OHSU

Research: Class of 1999

Baugh, A.C. "A Histologic Examination of Tooth Movement Into a Bio-Oss Implant Site in a Dog Model," Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999.

Periodontal diseases often cause osseous defects in the alveolar architecture of the involved teeth. This poses significant problems for dentists, periodontists and orthodontists in the clinical management of these teeth, as well as compromises their prognosis and longevity. Several therapies have been directed toward correcting these defects. Perhaps the most beneficial and definitive treatment once the disease has been brought under control is the restoration of the defect using a fill-in or implant material. Recently, a new bone substitute - Bio-Oss - has appeared on the market for reconstructive purposes. This study determined the fate of Bio-Oss under the pressure of tooth movement and identified whether the material can be a suitable bone substitute where orthodontic movement is part of the treatment plan. Results indicated that Bio-Oss did not significantly alter alveolar-root interaction on the pressure side of the moving tooth, nor did the material increase the incidence or severity of root resorption on the side adjacent to the graft. Bio-Oss particles also were found to become completely incorporated into newly formed host bone with no inflammatory response. This study also showed no significant reduction in the amount of Bio-Oss present; however, in the 16-week sample groups, osteoclastic activity was noted on the margins of the Bio-Oss particles. This response may be the initiation of the biodegradative/resorptive response.  

Capps, L.T. "Apical Root Resorption of Maxillary Central Incisors in Orthodontically Treated Patients," Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999. 

ABSTRACT:  

This study assessed the prevalence of apical root resorption in maxillary incisors of orthodontically treated patients. The purpose was to establish a correlation between apical root resorption and preexistent idiopathic root shortness. Studies of 78 cases on the variables of gender, age, molar class, root length, extraction/nonextraction, tooth length, and treatment length (time) suggested that longer roots may have a tendency to undergo more root resorption. A comparison of larger samples of an orthodontic and non-orthodontic population with apparent periapical root resorption would contribute to better understanding of these findings.  

DeSantos, B. "The Effects of Successive Sealant Coats on Decalcification and Bond Strength," Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999.

ABSTRACT:  

The effects of successive sealant coats on decalcification and bond strength were investigated with two orthodontic bonding systems: Transbond XT (3M Unitek, Monrovia, CA) and Enlight (Ormco Corp., Orange, CA). One hundred thirty-two extracted human premolars were divided into the Decalcification Group and Bond Strength Group. No differences were observed between the two bonding systems in terms of decalcification. Within the Bond Strength Group, however, Transbond XT demonstrated a significantly higher bond strength than Enlight. In general, the sealant enhanced the bond strength. Bond failure results further determined that Enlight would tend to be easier to clean up after debonding as, compared to Transbond, more resin remains on the bracket.  

Gardner, J.P. "An Investigation of Bond Strengths Achieved to Artglass and Charisma and the Effects of Two Different Surface Roughening Procedures." Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999.

ABSTRACT:  

The increased number of adult patients seeking orthodontic treatment has presented several problems. One of these is the difficulty in determining how to bond to aesthetic restorative materials already in place in the dentition, as the variety of materials used in such restorations may impact the strength of direct bonding. Currently, there are a number of new materials on the market claiming to have properties unlike those of conventional restoratives. One such material is a so-called Polymer Glass, Artglass, which is a composite material and is gaining in popularity. The present study evaluated orthodontic bracket bond strengths achieved to Artglass vs. conventional composite with and without mechanical surface treatment. When comparing Artglass to Chrisma, the data suggest that Charisma did achieve significantly greater bond strengths than did Artglass.  

Graf, S.J. "Load Transfer from a Nickel-Titanium Archwire to a Ceramic Bracket." Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999.

ABSTRACT:  

This study examined the load transfer from a nickel-titanium archwire to a ceramic bracket when deflected by a vertical force. Finite element models were designed for a nickel-titanium archwire/porcelain bracket system and a stainless steel archwire/porcelain bracket system. Comparisons of force-deflection curves found similarities, validating the finite element models. When comparing the stainless steel wires and NiTi wires, the stainless steel wire was found to cause less stress on the porcelain bracket and to be deflected five to ten times less than the NiTi wire. The degree of stress produced in the bracket by the NiTi wire changes in relationship to the metal's superelastic properties to the extent that a decrease in stress is observed in the region where the superelastic qualities of the metal are expressed. The greatest amount of tensile stress in the bracket was observed at the base of the wire slot nearest the application of force.  

Latham, E.M. "Arch Circumference Changes in Vertical vs. Horizontal Growers from the Mixed to the Permanent Dentition." Orthodontic Certificate Thesis, Oregon Health & Science University, June 1999.

ABSTRACT:  

The purpose of this study was to explore the effects of skeletal growth direction in the progressive alteration of dental arch space requirements from the mixed to permanent dentition. Change in arch length discrepancy was evaluated in terms of facial skeletal growth direction in a sample of 65 subjects. No cause and effect relationships between growth direction and arch circumference changes from the mixed to permanent dentitions were determined. However, a trend was seen towards increases in arch circumference and decreases in crowding with a more horizontal growth direction. The facial axis angle was found to remain relatively stable with growth in both the vertical and horizontal groups, with mean changes from the mixed to the permanent dentitions of -0.1 ± 2.2 and 0.7 ± 2.0 degrees respectively. The y-axis also showed little change with growth in both vertical and horizontal groups, with mean changes of 0.4 ± 2.0 and 0.0 ±2.3 degrees respectively.