Retention of a core material supported by three post head designs

STATEMENT OF PROBLEM: There are few studies on the retention of core build-up materials to prefabricated post head designs, especially for a new ceramic post design. PURPOSE: This in vitro study compared the retention of 2 types of core build-up materials (Ti-Core titanium-reinforced composite and a GC Miracle Mix silver-reinforced glass ionomer) supported by 3 post head designs (Flexi-Post, AccessPost, and Cerapost dowel). For all test groups, heads of the posts were placed into the core material at a 90-degree angle to the surface. Test specimens (unloaded) were then placed into a special jig and retention test was performed using an 810 MTS testing machine.Material and Methods: This study consisted of 6 groups with 10 specimens per group. A 3 x 2 factorial design was used to test for statistical significance and results were considered significant when P <.05. RESULTS: Results of the retention test were as follows: group 1, Flexi-Post/Ti-Core 220.0 lb (982.1 N), group 2, AccessPost/Ti-Core 212.7 lb (949.6 N), group 3, Cerapost/Ti-Core 41. 8 lb (186.6 N), group 4, Flexi-Post/Miracle Mix 43.4 lb (193.8 N), group 5, AccessPost/Miracle Mix 61.6 lb (275 N), and group 6, Cerapost/Miracle Mix 7.5 lb (33.5 N). Results of the ANOVA revealed a highly significant difference between posts and cores (P <.0001). CONCLUSION: Post head designs of the stainless steel AccessPost and Flexi-Post dowels offers greater retention then the smooth ceramic head design of the Cerapost dowel. In addition, the composite core material (Ti-Core) offers greater retentive strength values than the glass ionomer material (Miracle Mix).     

Fracture strengths of three core restorative materials supported with or without a prefabricated split-shank post

Purpose. The aim of this study was to compare the fracture strengths of three restorative materials, a lanthanide reinforced composite (Ti-Core Natural), a silver amalgam (Tytin), and a hybrid glass ionomer (Advance), supported by either a multitiered, threaded split-shank post (Flexi-Flange) or with a dentin spur without a post. Material and methods. A total of 60 recently extracted single-rooted human teeth were divided into six groups of 10. All groups were stored at 100% humidity at room temperature for 1 week before testing. Each specimen was placed in a special jig at a 45-degree angle to the buccolingual axis and subjected to a load that was recorded in pounds and converted to Newtons on a universal testing machine, with a crosshead speed of 0.63 cm/minute until failure. Two-way analysis of variance followed by the Newman-Keuls pairwise multiple comparisons test were used to compare the results. Results. There was a statistically significant difference between core materials (p < 0.001), but not regarding post conditions. Ti-Core Natural material had a significantly larger mean failure threshold for fracture than either Tytin silver amalgam or Advance material and the latter two core materials (Tytin and Advance) do not differ from each other. There was no statistical difference between Ti-Core material supported by a post and Ti-Core material supported without a post. (J Prosthet Dent 1997;78:560-5.)     

Effect of design of pre-fabricated posts and post heads on the retention of various cements and core materials

The retention of new Para Post (PP) rounded undercut post head (PP-XT) was compared with the conventional flattened head (PP-P), using amalgam Dentacore and Synergy composite as core materials. The retention of the posts PP (passive serrated), PP-P (passive serrated with venting channels), PP-XP (passive, raised diamond-style pattern) and PP-XT (threaded on the coronal portion, and passive, raised diamond-shaped pattern on the apical portion), cemented with zinc phosphate cement (ZPC) or Duo Cement to extracted teeth, was evaluated. Tensile strength plots were recorded using an Instron instrument, while pulling the post and core in opposite directions. The following conclusions were drawn from this study: (i) The round undercut PP-XT head was more retentive than the PP-P head with both core materials. (ii) Amalgam was more retentive than Synergy with both head designs. (iii) PP-XT was the most retentive post to extracted tooth canals and PP-XP was the least retentive with either ZPC or Duo Cement. Post retention with (iv) ZPC in decreasing order of magnitude: PP-XT > PP-P > PP > PP-XP; and with Duo Cement: PP-XT > PP > PP-P > PP-XP - ZPC exhibited the highest retention of cemented posts.     

