| Objective: To design a method that can quantify resin cement accurately so that we could optimize the volume of resin cement used in cementation,and study the effect of the method on cementation.To reduce excess cement as much as possible and facilitate clinical work.Methods:(1)The steps and application of the cementation method.(1)A device which could quantify resin cement accurately was designed and obtained,and the accuracy test was performed immediately when the device was finished.The volume of cement required for cementation was replicated by light body silicone rubber.The corresponding volume of cement was obtained by the device,and the crowns were loaded by brushing cement into the intaglio surfaces,including the occlusal surface.Then the crowns were completely seated and light polymerized.(2)4 models with different height and different convergence angle were designed and obtained from digital software and equipment.40 die-stone models were produced and divided into 4 groups: C6H4(6 °,4 mm),C6H6(6 °,6 mm),C12H4(12 °,4 mm),C12H6(12 °,6 mm)(n = 10).The printed resin copings obtained from a printer were cemented onto their respective die-stone models by using the cementation method.The volume of excess cement,marginal fit and internal fit were measured.(3)Apply SPSS 19.0 software to analyze the result statistically with two-way ANOVA(P = 0.05).(2)Factors that affect the volume of cement in cementation.(1)The brushes used in the previous experiment were collected and marked in advance,and 5 brushes were randomly selected from each group.The weight of the 20 brushes before and after cementation was measured to determine the volume of cement loss.(2)A Straumann clinical abutment was selected(5.5 mm,12 °).Height(4.0 mm,7.0 mm)and convergence angle(6 °,18 °)of the abutment were changed respectively on the premise of constant surface area by software.The 5 models with resin copings were obtained from a printer.And the effect of the change on the volume of cement required for cementation was researched.(3)Apply SPSS 19.0 software to analyze the result statistically with one-way ANOVA and LSD-t test(P = 0.05).(3)Control experiment.(1)10 clinical models with resin copings were selected as experimental group and control group was replicated from the experimental group.(2)The specimen in the experimental group was cemented by using the cementation method,and the specimen in the control group was cemented by manual mixing.The comparison was performed between the two groups after cementation.(3)Apply SPSS 19.0 software to analyze the result statistically with t-test(P = 0.05).Results:(1)The device was accurate enough and the minimum volume of resin cement was 0.83 mm3.The marginal fit was clinical acceptable,and there was no obvious internal voids in all groups.The cement thickness of axial surface in all groups was clinical recommended and the cement thickness of occlusal surface was greater than clinical recommendation in all groups.(2)The volume of cement lost in the brush was about 2.3 mg,CV = 9.48%.Height significantly affected the volume of cement required for cementation(P<0.01)while convergence angle did not(P = 0.074)on the premise of constant surface area.(3)Significant difference was found between experimental group and control group in the volume of excess cement(P<0.01).No significant difference was found in marginal fit and internal fit between experimental group and control group.Conclusion:(1)The marginal fit and internal fit would not be affected by using the cementation method.(2)The cementation method could significantly reduce excess cement in cementation. |
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