Method for preparing evaluation samples and evaluation method

Abstract

To evaluate coloring of a tooth due to penetration of a coloring substance into the tooth.SOLUTION: An evaluation method for evaluating penetration of a coloring substance into a tooth, includes: a cutting-out step of cutting out the tooth to obtain a test piece 21; an embedding step of embedding a test piece 21 in an embedding agent 22; a protection step of applying a coating agent 31 to completely cover an entire boundary between the test piece 21 and the embedding agent 22 in a coloring object surface 30a to obtain an evaluation sample 10; a coloring step of coloring the test piece 21 of the evaluation sample 10 using the coloring substance; an evaluation segment preparation step of cutting the evaluation sample 10 that has been subjected to the coloring step to obtain an evaluation segment, with a cross section of the test piece 21 exposed; and an evaluation step of evaluating the penetration of the coloring substance into the test piece 21 using the evaluation segment.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for producing an evaluation sample for evaluating the penetration of a coloring substance into teeth, and an evaluation method for evaluating the penetration of a coloring substance into teeth.

Background Art

[0002] Conventionally, oral compositions have been proposed for the purpose of suppressing tooth staining or removing stains. Using such an oral composition, Patent Document 1 evaluates the effect of suppressing the adhesion of tooth staining stains. In the evaluation method described in Patent Document 1, after immersing hydroxyapatite pellets in a test solution containing the oral composition, the pellets are immersed in a black tea solution to adhere tea-based coloring stains to the hydroxyapatite pellets. Then, the degree of coloring is quantified using a spectrophotometer to evaluate the effect of suppressing the adhesion of coloring stains.

[0003] Also, Patent Document 2 evaluates the stain removal effect. In the evaluation method described in Patent Document 2, stains are adhered to the dentin of bovine extracted teeth using green tea, black tea, and coffee. After immersing the dentin with adhered stains in a solution containing the oral composition, the dentin is polished with a toothbrush. Then, the degree of coloring is quantified using a spectrocolorimeter to evaluate the stain removal effect.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The evaluation method described in Patent Document 1 quantifies the degree of coloring on the surface of hydroxyapatite pellets. The evaluation method described in Patent Document 2 quantifies the degree of coloring on the surface of dentin.

[0006] In the evaluation methods as described in Patent Documents 1 and 2, tooth discoloration due to the penetration of coloring substances into the interior of the tooth is not considered.

Means for Solving the Problem

[0007] The method for producing an evaluation sample for solving the above problems is a method for producing an evaluation sample for evaluating the penetration of a coloring substance into the interior of a tooth, and includes a step of cutting out a test piece from the tooth, and a cutting-out step of obtaining the test piece by cutting out the tooth so that the test piece includes the enamel of the tooth, an embedding step of obtaining a test block by embedding the test piece in an embedding agent so that the enamel in the test piece is exposed, and a protection step of covering all of the boundaries between the test piece and the embedding agent with a coating agent while leaving the portion where the enamel is exposed on the surface of the test block where the enamel of the test piece is exposed.

[0008] The evaluation method for solving the above problems is an evaluation method for evaluating the penetration of a coloring substance into the interior of a tooth, comprising a step of cutting out a test piece from the tooth, a cutting-out step of obtaining the test piece by cutting out the tooth so that the test piece has the enamel of the tooth, an embedding step of obtaining a test block by embedding the test piece in an embedding agent so that the enamel in the test piece is exposed, a protecting step of obtaining an evaluation sample by covering all of the boundaries between the test piece and the embedding agent with a covering agent on the colored surface, with the surface of the test piece where the enamel is exposed being the colored surface, while leaving the portion where the enamel is exposed, a coloring step of coloring the test piece using the coloring substance on the evaluation sample, an evaluation section preparation step of obtaining an evaluation section in which a cross-section of the test piece on a plane intersecting the colored surface is exposed by cutting the evaluation sample that has undergone the coloring step, and an evaluation step of evaluating the penetration of the coloring substance into the test piece using the evaluation section.

