A finite element analysis of en-mass retraction of maxillary anterior teeth with double keyhole loops / 实用口腔医学杂志

Objective:To evaluate the biomechanical effects of en-mass retraction of maxillary anterior with double keyhole loops in different kinds of loading methods on maxillary anterior teeth.Methods:Three 3D finite element models of the maxillary with double keyhole loops were constructed using MIMICS software with CT data of a male patient who had maxillary first premolars extracted.The orthoclontic force was loaded by ① back winding of the archwire end,② archwire strengthening and ③ archwire strengthening com-bined with successive ligation on the top of the doube keyhole loops,respectively.The initial displacement of maxillary anterior teeth in different loading conditions was analysed with the help of ANSYS software.Results:From the loading condition 1 to 3,on the sagit-tal direction,the displacement difference of crown and root of the maxillary central incisor was reduced from 4.19E -03 mm to -8. 85E -03 mm,which means that the lingual crown tipping movement gradually turn into bodily movement and then to labial tipping crown movement.Meanwhile the displacement of lateral incisor decreased from 7.99E -03 mm to 5.84E -04 mm and that of canine decreased from 9.47E -03 mm to 8.54E -03 mm.Vertical movement of incisors became intrusion from extrusion and intrusion move-ment of canines become more significantly.Conclusion:Torque control of anterior teeth is different in three loading conditions,load-ing by ligation and successive ligation on the top of the double keyhole loops may make the anterior tooth movement as a whole.

Versatilidade do uso do arco DKL para fechamento dos espaços / Versatility of the use DKL “Double Key Loop” for space closure

Em alguns tratamentos ortodônticos, a extração dentária torna-se necessária e, nem sempre, os espaços são completamente fechados após o alinhamento e nivelamento. Existem diversas técnicas utilizadas para eliminar o espaço criado por razões ortodônticas, cabendo ao profissional a escolha da técnica que melhor domine e se adéque ao caso específico. O objetivo deste trabalho é apresentar a utilização de mecânica de fechamento de espaço com o arco DKL “Double Key Loop”.

In some orthodontics treatments, the dental extraction has been necessary and the lack of the spaces extraction are not completely closed after dental alignment and leveling. For eliminating the remaining spaces a number of orthodontics techniques have been used and the best way of its closure is a professional choice according to his abilities and adjust with the specific case. The purpose of this study is to present the use of closing spaces mechanics with the DKL “Double Key Loop” archwire.

Estudo fotoelástico do controle vertical com o arco de dupla chave na técnica Straight wire / Photoelastic study of the vertical control with double key loop archwire in the Straight wire technique

INTRODUÇÃO: em alguns casos, a extração de pré-molares torna-se necessária e nem sempre os espaços são completamente fechados após o alinhamento e nivelamento. O arco de dupla chave, ou Double Key Loop (DKL), é um arco retangular de aço para retração, com duas alças - uma mesial e outra distal ao canino. OBJETIVOS: este trabalho propôs-se a estudar o local onde a força é exercida, após a ativação desse arco, utilizando ativação na alça distal, ativação entre as alças e na alça distal, e ativação com Gurin®. MÉTODOS: foram montados nove modelos fotoelásticos de um arco dentário inferior, sem os primeiros pré-molares e os terceiros molares, com braquetes In-Ovation e arco DKL. O arco foi ativado e a região de incisivos, caninos e dentes posteriores foi fotografada, com interposição de filtros polarizadores de luz. RESULTADOS E CONCLUSÕES: após a análise do modelo fotoelástico, concluiu-se que a ativação com Gurin® pode produzir movimento de retração anterior com componente extrusivo; a ativação na alça distal pode produzir movimento de retração anterior sem componente extrusivo; e a ativação entre as alças e na alça distal pode produzir movimento de retração anterior com componente intrusivo.

INTRODUCTION: There are clinical situations in which the extraction of bicuspids becomes necessary and, eventually, the extraction spaces are completely closed after aligning and leveling the teeth. The Double Key Loop (DKL) is a stainless steel arch for retraction, with two loops (keys), one mesial and another distal to the canine. AIM: This study aims to study the area where the force is exerted after the activation of the distal loop, the activation of the loops among themselves and the distal loop, and the activation with Gurin®. METHODS: Nine photoelastic models of the inferior arch were made, without the first bicuspids and the third molars, with In-Ovation brackets and the DKL. With the interposition of polarizing filters, pictures of incisors canines and posterior teeth were taken, after the activation of the arch. RESULTS AND CONCLUSIONS: Based on the analysis of the photoelastic model, we concluded that the activation in the distal loop can produce an anterior retraction movement without an extrusive component, while the activation with Gurin® produces an extrusive component; besides that, the activation of the keys among themselves and the distal loop activation can produce an anterior retraction movement with an intrusive component.

Experimental 24 Hour Corneal Swelling by Extended Wear Contact Lenses

We evaluated corneal swelling induced by extended wear contact lenses(EWCLs) in New Zealand white rabbits domestically available in Korea. At first, we measured the corneal thickness prior to contact lens wearing with ultrasonic pachometer and examined the condition of the anterior segment of the eye. Then four soft EWCLs, one rigid gas permeable lens, and one disposable lens were applied on the corneas of the rabbits for 24 hours in closed eye condition achieved by transient tarsorrhapy. After 24 hours, the corneal thickness was remeasured and the condition of the external eye was reexamined to compare with the initial values. Conclusively, corneal swelling was developed after 24hour wearing of EWCLs in all rabbits. The percent corneal thickness changes decreased inthe following order; Ciba soft(Cooper Vision) 27.54%. Hyper II(International Contact Lens Lab.) 21.99%, Bescon III(International Contact Lens Lab.) 16.15%, Ciba thin(Cooper Vision) 14.22%, Optima FW(Bash and Lomb) 13.79%, Acuvue(Johnson and Johnson). The control group whitch did not wear any contact lens showed no change in the corneal thickness(p>0.05). The results of corneal swelling correlated well with the DK/L of each EWCLs. This experiment revealed that the EWCLs used widly in Korea could induce corneal swelling and so careful evaluation 0f the EWCLs wearers may be required.