The impact of print orientation on the fracture resistance and failure patterns of additively manufactured cobalt-chromium post and cores

Purpose

The aim of this study was to evaluate the impact of the print orientation of direct metal laser sintering (DMLS) posts and cores on the fracture resistance and failure patterns of endodontically treated mandibular premolar teeth.

Materials and Methods

Sixty intact human mandibular premolars were endodontically treated. The teeth were then randomly divided into four groups (n = 15). Cobalt-chromium (Co-Cr) metal posts were fabricated by traditional casting (Group C), and DMLS method in 0-, 45-, and 90-degree print orientations (Group DMLS 0, Group DMLS 45, and Group DMLS 90). The posts and cores were cemented with composite resin cement and subjected to compression test at a crosshead speed of 1 mm/min. Data was analyzed by using one-way analysis of variance ANOVA and multiple comparison post hoc Tukey tests (α = 0.05). Specimens were viewed under a stereo microscope with x20 magnification to evaluate the fracture types.

Results

No significant differences were found among the groups tested in terms of fracture resistance (p > 0.05). Group C and Group DMLS 0 group exhibited similar fracture patterns.

Conclusions

It is possible to produce post and core restorations with the DMLS technique and use them clinically.  Print orientation did not influence the fracture resistance. However, fracture patterns were different. Group C outperformed all DMLS groups in terms of fracture patterns.     

U.M.Aestheti Plus纤维桩修复牙体缺损的临床研究

目的 观察U.M.Aestheti Plus纤维桩修复牙体缺损12～30个月的临床效果。方法 选择31例使用过U.M.Aestheti Plus纤维桩修复的患者进行调查,总共35颗牙齿,临床使用期平均21个月,检查记录修复体的牙周情况、X线片和修复效果。结果 有2例修复体发生桩核折断,U.M.Aestheti Plus纤维桩修复的成功率为94%,牙周检查显示:U.M.Aestheti Plus纤维桩修复的牙齿与对照牙无显著性差异。结论 一般情况下,U.M.Aestheti Plus纤维桩可以用于牙体缺损的修复。     

Analysis of Fracture Resistance of Endodontically Treated Teeth Restored with Different Post and Core System of Variable Diameters: An In Vitro Study

The restoration of endodontically treated teeth requires the fabrication of a post and core; to provide retention and support for the final crowns. The purpose of this study was to evaluate fracture resistance of endodontically treated teeth restored with prefabricated zirconia post (CP), milled zirconia post (MZ), pressable ceramic post (PC) and cast metal post (Ni–Cr) of 1.4 and 1.7 mm diameter. 48 freshly extracted human maxillary central incisors were used for this study. The teeth were distributed in four groups of 12 teeth each. From each group, 6 teeth were selected for 1.4 mm diameter post and rest of the 6 teeth, is selected for 1.7 mm diameter post. All teeth were restored with metal crowns. Each specimen from the group was subjected to “load to fracture” in universal testing machine at 130° angle and the maximum load at failure was recorded. Statistically significant difference was found between the failure load of the groups studied. In group I (Ni–Cr)—1.4 mm diameter post and core recorded a maximum fracture load of 534.83 ± 1.28 N and 1.7 mm diameter post and core showed 294.33 ± 1.02 N. In group II (PC)—1.4 mm diameter post and core recorded a maximum fracture load of 205.33 ± 1.61 N and 1.7 mm post and core showed 375.00 ± 1.57 N. In group III (CP)—1.4 mm diameter post and cores recorded a maximum fracture load of 313.00 ± 0.73 N and 1.7 mm post and core showed 638.67 ± 0.81 N. In group IV (MZ)—1.4 mm diameter post and cores recorded a maximum fracture load of 312.00 ± 0.86 N and 1.7 mm post and core showed 415.00 ± 0.89 N. Prefabricated zirconia post (1.7 mm) with pressable ceramic core (Cosmo post)—exhibited higher fracture resistance. Milled zirconia and prefabricated zirconia post—showed same value with 1.4 mm diameter post. Pressable ceramic post and core showed satisfactory result with 1.7 mm post, but showed lesser values with 1.4 mm diameter post.     

