Transient forces generated by projectiles on variable quality mouthguards monitored by instrumented impact testing

Abstract

Objectives-(a) To determine the forcetime trace that occurs when a spring mounted simulated upper jaw is impacted; (b) to examine if mouthguards of variable quality have significant influence on such force-time traces; (c) to attempt to relate physical events to the profile of the force-time traces recorded. Methods-A simulated jaw, consisting of ceramic teeth inserted into a hard rubber arch reinforced with a composite jawbone, was fitted with various mouthguards as part of a previous round robin study. A clinical assessment distinguished good, bad, and poor mouthguards, and these were each fitted to the jaw, which was then submitted to instrumental impact tests under conditions expected to produce tooth fractures. The force-time trace was recorded for such impact events. Results-The spring mounting method caused two distinct peaks in the forcetime trace. The initial one was related to inertia eVects and showed an increase in magnitude with impactor velocity as expected. The second peak showed features that were related to the diVerences in the mouthguards selected. Conclusions-The use of a force washer within a conical ended impactor enabled force-time traces to be recorded during the impact of a spring mounted simulated jaw fitted with mouthguards of variable quality. The spring mounting system causes an initial inertial peak followed by a second peak once the spring mount has fully compressed. Good fitting guards, which keep most teeth intact, result in high stiVness targets that in turn generate high reaction forces in the impactor. If the spring mounting is omitted, the two peaks are combined to give even higher reaction forces. The force-time trace oVers some potential for assessing both overall mouthguard performance and individual events during the impact sequence. Mouthguards with good retention to the jaw remained attached during the impact event and helped to preserve the structural integrity of the target. This in turn developed high forces in the second part of the force-time trace. Guards that detached during impact and allowed tooth fractures showed lower forces in the second part of the test. The force profile measured oVered some quantitative support to, and agreement with, the observed clinical quality of the mouthguards. (Br J Sports Med 2001;35:257-262)

Characterization of mouthguards: Impact performance

“…The degree of retention of the MGs was tested classically. 39 Each MG was placed on the maxillary steel model. Then, the steel model was manually turned over.…”

“…39 Each MG was placed on the maxillary steel model. 39 Each MG was placed on the maxillary steel model.…”

The influence of impact object characteristics on impact force and force absorption by mouthguard material

“…Many recent research studies (4–30) have provided the necessary data to show that there is an effective way to prevent tooth or maxillofacial trauma using a mouthguard (MG) (Tables 1 and 2). However, there are various types of mouthguards including the boil & bite, mass‐produced and marketed to precision‐manufactured, custom‐made types.…”

Effect of Mouthguards on Head Responses and Mandible Forces in Football Helmet Impacts

“…3,15,17,20,39 While there is a consensus that mouthguards prevent oral injuries, their effectiveness in preventing concussion is either unproven or they have no effect on risks. A number of studies have found no effect of mouthguards on concussion risks.…”

“…15,39 This study describes the development of an articulating mandible, compliant TMJ joints, dentition, and instrumentation for the Hybrid III headform. 1 The design and development were conducted by Biokinetics (www.biokinetics.com).…”