While the durability of thermoplastic aligners has been the subject of numerous studies, the durability of thermoplastic retainers has received significantly less attention. Patients are often advised to wear their thermoplastic retainers indefinitely, so the durability of the materials used in their fabrication is crucial to determining whether they are worth the cost. Limited studies have evaluated the properties of thermoplastic retainer materials and the effects of thermocycling on their mechanical properties. Thus, this study aimed to examine six thermoplastic retainer materials after thermoforming with and without thermocycling. The materials’ flexural modulus, hardness, and surface roughness values were measured after thermoforming (Group 1) and after thermoforming with subsequent thermocycling for 10,000 cycles (Group 2). After thermoforming, there was a significant difference in flexural modulus and hardness values between most of the materials. However, their surface roughness was not significantly different (p < 0.05). After thermocycling, the flexural modulus and hardness increased significantly for most tested materials (p < 0.05) compared to Group 1. Concerning the surface roughness, only two materials showed significantly higher values after thermocycling than Group 1. Thus, all the mechanical properties of the evaluated materials differed after thermoforming, except the surface roughness. Moreover, while thermocycling made the materials stiffer and harder in general, it also made some of them rougher.

To overview dental magnification loupes and to present the updated scientific evidence supporting its use. The practice of dentistry places considerable stress on the operators' visual acuity and musculoskeletal system. The use of magnification loupes has spanned many decades with claims of supporting visual and postural capacities of dental professionals and enhancing diagnostic and procedural accuracy. Galilean and prismatic loupes both provide lightweight and clinically appropriate magnifications between 2.5× and 5.0×, with beneficial features such as a fixed working distance and downward lens inclinations. Studies have found significantly increased detection and diagnostic abilities due to enhanced visibility and improved treatment outcomes for some investigated procedures. Postural studies have found improved positioning of the upper body when using loupes as compared to the positioning when using the naked eye, with practitioners experiencing reductions in musculoskeletal symptoms when using magnification loupes. The current evidence supports the presence of some visual advantages of loupe magnification in diagnosis and treatment delivery. However, more clinical trials are needed to investigate different procedure outcomes over the long term. Further, there is robust scientific evidence advocating the use of loupe magnification for postural and musculoskeletal support. Dentistry is a visually and physically demanding profession with a high prevalence of musculoskeletal disorders among dental professionals. The use of loupe magnification potentially benefits both the dental healthcare provider and patients. Therefore, there is reason to consider the use of loupe magnification as an integral part of dental education and training, as well as a tool in the dental clinician's armamentarium.

Due to the fact that retainers are often recommended for a lifetime, their endurance and longevity are directly related to the quality of the materials used in their production. Our study examined the water sorption, water solubility, and Fourier transform infrared (FTIR) spectroscopy of six commercially available thermoplastic retainer materials (Essix Plus, Zendura, Duran Plus, Tru-Tain DX, Imprelon S pd, and Essix ACE). Moreover, this study evaluated the effect of thermoforming and thermocycling on the water sorption and solubility and surface molecular composition of the tested materials. The present study found that the type of retainer material affected water sorption and solubility capabilities. In addition, the aging methods employed significantly affected some retainer materials’ water sorption and solubility. Moreover, the surface molecular composition evaluated by FTIR spectroscopy revealed that most of the evaluated materials had similar FTIR spectra except for Zendura. All materials had a spectrum that resembled polyethylene terephthalate glycol (PETG) while Zendura had a spectrum similar to semi-rigid polyurethane (PU). Only Zendura had relatively unstable surface structural composition evaluated under the effects of (thermoforming and thermocycling) compared to all tested materials.

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.