不同因素对可摘局部义齿铸造支架适合性影响的实验研究
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摘要
前言
可摘局部义齿(RPD)修复是牙列缺损最常用的修复方法。修复时，磨除基牙的牙体组织较少，对基牙的要求不像固定义齿那样严格，适应范围广，制作方法简单，患者可以自行摘戴，便于义齿的清洁，同时，由于基牙负担的(牙合)力较小，夜间义齿摘除后基牙及支持组织解除压力，经休息调整后，可以维持长时间的健康状态。义齿对恢复伴有软组织及牙槽嵴缺损的病例，具有较好的修复效果。铸造法完成的可摘局部义齿和胶连法相比，具有异物感小，义齿强度大，固位力强，外露金属少、舒适、美观等特点。
作为金合金的替代材料，镍铬合金和钴铬合金等非贵金属合金由于其物理强度大、耐腐蚀、价格低廉而广泛应用于可摘局部义齿(RPD)铸造支架的制作。
非贵金属合金铸造收缩较大，往往造成修复体的适合性差。修复体在口腔中难以就位。要制作满意的修复体就要补偿非贵金属合金的这种收缩。目前解决金属铸造收缩的办法主要是利用包埋材料的膨胀来补偿。除包埋材料本身外，印模材料、蜡型材料以及在使用这些材料时的方法等均对铸造收缩产生重要影响。
本实验的目的就是通过研究不同包埋材料、铸圈使用与否和不同的铸道安插方式对非贵金属合金铸造支架适合性的影响，找出最佳的组合方式，指导修复体的制作。
材料与方法
本实验采用多因素实验设计，研究各个因素对铸件适合性的影响。研究因素包括：1)三种包埋材料(X-20包埋材、GILVEST
包埋材、Heravest包埋材厂2）有圈和无圈，3）铸道设计，正插法和
反插法。所有的因素综合起来，共分为 12种组合门 x 2 x 2＝
12厂每组制作5个铸件，共60个。基底合金选用镍铬合金（Ver－
aBond，含镍77．95呢，铬12．60呢，美国产）。
1．模具的制作
使用环氧树脂制作模具，模具分两部分。下部为人上颌无牙
颌模型，其上在位于跨小凹前2毫米处留有贯穿两侧颊粘膜皱壁，
宽为14毫米，厚为二毫米的凹陷，上部为与下部相对应的阴模。
上、下对合压制的蜡型即为模拟上颌活动支架的蜡型。
2．翻制耐火模型
2．二 翻制琼脂印模 上颌模具置于复制型盒中心，将融化的
琼脂注人复制型盒中，待琼脂完全固化后，打开型盒，取出模型。
2．2 灌注铸模 将X－20包埋材、GILVEST包埋材0erav－
est包埋材三种包埋材按照厂商推荐的粉液比例称量出所需粉和
液。先手工调拌10秒，再使用真空搅拌机（WHIP－MIX，USA，
G568CX）以 1725转／分真空调拌30秒。将60个琼脂阴模随机分
为三组，每组20个。随机选其中20个印模灌注X－20包埋材，20
个灌注GILVEST包埋材，剩下的20个灌注Heravest包埋材。凝
固后脱出铸模，干燥2小时。于燥后的耐火模型浸人已熔沸的蜂
蜡中20秒。
3．蜡型制作
室温下，使用牙科红蜡片（上海齿科材料厂）制作蜡型。将蜡
片用恒温熔蜡器熔化后浇人模具上部结构内，在熔化的蜡稍凉且
末硬时，将模具上部与耐火模型以最大指压对合加压至完全就位，
待蜡硬固后分开模具。用蜡刀去除蜡型飞边。每种耐火模型上的
蜡型都采用两种铸道安插方式。其中10个蜡型采用正插法，10
个采用反插法。
4．蜡型包埋
·2·
每种铸道设计的蜡型随机平均分为两组，一组采用有圈包埋
法，另一组采用无圈包埋法，即采用纸圈包埋。用清洗液清洗蜡型
去除表面油脂，轻轻吹干表面。将相同直径和高度的金属铸圈和
纸圈分别固定在底座上。将与灌注铸模所用包埋材相同的磷酸盐
包埋材，按照厂商推荐的比例用真空搅拌机（WHIP－MIX，USA，
G568CX）以1725转／规行真空调拌30秒，将包埋材缓缓注人铸
圈内，同时保证蜡型水平放置且位于铸圈中上互乃交界处，震荡排
除气泡。置于操作台上干燥，室温放置，24小时后进行铸造。
5．焙烧、铸造
在室温下将铸圈铸道口向下放人电阻炉内焙烧除蜡。电阻炉
先缓慢升温至300℃维持30分钟，后继续升温，在二小时内由
300T升至 900℃维持 15分钟后铸造。使用高频离心铸造机将熔
化的镍铬合金（VeraBond，含镍77．95％，铬12．60％，美国产）注
人铸型腔。
6．铸件的分离
待铸圈在室温下冷却后喷砂取出铸件，去除多余包埋材。铸
件表面使用直径 50微米的氧化铝颗粒在 0．3 MPa压力下，每面喷
10秒，清除铸件表面剩余包埋材及氧化层。用金刚砂片切去铸
道，磨除表面金属小瘤，最后进行电解抛光。然后分组编号。
7．测量
将完成的铸件在模具上就位，由于其铸造后铸件精度发生改
变，铸件不能完全就位，测量上下模具间的间隙，其大小反映出铸
件适合性的改变。测量已在模具上标记的3个点（分别在双侧牙
槽崎顶和聘中缝处人
8．统计学处理
所测数据应用SPSS10．0软件进行多因素方差分析，确定各个
因素对铸件适合性的影响。
·3·
实验结果
1．从多因素方差分析的结果可以看出，包埋材料和包埋方法
对支架适合性的影响存在显著差异h＜
During the years since the cobalt - chromium casting alloys be-came available for cast removable partial denture ( RPD) restorations, they have continued to increase in popularity.
High - fusing casting alloys, referred to as base metal, include Ni - Cr and Co - Cr alloys, have a high cast shrinkage. That may re-sult a bad fit denture. The denture will take seat with difficulty. It must cost a lot of clinical time to adjust the frameworks to seat in the patients' mouth. Therefore, compensation of this shrinkage became very important in the procedure of making a cast denture. Usually, we use the expansion of investment to compensate it.
Therefore the purpose of this study was to find the best combina-tion of investment materials, method, and the design of sprucing , which can produce the best castings.
