Patent Publication Number: US-2022226146-A1

Title: A method of manufacturing an intraoral device

Description:
FIELD 
     The present invention relates to a method of manufacturing an intraoral device, and more particularly to a multiple (i.e. at least two) material intraoral device having a soft lining. 
     BACKGROUND 
     Various forms of intraoral devices are known. One known form of an intraoral device is a mandibular advancement device that has application in the treatment of sleep disorders such as snoring or obstructive sleep apnoea (OSA), or certain temporomandibular joint disorders. Another known form of an intraoral device is a mouthguard for the protection of the teeth from impact injury (for example, a mouthguard for use during contact sports). Yet another known form of an intraoral device is a retainer or plate-type device for orthodontic applications, such as the adjustment of a patient&#39;s bite or the realignment of teeth. 
     The effectiveness of such devices often relies on the patient using the device as directed and the accuracy of manufacturing the device to fit the teeth and jaw of the patient. Typical known devices are made by hand and are subject to human errors and use materials that are proned to expansion and contraction problems. Such techniques include the lost wax technique, relining press technique, injection mould techniques and milling a single material. Known methods are also disadvantageous because they produce large amounts of scrap and waste. 
     Whilst digitally produced devices are known, they are typically formed from a single material. Such materials are typically selected for the balance of mechanical properties such as flexural strength, flexural modulus, fracture toughness and water sorption. However, they are not optimised for properties that result in higher patient comfort such as shore A hardness or elongation at break, and due to their stiffness are difficult to optimise retention (seating on the teeth), resulting in frequent device remakes. 
     There is a need for an intraoral device having a soft lining for patient comfort. There are handmade devices that use soft linings using the lost wax technique, thermofoil suck-down or injection system. However, the manufacturing process of these devices is not suitable with automated and digital manufacturing methods. 
     Accordingly, there is a need for an at least two material milled intraoral device with a soft lining. Having the soft lining milled may at least ensure dimensional precision (CNC type accuracy), resulting in an intimate and comfortable fit for the patient, while the harder base may at least provide structural integrity. 
     SUMMARY 
     It is an object of the present invention to substantially overcome, or at least ameliorate one or more of the disadvantages of existing arrangements, or at least provide a useful alternative to the existing arrangements. 
     There is disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression, said cavity being milled to include an offset; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; 
     milling said first material to obtain a device shape; 
     cleaning said device; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is also disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression to obtain a device shape, said cavity being milled to include an offset; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; 
     cleaning said device; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is also disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression, said cavity being milled to include an offset; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; 
     milling said first material to obtain a device shape; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression, said cavity being milled to include an offset; 
     filling said cavity with at least a second material; 
     milling said second material to correspond to said impression; 
     milling said first material to obtain a device shape; 
     cleaning said device; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is also disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression to obtain a device shape, said cavity being milled to include an offset; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is also disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression to obtain a device shape, said cavity being milled to include an offset; 
     filling said cavity with at least a second material; 
     milling said second material to correspond to said impression; 
     cleaning said device; and wherein 
     said first and second materials are comparatively hard and soft. 
     Preferably, said offset is 0.5 mm to 1.5 mm. 
     Preferably, said cavity includes a base, upwardly extending side walls to a lip, said lip including a shelf. 
     Preferably, said first material is a relatively rigid polymer such as acrylic, polyamide or polycarbonate. 
     Preferably, said second material is an elastomeric material such as silicone, plasticized acrylic, thermoplastic polyurethane or vinyl copolymers. 
     Preferably, said second material is a heat formable material such as polycaprolactone. 
     Preferably, said device is CNC milled. 
     Preferably, where the filling of the secondary material is a partial filling of the cavity, to reduce material wastage. 
     Preferably, where the filling material is viscous, after filling any air pockets located within said second material shall be removed prior to curing. 
     Preferably where the filling material is formed by thermoforming. 
     There is disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a 3D printing machine and a milling machine; 3D printing a first material with an offset substantially corresponding to said impression; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; 
     milling said first material to obtain a device shape; 
     cleaning said device; and wherein 
     said first and second materials are comparatively hard and soft. 
     There is disclosed herein a method of manufacturing an intraoral device including: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression; 
     forming by pressure and/or heat a foil over the cavity; 
     milling the cavity with an offset; 
     placing the foil over the blank to form a closed volume; 
     filling volume closed with at least a second material and allowing said second material to cure; and wherein 
     said first and second materials are comparatively hard and soft. 
     Preferably, said device is cleaned using a micromotor tool. 
     Preferably device is cleaned using dry ice. 
     Preferably, an intraoral device is made by the method above. 
     Preferably, the thickness of the first material is between 0.5 mm and 4.0 mm. 
     Preferably, the thickness of the second material is between 0.5 and 1.5 mm. 
     Preferably, the flexural modulus of the first material is between 1000 MPa and 4000 MPa. 
     Preferably, the Shore A hardness of the second material is between 55 and 99. 
     Preferably the device is a mouthguard. 
