A method for testing the strength of a gold-porcelain bonded tooth

Abstract

This invention relates to the field of tooth strength testing technology, specifically to a method for testing the strength of porcelain-metal bonded teeth. The method includes: acquiring stress data of the porcelain-metal bonded tooth under different force directions at various oral temperatures; obtaining strength performance values ​​based on the stress data of the tooth under different force directions at various oral temperatures; determining the target force direction and non-target force direction based on the differences in strength performance values ​​of the tooth under the same force direction at different oral temperatures; obtaining crack propagation characteristic values ​​based on the differences in stress data variation characteristics of the curve segments corresponding to different force directions at various oral temperatures; obtaining fracture resistance values ​​based on the differences in crack propagation characteristic values ​​of the tooth under the target force direction and non-target force direction at various oral temperatures; and evaluating the comprehensive strength performance of the tooth by combining the strength performance values ​​and the fracture resistance values. This invention enables the strength test results of porcelain-metal bonded teeth to accurately reflect their real-world performance in practical scenarios.

Description

Technical Field

[0001] This invention relates to the field of tooth strength testing technology, and specifically to a method for testing the strength of a porcelain-metal bonded tooth. Background Technology

[0002] With the continuous advancement of dental restoration technology, porcelain-metal composites (restorations combining metal and porcelain materials) have been widely used in the field of dental restoration. This material combines the strength of metal with the aesthetics of porcelain, meeting patients' needs for dental restorations that offer both good aesthetics and strong mechanical strength. Porcelain-metal composites are commonly used in clinical treatments such as tooth defects, crown restorations, and bridge restorations, exhibiting good biocompatibility and corrosion resistance. However, they still have certain limitations in terms of strength. Especially during long-term use, a potential problem with porcelain-metal composites is that while the porcelain layer provides excellent appearance, its relatively high brittleness makes it prone to cracking under significant chewing forces.

[0003] In actual eating, the strength and temperature of the food put into the mouth vary each time, so the chewing force and oral temperature of the teeth are affected by various foods. Therefore, teeth in different positions may be subjected to chewing forces in different directions and be in different oral temperatures. As a result, the performance test results based on only a single condition cannot reflect the true strength of the porcelain-metal bonded teeth in real-world scenarios. Summary of the Invention

[0004] To address the problem that existing methods for testing the strength of porcelain-metal bonded teeth fail to reflect the actual strength of these teeth in real-world scenarios, this invention aims to provide a method for testing the strength of porcelain-metal bonded teeth. The specific technical solution adopted is as follows:

[0005] This invention provides a method for testing the strength of porcelain-metal bonded teeth, the method comprising the following steps:

[0006] To obtain stress data of porcelain-metal bonded teeth under different force directions at various oral temperatures;

[0007] Based on the stress data changes of the tooth in each direction of force at different oral temperatures, the tooth fracture time and initial fracture time are determined; based on the tooth fracture time and initial fracture time in each direction of force at different oral temperatures, the strength performance values ​​of the tooth in each direction of force at different oral temperatures are obtained; based on the differences in the strength performance values ​​of the tooth in the same direction of force at different oral temperatures, the target force direction and non-target force direction are determined.

[0008] Based on the differences in stress data variation characteristics between curve segments corresponding to different force directions at various oral temperatures, the crack propagation characteristic values ​​of teeth in each force direction at various oral temperatures are obtained. The curve segments are obtained by dividing the time period between the initial fracture time and the tooth fracture time according to the magnitude of the stress data. Based on the differences in crack propagation characteristic values ​​of teeth in the target force direction and non-target force direction at various oral temperatures, as well as the crack propagation characteristic values ​​in the non-target force direction, the fracture resistance value of teeth at various oral temperatures is obtained.

[0009] The overall strength performance of teeth is evaluated by combining strength performance values ​​and fracture resistance performance values.

[0010] Preferably, determining the tooth fracture time and initial fracture time based on the stress data changes of the tooth in each direction of force at different oral temperatures includes:

[0011] For any oral temperature:

[0012] The stress data of the tooth in the candidate direction are arranged in chronological order to obtain the stress data sequence of the candidate direction; the time corresponding to the maximum value in the stress data sequence is determined as the time of tooth fracture.

[0013] The last moment of the rising phase of the data value in the stress data sequence is determined as the initial fracture moment;

[0014] The candidate direction can be any direction in which the force is applied.

[0015] Preferably, the strength performance values ​​of the teeth in each direction of force at each oral temperature include:

[0016] For any oral temperature:

[0017] The normalized result of the product of the maximum value in the stress data sequence and the time from the start of stress on the tooth to the time of tooth fracture in the candidate direction is taken as the endurance performance value of the tooth in the candidate direction at any oral temperature.

[0018] The normalized result of the product of the stress data of the initial fracture moment of the tooth in the candidate direction and the proportion of the time from the start of stress to the initial fracture moment of the tooth in the candidate direction is used as the degree of difficulty of tooth fracture in the candidate direction at any oral temperature.

