Fluxo digital na confecção de protetores bucais – efeito nas propriedades mecânicas, adaptação e desempenho biomecânico.

Abstract

Using different models to fabricate custom mouthguards (MGs) can affect the mechanical properties and physical characteristics of ethylene vinyl acetate (EVA). This study aimed to evaluate the effect of the digital workflow on the physical and mechanical properties of customized mouthguards. The study was divided into 2 specific objectives: 1) Evaluate the impact of different materials for conventional models (dental stone) or 3D-printed models on EVA's physical and mechanical properties, and its surface characteristics. 2) Evaluate the adaptation, thickness, and impact absorption of customized EVA mouthguard thermoplastic materials (MTGs) produced using conventional or 3D-printed models. In the first objective, EVAs were plasticized using 4 types of models: Type IV dental stone (GTIV), Resinous Type IV dental stone (GTIVR), 3D resin with surface treatment (RI3DcT), and 3D resin without surface treatment (RI3DsT). The plasticized EVAs were cut according to ISO 37-II standard (n = 30) and used to measure Shore A hardness, maximum force of rupture (F, N), elongation (EL, mm), and maximum rupture strength (MBS, MPa). Macrophotography and scanning electron microscopy were used to classify the surface alteration of EVA. In objective 2, a typodont model with simulated gingival tissue was used as a reference for the fabrication of mouthguards with two model materials: Type IV dental stone (GIV-MTG) and 3D printed resin (3DPr-MTG) (n = 10). The thickness of the mouthguard (mm), internal adaptation (mm), and area of voids (mm2) between the two layers of EVA were measured using cone-beam computed tomography and Mimics software (Materialize). The impact absorption of the mouthguard was measured using a pendulum impact test with a steel ball at 30° on the typodont model with and without mouthguards. Shore A values decreased significantly, regardless of the model type. The RI3DcT model and GTIV showed higher values of F, EL, and MBS than GTIVR and RI3DsT (p <0.05). RI3DsT resulted in severe surface alteration of EVA and greater reduction in mechanical properties in contact with the model. 3DPr-MTG showed similar thickness (P = 0.371), shock absorption to GIV-MTG (87.0%), and better adaptation than GIV-MTG (P < 0.001). The use of water-soluble gel coating during post-curing improved the mechanical properties of EVA similarly when plasticized over Type IV dental stone models. 3DPr-MTG performed similarly to GIV-MTG