The evaluation and comparison of marginal adaptation in metal ceramic and all ceramic restorations fabricated by two methods: CAD/CAM and conventional

Document Type: Original Article

Authors

1 Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran

2 (M.Sc. of Biostatistics) Dental Schools, Mashhad University of Medical Sciences, Mashhad, Iran

Abstract

Introduction: Marginal fit is a key factor for long term clinical success through any dental restorations. Poor marginal adaptation causes cement dissolution. This can lead to dental caries, gingival irritation, periodontal diseases, and finally treatment failure. The aim of this study was measurement and comparison of marginal gap quantities in metal ceramic and all ceramic dental restorations fabricated by various methods. Methods & Materials: A total of 60 complete crowns in 6 groups (n=10) were fabricated as. Follows: Group A: Conventional metal-ceramic collarless restorations. Group B: Metal-ceramic collarless restorations with CAD/CAM wax copings and porcelain layering. Group C: Metal-ceramic collarless restorations with Ceramill Sintron metal copings and porcelain layering. Group D: All ceramic e-max. Press (lithium disilicate) restorations. Group E: All ceramic restorations with CAD/CAM zirconia copings and porcelain layering. Group F: All ceramic CAD/CAM translucent zirconia (Zolid). Replica technique and optical microscope (60 x magnifications) used to gap measurement. Mann whitney and kruskal-wallis tests used to analyze the data. Results: The lowest mean marginal gap seen in group C (29.12) and the highest mean marginal gap seen in group E(78.19)The mean marginal adaptation was better in metal ceramic restorations than all ceramic restorations and the difference was significant (P˂0.001). Conclusion: According to our study, marginal gap of metal ceramic and all ceramic restorations was clinically acceptable (less than 120 microns).
 
 

Keywords

Main Subjects


Introduction

Poor marginal adaptation in dental restorations causes cement dissolution. This can lead to plaque accumulation, recurrent caries. Dental pulp inflammation, periodontal disease and finally treatment failure. (1, 2, 3, 4, 5, 8, 13)

Metal ceramic restorations are still the gold standard choice of fixed dental prosthesis. Popularity of metal ceramic restorations is due to their strength and marginal adaptation. Unfortunately, these restorations are like a barrier prevent light transmission through restorations (18, 29)

If esthetic is essential, we should use collarless metal ceramic or all ceramic restorations, Marginal adaptation of these restoration is lower than cast metal ceramic restorations but clinically acceptable.(7)

High strength cores of alumina and zirconia made them as an excellent material in anterior and posterior metal free restorations in all types of occlusions. Marginal adaptation is a normal concern in this restorations (4) CAD/CAM method improved design, fabrication and accuracy of dental restorations. It is faster, accurate and comfortable. Although today chair side in office method of fabrication needs more time and cost, probable errors such as scanning procedure, software designing, milling and distortion during and after sintering can affect marginal adaptation (14-17)

    Novel sintron technology introduced by Amman Girrbach company, allowed chrome-cobalt soft milling without cooling agent and difficulties. Advantages
are: 1) simpler and comfortable milling

2) No need to wax up, investing, casting steps 3) maximum speed, time saving

4) Accuracy because of digital technology    

5) Avoid repeated sending to dental laboratory 6) in office fabrication. (22)

The purpose of this study was evaluation and comparison of marginal adaptation in metal ceramic and all ceramic restorations fabricated by two methods: CAD/CAM and conventional.

 

Materials and methods

      1. Cast and die production

In this in-vitro study, first, one upper jaw and one lower jaw plastic model of dental arches selected and hand articulated for better stability after die preparation. The upper first molar selected and prepared for complete coverage crown with an 1 mm depth round shoulder finishing line manually. Then each die surveyed to avoid undercuts. Afterward, impression done by additional silicone material and after pouring with gypsum, working cast and die were fabricated. (Fig. 1)

2. Restoration fabrication

60 restorations divided into 6 groups (n=10) Groups A, B, C were metal ceramic and groups D, E, F were all ceramic. (Fig. 2)

* Group A: Conventional wax up method used to producing wax copings and then converted to metal copings by lost wax technique. Porcelain layering done and then shoulder porcelain

Added with direct lift technique. (Fig. 3)

Group B: in this group wax copings made from CAD/CAM able wax blocks and converted to metal copings by lost wax technique and then porcelain layering and adding shoulder porcelain done like group A. (Fig. 4)

Group C: in this group sintron technology used. Copings were milled from soft presinterd chrom cobalt alloy by CAD/CAM and then sintered in special oven under pressure of agron gas. Final strength of these copings is comparable with conventional method. Adding porcelain steps are like group A (Figure. 5)

Group D: Restorations of this groups were lithium disilicate (e max-press). First a full contoured wax up performed. After lost wax technique e max ingots pressed to the mold space by special plunger. Finally a full contoured all ceramic restoration produced. (Fig 6)

Group E: Restorations in this group were named zircon. Zircon core milled by CAD/CAM from
pre-sintered zirconia blocks. Then sintered and porcelain layering done. (Fig. 7, 8)

Group F: restorations in this group named Zolid. Full contoured restoration milled from pre-sintered zirconia blocks by CAD/CAM and then sintered in special oven. (Fig. 9)

3. Marginal gap measurement

For this purpose, replica technique used. Silicon replica of all restorations sectioned as seen in fig 10.
8 points of each silicon replica measured by optical stereomicroscope under 60X magnification. (Fig. 11)

Statistical analysis

In this in vitro study, at first Shapiro-Wilk test was done for evaluating data normality. It was found that data in some groups have not normal distribution. Kruskal-wallis test used for data analysis and comparison in each 6 groups. Mann-Whitney test used for data comparison between metal ceramic and all ceramic groups.

