| ObjectiveA complete three-dimensional finite element model of the maxillary central incisor was established,and on this basis,two common dental fracture models were established—the three-dimensional finite element model in which the lip or lingual part of the shoulder collar was 0 after 1/3 of the maxillary central incisor’s neck was observially folded.For the 1/3 lip-lingual oblique fracture of the maxillary central incisor neck,this experiment explores an innovative treatment method that retains part of the broken crowns for bonding,restores the complete dentin shoulder collar,retains the band structure,and simplifies the restoration treatment The procedure restores its beauty and has good flexural resistance.After normal occlusal loading,compare all-ceramic crowns,broken crowns,fiber posts,resin cores,3M cement,residual tooth(dentin),Super-Bond C&B cement,periodontal ligament and alveolar bone The equivalent stress of S1 and S2,the stress peak value and stress distribution of S1,S3,to explore the influence of post-core crown restoration with different broken crowns with different heights of broken crowns on the force after broken crowns,and analyze broken crowns.The proper retention height of broken crown teeth for post-core crown restoration.To provide certain theoretical guidance and reference basis for clinical restoration of partial broken crowns when the collar of the lip and tongue side is 0 after the 1/3 of the upper jaw central incisor neck is obliquely folded.Methods1.Using CBCT and three-dimensional finite element software,the standard model of the maxillary central incisor and the 1/3 labiolingual oblique fracture model of the tooth neck were established.2.For 2 types of dental fractures(lip-tongue shoulder collar height:Group 1,2mm-0,and Group 2,0-2mm)were modeled according to 6 methods(A:the whole broken crown bonded post-core crown restoration model,and the height of the retained part of the broken crown was selected as B:2mm,C:4mm,D:6mm,and E:the simple post-core crown restoration model,and F:the post-core crown restoration model after crown extension).A total of 12 groups of post-core crown restoration models were built,including 1-A,1-B,1-C,1-D,1-E,1-F and 2-A,2-B,2-C,2-D,2-E,2-F.3.Analyze 12 sets of post-core crown restoration models under 6 restoration methods of 2 types of dental fractures.After normal occlusal loading,the equivalent stresses of the periodontal tissues and restorations of each tooth,the peak stresses and stress distributions of S1 and S3 Happening.Results1.The fractured crown bonded post-core crown restoration models of group 1-B and 1-C,after simulating normal occlusal loading,the equivalent stress of the fractured crown tooth slice,S1,S3 stress peak values are all smaller than other models,indicating that the tongue For teeth with missing shoulder collars,after retaining the 2mm,4mm-height broken crown bonded post-core crown,the stress concentration on the broken crown tooth piece is small,and it is not easy to be broken or displaced.2.In the 10 models of A,B,C,D,and E in the two groups of 1,2,after simulating normal occlusal loading,there is no significant difference in the force of the remaining tooth,that is,the dentin.It shows that the brace structure formed by the broken crown bonding and the dentin shoulder collar formed did not reduce the flexural resistance of the remaining teeth,and played a role in protecting the remaining teeth.3.Compared with other models in the F group of the 1 and 2 groups,it can be seen that the equivalent stress of the remaining tooth(dentin)of the F group and the stress peak value of S1 are larger than those of the other groups.It shows that after the crown extension post-core crown restoration for the labial or lingual shoulder-collar missing teeth,after the simulated median occlusion is loaded,stress concentration of the remaining teeth is more likely to be caused,and the flexural resistance of the remaining teeth is reduced.4.In the first and second two groups,the 8 groups of broken crown bondi ng repair models,A,B,C,and D,after simulating the median occlusion,the force of the Super-bond adhesive is relatively stable in either group 1 or grou p 2.However,the equivalent stress and peak value of the Super-bond adhesive in the first group were smaller than those in the second group,indicating tha t compared with patients with labial shoulder collar missing teeth,the lingual shoulder collar missing teeth fractured crowns After the post-core crown is bon ded,the stress concentration of the Super-bond adhesive is smaller,the bondin g is more stable,and it is not easy to cause the force displacement of the bro ken lingual crown.5.Comparison of the two groups of broken crown bonding groups with E and F groups shows that the S1 and S3 peak stress distribution of the broken crown bonded post-core crown repaired fiber post is the broken crown bonded group<pure post and core crown group<The crown lengthening group showed that for the teeth with missing labial or lingual shoulder collar after repairing with broken crown and post-core crown,the stress concentration of the fiber post was not easily caused,and the flexural resistance of the fiber post was enhanced.6.In the 10 models of B,C,D,E,and F in the first and second groups,it can be found that the maximum tensile stress and the maximum compressive stress of the resin core of the F group in the 1 or 2 groups are relatively small,indicating that the crown Extending the post-core crown repair will not easily lead to stress concentration of the resin core and enhance the stability of the resin core.7.A comparison between group 1-B and group 1-F in the first group showed that the peak stress of the all-ceramic crown,remaining tooth,fiber post,periodontal ligament and alveolar bone in the crown extension post-core crown restoration group was higher than that of the broken crown preserved post The nuclear crown restoration group is large,indicating that for the teeth with missing shoulder collar on the lingual side,the 2mm height of the broken crown and the post-core crown restoration is better than the crown extension post-core crown restoration.8.Comparing the 1-F and 2-F groups in the F group,the S1 and S3 stress peaks of the fiber posts in the 2-F group are higher than those in the 1-F group,indicating that the lack of the lingual shoulder collar is more likely to cause The fracture of the fiber post after crown extension post-core crown repair.Moreover,the equivalent stress of the alveolar bone and the peak S1 stress of the 1-F group are higher than those of the 2-F group,indicating that after the load of the simulated median occlusion,the lengthened post-core crown of the labial shoulder collar is missing,the alveolar bone Compared with other models,the stress is significantly reduced.However,the crown extension post-core crown restoration with missing lingual shoulder collar is more likely to cause stress concentration in the alveolar bone,and it is more likely to damage the periodontal support tissue in the long term.Conclusions1.For lingual shoulder-collar missing teeth,the post-core crown restoration with 2mm and 4mm broken crowns is better than the conventional complete broken crown bonding and post-core crown restoration,and can be used in clinical practice.2.For labial or lingual partial shoulder-collar missing teeth,the post-core crown restoration with the broken crown bonding is compared with the post-core crown and crown-extended post-core crown restorations.The S1 and S3 peak stress distribution law of the fiber post is broken.Crown bonding group<simple post and core crown group<crown extension group,indicating that for teeth with missing labial or lingual shoulder collar after repairing with broken crown bonding post and core crown,it is not easy to cause stress concentration of the fiber post and strengthen the fiber The bending resistance of the post,and the post-core crown restoration effect is good,and it can be used in clinical practice.3.For lingual shoulder-collar missing teeth,post-core crown restorations with 2mm and 4mm broken crowns are better than post-core crown restorations after crown extension.In addition,all-ceramic crowns for teeth with crown extensions are due to the imbalance of the crown-to-root ratio.The remaining teeth,fiber posts,periodontal ligament and alveolar bone bear greater stress,which is more likely to cause stress concentration,its flexural resistance is reduced,and the periodontal tissue will be damaged in the long term.4.After repairing the teeth with the labial or lingual shoulder-collar defect with the extension of the post-core crown,the stress on the alveolar bone of the labial shoulder-collar missing tooth is significantly less than that of the lingual shoulder-collar missing tooth.Therefore,the restoration of the crown extension post-core crown with missing lingual shoulder collar is more likely to cause stress concentration in the alveolar bone,and it is more likely to damage the periodontal support tissue in the long term. |
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