Conventional Amalgam Research Articles

Comparison of Marginal Fracture Between Conventional and Bonded Amalgam Restorations in Posterior Permanent Molar Teeth.

Background/objectives Dental amalgam has been a successful restoration for over a century. However, restoration failures due to secondary caries, fractured teeth or restorations, marginal deficiencies, tooth wear, and secondary caries remain significant concerns. Amalgam-bond, known for its ability to bond amalgam to the tooth structure and prevent percolation, forms a strong bond with vital dentin. This study aimed to compare the outcome of marginal fractures in bonded amalgam and conventional amalgam posterior restorations among patients at a tertiary care dental hospital. Materials and methods Sixty consecutive patients aged 25-35 years, meeting the inclusion and exclusion criteria, participated in this study. A thorough history, clinical examination, and standardized periapical radiographs were conducted. Patients were divided randomly into two equal groups, group A and group B. Group A received bonded amalgam restorations, while group B received conventional amalgam restorations. Polishing was performed at a recall visit after seven days, and a follow-up evaluation was done after two months. The final assessment of marginal fractures was recorded after six months. Results After six months, 28 (46.7%) patients showed no marginal fractures, including 11 males and 17 females. On the other hand, 32 (53.3%) patients exhibited marginal fractures, comprising 17 males and 15 females. The clinical success rate of group A was better than group B (p = 0.001). Conclusion Bonded amalgam demonstrates a high success rate and should be a routine choice for treating carious permanent molars in dental practice.

Marginal Integrity of Class-I Restorations, Restored with Amalgam and Bonded Amalgam; A Comparative Study

Objective: To compare the marginal integrity of Class-I amalgam and bonded amalgam restorations in maxillary and mandibular molars at seven days, three, six and twelve-months intervals.
 Study Design: Comparative prospective study.
 Place and Duration of Study: Department of Operative Dentistry, Armed Forces Institute of Dentistry, Rawalpindi Pakistan,from Jul 2017 to Jul 2018.
 Methodology: A total number of 114 patients of either gender with an age range of 14-45 years having Class-I cavities in first and second maxillary and mandibular molars on both sides were equally distributed in two groups. Group-A received conventional Amalgam, and Group-B received bonded amalgam restorations. All the fillings were placed and carved using routine instruments used for amalgam restorations, and the restorations were polished after 24 hours. The patients were initially evaluated for marginal ditching around restorations with the help of a dental mirror and explorer at seven days,followed by inspection at 3, 6 and 12 months.
 Results: Of the 114 participants, all showed excellent marginal integrity at seven-days intervals regardless of the restorative material used. However, marginal integrity deteriorated swiftly with time among those 57(50%) participants who acquired conventional Amalgam. Marginal integrity at 3, 6 and 12-months period was 51(89.5%), 35(61.4%) and 17(29.8%), respectively.Bonded amalgam restorations performed superiorly with 100%, 56(98.2%) and 43(75.4%) successful marginal integrity at 3, 6 and 12-months, respectively.
 Conclusion: Bonded amalgams can be a better substitute than non-bonded amalgam restorations with superior longevity in marginal integrity.Keywords: Amalgam, Bonded amalgam, Marginal integrity, Micro-leakage, Marginal deterioration, Restoration longevity.

Dosimetric evaluation of the effect of dental restorative materials in head and neck radiotherapy.

The aim of our study is to assess the dose enhancement from scattered radiation due to dental restorative materials used for occlusal and mesio-occlusal-distal (MOD) cavity filling during simulated head and neck radiotherapy. We have studied the dose enhancement ratio (DER) of conventional amalgam, high-copper amalgam, and resin composite dental restorative materials at cadaver mandible teeth using 2 therapeutic photon energies of 1.25 MeV (Co-60 gamma ray) and 6 MV (Linac X-ray) for irradiation. DER values at buccal position for Co-60 and 6 MV X-ray were 1.250 ± 0.013 and 1.151 ± 0.012, respectively. For dental cavity fillings, DER values for 6 MV X-ray were 1.065 ± 0.021, 1.100 ± 0.014, and 1.162 ± 0.016 for resin composite filling, low-copper amalgam filling, and high-copper amalgam filling, respectively. Our results revealed that DER regarding irradiation energy was minimum for 6 MV X-rays. With respect to dental restorative filling material, DER was minimum for resin composite filling. Regarding the cavity type, our results with standard deviation (SD) calculations revealed that DER was slightly but not significantly different for both Co-60 gamma ray (1.25 MeV) and 6 MV X-ray energies for both occlusal and MOD cavities. Our dosimetric results for a single beam geometry suggest that, among the three types of filling, resin composite filling is an ideal restorative filling material with minimal morbidity-inducing radiation dose enhancement that may result in increased osteoradionecrosis and secondary caries risk. There is a need for further dosimetric studies with actual clinical beam arrangements.

