An evaluation of the cytotoxic effects of orthodontic bonding adhesives upon a primary human oral gingival fibroblast culture and a permanent, human oral cancer-cell line

Comparative In Vitro Biocompatibility Study of the Two Orthodontic Bonding Materials of Different Types

In the present study, the in vitro biocompatibility and cell response to two commonly used orthodontic bonding materials of different types, one self-curing and one light-curing, were examined and compared in indirect and direct cell culture systems. The study was conducted on fibroblasts and macrophages as in vitro models to study the biocompatibility of dental materials. Differences were found between the light- and self-curing material in cytotoxicity and effects on fibroblasts' proliferation in indirect cell culture systems as well as in macrophages response in vitro in both direct and indirect cell culture systems. Based on the obtained results, we can conclude that the self-curing material is generally more cytotoxic for fibroblasts compared to the light-curing, while macrophages' response to these materials was dependent on the macrophages' state and differed between the examined materials. This indicates that more attention should be paid when choosing and applying these materials in practice due to their toxicity to cells. Prior to their use, all aspects should be considered regarding the patient's conditions, associated problems, microenvironment in the oral cavity, etc. Further studies on in vivo models should be conducted to fully understand the potential long-term effects of the use of mentioned materials in orthodontics.

Cytotoxicity evaluation of dental and orthodontic light-cured composite resins

INTRODUCTION

The aim of this study was to determine the cytotoxicity of light-cured composite resins (Clearfil ES-2, Clearfil ES Flow, Filtek Supreme XTE, Grengloo, Blugloo, Transbond XT, and Transbond LR) then to assess leachable components in contact with human gingival fibroblasts (GFs) and to quantity detected bisphenol A (BPA).

METHODS

Light-cured composite resin discs were immersed for 24 hours in gingival fibroblastic medium (n = 3 for each product) and in control medium (n = 2 for each product) contained in plate. Cytotoxicity of the products (n = 95) was determined by the measure of cell viability using MTT assay after reading the optical densities of the plates. The analysis of leachable components was done by gas phase chromatography and mass spectrometry (GC-MS) and detected BPA was quantified. The limit of quantification was 0.01 μg/mL. Statistical analyses were performed by using IBM SPSS Statistics 20 and Kruskal-Wallis and Mann-Whitney U-tests were applied.

RESULTS

Cell viabilities were between 85 and 90%. Many chemical compounds including triethylene glycol dimethacrylate (TEGDMA) and BPA were identified. The average concentrations were 0.67 μg/mL ± 0.84 in the control medium and 0.73 μg/mL ± 1.05 in the fibroblastic medium. Filtek Supreme XTE presented the highest concentration of BPA with 2.16 μg/mL ± 0.65 and Clearfil ES Flow presented the lowest with 0.25 μg/mL ± 0.35. No BPA was detected with Transbond XT and Transbond LR. Clearfil ES Flow, Filtek Supreme XTE, Grengloo and Transbond LR presented residual TEGDMA.

CONCLUSIONS

Light-cured composite resins are slightly cytotoxic opposite GFs and release many components including BPA and TEGDMA. Clinical precautions should be taken to decrease the release of these monomers.

Monomer release from orthodontic retentions: An in vitro study

INTRODUCTION

The adhesives used to bond orthodontic retentions are low-loaded composite resins with a resinous matrix containing bisphenol A diglycidyl ether dimethacrylate synthesized from bisphenol A (BPA), fluidizers such as triethylene glycol dimethacrylate (TEGDMA) and hydrophilic polymers such as hydroxyethylmethacrylate. BPA disrupts the endocrine balance, and TEGDMA has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to evaluate in vitro the release of monomers from orthodontic bonded retentions.

METHODS

A reproducible model of bonded retentions was carried out using calibrated molds. We analyzed the release of monomers by gas phase chromatography coupled with mass spectrometry.

RESULTS

This model allowed us to qualitatively and quantitatively evaluate the in-vitro release of monomers from orthodontic adhesives. The quantitative and qualitative analyses showed no BPA release above the 0.02 ppm detection limit. A greater release of TEGDMA was observed with Transbond LR (31.7 μg/mL) than with Transbond XT (13.12 μg/mL) (both, 3M Unitek, Monrovia, Calif). Other toxic components (iodobenzene, iodobiphenyl, triphenyl stibine, and so on) were also identified.