Material and methods
The factors of this study included; three type of invest materials, investing wax patterns ring and ringless and two designs of sprucing, top sprucing and inverted sprucing.
1. Mold fabrication
The mold with two parts was made of epoxy resin. The under part imitate the maxillary edentulous. The upper one is female of the un-der.
2. Duplicating the refractory casts
The under mold was duplicated with duplicating material to pro-duce 60 identical refractory casts. The three type phosphate ?bonded investment materials were accurately proportioned according to the manufacturers'instructions and mixed with its special liquid. The mix was vacuum spatulated 30s before it was poured into the molds. The refractory material set for 1 hour. The casts were carefully removed from the molds and dried in an oven for 2 hours. The casts were dipped in beeswax to obtain a smooth surface.
3. Wax pattern fabrication
Wax was melted in a wax melting pot and poured into the upper mold, before the wax became hard, matching the upper mold and the refractory cast with firm even finger pressure. The 60 refractory casts divided into two groups. One group was top sprued and the other was inverted sprued. Each wax pattern was painted with SOFU wax cleaner and dried with air.
4. Investing the wax pattern
Each refractory casts was invested within 1 hour, and use the same one poured the refractory casts. And then left to beach set for 24 hours.
5. Wax pattern elimination and casting
The invested patterns were placed in a thermostatically controlled oven at room temperature was then gradually raised to 300~(?)C in 1 hour , then to 900~(?)C in another hour. The temperature was maintained at 900~(?)C for 15 min. An high frecmency centrifugal casting machine (Tianjin, JN - A ) was used for casting. The Co - Cr alloy was cast in-to the mold cavity.
6. Casting separation
The recovered castings were sandblasted to remove investment.
The sprues were cut and all external nodules or fins were removed.
7. Measurement
The frameworks were completely seated in the two parts of the ep-oxy resin mold. Then measured the gap between the upper and under part.
8. Statistical analysis
Data were analyzed using the statistical package SPSS for Win-dows. The effect of all researching factors on the fit of RPD frame-works was evaluated.
Result
1. The effect of invest materials and methods on the fit of castings
are significant different, and their interaction is significant. The difference between the groups investing with metal rings or not is sig-nificant (P <0.01). In this study we dont find difference between top sprucing and inverted sprucing( P < 0.05 ).
2. The fits of use Heravest investment invested ring and ringless were not significantly different , ever though the discrepancy of fit of the ringless was consistently higher. But the fit of Heravest investment group was better than other groups.
