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A clinical evaluation of temporary restorative materials
A CLINICAL TEMPORARY
EVALUATION RESTORATIVE
OF MATERIALS
ROBERT B. WOLCOTT,
B.S., D.D.S., M.S., WILLIAM R. SHILLER, D.D.S., AND LEONARD M. KRASKE, D.D.S. Dental Research Facility, U. S. Naval Training Center, Great Lakes, Ill.
P
may include the complete elimination of carious lesions, with subsequent restoration of the tooth with a filling material. The clinician who is faced with an extensive program of rehabilitation may seek to allay the carious onslaught by rapid caries elimination and then placement into the cavity of a material which is of a semipermanent nature. These restorations would eventually be replaced with a more permanent material as time and the treatment schedule permit. Therefore, it seemed desirable to determine which temporary materials would be serviceable in such a program for a period of 6 months to 1 year. REVENTIVE
DENTISTRY
We established the following properties as being significant in evaluation of temporary restorative materials. They must (1) resist oral destruction for at least 6 months, (2) be easily manipulated in preparation and placement, (3) not be injurious to the dental pulp, and (4) be recognizable as temporary restorative materials. The physical properties of the various cements which would serve as temporary restorative materials are well known to the profession. However, clinical studies were desired to ascertain the in vivo durability, manipulative characteristics, appearance, and patient receptivity. MATERIALS
Four materials were chosen for the study. Those selected were representatives of a broad range of materials having diverse physical properties, yet which might prove valuable as temporary restorative materials. Excluded from the group were such materials as gutta-percha, which has definite contraindications for long-term usage ; copper phosphate cement, which has known irritational effectsA upon the dental pulp; and copper amalgam,3v4 which is difficult to manipulate in adjacent . Class II or compound restorations because of its slow setting qualities. Zinc Oxide-Fatty Acid Cement.-This material* has been developed as a substitute for the zinc oxide-eugenol cements. The manufacturer states that its formaThe opinions or assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Department of the Navy or the Naval Service at large, Toe-fil. 782
Volume 12 Number 4
CLINICAL
EVSALUATION
Fig. l.-The modified tion to 0.1 mm. accuracy. erence points of the tooth
OF TEMPORARY
RESTORATIVE
MATERIALS
78.5
Boley gauge capable of measuring the occlusal height of the restoraA plastic plane (x) is secured to wires y and z and rests on the refcusps.
tion involves a saponification process which results in an insoluble, nontoxic product. A small amount of polymerized resin is added as a bonding and reactive agent. It possesses many of the physical properties of the typical zinc oxide-eugenol materials and has the advantage of not affecting acrylic resin materials. Zinc Phos@ate Cement.-The zinc phosphate cements* are used principally as luting agents for prefabricatd (cast gold or baked porcelain) restorations and as bases for temporary restorations. * They set rapidly and attain nearIy ultimate strength within 24 hours, These cements demonstrate low solubility in distilled water, but much greater dissolution is encountered in certain dilute organic acids.” The zinc phosphate cement used in this investigation was obtained from the Federal Supply Catalog List and was manipulated in accordance with the manufacturer’s directions. Zinc Phosphate Cement With Alloy.---Many dentists have employed zinc phosphate cement which has been mixed with a generous quantity of silver alloy particles. The purpose of adding alloy to the cement is to increase its resistance to abrasion, decreaseits solubility, and thereby achieve greater durability. According to Mahler,6 the desired ratio of alloy to zinc phosphate powder is 3 2. Tests have indicated an increase in transverse strength, reduced solubility and disintegration, but no change in compressive strength. Mahler also stated that coarse filings give the material properties which are superior to cements having the fine-grained *Fleck%.
WOLCOTT,
784
SHILLER,
AND
J. Pros. Den. July-August, 1962
KRASKE
alloys, but this study utilized only materials available to the armed services, which included only fine-grained alloy.* The cement was mixed on a chilled slab combining small quantities of the powder-alloy mixture with the liquid. Thorough spatulation is necessary before adding further powder increments. This was continued until the mass assumed a doughlike consistency which could be handled easily by the dentist during the insertion into the cavity. If the mix is too thick, it will set too rapidly. This prevents good marginal adaptation and limits the number of teeth which can be filled with a single mix of the cement. If the mix is too thin, it is difficult to handle and produces a cement which has poor physical qualities. Silicophosphute Cements.-These cements are hybrid combinations of zinc phosphate cement with silicate cement. 6 They are prepared in a manner similar to the silicate cements. Silicophosphate cements are occasionally used as luting Since they contain small amounts of materials and as temporary restorations. fluoride, they may be expected to afford a degree of protection against the recurrence of caries. The cement used for this study was a commercial product? and was manipulated in accordance with instructions of the manufacturer. The cement was mixed in a manner similar to that of the silicate cements, using a cool slab and
Fig. 2 .-Loss
of filling
material
caused
by in vivo
disintegration.
