Onlay grafts in combination with endosseous implants in severe mandibular atrophy: one year results of a prospective, quantitative radiological study

In taking an overall view of the radiographs made of patients that underwen t simultaneous onlay-grafting and implant placement in the anterior mandibl e, changes are seen in the grafts. The impression arose that a number of st ages could be distinguished in this process of remodelling of the graft. Th e purpose of the present study was to objectivate the existence of those st ages in the first year after bone-grafting by densitometric and height meas urements of the onlay grafts using standardized extraoral radiographs (OLCR ) and densitometric analysis in a group of 8 patients. OLCRs were taken at regular intervals in the first year after surgery. The measurements were pe rformed in three fixed fields, both ventrally and dorsally of each implant. Generally the densitometric measurement fields were located at the (upper) cortex, the upper spongiosa and the lower spongiosa of the onlay graft. Th e OLCRs were also used for measurements of the height of the complete graft and of the thickness of the cortex of the graft, using a gauged caliper. T he results indicate the following remodelling of the structure of the onlay grafts: 1) decrease in the thickness and the radiographic density of the ( upper) cortex of the onlay graft predominantly in the first 6-month period; 2) no significant changes in the radiographic density of the upper spongeo us part of the graft; 3) a decrease of approximately 25% in the overall hei ght of the graft, particularly during the first 6-month period; 4) an incre ase in the radiographic density of the lower part of the spongeous bone in the second 6-month period. It is concluded that the remodelling of the graf t has a predictable pattern in time: the first half year being dominated by bone resorption, mainly confined to the cortex of the graft, whereas the s econd half year is characterized by an increase in bone density in the (rem aining) cortex as well as the lower spongeous parts of the graft.