the slot 34 is positioned in substantially the center of the wafer 20 in spaced apart relationship to the anterior end 26 of the wafer 20 the slot 34 defines a series of perforations 36 which extend posteriorly from the slot 34 the perforations 36 extend through the wafer 20 such that the slot 34 and perforations 36 define a tab portion 38 the slot 34 and perforations 36 are separable from the wafer 20 such that the tab portion 38 can be bent at an acute angle downward from the plane of the wafer 20 the slot 34 has a length sufficient to receive a thick portion 18 of the leaf gage booklet 10 inserted into the slot 34 an alternative embodiment of the wafer of the present invention is shown in fig3 the wafer 20 39 has a smaller and wider arcuate shape the shape of the wafer 20 39 can be easily altered or trimmed by the dentist so that the wafer 20 39 easily fits the shape of the individual patient 39 s mouth the wafer 20 39 has an anterior end 26 39 and a posterior end 28 39 the posterior end 28 39 defines a center portion 29 39 which curves anteriorly towards the anterior end 26 39 of the wafer 20 39 the anterior end 26 39 defines lateral portions 27 and 27 39 which curve posteriorly towards the.