[0019] By combining the endurance performance value and the degree of fracture difficulty, the strength performance value of the tooth in the candidate direction at any oral temperature is obtained. The endurance performance value is positively correlated with the strength performance value, and the degree of fracture difficulty is negatively correlated with the strength performance value.

[0020] Preferably, determining the target force direction and non-target force direction based on the difference in the strength performance values ​​of teeth in the same force direction at different oral temperatures includes:

[0021] Based on the difference in the strength performance of teeth in the same direction of force at different oral temperatures, the strength difference of teeth in each direction of force at different oral temperatures is obtained.

[0022] The inverse proportional normalization result of the strength difference value is determined as the difficulty of crack propagation in the tooth in each force direction;

[0023] The direction of force applied when the difficulty of crack propagation is less than the preset difficulty threshold is taken as the target direction of force applied, and the direction of force applied when the difficulty of crack propagation is greater than or equal to the preset difficulty threshold is taken as the non-target direction of force applied.

[0024] Preferably, obtaining the curve segments corresponding to different force directions at various oral temperatures includes:

[0025] For any oral temperature:

[0026] The time interval between the initial fracture time of the tooth in the candidate direction and the tooth fracture time at any oral temperature is denoted as the crack propagation time interval in the candidate direction.

[0027] The crack propagation time period is divided according to the peaks and troughs on the fitted curve to obtain multiple curve segments corresponding to different stress directions at any oral temperature. The fitted curve is obtained by curve fitting the stress data of the crack propagation time period of the tooth in the candidate direction at any oral temperature.

[0028] Preferably, obtaining the crack propagation characteristic value of the tooth in each stress direction at each oral temperature based on the difference in stress data variation characteristics between curve segments corresponding to different force directions at each oral temperature includes:

[0029] For any oral temperature:

[0030] Based on the differences in stress variation values ​​between different curve segments (excluding the last curve segment) in the candidate direction at any oral temperature, the crack propagation uniformity factor of the tooth in the candidate direction at any oral temperature is obtained. The differences in stress variation values ​​are negatively correlated with the crack propagation uniformity factor. The stress variation value of each curve segment is the range of stress data for each curve segment.

[0031] Based on the stress change rate of each curve segment corresponding to the candidate direction at any oral temperature, the crack propagation resistance value of the tooth in the candidate direction at any oral temperature is obtained; wherein, the stress change rate of each curve segment is the ratio of the stress change value of each curve segment to the duration of the same curve segment.

[0032] By combining the crack propagation uniformity factor, the crack propagation resistance value, and the duration of crack propagation time of the tooth in the candidate direction at any oral temperature, the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature is obtained.

[0033] Preferably, obtaining the crack propagation resistance value of the tooth in the candidate direction at any oral temperature based on the stress change rate of each curve segment corresponding to the candidate direction at any oral temperature includes:

[0034] Based on the stress change rate of the last curve segment corresponding to the candidate direction at any oral temperature and the difference between the stress change rate of the last curve segment and the stress change rate of other curve segments, the crack propagation resistance value of the tooth in the candidate direction at any oral temperature is obtained. The stress change rate of the last curve segment and the difference between the stress change rates are negatively correlated with the crack propagation resistance value.

[0035] Preferably, the step of combining the crack propagation uniformity factor, the crack propagation resistance value, and the duration of crack propagation time of the tooth in the candidate direction at any oral temperature to obtain the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature includes:

[0036] The product of the normalized value of the crack propagation time period of the tooth in the candidate direction at any oral temperature, the crack propagation uniformity factor, and the crack propagation resistance value is used as the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature.

[0037] Preferably, the step of obtaining the fracture resistance value of the tooth at each oral temperature based on the difference in crack propagation characteristic values ​​of the tooth in the target force direction and the non-target force direction at each oral temperature, and the crack propagation characteristic value in the non-target force direction, includes:

[0038] For any oral temperature:

[0039] The difference between the mean value of crack propagation characteristics of teeth in all target force directions and the mean value of crack propagation characteristics in all non-target force directions at any oral temperature is denoted as the first difference.

[0040] The fracture resistance value of the tooth at any oral temperature is obtained based on the mean value of crack propagation characteristics of the tooth in all non-target stress directions, the number of non-target stress directions, and the first difference. The mean value of crack propagation characteristics of all non-target stress directions is positively correlated with the fracture resistance value, while the number of non-target stress directions and the first difference are negatively correlated with the fracture resistance value.

[0041] Preferably, the evaluation of the overall strength performance of teeth by combining strength performance values ​​and fracture resistance performance values ​​includes:

[0042] The product of the fracture resistance value of the tooth at each oral temperature and the average value of the tooth's strength performance in all directions of stress is taken as the first characteristic value of each oral temperature.

[0043] The normalized result of the average of the first characteristic values ​​of all oral temperatures is determined as the comprehensive strength index.

