IADR Abstract Archives
Size of enamel-craze-line affects ultimate strength of human first premolars
Objectives: To date, there is no conclusive treatment guideline for craze lines whether to immediately remove the craze line and restore or observe for further signs. This study evaluates the effect of width and depth of craze lines on the ultimate strength of permanent maxillary first premolars using an experimental approach.
Methods: Fifty sound human first premolar teeth were extracted and machined to create artificial craze lines using a CNC machine. The samples were divided into 5 groups based on their craze line depth (D) and width (W); no craze line (group 1), D 2 mm W 1 mm (group 2), D 4 mm W 1 mm (group 3), D 2 mm W 0.5 mm (group 4) and D 4 mm W 0.5 mm (group 5). The compression test was done using a universal testing machine and the contact area was measured using a stereo microscope. The tooth ultimate strength was calculated by dividing the maximum force the tooth could withstand before crack by the contact area.
Results: The experimental results showed that teeth with craze lines had significantly lower average ultimate strength (c.a. 200- 600 MPa), as compared with that of sound teeth (784 MPa). The craze depth had more effect on more on the tooth ultimate strength than the craze width.
Conclusions: Reduction in tooth ultimate strength indicated that such craze lines needed to be addressed immediately in order to prevent tooth failure (fracture). However, in a clinical situation, a much smaller craze line is often encountered. Further investigation on the smaller craze sizes could be fruitful to identify a benchmark of a craze size that does not need urgent restoration.
Methods: Fifty sound human first premolar teeth were extracted and machined to create artificial craze lines using a CNC machine. The samples were divided into 5 groups based on their craze line depth (D) and width (W); no craze line (group 1), D 2 mm W 1 mm (group 2), D 4 mm W 1 mm (group 3), D 2 mm W 0.5 mm (group 4) and D 4 mm W 0.5 mm (group 5). The compression test was done using a universal testing machine and the contact area was measured using a stereo microscope. The tooth ultimate strength was calculated by dividing the maximum force the tooth could withstand before crack by the contact area.
Results: The experimental results showed that teeth with craze lines had significantly lower average ultimate strength (c.a. 200- 600 MPa), as compared with that of sound teeth (784 MPa). The craze depth had more effect on more on the tooth ultimate strength than the craze width.
Conclusions: Reduction in tooth ultimate strength indicated that such craze lines needed to be addressed immediately in order to prevent tooth failure (fracture). However, in a clinical situation, a much smaller craze line is often encountered. Further investigation on the smaller craze sizes could be fruitful to identify a benchmark of a craze size that does not need urgent restoration.