Experimental Study On The Effects Of Two Restoration Methods On Crack Propagation Of Cracked Teeth

Objective: To analyze the crack propagation of a mandibular first molar with different crack depths using three-dimensional finite element models of all-ceramic crown and all-ceramic onlays.Methods:control group A0 is the finite element model of the mandibular first molar with crack depth Ⅰ to the middle third of the crown.The crack depth Ⅱ to the cemento-enamel junction was the B0 control group.Because the crack depth affected the pulp,the experimental group was designed to use two different restoration methods,all-ceramic crown and all-ceramic onlays,after root canal therapy on the base model of the control group.A1group: Onlays repair of crack depth I;A2 group:crown repair with crack depthⅠ;B1 group: Onlays repair of crack depthⅡ;B2 group:crown repair with crack depthⅡ.Vertical loading(0°)and obliquely loading(45°)were applied to all models according to the force position of the teeth during chewing,and the bite force of maximum was 600 N.The crack stress intensity factor,J integral and maximum principal stress were analyzed by ANSYS Workbench.Results:1)Under vertical loading and obliquely loading,the maximum absolute value of stress intensity factor,the maximum value of J integral,and the maximum principal stress of the cracks in the experimental group decreased and the difference distribution decreased compared with the control group.The maximum principal stress of each onlays group was smaller than that of the crown group;2)Under the same condition,each index at crack depthⅡwas larger than that at crack depthⅠ;All indexes under obliquely loading were larger than those under vertical loading.Conclusion:1)Both onlays and crown could inhibit the crack propagation of cracked teeth,and onlays was slightly better than crown in reducing the maximum principal stress of cracks;2)The effect of oblique loading and deep crack on crack propagation is greater.