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Accuracy of casts produced from alginate and hydrocolloid impression materials
The accuracy of casts produced from two alginate hydrocolloids (irreversible), one hydrocolloid (reversible), and a polyether rubber were compared. The polyether impression material produced the most accurate casts. The hydrocolloid (reversible) casts were the second most accurate, and the alginate hydrocolloid (irreversible) produced the least accurate casts.
Accuracy of casts produced from alginate and hydrocolloid impression materials H o s e a F. S a w y e r, DDS, MS Ja m e s L. S a n d rik , PhD , M a y w o o d , R o b e rt N e im a n , MS, L o u is v ille ■ ■
Previous studies1 have indicated that all elastomeric impression materials have peculiar accur acy characteristics statistically2 related to each class of material. Questions have often been asked about the accuracy of casts produced from alginate impressions and hydrocolloid impres sions, compared with the accuracy of those pro duced from the elastomeric group.3 It has been found that a deviation from the master die in ex cess of 39^m (0.0016 inch) was clinically signif icant.4 This investigation was designed to com pare the accuracy of casts produced from hydro colloid impressions and to compare casts from both alginate and hydrocolloid impression mater ials with casts produced from previously studied elastomeric impression materials.
ginate impression materials were mixed under vacuum at the water-powder ratio recommended by the manufacturers.*t The hydrocolloidt was conditioned in a Surgident conditioner. Both the alginates and the hydrocolloid were used with the syringe technique. Each alginate impression was permitted to set on the master die at 38 C for 15 minutes. The hydrocolloid was permitted to set on the master die with a water coolant at room temperature circulating through the tray. Five impressions were produced for each material.
M a te ria ls and m e th o d s
A stainless steel die was constructed to permit many comparative measurements of horizontal and vertical dimensions to 0.0001 inch. The die was designed to simulate two intra-extra coronal cavity preparations about 1 inch apart (Fig 1). This die was attached to a metal base that was keyed for accurate seating of a specially made rim-lock, water-cooled tray (Fig 2). The master die was preheated to 38 C in a dry oven. The al806 ■ JADA, Vol. 93, October 1976
Fig 1 ■ Steel master die that was constructed for accurate meas urements to 0.0001 inch and that was designed to simulate two intra-extra coronal cavity preparations about 1 inch apart.
Fig 3 ■ Points used to measure horizontal dimensions of each cast. Preproductions of two ivorine teeth, present on master die, were removed from each cast before measurements. Dimensions of steel master die are shown.
Fig 2 ■ Specially made rim-lock, water-cooled tray.
After separation from the master die, the impres sion materials were poured immediately with a vacuum-mixed die stone, Silky Rock§. After the stone had set for 30 minutes, each cast was sep arated and assigned an appropriate identifying number. Horizontal and vertical dimensions of each cast were measured with a micrometer mi croscope and dial gauge indicator at the positions indicated (Fig 3 and 4). All variables involved in the impression, cast production, and measurement procedures were carefully standardized. All materials used were of the same batch number. Impregumll, a poly ether rubber impression material, was used as the control.
VERTICAI MEASUREMENT POINTS
Fig 4 ■ Points used to measure vertical dimensions of each cast.
R esults
The Table shows that casts from the two alginate materials tested deviated from the master die by a significant amount, at points 10-13 and 14-21 (Fig 4). The casts produced from the hydrocol loid impression materials were found to deviate -0.0007 to -0.0011 inch from the master die, a less significant amount than the other alginate materials. The JK-LM measurements (diagonal diameters of balls 1 and 2) were high in value for both algin ates and very favorable for the casts produced with hydrocolloid compared with casts produced from the standard Impregum. The internal spaces between the two axial walls (A'D'-B'C') of all casts produced from the alginates and the hydrocolloid were within an acceptable range. The external spaces between the two axial
Table ■ Mean deviation of stone casts from a master die at the various measuring points (in 0.0001 inch) for two alginates, one hydrocolloid, and a polyether impression material. Kerr Kerr Coe Alginate Alginate Impregum Hydrocolloid 10-13 -71 -160 -7 3 14-21 -6 5 -156 -11 2 AA' 8 8 5 3 AA'B -4 14 6 0 4 AB-CD -4 -5 1 JK-LM -1 7 -5 9 3 -1 A'D'-B'C1 13 22 -3 -8 22 4 AD-BC 76 10 EF-GH 28 17 4 43 All casts were poured immediately after impressions were removed from the die. Vertical dimensions of each cast produced were measured with a dial indicator at points 10-21. AA' measured the buccal width of the pulpal wall of the MOD preparation. AA'B measured the distance between the mesioaxial wall of preparation 1 to the distoaxial wall of preparation 2. AB-CD measured the buccolingual dimension of the pulpal floor of preparations. JK-LM measured the diagonal diameters of preparations 1 and 2.
A'D'-B'C1 measured the internal space between the axial walls of both preparations. AD-BC measured the external space between the axial walls of both preparations. EF-GH measured the extreme outside corners of the cast.
