CC BY-NC-ND 4.0 · Dental Journal of Advance Studies 2020; 8(03): 115-126
DOI: 10.1055/s-0040-1716315
Original Article

To Evaluate the Effect of Water Temperature and Duration of Immersion on the Marginal Accuracy and Microhardness of Provisional Restoration: An In Vitro Study

Sanjan Verma
1  Department of Prosthodontics, Bhojia Dental College and Hospital, Himachal Pradesh, India
,
Tarun Kalra
1  Department of Prosthodontics, Bhojia Dental College and Hospital, Himachal Pradesh, India
,
Manjit Kumar
1  Department of Prosthodontics, Bhojia Dental College and Hospital, Himachal Pradesh, India
,
Ajay Bansal
1  Department of Prosthodontics, Bhojia Dental College and Hospital, Himachal Pradesh, India
,
Ritu Batra
2  Department of Prosthodontics, JCD Dental College and Hospital Sirsa, Haryana, India
,
Abhishek Avasthi
1  Department of Prosthodontics, Bhojia Dental College and Hospital, Himachal Pradesh, India
› Author Affiliations
 

Abstract

Introduction Provisional restoration is a critical component of fixed prosthodontics treatment, which must satisfy many inter-relative factors such as biological, mechanical, and esthetic. These restorations should have accurate marginal adaptation and optimum strength to maintain functional demands. The present “in vitro” study was conducted to evaluate the effect of water temperature and duration of immersion, on the marginal adaptation and microhardness of four different commercially available provisional restorative materials.

Materials and Methods The 240 specimens were then seated on the stainless-steel die which simulated the prepared tooth, and evaluated for the marginal gap for four different provisional restorative materials and divided into four different groups A, B, C, and D. Each group was further divided into six subgroups according to temperature of water and time of immersion. In each group the samples were immersed in water at 20, 30, and 40 degrees, respectively for 5 and 10-minutes duration. Four different temporary restorative materials for crown fabrication were loaded each time to make temporary crowns.

Results Each sample was placed under travelling stereoscopic microscope (20× magnification) and photographed. Results for each surface were obtained, and the average of three surfaces was calculated. Knoop hardness was measured using a microhardness tester. The study was subjected to statistical analysis, to know the statistical significance, of the effect of difference in time and temperature changes at the time of final polymerization on surface microhardness and marginal integrity of four different provisional restorative materials.

Discussion The mean marginal discrepancies of bis-GMA (group B) at 20, 30, and 40°C for 5 and 10 minutes in water were smaller than the results of other groups. Microhardness evaluation showed that the poly ethyl methacrylate (PEMA) type resin exhibited significantly lower microhardness than the bis-acryl resin composites (Protemp 4 and Systemp.c&b) at both time and temperature intervals.

Conclusion The bis-acryl composites material has the least marginal discrepancy in comparison with PEMA and polymethyl methacrylate (PMMA). The bis-acryl composites materials exhibit superior surface microhardness followed by PEMA and PMMA.


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Introduction

The treatment modality in fixed prosthodontics is replacement and restoration of teeth by artificial substitute that are fixed in mouth[1]. This procedure involves preparation of the abutment teeth with removal of the protective layer of enamel exposing the sensitive dentine underneath. Following the preparation, the most important thing is that, the prepared tooth should be protected and it should be comfortable for the patient while the restoration is fabricated in the laboratory to accomplish this; immediate provisional restoration is given on prepared tooth. With this, patient’s confidence is achieved which influences the long-term prognosis of definite prosthesis. Interim restorations must be provided to patients during extended treatment periods.[2]

Temporization is part and parcel of fixed prosthodontics, which must satisfy many inter-relative factors such as biological, mechanical, and esthetic.[3] Provisional restoration helps in maintaining gingival health and vitality of tooth. They also help in preventing migration of abutment teeth, maintain aesthetic, helps in maintaining vertical dimension, and aid in developing anterior guidance and occlusal scheme.[4]

In anterior region provisional restorations give the clinician as well as the patient an idea about the color, contour, length, width, and shape of the teeth before fabrication of the final porcelain metal or all-porcelain restoration.[5]

The physical and mechanical properties of the material used for fabricating provisional restoration such as microhardness, flexural strength, resistance to wear, dimensionally stable, marginal adaptability, and resistance to staining and discoloration should be ideal. The marginal adaptation should be accurate and have optimum strength to maintain functional demands.

