Study On Thickness Of Axial Walls Of Chinese Mandibulal Incisor’s Crwons

Objective The purpose of this study measured the thickness of the axial walls of Chinese mandibular incisor’s crowns and provided an anatomic basis for all-ceramic or metal-ceramic full-crown restorations of Chinese mandibular incisors.Methods The samples were collected from the CBCT databases of Hospital of Stomatology affiliated to Zhejiang University School of Medcine from Jan.2011to Dec.2012. Fifty subjects with25-35years old were selected, including100mandibular central incisors and100mandibular lateral incisors without any defects and canal fillings. Operating software NNT built in CBCT-imaging systems was used to measured the thickness of the axial wall of the incisal third, middle third, cervical third and the distance from pulpal horn to mesial/distal incisal edges of the mandibular incisors. According to the standard tooth preparations of all-ceramic or metal-ceramic crowns of6th ed prosthodontics published by People’s Health Publishing House.the percentiles that the minimum thickness of axial walls of incisor’s crowns meets the standard tooth preparations of all-ceramic/metal-ceramic crowns were calcuated.Results Table1reveals the thickness of the axial walls of Chinese mandibular incisor’s crowns. Conclusion If the mininum tooth reduction follows the standard tooth preparation of all-ceramic or metal-ceramic crown of the textbook "Prothodontics" published by People’s Health Publishing House, either accidental pulp exposures or too thin axial walls occur in about48%of mandibular central incisors,44%of mandibular lateral incisors on the labial surface and lingual surface, about26%of the mandibular central incisors,22%of mandibular lateral incisors on the mesio-distal shoulders,and about21%of mandibular central incisors,15%of mandibular lateral incisors on the labial surface. Tooth preparation should be very careful at at the labial incisura1/3,lingual incisal third, and mesial cevical third to avoid pulp exposure. The standard tooth preparations of all-ceramic or metal-ceramic crowns for chinese mandibular incisors should be re-considered.