Evaluation of biologic effects of dental materials using four different cell culture techniques

abstract – The cytotoxicity of fresh and 1-day-old silicate cement, composite restorative material and zinc oxide-eugenol cement (ZOE) was tested using human epithelial cells (NCTC 2544) in four different cell culture systems: (1) ^5.1Cr-release from prelabeled cells after incubation for 4 and 24 h in the presence of the materials, (2) Implanting the materials on an agar overlay and visualizing any cytotoxic effects after 24 h by neutral red vital stain. (3) Cell growth during 5 d in the presence of the materials7hellip; (4) Colony-forming ability after exposure of the cells for 30 min to medium previously incubated with the materials for 24 h. Freshly prepared and 1-day-old ZOE exhibited a prominent cytotoxic effect in all four systems. A less marked effect was found for the composite material in systems 2, 3, and 4, while silicate cement appeared to be the least toxic material in these three systems. Neither silicate cement nor composite showed any cytotoxic effect in system 1 based on⁵¹Cr-release. It is concluded that the effects obtained by the cell culture techniques did not mimic the reactions obtained when the materials are tested under conditions which reflect their clinical use.     

Evaluation of biocompatibility of metallic dental materials in cell culture model

Biocompatibility of metals for dental use was tested using a three-dimensional model consisting of oral keratinocytes cultured on de-epidermised sub-mucosa. The toxicity of orthodontic metallic wire and soldering material was assessed through parameters such as the morphology and growth rate of the keratinocytes, as well as by classical histology, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The sharp composition of metallic wires and soldering materials was assessed by Auger Electron Spectroscopy (AES). The results of our experiment showed that the new model revealed inhibition of keratinocyte growth and stratification near soldering material, whereas mucosal cells were able to grow and layer out on dental wire. It is concluded that this experimental model, which simulates the oral environment, is useful for studying the effects of materials for dental use for its sensibility and reproducibility. Moreover it can provide morpho-functional information which cannot be achieved by traditional methods.     

Sensitivity of different human cell lines in the biologic evaluation of dental resin-based restorative materials

Abstract— Three different cell lines of human origin, i.c. human epithelica cells (NCTC 2544), and epithelial and fibroblast like cells from human gingiva, were tested for their sensitivity fo three different dental resin-based restorative materials using four different assay techniques. The techniques applied were cell growth measurements by cell number, ⁵³Cr-release, Agar overlay with neutral red staining and colony formation. The ranking of teh cells according to their sensitivity ot the materials varied with the assay technique applied, with no cell line being consistently more sensitive than the others. It is also suggested that the type of medium applied could be important for the result obtained.     

Evaluation of the fracture resistance of reattached incisal fragments using different materials and techniques

Abstract – Objectives: When coronal fracture occurs in anterior teeth, fragment reattachment can be a valid alternative to a direct restoration. The aim of this study was to evaluate the influence of the material and the technique used to reattach the fragment. Materials and methods: Eighty sound maxillary and mandibular incisors were selected and randomly divided into eight groups (n = 10). The incisal third of each tooth was removed using a saw machine. The fragments in groups 1–4 were reattached using resin‐based materials: group 1 adhesive, group 2 flow, group 3 composite, group 4 cement; in groups 5–8, the same materials mentioned before were used but a bevel was also performed on both labial and lingual surfaces. Shear bond strength (SBS) was calculated by applying a load incisal to the reattachment line. A two‐way Anova was used to evaluate the influence of materials and techniques on the SBS. Results: The technique used was statistically significant (P < 0.001), while the material was not (P = 0.793). Conclusions: The choice of material seems to have no influence on the SBS, whereas a bevel performed on the labial and lingual surfaces can significantly improve the SBS of the reattached fragment.     

Evaluation of the cytotoxicity of four dental materials in vitro assessed by cell viability and enzyme cytochemistry

The cytotoxic effects of zinc phosphate and silicate cements, Concise composite and zinc oxide/eugenol were evaluated after 24 h in an in vitro system which simulates the clinical usage of the material, and the results compared with those using phenol. Data of gross changes affecting cell viability placed these materials in ranking order of increasing severity: Concise less than zinc phosphate less than Silicap much less than zinc oxide/eugenol. More discrete changes involving alterations in enzyme cytochemistry were assessed and the significance of the results discussed. The presence of dentine powder in the system reduced the cytotoxic effects on these materials.     

