Risk aspects of dental restoratives: From amalgam to tooth-colored materials

Dental materials' choice of patients has considerably changed. Whereas cast gold and amalgam have been the predominant biomaterials for decades, today toothcolored materials like resin-based composites and ceramics are more and more successful. However, are we going to replace a good but biologically questionable material(amalgam) with an equal material(resin composite) being more esthetic but also biologically questionable? For amalgam, long-term clinical studies reported some significant hints that in single cases amalgam may be a health hazard for patients, finally Norway banned amalgam completely. The main advantage of a resin-based composite over amalgam is its tooth-like appearance and more or less absence of extensive preparation rules. For many years it was believed that resin-based composites may cause pulpal injury. However, pulpal injury associated with the use of resin-based composites is not correlated with their cytotoxic properties. Nevertheless, resin-based composites and other dental materials require rigorous safety evaluation and continuous monitoring to prevent adverse events similar like with amalgam. Because of nonbiocompatible pulp responses to resin-based composites and amalgam, they should not be placed in direct contact with the dental pulp. The less dentin remaining in the floor of preparations between resin-based composites or other dental materials is more likely to cause pulpitis. Percentage of patients and dental practitioners who display allergic reactions is between 0.7% and 2%. The release of cytotoxic monomers from resin-based materials is highest after polymerization and much lower after 1 wk. Substances released from resin-based composites have been shown to be toxic in cytotoxicity tests. Nevertheless, in vitro cytotoxicity assays have shown that amalgam has greater toxic effects than resin-based composites, sometime 100-700-fold higher. Altogether, the risk of side-effects is low, but not zero, especially for dental personnel.

PHOTOCURING STUDY OF NEW DENTAL RESINS BASED ON MULTIFUNCTIONAL ACRYLIC ISOCYANURATE BY PHOTOCALORIMETRY

Photocuring of new dental resins composed of tri(2-hydroxyethyl) isocyanurate triacrylate (THITA) alone and its mixtures with trimethylolpropane triacrylate (TMPTA) or pentaerythritol triacrylate (PETA) initiated by camphorquinone/amine system was studied by photocalorimetry. Among several different amines as coinitiators, 2-ethyl-4-dimethylaminobenzoate (AM-3), N,N-dimethylbenzylamine (AM-5) and 2,4,6-[tri(dimethylaminomethyl)]phenol (AM-6) are most effective. Upon irradiation, photopolymerization can occur immediately and no induction period appears in N-2 nor in air. Comparing the THITA/TMPTA and THITA/PETA mixtures, the parameters of photopolymerization and hardness of photocured samples show a small difference and only change slightly with varying molar ratios of mixture. In the presence of inorganic filler, the hardness of photocuring resins is almost the same as that for commercial products.

Orthodontic Management of Multiple Impacted Teeth in a Patient with Gardner’s Syndrome: A Case Report

Gardner syndrome (also known as familial colorectal polyposis) is a rare autosomal dominant condition. It is characterized by osteomas, familial polyposis of the colon, cutaneous epidermoid cysts, soft tissue tumors, as well as certain dental anomalies. We report the case of a 29 years old male patient with Gardner’s syndrome who presented with no intestinal polyps but instead had an osteoma on the left side of the mandible and multiple impacted teeth. The case showed the possibility to manage the multiple impacted teeth without jeopardizing the health of the teeth in terms of mobility or significant root resorption taking into consideration the increased bone density in such patients.

The Role of Leukocyte and Platelet-Rich Fibrin in Enhancing the Healing of Extraction Sockets: An Overview of the Literature

Introduction: Leukocyte and platelet-rich fibrin (L-PRF) is an emerging material in dentistry, however, there are controversies surrounding its effectiveness. Despite the amount of literature available, debates regarding its effect continue. This review aims to summarize and clarify the data surrounding the use of L-PRF in promoting the healing of extraction sockets, which may offer a better outcome for future treatments. Purpose: The purpose of this review is to evaluate the current literature on the use of L-PRF in promoting the healing of extraction sockets, and to provide a comprehensive overview of the available evidence. Methods: A comprehensive computer-based search of databases such as PubMed, Medline, and Cochrane Library was conducted. Results: The results of this review suggest that L-PRF has shown promise in promoting early healing of extraction sockets, but the evidence for its effectiveness over a longer period is limited. Conclusion: Although L-PRF has shown promising results in the early healing periods, its effectiveness over a longer healing period cannot be confirmed based on the available data. More clinical trials with standardized protocols and consistent measurement methods are needed to establish the role of L-PRF in enhancing the healing of extraction sockets.

