CN107082568A - Gear division devitrified glass and its preparation and application that a kind of lithium sodium is co-doped with - Google Patents

Abstract

The gear division devitrified glass being co-doped with the invention discloses a kind of lithium sodium and its preparation and application, the component of the gear division devitrified glass, which is constituted, is as mass fraction：SiO₂65% ~ 75%, Li₂O 5% ~ 20%, Na₂O 5% ~ 20%, P₂O₅4% ~ 6% and ZrO₂4% ~ 6%, above material quality fraction sum is 100%.Above raw material is obtained into glass block by fusion-cast method, obtains being easy to the glass intermediate R of machining after crystallization is handled₂SiO₃(R=Li, Na), then carries out secondary heat treatment and obtains with R₂Si₂O₅(R=Li, Na) is the devitrified glass finished product of principal crystalline phase.The finished product has the mechanical properties such as excellent bending strength, can be used as gear division full ceramic restoration material.

Description

A kind of lithium-sodium co-doped dental glass-ceramics and its preparation and application

technical field

The invention belongs to the field of glass-ceramics, in particular to a lithium-sodium co-doped dental glass-ceramics and its preparation and application.

Background technique

Teeth are an important part of the human body. In today's society, the problem of dental restoration is becoming more and more prominent. Choose suitable restoration materials to make higher strength and more beautiful dentures (commonly known as "dentures") to restore and decorate the teeth to restore the teeth. Biological function and beautiful appearance have become research hotspots. Silicate glass-ceramic materials for dental all-ceramic restorations (such as lithium disilicate Li ₂ Si ₂ O ₅ , Li ₂ O·2SiO ₂ ) are closer to natural teeth due to their mechanical properties and semi-permeability, and are easy to machine. advantage, and has a broader application prospect. At present, the commonly used glass-ceramic molding processes include hot die-casting and computer-aided design and manufacturing (CAD/CAM). Hot die-casting is mainly to make the glass-ceramic reach the softened state of the glass and then apply external pressure to fill the mold cavity. CAD/CAM mainly utilizes the good mechanical processing performance of glass-ceramic intermediate products for molding and further heat treatment to obtain dental glass-ceramic restorations, and the digital design and manufacture of CAD/CAM can also greatly meet people's individual needs and high-efficiency change. Correspondingly, the representative commercial glass-ceramic dental materials on the market are products such as Ivoclar’s IPS E.Max Press series and IPS E.Max CAD, whose mechanical properties and aesthetic properties have been greatly improved; while domestic Market-related research and industrialization started relatively late. Although there are some commercial products, their mechanical properties and stability are still far behind international leading products. Therefore, it is of great significance to develop a dental glass-ceramic restoration with independent intellectual property rights, higher mechanical properties, wider application range, stability and service life.

In terms of existing achievements, domestic patent application numbers CN201410271711.2, CN201510246538.5, and CN201610084411.2 mainly adopt the powder hot die-casting method, and their main performance indicators such as bending strength are still lower than those of mainstream products in the international market (360~400MPa). Not a small gap.

Contents of the invention

The object of the present invention is to provide a lithium-sodium co-doped dental glass-ceramics and its preparation and application. The present invention obtains a glass block by melting and casting, and obtains a glass intermediate that is easy to be machined after crystallization treatment, and then performs secondary heat treatment to obtain R ₂ Si ₂ O ₅ (R=Li, Na) as the main crystal phase, A glass-ceramic product with some metasilicate crystals. The finished glass-ceramic product has excellent mechanical properties such as bending strength, and can be used as a dental all-ceramic restoration material.

In order to realize the above-mentioned purpose of the invention, the present invention adopts following technical scheme:

A lithium-sodium co-doped dental glass-ceramic, the composition of which is calculated by mass fraction: SiO ₂ 65%-75%, Li ₂ O 5%-20%, Na ₂ O 5%-20%, P ₂ O ₅ 4%~6% and ZrO ₂ 4%~6%, the sum of the mass fractions of the above components is 100%.

Further preferably, the mass ratio of P ₂ O ₅ to ZrO ₂ is 1:1.

