A thickened multi-layer orthodontic membrane for patients with periodontal disease

Abstract

The present invention discloses a thickened multi-layer orthodontic membrane for periodontal patients, belonging to the fields of orthodontics and periodontology. It includes an intermediate layer, with a first outer layer and a second outer layer respectively arranged on both sides of the intermediate layer. A thickened layer is provided in the molar occlusal surface area on the side of the first outer layer away from the intermediate layer. The membrane of the present invention has a non-uniform thickness and is thickened at the molar occlusal surface, which can relieve the premature contact when retracting the anterior teeth of periodontal patients and avoid further loosening of the teeth. The membrane is a multi-layer composite structure, with a large hardness and strong anti-fracture performance of the outer layer, which improves the wear resistance of the membrane. When periodontal patients wear braces to eat, it can not only relieve the premature contact of the anterior teeth, but also make the braces serve as a periodontal splint to avoid further loosening of the teeth. Through the intermediate layer, the overall elastic modulus of the membrane is relatively low to provide a softer orthodontic force required by periodontal patients and avoid the "tooth extraction force" when removing and wearing the braces. The present invention can also be applied to other orthodontic designs that require raising the posterior teeth.

Description

Technical Field

[0001] The present invention relates to the fields of orthodontics and periodontology, and in particular to a thickened multi-layer orthodontic membrane for periodontal patients. Background Art

[0002] Malocclusion generally refers to the deformities of teeth, jaws, and craniofacial regions caused by genetic and environmental factors during the growth and development process, and can also be caused by reasons such as trauma and periodontal disease after the completion of growth and development. In 2000, the Orthodontic Special Committee of the Chinese Stomatological Association conducted a prevalence survey of malocclusion in 7 regions across the country, showing that the prevalence rate among children and adolescents in China was 67.82%. Malocclusion not only affects the facial aesthetics but also has an impact on the development of the dentofacial region and the functions of the oral cavity. With the development of China's economic level, the demand for the correction of malocclusion has gradually increased. The orthodontic appliances used during treatment are divided into fixed orthodontic appliances, removable orthodontic appliances, and bracketless invisible orthodontic appliances. Compared with the traditional fixed orthodontic method, bracketless invisible orthodontics has the advantages of being transparent and beautiful, convenient for cleaning, and high in comfort, and has been widely used clinically. The bracketless invisible orthodontic technology generates a digital 3D dental model of the patient through digital scanning, designs the step-by-step tooth movement by computer, prints a series of dental models by 3D printing, and then uses a thermoforming film material to perform vacuum thermoforming on the model to produce transparent dental braces. During orthodontic treatment, the patient sequentially replaces the dental braces, and the thermoforming film material provides the orthodontic force through the resilience to move the teeth. To improve the efficiency of tooth movement, different-shaped attachments are usually designed on the tooth surface by computer to achieve tooth movement in different directions.

[0003] Among adults in China, the incidence rate of periodontal disease is greater than 50%, which is manifested as gingival bleeding, tooth loosening, reduction of alveolar bone height, gingival recession, the appearance of "black triangles", and in severe cases, tooth fan-shaped displacement, resulting in tooth protrusion and occlusal trauma, causing further alveolar bone resorption. Orthodontic treatment can alleviate the aesthetic problems of tooth protrusion and "black triangles" caused by periodontal disease, relieve occlusal trauma, and avoid further alveolar bone resorption. Periodontal patients still need to cooperate with regular periodontal maintenance during the orthodontic treatment process, so invisible orthodontics is often selected for the convenience of periodontal maintenance operations.

[0004] The difference between orthodontic patients with periodontal disease and those with periodontal health is that periodontal patients often have loose teeth and a large clinical crown-root ratio, so orthodontic forces are required to be gentler. For those with periodontal health, the appropriate orthodontic force is 0.35N to 1.25N. In order to provide sufficient correction force, commercially available orthodontic membranes usually use membranes with a tensile elastic modulus of 1800 to 2200MPa. Studies have shown that the correction force generated by commercially available orthodontic membranes is about 3.0 to 5.0N, which is more suitable for orthodontic forces. However, periodontal patients require less force for orthodontics. At the same time, in order to avoid the "tooth extraction force" caused by the hard material when removing and wearing invisible braces, a smaller elastic modulus and softer appliance is required. There is currently no orthodontic membrane specifically for periodontal patients.

