comparison of extraction and non-extraction orthodontic treatment using the objective grading system

statement of problem: the extraction versus non-extraction debate is almost as old as the advent of orthodontic practice and up to now, this dilemma remains. recently, the american board of orthodontics (abo) has developed a method by the name of objective grading system (ogs) in order to evaluate the results of orthodontic treatment. aim: the aim of the present study was to evaluate and compare the patients’ final occlusion after extraction and non-extraction therapy using the ogs. materials and methods: sixty sex-matched cases with an age range of 15-20 year old were selected and evenly divided into 2 groups as follows: 30 patients were treated by extraction of 4 premolars and 30 received a non-extraction treatment. all patients had class 1 malocclusion before treatment and were well treated with the standard edgewise system in a private clinic. with the aid of an abo measuring gauge, 8 parameters of occlusion were measured 3 times, each. reproducibility of the measurements were evaluated by use of the phi correlation coefficient and the total ogs scores between the two groups were compared using levene`s test and student t- test with the significant level at 95%. results: the mean osg scores were significantly more negative in the non–extraction group (-6.58  8.63) as compared to the extraction group (-28.65  6.67, p < 0.004). acceptable occlusion was observed in 73.4% of the extraction and 43.4% of the non-extraction cases. conclusion: in this study according to the abo grading system (ogs), the final occlusion of patients treated with extraction seemed more acceptable than non-extracted cases.