If a crown is luted for a short time, there are release of stresses and polymerization shrinkage.[6] Marginal gap is measured as the perpendicular distance from the axial wall of preparation to the marginal surface of restoration. Due to poor marginal fit the fluids and bacteria may pass, that can make the tooth more prone to caries or pulpal infections. This can cause irritation to the soft tissue and lead to plaque deposition and periodontal diseases ranging from gingival recession, gingival inflammation with bleeding, especially in cases when the subgingival margins are prapared.[7]

Cutting of specimens and embedding them, direct visual examination, through stereo- or electron-microscopy are the various methods to check the marginal adaptation.[8]

Hardness of a material can be used for its density, and a denser material is more resistant to wear and surface deterioration.[9] Evaluation of microhardness tells us the material’s capacity to maintain the diagnostic elements, i.e., the vertical dimensions of occlusion, and up to cementation of definitive prosthesis.[10]

Thus, need arises to evaluate and investigate the marginal fit and microhardness of the different available provisional restorative materials. The present “in vitro” study was conducted to evaluate the effect of water temperature and duration of immersion, on the marginal adaptation and microhardness of four available materials used for fabrication of provisional restorations.


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Materials and Methods

Two dies of stainless steel material were fabricated. The first die simulated the reverse architecture, i.e., negative replica of an unprepared tooth (female component), with dimensions of 12-mm base and axial wall height of 8.5 mm ([Fig. 1]).

Zoom Image
Fig. 1 Stainless steel die (negative replica of unprepared tooth).

The second die simulating the prepared tooth (male component) with a base of 12-mm diameter. In the central base of die a prepared tooth was extended axially having axial height of 7 mm, 1-mm shoulder margin with overall axial reduction of 1.5-mm clearance ([Figs. 2] [3]).

Zoom Image
Fig. 2 Stainless steel die (prepared tooth).
Zoom Image
Fig. 3 Sample on master die.

The two dies were made to seat accurately over each other by means of trichannel interlock system so that the same position is achieved every time on repeated removal and seating. Thus, spaces of 1 mm at the margin and 1.5 mm in the axial area are created for the provisional restorative material to form the crowns.

For this study water bath with equistat (MAC) having cut off temperature up to 99.9°C was used. The time and duration of immersion of ten samples each for provisional restorative crowns were 5 and 10 minutes at 20, 30, and 40 degrees, respectively.

Zeiss stereomicroscope was used and photograph was taken each time with Nikon camera (Nikon Corp). An image analyzing software (Image J) was then used to measure the distance, by drawing a parallel line from the crown margins and prepared tooth margin on the die. A millimeter ruler was placed in the field of view and photographed to computer program calibrations. Results for each surface were obtained at three points and an average value for each sample was calculated ([Fig. 4]).

Zoom Image
Fig. 4 Travelling Stereoscopic Microscope 20× (ZEISS).

Knoop hardness was measured after specimen fabrication with a microhardness tester (Chennai Metco) of 10-g load indenter ([Fig. 5]).

Zoom Image
Fig. 5 Knoop hardness tester.

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Methodology

Preparation of Samples

Total 240 provisional crowns were fabricated from four different provisional restorative materials and divided into four different groups A, B, C, and D. Each group was further divided into six subgroups according to temperature of water and time of immersion. In each group the samples were immersed in water at 20, 30, and 40 degrees, respectively for 5 and 10-minutes duration. Four different temporary restorative materials for crown fabrication were loaded each time to make temporary crowns having 1-mm shoulder margin and over all width of 1.5 mm.

A thin layer of petrolatum jelly was applied with camel hair brush on the replica of die to serve as a releasing agent for retrievability. All provisional crowns (each of the four materials) were fabricated directly on the stainless steel die and materials were mixed according to the manufacturer’s recommendation.

