To evaluate the biomechanical behavior of 5 types of commonly used implant/abutment connectors, using Finite Element Methods (FEM). Five models of implant-abutment connections were designed using computer-aided design (CAD) software: Tri-channel (M1), Conical internal hexagon (M2), Morse taper with an integrated screw (M3), Internal hexagon (M4), and Tube-in-tube (M5). The bone was modeled as coaxial cylinders, with the inner cylinder representing spongy bone and the outer 1 mm-thick cylinder representing cortical bone. A premolar crown geometry was designed onto the abutment with a 40 µm-thick cement layer. Three loading scenarios were applied to each model: (1) a 100 N compressive load, (2) a 50 N oblique load at 45° (relative to the implant axis), and (3) a 50 N lateral load. All stress and deformation values remain within the tolerable limits for the materials used. Notably, M1, M4, and M5 exhibited optimal biomechanical performance. M1 and M4 recorded the lowest stresses in implant components, 24.4 to 24.8 MPa in the abutment and 27.5 to 27.9 MPa in the screw under compression, along with minimal crown deformation (8.6 µm compared to M3's 11.7 µm). In contrast, M3 experienced the highest implant-component stresses (68.5 MPa in the abutment and 120.2 MPa in the screw) but showed the lowest cortical bone stress at 7.7 MPa, versus 10.2 MPa in M4. For long-term durability, implants with an internal hexagon (M4) or tri-channel (M1) design are preferable, as they minimize stress and deformation within the implant complex, thereby reducing the risk of prosthetic failure. While the Morse taper (M3) design may benefit patients with compromised bone density, its higher implant-component stresses warrant caution. This study provides valuable insights to support evidence-based selection of implant-abutment connection designs. Among the 5 evaluated systems, the Tri-channel (M1) and Internal Hexagon (M4) designs demonstrated superior biomechanical performance by minimizing stress concentrations within the implant components and surrounding bone. These configurations are therefore recommended for routine clinical use to enhance prosthetic stability, reduce the likelihood of mechanical complications such as screw loosening or fracture, and prolong implant longevity. Conversely, although the Morse Taper with integrated screw (M3) design showed the lowest stress on cortical bone - suggesting potential benefit for patients with reduced bone quality - it exhibited the highest stress levels within implant components, indicating a higher mechanical failure risk. Clinicians should weigh these biomechanical trade-offs when planning treatment, particularly in patients with high functional loads or compromised bone conditions.

To evaluate the biomechanical performance of various designs of cantilevered three-unit implant-supported prostheses, using two distinct prosthetic materials and under different loading conditions. Three mandibular models were created with varying implant positions to support a 3-unit prosthesis using two materials (Zirconia and PEKK), resulting in three different designs: distal cantilever (M1), fixed-fixed (M2), and mesial cantilever (M3). The geometric model was created by segmenting a CBCT scan of an edentulous mandible using Mimics software, followed by refinement in 3-Matic to generate a trabecular bone core encased by a 2 mm-thick cortical shell and a 1 mm-thick mucosal layer. Implant CAD files were integrated, and the models were processed in SolidWorks to finalize solid geometries. These were then imported into ANSYS for mesh generation and finite element analysis, with materials assumed to be isotropic and elastic. Models underwent 3 different static loading protocols (Vertical 100 N, 30° Oblique 50 N, 45° Oblique 50 N). Von Mises stress and total deformation were calculated. Model 2 demonstrated the best performance. Under vertical loading, PEKK prostheses showed lower stress than zirconia in the prosthetic body (10-45 %) and the cortical bone (3-40 %), but higher stresses in the implant (4-10 %). Compared to vertical loading, oblique loading generated higher stress but remained within a safe range without compromising function. The fixed-fixed design showed optimal biomechanical performance. The mesial cantilever was more favorable than the distal for stress distribution. Zirconia provided superior stress dissipation, while PEKK showed reduced stress in the prosthetic body but increased stress I the implant and bone. The study provides prosthodontists with evidence recommending design and materials for 3-unit implant-supported prostheses. Zirconia is ideal for cantilevered designs, resisting high bending forces and minimizing implant stress, while PEKK is more suitable for fixed-fixed designs with lower stress levels.

To assess the biomechanical performance of cantilevered 2-unit implant-supported prostheses with zirconia and polyetherketoneketone (PEKK) under 3 loading conditions. A cone beam computer tomography (CBCT) scan of an edentulous mandible was segmented using Mimics software and refined in 3-Matic software to create trabecular and cortical bone structures. Implant CAD files were integrated using SolidWorks software, generating 4 models with varying implant positions: M1 (first premolar implant supporting a second premolar), M2 (second premolar implant supporting a first premolar), M3 (second premolar implant supporting a first molar), and M4 (first molar implant supporting a second premolar). Prostheses were constructed from zirconia or PEKK. Finite element analysis (FEA) in ANSYS software simulated static loading: vertical (100 N) and oblique (30° and 45°, 50 N). von Mises stress and total deformation were analyzed. Vertical loading showed the highest von Mises stress at cantilever connectors, with M3 displaying the highest cortical bone stress (117 MPa). Zirconia models had slightly higher prosthetic stress, while PEKK models exhibited greater implant and cortical bone stress. Oblique loading caused higher stress in implants and prostheses but remained below yield limits. Maximum deformation was under 25 micrometers for the implant and bone, and 65 micrometers for the prosthesis. Single implants can support 2-unit cantilevered prostheses when additional implants are unfeasible. The location of the cantilever has minimal impact compared to its size, as a larger cantilevered part increases stress. Zirconia better resists bending forces and reduces implant stress compared to PEKK. This study guides prosthodontists in designing 2-unit implant-supported prostheses, emphasizing that multiple implants optimize stress distribution, and that zirconia is preferable for cantilevered designs.