Advantages of the Invention

[0009] According to the present invention, an evaluation sample for evaluating tooth discoloration due to the penetration of a coloring substance into the interior of a tooth can be obtained. Further, tooth discoloration due to the penetration of a coloring substance into the interior of a tooth can be evaluated.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of an evaluation method for evaluating the penetration of a coloring substance into the inside of a tooth will be described with reference to FIGS. 1 to 6. As shown in FIG. 1, the evaluation method of this embodiment includes a tooth cutting step S11, an embedding step S12, a surface polishing step S13, a protection step S14, a coloring step S21, an evaluation section preparation step S31, and an evaluation step S32. The evaluation method is performed in the order of the tooth cutting step S11, the embedding step S12, the surface polishing step S13, the protection step S14, the coloring step S21, the evaluation section preparation step S31, and the evaluation step S32.

[0012] Among the above steps, by performing the tooth cutting step S11, the embedding step S12, the surface polishing step S13, and the protection step S14 in order, an evaluation sample 10 can be obtained. That is, performing these steps in order corresponds to a method for producing the evaluation sample 10.

[0013] Furthermore, by performing the coloring step S21, the evaluation section preparation step S31, and the evaluation step S32 in order on the obtained evaluation sample 10, the penetration of the coloring substance into the inside of the tooth can be evaluated. That is, in addition to the above steps in the method for producing the evaluation sample 10, performing the coloring step S21, the evaluation section preparation step S31, and the evaluation step S32 in order corresponds to the evaluation method of this embodiment.

[0014] The method for producing the evaluation sample 10 may include other steps in addition to the above steps. For example, the method for producing the evaluation sample 10 may include a cleaning step or a drying step. Also, in the embedding step S12, if the enamel is exposed in the test piece described later and it is embedded in that state, the surface polishing step S13 may be omitted.

[0015] The evaluation method may include a processing step of processing the evaluation sample 10. For example, in the evaluation method, as a processing step performed between the protection step S14 and the coloring step S21, an adhesion step of attaching a specific composition can also be performed. An example of the specific composition used in the adhesion step is a composition that can be expected to have an effect of suppressing tooth coloring.

[0016] For example, in the evaluation method, as a processing step performed between the coloring step S21 and the evaluation section preparation step S31, a coloring matter removal step of removing the coloring matter using a specific composition can also be performed. An example of the specific composition used in the coloring matter removal step is a composition that can be expected to have an effect of removing tooth coloring.

[0017] Hereinafter, a method for producing the evaluation sample 10 for evaluating tooth coloring due to penetration of a coloring matter into the tooth, and details of the evaluation method for evaluating tooth coloring due to penetration of a coloring matter into the tooth using the evaluation sample 10 will be described.

[0018] <Tooth cutting step> The tooth cutting step S11 is a step of cutting out a test piece by cutting the tooth used for producing the evaluation sample 10. The cutting method is not particularly limited as long as it can cut the tooth. Hereinafter, the tooth cutting step S11 is also simply referred to as the "cutting step S11".

[0019] Examples of the teeth used in this embodiment include human teeth or bovine teeth. FIG. 2 shows a schematic diagram of a tooth 20. The cutting step S11 cuts out the test piece 21 so that the test piece 21 includes the enamel of the tooth 20. In the cutting step S11, for example, the test piece 21 is obtained by cutting the tooth 20 in a ring shape. In FIG. 2, the line where the blade is inserted when cutting the tooth 20 in a ring shape is illustrated by a broken line.

[0020] If the test piece 21 has the enamel of the tooth 20, the test piece 21 may be obtained by further cutting the sectioned fragment of the tooth 20 into smaller pieces. For example, the test piece 21 may be a sectioned fragment of the tooth 20 processed into a block shape. Note that it is not essential to section the tooth 20. The cutting mode can be appropriately changed according to the size of the tooth 20.

[0021] <Embedding process> The embedding process S12 is a process of obtaining the test block 30. FIG. 3 shows an example of the test block 30.