银汞桩核与分体式铸造桩核用于磨牙修复的疗效对比观察

目的:比较银汞桩核和分体式铸造桩核用于修复磨牙严重缺损病例的临床疗效.方法:将78例磨牙牙体严重缺损病例随机分为银汞桩核修复组40个牙和分体铸造桩核修复组41个牙,并随访观察2～3年.结果:两种桩核修复的临床疗效无显著差异(P＞0.05).结论:银汞桩核和分体式铸造桩核用于修复牙体严重缺损的磨牙都能取得较好的临床效果.     

Restoring a Failed Prefabricated Post and Core With a Sleeve Casting: A Clinical Report

A clinical case is described, and a technique is explained for making a custom sleeve cast post and core to salvage a fractured crown previously treated with an unretrievable prefabricated post. The restorative problem was to design and fabricate some sort of cast post and core that could be cemented to the remaining post. The amalgam and cement in the pulp chamber and coronal portion of the root canal were carefully removed so that a direct pattern could be made to form a tube which would surround the coronal part of the existing post like a sleeve. This sleeve casting was designed to provide attachment for a core to support a new restoration. This direct pattern technique results in a retained core that joins the already cemented post and provides a sound core for the retention of a new crown.     

3种预成桩与4种核成型材料的结合力比较

目的 比较3种不同材质的预成桩钉与4种核成型材料的结合力.方法 预成不锈钢桩、玻璃纤维树脂桩和渗透陶瓷桩分别与ParaCore、Clearfill、Durafill和F2000复合体核材料结合,测试不同桩-核材料间的结合力并对其进行比较.结果 3种预成桩中,具有机械固位设计的不锈钢桩组与树脂核的结合力最高;4种成核材料与桩的结合力分别是ParaCore组和Clearfill组高于Durafill组和F2000复合体组,F2000复合体与桩的结合力最低.结论 临床选用桩时可考虑利用机械锁结固位,并通过表面粗糙化处理来增加桩-核的结合;采用结合力强、流动性好的树脂材料成核,可获得更好的桩-核结合效果.     

桩核粘结剂的有限元优化设计分析

目的：利用Ansys的Design Xplorer模块分析桩核粘结剂对牙根牙本质应力状况的影响。方法：将桩核粘结剂的弹性模量（变量W）和粘结,层厚度（变量H）同时设为优化目标,进行双目标稳健分析,研究其对牙根应力峰值（EQV）的影响。结果：W在7.5-14.5GPa之间变化时,EQV变化幅度为0.8%;W在1-7.5GPa之间时,EQV变化幅度为8.3%;W在14.5-20GPa之间时,EQV变化幅度为4.5%。当W取中间值,H在0.01-0.30mm之间时,EQV变化幅度仅为3.0%。W对牙根EQV应力峰值的敏感度为96.5%,H敏感度为3.5%。结论：桩核粘结剂对牙根的应力影响主要取决于其弹性模量;当桩核粘结剂的弹性模量在7.5-14.5GPa之间时,牙根应力值较小。     

玻璃纤维桩核与铸造金属桩核修复残根残冠及无桩修复牙体的临床效果评价

目的 评价玻璃纤维桩核与铸造金属桩核修复残根残冠及无桩修复根管治疗后残冠的生存率和并发症。方法 96名患者共142颗患牙进行根管充填,然后依据不同的情况进行玻璃纤维桩核、铸造纯钛桩核、无桩固位的 冠修复。结果 在89名患者的135颗牙齿中,73颗牙齿（54.1%）使用玻璃纤维桩修复、复合树脂桩核,最后进行金瓷冠或全瓷冠修复,在（5.7±1.9）年平均观察期内的留存率达到97.3%;40颗牙齿采用铸造纯钛桩核修复,在（6.2±2.2）年平均观察期内的留存率达到了87.5%;22颗牙齿采用无桩修复,在（5.4±1.8）年平均观察期内的留存率是90.9%。玻璃纤维桩、铸造纯钛桩核、无桩修复的患牙三者间的成功率差异无统计学意义。修复最常见的并发症包括：根折（6.7%）、固 位丧失（2.2%）、继发龋（1.5%）、根尖周炎（0.7%）。结论 在实施高质量的根管治疗和规范的修复操作技术的前提下,无论是玻璃纤维桩修复还是铸造金属桩核修复或无桩修复的基牙在超过5年的观察期内均能获得较高的留存率, 但并发症尤其是根折裂应引起必要的重视。     

