Effect of titanium dioxide nanoparticle reinforcement on flexural strength of denture base resin: A systematic review and meta-analysis

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Miniature specimens for fracture toughness evaluation of dental resin composites

Objective

Millimeter-scale (“miniature”) specimens enable in-situ evaluation of mechanical properties of engineering materials at reduced cost. Here three such specimens for measuring fracture toughness (K_C) are developed and implemented to new dental materials. The latter include concurrent methacrylate-based and new ether-based resin composites designed to reduce polymerization stress and enhance service life in restored teeth.

新型抗菌树脂材料研究进展

复合树脂材料目前被广泛应用于牙体缺损的修复治疗，以恢复牙齿的正常形态和色泽。但目前临床使用的树脂材料常缺乏有效的抗菌性能，远期治疗效果常因修复材料与牙体组织不密合、菌斑滞留、形成继发龋等影响使用寿命。近年来，合成具有抗菌活性的复合树脂材料是口腔修复材料研究的一个热点，对于抗菌剂的加入，其种类、方式、机制等也开展了大量的研究。文章就近年来抗菌性树脂材料的研究进展做一综述。     

酸蚀处理对新型自粘结树脂水门汀粘结强度的影响

目的:评价酸蚀处理对新型自粘结树脂水门汀Unicem与牙本质和牙釉质之间粘结强度的影响。方法:选取新鲜拔除的无龋坏人第三磨牙36个,制备颊侧牙本质粘结面和近、远中牙釉质粘结面,随机分为3组,每组12个牙,分别选用Unicem、磷酸酸蚀配合Unicem和Panavia F(对照组)进行粘结处理,分别测试牙本质、牙釉质粘结强度,并通过扫描电镜观察粘结界面。结果:在牙本质粘结强度上,Unicem组(12.84±2.29 MPa)与Panavia F组(14.93±3.73 MPa)之间无显著性差异(P>0.05),但均显著高于磷酸酸蚀配合Unicem组(9.12±1.54 MPa)(P<0.05);牙釉质粘结强度上,磷酸酸蚀配合Unicem组(17.24±7.62 MPa)和Panavia F组(17.99±3.66 MPa)无显著性差异(P>0.05),但均显著高于Unicem组(6.47±1.54MPa)(P<0.05)。结论:酸蚀处理可以显著提高自粘结树脂水门汀Unicem牙釉质粘结强度,却降低了牙本质粘结效果。     

Clinical study of indirect composite resin inlays in posterior stress-bearing cavities placed by dental students: results after 4 years

Objectives

This longitudinal randomized controlled clinical trial evaluated the longevity of composite resin inlays in single- or multi-surface cavities up to 4 years.

Methods

21 dental students placed 75 Artglass and 80 Charisma composite resin inlays in class I and II cavities in posterior teeth (89 adult patients) luted with dual-curing resin cements. Clinical evaluation was performed up to 4 years using modified USPHS criteria.

Results

87.2% of Artglass and 76.6% of Charisma inlays were assessed to be clinically excellent or acceptable. Up to the 4-year recall 5 Artglass and 11 Charisma inlays failed mainly because of postoperative symptoms, bulk fracture, and loss of marginal integrity. No significant differences between both composite resin materials could be detected at 4 years for all clinical criteria (Mann-Whitney U-test, p > 0.05). The comparison of restoration performance with time yielded a significant increase in marginal discolouration and postoperative symptoms (p < 0.05), deterioration of surface texture quality, marginal and restoration integrity (p < 0.05) for both inlay systems. However, the changes were mainly effects of scoring shifts from alfa to bravo. Small inlays compared to large inlays and premolar restorations compared to molar restorations showed significant better outcome for some of the tested clinical parameters for the Artglass inlays (p < 0.05). For Charisma inlays no such influences were revealed.

Conclusions

Clinical assessment of Artglass and Charisma composite resin inlays exhibited an annual failure rate of 3.2% and 5.9% that is within the range of published data. Within the limitations of this study indirect composite inlays are a competitive restorative procedure in stress-bearing preparations.     

Titanium dioxide and modified titanium dioxide by silver nanoparticles as an anti biofilm filler content for composite resins

Objective

The aim of this study was to evaluate the antibacterial activity of a composite resin modified by TiO₂ and TiO₂/Ag nanoparticles and their influence over different properties.