[0005] During the orthodontic process of periodontal patients, the fan-shaped front teeth that are retracted are prone to premature contact, causing occlusal trauma and aggravating tooth looseness. Therefore, when retracting the front teeth, it is often necessary to raise the occlusal surface in the molar area to relieve the premature contact of the front teeth. When using bracketless invisible correction technology, raising the molars is achieved by designing a large rectangular attachment on the occlusal surface of the molars, that is, after designing the attachment, the resin is not bonded, and a rectangular raised cavitation of about 5mm*5mm and about 1mm high can be obtained on the occlusal surface of the molars of the invisible appliance. However, the occlusal surface of the molar area is the area in the mouth where the dentition bears the greatest force. If the raised rectangle is too small, the occlusal contact surface of the molars becomes smaller, which reduces the patient's chewing efficiency and increases discomfort. The raised area is a cavitation with a small bearing capacity, which easily causes the braces to deform.

[0006] The hot pressing film material currently used to make invisible braces is a film with uniform thickness. Due to the uneven distribution of internal stress during hot pressing film forming, the thickness of the braces on the labial side of the incisor is thinner than other positions. To solve this problem, some patents have designed non-uniform thickness hot pressing film films to thicken the labial side of the incisor. Patent CN115252183A designs a multi-layer orthodontic film with non-uniform thickness. The strength of the film is increased by compounding multiple polymers. The film is thick around the edges and thin in the middle. The final hot pressing-formed braces are thinner at the incisor end, and the thickness is uniform at other positions to make up for the disadvantages of thin braces and low force at the force-applying parts caused by traditional uniform film. Patent CN219153603U designs an uneven wall thickness dental orthodontic film and its manufacturing mold. The braces made of this film are thick on the labial side of the incisor and thin on the occlusal surface of the molar. Thickening the labial side of the incisor makes the braces more comfortable to wear. Patent CN109965994A designs a partitioned dental diaphragm and a manufacturing method thereof, wherein the diaphragm is thickened to different thicknesses on the labial side and the lingual side of the incisor area and the molar area according to the characteristics of hot pressing.

[0007] The above patented orthodontic diaphragms improve the disadvantage of thin labial surfaces of incisors and molars when making orthodontic diaphragms of uniform thickness, but still fail to solve the problem that orthodontic patients with periodontal disease need softer diaphragms and feel uncomfortable with the raised molar area and poor chewing efficiency. Summary of the Invention

[0008] The object of the present invention is to provide a molar thickened multi-layer orthodontic membrane for periodontal disease patients, which solves the problems that the existing orthodontic membranes are not suitable for orthodontic patients with periodontal disease, the softness is insufficient, the elevation of the molar area is uncomfortable, and the chewing efficiency is poor.

[0009] To solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A molar thickened multi-layer orthodontic membrane for periodontal disease patients of the present invention includes an intermediate layer, and a first outer layer and a second outer layer are respectively arranged on both sides of the intermediate layer, and a thickened layer is arranged in the molar occlusal surface area on the side of the first outer layer away from the intermediate layer.

[0011] Furthermore, the first outer layer, the second outer layer, the intermediate layer and the thickened layer are made into a single piece by an injection molding method, and the single piece is made into a multi-layer composite membrane by layer-by-layer molding.

[0012] Furthermore, the thickness of the intermediate layer is greater than the thicknesses of the first outer layer and the second outer layer.

[0013] Furthermore, the intermediate layer has the lowest tensile elastic modulus, the first outer layer and the second outer layer have a medium tensile elastic modulus, and the thickened layer has the highest tensile elastic modulus.

[0014] Furthermore, the total thickness of the first outer layer, the second outer layer and the intermediate layer is 0.6 - 1.0 mm.

