Australian Dental Journal, October, 1977
35 1
Volume 22, No. 5
The influence of the dentist upon dimensional change and creep of amalgam
A. J. Spanauf, B.D.S. (Svd.!, Ph.D. Department of Restorative Dentistry, University of Nijmegen M. M. A. Vrijhoef, Ph.D. Department of Dental Materials, Science and Technology, University of Nijmegen AND
R. De. Oraaf, Ph.D.
Department of Statistical Consultation, University of Niimegen
ABSTRACT-Alaboratory study showed insignificant effect on dimensional change was brought about by the operator's skill, packing technique employed, and alloy. However, creep was significantly affected by the operator's skiU and the type of alloy. (Received for publication May, 1976) Introduction
In recent years successful attempts have been made to correlate laboratory findings with those obtained from clinical workl-4. Hitherto, in lab1MahIer D. B., TerkIa, L. G.. Van Eysden, J. and Reisblck M H.-Marginal fracture versus mechamcal properti& of amaIgam. J. D. Rcs.. 49:6, 1452-1457
--.
k ~ .- ..n- ~ \,- to7n
t,~
'Binon P Phllli-.':. W.. Swart& M. L.Norman. R. D. and &ha. &Unical behaviour of amalnam as re-
oratory studies, physical properties were investigated without introducing the dentists as a factor which may have an influence upon the properties. However, clinical studies have revealed the factor dentist to be a very important one 5.6. This investigation was undertaken to determine the influence of the dentists upon creep and dimensional change during setting. This influence was investigated for two different condensation techniques and two distinct alloy systems. Materials and methods
-.
_-. _-- ,-_-. , -- . 8Osborne J. W Gale E N. and Ferguson 0. W.One-Gear an2 two-y'tear'clinical evaluation 'of a com@te. ve:~! amalgam. J. Pros. D., 30:5, 795-800 (NOV.)
The dental amalgam alloys, Standalloy F* and Caves 68** (non zinc) alloy were mixed with mercury using a 1:1 alloy/mercury ratio in a Silamat*** mixing machine for six seconds. By
1Y79.
8Osbornc J W Fer uson G W Cunningham P R and hckun; R. 8.-&c-;ear 'klinical evaluitio; oi the lathe v e k s spherical amalgam. Annual Meeting of the International Assodation for Dental Research, Chicago. 111.. Abstract no. 740. 1971.
*Degussa. Frankfurt am Main West Germany. **KW en Sndtjes, I - I ~ w ~ ch ~e , NC~IEXIZIII~S, +**Vivadent, Schaan, Liechtenstdn,
322
Australian Dental Journal, October, 1977
means of hand packing, or mechanical packing using the Bergendal vibrator, cylindrical specimens were obtained from a cylindrical steel mould according to ADA Specification No. I having an internal diameter of 4.00 mm. The specimens were TABLE 1 The different factors and levels ivithitr the experimental design Factor
D
levels of a fourth factor. No interaction was assumed between the block factor on the one hand and, on the other hand, the factors dentist (D), packing technique (P) and alloy system (A), respectively. A detailed description of the statistical analysis has been given by Kempthorneg. We wish to point out that the statistical tests concerning the interactions PA and DPA depend on the fact whether we have a model with block effects or
Level
Dentist
1
2
1
2
3
3
P
Packing technique
1 2
Bergendal Hand
A
Alloy system
1 2
Cavex 68 (nz) Standalloy F
packed immediately after mixing by three dentists. The operators were instructed to work in a manner similar to that in their practice. The mix was packed within four minutes of the beginning of trituration using similar force to that used clinically. After setting for a period varying from six to ten minutes the specimens were removed carefully from the mould to avoid distortions of any kind, annealed at 37OC for one day and prepared and tested as reported previously7. Experimental design and statistical model
Table 1 summarizes the factors and the respective levels investigated. We have three replications of the 3 x 22 scheme of treatment combinations. In order to reduce the experimental variability caused by time influence, each replication was divided into two blocks. However, this division into blocks introduced a partial confounding8 between block effects and interaction PA and DPA. Each block took about two and one-quarter hours for its completion. Randomization was carried out with respect to block sequence within any replication and the treatment sequence within any block. The main effects and interaction effects of thc factors dentist (D), packing technique (P), and alloy system (A) have been investigated by means of a four-way analysis of variance. We have used a statistical model in which the blocks are the ~
TSpanauf A. J Vrijhoef, M. M. A.,and De Graaf, R.The InfluenLe of some manipulative factors on creep. Austral. D. J., 22:3, 203-207 (June) 1977. SCochran, W . G. and Cox, G. M.-Experimental designs. New York, John Wiley and Sons, 2nd ed., 1966 (p. 183).