桩核冠修复材料对牙体应力的影响

目的：通过不同的桩核冠材料修复牙的牙体应力分析，为临床选择修复材料提供生物力学依据。方法：建立上中切牙桩核修复的三维有限元模型，分别分析金合金桩核-镍铬全冠、金合金桩核-金合金全冠、金合金桩核-陶瓷全冠和镍铬桩核-镍铬全冠、镍铬桩核-金合金全冠、镍铬桩核-陶瓷全冠6种情况下牙体应力的情况。结果：镍铬合金桩核组牙体内最大Von Mises应力为113.70MPa，金合金桩核组为74.03MPa，较前者降低了34.89％。结论：桩核材料对牙体应力分布和应力峰值的影响明显，而冠材料对牙体应力的影响不大。用弹性模量较低的桩核材料进行修复有助于降低牙体折裂的可能性。     

不同粘固材料对纤维桩固位力的影响

目的：研究纤维桩钉在用5种不同粘固材料的固位力,为临床选择纤维桩粘固材料提供依据。方法：将纤维桩用5种粘固材料（HY-BOND玻璃离子水门汀;PermaCem双固化树脂水门汀;LuxaCore双固化树脂;Dulink双固化树脂水门汀;Rely-X Unicem双固化树脂水门汀）粘固于离体人牙根管内,万能电子力学试验机测试其固位力,电子探针分析界面情况。结果：纤维桩在用不同粘固材料的固位力由大到小顺序为：Dulink组、PermaCem组、LuxaCore组、Rely-X Unicem组、HY—BOND玻璃离子组,各组间固位力有显著性差异（P〈0．05）。结论：不同类型粘固材料对纤维桩的粘结力不同,树脂水门汀固位力优于玻璃离子水门汀,且显示了良好的粘结完整性。     

桩道预备及桩核修复对根尖封闭性的影响

目的比较即刻、延迟桩道预备及桩核修复对根尖封闭性的影响。方法选择60颗离体下颌单根管前磨牙,使用ProTaper镍钛锉和冠向下法进行根管预备。将样本分为5组,除阳性对照组外其余样本均用AH-Plus封闭剂、侧方加压法进行根管充填。A组为即刻桩道预备组,B组为延迟桩道预备组,C组为无桩道预备组,D组为阳性对照组,E组为阴性对照组。其中A、B组再各分为2个亚组,A1、B1组为桩道预备后采用暂封材料封闭,A2、B2组为桩道预备后立即行纤维桩核修复。使用印度墨水染色法测定各组牙齿的根尖微渗漏情况,体视显微镜下测量染料渗入根管内壁的长度,并行统计学分析。结果A1、A2、B1、B2、C组染料渗入长度分别为（0.52±0.47）、（0.49±0.44）、（1.17±0.77）、（1.12±0.54）、（0.23±0.40）mm,阳性对照组染料渗入根管全长,阴性对照组无染料渗入。经统计学分析,A1与A2、B1与B2组间染料渗入长度没有统计学差异（P>0.05）;但B1、B2组的染料渗入长度与A1、A2、C组间的差异有统计学意义（P<0.05）,B组渗入长度较长;A1、A2和C组间的差异无统计学意义（P>0.05）。结论延迟桩道预备会削弱充填材料及AH-Plus封闭剂封闭根尖的能力。     

根管治疗后玻璃纤维桩使用适应症的临床研究

目的:评价根管治疗后患牙放置玻璃纤维桩与否对修复后长期成功率的影响.方法:临床上选择87例患者共119颗患牙,经完善的根管治疗后,根据剩余牙冠组织多少将患牙分成3组:两壁组,单壁组和无壁组,每组再按是否使用玻璃纤维桩随机分为两个亚组,之后患牙行金属烤瓷冠修复.并经过3年的临床疗效的追踪观察.结果:3年后总的总的成功率为...     