A method for preparing the above-mentioned lithium-sodium co-doped dental glass-ceramics, comprising the following steps:

(1) Mix the raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ) according to the ratio, ball mill them evenly and dry them; -4 hours; rapidly cooling the molten glass to obtain a glass frit;

(2) Crush the glass frit and ball mill to obtain glass powder for remelting;

(3) Cast the remelted molten glass into the preheated mold, then put it into the furnace for annealing, and cool down with the furnace;

(4) Crystallize the annealed shaped glass to obtain a glass-ceramic intermediate containing R ₂ SiO ₃ (R=Li, Na) as the main crystal phase;

(5) Subsequent secondary heat treatment is performed to obtain a finished glass-ceramic product containing R ₂ Si ₂ O ₅ (R=Li, Na) as the main crystal phase.

In the step (1), the ball milling time is 3 to 10 hours, preferably 5 to 9 hours, more preferably 8 hours; the pre-calcination is to keep warm at 300 to 350°C for 0.5 to 1 hour, preferably at 330°C for 1 hour hour; calcining is calcination at 840~880°C for 0.5~1 hour, preferably at 850°C for 1 hour; melting is at 1300~1550°C for 0.5~4 hours, preferably at 1400~1500°C for 0.5~2 hours, preferably Keep the temperature at 1500°C for 1 hour; quench the glass liquid with pure water.

In the step (2), the ball milling procedure is the same as that in the step (1); the glass does not need to be calcined before remelting, and the remelting is carried out at 1500° C. for 0.5 to 1 hour.

In the step (3), the mold preheating temperature is 450-550°C, preferably 500-550°C, more preferably 550°C; the furnace annealing temperature is set at 450-600°C, preferably 500-600°C, further It is preferred to heat it at 500°C for 10 minutes and immediately raise it to 550°C and hold it for 10 to 30 minutes, then cool with the furnace.

In the step (4), the crystallization stage of the annealed shaped glass is divided into two stages of nucleation and crystallization, the nucleation treatment temperature is 580-630°C, preferably 600°C; the nucleation time is 0.5-1 hour , preferably 0.5 hours; the crystallization treatment temperature is 630~700°C, preferably 650°C; the crystallization time is 0.5~ ₁ hour, preferably ₁ hour; K) The glass-ceramic intermediate with the main crystal phase has good machining performance, and can be combined with computer-aided design and manufacturing technology (CAD/CAM) for machining such as cutting.

In the step (5), the glass-ceramic intermediate or the mechanically processed prosthesis is subjected to a second heat treatment, the heat treatment temperature is 750-880°C, preferably 800-860°C, more preferably 860°C; the second heat treatment time is 0.5~3 hours, preferably 1 hour; after the secondary heat treatment, the size change of the glass-ceramics is small, and the crystal of R ₂ SiO ₃ (R=Li, Na) is transformed into R ₂ Si ₂ O ₅ (R=Li, Na) , to obtain a glass-ceramic with R ₂ Si ₂ O ₅ (R=Li, Na) as the main crystal phase, which has excellent mechanical and aesthetic properties.

The heating rate corresponding to the temperature of each step above is 2-10°C/min, preferably 3-5°C/min, more preferably 4°C/min.

Significant advantage of the present invention is:

(1) The present invention utilizes high field strength Na ⁺ to replace Li ⁺ , and can promote the crystallization process through the elastic energy generated by lattice distortion. Therefore, in the glass annealing stage, the formation of fine crystal nuclei of some metasilicates can be induced, combined with segmental heat treatment, and finally a dendritic cross-linked interlocking R ₂ Si ₂ O ₅ (R=Li, Na) crystal structure is obtained. Evenly distributed in the remaining glass matrix, thereby significantly improving the strength of the glass-ceramic, and its three-point bending mechanical properties exceeded 380MPa, surpassing the current mainstream products in the market;

(2) Secondly, high-concentration Li ₂ O and Na ₂ O co-doping enhances the mixed alkali effect, can significantly reduce the softening point, and adjust the thermal expansion coefficient of the system;