[0044] If the overall strength index is greater than the preset strength threshold, the strength performance of the porcelain-metal bonded tooth is determined to meet the requirements; if the overall strength index is less than or equal to the preset strength threshold, the strength performance of the porcelain-metal bonded tooth is determined to not meet the requirements.

[0045] The present invention has at least the following beneficial effects:

[0046] This invention first collects stress data on porcelain-metal teeth under different oral temperatures and in different force directions. Based on the stress data changes of teeth under different oral temperatures and in different force directions, the strength performance of teeth under different oral temperature conditions is evaluated, and the force directions are divided into target force directions and non-target force directions. By analyzing the difference in crack propagation characteristic values ​​between target force directions and non-target force directions, the fracture resistance of porcelain-metal teeth under different force directions can be accurately assessed. Finally, by combining the strength performance value and fracture resistance performance value, the comprehensive strength performance of the teeth is evaluated, which improves the accuracy of the comprehensive strength performance evaluation results of porcelain-metal teeth. This allows the strength test results of porcelain-metal teeth to accurately reflect the real-world strength performance of porcelain-metal teeth in actual scenarios, thereby effectively reducing the risk of tooth breakage, extending their service life, and improving the oral health and comfort of the wearer. Attached Figure Description

[0047] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a flowchart of a method for testing the strength of a porcelain-metal bonded tooth, as provided in an embodiment of the present invention. Detailed Implementation

[0049] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of a method for testing the strength of porcelain-metal bonded teeth according to the present invention is provided in conjunction with the accompanying drawings and preferred embodiments.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0051] The following description, in conjunction with the accompanying drawings, details a specific scheme for testing the strength of a porcelain-metal bonded tooth provided by this invention.

[0052] An example of a method for testing the strength of porcelain-metal bonded teeth:

[0053] This embodiment proposes a method for testing the strength of porcelain-metal bonded teeth, such as... Figure 1 As shown, a method for testing the strength of a porcelain-metal bonded tooth in this embodiment includes the following steps:

[0054] Step S1: Obtain stress data of the porcelain-metal bonded teeth under different force directions at various oral temperatures.

[0055] The chewing force in the oral cavity is not constant and is affected by many factors, such as the temperature of the food, the chewing method (light chewing, heavy chewing), and individual chewing habits. For example, hard foods (such as nuts and bones) and soft foods (such as bread and vegetables) exert very different pressures on the teeth, and the direction of force on the teeth is different. In addition, the temperature in the oral cavity fluctuates with the temperature of food and drinks. Therefore, this variation cannot be fully simulated by a single static strength test.

[0056] When a porcelain-metal bonded tooth fractures, the crack usually propagates from the weaker direction of stress (such as a microcrack in the enamel) and does not necessarily lead to the entire tooth breaking. In teeth with better strength, a more uniform fracture pattern is typically observed, and good strength means that crack propagation under load is relatively slow. However, if the strength is poor, the crack may suddenly propagate in the weaker direction of stress and rapidly cause the entire tooth to break.

[0057] This embodiment analyzes the stress data of porcelain-metal teeth under different oral temperatures and in different stress directions, as well as the strength performance of the tooth material under different oral temperature conditions. It also analyzes the difference in crack propagation characteristic values ​​between the target stress direction and the non-target stress direction, evaluates the fracture resistance of porcelain-metal teeth under different stress directions, and finally determines the overall strength performance of porcelain-metal teeth.

[0058] First, in this embodiment, the force directions of the porcelain-metal bonded tooth are set to 0°, 30°, 60°, 90°, 120°, and 150°, respectively, and the simulated oral temperatures are set to 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, and 40°C, respectively. In specific applications, the implementer can set the force direction and oral temperature according to the specific situation. At any simulated oral temperature, a stress sensor is placed on the porcelain-metal bonded tooth, and a pressure is applied to any force direction of the porcelain-metal bonded tooth using a simulated three-point bending test. The stress sensor records the stress data of the porcelain-metal bonded tooth at all moments from the start of the force application until complete fracture.

[0059] Thus, this embodiment has collected stress data for the porcelain-metal bonded tooth at various oral temperatures and under different stress directions from the start of stress to complete fracture at all times.

[0060] Step S2: Determine the tooth fracture time and initial fracture time based on the stress data changes of the tooth in each force direction at each oral temperature; obtain the strength performance value of the tooth in each force direction at each oral temperature based on the tooth fracture time and initial fracture time in each force direction at each oral temperature; determine the target force direction and non-target force direction based on the difference in the strength performance value of the tooth in the same force direction at different oral temperatures.

[0061] In the initial stage of the simulation experiment, the stress on the porcelain-metal bonded tooth increased linearly with the uniform increase of external force. When it approached fracture, the stress increased non-linearly due to the crack propagation on the tooth. At the moment of fracture, the stress of the tooth rose sharply to a peak and then dropped sharply. The temperature in the oral cavity fluctuates with the temperature of food and drinks. The smaller the difference in strength of a certain direction of force on the tooth under different oral temperature environments, the more consistent the strength of that direction of force is under different temperatures. This indicates that the tooth itself has good toughness and compressive strength in that direction of force, and can maintain stable strength in hot and cold food environments. However, when the strength of the porcelain-metal bonded tooth is poor, the crack will start to propagate from the weaker direction of force (such as microcracks in the enamel) and cause the entire tooth to break. Therefore, it is necessary to obtain the target force direction and non-target force direction of the tooth.

