Regarding Model I-A, as seen in Fig. 4, the maximum von Mises stress when applied the force vertically was 64.8 MPa on the marginal isthmus area of amalgam. In contrast, it was 49.5 MPa on enamel, especially on the marginal cavity of enamel. Therefore, the maximum von Mises stress concentrated on the inner cavity area of the dentin, and its value was 31.2 MPa. In addition, the enamel registered 116.93 MPa, which is the highest value of the Maximum von Mises stress when the force direction was applied at the type I lateral loud; it dropped off respectively at type IV, III, and II lateral load recording 103.2 MPa, 94.8 MPa, and 86.1 MPa. The Maximum von Mises stress values on the amalgam at type III, IV, I, and II lateral loads were 97.1 MPa, 84 MPa, 34 MPa, and 20.4 MPa, respectively. In contrast, it was 56.2 MPa, 54.9 MPa, 52.5 MPa, and 32.7 MPa on the dentin at type I, III, II, and IV lateral load directions, respectively.
About Model I-B, as seen in Fig. 5, the maximum von Mises stress, when applied the force vertically, was 77.1 MPa on the marginal amalgam in the vertical force direction. In contrast, it was 65.7 MPa on the enamel and 44.6 MPa on the dentin. The lowest value of maximum von Mises stress was recorded on IRM, which was 24.4MPa. The Maximum von Mises Stress was registered 155.4MPa, 146.3MPa, 130.5MPa, and 119.3MPa on enamel at type I, III, IV, and II lateral loads, respectively. The Maximum von Mises stress values on the amalgam were 59.4MPa, 51.3MPa, 50.5MPa, and 46.6MPa type III, I, II, and IV lateral loads, respectively. The maximum von Mises stress on dentin were 59.4MPa, 51.3MPa, 50.5 MPa, 46.6MPa at type III, I, II, and IV lateral loads, and was registered 38.6MPa, 13MPa, 11.6MPa and 17.6MPa on IRM at the same force directions sequence.
Concerning Model II-A, as shown in Fig. 6, the maximum von Mises stress, when applied vertically, records 86.2MPa on the occlusal area of SSC, and it is reduced to 23.9 MPa on dentin, especially on the cervical margin of dentin. The maximum von Mises stress concentrated on the occluso-buccal side of the amalgam, and its value was 21.6 MPa. The SSC registered the highest value of the Maximum von Mises stress, 274.6MPa, when the force direction was applied at the type I lateral load of the tooth. It dropped off respectively at type II, III, and IV lateral loads, recording 273.9 MPa, 245.5MPa, and 196.9 MPa. The Maximum von Mises Stress values on the amalgam at type II, I, IV, and III lateral loads were 66.6 MPa, 26.5 MPa, 16.1 MPa, and 15.9 MPa, respectively. In contrast, 46 MPa, 42 MPa, 39.6 MPa, and 31.2 MPa on the dentin at type I, III, II, and IV lateral loads, respectively.
About Model II-B, as seen in Fig.7, The Maximum von Mises stress was 183.9MPa on the SSC at vertical force direction. While it decreased on the tooth structures, its value was 31.1MPa on the dentin. The lowest value of Maximum von Mises stress was recorded at around 0.4 MPa on IRM and amalgam. The Maximum von Mises Stress was registered 327MPa, 281.8MPa, 203.3MPa, and 191.8MPa on SSC at type I, II, III, and IV lateral loads, respectively, while it was decreased on dentin, and its values were 52.7 MPa, 49.7 MPa, 44.3 MPa and 37.6 MPa at type III, I, II and IV lateral load respectively. On the amalgam and IRM, The Maximum von Mises Stress value is almost 1.0 MPa.
Regarding Model III-A, as shown in Fig. 8, the maximum von Mises stress record 81.1MPa on the occlusal area of Zr, and it is reduced to 21.6 MPa on dentin, especially on the cervical margin of dentin. The maximum von Mises stress concentrated on the occluso-buccal side of the amalgam, and its value was 20.6MPa. The Zr registered the highest value of the maximum von Mises stress, 272.0MPa, when the force direction was applied at the type I lateral load of the tooth. It dropped off respectively at type II, III, and IV lateral loads, recording 271.5 MPa, 224.5MPa, and 174.5 MPa. The maximum von Mises stress values on the amalgam at type III, I, II, and IV lateral loads were 62.8MPa, 25.2MPa, 15.2MPa, and 14MPa, respectively. In contrast, it was 46.5 MPa, 41.7 MPa, 38.5 MPa, and 31.2 MPa on the dentin at type I, III, II, and IV lateral loads, respectively.
