Dental Amalgam Research Articles

Reação Liquenóide oral: relato de caso

Introdução: As alterações liquenóides são reações patológicas que se caracterizam como uma resposta imunológica a um agente alergênico como materiais restauradores, medicações sistêmicas ou alimentos, podendo ser observadas em pele e em mucosa. Detalhamento do caso: O objetivo do presente estudo é relatar o caso clínico de uma paciente, CMS, 41 anos diagnosticada com reação liquenóide oral associada a restaurações de amálgama dental e a conduta utilizada para o tratamento desta alteração. exame complementar de escolha é a biópsia incisional, mas optou-se em substituir a restauração de amálgama para observar se haveria regressão da lesão, sendo uma manobra semiotécnica menos invasiva. Após o período de três meses houve cessão total da lesão e até o presente momento não houve recidivas. Discussão: Por ser diagnóstico diferencial de outras lesões como o líquen plano, faz-se necessário os exames clínicos minuciosos para o correto diagnóstico e tratamento. A remoção do agente causal leva à melhora significativa do quadro.

Dental caries on CT in the ER population: prevalence and reporting practices.

Although dental caries can be identified on CT and may be treatable, the literature provides little, if any, guidance on the responsibility of a neuroradiologist in reporting them. Untreated dental caries can impact diet and nutrition and can result in a variety of complications such as an odontogenic abscess, tooth loss, sinusitis, and dental pain, which can impact quality of life. The estimated prevalence of untreated dental caries in adults is 27%. In our experience, the prevalence of untreated dental caries in patients presenting to the Emergency Department (ED) is higher but dental caries are often unmentioned or unrecognized. We aim to determine the frequency of unreported dental caries and propose a paradigm for reporting and management. Our research was IRB-approved and HIPPA compliant. We searched the radiology database for adult patients who underwent a CT of the facial bones while in the Emergency Department between January 1, 2015 and June 30, 2015. The examinations were reviewed by a faculty neuroradiologist for the presence of untreated dental caries. Untreated dental caries were documented and characterized by depth. Caries that were partially or completely obscured by dental amalgam artifact were excluded. The radiology reports were reviewed to evaluate reporting frequency. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) software. A total of 200 patients (113 male, 87 female; age 18-98years) underwent 200 CT examinations of the facial bones. One hundred fourteen (57%) patients had at least one dental caries. When caries were present, 14.9% of radiology reports included caries in the findings section and 9.6% of the reports mentioned caries in the impression. The presence of dental caries should be mentioned in the radiology report. The prevalence of untreated dental caries is higher in our cohort than reported in the general population, and dental caries are underreported by neuroradiologists at our institution. A paradigm for reporting and management was created upon collaboration with faculty from the University of Vermont Dental and Oral Health practice. A visit with a dentist should be recommended within 6months if caries are limited to the enamel, within 3months if caries involve the dentin, and within 2weeks if caries extend in to the pulp. Further research is necessary to determine the clinical impact of improved reporting.

The causes of failure and the longevity of direct coronal restorations: A survey among dental surgeons of the town of Abidjan, Côte d'Ivoire.

Objective:This study aimed to itemize the causes for the failure of direct coronal restorations (DCRs) according to the practitioners of Côte d'Ivoire in order to provide recommendations for good practice.Materials and Methods:A descriptive, self-reporting, prospective survey was carried out among 109 dental surgeons (DSs) in the town of Abidjan based on 587 randomly selected practitioners supplied by the National Board of the Order.Results:The results show that 98.10% of the surveyed DSs had previously encountered cases of failure. Fracturing of the restoration, which is the basis for the hiatus, is the main cause of failure according to 51.40% of the surveyed practitioners, followed by pain “under the restoration” cited by 26.20% of them. Failure occurs within 6 months (30.85% of those surveyed), after 5 years (9.6% of those surveyed) for restorations with composite or glass ionomer cement (GIC), while for DCRs with amalgam, failure occurs within 6 months (28.70%), after 5 years (16%) and beyond 10 years (3.20%).Conclusion:The practitioners often encountered failures of DCRs, with fracture of the restoration as the cause. Dental amalgam appears to have a greater longevity than adhesive restorations. Faced with a failure, they more often opted for a replacement of the DCRs rather than a repair.

