光照射后固化对于大块充填树脂性能的影响

光照射后固化因为有利于大块充填树脂各种性能的提高,日益引起关注.其中光照射后固化对于提高复合树脂双键转化率、增加硬度、减小聚合收缩应力均有较好的效果.温度、光固化反应的双键转化率、树脂组成成分和浸泡溶剂等因素都可以影响大块充填树脂的光照射后固化.本文将对以上内容及其对临床意义进行综述.     

大块充填树脂的研究进展

目前大块充填树脂已经越来越广泛应用于临床。一次4-6mm的固化深度是大块充填树脂最突出的优点,便于临床操作。树脂的聚合收缩和边缘微渗漏及性能的长期稳定性与材料的临床应用效果密切相关。如何保证树脂具有较高的固化深度,较低的聚合收缩和边缘微渗漏,以及临床效果评价是大块充填树脂的研究热点,本文将对上述方面的研究进展进行综述。     

树脂类根管封闭剂粘接耐久性的研究进展

树脂类封闭剂是新型的根管充填封闭剂,具有良好的牙本质粘接能力、稳定的理化性和较好的生物相容性等优点,但因其聚合收缩、吸水降解等缺点使其在长期的口内功能状态下对根管的密闭性能受到影响,进而导致根管治疗失败.通过检测不同树脂类封闭剂与根管牙本质粘接耐久性,筛选粘接耐久性较好的封闭剂可提高根管治疗成功率.     

大块充填复合树脂修复后的临床效果的研究进展

目前大块充填复合树脂逐渐应用于牙科治疗中,一些研究发现其除了具有操作简单的优势外,还具有良好的临床效果。单体转化率是反映树脂固化程度的重要指标,也是决定树脂的机械性能和生物学性能的重要因素。牙尖变形、边缘微渗漏是由于复合树脂的聚合收缩产生的收缩应力造成的,对充填体的耐久度、边缘封闭性有一定的影响,可以认为是衡量树脂粘接修复后的临床效果的常见指标。该文主要通过单体转化率、牙尖变形和边缘微渗漏这三方面对大块充填复合树脂修复后的临床效果以及原因机理做一个总结描述。     

复合树脂聚合收缩应力的研究进展

复合树脂作为常用的牙色充填材料,具有美观、操作方便等优点,但也存在聚合收缩、不耐磨、变色等问题.其中,聚合收缩可引起充填复合树脂与牙体之间形成间隙、釉质裂纹和牙尖移动,导致充填失败.影响收缩应力大小的因素包括复合树脂的组成、窝洞形态和临床操作.通过减小聚合收缩应力可提高复合树脂充填的成功率.     

3种树脂材料修复离体牙Ⅱ类洞的边缘裂隙和 微渗漏比较

目的 研究3种树脂材料修复离体牙Ⅱ类洞的边缘裂隙及微渗漏情况。方法 选取符合纳入标准的60颗离体磨牙,随机分为大块充填树脂组、传统树脂组和树脂嵌体组3组,每组20颗。制备Ⅱ类洞,并按照其充填或制作标准进行修复。扫描电镜下测量边缘裂隙宽度,经1%亚甲蓝染色,去除面2.0 mm釉质,抛光后在体式显微镜下观察边缘染色深度。结果 树脂嵌体组的边缘裂隙最小,大块充填树脂组次之,传统树脂组最大,差异具有统计学意义(P<0.05);树脂嵌体组的染色深度明显小于大块充填树脂组和传统树脂组,差异具有统计学意义(P<0.05);大块充填树脂组与传统树脂组间染色深度差异无统计学意义(P>0.05)。结论 从修复体的边缘裂隙和微渗漏两个方面来看,树脂嵌体效果良好,值得临床推广应用。     

