Effect of headgear on the force system of multi-bracket appliances on a dried human skull

Abstract

We used strain gauges on a dried adult human skull to measure the effect of headgears on the force system of multi-bracket appliances. Extraoral anchorage is often used as an auxiliary to multi-bracket appliances which are employed extensively in orthodontic treatment. This type of anchorage is used to reinforce intraoral anchorage and create forces that supplement the intraoral force system.
An edgewise appliance, which is often used clinically, was fitted to a skull. A force system simlar to that used clinically was reproduced by application of extraoral force to the dental arches of the skull using a facebow headgear or a J-hook headgear.
When the straight-pull type of facebow headgear was used, we noted distal movement (accompanied by lateral expansion) of the maxillary arch as well as a distribution of strain that would tend to elongate the anterior portion of the maxillary arch. When a high-pull type of facebow headgear was used, there was less lateral expansion of the maxillary arch than when a straight-pull type was used. We also noted distal movement and the distribution of strain that depressed the anterior portion in the maxillary dental arch when a high-pull type was used. The J-hook headgear produced the greatest compressive strain when force was applied to hooks placed between the maxillary lateral incisors and canines. Expansion of the dental arches was small when J-hook headgears were used.
These results suggest that the headgear is an effective auxiliary to multi-bracket appliances. Shika Igaku (J Osaka Odontol Soc) 1996 Mar; 59(1): 64-74.