J A de Alba | PubMed Health

PubMed1982

Experimental force analysis of the contraction utility arch wire.

An experimental apparatus consisting of a metal framework, a strain gauge, and a Wheatstone bridge was used to measure the retraction force delivered to the mandibular incisors by a contraction utility arch wire (0.016 by 0.016 inch blue Elgiloy). The contraction utility arch wire was activated 1 mm. and retraction forces were recorded as the deflection of a point image on an oscilloscope. The results indicated that the retraction forces at the incisor positions were reasonably within an optimal force range to move teeth quickly with minimal tissue damage and discomfort. However, the lateral incisor positions in both ovoid and narrow arch forms received significantly more force than the central incisor positions, and the narrow tapered arch form delivered more retraction force than the ovoid arch form.

Dental Stress Analysis↗

PubMed1980

Canine retraction with J hook headgear.

Several methods have been described for accomplishing distal movement of canines without losing posterior anchorage. An accepted method in canine retraction is the use of headgear with J hooks. Since it incorporates extraoral anchorage, it is most effective in maximum-anchorage cases. It was the purpose of this study to analyze the distribution of force transmitted to the alveolus and surrounding structures by means of photoelastic visualization, utilizing J hook headgear for maxillary canine retraction. A three-dimensional model representing a human skull was used. This model was constructed with different birefringent materials to simulate bone, teeth, and periodontal membranes. Three different vectors of force were applied representing high-, medium-, and low-pull headgear, which were placed at angles of 40, 20, and 0 degrees to the occlusal plane. The photoelastic analysis was made by means of a circular-transmission polariscope arrangement, and the photoelastic data were recorded photographically. The stress areas created by the three different vectors of force were associated with various degrees of canine tipping. This effect was greater with the low-pull force component than with the medium-pull traction. The high-pull headgear produced the least tipping tendency, being closer to a bodily movemment effect. Further, stresses were transmitted to deeper structures of the simulated facial bones; these regions were the frontozygomatic, zygomaticomaxillary, and zygomaticotemporal sutures.

Alveolar Process↗