Thesis (M.S.)--University of Michigan, 1977.

Thesis (M.S.)--University of Michigan, 2006. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1977.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1977. / Typescript (photocopy). Includes bibliographical references (leaves 45-50). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1977. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-50).

No description available.

Introduction: Dental implant abutments can be exposed to a variety of oral prophylaxis procedures. Instrumentation of restored dental implants could subject the apical collar of the implant restorative abutment to surface scratching. Scratched surfaces may pose a threat to the integrity of the soft-tissue seal around the apical portion of the abutment which eventually may compromise the alveolar support of the implant. The aim of this study was to objectively measure surface roughness on the apical collar of metal implant abutments induced by probing and scaling instruments. Materials and Methods: 14 standard transmucosal 3 in 1, 4.5 mm diameter abutments made of titanium alloy (BioHorizons, Atlanta, GA) and 4 instruments, UNC-15 metal probe, Periowise plastic probe, McCall SM 17/18 metal scaler and universal plastic scaler were used to conduct the study. 4 abutments were used for non-treated measures and 10 abutments were used for instrumentation measures. All abutments were divided into four sections. Abutments used for instrumentation were treated with one of the four indicated instruments, one instrument per each section. Surface roughness of untreated and treated surfaces was assessed using a contact profilometer. Analysis of variance (ANOVA) was used to compare surface roughness between untreated and treated surfaces. Results: ANOVA showed significant differences in surface roughness between the treated and untreated surfaces (p< 0.0001). Add hoc analysis using Tukey-Kramer HSD test showed no statistical differences between untreated measures and metal probe measures (p>0.05). On the other hand, statistical differences were noted between untreated measures with plastic probe measures (p= 0.05), plastic scaler measures (p=0.05) and metal scaler measures (p=0.05). The metal scaler measures were higher than plastic probe measures (p=0.05), and plastic scaler measures (p=0.05). Conclusions: Probing around implant abutments with a metal probe seems to have no relevant effect on abutment surfaces. In contrast, instrumentation with scalers (both metal and plastic) and plastic probe may cause adverse surface changes. It is not known if these changes have clinical relevance. / Oral Biology

Thesis (M.S.)--University of Michigan, 1999. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

The passive force-deflection relationship for abutment walls is important for bridges subjected to thermal expansion and seismic forces, but no test results have been available for skewed abutments. To determine the influence of skew angle on the development of passive force, lab tests were performed on a wall with skew angles of 0º, 15º, 30º, and 45º. The wall was 1.26 m wide and 0.61 m high and the backfill consisted of dense compacted sand. As the skew angle increased, the passive force decreased substantially with a reduction of 50% at a skew of 30º. An adjustment factor was developed to account for the reduced capacity as a function of skew angle. The shape of the passive force-deflection curve leading to the peak force transitioned from a hyperbolic shape to a more bilinear shape as the skew angle increased. However, the horizontal displacement necessary to develop the peak passive force was typically 2 to 3.5% of the wall height. In all cases, the passive force decreased after the peak value, which would be expected for dense sand; however, at higher skew angles the drop in resistance was more abrupt than at lower skew angles. The residual passive force was typically about 35 to 45% lower relative to the peak force. Lateral movement was minimal due to shear resistance which typically exceeded the applied shear force. Computer models based on the log-spiral method, with apparent cohesion for matric suction, were able to match the measured force for the no skew case as well as the force for skewed cases when the proposed adjustment factor was used.