PubMed · 4283504
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C M Guzay. 1974. Motion. Part 3.. https://pubmed.ncbi.nlm.nih.gov/4283504/
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STATEMENT OF PROBLEM: Clinical stresses and situations in the mouths of patients are substantially different; thus, it is not possible to make an exact in vivo comparison of the efficiency of various mouth guards. PURPOSE: This study developed a device and a method to test and quantify the potential of mouth guards to absorb shock and evaluated and compared 5 designs for mouth guards. MATERIAL AND METHODS: Strain gauges and accelerometer sensors were mounted in various positions on the maxilla and inside an artificial skull. Sensors quantified the response of several areas of the skull to inputs of force on the maxillary teeth protected by the mouth guard being investigated. Input of force was applied to the maxillary teeth with a modal hammer equipped with a load cell. Five mouth guards of each of 5 designs were manufactured and placed in position before force was applied to the maxillary teeth. All inputs were measured and analyzed and, from those results, a method was developed to quantify the relative potential of the mouth guards to absorb shock. This method was then used to quantify the shock absorption potential of the 5 types of mouth guard designs. RESULTS: All 5 types of mouth guards provided some measure of protection and were better than no protection. However, the level of protection provided by the 5 mouth guard designs differed.
In the past, most frictional resistance studies have been conducted in a steady state condition that does not simulate the dynamics of the oral environment. Various oral functions as chewing, swallowing, speaking, etc, as well as the oral tissues contacting any orthodontic appliances, result in periodic, repetitive, minute relative motion at the bracket/arch wire interfaces several thousand times each day. This in turn affects the normal forces at the interfaces, and because frictional resistance is directly proportional to the normal force, a pilot study was undertaken to emulate the dynamic environment of the oral cavity and its effect on frictional resistance. Tests of a limited sample of stainless steel arch wires and brackets typically used in sliding mechanics revealed that frictional resistance was effectively reduced to zero each time minute relative movements occurred at the bracket/arch wire interfaces. Factors such as the degree of dental tipping, relative arch wire/slot clearances, and method of tying, did not have a measurable effect on frictional resistance in the simulated dynamics of the oral environment.
The aim of the present study was to utilize a strain gauge, which enabled the force applied to produce firmly attached crimpable hooks to rectangular stainless steel arch wires, to be measured. In vitro testing of two hooks, American Orthodontic (AO) and TP Orthodontic (TP), and two dimensions of stainless steel archwire, 0.019 x 0.025 and 0.018 x 0.025-inch, was carried out using an Instron Universal Testing machine. The results demonstrate that there was a significant difference in the behaviour of the two types of crimpable hooks, with almost twice the force needed to dislodge the TP hooks compared with the AO hooks (11.7 and 6.22 N, respectively). When using TP hooks attached to either 0.019 x 0.025 or 0.018 x 0.025-inch stainless steel wires, the archwire size makes little difference to the force required to produce movement. The clinical significance of these findings is discussed.