Effect of endodontic sealers on dowels luted with resin cement

PURPOSE: This study evaluated the retention of prefabricated parallel-sided dowels luted with resin cement in extracted teeth that were obturated with gutta percha using a eugenol sealer or a calcium hydroxide sealer. MATERIALS AND METHODS: Extracted maxillary incisor roots (N = 51) were instrumented to simulate conventional root canal therapy and divided into 3 groups (n = 17). One group was not obturated. Second and third groups were obturated with gutta percha using a eugenol-containing or calcium hydroxide-containing sealer. Gutta percha was removed using a heated plugger, and dowel spaces were prepared to a 7 mm depth. Dowel space walls were acid etched and primed, and prefabricated stainless steel dowels were luted using resin cement. After 24 hours, the load required to dislodge each dowel along a path parallel to its long axis was measured and recorded. A one-way analysis of variance (alpha = 0.05) was performed to identify differences in the means among groups. The incidence of failure within the cement or at the dentin-cement interface was also recorded. RESULTS: No statistically significant difference was found among the control (159.9 +/- 96.3 N), eugenol sealer (153.1 +/- 77.3 N), and calcium hydroxide sealer (192.0 +/- 89.3 N) groups. Nearly all specimens displayed adhesive failure at the dentin-resin cement interface. CONCLUSIONS: Conventional endodontic obturation using a eugenol-containing or a calcium hydroxide-containing endodontic sealer did not affect retention of prefabricated stainless steel dowels luted with resin cement.     

应用预成弹性印模桩临床制取桩核印模的初步观察

目的：评估本课题组自主研制的预成弹性印模桩临床制取桩核印模的效果。方法：用预成弹性印模桩法(实验组)和传统方法(对照组)分别对70颗牙体大面积缺损、根管治疗后要求桩核冠修复的单根管患牙各制取桩核印模,观察两种方法制取桩核印模的完整性。结果：实验组和对照组印模桩核区印模缺陷的发生率分别为44.29%、74.29%,两者之间的差异有统计学意义(P<0.01);实验组和对照组印模缺陷在根尖部的发生率分别为2.96%、41.43%,两者之间的差异有统计学意义(P<0.01);实验组和对照组印模缺陷在桩体部的发生率分别为4.29%、35.71%,两者之间的差异有统计学意义(P<0.01);实验组和对照组桩核印模的可用率分别是93.75%、60.00%,实验组的临床可用率显著高于对照组,两者之间的差异有统计学意义(P<0.01)。结论：应用预成弹性印模桩制取桩核印模能够提高印模桩核区的完整性。     

两种纤维桩短期修复效果的临床观察

目的 观察两种玻璃纤维桩修复系统修复牙齿缺损的短期临床疗效。方法 选择北京宣武中医医院口腔科门诊和北京大学口腔医院特诊科因牙体缺损进行桩核冠修复的符合纳入标准的120例患者,经知情同意后,随机分2组,每组 60例,分别采用 Tenax Fiber White纤维桩与国产 OUYA FIBER纤维桩修复系统修复,修复后 1周与 3个月复诊,检查纤维桩修复的临床效果。结果 Tenax Fiber White纤维桩与OUYA FIBER纤维桩修复1周后,检查纤维桩修复体的总体情况、边缘密合性、边缘着色情况,两组满意率均达到 98%以上;3个月后复查,通过 X线片检查纤维桩的总体情况和基牙情况,以及咀嚼功能恢复情况,两组满意率均达到 96%以上;2组间比较差异无统计学意义（P>0.05）。结论 OUYA FIBER纤维桩与Tenax Fiber White纤维桩在3个月的观察期间的总体疗效相当,值得推广应用,但仍需对其疗效进行长期的临床观察。     

