Abstract
This chapter reviews T-Scan use in orthodontics from diagnosis to case finishing, and then in retention, while defining normal T-Scan recording parameters for orthodontically-treated subjects versus untreated subjects. T-Scan use in the case-finishing process is also described, which compensates for changes in the occlusion that occur during “post-orthodontic settling,” as teeth move freely within the periodontium to find an equilibrium position when the orthodontic appliances have been removed. T-Scan implementation is necessary because, often, despite there being a post treatment, visually “perfect” angle's Class I relationship established with the orthodontic treatment, ideal occlusal contacts do not result solely from tooth movement. Creating simultaneous and equal force occlusal contacts following fixed appliance removal can be accomplished using T-Scan data to optimize the end-result occlusal contact pattern. The T-Scan software's force distribution and timing indicators (the two- and three-dimensional force views, force percentage per tooth and arch half, the center of force trajectory and icon, the occlusion time [OT], and the disclusion time [DT]), all aid the Orthodontist in obtaining an ideal occlusal force distribution during case-finishing. Fortunately, most orthodontic cases remain asymptomatic during and after tooth movement. However, an occlusal force imbalance or patient discomfort may occur along with the malocclusion that needs orthodontic treatment. Symptomatic cases require special documentation at the baseline, and careful monitoring throughout the entire orthodontic process. The clinical use of T-Scan in these “fragile” cases of patient muscle in-coordination, mandibular deviation, atypical pain, and/or TMJ idiopathic arthritis, are illustrated by several case reports. The presented clinical examples highlight combining T-Scan data recorded during case diagnosis, tooth movement, and in case finishing, with patients that underwent lingual orthodontics and orthognathic surgery, orthodontic treatment using clear aligners, or conventional fixed treatment with a camouflage treatment plan, which require special occlusal finishing (when premolars are extracted in only one arch).
TopIntroduction
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:
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Evaluating the intercuspation of stone dental casts.
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Subjectively Interpreting articulating paper marks.
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Subjectively Interpreting Shim stock removal “feel,” of the perceived resistance of withdrawing the film from between opposing contacting teeth.
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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:
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Observing imprints in high fluidity impression materials.
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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 created imprints 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-occlusal contacts.
Key Terms in this Chapter
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).
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.
Clear Aligner Therapy: An orthodontic technique consisting of a series of clear plastic removable appliances (“aligners”), that move teeth in small increments from their original state to a final, treated state. Invisalign® is a trademark of Align Technology.
ClinCheck™: Align developed a special software program that assists in the planning of the customized orthodontic movements, and fabricates the aligners following the prescription of the orthodontist.
Fixed Orthodontic Appliances: Brackets that are adhered to the teeth (facially or lingually) with arch wires, that together move teeth through the alveolar bone to improve interarch tooth orientation, and occlusal contact relationships.
Vertical Pattern: Two differing terms describe a patient’s facial type: 1) Brachyfacial Type: This facial 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. 2) Dolichofacial Type: This facial type is 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.
Orthodontics: Formally orthodontics and dentofacial orthopedics, is the specialty of dental medicine that is concerned with the study and treatment of malocclusions.
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.