Incidence of attention-deficit and hyperactivity disorder among school children in Riyadh city and its association with body burden of mercury leached from dental amalgam fillings: A cross-sectional study

Objectives: The objectives of this study are to determine the association between the incidence of attention-deficit and hyperactivity disorder (ADHD) in children of mothers with and without amalgam fillings. Design: The study design was a cross-sectional descriptive study. Setting: The study was conducted at a dental college's clinic in Riyadh, Saudi Arabia. Participants: In total, 869 children (512 males and 357 females) aged 6–12 years and 796 mothers were included. Children suffering from hearing impairment, language impairment, or learning disabilities or those diagnosed with mental health problems were excluded from the study. Primary and Secondary Outcome Measures: The primary outcome measures included the results of the Vanderbilt scale used for ADHD diagnosis in children and the mercury concentration in 1 ml saliva samples obtained from both the mother and the children. The secondary outcome measures included the number of dental amalgam restorations in the oral cavity determined through a dental examination of children and their mothers. Methodology: A consent form was signed by the mothers who agreed to participate in our study, they were all examined for amalgam presence and a saliva samples were collected and digested. Results: Children with ADHD showed significantly higher levels of mercury in saliva than did children without ADHD. The mothers who had dental amalgam fillings during pregnancy had significantly higher mercury levels than did the mothers who did not have dental amalgam fillings. Conclusion: Prenatal mercury exposure is associated with a higher risk of ADHD behavior. Further research can be carried out to identify the toxic effects of mercury on different body organs owing to dental amalgam fillings. The study scale can be further increased to obtain a more accurate percentage of ADHD cases in Saudi Arabia.

A Study on the Knowledge and Awareness among Dental Students of Mercury Toxicity and Amalgam Disposal

Dental amalgam consists of 50% mercury. An average amalgam filling consists of 1 gram of mercury which continously leaks mercury vapour due to the low vapour pressure of mercury. Mercury vapour can spread rapidly throughout the human body. It crosses cell membranes easily. Mercury can penetrate the blood brain barrier and result in mercury accumulation in the brain. Mercury is among the top three most toxic substances that affects people in large numbers. Amalgam is the largest source of mercury. As amalgam is the number one source of mercury production, dentists and dental students are at a very high risk of mercury poisoning due to repeated exposure to dental amalgam. This study intends to assess the knowledge and awareness levels among dental students of mercury toxicity and its potential risks, and the various disposal methods for amalgam. Though most of the students were aware of mercury toxicity and amalgam disposal methods as a whole, only a handful were aware about the absorption efficiency rate and the critical threshold of mercury, which was as low as 20.83% and 21.66% respectively. Almost 50% of the students interviewed had answered less than 8 out of 15 questions correctly. It is recommended that more effective methods for delivering information regarding mercury, its complications and management are deviced.

Recent Advances in Dental Composites: An Overview

Composite resins are widely used aesthetic materials in restorative dentistry. These materials were introduced to overcome the inherent shortcomings of amalgam restorative materials. Dental amalgams are unesthetic and toxic. Earlier composites lack in mechanical properties to withstand the masticatory forces. Various filler particles have been added to composite resins to improve their physical and mechanical properties. Filled composite resins exhibit high compressive strength, abrasion resistance, ease of application and high translucency. Depending on the filler size and shapes, various composites have been developed until now. This article is a review of numerous types of composites that are technologically advanced to modify their properties.

Human exposure to mercury and its hematological effects: a systematic review.