低聚合收缩树脂修复楔状缺损的临床疗效观察

目的;评估采用低聚合收缩树脂FiltekTM P90修复楔状缺损的临床疗效.方法:选择52例患者、共180颗楔状缺损患牙,采用自身对照设计,随机选择每例患者的一侧患牙为实验组,采用FiltekTM P90树脂充填;对侧同名牙为对照组,直接采用FiltekTM Z350 XT树脂充填.对所有楔状缺损修复体于修复后半年、1年进行对比观察.采用改良美国公共卫生署直接临床评价系统(USPHS)比较2组修复体的质量,采用SPSS19.0软件包对数据进行x2检验,评价FiltekTM P90树脂充填楔状缺损的临床效果.结果:治疗后半年复查,实验组成功率为96.55％,对照组为95.40％.治疗后1年复查,实验组成功率为94.05％,对照组为90.48％.半年及1年复查结果显示,在成功率、固位、边缘着色、边缘密合性、表面形态、色泽协调性、继发龋、牙髓反应等方面,实验组与对照组差异无统计学意义(P＞0.05).结论:FiltekTM P90树脂充填楔状缺损能够取得良好的临床效果,值得推广应用.     

四种复合树脂充填修复磨牙的临床评估

目的:采用改良的USPHS评价标准和扫描电镜,评估4种复合树脂充填修复磨牙的临床效果。方法:选择4种复合树脂(通用型树脂3M Filtek Z350 XT和Dentsply Spectrum TPH3,后牙专用型树脂3M Filtek P60和大块树脂Voco X-tra fil)充填修复后牙I类洞缺损,在充填术后1、12个月,采用USPHS分级评价标准评估其临床效果。同时在扫描电镜下进一步观察充填体的表面微观形貌。结果:术后1月,大块树脂组在颜色匹配性能上显著逊色于3种传统树脂组(P<0.05),其余性能指标方面4组无统计学差异(P>0.05)。术后12月,大块树脂各项性能显著逊色于其余3组(P<0.05);大块树脂各项指标均显著下降(P<0.05),而其余3组各项指标无显著下降(P>0.05)。扫描电镜观察显示,Z350组表面最光滑,X-tra组表面较粗糙。结论:大块树脂在各方面性能指标上的长期效果均不如传统分层充填树脂,尤其表现在颜色匹配性上。     

3种大块后牙充填树脂体外操作时间与微渗漏的对比观察

目的以传统分层充填树脂为对照比较3种大块充填后牙树脂体外充填所用时间及微渗漏的情况。方法选取符合纳入标准的第三磨牙40颗于面统一制备4 mm×4 mm×4 mm的Ⅰ类洞,随机分成A、B、C、D四组,分别用Sonic Fill超声充填树脂,Sure Fil SDR整层充填流动树脂,Tetric N-Ceram bulk Fill大块充填树脂,Filtek Z350后牙树脂充填,记录每次充填完成的时间,充填样本经冷热循环实验后置于印度墨水中浸泡24 h,干燥后沿样本近远中向剖开,于体视显微镜下观察样本染料渗入深度,并测量计数,进行统计学分析。结果四组操作时间的差异比较,A、B组差异无统计学意义(P>0.05),其余各组两两比较差异均有统计学意义(P<0.05),C组耗时最少,传统分层充填D组耗时最多。四组微渗漏均有发生,数值差异无统计学意义(P>0.05)。结论 3种后牙大块充填树脂均可达到与传统分层充填相同的边缘封闭性,且较后者操作时间短,操作简单。     

充填厚度对光固化大块复合树脂充填效果的影响

目的 研究充填厚度对大块复合树脂充填效果的影响.方法 2种大块充填树脂Filtek Bulk Fill Posteri-or(FBF)和Tetric N-Ceram Bulk Fill(TBF)为实验组,2种传统光固化复合树脂Filtek Z100(Z100)和Spec-trum TPH(ST)为对照,测试不同固化厚度...     