TABLE 2 The resultirig critical levels (p-values) as found for testing hypotheses with respect to the main effects and interactions of the factors D , P, A Main, interaction effects
BLOCK D P A DP DA PA DPA
Dimensional behaviour
Creep
>0.10
0.04 0.01
>0.10 0.004 >0.10 0.09
0.04 0.04 >0.10
>O.lO
o. 10 >0.10 >0.10 >0.10
not. Alternatively, the test with respect to the block effects depends on the fact whether we have a model with or without these interactions. We have examined the block effects under a model with interactions PA and DPA. The creep measurements have been analyzed with the omission of one creep determination which was considered to be an outlier. Therefore the analysis according to Kempthorne was not applicable for the creep data and a more general method of analysis was used. Results
In Table 2 the final results of the statistical testing in terms of critical levels (or so called pvalues) are collected with respect to dimensional change and creep. Testing at the a = 0.05 level the factor packing technique as well as the interaction dentist-alloy system and packing techniquealloy system turn out to be significant with respect to dimensional change. As to creep, the dentist as well as the alloy system factor are significant. Table 3 gives the mean creep and mean dimensional change (least squares estimates based on the used model) for the separate combinations of dentists, packing techniques, and alloys. The standard error of the respective mean values for the dimensional change equals approximately
9
Kempthorne. 0.-The design and analysis of experiments. New York. John Wiley and Sons, 2nd ed., 1966.
Australian Dental Journal, October, 1977
353
TABLE3 Mean dimensional change and creep values after one day annealing at 37'C for the different combinations of dentists. uackina fechniaues and allov systems Dentist
Packing technique
Alloy system
1
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
2
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
3
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
Dimensional change rm/cm
- 13.6 - 18.6 - 14.1 - 15.6 - 15.9 - 19.2 - 12.2 - 2.8 - 15.8 - 11.5 - 14.8
-
17.8 20.4 17.6 21.7 11.6 21.6 13.4 17.5 12.6 19.2 11.4 20.3
4.1
TABLE? 4 Least squares estimates in pm/cm for the differences between the levels of a factor with regard to the dimensional behaviour after one day annealing at 37' Difference between 2 levels of a factor
D2 D3 D3 P2 A2
- D1 - D1
- D2 - P1
- A1
Mean value
3.0 3.9 1.o
5.1$
2.4
Separate values D1
D2
1.2
-
-
10.0$ 3.0
-3.2
D3
P1
PZ
A1
A2
4.2t
-1.5 2.5 3.9
7.4$ 5.4 -2.0
7.5$
-1.3
-0.2 -1.4 -1.3 1.4
6.lt 9.3$ 3.2 8.9#
-
-
6.2$
-
-
t Difference deviates significantly from zero at 0.10 level
$Difference deviates significantly from zero at 0.01 level
TABLE 5 Least squares estimates given in 10-6s-1 for fhe difjerences between the levels of one facfor with regard to the creep after one day annealing at 37' Differences between 2 levels of a factor
D2 D3 D3 P2 A2
- D1 - D1 - D2
- A1 P1 -
Separate values
Mean value
-3.4t -3.5t -0.2 -0.3 6.1:
D1
D2
D3
-
-
-
-
0.5
3.4t
-1.2 7.0#
-0.1 7.8;
P1
-2.5 -3.2 -0.7
-
6.4$
P2 ~~
4.2* -3.8* 0.4
-
5.7%
A1
A2
-5.2t -5.7"
-1.5
-0.5
0.1
-
-1.3 0.2 -0.6
-
* Difference t Difference
deviates significantly from zero at 0.10 level deviates significantly from zero at 0.05 level $ Difference deviates significantly from zero at 0.01 level
2.7 pmlcm. The standard error of the respective mean values for the creep equals approximately 1.6 x 1es-1. The overall mean value amounts to -13.2 pm/cm for the dimensional change (standard error 0.7 pm/cm) and 17.2 x 1 O - W for the creep (standard error 0.5 x 104s-1). As to the differences between the dentists, packing techniques, or alloys, Table 3 gives no quick information. Therefore, the estimates of two types of difference between the levels of any factor have been computed. For both, the mean differ-