Mercury is a metal found in the environment from natural and anthropogenic sources. It is highly toxic to ecosystems and living beings. Most human exposures come from ingestion of contaminated seafood, outgassing from dental amalgam or occupational exposure (e.g. gold mining), among other cases. Large populations are exposed to mercury, making it a very important issue from the public health perspective. Adverse health effects are commonly seen in the nervous system, but every organ is a potential target, such as the bone marrow. The main goal of this study was to assess the available evidence on human exposure to mercury and its hematological effects. A search strategy was constructed, including key terms (MeSH, text word and equivalents) for querying 2 repositories of master dissertation and PhD thesis (Fiocruz/ARCA and University of São Paulo) and 4 different electronic databases: BVS/LILACS, MEDLINE/PubMed, Scopus and TOXLINE/NIH, for articles published from 1950 to February 2018. There was no language restriction and a tool (EPHPP) was used to assess the quality of included studies. According to pre-established criteria, 80 studies were retrieved, all of them observational (48 case reports, 24 cross-sectional, 6 case series and 2 cohorts), comprising 9,284 people. Despite the fact that most exposed ones (6,012) had normal blood cell count and mercury hematological effects did not seem very usual (1,914 cases: 14 severe and 29 deaths), three studies reported association (β) for anemia, lymphopenia, neutrophilia and basophilia. We concluded that the gathered information pointed to mercury hematotoxic effects, some of them may be serious and even fatal.

Occupational Exposure to Mercury in Dental Professionals Performing Mercury Dental Amalgam Restoration Removal Procedures: A Computational Fluid Dynamics Air Quality Risk Assessment Model Supported by In-Vitro Results

Aim: To quantify risks associated with exposure to dental amalgam mercury resulting from aerosolization during and following dental fillings removal procedures performed by dental professional over a lifetime of professional practice. Methods: A computational fluid dynamics model was generated using particle size, density, and compositional data obtained from in-vitro aerosolization experiments simulating the environment and breathing conditions of a dental professional performing a dental amalgam restoration removal procedure. Analysis was carried out using scanning electron microscopy and inductively coupled plasma – optical emission spectrometry. Data was collected in 2018-2019. Results: Experiments reveal that approximately 58% of mercury contained within the amalgam material is vaporized during removal procedures, and that aerosolized particles, ranging in size from 0.85 to 570 microns, may remain in suspension for nearly two minutes in the area surrounding the working surface. For dental professionals performing on average 9 such restorations per week, the estimated chronic daily intake (CDI) of mercury is 49 micrograms/kilogram-day, which exceed – by more than 20 times – the CDI recommended by the World Health Organization. Data analysis was performed in 2019. Conclusion: Because the CDI exceed recommended safe exposure limits, dental professionals should wear respiratory and personal protective equipment to protect them from exposure to both mercury vapour and mercury-containing particulates for at least two minutes following removal procedures.

Silver recovery from dental amalgam wastes

Alloys produced with mercury and other metals are called amalgam Dental amalgams are important alloys and contain mercury with the addition of silver tin and copper Therefore these amalgams have high economic value and need to be evaluated This experimental study deals with recovering their metal contents by physical and chemical separation techniques Within the framework of this study distilled non contact dental amalgam wastes were subjected to size reduction leaching with nitric acid and cementation with copper Leach liquor was filtered and both solution and leach residue were characterized Results have shown that leaching efficiency was above and leach solution contained g L Ag and g L Cu ions Later silver was recovered from solution by cementation with copper The basic parameters in the cementation experiments such as cementator quantity stirring speed pH and temperature were examined Cementation efficiency reached above and chemical analysis has shown that silver concentration of solution decreased from g L to mg L