(3) By adding P ₂ O ₅ and ZrO ₂ as dual nucleating agents, especially when the ratio of P ₂ O ₅ and ZrO ₂ is 1:1, the coordinated effect of the two can be fully exerted, effectively reducing the energy potential of the system barrier, which promotes the precipitation and growth of the main crystal phase, forming a fine interlocking crystal structure; and, the precipitation of Zr-containing crystals also improves the mechanical properties of the system. In addition, an appropriate amount of P ₂ O ₅ and ZrO ₂ also strengthens the network structure of the glass, which not only improves the strength of the system, but also significantly reduces the dissolution of alkali metal elements and improves the biocompatibility of the glass-ceramic;

(4) The preparation raw materials of the present invention are simple and easy to obtain, the process is stable, and the conditions for practical and industrialization are met.

Description of drawings

Fig. 1 is an SEM image of the R ₂ Si ₂ O ₅ (R=Li, Na) glass-ceramics obtained through secondary heat treatment in Example 1.

detailed description

A lithium-sodium co-doped dental glass-ceramic, the composition of which is calculated by mass fraction: SiO ₂ 65%-75%, Li ₂ O 5%-20%, Na ₂ O 5%-20%, P ₂ O ₅ 4%~6% and ZrO ₂ 4%~6%, the sum of the mass fractions of the above components is 100%.

Further preferably, the mass ratio of P ₂ O ₅ to ZrO ₂ is 1:1.

A method for preparing the above-mentioned lithium-sodium co-doped dental glass-ceramics, comprising the following steps:

(1) Mix the raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ) according to the ratio, ball mill them evenly and dry them; -4 hours; rapidly cooling the molten glass to obtain a glass frit;

(2) Crush the glass frit and ball mill to obtain glass powder for remelting;

(3) Cast the remelted molten glass into the preheated mold, then put it into the furnace for annealing, and cool down with the furnace;

(4) Crystallize the annealed shaped glass to obtain a glass-ceramic intermediate containing R ₂ SiO ₃ (R=Li, Na) as the main crystal phase;

(5) Subsequent secondary heat treatment is performed to obtain a finished glass-ceramic product containing R ₂ Si ₂ O ₅ (R=Li, Na) as the main crystal phase.

In the step (1), the ball milling time is 3 to 10 hours, preferably 5 to 9 hours, more preferably 8 hours; the pre-calcination is to keep warm at 300 to 350°C for 0.5 to 1 hour, preferably at 330°C for 1 hour hour; calcining is calcination at 840~880°C for 0.5~1 hour, preferably at 850°C for 1 hour; melting is at 1300~1550°C for 0.5~4 hours, preferably at 1400~1500°C for 0.5~2 hours, preferably Keep the temperature at 1500°C for 1 hour; quench the glass liquid with pure water.

In the step (2), the ball milling procedure is the same as that in the step (1); the glass does not need to be calcined before remelting, and the remelting is carried out at 1500° C. for 0.5 to 1 hour.

In the step (3), the mold preheating temperature is 450-550°C, preferably 500-550°C, more preferably 550°C; the furnace annealing temperature is set at 450-600°C, preferably 500-600°C, further It is preferred to heat it at 500°C for 10 minutes and immediately raise it to 550°C and hold it for 10 to 30 minutes, then cool with the furnace.

In the step (4), the crystallization stage of the annealed shaped glass is divided into two stages of nucleation and crystallization, the nucleation treatment temperature is 580-630°C, preferably 600°C; the nucleation time is 0.5-1 hour , preferably 0.5 hours; the crystallization treatment temperature is 630~700°C, preferably 650°C; the crystallization time is 0.5~ ₁ hour, preferably ₁ hour; K) The glass-ceramic intermediate with the main crystal phase has good machining performance, and can be combined with computer-aided design and manufacturing technology (CAD/CAM) for machining such as cutting.

