A Volumetric Assessment with a 3D Scanner of an Eye Reconstruction Fabricated Using the Traditional Handmade Method. A Comparative Pilot Case Study
Sonia Regina Bordin-Aykroyd, Brito Dias R, Lynch E , Coto N P
Purpose: Precision in anatomical details and the quantification of volume loss is important in bucco-maxillofacial prosthetic reconstruction for the accurate symmetrical rehabilitation of patients with bucco maxillo-facial loss or malformations. The objective of this case study was to determine if a prosthetic eye made by the traditional handmade system, using hydrocolloid impression, had the same size as the natural eye and evaluate the role of 3D scanners in this process. In order to determine if the two eyes had the same size, a 3D scanner was used to measure and compare the volume of the depressions created by theses eyes after hydrocolloid impressions where taken. These depression measurements enabled us to calculate the thickness of the eyes, quantifying the accuracy of the traditional confection method.
Materials &Methods: The comparison was made, after randomly assigning one patient out of 100, who had ocular prosthesis previously constructed in the traditional way, with the use of hydrocolloid material for the impression of the anophthalmic cavity. Stone models were made from hydrocolloid molds of the surface of the eyelids containing: the natural eye, the prosthetic eye, the eyelid of the empty anophthalmic cavity and the mold of the prosthetic eye alone. Following this, measuring tests using a 3D scanner were made and the results were compared.
Results: The surface volume of the empty anophthalmic cavity eyelid was 23% smaller than that of the natural eye; while, with the prosthetic eye in place, it was 8% smaller. This indicated that in order to have a closer appearance to the natural eye and a more natural contour, the prosthetic eye would need to be increased in volume. The volume measurement of the prosthetic eye was made using the 3D scanner and was 2750 mm3. A further measurement, using the computer model, suggested that for the eyelids surface volume to be the same, the prosthetic eye would need to be increased by 2,5 to 5 %, in thickness, depending where the increment was made.
Conclusion: These findings suggest that the traditional handmade method of constructing prosthetic eyes, with impressions from hydrocolloid materials, can produce a series of discrepancies during the confection process, and can lead to a significant difference in size from that of the natural eye. 3D scanners could offer a valuable impression method for bucco maxillo-facial reconstruction, as it allows for the delineation of the area of interest to be rebuilt.