Sawyer—Sandrik—Neiman: ALGINATE, HYDROCOLLOID MATERIALS ■ 807
walls (AD-BC) of casts produced from both al ginates were not acceptable compared with that for the casts produced from the hydrocolloid. The EF-GH measurements of casts produced from both alginates and the hydrocolloid were found to deviate significantly compared with the measurements of casts produced from the control, Impregum.
castings have been fabricated for a number of years. This study indicates that more dimensionally accurate casts are produced from hydrocol loid compared with casts produced from algin ate. The most accurate casts were produced from the polyether impression material.
We thank the Whip-Mix Corp. for materials and technical assis tance and the manufacturers mentioned for supplying the ma terials tested.
Discussion The results clearly indicate the dimensional su periority of casts produced from hydrocolloid impressions compared with casts produced from alginate impressions. Although both undergo shrinkage, the alginate materials tested were found to deviate from the master die by an amount considered to be clinically unacceptable. Also, the dimensional accuracy of casts pro duced from the hydrocolloid impression mater ial was generally less than that for the casts pro duced from the control polyether impression material.
Conclusion It is recognized that alginate impression mater ials have been used to obtain casts from which
808 ■ JADA, Vol. 93, October 1976
Dr. Sawyer's address is 8575 Spruce St, Orland Park, III 60462. Dr. Sandrik is an assistant professor in the department of dental materials, School of Dentistry, Loyola University of Chicago. Mr. Neiman is vice-president, research, the Whip-Mix Corp., Louisville. Address requests for reprints to Dr. Sawyer. *Coe Alginate, Coe Mfg. Co., Chicago, 60680. tKerr Alginate, Kerr Mfg. Co., Romulus, Mich 48174. tKerr Hydrocolloid, Kerr Mfg. Co., Romulus, Mich, 48174 §Whip-Mix Corp., Louisville, 40217. IPremier Dental Products Co., Norristown, Pa 19401. 1. Sawyer, H.F., and others. Accuracy of casts produced from seven rubber impression materials. JADA 87:126 July 1973. 2. Sawyer, H.F., and others. Accuracy of casts produced from three classes of elastomer impression materials. JADA 89:644 Sept 1974. 3. Phillips, R.W. Skinner’s science of dental materials, ed 7. Philadelphia, W. B. Saunders Co., p 136. 4. Christianson, G.J. Marginal fit of gold inlay castings. J Prosthet Dent 16:297 March-April 1966. 5. Council on Dental Materials and Devices. Guide to dental materials and devices, ed 7. Chicago, American Dental Associa tion, 1975, p 71.
Accuracy of casts produced from alginate and hydrocolloid impression materials H o s e a F. S a w y e r, DDS, MS Ja m e s L. S a n d rik , PhD , M a y w o o d , R o b e rt N e im a n , MS, L o u is v ille ■ ■
Previous studies1 have indicated that all elastomeric impression materials have peculiar accur acy characteristics statistically2 related to each class of material. Questions have often been asked about the accuracy of casts produced from alginate impressions and hydrocolloid impres sions, compared with the accuracy of those pro duced from the elastomeric group.3 It has been found that a deviation from the master die in ex cess of 39^m (0.0016 inch) was clinically signif icant.4 This investigation was designed to com pare the accuracy of casts produced from hydro colloid impressions and to compare casts from both alginate and hydrocolloid impression mater ials with casts produced from previously studied elastomeric impression materials.
ginate impression materials were mixed under vacuum at the water-powder ratio recommended by the manufacturers.*t The hydrocolloidt was conditioned in a Surgident conditioner. Both the alginates and the hydrocolloid were used with the syringe technique. Each alginate impression was permitted to set on the master die at 38 C for 15 minutes. The hydrocolloid was permitted to set on the master die with a water coolant at room temperature circulating through the tray. Five impressions were produced for each material.
M a te ria ls and m e th o d s
A stainless steel die was constructed to permit many comparative measurements of horizontal and vertical dimensions to 0.0001 inch. The die was designed to simulate two intra-extra coronal cavity preparations about 1 inch apart (Fig 1). This die was attached to a metal base that was keyed for accurate seating of a specially made rim-lock, water-cooled tray (Fig 2). The master die was preheated to 38 C in a dry oven. The al806 ■ JADA, Vol. 93, October 1976
Fig 1 ■ Steel master die that was constructed for accurate meas urements to 0.0001 inch and that was designed to simulate two intra-extra coronal cavity preparations about 1 inch apart.
Fig 3 ■ Points used to measure horizontal dimensions of each cast. Preproductions of two ivorine teeth, present on master die, were removed from each cast before measurements. Dimensions of steel master die are shown.
Fig 2 ■ Specially made rim-lock, water-cooled tray.