[0062] In the At oral temperature, the tooth is in the first... In the stress data for each direction of force application, the larger the peak value of the stress data for the porcelain-metal fusion tooth, the stronger the stress. The structural design in each stress direction can effectively disperse and withstand greater pressure; and the longer the nonlinear increase time of crack propagation, the more likely the crack will propagate in the first direction. The expansion in the first direction of force is slower, indicating that the first... Materials in the direction of stress are more resistant to further crack propagation. This, in summary, explains the situation in the first... The higher the strength of the porcelain-metal bonded tooth in each direction of stress, the greater the strength.

[0063] For any oral temperature:

[0064] Taking any force direction as an example, the method provided in this embodiment can be used to process other force directions as well. Specifically, any force direction is designated as a candidate direction. The stress data of the tooth in the candidate direction are arranged in chronological order to obtain a stress data sequence for the candidate direction. The time corresponding to the maximum value in the stress data sequence is determined as the tooth fracture time. The last moment of the rising phase of the data value in the stress data sequence is determined as the initial fracture time. It should be noted that the last moment of the rising phase of the data value in the stress data sequence in this embodiment is the last moment of the first rising phase of the data value from the beginning of the force application to the tooth.

[0065] The normalized result of the product of the maximum value in the stress data sequence and the duration from the onset of stress to tooth fracture in the candidate direction is taken as the tooth's endurance performance value in the candidate direction at that oral temperature. Normalization can be performed using a maximum-minimum normalization method or other normalization methods.

[0066] The smaller the stress data at the initial fracture moment of the tooth in the candidate direction, the more likely the tooth is to fracture in the candidate force direction at that oral temperature. Therefore, the normalized result of the product of the stress data at the initial fracture moment of the tooth in the candidate direction and the proportion of time from the start of force application to the initial fracture moment in the candidate direction is used as the degree of difficulty of tooth fracture in the candidate direction at that oral temperature. In this embodiment, the product of the maximum value in the stress data sequence and the time from the start of force application to the fracture moment of the tooth in the candidate direction, as well as the normalization method for the stress data at the initial fracture moment of the tooth in the candidate direction and the proportion of time from the start of force application to the initial fracture moment of the tooth in the candidate direction, is processed using the maximum-minimum value normalization method. In specific applications, implementers can choose other data normalization methods for processing, which will not be elaborated further here. The method for obtaining the percentage of time from the start of force application to the initial fracture time of a tooth under the candidate direction is as follows: the ratio between the time from the start of force application to the initial fracture time of a tooth under the candidate direction and the total time from the start of force application to the end of force application is used as the percentage of time from the start of force application to the initial fracture time of a tooth under the candidate direction.

[0067] The lower the fragility of the tooth in the candidate direction at the oral temperature, and the higher the endurance value of the tooth in the candidate force direction at the oral temperature, the higher the strength value of the tooth in the candidate force direction at the oral temperature. Therefore, in this embodiment, the endurance value and fragility of the tooth are combined to obtain the strength value of the tooth in the candidate direction at the oral temperature. The endurance value and the strength value are positively correlated, and the fragility of the tooth is negatively correlated with the strength value.

[0068] In this embodiment, a specific calculation formula for the strength performance value is given, the first... At the oral temperature, the tooth is in the first The strength performance value in each direction of force can be expressed as:

[0069]

[0070] in, Indicates the first At the oral temperature, the tooth is in the first Strength performance values ​​in each direction of stress. Indicates the first At the oral temperature, the tooth is in the first Endurance performance values ​​in each direction of force application. Indicates the first At the oral temperature, the tooth is in the first The degree of fracture difficulty in each direction of force. This represents an exponential function with the natural constant as its base. This represents the normalization function.

[0071] When the At the oral temperature, the tooth is in the first The greater the endurance value in the first direction of force application, the better. At the oral temperature, the tooth is in the first The smaller the fracture difficulty in each stress direction, the more likely the fracture will occur. At the oral temperature, the tooth is in the first The larger the strength performance value in each direction of force, the better.

[0072] Using the above method, the strength performance values ​​of teeth in each direction of force can be obtained at various oral temperatures.