In the step (5), the glass-ceramic intermediate or the mechanically processed prosthesis is subjected to a second heat treatment, and the heat treatment temperature is 750-880°C, preferably 800-860°C, more preferably 860°C; after the second heat treatment , small size change of glass-ceramic, R ₂ SiO ₃ (R=Li, Na) crystal transforms into R ₂ Si ₂ O ₅ (R=Li, Na), and obtains R ₂ Si ₂ O ₅ (R=Li, Na) A glass-ceramic with a main crystal phase, which has excellent mechanical and aesthetic properties.

The heating rate corresponding to the temperature of each step above is 2-10°C/min, preferably 3-5°C/min, more preferably 4°C/min.

Table 1 is a list of dental glass-ceramic components (mass percentage) in Examples 1-4

Example 1

According to the ratio of each component in Table 1, weigh a certain amount of analytically pure raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ), and mix them with a ball mill for 8 hours. uniform; then put the powder into a platinum crucible, place it in the air atmosphere of a box-type resistance furnace, heat it at 4°C/min to 330°C and 850°C for 1 hour each to remove nitrogen and carbon, continue to heat up to 1500°C, and keep warm 1 hour; then, take out the crucible, pour the melt into deionized water to quench, and dry to obtain fragments of glass melt; ball mill again, and the powder is directly heated to 1500°C/1 hour for remelting; the remelted glass is cast Put it into the mold that has been preheated at 550°C, quickly put it into the resistance furnace, heat it at 500°C for 10 minutes, then immediately rise to 550°C and keep it for 30 minutes, then cool with the furnace. The cast glass block is first subjected to 625°C/1 hour nucleation and 680°C/1 hour crystallization to complete the crystallization treatment, and obtain a glass-ceramic intermediate with Li ₂ SiO ₃ as the main crystal phase, and the three-point bending strength The value is 152MPa, and the HV1 Vickers hardness value is 348, which has good machinability; followed by a second heat treatment at 860°C/1 hour to obtain a glass-ceramic with Li ₂ Si ₂ O ₅ as the main crystal phase, The density is 2.4855g/cm ³ , the three-point bending strength is 382MPa, the HV1 Vickers hardness is 627, and the coefficient of thermal expansion is 11.0*10 ^-6 K ^-1 . Relevant tests refer to "GB 30367-2013 Dentistry_Ceramic Materials", and the mechanical properties meet the requirements of dental all-ceramic restorations.

Example 2

According to the ratio of each component in Table 1, weigh a certain amount of analytically pure raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ), and mix them with a ball mill for 8 hours. uniform; then put the powder into a platinum crucible, place it in the air atmosphere of a box-type resistance furnace, heat it at 4°C/min to 330°C and 850°C for 1 hour each to remove nitrogen and carbon, continue to heat up to 1500°C, and keep warm 1 hour; then, take out the crucible, pour the melt into deionized water to quench, and dry to obtain fragments of glass melt; ball mill again, and the powder is directly heated to 1500°C/1 hour for remelting; the remelted glass is cast Put it into the mold that has been preheated at 550°C, quickly put it into the resistance furnace, heat it at 500°C for 10 minutes, then immediately rise to 550°C and keep it for 30 minutes, then cool with the furnace. The cast glass block is first subjected to 610°C/1 hour nucleation and 665°C/1 hour crystallization to complete the crystallization treatment, and obtain a glass-ceramic intermediate with Li ₂ SiO ₃ and Na ₂ SiO ₃ as the main crystal phase , the three-point bending strength value is 173MPa, and the HV1 Vickers hardness value is 372, which has good machinability; followed by a second heat treatment at 840°C/1 hour, and the main crystal phase is Li ₂ Si ₂ O ₅ , glass-ceramics with part of LiNaSi ₂ O ₅ , the density is 2.4902g/cm ³ , the three-point bending strength is 407MPa, the HV1 Vickers hardness is 665, and the coefficient of thermal expansion is 11.3*10 ^-6 K ^-1 . Relevant tests refer to "GB 30367-2013 Dentistry_Ceramic Materials", and the mechanical properties meet the requirements of dental all-ceramic restorations.