combining at least three-fourths of the total amount of the powder into the liquid at once with thorough spatulation. The mixing should be complete within 1 minute, CLINICAL
PROCEDURES
Twenty-three young men who had- completed their recruit basic training were chosen to be the test group. Only those men who volunteered and showed *The desired ratio of 3 parts weight of cement powder and then tGermicida1 Kryptex.
by weight of alloy was thoroughly stored in stoppered bottles.
mixed
with
2 parts
by
Volume 12 Number 4
CLINICAL
EVALUATION
OF TEMPORARY
RESTORATIVE
MATERIALS
785
Zinc Oxide FoHy Add
stone
Fig. 3.-Clinical models.
evaluation
of the cements
by three
investigators
using
blind
evaluation
of
lvillingness to cooperate were used. Each had at least twelve carious posterior teeth, and roentgenographic and clinical examinations revealed that no extractions were imminent or anticipated. Under local anesthesia, each quadrant was treated by complete elimination of all caries with modern operating techniques and the use of a generous quantity of air-water spray. The preparations conformed closely to those recommended for amalgam. Although a majority of the preparations were of the Class II variety, all classes of cavities were represented. A rubber dam was applied in most cases. The cavities were cleaned, dried, and then lined with a copal resin varnish. In those teeth in which an exposure of pulp was encountered or suspected, a calcium hydroxide base was placed, and the remainder of the dentin area was covered with the liner. Manipulation of the cements was further standardized by having all of the materials weighed and mixed by the technician assigned to assist in the study. Operator variables were minimized by having the cavities prepared and the materials inserted by two dentists. The temporary materials were placed in posterior quadrants with an effort to vary the location from one patient to another so that each material would undergo similar clinical experience. Each tooth was filled separately, and where three or more teeth in sequence required restoration in a quadrant, alternate placement was necessary. The proximal surfaces of the “set” restoration were coated with cocoa butter or separated from the unfilled teeth with a strip of metal or cellophane matrix band material. Overhanging cement was easily avoided in the initially placed restorations of a quadrant, but it was more difficult to control proximal excess in subsequently placed restorations. Some crude carving and shaping of the cement was done before it was set. The occlusion was quickly corrected with a large round bur while the field was cleared with a generous water spray. The
WOLCOTT,
786
SHILLER,
AND
KRASKE
J. Pros. July-August,
Den. 1962
patient was instructed to return if any difficulty was encountered. Cavities in the anterior teeth were restored with silicate cements. During the course of the study, those restorations which failed were replaced with amalgam. After a 6 month period, the study was terminated, and most of the temporary restorations were then replaced with permanent restorations. A total of 299 restorations were placed in the 23 patients; but 6 patients, in whom a total of sixty-two restorations had been placed, were dropped during the course of the study for reasons beyond the control of the investigators. Of the remaining 237 restorations, only the Class I and Class II types were evaluated in this study. There were forty-one zinc oxide restorations, forty-seven zinc phosphate cement restorations, fifty silicophosphate restorations, and fifty-one zinc phosphatealloy restorations, making a total of 189. METHODS
OF EVALUATION
After all restorations were inserted, complete arch impressions were made with an alginate impression material. The impressions were poured in stone immediately. At the end of the 6 month test period, impressions and casts were again made using the same techniques that were used initially. All evaluations were made on the stone casts. One was a measurement of the disintegration of the material as evidenced by a reduction in the occlusal height of the restoration. This occlusal height was measured in the initial and final casts with a modified Boley gauge (Fig. 1). A plastic plane was secured to the two immovable wires. This permitted the plane to rest upon the tooth cusps which served as reference points as the adjustable wire moved to contact the occlusal surface of the restoration. This instrument proved to be accurate to 0.1 mm. Another evaluation consisted of a blind clinical appraisal by each of the three investigators. An arbitrary grading index was used to assign a numerical value to each restoration in the casts (Table I). Increased weight was given in this index to restorations which had fractured or had lost a large amount of material. This was done because of the practical nature of the study. It was felt that any restoration with a score of 2 or less was still serviceable as a temporary restoration, whereas one with a score of 4 or above was not affording sufficient protection and should be replaced. The means of the numerical values were compared to obtain an indication of the relative practical durability of each restorative material.
TABLE
VALUE
0 : 1
I.
EVALUATION
INDEX
DETERMINATION
The restoration in the final cast appeared normal: no changes were evident. The restoration possessed an exposed margin or crevice 0.5 to 1 mm. in extent. The restoration possessed a 1 to 2 mm. exposed margin or crevice. The restoration had a fracture line or an exposed margin over 2 mm. deep. There was a gross loss of restorative material.
y&g; $2
CLINICAL
EV,ALUATION
OF
TABLE
-.---I_
TEMPORARY
II.