A comparative study of the corrosion stability of dental amalgams with electrochemical impedance measurements

AbstractThe corrosion susceptibility of a selection of amalgams used in dentistry has been examined with the electrochemical impedance method. The results are compared with data derived from cyclic voltammetry performed with these materials before. Most examined materials including a conventional amalgam show similar corrosion resistance; however, only one product shows a significantly higher corrosion resistance.

Direct contra naïve-indirect comparison of clinical failure rates between high-viscosity GIC and conventional amalgam restorations: an empirical study.

BackgroundNaïve-indirect comparisons are comparisons between competing clinical interventions’ evidence from separate (uncontrolled) trials. Direct comparisons are comparisons within randomised control trials (RCTs). The objective of this empirical study is to test the null-hypothesis that trends and performance differences inferred from naïve-indirect comparisons and from direct comparisons/RCTs regarding the failure rates of amalgam and direct high-viscosity glass-ionomer cement (HVGIC) restorations in permanent posterior teeth have similar direction and magnitude.MethodsA total of 896 citations were identified through systematic literature search. From these, ten and two uncontrolled clinical longitudinal studies for HVGIC and amalgam, respectively, were included for naïve-indirect comparison and could be matched with three out twenty RCTs. Summary effects sizes were computed as Odds ratios (OR; 95% Confidence intervals) and compared with those from RCTs. Trend directions were inferred from 95% Confidence interval overlaps and direction of point estimates; magnitudes of performance differences were inferred from the median point estimates (OR) with 25% and 75% percentile range, for both types of comparison. Mann-Whitney U test was applied to test for statistically significant differences between point estimates of both comparison types.ResultsTrends and performance differences inferred from naïve-indirect comparison based on evidence from uncontrolled clinical longitudinal studies and from direct comparisons based on RCT evidence are not the same. The distributions of the point estimates differed significantly for both comparison types (Mann–Whitney U = 25, nindirect = 26; ndirect = 8; p = 0.0013, two-tailed).ConclusionThe null-hypothesis was rejected. Trends and performance differences inferred from either comparison between HVGIC and amalgam restorations failure rates in permanent posterior teeth are not the same. It is recommended that clinical practice guidance regarding HVGICs should rest on direct comparisons via RCTs and not on naïve-indirect comparisons based on uncontrolled longitudinal studies in order to avoid inflation of effect estimates.

Poor quality evidence suggests that failure rates for atraumatic restorative treatment and conventional amalgam are similar

The Medline, Cochrane CENTRAL, Biomed Central, Database of Open Access Journals (DOAJ), OpenJ-Gate, Bibliografia Brasileira de Odontologia (BBO), LILACS, IndMed, Sabinet, Scielo, Scirus (Medicine), OpenSIGLE and Google Scholar databases were searched. Hand searching was performed for journals not indexed in the databases. References of included trials were checked. Prospective clinical trials with test and control groups with a follow up of at least one year were included. Data abstraction was conducted independently and clinical and methodologically homogeneous data were pooled using a fixed-effects model. Eighteen trials were included. From these 32 individual dichotomous datasets were extracted and analysed. The majority of the results show no differences between both types of intervention. A high risk of selection-, performance-, detection- and attrition bias was identified. Existing research gaps are mainly due to lack of trials and small sample size. The current evidence indicates that the failure rate of high-viscosity GIC/ART restorations is not higher than, but similar to that of conventional amalgam fillings after periods longer than one year. These results are in line with the conclusions drawn during the original systematic review. There is a high risk that these results are affected by bias, and thus confirmation by further trials with suitably high numbers of participants is needed.

