The invention provides a heat formable tray having a bite block and a method of forming the tray to a patient and forming a final impression in a single visit to the dental office by the patient. A custom fitting variable dimension bite registration dental impression tray, is provided which includes a bite registration member, and a dental impression tray. The dental impression tray comprises a heat adjustable material having a softening point above 38 °C and below 120 °C. The variable dimension bite registration dental impression tray is used in a method for making an impression of dental tissue, comprising the steps of: a) providing a variable dimension bite registration dental impression tray, b) heating the dental impression tray to softened state, c) adjusting the dimensions of the dental impression tray, d) cooling the heat adjustable material so that it solidifies, and e) enveloping the tissue with the dental impression material, whereby a final dental tissue impression is obtained.