SUMMARY
RESTORATIVE
MATERIALS
787
OF DATA
---
MATERIAL
CRUSHING STRENGTH (P.S.I.)
SOLUBILITY (%)*
MEASURED LOSS OF FILLING MATERIAL (DISINTEGRATION)
FAILURE ZATES DURING 6 MONTH PERIOD (OS,)
CLINICAL EVALUATION OF DETEKIORATION
I Zinc Zinc
oxide phosphate
984 9,930
1.060 0.045
0.204 p < Silicophosphate 22,816 0.560 0.072 p < Zinc phosphate-alloy 0.020 0.137 14,780 p < --.___-__ _----*Tested in accordance with A.D.A. specifications for zinc tInsufficient quantity of restorations remained to measure tp
PHYSICAL
mm. 0.05 mm. 0.01 mm. 0.05
95$ 47
/
14 8
phosphate cement. at end of test period. and zinc phosphate-alloy,
--5.96% 3 63 1.82
I
1.58
for
which
TESTING
In order to compare the physical properties of the various cements with the clinical evaluation, laboratory tests were performed. These included crushing strength and solubility. All specimens were prepared in an identical manner to that employed in the in vivo tests. RESULTS
Measurements of the occlusal heights of restorations in the initial and final casts revealed that the silicophosphate had undergone the least disintegration (Fig. 2). An insufficient number of zinc oxide restorations remained at the end of the test period to evaluate the results. Of the materials measured, zinc phosphate restorations disintegrated the most after 6 months, while the zinc phosphate-alloy material was intermediate. Independent evaluations of the stone casts were made by the three investigators (Fig. 3). The findings of investigators A and B, which were calibrated together prior to the evaluation, were in much closer agreement with each other than with those of investigator C. However, in all cases the materials were given similar relative ranks in the evaluations. Thus, zinc phosphate-alloy cement showed the least changes and zinc phosphate cement and zinc oxide showed the most. Silicophosphate cement was ranked rather closely to zinc phosphate-alloy cement. The percentage of failures of each type of material and that for all types of preparations were plotted against time (Fig. 4). Thus, at the twenty-sixth week, 95 per cent of the zinc oxide restorations, 47 per cent of the zinc phosphate restorations, 14 per cent of the silicophosphate restorations, and 8 per cent of the zinc phosphate-alloy restorations had failed. The type and location of the cavity preparation apparently made little difference in the failure rates of the various materials. Fig. 5 illustrates these rates when only Class II restorations were considered. The data coincide closely with those in Fig. 2.
788
Fig. 4 .-Failure included: (A) zinc (C) silicophosphate
WOLCOTT,
SHILLER,
AND
KRASKE
J. Pros. Den. July-August, 1962
rates of each cement during a 6 month period. All types of cavities are oxide-fatty acid (N=41, 39 failed); (B) zinc phosphate (N=47, 22 failed); (N=50, 7 failed); (D) zinc phosphate-alloy (N=51, 4 failed).
The crushing strength of the materials showed good relationship with the measured loss of occlusal filling material (Table 11). Silicophosphate showed the greatest crushing strength and the least measured loss of filling material. For the other cements, the loss of filling material increased as the crushing strength decreased. The failure rates and the deterioration index averages of the two weakest materials (zinc oxide and zinc phosphate cement) showed this same relationship. This relationship did not hold, however, for silicophosphate and zinc phosphate-alloy cement. Thus, silicophosphate had greater crushing strength than the zinc phos-. phate-alloy cement, but it also had a greater failure rate and a higher deterioration index average. The failure rate differences between these two materials are not statistically significant, and the deterioration index differences probably are insignificant. When comparing the solubility of these materials, it was found that, in general, as the solubility increased, so did the failure rate, deterioration, and disintegration. The one exception to this was the silicophosphate cement, which had greater solubility than zinc phosphate cement but had a lower failure rate, deterioration index, and disintegration measurements. It is unfortunate that these same solubiIity tests were not performed using a weak organic acid solution as the solvent. This would have approximated the oral environment more closely and would be expected to show that zinc phosphate cement has much greater solubility in these fluids than does silicophosphate cement.6s8 There was some evidence of gingival irritation in the interproximal areas which was attributed largely to the overhanging of the restorations placed in adjoining Class II cavities. Overhanging material at the gingival margins was dificult to control in such situations. It was interesting to note, however, that no patient complained of this irritation, and in no instance was the inflammation of such magnitude as to require remedial care.