     Preferably a cutter used to mill or machine the second material has a ball head geometry with a plurality of blades extending radially from the ball head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention will now be described, by way of an example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows an intraoral device blank after the first initial milling; 
         FIG. 2  shows a simple cross-section view of the final product layers of the intraoral device of an embodiment of the present invention; 
         FIG. 3  shows the application of the lining material to the blank of  FIG. 1 ; 
         FIG. 4  shows the device of  FIG. 3  manually pressed to remove air pockets; 
         FIG. 5  shows the device of  FIG. 3  filled and cured; 
         FIG. 6  shows the device of  FIG. 5  with the air pockets being lanced; 
         FIG. 7  shows the device of  FIG. 5  being inspected for air pockets; 
         FIG. 8  shows the device of  FIG. 5  being placed in a curing flask; 
         FIG. 9  shows the device of  FIG. 5  after the soft lining has been milled; 
         FIG. 10  shows the device of  FIG. 9  after milling with burs being removed by dry ice; 
         FIG. 11  shows a 3D printed version of the device of  FIG. 1 ; 
         FIG. 12  shows another cross-section view of an intraoral device; and 
         FIG. 13  shows another cross-section view of an intraoral device. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     One form of a known intraoral device is disclosed in International Patent Publication No. WO 2017/106896, the content of which is incorporated herein by reference in its entirety. This publication relates to a form of intraoral device known as a mandibular advancement splint (MAS) or mandibular advancement device for the treatment of snoring and obstructive sleep apnoea (OSA). This mandibular advancement device includes a lower part and an upper part, which are adapted to be fitted to the respective upper and lower jaw of a patient for use in sleep. The various parts of this mandibular advancement device are designed to advance the lower jaw of a patient in an anterior direction, thereby carrying the tongue forward and reducing the likelihood of the tongue impacting on the airway of the patient. The present invention could be used to make such a device. 
     Referring to  FIGS. 2, 11, 12 and 13 , for example, a typical intraoral device  1  includes a body  5  formed from a relatively rigid material such as acrylic, polyamide, polycarbonate or the like. The body  5  is adapted to be fitted in the oral cavity of a patient. The body  5  typically includes a front central portion  7  and a pair of longitudinally extending arms  8 ,  9 . A cavity  11  extends along the central portion and arms and includes a base  12  and upwardly extending walls  13  as best seen in  FIG. 2 . The base  12  is adapted to be moulded to the shape of the patient&#39;s teeth. 
     The manufacturing of the intraoral device  1  will now be described with reference to the drawings and images. 
     An impression of a patient&#39;s teeth can be acquired from a physical record taken with polyvinyl siloxane (PVS) or similar material that is then poured up and digitised. Preferably, the physical record is acquired digitally using an intraoral scan of the teeth or a cone beam computed tomography (CBCT) scan of the teeth. For mandibular advancement splints (MAS) or devices, the dentist may use a bite gauge tool to capture a protrusive relationship. Once the impression of the patient&#39;s teeth is obtained in a digital form, the impression is uploaded to a repository of cases to be processed. The files are inspected for defects such as incomplete scan, warps or defects. Assuming that these files pass the requirements, computer-aided design (CAD) software is used to design at least two bodies, formed from a hard and a soft material. These CAD files are exported as STL or similar file type and then imported into milling software. One or more of the processors may be utilised during the process. The multiple milling stages are calculated in computer numerical control (CNC) software at a similar time, taking care to ensure that the files are not misaligned. Referring to  FIG. 1 , for example, the technician would take a blank  20  of suitable, preferably rigid and/or hard structural material (such as PMMA or polyamide) and mill (or otherwise remove material from the blank as shown in  FIG. 1 ), using a milling machine, the cavity  11  in the general form of teeth. The milled cavity  11  would be offset from the accurate impression by 0.5 to 1.5 mm. This may also be known as a first general milling run. 
     As best seen in  FIG. 2 , the walls  13  of the cavity  11  include a shelf  22  to accommodate a flange  25  of a soft lining or insert  26 . In other words, the soft lining or insert  26  is adapted to fill the cavity  11 . The soft lining or insert  26  may be an elastomeric material such as silicone, plasticized acrylic, thermoplastic polyurethane, or vinyl copolymers. The soft lining or insert  26  may alternatively be a heat formable material such as polycaprolactone. It will be understood that the soft lining or insert  26  is soft relative to the material of the blank  20 . The flange  25  may at least increase the surface area of the soft lining or insert  26  and mitigate failure of the bonding of the two materials  5 ,  26  at the junction of the soft lining  26  and the hard surface (body)  5 . This arrangement may also prevent the problem of delamination during the milling process. Multiple shelves  22  forming retention grooves  40  may be present, for example, as seen in  FIG. 12 . The soft lining or insert  26  at the base  12  facing the cavity  11  has a fit surface  14  that is cleaned (or prepared with a primer, bond agent, plasma surface treatment, sand blasting treatment or the like) and the cavity  11  is packed completely or partially, manually or with the aid of a machine as see in  FIG. 3 . At this step care must be taken while applying the soft lining material  26  to remove air pockets, particularly when the soft lining material  26  is viscous to facilitate the filling of the cavity  11 . If air pockets exist, they can be lanced/pierced using a probe or the like as shown in  FIG. 6  providing a path for air to escape before being recompressed ( FIG. 8 ). The soft lining or insert  26  may alternately be pressed under forces using pneumatic press, vacuum chambers or other like pressurised application methods (mechanical or hydraulic) as shown in  FIGS. 4  and  8 . The shelf or shelves  22  could also be milled in the reverse configuration as shown in  FIG. 13 . 