Group A: The polyethyl methacrylate (PEMA) powder (Tempron) was saturated with liquid monomer and hand mixed for 20 to 30 seconds. The powder/liquid ratio as recommended by the manufactures is 1.0 g/0.5 mL (up to the first gradation on the powder measure and the first gradation on the liquid pipette supplied by the manufacturer). To minimize the shrinkage, use as little liquid as possible. The uniform mix of the material was poured in the matrix and allowed to become matt finished before being placed over the replica. Setting time of the material was 3 to 4 minutes at room temperature. Before it fully sets, the crowns were dipped in and out of water simultaneously several times to prevent shrinkage. Temperature of water bath was kept variable at 20, 30, and 40 degrees as per the need of our study ([Fig. 6]).

Zoom Image
Fig. 6 Four different types of materials used.

Group B and C: Each bis-acryl material (Protemp 4 and Systemp.c&b) was dispensed according to manufacturer’s instructions from a cartridge through a mixing tip using a dispensing gun and then placed in similar manner onto simulating stainless steel die having prepared and unprepared tooth ([Fig. 6]).

Group D: The polymethyl methacrylate (PMMA) powder (SC-10) was saturated with liquid monomer and hand mixed for 1 minute. The powder/liquid ratio as recommended by the manufactures was 1.0 g/0.5 mL. To minimize the shrinkage only required amount of liquid was used. The uniform mix of the material was poured in the matrix and allowed to become matt finished before being placed over the replica. Before the material was fully set, it was dipped in and out of water several times to prevent shrinkage. Immersion time and temperature were changed as per the criteria of study at 5 and 10 minutes for 20, 30, and 40 degrees ([Fig. 6]).


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#

Immersion Protocol

Final polymerization of the samples was then continued in water bath with Equistat at different water temperatures of 20, 30, and 40 degrees. For each sample, the duration of immersion was continued for 5 and 10 minutes, respectively.

Testing of Samples for Marginal Accuracy

The 240 specimens were then seated on the stainless-steel die which simulated the prepared tooth and evaluated the marginal gap ([Fig. 7]). Each sample was placed under travelling stereoscopic microscope (20× magnification) and photographed (Nikon camera, Nikon Corp.; [Fig. 8]). The image analyzing software (Image J) was then used to measure the distance, by drawing a parallel line from the crown margins and prepared tooth margin on the die ([Fig. 9]). Results for each surface were obtained, and the average of three surfaces was calculated.

Zoom Image
Fig. 7 Digitally checking of marginal discrepancy on stereomicroscope.
Zoom Image
Fig. 8 Marginal discrepancy seen on stereomicroscope.
Zoom Image
Fig. 9 Marginal discrepancy on stereo microscope between crown margin and finish line.

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Testing of Samples for Microhardness

After evaluating the marginal gap, each sample was placed under the hardness testing procedure. Knoop hardness was measured using a microhardness tester (Chennai Metco), with a 10-g indenter load. The microhardness tester has a diamond tip, which penetrates the specimen with a 10-g load for 10 seconds. When the microhardness tester was activated, the rhomboidal cutting tip presses the specimen surface generating a rhomboidal-shaped geometric figure which could be visualized under magnification by the contrast between the indented surface and the specimen surface. The rhomboid cutting tip allowed to determine the superficial microhardness by the measurement of its major diagonal, which was subjected to a mathematical equation to obtain the results. The microhardness tester automatically performs calculations. The specimen’s surface was divided into three parts and one indentation was made in the center of each part for all the specimens.


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#

Results

The study was subjected to statistical analysis, to know the statistical significance, of the effect of difference in time and temperature changes at the time of final polymerization on surface microhardness and marginal integrity of four different provisional restorative materials.

Two-way analysis of variance (ANOVA) test was used for intergroup comparison and descriptive statistics for mean and standard deviation.

Marginal Discrepancy

Marginal discrepancy is shown in [Table 1] ([Fig. 10]) for Tempron, [Table 2] ([Fig. 11]) for Protemp 4, [Table 3] ([Fig. 12]) for Telieo Systemp.c&b, and [Table 4] ([Fig. 13]) for SC-10.