[0073] The more consistent the strength performance values ​​of teeth in the same direction of force under different oral temperatures, the more stable the strength of the teeth can be in hot and cold food environments under that direction of force. Therefore, the strength difference value of teeth in different directions of force under different oral temperatures is determined based on the differences in the strength performance values ​​of teeth in the same direction of force under different oral temperatures. Specifically, for any direction of force: the absolute value of the difference between the strength performance values ​​of teeth in that direction of force under each of two oral temperatures is calculated, and this absolute value is taken as the difference between the strength performance values ​​of teeth in that direction of force under these two oral temperatures; there is a difference in strength performance value of teeth in that direction of force under each of two oral temperatures, and the sum of all the differences in strength performance values ​​is taken as the strength difference value of teeth in that direction of force under different oral temperatures; then, the strength difference value is inversely normalized, and the result of the inverse normalization is determined as the crack propagation difficulty of teeth in that direction of force. In this embodiment, the specific process of inversely normalizing the strength difference value is as follows: the exponential function value with the natural constant as the base and the negative strength difference value as the exponent is determined as the crack propagation difficulty of teeth in that direction of force. Using the above method, it is possible to obtain the difficulty of crack propagation in teeth in each direction of force.

[0074] The direction of force application where the difficulty of crack propagation is less than a preset difficulty threshold is designated as the target force direction, and the direction of force application where the difficulty of crack propagation is greater than or equal to the preset difficulty threshold is designated as the non-target force direction. In this embodiment, the preset difficulty threshold is 0.45. In specific applications, the implementer can set it according to the specific circumstances.

[0075] Thus, the method provided in this embodiment divides all force directions into target force directions and non-target force directions.

[0076] Step S3: Based on the differences in stress data variation characteristics between curve segments corresponding to different force directions at each oral temperature, obtain the crack propagation characteristic value of the tooth in each force direction at each oral temperature. The curve segment is obtained by dividing the time period between the initial fracture time and the tooth fracture time according to the magnitude of the stress data. Based on the differences in crack propagation characteristic values ​​of the tooth in the target force direction and the non-target force direction at each oral temperature, as well as the crack propagation characteristic value in the non-target force direction, obtain the fracture resistance value of the tooth at each oral temperature.

[0077] When a porcelain-metal bonded tooth fractures, the crack often propagates from the weaker stress direction (such as a microcrack in the enamel) and eventually breaks. Stronger teeth typically exhibit a more uniform fracture pattern, and good strength means that crack propagation under load is relatively slow. If the strength is poor, the crack may suddenly propagate in the weaker stress direction and rapidly cause the entire tooth to break. Therefore, at the same oral temperature, the greater the difference in stress data sequences between the target and non-target stress directions, the worse the tooth's fracture resistance.

[0078] Teeth with good strength usually exhibit a more uniform fracture mode, and good strength means that crack propagation will be relatively slow under load; the above description is reflected in the stress data as follows: the stress data fluctuates relatively evenly and for a long period of time between the initial fracture time and the tooth fracture time.

[0079] The following embodiment will still use an oral temperature as an example for explanation. Other oral temperatures can be processed using the method provided in this embodiment.

[0080] Specifically, for any oral temperature:

[0081] The time interval between the initial fracture time of the tooth in the candidate direction and the tooth fracture time at the oral temperature is denoted as the crack propagation time interval in the candidate direction.

[0082] A curve was obtained by curve fitting of the stress data of the tooth during the crack propagation time in the candidate direction at the oral temperature. The x-axis of the fitted curve represents time, and the y-axis represents the stress data. Curve fitting is a prior art technique and will not be elaborated further here. The peaks and troughs of the fitted curve were obtained and used as dividing points to divide the fitted curve into multiple curve segments. The method for obtaining the peaks and troughs is a prior art technique and will not be elaborated further here.

[0083] Next, the range of stress data for each curve segment is used as the stress variation value for each curve segment, and each curve segment has a corresponding stress variation value. The closer the stress variation values ​​are among all curve segments in the candidate direction (excluding the last curve segment) at this oral temperature, the more uniform the fracture mode of the tooth during the crack propagation period, and the better its strength in the candidate direction. Based on this, the crack propagation uniformity factor of the tooth in the candidate direction at this oral temperature is obtained according to the differences in stress variation values ​​among different curve segments in the candidate direction (excluding the last curve segment). The differences in stress variation values ​​are negatively correlated with the crack propagation uniformity factor. In this embodiment, a specific calculation method for the crack propagation uniformity factor of the tooth in the candidate direction at the oral temperature is given: calculate the absolute value of the difference between the stress change values ​​of every two curve segments in the candidate direction except the last curve segment at the oral temperature, and take the absolute value as the difference between the stress change values ​​of the corresponding two curve segments. Calculate the sum of the differences between the stress change values ​​of all pairs of curve segments except the last curve segment, and take the exponential function value with the natural constant as the base and the negative sum as the crack propagation uniformity factor of the tooth in the candidate direction at the oral temperature.

[0084] Furthermore, the ratio between the stress change value of each curve segment and the duration of the same curve segment is taken as the stress change rate of each curve segment, and each curve segment has a corresponding stress change rate.

[0085] Based on the stress change rate of the last curve segment corresponding to the candidate direction at the oral temperature and the difference between the stress change rate of the last curve segment and the other curve segments, the crack propagation resistance value of the tooth in the candidate direction at the oral temperature is obtained. The stress change rate of the last curve segment and the difference between the stress change rates are negatively correlated with the crack propagation resistance value.

