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.

The influence of the recipient site on bone grafts to the face.

This study investigates the relationship of resorptive and depository surfaces to the maintenance of bone graft volume in the growing rabbit facial skeleton. Bone grafts fare best (1) when their periosteal surface is placed in contact with soft tissue and their cancellous surface in contact with bone and (2) when bone is grafted to periosteal depository recipient sites. Fluorescent microscopy failed to demonstrate any difference in the rates of calcification in any of the grafts studied.

Facial variations related to headform type.

A comparison and evaluation of a range of basic anatomic relationships underlying facial form in Angle Class I and Class II dolichocephalic, brachycephalic, mesocephalic, and dinaric types of headform. Interrelated composites of these structural factors and their contributions to different malocclusion tendencies are described.

Age-related differences in mandibular ramus growth: a histologic study.

Histologic reconstructions of remodeling variations of the mandibular ramus are demonstrated. This is significant because morphogenic relationships between the ramus and corpus establish mandibular arch position. Ground and polished microscopic sections were obtained from the ramus of 30 well-preserved human mandibles, dental age 1 to 13 years. The distribution of the various types of endosteal and periosteal bone tissues and resorptive versus depository surfaces was recorded. Fourteen of the 30 specimens and the majority of the mandibles at all ages examined exhibited the classic pattern of deposition and resorption (Type A or classic pattern) described by Enlow. Nine mandibles followed a second variation (Type B or vertical variation) involving a gonial angle alignment change. Seven followed a pattern of deposition and resorption similar to what Björk might have called a forward rotating pattern (Type C or rotation variation). The differences in these patterns are large enough to suggest that a common description of one pattern of remodeling for all mandibles is incomplete. Unfortunately, the process of mandibular growth and remodeling does not appear to correlate well with dental age and the basis for changes in patterns may be more complex than first imagined. If temporal differences exist, they are not related directly to dental development. In theory, the differences in pattern are great enough to influence the outcome of mandibular orthopedic treatment.

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.

Developmental effects of impaired breathing in the face of the growing child.

Craniofacial morphology and occlusal pattern are evaluated in 71 subjects having impaired breathing as diagnosed by an otolaryngologist, and in an equal number of controls. The impaired group demonstrate characteristic combinations of craniofacial deformities and malocclusions, with the younger individuals demonstrating a lesser expression of malocclusion progression and morphologic deformities. This suggests that early recognition of such facial patterns may be utilized to identify those breathing compromised individuals who have a likely tendency to develop certain types of malocclusion.

Class I and Class III malocclusion sub-groupings related to headform type.

Different headform types establish different lines of craniofacial growth resulting in anatomic sub-groupings of Classes I, II, and III with characteristic morphologic features. Several key basicranial and facial relationships are involved, with the nasal region particularly significant in group distinctions.