可塑纤维桩修复对根管治疗牙抗折强度的影响

目的比较不同桩修复离体牙对修复体整体抗折强度的影响。方法将32颗上颌前磨牙行根管治疗并从唇侧釉牙骨质界上2 mm处截断后随机分为4组,A组采用镍铬金属铸造桩核加铸造冠修复,B组采用Tenax FiberWhite纤维桩、树脂核加铸造冠修复,C组采用EverStick可塑纤维桩单根（直径1.5 mm）、树脂核加铸造冠修复,D组采用EverStick可塑纤维桩双根（直径1.5 mm和1.2 mm）、树脂核加铸造冠修复。所有离体牙均由自凝树脂包埋,电子万能试验机加载头与牙体长轴成45°,以1 mm/min的加载速度加载直至试件任何部分折裂,记录读数并观察修复体折裂模式。结果A、B、C、D组间修复体的整体抗折强度差异无统计学意义（P>0.05）。各纤维桩组牙体折裂位置较铸造桩更接近牙颈部。结论尽管可塑纤维桩自身的弯曲强度较低,但是修复离体牙后整体抗折强度较高,可以满足临床要求。各纤维桩组折裂模式较铸造桩组更有利于修复体失败后的再修复。     

循环加载对不同桩核修复后牙体抗折强度的影响

目的 用循环加载的方式模拟核桩冠修复一段时间后的状况,比较不同桩核修复后牙体的抗折强度,了解其远期修复效果。方法 15颗下颌离体前磨牙随机分为3组,分别为铸造金属桩核组（A组）、玻璃纤维加强复合树脂桩核组（B组）、树脂充填组（C组）,每组5个试件。所有试件在完成桩核修复后均做金属冠修复,经过300 000次循环加载和1 000次5~55 ℃冷热循环后,再在力学测试机上测试试件的抗折强度,记录试件断裂时的力值和试件破坏形式。结果 B组和C组抗折强度显著高于A组（P<0.05）。A组主要为不可修复性折裂,其他两组主要为可修复性折裂。结论 临床修复残根残冠时,可以优先考虑纤维桩加树脂核修复或者树脂充填修复。     

牙本质肩领的应用对不同桩核修复后修复体抗折性能的影响

目的：比较不同桩核系统及不同的牙体预备方法对残根抗折强度的影响。方法：40颗下颌前磨牙在釉牙骨质界处截冠后随机均分为四组。A组：金属桩修复的无肩领组。B组：金属桩修复的有肩领组。C组：纤维桩树脂核修复的无肩领组。D组：纤维桩树脂核修复的有肩领组。每组样本都采用金属全冠修复。实验标本包埋于树脂块中,在电子万能测力机上以1mm/min的速度加载直至断裂。结果：A组的抗折裂载荷最高,为3.0369±0.3388KN;D组的抗折强度最低,为2.0188±0.3864KN,A-C、A-B、C-D组间差异有显著性（P〈0.05）。可修复性断裂多见于纤维桩树脂核修复组,而不可修复性的破坏多见于铸造桩核组（P〈0.05）。结论：当牙体大部分缺损达釉牙骨质界时,通过冠延长术勉强预备牙本质肩领可显著降低桩核修复后牙根的抗折强度。而如不制备牙本质肩领,传统的金属桩核比纤维桩树脂核能承受更大的咀嚼力量。     

冠折年轻恒牙根管治疗后不同修复方法的抗折强度研究

目的:对比不同修复方法的根管治疗后的冠折年轻恒牙的抗折强度差异。方法:选择30颗牙体完好的单根管的下颌第一前磨牙,经根管治疗后,随机分成6组:A组不截冠为对照组,其余五组沿着牙冠各轴面水平向中线的连线进行截冠;B组采用聚合瓷贴面修复;C组直接树脂修复;D组预成玻璃纤维桩+树脂修复;E组预成玻璃纤维桩+树脂核+聚合瓷冠修复;F组一体化纤维桩核+聚合瓷冠修复。将6组样本置于电子万能试验机上,与牙体长轴呈30°加载,直至牙体折裂或修复体脱落,记录样本牙折裂时的最大载荷数值和折裂模式并进行统计分析。结果:B、C、D、E组抗折强度与对照组A及F组相比明显下降,差异有显著性(P<0.05);E组抗折强度高于B、C、D组,差异有显著性(P<0.05);D组抗折强度高于B、C组,差异有显著性(P<0.05)。折裂模式:A组表现为受压部位的牙体折裂;B、C组表现为修复材料碎裂或脱落;D表现为树脂核部分碎裂;E组出现冠折裂和桩核分离;F组只有冠折裂。各组均未出现根折裂。结论:年轻恒牙冠折后不同修复方法对抗折强度有影响,但均能满足日常咀嚼的抗折强度需求;纤维桩修复组抗折强度高于直接修复组,一体化纤维桩核冠修复组的抗折强度最高。     

