The paper develops a mathematical model for integrated production and maintenance scheduling to optimize backorder quantity. It is assumed that at the end of each uptime, deterministic preventive maintenance is scheduled to incur backlog to reduce inventory carrying cost. The overall incurred cost of the proposed mathematical model is derived and used as a basis for optimal determination of backorder quantity in joint production-inventory model. The proposed model is extended emphasis on increase in production rate accomplished through production overtime period. An optimal overtime production period (T_p') is determined to minimize backordering cost per unit time in the joint production-inventory model. Wide variety of situations and effects are discussed for the extended production-inventory model. The model is validated with illustrating numerical examples, and sensitivity analysis to show the effectiveness and the robustness of the proposed integrated model.