An application of nanotechnology in advanced dental materials

Transcriptome changes in humans acutely exposed to nanoparticles during grinding of dental nanocomposites

Aim: Today, there is a lack of research studies concerning human acute exposure to nanoparticles (NPs). Our investigation aimed to simulate real-world acute inhalation exposure to NPs released during work with dental nanocomposites in a dental office or technician laboratory. Methods: Blood samples from female volunteers were processed before and after inhalation exposure. Transcriptomic mRNA and miRNA expression changes were analyzed. Results: We detected large interindividual variability, 90 significantly deregulated mRNAs, and 4 miRNAs when samples of participants before and after dental nanocomposite grinding were compared. Conclusion: The results suggest that inhaled dental NPs may present an occupational hazard to human health, as indicated by the changes in the processes related to oxidative stress, synthesis of eicosanoids, and cell division.

Do effervescent vitamin tablets affect the surface roughness, microhardness, and color of human enamel and contemporary composite resins?

PURPOSE

To compare the impact of four effervescent vitamin tablets on the surface roughness, microhardness, and color of human enamel and contemporary composite resins.

MATERIAL AND METHODS

Sixty enamel and a total of 240 anterior (Gradia Direct Anterior), posterior (Gradia Direct Posterior), and universal composite resin (Filtek Ultimate) specimens (n = 60 per group) were fabricated. Each group was subdivided into five subgroups (n = 12, per subgroup). The specimens were subsequently immersed in YOUPLUS, Redoxon, Sunlife Immuvit, and Sambucol effervescent vitamin solutions for 2 min per day over 30 days. Distilled water was used as control. Subsequently, surface roughness (Ra) was detected using a profilometer, and microhardness (VHN) was measured using a microhardness tester. A spectrophotometer device was used to record the L,a,b color coordinates of the specimens after 24 h, 7 days, and 30 days, and the color changes (ΔE00) of the groups were calculated. The data were analyzed by ANOVA, two-way ANOVA, Kruskal-Wallis, Levene's, and Fisher's least significant difference (LSD) tests (p < 0.05). SEM analysis was conducted on one randomly selected specimen per group (×1000).

RESULTS

In terms of surface roughness, material X vitamin interactions were found significant (p < 0.05). The increase in Ra from 24 h to 30 days was found significant (p < 0.05) except for Gradia Direct Anterior X Redoxon, Sunlife Immuvit and Sambucol, Filtek Ultimate X Sunlife Immuvit and Sambucol, and all control groups. Ra changes were also concluded by SEM. Regarding VHNs, material X vitamin interactions were significant (p < 0.005), except for all Filtek Ultimate subgroups. The changes in VHNs of the groups from 24 h to 30 days were significant for all enamel and Gradia Direct Anterior X YOUPLUS, Gradia Posterior X YOUPLUS, Sunlife Immuvit, and Sambucol groups (p < 0.05). In terms of ΔE00, significant differences were observed between the 7 days and 30 days in the enamel (p = 0.047), Gradia Direct Anterior (p = 0.019), and Gradia Direct Posterior groups (p = 0.038).

CONCLUSIONS

Daily consumption of effervescent vitamin tablets can increase surface roughness, decrease microhardness, and influence the color of human enamel and contemporary anterior, posterior, and universal composite resins after a 30-day period.

Dental biomaterials redefined: molecular docking and dynamics-driven dental resin composite optimization

BACKGROUND

Dental resin-based composites are widely recognized for their aesthetic appeal and adhesive properties, which make them integral to modern restorative dentistry. Despite their advantages, adhesion and biomechanical performance challenges persist, necessitating innovative strategies for improvement. This study addressed the challenges associated with adhesion and biomechanical properties in dental resin-based composites by employing molecular docking and dynamics simulation.

METHODS

Molecular docking assesses the binding energies and provides valuable insights into the interactions between monomers, fillers, and coupling agents. This investigation prioritizes SiO2 and TRIS, considering their consistent influence. Molecular dynamics simulations, executed with the Forcite module and COMPASS II force field, extend the analysis to the mechanical properties of dental composite complexes. The simulations encompassed energy minimization, controlled NVT and NPT ensemble simulations, and equilibration stages. Notably, the molecular dynamics simulations spanned a duration of 50 ns.

RESULTS

SiO2 and TRIS consistently emerged as influential components, showcasing their versatility in promoting solid interactions. A correlation matrix underscores the significant roles of van der Waals and desolvation energies in determining the overall binding energy. Molecular dynamics simulations provide in-depth insights into the mechanical properties of dental composite complexes. HEMA-SiO2-TRIS excelled in stiffness, BisGMA-SiO2-TRIS prevailed in terms of flexural strength, and EBPADMA-SiO2-TRIS offered a balanced combination of mechanical properties.

CONCLUSION

These findings provide valuable insights into optimizing dental composites tailored to diverse clinical requirements. While EBPADMA-SiO2-TRIS demonstrates distinct strengths, this study emphasizes the need for further research. Future investigations should validate the computational findings experimentally and assess the material's response to dynamic environmental factors.

Biofilm Formation on Hybrid, Resin-Based CAD/CAM Materials for Indirect Restorations: A Comprehensive Review

Hybrid materials are a recent addition in the field of restorative dentistry for computer-aided design/computer-aided manufacturing (CAD/CAM) indirect restorations. The long-term clinical success of modern dental restorative materials is influenced by multiple factors. Among the characteristics affecting the longevity of a restoration, the mechanical properties and physicοchemical interactions are of utmost importance. While numerous researchers constantly evaluate mechanical properties, the biological background of resin-based CAD/CAM biomaterials is scarcely investigated and, therefore, less described in the literature. This review aims to analyze biofilm formation on the surfaces of novel, hybrid, resin-based CAD/CAM materials and evaluate the methodological protocols followed to assess microbial growth. It is demonstrated that the surface structure, the composition and the finishing and polishing procedures on the surface of a dental restorative material influence initial bacterial adhesion; however, most studies focus on in vitro protocols, and in vivo and/or in situ research of microbiomics in CAD/CAM restorative materials is lacking, obstructing an accurate understanding of the bioadhesion phenomenon in the oral cavity.

Sixty-month comperative evaluation of a glass hybrid restorative and a composite resin in non-carious cervical lesions of bruxist individuals

OBJECTIVE

To compare the clinical performance of a glass hybrid (GH) restorative and a nano-ceramic composite resin (CR) in the restoration of non-carious cervical lesions (NCCLs) of bruxist individuals in a 60-month randomized clinical trial.

MATERIALS AND METHODS

Twenty-five bruxist candidates having NCCLs were recruited in this clinical study. The depth, height (cervico-incisal), width (mesio-distal), internal angles of the NCCLs, degree of tooth wear (TWI) and gingival index (GI) were measured. One hundred-and-forty-eight NCCLs were restored either with a GH restorative (Equia Forte Fil) or a CR (Ceram.X One Universal). Modified USPHS criteria was used to evaluate restorations after 1 week and 12, 24, 36 and 60 months. Pearson's Chi-Square, Fisher's Exact and Cochran Q tests were run for analysis. Survival rates of the restorations were compared with Kaplan-Meier analysis (p < 0.05).

RESULTS

After 60 months, 97 restorations in 15 patients were examined. The recall rate was 60.0%. Retention rates were 73.5% for CR and 66.7% for GH. A total of 29 restorations were lost (13CR (26.5%), 16GH (33.3%)). There was not a significant difference between tested restoratives in retention (p = 0.464), marginal adaptation (p = 0.856) and marginal discoloration (p = 0.273). There was no relationship between internal angle, depth, height or width and retention of the GH or CR restorations (p > 0.05). The increase in retention loss and marginal discoloration of both restorations over time were significant (p < 0.001). Sensitivity or secondary caries were not detected after 60 months.

CONCLUSION

GH and nano-ceramic CR showed similar clinical performances in NCCLs after 60 months in patients with bruxism.

CLINICAL SIGNIFICANCE

After 60 months, CR and GH materials showed clinically acceptable performances in restoration of NCCLs in patients with bruxism.

The optical behavior of nano filled resin composite loaded with graphene oxide nanoparticles

OBJECTIVES

Assessment of the effect of incorporation of graphene oxide nanoparticles (GONPs), different concentrations into resin composite with different thicknesses on its color modulation.