纤维树脂桩核系统修复牙根发育不完全牙后抗折强度的分析

目的通过对经根管治疗后使用玻璃纤维桩核进行修复的牙根发育不完全牙各部位抗折强度的测量比较,以期为临床使用桩核系统修复根尖诱导成形术后的牙降低根折风险提供依据。方法收集符合纳入标准的因正畸需要拔除的根尖发育不完全,根尖孔未形成的第1、2前磨牙45颗,随机分成3组。分别为纤维桩复合树脂水门汀组(实验组)、复合树脂水门汀组(阳性对照组)、根管充填后不作处理组(阴性对照组),每组样本15颗,常规桩道预备后用复合树脂和桩核系统进行修复,将修复后的样本牙进行包埋,采用TY-8000型电子万能测试机分别测量牙根颈1/3和中1/3区域的抗折强度,比较经纤维桩核系统修复后牙根不同部位的抗折强度。采用SAS软件包对所得数据进行统计学分析。结果实验组的牙根颈部、中部的抗折强度分别为(999±75.40)N和(799±21.77)N,阴性对照组分别为(501±38.4)N和(472±22.98)N,阳性对照组分别为(704±88.39)、(550±20.14)N。实验组的牙根各部位的抗折能力均最强,与阳、阴性对照组均有显著差异(P<0.0001)。结论纤维桩核系统对牙根抗折性能有显著影响,植入纤维树脂桩的牙齿在牙根颈1/3和中1/3区域都显示出比植入复合树脂粘接材料和仅经根管充填后的牙齿具有更大的抗折强度。     

2种桩核修复无箍效应的上颌前牙缺损疗效观察

目的 探讨成品金属螺纹桩树脂核和纤维桩树脂核修复无箍效应的上颌前牙缺损的临床疗效.方法 剩余牙体组织轴壁高度小于2 mm的上颌前牙162颗,随机分为2组,螺纹桩组81颗,行成品金属螺纹桩树脂核修复,纤维桩组81颗,纤维桩树脂核修复,2组均采用氧化锆全瓷冠修复,临床随访10 ～ 26个月,观察是否出现牙根折裂及折裂模式.结果 螺纹桩组中,没有发生修复体水平折裂,4颗发生斜行折裂;纤维桩组中,10颗发生修复体水平折裂,1颗斜行折裂.2组的水平折裂率差异有统计学意义(x2=4.38,P＜0.05),斜行折裂率差异无统计学意义(x2 =3.12,P＞0.05).结论 在无箍效应的情况下,纤维桩树脂核修复上颌前牙缺损比螺纹桩树脂核修复更容易出现水平折裂.     

2种桩系统修复前磨牙近中面洞型的抗力研究

目的 比较研究根管治疗后前磨牙近中面洞型经3种方法 修复后的抗力,并评价聚乙烯纤维桩系统(Ribbond桩)修复牙体缺损对修复体抗力的影响。方法 40颗完整离体单根前磨牙分成4组。第一组为对照组,另外三组根管治疗后预备近中面洞型。第二组使用复合树脂直接充填;第三、四组分别用石英纤维桩(DTLightpost)和Ribbond桩制作桩,复合树脂直接充填。热循环10000次后,置于INSTRON测试仪上测试断裂载荷,记录试件折裂时测试机读数及试件折裂模式。结果 对照组、复合树脂组、石英纤维桩组、聚乙烯纤维桩系统组的断裂载荷依次为:(1191.04±362.59)N,(578.81±117.87)N,(909.33±250.20)N,(831.56±220.16)N。实验组断裂载荷均显著低于对照组(P<0.05),石英纤维桩和聚乙烯纤维桩系统两组间无统计学差别(P=0.50),且均高于树脂直接充填组(P<0.05)。结论 使用石英纤维桩和Ribbond桩修复前磨牙近中面洞型均显著提高了抗折能力,且Ribbond桩能够显著改善折裂模式。?     