It’s not amalgam, it is white amalgam

IntroductionA new class of restorative GIC, named Zirconomer, with increased strength and durability has been developed. It shows strength of amalgam, so it is also called white amalgam. Inclusion of zirconia fillers reinforces the structural integrity of that material, imparts its outstanding posterior esthetics, completely eliminates mercury hazards, and also it is fluoride rich, especially in cases with high caries risk. It is an ideal requirement for restorative material it has a good color stability, a co-efficient of thermal expansion, biocompatibility similar to that of natural tooth, remarkable edge strength, excellent marginal seal, and the ability to adhere chemically to enamel and dentin. Glass ionomer cements are esthetically more pleasing than metallic restorations, on the contrary, their use in dentistry as a restorative material in stress-bearing areas is limited due to poor mechanical properties. New GIC formulations are being introduced every day with improved physical and mechanical properties. ObjectivesZirconomer compared to Amalgam restoration. Materials and methodsArticles found through Medline search; Pubmed, Scopus, Cochrane Library databases covering years starting from 2010 to 2018 were reviewed. Key search words “Zirconomer,” “zirconium oxide,” “non-metal restorations,” “ceramic oxides,” “veneering ceramic,” “zirconia reinforced glass ionomer cement,” “zirconiabased fixed dental prostheses” and silver amalgam were used. Both in-vivo and in-vitro studies into zirconia-based restoration behavior were included. ResultsZirconomer restorations are found to be best alternative now to both GICs with its other modifications as well as dental amalgam for teeth restorations. Some bacterial retention on final could be expected when used. ConclusionsZirconomer and its family restorations are recommended for restorations of deciduous or permanent teeth. Further in-vitro and in-vivo works are needed to confirm their remarkable behavior. Conflict of interestThe authors declared that there is no conflict of interest.

Lichenoid hypersensitivity reaction against to dental amalgam: Case report

Amalgam or its components may cause delayed hypersensitivity reactions and constitute lesions compatible with lichenoid mucositis in relation to localization. A white colored lesion was detected in the buccal mucosa of a 37-year-old male patient with amalgam filling in the tooth number 46. The lesion was histopathologically reported as lichenoid mucositis. This rare lesion with a specific morphology is presented with the literature.

Solving dental amalgam dilemma: An integrated toxicology and its management strategies – A systematic review

Mercury (Hg) has been well known as one of the most toxic nonradioactive materials. Anthropogenic mercury is now a major worldwide concern and is an international priority toxic pollutant. Mercury vapour release from amalgam is the most important form of mercury that determines human exposure. Autopsy studies have shown higher levels of mercury in the tissues of human with amalgam fillings as opposed to those who were not similarly exposed. study objective is to sensitize the dentist and dental staff about mercury toxicity and strategies for proper handling of amalgam in order to reduce the health hazards caused by mercury for both dentist, patient and environment. Data search included PubMed, PubMed Central, Cochrane and Google Scholar until January 2019, out of 59 publications, 43 full text articles were deemed important were analysis. Discussion focus on an integrated toxicological based on release, uptake. toxicology and management protocol to understand interrelationship of these substantial contents. Added insight of Indian scenario in this review educate dental fraternity of correspondence between consumerism and bionomic loop, where safety consensuses are questionable. Growing advances in technology and raising aesthetic demands have led way aesthetic dentistry. Hence promoting the use of cost-effective and clinically effectual mercury free alternatives for dental restoration is inevitable in years to come.

Extensive amalgam tattoo (amalgam pigmentation) on the palatal mucosa: a short case report

Introduction: An amalgam tattoo is the most common form of exogenous oral pigmentation caused by the diffusion of dental amalgam into the soft tissue. Observation: Here we describe a case of diffuse pigmentation of amalgam on the hard palate. Discussion: Mucosal hyperpigmentation can occasionally be confused with melanotic lesions, thereby requiring a biopsy for differential diagnosis. Once the diagnosis of an amalgam tattoo has been established, the removal of the lesion is not necessary, except for aesthetic reasons.

The Effect of Two Adhesive Agents on Shear Bond strength Between Fresh Dental Amalgam and Resin Composite