Volun1e 12 Sumber 4
CLINICAL
EVSALUATION
OF TEMPORARY
Fig. 5.-Failure rates of each cement in (N=29, 29 failed); (B) zinc phosphate (N=34, (D) zinc phosphate-alloy (N=39, 3 failed).
the Class 21 failed);
RESTORATIVE
MATERIALS
II cavities: (A) zinc oxide-fatty acid (C) silicophosphate (N=32, 7 failed);
DISCUSSION
The material which conforms best to the standards established for evaluating a temporary restorative material would possess qualities of easy handling, be readily identified, possess good durability, and be harmonious with the vital tooth structures. Based on a 6 month evaluation, it appears that the silicophosphate cement and the zinc phosphate-alloy cement possess the most ideal characteristics. These include good resistance to dissolution and disintegration, a remarkably low number of mass or marginal fractures, and little evidence of gingival irritation. It is obvious that the silicophosphate was more readily identified as a cement. On the other hand, the zinc phosphate-alloy material has the color characteristics of amalgam and could be confused with a poorly placed amalgam restoration. In no instance was there evidence that any material caused postoperative pain. This may have been the result of the routine use of a cavity liner, which prevented acid penetration of the tubules during the placement of the restorations. Furthermore, there was no evidence that it served as a thermal conductor despite the presence of alloy in the cement. The sound appearance of the restorations suggested that the zinc phosphate-alloy and silicophosphate cements were capable of remaining in good functional condition for 1 year and perhaps longer. The discrepancies that occurred were of a minor nature, such as marginal crevices which did not appear to increase in size at a rate which would render the restoration useless or dangerous. One must recognize that the cements possess physical properties which are not comparable to those of silver amalgam. Therefore, the dentist must not leave the restoration in hyperocclusion. It is interesting to note that many restorations of zinc phosphate-alloy and the silicophosphate cement were of a large, multisurface type which replaced tooth cusps. Despite their size, they were capable of withstanding occlusal forces for a period of 6 months.
790
WOLCOTT,
SHILLER,
AND
KRASKE
J. Pros.
July-August,
Den.
1962
The handling qualities of these two cements were considered comparable to those of the related materials, namely, the silicate cements and the zinc phosphate cements. In both instances, practice in mixing was necessary to control setting time to obtain the optimal physical properties and to adjust to the handling characteristics. The zinc oxide-fatty acid type of material responded poorly to the test. As the physical properties predicted, it was incapable of withstanding the occlusal forces and showed evidence that it was quite soluble or it disintegrated in the oral fluids. However, this material was easily handled and could be readily removed from the cavities, indicating that it would have clinical value in certain crown and bridge restorative procedures for short periods of time. The zinc phosphate cement gave moderately successful results. There was evidence that it was not capable of withstanding long-term clinical exposures to masticatory forces, and it showed evidence that it disintegrated somewhat in the oral fluids or under the abrasive forces of occlusion. SUMMARY
1. Temporary restorative materials can be used to restore teeth rapidly as a measure in preventive dentistry. Certain materials are capable of effectively restoring teeth for a period of at least 6 months. 2. Of the materials tested, the silicophosphate cement and the combination zinc phosphate-alloy cement revealed the least clinical changes during 6 months. 3. The silicophosphate cement has the advantages of color harmony, of possessing a small amount of fluoride, and of having good physical qualities. 4. The combination zinc phosphate-alloy cement has good physical qualities and is comparable to silicophosphate cement. Its principal disadvantage lies in its appearance. 5. A copal liner beneath cement restorations affords good protection to pulp. Appreciation is expressed to Prof. R. W. Phillips, Miss Marjorie Perkins for their assistance in the conduct of this investigation.
Swartz,
and Thomas
REFERENCES
Massler, M.: Effects of Filling Materials on the Pulp, J. Tennessee D.A. 35:353-374, 1955. M. : Pulp Protection and Preservation. Practical Dental Monographs, Chicago, 1958, Year Book Publishers, Inc. Anonymous : Dental Materials : Copper Amalgam, Austral. J. Den, 58:321-322, 1954. :: Skinner, E. W., and Phillips, R. W.: The Science of Dental Materials, ed. 5, Philadelphia, 1960, W. B. Saunders Company. 5. Norman, R. D., Swartz, M. L., and Phillips, R. W.: Studies on the Solubility of Certain Dental Materials, J. D. Res. 36:977-985, 1957. 6. Mahler, D. B., and Armen, G. K. : Addition of Amalgam Alloy to Zinc Phosphate Cement, J. PROS. DEN. 12:157-164, 1962. Silicophosphate Cement as a Permanent Filling Material, D. Pratt. 2:3707. Ross, J3E:1F5e
d: Massler,
8. Paffenbarger, G: C., and Caul, H. J.: Dental Cements, Proc. D. Centenary, pp. 232-238, 1940. Studies on the Solubility 9. Norman, R. D., Swartz, M. L., and Phillips, R. W.: Additional of Certain Dental Materials, J. D. Res. 38:1028-1037, 1959. DENTAL RESEARCH FACILITY U. S. NAVAL TRAINING CENTER GREAT LAKES, ILL.
