| Objective: To evaluate the influence of remaining dentin thickness of residual dentin on the fracture resistance of fiber post-core crown.Methods: 54 single rooted mandibular human first premolars were selected in vitro at Department of Stomatology of Xinjiang Medical University,which extracted freshly for orthodontic reasons and randomly divided into three groups A,B and C with 18 tooth in each group,each group used 1.3mm,1.6mm and 1.9mm diameter fiber post supporting drills to prepare the post space,and record the thickness of eight dentin walls,it's buccal,lingual,mesial,distal,buccal-mesial,buccal-distal,lingual-mesial,lingual-distal walls respectively.All the test specimens restored with fiber post,resin core and CAD/CAM zirconia porcelain crown.Static loading was performed at a speed of 1mm/min at 45° by electronic universal test machine,and the maximum fracture resistance and failure mode was recorded untill the specimen fracture occurred at any point.Results: The average fracture loads of Group A/B/C showed a trend of decreasing.The minimum average fracture load is group C,and the max is group A.The faracture resistance of Group A/B/C showed statistical difference(P<0.05);LSD test showed the fracture resistance of A/B and A/C were statistically significant(P<0.05),B/C showed no statistical difference.The thickness of buccal,lingual,mesial,distal,buccal-mesial dentin walls of Group A/B/C showed statistical difference(P<0.05),and thickness of the rest buccal-distal,lingual-mesial,lingual-distal walls showed no statistical difference.Conclution: When the height of ferrule is the same,the remaining dentin wall thickness of premolar will be different after the preparation of different diameter post dirlls,and the fracture resistance will also be different.In clinical practice,it is not necessary to increase the diameter of fiber post to enhance its fracture resistance,otherwise it will increase the possibility of catastrophic fuilure,which is not conducive to secondary restoration. |
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