[0086] In this embodiment, a specific formula for calculating the crack propagation resistance value is given. At the oral temperature, the tooth is in the first The crack propagation resistance value in each stress direction can be expressed as:

[0087]

[0088] in, Indicates the first At the oral temperature, the tooth is in the first The crack propagation resistance value in each stress direction. Indicates the first At the oral temperature, the tooth is in the first The rate of stress change in the last curve segment corresponding to each force direction Indicates the first At the oral temperature, the tooth is in the first The first force direction corresponds to the first The rate of stress change in each curve segment, Indicates the first At the oral temperature, the tooth is in the first The number of curve segments corresponding to each force direction. This indicates the absolute value sign.

[0089] When the At the oral temperature, the tooth is in the first The smaller the rate of stress change in the last curve segment corresponding to the first force direction, and the... At the oral temperature, the tooth is in the first The smaller the difference in stress change rate between the last curve segment corresponding to the first force direction and other curve segments, the stronger the stress change rate. At the oral temperature, the tooth is in the first The stronger the resistance to crack propagation in the first stress direction, that is, the stronger the crack propagation resistance in the second stress direction. At the oral temperature, the tooth is in the first The greater the crack propagation resistance value in each stress direction, the better.

[0090] Then, the product of the normalized value of the crack propagation time period of the tooth in the candidate direction at the oral temperature, the crack propagation uniformity factor of the tooth in the candidate direction at the oral temperature, and the crack propagation resistance value of the tooth in the candidate direction at the oral temperature is used as the crack propagation characteristic value of the tooth in the candidate direction at the oral temperature. The normalization method for the crack propagation time period is as follows: the ratio of the crack propagation time period of the tooth in the candidate direction at the oral temperature to the total time between the initial and final moments of force application in the tooth in the candidate direction at the oral temperature is used as the normalized value for the crack propagation time period.

[0091] The larger the crack propagation characteristic value under the non-target force direction of the tooth, the fewer the number of non-target force directions of the tooth, and the smaller the difference in crack propagation characteristic value between the target force direction and the non-target force direction, the more uniform the fracture mode is exhibited during the crack propagation process under the non-target force direction, and the slower the crack propagation is, indicating that the tooth has better fracture resistance.

[0092] In this embodiment, the mean values ​​of crack propagation characteristics of the tooth in all target stress directions and the mean values ​​of crack propagation characteristics of the tooth in all non-target stress directions at the oral temperature are calculated respectively. The difference between these two means is denoted as the first difference. Based on the mean values ​​of crack propagation characteristics of the tooth in all non-target stress directions, the number of non-target stress directions, and the first difference, the fracture resistance value of the tooth at the oral temperature is obtained. The mean values ​​of crack propagation characteristics in all non-target stress directions are positively correlated with the fracture resistance value, while the number of non-target stress directions and the first difference are both negatively correlated with the fracture resistance value.

[0093] In this embodiment, a specific calculation formula for the fracture resistance value is given, the first... The fracture resistance value of a tooth at a specific oral temperature can be expressed as:

[0094]

[0095] in, Indicates the first The fracture resistance value of teeth at a specific oral temperature. Indicates the first The mean value of crack propagation characteristics of a tooth in all non-target force directions at a given oral temperature. Indicates the first The mean value of crack propagation characteristics of a tooth in all target force directions at a given oral temperature. Indicates the number of non-target force directions. This represents an exponential function with the natural constant as its base.

[0096] This indicates the first difference; the larger the value, the greater the overall difference between the crack propagation characteristic value of the tooth in the target force direction and the crack propagation characteristic value in the non-target force direction.

[0097] Using the above method, the fracture resistance values ​​of teeth at various oral temperatures can be obtained.

[0098] Step S4: Combine the strength performance value and fracture resistance performance value to evaluate the overall strength performance of the tooth.

[0099] Good fracture resistance means that teeth can effectively resist the stresses applied during daily use (such as chewing and biting), and are not prone to overall fracture even when cracks or damage occur. The greater the strength performance value of teeth in each direction of stress at different oral temperatures, the more evenly the teeth can withstand stress in multiple directions. Whether it is chewing, impact or other external forces, the teeth can maintain structural integrity under various stress conditions. Therefore, the better the fracture resistance of teeth and the greater the strength performance value of teeth in different directions of stress at different oral temperatures, the stronger the overall strength performance of the teeth.

[0100] For any given oral temperature, calculate the average strength performance of the tooth in all stress directions at that temperature. The product of this average and the fracture resistance of the tooth at that temperature is recorded as the first characteristic value of that oral temperature. Using this method, the first characteristic value for each oral temperature can be obtained. The normalized result of the average of all the first characteristic values ​​of the oral temperatures is determined as the comprehensive strength index. There are many data normalization methods; implementers can choose an appropriate normalization method based on specific circumstances to perform normalization processing, so that the normalized result of the average of all the first characteristic values ​​of the oral temperatures takes the value (0, 1).