[0022] In the embedding process S12, as shown in FIG. 3, the test piece 21 is embedded in the embedding agent 22. The embedding agent 22 has plasticity capable of embedding the test piece 21 in the embedding process S12, and can obtain rigidity that can withstand the physical external forces generated in the surface polishing process S13, the protection process S14, and the evaluation section preparation process S31 described later by drying or UV curing after embedding. Any embedding agent 22 can be used as long as it meets these requirements. Specific examples of the embedding agent 22 include paraffin, resin, etc. The type of paraffin is not particularly limited, and for example, purified paraffin for tissue embedding can be used. The type of resin is not particularly limited, and for example, a room temperature polymerization resin can be used.

[0023] The size of the test block 30 is not particularly limited as long as it is larger than the test piece 21, but it is preferably a size that is easy to handle in the evaluation section preparation process S31 described later.

[0024] The shape of the test block 30 is not particularly limited, but it is preferably a frustum or a column. The frustum or the column is a solid having two parallel surfaces. Examples of the frustum include a frustum of a pyramid and a frustum of a cone. Examples of the frustum of a pyramid include a frustum of a quadrangular pyramid.

[0025] Examples of the column include a prism and a cylinder. Examples of the prism include a quadrangular prism. Among the above-mentioned solids, the shape of the test block 30 is preferably a frustum of a square pyramid or a quadrangular prism, and more preferably a frustum of a square pyramid. As for the frustum of a square pyramid as the shape of the test block 30, a frustum of a square pyramid with an isosceles trapezoid cross-section is particularly preferred. As for the quadrangular prism as the shape of the test block 30, a cuboid or a cube is preferred. It should be noted that each of the above-mentioned solids is not limited to a precise shape, and includes solids in which the corners are chamfered for each solid.

[0026] In the test block 30, the enamel 21a in the test piece 21 is exposed on one of the surfaces of the test block 30. In the test block 30, the test piece 21 is embedded in the embedding agent 22 except for the exposed enamel 21a. More specifically, all of the cut surfaces in the cutting step S11 are embedded in the embedding agent 22.

[0027] As described above, the test block 30 is a step of embedding the test piece 21 in the embedding agent 22 so that the enamel 21a in the test piece 21 is exposed. Hereinafter, the surface on which the enamel 21a of the test piece 21 in the test block 30 is exposed is referred to as the colored surface 30a. When the test block 30 is a frustum of a pyramid or a prism, the colored surface 30a preferably corresponds to one of the two parallel surfaces provided by the frustum of a pyramid or the prism.

[0028] <Surface polishing step> The surface polishing step S13 is a step of polishing the colored surface 30a of the test block 30. For polishing, for example, waterproof abrasive paper can be used. The polishing may be performed manually by an operator or using a polishing machine.

[0029] In the test block 30 obtained by the embedding step S12, the embedding agent 22 may adhere to the enamel 21a exposed on the colored surface 30a. By performing the surface polishing step S13, the embedding agent 22 adhering to the enamel 21a exposed on the colored surface 30a can be removed.

[0030] In the surface polishing step S13, the enamel 21a may be smoothed by polishing. In the surface polishing step S13, it is acceptable for a part of the enamel 21a to be shaved off, but it is not preferable for the enamel 21a to be removed and the dentin or the like of the test piece 21 to be exposed.

[0031] <Protection step> The protection step S14 is a step of applying a coating agent 31 to the colored surface 30a of the test block 30.

[0032] As the coating agent 31, for example, dental varnish, nail top coat, etc. can be used. Figures 4 and 5 show an example of the evaluation sample 10.

[0033] As shown in Figures 4 and 5, in the protection step S14, on the colored surface 30a, the coating agent 31 is applied so as to cover all of the boundaries between the test piece 21 and the embedding agent 22 while leaving the portions where the enamel 21a of the test piece 21 is exposed. As a result, as shown in Figure 4, the coating agent 31 is applied in a ring shape. The test piece 21 is exposed within the coating agent 31 applied in a ring shape. As the evaluation sample 10, not limited to the boundary between the test piece 21 and the embedding agent 22, all of the embedding agent 22 on the colored surface 30a may be covered with the coating agent 31.

