A longitudinal study of the stability of the dentition following orthodontic treatment

Rossouw, Paul Emile (1992)

Thesis (PhD) -- Stellenbosch University , 1992.

Thesis

ENGLISH ABSTRACT: The maintenance of dental alignment following orthodontic treatment has been, and continues to be, a challenge for the orthodontist (McReynolds and Little, 1991). Orthodontists should endeavour to establish normal occlusions and function to the end that physiologic balance and retentive stability may be achieved (Goldstein, 1953). Many philosophies and theories have been formulated in response to this challenge, but few have successfully withstood the test of rigorous post-orthodontic evaluation. The present study comprises longitudinal assessments of dentofacial changes which occurred in South African Caucasian subjects during their orthodontic treatment as well as a mean of 7 years following active treatnent. The sample consists of 88 Caucasian subjects; 33 males and 55 female sUbjects who have undergone conventional edgewise orthodontic treatment (Lindquist; 1985). The treatment includes extraction (56%) and nonextraction (44%) therapy. Due to the intricate structure of the craniofacial complex, it is deemed important to discuss the major components of this complex separately and then to compare the variables describing the area with post-orthodontic lower incisor crowding. Lower incisor crowding or irregularity, most often referred to as relapse when occurring in the post-orthodontic dentition, is a phenom~non that is clinically visible and easily assessed using the Little Irregularity Index (Little, 1975). A variety of orthodontic study cast and cephalometric variables represent the changes which occur at the three time intervals selected for this study, namely pre-treatment (T1), post-treatment (T2) and following active treatment (T3). statistical analysis of th~ data was undertaken by the Institute for Biostatistics of the Medical Research Council, Tygerberg, RSA utilising the SAS (1985). The significance level of the results of this study is set at p = 0.05. x No previous study has documented the evaluated and described the various craniofacial skeleton in this format. literature parts or has of the The thesis is divided into thirteen chapters.

AFRIKAANSE OPSOMMING: Die instandhouding van tandbelyning na voltooiing van ortodontiese behandeling was en sal nag steeds in die toekoms 'n uitdaging bied vir ortodontiste (McReynolds en Little, 1991). Die ortodontis se strewe moet wees am 'n normale okkli'lsie in die ortodontiese pasient te veE)tig, waartydens die funksie van die kake herstel word, asook fisiologiese harmonie en stabiliteit van die okklusie gevestig ~lOrd (Goldstein, 1953) • Menige filosofiee en teoriee is al voorgestel om hierdie doelwitte te kan bereik, maar baie min het nag daarin geslaag. Tydens die huidige longitudinale studie is gepoog om In ondersoek te doen van die veranderinge wat plaasvind in die dentofasiale omgewing van agt-en-tagtig Suid-Afrikaanse Kaukasiese pasiente tydens hulle ortodontiese behandeling, asook na die verloop van 'n gemiddeld van sewe jaar sedert die behandeling voltooi was. Die monster het uit 33 manlike en 55 vroulike pasiente bestaan wat met 'n konvensionele vierkantsdraad ("edg~wise") ortodontiese tegniek behandel was (Lindquist, 1985). Die behandeling het 56% ekstraksie en 44% ni~-ekstraksie behandelingsbeplannings ingesluit. Weens die baie komplekse kraniofasiale omgewing is dit besluit am elke deel waaruit hierdie omgewing bestaan, afsonderlik te beskryf en te bespreek. Die veranderlikes wat elke deel beskryf is vervolgens gekorreleer met die na-behandelings ondersnytand-bondeling. Ondersnytandbondeling is 'n verskynsel wat klinies sigbaar is en meestal na verwys word as terugval indien dit voorkom in die na-behandelings resultaat. Dit kan maklik gemeet word met behulp van die "Little Irregularity Index" (Little, 1975). 'n Verskeidenheid van ortodontiese studiemodelle en kefalometrie~Je verander.likes is tydens die voor-behandelings (T1), na-behandelings (T2) asook na verloop van 'n gemidd.eld van sewe jaar na afhandeling van die behandeling (T3) gemeet. Die statistiese verwerkinge is deuI' die Institu,ut vir Biostatistiek van die Mediese Navorsingsraad, Tygerberg, R.S.A. gedoen deur middel van die SAS (1985). Die betekenisvolheidsperk van die studie is op P = 0.05 gestel. Geen studie het al voorheen die literatuur gedefineerde areas van die kranio-fasiale skelet formaat ondersoek of be~kryf nie. Die proefskrif bestaan uit dertien hoofstukke.

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