A comparative evaluation of metal ring investing v/s ring less investing techniques and effect of use of die spacer on the marginal fit of metal crown - An in-vitro study.

Dr Anita Mahiwal; Dr Kusum Singh; Dr Sumit Kumar Sharma; Dr Garima Gothwal

Volume : X, Issue : VIII, August - 2020

A comparative evaluation of metal ring investing v/s ring less investing techniques and effect of use of die spacer on the marginal fit of metal crown - An in-vitro study.

Dr Anita Mahiwal, Dr Kusum Singh, Dr Sumit Kumar Sharma, Dr Garima Gothwal

Abstract :

Aim– To compare the marginal discrepancy of lost wax casting technique produced with the conventional casting technique using a metal ring vs. a ring less system and the effect of use of die spacer on the marginal discrepancy of full metal crown. Method– Total 40 metal crowns are faicated using a stainless steel die of the standard dimensions. These samples were divided into 4 groups, 10 samples in each group as follows Group–1: Crowns without die spacer, cast with metal ring. Group–2: Crowns without die spacer, cast with ring less casting. Group–3: Crowns with die spacer, cast with metal ring. Group–4: Crowns with die spacer, cast with ring less casting. Castings were seated on metal die after sand blasting; no other modifications were made to improve the seating. The marginal discrepancy measurement of the specimens were made using an Optical Microscope (Olympus BX–Model, Japan) at four locations marked on the die as well on the crown in the same alignment. These measurements were used for the statistical analysis by Student t’ test. Results– marginal discrepancies of Group–1, Group–2, Group–3 and Group–4 was found to be 187.07µm, 149.86µm, 106.91µm and 62.42µm respectively. No significant difference was observed between Group–1and Group–2. On comparison of the marginal discrepancies of Group–1 and Group–3 there was an expected improvement in marginal discrepancy (p<0.01). Marginal discrepancies of Group3 Group–4 showed expected improvement in marginal discrepancy (p<0.01). In marginal discrepancies of Group–2 and Group–4 there was highly significant improvement (p<0.001). Conclusion – the lowest marginal discrepancy was obtained using ring less casting technique with die spacer (62.42µm) with a significant difference from the marginal discrepancy obtained without die spacer and with the metal ring casting technique.