After separation from the master die, the impres sion materials were poured immediately with a vacuum-mixed die stone, Silky Rock§. After the stone had set for 30 minutes, each cast was sep arated and assigned an appropriate identifying number. Horizontal and vertical dimensions of each cast were measured with a micrometer mi croscope and dial gauge indicator at the positions indicated (Fig 3 and 4). All variables involved in the impression, cast production, and measurement procedures were carefully standardized. All materials used were of the same batch number. Impregumll, a poly ether rubber impression material, was used as the control.
VERTICAI MEASUREMENT POINTS
Fig 4 ■ Points used to measure vertical dimensions of each cast.
R esults
The Table shows that casts from the two alginate materials tested deviated from the master die by a significant amount, at points 10-13 and 14-21 (Fig 4). The casts produced from the hydrocol loid impression materials were found to deviate -0.0007 to -0.0011 inch from the master die, a less significant amount than the other alginate materials. The JK-LM measurements (diagonal diameters of balls 1 and 2) were high in value for both algin ates and very favorable for the casts produced with hydrocolloid compared with casts produced from the standard Impregum. The internal spaces between the two axial walls (A'D'-B'C') of all casts produced from the alginates and the hydrocolloid were within an acceptable range. The external spaces between the two axial
Table ■ Mean deviation of stone casts from a master die at the various measuring points (in 0.0001 inch) for two alginates, one hydrocolloid, and a polyether impression material. Kerr Kerr Coe Alginate Alginate Impregum Hydrocolloid 10-13 -71 -160 -7 3 14-21 -6 5 -156 -11 2 AA' 8 8 5 3 AA'B -4 14 6 0 4 AB-CD -4 -5 1 JK-LM -1 7 -5 9 3 -1 A'D'-B'C1 13 22 -3 -8 22 4 AD-BC 76 10 EF-GH 28 17 4 43 All casts were poured immediately after impressions were removed from the die. Vertical dimensions of each cast produced were measured with a dial indicator at points 10-21. AA' measured the buccal width of the pulpal wall of the MOD preparation. AA'B measured the distance between the mesioaxial wall of preparation 1 to the distoaxial wall of preparation 2. AB-CD measured the buccolingual dimension of the pulpal floor of preparations. JK-LM measured the diagonal diameters of preparations 1 and 2.
A'D'-B'C1 measured the internal space between the axial walls of both preparations. AD-BC measured the external space between the axial walls of both preparations. EF-GH measured the extreme outside corners of the cast.
Sawyer—Sandrik—Neiman: ALGINATE, HYDROCOLLOID MATERIALS ■ 807
walls (AD-BC) of casts produced from both al ginates were not acceptable compared with that for the casts produced from the hydrocolloid. The EF-GH measurements of casts produced from both alginates and the hydrocolloid were found to deviate significantly compared with the measurements of casts produced from the control, Impregum.
castings have been fabricated for a number of years. This study indicates that more dimensionally accurate casts are produced from hydrocol loid compared with casts produced from algin ate. The most accurate casts were produced from the polyether impression material.
We thank the Whip-Mix Corp. for materials and technical assis tance and the manufacturers mentioned for supplying the ma terials tested.
Discussion The results clearly indicate the dimensional su periority of casts produced from hydrocolloid impressions compared with casts produced from alginate impressions. Although both undergo shrinkage, the alginate materials tested were found to deviate from the master die by an amount considered to be clinically unacceptable. Also, the dimensional accuracy of casts pro duced from the hydrocolloid impression mater ial was generally less than that for the casts pro duced from the control polyether impression material.
Conclusion It is recognized that alginate impression mater ials have been used to obtain casts from which
808 ■ JADA, Vol. 93, October 1976
Dr. Sawyer's address is 8575 Spruce St, Orland Park, III 60462. Dr. Sandrik is an assistant professor in the department of dental materials, School of Dentistry, Loyola University of Chicago. Mr. Neiman is vice-president, research, the Whip-Mix Corp., Louisville. Address requests for reprints to Dr. Sawyer. *Coe Alginate, Coe Mfg. Co., Chicago, 60680. tKerr Alginate, Kerr Mfg. Co., Romulus, Mich 48174. tKerr Hydrocolloid, Kerr Mfg. Co., Romulus, Mich, 48174 §Whip-Mix Corp., Louisville, 40217. IPremier Dental Products Co., Norristown, Pa 19401. 1. Sawyer, H.F., and others. Accuracy of casts produced from seven rubber impression materials. JADA 87:126 July 1973. 2. Sawyer, H.F., and others. Accuracy of casts produced from three classes of elastomer impression materials. JADA 89:644 Sept 1974. 3. Phillips, R.W. Skinner’s science of dental materials, ed 7. Philadelphia, W. B. Saunders Co., p 136. 4. Christianson, G.J. Marginal fit of gold inlay castings. J Prosthet Dent 16:297 March-April 1966. 5. Council on Dental Materials and Devices. Guide to dental materials and devices, ed 7. Chicago, American Dental Associa tion, 1975, p 71.