Example 3

According to the ratio of each component in Table 1, weigh a certain amount of analytically pure raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ), and mix them with a ball mill for 8 hours. uniform; then put the powder into a platinum crucible, place it in the air atmosphere of a box-type resistance furnace, heat it at 4°C/min to 330°C and 850°C for 1 hour each to remove nitrogen and carbon, continue to heat up to 1500°C, and keep warm 1 hour; then, take out the crucible, pour the melt into deionized water to quench, and dry to obtain fragments of glass melt; ball mill again, and the powder is directly heated to 1500°C/1 hour for remelting; the remelted glass is cast Put it into the mold that has been preheated at 550°C, quickly put it into the resistance furnace, heat it at 500°C for 10 minutes, then immediately rise to 550°C and keep it for 30 minutes, then cool with the furnace. The cast glass block is first subjected to nucleation at 605°C/1 hour and crystallization at 655°C/1 hour to complete the crystallization treatment, and obtain a glass-ceramic intermediate with Na ₂ SiO ₃ and Li ₂ SiO ₃ as the main crystal phase , the three-point bending strength value is 177MPa, and the HV1 Vickers hardness value is 370, which has good machinability; followed by a second heat treatment at 840 ° C / 1 hour to obtain Na ₂ Si ₂ O ₅ as the main crystal phase , and LiNaSi ₂ O ₅ glass-ceramics, the density value is 2.4860g/cm ³ , the three-point bending strength value is 409MPa, the HV1 Vickers hardness value is 671, and the thermal expansion coefficient is 11.4*10 ^-6 K ^-1 . Relevant tests refer to "GB 30367-2013 Dentistry_Ceramic Materials", and the mechanical properties meet the requirements of dental all-ceramic restorations.

Example 4

According to the ratio of each component in Table 1, weigh a certain amount of analytically pure raw materials (SiO ₂ , Li ₂ CO ₃ , Na ₂ CO ₃ , NH ₄ H ₂ PO ₄ and ZrO ₂ ), and mix them with a ball mill for 8 hours. uniform; then put the powder into a platinum crucible, place it in the air atmosphere of a box-type resistance furnace, heat it at 4°C/min to 330°C and 850°C for 1 hour each to remove nitrogen and carbon, continue to heat up to 1500°C, and keep warm 1 hour; then, take out the crucible, pour the melt into deionized water to quench, and dry to obtain fragments of glass melt; ball mill again, and the powder is directly heated to 1500°C/1 hour for remelting; the remelted glass is cast Put it into the mold that has been preheated at 550°C, quickly put it into the resistance furnace, heat it at 500°C for 10 minutes, then immediately rise to 550°C and keep it for 30 minutes, then cool with the furnace. The cast glass block is first subjected to nucleation at 590°C/1 hour and crystallization at 640°C/1 hour to complete the crystallization treatment, and obtain a glass-ceramic intermediate with Na ₂ SiO ₃ as the main crystal phase, and the three-point bending strength The value is 161MPa, and the HV1 Vickers hardness value is 355, which has good machinability; followed by a second heat treatment at 820°C/1 hour to obtain a glass-ceramic with Na ₂ Si ₂ O ₅ as the main crystal phase, The density is 2.4802g/cm ³ , the three-point bending strength is 390MPa, the HV1 Vickers hardness is 647, and the coefficient of thermal expansion is 11.7*10 ^-6 K ^-1 . Relevant tests refer to "GB 30367-2013 Dentistry_Ceramic Materials", and the mechanical properties meet the requirements of dental all-ceramic restorations.

The present invention obtains Li ₂ O and Na ₂ O co-doped dental restoration glass-ceramics through the above implementation. Its remarkable effect is concentrated in excellent machinability and bending strength.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (10)

1. the gear division devitrified glass that a kind of lithium sodium is co-doped with, it is characterised in that：Its component is constituted：SiO₂ 65%~ 75%, Li₂O 5% ~ 20%, Na₂O 5% ~ 20%, P₂O₅4% ~ 6% and ZrO₂4% ~ 6%, above constituent mass fraction sum is 100%.

2. the gear division devitrified glass that a kind of lithium sodium according to claim 1 is co-doped with, it is characterised in that：P₂O₅And ZrO₂Matter Amount is than being 1:1.

