The optimum level of radiopacity in posterior composite resins

Evaluation of Radiopacity of Bulk-fill Flowable Composites Using Digital Radiography

New flowable composites that may be bulk-filled in layers up to 4 mm are indicated as a base beneath posterior composite restorations. Sufficient radiopacity is one of the several important requirements such materials should meet. The aim of this study was to evaluate the radiopacity of bulk-fill flowable composites and to provide a comparison with conventional flowable composites using digital imaging. Ten standard specimens (5 mm in diameter, 1 mm in thickness) were prepared from each of four different bulk-fill flowable composites and nine different conventional flowable composites. Radiographs of the specimens were taken together with 1-mm-thick tooth slices and an aluminum step wedge using a digital imaging system. For the radiographic exposures, a storage phosphor plate and a dental x-ray unit at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time was 0.2 seconds. The gray values of the materials were measured using the histogram function of the software available with the system, and radiopacity was calculated as the equivalent thickness of aluminum. The data were analyzed statistically (p<0.05). All of the tested bulk-fill flowable composites showed significantly higher radiopacity values in comparison with those of enamel, dentin, and most of the conventional flowable composites (p<0.05). Venus Bulk Fill (Heraeus Kulzer) provided the highest radiopacity value, whereas Arabesk Flow (Voco) showed the lowest. The order of the radiopacity values for the bulk-fill flowable composites was as follows: Venus Bulk Fill (Heraeus Kulzer) ≥ X-tra Base (Voco) > SDR (Dentsply DeTrey) ≥ Filtek Bulk Fill (3M ESPE). To conclude, the bulk-fill flowable restorative materials, which were tested in this study using digital radiography, met the minimum standard of radiopacity specified by the International Standards Organization.

Radiopacity of 28 Composite Resins for Teeth Restorations

AIM

Radiopacity is a fundamental requisite to check marginal adaptation of restorations. Our objective was to assess the radiopacity of 28 brands of light-cured composite resins and compare their radiopacity with that of enamel, dentin, and aluminum of equivalent thickness.

MATERIALS AND METHODS

Composite resin disks (0.2, 0.5, and 1 mm) were radiographed by the digital method, together with an aluminum penetrometer and a human tooth equivalent tooth section. The degree of radiopacity of each image was quantified using digital image processing. Wilcoxon nonparametric test was used for comparison of the mean thickness of each material.

RESULTS

All of the materials tested had an equal or greater radiopacity than that of aluminum of equivalent thickness. Similar results for enamel were found with the exception of Durafill, which was less radiopaque than enamel (p < 0.05). All the specimens were more radiopaque than dentin, except for P90 (which was equally radiopaque) and Durafill (which was less radiopaque). The thickness of the specimens may influence the similarity to the enamel's radiopacity. All of the composite resins comply with specification #27 of the American Dental Association. The radiopacity of Amelogen Plus, Aph, Brilhiante, Charisma, Concept Advanced, Evolux X, Exthet X, Inten S, Llis, Master Fill, Natural Look, Opallis, P60, Tetric, Tph, Z100, and Z250 was significantly higher than that of enamel (p < 0.05).

CONCLUSION

With these composites, it is possible to observe the boundaries between restoration and tooth structure, thus allowing clinicians to establish the presence of microleakage or restoration gap.

CLINICAL SIGNIFICANCE

Suitable radiopacity is an essential requisite for good-quality esthetic restorative materials. We demonstrate that only some composites have the sufficient radiopacity to observe the boundaries between restoration and tooth structure, which is the main cause of restoration failure.

Laboratory evaluation of the physicochemical properties of a new root canal sealer based on Copaifera multijuga oil-resin

AIM

To compare a new root canal sealer based on Copaifera multijuga oil-resin (Biosealer) using three other established sealers (Sealer 26, Endofill and AH plus) in terms of their physicochemical properties.

METHODOLOGY

The study was carried out according to the requirements of Specification Number 57 of the American Dental Association (ADA) and consisted of the following tests: setting time, flow, film thickness, dimensional stability, radiopacity and solubility/disintegration. Data were analysed statistically using anova and Tukey's test for multiple comparisons. The significance level was set at 5% for all analyses.

RESULTS

Sealer 26 and AH Plus had the longest setting time (P < 0.05). All materials presented flow in with the ADA's guidelines. Regarding film thickness, Sealer 26 did not have a satisfactory performance, as it had a higher mean value than the maximum allowed by the ADA (0.05 mm), being significantly different from the other materials (P < 0.05), which had mean values for film thickness in accordance with the ADA's recommendations. Regarding the solubility and disintegration, only Endofill did not meet the ADA's specifications and presented the worst results of all materials (P < 0.05). Sealer 26 presented the greatest dimensional changes and differed significantly from all other sealers (P < 0.05). Biosealer had the lowest radiopacity values and was significantly different from the other sealers (P < 0.05).