     As seen in  FIG. 7 , the filled in blank  20  can be held up to the light to check for air pockets. The filled in blank  20 , along with the soft lining or insert  26 , as shown in  FIG. 8  is then cured at relevant processing conditions for the soft lining or insert  26 . This may involve water, heat, light and/or pressure as per supplier instructions. 
     As seen in  FIG. 9 , the soft lining material  26  is then milled or machined to the desired dimensions of the impression using a specialised cutter. A specialised cutter would change depending upon the type of soft lining material  26  that is being utilised. The cutter may, for example, have a ball head geometry with a plurality of blades extending radially from the ball head. 
     The blank  20  is then rotated and the excess hard material is removed to form the body  5 , thus obtaining the shape of the device  1 . Any minor burrs remaining after milling may be removed (thereby cleaning the device) using a micro motor hand piece or the like with a brush burr, or alternatively may be removed using dry ice CO2 blasting or the like, as shown in  FIG. 10 . The blank  20  and/or the body  5  may have a thickness of between 0.5 to 4.0 mm and/or a flexural modulus of between 1000 MPa and 4000 MPa. The soft lining material  26  may have a Shore A hardness of between 55 and 99. 
     It will be appreciated that a method of manufacturing an intraoral device may include (and is not limited to) any one or more of the following steps: 
     obtaining an impression of at least one row of a patient&#39;s teeth; 
     transferring said impression into a processor; 
     said processor communicating with a milling machine; 
     milling a blank of a first material to form a cavity in said blank substantially corresponding to said impression, said cavity being milled to include an offset; 
     filling said cavity with at least a second material and allowing said second material to cure; 
     milling said second material to correspond to said impression; 
     milling said first material to obtain a device shape; 
     cleaning said device; and wherein
         said first and second materials are comparatively hard and soft.       

     In alternate embodiments, the full shape of the body  5  of the device  1  is obtained by milling the blank  20 . The soft lining or insert  11  is then added to the cavity  11 , and subsequently milled or machined to the desired impression. In further alternate embodiments, instead of using a blank and milling, the body  5  of the device  1  could be 3D printed using acrylic, polyamide, polycarbonate using technology such as FDM, SLS, DLP as generally shown. The offset of 0.5 mm to 1.5 mm may still be provided, and the 3D printer could also include a locator  30  (see  FIG. 11 ) for assistance to the technicians. The cavity  11  could then be packed with the soft lining material  26  or sucked down. The device  1  could then follow the usual steps of the milling, locating using the fixtures  30  and mill the fit surface  14 . 
     As mentioned above, a suckdown method could also be used using a suitable structural material such as PMMA or polyamide with an offset to accommodate the soft lining as mentioned above. In this case one or more air holes would be used at the central portion  7  and arms  8  and  9  for air to escape. A primer would then be applied along with a bonding agent then the suckdown dual laminate would occur. 
     The present invention at least in a preferred embodiment has significant advantages over the prior art. For example, it may at least provide comfort for the patient (soft lining plus strength) with greater compliance to the patient&#39;s teeth and fewer breakages. The method may also provide enhanced accuracy of fit, which may again lead to greater patient comfort, fewer areas of high contact pressure and more even pressure across the teeth. Due to the enhanced accuracy, there is also less tooth movement. 
     The method may also provide a lower risk of delamination than traditional suckdown methods due to the shelf/lip design and lancing technique, which provides a longer life device. There is a reduced need for remakes, and no physical working model is required, thus saving costs and by-products. 
     Alternative embodiments could include using dry ice CO2 blasting to remove the burrs left on a fit surface, instead of manually doing the same with a micro motor and brush burr and also applying the technique to 3D printed parts as mentioned above. Further, the soft lining material can be deposited/dispensed by CNC robotic dispensing systems, thus providing less waste instead of packing the cavity with greater control dispensing amount of material required on marginally more than required. Greater control equals fewer errors as the process is automated, and new materials may also become available for use, instead of only acrylic or polyamide. Plasma surface treatment or sand blasting may also improve the soft lining bond strength. The milling of the soft lining material is particularly advantageous. 
     Accordingly, the present invention at least in the preferred embodiment may at least provide an extremely precise fitting of a dual material device fabricated digitally and automatically. The arrangement may at least remove most (if not all) human errors and remove inherent errors from the expansion and contraction of materials which are characteristics of traditional processes. The highly desirable characteristics of dual laminate materials may at least provide a balance of flexibility and comfort including strength and durability. The device could, in a preferred form, be a sleep apnea device. However, the device could also be a bruxism splint, mouthguard, denture, hearing aid or the like. 
     Although the invention has been described with reference to preferred embodiments, it will be appreciated by those persons skilled in the art that the invention may be embodied in many other forms.