MATERIALS AND METHODS

GONPs were prepared using the chemical reduction method and characterized using a transmission electron microscope and X-ray diffraction. The minimum concentrations of GONPs that provided the most effective antibacterial action (0.05 wt% and 0.2 wt%.) were prepared to be the concentration added to the tested resin composite. Calculations were done to find the required volume of the GONPs solution needed according to the mass of the resin composite. 70 nano-filled resin composite discs were prepared with 10 mm diameter × 3 mm height. 10 resin composite discs were prepared without GONPs incorporation and served as a control (G0). The other 60 resin composite specimens were divided into 2 equal groups (G1& G2) according to the concentration of the loaded nanoparticles in the specimens. Each group was divided into 3 equal subgroups according to the thickness of the resin composite containing GONPs; [T1: GONPs dispersed in the bottom 1 mm of the disc, while the top 2 mm of the disc was of resin composite only. T2: GONPs dispersed only in the bottom 2 mm of the disc and T3: GONPs dispersed in the total thickness of the disc (3 mm)]. ∆E values were calculated using a Vita Easy shade Spectrophotometer.

RESULTS

Incorporation of GONPs into resin composite induced significant color change and among all the 6 experimental groups, G1T1 group (of 0.05 wt% concentration GONPs dispersed only in the bottom 1 mm of the disc) showed a non-significant color change.

CONCLUSION

Dispersion of GONPs has a detectable effect on the color change of resin composite. Meanwhile, dispersion in low concentration for only the bottom 1 mm thickness of resin composite has an undetectable effect on its color.

Comparative Evaluation of Fracture Toughness and Flexural Strength of Four Different Core Build-up Materials: An In Vitro Study

AIM

To evaluate and compare the fracture toughness and flexural strength of four different core build-up materials.

MATERIALS AND METHODS

A total of 60 samples were divided into four groups (n = 15) group I: dual cure composite resin reinforced with zirconia particles (Luxacore Z), group II: light cure composite resin (Lumiglass DeepCure), group III: zirconia reinforced glass ionomer cement (GIC) (Zirconomer Improved), and group IV: chemically cure composite resin (Self Comp) respectively. All the core build-up materials were manipulated according to the manufacturer's instructions and poured into the mold. A universal testing machine applied a central load to the specimen in a 3-point bending mode. Fracture of the specimen was identified and the reading was recorded by the universal testing machine. The data were analyzed statistically using one-way analysis of variance (ANOVA) and then compared.

RESULTS

Group I showed the highest flexural strength (48.65 MPa) among all the groups while group IV showed the lowest flexural strength (17.90 MPa). Group I showed the highest fracture toughness (99.12 MPa) among all the groups while group IV showed the lowest fracture toughness (36.41 MPa.cm-0.5). When mean flexural strength and fracture toughness values of all four groups were compared by using one-way ANOVA, the compared data was highly significant.

CONCLUSION

Based on the findings of this study, dual cure composite resin was the material of choice in terms of flexural strength and fracture toughness for core build-up material followed by light cure composite resin.

CLINICAL SIGNIFICANCE

The core buildup material serves to strengthen the tooth structure, allowing it to withstand the forces of chewing and preventing the risk of tooth fractures. This material is essential in restoring damaged or decayed teeth, as it provides a stable foundation for further dental work. By reinforcing the tooth structure, the core buildup material ensures that the tooth can function properly and remain healthy for years to come. How to cite this article: Nakade P, Thaore S, Bangar B, et al. Comparative Evaluation of Fracture Toughness and Flexural Strength of Four Different Core Build-up Materials: An In Vitro Study. J Contemp Dent Pract 2024;25(2):191-195.

Biocompatibility of 3D-Printed Dental Resins: A Systematic Review

BACKGROUND

The biocompatibility of 3D-printed dental resins has become a critical concern in modern dentistry due to the increasing utilization of additive manufacturing (AM) techniques in dental applications. These resins serve as essential materials for fabricating dental prostheses, orthodontic devices, and various dental components. As the clinical adoption of 3D printing in dentistry grows, it is imperative to comprehensively assess the biocompatibility of these materials to ensure patient safety and dental treatment efficacy. This systematic review aimed to evaluate the existing body of literature on the biocompatibility of 3D-printed dental resins, thereby providing valuable insights into the potential biological risks associated with their use.

METHODS

The search strategy to identify relevant papers was implemented across PubMed/MEDLINE, Scopus, Web of Science, Embase, Cochrane Library, CINAHL, and Google Scholar to identify relevant studies. Study selection was not limited to any particular timeframe of publishing. The revised CONSORT criteria were used to ascertain the authenticity and dependability of the review's outcomes. Comprehensive screening and eligibility assessment processes were conducted to select studies meeting predefined criteria. Biocompatibility-related parameters, including toxicity, mechanical properties, cell viability, and other relevant outcomes, were analyzed across selected studies using a standardized variable extraction protocol.

RESULTS

A total of 9 studies were included in the systematic review. The findings encompassed various aspects of biocompatibility assessment, including material composition, mechanical properties, cell viability, and cytotoxicity. Some studies revealed significant improvements in flexural strength and cell viability with specific resin formulations, demonstrating their potential for enhanced clinical utility. Conversely, certain resins exhibited cytotoxicity, while others displayed promising biocompatibility profiles.

CONCLUSION

As per the assessed findings, material composition, post-processing techniques, and manufacturing methods emerged as critical factors influencing biocompatibility outcomes. While some resins exhibited favorable biocompatibility profiles, others raised concerns due to cytotoxicity. These findings emphasize the need for careful consideration when selecting and implementing 3D-printed dental resins, with a focus on materials engineering and comprehensive biocompatibility testing. Further research is warranted to elucidate the long-term biocompatibility and clinical implications of these materials.

The effect of different concentration of emodin nanoparticles, as an antibacterial agent, on the flexural resistance of acrylic resin used in orthodontics: An in vitro study

OBJECTIVE

The aim of this study was to investigate the impact of emodin nanoparticles (n-Emo) on the flexural strength of acrylic resin used in orthodontics.

METHODS

A total of 24 acrylic resin discs were prepared according to ISO:20795-1 and divided into four groups (n=6): 0% n-Emo, 0.5% n-Emo, 1% n-Emo, and 2% n-Emo. The flexural strength of each group was measured using the Universal Testing Machine. One-way analysis of variance (ANOVA) and Tukey tests were used to analyse the data.

RESULTS

The highest flexural strength values were observed in the groups containing 0% and 0.5% concentrations of n-Emo, while the lowest mean flexural strength was recorded in the group containing 2% concentration of n-Emo. There were significant difference in flexural strength values between the groups containing 0% with those containing 1% and 2% concentrations (P=0.045, P=0.011, respectively), as well as between those containing 0.5% and 2% concentrations of n-Emo (P=0.041).

CONCLUSIONS

The results of the study showed that the incorporation of n-Emo had a negative impact on the flexural strength of the acrylic resin utilized in orthodontics. Nonetheless, the mean flexural strength values of all groups fell within the normal range, implying that the addition of n-Emo did not jeopardize the mechanical properties of the acrylic resin. It is therefore conceivable that the use of n-Emo as an antimicrobial agent in acrylic resin could be a promising approach to reducing enamel demineralisation and dental caries, while preserving its mechanical properties. This study was approved by the ethics committee of the Tehran University of Medical Sciences (1401-2-398-54892).

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion

OBJECTIVE

This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers.

MATERIALS AND METHODS

Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined.

RESULTS

After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion.

CONCLUSIONS

Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing.

CLINICAL SIGNIFICANCE

Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Influence of inorganic nanoparticles on dental materials' mechanical properties. A narrative review

Inorganic nanoparticles have been widely incorporated in conventional dental materials to help in improving their properties. The literature has shown that incorporating nanoparticles in dental materials in different specialties could have a positive effect on reinforcing the mechanical properties of those materials; however, there was no consensus on the effectiveness of using nanoparticles in enhancing the mechanical properties of dental materials, due to the variety of the properties of nanoparticles itself and their effect on the mechanical properties. This article attempted to analytically review all the studies that assessed the effect of different types of inorganic nanoparticles on the most commonly used dental materials in dental specialties such as polymethyl methacrylate, glass ionomer cement, resin composite, resin adhesive, orthodontic adhesive, and endodontic sealer. The results had shown that those inorganic nanoparticles demonstrated positive potential in improving those mechanical properties in most of the dental materials studied. That potential was attributed to the ultra-small sizes and unique physical and chemical qualities that those inorganic nanoparticles possess, together with the significant surface area to volume ratio. It was concluded from this comprehensive analysis that while a definitive recommendation cannot be provided due to the variety of nanoparticle types, shapes, and incorporated dental material, the consensus suggests using nanoparticles in low concentrations less than 1% by weight along with a silane coupling agent to minimize agglomeration issues and benefit from their properties.

