A two-dimensional finite element method was used to analyze the changes in mechanical behavior of the supporting structures when a fixed prosthesis replaced a mandibular first molar. In the unrestored situation, as the degree of bone resorption increased there was a corresponding increase in stress in the periodontium. Tilting of the molar abutment induced additional stress on the mesial side of the root. The presence of a fixed prosthesis markedly reduced the magnitude and distribution of stress in the periodontium. The mechanical advantage obtained by a fixed prosthesis was greater in the situation of a tilted second molar with reduced bone support than with higher bone levels.