Revised, Computed Tomography-Based Lekholm and Zarb Jawbone Quality Classification

Purpose: To propose a revised Lekholm and Zarb classification that takes into account all possible combinations of compact and trabecular bone and to provide guidelines for increased reproducibility of the classification. Materials and Methods: Three new classes were added to the previous classification. The new classes have been designated as subclasses of bone types 2 and 3, as follows: Type 2b: Thick layer of compact bone surrounding a core of medium-density trabecular bone; Type 2c: Thick layer of compact bone surrounding a core of low-density trabecular bone; and Type 3b: Thin layer of compact bone surrounding a core of medium-density trabecular bone. Three interpretation guidelines were recommended to increase the reproducibility of the revised classification. Three experienced examiners were trained using the revised classification and provided with computed tomography (CT) sectional images of edentulous jawbones for classification. Each examiner classified the images twice with at least a 1-week interval. The intraobserver agreement was measured. Results: The kappa statistic for the intra-observer agreement of the examiners ranged from 0.835 to 0.919 (P .001). Conclusion: The high reproducibility of the proposed revised CT-based Lekholm and Zarb classification obtained in the current study suggests its efficacy in distinguishing between the various combinations of compact and trabecular bone.