Influence of abrasive dentifrices on polymeric reconstructive material properties after simulated toothbrushing

To assess the influence of dentifrices with different abrasiveness levels on the properties of dental reconstructive materials. Forty-eight cylinders were obtained from four polymeric materials, being two CAD/CAM acrylic resins (Ivotion-Dent and Ivotion-Base), one injected acrylic resin (IvoBase-Hydrid) and one light-cured resin composite (Empress Direct). Specimens were allocated to four subgroups for toothbrushing simulation according to the dentifrice relative dentin abrasivity (RDA) and silica content: (i) RDA 0 = 0%; (ii) RDA 50 = 3%; (iii) RDA 100 = 10%; and (iv) RDA 120 = 25%. Specimens were then subjected to toothbrushing. Surface analyses [surface roughness Ra (SR) and scanning electron microscopy (SEM)] along with hardness and optical properties [translucency parameter (TP) and contrast ratio (CR)] were evaluated before and after toothbrushing. Statistical analyses were performed using ANOVA and Tukey test. A significant increase in SR was observed after toothbrushing with higher RDA toothpastes for Ivotion-Dent (100 and 120) and IvoBase-Hybrid (120). Ivotion-Base and Empress Direct presented no significant differences in SR when analyzed as a function of timepoint and RDA levels. Hardness was not influenced by toothbrushing with different RDA dentifrices, except for Empress Direct with RDA 0 toothpaste, where a decrease in the hardness was observed. TP of Ivotion-Dent and Empress Direct significantly decreased after toothbrushing with higher RDA dentifrices and CR of Ivotion-Dent, Empress Direct and IvoBase-Hybrid significantly increased with higher RDA dentifrices. The levels of dentifrice abrasiveness affected differently the SR, hardness and optical properties of polymeric reconstructive materials after toothbrushing.

A comparative evaluation of mechanical wear of adhesives used for bonded retainers that underwent brushing for 1 hour under 36 mm of linear action, using computer-aided 3D scan-an in vitro study

OBJECTIVES

The aim of the present study was to comparatively evaluate the mechanical wear of adhesives used in bonded retainers.

MATERIALS AND METHODS

Eighty mandibular acrylic teeth were included in the study that were divided into 4 different groups based upon the composite used. Each acrylic tooth was bonded with a retainer wire and composite of their respective group (Heliosit, Restofill, Tetric-N-flow, and Filtek Z350 XT). These bonded acrylic teeth were subjected to 3D scan in order to evaluate the volume and surface area of the composite. The 3D scans were recorded using MEDIT 3D scanner. After evaluating, the samples were subjected to brushing with the aid of a custom-made brushing simulator using a toothbrush with soft bristles and toothpaste slurry. The samples were subjected to 1 hr of brushing. These samples were again subjected to 3D scans to evaluate (post-test volume and surface area) and underwent statistical analysis.

RESULTS

The results showed the Heliosit group exhibited the highest mean volume (1.76 mm3) and surface area (4.81 mm2) difference between the pre-test and post-test values whereas the least mean volume difference (1.10 mm3) and surface area difference (3.21 mm2) were seen in the Tetric-N-flow group.

CONCLUSION

All the four composites underwent change in the mean surface area and volume after being subjected to brushing, suggesting that the composites routinely used for bonding fixed bonded lingual retainers are subjected to changes due to abrasion. The Heliosit group, which showed least filler loading among the 4 composites, exhibited least resistance to wear, whereas the Tetric-N-flow group which had highest filler loading among the composites exhibited highest resistance to wear.

CLINICAL RELEVANCE

The most crucial phase during orthodontic treatment is the retention phase. This phase is responsible for the long-term results of the treatment. The retainers that are placed in the oral cavity are subjected to changes due to oral environment, chemical changes, and mechanical changes. These changes have a direct effect on the retainers, which tend to alter their properties. Thus, the effects of these changes are to be studied thoroughly.

Hazards Associated With Nanotechnology in Clinical Dentistry

Nanotechnology has transformed the field of dentistry with immense potential to provide comprehensive oral health care using nanomaterials, advanced clinical tools, and devices. New materials with superior properties can be developed using nanotechnology by making use of their atomic or molecular properties. Although there are numerous ways in which nanomaterials impact our health, the primary cause is that they comprise chemicals that may have an inadvertent reaction in the body. Moreover, they are used on a daily basis, increasing human contact with them. It is observed to be smaller in size than the physiological barrier in our bodies, making it much simpler for them to pass through and enter the body and they are being used more frequently. It is observed to be smaller in size than the physiological barrier in our bodies, making it much simpler for them to pass through and enter the body and being used more frequently. Although there are numerous ways in which nanomaterials impact our health, the primary cause is they comprise chemicals that may have an inadvertent reaction in the body. The review discusses various types of toxicity, including the cytotoxicity of composites, carbon nanoparticles, silver nanoparticles (SNPs), and quantum dots. It also covers genotoxicity, the effect of nanoparticles on salivary secretion, oral and gastrointestinal mucosa passage of nanoparticles, the tooth surface microenvironment, and interactions with engineered nanomaterials (ENMs). It is concluded that there is scarce information regarding the presence of chemicals that are released from nanoparticles used in dental materials. Nanotechnology is at an infant stage, although it has progressed by leaps and bounds, hailing a new age that provides better treatment modalities in various branches of dentistry. Although the development and application of nanodentistry are of considerable interest, knowledge regarding the possible toxicity of such materials must be meticulously evaluated, and potential benefits must be weighed against the risks to identify potential gaps in the safety assessment. Further research is needed on workplace exposure to nanoparticles in dentistry.

Nanotechnology Innovations Transforming Oral Health Care and Dentistry: A Review

Nanotechnology has revolutionized dentistry by transforming how oral health care is conceptualized, delivered, and maintained. Harnessing nanomaterials and advanced clinical instruments has opened new avenues for precision and innovation across various aspects of dental care. Nanotechnology offers the potential for precise pain management, tooth restoration, and alleviating dental hypersensitivity. Nanomaterials can occlude exposed dentinal tubules, enhancing patient comfort and overall oral well-being. Orthodontic therapy is also revolutionized by nanomaterials with shape memory properties, enabling rapid and more efficient tooth movement. The development of groundbreaking products and therapeutic alternatives is supported by ongoing research efforts, enabling the formation of dental implants, fillings, and prosthetic devices that closely mimic natural tooth characteristics. Nano-delivery systems are being devised for precise drug delivery within the oral cavity, ensuring optimal therapeutic outcomes with minimal side effects. The integration of nanotechnology in dentistry represents a groundbreaking evolution beyond the conventional boundaries of oral health care, enabling the development of innovative diagnostic techniques and improved oral well-being.

The Effect of Ground and Unground Enamel on the Clinical Performance of Direct Composite Build-up After Orthodontic Treatment: Five Years of Follow-up

PURPOSE

To assess the clinical performance of restorations with ground and unground enamel for diastema closure.

METHODS AND MATERIALS

Twenty-four patients attended and received two to ten composite build-ups for diastema closure. The restorations were performed separately by grinding and not grinding the enamel on the proximal surfaces on symmetric teeth. A nanofill direct composite (Filtek Ultimate Universal Restorative System, 3M ESPE, St Paul, MN, USA) was used with a three-step etch-and-rinse adhesive (Scotchbond Multi-Purpose, 3M ESPE) for restorations. Restorations were evaluated according to the modified United States Public Health Service (USPHS) criteria at baseline and 1-, 2-, 3-, 4-, and 5-year recalls.

RESULTS

The cumulative success rate of direct composite build-up with ground and unground enamel was 100% and 88.7%, respectively. Six restorations with unground enamel failed due to fracture. No significant difference was found between the restorations with ground enamel and unground enamel with regard to the evaluation criteria.

CONCLUSION

The 5-year success rates of restorations with ground and unground enamel were excellent. The success rate of restorations with ground enamel was higher than that of restorations with unground enamel. Fracture was the reason for failure in the restorations with unground enamel.