ences (main effects) and the two levels of any other factor, the separate differences have been computed and given in Tables 4 and 5. The last differences give an illustration of the two-factor interactions. Dimensiooal changes Averaged over the levels of the other factors the differences between the dentists are not significant. However, the more or less significant interactions dentist-packing technique (DP) and the dentist-alloy system (DA) suggest differences
354
between the dentists for one of the packing techniques and one of the alloys. Investigation of the DP interaction by means of the simultaneous testing method according to Scheff6 gives the indication that the DP interaction might be caused mainly by the differences between dentist 1 and dentist 2; the difference between those two dentists for hand packing is dissimilar from that for Bergendal packing. Testing of the hypothesis that these differences are equal gives a pvalue of 0.09. Separate r tests give that packing by dentist 2 results in less contraction in comparison with dentist 1 (p0.10). It h found with respect to the D A interaction that it might be caused mainly by the dissimilar difference between dentist 1 and dentist 3 with respect to on the one hand the Caves 68 alloy and on the other hand Standalloy F. Testing according to Scheff6 of the hypothesis that these differences equal each other gives a p-value of 0.04. A separate r test gives for Standalloy F less contraction for dentist 3 in comparison with dentist 1 @O.IO). For the sake of completeness, we mention that a r test also indicates less contraction for dentist 2 in comparison with dentist 1 for Standalloy F (0.05
35 1
Volume 22, No. 5
The influence of the dentist upon dimensional change and creep of amalgam
A. J. Spanauf, B.D.S. (Svd.!, Ph.D. Department of Restorative Dentistry, University of Nijmegen M. M. A. Vrijhoef, Ph.D. Department of Dental Materials, Science and Technology, University of Nijmegen AND
R. De. Oraaf, Ph.D.
Department of Statistical Consultation, University of Niimegen
ABSTRACT-Alaboratory study showed insignificant effect on dimensional change was brought about by the operator's skill, packing technique employed, and alloy. However, creep was significantly affected by the operator's skiU and the type of alloy. (Received for publication May, 1976) Introduction
In recent years successful attempts have been made to correlate laboratory findings with those obtained from clinical workl-4. Hitherto, in lab1MahIer D. B., TerkIa, L. G.. Van Eysden, J. and Reisblck M H.-Marginal fracture versus mechamcal properti& of amaIgam. J. D. Rcs.. 49:6, 1452-1457
--.
k ~ .- ..n- ~ \,- to7n
t,~
'Binon P Phllli-.':. W.. Swart& M. L.Norman. R. D. and &ha. &Unical behaviour of amalnam as re-
oratory studies, physical properties were investigated without introducing the dentists as a factor which may have an influence upon the properties. However, clinical studies have revealed the factor dentist to be a very important one 5.6. This investigation was undertaken to determine the influence of the dentists upon creep and dimensional change during setting. This influence was investigated for two different condensation techniques and two distinct alloy systems. Materials and methods
-.
_-. _-- ,-_-. , -- . 8Osborne J. W Gale E N. and Ferguson 0. W.One-Gear an2 two-y'tear'clinical evaluation 'of a com@te. ve:~! amalgam. J. Pros. D., 30:5, 795-800 (NOV.)
The dental amalgam alloys, Standalloy F* and Caves 68** (non zinc) alloy were mixed with mercury using a 1:1 alloy/mercury ratio in a Silamat*** mixing machine for six seconds. By
1Y79.