Table 1

Comparison of marginal gap in Tempron at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

25.80

4.34

1.37

20.00

33.00

3.313

0.011

B

20°C for

10 min

10

24.10

3.92

1.24

19.00

30.00

A

30°C for

10 min

10

26.90

5.08

1.60

20.00

33.00

B

30°C for

10 min

10

25.80

4.28

1.35

20.00

33.00

B

40°C for

5 min

10

21.10

2.64

0.83

18.00

25.00

A

40°C for

10 min

10

21.80

3.88

1.22

16.00

29.00

A

Total

60

24.25

4.47

0.57

16.00

33.00

Zoom Image
Fig. 10 Comparison of marginal discrepancy in Tempron at different time and temperature.
Table 2

Comparison of marginal gap in Protemp 4 at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

21.30

3.05

0.96

18.00

28.00

3.313

0.011

B

20°C for

10 min

10

20.70

2.54

0.80

18.00

25.00

A

30°C for

5 min

10

22.60

3.68

1.16

18.00

30.00

B

30°C for

10 min

10

21.90

2.92

0.92

18.00

28.00

B

40°C for

5 min

10

18.20

2.09

0.66

14.00

21.00

A

40°C for

10 min

10

19.10

2.60

0.82

14.00

23.00

A

Total

60

20.63

3.14

0.40

14.00

30.00

Zoom Image
Fig. 11 Comparison of marginal discrepancy in Protemp 4 at different time and temperature.
Table 3

Comparison of marginal gap in system C & B at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

54.50

6.83

2.16

44.00

65.00

19.692

<0.001

B

20°C for

10 min

10

54.30

3.77

1.19

50.00

60.00

B

30°C for

5 min

10

55.40

7.35

2.32

48.00

66.00

B

30°C for

10 min

10

55.40

6.29

1.98

48.00

65.00

B

40°C for

5 min

10

38.00

5.96

1.88

30.00

51.00

A

40°C for

10 min

10

38.30

6.20

1.96

32.00

52.00

A

Total

60

49.31

9.92

1.28

30.00

66.00

Zoom Image
Fig. 12 Comparison of marginal discrepancy in Systemp.c&b at different time and temperature.
Table 4

Comparison of marginal gap in SC10 at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

299.90

31.98

10.11

228.00

337.00

0.993

0.431

A

20°C for

10 min

10

316.20

14.72

4.65

295.00

338.00

A

30°C for

5 min

10

306.30

20.27

6.41

283.00

337.00

A

30°C for

10 min

10

312.60

18.26

5.77

290.00

338.00

A

40°C for

5 min

10

317.90

21.52

6.80

285.00

364.00

A

40°C for 10 min

10

311.70

15.60

4.93

295.00

338.00

A

Total

60

310.76

21.17

2.73

228.00

364.00

Zoom Image
Fig. 13 Comparison of marginal discrepancy in SC 10 at different time and temperature.

Intergroup comparison is shown in [Table 5].

