Australasian Dentist Magazine Nov Dec 2021

Category AustrAlAsiAn Dentist 49 apically. A thin gingival biotype is more prone to recession, thereby causing black triangles. Volume of soft tissue in the gingival embrasure region depends on the existing bone, the height of the bone and the interproximal space between the tooth surface. Shape of teeth: the incidence of GBts in square shaped teeth is less than triangular shaped teeth, due to a shorter inter-proximal distance from the osseous crest to the free gingival margin compared to triangular-shaped teeth. interproximal reduction (iPr) of enamel between the triangular crowns will broaden the contact area and also move it apically leading to reduced open gingival embrasures. Care is required not to distort the proportional relationships of the teeth to each other, and the progression of connector heights should be maintained. in adults with attrition, the brackets need to be placed perpendicular to the long axis of the tooth and not parallel to the incisal edge. As patients get older, there is a decrease in the width/length ratio as the crown of the tooth wears and becomes shorter. this changes the position and proportion of the contact point. liniCal Figure 6 Figure 10 Figure 7 width of the embrasure should increase as it progresses away from the midline. Papilla height: 40% of the central incisor height is the accepted ideal. if the papilla height does not reach the connector, then a gingival embrasure, or an unaesthetic “black triangle” results. gingival height: the most superior aspect of the gingival shape/margin is for the centrals and cuspids to be the same length, with the lateral incisors being slightly inferior. Zenith: Defined as the apex of the gingival shape and should be slightly distal to the long axis of the tooth on the maxillary centrals and canines, whereas maxillary lateral it should be coincident. Orthodontic approach Diastema closure: Closure of the interdental space should be attained with a bodily movement of the two adjacent teeth. so as to reduce the diastema and create a contact point, without periodontal attempts to build up the missing papilla. Proper closure of the diastema causes some degree of coronal “creeping” of the interproximal gingival tissue. Direction of movement of teeth: the height of the alveolar bone and papilla can be induced by placing the interdental contact points more apically via extrusion of teeth, causing alterations within the supporting structures, changes in bone level and the soft tissue contours, thereby creating new papillae. the less distance there is between the inter-proximal contact and the bone crest, the less likely the presence of a GBt. extrusive and intrusive tooth movement can maintain the alveolar bone level and reduce GBts. thickness of the labiolingual bone and soft tissue plays a role in orthodontic treatment. During tooth movement towards the lingual, the gingival tissue will thicken and move in the occlusal direction of the facial aspect of the tooth. Conversely, the movement of the teeth toward the labial will cause the gingival tissue to become thin and move more Figure 8 Divergent roots: Divergent roots can also be caused by the incorrect bonding of brackets not perpendicular to the axis of the tooth. Kurth et al. noticed that a mean root angulation of 3.65° in normal gingival embrasures and an increase in root divergence by 1° increased the probability of occurrence of an open gingival embrasure from 14 to 21%. As the roots become more parallel the contact point becomes more apical and lengthens. result is the crowns becoming closer and the trans-septal fibres fill the space and relax, therefore reducing or eliminating the open space. During orthodontic treatment, bracket slots should be bonded perpendicular with the long access of the tooth and not to the incisal edge (case specific). if brackets placement is done based on incisal edges, greater root divergence may result causing an open gingival embrasure. For patients with previously-treated Figure 9 IPR is performed with diamond strips or fine burs to remove the interproximal enamel and change the mesial contour of the teeth (0.5-0.75mm of enamel is removed)