Survival predictions of four types of dental restorative materials.

The present study assessed the survival predictions made for four different types of dental restorative materials, using a mixture model involving the standard Weibull distribution function. A large number of amalgam, anterior resin, glass polyalkenoate (ionomer) cement, and pit and fissure sealant restorations were examined over varying periods of up to 18 years. The materials had been placed by numerous staff and students at a teaching hospital. Based on maximum likelihood estimations of the parameters of the mixture model distribution, survival curves were generated and found to agree closely with the actuarial survival curves estimated from the same data. As the years of data used to fit the mixture model curves decreased, then the fitted curves started to exhibit obvious divergences from the actuarial curves at 12-13 years for amalgams, 3-4 years for anterior resins and sealants, and 1-2 years for glass polyalkenoate (ionomer) cements. At least 5 per cent of restorations needed to have failed over any period to allow close agreement of the two curves, with the slower failing materials requiring longer observation periods.     

Biologic evaluation of filling materials. A comparison of results using cell culture techniques, implantation tests and pulp studies.

The paper presents a comparison of results from cell culture studies, implantation tests and pulp studies using silicate cement, composite material and zinc oxide/eugenol cement. The three techniques allow differentiation between reactions produced by the materials, but a poor correlation exists between the results from the different techniques. This information is considered important for a selection of techniques for biologic testing of dental materials.     

In vitro toxicity evaluation of 12 kinds of dental materials using a modified cell culture technique]

In view of the fact that up to date the various cell toxicity tests could not come to an identical result and compare with each other. This paper, referring to the covering documents of F.D.I. and I.S.O., summing up the principles and characteristics of various cell culture techniques, establishes a modified cell toxicity test. This method, with more respects of wide observations and tangible results, is easy to grasp, well to repeat and can be reserved for checking the results, meanwhile, it can be avoided the contradiction caused by the different experiments on one kind of material. Therefore, it is very worthy of appraising the biological safety of the materials. The study of 12 kinds of dental materials expressed that the toxicity order of copper alloy was mean value of 0 (Jiao Tong University), copper alloy tridium was mean value of 3 (U.S.A.), copper alloy T was mean value of 2 (Jiao Tong University) and the others were mean value of 0-1. This paper also discussed several problems with common concerns in studying the cell toxicity of the biomaterials.     

Toxicity of Pulpispad using four different cell types

The cytotoxic effect of a zinc oxide-eugenol-based paste (Pulpispad) was evaluated in vitro after setting for 1 day and 1 week. Target cells were L929 cells, gingival, periodontal ligament and pulpal fibroblasts. The material was incubated with the cells for 4 and 24 hours, and its toxicity was evaluated with the 51Cr-release method. Pulpispad was highly cytotoxic to all cell lines even after setting for 1 week. The use of Pulpispad is not recommended for future clinical application. The various responses among the four cell lines indicated that diploid cell lines can, under certain circumstances, be less sensitive than aneuploid cell lines. It is therefore suggested that in the evaluation of biomaterials the choice of cell lines should be carefully considered, as they can display varying sensitivities.     

Cytotoxic effects of dental cements on two cell culture systems

Abstract Four dental cements and one bis-GMA composite were tested in cultures of human periodontal ligament fibroblasts and mouse 3T3 fibroblasts. It was found that these cell types reacted to the cements with different intensities, and that there were differences in evaluation by phase contrast microscopy and succinic dehydrogenase histochemistry.     

Evaluation of gloss changes of two denture acrylic resin materials in four different beverages.

