New classification for bone type at dental implant sites: a dental computed tomography study

Abstract

Objective: This study proposed a new classification method of bone quantity and quality at the dental implant site using cone-beam computed tomography (CBCT) image analysis, classifying cortical and cancellous bones separately and using CBCT for quantitative analysis.

Methods: Preoperative CBCT images were obtained from 128 implant patients (315 sites). First, measure the crestal cortical bone thickness (in mm) and the cancellous bone density [in grayscale values (GV) and bone mineral density (g/cm³)] at the implant sites. The new classification for bone quality at the implant site proposed in this study is a "nine-square division" bone classification system, where the cortical bone thickness is classified into A: > 1.1 mm, B:0.7-1.1 mm, and C: < 0.7 mm, and the cancellous bone density is classified into 1: > 600 GV (= 420 g/cm³), 2:300-600 GV (= 160 g/cm³-420 g/cm³), and 3: < 300 GV (= 160 g/cm³).

Results: The results of the nine bone type proportions based on the new jawbone classification were as follows: A1 (8.57%,27/315), A2 (13.02%), A3 (4.13%), B1 (17.78%), B2 (20.63%), B3 (8.57%) C1 (4.44%), C2 (14.29%), and C3 (8.57%).

Conclusions: The proposed classification can complement the parts overlooked in previous bone classification methods (bone types A3 and C1).

Trial registration: The retrospective registration of this study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH 108-REC2-181.

Keywords: Bone classification; Cancellous bone density; Cortical bone thickness; Dental CBCT; Jawbone.

Fig. 1

The measurement of cancellous bone density and cortical bone thickness at the dental implant site

Fig. 2

Schematic diagram of the new bone classification; three different thicknesses (A, B, and C) of cortical bone and three different densities (1, 2, and 3) of cancellous bone

Fig. 3

a The distribution of cortical bone thickness. (A: red, B: blue, C: purple); b The distribution of cancellous bone density (1: red, 2: blue, 3: purple)

Fig. 4

Example of the nine bone types based on the new bone classification

Fig. 5

The constructions of the four jawbone regions for each bone type are based on the new bone classification

Fig. 6

The case number of nine bone types in the four jawbone regions

Fig. 7

The relationship between bone mineral density (BMD) and grayscale value (GV). The transfer formula between BMD and GV is also listed in this figure

Fig. 8

Percentage of low-, intermediate- and high-density in the posterior mandible region compared with previous studies [42, 43]