[0015] Furthermore, the intermediate layer has a tensile elastic modulus of 500 - 1500 MPa and a thickness of 0.5 - 0.75 mm; the first outer layer and the second outer layer have a tensile elastic modulus of 1500 - 2500 MPa, a hardness of 70 - 80 D, and a thickness of 0.05 - 0.25 mm; the thickened layer has a tensile elastic modulus of 2000 - 3000 MPa, a hardness of 75 - 90 D, and a thickness of 0.5 - 1.0 mm.

[0016] Furthermore, the first outer layer, the second outer layer, the intermediate layer and the thickened layer are all made of thermoplastic polymer materials.

[0017] Compared with the prior art, the beneficial technical effects of the present invention:

[0018] A multi-layer orthodontic membrane sheet with thickened molars for periodontal disease patients according to the present invention has the following advantages: 1. The membrane sheet has a non-uniform thickness and is thickened on the occlusal surface of the molars, which can relieve the premature contact when retracting the anterior teeth of periodontal disease patients and avoid further loosening of the teeth; 2. The membrane sheet is a multi-layer composite structure. The outer layer has high hardness and strong fracture resistance, which improves the wear resistance of the membrane sheet. When periodontal disease patients wear braces to eat, it can not only relieve the premature contact of the anterior teeth, but also make the braces act as a periodontal splint to avoid further loosening of the teeth; through the intermediate layer, the overall elastic modulus of the membrane sheet is relatively low to provide a softer orthodontic force required by periodontal disease patients and avoid the "tooth extraction force" when removing and wearing the braces; 3. The present invention can also be applied to other orthodontic designs that require raising the posterior teeth. For example, patients with anterior open bite need to depress the posterior teeth to establish an occlusal relationship for the anterior teeth. Thickening the occlusal surface of the molar area of the orthodontic appliance will make the efficiency of depressing the molars higher; patients with deep overbite have a deep bite and there is no space to place the orthodontic appliance between the upper and lower anterior teeth. The occlusal surface of the molar orthodontic appliance can be thickened to help open the bite and increase the space for the anterior teeth. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 It is a top view of the thickened multi-layer orthodontic membrane sheet for molars of the present invention used for periodontal disease patients;

[0021] Figure 2 It is a cross-sectional view of the thickened multi-layer orthodontic membrane sheet for molars of the present invention used for periodontal disease patients;

[0022] Figure 3 It is a usage state diagram of the thickened multi-layer orthodontic membrane sheet for molars of the present invention used for periodontal disease patients;

[0023] Figure 4 It is the uniaxial tensile curve of three materials in the embodiment of the present invention;

[0024] Figure 5 It is the stress relaxation curve of three materials in the embodiment of the present invention.

[0025] Description of reference numerals: 1. First outer layer; 2. Second outer layer; 3. Intermediate layer; 4. Thickened layer. DETAILED DESCRIPTION OF THE INVENTION

[0026] As Figures 1-3 shown, a thickened multi-layer orthodontic membrane sheet for molars of a periodontal disease patient includes an intermediate layer 3. A first outer layer 1 and a second outer layer 2 are respectively arranged on both sides of the intermediate layer 3. A thickened layer 4 is arranged in the occlusal surface area of the molars on the side of the first outer layer 1 away from the intermediate layer 3; in the present invention, the occlusal surface area of the molars is thickened, which can raise the molars when retracting the anterior teeth and avoid premature contact, so as to solve the problems of reducing the chewing efficiency and discomfort of patients by the existing methods of raising the molars.

[0027] The first outer layer 1, the second outer layer 2, the intermediate layer 3 and the thickened layer 4 are made into a single piece by injection molding, and a multi-layer composite film is made by layer-by-layer molding.

[0028] The thickness of the intermediate layer 3 is greater than the thicknesses of the first outer layer 1 and the second outer layer 2.

[0029] The intermediate layer 3 has the lowest tensile elastic modulus, the first outer layer 1 and the second outer layer 2 have a medium tensile elastic modulus, and the thickened layer 4 has the highest tensile elastic modulus.