Perspectives on the Application of Nanomaterials in Medical and Dental Practices

A new field of study called nanotechnology concentrates on manipulating matter at atomic and molecular levels. Modern medicine may benefit tremendously from developments in the field of nanotechnology, and as a result, nanomedicine has emerged as a key location of education in the specific area of nanotechnology. This article aims to describe nanotechnology's possible applications in therapeutics. Nanotechnology and nanomedicine have allowed for the development of new dental materials that are stronger, more resistant to microbial seeding, etc. Other examples include high-strength denture bases, antimicrobial dental glue, aesthetic restorative materials comprised of small particles, and interface adorning for dental posts. Nanotechnology has been perfectly utilized in the medical industry for tissue engineering, biosensors, nanoscale diagnostic tools, and medication delivery using nanoparticles.

Non-Destructive In Vitro Evaluation of an Internal Adaptation of Recent Pulp-Capping Materials in Permanent Teeth Using OCT and Micro-CT

The objective of this study was to assess and compare the internal adaptation of various pulp-capping materials, namely TheraCal, Biodentine, and mineral trioxide aggregate (MTA), on the dentin of permanent teeth through the utilization of micro-computed tomography (MCT) and optical coherence tomography (OCT). Thirty permanent molars were divided into three groups using a random process: group A (TheraCal), group B (Biodentine), and group C (MTA, which served as the control group). On the buccal surface of each tooth, a class V cavity of a standardized cylindrical shape was prepared. Subsequently, the respective pulp-capping material was applied to the cavity based on the assigned group, followed by restoration with composite resin. Based on the MCT results, it was observed that group A had a considerably larger gap volume in comparison to groups B and C (p < 0.001). There was no significant difference in gap volume between groups B and C. Regarding the OCT findings, group A displayed a substantially higher level of light reflection than groups B and C (p < 0.001). Group C exhibited a significantly lower level of light reflection in comparison to group B (p < 0.001). Biodentine and MTA revealed similar outcomes in terms of how well they adhered to the dentinal surface in permanent teeth. Both materials exhibited superior performance in comparison to TheraCal. The utilization of OCT in clinical practice could be advantageous as it enables dentists to monitor and evaluate restorations during post-treatment follow-up. It is imperative to intensify efforts aimed at making OCT equipment more accessible and applicable, overcoming its current limitations, and allowing for its widespread utilization in clinical practice.

Staining ability of herbal tea preparations on a nano-filled composite restorative material - an in-vitro study

Background: Discoloration of tooth-colored restorations due to various factors is one of the principal causes behind the failure of aesthetics. There has been an surge in the consumption of herbal beverages in recent times and the dietary factors play a potential role in the discoloration tooth-coloured restorations. This study was done to juxtapose the staining ability of green tea (GT), moringa tea (MT), and hibiscus tea (HT) on a nano-filled composite restorative material. Methods: The study was conducted in-vitro on composite samples prepared using moulds. 112 discs were prepared from Filtek TM Z350XT composite using a brass mould lined with mylar strips. Samples were divided into GT, MT, HT, and artificial saliva (AS) groups and immersed in freshly prepared beverages for 15 minutes each day for 45 days. Digital reflectance spectrophotometer was utilized to record color at baseline, 30, and 45 days. Repeated-measures ANOVA with a post-hoc Bonferroni test was used to compare groups within each group. ANOVA with a post-hoc Games Howell test was used to compare mean differences in ΔE among the groups. Results: Maximum discoloration was observed in the GT, followed by HT and MT, with the least being in the AS group at the end of 30 and 45 days (P<0.001 and P<0.001) respectively. Conclusions: The universal nano-filled composite material showed clinically detectable discoloration when exposed to Green Tea, Hibiscus Tea, and Moringa Tea which increased with time. Herbal beverages have the potential to cause discoloration of the composite resin which is often the choice of material for anterior aesthetic restorations.

Investigating the impact of flowable composite liner on the fracture strength and microleakage of large composite resin restorations of primary anterior teeth

PURPOSE

To investigate the effect of pre-cured and co-cured flowable composite liner on fracture strength and microleakage of primary anterior teeth with extended composite resin restorations.

METHODS

In the current in vitro experimental study, the crowns of 54 extracted primary canine teeth were cut 1 mm above the CEJ, and a pulpectomy procedure was performed. The samples were randomly divided into three groups to restore the coronal part up to 4 mm above the CEJ. In group 1, the samples were built up with Filtek Z250 packable composite resin. In group 2 (pre-cure), first, 1 mm of Filtek Z350 XT flowable liner was applied to the sample, and after curing, the restoration process continued using packable composite resin. In group 3 (co-cure), the flowable composite liner was cured while the first layer of packable composite resin was applied; then, the same restorative procedure similar to the other groups was followed. The samples' cross-sectional area in the fracture strength test was calculated by AutoCAD software. Subsequently, the samples were subjected to a force in a universal testing machine. The samples related to the microleakage experiment were cut vertically, and then, the dye penetration percentage (10% methylene blue) was measured under a stereomicroscope. ANOVA was used to analyze the data.

RESULTS

Mean fracture strength in group 2 was significantly higher than in group 1 (P = 0.016). The microleakage mean in group 3 was significantly lower than in groups 1 (P = 0.000) and 2 (P = 0.026).

CONCLUSION

The flowable composite liner and its relevant separate curing increased the fracture strength of composite resin restorations. However, less microleakage was reported in the group where the liner was applied as a co-cure.

Evaluation of Compressive and Flexural Strengths of Two Resin-based Core Materials with an Alkasite Material: An In Vitro Study

AIM

To compare and evaluate the compressive and flexural strengths of two resin-based core build-up materials with an alkasite material.

MATERIALS AND METHODS

ParaCore, Tetric N ceram Bulk-fill composite, and Cention N were used. A total of 90 specimens were prepared. Customized cylindrical split molds of dimension 6 ± 1 mm (height) × 4 ± 1 mm (diameter) were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular split metal molds of dimensions 25 ± 1 mm (length) × 2 ± 1 mm (width) × 2 ± 1 mm (height) were used to fabricate 15 samples of each core material for testing the flexural strength. Then the samples were tested using a Universal testing machine (UTM).

RESULTS

The compressive and flexural strengths of Cention N were significantly less than ParaCore® but higher than Tetric® N-CeramTM Bulk-fill core build-up material.

CONCLUSION

Within the limitations of this study, it was concluded that Cention N may be used as an alternative to other core build-up materials after further in-vitro and in-vivo studies.

CLINICAL SIGNIFICANCE

Cention N had the added advantage that self-cure polymerization alone was sufficient to achieve good physical properties when compared to the other two resin-based core build-up materials.

Comparative Evaluation of Compressive and Diametral Tensile Strength in Die Stone Reinforced With Different Types of Nanoparticles: An In Vitro Study

AIM

To investigate the effect of different types of nanoparticles on the compressive strength (CS) and diametral tensile strength (DTS) of type IV dental stones.

MATERIALS AND METHODS

A total of 100 specimens were made from the mould for all five groups. Four commercially available nanoparticles (aluminium oxide (Al2O3), silicon dioxide (SiO2), zinc oxide (ZnO), and zirconium oxide (ZrO2)) were used in this study in a concentration of 10%. CS and DTS tests were performed in a universal test machine. The data were statistically analysed using ANOVA and Student's t-test.

RESULTS

The interaction between nanoparticles and the type of dental stone was found to be statistically significant (p < 0.05). CS and DTS values decreased by adding all four nanoparticles. The lowest CS and DTS were observed in 10% ZnO nanoparticles when added to type IV dental stone.

CONCLUSION

It was concluded that the addition of nanoparticles (Al2O3, SiO2, ZnO, and ZrO2) to die stone significantly decreased the CS and DTS for all groups. Among all groups, the incorporation of 10% ZrO2 nanoparticles (group E) to die stone showed significantly less decrease in CS and DTS compared to Al2O3, SiO2, and ZnO. Incorporation of ZnO nanoparticles, on the other hand, showed a significantly more amount of decrease in the CS and DTS compared to Al2O3, SiO2, and ZrO2.

Micromechanical interlocking structure at the filler/resin interface for dental composites: a review

Dental resin composites (DRCs) are popular materials for repairing caries or dental defect, requiring excellent properties to cope with the complex oral environment. Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs. Various chemical and physical modification methods on filler/resin interface have been introduced and studied, and the physical micromechanical interlocking caused by the modification of fillers morphology and structure is a promising method. This paper firstly introduces the composition and development of DRCs, then reviews the chemical and physical modification methods of the filler/resin interface, mainly discusses the interface micromechanical interlocking structures and their enhancement mechanism for DRCs, finally give a summary on the existing problems and development potential.

