An analysis of the relationship between mandibular alveolar bone loss and a low Frankfort-mandibular plane angle

A group of complete denture patients was studied to determine the effect of a low Frankfort-mandibular plane angle on the loss of residual ridge height in the mandible. Measurements were made from tracings of cephalometric films. The low-FMA group did not experience statistically greater amounts of alveolar ridge loss when compared with the group with an FMA larger than 20 degrees. The loss of residual ridge height for both groups followed a linear relationship from year 5 to year 20. There was some indication that the residual ridge height was smaller initially in the low-FMA group. The relative effect of the loss of residual ridge height, combined with smaller residual ridge height originally, indicates that the low-FMA patients are more likely to have anatomic deficiencies and problems with complete dentures associated with this lack of mandibular residual ridge height.