[0030] The total thickness of the first outer layer 1, the second outer layer 2 and the intermediate layer 3 is 0.6 - 1.0 mm.

[0031] The intermediate layer 3 has a tensile elastic modulus of 500 - 1500 MPa and a thickness of 0.5 - 0.75 mm; the first outer layer 1 and the second outer layer 2 have a tensile elastic modulus of 1500 - 2500 MPa, a hardness of 70 - 80 D, and a thickness of 0.05 - 0.25 mm; the thickened layer 4 has a tensile elastic modulus of 2000 - 3000 MPa, a hardness of 75 - 90 D, and a thickness of 0.5 - 1.0 mm.

[0032] As Figure 3 shown, the transparent part on the outer side of the teeth in the figure is an invisible dental appliance worn for the entire dentition, and the thickened part is padded between the upper and lower molars so that there is no occlusal contact between the front teeth.

[0033] Since the orthodontic appliance made using the orthodontic film of the present invention needs to be worn by the patient during meals, materials with a high elastic modulus and high hardness are placed on the outside as the first outer layer 1 and the second outer layer 2, which can prevent the orthodontic appliance from being cracked by excessive biting force during chewing; and the occlusal surface in the molar area is the area that bears the greatest biting force during chewing, so materials with a higher hardness need to be placed on the occlusal surface, that is, the thickened layer 4 uses materials with the highest tensile elastic modulus; the intermediate layer 3 with low tensile elastic modulus and low stress relaxation rate materials provides the main orthodontic force, making the overall tensile elastic modulus of the film low, the orthodontic force more gentle, more suitable for patients with periodontal disease, and at the same time can also reduce the force generated by the severe deformation of the dental appliance when the patient removes and wears it, avoiding the "tooth extraction force" effect caused by excessive force.

[0034] Commercially available diaphragms have a relatively large elastic modulus, but a relatively fast stress relaxation rate, that is, the initial orthodontic force provided is large, but the force quickly begins to decay, which does not meet the requirement of continuous light force in orthodontics. Compared with existing diaphragms, the diaphragm of the present invention has a smaller elastic modulus, is softer, has a low stress relaxation rate, provides a lighter force, and tries to keep the magnitude of the light force stable, solving the problems of excessive orthodontic force on periodontal patients and excessive occlusal force during removal and wearing of existing thermoformed membranes for invisible orthodontics.

[0035] Conventional invisible orthodontic appliances need to be removed during meals because the diaphragm material is not wear-resistant, and periodontal patients have loose teeth. The diaphragm in the present invention has a multi-layer structure, which is composed of multiple single-layer diaphragms formed by molding. The middle layer is soft, has a low elastic modulus and a low stress relaxation rate, providing the continuous light force required for orthodontics. The two outer layers on both sides have high hardness. The thickened area on the occlusal surface of the molars, as the main area to bear the occlusal force, requires greater hardness, so that the overall diaphragm can take into account low elastic modulus, low stress relaxation rate and strong wear resistance, allowing periodontal patients to wear it during meals, while relieving the anterior tooth occlusal interference by raising the molars, playing the role of a periodontal splint, connecting the entire dental arch into a whole to disperse the occlusal force, and avoiding further aggravation of the looseness of loose teeth.

[0036] The structure of the present invention is as Figure 1 shown, the shaded part is the thickened area of the molars. The size of the thickened area of the molars is 2 cm in length, 0.8 cm in width and 0.5 mm in thickness. The included angle C between the two thickened areas is 25°; to adapt to the dental arches of different people, the diaphragm is divided into three models: large, medium and small, as shown in Table 1

[0037] Table 1 Model data

[0038]

[0039]

[0040] During use, the direction of width a is aligned with the incisor area of the dental arch, and the thickened area of the molars is placed on the occlusal surfaces of the first and second molars.

[0041] The first outer layer 1, the second outer layer 2, the middle layer 3 and the thickened layer 4 are all made of thermoplastic polymer materials.

[0042] Currently, commonly used thermoplastic polymer materials mainly include polyethylene terephthalate, polyethylene terephthalate-1,4-cyclohexanedimethanol ester, thermoplastic polyurethane, polycarbonate, ethylene-vinyl acetate copolymer, and polyamide.