 

 

 

 

 

Figure1.Upper and lower dental arches

 

 

 

 

 

 

Figure 2.60 fabricated restorations

 

 

  

 

 

Fifure 3.Conventional casting metal coping

 

 

 

 

 

 

 

Figure4.CAD/CAMable wax blocks

 

 

 

 

 

 

Figure 5. Presintered soft chrome cobalt blocks

 

 

 

 

 

 

Figure 6.e.max Press ingots and plunger

 

 

 

 

Figure7. CAD/CAM designing

 

 

 

 

 

 

Figure 8. Presintered zircona blocks

 

 

 

 

 

 

Figure 9. Presintered Zolid blocks

 

 

 

Figure 10.Occlusal view of replica and 8 measurement points

 

 

 

 

 

 

 

Figure 11. Photographs of cross sections of replica

 

  

 

 

 


        Results

 

In this study, marginal gap of two groups of the restorations (metal ceramic and all ceramic) and their subdivisions (A, B, C, D, E, F) measured. As it can be seen in table 1 the lowest mean marginal gap was in group C and the greatest in group E. There was significant difference between 6 groups statistically (p<0,001). In paired comparison between 6 groups, it was found that mean marginal gap in group C was significantly lower than groups A, D, E, F. Also mean marginal gap in group F was lower than groups D and E. Groups F and D also were significantly lower than group E. Between other groups there was no significant difference. (Table 2) Data distribution in 6 groups has shown (Chart 1). As you can see in this chart, there are large gaps in groups 3 and 5.

Regarding the table 3, the lower mean marginal gap existed in metal ceramic restorations and the difference was significant statistically (p<0,001).Data distribution between metal ceramic and all ceramic has shown in chart 2.


Group

Number

Mean±SD

Min

Max

Median± IQR

Kruskal-Wallis test

A

80

135.4±69.3

49.8

372.3

106.9±86.7

P<0.001

B

80

92.5±54.8

39.1

369.4

72.8±35.7

C

80

195.2±123.3

54.3

680.3

152.4±142.0

D

80

155.9±73.7

69.5

607.0

136.7±63.7

E

80

181.0±85.5

65.2

602.1

176.9±69.07

F

80

168.7±45.1

87.6

347.7

165.0±56.4

IQR: Inter Quantile Range , Min: Minimum , Max: Maximum, SD: Standard Deviation

 

 

 

 

 

 

 Table1 .Mean، Standard of deviation, minimum, maximum and median marginal gap measurement
of the study groups

 

 

 

 

 

 

Table 2.Paired comparison of 6 groups of the study

Group1-group2

p-value

C-B

1.000

C-A

.006

C-F

<0.001

C-D

<0.001

C-E

<0.001

B-A

.824

B-F

<0.001

B-D

<0.001

B-E

<0.001

A-F

.001

A-D

<0.001

A-E

<0.001

F-D

1.000

F-E

<0.001

D-E

.001

 

 

 

 

 

 

 

 

Table3. Mean، Standard of deviation، Minimum، maximum .Median Data of marginal gap of metal ceramic and all ceramic restorations and their statistical results

Group

Number

Mean±SD

Min

Max

Median±IQR

Mann Whitney test

Metal ceramic

240

141.0±96.9

39.1

680.3

105.9±99.3

P<0.001

All-ceram

240

168.6±70.7

65.2

607.0

155.5±68.8

IQR: Inter Quantile Range , Min: Minimum , Max: Maximum, SD: Standard Deviation

 

 

.

Chart 1. Marginal adaptation data distribution status for all study groups separately

 

 

 

 

 

Chart 2. Marginal adaptation data distribution status for metal ceramic and all ceramic groups

 

 

 

 

 


Discussion

The marginal gap in all 60 restorations was within acceptable range (

Also, there are several methods for gap measurement. We used replica technique and volume of silicon and its contraction can affect measurements. Another problem is that this technique is 2-dimentional. (23) On the other hand, there are several methods for adding shoulder porcelain. The best method is platinum foil. Other methods are refractory die, direct lift and porcelain wax. Direct lift is the simplest method and we used this method but it has greater marginal discrepancy (21).

Variation in different studies may also be related to in-vitro vs in-vivo study, single unit vs multiunit restorations, laboratory equipment and material and method of gap measurement.

 

Conclusion

 According to our study all restorations in all groups have clinically acceptable marginal gap, however metal ceramic restorations showed better marginal adaptation than all ceramic ones.

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