Mechanical and Biocompatibility Properties of 3D-Printed Dental Resin Reinforced with Glass Silica and Zirconia Nanoparticles: In Vitro Study

This study aimed to assess the mechanical and biocompatibility properties of dental resin reinforced with different nanoparticle additives. Temporary crown specimens were 3D-printed and grouped based on nanoparticle type and amount, including zirconia and glass silica. Flexural strength testing evaluated the material's ability to withstand mechanical stress using a three-point bending test. Biocompatibility was tested using MTT and dead/live cell assays to assess effects on cell viability and tissue integration. Fractured specimens were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) for fracture surface examination and elemental composition determination. Results show that adding 5% glass fillers and 10-20% zirconia nanoparticles significantly improves the flexural strength and biocompatibility of the resin material. Specifically, the addition of 10%, 20% zirconia, and 5% glass silica by weight significantly increases the flexural strength of the 3D-printed resins. Biocompatibility testing reveals cell viabilities greater than 80% in all tested groups. Reinforced 3D-printed resin holds clinical potential for restorative dentistry, as zirconia and glass fillers have been shown to enhance mechanical and biocompatibility properties of dental resin, making it a promising option for dental restorations. The findings of this study may contribute to the development of more effective and durable dental materials.

Performance of bulk-fill versus conventional nanocomposite resin restorations supporting the occlusal rests of removable partial dentures: An in vitro investigation

STATEMENT OF PROBLEM

Placing removable partial denture (RPD) rests on composite resin restorations has long been a debatable issue. Despite developments in composite resins such as nanotechnology and bulk-filling techniques, studies investigating the performance of composite resin restorations when used to support occlusal rests remain scarce.

PURPOSE

The purpose of this in vitro study was to investigate the performance of bulk-fill versus incremental (conventional) nanocomposite resin restorations when they are used to support RPD rests under functional loading.

MATERIAL AND METHODS

Thirty-five caries-free intact maxillary molars of similar coronal size were collected and divided into 5 equal groups (n=7): Enamel (Control) group: rest seats prepared entirely in enamel; Class I Incremental group: Class I cavities restored with incrementally placed nanohybrid resin composite resin (Tetric N-Ceram); Class II Incremental group: Mesio-occlusal (MO) Class II cavities restored with Tetric N-Ceram; Class I Bulk-fill group: Class I cavities restored with high-viscosity bulk-fill hybrid resin composite (Tetric N-Ceram Bulk-Fill); and Class II Bulk-fill group: MO Class II cavities restored with Tetric N-Ceram Bulk-Fill. Occlusal rest seats were prepared mesially in all groups, and clasp assemblies were fabricated and cast in cobalt-chromium alloy. Specimens with their clasp assemblies were subjected to thermomechanical cycling using a mechanical cycling machine (250 000 masticatory cycles) and 5000 thermal cycles (5 °C to 50 °C). Surface roughness (Ra) was measured with a contact profilometer before and after cycling. Fracture analysis was done using stereomicroscopy, and margin analysis was done with a scanning electron microscope (SEM) before and after cycling. Statistical analysis of Ra was conducted using ANOVA followed by the Scheffé test for between-group comparison and paired t test for within-group comparison. The Fisher exact probability test was used for fracture analysis. The Mann-Whitney test was used for between-group comparison and Wilcoxon signed rank test for within-group comparison for the SEM images (α=.05).

RESULTS

Mean Ra increased significantly after cycling in all groups. Significant differences in Ra were found between enamel and all 4 resin groups (P<.001), with no significant differences between incremental and bulk-fill resin groups for both Class I and II specimens (P>.05). No significant differences were found between the 2 resin groups with regard to fracture and margin analysis (P>.05).

CONCLUSIONS

The surface roughness of enamel was significantly lower than that of both incremental and bulk-fill nanocomposite resins before and after functional loading. Incremental and bulk-fill nanocomposite resins showed comparable performance in terms of surface roughness, fracture behavior, and marginal adaptation.

Influence of Filler Particle Sizes on the Physical Properties of Bulk-Fill Composites Compared to Conventional Composites

INTRODUCTION

Filler size affects how the material is coated and finished, while filler stacking affects how strong the material is, how flexible it is, how resistant it is to wear, and how much it shrinks when it polymerizes. The purpose of this research was to compare micro-hybrid, nano-composite, and bulk-fill composites with respect to their compressive strength, diametric tensile strength, and flexural strength.

MATERIALS AND METHODS

To organize the samples according to International Organization for Standardization (ISO) 4049 and American Dental Association (ADA) detail number 27, we used a custom-made Teflon mold. A total of 45 samples were used, with 15 samples in each group. The sample was mounted on a state-of-the-art general testing machine to determine its compressive strength and polar rigidity. The 3-point bowing test was used to determine flexural strength. A one-way analysis of variance (ANOVA) was used for quantitative analysis, followed by a post hoc test with a significance level of P < 0.05.

RESULTS

The Tetric N Ceram Bulk Fill, the Filtek Z350 XT nanocomposite, and the T-Econom micro-hybrid composite all had different levels of flexural and compressive strength. This difference was statistically significant. Nanocomposites have superior compressive and flexural strengths to their counterparts analyzed in the present study.

CONCLUSION

Nano-composite combines the properties of being strong and looking good. It can be used in both front and back restorations that need to be strong enough to withstand the forces of chewing.

Evaluation and comparison of the effect of incorporating zinc oxide and titanium dioxide nanoparticles on the bond strength and microleakage of two orthodontic fixed retainer adhesives

BACKGROUND

An adhesive with both proper mechanical and antimicrobial properties seems to be beneficial. We aimed to investigate the effect of zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles (NPs) on bond strength and microleakage of two different fixed retainer adhesives.

METHODS

In this in vitro experimental study, 168 extracted human incisors were randomly divided into six groups of 28 (eight double-tooth specimens for the bond strength test and 12 specimens for the microleakage test). In three groups: Transbond XT (3M Unitek, Monrovia, CA) without NPs, with 1% ZnO NPs and with 1% TiO2 NPs were applied. The other three groups included Ortho Connect Flow (GC orthodontics, Tokyo, Japan) composite with the same order to bond a 0.175-inch multistrand wire to the lingual surfaces of the teeth. The bond strength was measured using the Universal Testing Machine, and the adhesive remnant index was reported using a stereomicroscope (Nikon, SMZ800, Tokyo, Japan). The dye-penetration method was used to determine the microleakage.

RESULTS

For bond strength, there was no significant difference among groups. For microleakage, there was no significant difference between GC and Transbond XT groups. However, in subgroups of Transbond XT, the addition of TiO₂ NPs increased the microleakage significantly in comparison with ZnO and control groups (P = 0.011). There was no significant statistical difference between the groups in terms of residual adhesives (P = 0.166).

CONCLUSIONS

Through the incorporation of 1% TiO₂ and ZnO NPs into the fixed retainer adhesive, the bond strength was maintained within the clinically acceptable range. The addition of TiO2 NPs to Transbond XT significantly increased the percentage of microleakage.

Quantitative evaluation of the degradation amount of the silane coupling layer of CAD/CAM resin composites by water absorption

PURPOSE

Degradation of silane coupling layers by water ingress in computer-aided design/computer-aided manufacturing (CAD/CAM) of resin composites has been reported qualitatively. In this study, we quantitatively evaluated how water absorption of CAD/CAM resin composites affects the silane coupling layer by in vitro and in silico methods.

METHODS

A Katana Avencia block (KAB) and an experimental matrix block composed of only a matrix resin were used to evaluate the effect of water immersion for seven days on the elastic modulus. X-ray photoelectron spectroscopy (XPS) with fluorine-labeling of the KAB was performed to evaluate the atomic percentage of F1s, which represents the hydrolysis amount by water immersion. In silico analysis of the three-dimensional model of the KAB was performed to determine the coupling ratios before and after water immersion.

RESULTS

The elastic modulus of the KAB was 8.2 GPa before and 6.9 GPa after immersion in water. The atomic percentages of F1s in the after- and before-immersion groups were 14.31% and 11.52%, respectively, suggesting that hydrolysis of the silane coupling layer occurred during water immersion. From in silico analysis of the three-dimensional model of the KAB, the coupling ratio was predicted to be 78.2% before water immersion. After water immersion, the coupling ratio was predicted to be 68.4%.

CONCLUSIONS

The in vitro and in silico approaches established in this study were able to predict the silane coupling ratios of CAD/CAM resin composites, and they showed that the silane coupling ratio decreased by water absorption.