Preparation and Characterization of High-Copper Restorative Dental Alloys Corrected

A series of restorative dental alloys related to the ternary system Ag-Sn-Cu were prepared using high purity 99.99% elemental constituents. The effect of increasing the copper concentration on the micro-structural and mechanical properties of conventional dental amalgam alloy was investigated. Copper content was varied in the range of 10-30wt% and that of silver in the range of 40-60wt%, while tin percentage was kept constant between 28-30wt%. Selected desired compositions were weighed, melted, and homogenized for 1h in fused-alumina crucible using wire-resistance tube furnace at 1100oC under an inert atmosphere of argon gas. Two types of alloys were prepared, the first one was by quenching in water the alloy melt from a peak temperature of 725oC, while the second type was by slow furnace-cooling of the melt down to the room temperature. Annealing of the alloys at 350- 400oC for 24 hrs was also conducted to enhance the growth of the γ-phase. The resultant alloys were then cooled to room temperature (R.T) and milled mechanically to obtain a powder having particles sizes in the range between 30-80μm. The resultant powdered alloys was then stress-relieved at 100oC for 1h. XRD analysis, optical microscopy, micro hardness, and compression strength tests were all used for the characterization and properties determination at different Cu-concentrations for the as-prepared and amalgamated alloys in addition to the powders.. The obtained relative values for the above-mentioned properties were closely related to those listed in the literatures and lies between those of mechanically-milled and those of spherical particles. Also the γ2 – phase was disappeared at high copper content of > 20wt%.

Conservative Glass Ionomer Cement Occlusal Restorations can be as Effective as Conventional Amalgam Occlusal Restorations

Six-year success rates of occlusal amalgam and glass-ionomer restorations placed using three minimal intervention approaches. Mandari GJ, Frencken JE, Van’t Hof MA. Caries Res 2003;37:246-53. Kevin J. Donly, DDS, MS To compare the success at 6 years of 3 caries treatment approaches: (1) a conventional amalgam occlusal restoration placed in a university setting; (2) a modified-conventional low-viscosity glass ionomer cement occlusal restoration; and (3) an ultraconservative low-viscosity glass ionomer cement occlusal restoration, the latter two placed in a field setting. Government Randomized controlled trial Level 1: Good-quality, patient-oriented evidence Grade A: Consistent, good-quality patient-oriented evidence

Repair of amalgam restorations with conventional and bonded amalgam: an in vitro study

Purpose: This study evaluated microleakage on amalgam restorations repaired by amalgam and bonded amalgam. Methods: Thirty extracted human pre-molars were restored by amalgam. A simulated defect was prepared and assigned to two treatment groups (n=15): G1 - repaired by amalgam (Permite C-SDI); G2 - repaired by bonded amalgam (Caulk 34% Tooth Conditioner Gel – Dentsply + Prime & Bond 2.1 – Dentsply + Permite C- SDI). The teeth were immersed in a 50% silver nitrate solution, thermocycled and then, sectioned longitudinally through the restoration center and examined by 3 examiners using a stereomicroscope. Microleakage was evaluated in a 0-4 scale for dye penetration. Microleakage data were analyzed by Kruskal Wallis and Dunn test. Results: The bonded amalgam technique was significantly the most effective in repair/tooth interfaces sealing (score 0=53.3%, P=0.0012). For repair/restoration interfaces, conventional amalgam was also statistically more effective in the sealing (score 0=86.7%, P<0.001). Conclusion: None of materials eliminated microleakage completely. The use of adhesive systems had significant effect on the ability to seal the repair/tooth interface, however, for repair/restoration interface, it can increase microleakage.