Objective: To assess and compare the results on the bond strength of two adhesive agents that bond fresh amalgam to two types of composite restorations, and to check the mode of bond failure.
 Methods: Sixty standardized circular cavities were prepared in a block of polymethyl methacrylate with standardized dimensions. Fresh amalgam was condensed to fill the cavity, then a gelatin mold with standardized dimensions was placed over the fresh amalgam,and the composite resin was bonded to the amalgam. Samples were assigned into three main groups, each containing (20) samples. G1: Amalgam bonded to composite without adhesive agent, G2: Amalgam bonded to composite by single bond universal adhesive, G3: Amalgam bonded to composite by scotch bond MPP, and each group was divided into two subgroups of (n=10) (Nanofill and Nanohybrid composite) to measure shear bond strength, which was followed by evaluation of debonding in all samples under a stereomicroscope to assess the mode of failure.
 Results: All The results showed that G3 has higher shear bond strength than G1 and G2, and this is statistically significant at (p=0.001, p=0.005) respectively, while G1 has the lowest shear bond strength and a statistically non-significant difference from G2 at (p=0.539). It was also found that the type of composite resin has no effect on bond strength and statistically non-significant difference was found for any of the sub-groups. Following debonding of all the samples, they were examined under a stereomicroscope, and the adhesive failure present was about (%65), and mixed failure present about (%35), while cohesive failure was (%0).
 Conclusions: Highest bond strength was found with Scotch bond multi-purpose plus (SBMPP) agent compared to other groups. The strength of the fresh amalgam bonding to the composite resin without an adhesive agent was low. The bond strength with single bond universal adhesive was lower than with the SBMPP system.

Comparative Analysis of Microleakage of Zirconia-infused Glass Ionomer Cement with Miracle Mix and Amalgam: An In Vitro Study.

ContextVarious restorative materials are introduced in dentistry to achieve adequate strength and restore aesthetics. Dental amalgam is a versatile material with self-sealing property, but is unaesthetic. Other restorative materials like composites require conservative preparation, but exhibit polymerisation shrinkage resulting in microleakage. To overcome these drawbacks, a high strength restorative material reinforced with ceramic and zirconia fillers known as Zirconomer (Shofu Inc., Japan) has been introduced.AimsThis in vitro study aims to evaluate and compare the microleakage of zirconia-infused glass ionomer cement (Zirconomer) with Miracle Mix (GC Fuji Miracle Mix, Japan) and amalgam.Materials and methodsIn this in vitro study, 30 non-carious premolar teeth were randomly divided into three groups (n=10) depending on the restorative material used—Silver Amalgam (DPI, India), Miracle Mix, and Zirconomer. Standard Class V cavities were prepared on the buccal surface of 30 non-carious extracted premolars. The restored teeth were thermocycled and then immersed in 2% methylene blue dye for 24 hours. All teeth were bisected longitudinally in a buccolingual direction and observed under a stereo microscope at 40X magnification for the evidence of dye penetration. The data were analyzed using one-way analysis of variance (ANOVA) and Kruskal-Walis tests (p<0.01).ResultsZirconomer showed the least microleakage in Class V cavity restoration with a statistically significant difference to amalgam and Miracle Mix.ConclusionsZirconomer has proven to be an excellent restorative material as it showed the least microleakage followed by Miracle Mix and amalgam. Zirconomer raises the bar for restorative reinforced glass ionomers by outperforming conventional glass ionomers and amalgam restoration.

Healing of Oral Lichenoid Lesions following Replacement of Dental Amalgam Restorations with Feldspathic Ceramic Inlay-Onlay Restorations: Clinical Results of a Follow-Up Period Varied from Three Months up to Five Years.

Objective Previous studies have shown the effect of amalgam removal on the healing of oral lichenoid lesions (OLLs); however, no specific replacement materials have been suggested. The present series evaluated long-term results following the complete replacement of amalgam restorations with feldspathic ceramic inlay-onlay restorations for a group of patients with OLLs whose lesions were suspected to be related to amalgam restorations. Materials and Methods Twenty-four patients who had OLLs suspected to be related to their amalgam restorations were initially recruited. The patients underwent patch tests for a series of dental materials, in addition to clinical and histopathological examination. Sixteen (67%) of the 24 patients had their amalgam replaced with feldspathic ceramic inlay-onlay restorations and were examined within a follow-up period of 3 months to 5 years. Results After 3 months of clinical follow-up, complete healing (63%) was noted in all patients with OLLs whose lesions were in only close contact with their amalgam restorations. Healing was significantly related to the combination of lesions with close contact with the amalgam restoration and a diagnosis of OLL (x2 test, P=0.02). Conclusion Feldspathic ceramic can be safely used as a replacement material for patients with OLLs to diminish adverse reactions to amalgam restorations.