不同桩核修复上颌前磨牙残根残冠的临床研究

目的：比较不同桩核修复方式和树脂直接充填入根管修复上颌前磨牙残根残冠后的临床效果,为临床工作提供指导。方法78例患者93颗上颌前磨牙残根残冠进行完善的根管治疗后,根据不同的情况使用铸造金属桩核、纤维桩+树脂核、树脂直接充填后全冠修复,观察3年,通过临床和X线片检查,评估各种修复方式的临床效果。结果3种修复方式成功率无明显差异。纤维桩+树脂核组、树脂直接充填入根管组常见的并发症为桩松动脱落、桩折裂,铸造金属桩核组常见的并发症为牙折裂。结论3种修复方式均有较高的修复成功率,考虑到不可修复性牙折,应谨慎选用铸造金属桩核。     

不同桩核系统修复上颌前磨牙双根管的抗折力研究

目的 比较不同桩核系统修复上颌前磨牙双根管的抗折强度.方法 将36颗因正畸拔除的上颌第一前磨牙,沿釉牙本质界冠方2mm水平切除牙冠,常规根管治疗后随机分为A、B、C三组,A组给予铸造镍铬合金桩核+金属全冠;B组给予MACROLOCKT石英纤维桩+树脂核+金属全冠,C组给予TENAX玻璃纤维桩+树脂核+金属全冠修复.应用力学试验机进行抗力性检测,记录试件破坏时施力的大小,观察试件破坏的形式及部位.结果 A组、B组、C组的离体牙桩核冠修复后牙体折断时的最大载荷分别为(1059.11±123.54)N、(1075.17±64.37)N、(1341.81 ±128.11)N.三组抗折强度两两比较,没有显著性差异(P＞0.05).A组不可复性折断明显多于B组和C组,差异有统计学意义(P＜0.05),B组与C组的抗折强度、破坏性折断例数比较,差异无统计学意义(P＞0.05).结论 采用不同桩核系统修复上颌前磨牙双根管的抗折强度无明显差异.玻璃纤维桩与石英纤维桩极大降低了根折率,有利于此类根管的保留和再修复.     

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目的比较3种纤维桩修复下颌第一前磨牙的抗折性,并分析影响因素。方法选择2006年12年至2007年2月南昌大学附属口腔医院外科门诊因正畸需要而拔除的下颌第一前磨牙36颗,保留2mm的牙本质肩领,随机分成A、B、C3组,牙体预备后分别用3种纤维桩(A组:石英纤维桩-复合树脂核;B组:碳纤维桩-复合树脂核;C组:玻璃纤维桩-复合树脂核)及后牙树脂完成桩核修复,固定于万能材料测试机上加载直至标本发生折裂,记录标本破坏时的瞬间力值及实验牙的折裂类型。采用SPSS13.0软件包对结果作单因素方差分析。结果破坏性力学试验的测试结果为A组(399.24±33.84)N,B组(358.11±22.82)N,C组(220.32±23.98)N,对各组样本的破坏性试验力值进行单因素方差分析表明:3组的抗折强度为A>B>C(P<0.01)。结论石英纤维桩、碳纤维桩、玻璃纤维桩抗折强度依次递减,折断模式都有利于重新修复,均适用于临床修复。     

Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns

PURPOSE

Marginal fit is a very important factor considering the restoration''s long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system).

MATERIALS AND METHODS

20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test.

RESULTS

The means and standard deviations of the marginal fit were 61.52 ± 2.88 µm for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 ± 3.51 µm after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 ± 1.78 µm before porcelain veneering and 82.03 ± 1.85 µm after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well.

CONCLUSION

The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.     

