that fixed and removable appliances produce both qualitative and quantitative differences in treatment response. Further studies are planned to create a rational decision tree that can be used to aid the clinician in the differential diagnosis and treatment of deep overbite.

Recognition of malocclusion: an education outcomes assessment.

The purpose of this study was to assess the outcome of predoctoral orthodontic dental education in an American dental school. A test was used that measured the clinical abilities of dental students in the diagnosis of malocclusion in children, as well as their didactic abilities in answering select questions from recent national board examinations in orthodontics. The records of 7 children with different types of malocclusion were selected from the practice of a board-certified orthodontist. These cases were presented to dental students who were asked to make diagnoses and recommendations for treatment. The results of the didactic and clinical tests were used to assess the outcome of the predoctoral dental curriculum in imparting orthodontic knowledge to future general dentists. Didactic knowledge increased over the 4 years of dental education. First year students answered 30% of the questions correctly, whereas fourth year students answered 59% correctly. The relationship between clinical diagnostic skills and dental education, however, was not as strong. The fourth year students answered 70% of questions concerning the 7 cases correctly. These results indicate that fourth year dental students demonstrated only slight improvement compared with first year students, who answered 65% of the questions correctly. Thus, this study indicated that orthodontic diagnostic skills, as measured by the clinical test used, did not improve substantially during 4 years of undergraduate dental education.