Evaluating the Benefits of Platelet Rich-Fibrin in Periodontal Regeneration: A Literature Review

Introduction: Platelet Rich-Fibrin (PRF) is a biological matrix derived from a patient’s own blood, rich in growth factors and platelets. Its use in various periodontal and non-periodontal procedures is gaining recognition due to its potential in promoting tissue regeneration. The purpose of this review was to evaluate the benefits of using PRF in intra-bony defect regeneration, guided-bone regeneration, and sinus floor elevation. Methods: The study searched PubMed for manuscripts published between 2017 and 2022 to better understand the clinical and radiological effects of PRF. The manuscripts were divided into the following sections: intra-bony defect regeneration, guided-bone regeneration, and sinus floor elevation. Results: In intra-bony defects, PRF improved clinical and radiological parameters when compared with OFD alone, with a significant difference in wound healing at 7 days. In GBR, a CBCT evaluation shows no statistical difference between the PRF-autogenous bone complex group and the bovine bone-collagen membrane complex regarding volume change of the augmented bone with a 16% rate of bone loss following a 6-month healing period. Also, a slight increase in bone thickness has been seen when liquid PRF is used. In sinus floor elevation, results revealed no differences in graft volume between PRF group and control group at any of the evaluated time points. Although higher implant stability immediately postoperatively, higher new bone formation, the lesser amount of residual graft and earlier implant placement. Conclusion: Platelet Rich-Fibrin is widely accepted for use in periodontal surgery and dentistry due to its minimally invasive nature and low risk of adverse effects, with positive results in tissue regeneration. There is evidence that PRF leads to improved and faster healing, as well as cost-effective regenerative procedures compared to other treatments.

TGF-β2 downregulates osteogenesis under inflammatory conditions in dental follicle stem cells

Bone formation is important for the reconstruction of bone-related structures in areas that have been damaged by inflammation.Inflammatory conditions such as those that occur in patients with rheumatoid arthritis, cystic fibrosis, and periodontitis have been shown to inhibit osteoblastic differentiation. This study focussed on dental follicle stem cells(DFSCs), which are found in developing tooth germ and participate in the reconstruction of alveolar bone and periodontal tissue in periodontal disease. After bacterial infection of inflamed dental tissue, the destruction of bone was observed. Currently, little is known about the relationship between the inflammatory environment and bone formation. Osteogenic differentiation of inflamed DFSCs resulted in decreased alkaline phosphatase(ALP) activity and alizarin red S staining compared to normal DFSCs. Additionally, in vivo transplantation of inflamed and normal DFSCs demonstrated severe impairment of osteogenesis by inflamed DFSCs. Protein profile analysis via liquid chromatography coupled with tandem mass spectrometry was performed to analyse the differences in protein expression in inflamed and normal tissue. Comparison of inflamed and normal DFSCs showed significant changes in the level of expression of transforming growth factor(TGF)-β2. Porphyromonas gingivalis(P.g.)-derived lipopolysaccharide(LPS) was used to create in vitro inflammatory conditions similar to periodontitis. The osteogenic differentiation of LPS-treated DFSCs was suppressed, and the cells displayed low levels of TGF-β1 and high levels of TGF-β2. DFSCs treated with TGF-β2 inhibitors showed significant increases in alizarin red S staining and ALP activity. TGF-β1 expression was also increased after inhibition of TGF-β2. By examining inflamed DFSCs and LPS-triggered DFSCs, these studies showed both clinically and experimentally that the increase in TGF-β2 levels that occurs under inflammatory conditions inhibits bone formation.

