Evaluation of dental, skeletal, functional, and postural changes pre and post neuro-occlusion rehabilitation with reflex releasing diagnostic splint in children with functional mandibular shifts with deciduous and early mixed dentition- A case control study

Symmetric bilateral activity of masticatory muscle has been considered to keep mandible in centric relation (CR) to cranium.  This is the physiological rest position of mandible which while stomatognathic functions (speech, respiration, mastication etc.) provide symmetric proprioception and in turn promote balance growth of facial skeleton including components of temporomandibular joint (TMJ) bilaterally. However, mandible while occluding tends to reach in maximum intercuspation position (MIP). If MIP is achieved in without much deviation of mandible as that of centric relation, called as centric occlusion (CO) with unstrained position of TMJ and symmetrical tonicity and activity of associated muscles.However, many times premature contacts (PC) because of environmental causes in deciduous or in mixed dentition, may deviate mandible to the position other than ideal CO known as CO-CR discrepancy or Functional mandibular shift (FMSH). FMSH in transverse/ coronal plane are clinically evident as unilateral posterior crossbite (UPXB), while that of in sagittal plane as pseudo-class III or developing Class II.

To differentiate between skeletal and functional malocclusion, a clinician needs to bring mandible in CR and then to closely observe closing path of mandible to find premature contact responsible for function shift. Some conventional qualitative methods to achieve CR are- swallowing with tongue tip at incisive papilla, phonetics with word ‘Mississippi’. Electromyographic studies found that jaw movements are quickly learned and UPXB may persist even at rest position ready to occlude in MIP. While similar muscular activity was found when mouth was opened wide. Other quantitative methods eg. Transcutaneous Electrical Nerve Stimulation (TENS), Electromyography (EMG), Jaw tracing device and T-Scan are getting popularity in Neuromuscular dentistry (NMD) set up now a days. All these methods are applied in patients with known temporomandibular disorders. Researches could find 50% correction only of centric relation in patients with FMSH. Firstly, because not guaranteed results and also for being expensive these methods cannot be applied in fields or routine clinical checkup. Secondly if machine gets corrupted, its repair is usually time consuming and expensive both.

The phonetics ‘Mississippi’ does not help mandible open wide. In prosthodontics it relocates mandible for minimum required vertical opening while function of speech. Therefore, this word is denoted here as ‘short phonetics’.

Some new words are searched i.e. Aam, Raam and Naam (denoted as long phonetics) to facilitate little children pronounce easily. The vowel ‘Aa’ helps open mouth wide stretching bilateral muscles and breaking the faulty proprioception from PDL and muscle itself. The consonants ‘R’ and ‘N’ help tongue to touch incisive papilla on palate thereby helping transverse maxillo-mandibular relation. The consonant ‘M’ is the bilabial sound, helps bringing mandible in sagittal and vertical alignment. According to Devnagari varnmala these innovative words include ‘Swara’ the first sound to start, to the last group of bilabial sound. Words are popular in India and easy to memorize by children.

Therefore, the study aimed to validate the effect of long phonetic method to get mandibular centric relation by quantifying bilateral activity of muscles of mastication both pre-phonetics and after phonetics with the help of surface EMG method. Once it is validated, the long phonetics can be applied in clinics and field studies without use of cumbersome machines.