PURPOSE: Oral function is impaired and skeletal growth altered in the patient with a unilateral facial skeletal cleft. Reconstructive surgery with alveolar bone graft (ABG) restores continuity of the maxilla and encourages more symmetric skeletal growth. While placement of an osseointegrated dental implant further improves oral function, it is not clear whether the dental implant affects midfacial skeletal development. Our previous finite element (FE) model demonstrated that the unilateral cleft creates a non-uniform and asymmetric stress-strain distribution within the maxilla during functional tasks and that ABG normalizes this stress-strain distribution. This study intends to: 1. confirm this finding through a patient-specific finite element model and, 2. demonstrate whether the loaded dental implant would further reduce the severity of the asymmetric stress-strain distribution.

METHODS AND MATERIALS: We developed three-dimensional FE models of the patient-specific maxilla with a unilateral cleft based upon CT scan data. The models were further elaborated by adding ABG alone to the cleft, followed by ABG with a loaded dental implant. We analyzed the stress-strain distribution pattern within the maxilla under an evenly distributed occlusal loading on the entire dentition without change in the material models or boundary conditions. The severity of asymmetric stress-strain distribution was quantified using the Asymmetric Index at nasal buttress, alveolar process near the canines, and first molars.

RESULTS: We found a significant reduction in the Asymmetric Index in the maxilla following ABG. The addition of a functionally loaded dental implant further reduced the Asymmetric Index compared to that without the implant.

CONCLUSIONS: This patient specific finite element model confirmed that ABG considerably reduces the asymmetric stress-strain distribution in the maxilla of the patient with a unilateral cleft. The loaded dental implant further reduces such asymmetric stress-strain distribution. These findings suggest that once the alveolar cleft has been reconstructed with a bone graft, placement of an osseointegrated dental implant is an effective way of promoting symmetric structural loading of the maxilla. Without loading, the graft would undergo remodeling with a volumetric decrease in the bone within the cleft region.
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