Fracture Toughness Measurement of Dental Ceramics Using the Indentation Fracture Method with Different Formulas

Abstract

This study examined fracture toughness (KIc) measurements obtained using the indentation fracture (IF) method with a view to improving their reliability.The KIc values of five dental ceramics were measured using the IF method with five different formulas, and the single-edge precracked beam (SEPB) method was used as a control. The elastic moduli of the dental ceramics were evaluated by dynamic hardness test. Load conditions of the dental ceramics that produced a median/radial crack for the IF method formulas were investigated.Based on the resultant c/a and P/c1.5 values, the indentation load (P) required for median/radial crack occurrence varied greatly from 29.4 to 196 N depending on the ceramic used. Among the five formulas, none of the KIc values obtained by the IF method with Miyoshi's formula differed significantly (p >0.05) from the values obtained using SEPB method.These results suggested that, after an appropriate indentation load is determined, reliable KIc values for small dental ceramic specimens can be easily obtained using the IF method if Miyoshi's formula is used in combination with the dynamic hardness test.

Marginal and Internal Fit of All-ceramic Crowns Fabricated with Two Different CAD/CAM Systems

“…All-ceramic crowns can be fabricated using two types of computer-aided design/computer-aided manufacturing (CAD/CAM) systems [6][7][8] : a doublelayer type which has a high-strength core, and a single-layer type without core (the entire crown is fabricated by a CAD/CAM system). The addition of porcelain to the copings of double-layer type may cause a negative effect on the fit of the crowns 3,9) . In the case of single-layer type of CAD/CAM crowns milled from ceramic blocks, they are not subjected to the porcelain firing cycle.…”

The Effect of Magnesium Oxide Supplementation to Aluminum Oxide Slip on the Jointing of Aluminum Oxide Bars

“…In the current study, the indentation fracture method was used to determine fracture toughness. Maehara et al 19) compared several formulas for calculating KIC values using the indentation fracture method to the single-edge precracked beam (SEPB) method. They concluded that the formula proposed in JIS R 1607 was substantially comparable to SEPB method and fully acceptable for 19) .…”

“…Maehara et al 19) compared several formulas for calculating KIC values using the indentation fracture method to the single-edge precracked beam (SEPB) method. They concluded that the formula proposed in JIS R 1607 was substantially comparable to SEPB method and fully acceptable for 19) . According to the formula for fracture toughness calculation, crack length is one of the predominant factors affecting toughness.…”

“…To determine fracture toughness, the indentation fracture method was used 18,19) . Three rectangular bar specimens (1.5×4×36 mm) were prepared and fired according to the same firing schedule (Table 3) for each jointing material.…”

Analysis of Internal Defects in All-ceramic Crowns Using Micro-focus X-ray Computed Tomography

“…All-ceramic crowns have been examined by many researchers in terms of material strength [4][5][6] and fracture resistance 7,8) . However, few studies have been performed to examine the internal defects.…”