Table 5

Intergroup comparison of marginal gap

Descriptives

Marginal gap

N

Mean

Std. deviation

Std. error

95% CI for mean

Minimum

Maximum

Lower bound

Upper bound

Group A at 20°C for 5 min

10

25.8000

4.34102

1.37275

22.6946

28.9054

20.00

33.00

Group A at 20°C for 10 min

10

24.1000

3.92853

1.24231

21.2897

26.9103

19.00

30.00

Group A at 30°C for 5 min

10

26.9000

5.08702

1.60866

23.2610

30.5390

20.00

33.00

group A at 30°C for 10 min

10

25.8000

4.28952

1.35647

22.7315

28.8685

20.00

33.00

Group A at 40°C for 5 min

10

21.1000

2.64365

0.83600

19.2088

22.9912

18.00

25.00

Group A at 40°C for 10 min

10

21.8000

3.88158

1.22746

19.0233

24.5767

16.00

29.00

Group B at 20°C for 5 min

10

21.3000

3.05687

0.96667

19.1132

23.4868

18.00

28.00

Group B at 20°C for 10 min

10

20.7000

2.54078

0.80346

18.8824

22.5176

18.00

25.00

Group B at 30°C for 5 min

10

22.6000

3.68782

1.16619

19.9619

25.2381

18.00

30.00

Group B at 30°C for 10 min

10

21.9000

2.92309

0.92436

19.8089

23.9911

18.00

28.00

Group B at 40°C for 5 min

10

18.2000

2.09762

0.66332

16.6995

19.7005

14.00

21.00

Group B at 40°C for 10 min

10

19.1000

2.60128

0.82260

17.2392

20.9608

14.00

23.00

Group C at 20°C for 5 min

10

54.5000

6.83537

2.16153

49.6103

59.3897

44.00

65.00

Group C at 20°C for 10 min

10

54.3000

3.77271

1.19304

51.6012

56.9988

50.00

60.00

Group C at 30°C for 5 min

10

55.4000

7.35149

2.32475

50.1411

60.6589

48.00

66.00

Group C at 30°C for 10 min

10

55.4000

6.29285

1.98997

50.8984

59.9016

48.00

65.00

Group C at 40°C for 5 min

10

38.0000

5.96285

1.88562

33.7344

42.2656

30.00

51.00

Group C at 40°C for 10 min

10

38.3000

6.20125

1.96101

33.8639

42.7361

32.00

52.00

Group D at 20°C for 5 min

10

299.9000

31.98767

10.11539

277.0174

322.7826

228.00

337.00

Group D at 20°C for 10 min

10

316.2000

14.72564

4.65666

305.6659

326.7341

295.00

338.00

Group D at 30°C for 5 min

10

306.3000

20.27067

6.41015

291.7992

320.8008

283.00

337.00

Group D at 30°C for 10 min

10

312.6000

18.26472

5.77581

299.5342

325.6658

290.00

338.00

Group D at 40°C for 5 min

10

317.9000

21.52750

6.80759

302.5002

333.2998

285.00

364.00

Group D at 40°C for 10 min

10

311.7000

15.60662

4.93525

300.5357

322.8643

295.00

338.00

Total

240

101.2417

122.30985

7.89507

85.6889

116.7945

14.00

364.00

ANOVA

Marginal gap

Sum of squares

df

Mean square

F

Sig.

Between groups

3547738.983

23

154249.521

1205.903

0.000

Within groups

27629.000

216

127.912

Total

3575367.983

239


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Microhardness

Microhardness is shown in [Table 6] ([Fig. 14]) for Tempron, [Table 7] ([Fig. 15]) for Protemp 4, [Table 8] ([Fig. 16]) for Telieo Systemp. c&b, and [Table 9] ([Fig. 17]) for SC10. Intergroup comparison is shown in [Table 10].

Table 6

Comparison of microhardness in Tempron at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

12.60

1.71

0.54

10.00

15.00

1.348

0.259

A

20°C for

10 min

10

12.50

1.58

0.50

10.00

15.00

A

30°C for

5 min

10

12.10

1.44

0.45

10.00

15.00

A

30°C for

10 min

10

12.60

1.42

0.45

10.00

15.00

A

40°C for

5 min

10

13.40

2.06

0.65

10.00

16.00

A

40°C for

10 min

10

13.90

2.42

0.76

10.00

17.00

A

Total

60

12.85

1.83

0.23

10.00

17.00

Zoom Image
Fig. 14 Comparison of surface microhardness in Tempron at different time and temperature.
Table 7

Comparison of micro hardness in Protemp 4 at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

19.50

1.90

0.60

17.00

24.00

0.674

0.645

A

20°C for

10 min

10

19.80

2.20

0.69

17.00

24.00

A

30°C for

5 min

10

19.40

1.26

0.40

18.00

22.00

A

30°C for

10 min

10

19.90

1.72

0.54

18.00

24.00

A

40°C for

5 min

10

20.70

1.33

0.42

19.00

23.00

A

40°C for

10 min

10

19.80

1.98

0.62

17.00

24.00

A

Total

60

19.85

1.74

0.22

17.00

24.00

Zoom Image
Fig. 15 Comparison of surface microhardness in Protemp 4 at different time and temperature.
Table 8

Comparison of microhardness in system C and B at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

