Comparison of nonexposed and exposed bisphosphonate-induced osteonecrosis of the jaws: a retrospective analysis from the Copenhagen cohort and a proposal for an updated classification system

OBJECTIVE: Nonexposed osteonecrosis of the jaws (NE-ONJ) does not fit into the current definition of osteonecrosis, which requires exposed bone. A modification of the classification of bisphosphonate-induced osteonecrosis of the jaws (ONJ) is proposed. This study aimed to test proposed criteria for NE-ONJ and compare NE-ONJ with exposed ONJ (E-ONJ) in a retrospective analysis.

STUDY DESIGN: In 102 patients with E-ONJ diagnosed according to Ruggiero et al. (2006, 2009), criteria for NE-ONJ were developed. Subgroups of NE-ONJ and E-ONJ were tested against each other using nonparametric and parametric statistics.

RESULTS: Among 102 patients with ONJ, 14 had NE-ONJ and 88 had E-ONJ. NE-ONJ and E-ONJ were similar in all important data (P > .05) except bone exposure.

CONCLUSIONS: NE-ONJ belongs to the same disease condition as E-ONJ. NE-ONJ may be otherwise classified as ONJ stage 1, 2, or 3 and is different from ONJ stage 0. We propose to include the criteria for NE-ONJ into the classification.