Description:FIELD OF INVENTION:
The present invention relates to a custom 3D printed orthodontic lower arch appliance for patients with neuropathological chewing. More specifically, the present invention discloses a Neuro Bite Shield comprising a lower arch with posterior bite block and an upper Essix appliance to protect the tongue and prevent the extrusion of teeth.

BACKGROUND OF INVENTION:
Epilepsy is defined by the World Health Organization (WHO) as a chronic affection of multiple etiologies, characterized by recurring episodes of paroxysmal brain dysfunction caused by a sudden disorderly and excessive neuronal discharge. It is a chronic disease characterized by the risk of recurrent seizures.

Epileptic encephalopathy refers to any condition where epilepsy, seizures, seizure-related brain activity, or a combination of all three contribute to brain dysfunction. It can result in severe cognitive and behavioural impairments. Cognitive and behavioural impairments may include motor difficulties, language impairments, or attentional and executive dysfunction. Over time, these can worsen, stay the same, or improve with effective seizure treatments. However, the seizures associated with epileptic encephalopathy are often resistant to treatment. Epileptic encephalopathy typically occurs early in a child’s life, starting in infancy, and can be characterized by generalized (abnormal activity in both halves of the brain) or focal seizures (starting in one part of the brain) that are recurrent, severe and often resistant to antiepileptic medications. Damage to the brain from the frequent seizure activity often leads to delays in development or the loss of developed skills. However, in some cases, a child’s development impairment can also be a result of the underlying condition causing the epilepsy. These conditions are referred to as Developmental Epileptic Encephalopathies (DEE) to acknowledge the presence of multiple causes for the developmental damages.

GNAO1 (G Protein Subunit Alpha O1)- associated epileptic encephalopathy and movement disorder is a rare neurodevelopmental syndrome including hyperkinetic movements, epilepsy, developmental delay and intellectual disability. The characteristic continuous dystonic posturing is life-threatening. It is associated with GNAO1-related disorders encompassing a broad phenotypic continuum that includes hyperkinetic movement disorders and/or epilepsy and is typically associated with delay in physical and mental development leading to intellectual disability.

With respect to the age of onset, three clusters in this continuum can be observed: (1) infantile-onset developmental and epileptic encephalopathy (DEE) with or without prominent movement disorder; (2) infantile- or early childhood-onset prominent movement disorder and neurodevelopmental disorder with or without childhood-onset epilepsy with varying seizure types; and (3) later childhood- or adult-onset movement disorder with variable developmental delay and intellectual disability. Epilepsy can be either DEE (onset typically within the first year of life of drug-resistant epilepsy in which developmental delays are attributed to the underlying diagnosis as well as the impact of uncontrolled seizures) or varying seizure types (onset typically between ages three and ten years of focal or generalized tonic-clonic seizures that may be infrequent or well controlled with anti-seizure medications).

GNAO1 is a protein coding gene which encodes the GNAO1, or guanosine nucleotide‐binding protein G(o) subunit α. The GNAO1 gene has been associated with neurodevelopmental disorders, including early onset developmental and epileptic encephalopathy (DEE), developmental delay without epilepsy, and a range of movement disorders. The G‐protein α subunit along with dimerized β and γ subunits, forms a heterotrimeric G‐protein complex. G‐protein α subunits contain guanosine triphosphate (GTP)‐binding sites and dissociate from both the G‐protein–coupled receptor and the β‐γ dimer of the complex when activated. Alpha subunits are generally classified as stimulatory, inhibitory, or other (o). GNAO1 encodes an “o” type α subunit; beyond GTP binding which has a less well‐established role in signalling. GNAO1 is highly expressed in the central nervous system and is involved in neuronal excitability and neurotransmission.

Movement disorders associated with GNAO1 (G Protein Subunit Alpha O1)- associated epileptic encephalopathy and movement disorder are characterized by dystonia and choreoathetosis, most commonly a mixed pattern of persistent or paroxysmal dyskinesia that affects the whole body. Exacerbations of the hyperkinetic movement disorder, which can be spontaneous or triggered (e.g., by intercurrent illness, emotional stress, voluntary movements), can last minutes to weeks. Hyperkinetic crises (including status dystonicus) are characterized by temporarily increased and nearly continuous involuntary movements or dystonic posturing that can be life-threatening.

Deaths in early childhood have been reported due to medically refractory epilepsy or hyperkinetic crises, but the phenotypic spectrum includes milder presentations, including in adults. Most of the adults with GNAO1-related disorder remain underrecognized and underreported due to lack of advanced genetic testing.