EVALUATION RESTORATIVE
OF MATERIALS
ROBERT B. WOLCOTT,
B.S., D.D.S., M.S., WILLIAM R. SHILLER, D.D.S., AND LEONARD M. KRASKE, D.D.S. Dental Research Facility, U. S. Naval Training Center, Great Lakes, Ill.
P
may include the complete elimination of carious lesions, with subsequent restoration of the tooth with a filling material. The clinician who is faced with an extensive program of rehabilitation may seek to allay the carious onslaught by rapid caries elimination and then placement into the cavity of a material which is of a semipermanent nature. These restorations would eventually be replaced with a more permanent material as time and the treatment schedule permit. Therefore, it seemed desirable to determine which temporary materials would be serviceable in such a program for a period of 6 months to 1 year. REVENTIVE
DENTISTRY
We established the following properties as being significant in evaluation of temporary restorative materials. They must (1) resist oral destruction for at least 6 months, (2) be easily manipulated in preparation and placement, (3) not be injurious to the dental pulp, and (4) be recognizable as temporary restorative materials. The physical properties of the various cements which would serve as temporary restorative materials are well known to the profession. However, clinical studies were desired to ascertain the in vivo durability, manipulative characteristics, appearance, and patient receptivity. MATERIALS
Four materials were chosen for the study. Those selected were representatives of a broad range of materials having diverse physical properties, yet which might prove valuable as temporary restorative materials. Excluded from the group were such materials as gutta-percha, which has definite contraindications for long-term usage ; copper phosphate cement, which has known irritational effectsA upon the dental pulp; and copper amalgam,3v4 which is difficult to manipulate in adjacent . Class II or compound restorations because of its slow setting qualities. Zinc Oxide-Fatty Acid Cement.-This material* has been developed as a substitute for the zinc oxide-eugenol cements. The manufacturer states that its formaThe opinions or assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Department of the Navy or the Naval Service at large, Toe-fil. 782
Volume 12 Number 4
CLINICAL
EVSALUATION
Fig. l.-The modified tion to 0.1 mm. accuracy. erence points of the tooth
OF TEMPORARY
RESTORATIVE
MATERIALS
78.5
Boley gauge capable of measuring the occlusal height of the restoraA plastic plane (x) is secured to wires y and z and rests on the refcusps.
tion involves a saponification process which results in an insoluble, nontoxic product. A small amount of polymerized resin is added as a bonding and reactive agent. It possesses many of the physical properties of the typical zinc oxide-eugenol materials and has the advantage of not affecting acrylic resin materials. Zinc Phos@ate Cement.-The zinc phosphate cements* are used principally as luting agents for prefabricatd (cast gold or baked porcelain) restorations and as bases for temporary restorations. * They set rapidly and attain nearIy ultimate strength within 24 hours, These cements demonstrate low solubility in distilled water, but much greater dissolution is encountered in certain dilute organic acids.” The zinc phosphate cement used in this investigation was obtained from the Federal Supply Catalog List and was manipulated in accordance with the manufacturer’s directions. Zinc Phosphate Cement With Alloy.---Many dentists have employed zinc phosphate cement which has been mixed with a generous quantity of silver alloy particles. The purpose of adding alloy to the cement is to increase its resistance to abrasion, decreaseits solubility, and thereby achieve greater durability. According to Mahler,6 the desired ratio of alloy to zinc phosphate powder is 3 2. Tests have indicated an increase in transverse strength, reduced solubility and disintegration, but no change in compressive strength. Mahler also stated that coarse filings give the material properties which are superior to cements having the fine-grained *Fleck%.
WOLCOTT,
784
SHILLER,
AND
J. Pros. Den. July-August, 1962
KRASKE
alloys, but this study utilized only materials available to the armed services, which included only fine-grained alloy.* The cement was mixed on a chilled slab combining small quantities of the powder-alloy mixture with the liquid. Thorough spatulation is necessary before adding further powder increments. This was continued until the mass assumed a doughlike consistency which could be handled easily by the dentist during the insertion into the cavity. If the mix is too thick, it will set too rapidly. This prevents good marginal adaptation and limits the number of teeth which can be filled with a single mix of the cement. If the mix is too thin, it is difficult to handle and produces a cement which has poor physical qualities. Silicophosphute Cements.-These cements are hybrid combinations of zinc phosphate cement with silicate cement. 6 They are prepared in a manner similar to the silicate cements. Silicophosphate cements are occasionally used as luting Since they contain small amounts of materials and as temporary restorations. fluoride, they may be expected to afford a degree of protection against the recurrence of caries. The cement used for this study was a commercial product? and was manipulated in accordance with instructions of the manufacturer. The cement was mixed in a manner similar to that of the silicate cements, using a cool slab and
Fig. 2 .-Loss
of filling
material
caused
by in vivo
disintegration.