Objective: The objective of this study was to evaluate the effect of different surface treatment methods on the shear bond strength (SBS) of metal brackets bonded to two types of CAD/CAM composite restorations: milled and 3D-printed. Materials and Methods: A total of 160 flat-shaped specimens (10 × 10 × 2 mm³) were prepared from four different CAD/CAM composites; two milled (Lava Ultimate™ [LU] and Grandio™ [GR]) and two 3D-printed (Crowntec™ [CT] and C&B Permanent™ [CB]). These specimens underwent thermocycling (5000 cycles at 5–55 °C), then were categorized based on the surface treatment into four groups (n = 10): Group C (control, no surface treatment), Group HF (treated with 9.6% hydrofluoric acid), Group DB (mechanical roughening by a diamond bur), and Group SB (sandblasting using aluminum oxide). Metal brackets were bonded using Transbond XT Primer and universal adhesive, stored in artificial saliva for 24 h, then thermocycled again. Shear bond strength (SBS) was tested using a universal testing machine until bracket debonding occurred. The adhesive remnant index (ARI) was assessed using a stereomicroscope to quantify the residual adhesive following debonding. Result: Regarding material, GR and LU restorations had significantly higher SBS values compared to CT and CB, ranging from 13.90 MPa to 20.35 MPa. Regarding surface treatment, SB and HF groups showed significantly higher SBS values. The ARI scores showed different adhesive modes of failure, with higher instances of scores 0 and 1, which indicate no or minimal adhesive remaining. Conclusions: Both milled and 3D-printed materials had adequate SBS for clinical use, with milled materials showing superior results. Surface treatments like sandblasting and HF significantly improved bond strength, with adhesive failure being common.

To investigate the biomechanical performance of fixed dental prostheses supported by either tooth–implant or implant–implant configurations, fabricated from zirconia or polyetherketoneketone (PEKK), under oblique loading using three-dimensional finite element analysis (FEA). Three mandibular posterior models were developed: M1 (implant at the first molar and natural tooth at the first premolar), M2 (implant at the first premolar and natural tooth at the first molar), and M3 (implants at both the first premolar and first molar). Each model was restored with a three-unit prosthesis fabricated from either zirconia or PEKK. The digital workflow included anatomical segmentation using Mimics software, refinement of bone and soft tissues with 3-Matic software, and integration of implants, abutments, and prosthetic components, followed by meshing and FEA using ANSYS software. All models were subjected to oblique loading of 50 N at 30° and 45°, and von Mises stress and deformation were recorded. M3 exhibited the most favorable biomechanical behavior, showing the lowest von Mises stress across almost all components. The hybrid tooth–implant models (M1 and M2) showed higher stress concentrations, particularly M2 with PEKK (loading angle 45°), which recorded the highest implant stress (312 MPa) and the greatest deformation (75 µm). The highest screw stress was recorded in M1 with PEKK, reaching 483 MPa. Zirconia exhibited higher stress within the prosthesis, but lower deformation, whereas PEKK resulted in greater deformation in the tooth and periodontal ligament (PDL). Implant–implant-supported prostheses showed the most favorable biomechanical behavior under oblique loading. Tooth–implant models, especially with anterior implant placement, exhibited higher stress and deformation. Zirconia offered greater rigidity and dimensional stability, while PEKK provided better stress dissipation but required careful design to manage its flexibility.

Objective: To evaluate the effect of different surface treatment methods on the shear bond strength (SBS) of metal brackets bonded to two types of CAD/CAM composite restorations: milled and 3D-printed. Materials and Methods: A total of 160 flat-shaped specimens (10×10×2 mm³) were prepared from four different CAD-CAM composites; two milled (Lava Ultimate™ [LU], and Grandio™ [GR]) and two 3D-printed (Crowntec™ [CT] and C&B Permanent™ [CB]). These specimens underwent thermocycling (5000 cycles at 5-55 °C), then were categorized based on the surface treatment into four groups (n=10): Group C (control, no surface treatment), Group HF (treated with 9.6 % hydrofluoric acid), Group DB (mechanical roughening by a diamond bur), and Group SB (sandblasting using aluminum oxide). Metal brackets were bonded, stored in artificial saliva for 24 hours, then thermocycled again. Shear bond strength (SBS) was tested using a universal testing machine until bracket debonding occurred. The adhesive remnant index (ARI) was assessed using a stereomicroscope to quantify the residual adhesive following debonding. Result: Regarding material, GR and LU restorations had significantly higher SBS values compared to CT and CB, ranging from 13.90 MPa to 20.35 MPa. Regarding surface treatment, SB and HF groups showed significantly higher SBS values. The ARI scores showed different adhesive modes of failure, with higher instances of scores 0 and 1 which indicate no or minimal adhesive remaining. Conclusion: Both milled and 3D-printed materials had adequate SBS for clinical use, with milled materials showing superior results. Surface treatments like sandblasting and HF significantly improved bond strength, with adhesive failure being common.