Orthodontic T-Scan Applications

Orthodontic T-Scan Applications

Julia Cohen-Levy, DDS, MS, PhD (Private Practice, France)
DOI: 10.4018/978-1-4666-6587-3.ch011
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Abstract

This chapter reviews T-Scan use in Orthodontics, defines normal T-Scan recordings for orthodontically treated subjects versus untreated subjects, and explains T-Scan use in the case-finishing process. After orthodontic appliance removal changes in the occlusion result from “settling,” because teeth can move freely within the periodontium. Despite a post treatment, visually “perfect” Angle's Class I relationship, ideal occlusal contacts often do not result solely from tooth movement. Creating simultaneous and equal contacts following fixed appliance removal can be accomplished using T-Scan data to optimize the end-result occlusal contact pattern. The software's force distribution and timing indicators (the 2 and 3-Dimensional ForceViews, force percentage per tooth and arch half, the Center of Force, and the Occlusion and Disclusion Times) aid in obtaining an ideal occlusal force distribution during case-finishing. Several case reports highlight combining lingual orthodontic treatment with Orthognathic surgery, where each presented case utilized T-Scan data during active treatment and retention.
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Introduction

The dental occlusion develops progressively, under the guidance of functional and genetic influences throughout the differing stages of dental arch morphogenesis, and then subsequently through a variety of adaptations made notably to the Temporomandibular joint and the masticatory muscles.

When dealing with complex malocclusions, Orthodontists modify all dental contacts to achieve a new position of occlusal equilibrium, and take responsibility for its functional integration. Fully aware of these implications, they devote special attention to the quality of the final occlusion of their treated cases, whatever the therapeutic occlusal philosophy is that they ascribe to follow.

It is uniformly understood and agreed upon, that at the completion of orthodontic treatment the occlusal contacts of all teeth should demonstrate simultaneous contact timing and be of equal force intensity, thereby creating a uniform and symmetrical distribution of masticatory force. It has been recommended that the anterior teeth be slightly less loaded than the posterior teeth (Roth, 1970; Dawson, 2006).

In Orthodontics, and other dental medicine disciplines as well, such as Prosthodontics and Periodontics, the assessment of occlusal quality has relied mostly on the visual inspection of occlusal contacts, by using:

  • The intercuspation of stone dental casts.

  • Subjectively Interpreting articulating paper marks.

  • Listening to oral patient “feel” feedback.

Alternative, but more time-consuming occlusal indicator techniques have been described, that are often employed within research studies. These alternative occlusal indicator methods are:

  • Observing imprints in high fluidity impression materials.

  • Analyzing force distribution statically within pressure sensitive wax - Dental Prescale 50H (Fuji Photo Film Corporation, Tokyo, Japan) and its analyzing apparatus (Occluzer ™ FPD703, Fuji Photo Film Corporation, Tokyo, Japan).

After the patient imprints the above static dental material indicators, the indicators require digital scanning, followed later by computer processing to retrieve and analyze their force data. Unfortunately, their effectiveness in generating force distribution representations is offset by the significant chair time used to complete data retrieval. Furthermore, neither of these techniques gives the clinician information about the “timing” of the contacts. They offer no indication as to the location of the first contact, the sequence of contacts from 1st contact through until maximum intercuspation, nor the distribution of contacts within the maximum intercuspated position. Therefore with these methods, the clinician does not have the required tools to properly evaluate the ‘simultaneity’ or ‘timing’ of the post orthodontic occlusal contact result.

Key Terms in this Chapter

Lingual Orthodontics: Orthodontic multi-bracket custom cast appliance system, where braces are placed behind the teeth on the lingual side. Brackets are miniaturized and can be customized.

Orthognathic Surgery: The correction of abnormal skeletal and dental relationships through the surgical movement of the bones of the maxilla and/or the mandible. These surgical corrections often produce ideal visual occlusal relationships that demonstrate compromised occlusal force strength capability, and non-ideal occlusal force balance.

Occlusion: Occlusion describes the relationships between the maxillary and mandibular teeth. Static occlusion refers to contact between teeth when the mandible is closed into complete tooth interdigitation and is stationary. Dynamic occlusion refers to occlusal contacts made when the mandible is moving excursively. Centric Occlusion is referred to as a person's habitual bite, the bite of convenience, or the intercuspation position (ICP) (not to be confused with Centric Relation).

Orthodontics: Formally Orthodontics and Dentofacial Orthopedics, is the specialty of Dental Medicine that is concerned with the study and treatment of malocclusions.

Vertical Pattern: Two differing terms. Describes the patient’s facial type. Brachyfacial type is characterized by a short and wide face, usually presentation with a flat mandibular plane angle, and a closed gonial angle. A deep bite is frequently associated with this facial type and Dolichofacial type which is a facial type characterized by a long and narrow face where the maxilla exhibits excessive vertical growth and the mandibular plane is steeper than normal. This growth pattern results in long and narrow alveolar dental arches, and produce a clockwise rotation of the mandible during growth. This is what opens the mandibular plane angle, and sometimes creates a skeletal open occlusion.

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