combining at least three-fourths of the total amount of the powder into the liquid at once with thorough spatulation. The mixing should be complete within 1 minute, CLINICAL
PROCEDURES
Twenty-three young men who had- completed their recruit basic training were chosen to be the test group. Only those men who volunteered and showed *The desired ratio of 3 parts weight of cement powder and then tGermicida1 Kryptex.
by weight of alloy was thoroughly stored in stoppered bottles.
mixed
with
2 parts
by
Volume 12 Number 4
CLINICAL
EVALUATION
OF TEMPORARY
RESTORATIVE
MATERIALS
785
Zinc Oxide FoHy Add
stone
Fig. 3.-Clinical models.
evaluation
of the cements
by three
investigators
using
blind
evaluation
of
lvillingness to cooperate were used. Each had at least twelve carious posterior teeth, and roentgenographic and clinical examinations revealed that no extractions were imminent or anticipated. Under local anesthesia, each quadrant was treated by complete elimination of all caries with modern operating techniques and the use of a generous quantity of air-water spray. The preparations conformed closely to those recommended for amalgam. Although a majority of the preparations were of the Class II variety, all classes of cavities were represented. A rubber dam was applied in most cases. The cavities were cleaned, dried, and then lined with a copal resin varnish. In those teeth in which an exposure of pulp was encountered or suspected, a calcium hydroxide base was placed, and the remainder of the dentin area was covered with the liner. Manipulation of the cements was further standardized by having all of the materials weighed and mixed by the technician assigned to assist in the study. Operator variables were minimized by having the cavities prepared and the materials inserted by two dentists. The temporary materials were placed in posterior quadrants with an effort to vary the location from one patient to another so that each material would undergo similar clinical experience. Each tooth was filled separately, and where three or more teeth in sequence required restoration in a quadrant, alternate placement was necessary. The proximal surfaces of the “set” restoration were coated with cocoa butter or separated from the unfilled teeth with a strip of metal or cellophane matrix band material. Overhanging cement was easily avoided in the initially placed restorations of a quadrant, but it was more difficult to control proximal excess in subsequently placed restorations. Some crude carving and shaping of the cement was done before it was set. The occlusion was quickly corrected with a large round bur while the field was cleared with a generous water spray. The
WOLCOTT,
786
SHILLER,
AND
KRASKE
J. Pros. July-August,
Den. 1962
patient was instructed to return if any difficulty was encountered. Cavities in the anterior teeth were restored with silicate cements. During the course of the study, those restorations which failed were replaced with amalgam. After a 6 month period, the study was terminated, and most of the temporary restorations were then replaced with permanent restorations. A total of 299 restorations were placed in the 23 patients; but 6 patients, in whom a total of sixty-two restorations had been placed, were dropped during the course of the study for reasons beyond the control of the investigators. Of the remaining 237 restorations, only the Class I and Class II types were evaluated in this study. There were forty-one zinc oxide restorations, forty-seven zinc phosphate cement restorations, fifty silicophosphate restorations, and fifty-one zinc phosphatealloy restorations, making a total of 189. METHODS
OF EVALUATION
After all restorations were inserted, complete arch impressions were made with an alginate impression material. The impressions were poured in stone immediately. At the end of the 6 month test period, impressions and casts were again made using the same techniques that were used initially. All evaluations were made on the stone casts. One was a measurement of the disintegration of the material as evidenced by a reduction in the occlusal height of the restoration. This occlusal height was measured in the initial and final casts with a modified Boley gauge (Fig. 1). A plastic plane was secured to the two immovable wires. This permitted the plane to rest upon the tooth cusps which served as reference points as the adjustable wire moved to contact the occlusal surface of the restoration. This instrument proved to be accurate to 0.1 mm. Another evaluation consisted of a blind clinical appraisal by each of the three investigators. An arbitrary grading index was used to assign a numerical value to each restoration in the casts (Table I). Increased weight was given in this index to restorations which had fractured or had lost a large amount of material. This was done because of the practical nature of the study. It was felt that any restoration with a score of 2 or less was still serviceable as a temporary restoration, whereas one with a score of 4 or above was not affording sufficient protection and should be replaced. The means of the numerical values were compared to obtain an indication of the relative practical durability of each restorative material.
TABLE
VALUE
0 : 1
I.
EVALUATION
INDEX
DETERMINATION
The restoration in the final cast appeared normal: no changes were evident. The restoration possessed an exposed margin or crevice 0.5 to 1 mm. in extent. The restoration possessed a 1 to 2 mm. exposed margin or crevice. The restoration had a fracture line or an exposed margin over 2 mm. deep. There was a gross loss of restorative material.
y&g; $2
CLINICAL
EV,ALUATION
OF
TABLE
-.---I_
TEMPORARY
II.