Clinical performance and chemical-physical properties of bulk fill composites resin —a systematic review and meta-analysis

Objectives: The objective of this study was to perform a meta-analysis of clinical and laboratory studies to compare the performance of bulk-fill and conventional composite resins in terms of polymerization shrinkage, polymerization stress, cusp deflection, marginal quality, degree of conversion, microhardness, flexural strength, fracture strength and clinical performance. Data: One hundred three articles were included in this study, and the Peto method was used to compare the bulk-fill and conventional composites using the RevMan software. Sources: Searches were performed in the PubMed and Scopus databases. Study selection: Laboratory studies and randomized clinical trials comparing one of the previous detailed outcomes between bulk-fill and control composites were included. Conclusions: The bulk-fill composite resins showed less shrinkage, polymerization stress, cusp deflection and microhardness than conventional composites, while both materials presented a similar marginal quality, flexural strength and fracture strength. Also, bulk-fill materials with regular viscosity showed similar shrinkage. The conversion of bulk-fill materials with flowable consistency were similar to conventional composite resins with a thickness of up to 2 mm and greater than conventional composites with a thickness greater than 2 mm. Despite these in vitro differences, the clinical performance of bulk-fill and conventional composite resins was similar in randomized clinical trials, with one to ten years of follow up. In conclusion, the bulk-fill materials show better or similar performance to the conventional materials in clinical trials and laboratory studies in terms of volumetric shrinkage, polymerization stress, cusps deflection and marginal quality, with the only exception being the lower level of microhardness observed for bulk-fill composites with thickness up to 2 mm.     

Light and viscosity effects on the curing potential of bulk-fill composites placed in deep cavities

Odontology - To determine the influence of light curing units (LCUs) and material viscosity on the degree of conversion (DC) of bulk-fill (BF) resin-based composites (RBCs) placed in deep cavity...     

A review of polymerization shrinkage stress: current techniques for posterior direct resin restorations

In general excellent results cannot be guaranteed when using resin-based composites for posterior restorations. This is due to polymerization shrinkage which can still be regarded as the primary negative characteristic of composite resins. A review of available literature regarding the polymerization process, its flaws, and suggested strategies to avoid shrinkage stress was conducted. Several factors responsible for the polymerization process may negatively affect the integrity of the tooth-restoration complex. There is no straightforward way of handling adhesive restorative materials that can guarantee the reliability of a restoration. At present, the practitioner has to coexist with the problem of polymerization shrinkage and destructive shrinkage stress. However, evolving improvements associated with resin-based composite materials, dental adhesives, filling, and light curing techniques have improved the predictability of such restorations. This critical review paper is meant to be a useful contribution to the recognition and understanding of problems related to polymerization shrinkage and to provide clinicians with the opportunity to improve the quality of composite resin restorations.     

An alternative method to reduce polymerization shrinkage in direct posterior composite restorations

BACKGROUND: Polymerization shrinkage is one of dental clinicians' main concerns when placing direct, posterior, resin-based composite restorations. Evolving improvements associated with resin-based composite materials, dental adhesives, filling techniques and light curing have improved their predictability, but shrinkage problems remain. METHODS: The authors propose restoring enamel and dentin as two different substrates and describe new techniques for placing direct, posterior, resin-based composite restorations. These techniques use flowable and microhybrid resin-based composites that are polymerized with a progressive curing technique to restore dentin, as well as a microhybrid composite polymerized with a pulse-curing technique to restore enamel. Combined with an oblique, successive cusp buildup method, these techniques can minimize polymerization shrinkage greatly. CONCLUSIONS: Selection and appropriate use of materials, better placement techniques and control polymerization shrinkage may result in more predictable and esthetic Class II resin-based composite restorations. CLINICAL IMPLICATIONS: By using the techniques discussed by the authors, clinicians can reduce enamel microcracks and substantially improve the adaptation of resin-based composite to deep dentin. As a consequence, marginal discoloration, recurrent caries and postoperative sensitivity can be reduced, and longevity of these restorations potentially can be improved.     

