Changes in Incisor Third-Order Inclination Resulting from Vertical Variation in Lingual Bracket Placement

Abstract

Objective: To test the null hypothesis that third-order measurements are not correlated to lingual incisor features seen on radiographs. Material and Methods: The lateral headfilms of 38 untreated, norm-occlusion subjects without incisor abrasions or restorations were used for third-order measurements of upper and lower central incisors and assessment of the inclination of four sites suitable for lingual bracket placement with reference to the occlusal plane perpendicular. Lingual sections were determined by the tangents at the incisal fossa (S1), at the transition plateau between incisal fossa and the cingulum (S2), by a constructed line reaching from the incisal tip to the cingulum (S3), and by a tangent at the cingulum convexity (S4). Third-order angles were also assessed on corresponding dental casts using an incisor inclination gauge. Regression analysis was performed using the third-order measurements of both methods as the dependent variables and the inclination of the lingual enamel sections (S1, S2, S3, S4) as the independent variables. Results: The null hypothesis was rejected. For the most common bracket application sites located on the lingual shovel (S1 and S2), third-order inclination changes of 0.4-0.7 degrees are expected for each degree of change in the inclination of the lingual surface. The impact of bracket placement errors on third-order angulation is similar between sections S1 and S2 and the cingulum convexity (S4). Section S3 proved to be least affected by interindividual variation. Conclusion:The third-order measurements are correlated to lingual incisor features. Accordingly, third-order changes resulting from variation in lingual bracket placement can be individually predicted from radiographic assessments. (Angle Orthod. 2009;79:747-754.)

Occurrence and severity of enamel decalcification adjacent to bracket bases and sub-bracket lesions during orthodontic treatment with two different lingual appliances

“…The phenomenon of SBL has rarely been described in the literature ( 13 ). Lingual or palatal enamel curvatures display much more pronounced inter-individual inconsistencies of shape, when compared with the relatively consistent buccal enamel curvatures which calls for a customization of lingual bracket bases ( 1 , 18 ). Lingual bracket bonding is normally accomplished using very thin layers of bonding materials at the bracket base/enamel interface ( 13 ).…”

Analysis of the torque capacity of a completely customized lingual appliance of the next generation

“…Additionally, the distance between the point of force application and the center of resistance might be different in lingual and labial appliances [18]. Hence, torque control is more difficult, but crucial in lingual orthodontics [6,19]. The reduction in thickness of the lingual appliance and in positioning thickness constituted a major developmental progress not only in terms of patient comfort, but also in clinical performance of the appliance.…”

Analyse der Torquekapazität einer vollständig individuellen lingualen Apparatur (WIN)

“…Zusätzlich kann auch der Abstand zwischen Kraftansatzpunkt und Widerstandszentrum bei lingualen und vestibulären Apparaturen variieren [18]. Daher ist die Torque kontrolle in der lingualen Orthodontie schwieriger, aber ent scheidend [6,19]. In diesem Zusammenhang stellten die Reduk tion der Dicke der lingualen Brackets sowie ihrer Positionie rungsdicke wesentliche entwicklungstechnische Fortschritte dar, und das nicht nur hinsichtlich des Patientenkomforts, son dern auch bezüglich der klinischen Leistungsfähigkeit der Appa ratur.…”