Discussion
The design of wax pattern in this study was imitate the posterior palatal plate RPD framework. The complex shape decided various fac-tors that may influence the fit of castings. Addition to the factors such as investment materials and special liqui
可摘局部义齿(RPD)修复是牙列缺损最常用的修复方法。修复时，磨除基牙的牙体组织较少，对基牙的要求不像固定义齿那样严格，适应范围广，制作方法简单，患者可以自行摘戴，便于义齿的清洁，同时，由于基牙负担的(牙合)力较小，夜间义齿摘除后基牙及支持组织解除压力，经休息调整后，可以维持长时间的健康状态。义齿对恢复伴有软组织及牙槽嵴缺损的病例，具有较好的修复效果。铸造法完成的可摘局部义齿和胶连法相比，具有异物感小，义齿强度大，固位力强，外露金属少、舒适、美观等特点。
作为金合金的替代材料，镍铬合金和钴铬合金等非贵金属合金由于其物理强度大、耐腐蚀、价格低廉而广泛应用于可摘局部义齿(RPD)铸造支架的制作。
非贵金属合金铸造收缩较大，往往造成修复体的适合性差。修复体在口腔中难以就位。要制作满意的修复体就要补偿非贵金属合金的这种收缩。目前解决金属铸造收缩的办法主要是利用包埋材料的膨胀来补偿。除包埋材料本身外，印模材料、蜡型材料以及在使用这些材料时的方法等均对铸造收缩产生重要影响。
本实验的目的就是通过研究不同包埋材料、铸圈使用与否和不同的铸道安插方式对非贵金属合金铸造支架适合性的影响，找出最佳的组合方式，指导修复体的制作。
材料与方法
本实验采用多因素实验设计，研究各个因素对铸件适合性的影响。研究因素包括：1)三种包埋材料(X-20包埋材、GILVEST
包埋材、Heravest包埋材厂2）有圈和无圈，3）铸道设计，正插法和
反插法。所有的因素综合起来，共分为 12种组合门 x 2 x 2＝
12厂每组制作5个铸件，共60个。基底合金选用镍铬合金（Ver－
aBond，含镍77．95呢，铬12．60呢，美国产）。
1．模具的制作
使用环氧树脂制作模具，模具分两部分。下部为人上颌无牙
颌模型，其上在位于跨小凹前2毫米处留有贯穿两侧颊粘膜皱壁，
宽为14毫米，厚为二毫米的凹陷，上部为与下部相对应的阴模。
上、下对合压制的蜡型即为模拟上颌活动支架的蜡型。
2．翻制耐火模型
2．二 翻制琼脂印模 上颌模具置于复制型盒中心，将融化的
琼脂注人复制型盒中，待琼脂完全固化后，打开型盒，取出模型。
2．2 灌注铸模 将X－20包埋材、GILVEST包埋材0erav－
est包埋材三种包埋材按照厂商推荐的粉液比例称量出所需粉和
液。先手工调拌10秒，再使用真空搅拌机（WHIP－MIX，USA，
G568CX）以 1725转／分真空调拌30秒。将60个琼脂阴模随机分
为三组，每组20个。随机选其中20个印模灌注X－20包埋材，20
个灌注GILVEST包埋材，剩下的20个灌注Heravest包埋材。凝
固后脱出铸模，干燥2小时。于燥后的耐火模型浸人已熔沸的蜂
蜡中20秒。
3．蜡型制作
室温下，使用牙科红蜡片（上海齿科材料厂）制作蜡型。将蜡
片用恒温熔蜡器熔化后浇人模具上部结构内，在熔化的蜡稍凉且
末硬时，将模具上部与耐火模型以最大指压对合加压至完全就位，
待蜡硬固后分开模具。用蜡刀去除蜡型飞边。每种耐火模型上的
蜡型都采用两种铸道安插方式。其中10个蜡型采用正插法，10
个采用反插法。
4．蜡型包埋
·2·
每种铸道设计的蜡型随机平均分为两组，一组采用有圈包埋
法，另一组采用无圈包埋法，即采用纸圈包埋。用清洗液清洗蜡型
去除表面油脂，轻轻吹干表面。将相同直径和高度的金属铸圈和
纸圈分别固定在底座上。将与灌注铸模所用包埋材相同的磷酸盐
包埋材，按照厂商推荐的比例用真空搅拌机（WHIP－MIX，USA，
G568CX）以1725转／规行真空调拌30秒，将包埋材缓缓注人铸
圈内，同时保证蜡型水平放置且位于铸圈中上互乃交界处，震荡排
除气泡。置于操作台上干燥，室温放置，24小时后进行铸造。
5．焙烧、铸造
在室温下将铸圈铸道口向下放人电阻炉内焙烧除蜡。电阻炉
先缓慢升温至300℃维持30分钟，后继续升温，在二小时内由
300T升至 900℃维持 15分钟后铸造。使用高频离心铸造机将熔
化的镍铬合金（VeraBond，含镍77．95％，铬12．60％，美国产）注
人铸型腔。
6．铸件的分离
待铸圈在室温下冷却后喷砂取出铸件，去除多余包埋材。铸
件表面使用直径 50微米的氧化铝颗粒在 0．3 MPa压力下，每面喷
10秒，清除铸件表面剩余包埋材及氧化层。用金刚砂片切去铸
道，磨除表面金属小瘤，最后进行电解抛光。然后分组编号。
7．测量
将完成的铸件在模具上就位，由于其铸造后铸件精度发生改
变，铸件不能完全就位，测量上下模具间的间隙，其大小反映出铸
件适合性的改变。测量已在模具上标记的3个点（分别在双侧牙
槽崎顶和聘中缝处人
8．统计学处理
所测数据应用SPSS10．0软件进行多因素方差分析，确定各个
因素对铸件适合性的影响。
·3·
实验结果
1．从多因素方差分析的结果可以看出，包埋材料和包埋方法
对支架适合性的影响存在显著差异h＜
During the years since the cobalt - chromium casting alloys be-came available for cast removable partial denture ( RPD) restorations, they have continued to increase in popularity.
High - fusing casting alloys, referred to as base metal, include Ni - Cr and Co - Cr alloys, have a high cast shrinkage. That may re-sult a bad fit denture. The denture will take seat with difficulty. It must cost a lot of clinical time to adjust the frameworks to seat in the patients' mouth. Therefore, compensation of this shrinkage became very important in the procedure of making a cast denture. Usually, we use the expansion of investment to compensate it.