Fracture load of composite resin and feldspathic all-ceramic CAD/CAM crowns

STATEMENT OF PROBLEM: Various machinable materials are currently used with computer-aided design/computer-assisted manufacturing (CAD/CAM) technologies for the chairside fabrication of restorations. However, properties of these new machinable materials, such as fracture load, wear, marginal deterioration, and color stability, should be investigated in vitro under replicated clinical conditions prior to time-consuming clinical studies. PURPOSE: This study investigated the effect of cyclic loading fatigue and different luting agents under wet conditions on the fracture load of CAD/CAM machined composite resin and all-ceramic crowns. MATERIALS AND METHODS: Ninety-six intact human maxillary premolars were prepared for composite resin and all-ceramic crowns with the following preparation criteria: 6-degree axial taper, 1.5-mm shoulder finish line placed 0.5 mm occlusal to the cemento-enamel junction, 1.5-mm axial reduction, 2-mm occlusal reduction, and 5-mm occluso-gingival height. Sixteen unprepared premolars served as controls. Forty-eight all-ceramic crowns (Vita Mark II) and 48 millable composite resin crowns (MZ100 Block) were fabricated using a CAD/CAM system (Cerec 3). Three luting agents-RelyX ARC (RX), GC Fuji CEM (FC), and zinc phosphate cement (ZP)-were used for cementation (n = 16). After 1-week storage in water, half of the specimens (n=8) in each subgroup were cyclically loaded and thermal cycled under wet conditions for 600,000 masticatory cycles and 3500 thermal cycles (58 degrees C/4 degrees C; dwell time, 60 seconds) in a masticatory simulator; the other half (n = 8) were fractured without cyclic loading. All specimens were loaded in a universal testing machine with a compressive load (N) applied along the long axis of the specimen at a crosshead speed of 1 mm/min until fracture. Fracture loads (N) were recorded for each specimen. Three-way analysis of variance was used to detect the effects of the experimental factors (crown material, luting agent, and loading conditions) on the fracture load. The comparison with the unprepared natural teeth as controls was done by means of t tests (alpha=.05). RESULTS: Analysis of variance revealed a statistically significant influence of the luting agent and the cyclic loading (P < .001), whereas the crown material had no significant influence. Cyclic loading fatigue significantly decreased the mean fracture load of test groups independent of the 3 luting agents used: MZ100/ZP, 827.1 to 552.5 N; MZ100/FC, 914.7 to 706.2 N; MZ100/RX, 955.9 to 724.4 N; Vita/ZP, 772.3 to 571.5 N; Vita/FC, 923.6 to 721.1 N; and Vita/RX, 929.1 to 752.7 N. However, there was no significant difference in the mean fracture load of control specimens before and after cyclic loading (1140.1 N and 1066.2 N, respectively). Adhesive luting agents RelyX ARC and GC Fuji CEM increased fracture load significantly compared to zinc phosphate cement. CONCLUSIONS: Cyclic loading fatigue significantly reduced the fracture loads of composite resin and all-ceramic crowns, whereas adhesive cementation significantly increased the fracture loads.     

Effect of restoration method on fracture resistance of endodontically treated maxillary premolars

PURPOSE: The aim of the present study was to compare the fracture resistance of endodontically treated maxillary premolars with mesio-occlusodistal (MOD) cavities restored using various restorative materials and luting agents. MATERIALS AND METHODS: Eighty extracted human maxillary premolars satisfying certain predetermined criteria were subjected to seven different restoration methods (10 premolars per method). After endodontic treatment, an MOD cavity was prepared in each specimen, and restoration was carried out by one of the following methods: group 1 = control (intact premolars); groups 2 and 3 = restoration using a photo-cure resin composite with and without bonding, respectively; groups 4 and 5 = restoration using a cast-metal inlay with zinc phosphate and adhesive resin cements, respectively; groups 6 and 7 = restoration using a cast-metal onlay with zinc phosphate and adhesive resin cements, respectively; and group 8 = restoration using a hybrid resin onlay. A fracture test was conducted to determine the fracture resistance and fracture mode of each specimen. RESULTS: Fracture resistance was greatest for teeth restored using a cast-metal onlay cemented with adhesive resin cement, but those fractures that did occur were generally unrestorable. Fracture resistance of teeth restored using a cast-metal inlay was also high. Fracture resistance for teeth restored using a resin composite was significantly lower, but the majority of these fractures were restorable. CONCLUSION: Endodontically treated maxillary premolars with MOD cavities could be successfully restored by cast onlay and inlay restorations luted with adhesive resin cement, but their failure mode was often unfavorable.     

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

PURPOSE

All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident.

MATERIALS AND METHODS

Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns.

RESULTS

The mean fracture strengths were as follows: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain.

CONCLUSION

The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.     

FRACTURE RESISTANCE OF WEAKENED TEETH RESTORED WITH CONDENSABLE RESIN WITH AND WITHOUT CUSP COVERAGE

Objectives:

This in vitro study evaluated the fracture resistance of weakened human premolars (MOD cavity preparation and pulp chamber roof removal) restored with condensable resin composite with and without cusp coverage.

