This retrospective study aimed to describe the prevalence of radiographic abnormalities in bitewing radiographs of proximal class II composite restorations. Bitewing radiographs of proximal composite restorations of adult patients who underwent restorative care at predoctoral clinics at the University of Maryland School of Dentistry from August 2014 to July 2016 were identified. Atypical radiographic features were categorized by type of material and location. The information recorded for patients included age, sex, tooth, and restored surface. Out of the 669 examined restorations, 16.5% radiographs showed no atypical radiographic findings and 83.5% restorations had unusual radiographic signs. The types of atypical radiographic findings were distributed as 16.5% internal voids, 3% overhang, 7.8% interlayer lines, 12.6% secondary caries, 20.7% interfacial gaps and 23.1% had multiple atypical findings. There is high prevalence of atypical radiographic findings in class II composite restorations, particularly in the body of the composite, premolars, and disto-occlusal restorations.