| Popis: |
Forty-eight freshly extracted human teeth were bevelled with high or low speed fissure burs and then retrofilled using zinc or non-zinc containing amalgam. The teeth were stained, photographed and examined for cracks at time of bevelling at amalgam placement, and then at six, twelve, twenty-four, and thirty months following preparation. During this time, the teeth were stored in normal saline and incubated at 37°C. Crack formation occurred at various times during the experiment. After bevelling and retrofitting 27% of the cracks occurred, at six months an additional 6% developed and at one year an additional 44 % were observed to have cracks. A total of 18 of the 48 teeth (37%) showed cracks by the 30th month, with 77% of the cracks appearing by the end of the first year. The use of low speed and zinc amalgam is no more likely to cause cracking than high speed and non-zinc amalgam when measured at thirty months. |
