Mirza Shahzad Baig1, Charles H Lloyd2, Garry J P Fleming3. 1. Materials Science Unit, Dublin Dental University Hospital, Trinity College Dublin, Dublin 2, Ireland. 2. Division of Oral and Maxillofacial Clinical Sciences, Dundee Dental Hospital and School, Park Place, Dundee DD1 4HR, Scotland, United Kingdom. 3. Materials Science Unit, Dublin Dental University Hospital, Trinity College Dublin, Dublin 2, Ireland. Electronic address: garry.fleming@dental.tcd.ie.
Abstract
OBJECTIVES: To investigate the single-edge notched (SEN) bend fracture toughness (KIC) testing methodology as a reproducible and discriminatory mechanical testing protocol for encapsulated and hand-mixed glass-ionomers (GI). METHODS: SEN bend test-pieces (35.0±0.1mm length, 6.0±0.1mm width, 3.0±0.1mm thickness with a sharp notch formed at mid-length by embedding a scalpel blade) were prepared for KIC testing using three encapsulated GI products (Chemfil Rock, Fuji IXGP Fast Capsule and Ionofil Molar AC). In addition, test-pieces were prepared from a hand-mixed GI product (Ionofil Molar) which contained between 100% and 20% of the manufacturer's recommended powder content (in 10% decrements) for a constant weight of liquid. Groups of 20 test-pieces were prepared for each encapsulated GI product (n=3) and hand-mixed GI powder:liquid mixing ratio (n=9). Data were statistically analyzed and the coefficients of variation (CoV) determined for each encapsulated GI product and hand-mixed GI powder:liquid mixing ratio. RESULTS: The KIC testing methodology failed to discriminate between the encapsulated GI products that were investigated (p=0.225). For the hand-mixed GI, the KIC testing methodology also failed to discriminate between the powder:liquid mixing ratios investigated (R(2)=0.576). The pooled CoV (10%) for the encapsulated GI products and for the powder:liquid mixing ratio groups (12%) identified the reproducibility of the test for this experiment. For the hand-mixed GI mixing ratio groups with between 100% to 50% of the recommended powder content, no trend could be discerned. SIGNIFICANCE: The KIC testing methodology failed to discriminate between different encapsulated GI products and hand-mixed GI powder:liquid mixing ratio groups investigated, despite KIC being an intrinsic material property and the coefficient of variation being acceptable.
OBJECTIVES: To investigate the single-edge notched (SEN) bend fracture toughness (KIC) testing methodology as a reproducible and discriminatory mechanical testing protocol for encapsulated and hand-mixed glass-ionomers (GI). METHODS: SEN bend test-pieces (35.0±0.1mm length, 6.0±0.1mm width, 3.0±0.1mm thickness with a sharp notch formed at mid-length by embedding a scalpel blade) were prepared for KIC testing using three encapsulated GI products (Chemfil Rock, Fuji IXGP Fast Capsule and Ionofil Molar AC). In addition, test-pieces were prepared from a hand-mixed GI product (Ionofil Molar) which contained between 100% and 20% of the manufacturer's recommended powder content (in 10% decrements) for a constant weight of liquid. Groups of 20 test-pieces were prepared for each encapsulated GI product (n=3) and hand-mixed GI powder:liquid mixing ratio (n=9). Data were statistically analyzed and the coefficients of variation (CoV) determined for each encapsulated GI product and hand-mixed GI powder:liquid mixing ratio. RESULTS: The KIC testing methodology failed to discriminate between the encapsulated GI products that were investigated (p=0.225). For the hand-mixed GI, the KIC testing methodology also failed to discriminate between the powder:liquid mixing ratios investigated (R(2)=0.576). The pooled CoV (10%) for the encapsulated GI products and for the powder:liquid mixing ratio groups (12%) identified the reproducibility of the test for this experiment. For the hand-mixed GI mixing ratio groups with between 100% to 50% of the recommended powder content, no trend could be discerned. SIGNIFICANCE: The KIC testing methodology failed to discriminate between different encapsulated GI products and hand-mixed GI powder:liquid mixing ratio groups investigated, despite KIC being an intrinsic material property and the coefficient of variation being acceptable.