Comparison of bleaching effects when applied to white-spot lesions before or after resin infiltration: An in vitro study

BackgroundThe purpose of this study was to compare color alterations (ΔE) of white-spot lesions (WSLs) bleached before versus after resin infiltration (RI).MethodsUsing the facial surfaces of bovine maxillary incisors, WSLs were created and the teeth were allocated into 2 groups (n = 45/group): bleach then RI (B-RI group) and RI then bleach (RI-B group). To determine ΔE, Commission Internationale de l’Eclairage L1 a1 b1 (L1 represents lightness, ranging from black to white [0-100]; a1 represents green to red chromaticity [–150-+100]; and b1 represents blue to yellow chromaticity [–100-+150]) measurements were obtained at baseline, after WSL formation, and after RI and bleaching. Representative specimens were evaluated by means of scanning electron microscopy. Statistical analyses included the Mann-Whitney U and Wilcoxon signed rank tests (P ≤ .0016) and repeated measures analysis of variance (P ≤ .05).ResultsNo differences in ΔE were found comparing B-RI with RI-B groups or when the B-RI group was compared with bleached enamel. A statistically significant difference was found when the RI-B group was compared with bleached enamel (ΔE, 0.81; P < .001), but the difference was deemed not clinically significant. Scanning electron microscopy revealed that bleaching after RI increased surface roughness of the resin.ConclusionsThere were no clinically significant differences in ΔE of WSLs when bleach was applied before or after RI; however, applying bleaching agent after RI roughened the surface of the resin material.Practical ImplicationsResults indicate that ΔE were not clinically significantly different between WSLs bleached before versus after RI, although it is best to sequence bleaching before RI therapy, as bleaching after RI roughened the restoration’s surface.     

The effect of zinc oxide-eugenol on the shear bond strength of a commonly used bonding system

Abstract – It has been claimed that eugenol has a detrimental effect on resin composites and dentin bonding systems. The aim of the present study was to examine whether zinc oxide-eugenol (ZOE) cement would reduce the efficacy of a bonding system. Human third molars were selected for the study, and cylindrical posts of a resin composite (Z100) were bonded vertically to a standardized flat dentinal surface, prepared on the buccal surface of the teeth and treated with Scotchbond Multi-Purpose. The tooth surfaces involved were either freshly cut, or had been exposed to ZOE cement for 6 days, with and without a subsequent thorough cleansing with ethanol. The bond strength in shear was measured after 24 hours. The results showed that ZOE cement had no negative effect on the bond strength of the resin composite (Z100) to dentin when this bonding system was used. The mean shear bond value for the specimens covered with ZOE cement for 6 days was 28.1 MPa. For specimens covered with ZOE cement and cleansed with 96% ethanol, the mean shear bond value was 23.5 MPa. The corresponding value for the controls was 19.0 MPa. These findings suggested that eugenol-containing temporary filling materials may be used safely prior to inserting resin based restorative materials, when Scotchbond Multi-Purpose is employed as the bonding agent.     

Influence of surface roughness on streptococcal adhesion forces to composite resins

Objective

To determine streptococcal adhesion forces with composite resins with different surface roughness.

Methods

Polishing and grinding were applied to obtain smooth (roughness 20 nm), moderately rough (150 nm) and rough (350 nm) surfaces of two orthodontic, light-cured composites. Adhesion forces between Streptococcus sanguinis and Streptococcus mutans and the composite surfaces were measured using atomic force microscopy in absence or presence of a salivary conditioning film. Initial adhesion forces were measured as well adhesion after 120 s of contact, as longer contact times are known to result in stronger adhesion forces (“bond-strengthening”). Surface roughness in absence and presence of salivary conditioning films were compared using ANOVA, while adhesion forces were subjected to a Weibull analysis.

Results

Initial adhesion forces in absence of a salivary conditioning film amounted between −0.7 and −0.9 nN for smooth composite resins and increased between −1.0 and −2.0 nN for the roughest surfaces. Streptococcal adhesion forces after bond-strengthening were significantly stronger than upon initial contact, irrespective of the composite type. Salivary conditioning films significantly decreased the surface roughness of the composites, as well as the streptococcal adhesion forces. Yet, also in the presence of a conditioning film, rougher composite surfaces exerted stronger adhesion forces, irrespective of composite type or bacterial strain.

Conclusion

Streptococcal adhesion forces to orthodontic composite resins increase with increasing roughness of the composite surfaces. Composite surface roughness less affects adhesion forces with S. mutans than with S. sanguinis.     

Analysis of interfacial fracture in dental restorations

Objectives

To provide a brief summary of the background theory of interfacial fracture mechanics and develop an analytical framework that identifies the critical factors for the analysis of the initiation and propagation of adhesion failure in composite restorations.

Methods

A conceptual framework utilizing interfacial fracture mechanics and Toya's solution for a partially delaminated circular inclusion in an elastic matrix, which can be applied (with caution) to approximate polymer curing induced cracking about composite resins for class 1 cavity restorations.

Results

The findings indicate that: (1) most traditional shear tests are not appropriate for the analysis of the interfacial failure initiation; (2) material properties of the restorative and tooth material have a strong influence on the energy realize rate; (3) there is a strong size effect; and (4) interfacial failure once initiated is characterized by unstable propagation along the interface almost completely encircling the composite.

Significance

The work is important for the analysis of the reliability of composite class I restorations and provides an adequate interpretation of recent adhesion debonding experimental results utilizing tubular geometry of specimens. The approach clearly identifies the critical parameters including; curing strain, material modulii, size and interfacial strain energy release rate for reliable development of advanced restorative materials.