[0034] The coating agent 31 is not limited to the above liquid form, and for example, adhesive tapes such as sealing tape and masking tape can also be used. In this case, the protection step S14 is a step of attaching the coating agent 31 to the colored surface 30a of the test block 30.

[0035] <Coloring step> The coloring step S21 is a step of coloring the test piece 21 of the evaluation sample 10 using a coloring material.

[0036] The coloring method is not particularly limited. For example, the test piece 21 can be colored by immersing the evaluation sample 10 in a solution containing a coloring substance. After taking out the evaluation sample 10 from the solution containing the coloring substance, it is preferable to dry the evaluation sample 10. Examples of the coloring substance include synthetic coloring agents, natural coloring agents, green tea, black tea, coffee, and the like. The immersion time for immersing the evaluation sample 10 can be adjusted as appropriate.

[0037] <Evaluation section preparation step> The evaluation section preparation step S31 is a step of obtaining an evaluation section 11 in which the cross-section of the test piece 21 is exposed by cutting the evaluation sample 10 that has undergone the coloring step S21.

[0038] In the evaluation section preparation step S31, the evaluation sample 10 is cut along a plane intersecting the colored surface 30a. For example, the evaluation sample 10 can be cut along a plane orthogonal to the colored surface 30a. An example of the cross-section when the evaluation sample 10 is cut along a plane orthogonal to the colored surface 30a is the cross-section obtained by cutting the evaluation sample 10 at a position corresponding to the line 5-5 in FIG. 4. In this case, the cross-sectional structure illustrated in FIG. 5 is exposed.

[0039] FIG. 6 shows an example of the evaluation section 11. As shown in FIG. 6, since the cross-section of the test piece 21 is exposed, the colored region A in which the coloring substance has penetrated into the test piece 21 can be observed. The cutting method is not particularly limited as long as it can cut teeth, but a method that can cut at a low temperature without excessively heating the test piece 21 is preferable. For example, the evaluation sample 10 can be cut using a diamond cutter as the cutting device.

[0040] Also, when cutting the evaluation sample 10, it is preferable to cut the evaluation sample 10 while it is fixed. For example, it is preferable that the cutting device is equipped with a clamp or the like that can grip the evaluation sample 10. For example, it is preferable to cut the evaluation sample 10 while gripping two parallel surfaces of the evaluation sample 10.

[0041] In the evaluation slice production step S31, after obtaining the evaluation slice 11 with the cross-section of the test piece 21 exposed by cutting the evaluation sample 10, a cross-section polishing step of polishing the cross-section of the evaluation slice 11 may be further performed. In the cross-section polishing step, for example, waterproof abrasive paper can be used. The polishing may be performed manually by an operator or using a polishing machine.

[0042] <Evaluation step> The evaluation step S32 is a step of evaluating the penetration of the coloring substance into the test piece 21 using the evaluation slice 11.

[0043] The evaluation method is not particularly limited. For example, by binarizing an image of the cross-section of the test piece 21 in the evaluation slice 11, the penetration of the coloring substance into the test piece 21 can be quantitatively evaluated. As another example, by measuring the L value using a spectrophotometer, the penetration of the coloring substance into the test piece 21 can also be quantitatively evaluated.

[0044] <Function of this embodiment> The function of this embodiment will be described. FIG. 7 shows the evaluation slice 91 of the comparative example.

[0045] The evaluation slice 91 shown in FIG. 7 is obtained by cutting the evaluation sample of the comparative example. The evaluation sample of the comparative example is different from the evaluation sample 10 of this embodiment in that the protection step S14 is not performed. For other configurations, it is common with the evaluation sample 10 of this embodiment. By performing the coloring step S21 and the evaluation slice production step S31 in the same manner as this embodiment using the evaluation sample of the comparative example, the evaluation slice 91 of the comparative example is produced.