Evaluation of the effect of dental filling material on IMRT treatment planning in patient with nasopharyngeal cancer

Introduction: Presence of dental filling material (DFM) such as amalgam in treatment patient with nasopharyngeal cancer (NPC) is common. Streaking artifact Arising from this high density material in computed tomography (scan), may lead to perturbation in dose calculation and dose delivery. Widespread performance of intensity-modulated radiotherapy (IMRT) for NPC using anterior beams that pass through the part severely affected by artefacts prior to reaching the target volume, raise concern about the effect of dental amalgam. This study quantifies the effect of dental amalgam on dose distribution target volume and organ at risk, normal tissue complication probability (NTCP) and tumor control probability (TCP). Materials and Methods: IMRT optimization two groups of 15 early-stage NPC patients with or without dental amalgam by prescribe 70 Gy to planning target volume performed by using the prowess panther treatment planning system. We used one plan nine field arrangement (F9E) and three plan of seven field (F7, F7E, F7P) arrangement with different angle. The dose volume histograms (DVHs), monitor units (MUs), Homogeneity index (HI), conformity index (CI) and TCP of PTVs, NTCP spinal cord, brain stem and parotid gland were analyzed. Results: Mean dose PTV in F7, FVE, F7P and F9E plan were 71.25±1.55, 72.06±0.96, 71.65 ±1.28 and 71.82±0.53 respectively in patients with DFM and 71.52±1.02, 71.51 ± 0.61, 71.30 ± 0.61 and 71.95 ± 0.80 in patient without DFM, Showing slight increase in mean dose of target volume. V95 of PTV shows insignificant different in two group. Mean TCP in F7, FVE, F7P and F9E plan were 95.06±0.45%, 95.18±0.54%, 94.93 ±0.68% and 95.05±0.42% in patient with DFM and 94.86±0.62%, 94.74 ± 0.43%, 94.80 ± 0.58% and 95.50 ± 0.40% in patient without DFM that shows insignificant different in two group. Mean HI of PTV-70 in four plans in presence of DFM shows a slight decrease compared than the other. Mean and maximum dose Spinal cord, brain stem and parotid and their NTCP in presence of DFM show a slight decrease. Conclusion: According to the results, dental amalgam led to slight increase in TCP, mean dose target volume and slight decrease in mean dose some OARs and their NTCP. Average dose target volume and some organ at risk that consider for this study demonstrates no meaningful difference exist in DVH and biological parameter in two group of patient.

Mercury pollution in modern times and its socio-medical consequences

Mercury plays a critical role in serious health problems due to environmental or occupational exposures. Aquatic ecosystems are an essential component of the global biogeochemical cycle of mercury, as inorganic mercury can be converted to toxic methyl mercury in these environments and reemissions of elemental mercury rival anthropogenic mercury releases on a global scale.The history of the Minamata disease, a typical example of industrial pollution, has shown how corporate secrecy and ignorance on part of the health authorities may influence the devastating spread of environmental contamination and the progress of disease. While the Minamata Convention, in place since 2017, is aiming to lower mercury exposure and to prevent adverse effects, there are still knowledge gaps in the areas of global environmental mercury exposure. Areas of uncertainty in the global biogeochemical cycle of mercury include oxidation processes in the atmosphere, land-atmosphere and ocean-atmosphere cycling, and methylation processes in the ocean. Pollution related to climate change (especially in boreal and arctic regions), bioaccumulation and biomagnification of methyl mercury in the food chain, especially in fish and marine mammals, needs to be addressed in more detail. Information is lacking on numerous hidden contaminant exposures i.e. from globally applied traditional medicine, mercury containing skin creams and soaps, dental amalgam, ethyl mercury containing vaccines and latex paint additives, as well as on mercury releases from power plants, e-waste/fluorescent lamps, wildfire emissions, and global artisanal small-scale gold mining activities.Mercury occurs in various forms with different levels of toxicity. While much is already known and documented on the health effects of mercury, present knowledge and translation into preventive actions is still incomplete. Risks for long term health effects trough prolonged low dose exposure and trough cumulative exposures of various mercury forms should be further addressed. Preventive actions should include adequate human biomonitoring programs. Research data should be translated swiftly into management tools for local policy makers and health professionals, also paying attention at the major differences in mercury contamination across the globe.