OBJECTIVES: The primary disadvantages of the materials which are used in construction of complete and removable partial dentures is that their esthetic, physical and mechanical properties change rapidly with time in the oral environment. For esthetics, color stability is one of the criteria that needs careful attention. Color may provide important information on the serviceability of these materials. Color change affects the gloss of these materials. The objective of the present study was to determine the gloss changes resulting from the testing process in four different beverages in one heat-polymerized denture base resin and one cold-polymerized denture base repair resin. METHODS: Thirty-six samples were fabricated for each material. Each sample had a smooth polished and a rough unpolished surface. The gloss measurements were made with a glossmeter before testing. Four different beverages (tea, coffee, cola and cherry juice) were used for testing. Two angles of illumination (20 and 60 degrees) were used for the gloss measurements. The samples were immersed in water, tea, coffee, cola and cherry juice solutions. The gloss of the samples was measured again with the glossmeter at the end of the 45th day and 135th day of testing. The arithmetic mean and standard deviation of each of the samples were calculated and compared with each other statistically by using the Wilcoxon test (within times) (p < or = 0.05 significant), the Kruskal-Wallis analysis of variance (p < or = 0.05 significant) and the Mann-Whitney U-test with Bonforoni correction (when the difference between the samples was significant) (p < or = 0.05 significant). RESULTS: The results of this study revealed that gloss changes occurred after testing in heat-polymerized denture base resin and cold-polymerized denture base repair resin. The significance of the gloss changes exhibited by each sample, kept for different lengths of time in the same solution, were compared using the Wilcoxon test. The results were statistically significant (p < or = 0.05). According to the Kruskal-Wallis analysis of variance, the difference between measurements for angles of illumination was statistically significant (p < or = 0.05). Also according to the Mann-Whitney U-test, the difference between two polished surfaces or two unpolished surfaces was statistically insignificant (p > 0.05), but the difference between smooth polished and rough unpolished surfaces was statistically significant (p < or = 0.05). SIGNIFICANCE: It was found that either the gloss of heat-polymerized denture base resin or the gloss of cold-polymerized denture base repair resin was affected by tested agents, and the four beverages demonstrated noticeable gloss changes. Cherry juice demonstrated the least change, while tea exhibited the greatest change.     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Evaluation of autogenous bone combined with porous hydroxyapatite.

The aim of this study was to evaluate clinically, histologically, and histometrically the use of autogenous bone combined with porous hydroxyapatite (Interpore 200®) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. After a healing period of 3 months. maxillary sinus augmentation procedures were performed in each monkey, and the sinuses were grafted with autogenous bone from the monkeys' tibia mixed in a 3:1 ratio with porous hydroxyapatite. At the same time. 2 pure titanium plasma-sprayed IMZB cylinder implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received similar treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants unloaded group and delayed implants unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation. The porous hydroxyapatite granules appeared integrated with the newly formed bone. Histometric analyses revealed that delayed implant placement resulted in a greater amount of direct mineralized bone-to-implant contact in the augmented area than the simultaneous implant placement. Furthermore, the percentage of direct mineralized bone-to-implant contact was far more significant in the residual bone than in the augmented area. It was concluded that the autogenous bone/porous hydroxyapatite graft combination enhanced bone formation and mineralized bone-to-implant contact in the augmented sinuses and that the delayed implant placement may be favorable for sinus augmentation procedures.     

Volumetric polymerisation shrinkage of different dental restorative materials.

STATEMENT OF PROBLEM: Polymerisation shrinkage is a critical limitation of dental resins and may contribute to micro leakage. PURPOSE: The purpose of this study is to record and compare volumetric changes of various dental composites and compomers, exposed for 40 seconds to a commercial halogen light source. MATERIAL AND METHODS: Eleven light-polymerised composites and compomers were evaluated using a dilatometer that recorded the polymerisation shrinkage every 0.5 second. The mercury column pressure was measured electronically with a pressure-sensitive transducer, and the data recorded and stored in a computer. The computer also recorded the temperature, controlled the light-source and displayed the data in graphic format. Every material was tested ten times. The data were analysed by means of an ANOVA (P < 0.05). RESULTS: A high rate of shrinkage occurred for all materials in the first ten seconds of polymerisation. Surefil showed the lowest rate while TPH displayed the highest. Of the higher filled materials, Surefil (0.96%) showed the least shrinkage, followed by Z250 (0.99%), Dyract AP (1.18%), Herculite (1.27%), Compoglass (1.32%), Amelogen (1.34%) and TPH-Spectrum (1.6%). Overall, the flowable materials exhibited significantly more shrinkage (P < 0.05). For this group Compoglass Flow (2.3%) showed the least shrinkage followed by Filtec Flow (2.31%). Permaflo (3.6%) exhibited the most shrinkage followed by Dyract Flow (3%). CONCLUSION: Within the limitations of this study, it is concluded that significant differences exist among the polymerisation shrinkage of the most resins tested. An increase in the filler content of a material significantly lessens the polymerisation shrinkage while an increase in the monomer concentration causes significantly more polymerisation shrinkage. CLINICAL SIGNIFICANCE: The more flowable a composite material becomes, the more the restoration will shrink. Clinicians should take this into account when they decide on cavity design and materials to use.     