CONCLUSIONS

Toxic and carcinogenic molecules not mentioned in the material safety data sheets were identified.

Biocompatibility evaluation of orthodontic composite by real-time cell analysis

INTRODUCTION

The aim of this study was to evaluate the cytotoxic effects of three different light-cured orthodontic composites.

MATERIAL AND METHODS

Light Bond (Reliance orthodontic products), Grengloo (Ormco corporation), and Kurasper F (Kuraray Europe GmbH) were selected for the experiment. Specimens were prepared according to the manufacturers' instructions, measuring 5 mm in diameter and 2 mm in thickness. Fibroblast cells were obtained from healthy gingival connective tissues. The composite cylinders were incubated in Dulbecco's modified Eagle's culture medium for 72 h according to ISO 10993-5 standards. The xCELLigence method was used to evaluate fibroblast cell vitality. After seeding 200 mL of the cell suspensions into the wells (20,000 cells/well) of the E-plate 96, gingival fibroblasts were treated with bioactive components released by the orthodontic composite materials and monitored every 15 min for 121 h.

RESULTS

There were no significant differences between the human gingival fibroblast (HGF) cell indexes of the control and all testing groups (p > 0.05) at 24 and 48 h. Light Bond demonstrated statistically significant decrease in HGF index (p < 0.05) at 72 h, but there was no significant difference among the Kurasper F, Grengloo, and untreated control groups (p > 0.05). Light Bond (p < 0.001) and Grengloo (p < 0.05) groups had lower HGF cell index values when compared to untreated control group, but Kurasper F demonstrated no significant differences between the control groups at 96 h (p > 0.05).

CONCLUSION

Orthodontic composite materials include biologically active components and may change oral tissue. So, biocompatible orthodontic bonding composites should be used.

Orthodontic bracket designs and their impact on microbial profile and periodontal disease: A clinical trial

Aim:

The aim of the present study was to compare the undisturbed plaque formation on teeth bonded with Preadjusted (Captain Ortho, Libral Traders, Mumbai, India) and Begg Brackets (Captain Ortho, Libral Traders, Mumbai, India) with nonbonded control sites via a de novo plaque growth over a period of 7 days.

Materials and Methods:

A clinical trial with the split-mouth design was set up enrolling 10 dental students. Within each subject sites with (Preadjusted) (P-site), Begg brackets (B-site) and control sites were followed. Plaque index and gingival index were recorded on days 3 and 7. Supra-gingival and sub-gingival plaque samples were taken from the brackets and the teeth on days 3 and 7, and were sent for aerobic and anaerobic culturing. The total number of bacterial colony forming units (CFU) was assessed for each sample using a colony counter. Tukeys and Dunnett test then statistically analyzed data.

Results:

The mean plaque index and gingival index increased on P-site and B-site on the third and 7^th day. The shift from aerobic to anaerobic species was observed earlier in P-sites than in B-sites. The CFU were significantly higher for all sites on day 7 when compared with day 3. The aerobe/anaerobe CFU ratio was significantly lower in P-sites than in B-sites and then control showing an increase in the number of anaerobic species on the 3^rd and 7^th day (P < 0.05). Based on observed means, the mean difference was significant (P < 0.05).

Conclusion:

The present data suggest that Preadjusted brackets accumulated more plaque than Begg brackets. Bracket design can have a significant impact on bacterial load and on periodontal parameters.

Antimicrobial and fluoride release capacity of orthodontic bonding materials

OBJECTIVE

The aim of this study was to evaluate the antimicrobial and fluoride releasing capacity of 3 bonding materials.

MATERIAL AND METHODS

Thirty nine specimens with standardized surface smoothness and dimensions were prepared. The antimicrobial capacity of the materials against S. mutans, L. casei and C. albicans was evaluated by determining the percentage of growth inhibition of these microorganisms in an inoculated medium, obtained by optical density readouts on a spectrophotometer. The potential to interfere in microbial growth on the surface of the studied materials was observed by means of scanning electron microscopy (SEM). The fluoride release capacity in ultrapure water for 14 days was analyzed by means of ion chromatography.

RESULTS

The PLUS group presented the highest percentage of microbial inhibition and the most contamination-free surface. The FUJI group presented the best fluoride release capacity.

CONCLUSIONS

The TransbondTM Plus Color Change was the one that presented the best general behavior considering the evaluated aspects.