Most patients with a GNAO1 neurodevelopmental disorder are diagnosed as infants or young children. The GNAO1 diagnosis is made through genetic testing. Many of the patients begin experiencing seizures, abnormal movements and developmental delays in their infancy. Some scientists suggest that GNAO1 could become one of the more common rare diseases around the world as the cost for diagnostic tests is reduced and more patients are tested.

Neuropathological chewing is one of the symptoms of GNAO1 associated epileptic encephalopathy and movement disorder and manifests as involuntary and uncontrolled chewing of the tongue resulting from epileptic seizures in patients. The uncontrolled chewing of results in bites and lacerations of the tongue which pose the danger of entrapment of tongue in the bite and extrusion of teeth.

Research has been undergoing to develop devices for the management of neuropathological chewing. One such device is a “Modified cap splint appliance” which is designed to cover upper and lower teeth completely and act as a single assembly but provided with an anterior open bite space, creating very little room for proper tongue movement. However, adequate oral access may not maintain to facilitate proper oral hygiene and suctioning which may lead to serious bacterial infections and pulmonary sequelae. Moreover, the cement bond generally fails due to thermal expansion of the acrylic material, and it is a fixed appliance which cannot be removed and modified according to patient needs.

Another device namely “Taped mouth prop (Molt mouth prop), rubber bite-block (Mekesson rubber bite-block)” has been designed to prevent self-injurious oral trauma in patients, however, it has been reported to get distorted and displaced easily.

Another device, a “Modified oral screen” is a myofunctional appliance designed for use in early interceptive treatment of dental arch deformities. However, the device when placed in the patients’ mouth can get pushed out due to the involuntary movements of the jaw. Notably, additional sutures are required to be placed in the soft tissues to secure the appliance thus causing unwanted new injuries.

Another such device namely “Soft acrylic splint” is positioned directly on the teeth, cemented to the teeth, or held in place by extraoral straps or by retention loops of orthodontic wire. However, it has been reported to cause discomfort and unwanted new injuries to the soft tissues.

The “Wire reinforced methyl methacrylate bite opening appliance” is designed and reinforced by two stainless steel wires which were adapted to the palatal contours and connected the two methyl methacrylate blocks with an additional stainless-steel wire attached to each block and extended extra orally and a Trach tape fastened to each extraoral wire and fastened on the patient's occipit. This structure provides a bulky appearance and causes discomfort to the patient with the wire components causing injury to the soft tissues.

The drawbacks of the devices in the state of the art underscores the need for an appliance which is easy to fabricate and deploy in the patient for preventing tongue and teeth injuries in patients without causing harm to the soft tissues.

OBJECT OF THE INVENTION:
To obviate the drawbacks of the existing state of the art, the present invention discloses a customized 3D printed orthodontic lower arch appliance including a posterior bite block to protect the tongue and upper Essix appliance of patients exhibiting neuropathological chewing.

The main object of the invention is to provide a custom 3D printed lower arch appliance, the Neuro Bite Shield, with posterior bite block and an upper Essix appliance to protect the tongue and prevent the extrusion of teeth.

Another object of the invention is to provide the Neuro Bite Shield to overcome the impact of neuropathological chewing in patients.

Another object of the invention is to provide the Neuro Bite Shield which is designed to withstand extreme involuntary bite forces and prevent trauma related to tongue injuries thus enabling protection of hard and soft tissues.

Another object of the invention is to provide the Neuro Bite Shield that enables the opening of dental occlusion, with the contoured bite blocks reflecting the tongue forward, secondarily improving the patency of the airway.

Another object of the invention is to provide the Neuro Bite Shield that prevents soft and hard tissue trauma by facilitating the inability to articulate the teeth except for the most posterior teeth.

Another object of the invention is to provide the Neuro Bite Shield that requires no interdental wiring for fixation to the dentition while permitting a full range of mandibular movement, thus facilitating hygiene measures by the open bite position.