Post retention and post/core shear bond strength of four post systems

As clinicians we continue to search for a post system which will give us maximum retention while maximizing resistance to root fracture. The introduction of several new post systems, with claims of high retentive and resistance to root fracture values, require that independent studies be performed to evaluate these claims. This study tested the tensile and shear dislodgment forces of four post designs that were luted into roots 10 mm apical of the CEJ. The Para Post Plus (P1) is a parallel-sided, passive design; the Para Post XT (P2) is a combination active/passive design; the Flexi-Post (F1) and the Flexi-Flange (F2) are active post designs. All systems tested were stainless steel. This study compared the test results of the four post designs for tensile and shear dislodgment. All mounted samples were loaded in tension until failure occurred. The tensile load was applied parallel to the long axis of the root, while the shear load was applied at 450 to the long axis of the root. The Flexi-Post (F1) was significantly different from the other three in the tensile test, however, the Para Post XT (P2) was significantly different to the other three in the shear test and had a better probability for survival in the Kaplan-Meier survival function test. Based on the results of this study, our recommendation is for the Para Post XT (P2).     

纤维树脂桩核固位的研究进展

纤维树脂桩核以其诸多的优点得到越来越多口腔医生的关注和广泛的临床应用。纤维树脂桩核成功应用于临床的重要保证之一是可靠的固位,因此,学者们对纤维树脂桩核的固位进行了大量的研究。本文就近年来有关纤维树脂桩核固位的研究作一综述。     

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牙齿美学修复是口腔临床中的热点,包括纤维增强树脂桩和全瓷桩的牙色桩核也得到了广泛的应用.但是,要做好美学桩核的修复须要严格掌握美学桩核修复的适应证、美学桩核类型选择的原则,以及美学桩核修复中每个操作过程的细节和标准.     

The behaviour of post-retained core materials supported by coronal tooth structure in vitro

This study was designed to investigate the effect of retaining coronal tooth substance on the performance of post-retained core materials, and to compare the fracture resistance of the system with an intact tooth prepared to similar dimensions. Ten teeth restored with post-retained silver amalgam, and 10 teeth restored with silver-glass cermet, all with a retained single wall of coronal tooth substance, were compared with 10 unrestored teeth prepared to similar dimensions when subjected to a shearing load. The results showed no statistically significant difference between the unrestored teeth and those restored with a silver-glass cermet. Whilst the teeth restored with silver amalgam had a significantly higher fracture resistance ( P > 0.01) there was greater tendency to root fracture.     

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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。     

Diametral and compressive strength of dental core materials.

STATEMENT OF PROBLEM: Strength greatly influences the selection of core materials. Many disparate material types are now recommended for use as cores. Cores must withstand forces due to mastication and parafunction for many years. PURPOSE: This study compared the compressive and diametral tensile strengths of 8 core materials of various material classes and formulations (light-cured hybrid composite, autocured titanium containing composite, amalgam, glass ionomer, glass ionomer cermet, resin-modified glass ionomer, and polyurethane). MATERIAL AND METHODS: Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive and diametral strengths with associated standard errors were calculated for each material (n = 10). Analyses of variance were computed (P <.0001) and multiple comparisons tests discerned many differences among materials. RESULTS: Compressive strengths varied widely from 61.1 MPa for a polyurethane to 250 MPa for a resin composite. Diametral tensile strengths ranged widely from 18.3 MPa for a glass ionomer cermet to 55.1 MPa for a resin composite. Some resin composites had compressive and tensile strengths equal to those of amalgam. CONCLUSION: Light-cured hybrid resin composites were stronger than autocured titanium containing composites. The strengths of glass ionomer-based materials and of a polyurethane material were considerably lower than for resin composites or amalgam.     

自制树脂核桩辅助桩核蜡型制作的效果

目的：比较改良的核桩蜡型制作法（简称＂改良法＂）和传统蜡型制作法（简称＂传统法＂）在后牙残根修复中的效果。方法：取单根管的下颌第一前磨牙和双根管的上颌第一前磨牙各10颗,并分为单根管组和双根管组,每组分别用改良法和传统法制作核桩蜡型,统计分析两种方法制作一次性成功率,并分析失败原因。结果：单根管组传统法和改良法一次性成功率分别为20%和77%,差别有统计意义（χ2=16.88,P〈0.01）,双根管组两种方法一次制作成功率分别为11%和63%,差别也有统计意义（χ2=17.01,P〈0.01）。传统法失败的原因依次为：侧壁缺损、颈部折断和长度不足,改良法则为：侧壁缺损和长度不足。结论：无论在单根管组还是在双根管组,改良的核桩蜡型制作法的一次性成功率高于传统方法,同时能保证核桩长度及和根管壁的密合性,适于后牙残根的修复,能给临床医师和技师带来便利。     

纤维桩核修复牙体大面积缺损的临床疗效观察

目的：观察纤维桩核加烤瓷冠或金属桩核加烤瓷冠修复牙体大面积缺损的临床疗效。方法：将228颗经过完善根管治疗的牙体大面积缺损的患牙随机分为两组,实验组109颗植入纤维桩后行烤瓷冠修复,对照组119颗植入成品自攻金属桩钉后行烤瓷冠修复。经18个月随访,通过X线牙片和临床检查以成功和失败作为判断标准,统计分析结果。结果：实验组108颗修复体及基牙完好,成功率99．1％;对照组112颗修复体及基牙完好,成功率94．1％。结论：目前运用纤维桩进行残根残冠修复,操作快捷方便并具有良好的生物相容性,可作为牙体大面积缺损的主要修复手段。     