16.10

1.96

0.62

14.00

20.00

4.223

0.00

A

20°C for

10 min

10

16.80

1.68

0.53

15.00

20.00

A

30°C for

5 min

10

17.30

1.82

0.57

15.00

20.00

A

30°C for

10 min

10

17.50

1.71

0.54

15.00

20.00

A

40°C for

5 min

10

17.90

1.91

0.60

15.00

20.00

A

40°C for

10 min

10

19.60

1.83

0.58

17.00

22.00

B

Total

60

17.53

2.06

0.26

14.00

22.00

Zoom Image
Fig. 16 Comparison of surface microhardness in Systemp.c&b at different time and temperature.
Table 9

Comparison of microhardness in SC10 at different time and temperature

N

Mean

Std. deviation

Std. error

Minimum

Maximum

F-value

p-Value

Duncan grouping

20°C for

5 min

10

9.90

1.66

0.52

7.00

12.00

0.871

0.507

A

20°C for

10 min

10

10.20

1.31

0.41

8.00

12.00

A

30°C for

5 min

10

10.40

1.42

0.45

7.00

12.00

A

30°C for

10 min

10

10.50

1.50

0.47

7.00

12.00

A

40°C for

5 min

10

11.00

2.10

0.66

7.00

14.00

A

40°C for

10 min

10

11.30

2.26

0.71

8.00

16.00

A

Total

60

10.55

1.74

0.22

7.00

16.00

Zoom Image
Fig. 17 Comparison of surface microhardness in SC10 at different time and temperature.
Table 10

