Assessment of Occlusal Contacts Leading to Orthodontic Relapse . A Case Study

There is still a debate regarding the role of occlusal contacts in maintaining the stability of orthodontic treatment results. Occlusal contact distribution in post orthodontic patients was examined in various studies [1,2,3]. Authors put emphasis on the distribution of occlusal contacts in multi-bite recordings with the use of T-scan III occlusal analysis system [2], on the length of the Disclusion Time [DT] in orthodontically treated and nonorthodontically treated patients [1], the presence of non-working side contacts in later obtrusion and protrusion movements [3].


Introduction
There is still a debate regarding the role of occlusal contacts in maintaining the stability of orthodontic treatment results.Occlusal contact distribution in post orthodontic patients was examined in various studies [1,2,3].Authors put emphasis on the distribution of occlusal contacts in multi-bite recordings with the use of T-scan III occlusal analysis system [2], on the length of the Disclusion Time [DT] in orthodontically treated and nonorthodontically treated patients [1], the presence of non-working side contacts in later obtrusion and protrusion movements [3].
There is still a controversy regarding the role of canine guidance in protecting occlusion.The prevalence of canine guidance was stated to be less than group function in the examined group [4,5].An effort was made to classify the stages of canine disclusion in another study [6].The above mentioned study argues that already existing lateral movement pattern schemes are not enough to describe the full variety of occlusal patterns in lateral excursive movements.Studies [4,5,6] consider both canine guidance and group function to be physiologic for the lateral excursive movements.
One of the earlier studies attempted to classify the lateral excursive movements with the use of T-scan II occlusal analysis system [7].Classification consisting of 6 groups was described in this study.The groups were divided concerning the amount of disclusion from maximum interception into maximum canine excursion.
Another group of authors claim that gingival recessions and clefts are influenced by occlusal trauma [8], which has been studied in maximum interception and excursive movements.

Abstract
The probable mechanism of the orthodontic relapse was described in the article.T-scan III occlusal analysis system was used to examine occlusal contacts in post-orthodontic patient according to the author's protocol.

Assessment of Occlusal Contacts Leading to Orthodontic Relapse. A Case Study
Copyright:

© 2017 Koval
During the first check-up visit the bonded retainer on the lower jaw was checked as well as the existence of occurring relapse in both jaws.The clinical examination revealed the occurrence of the small diastema between the teeth #8 and 9 [figure.

Discussion
According to our observations both diastema and spacing are caused by the buccal tooth inclination.The latter, according to our observations, is primarily caused by the excursive occlusal contacts.
The author`s procedure of analyzing the existing occlusal contacts is described.T-scan III occlusal analysis is used to examine occlusal contacts during function.The standard protocol includes 5 recordings: centric occlusion, multi-bite, left and right excursive movement and protrusive movement.The centric occlusion recording is aimed to analyze the sequence of the appearing contacts, their duration, the duration of the A-B period, which indicates the time necessary for the teeth to occlude, the force distribution along the dental arches and the points of the greatest force located in each dental arch.The protrusion movement is of the greatest interest in the described above case.The same rule is applied to the duration of the C-D period in protrusion movements as in lateral excursions.The C-D period duration is said to be not more than 0,5 seconds as well.

Figure 6 :Figure 7 :
Figure 6: The protrusive excursion at the start of the T-scan III occlusal analysis procedure The multi-bite recording shows the repeatability of the A-B period duration, which is the first significant factor.It indicates the presence or absence of any potential contacts that might interfere with the closing movement of the jaws.The second value, that influences the occlusion, is the level of the overall force, exhibited during the closure cycle.In some cases the overall force, which is indicated by the black line in the diagram, can be lower in the second and third cycles of closure on the multi-bite recording.Both left and right excursive movement is of extreme importance.The duration of the Disclusion Time [DT] is measured.The Disclusion Time is indicated by the C-D time span on the diagram.As stated in the literature, the duration of the C-D period should not exceed 0,5 seconds.
Our observations show that the length of the protrusion movement as well as the existence of the working contacts during the extended C-D period in protrusive movements are factors contributing to anterior spacing.Elimination of the contacts that lengthen the C-D [e.g.The Disclusion Time] in protrusive movement removes the potential cause of the reoccurring spacing.Space opening mechanism