title: Risks for jaw osteonecrosis drastically increases after 2 years of bisphosphonate therapy.
abstract: METHODS
  This study consisted of 191 patients older than 40 years with osteonecrosis of the jaw (ONJ) drawn from dental practices in the geographic locations of 3 practice-based research networks (PBRNs). Control patients (n = 573) enrolled were individuals older than 40 years without prior history of ONJ. Three control patients were matched with each ONJ case. The ONJ cases originated from primary, secondary, and tertiary care centers. For each ONJ case diagnosed at a primary care center, the 3 matched controls were selected from the same primary care center. However, controls for cases obtained from secondary or tertiary care centers were selected when possible from the general dental practice that referred the case or from another practice in the same geographic area.
  
  
  METHODS
  The key risk factor in this study was bisphosphonate therapy.
  
  
  METHODS
  The main outcome measure was ONJ. The definition of ONJ was maxillary or mandibular exposed bone of any size that clinically appeared necrotic, without regard for duration or cause. Therefore, all types of jaw osteonecrotic lesions were included in this study; but patients were limited to those diagnosed with onset of ONJ after January 1, 2003, without prior history of facial trauma or sickle cell disease.
  
  
  RESULTS
  The results indicate that 83% of cases and 15% of controls received bisphosphonate therapy for a mean duration (standard error) of 5.6 (0.7) and 4.2 (0.6) years, respectively. Therapy with either intravenous or oral bisphosphonates was highly predictive of ONJ; however, intravenous bisphosphonates (odds ratio [OR] = 299.5; 95% confidence interval [CI] = 70.0- 1282.7) were more associated with ONJ than oral bisphosphonates (OR = 9.8; 95% CI = 5.3- 18.1). Risk of developing ONJ existed within the first 2 years and increased fourfold after 2 years of bisphosphonate use (P < .0001).
  
  
  CONCLUSIONS
  The authors concluded that ONJ is causally linked to both intravenous and oral bisphosphonate use, and risk of ONJ escalates tremendously after 2 years of bisphosphonate therapy. The authors also concluded that oral suppuration and dental extractions are independent ONJ risk factors.
authors.affiliation: University of Pennsylvania School of Dental Medicine, Department of Oral Medicine, Robert Schattner Room 211, 240 S. 40th Street, Philadelphia, PA 19104, USA. akintoye@dental.upenn.edu
authors.forename: Sunday O
authors.initials: SO
authors.lastname: Akintoye
authors.forename: Elliot V
authors.initials: EV
authors.lastname: Hersh