A simple,sensitive and non-destructive technique for characterizing bovine dental enamel erosion:attenuated total reflection Fourier transform infrared spectroscopy

Although many techniques are available to assess enamel erosion in vitro, a simple, non-destructive method with sufficient sensitivity for quantifying dental erosion is required. This study characterized the bovine dental enamel erosion induced by various acidic beverages in vitro using attenuated total reflection Fourier transform infrared （ATR-FTIR） spectroscopy. Deionized water （control） and 10 acidic beverages were selected to study erosion, and the pH and neutralizable acidity were measured. Bovine anterior teeth （110） were polished with up to 1 200-grit silicon carbide paper to produce flat enamel surfaces, which were then immersed in 20 mL of the beverages for 30 min at 37 ℃. The degree of erosion was evaluated using ATR-FTIR spectroscopy and Vickers＇ microhardness measurements. The spectra obtained were interpreted in two ways that focused on the ~1, ~3 phosphate contour： the ratio of the height amplitude of ~3 P04 to that of/11 P04 （Method 1） and the shift of the v3 P04 peak to a higher wavenumber （Method 2）. The percentage changes in microhardness after the erosion treatments were primarily affected by the pH of the immersion media. Regression analyses revealed highly significant correlations between the surface hardness change and the degree of erosion, as detected by ATR-FTIR spectroscopy （P〈0.001）. Method 1 was the most sensitive to these changes, followed by surface hardness change measurements and Method 2. This study suggests that ATR- FTIR spectroscopy is potentially advantageous over the microhardness test as a simple, non-destructive, sensitive technique for the quantification of enamel erosion.

Laser and Its Application in Periodontology: A Review of Literature

Introduction: The use of lasers is an emerging therapy in periodontology, however, controversies regarding its use. Despite the vast amount of literature that is currently available, debates regarding the use of lasers in periodontal therapy continue. This review aims to summarize and clarify the myths surrounding the use of lasers in periodontal therapy, which may offer new hope for the treatment’s future. Methods: A comprehensive computer-based search was done using various databases like PubMed, Medline, and Cochrane Library. Results: Laser therapy has influenced periodontal treatment in many aspects. The advantages of laser over conventional instruments were reported, which include pain relief, inflammation reduction, tissue repair acceleration, wound healing, reduction of scar formation, removal of granulation tissue and epithelial lining, and treatment of periodontal pockets. Today, the laser starts to get more people’s attention. However, an evidence-based approach to using lasers in periodontal treatment must be developed. The potential risks associated with lasers should also be considered. There must be careful and strict safety precautions implemented. Conclusion: Although laser therapy has shown promising results in the treatment of periodontal disease, further research is needed before the clinical use of lasers in evidence-based practice. Further long-term studies and clinical studies in human models are needed to generalize laser therapy in periodontology.

Synthesis of CaO-SiO₂Compounds Using Materials Extracted from Industrial Wastes

Mineral trioxide aggregate (MTA) cement is an attractive material in endodontic dentistry. The purpose of this study was to produce calcium silicate, which is a major component of MTA, from waste materials. A dental alginate impression gel and used chalks were selected and mixed in a suitable ratio (Code: EXP). As a control, CaCO3 and a commercial diatomite were used (Code: CON). Each powder was heated to 850。C and 1000。C, and then kneaded with water. TG-DTA, compressive tests, SEM observations, elemental mapping analyses, and XRD analyses were performed. TG-DTA indicated that weight reduction of CaCO3 started at 600。C, and it completely decomposed on heating at 850。C. The strength was affected by the temperature. After heating, CaCO3 was transformed into CaO and/or Ca2SiO4, and Ca(OH)2 was formed by mixing with water. There were no differences between EXP and CON. These data suggested that recycled wastes might be promising MTA sources.