8Osbornc J W Fer uson G W Cunningham P R and hckun; R. 8.-&c-;ear 'klinical evaluitio; oi the lathe v e k s spherical amalgam. Annual Meeting of the International Assodation for Dental Research, Chicago. 111.. Abstract no. 740. 1971.
*Degussa. Frankfurt am Main West Germany. **KW en Sndtjes, I - I ~ w ~ ch ~e , NC~IEXIZIII~S, +**Vivadent, Schaan, Liechtenstdn,
322
Australian Dental Journal, October, 1977
means of hand packing, or mechanical packing using the Bergendal vibrator, cylindrical specimens were obtained from a cylindrical steel mould according to ADA Specification No. I having an internal diameter of 4.00 mm. The specimens were TABLE 1 The different factors and levels ivithitr the experimental design Factor
D
levels of a fourth factor. No interaction was assumed between the block factor on the one hand and, on the other hand, the factors dentist (D), packing technique (P) and alloy system (A), respectively. A detailed description of the statistical analysis has been given by Kempthorneg. We wish to point out that the statistical tests concerning the interactions PA and DPA depend on the fact whether we have a model with block effects or
Level
Dentist
1
2
1
2
3
3
P
Packing technique
1 2
Bergendal Hand
A
Alloy system
1 2
Cavex 68 (nz) Standalloy F
packed immediately after mixing by three dentists. The operators were instructed to work in a manner similar to that in their practice. The mix was packed within four minutes of the beginning of trituration using similar force to that used clinically. After setting for a period varying from six to ten minutes the specimens were removed carefully from the mould to avoid distortions of any kind, annealed at 37OC for one day and prepared and tested as reported previously7. Experimental design and statistical model
Table 1 summarizes the factors and the respective levels investigated. We have three replications of the 3 x 22 scheme of treatment combinations. In order to reduce the experimental variability caused by time influence, each replication was divided into two blocks. However, this division into blocks introduced a partial confounding8 between block effects and interaction PA and DPA. Each block took about two and one-quarter hours for its completion. Randomization was carried out with respect to block sequence within any replication and the treatment sequence within any block. The main effects and interaction effects of thc factors dentist (D), packing technique (P), and alloy system (A) have been investigated by means of a four-way analysis of variance. We have used a statistical model in which the blocks are the ~
TSpanauf A. J Vrijhoef, M. M. A.,and De Graaf, R.The InfluenLe of some manipulative factors on creep. Austral. D. J., 22:3, 203-207 (June) 1977. SCochran, W . G. and Cox, G. M.-Experimental designs. New York, John Wiley and Sons, 2nd ed., 1966 (p. 183).
TABLE 2 The resultirig critical levels (p-values) as found for testing hypotheses with respect to the main effects and interactions of the factors D , P, A Main, interaction effects
BLOCK D P A DP DA PA DPA
Dimensional behaviour
Creep
>0.10
0.04 0.01
>0.10 0.004 >0.10 0.09
0.04 0.04 >0.10
>O.lO
o. 10 >0.10 >0.10 >0.10
not. Alternatively, the test with respect to the block effects depends on the fact whether we have a model with or without these interactions. We have examined the block effects under a model with interactions PA and DPA. The creep measurements have been analyzed with the omission of one creep determination which was considered to be an outlier. Therefore the analysis according to Kempthorne was not applicable for the creep data and a more general method of analysis was used. Results
In Table 2 the final results of the statistical testing in terms of critical levels (or so called pvalues) are collected with respect to dimensional change and creep. Testing at the a = 0.05 level the factor packing technique as well as the interaction dentist-alloy system and packing techniquealloy system turn out to be significant with respect to dimensional change. As to creep, the dentist as well as the alloy system factor are significant. Table 3 gives the mean creep and mean dimensional change (least squares estimates based on the used model) for the separate combinations of dentists, packing techniques, and alloys. The standard error of the respective mean values for the dimensional change equals approximately
9
Kempthorne. 0.-The design and analysis of experiments. New York. John Wiley and Sons, 2nd ed., 1966.
