Assessment of nose protector for sport activities: finite element analysis

Mouthguard Use Effect on the Biomechanical Response of an Ankylosed Maxillary Central Incisor during a Traumatic Impact: A 3-Dimensional Finite Element Analysis

(1) Background: Trauma is a very common experience in contact sports; however, there is an absence of data regarding the effect of athletes wearing mouthguards (MG) associated with ankylosed maxillary central incisor during a traumatic impact. (2) Methods: To evaluate the stress distribution in the bone and teeth in this situation, models of maxillary central incisor were created containing cortical bone, trabecular bone, soft tissue, root dentin, enamel, periodontal ligament, and antagonist teeth were modeled. One model received a MG with 4-mm thickness. Both models were subdivided into finite elements. The frictionless contacts were used and a nonlinear dynamic impact analysis was performed in which a rigid object hit the model at 1 m·s^-1. For each model, an ankylosed periodontal ligament was simulated totaling 4 different situations. The results were presented in von-Mises stress maps. (3) Results: A higher stress concentration in teeth and bone was observed for the model without a MG and with ankylosed tooth (19.5 and 37.3 MPa, respectively); the most promising mechanical response was calculated for patients with healthy periodontal ligament and MG in position (1.8 and 7.8 MPa, respectively). (4) Conclusions: The MG's use is beneficial for healthy and ankylosed teeth, since it acts by dampening the generated stresses in bone, dentin, enamel and periodontal ligament. However, patients with ankylosed tooth are more prone to root fracture even when the MG is in position compared to a healthy tooth.

A FEA-Based Methodology to Predict the Osteotome Wear Status during Nasal Bone Surgical Operations

A FEA-based methodology was developed in order to predict the wear status of an osteotome (surgical instrument) during its use in a lateral nasal bone osteotomy considering its fatigue strength. The latter parameter was determined by appropriate FEM-evaluation of the perpendicular impact test results. For the simulation of the surgical procedure, two scenarios were examined: (i) when utilizing a brand new osteotome and (ii) when utilizing an already used osteotome characterized by decreased fatigue strength. The actual nasal bone geometry used in the FEA model was obtained from a high-resolution, maxillofacial, computed tomography (CT) scan of a single patient. In both cases examined, depiction of fracture patterns for the osteotome and the nasal bone were obtained. The wear of a new osteotome and an already used osteotome was also calculated and compared. The developed von Mises stresses in both the osteotome and nasal bone were depicted. The proposed methodology allowed an accurate prediction of the critical number of impacts that the osteotome can receive during the lateral nasal osteotomy which is followed in all rhinoplasties. Based on the developed methodology, a preventive replacement of the osteotome before its extensive fracture can be determined, thereby minimizing the risk of postoperative complications.

Improvement of the Shock Absorption Ability of a Face Guard by Incorporating a Glass-Fiber-Reinforced Thermoplastic and Buffering Space

This study aimed to evaluate the shock absorption ability of trial face guards (FGs) incorporating a glass-fiber-reinforced thermoplastic (GF) and buffering space. The mechanical properties of 3.2 mm and 1.6 mm thick commercial medical splint materials (Aquaplast, AP) and experimental GF prepared from 1.6 mm thick AP and fiberglass cloth were determined by a three-point bending test. Shock absorption tests were conducted on APs with two different thicknesses and two types of experimental materials, both with a bottom material of 1.6 mm thick AP and a buffering space of 30 mm in diameter (APS) and with either (i) 1.6 mm thick AP (AP-APS) or (ii)  1.6 mm thick GF (GF-APS) covering the APS. The GF exhibited significantly higher flexural strength (64.4 MPa) and flexural modulus (7.53 GPa) than the commercial specimens. The maximum load of GF-APS was 75% that of 3.2 mm AP, which is widely used clinically. The maximum stress of the GF-APS only could not be determined as its maximum stress is below the limits of the analysis materials used (<0.5 MPa). Incorporating a GF and buffering space would enhance the shock absorption ability; thus, the shock absorption ability increased while the total thickness and weight decreased.

Does facial soft tissue protect against zygomatic fractures? Results of a finite element analysis

INTRODUCTION

Zygomatic fractures form a major entity in craniomaxillofacial traumatology. Few studies have dealt with biomechanical basics and none with the role of the facial soft tissues. Therefore this study should investigate, whether facial soft tissue plays a protecting role in lateral midfacial trauma.

METHODS

A head-to-head encounter was simulated by way of finite element analysis. In two scenarios this impact - with and without soft tissues - was investigated to demonstrate the potential protective effects. To achieve realism, a transient simulation was chosen, which considers temporal dynamics and realistic material parameters derived from CT grey values.

RESULTS

The simulation results presented a typical zygomatic fracture with all relevant fracture lines. Including soft tissues did not change the maximum bony stress pattern, but increased the time period from impact to maximal stresses by 1.3 msec.

CONCLUSIONS

Although this could have clinical implications, facial soft tissues may be disregarded in biomechanical simulations of the lateral midface, if only the bony structures are to be investigated. Soft tissue seems to act as a temporal buffer only.

Nonfatal sport-related craniofacial fractures: characteristics, mechanisms, and demographic data in the pediatric population

BACKGROUND

Few reports exist on sport-related craniofacial fracture injuries in the pediatric population. Most patients with craniofacial injuries are adults, and most studies on pediatric sport injuries do not focus specifically on craniofacial fractures. The authors' goal was to provide a retrospective, descriptive review of the common mechanisms of sport-related craniofacial injuries in the pediatric population, identifying the characteristics of these injuries and providing a description of the demographics of this population.

METHODS

The study population included children between the ages of 0 and 18 years who were seen in the emergency department at Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center between 2000 and 2005. Of the 1508 patients identified, 167 had injuries caused by sport-related trauma (10.6 percent).

RESULTS

After evaluation in the emergency department, 45.5 percent were hospitalized, and 15.0 percent of these were admitted to the intensive care unit. The peak incidence of sport-related injuries occurred between the ages of 13 and 15 years (40.7 percent). Nasal (35.9 percent), orbital (33.5 percent), and skull fractures (30.5 percent) were most common, whereas fractures of the maxilla (12.6 percent), mandible (7.2 percent), zygomaticomaxillary complex (4.2 percent), and naso-orbitoethmoid complex (1.2 percent) were observed less frequently. Baseball and softball were most frequently associated with the craniofacial injuries (44.3 percent), whereas basketball (7.2 percent) and football (3.0 percent) were associated with fewer injuries. The most common mechanisms of injury were throwing, catching, or hitting a ball (34.1 percent) and collision with other players (24.5 percent).

CONCLUSION

These data may allow targeted or sport-specific craniofacial fracture injury prevention strategies.