Design of Customized Mouthguards with Superior Protection Using Digital-Based Technologies and Impact Tests

Abstract

Background: In contact sports, an impact on the jaw can generate destructive stress on the tooth-bone system. Mouthguards can be beneficial in reducing the injury risk by changing the dynamics of the trauma. The material properties of mouthguards and their geometrical/structural attributes influence their protective performance. Custom-made mouthguards are the gold standard, and different configurations have been proposed to improve their protection and comfort. However, the effects of different design variables on the performance of customized mouthguards are not well understood.

Results: Herein, we developed a reliable finite element model to analyze contributing factors to the design of custom-made mouthguards. Accordingly, we evaluated the isolated and combined effect of layers' stiffness, thickness, and space inclusion on the protective capability of customized mouthguards. Our simulations revealed that a harder frontal region could distribute load and absorb impact energy through bending if optimally combined with a space inclusion. Moreover, a softer layer could enlarge the time of impact and absorb its energy by compression. We also showed that mouthguards present similar protection with either permanently bonded or mechanically interlocked components. We 3D-printed different mouthguards with commercial resins and performed impact tests to experimentally validate our simulation findings. The impact tests on the fabricated mouthguards used in this work revealed that significantly higher dental protection could be achieved with 3D-printed configurations than conventionally fabricated customized mouthguards. In particular, the strain on the impacted incisor was attenuated around 50% more with a 3D-printed mouthguard incorporating a hard insert and space in the frontal region than a conventional Playsafe® Heavypro mouthguard.

Conclusions: The protective performance of a mouthguard could be maximized by optimizing its structural and material properties to reduce the risk of sport-related dental injuries. Combining finite element simulations, additive manufacturing, and impact tests provides an efficient workflow for developing functional mouthguards with higher protectiveness and athlete comfort. We envision the future with 3d-printed custom-mouthguards presenting distinct attributes in different regions that are personalized by the user based on the sport and associated harshness of the impact incidences.

Keywords: 3D Printing; Customized Mouthguard; Dental Protection; Energy Absorption; Finite Element Analysis; Impact test; Load Distribution.

Fig. 1

Anatomical human skull, jaw, teeth, and periodontal ligament (PDL) finite element models for direct puck impact simulation. Incisors comprise dentin (green) and enamel (white) parts. The PDL (pink) covers the root of the incisors and connects them to the maxilla bone

Fig. 2

Schematics of impact test scenario on a mouthguard (a) and developed impact test setup (b)

Fig. 3

Representative compression and tension stress-strain curves for the soft EVA (a) and hard SBS (b) samples (EVA: Ethylene-vinyl acetate; SBS: Styrene-butadien styrene). The stress values of EVA curves were scaled up and down to represent stiffer and softer behavior for the rubber-like component of a mouthguard in simulations

Fig. 4

(a) Dynamic finite element simulation of puck impact to teeth protected with a representative 3 mm mouthguard composed of a soft layer (blue), hard insert (yellow), and space in front of the incisors. (b) Representative visualization of the transferred von Mises (v-m) stress to teeth protected with a standard 4 mm mouthguard composed of single EVA material. Maximum effective stress field on incisors during puck impact without (c) and with (d) mouthguard protection showing higher transferred stress to crown and root when a mouthguard is not present (red arrows). (e) Comparison of maximum von Mises stress in incisors following impact with 3 mm and 4 mm mouthguard designs (EVA: Ethylene-vinyl acetate; PC: Polymeric Component-Hard Insert)

Fig. 5

Effect of space inclusion (1 mm) as well as hard insert modulus (PC: E = 2.40 GPa vs. SBS: E = 1.8 GPa) and thickness (1 mm vs. 1.5 mm) on incisors and lateral incisors protection in different mouthguard designs with 4 mm thickness (EVA: Ethylene-vinyl acetate; SBS: Styrene-butadien styrene; PC: Polymeric Component). Results show that higher protection is achieved in spaced mouthguard designs consisting of a harder insert in the frontal region

Fig. 6

Finite Element simulation and analysis of the protective performance of multi-layered mouthguards with a space inclusion (EVA: Ethylene-vinyl acetate; SBS: Styrene-butadien styrene; PC: Polymeric Component). (a) Design configuration with interlocking features for hard (yellow) and soft (purple) layers defined by a surface-to-surface contact algorithm on the interface of removable components. Qualitative evaluation of impact-induced stress fields on incisors protected with multi-layered mouthguards consisting of permanently bonded (b) or interlocked (c) components. (d) Evolution of impact-induced maximum principal stress on central incisors with and without mouthguard protection. The thickness of all mouthguards was fixed at 3 mm. The presence of a standard mouthguard (without space in front of incisors) composed of a soft EVA material enlarged the time of impact (dash double-dotted blue line) compared to the unprotected impact condition (dashed red line). The space inclusion delays the time of stress evolution on incisors following the impact onset (all solid lines). Examination of different configurations shows that the mechanical properties of each component contribute to the protective performance of a mouthguard with removable parts (e.g., solid orange, purple, and green lines)

Fig. 7

(a) Representative 3D-printed and conventional Heavypro customized mouthguards. (b) Experimental results with an impactor speed of 3 m/s show that 3D-printed mouthguards with a hard insert and space in front of the incisors provide higher protection among different design configurations, including Playsafe Heavypro® (KIBT: KeyOrtho IBT resin; Ins: Insert; Sp.: Spaced; wrt: with respect to)