Intergroup comparison of microhardness

Descriptives

Microhardness

N

Mean

Std. deviation

Std. error

95% CI for mean

Minimum

Maximum

Lower bound

Upper bound

Group A at 20°C for 5 min

10

12.6000

1.71270

0.54160

11.3748

13.8252

10.00

15.00

Group A at 20°C for 10 min

10

12.5000

1.58114

0.50000

11.3689

13.6311

10.00

15.00

Group A at 30°C for 5 min

10

12.1000

1.44914

0.45826

11.0633

13.1367

10.00

15.00

Group A at 30°C for 10 min

10

12.6000

1.42984

0.45216

11.5772

13.6228

10.00

15.00

Group A at 40°C for 5 min

10

13.4000

2.06559

0.65320

11.9224

14.8776

10.00

16.00

Group A at 40°C for 10 min

10

13.9000

2.42441

0.76667

12.1657

15.6343

10.00

17.00

Group B at 20°C for 5 min

10

19.5000

1.90029

0.60093

18.1406

20.8594

17.00

24.00

Group B at 20°C for 10 min

10

19.8000

2.20101

0.69602

18.2255

21.3745

17.00

24.00

Group B at 30°C for 5 min

10

19.4000

1.26491

0.40000

18.4951

20.3049

18.00

22.00

Group B at 30°C for 10 min

10

19.9000

1.72884

0.54671

18.6633

21.1367

18.00

24.00

Group B at 40°C for 5 min

10

20.7000

1.33749

0.42295

19.7432

21.6568

19.00

23.00

Group B at 40°C for 10 min

10

19.8000

1.98886

0.62893

18.3773

21.2227

17.00

24.00

Group C at 20°C for 5 min

10

16.1000

1.96921

0.62272

14.6913

17.5087

14.00

20.00

Group C at 20°C for 10 min

10

16.8000

1.68655

0.53333

15.5935

18.0065

15.00

20.00

Group C at 30°C for 5 min

10

17.3000

1.82878

0.57831

15.9918

18.6082

15.00

20.00

Group C at 30°C for 10 min

10

17.5000

1.71594

0.54263

16.2725

18.7275

15.00

20.00

Group C at 40°C for 5 min

10

17.9000

1.91195

0.60461

16.5323

19.2677

15.00

20.00

Group C at 40°C for 10 min

10

19.6000

1.83787

0.58119

18.2853

20.9147

17.00

22.00

Group D at 20°C for 5 min

10

9.9000

1.66333

0.52599

8.7101

11.0899

7.00

12.00

Group D at 20°C for 10 min

10

10.2000

1.31656

0.41633

9.2582

11.1418

8.00

12.00

Group D at 30°C for 5 min

10

10.4000

1.42984

0.45216

9.3772

11.4228

7.00

12.00

Group D at 30°C for 10 min

10

10.5000

1.50923

0.47726

9.4204

11.5796

7.00

12.00

Group D at 40°C for 5 min

10

11.0000

2.10819

0.66667

9.4919

12.5081

7.00

14.00

Group D at 40°C for 10 min

10

11.3000

2.26323

0.71570

9.6810

12.9190

8.00

16.00

Total

240

15.1958

4.12249

0.26611

14.6716

15.7200

7.00

24.00

ANOVA

Marginal gap

Sum of squares

df

Mean square

F - Value

Sig.

Between groups

3369.296

23

146.491

45.693

0.000

Within groups

692.500

216

3.206

Total

4061.796

239


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Discussion

The present “in vitro” study was conducted to evaluate the marginal adaptation and microhardness of four different commercially available provisional restorative materials when dipped into water at different temperatures for different time intervals.

Margin fit of provisional crowns has been investigated by many researchers. The results depended on the design of a master die, the amount of resin, the technique used, and the type of the resin.[11]

Though the current data could not be compared directly with other investigators, the mean marginal discrepancies of bis-GMA (group B) at 20, 30, and 40°C for 5 and 10 minutes in water were smaller than the results of other group. Clinically to get a good marginal adaptation the provisional restoration can be readjusted and relined for number of times. There was very minute difference found in marginal fit between 20 and 30°C. Polymerization increases in warmer water and it is recommended that for better marginal fit polymerization should be performed at 30°C. However, as recommended by manufacturer’s instruction it should be store at 25°C. But in this study, it was seen that the least marginal gap was at 40 degrees for 5 minutes in bis-GMA which was 18.2 µm.

Reason for poor marginal fit at high temperature is due to vaporization of free monomer. At high temperature there is complete polymerization so more shrinkage and more dimensional changes.[11] Even in cold water between 0 and 10°C there is delayed polymerization and poor marginal fit.[12]

The mean gap formation for all the bis-acryl composite materials was comparable (Protemp 4 and Systemp.c&b); however, PEMA (Tempron) and PMMA (SC-10) had significantly greater marginal discrepancy. The least marginal gap formation was observed for Protemp 4 and the highest discrepancy was observed for SC-10.

In this study for Group B, it was evaluated that the least mean marginal discrepancy of 18.2 µm was evaluated at 40-degree immersion for 5 minutes duration. And the highest mean marginal discrepancy of 22.6 µm was seen at 30-degrees immersion temperature for the duration of 5 minutes. For Group A, it was evaluated that the least mean marginal discrepancy of 21.1 µm was evaluated at 40-degrees immersion for 5 minutes duration and the highest mean marginal discrepancy of 26.9 µm was seen at 30 degrees immersion temperature for the duration of 5 minutes. For Group C, it was evaluated that the least mean marginal discrepancy of 38.0 µm was evaluated at 40-degree immersion for 5- and 10-minutes duration. And the highest mean marginal discrepancy of 55.4 µm was seen at 30-degree immersion temperature for the duration of 5 and 10 minutes. For Group D, it was evaluated that the least mean marginal discrepancy of 299.9 µm was evaluated at 20-degree immersion for 5-minutes duration. And the highest mean marginal discrepancy of 317.9 µm was seen at 40-degrees immersion temperature for the duration of 5 minutes. Using Duncan-test the results were compared and statistically analyzed; test revealed that the marginal gap is comparable in 20, 30, and 40°C for 5 and 10 minutes which was a significant difference. The ANOVA test revealed a significant difference (p = 0.001) in marginal gap at different time and temperature.

According to Adnan et al, bis-acryl resin composite materials had better marginal adaptability as compared with polyethyl methacrylates.[13] Verma et al also reported that marginal fit of provisional restorations made from the bis-GMA and conventional acrylic resins were better. There was more marginal gap in PMMA.[14] According to Young et al, it was found that marginal fit was better with bis-acryl composite resin than PMMA.[15]

The surface hardness of a material is affected by strength, proportional limit, ductility, malleability, and resistance to abrasion.

