Stress distribution in angulated bendable one-piece and two-piece implant-supported single crowns in the posterior maxilla: a finite element analysis

BACKGROUND: This finite element analysis compared stress distribution and displacement in the implant-crown complex and peri-implant bone between angulated bendable one-piece and two-piece implants supporting posterior maxillary single crowns under standardized modeling conditions. METHODS: A three-dimensional finite element model of a maxillary first molar single crown in Misch bone density category 3 was generated. Two base models representing a bendable one-piece implant and a two-piece angulated implant system (15°, 4.1 × 11.5 mm) were each evaluated with 2 crown materials (monolithic zirconia and lithium disilicate) and a 0.05-mm cement layer. The bendable one-piece implant was analyzed in its final post-adjustment geometry. All component interfaces were defined as idealized bonded contacts, and a 100-N oblique load at 30° was applied to the occlusal surface in a linear static analysis. RESULTS: Implant von Mises stresses were markedly higher in the bendable one-piece models (518-529 MPa) than in the two-piece angulated models (109-112 MPa), representing an approximately 4.7-times-higher stress level. Cement-layer stresses ranged from 22 to 29 MPa and were higher in the two-piece configurations. Crown displacement was approximately two times higher in the two-piece configurations (0.036-0.037 mm) than in the one-piece configurations (0.018 mm). Peri-implant bone principal stresses were also higher in the one-piece models, whereas differences between zirconia and lithium disilicate crowns were modest. CONCLUSIONS: Within the limitations of this finite element analysis, the two-piece angulated configuration was associated with lower implant and peri-implant bone stresses than the bendable one-piece configuration, although it showed higher cement-layer stress and crown displacement. These results represent comparative behavior within an idealized model.