Degree of conversion and in vitro temperature rise of pulp chamber during polymerization of flowable and sculptable conventional,bulk-fill and short-fibre reinforced resin composites

ObjectiveDetermine the degree of conversion (DC) and in vitro pulpal temperature (PT) rise of low-viscosity (LV) and high-viscosity (HV) conventional resin-based composites (RBC), bulk-fill and short-fibre reinforced composites (SFRC).MethodsThe occlusal surface of a mandibular molar was removed to obtain dentine thickness of 2 mm above the roof of the pulp chamber. LV and HV conventional (2 mm), bulk-fill RBCs (2–4 mm) and SFRCs (2–4 mm) were applied in a mold (6 mm inner diameter) placed on the occlusal surface. PT changes during the photo-polymerization were recorded with a thermocouple positioned in the pulp chamber. The DC at the top and bottom of the samples was measured with micro-Raman spectroscopy. ANOVA and Tukey’s post-hoc test, multivariate analysis and partial eta-squared statistics were used to analyze the data (p < 0.05).ResultsThe PT changes ranged between 5.5–11.2 °C. All LV and 4 mm RBCs exhibited higher temperature changes. Higher DC were measured at the top (63–76%) of the samples as compared to the bottom (52–72.6%) in the 2 mm HV conventional and bulk-fill RBCs and in each 4 mm LV and HV materials. The SFRCs showed higher temperature changes and DC% as compared to the other investigated RBCs. The temperature and DC were influenced by the composition of the material followed by the thickness.SignificanceExothermic temperature rise and DC are mainly material dependent. Higher DC values are associated with a significant increase in PT. LV RBCs, 4 mm bulk-fills and SFRCs exhibited higher PTs. Bulk-fills and SFRCs applied in 4 mm showed lower DCs at the bottom.     

Comparison of physical and biological properties of a flowable fiber reinforced and bulk filling composites

ObjectiveTo evaluate in vitro the mechanical, biological, and polymerization behavior of a flowable bulk-fill composite with fibers as a dispersed phase.MethodsEverX Flow? (GC Corporation) (EXF), one conventional bulk-fill composite (Filtek? Bulk Fill Posterior Restorative, 3 M (FBF)), and one flowable bulk composite without fibers (SDR® flow+, Dentsply (SDR)) were tested. Samples were characterized in terms of flexural strength (ISO 4049), fracture toughness (ISO 20795-1), and Vickers hardness. Polymerization stress and volumetric shrinkage were evaluated. The in vitro biological assessment was achieved on cultured primary Human Gingival Fibroblast cells (HGF). The cell metabolic activity was evaluated using Alamar Blue assay at 1, 3, and 5 days of contact to the 3 tested composite extracts (ISO 10993) and cell morphology was evaluated by confocal microscopy. Data were submitted to One-Way analysis of variance (ANOVA) and independent t-test (α = 0.05).ResultsFBF showed statistically higher Vickers hardness and flexural modulus than EXF and SDR. However, EXF showed statistically higher K_IC than FBF and SDR. EXF had the statistically highest shrinkage stress values and FBF the lowest. Archimedes volumetric shrinkage showed significantly lower values for FBF as compared to the other two composites. Slight cytotoxic effect was observed for the three composites at day one. An enhancement of metabolic activity at day 5 was observed in cells treated with EXF extracts.SignificanceEXF had a significantly higher fracture toughness validating its potential use as a restorative material in stress bearing areas. EXF showed higher shrinkage stress values, and less cytotoxic effect.Fiber reinforced flowable composite is mainly indicated for deep and large cavities, signifying the importance for assessing its shrinkage stress and biological behavior.     