Investigation of mercury pathways from dental amalgam by micro-PIXE

Mercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and environment. It is an interesting question if the pathway is by Hg diffusion through the tissue of the tooth or dissolution in saliva or direct evaporation through inhaled air into the lung. Our previous study Meesat et al. (2017) of a high-Cu amalgam showed no evidence of diffusion through the enamel. However, a compositional change was observed on the biting surface of the amalgam which is indicative of tribochemical changes.To investigate the above observation in more detail, 17 adult teeth with amalgam fillings were obtained as operation-waste from dental clinics. The samples were embedded and sliced into 1 mm sections in the coronal plane of the tooth using a low/speed diamond saw with water-based cooling. Elemental maps from teeth treated with dental amalgam were measured using micro-PIXE.In common with our previous study Meesat et al. (2017), sharp interfaces between the enamel and amalgam were observed with no strong evidence for Hg diffusion in the enamel. Little evidence exists consistent with the presence of tribochemical alteration by mastication. However, Zn was observed to be localized at different sites in the amalgam/enamel interface.

New silyl-functionalized BisGMA provides autonomous strengthening without leaching for dental adhesives

Resin-based composite has overtaken dental amalgam as the most popular material for direct restorative dentistry. In spite of this popularity the clinical lifetime of composite restorations is threatened by recurrent decay. Degradation of the adhesive leads to gaps at the composite/tooth interface–bacteria, bacterial by-products and fluids infiltrate the gaps leading to recurrent decay and composite restoration failure. The durability of resin-dentin bonds is a major problem. We address this problem by synthesizing silyl-functionalized BisGMA (e.g., silyl-BisGMA), formulating dental adhesives with the new monomer and determining the physicochemical properties and leaching characteristics of the silyl-BisGMA adhesives. Silyl-BisGMA was synthesized by stoichiometric amounts of BisGMA and 3-isocyanatopropyl trimethoxysilane (IPTMS). The control adhesive was a mixture based on HEMA/BisGMA (45/55, w/w). In the experimental formulations, BisGMA was partially or completely replaced by silyl-BisGMA. Water miscibility, polymerization behavior (Fourier transform infrared spectroscopy, FTIR), thermal property (modulated differential scanning calorimetry, MDSC), mechanical properties in dry and wet conditions (dynamic mechanical analysis, DMA), and leached species (HPLC) were investigated. Data from all tests were submitted to appropriate statistical analysis (α = 0.05). Silyl-BisGMA-containing adhesives exhibited comparable water miscibility, lower viscosities, and significantly improved degree of conversion of CC bond as compared to the control. After 4 weeks aqueous aging, the glass transition temperature and rubbery moduli of the experimental copolymers were significantly greater than the control (p < 0.05). HPLC results indicated a substantial reduction of leached HEMA (up to 99 wt%) and BisGMA (up to 90 wt%). By introducing silyl-functional group, the new BisGMA derivative exhibited potential as a monomer that can lead to dental adhesives with improved mechanical properties and reduced leaching under conditions relevant to the oral environment. Statement of SignificanceThe low-viscosity adhesive that bonds the composite to the tooth (enamel and dentin) is intended to seal and stabilize the composite/tooth interface, but it degrades leading to a breach at the composite/tooth margin. As the most popular crosslinking monomer in adhesives, Bisphenol A-glycerolate dimethacrylate (BisGMA) has limitations, e.g. susceptible to hydrolysis and concomitant property degradation. A methoxysilyl-functionalized BisGMA derivative (silyl-BisGMA) was introduced in this work to respond to these limitations. Our results indicated that by introducing silyl-BisGMA, higher crosslinked networks were obtained without sacrificing the homogeneity, and the leached amount of HEMA was reduced up to 99%. This novel resin offers potential benefits including prolonging the functional lifetime of dental resin materials.