Hourglass Mandibular Anatomic Variant Incidence and Treatment Considerations for All-On-Four Implant Therapy: Report of 10 Cases

PurposeThe purpose of this study was to determine the incidence and treatment of hour glass variant mandibles for All On Four implant placement.Materials and MethodsCone beam CAT scans were analyzed for 719 patients to determine the incidence of alveolar constriction in the mandible. Ten patients with alveolar constriction were treated over a 2-year period and retrospectively studied after 1 year in function.ResultsOf 719 mandibles studied, 28 have “hour glass” variants identified for an incidence of 3.89%. Treatment of these cases were variously done including the use of guided bone regeneration, the use of long implants, bone reduction, and angulation strategies.ConclusionsThe hour glass mandibular finding is a developmental or genetic variant that poses a significant anatomic difficulty for dental implant surgery for All On Four immediate function.