Dr. Priyanka Devkar , Dr. Saloni Mistry2 , Dr. Swati Sharma
1
Post-graduate Student
2
Professor and Head of Department,
3
Reader,
Department of Prosthodontics, Crown & Bridge.,
Y.M.T Dental College, Navi Mumbai
ABSTRACT
Orofacial pain along with temporomandibular joint disorder is a stomato-gnathic system
disturbance, which consists of irregularities in temporomandibular joint, muscle spasm and pain
associated with trigger points.
Various methods such as splint therapy, orthodontics, physiotherapy, pain killers, psychotherapy
are used to treat orofacial pain conventionally. But since, the etiology of orofacial pain is not specific
the proposed treatment modalities are largely symptomatic. In spite of its diverse etiology, occlusal
instability and muscle hyperactivity due to its prolonged disclusion time, are considered as an important
etiological factor for orofacial pain.
Disclusion time reduction (DTR) is an objective treatment protocol which uses T scan and
Electromyography. It is a computer guided occlusal adjustment procedure to reduce the time required
for excursive movements which has been shown to treat myofascial pain symptoms.
This article is a review of digitally advanced treatment option which is a futuristic concept for
progressive prosthodontics. It is a synergism of advanced diagnostic tools and appropriate prosthodontic
knowledge which bridges the gap between older and newer concept of temporomandibular dysfunction
treatment modalities.
Keywords: Disclusion time reduction, occlusal interference, T-Scan, MPDS
Citation: Devkar P, Mistry S, Sharma S. DTR: Disclussion Time Reduction …Door to Revolution! J
Prosthodont Dent Mater 2022;3(1):3-8.
INTRODUCTION
Stomatognathic system consists of teeth, muscle and TMJ which works in harmony with each
other1
. Any discrepancy in these factors leads to disharmony which consists of trigger point induced
pain, jaw movement irregularities and muscle spasm.
Occlusion is of two types static and dynamic occlusion. Occlusal discrepancy can be of two
types, occlusal disharmony which is seen in static occlusion and occlusal interference which is seen in
dynamic jaw movements. These occlusal discrepancies can cause pathological wear of teeth such as
attrition, abrasion, occlusal facets and complete wear of enamel surface.
MECHANISM OF MUSCLE HYPERACTIVITY:
Occlusal interferences in dynamic occlusion are known to cause increased disclusion time. This
prolonged disclusion time has effect on muscles of mastication. Prolonged excessive tooth contact
compresses periodontal ligaments which activate excessive muscle contraction of muscles of
mastication. These afferent fibers synapse with efferent fibers of the trigeminal nerve that emanate in
mesencephalic nucleus and further instruct to cause muscle contraction. Thus, when more occlusal
interferences are present for longer duration of time, it results in excessive compression of periodontal
ligament, causing muscle contraction for more period of time. Because of this constant source for muscle
activity results in accumulation of lactic acid causing clinical symptom named muscle hyper activity.
This hyperactivity leads to various symptoms such as headaches, migraines, early morning facial
stiffness, trauma to musculoskeletal tissues (muscles, ligaments, tendons), back pain, nervous tension,
or stress, which are symptoms observed commonly in temporomandibular disorder (TMD) patients.
Hence occlusal interferences present during excursive movements have been considered to be
contributory etiological factors for occluso-muscular pain and in TMDs.
DISCLUSION TIME REDUCTION:
Disclusion Time is defined as the duration of the time that working and non- working molars
and premolars are in contact during a mandibular excursive movement, that is commenced from
complete habitual intercuspation, and extends through the contact of solely anterior guiding surfaces3
.
The therapeutic goal is to quickly disclude the posterior teeth in less than 0.5 seconds per excursion,
primarily in right and left excursions and secondarily in protrusive excursions.
According to sutter4
, good occlusion criteria is as followed:
• Simultaneous contact of all teeth in maximum intercuspation
Instant mouth opening. • Reduced muscle tension • Absence of pain • Increased chewing efficiency • No slide in occlusion. (Except excursions) If time taken to disclude is more than 0.4 seconds then it is considered as prolonged disclusion time due to excessive occlusal interferences. These occlusal interferences were previously reduced by selective grinding of non-functional cusps. Which involves evaluation of occlusal interferences by the use of gold standard technique that is an articulating paper. However, studies have shown that articulating paper demonstrate high degree of false positive marking5,6. Also, disclusion time of 0.4 seconds per excursion is cannot be confirmed visually or with the markings of articulating paper. Hence more reliable technique is introduced by Dr. Robert Kerstien in 1991 called “Immediate Complete Anterior Guidance Development” (ICAGD)7 . It is a measurement-driven, computer-guided occlusal adjustment procedure, whose primary therapeutic goal is to measurably decrease the time required for all molars and premolars to disclude from each other (known as the disclusion time) in <0.4 s during right and left mandibular excursions commenced from complete intercuspation in maximum intercuspal position (MIP). This reduction in disclusion time along with ICAGD is called as Disclusion Time Reduction Therapy. Disclusion Time Reduction (DTR) Therapy is a specialized dental treatment procedure that requires the use of T-Scan® in tandem with an EMG link to evaluate occlusal forces in relation to muscle activity. The treatment phase of DTR Therapy requires computer-guided adjustments with a goal to reduce excessive posterior periodontal ligament compressions by reducing the disclusion time (per unit in time) to under 0.4 seconds. The desired result is to have the muscles return to baseline activity, reducing lactic acid production and myalgic pain. The ICAGD is addition of tooth structure or enameloplasty; it is guided by the time measurement capability of T-Scan occlusal analysis system. Here the excursive movement is adjusted with timeduration and numerical end-points must be achieved to verify whether the guidance was properly accomplished. ICAGD has repeatedly shown to successfully treat myofascial pain symptoms without requiring the treated patient to wear a splint or deprogrammer.