Concerning Model III-B seen in Fig. 9, The Maximum von Mises stress was 173.4MPa on the Zr at vertical force direction. While it decreased on the tooth structures, its value was 28.1 MPa on the dentin. The lowest value of Maximum von Mises stress was recorded at around 0.4 MPa on IRM and amalgam. Regarding the lateral force directions, The maximum von Mises stress was registered 294.4MPa, 245.2MPa, 198.8MPa, and 185.7MPa on SSC at types I, II, III, and IV lateral loads, respectively, while it was decreased on dentin. Its values were 49.8MPa, 48.3MPa, 41MPa, and 34.3MPa at type III, I, II, and IV lateral loads, respectively. The maximum von Mises stress value on the amalgam and IRM is almost 1.0MPa.
Upon Comparison of Class II Cavity with MOD Extension, the dentin of the model I-A was significantly higher than the dentin of the model II-A and the dentin of the model III-A under vertical force. While the SSC recorded the highest value of maximum von Mises stress, which was 86.2 MPa, then Zr 81.1MPa was followed by amalgam 64.8MPa, as seen in table 2. Regarding the lateral force directions, the dentin of model I-A recorded the highest values of von Mises stress. Therefore, a significant difference between the dentin of model I-A and other models can be noticed. However, there was no significant difference between model II-A and model III-A. According to the final restorative material, the SSC registered the highest value of maximum von Mises stress, followed by Zr, then amalgam, as shown in Table 2.
Table 2: the maximum von Mises stress in Class II cavity with MOD Models
|
Model I-A Amalgam
|
Dentin
|
Model II-A SSC Dentin
|
Model III-A
Zr
|
Dentin
|
Vertical load
|
64.842
|
31.231
|
86.284 23.93
|
81.189
|
21.67
|
Type I lateral load
|
34.081
|
56.264
|
274.61 46.061
|
272.09
|
46.584
|
Type II lateral load
|
20.422
|
52.556
|
273.99 39.613
|
271.58
|
38.526
|
Type III lateral load
|
97.184
|
54.938
|
245.58 42.028
|
224.59
|
41.776
|
Type IV lateral load
|
84.055
|
32.726
|
196.96 31.206
|
174.51
|
31.274
|
Upon comparison of Pulpotomy with MO cavity extension, it can be observed that the maximum von Mises stress under vertical force in the dentin of model I-B is higher than the dentin of model II-B by 30.28% and higher than the dentin of model III-B by 37% (Table 3). In the lateral force, the dentin of model I-B is significantly higher than model II-B's and model III-B's dentin. Regarding the IRM models part (Table 4), there was a significant difference between model I-B and the other models, while there was no significant difference between model II-B and model III-B in the all-directional force.
Table 3: The maximum von Mises stress in pulpotomy with MO cavity Models
|
Model I-B Amalgam
|
Dentin
|
Model II-B SSC Dentin
|
Model III-B.
Zr
|
Dentin
|
Vertical load
|
77.117
|
44.656
|
183.95 31.13
|
31.13
|
173.42
|
Type I lateral load
|
40.281
|
51.342
|
327 49.787
|
49.787
|
294.48
|
Type II lateral load
|
27.093
|
50.55
|
281.82 44.394
|
44.394
|
245.26
|
Type III lateral load
|
141.6
|
59.493
|
203.37 52.716
|
52.716
|
198.82
|
Type IV lateral load
|
54.526
|
46.625
|
191.84 37.664
|
37.664
|
185.79
|
Table 4: The maximum von Mises stress in IRM.
|
Model I-B
|
Model II-B
|
Model III-B
|
Vertical load
|
24.465
|
0.3437
|
0.3137
|
Type I lateral load
|
13.068
|
1.3895
|
0.4254
|
Type II lateral load
|
11.606
|
0.4882
|
0.4516
|
Type III lateral load
|
38.621
|
1.4712
|
1.1942
|
Type IV lateral load
|
17.632
|
1.1968
|
0.657
|