[0046] In the comparative example, since the protection step S14 is not performed, that is, the boundary between the test piece 21 and the embedding agent 22 is not protected by a coating agent, the coloring matter may penetrate from the boundary between the test piece 21 and the embedding agent 22. More specifically, if there is a gap where the test piece 21 and the embedding agent 22 are not in close contact, the coloring matter may penetrate into the gap. FIG. 7 shows an arrow B indicating the boundary between the test piece 21 and the embedding agent 22. For example, when the coloring matter penetrates from the boundary between the test piece 21 and the embedding agent 22, the coloring matter may penetrate from the side surface of the test piece 21. In this case, as shown in FIG. 7, the coloring may reach the lateral region AX. At this time, the larger the gap between the test piece 21 and the embedding agent 22, the faster the coloring matter penetrates. Also, for example, the more the coloring reaches the lateral region AX and the more the coloring matter penetrates, there is a possibility that the coloring matter reaches the boundary between the bottom surface of the test piece 21, that is, the surface on the side opposite to the enamel 21a, and the embedding agent 22. When the coloring matter penetrates in this way, the coloring matter may penetrate from the bottom surface of the test piece 21. In this case, as shown in FIG. 7, the coloring may reach the bottom surface region AY. The more the lateral region AX and the bottom surface region AY and the like are colored and the more the coloring matter penetrates, there is a possibility that the colored region A spreads over the entire test piece 21.

[0047] In the test piece 21 produced by cutting out the tooth 20, the side surface and the bottom surface of the test piece 21 may be dentin, tooth root, dental pulp, etc. Even if the dentin, tooth root, dental pulp, etc. in the test piece 21 are embedded in the embedding agent 22, in the case of the comparative example, the coloring matter that has penetrated from the boundary between the test piece 21 and the embedding agent 22 may penetrate from the dentin, tooth root, dental pulp, etc. That is, there is a possibility that the coloring matter penetrates from other than the enamel 21a.

[0048] In contrast, according to the evaluation sample 10 of the present embodiment, the boundary between the test piece 21 and the embedding agent 22 is protected by the coating agent 31. For this reason, the infiltration of the coloring substance from the boundary between the test piece 21 and the embedding agent 22 is suppressed. As a result, as shown in FIG. 6, the colored region A is the region where the coloring substance has penetrated only from the enamel 21a. In other words, the colored region A is the region where the coloring substance has penetrated from the enamel 21a toward the center of the evaluation sample 10.

[0049] <Effect of the present embodiment> The effect of the present embodiment will be described. (1) According to the present embodiment, it is possible to evaluate the tooth discoloration caused by the penetration of the coloring substance into the tooth, rather than the discoloration adhering to the tooth surface.

[0050] For example, a test substance such as a hydroxyapatite pellet does not mimic the actual tooth structure. Even if such a test substance is colored, it is impossible to mimic the penetration of the coloring substance into the teeth in the oral cavity. That is, it is impossible to evaluate the tooth discoloration caused by the penetration of the coloring substance into the tooth.

[0051] For example, in an extracted tooth, structures other than enamel are exposed. When trying to color such a tooth, there is a risk that the coloring substance may penetrate from, for example, dentin, tooth root, dental pulp, etc. Similarly, when processing an extracted tooth, if trying to color the processed tooth, there is a risk that the coloring substance may penetrate from structures other than enamel. For this reason, when using an extracted tooth, there is a problem that the coloring progresses from a location that is not exposed in the actual teeth in the oral cavity, that is, a location where the coloring substance cannot penetrate.

[0052] In this regard, according to the evaluation sample 10 of the present embodiment, the penetration of the coloring substance from outside the enamel can be suppressed. As a result, it is possible to evaluate the penetration of the coloring substance in an environment similar to that of the actual teeth in the oral cavity.

[0053] (2) According to this embodiment, since the evaluation section 11 is produced by cutting the evaluation sample 10, a cross-section with few irregularities can be obtained. Thereby, variations caused by the operator performing the cutting can be reduced with respect to the smoothness of the cross-section in the evaluation section 11.