Evaluation of Surface Roughness of Different Esthetic Restorative Materials after Immersion in Different Acidic Media

Abstract: Background: Dental erosion that resulted from increasing the acidity of oral conditions not only affects tooth substrates but also the performance of some esthetic restorations. Objective: The aim of the current study was to measure and evaluate the surface roughness of different tooth colored restorative materials (resin composites) after immersion for certain time in different acidic food and drinks. Material and method: Three types of composite restoration have been used in this study. The three types were of three main groups. Each group of twenty specimens (n= 20) were divided according to type of acidic media they were immersed in into five sub-groups (n=4). Different acidic beverages and drinks were used in this study include Coke Cola soft drink, orange juice, Pepsi soft drink, sports drink, and lemon juice. Immersion of specimens’ in previously mentioned acidic drinks were for 5 minutes then they have been immersed in distilled water to simulate to great extent what happened in oral cavity. These procedures repeated daily for 14 days. Surface roughness for specimens have been measured by a profilo-meter (Talysurf CLI 1000, Leicester, England) device before and after immersion. Data were collected, tabulated and analyzed using one-way ANOVA. Results: The assessment of surface roughness by one-way ANOVA and Tukey's post hoc tests showed significant differences for composite material types as well as an interaction between these parameters for each composite after immersion in different acidic beverages (P<.05). Conclusion: Within the limitation of this study, results revealed that composition of both resin composite and different acidic beverages and drinks play an important role in initiation and conduction of surface roughness at the outer surface of resin composite restoration.

Analysis of Monomer Release from Different Composite Resins after Bleaching by HPLC

(1) Background: This study aimed to examine the effect of bleaching agents on the release of triethylenae glycol dimethacrylate, 2-hydroxyethyl methacrylate, bisphenol A, urethane dimethacrylate, and bisphenol A-glycidyl methacrylate monomers, which are released from different composite resins, using the high-performance liquid chromatography (HPLC) method. (2) Methods: Ninety disc-shaped specimens were produced and immersed in artificial saliva. After different bleaching applications [office type bleaching (OB) and home type bleaching (HB)], the specimens were immersed in a 75 wt% ethanol/water solution, and the released monomers were analyzed by HPLC at predefined time intervals: 1, 7, and 28 days. The Kruskal−Wallis and Mann−Whitney U tests were conducted for statistical analysis (p = 0.05). (3) Results: The monomers were released at all times from all composite specimens. The monomer release was increased over time. The highest monomer release was detected on day 28. Bleaching applications affected monomer release. No statistical difference was found between OB and HB applications (p > 0.05). The most released monomer was Bisphenol-A in all composites. (4) Conclusion: Given that a residual monomer release from composite resins has a toxic effect and that bleaching treatments increase this release, a treatment protocol should be made in accordance with the manufacturer’s instructions.

Evaluation of the Surface Roughness of Resin Composites before and after Applying Different Bleaching Materials

Abstract: Background: Bleaching is a conservative treatment and has been shown to be both efficient and safe but the effects of bleaching on teeth and dental materials have been studied in several studies. Objective: The aim of the current study was to evaluate the surface roughness of resin composites before and after applying different bleaching materials. Material and method: Three types of resin composites were used in this in vitro study. Two types of bleaching techniques were used: in office and at home bleach. Sixteen specimens of each resin composite type were fabricated and used in this study. Surface roughness of the samples was measured using a profilometer (Talysurf CLI 1000, Leicester, England). The surface roughness measurements and data were statistically analyzed using the one-way ANOVA and Tukey's tests through SPSS version 21 (SPSS Inc. Chicago, IL, USA). The assessment of surface roughness was done using one-way ANOVA and Tukey's post hoc tests. P < 0.05 was considered statistically significant. Results: The assessment of surface roughness by one-way ANOVA and Tukey's post hoc tests showed significant differences for composite material types as well as an interaction between these parameters for each tested bleaching gels (P<.05). Conclusion: The composition of both resin composite and bleaching material play an important role in initiation and conduction of surface roughness at the outer surface of resin composite restoration.

Posterior ceramic versus metal restorations: A systematic review and meta-analysis

OBJECTIVES

The goal of this systemic review and meta-analysis was to evaluate the longevity of indirect adhesively-luted ceramic compared to conventionally cemented metal single tooth restorations.

DATA

Randomized controlled trials (RCT) investigating indirect adhesively-luted ceramic restorations compared to metal or metal-based cemented restorations in permanent posterior teeth.

SOURCES

Three electronic databases (PubMed, CENTRAL (Cochrane) and Embase) were screened. No language or time restrictions were applied. Study selection, data extraction and quality assessment were done in duplicate. Risk of Bias and level of evidence was graded using Risk of Bias 2.0 tool and Grade Profiler 3.6.

RESULTS

A total of 3056 articles were found by electronic databases. Finally, four RCTs were selected. Overall, 443 restorations of which 212 were adhesively-luted ceramic restorations and 231 conventionally cemented metal restorations have been placed in 314 patients (age: 22-72 years). The highest annual failure rates were found for ceramic restorations ranging from 2.1% to 5.6%. Lower annual failure rates were found for metal (gold) restorations ranging from 0% to 2.1%. Meta-analysis could be performed for adhesively-luted ceramic vs. conventionally cemented metal restorations. Conventionally cemented metal restoration showed a significantly lower failure rate than adhesively-luted ceramic ones (visual-tactile assessment: Risk Ratio (RR)[95%CI]=0.31[0.16,0.57], low level of evidence). Furthermore, all studies showed a high risk of bias.

CONCLUSION

Conventionally cemented metal restorations revealed significantly lower failure rates compared to adhesively-luted ceramic ones, although the selected sample was small and with medium follow-up periods with high risks of bias.

Effect of different surface pretreatment methods on repair bond strength of resin composite subjected to pH-cycling

Objectives: The aim of this study was to evaluate the effect of two different repair methods (Er:YAG laser and bur) with or without silane application on the microtensile bond strength of a nanohybrid resin composite aged with two different aging methods (pH cycling and thermocycling). Material and Method: Resin composite blocks (Clearfil Majesty Esthetic, Kuraray, Japan) were randomly assigned into two groups for aging process: (a) pH cycling (b) thermocycling (5,000 cycles). After aging, the blocks were assigned to one of the following repair procedures: (1) Er:YAG laser (LightWalker STE-E, Fotona Medical Lasers, Ljubljana, Slovenia) (2) Er:YAG laser+silane (3) bur (4) bur+silane and (5) no-pretreatment group and (6) Cohesive control (cohesive strength of the resin). Resin composite (Clearfil Majesty Esthetic) was bonded to the conditioned substrates incrementally and light polymerized. Repaired samples were thermocycled (5.000 cycles). The microtensile bonding test was performed. The data were analyzed using Scheirer-Ray-Hare, Kruskal-Wallis Mann-Whitney U tests, Chi-square and Z tests with Bonferroni correction (p=0.05). Results: No statistically significant difference was found between the aging methods applied to filling material (p=0.821) and the interaction of applied surface treatments and aging (p=0.289). All repair procedures achieved bond strength values higher than the no-pretreatment group but they did not reach the resin composite’s cohesive bond strength. Failure modes distribution was found statistically different according to repair procedure and also aging methods (p

Accelerated Aging Effects on Color Change, Translucency Parameter, and Surface Hardness of Resin Composites

Background

The aging process can induce a change in the surface microstructure of materials, the chemical compositions of matrices, and the filler particles of resin composites. This study is aimed at evaluating the effects of accelerated artificial aging (AAA) on the color change, translucency parameter (TP), and surface hardness of resin composites.

Methods

Five resin composite materials (Tetric N-Ceram, Filtek Z250, Charisma Smart, Herculite Classic, and Escom100) were evaluated. A spectrophotometer was used for color measurements (L∗, a∗, and b∗). TP and color changes (ΔE₀₀) were calculated using the CIEDE2000 formula. The resin materials were subjected to aging for 300 hours. The hardness and TP values were measured before and after AAA. One- and two-way ANOVA and the Tukey test were used. The significance level was accepted as p < 0.05.

Results

Escom100 had significantly higher ΔE₀₀ values than the other resin composites, and Charisma Smart had significantly lower ΔE₀₀ values than the other tested materials (p < 0.05). Before and after AAA, Charisma Smart had the lowest TP values, and Filtek Z250 exhibited the highest hardness values (p < 0.05). For TP and surface hardness, the effect size value of the composite material was found to be higher than that of AAA.