SUMMARY OF THE INVENTION:
The present invention discloses a custom 3D printed orthodontic lower arch appliance for patients with neuropathological chewing. The appliance called the Neuro Bite Shield comprises of a lower arch with posterior bite block and an upper Essix appliance to protect the tongue and prevent the extrusion of teeth. The Neuro Bite Shield is a protective device designed to withstand the strong biting forces in patients with epileptic encephalopathy. It is light in weight and fabricated by 3D printing using acrylic light polymerizing clear resin. The device is fabricated from the casts of the upper and lower arch impressions of the jaws of the patient made by using putty material, which are then scanned using intra oral scanning device to register the bite. This scanned data is saved as a STL file and used for custom designing the appliance according to the patient’s needs and oral physiology followed by 3D printing, finishing and polishing to provide a clean surface without rough edges. The design of Neuro Bite Shield enables the opening of dental occlusion and improves the patency of the airway while preventing soft and hard tissue trauma by facilitating the inability to articulate the teeth except for the most posterior teeth. The shield is unique in that it does not require any interdental wiring for fixation to the dentition. The device permits a full range of mandibular movement, and the open bite position of the device facilitates oral hygiene measures. The device has been free of any breakage or detachment and no splint has been reported till date.

BRIEF DESCRIPTION OF DRAWINGS:
Fig. 1: depicts the Line drawings of the appliance and designing of the appliance done using Materialise 3 matic software software.
Fig. 2: depicts Severe dytsonia with neck flexion and extension causing change in patinet’s posture
Fig. 3: depicts the extraoral appearance of the patient
Fig. 4: depicts the severely lacerated tongue of the patient.
Fig. 5: depicts the hard tissue examination revealing multiple missing upper and lower teeth.
Fig. 6: depicts the preoperative image of tongue showing a highly inflamed tongue with lacerations on dorsal and ventral aspects of the tongue.
Fig. 7: depicts the casting of the upper and lower arch impression using putty impression material.
Fig. 8: depicts the pouring of the upper and lower working casts using dental stone.
Fig. 9: depicts the scanned upper and lower patient casts and bite registered using intra oral scanning device.
Fig. 10: depicts the 3BL Formlabs machine.
Fig. 11: depicts the 3D printed appliance before and after trimming, finishing and polishing.
Fig. 12: depicts the postoperative images after appliance delivery.
Fig. 13a: depicts the tongue of the patient in the 1st week follow-up after appliance delivery.
Fig. 13b: depicts the 18-day follow-up after appliance delivery.
Fig. 13c: depicts the 3rd week follow-up after appliance delivery.
Fig. 13d: depicts the follow-up after 25 days of appliance delivery.
Fig. 13e: depicts the follow-up after 4 weeks of appliance delivery.

DETAILED DESCRIPTION OF THE INVENTION:
To overcome the drawbacks of the state-of-art, the present invention discloses a custom 3D printed lower arch appliance for patients with neuropathological chewing. The appliance namely the Neuro Bite Shield, comprises of a lower arch with posterior bite block and an upper Essix appliance to protect the tongue and prevent the extrusion of teeth. The appliance is a removable lower occlusal splint with posterior bite blocks on either side with a dual function of protecting the tongue as well as to prevent the extrusion of teeth and avoid entrapment of the tongue in the bite caused by severe biting forces. The Neuro Bite Shield is a protective device designed to withstand the strong biting forces in patients with epileptic encephalopathy. The resin used in the device is chosen based on factors like biocompatibility, strength, flexibility, and ease of use in a 3D printer. The device is light in weight and fabricated by 3D printing using acrylic light polymerizing clear resin commercially available as Dental LT clear (DLC). Its advantages are high performance, aesthetics, accuracy and biocompatibility. DLC resin is durable, fracture resistant, and can be polished to a high optical transparency. It is suitable for hard splint soft splint and aligner fabrication. Alternatives like Dentona Flexisplint (DFS), Cosmos Bite Splint (CBS), ProArt Print Splint (PPS) are also available.

Fig. 1 depicts the line drawings and casts of the Neuro Bite Shield. The shield comprises of a lower arch and a posterior bite block which is custom designed to fit in the jaw of the patient thus preventing bite wounds in the tongue and teeth extrusion.

Method of preparation of the shield:
The Neuro Bite Shield is fabricated from an acrylic light polymerizing clear resin by 3D printing. The upper and lower arch impressions of the jaws of the patient were made using putty material, and working casts were made by pouring dental stone into the impression. Patient casts were scanned using intra oral scanning device and bite was registered. The precision of the cast scanning ensures a comfortable and effective fit, improving functionality.

The scanned data of the casts was saved as a STL file and used for designing the appliance using Materialise 3 matic software. The custom designed appliance made according to the patient’s needs and oral physiology was then 3D printed followed by finishing and polishing to avoid rough surface.