SUMMARY
RESTORATIVE
MATERIALS
787
OF DATA
---
MATERIAL
CRUSHING STRENGTH (P.S.I.)
SOLUBILITY (%)*
MEASURED LOSS OF FILLING MATERIAL (DISINTEGRATION)
FAILURE ZATES DURING 6 MONTH PERIOD (OS,)
CLINICAL EVALUATION OF DETEKIORATION
I Zinc Zinc
oxide phosphate
984 9,930
1.060 0.045
0.204 p < Silicophosphate 22,816 0.560 0.072 p < Zinc phosphate-alloy 0.020 0.137 14,780 p < --.___-__ _----*Tested in accordance with A.D.A. specifications for zinc tInsufficient quantity of restorations remained to measure tp
PHYSICAL
mm. 0.05 mm. 0.01 mm. 0.05
95$ 47
/
14 8
phosphate cement. at end of test period. and zinc phosphate-alloy,
--5.96% 3 63 1.82
I
1.58
for
which
TESTING
In order to compare the physical properties of the various cements with the clinical evaluation, laboratory tests were performed. These included crushing strength and solubility. All specimens were prepared in an identical manner to that employed in the in vivo tests. RESULTS
Measurements of the occlusal heights of restorations in the initial and final casts revealed that the silicophosphate had undergone the least disintegration (Fig. 2). An insufficient number of zinc oxide restorations remained at the end of the test period to evaluate the results. Of the materials measured, zinc phosphate restorations disintegrated the most after 6 months, while the zinc phosphate-alloy material was intermediate. Independent evaluations of the stone casts were made by the three investigators (Fig. 3). The findings of investigators A and B, which were calibrated together prior to the evaluation, were in much closer agreement with each other than with those of investigator C. However, in all cases the materials were given similar relative ranks in the evaluations. Thus, zinc phosphate-alloy cement showed the least changes and zinc phosphate cement and zinc oxide showed the most. Silicophosphate cement was ranked rather closely to zinc phosphate-alloy cement. The percentage of failures of each type of material and that for all types of preparations were plotted against time (Fig. 4). Thus, at the twenty-sixth week, 95 per cent of the zinc oxide restorations, 47 per cent of the zinc phosphate restorations, 14 per cent of the silicophosphate restorations, and 8 per cent of the zinc phosphate-alloy restorations had failed. The type and location of the cavity preparation apparently made little difference in the failure rates of the various materials. Fig. 5 illustrates these rates when only Class II restorations were considered. The data coincide closely with those in Fig. 2.
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Fig. 4 .-Failure included: (A) zinc (C) silicophosphate
WOLCOTT,
SHILLER,
AND
KRASKE
J. Pros. Den. July-August, 1962
rates of each cement during a 6 month period. All types of cavities are oxide-fatty acid (N=41, 39 failed); (B) zinc phosphate (N=47, 22 failed); (N=50, 7 failed); (D) zinc phosphate-alloy (N=51, 4 failed).
The crushing strength of the materials showed good relationship with the measured loss of occlusal filling material (Table 11). Silicophosphate showed the greatest crushing strength and the least measured loss of filling material. For the other cements, the loss of filling material increased as the crushing strength decreased. The failure rates and the deterioration index averages of the two weakest materials (zinc oxide and zinc phosphate cement) showed this same relationship. This relationship did not hold, however, for silicophosphate and zinc phosphate-alloy cement. Thus, silicophosphate had greater crushing strength than the zinc phos-. phate-alloy cement, but it also had a greater failure rate and a higher deterioration index average. The failure rate differences between these two materials are not statistically significant, and the deterioration index differences probably are insignificant. When comparing the solubility of these materials, it was found that, in general, as the solubility increased, so did the failure rate, deterioration, and disintegration. The one exception to this was the silicophosphate cement, which had greater solubility than zinc phosphate cement but had a lower failure rate, deterioration index, and disintegration measurements. It is unfortunate that these same solubiIity tests were not performed using a weak organic acid solution as the solvent. This would have approximated the oral environment more closely and would be expected to show that zinc phosphate cement has much greater solubility in these fluids than does silicophosphate cement.6s8 There was some evidence of gingival irritation in the interproximal areas which was attributed largely to the overhanging of the restorations placed in adjoining Class II cavities. Overhanging material at the gingival margins was dificult to control in such situations. It was interesting to note, however, that no patient complained of this irritation, and in no instance was the inflammation of such magnitude as to require remedial care.