Conclusions

After AAA, the investigated resin composites had ΔE₀₀ values that were above clinically acceptable thresholds. After aging, the tested materials generally exhibited decreases in L∗ values and a∗ values, while increases in b∗ values were observed. The ΔTP values of the resin composites were similar. AAA significantly increased the surface hardness of the tested materials.

Evaluation of Shear Bond Strength of Resin-Based Composites to Biodentine with Three Types of Seventh-Generation Bonding Agents: An In Vitro Study

Background and Aim. Biodentine refers to a bioactive material commonly applied for dental restoration in clinical practice, but poor adhesion of the Biodentine to the restorative materials could affect the quality and long-term integrity of the final restoration. The study aimed to assess shear bond strength (SBS) of two resin-based composites to Biodentine using three commercially available 7th generation bonding agents. Methods. Forty-eight acrylic blocks having central holes with a nominal diameter of 4 mm and a depth of 2 mm were prepared. The holes of the acrylic blocks were filled with Biodentine, which was prepared following the guidelines provided by the manufacturer. Then, the specimens were divided into six groups (n = 8). Groups 1, 2, and 3, Tetric N-Ceram composite bonded to Biodentine with Tetric N-bond, Xeno V+, Bond Force bond, respectively. Group 4, 5, and 6, Filtek Z350 bonded to Biodentine with the same three adhesives. The specimens were placed in distilled water for 24 hours and tested for the SBS in a universal testing machine at a crosshead speed of 1 mm/min. The test data were listed in a table and independent samples t-test and analysis of variance (ANOVA) were conducted as a part of the statistical analysis. Results. The Tetric N bonding agent achieved the highest SBS followed by Bond Force, and Xeno V and highly significant difference was found. On the other hand, an overall increase in the SBS values of the Tetric N-Ceram resin was noticed in comparison with the Filtek Z350 and the differences was statistically significant. Although the specimens failed in adhesive, cohesive and mixed fracture modes but the cohesive was found to be the dominant failure mode in all groups. Conclusion. Among the tested bonding agents and resin composites, the Tetric N-Ceram composite bonded by Tetric N-bond self-etch adhesive with the Biodentine showed the highest SBS compared to the other combinations.

A Bibliometric Analysis of Electrospun Nanofibers for Dentistry

Electrospun nanofibers have been widely used in dentistry due to their excellent properties, such as high surface area and high porosity, this bibliometric study aimed to review the application fields, research status, and development trends of electrospun nanofibers in different fields of dentistry in recent years. All of the data were obtained from the Web of Science from 2004 to 2021. Origin, Microsoft Excel, VOSviewer, and Carrot² were used to process, analyze, and evaluate the publication year, countries/region, affiliations, authors, citations, keywords, and journal data. After being refined by the year of publication, document types and research fields, a total of 378 publications were included in this study, and an increasing number of publications was evident. Through linear regression calculations, it is predicted that the number of published articles in 2022 will be 66. The most published journal about electrospun dental materials is Materials Science & Engineering C-Materials for Biological Applications, among the six core journals identified, the percent of journals with Journal Citation Reports (JCR) Q1 was 60%. A total of 17.60% of the publications originated from China, and the most productive institution was the University of Sheffield. Among all the 1949 authors, the most productive author was Marco C. Bottino. Most electrospun dental nanofibers are used in periodontal regeneration, and Polycaprolactone (PCL) is the most frequently used material in all studies. With the global upsurge in research on electrospun dental materials, bone regeneration, tissue regeneration, and cell differentiation and proliferation will still be the research hotspots of electrospun dental materials in recent years. Extensive collaboration and citations among authors, institutions and countries will also reach a new level.

Comparison of Microleakage in Nanocomposite and Amalgam as a Crown Foundation Material Luted with Different Luting Cements under CAD-CAM Milled Metal Crowns: An In Vitro Microscopic Study

Microleakage is a persistent problem despite advancement in materials and techniques in fixed prosthodontics. This leads to the importance of sound crown foundation material and luting agents used to maintain the marginal seal. The literature is deficient with studies, comparing microleakage under various crown foundation materials and luting agents, especially with CAD-CAM (computer-aided design and computer-aided manufacturing) metal crowns. This study was aimed to compare microleakage in a nanocomposite/dentinal bonding agent and amalgam/cavity varnish as crown foundation materials luted with two different luting cements: resin-reinforced glass ionomer cement and self-adhesive resin cement, under both dry and contaminated conditions. A hundred intact, caries-free human molars were prepared to receive crown foundation material and extra coronal restorations. Amalgams with cavity varnish and nanocomposites with dentinal bonding agent in both ideal and contaminated conditions were used as crown foundation materials. After restoration, each sample was cemented with a CAD-CAM milled metal crown using two different luting agents—resin-reinforced glass ionomer cement and self-adhesive resin cements both in ideal and contaminated conditions. Cementation was followed by thermocycling of samples, immersion in erythrosine B dye, embedding in clear auto polymerizing acrylic resin and sectioning to evaluate microleakage using stereomicroscope. The mean microleakage between different luting cements on the experimental side of the facial surface was 137.64 μm and 211.01 μm for resin-reinforced GIC and for self-adhesive resin cement was 119.78 μm and 150.42 μm, under ideal and contaminated condition, respectively. There was a significant difference in mean micro-leakage between different crown foundation material and cement groups used in the study. The composites and amalgam, both when used as crown foundation material and luted with use of technically advanced CAD-CAM metal crown with self-adhesive resin cement (in both ideal or contaminated condition), showed less microleakage than in resin-reinforced glass ionomer cement. Overall, the self-adhesive resin cement showed comparatively reduced microleakage in all combinations with different crown foundations. Thus, this combination can be used in daily clinical practice to provide better protection from further decay.

Eight-year clinical evaluation of two types of resin composite in non-carious cervical lesions

OBJECTIVES

In this clinical study, the 8-year clinical performances of a flowable resin composite was compared with that of a conventional resin composite.

MATERIALS AND METHODS

Ninety non-carious cervical lesions (NCCLs) in 19 participants were involved in this trial. NCCLs were restored with a flowable composite (Clearfil Flow FX: FX, Kuraray Noritake, Japan) or a conventional resin composite (Clearfil AP-X: AP) in conjunction with a one-step self-etch adhesive (Clearfil S3 Bond). Each participant had both types of resin composite restorations that were randomly allocated. The restorations were evaluated at baseline and annually up to 8 years using modified USPHS criteria. The data were statistically analyzed using the Fisher's exact test, Kaplan-Meier method, and a multivariate Cox-regression with frailty models (p < 0.05).

RESULTS

The 8-year participant recall rate was 95%. One hundred percent retention was recorded for AP, whereas four out of 46 restorations were lost for FX during the 8 years. The incidence of marginal staining increased over time regardless of the type of resin composite, showing 48% for AP and 57% for FX after 8 years. Wear of the resin composite occurred only for the flowable material and there was a significant difference between the types of resin composite (p = 0.024). Overall survival rates at 8 years for AP and FX were 98% and 82% respectively (p = 0.110).

CONCLUSIONS

The flowable resin composite presented lower wear resistance and showed a lower survival rate compared with the conventional composite after eight years of clinical service.

CLINICAL RELEVANCE

Flowable resin composites may show greater wear after long-term clinical service.

TRIAL REGISTRATION NUMBER

UMIN000028745, Date of registration: August 19, 2017.

Longevity of Direct Resin Composite Restorations in Maxillary Anterior Crown Fractures: A 4-year Clinical Evaluation

OBJECTIVES

To investigate the longevity of direct composites for Class IV restorations and the possible reasons of failure.

METHODS AND MATERIALS

The longevity of 168 Class IV restorations in 50 adult patients was evaluated, in terms of modified United States Public Health Service criteria, for 4 years. Restorations were performed using a monochromatic layered microhybrid, resinbased composite (RBC) (Essentia, Universal Shade, GC Corporation, Japan; n=76) and polychromatic layered micro/nanohybrid (MD and LE shades, Essentia, GC Corporation, Japan; n=92) RBCs, by a single operator.

RESULTS

The majority of the teeth (n=156) remained acceptable at the end of 4 years, and the overall survival (OS) rate was considered as 92.86%. Survival rates for the monochromatic layering technique (MLT) and polychromatic layering technique (PLT) were 90.8% and 94.6%, respectively. Mean survival was 46 months for MLT and 47 months for PLT, indicating no significant difference (p=0.343). Fracture of the restoration was the most common reason for failure (4.2% out of 7.1% of general failures) for both the layering techniques.