Comparison of fracture resistance of endodontically treated teeth using different coronal restorative materials: Anin vitrostudy

Aim/Objective:To evaluate the in vitro effect of bonded restorations on the fracture resistance of root canal-treated teeth.Materials and Methods:One hundred twenty extracted, maxillary, permanent premolars were collected. After preparing the access cavity, the teeth were biomechanically prepared and obturated. Samples were divided into six groups based on the type of restorative material used to restore them. Teeth were embedded in acrylic resin and their fracture strength was measured using a Universal Testing Machine. Data were evaluated statistically using one-way ANOVA-F and unpaired t-test.Results:Teeth restored with bonded amalgam and composite resin showed higher fracture resistance than those restored with conventional amalgam. Fracture strengths of bonded restorations and intact teeth were not statistically different. The results suggested that the group restored with conventional amalgam had the lowest fracture resistance. No statistically significant differences were found between the bonded amalgam and composite resin groups.Conclusion:Conventional amalgam core showed the least fracture resistance whereas; composite resin and bonded amalgam core showed fracture resistance was similar to that of natural tooth.

Effect of bonded restorations on the fracture resistance of root filled teeth

To evaluate the fracture resistance of root filled maxillary premolars restored with different techniques. One hundred and twenty single-rooted maxillary premolar teeth were divided randomly into six groups of 20 teeth and subjected to the following procedures: group 1: intact teeth. Group 2: endodontic access cavities prepared. Group 3: MOD cavities were prepared, root canals were filled and no restoration was placed. Group 4: teeth were prepared as group 3 and restored conventionally with amalgam. Group 5: teeth were prepared as group 3 and restored with amalgam using a bonding material. Group 6: teeth were prepared as group 3 and restored with composite resin using the same bonding material. Teeth were embedded in acrylic resin and the loads for fracture strength were applied vertically with a constant speed of 1 mm min(-1). Data were evaluated statistically with anova and Tukey's tests. The mean force of fracture values were 1191.41, 599.86, 233.03, 494.72, 962.81 and 856.48 N for groups 1, 2, 3, 4, 5 and 6, respectively. The fracture resistance of group 5 was similar to group 1 (P > 0.05). The mean force at fracture of group 5 and group 6 was not significantly different. The fracture resistance of groups 5 and 6 was significantly higher than group 4 (P < 0.001). The group, restored with conventional amalgam, had the weakest resistance to fracture when compared with the bonded restorations. No statistically significant differences were found between the bonded amalgam and composite resin groups.

Microleakage in Conventional and Bonded Amalgam Restorations: Influence of Cavity Volume

This study verified the relationship between the volume and microleakage of conventional and bonded amalgam restorations. Also, the microleakage influence of intermediate materials, substrates and the direction of sectioning was investigated. Fifty-six bovine incisors were selected. Standard Class V cavities were prepared in buccal and lingual surfaces. For each tooth, two cavity sizes were prepared, corresponding to two cavity volumes: one larger (A) and the other smaller (B). The cervical wall was located in cementum/dentin and the incisal wall in enamel. The teeth were distributed in four groups (n=28) according to the intermediate material employed (glass-ionomer cement, resin cement, adhesive system and copal varnish-control). The materials were applied following manufacturers' directions. After restoration, the teeth were submitted to thermal cycling. They were then immersed in a dye solution and sectioned in two directions inciso-cervical (IC) and mesio-distal (MD) sections to evaluate the microleakage. Data were subjected to non-parametric statistical analysis (Wilcoxon's paired test and Kruskal-Wallis test). No significant difference was found between the two cavity sizes. Leakage in enamel was statistically lower than in the cementum/dentin interface (p < 0.05). In some situations, glass-ionomer or resin cement lined amalgam restorations presented less dye leakage than copal varnish lined restorations (p < 0.05). No significant difference was observed in microleakage between IC or MD sectioning. Within the limitations of this study, it was concluded that cavity size and direction of section were not significant factors for microleakage, while substrate and intermediate materials had a significant effect on the sealing ability in amalgam restorations.

