Oral environment temperature changes induced by cold/hot liquid intake

The use of NiTi shape memory alloys, introduced into orthodontics because of their ability to develop light continuous forces that prove more effective than heavy intermittent forces in the teeth movement, requires the mastering of the functional properties of NiTi wires. More specifically, the recovery force acting on the teeth is a sensitive function of temperature: knowledge of oral temperature modifications is therefore required to understand the stress state modification felt during orthodontic therapy. The temperature modifications induced by cold or hot drink intake in the oral cavity were investigated by using arch wires, fixed to removable Hawley retainers, similar to those currently used in orthodontic practice, by means of six temperature sensors placed in correspondence with specific teeth. Similarly, the temperature changes were detected on a metallic frame, fixed onto the palatal zone to a Hawley retainer, where a palatal expander was placed to correct unilateral or bilateral crossbites in deciduous or in early mixed dentition. The maximum temperature change was observed in the interincisor area: The temperature modification on other teeth depends on the modality of drink intake, with the highest temperature variations being detected in the palatal zone. Hence modifications in the stress state during orthodontic therapy with NiTi wires are to be expected. (Am J Orthod Dentofac Orthop 1997;112:58-63.)