Volun1e 12 Sumber 4
CLINICAL
EVSALUATION
OF TEMPORARY
Fig. 5.-Failure rates of each cement in (N=29, 29 failed); (B) zinc phosphate (N=34, (D) zinc phosphate-alloy (N=39, 3 failed).
the Class 21 failed);
RESTORATIVE
MATERIALS
II cavities: (A) zinc oxide-fatty acid (C) silicophosphate (N=32, 7 failed);
DISCUSSION
The material which conforms best to the standards established for evaluating a temporary restorative material would possess qualities of easy handling, be readily identified, possess good durability, and be harmonious with the vital tooth structures. Based on a 6 month evaluation, it appears that the silicophosphate cement and the zinc phosphate-alloy cement possess the most ideal characteristics. These include good resistance to dissolution and disintegration, a remarkably low number of mass or marginal fractures, and little evidence of gingival irritation. It is obvious that the silicophosphate was more readily identified as a cement. On the other hand, the zinc phosphate-alloy material has the color characteristics of amalgam and could be confused with a poorly placed amalgam restoration. In no instance was there evidence that any material caused postoperative pain. This may have been the result of the routine use of a cavity liner, which prevented acid penetration of the tubules during the placement of the restorations. Furthermore, there was no evidence that it served as a thermal conductor despite the presence of alloy in the cement. The sound appearance of the restorations suggested that the zinc phosphate-alloy and silicophosphate cements were capable of remaining in good functional condition for 1 year and perhaps longer. The discrepancies that occurred were of a minor nature, such as marginal crevices which did not appear to increase in size at a rate which would render the restoration useless or dangerous. One must recognize that the cements possess physical properties which are not comparable to those of silver amalgam. Therefore, the dentist must not leave the restoration in hyperocclusion. It is interesting to note that many restorations of zinc phosphate-alloy and the silicophosphate cement were of a large, multisurface type which replaced tooth cusps. Despite their size, they were capable of withstanding occlusal forces for a period of 6 months.
790
WOLCOTT,
SHILLER,
AND
KRASKE
J. Pros.
July-August,
Den.
1962
The handling qualities of these two cements were considered comparable to those of the related materials, namely, the silicate cements and the zinc phosphate cements. In both instances, practice in mixing was necessary to control setting time to obtain the optimal physical properties and to adjust to the handling characteristics. The zinc oxide-fatty acid type of material responded poorly to the test. As the physical properties predicted, it was incapable of withstanding the occlusal forces and showed evidence that it was quite soluble or it disintegrated in the oral fluids. However, this material was easily handled and could be readily removed from the cavities, indicating that it would have clinical value in certain crown and bridge restorative procedures for short periods of time. The zinc phosphate cement gave moderately successful results. There was evidence that it was not capable of withstanding long-term clinical exposures to masticatory forces, and it showed evidence that it disintegrated somewhat in the oral fluids or under the abrasive forces of occlusion. SUMMARY
1. Temporary restorative materials can be used to restore teeth rapidly as a measure in preventive dentistry. Certain materials are capable of effectively restoring teeth for a period of at least 6 months. 2. Of the materials tested, the silicophosphate cement and the combination zinc phosphate-alloy cement revealed the least clinical changes during 6 months. 3. The silicophosphate cement has the advantages of color harmony, of possessing a small amount of fluoride, and of having good physical qualities. 4. The combination zinc phosphate-alloy cement has good physical qualities and is comparable to silicophosphate cement. Its principal disadvantage lies in its appearance. 5. A copal liner beneath cement restorations affords good protection to pulp. Appreciation is expressed to Prof. R. W. Phillips, Miss Marjorie Perkins for their assistance in the conduct of this investigation.
Swartz,
and Thomas
REFERENCES
Massler, M.: Effects of Filling Materials on the Pulp, J. Tennessee D.A. 35:353-374, 1955. M. : Pulp Protection and Preservation. Practical Dental Monographs, Chicago, 1958, Year Book Publishers, Inc. Anonymous : Dental Materials : Copper Amalgam, Austral. J. Den, 58:321-322, 1954. :: Skinner, E. W., and Phillips, R. W.: The Science of Dental Materials, ed. 5, Philadelphia, 1960, W. B. Saunders Company. 5. Norman, R. D., Swartz, M. L., and Phillips, R. W.: Studies on the Solubility of Certain Dental Materials, J. D. Res. 36:977-985, 1957. 6. Mahler, D. B., and Armen, G. K. : Addition of Amalgam Alloy to Zinc Phosphate Cement, J. PROS. DEN. 12:157-164, 1962. Silicophosphate Cement as a Permanent Filling Material, D. Pratt. 2:3707. Ross, J3E:1F5e
d: Massler,
8. Paffenbarger, G: C., and Caul, H. J.: Dental Cements, Proc. D. Centenary, pp. 232-238, 1940. Studies on the Solubility 9. Norman, R. D., Swartz, M. L., and Phillips, R. W.: Additional of Certain Dental Materials, J. D. Res. 38:1028-1037, 1959. DENTAL RESEARCH FACILITY U. S. NAVAL TRAINING CENTER GREAT LAKES, ILL.