The material used for the fabrication of the shield is Dental LT clear (DLC) comprising of an acrylic light polymerizing clear resin which exhibits high performance, is aesthetic in appearance, is accurate to deploy and biocompatible. The resin is manufactured by Formlabs, Somerville, MA, USA. DLC resin is durable, fracture resistant, and can be polished to a high optical transparency. It is suitable for hard splint soft splint and aligner fabrication. The occlusal splint fabrication is done by 3D printing and the fabrication process involves several key stages like scanning of dental impression/cast, designing, slicing, printing, and post processing. The slice thickness ranges from 0.1mm-0.5mm. we have used slice thickness of 0.1mm.

The Neuro Bite Shield is custom designed according to the anatomy of each patient as the various dimensions of dental arches differs in each individual. The dimensions are calculated during designing of the available appliance in the software (Materialise 3 matic, Leuven, Belgium).

The Neuro Bite Shield is an original appliance made solely to prevent trauma and protect hard and soft tissues. While there may be surface-level visual similarities with other appliances, the purpose, function, and mechanical requirements of the appliance are fundamentally different which clearly demonstrate the novelty and functionality of the design. The design of the Neuro Bite Shield overcomes the drawbacks of the state of the art by enabling the opening of dental occlusion, with the contoured bite blocks reflecting the tongue forward, secondarily improving the patency of the airway. The shield further prevents soft and hard tissue trauma by facilitating the inability to articulate the teeth except for the most posterior teeth. The shield requires no interdental wiring for fixation to the dentition. It is a removable lower arch appliance and can be placed and removed just like any other appliance (eg: retainer, soft splint), where the indentations in the appliance meets the crown portion of the lower teeth. A full range of mandibular movement is permitted, and oral hygiene measures are facilitated by the open bite position. Notably, breakage or detachment of the splint has never been reported till date.

Deployment and working of the shield:
The appliance is easy to place over the dental arch and remove. The deployment procedure comprises aligning of shield with arch morphology and gently pressing it into position to ensure passive fit. The indentations in the appliance fit perfectly on the crown portion of the lower teeth. Neuro bite shield is a removable lower arch appliance specifically designed for neuropathological chewing, a condition characterized by uncontrollable, involuntary jaw movements with significantly higher bite forces than normal that causes severe injury to the tongue, hard and soft tissues. The shield is built to withstand extreme involuntary bite forces and prevent tongue injuries. The posterior bite blocks serve a critical protective function, by creating an anterior open bite, thereby preventing the tongue from being trapped or injured due to involuntary chewing forces. Given the high occlusal forces in neuropathological chewing (which can exceed 1000 N or more with some cases reporting forces as high as 1200-1500 N), the appliance is designed to resist distortion and displacement, as it is retentive thereby ensuring effective protection.

EXAMPLE:
FABRICATION AND DEPLOYMENT OF THE NEURO BITE SHIELD
Pathology of the patient:
A 13-year-old child with childhood onset GNAO1-associated epileptic encephalopathy and status dystonicus presented with severe lacerations of the tongue due to persistent neuropathological chewing was admitted to the Pediatric Intensive Care Unit (PICU) at Amrita Institute of Medical Sciences, Kochi. GNAO1-associated epileptic encephalopathy and movement disorder is a rare neurodevelopmental syndrome involving involuntary, uncontrolled hyperkinetic movements, epilepsy, developmental delay and intellectual disability. The characteristic continuous dystonic posturing is life-threatening. Symptoms of GNAO1-associated epileptic encephalopathy showing severe dytsonia with neck flexion and extension causing changes in the child’s posture has been depicted in Fig. 2.

The patient was tracheostomized, tube fed and was treated with the required antiepileptic and antidystonic medications as conventional management options were inadequate in preventing further injuries to the tongue. The condition of the severely lacerated tongue has been depicted in Figs. 3 and 4. The upper and lower jaw of the patient revealing multiple missing upper and lower teeth due to neuropathological chewing have been depicted in Fig. 5. Similarly, Fig. 6 depicts the preoperative image of the highly inflamed tongue with lacerations on dorsal and ventral aspects.