Comparison of three core buildup materials used in conjunction with two post systems in endodontically treated anterior teeth

Fifty extracted maxillary central incisors with the crowns removed 1 mm coronal to the labial cementoenamel junction were endodontically treated. Post spaces were made 7 mm into the roots prior to cementing a 13-mm post with zinc phosphate cement. Twenty-five of the teeth were restored using a #6 (0.060-inch) Para-Post, and the remaining 25 teeth were restored with a #6 Para-Post Plus. Three core buildup materials, Ketac-Silver, Miracle Mix, and Tytin alloy were used in conjunction with the posts. Cast gold copings 10 mm in height with 1 mm collar on the root were cemented to the buildups. The teeth were loaded to failure at 130 degrees to the long axis of the root from the lingual with an Instron testing machine. The mean failure load of all of the teeth in this study was 21.6 kg. All of the teeth failed when the posts dislodged from the canals. The Para-Post Plus was not significantly more retentive than the Para-Post. No failures occurred within the buildup materials. No significant differences were demonstrated between the mean failure loads of the different buildup materials. Increased buccolingual root diameter, however, had a positive correlation (r = 0.46) with higher failure loads which was statistically significant (p less than 0.001).     

Comparison of two heat-pressed all-ceramic dental materials

OBJECTIVES: The processing route for two heat-pressed all-ceramic materials (Empress and OPC) is virtually identical. The purpose of this study was to determine the mechanical properties of both materials and determine if significant differences exist between them. METHODS: X-ray powder diffraction of the ceramics before and after processing was carried out to identify the crystal phases present. The mechanical properties of both materials were tested. Specimens were tested for hardness, fracture toughness (indentation method) and flexural strength (biaxial method). The results were statistically evaluated and tested for differences using a Mann-Whitney test. Secondary electron imaging of both materials was carried out before and after processing. RESULTS: X-ray powder diffraction revealed that OPC changes as a result of heat-pressing from being a complex mixture of crystalline oxides to a glass-ceramic. In contrast Empress is a glass-ceramic before and after processing. X-ray diffraction identified leucite as the main crystalline phase in both ceramics. The biaxial flexural strength of OPC was 153.6 (17.8) MPa and for Empress was 134.4 (11.5) MPa. The hardness of OPC was 7.28 (0.62) GPa and for Empress was 6.94 (0.79) GPa. Indentation fracture toughness of OPC was 1.36 (0.29) MPam0.5 and for Empress was 1.33 (0.08) MPam0.5. Secondary electron images show Empress to be the same before and after processing while OPC is clearly very different. Empress also appears to have a higher glass content compared with OPC. SIGNIFICANCE: The results of X-ray diffraction show that Empress is pre-cerammed whilst OPC is not. Statistical analysis revealed that no significant difference exists between the two materials for any of the mechanical properties tested at a 95% (p < 0.05) confidence level. It was concluded that no difference exists between the two materials on completion of processing.     

Effect of prefabricated metal post-head design on the retention of various core materials

Retention of various post heads to core restorative materials is an important factor in the selection of prefabricated post systems and restorative materials for the restoration of endodontically treated teeth. This study examines the retention of a post-core prefabricated system in relation to core material and post-head design. A total of 60 samples were prepared using two different post systems (ParaPost Plus (PP) and ParaPost Unity (PU), with amalgam, composite or glass-ionomer as one of the core materials. The samples were tested using the Instron testing machine. The PP was superior to the PU prefabricated post with respect to the retention of various core materials. Retention values in descending order of magnitude were found to be: composite, amalgam and glass-ionomer (significantly lower). The rhomboid serrated design of PP was superior in retention to the rounded smooth UP system. Composite material proved to be superior in retention, closely followed by amalgam, with glass-ionomer significantly less retentive.     

Bond integrity of dental core materials to esthetic intraradicular posts

Bond strengths between various materials for endodontic post-core buildups are unknown. The study determined the diametral tensile strength of three esthetic post systems bonded directly or indirectly to four core materials, and subsequent scanning electron microscopy was performed on the fractures. Cylindric core buildup was made around the parallel-sided section of the posts using a custom-made jig. Strength was tested after 14 days. A significant difference was found between the control group and the other groups (P = .0001). SEM observations were in agreement with the results. Apart from the control group, the results suggested that directly and indirectly performed post-core buildups have similar diametral tensile strength values.