Therefore the purpose of this study was to find the best combina-tion of investment materials, method, and the design of sprucing , which can produce the best castings.
Material and methods
The factors of this study included; three type of invest materials, investing wax patterns ring and ringless and two designs of sprucing, top sprucing and inverted sprucing.
1. Mold fabrication
The mold with two parts was made of epoxy resin. The under part imitate the maxillary edentulous. The upper one is female of the un-der.
2. Duplicating the refractory casts
The under mold was duplicated with duplicating material to pro-duce 60 identical refractory casts. The three type phosphate ?bonded investment materials were accurately proportioned according to the manufacturers'instructions and mixed with its special liquid. The mix was vacuum spatulated 30s before it was poured into the molds. The refractory material set for 1 hour. The casts were carefully removed from the molds and dried in an oven for 2 hours. The casts were dipped in beeswax to obtain a smooth surface.
3. Wax pattern fabrication
Wax was melted in a wax melting pot and poured into the upper mold, before the wax became hard, matching the upper mold and the refractory cast with firm even finger pressure. The 60 refractory casts divided into two groups. One group was top sprued and the other was inverted sprued. Each wax pattern was painted with SOFU wax cleaner and dried with air.
4. Investing the wax pattern
Each refractory casts was invested within 1 hour, and use the same one poured the refractory casts. And then left to beach set for 24 hours.
5. Wax pattern elimination and casting
The invested patterns were placed in a thermostatically controlled oven at room temperature was then gradually raised to 300~(?)C in 1 hour , then to 900~(?)C in another hour. The temperature was maintained at 900~(?)C for 15 min. An high frecmency centrifugal casting machine (Tianjin, JN - A ) was used for casting. The Co - Cr alloy was cast in-to the mold cavity.
6. Casting separation
The recovered castings were sandblasted to remove investment.
The sprues were cut and all external nodules or fins were removed.
7. Measurement
The frameworks were completely seated in the two parts of the ep-oxy resin mold. Then measured the gap between the upper and under part.
8. Statistical analysis
Data were analyzed using the statistical package SPSS for Win-dows. The effect of all researching factors on the fit of RPD frame-works was evaluated.
Result
1. The effect of invest materials and methods on the fit of castings
are significant different, and their interaction is significant. The difference between the groups investing with metal rings or not is sig-nificant (P <0.01). In this study we dont find difference between top sprucing and inverted sprucing( P < 0.05 ).
2. The fits of use Heravest investment invested ring and ringless were not significantly different , ever though the discrepancy of fit of the ringless was consistently higher. But the fit of Heravest investment group was better than other groups.