CONCLUSIONS

Under the conditions of this mid-term clinical study, MLT and PLT as well as microhybrid and nanohybrid resin composite materials, showed similar clinical durability. In terms of simplicity, monochromatic layering can be preferred for Class IV restorations, when the right indication criteria are met.

Developments in resin-based composites

With the phasing down of dental amalgam use in response to the Minamata Convention, it is likely that resin-based composite restoratives will be the dental material of choice for the direct restoration of compromised dentition in the UK, at least for the foreseeable future. The current materials have a finite lifespan, with failures predominately due to either secondary caries or fracture. Consequently, there is considerable in vitro research reported each year with the intention of producing improved materials. This review describes the recent research in materials designed to have low polymerisation shrinkage and increased mechanical properties. Also described is research into materials that are either antimicrobial or are designed to release ions into the surrounding oral environment, with the aim of stimulating remineralisation of the surrounding dental tissues. It is hoped that by describing this recent research, clinicians will be able to gain some understanding of the current research that will potentially lead to new products that they can use to improve patient treatment in the future.

Provides an overview of recent research developments aimed at improving the performance of resin-based composites.

Details the recent developments in monomers and fillers to produce resin-based composites that either have lower polymerisation shrinkage or better mechanical properties compared to current commercially available products.

Describes recent research on developing resin-based composites that can act as potential sources of antimicrobial or remineralising agents.

Effect of Different Concentrations of Silver Nanoparticles on the Quality of the Chemical Bond of Glass Ionomer Cement Dentine in Primary Teeth

Background: The nanotechnologies have been applied for dental restorative materials manufacturing such as glass ionomer cement, composites, tooth regeneration, and endodontic sealers. The study aimed to investigate the chemical bond of conventional glass ionomer cement and to evaluate the addition of different concentrations of silver nanoparticles (AgNPs) on the quality of the chemical bond of glass ionomer cement to primary dentin.

Methods: Silver nanoparticle (AgNP) powder was added in concentrations of 0.2, 0.4, and 0.6% to the conventional powder of GIC Fuji II. Then, the powder was added to the liquid and mixed with the recommended powder/liquid ratio of 3.6:1 g. The Fourier-transform infrared spectra (FTIR) of teeth with 0.2%, 0.4%, and 0.6% w/w of silver nanoparticles in GIC fills and the control tooth were obtained. The conventional glass ionomer was used as a control group. The control and the plain silver tooth were subjected to FTIR analysis using an ATR–FTIR spectrophotometer (ThermoFisher Scientific, Waltham, MA, United States) with zinc selenide (ZnSe) ATR crystal (attenuated total reflection) and OPUS v7.5 software. All spectra were recorded in the range of 500–3,500 cm⁻¹ in the transmission mode with an ATR module.

Results: The AgNPs added at 0.2, 0.4, and 0.6% concentration to GIC provided some information in the context of bond interaction with the dentin. Various bond peaks were seen for calcium, carbonate, phosphate, and amide. In our study, only the amide and phosphate were generated. The amide peaks were almost similar to the control, 0.2%, 0.4%, and 0.6%, with the peaks in the range of 1250–1650 cm⁻¹. There was a clear shift in the phosphate peak from the control, 0.2, and 0.4%, which was about 1050 cm⁻¹, whereas for 0.6%, there was a clear shift from 1050 cm⁻¹ to 880 cm⁻¹.

Conclusion: GIC supplemented with AgNPs showed that a concentration above 0.4% of AgNPs altered the bond quality in dentin interaction. In conclusion, adding AgNPs at a minimal level improves the mechanical properties and maintains the same bond quality as GIC.

Brushing Effect on the Properties of Glass Ionomer Cement Modified by Hydroxyapatite Nanoparticles or by Bioactive Glasses

This study evaluated the physical and mechanical properties of glass ionomer cement (GIC) associated with 5% hydroxyapatite nanoparticles (NPHAps) and 10% bioactive glass (BAG) 45S5 before and after brushing at different storage times. Surface roughness was evaluated using a rugosimeter, Vickers hardness using a microdurometer, and mass variation measured in an analytical balance at 1, 7, 15, 30, and 60 days before and after the brushing test, with the aid of toothbrushing simulator and soft bristle toothbrushes. Nonnormal distribution was observed, and the nonparametric Wilcoxon and Kruskal–Wallis tests followed by Dunn's were performed, with a significance level of 5%. We observed higher values for mass loss on the first day for all groups. The surface roughness was lower in the control and NP groups, 30 days after brushing. Higher values for hardness were found in the control group and lower ones for NP, after brushing. The control and BAG groups presented a decrease in hardness over time. The NP group presented the highest values before brushing, while the control group had the highest values after brushing. The association of NPHPa with the GIC is the most promising combination, since it presented satisfactory values for surface hardness. However, conventional GIC not associated with NPHPa or BAG is still an option, since it is available in the market and the most economically viable option.

Effect of Printing Layer Thickness and Postprinting Conditions on the Flexural Strength and Hardness of a 3D-Printed Resin

Background

Recently, dentists can utilize three-dimensional printing technology in fabricating dental restoration. However, to date, there is a lack of evidence regarding the effect of printing layer thicknesses and postprinting on the mechanical properties of the 3D-printed temporary restorations with the additive manufacturing technique. So, this study evaluated the mechanical properties of a 3D-printed dental resin material with different printing layer thicknesses and postprinting methods.

Methods

210 specimens of a temporary crown material (A2 EVERES TEMPORARY, SISMA, Italy) were 3D-printed with different printing layer thicknesses (25, 50, and 100 μm). Then, specimens were 3D-printed using DLP technology (EVERES ZERO, DLP 3D printer, SISMA, Italy) which received seven different treatment conditions after printing: water storage for 24 h or 1 month, light curing or heat curing for 5 or 15 minutes, and control. Flexural properties were evaluated using a three-point bending test on a universal testing machine (ISO standard 4049). The Vickers hardness test was used to evaluate the microhardness of the material system. The degree of conversion was measured using an FT-IR ATR spectrophotometer. Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test (p ≤ 0.05).

Results

The 100 μm printing layer thickness had the highest flexural strength among the other thickness groups. As a combined effect printing thickness and postprinting conditions, the 100 μm with the dry storage group has the highest flexural strength among the tested groups (94.60 MPa). Thus, the group with 100 μm thickness that was heat cured for 5 minutes (HC 5 min 100 μm) has the highest VHN value (VHN = 17.95). Also, the highest mean DC% was reported by 50 μm layer thickness (42.84%).

Conclusions

The thickness of the 100 μm printing layer had the highest flexural strength compared to the 25 μm and 50 μm groups. Also, the postprinting treatment conditions influenced the flexural strength and hardness of the 3D-printed resin material.

Effect of simulated tootbrushing on surface roughness of sealant agent coupled nanohybrid composite resins

OBJECTIVE

To investigate the effect of toothbrushing on the surface roughness (R_a ) of different sealant agent coupled nanohybrid composite resins.

MATERIALS AND METHODS

One hundred sixty disc-shaped (10 × 2 mm) specimens were prepared from four different nanohybrid composite resins (Z-550, Tetric EvoCeram, Clearfill Majesty, Ice). Specimen groups were divided into four subgroups for conventional polishing (control) and to apply three different surface sealant agents (Palaseal, Optiglaze, Biscover LV) (n = 10). The R_a values of the specimens were recorded before (R_a 0) and after 10,000 cycles of toothbrushing (R_a 1). The surface properties of the specimens were evaluated with scanning electron microscope (SEM). Data were statistically analyzed by two-way analysis of variance (ANOVA), Tukey HSD, and paired sample t tests.

RESULTS

Composite resin material, surface treatment, and their interaction were significant on R_a values (p < 0.001). Significant decrease in R_a 0 values observed for surface sealant agent coupled Clearfill Majesty and Tetric EvoCeram composite resin groups compared with the control groups (p < 0.05). After simulated one-year toothbrushing, the control group of Clearfill Majesty had the highest R_a 1 value (p < 0.001). The R_a 1 values of all groups were significantly higher than the R_a 0 values (p < 0.05).

CONCLUSIONS

Simulated 1-year toothbrushing increased the surface roughness of all nanohybrid composite resin materials. Optiglaze and Biscover LV sealant agents on Tetric EvoCeram, and all tested sealant agents on Clearfill Majesty enabled smoother surfaces than conventional polishing after toothbrushing.

CLINICAL SIGNIFICANCE

Because toothbrushing increases the surface roughness of tested nanohybrid composite resins, the application of surface sealant agents on some of the tested resins can be considered for smoother surfaces.