Cell Proliferation Ability of Mouse Fibroblast-Like Cells and Osteoblast-Like Cells on a Ti-6Al-4V Alloy Film Produced by Selective Laser Melting

Successful regeneration of tissues and organs relies on the application of suitable substrates or scaffolds in scaffold-based regenerative medicine. In this study, Ti-6Al-4V alloy films (Ti alloy film) were produced using a three-dimensional printing technique called Selective Laser Melting (SLM), which is one of the metal additive manufacturing techniques. The thickness of produced Ti alloy film was approximately 250 μm. The laser-irradiated surface of Ti alloy film had a relatively smooth yet porous surface. The non-irradiated surface was also porous but also retained a lot of partially melted Ti-6Al-4V powder. Cell proliferation ability of mouse fibroblast-like cells (L929 cells) and mouse osteoblast-like cells (MC3T3-E1 cells) on both the surfaces of Ti alloy film was examined using WST assay. Both L929 and MC3T3-E1 cells underwent cell proliferation during the culture period. These results indicate that selective laser melting is suitable for producing a cell-compatible Ti-6Al-4V alloy film for biomaterials applications.

高分子聚合材料表面润湿性对成纤维细胞贴附能力的影响

目的:研究高分子聚合体表面润湿性对成纤维细胞初期贴附能力的影响。方法:使用薄膜等离子体聚合法在圆形盖玻片表面生成六甲基二硅氧烷(Hexamethyldisiloxane,HMDSO)薄膜聚合体,然后用低温氧等离子体轰击聚合体表面,根据轰击时间的不同形成一系列的不同润湿性表面,将成纤维细胞系L929接种于不同润湿性表面,观察6h、12h时细胞的贴附率,并观察细胞的形态。结果:随着氧等离子体轰击时间的增加,HMDSO聚合体表面接触角从106°下降为0°,显示表面由高度憎水变为高度亲水。成纤维细胞在亲水表面较憎水表面有更高的早期贴附率,细胞伸展更充分。结论:高分子聚合体的表面润湿性对成纤维细胞的早期贴附和伸展有显著的影响。亲水性表面更有利于细胞的早期贴附和伸展。

高分子聚合体表面润湿性研究模型的建立

目的:利用低温等离子体轰击法建立高分子聚合体表面润湿性研究模型。方法:使用氧低温等离子体轰击六甲基二硅氧烷薄膜聚合体表面,测定表面接触角,建立轰击时间-表面接触角曲线,建立线型回归方程。观察在不同介质中保存时材料表面接触角的变化情况。结果:经过氧等离子体轰击后,六甲基二硅氧烷薄膜聚合体表面接触角明显下降,与处理时间呈现负相关性。在空气中保存时,表面接触角随时间逐渐上升,0度接触角表面24 h后上升为20°左右,而在双蒸水中保存的表面接触角基本保持不变。结论:氧等离子体轰击法能可控性地改变六甲基二硅氧烷薄膜聚合体表面润湿性,处理后的表面在水中接触角保持稳定,该方法可以用来建立表面润湿性研究模型。

QCM-D技术在不同润湿性表面蛋白吸附研究中的应用

目的:利用石英晶体微平衡-分散(QCM-D)技术研究白蛋白在高度亲水和高度疏水表面的吸附情况。方法:利用等离子聚合技术在8片圆形石英传感器上形成六甲基二硅氧烷薄膜聚合体薄膜,将4片上述试样采用低温氧等离子体轰击80 s,这两种表面分别代表高度疏水及高度亲水表面。将处理后的两种传感器装入QCM-D检测仪,将400 mg/L的牛血白蛋白溶液引入传感检测室,观察共振频率和离散因子随时间的变化,计算出蛋白的吸附量。结果:白蛋白在两种表面的吸附主要在早期10 s中完成,此后吸附变慢,在30 min左右达到吸附-离散平衡,30 min时白蛋白在高度疏水表面的平均吸附量为294.6 ng/cm2,而在高度亲水表面平均吸附量为235.1 g/cm2,两者有显著性差异。结论:QCM-D可以用来精确测定蛋白质在石英传感器表面的吸附,高度疏水性表面对白蛋白有较高的吸附能力。