Future perspectives of resin-based dental materials

ObjectiveThis concise review and outlook paper gives a view of selected potential future developments in the area of resin-based biomaterials with an emphasis on dental composites.MethodsA selection of key publications (1 book, 35 scientific original publications and 1 website source) covering the areas nanotechnology, antimicrobial materials, stimuli responsive materials, self-repairing materials and materials for tissue engineering with direct or indirect relations and/or implications to resin-based dental materials is critically reviewed and discussed. Connections between these fields and their potential for resin-based dental materials are highlighted and put in perspective.ResultsThe need to improve shrinkage properties and wear resistance is obvious for dental composites, and a vast number of attempts have been made to accomplish these aims. Future resin-based materials may be further improved in this respect if, for example nanotechnology is applied. Dental composites may, however, reach a completely new quality by utilizing new trends from materials science, such as introducing nanostructures, antimicrobial properties, stimuli responsive capabilities, the ability to promote tissue regeneration or repair of dental tissues if the composites were able to repair themselves.SignificanceThis paper shows selected potential future developments in the area of resin-based dental materials, gives basic and industrial researchers in dental materials science, and dental practitioners a glance into the potential future of these materials, and should stimulate discussion about needs and future developments in the area.     

Physico-mechanical characteristics of commercially available bulk-fill composites

Objectives

Bulk-fill composites have emerged, arguably, as a new “class” of resin-based composites, which are claimed to enable restoration in thick layers, up to 4 mm. The objective of this work was to compare, under optimal curing conditions, the physico-mechanical properties of most currently available bulk-fill composites to those of two conventional composite materials chosen as references, one highly filled and one flowable “nano-hybrid” composite.

Methods

Tetric EvoCeram Bulk Fill (Ivoclar-Vivadent), Venus Bulk Fill (Heraeus-Kulzer), SDR (Dentsply), X-tra Fil (VOCO), X-tra Base (VOCO), Sonic Fill (Kerr), Filtek Bulk Fill (3M-Espe), Xenius (GC) were compared to the two reference materials. The materials were light-cured for 40 s in a 2 mm × 2 mm × 25 mm Teflon mould. Degree of conversion was measured by Raman spectroscopy, Elastic modulus and flexural strength were evaluated by three point bending, surface hardness using Vickers microindentation before and after 24 h ethanol storage, and filler weight content by thermogravimetric analysis. The ratio of surface hardness before and after ethanol storage was considered as an evaluation of polymer softening. Data were analyzed by one-way ANOVA and post hoc Tukey's test (p = 0.05).

Results

The mechanical properties of the bulk-fill composites were mostly lower compared with the conventional high viscosity material, and, at best, comparable to the conventional flowable composite. Linear correlations of the mechanical properties investigated were poor with degree of conversion (0.09 < R < 0.41) and good with filler content (R > 0.8). Softening in ethanol revealed differences in polymer network density between material types.

Conclusion

The reduction of time and improvement of convenience associated with bulk-fill materials is a clear advantage of this particular material class. However, a compromise with mechanical properties compared with more conventional commercially-available nano-hybrid materials was demonstrated by the present work.

Significance

Given the lower mechanical properties of most bulk-fill materials compared to a highly filled nano-hybrid composite, their use for restorations under high occlusal load is subject to caution. Further, the swelling behaviour of some of the bulk-fill materials may be a reason for concern, which highlights the critical requirement for a veneering material, not only to improve aesthetic quality of the translucent material, but to reduce the impact of degradation.     

The benefits of glass ionomer self-adhesive materials in restorative dentistry

Bonded, resin-based composite restorative materials have potential advantages. If the dentin bond achieved is not greater than the polymerization stress, loss of retention is likely, resulting in areas of microleakage and postoperative sensitivity. Class 5 lesions restored with no preparation have been used for testing the clinical performance of new adhesive restorative systems. Laboratory studies have demonstrated that bond strength varies according to the depth of dentin and the degree of calcification. Until the later generations of dentin bonding agents, retention rates for bonded, resin-based composites were typically more erratic and lower than glass ionomer (GI) and resin-modified glass ionomer (RMGI) restorative materials. Providing stress relief during setting is inherent in GI and RMGI materials, which helps to explain their good retention rates, despite their low bond strengths. GI and RMGI liners and lightly filled resin bonding agents provide similar stress relief. Current evidence supports the use of both RMGI and composite restorations placed with a liner of lightly filled resin in adhesive Class 5 restorations. Bonded, resin-based composite has the advantage of finishing to a high-gloss surface, making it more acceptable in areas of the mouth that are highly visible.