Long-term survival of endodontically treated molars without crown coverage: A retrospective cohort study

Teeth are weakened after endodontic treatment and should, ideally, be crowned, especially posterior teeth. However, this is not always possible. Information about the longevity of endodontically treated teeth without crown coverage may assist in selecting appropriate treatment modalities. The aims of this cohort study were to evaluate the survival rate for endodontically treated molars without crown coverage and to identify possible related factors. A total of 220 endodontically treated permanent molar teeth in 203 subjects on a waiting list for fixed prosthodontic treatment at the Faculty of Dentistry-Mahidol University, Thailand, were included. Follow-up data were derived from a clinical examination and review of the dental record and radiographs. Subjects were not included in the study if teeth had provisional crowns, definitive restorations with cuspal coverage, or with dowel and core and/or crown restorations. The outcome evaluated was defined as a failure if there were negative findings in the condition of a tooth that required a restoration, tooth repair, or extraction. Tooth loss due to endodontic and periodontal reasons was excluded. The independent variables assessed were patient age, gender, location (maxilla or mandible), the existence of an opposing dentition and adjacent teeth, remaining tooth structure, and types of restorative material. Kaplan-Meier analysis with a 95% confidence level was used to calculate the survival probability, and a log-rank test was used to determine whether significant differences existed. Overall survival rates of endodontically treated molars without crowns at 1, 2, and 5 years were 96%, 88%, and 36%, respectively. With greater amounts of coronal tooth structure remaining, the survival probability increased. Molar teeth with maximum tooth structure remaining after endodontic treatment had a survival rate of 78% at 5 years. Restorations with direct composite had a better survival rate than conventional amalgam and reinforced zinc oxide and eugenol with polymethacrylate restorations. Within the limitations of this study, the amount of remaining tooth structure and types of restorative material have significant association with the longevity of endodontically treated molars without crown coverage.

Ions released from dental amalgams in contact with titanium.

The ions released from conventional and high-copper amalgams in contact with titanium were quantitatively analyzed in a 0.9% NaCl solution at 37 degrees C when the surface area ratio of titanium/amalgam was set up as 1/10, 1/1, or 10/1. The corrosion potentials of the amalgams and titanium were measured under the same conditions. Surface analyses on the amalgams were also employed using SEM with WDS. Though the potential of the conventional amalgam was always lower than that of titanium, that of the high-copper amalgam was reversed during the early stage of immersion and remained lower. When the surface area ratio of titanium grew at 10/1, tin and copper ions released from the conventional and high-copper amalgam, respectively, increased significantly compared with those of each amalgam that was not in contact with titanium. The galvanic corrosion in such a large surface area of titanium possibly led to the heavy corrosion of the amalgams.

Adsorption of released ions from dental amalgams on titanium

Effects of titanium plate in contact with amalgams of ‘Hi Atomic M’ (HA) and ‘Lumi Alloy’ (LM) on the release of metal ions from those amalgams into 0.9% NaCl solution were investigated using inductively coupled plasma atomic emission spectroscopy, electron probe microanalysis and XPS. Except for Hg, the release of ions increased about ten times on Ti contact, whereas that of Hg was diminished several-fold. No measurable amounts of Ti ions were found in solution. Where the Ti is in contact with the amalgam, every element was deposited almost proportionally to the solution composition. Tin oxide containing several percent of In2O3 covered the top surface of Ti connected to the conventional HA amalgam. However, the dominant species on Ti connected to the high-copper LM amalgam were Cu and Sn oxides. On the Ti connected to the amalgams, the concentrations of other elements were very low. Copyright © 2002 John Wiley & Sons, Ltd.

Vertical root fracture in endodontically treated teeth: a review of 25 cases.

We sought to examine the clinical conditions under which 25 endodontically treated teeth underwent vertical root fracture (VRF) and to relate this condition to the time elapsed from endodontic treatment to fracture. This was a retrospective study in which we reviewed 25 case histories of patients with postendodontic VRF and studied the effect of various pretreatment and posttreatment factors as they related to VRF. The mean time to VRF was 54 months; this was not significantly influenced by the presence or absence of prior restoration or by the presence or absence of a crown fitting. The use of a prefabricated, cylindrical, cemented intraradicular retainer increased the time between endodontics and VRF. Teeth restored with conventional amalgam took significantly longer to undergo VRF than those restored with composite or bonded amalgam. In contrast, amalgam-restored teeth suffered more coronal fractures before VRF than did teeth in the other 2 groups.

