Development and validation of an occlusal cant index

BACKGROUND: Occlusal cant (OC) is a malocclusion trait lacking indexing or classification that describes the extent and severity of tilt in the occlusal plane. The aims of this study were to develop an occlusal cant index (OCI) based on the degree of OC detection among orthodontists and laypeople and to validate the newly developed OCI by a panel of experts using content validity. METHODS: The ability to perceive OC was assessed in 134 participants (orthodontists = 67 and laypeople = 67). A frontal photograph of a model with an ideal smile with 0° of OC was obtained and manipulated to create various degrees of OC from 1–5° at the right and left sides. A set of 11 electronic photographs was displayed to the participants. The participants were asked to report whether they detected an OC in each photograph. The collected data was used as a baseline to develop an OCI. Then, a content validation of the OCI was performed using a questionnaire provided to a panel of experts comprising ten orthodontists. RESULTS: The OCI was designed based on the threshold of OC detection. In both orthodontists and laypeople, the accuracy of OC detection increased as the amount of tilt increased. The threshold point of OC detection in orthodontists was at 2°, while in laypeople it was at 4°. There was a significant difference between orthodontists and laypeople in their ability to detect OC at 2–3° of tilt. The content validity index (CVI) showed excellent validity between the item-level CVI and the scale-level CVI of the OCI. CONCLUSION: The OCI was developed and implemented for diagnostic, communication, and research purposes. The index showed strong evidence supporting content validity.