Australian Dental Journal, October, 1977
353
TABLE3 Mean dimensional change and creep values after one day annealing at 37'C for the different combinations of dentists. uackina fechniaues and allov systems Dentist
Packing technique
Alloy system
1
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
2
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
3
Bergendal Bergendal Hand Hand
Cavex 68 (nz) Standalloy F Cavex 68 (nz) Standalloy F
Dimensional change rm/cm
- 13.6 - 18.6 - 14.1 - 15.6 - 15.9 - 19.2 - 12.2 - 2.8 - 15.8 - 11.5 - 14.8
-
17.8 20.4 17.6 21.7 11.6 21.6 13.4 17.5 12.6 19.2 11.4 20.3
4.1
TABLE? 4 Least squares estimates in pm/cm for the differences between the levels of a factor with regard to the dimensional behaviour after one day annealing at 37' Difference between 2 levels of a factor
D2 D3 D3 P2 A2
- D1 - D1
- D2 - P1
- A1
Mean value
3.0 3.9 1.o
5.1$
2.4
Separate values D1
D2
1.2
-
-
10.0$ 3.0
-3.2
D3
P1
PZ
A1
A2
4.2t
-1.5 2.5 3.9
7.4$ 5.4 -2.0
7.5$
-1.3
-0.2 -1.4 -1.3 1.4
6.lt 9.3$ 3.2 8.9#
-
-
6.2$
-
-
t Difference deviates significantly from zero at 0.10 level
$Difference deviates significantly from zero at 0.01 level
TABLE 5 Least squares estimates given in 10-6s-1 for fhe difjerences between the levels of one facfor with regard to the creep after one day annealing at 37' Differences between 2 levels of a factor
D2 D3 D3 P2 A2
- D1 - D1 - D2
- A1 P1 -
Separate values
Mean value
-3.4t -3.5t -0.2 -0.3 6.1:
D1
D2
D3
-
-
-
-
0.5
3.4t
-1.2 7.0#
-0.1 7.8;
P1
-2.5 -3.2 -0.7
-
6.4$
P2 ~~
4.2* -3.8* 0.4
-
5.7%
A1
A2
-5.2t -5.7"
-1.5
-0.5
0.1
-
-1.3 0.2 -0.6
-
* Difference t Difference
deviates significantly from zero at 0.10 level deviates significantly from zero at 0.05 level $ Difference deviates significantly from zero at 0.01 level
2.7 pmlcm. The standard error of the respective mean values for the creep equals approximately 1.6 x 1es-1. The overall mean value amounts to -13.2 pm/cm for the dimensional change (standard error 0.7 pm/cm) and 17.2 x 1 O - W for the creep (standard error 0.5 x 104s-1). As to the differences between the dentists, packing techniques, or alloys, Table 3 gives no quick information. Therefore, the estimates of two types of difference between the levels of any factor have been computed. For both, the mean differ-
ences (main effects) and the two levels of any other factor, the separate differences have been computed and given in Tables 4 and 5. The last differences give an illustration of the two-factor interactions. Dimensiooal changes Averaged over the levels of the other factors the differences between the dentists are not significant. However, the more or less significant interactions dentist-packing technique (DP) and the dentist-alloy system (DA) suggest differences
354
between the dentists for one of the packing techniques and one of the alloys. Investigation of the DP interaction by means of the simultaneous testing method according to Scheff6 gives the indication that the DP interaction might be caused mainly by the differences between dentist 1 and dentist 2; the difference between those two dentists for hand packing is dissimilar from that for Bergendal packing. Testing of the hypothesis that these differences are equal gives a pvalue of 0.09. Separate r tests give that packing by dentist 2 results in less contraction in comparison with dentist 1 (p0.10). It h found with respect to the D A interaction that it might be caused mainly by the dissimilar difference between dentist 1 and dentist 3 with respect to on the one hand the Caves 68 alloy and on the other hand Standalloy F. Testing according to Scheff6 of the hypothesis that these differences equal each other gives a p-value of 0.04. A separate r test gives for Standalloy F less contraction for dentist 3 in comparison with dentist 1 @O.IO). For the sake of completeness, we mention that a r test also indicates less contraction for dentist 2 in comparison with dentist 1 for Standalloy F (0.05