[0054] (3) By producing the test block 30 as a frustum or a columnar body, an evaluation sample 10 that is easy to cut can be produced. Specifically, since the evaluation sample 10 can be cut while gripping two parallel surfaces in the evaluation sample 10, variations caused by the operator performing the cutting can be further reduced.

[0055] (4) The irregularities on the cross-section of the evaluation section 11 may create a shadow when photographing the cross-section. If a shadow is created, there is a risk that the reproducibility of the photographing will decrease. In this regard, according to this embodiment, by polishing the cross-section of the evaluation section 11, the cross-section can be made smoother. Thereby, variations caused by the operator photographing the cross-section can be reduced.

[0056] (5) According to this embodiment in which the evaluation sample 10 is produced by embedding the test piece 21 cut out from the tooth 20 in the embedding agent 22, evaluation can be performed regardless of the size of the tooth 20. For example, when the tooth 20 is large, an evaluation sample 10 having a size that is easy to observe the cross-section can be produced by processing the tooth 20 into a block shape. For example, when the tooth 20 is small, an evaluation sample 10 having a size that is easy to grip during the evaluation section production step S31 can be produced by embedding it in the embedding agent 22.

[0057] (6) According to the evaluation method further including an adhesion step, for a specific composition to be used, the effect of suppressing tooth coloring due to penetration of a coloring substance into the tooth can be quantified. (7) According to the evaluation method further including a coloring substance removal step, for a specific composition to be used, the effect of removing tooth coloring due to penetration of a coloring substance into the tooth can be quantified.

[0058] (Modification example) This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically non - conflicting range.

[0059] · In the above - described embodiment, as the coloring step S21, an example of a method of immersing the evaluation sample 10 in a solution containing a coloring substance was illustrated. Alternatively, the test piece 21 can also be colored by applying a solution containing a coloring substance to the evaluation sample 10. Even in this case, when the boundary between the test piece 21 and the embedding agent 22 is not protected, there is a risk that the coloring substance will penetrate from the boundary between the test piece 21 and the embedding agent 22. Even when coloring is performed as described above, by using the evaluation sample 10 in which the boundary between the test piece 21 and the embedding agent 22 is protected, the penetration of the coloring substance from the boundary between the test piece 21 and the embedding agent 22 can be suppressed.

[0060] · In the above - described embodiment, the tooth discoloration caused by the penetration of the coloring substance into the tooth was quantitatively evaluated. The evaluation method is not limited to this mode, and the tooth discoloration caused by the penetration of the coloring substance into the tooth may be qualitatively evaluated. For example, the presence or absence of penetration of the coloring substance may be evaluated only visually.

Example

[0061] The evaluation method will be described in more detail based on the following examples. Note that the evaluation method is not limited to the configuration described in the example section. <Preparation of evaluation sample> The evaluation samples described in the following Example 1, Comparative Example 1, and Comparative Example 2 were prepared. An overview of Example 1, Comparative Example 1, and Comparative Example 2 is shown in Table 1.

[0062]

Table 1

[0063] In the cutting step S11, bovine teeth were used. In the embedding step S12, a test block 30 in the shape of a frustum of a square pyramid with an isosceles trapezoid cross-section was produced using a room-temperature polymerizing resin (Orthofast, manufactured by GC).

[0064] In the surface polishing step S13, the colored surface 30a was polished with abrasive paper of grit #250 and then polished with abrasive paper of grit #600. In the protection step S14, a nail top coat was applied as the coating agent 31.

[0065] (Comparative Example 1) The extracted bovine teeth were used as evaluation samples. (Comparative Example 2) Evaluation samples were produced in the same manner as in Example 1 except that the protection step S14 was omitted. That is, the test block with the polished colored surface was used as the evaluation sample.

[0066] <Production of Evaluation Sections> The evaluation sections described in the following Example 2 and Comparative Examples 3 to 5 were produced. (Example 2) Using the evaluation sample 10 of Example 1, an evaluation section 11 was produced by performing the coloring step S21 and the evaluation section production step S31.