INDICATIONS OF DTR:
• Patient with TMD and primarily exhibit muscle contraction.
• Patient suffering from MPDS, who have posterior teeth interference leading to
prolonged disclusion time.
CONTRA INDICATIONS OF DTR:
• Patient with myofascial pain having Class II division II malocclusion, severe class III
malocclusion.
• Patient with severe open bite.
• Pain primarily due to TMD such as internal derangement. (Lock Jaw, dislocation,
avascular necrosis of joint, tumors of TMDs.)
• Patient younger than 18 years of age8,9.
DIAGNOSTIC TOOLS:
Proper case history record.
Medical and dental history.
Chief complaint in detail.
CBCT – It is done to evaluate any structural damage or hard tissue damage.
Bio JVA – Assessing TMJ soft tissue damage.
T scan – To evaluate Occlusal Interferences.
Bio EMG – to evaluate muscle activity.
After thorough examination if occlusal discrepancy along with muscle hyper activity is present then
DTR therapy is indicated.
Procedure begins with the use of Bio -EMG and T scan. In this self-adhesive bipolar EMG electrodes
placed bilaterally over the bodies of the superficial masseter and the anterior temporalis muscles parallel
to the direction of the muscle fibers, a recording was activated. At the same moment patients digital
occlusal scan is recorded via T scan and both Bio-EMG and T-Scan data acquisition occurs
simultaneously. Patient is asked to close voluntarily in maximum intercuspation and to keep intact for
2-3 seconds. After this movement patient is asked to perform lateral excursive movements where in only
anterior teeth (incisors and canines) are in contact. The procedure was repeated on contralateral side as
well as on protrusive movement of the jaw. After this evaluation of occlusal contacts and their muscle
activity, it was correlated to each other. Patient suffering from myofunctional pain will show prolonged
amount of disclusion time (more than 0.4 seconds) and enhanced activity of muscle (temporalis and
masseter muscle). This is significantly related to prolonged posterior tooth contact.
This occlusal interference can be removed via either enameloplasty or build up at the level of cuspid
area. This can be decided based on wear pattern present on incisal aspect of canine as well as the
posterior interference area. The interference is removed along with the help of articulating paper where
interference is depicted in the manner of bull’s eye appearance. With the help of 0.018 mm round bur
enameloplasty is performed. Patient is asked to close in maximum intercuspation and is asked to perform
excursive movements to evaluate the interference. Procedure is repeated till one achieves posterior
disclusion on excursive movement .
Once the visual posterior disclusion is achieved on excursive movements patient is again evaluated for
disclusion time with the help of Bio EMG and T SCAN. The procedure is continued till patient achieves
disclusion time which is less than 0.4 seconds. This reduction shortens the contraction time of the
masticatory muscle because of which feedback loop no longer adds contraction to baseline functional
movements. Once optimum disclusion time is achieved with reduced disclusion time periodic follow up
is required to observe patients’ symptoms and sign. Patient recall is done at 7 days, 14 days, 1st month,
2nd month ,6th months and yearly follow up is necessary.
DISCUSSION
The etiology of pathological tooth wear is often multifactorial. When tooth wear involves the occlusal
surface, the centric stops are diminished and the masticatory system tends to seeks out a new balance
point, by prolonging tooth contact interactions which aggravates occlusal wear. Occlusal equilibration
based on articulating paper has higher subjective influence and this leads to discretion in interpretation.
In chronic MPDS, patient experience non resolving pain, and reaches chronic hyper active state.
Removal of occlusal interferences tends to reduce myofunctional pain. According to study conducted
by Kerstien et al in 1991, 102 patient who had under gone DTR therapy showed statistically significant
reduction in muscle contraction thereby reducing myofunctional pain3
.A 3-year clinical observational
study conducted by Thumati et al in 2015 also showed significant reduction in muscle contraction by
DTR therapy10. Disclusion Time Reduction is an operator-determined software calculation, which
improves the precision of the Disclusion Time values automatically generated by the T-Scan software.
ICAGD is a computer-guided exclusively focused occlusal adjustment procedure that shortens
prolonged excursive movement and posterior occlusal surface contact frictional durations (known as the
posterior Disclusion Time). This is easy to perform, requires little armamentarium and has degree of
patient’s acceptance as it does not involve splint therapy. It is computer based, precised technique which
involves minimum occlusal reduction followed by improved chewing efficiency. Hence this technique
can be considered as one of the treatment modalities for determining stable occlusion.
CONCLUSION
This review focuses on a DTR therapy which treats myofascial pain by synergism of advanced
diagnostic aid and conventional technique. It focuses on newer technique to establish occlusal
equilibration. It combines the advantages of both techniques, that is visual interpretation by gold
standard articulating paper method and force per tooth v/s time data which is given by digital technique.
Also, Bio -EMG guides us to evaluate the muscle activity simultaneously while performing the
procedure. Hence DTR therapy is more precise and gives predictable outcome. However, this therapy is
very technique sensitive and requires a learning curve also more clinical studies are required for its
application clinical use
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