Toxic effects of dental materials

Dental materials and clinical accessories may potentially cause adverse reactions in dentists, auxiliaries or patients. The introduction of new dental materials and a general awareness of adverse effects has been accompanied by an increase in the number of complaints related to dental treatment and to occupational exposure. Resin-based materials with various monomers, used as restorative composite materials, orthodontic adhesives and appliances, prosthodontic resins and impression materials, have all been involved. Reactions to metals used in extra-oral appliances in orthodontics seem to be relatively frequent, but few reactions have been reported following the use of other alloy systems. Some reactions may be due to toxic or allergic effects, but some are unexplained. Adverse reactions to any substance will usually be detected first in a setting where the exposure is greatest. This also holds true for dentistry, where some of the adverse reactions may be due to lack of knowledge about the toxic, irritant and allergenic properties of dental materials.     

Cytotoxic effects of four different endodontic materials in human periodontal ligament fibroblasts

The purpose of this study was to compare the cytotoxicity, induced apoptosis and/or necrosis, and apoptotic mechanisms in human periodontal ligament (PDL) fibroblasts treated with four different endodontic materials: White ProRoot mineral trioxide aggregate (MTA) (MTA/Dentsply; Tulsa Dental, Memphis, TN), Diaket (ESPE, Seefeld, Germany), Endion (VOCO, Cuxhaven, Germany), and CYMED 8410 (NANO, Kaohsiung, Taiwan). The effects of these four materials on the viability of PDL fibroblasts were determined by MTT (3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-SH-tetrazolium bromide) assay. Apoptotic pathways were evaluated via several mechanisms. Exposure to MTA for 24, 48, and 72 hours resulted in no significant differences in MTT reduction and viable cell number compared with controls. However, treatment of PDL fibroblasts with Diaket, Endion, and CYMED 8410 for 24, 48, and 72 hours resulted in cytotoxicity with MTT and a reduction of viable cell number with trypan blue dye exclusion test compared with controls (from p < 0.05 to p < 0.001). Annexin V-FITC/PI staining showed that Diaket, Endion, and CYMED 8410 induced higher percentages of apoptosis and/or necrosis than in controls (45.6%, 25.5%, and 6.3%, respectively). Results of cell-cycle analyses were concordant with annexin V-FITC/PI staining findings. These results suggest that MTA is a very biocompatible filling material. However, Diaket, Endion, and CYMED 8410 are toxic to PDL fibroblasts in vitro. The main form of cell death induced by these filling materials was determined to be apoptosis and/or necrosis.     

Evaluation of antimicrobial activity of fluoride-releasing dental materials using a new in vitro method.

OBJECTIVE: The aim of this study was to research the antimicrobial activity of fluoride-releasing dental materials on strains of mutans streptococci using a new in vitro method. METHOD AND MATERIALS: Using microplaques for the cell cultures, specimens were made with a conventional glass ionomer (Ketac-Cem), a photo-cured ionomer (Vitremer), and a compomer (Dyract). Three groups were made, each focusing on a distinct situation: In the first group, the antimicrobial activity was tested after curing; in the second, the materials were exhausted from their disposable fluoride for 14 days; and in the third group, fluoride was reincorporated into the specimens after a topical application of 2% sodium fluoride gel for 4 minutes. RESULTS: The results demonstrated that the photo-cured ionomer had the best antimicrobial activity of all groups, followed by the conventional glass ionomer and compomer groups, respectively. All materials studied presented antimicrobial activity in all stages of the experiment, which was statistically proven using the Student's t test. CONCLUSIONS: The fluoride-releasing materials studied in the current report demonstrated antimicrobial activity on strains of mutans streptococci in every group studied. This new method demonstrated more accuracy and practicability than others commonly used.