Discussion
The design of wax pattern in this study was imitate the posterior palatal plate RPD framework. The complex shape decided various fac-tors that may influence the fit of castings. Addition to the factors such as investment materials and special liqui
引文
1. Combe EC. Notes on Dental Material 5th Edition. Churchill Living Stone 1986;318-324.
2．D．F．威廉姆斯主编，医学与牙科材料，科技出版社。1999；368—9．
3．徐君武，袁井圻，王忠义主编．口腔修复学．人民军医出版社 2001；419—9．
4. Craing RG. Restorative Dental Materials, 10th Edition. St. Louis Mosby Yearbook 1997; 146-53.
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6. Anusarice AJ, Editor. Skinner's Science of Dental Material, 10th Edition, Chicago. WB Saunders Co. 1996;454-6.
7. Diwan R, Talic Y, Omar N. et al. The Effect of Storage Time of Removable Partial Denture Wax Pattern on the Accuracy of Fit of the Cast Framework. J Prosthet Dent 1997;77(4): 375-81.
8．陈治清 主编．口腔材料学(第二版)．人民卫生出版社 2001；151—2，143—14．
9. Earnshaw R, Morey EF, Edelman DC, et al. The effect of potential investment expansion and hot strength on the fit of full crown castings mode with phosphate-bonded investment. J Oral Rehabil 1997;24(7): 532-9.
10. Fenlon MR, Juszczyk AS, Hughes RJ, et al. Accuracy of fit of cobalt-chromium removable partial denture frameworks on master casts. Eur J Prosthodont Rest Dent 1993; 1(3): 127-30.
11． Hansson O.Casting Accuracy of a nickel and beryllium-free Cobalt-Chromium alloy for crown and bridge prostheses and resin-bonded bridges.Swed Dent J 1985 ; 9(3) : 105-15．
12． Burnett CA, Maguire H. Sprue design in removable partial denture casting.J Dent 1996; 24(1-2) : 99-103．
13． Augthun M, Zyfuss M, Spiekermann H.The influence of spruing technique on the development of tension in a cast partial denture framework. Int J Prosthodont 1994; 7 (1) :72-6．
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22． Soo S, Palmer R, Curtis RV.Measurement of the setting and thermal expansion of investment used for the superplastic forming of dental implant superstructures.J Dent Mater 2001 May;17(3) :247-252．
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10. Fenlon MR, Juszczyk AS, Hughes RJ, et al. Accuracy of fit of cobalt-chromium removable partial denture frameworks on master casts. Eur J Prosthodont Rest Dent 1993; 1(3): 127-30.
11． Hansson O.Casting Accuracy of a nickel and beryllium-free Cobalt-Chromium alloy for crown and bridge prostheses and resin-bonded bridges.Swed Dent J 1985 ; 9(3) : 105-15．
12． Burnett CA, Maguire H. Sprue design in removable partial denture casting.J Dent 1996; 24(1-2) : 99-103．
13． Augthun M, Zyfuss M, Spiekermann H.The influence of spruing technique on the development of tension in a cast partial denture framework. Int J Prosthodont 1994; 7 (1) :72-6．
14． Verxett RG, Duke ES. The effect of sprue attachment design on castability and porosity.J Prosthet Dent 1989; 61(4) :418-24．
15． Peregrina AM, Rieger MR. Evaluating six sprue designs used in making high-palladium alloy castings.J Prosthet Dent 1986 ;56 (2) :192-6．
16． Mohammed H, Hassaballa MA, Talic YF. Button versus button-less castings for removable partial denture frameworks.J Prosthet Dent. 1994;72(4) :433-44．
17． Firtell DN, Muncheryan AM, Green AJ. Laboratory accuracy in casting removable partial denture frameworks.J Prosthet Dent 1985; 54:856-62．
18． Papadopoulos T and Axelsson M.Influence of Heating Rate in Thermal Expansion of Dental Phosphate-Bonded Investment material.Scand J Dent Res 1990; 98(1) :60-5．
19． Lacy AM.Three factors affecting investment setting expansion and casting size.J Prosthet Dent 1983 ;49(1) :528．
20． Jorgensen KD and Okamoto A.Restraining Factors Affecting Setting Expansion of Phosphate Investments.Scand J Dent Res 1986;94(2) :178-81．
21． Ito M, Kuroiwa A, Nagasawwa S, et al. Effect of wax melting
range and investment liquid concentration on the accuracy of a three-quarter-crown casting.J Prosthet Dent 2002 Jan; 87 (1) :57-61
22． Soo S, Palmer R, Curtis RV.Measurement of the setting and thermal expansion of investment used for the superplastic forming of dental implant superstructures.J Dent Mater 2001 May;17(3) :247-252．