This thesis examines the posttreatment stability and relapse in long- and short-term studies. It attempts to identify potential predictors of relapse by specifically evaluating the stability and relapse associated with nonextraction treatment, extraction versus nonextraction treatment, and early versus late extraction treatment. It provides values for the percent relapse and rate of relapse of the parameters evaluated and compares the long-term and short-term studies in order to potentially provide information about the effectiveness or shortcomings of the various treatment types in maintaining a stable posttreatment outcome and about the progression of relapse over time. The results yielded the following findings. Among the significant posttreatment results, no parameter showed consistency in the posttreatment outcome with any specific treatment type. The parameters that were found to undergo the greatest percent relapse were the mandibular intercanine width, following by mandibular arch length, and mandibular interfirst molar width, while those with the highest rate of relapse were the mandibular intercanine width, following by the mandibular arch length, and the mandibular incisor irregularity. Overall, the long-term studies experienced greater percent relapse than the short-term studies. On the other hand, greater rates of relapse were noted in the short-term studies compared to the long-term studies. The rate of relapse was greater in the extraction patients compared to the nonextraction patients ( excluding the results for the overbite and the mandibular intersecond premolar width). In addition, both the percent relapse and rate of relapse were greater in the late extraction group compared to the early extraction group (excluding the mandibular intercanine width). In conclusion, the long-term versus short-term results suggest that relapse continues to occur several years postretention and suggests that greater relapse occurs soon after the end of the retention phase and gradually less as time passes. In addition, the rate of relapse results suggest that nonextraction treatment is more stable than extraction treatment. Lastly, the percent relapse and rate of relapse results suggest that early extraction treatment is more stable than late extraction treatment.

Indiana University-Purdue University Indianapolis (IUPUI) / A method was devised for the measurement and tabulation of load-deflection values for various wire spring configurations that are commonly used for orthodontic procedures. 1. The deflection of a simple cantilever varies as the third power of the length. 2. The incorporation of a helix into a cantilever at the area of maximum stress markedly increased the deflection. 3. The addition of a helix into a short lever produced a proportionately greater amount of deflection than did the addition of a helix into a long lever. 4. Under continued loading, the rate increased on all springs tested. 5. The load-deflection characteristic of a base arch is approximately the same as that of a simple cantilever. 6. Alteration of the spring height greatly affects the load-deflection values of the retraction springs. Reducing the spring height from 10 mm. to 8 mm., resulted in an increase of approximately 1.5 times as much force being delivered.

Indiana University-Purdue University Indianapolis (IUPUI) / The constructed cephalometric line sella-nasion minus seven degrees (SN-7°) has long been used as a substitute for the Frankfort horizontal in the descriptive analysis of orthodontic cases, due to the difficulty in locating anatomic porion. To eliminate this problem, the cephalostat was modified by replacing the original ear rods with hollow, cylindrically shaped shafts which permit the consistent visualization of anatomic porion. Location accuracy was tested by the double determination method. Then, using anatomic porion, the hypothesis that the constructed line SN-7° is an accurate and reliable substitute for Frankfort horizontal in the descriptive analysis of cases was tested. In an adult sample, the mean Frankfort horizontal - sella-nasion angle was 9.03° (S.D.=2.58) with a range of 2.0° to 17.5°. It was concluded that neither SN-7° nor any other constructed line is a reliable substitute for the Frankfort horizontal, due to the wide range of values determined. The mean Frankfort horizontal - mandibular plane angle was determined to test the hypothesis that when anatomic porion is utilized to construct the Frankfort horizontal, this angle is significantly different from that measured in other similar samples. The mean angle was 19.50° (S.D.=5.74) with a range of 8.0° to 35.5°. This value was significantly less than those determined for the Frankfort horizontal – mandibular plane angle in previous research.

Indiana University-Purdue University Indianapolis (IUPUI) / This investigation was designed to determine the effects of recycling orthodontic bonded attachments in the Esmadent bracket and band reconditioner. The machine contains an oven for bonding resin burnoff, and an electropolishing bath for tarnish removal. It was hypothesized that electropolishing removed sufficient surface metal from the attachment to significantly affect its integrity and function. The parameters selected for evaluation were slot width, mesh dimension, attachment weight, and the resistance of the bracket wings to compressive stress. Medium twin, 0.018 in. slot brackets, welded to mesh bonding pads, were recycled according to the manufacturer's recommendations with the following results. 1. After 2 cycles, the slot width had increased by 0.0005 in., and by 3 cycles, the slot width was greater than 0.019 in. 2. Photographic assessment of the mesh backing showed an increase in pore size, with increasing numbers of cycles. 3. Attachment weight and resistance of the bracket wings to compressive stress decreased with increasing numbers of cycles. The causative agent was determined to be the electropolishing cycle. From a clinical standpoint, change in bracket slot width appears to be the limiting factor. Only one, or possibly two cycles may be tolerated before the ability of the wire to move the bracket, and thus the tooth, is compromised.

Thesis (M.S.)--University of Southern California, 1995. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Southern California, 1995. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (doctoral)--Universidad Nacional de Córdoba, 1945.

Thesis--Lund. / Added title page, with thesis note, inserted.

Thesis--Lund. / Added title page, with thesis note, inserted.

Thesis (doctoral)--Universidad Nacional de Córdoba, 1945.