Retinoblastoma protein (pRb) phosphorylation plays a central role in mediating cell cycle G1/S stage transition, together with E2F transcription factors. The binding of pRb to E2F is thought to be controlled by the sequential and cumulative phosphorylation of pRb at various amino acids. In addition to well characterized roles as a tumor suppressor, pRb has more recently been implicated in osteoprogenitor and other types of stem cell maintenance, proliferation and differentiation, thereby influencing the morphogenesis of developing organs. In this study, we present data characterizing the expression of pRb and three phosphorylated pRb (ppRb) isoforms-ppRbS780, ppRbS795, ppRbS807/811-in developmentally staged mouse molar and incisor teeth. Our results reveal distinct developmental expression patterns for individual ppRb isoforms in dental epithelial and dental mesenchymal cell differentiation, suggesting discrete functions in tooth development.