[0101] If the overall strength index is greater than the preset strength threshold, the strength performance of the porcelain-metal bonded tooth is deemed to meet the requirements. If the overall strength index is less than or equal to the preset strength threshold, the tooth has low fracture resistance when subjected to external forces such as daily chewing and impacts, and the porcelain-metal bonded tooth may easily crack, break, or shatter. In this case, introducing more high-toughness materials, such as adding bauxite and zircon, can improve the fracture resistance of the tooth, making it less prone to cracking under external forces. In this case, the strength performance of the porcelain-metal bonded tooth is deemed not to meet the requirements. When the strength performance of the porcelain-metal bonded tooth does not meet the requirements, an oxide film such as Al2O3 or ZrO2 can be sprayed onto the metal substrate or ceramic surface to form a transition layer, reducing interface defects and enhancing bonding strength. Introducing high-toughness materials such as bauxite and zircon can significantly improve the fracture resistance of the tooth, improve durability, enhance strength performance in different stress directions, and improve adaptability to changes in oral temperature. In this embodiment, the preset strength threshold is 0.6. In specific applications, the implementer can set it according to the specific situation.

[0102] Thus, by using the method provided in this embodiment, the strength of the porcelain-metal bonded tooth has been accurately tested. This test can effectively reduce the risk of tooth breakage, extend its service life, and thereby improve the wearer's oral health and comfort.

[0103] This embodiment first collects stress data of the porcelain-metal teeth under different oral temperatures and in different force directions. Based on the changes in stress data of the teeth under different oral temperatures and in different force directions, the strength performance of the teeth under different oral temperature conditions is evaluated, and the force directions are divided into target force directions and non-target force directions. By analyzing the difference in crack propagation characteristic values ​​between target force directions and non-target force directions, the fracture resistance of the porcelain-metal teeth under different force directions can be accurately assessed. Finally, by combining the strength performance value and the fracture resistance performance value, the comprehensive strength performance of the teeth is evaluated, which improves the accuracy of the comprehensive strength performance evaluation results of porcelain-metal teeth. This allows the strength test results of porcelain-metal teeth to accurately reflect the real performance of the strength of porcelain-metal teeth in actual scenarios, thereby effectively reducing the risk of tooth breakage, extending their service life, and improving the oral health and comfort of the wearer.

[0104] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing the strength of porcelain-metal bonded teeth, characterized in that, The method includes the following steps: To obtain stress data of porcelain-metal bonded teeth under different force directions at various oral temperatures; Based on the stress data changes of the tooth in each direction of force at different oral temperatures, the tooth fracture time and initial fracture time are determined; based on the tooth fracture time and initial fracture time in each direction of force at different oral temperatures, the strength performance values ​​of the tooth in each direction of force at different oral temperatures are obtained; based on the differences in the strength performance values ​​of the tooth in the same direction of force at different oral temperatures, the target force direction and non-target force direction are determined. Based on the differences in stress data variation characteristics between curve segments corresponding to different force directions at various oral temperatures, the crack propagation characteristic values ​​of teeth in each force direction at various oral temperatures are obtained. The curve segments are obtained by dividing the time period between the initial fracture time and the tooth fracture time according to the magnitude of the stress data. Based on the differences in crack propagation characteristic values ​​of teeth in the target force direction and non-target force direction at various oral temperatures, as well as the crack propagation characteristic values ​​in the non-target force direction, the fracture resistance value of teeth at various oral temperatures is obtained. The overall strength performance of teeth is evaluated by combining strength performance values ​​and fracture resistance performance values; The process of determining the tooth fracture time and initial fracture time based on the stress data changes of the tooth in each direction of force at various oral temperatures includes: For any oral temperature: The stress data of the tooth in the candidate direction are arranged in chronological order to obtain the stress data sequence of the candidate direction; the time corresponding to the maximum value in the stress data sequence is determined as the time of tooth fracture. The last moment of the rising phase of the data value in the stress data sequence is determined as the initial fracture moment; The candidate direction can be any direction in which force is applied. The process of obtaining the strength performance values ​​of teeth in each direction of force at various oral temperatures includes: For any oral temperature: The normalized result of the product of the maximum value in the stress data sequence and the time from the start of stress on the tooth to the time of tooth fracture in the candidate direction is taken as the endurance performance value of the tooth in the candidate direction at any oral temperature. The normalized result of the product of the stress data of the initial fracture moment of the tooth in the candidate direction and the proportion of the time from the start of stress to the initial fracture moment of the tooth in the candidate direction is used as the degree of difficulty of tooth fracture in the candidate direction at any oral temperature. By combining the endurance performance value and the degree of fracture difficulty, the strength performance value of the tooth in the candidate direction at any oral temperature is obtained. The endurance performance value is positively correlated with the strength performance value, and the degree of fracture difficulty is negatively correlated with the strength performance value. The determination of the target and non-target force directions based on the differences in the strength performance values ​​of teeth in the same force direction at different oral temperatures includes: Based on the difference in the strength performance of teeth in the same direction of force at different oral temperatures, the strength difference of teeth in each direction of force at different oral temperatures is obtained. The inverse proportional normalization result of the strength difference value is determined as the difficulty of crack propagation in the tooth in each force direction; The direction of force applied when the difficulty of crack propagation is less than the preset difficulty threshold is taken as the target direction of force applied, and the direction of force applied when the difficulty of crack propagation is greater than or equal to the preset difficulty threshold is taken as the non-target direction of force applied.