Identification of cu6sn5 and cu10sn3 Phases in Admixed Dispersal Phase Dental Amalgam by High Resolution Trasmission Electron Microscopy Combined with Convergent Beam Electron Diffraction.

Abstract Creep process in dental amalgams has been a subject of study. The performance of dental amalgams depends on the creep resistance of different products offered in the market. Creep process occurs at mouth temperatures which are slightly lower than Gamma 1 matrix phase (Ag2Hg3) melting point (310°K). One successful attempt to improve the creep resistance has been the addition of a dispersed phase (particles of eutectic Ag-Cu phase) in conventional amalgams. By this method, a new phase (η- Cu6Sn5) has been produced which inhibits the detrimental gamma 2 (Sn8Hg) formation. It has been proposed that the presence of finely distributed particles of η-Cu6Sn5 in the matrix lowers the creep rate. This behavior has been attributed to the pinning effect of these fine particles on the dislocations produced during the creep process (1). The presence of η-Cu6Sn5 phase finely dispersed in the matrix has been explained by the initial formation of reaction rings around the eutectic Ag-Cu spherical particles.

Creep Mechanism Determination on Dispersed Phase Amalgams using High Resolution Electron Microscopy (HRTEM) Observation

Abstract Creep mechanism determination on dental amalgams has been a subject of interest in recent research works. Most of these studies conclude that the creep behavior can be explained by the well-known expression: ɛ = A σnexp (-Q/RT). Reported values for n (potential coefficient of stress) are in the order of 3 for phase dispersed dental amalgams and 2 for conventional amalgams. It suggests a grain sliding creep mechanism for conventional amalgams and a climb dislocation mechanism for creep in phase dispersed amalgams due to interactions with the dispersed CuxSny particles typical of this kind of amalgam(l). For both cases, the creep process occurs inside the γ (Ag2Hg3) phase matrix of low melting point (310 °K) which is slightly higher than typical mouth temperatures of about 400 °K (37 °C). In this work some microestructural evidences are obtained to support the behavior described above by using High Resolution Transmission Electron Microscopy (HRTEM).

Tin passivation by copper in dental amalgams

Abstract Odontologists have been using dental amalgams for more than a century. In the conventional amalgams, the important formation of a phase Sn 7–8 Hg called γ 2 was considered to be responsible for the inferior resistance to corrosion of this first generation of materials. The progressive increase of the copper content in formulae corresponds to the recent improvement of the resistance to corrosion of the dental amalgams. The decrease of the content in γ 2 -phase in the structure was only suggested to explain this phenomenon. We proposed a second reason, a chemical one. It was found by corrosion tests in a medium with a mineral composition similar to natural saliva (SAGF medium: Gal–Fovet artificial saliva). © 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS amalgams / tin / copper / corrosion / thermodynamics / thiocyanates

A study of alternative metal particle structures and mixtures for dental amalgams based on mercury additions.

The perception that mercury in dental amalgam is toxic to the human organism has prompted worldwide efforts by the scientific community to develop alternative amalgam-like materials that utilize little or no mercury. In this investigation, an attempt is made to develop a new dental alloy system by adding liquid mercury to silver-coated Ag4Sn intermetallic particles in lesser amounts than are used in conventional amalgam alloys. An effort to precipitate the important eta-prime (Cu6Sn5) phase was made by adding pure Cu and Sn powders to the alloy formulation during trituration. Tytin a popular Ag-Sn-Cu single-composition, spray-atomized conventional dental alloy was used as the control to obtain baseline data for comparisons of microstructures and mechanical properties. Amalgamation of the coated particles with mercury, with or without the addition of Cu and Sn powders, mostly produced specimens with chemically non-coherent microstructures that were relatively weak in compression. These results were due, in part, to mercury's inability to chemically wet the Ag-coated particles and Cu and Sn powders because of naturally occurring surface oxide films. The strongest specimens tested had silver dendritic coatings, resulting in compression strength values up to 40% of the control's. Their higher strength is attributed to mechanical interlocking at the particle/matrix interfaces.