Effect of [6]-shogaol on cytosolic Ca2+ levels and proliferation in human oral cancer cells (OC2)

The effect of [6]-shogaol (1) on cytosolic free Ca(2+) concentrations ([Ca(2+)](i)) and viability has not been explored previously in oral epithelial cells. The present study has examined whether 1 alters [Ca(2+)](i) and viability in OC2 human oral cancer cells. Compound 1 at concentrations > or = 5 microM increased [Ca(2+)](i) in a concentration-dependent manner with a 50% effective concentration (EC(50)) value of 65 microM. The Ca(2+) signal was reduced substantially by removing extracellular Ca(2+). In a Ca(2+)-free medium, the 1-induced [Ca(2+)](i) elevation was mostly attenuated by depleting stored Ca(2+) with thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor). The [Ca(2+)](i) signal was inhibited by La(3+) but not by L-type Ca(2+) channel blockers. The elevation of [Ca(2+)](i) caused by 1 in a Ca(2+)-containing medium was not affected by modulation of protein kinase C activity, but was inhibited by 82% with the phospholipase A2 inhibitor aristolochic acid I (20 microM). U73122, a selective inhibitor of phospholipase C, abolished 1-induced [Ca(2+)](i) release. At concentrations of 5-100 microM, 1 killed cells in a concentration-dependent manner. These findings suggest that [6]-shogaol induces a significant rise in [Ca(2+)](i) in oral cancer OC2 cells by causing stored Ca(2+) release from the thapsigargin-sensitive endoplasmic reticulum pool in an inositol 1,4,5-trisphosphate-dependent manner and by inducing Ca(2+) influx via a phospholipase A2- and La(3+)-sensitive pathway.

Fendiline-evoked [Ca2+]i rises and non-Ca2+-triggered cell death in human oral cancer cells

The effect of fendiline on cytosolic free Ca(2+) concentrations ([Ca(2+)](i)) and proliferation has not been explored in human oral cancer cells. This study examined whether fendiline altered Ca(2+) levels and caused cell death in OC2 human oral cancer cells. [Ca(2+)](i) and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Fendiline at concentrations above 10 microM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). The fendiline-induced Ca(2+) influx was sensitive to blockade of L-type Ca(2+) channel blockers. In Ca(2+)-free medium, after pretreatment with 50 microM fendiline, 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor)-induced [Ca(2+)](i) rises were inhibited; and conversely, thapsigargin pretreatment nearly abolished fendiline-induced [Ca(2+)](i) rises. Inhibition of phospholipase C with 2 microM U73122 did not change fendiline-induced [Ca(2+)](i) rises. At concentrations between 5 and 25 microM, fendiline killed cells in a concentration-dependent manner. The cytotoxic effect of 15 microM fendiline was not reversed by prechelating cytosolic Ca(2+) with BAPTA/AM. Collectively, in OC2 cells, fendiline induced [Ca(2+)](i) rises by causing Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx from L-type Ca(2+) channels. Furthermore, fendiline-caused cytotoxicity was not via a preceding [Ca(2+)](i) rise.

Orthodontic adhesives induce human gingival fibroblast toxicity and inflammation

OBJECTIVE

To test the null hypothesis that the resin base and the resin hybrid glass ionomer base adhesives do not cause inflammation after contacting primary human gingival fibroblasts in vitro.

MATERIALS AND METHODS

The resin base and resin hybrid glass ionomer base adhesives were used to treat human gingival fibroblasts to evaluate the survival rate using MTT colorimetric assay to detect the level of cyclooxygenase-2 (COX-2) mRNA by reverse transcription polymerase chain reaction (RT-PCR) technique and COX-2 protein expression using Western blot analysis. The results were analyzed using one-way analysis of variance (ANOVA). Tests of differences of the treatments were analyzed using the Tukey test and a value of P < .05 was considered statistically significant.

RESULTS

The paste and primer of the resin base adhesive and the liquid of glass ionomer adhesive showed decreasing survival rates after 24 hours of treatment (P < .05). All orthodontic adhesives induced COX-2 protein expression in human gingival fibroblasts. The exposure of quiescent human gingival fibroblasts to adhesives resulted in the induction of COX-2 mRNA expression. The investigations of the time-dependent COX-2 mRNA expression in adhesive-treated human gingival fibroblasts revealed different patterns.