2. The method for testing the strength of porcelain-metal bonded teeth according to claim 1, characterized in that, Obtaining the curve segments corresponding to different force directions at various oral temperatures, including: For any oral temperature: The time interval between the initial fracture time of the tooth in the candidate direction and the tooth fracture time at any oral temperature is denoted as the crack propagation time interval in the candidate direction. The crack propagation time period is divided according to the peaks and troughs on the fitted curve to obtain multiple curve segments corresponding to different stress directions at any oral temperature. The fitted curve is obtained by curve fitting the stress data of the crack propagation time period of the tooth in the candidate direction at any oral temperature.

3. The method for testing the strength of porcelain-metal bonded teeth according to claim 2, characterized in that, The method of obtaining crack propagation characteristic values ​​of teeth in each stress direction at each oral temperature based on the differences in stress data variation characteristics between curve segments corresponding to different stress directions at each oral temperature includes: For any oral temperature: Based on the differences in stress variation values ​​between different curve segments (excluding the last curve segment) in the candidate direction at any oral temperature, the crack propagation uniformity factor of the tooth in the candidate direction at any oral temperature is obtained. The differences in stress variation values ​​are negatively correlated with the crack propagation uniformity factor. The stress variation value of each curve segment is the range of stress data for each curve segment. Based on the stress change rate of each curve segment corresponding to the candidate direction at any oral temperature, the crack propagation resistance value of the tooth in the candidate direction at any oral temperature is obtained; wherein, the stress change rate of each curve segment is the ratio of the stress change value of each curve segment to the duration of the same curve segment. By combining the crack propagation uniformity factor, the crack propagation resistance value, and the duration of crack propagation time of the tooth in the candidate direction at any oral temperature, the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature is obtained.

4. The method for testing the strength of porcelain-metal bonded teeth according to claim 3, characterized in that, The step of obtaining the crack propagation resistance value of the tooth in the candidate direction at any oral temperature based on the stress change rate of each curve segment corresponding to the candidate direction at any oral temperature includes: Based on the stress change rate of the last curve segment corresponding to the candidate direction at any oral temperature and the difference between the stress change rate of the last curve segment and the stress change rate of other curve segments, the crack propagation resistance value of the tooth in the candidate direction at any oral temperature is obtained. The stress change rate of the last curve segment and the difference between the stress change rates are negatively correlated with the crack propagation resistance value.

5. The method for testing the strength of porcelain-metal bonded teeth according to claim 3, characterized in that, The method of combining the crack propagation uniformity factor, the crack propagation resistance value, and the duration of crack propagation in the candidate direction at any oral temperature to obtain the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature includes: The product of the normalized value of the crack propagation time period of the tooth in the candidate direction at any oral temperature, the crack propagation uniformity factor, and the crack propagation resistance value is used as the crack propagation characteristic value of the tooth in the candidate direction at any oral temperature.

6. The method for testing the strength of porcelain-metal bonded teeth according to claim 1, characterized in that, The fracture resistance value of the tooth at each oral temperature is obtained based on the difference in crack propagation characteristic values ​​of the tooth in the target stress direction and the non-target stress direction at each oral temperature, as well as the crack propagation characteristic value in the non-target stress direction. This includes: For any oral temperature: The difference between the mean value of crack propagation characteristics of teeth in all target force directions and the mean value of crack propagation characteristics in all non-target force directions at any oral temperature is denoted as the first difference. The fracture resistance value of the tooth at any oral temperature is obtained based on the mean value of crack propagation characteristics of the tooth in all non-target stress directions, the number of non-target stress directions, and the first difference. The mean value of crack propagation characteristics of all non-target stress directions is positively correlated with the fracture resistance value, while the number of non-target stress directions and the first difference are negatively correlated with the fracture resistance value.

7. The method for testing the strength of porcelain-metal bonded teeth according to claim 1, characterized in that, The combined strength performance value and fracture resistance performance value are used to evaluate the overall strength performance of teeth, including: The product of the fracture resistance value of the tooth at each oral temperature and the average value of the tooth's strength performance in all directions of stress is taken as the first characteristic value of each oral temperature. The normalized result of the average of the first characteristic values ​​of all oral temperatures is determined as the comprehensive intensity index. If the overall strength index is greater than the preset strength threshold, the strength performance of the porcelain-metal bonded tooth is determined to meet the requirements; if the overall strength index is less than or equal to the preset strength threshold, the strength performance of the porcelain-metal bonded tooth is determined to not meet the requirements.

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