Retentive Properties of Novaloc-TiN and Locator Overdenture Attachments: An In Vitro Physical and Thermal Analysis

PURPOSE: To compare the in-vitro retentive forces of Novaloc-TiN and Locator attachment systems for two-implant overdentures before and after insertion-removal and compressive cyclic loading, representing up to 12 months of wear. MATERIALS AND METHODS: Insertion-removal and compression-cycles of two-implant Novaloc (Novaloc® TiN, Straumann) and Locator (Locator®, Straumann) overdenture attachments embedded into 3D-printed acrylic blocks were performed (n=10 each). For compressive cycling, a force approximating 66.7-N was applied at the center of the blocks using a Bose ElectroForce Fatigue Testing machine over a sum of 300,000 cycles per sample. The retentive force was recorded at baseline and after certain insertion-removal (23, 270, 540, and 1080) and compression-cycles (5k, 25k, 75k, 150k, and 300k). Deformation and crystallization were assessed using micro-computed tomography and differential scanning calorimetry coupled with thermal gravimetric analysis. RESULTS: Compressive cycling of two-implant overdenture yielded a greater retentive force for Locator attachments relative to Novaloc-TiN attachments at simulated mastication equivalent to one-week, one, three, six and 12-months of wear. However, Locator attachments displayed fluctuating retentive forces throughout the 300,000-cycle duration. Retention forces for Novaloc system had no significant differences between baseline and the following 300,000 cycles, indicating consistent retention throughout the cycling duration. Similarly, insertion-removal cycles resulted in retention loss for Locator, whereas Novaloc showed more consistency. CONCLUSIONS: Novaloc-TiN system offers superior durability following compressive and insertion-removal cycling. This indicates more longevity for retentive forces relative to Locator attachment system, despite the lower overall retentive forces of Novaloc attachments.