国产碳纤维桩三点弯曲实验

目的：比较国产碳纤维桩与进口碳纤维桩和镍铬合金铸造金属桩在弯曲强度方面的差异,为国产碳纤维桩的临床应用提供理论依据.方法：将中科院化学所提供直径为1.5mm的碳纤维桩放置在100kN WDW4100微机控制电子万能实验机上,在与桩垂直的方向上加力,直致材料断裂,记录最大载荷值.同时,用相同直径的进口碳纤维桩和镍铬合金铸造金属桩做对照组进行对比实验.结果：国产碳纤维桩的弯曲强度1837.5393±227.4421MPa,进口碳纤维桩的弯曲强度1247.9500±77.4050 MPa,镍铬合金铸造金属桩的弯曲强度909.7943±69.7955 MPa.结论：国产碳纤维桩的弯曲强度大于临床常用镍铬合金铸造金属桩的弯曲强度,因此能够满足临床要求.     

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目的    观察玻璃纤维桩加树脂核和铸造镍铬金属桩核修复上颌前磨牙的临床效果。方法    对2005年3月至2007年7月在北京市通州区新华医院口腔科行上颌前磨牙桩核冠修复的143例患者的176颗患牙,随机分为A、B两组,各88颗。分别使用玻璃纤维桩加树脂核和铸造镍铬金属桩制作桩核,然后用烤瓷全冠进行修复,随访2年,观察比较临床效果。结果    A组成功86颗,失败2颗,成功率97.7%;B组成功85颗,失败3颗成功率96.6%。两组修复成功率差异无统计学意义（P＞0.05）。结论    玻璃纤维桩加树脂核和铸造金属桩核修复上颌前磨牙,临床效果基本相同。但玻璃纤维桩在失败后的再次修复方面具有铸造桩核不能比拟的优势,因此在上颌前磨牙的桩核修复方面首选玻璃纤维桩。     

国产碳纤维桩修复离体牙抗折力实验

目的:比较国产碳纤维桩与进口碳纤维桩、镍铬合金铸造金属桩修复的离体牙在抗折力方面的差异,为国产碳纤维桩的临床应用提供理论依据。方法:将因牙周病拔除的上颌尖牙,去除牙冠后,用国产碳纤维桩 树脂核 金属冠修复后放置在万能实验机上,加载与牙长轴呈135°角的压力,直至修复体折断,记录最大载荷,同时用进口碳纤维桩、镍铬合金铸造金属桩做对照组,进行对比实验。结果:国产碳纤维桩的抗折力1152.200±282.9023N,进口碳纤维桩的抗折力1368.100±402.5478N,镍铬合金铸造金属桩的抗折力1210.4±422.7217N。结论:国产碳纤维桩修复离体牙的抗折力,与临床常用的镍铬合金铸造金属桩修复离体牙的抗折力无显著差异,能够满足临床要求。     

纤维桩主辅桩在喇叭口状根管桩核修复中的临床效果观察

目的：评价纤维桩主辅桩十全瓷冠修复喇叭口状残冠残根的临床效果。方法：选择28例患者37颗需修复的喇叭口状单根管残冠残根为研究对象。患牙经根管治疗后行纤维桩主辅桩＋复合树脂核及全瓷冠修复,于修复完成后随访18-26个月,评价修复体完整性、边缘适合性、牙周及根尖周组织健康状况等。结果：37个修复体完整,成功率100％;冠边缘适合性好达91．89％,可接受8．11％;色泽匹配好达75．68％;牙龈状况好达83．79％;纤维桩及树脂核无松动、折裂、缝隙等;根尖未见异常,无根折发生。结论：纤维桩主辅桩系统临床修复喇叭口状残冠残根取得良好的临床效果,可作为保存此类残冠残根简便有效的修复方式。