Stable cranial parameters to evaluate the occlusal plane orientation in the frontal plane: a systematic review

INTRODUCTION: A systematic review of the literature available up to October 2020 has been conducted to determine which cranial plane could represent a stable and reliable parameter to evaluate the orientation of the occlusal plane in a frontal view. EVIDENCE ACQUISITION: An electronic research was performed across the following electronic databases: PUBMED, EBSCO, SCOPUS, WoS, COCHRANE LIBRARY, SciELO, EMBASE and GOOGLE SCHOLAR. Observational studies based on imaging and anthropometry were identified, and all languages have been included. The articles were selected and analyzed by three authors independently. PICO format was adopted to analyze the studies and AXIS guidelines were used to assess the quality of evidence. EVIDENCE SYNTHESIS: We found eleven articles eligible for full-text analysis. All studies included only young subjects and analyzed the occlusal plane in relation to the frontal plane traced between the right and left tragus (Camper’s and Frankfurt planes), to the interpupillary plane, and to other soft and hard tissues references. The outcomes of selected studies were various, with a low quality of evidence, and they did not allow to infer a stable cranial relation between the occlusal plane and other bone structures. CONCLUSIONS: The evidence does not support that the interpupillary plane represent a reliable parameter to evaluate the occlusal plane orientation in a frontal view; instead, the Frankfurt plane could be a much more stable reference parameter, from a morphological perspective. It is necessary to perform an observational study upon craniums to define which are the most stable cranial reference planes to determine the orientation of the occlusal plane in dentate subjects.