[0043] The intermediate layer 3 can be composed of one or more single-layer structures, and each layer can be composed of one material or two or more materials together. The first outer layer 1 and the second outer layer 2 can be composed of one or more single-layer structures, and each layer can be composed of one material or two or more materials together. The first outer layer 1 and the second outer layer 2 can be the same or different materials. The first outer layer 1 and the second outer layer 2 can be the same or different materials from the intermediate layer 3. The thickening layer 4 can be the same or different materials from the first outer layer 1 and the second outer layer 2.

[0044] As a possible implementation:

[0045] Example 1 provides a molar thickening multi-layer orthodontic membrane sheet for periodontal disease patients, including one layer of intermediate layer 3, one layer of the first outer layer 1 and the second outer layer 2 respectively, and one layer of thickening layer 4. This multi-layer membrane sheet is made into a single sheet by injection molding, and the single-layer membrane sheets are made into a multi-layer composite membrane sheet by layer-by-layer molding.

[0046] As shown in Table 2, the thermoplastic polyurethane used for the first outer layer 1, the second outer layer 2 and the thickening layer 4 has a high elastic modulus, a large elongation at break, and has good anti-fracture ability, but has strong water absorption, poor hydrolysis stability, and a large stress relaxation rate. The poly(ethylene terephthalate)-1,4-cyclohexanedimethanol ester used for the intermediate layer 3 has relatively good hydrolysis stability, a small stress relaxation rate, extremely strong transparency, is not easy to turn yellow, but has a lower anti-fracture ability than thermoplastic elastomers. Therefore, the intermediate layer 3 has a large thickness while the first outer layer 1 and the second outer layer 2 have a small thickness, which can make the membrane sheet have a lower elastic modulus, a small stress relaxation rate, good transparency, and the outer layer makes the membrane sheet wear-resistant and has strong anti-fracture ability.

[0047] Table 2 Materials and properties of each layer

[0048]

[0049] The mechanical properties of the membrane sheet of Example 1 were compared with commercially available invisible orthodontic membrane sheets Erkodur (Erkodent, Germany) and Prismlab (Prismlab, China). According to the national standard GB / T 1040.1-2018 and the industry standard YY / T1819-2022, the two materials were made into dumbbell-shaped standard specimens by punching method. The specimens should be free of distortion, the adjacent planes should be perpendicular to each other, and the surface and edges should be free of scratches, holes, depressions and burrs. 6 specimens of each material were prepared.

[0050] According to the industry standard YY / T 1819-2022, after the specimens are cut, unprocessed, and tested for uniaxial tension at room temperature (atmospheric temperature 23±2°C, relative humidity 50±10%). Three specimens are taken for each of the two materials, and a universal testing machine (AGS-X 1KN, Shimadzu) is used to perform uniaxial tension testing at a speed of 1 mm / min until the specimens break, obtaining the elastic modulus (Et), yield stress (σY), yield strain (εY), tensile strength (σM), and elongation at break (εtB). Take the average value, plot and compare, as Figure 4 shown.

[0051] Three dumbbell-shaped specimens are taken for each of the two materials. Under room temperature and dry conditions, they are immersed in a 37°C water bath for 24 hours. Then, under the condition of a 37°C water bath, stress relaxation testing is performed on the specimens using a universal testing machine. The stress relaxation testing is carried out according to the industry standard YY / T 1819-2022. The specimens are uniaxially tensioned to a displacement of 0.5 mm at a speed of 5 mm / min and held for 3 hours. Record the initial stress N0, and read the remaining stress N after keeping the displacement unchanged for 3 hours. The stress relaxation rate of the diaphragm is calculated according to the formula (N0-N) / 3, with the unit of MPa / h, as Figure 5 shown.

[0052] Compare the mechanical properties of the three materials, as shown in Table 3.