Fabrication of the Neuro Bite Shield:
In order to fabricate a customized Neuro Bite Shield for the patient, the upper and lower impressions of the jaw were taken using putty material, and working casts were poured. Upper and lower casts were scanned using intra oral scanning device (Dentsply Sirona) and the bite was registered. The procedure of taking impressions and the prepared casts have been depicted in Fig. 7. The upper and lower working casts poured using dental stone has been depicted in Fig. 8.
The precision of the cast scanning is important to ensure a comfortable and effective fit to improve functionality. Fig. 9 exhibits the scanned upper and lower patient casts and bite registered using intra oral scanning device. Using the scan, a custom designed 3D-printed lower arch appliance with 7mm posterior bite block was developed to protect the tongue and an upper Essix appliance was fabricated to prevent extrusion of teeth and improve child's quality of life. The device is fabricated in a 3BL Formlabs machine which is depicted in Fig. 10. The device is trimmed, finished and polished to make it ready to use, as depicted in Fig. 11.

The custom fabricated appliance was placed in the oral cavity, and the patient was kept under observation. The deployment of the Neuro Bite Shield in the oral cavity of the patient is depicted in Fig. 12. The postoperative images after appliance delivery clearly shows that the posterior bite blocks on the appliance creates an open bite thereby relieving tongue from further injury resulting in steady healing of the tongue.

Impact of the Neuro Bite Shield:
The patient was observed over a period of one month from the deployment of the Neuro Bite Shield. While dystonia persisted, the tongue was no longer trapped in the bite and the appliance was observed to be withstanding the severe biting forces of the patient.

The patient was closely monitored daily, diligently checking for any new tongue injuries. With each passing day, the tongue showed steady healing as is depicted in Figs. 13a-13e. The figures depict the transition from a badly lacerated tongue in the first week to a completely healed and healthy tongue by the end of the 4th week indicated by the slough formation to crusting and scab formation, which later fell away. The deployed Neuro Bite Shield deployed in the oral cavity protects the tongue lacerations and teeth extrusion thus enabling steady healing of the with each passing day. The shield can be undeployed by slight upward finger pressure to relieve the retention. It can be undeployed for cleaning of the appliance and oral cavity on a daily basis until the condition is resolved. Proper cleaning of the appliance should be done using chlorhexidine solution and Saline irrigation.

The present invention is an innovative approach which uses a 3D-printed appliance to mitigate the risk of recurrent tongue injury, demonstrating the potential of customized dental appliances in managing and enhancing patient care in complex neurodevelopmental syndromes.
, Claims:1. An orthodontic lower arch appliance, Neuro Bite Shield, for management of neuropathological chewing comprising:
- at least one posterior bite block to protect the tongue and
- at least one upper Essix appliance to prevent extrusion of teeth.
characterized in that the said Neuro Bite Shield is a removable lower occlusal splint for protecting the tongue as well as to prevent the extrusion of teeth and avoid entrapment of the tongue in the bite caused by severe biting forces.
2. The orthodontic lower arch appliance as claimed in claim 1, wherein said appliance light in weight and fabricated by 3D printing using acrylic light polymerizing clear resin.
3. The orthodontic lower arch appliance as claimed in claim 1 wherein a removable lower occlusal splint with posterior bite blocks on either side protects the tongue as well as prevents the extrusion of teeth and avoid entrapment of the tongue in the bite caused by severe biting forces.
4. The orthodontic lower arch appliance as claimed in claim 1 wherein scanned data of the casts is used for designing the appliance.
5. The orthodontic lower arch appliance as claimed in claim 1, wherein the occlusal splint fabrication is done by 3D printing with a slice thickness ranging from 0.1mm to 0.5mm.
6. The orthodontic lower arch appliance as claimed in claim 1, wherein said appliance can withstand biting forces exceeding 1000 N.
7. The orthodontic lower arch appliance as claimed in claim 1, wherein said appliance can withstand biting forces ranging from 1200-1500 N.
8. A method of fabrication of the orthodontic lower arch appliance as claimed in claim 1, the method comprising the steps of:
- getting the upper and lower impressions of the jaw using putty material,
- Upper and lower casts were scanned using intra oral scanning device (Dentsply Sirona) and the bite was registered.
- pouring of working casts,
- scanning of upper and lower casts using intra oral scanning device (Dentsply Sirona) and registering the bite,
- Using the scan, a custom designed 3D-printed lower arch appliance with 7mm posterior bite block was developed to protect the tongue and an upper Essix appliance was fabricated to prevent extrusion of teeth and improve child's quality of life.
- developing a custom designed 3D-printed lower arch appliance with a 7mm posterior bite block,
9. A method of deployment of the orthodontic lower arch appliance as claimed in claim 1, wherein the appliance is inserted in the lower arch wherein indentations present in the appliance fit perfectly to the crown portion of lower teeth.