3. a kind of method for preparing the gear division devitrified glass that lithium sodium as claimed in claim 1 or 2 is co-doped with, it is characterised in that：Bag Include following steps：

（1）By raw material SiO₂、Li₂CO₃、Na₂CO₃、NH₄H₂PO₄And ZrO₂By proportioning mixing, ball milling and drying；By pre-burning And founded after calcining, soaking time 0.5-4 hours；To the glass metal melted, chilling is carried out, glass frit is obtained；

（2）Glass frit is crushed, ball milling, obtain glass powder and carry out remelting；

（3）The glass metal of remelting is molded into preheated mould, is subsequently placed into furnace annealing, furnace cooling；

（4）Annealed formed glass is handled through crystallization and obtains R₂SiO₃For the devitrified glass intermediate of principal crystalline phase；Wherein R is Li and Na；

（5）R is obtained followed by secondary heat treatment₂Si₂O₅For the devitrified glass finished product of principal crystalline phase.

4. the method according to claim 3 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（1）In, Ball-milling Time is 3 ~ 10 hours, and pre-burning is to be incubated 0.5 ~ 1 hour at 300 ~ 350 DEG C, is calcined as in 840 ~ 880 DEG C of guarantors Temperature 0.5 ~ 1 hour, is founded to be incubated 0.5 ~ 4 hour at 1300 ~ 1550 DEG C, and chilling is to use pure water quenching；Described step（2） In, Ball-milling Time is 3 ~ 10 hours, and remelting is to be incubated 0.5 ~ 1 hour at 1500 DEG C.

5. the method according to claim 4 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（1）In, Ball-milling Time is 5 ~ 9 hours, and pre-burning is to be incubated 1 hour at 330 DEG C, calcines to be incubated 1 hour at 850 DEG C, founds To be incubated 0.5 ~ 2 hour at 1400 ~ 1500 DEG C；Described step（2）In, Ball-milling Time is 5 ~ 9 hours.

6. the method according to claim 5 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（1）In, Ball-milling Time is 8 hours, founds to be incubated 1 hour at 1500 DEG C；Described step（2）In, Ball-milling Time is 8 small When.

7. the method according to claim 3 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（3）In, mold preheating temperature is at 450 ~ 550 DEG C, and furnace annealing is at 450 ~ 600 DEG C；Described step（4）In, at crystallization Reason is divided into coring and crystallization two benches, and coring treatment temperature is 580 ~ 630 DEG C, and nucleation time is 0.5 ~ 1 hour, Crystallizing treatment temperature Spend for 630 ~ 700 DEG C, crystallization time 0.5 ~ 1 hour；Described step（5）In, the temperature of secondary heat treatment is 750 ~ 880 DEG C, The secondary heat treatment time is 0.5 ~ 3 hour.

8. the method according to claim 7 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（3）In, mold preheating temperature is at 500 ~ 550 DEG C, and furnace annealing is at 500 ~ 600 DEG C；Described step（4）In, at crystallization Reason is divided into coring and crystallization two benches, and coring treatment temperature is 600 DEG C, and nucleation time is 0.5 hour, and Crystallizing treatment temperature is 650 DEG C, crystallization time 1 hour；Described step（5）In, the temperature of secondary heat treatment is 800 ~ 860 DEG C, during secondary heat treatment Between be 1 hour.

9. the method according to claim 8 for preparing the gear division devitrified glass that lithium sodium is co-doped with, it is characterised in that：Described step Suddenly（3）In, furnace annealing is furnace cooling after rising to 550 DEG C immediately after being incubated 10 minutes at 500 DEG C and being incubated 10 ~ 30 minutes； Described step（5）In, the temperature of secondary heat treatment is 860 DEG C, and the secondary heat treatment time is 1 hour.

10. a kind of application of the gear division devitrified glass that lithium sodium as claimed in claim 1 or 2 is co-doped with materials of bone tissue, It is characterized in that：Described materials of bone tissue includes inlay, onlay, facing, part-crown, corona and tooth fixed bridge.