不同牙本质肩领形态对纤维桩核冠修复后下颌切牙抗折强度的影响观察

Effect of different shapes of dentin shoulder collar on the fracture strength of mandibular incisors after fi⁃ber post-core crown restoration

目的观察不同牙本质肩领形态对纤维桩核冠修复后下颌切牙抗折强度的影响。方法因牙周问题拔除的下颌切牙40颗,依据制备牙本质肩领形态的不同随机分为5组,分别为无肩领组、颊侧肩领组、舌侧肩领组、近中肩领组、完整肩领组,所有牙本质肩领高约2.0 mm、厚约1.0 mm。各组样本牙纤维桩核冠修复后包埋,固定于电子万能试验机上进行抗折试验,以1.0 mm/min的速度持续加载直至样本牙任意一处发生折裂,记录折裂时的荷载数值,即为抗折强度。记录所有样本牙的折裂形式,包括可修复性折裂与不可修复性折裂。绘制由力和位移两组参数组成的抗折力—位移曲线。结果无肩领组、颊侧肩领组、舌侧肩领组、近中肩领组、完整肩领组抗折强度分别为(94.89±32.14)、(211.52±92.46)、(171.04±43.02)、(162.79±54.32)、(209.15±51.16)N,其中无肩领组抗折强度显著低于颊侧肩领组、舌侧肩领组、近中肩领组、完整肩领组,(P均<0.05),且舌侧肩领组、近中肩领组抗折强度显著低于颊侧肩领组、完整肩领组,(P均<0.05)。无肩领组出现可修复性折裂6例、不可修复性折裂2例,颊侧肩领组出现可修复性折裂1例、不可修复性折裂7例,舌侧肩领组出现可修复性折裂8例、不可修复性折裂0例,近中肩领组出现可修复性折裂7例、不可修复性折裂1例,完整肩领组出现可修复性折裂7例、不可修复性折裂1例。各组抗折力—位移曲线图显示,曲线中出现一个明显转折点,但牙体仍能够继续承受荷载。结论保留2.0 mm完整牙本质肩领可以有效提高纤维桩核冠修复后下颌切牙的抗折强度;不能保留完整牙本质肩领时,保留颊侧肩领有助于提高纤维桩核冠修复后下颌切牙的抗折强度,但出现折列时多为不可修复性折裂。

Objective To observe the effect of different shapes of dentin shoulder collar on the fracture strength of mandibular incisors after fiber post-core crown restoration.Methods Totally 40 mandibular incisors extracted due to periodontal problems were randomly divided into 5 groups according to the different shapes of dentin shoulder collar:no shoulder collar group,buccal shoulder collar group,lingual shoulder collar group,mesial shoulder collar group and com-plete shoulder collar group.The heights of all the dentin shoulder collars were about 2.0 mm and the thicknesses were about 1.0 mm.The fiber post-core crowns of sample teeth in each group were embedded after restoration and fixed on the electronic universal testing machine for the flexural test.The specimens were continuously loaded at a speed of 1.0 mm/min until fracture occurred at any place of the sample teeth.The load value of the sample teeth fractured was recorded,named fracture strength.The fracture forms of all samples were recorded,including repairable fracture and irreparable fracture.The bending force-displacement curve composed of force and displacement parameters was drew.Results The fracture strength of mandibular incisors in no shoulder collar group,buccal shoulder collar group,lingual shoulder collar group,mesial shoulder collar group and complete shoulder collar group were(94.89±32.14)N,(211.52±92.46)N,(171.04±43.02)N,(162.79±54.32)N and(209.15±51.16)N,respectively.The fracture strength of no shoulder collar group was significantly lower than that of buccal shoulder collar group,lingual shoulder collar group,mesial shoulder collar group and complete shoulder collar group(all P<0.05),and the fracture strength of Lingual shoulder col-lar group and mesial shoulder collar group was significantly lower than that of buccal shoulder collar group and complete shoulder collar group(all P<0.05).There were 6 cases of repairable fracture and 2 cases of irreparable fracture in no shoulder collar group.There were 1 case of repairable fracture and 7 cases of irreparable fracture in buccal shoulder collar group.There were 8 cases of repairable fracture and 0 case of irreparable fracture in lingual shoulder collar group.There were 7 cases of repairable fracture and 1 case of irreparable fracture in mesial shoulder collar group.There were 7 cases of repairable fracture and 1 case of irreparable fracture in complete shoulder collar group.There were obvious turning points in the fracture resistance-displacement curves of each group,but the teeth could still bear the load.Conclusions Pre-serving 2.0 mm intact dentin shoulder collar can effectively improve the fracture strength of mandibular incisors after fiber post-core crown restoration.When the complete dentin shoulder collar cannot be retained,the buccal shoulder collar is helpful to improve the fracture strength of mandibular incisors after fiber post-core crown restoration,but the fracture is mostly irreparable when the fracture occurs.