Clinical Crown Height and Sulcus Depth: Tooth Preparation Implications

Objectives: This ongoing investigation measured periodontal crevicular depth and clinical crown height of posterior teeth in young adults, which influence margin placement of crown preparations. Recommended occlusal reduction typically ranges from 1.5 – 2 mm. Required tooth preparation wall height depends on axial wall taper and tooth diameter. Considering typical wall tapers used in clinical practice, approximately 3 mm of vertical wall height is considered prerequisite to ensure adequate retention and resistance form (Goodacre et al, J Prosthet Dent, 2001). Knowledge of clinical crown height and crevicular depth can help determine the proximity of the tooth preparation margin to the junctional epithelium. Methods: Periodontal probings were recorded for 46 healthy young adults (19 females, 27 males; mean age 23.8 yrs.) in six locations (Mesiofacial, facial, distofacial, distolingual, lingual and mesiolingual) for all first molars and premolars. Tooth orientation was considered for all measurements. Clinical crown height was previously measured at the same 2208 locations. Age, sex, malposition, arch constriction, existing restorations and wear patterns were recorded. Mean and standard deviations for crown height and crevicular depth were calculated and summed for each location on individual teeth. Results: At the four proximal line angle locations (MF, DF, DL, and ML) mean probing depths for the molar and premolar groups ranged from 1.3 – 2.8 mm. The corresponding mean values for clinical crown heights were surprisingly low (1.8 - 3.4 mm). At these locations, the summed mean values of clinical crown height and probing depth for premolars ranged from 4.1 – 5.2 mm, and for molars from 5.4 – 6.1 mm. Conclusion: Findings suggest that in this population, adequate retention and resistance form for molar and premolar crown preparations requires proximal margins to be placed within the gingival crevice. Further, resulting premolar margin position will be at, or into the junctional epithelium.