In this study bis-acryl resin composite materials showed better microhardness than conventional methacrylate-type resins. Mechanical strength of bis-acryl composites increases with cross linkage bifunctional acrylates in the base pastes. So, under pressure there was air entrapment thus leading to lower strength. Due to increased inorganic fillers the bis-acryl resins had better resistance to abrasion and less polymerization shrinkage.

When the provisional restorations were fabricated with a material with good wear resistance, the breakage was less and had better prognosis for longer duration of time.

The results for microhardness evaluation showed that the poly(ethyl methacrylate) type resin (Tempron) exhibited significantly lower microhardness than the bis-acryl resin composites (Protemp 4 and Systemp.c&b) at both time and temperature intervals. bis-GMA materials (Protemp 4 and Systemp.c&b) demonstrated the highest values of microhardness amongst all groups. All materials showed a statistically significant result.

The result of the present study is in accordance with the study of Diaz-Arnold et al who reported that the hardness of most materials decreased over time and all of the bis-acryl resin composite materials had better microhardness over conventional methyl methacrylate resins.[9]

Within the limitations of this study, the values obtained “in vitro” may not simulate oral environment. According to Kim and Watts,[16] shrinkage strain at 37°C is higher than at 23°C room temperature, which might affect the results obtained. Furthermore, for checking the marginal adaptation, specimens were not thermocycled, occlusally loaded, or experimentally aged. Therefore, further research is necessary to precisely correlate the implications of this study.


#

Conclusion

An “in vitro” study was undertaken to test the marginal adaptation and surface microhardness of four different commercially available provisional restorative materials. On comparative observation, Protemp 4 showed the lowest marginal discrepancy followed by Tempron, Systemp.c&b. The highest discrepancy was observed in SC-10. The observations were analyzed statistically and found to be significant according to two-way ANOVA test.

On subjecting samples for surface microhardness test, the KHN was highest for Protemp 4 followed by Systemp.c&b and Tempron. SC-by10 (Poly methyl methacrylate) exhibits least surface microhardness.

Hence, the following conclusions were drawn:

The bis-acryl composites material has the least marginal discrepancy in comparison with PEMA and PMMA. The is-acryl composite materials exhibit superior surface microhardness followed by PEMA and PMMA.


#
#

Conflictof Interest

None declared.


Address for correspondence

Manjit Kumar, MDS
Department of Prosthodontics, Bhojia Dental College and Hospital
Himachal Pradesh 173250
India   

Publication History

Publication Date:
30 August 2020 (online)

© .

Thieme Medical and Scientific Publishers Private Ltd.
A-12, Second Floor, Sector -2, NOIDA -201301, India


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Fig. 1 Stainless steel die (negative replica of unprepared tooth).
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Fig. 2 Stainless steel die (prepared tooth).
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Fig. 3 Sample on master die.
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Fig. 4 Travelling Stereoscopic Microscope 20× (ZEISS).
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Fig. 5 Knoop hardness tester.
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Fig. 6 Four different types of materials used.
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Fig. 7 Digitally checking of marginal discrepancy on stereomicroscope.
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Fig. 8 Marginal discrepancy seen on stereomicroscope.
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Fig. 9 Marginal discrepancy on stereo microscope between crown margin and finish line.
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Fig. 10 Comparison of marginal discrepancy in Tempron at different time and temperature.
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Fig. 11 Comparison of marginal discrepancy in Protemp 4 at different time and temperature.
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Fig. 12 Comparison of marginal discrepancy in Systemp.c&b at different time and temperature.
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Fig. 13 Comparison of marginal discrepancy in SC 10 at different time and temperature.
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Fig. 14 Comparison of surface microhardness in Tempron at different time and temperature.
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Fig. 15 Comparison of surface microhardness in Protemp 4 at different time and temperature.
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Fig. 16 Comparison of surface microhardness in Systemp.c&b at different time and temperature.
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Fig. 17 Comparison of surface microhardness in SC10 at different time and temperature.