[0067] In the coloring step S21, Pigment Red 201 was used as the coloring agent. The evaluation sample 10 of Example 1 was immersed in a 0.05% aqueous solution of Pigment Red 201 for 16 hours. In the evaluation section production step S31, with the colored surface 30a and the surface opposite to the colored surface 30a in the evaluation sample 10 held by a clamp, the test block 30 was cut with a diamond cutter. The cross-section of the evaluation section 11 was obtained as a plane perpendicular to the colored surface 30a. Then, the cross-section of the evaluation section 11 was polished with abrasive paper of grit #800 and then polished with abrasive paper of grit #1200.

[0068] (Comparative Example 3) The bovine tooth of Comparative Example 1 was immersed in a 0.05% aqueous solution of Red No. 201 pigment for 16 hours. The cross-section of the bovine tooth was exposed by cutting the colored bovine tooth using a diamond cutter. Thereafter, the cross-section of the bovine tooth was polished with abrasive paper of #800 grit, and then the cross-section of the bovine tooth was polished with abrasive paper of #1200 grit. The bovine tooth with the exposed cross-section was used as an evaluation section.

[0069] (Comparative Example 4) An evaluation section was obtained in the same manner as in Example 2, except that the evaluation sample of Comparative Example 2 was used instead of the evaluation sample 10 of Example 1.

[0070] (Comparative Example 5) Using the evaluation sample 10 prepared in the same manner as in Example 1, the coloring step S21 was performed in the same manner as in Example 2. Thereafter, the cross-section of the test piece 21 was exposed by breaking the colored evaluation sample 10 using pliers. The broken evaluation sample 10 was used as an evaluation section.

[0071] (Evaluation of Penetration of Colored Substance) The penetration of the colored substance was evaluated using the evaluation sections of Example 2 and Comparative Examples 3 to 5. 〔Cross-Section Evaluation〕 Regarding the cross-section of each evaluation section, the penetration of the colored substance was visually observed. The evaluation criteria are as follows. The evaluation was performed by 5 evaluators. The evaluation that accounted for the majority was taken as the final evaluation. The results are shown in Table 2.

[0072] ·Cross-Section Evaluation Criteria ○(Acceptable): The penetration of the colored substance from outside the enamel is suppressed, and the colored substance penetrates only from the enamel. ×(Unacceptable): The colored substance penetrates from outside the enamel.

[0073] 〔Evaluation of Measurement Reproducibility〕 Using a photographing table with lighting, the evaluation section was placed on the photographing table so that the cross-section of the evaluation section faced upward. The cross-section of the test piece in the evaluation section placed on the photographing table was photographed from above the evaluation section. Furthermore, the process of rotating the evaluation section 90° clockwise and then photographing again was repeated 3 times. In this way, for one evaluation section, photographing was performed 4 times each.

[0074] For the 4 images of the cross-section of the test piece taken, by performing binarization processing using Photoshop Elements (manufactured by Adobe), 4 measurement values for quantifying the penetration of the colored substance were obtained. Based on the 4 measurement values, the median was calculated. For each measurement value, the deviation (%) from the median was calculated as the value obtained by dividing the absolute difference between the median and the measurement value by the median. Based on the maximum value of the deviation from the median, the measurement reproducibility was evaluated. It can be said that the smaller the deviation from the median, the higher the measurement reproducibility. The evaluation criteria are as follows. For each evaluation section, the measurement reproducibility was evaluated, and the results are shown in Table 2.

[0075] · Measurement reproducibility evaluation criteria ◎ (Good): The deviation from the median is less than 5%. ○ (Fair): The deviation from the median is 5% or more and less than 15%. × (Poor): The deviation from the median is 15% or more.

[0076]

Table 2

[0077] · Comprehensive evaluation criteria ○ (Fair): The result of the cross-section evaluation is ○, and the result of the measurement reproducibility evaluation is ○ or ◎. × (Poor): At least one of the results of the cross-section evaluation and the measurement reproducibility evaluation is ×.