[0053] Table 3 Comparison of the mechanical properties of the three materials

[0054]

[0055] The tensile elastic modulus of Example 1 is smaller compared with Erkodur and Prismlab, that is, the provided orthodontic force is gentler. The yield strain of Example 1 is the largest among the three materials, and it can withstand greater elastic deformation; the tensile strength is the maximum strength that the diaphragm can withstand, and the tensile strength of the material in Example 1 is superior to Erkodur; the stress relaxation rate is the smallest among the three materials, that is, Example 1 can provide a more stable and continuous force.

[0056] In the industry standard YY / T 1819-2022, it is required that the tensile elastic modulus of dental diaphragms is between 700 and 3000 MPa, the yield stress is greater than or equal to 25 MPa, and the yield tensile strain ≥4%. The mechanical properties of the material in Example 1 all meet the requirements.

[0057] In summary, the multi-layer orthodontic diaphragm with thickened molars and non-uniform thickness for periodontal disease patients described in the present invention has the following advantages:

[0058] 1. The diaphragm has a non-uniform thickness and is thickened on the occlusal surface of the molars, which can relieve the premature contact when retracting the anterior teeth of periodontal disease patients and avoid further loosening of the teeth.

[0059] 2. The diaphragm is a multi-layer composite structure. The outer layer has high hardness and strong anti-fracture performance, which improves the wear resistance of the diaphragm. When periodontal disease patients wear braces to eat, it can not only relieve the premature contact of the anterior teeth, but also make the braces act as a periodontal splint to avoid further loosening of the teeth; through the middle layer, the overall elastic modulus of the diaphragm is relatively low, so as to provide a softer orthodontic force required by periodontal disease patients and avoid the "tooth extraction force" when removing and wearing the braces.

[0060] 3. The present invention can also be applied to other orthodontic designs that require raising the posterior teeth. For example, patients with anterior open bite need to intrude the posterior teeth to establish an occlusal relationship between the anterior teeth. Thickening the occlusal surface appliance in the molar area will make the efficiency of molar intrusion higher; patients with deep overbite have a deep bite and there is no space to place an appliance between the upper and lower anterior teeth. The occlusal surface appliance of the molars can be thickened to help open the bite and increase the space for the anterior teeth.

[0061] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A thickened multi-layer orthodontic membrane for patients with periodontal disease, characterized in that: It includes an intermediate layer (3), with a first outer layer (1) and a second outer layer (2) respectively arranged on both sides of the intermediate layer (3), and a thickened layer (4) is arranged in the molar occlusal surface area on the side of the first outer layer (1) away from the intermediate layer (3); The first outer layer (1), the second outer layer (2), the intermediate layer (3) and the thickened layer (4) are made into a single piece by an injection molding method, and the single piece is made into a multi-layer composite film by layer-by-layer molding; The thickness of the intermediate layer (3) is greater than the thicknesses of the first outer layer (1) and the second outer layer (2); The intermediate layer (3) has the lowest tensile elastic modulus, the first outer layer (1) and the second outer layer (2) have a medium tensile elastic modulus, and the thickened layer (4) has the highest tensile elastic modulus.

2. The multi-layer orthodontic membrane with thickened molars for periodontal patients according to claim 1, characterized in that: The total thickness of the first outer layer (1), the second outer layer (2) and the intermediate layer (3) is 0.6 - 1.0 mm.

3. The multi-layer orthodontic membrane for molar thickening for periodontal patients according to claim 1, wherein: The intermediate layer (3) has a tensile elastic modulus of 500 - 1500 MPa and a thickness of 0.5 - 0.75 mm; the first outer layer (1) and the second outer layer (2) have a tensile elastic modulus of 1500 - 2500 MPa, a hardness of 70 - 80 D, and a thickness of 0.05 - 0.25 mm; the thickened layer (4) has a tensile elastic modulus of 2000 - 3000 MPa, a hardness of 75 - 90 D, and a thickness of 0.5 - 1.0 mm.

4. The molar thickening multi-layer orthodontic membrane for periodontal patients according to claim 1, characterized in that: The first outer layer (1), the second outer layer (2), the intermediate layer (3) and the thickened layer (4) are all made of thermoplastic polymer materials.

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