Factors associated with orthodontists' assessment of difficulty.

The difficulty of achieving an ideal or normal occlusion might lie in the pretreatment occlusion, patient-associated factors, and the treatment. The purpose of this study was to identify factors that were related to the treating orthodontist's posttreatment categorization of a case as difficult or easy. Ten orthodontists each identified 10 easy cases and 10 difficult cases that they had treated. The initial malocclusion was measured with the peer assessment rating (PAR) index and the index of orthodontic treatment need (IOTN). Patient and treatment information was obtained from the treatment records. Statistical analysis with parametric or nonparametric testing was performed. Difficult cases had greater severity and need before treatment and greater residual malocclusion and need after treatment. Difficult cases had more chart entries for problems with hygiene and compliance. They were more likely to have had extractions and changes in treatment plan. Difficult cases also required more appointments and a longer treatment duration. Three logistic regression models were developed based on malocclusion severity, patient characteristics, and treatment characteristics. The models support a correlation between greater pretreatment malocclusion severity, 1-phase treatment, and the designation as a difficult case. This study supports a model in which malocclusion severity and factors associated with the patient and the treatment contribute to an orthodontist's categorization of a case as easy or difficult.