CONCLUSIONS

The hypothesis is rejected. For orthodontic patients with gingival inflammation, except for those with oral hygiene problems, the activation of COX-2 expression by orthodontic adhesive may be one of the potential mechanisms.

Influence of bracket design on microbial and periodontal parameters in vivo

AIM

To compare undisturbed plaque formation on teeth bonded with different types of orthodontic brackets with non-bonded control teeth, via a de novo plaque growth experiment over a 7-day period.

MATERIAL AND METHODS

A randomized controlled trial with split-mouth design was set up enroling 16 dental students. Within each subject sites with Speed(S) and GAC(G), brackets and control sites were followed. Clinical periodontal parameters were recorded at baseline, on days 3 and 7. Microbiological samples were taken from the brackets and the teeth on days 3 and 7.

RESULTS

Both anaerobe and aerobe colony-forming units (CFU) were significantly higher in S-sites than in G-sites (p=0.0002, p=0.02). The shift from aerobic to anaerobic species was observed earlier in S-sites than in G-sites. The aerobe/anaerobe CFU ratio was significantly lower in S-sites than in G-sites (p=0.01). On day 3, the crevicular fluid flow was significantly higher in S-sites than in control sites (p=0.01). On day 7, S-sites and G-sites showed a significantly higher crevicular flow than control sites (both p<0.0001). More hypertrophy was seen in S- than in G- and control sites (p=0.05). No significant differences for bleeding on probing were observed.

CONCLUSION

Bracket design can have a significant impact on bacterial load and on periodontal parameters.

Biocompatibility of various formula root filling materials for primary teeth

The aim of this study was to compare the effects of different materials used in primary root canal fillings on the cell viability of human osteosarcoma cell lines. The experimental group contained six different types of root canal filling materials, including zinc oxide (ZnO) + eugenol + formocresol (FC), Ca(OH)(2) + FC, Ca(OH)(2) + Iodoform, Ca(OH)(2) + Iodoform + camphorated parachlorophenol (CPC), Ca(OH)(2) + CPC, and Vitapex. Cell viability tests were performed using tetrazolium bromide colorimetric (MTT) assay on human osteosacorma cell lines (U2OS). The results were analyzed using one-way analysis of variance (ANOVA) and Student-Newman-Keul's test with p < 0.05 showed statistical differences. The ZnO + eugenol + FC group and Ca(OH)(2) + FC group showed the lowest survival rates (p < 0.05). The Ca(OH)(2) + Iodoform + CPC group and Ca(OH)(2) + CPC group showed significantly lower survival rates at concentrations above 6 microL/mL (p < 0.05). The Ca(OH)(2) + Iodoform group and Vitapex group showed the highest survival rates (p < 0.05). We concluded that the use of calcium hydroxide with iodoform as a root filling base material is a better option than other medications.

Independent [Ca2+]i increases and cell proliferation induced by the carcinogen safrole in human oral cancer cells

The effect of the carcinogen safrole on intracellular Ca2+ movement and cell proliferation has not been explored previously. The present study examined whether safrole could alter Ca2+ handling and growth in human oral cancer OC2 cells. Cytosolic free Ca2+ levels ([Ca2+]i) in populations of cells were measured using fura-2 as a fluorescent Ca2+ probe. Safrole at a concentration of 325 microM started to increase [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 40% by removing extracellular Ca2+, and was decreased by 39% by nifedipine but not by verapamil or diltiazem. In Ca2+-free medium, after pretreatment with 650 microM safrole, 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) barely induced a [Ca2+]i rise; in contrast, addition of safrole after thapsigargin treatment induced a small [Ca2+]i rise. Neither inhibition of phospholipase C with 2 microM U73122 nor modulation of protein kinase C activity affected safrole-induced Ca2+ release. Overnight incubation with 1 microM safrole did not alter cell proliferation, but incubation with 10-1000 microM safrole increased cell proliferation by 60+/-10%. This increase was not reversed by pre-chelating Ca2+ with 10 microM of the Ca2+ chelator BAPTA. Collectively, the data suggest that in human oral cancer cells, safrole induced a [Ca2+]i rise by causing release of stored Ca2+ from the endoplasmic reticulum in a phospholipase C- and protein kinase C-independent fashion and by inducing Ca2+ influx via nifedipine-sensitive Ca2+ entry. Furthermore, safrole can enhance cell growth in a Ca2+-independent manner.