[0078] <Evaluation results> In Comparative Example 3 where the evaluation sample of Comparative Example 1 was colored, since the bovine tooth was colored, the coloring matter had penetrated from the tooth root, dental pulp, etc.

[0079] In Comparative Example 4 where the evaluation sample of Comparative Example 2 was colored, since the boundary between the test piece and the embedding agent was not protected by a coating agent, the coloring matter had penetrated from the boundary. On the other hand, in Example 2 where the evaluation sample of Example 1 was colored, the penetration of the coloring matter from outside the enamel could be suppressed. From this result, it can be seen that according to the evaluation sample of Example 1 produced through the cutting step S11, embedding step S12, and protection step S14, the penetration of the coloring matter from outside the enamel can be suppressed.

[0080] In Example 2, evaluation sections were obtained by cutting the evaluation samples with a diamond cutter. According to such Example 2, the measurement reproducibility was good. Also in Comparative Example 4 where the evaluation samples were cut with a diamond cutter in the same manner as in Example 2, the measurement reproducibility was good.

[0081] In Comparative Example 3, although cutting was performed using a diamond cutter in the same manner as in Example 2 and Comparative Example 4, since the cutting target was the colored bovine tooth, sufficient gripping of the bovine tooth could not be achieved during cutting. For this reason, in Comparative Example 3, the smoothness of the cross section was lower than that in Example 2 and Comparative Example 4. Due to such factors, it is considered that the measurement reproducibility decreased compared to Example 2 and Comparative Example 4.

[0082] In Comparative Example 5, since the evaluation samples were broken, irregularities were observed on the cross section. The formation of shadows due to the irregularities during photography resulted in a low measurement reproducibility. As described above, according to Example 2, the penetration of the coloring matter from outside the enamel could be suppressed, and high measurement reproducibility could be confirmed.

Explanation of Reference Signs

[0083] 10… Evaluation sample 11… Evaluation section 20... teeth 21... test piece 21a... enamel 22... embedding agent 30... test block 30a... colored surface 31... coating agent A... colored region B... test piece - embedding agent boundary AX... lateral region AY... bottom surface region 91... evaluation section of comparative example

Claims

1. A method for preparing an evaluation sample for evaluating the penetration of a coloring substance into the interior of a tooth, comprising: a cutting step of cutting a test piece from a tooth, wherein the test piece is obtained by cutting the tooth such that the test piece includes the enamel of the tooth; an embedding step of obtaining a test block by embedding the test piece in an embedding agent such that the enamel in the test piece is exposed; a protecting step of covering all of the boundaries between the test piece and the embedding agent with a covering agent while leaving the exposed portion of the enamel on the surface of the test block where the enamel of the test piece is exposed.

2. An evaluation method for evaluating the penetration of a coloring substance into the interior of a tooth, comprising: a cutting step of cutting a test piece from a tooth, wherein the test piece is obtained by cutting the tooth such that the test piece includes the enamel of the tooth; an embedding step of obtaining a test block by embedding the test piece in an embedding agent such that the enamel in the test piece is exposed; a protecting step of obtaining an evaluation sample by covering all of the boundaries between the test piece and the embedding agent with a covering agent while leaving the exposed portion of the enamel on the surface of the test block where the enamel of the test piece is exposed, with the surface where the enamel is exposed being a coloring surface; a coloring step of coloring the test piece using the coloring substance on the evaluation sample; an evaluation section preparation step of obtaining an evaluation section in which a cross-section of the test piece on a plane intersecting the coloring surface is exposed by cutting the evaluation sample after the coloring step; an evaluation step of evaluating the penetration of the coloring substance into the test piece using the evaluation section.

3. The test block obtained in the embedding step is a frustum or a cylinder, The evaluation section preparation step obtains the evaluation section by cutting the evaluation sample while gripping two parallel surfaces in the evaluation sample. The evaluation method according to Claim 2.

Images