Interleukin-1βinduces human cementoblasts to support osteoclastogenesis

Injury of the periodontium followed by inflammatory response often leads to mot resorption. Resorption is accomplished by osteoclasts and their generation may depend on an interaction with the cells in direct contact with the root, the cementoblasts. Our study aimed to investigate the role of human cementoblasts in the formation of osteoclasts and the effect of interleukin （IL）- 1β hereupon. Extracted teeth from healthy volunteers were subjected to sequential digestion by type I collagenase and trypsin. The effect of enzymatic digestion on the presence of cells on the root surface was analyzed by histology. Gene expression of primary human cementoblasts （pHCB） was compared with a human cementoblast cell line （HCEM）. The pHCBs were analyzed for their expression of IL-1 receptors as well as of receptor activator of nuclear factor kappa-B ligand （RANKL） and osteoprotegerin （OPG）. In a co-culture system consisting of osteoclast precursors （blood monocytes） and pHCBs, the formation of osteoclasts and their resorptive activity was assessed by osteo-assay and ivory slices. The cells obtained after a 120 min enzyme digestion expressed the highest level of bone sialoprotein, similar to that of HCEM. This fraction of isolated cells also shared a similar expression pattern of IL-1 receptors （ILl-R1 and ILl-R2）. Treatment with IL-11~ potently upregulated RANKL expression but not of OPG. pHCBs were shown to induce the formation of functional osteoclasts. This capacity was significantly stimulated by pretreating the pHCBs with IL-1β prior to their co-culture with human blood monocytes. Our study demonstrated that cementoblasts have the capacity to induce osteoclastogenesis, a capacity strongly promoted by IL-1β. These results may explain why osteoclasts can be formed next to the root of teeth.

Osteocyte morphology and orientation in relation to strain in the jaw bone

Bone mass is important for dental implant success and is regulated by mechanoresponsive osteocytes. We aimed to investigate the relationship between the levels and orientation of tensile strain and morphology and orientation of osteocytes at different dental implant positions in the maxillary bone. Bone biopsies were retrieved from eight patients who underwent maxillary sinus-floor elevation with β-tricalcium phosphate prior to implant placement. Gap versus free-ending locations were compared using 1) a three-dimensional finite-element model of the maxilla to predict the tensile strain magnitude and direction and 2) histology and histomorphometric analyses. The finite-element model predicted larger, differently directed tensile strains in the gap versus freeending locations. The mean percentage of mineralised residual native-tissue volume, osteocyte number(mean ± standard deviations:97 ± 40/region-of-interest), and osteocyte shape(90% elongated,10% round) were similar for both locations. However, the osteocyte surface area was 1.5-times larger in the gap than in the free-ending locations, and the elongated osteocytes in these locations were more cranially caudally oriented. In conclusion, significant differences in the osteocyte surface area and orientation seem to exist locally in the maxillary bone, which may be related to the tensile strain magnitude and orientation. This might reflect local differences in the osteocyte mechanosensitivity and bone quality, suggesting differences in dental implant success based on the location in the maxilla.

Regulation of cell locomotion by nanosecond-laser-induced hydroxyapatite patterning

Hydroxyapatite,an essential mineral in human bones composed mainly of calcium and phosphorus,is widely used to coat bone graft and implant surfaces for enhanced biocompatibility and bone formation.For a strong implant-bone bond,the bone-forming cells must not only adhere to the implant surface but also move to the surface requiring bone formation.However,strong adhesion tends to inhibit cell migration on the surface of hydroxyapatite.Herein,a cell migration highway pattern that can promote cell migration was prepared using a nanosecond laser on hydroxyapatite coating.The developed surface promoted bone-forming cell movement compared with the unpatterned hydroxyapatite surface,and the cell adhesion and movement speed could be controlled by adjusting the pattern width.Live-cell microscopy,cell tracking,and serum protein analysis revealed the fundamental principle of this phenomenon.These findings are applicable to hydroxyapatite-coated biomaterials and can be implemented easily by laser patterning without complicated processes.The cell migration highway can promote and control cell movement while maintaining the existing advantages of hydroxyapatite coatings.Furthermore,it can be applied to the surface treatment of not only implant materials directly bonded to bone but also various implanted biomaterials implanted that require cell movement control.