Material and Methods:

Thirty human maxillary premolars were divided into three groups: Group A (control), sound teeth; Group B, wide MOD cavities prepared and the pulp chamber roof removed and restored with resin composite without cusp coverage; Group C, same as Group B with 2.0 mm of buccal and palatal cusps reduced and restored with the same resin. The teeth were included in metal rings with self-curing acrylic resin, stored in water for 24 h and thereafter subjected to a compressive axial load in a universal testing machine at 0.5 mm/min.

Results:

The mean fracture resistance values ± standart deviation (kgf) were: group A: 151.40 ± 55.32, group B: 60.54 ± 12.61, group C: 141.90 ± 30.82. Statistically significant differences were found only between Group B and the other groups (p<0.05). The condensable resin restoration of weakened human premolars with cusp coverage significantly increased the fracture resistance of the teeth as compared to teeth restored without cusp coverage.

Conclusion:

The results showed that cusp coverage with condensable resin might be a safe option for restoring weakened endodontically treated teeth.     

Effect of different ferrule designs on the fracture resistance and failure pattern of endodontically treated teeth restored with fiber posts and all-ceramic crowns

Objective

This study investigated the effect of different ferrule heights on endodontically treated premolars.

Materials and Methods

Fifty sound mandibular first premolars were endodontically treated and then restored with 7-mm fiber post (FRC Postec Plus #1 Ivoclar-Vivadent) luted with self-polymerized resin cement (Multilink, Ivoclar Vivadent) while the coronal section was restored with hybrid composite core build-up material (Tetric Ceram, Ivoclar-Vivadent), which received all-ceramic crown. Different ferrule heights were investigated: 1-mm circumferential ferrule without post and core (group 1 used as control), a circumferential 1-mm ferrule (group 2), non-uniform ferrule 2-mm buccally and 1-mm lingually (group 3), non-uniform ferrule 3-mm buccally and 2-mm lingually (group 4), and finally no ferrule preparation (group 5). The fracture load and failure pattern of the tested groups were investigated by applying axial load to the ceramic crowns (n=10). Data were analyzed statistically by one-way ANOVA and Tukey’s post-hoc test was used for pair-wise comparisons (α=0.05).

Results

There were no significant differences among the failure load of all tested groups (P<0.780). The control group had the lowest fracture resistance (891.43±202.22 N) and the highest catastrophic failure rate (P<0.05). Compared to the control group, the use of fiber post reduced the percentage of catastrophic failure while increasing the ferrule height did not influence the fracture resistance of the restored specimens.

Conclusions

Within the limitations of this study, increasing the ferrule length did not influence the fracture resistance of endodontically treated teeth restored with glass ceramic crowns. Insertion of a fiber post could reduce the percentage of catastrophic failure of these restorations under function.     

Fracture strength of teeth restored with all-ceramic posts and cores.

OBJECTIVE: The purpose of this in vitro investigation was to evaluate the fracture strength of endodontically treated teeth restored with different all-ceramic posts and cores. METHOD AND MATERIALS: Seventy-two endodontically treated human maxillary central incisors were divided into 3 groups with 24 teeth each and restored with 1 of the following methods: prefabricated zirconia ceramic posts and resin composite buildups; zirconia ceramic posts and copy-milled alumina ceramic cores (2-piece technique), or copy-milled all-ceramic posts and cores made from a zirconia-reinforced glass-infiltrated alumina ceramic (1-piece technique). Each group was divided into 3 subgroups of 8 samples each, consisting of teeth that did not receive crown restorations and were stored for 60 days, teeth restored with all-ceramic crowns and stored for 60 days, and teeth restored with all-ceramic crowns and subjected to 1.2 million loading cycles with 30 N in a chewing simulator. RESULTS: The mean fracture strengths ranged from 205 to 522 N. Prefabricated zirconia posts and resin composite buildups showed a statistically significantly lower fracture strength after chewing simulation than teeth restored with prefabricated zirconia posts and alumina ceramic cores. CONCLUSION: All-ceramic posts and cores made with the 2-piece technique showed promising fracture strengths under the tested conditions.     

Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar

Lin C-L, Chang Y-H, Chang C-Y, Pai C-A, Huang S-F. Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar. Eur J Oral Sci 2010; 118: 87–93. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The present study evaluated the failure risks of an endodontically treated premolar with severely damaged coronal hard tissue and restored with either a computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic endocrown or a classical crown configuration. Two, three-dimensional finite element maxillary premolar models were designed with endodontic treatment and restored with either a chairside economic reconstruction of esthetic ceramic (CEREC) ceramic endocrown or a classical crown. The Weibull function was incorporated with finite element analysis to calculate the long-term failure probability relative to different load conditions. Additionally, an in vitro fatigue-load fracture experiment was performed to validate the numerical simulation results. The results indicated that the stress values on the dentin and luting cement for the endocrown restoration were lower than those for the crown configuration. Weibull analysis revealed that the individual failure probability in the endocrown dentin and luting cement diminished more than those for the crown restoration. While the overall failure probabilities for the endocrown and the classical crown were similar, fatigue fracture testing revealed that the endocrown restoration had higher fracture resistance than the classical crown configuration (1,446 vs. 1,163 MPa). This investigation implies that the endocrown can be considered as a conservative, aesthetic, and clinically feasible restorative approach for endodontically treated maxillary premolars.     

玻璃陶瓷高嵌体和金属全冠修复根管治疗后下颌前磨牙的抗折强度

目的:比较玻璃陶瓷高嵌体和金属全冠修复经根管治疗后的下颌前磨牙的牙体抗折强度。方法:选择45颗完整的下颌前磨牙,经根管治疗后,随机分为3组。A组以流体树脂垫底,树脂充填作为对照组;B组和C组以流体树脂垫底后,牙体均预备为MOD洞型。B组以树脂充填后,再进行牙体预备,以钴铬合金金属全冠修复;C组牙体预备,以玻璃陶瓷高嵌体黏结修复。将3组标本用万能实验机垂直加载,直至标本发生纵裂,记录各样本牙裂时的最大载荷数值与折裂模式。采用SPSS13.0软件包对数据进行统计学分析。结果:A、B、C组的平均抗压载荷值分别为(234.44±44.36)、(267.11±65.55)、 (314.91±33.67) N。2个实验组与对照组相比差异均有显著性(P<0.05);B组的抗压载荷值高于C组,差异有显著性(P<0.05)。3组样本牙折裂模式两两比较,结果显示组间差异均有显著性(P<0.05)。结论:玻璃陶瓷高嵌体是保护经根管治疗后的下颌前磨牙的较好方法。     

Fracture resistance of endodontically treated maxillary premolars restored with CAD/CAM ceramic inlays

STATEMENT OF PROBLEM: Endodontically treated posterior teeth are more likely to fracture compared to posterior teeth with vital pulps. Reinforcement with an extracoronal restoration that covers the cusps is the most commonly recommended method for reducing the risk of fracture. It is not known whether bonded intracoronal restorations without cuspal coverage will reduce the risk of fracture. PURPOSE: The aim of this in vitro study was to investigate whether reinforcement of endodontically treated premolars with MOD preparations could be achieved by insertion of bonded CAD/CAM ceramic inlays. MATERIAL AND METHODS: Forty-five extracted maxillary premolars were equally distributed among 3 groups (END, CER, CTR). In group END (n=15), root canals were enlarged with a rotary NiTi system and obturated with heat-softened gutta-percha around a plastic carrier (Thermafil). After filling of the endodontic access cavities with autopolymerizing composite resin (Luxacore), standardized MOD cavity preparations were made and CAD/CAM ceramic inlays (CEREC) were fabricated and then bonded to the teeth with composite resin (Tetric) and an adhesive system (Syntac Classic). In group CER (n=15), teeth without endodontic treatment were restored with bonded inlays (CEREC). Sound premolars served as controls (group CTR, n=15). Teeth were then thermal cycled (1445 cycles, dwell time: 30 seconds, 5 degrees /55 degrees C). An eccentric load was applied on the buccal incline of the palatal cusp in a universal testing machine until cusp fracture (N). Fracture load was evaluated with the Mann-Whitney test, and type of fracture, with a chi-square analysis (alpha=.05). The type of fracture was determined by visual inspection: type I - supragingival fracture within the palatal cusp; type II - fracture below cemento-enamel junction of palatal cusp; and type III - fracture of palatal cusp and central portion of the tooth exposing the root canal cavity. RESULTS: No significant difference was found among the 3 groups with respect to load required for fracture. Mean fracture load +/- SD was recorded as follows: 291.6 +/- 113.7 N for group END, 363.2 +/- 140.3 N for group CER, and 296.5 +/- 170.5 N for group CTR. Regarding fracture modes, significantly more teeth from group END exhibited fractures of type III and II compared with control specimens. CONCLUSION: Teeth restored with bonded CAD/CAM ceramic inlays (CEREC) fractured with a significantly higher number of severe fractures compared to the control group.