CONCLUSION

The experimental sealer based on Copaifera multijuga oil-resin presented satisfactory results in the physicochemical tests required by the ADA.

Radiopacity of root filling materials using digital radiography

AIM

To evaluate radiopacity of root filling materials using digital radiography.

METHODOLOGY

The sealers tested were AH Plus, Endofill, EndoREZ and Epiphany. Gutta-percha (Dentsply Maillefer) and Resilon cones were also tested. Acrylic plates, containing six wells, measuring 1 mm in depth and 5 mm in diameter, were prepared for the test, and filled with the materials. The test samples were radiographed together with an aluminium stepwedge calibrated in millimetres, according to ANSI/ADA Specification 57. For the radiographic exposures, digital imaging plates and an X-ray machine at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time, 0.2 s. After the laser optic reading process, the software determined the radiopacity of the standardized areas, using grey-scale values, calculating the average radiographic density for each material.

RESULTS

The decreasing values of radiopacity of the studied materials, expressed in millimetres of aluminium equivalent, were: Resilon (13.0), AH Plus(TM) (11.2), gutta-percha (9.8), Epiphany (8.0), Endofill (6.9) and EndoREZ (6.6).

CONCLUSION

All materials had radiopacity values above 3 mm of aluminium recommended by ANSI/ADA Specification 57.

In vitro analysis of the radiodensity of indirect composites and ceramic inlay systems and its influence on the detection of cement overhangs

The purpose of this study was to evaluate the radiodensity of indirect restorative systems and to determine its influence on detection of resin cement overhangs. Sixty sound molars with similar dimensions were selected, and MOD inlay preparations were made in a standardized fashion with 6 degrees taper of the walls. Restorations were made with a porcelain, Duceram LFC, and with three indirect composites, Solidex, Artglass, and Targis. Digital radiographic images were taken before and after cementation of the inlays (Digora system) and were analyzed on two regions, the cervical and the isthmus floor. Digital radiodensity measurements were performed on standardized points symmetrically distributed over each restoration and tooth structure. Cement overhangs were detected through visual analysis by three evaluators. Data were statistically analyzed utilizing ANOVA following Tukey's test (p < 0.05), showing that Solidex presented lower radiodensity than Duceram LFC, and both Artglass and Targis presented similar higher levels of radiodensity than the other groups. Radiodensity of cervical regions was always greater than for isthmus floor regions. Detection of the resin cement overhangs is easier observed on Solidex and Duceram LFC. Radiodensity is highly influenced by restorative material type and tooth regions. The detection of radiopaque resin cement overhangs is influenced by radiodensity of restorative materials.

Measuring the radiopacity of luting cements, dowels, and core build-up materials with a digital radiography system using a CCD sensor

PURPOSE

This study assessed the radiopacity of five luting cements, five dowels, and five core build-up materials using two target distances.

MATERIALS AND METHODS

Materials were analyzed using a modified version of ISO protocol 4049. samples 1 mm thick were digitally radiographed alongside a stepwedge of aluminum alloy 1100 using a Trophy RVG-4 CCD sensor and 70 kVp X-ray generator. The gray-scale values of the stepwedge and sample were converted to X-ray absorbencies. The relationship between X-ray absorbance and aluminum thickness was linear for thicknesses less than 10 mm and followed a power-law relationship above 10 mm. These relations were used to convert the absorbencies of the samples into aluminum thicknesses. The radiopacity data was subjected to ANOVA/Student-Newman-Keuls testing.

RESULTS

All materials were more radiopaque than equivalent thicknesses of aluminum. Each product category contained a wide range of radiopacities. Syringe-dispensed materials tended to be less radiopaque than materials dispensed by mechanically assisted syringe or mixed by hand (p < 0.01). Target distance did not affect the measured radiopacity so long as the exposure time was suitably adjusted (p= 0.86).

CONCLUSIONS

All luting cements and core materials met or exceeded the ISO minimums. The tested metal-reinforced glass ionomer core build-up materials were extremely radiopaque. Some publications suggest that excessively radiopaque core materials can hinder a clinician's ability to spot voids or marginal defects.

Radiodensity of enamel and dentin of human, bovine and swine teeth

Several studies have aimed to evaluate the characteristics of hard dental tissues from animal species in order to adequately substitute the usage of human teeth. The purpose of this study was to evaluate the radiodensity of enamel and dentin of human, bovine and swine teeth. Five specimens of 2 mm in thickness were obtained from human, bovine and swine teeth and the radiographic images were taken positioning it on a phosphor plaque digital system, Digora (Soredex, Helsinki, Finland). The radiodensity of each specimen was obtained and data were compared by ANOVA following Tukey test (P < 0.05). The results showed that human and bovine enamel presented similar radiodensity, which was higher than the one from swine enamel; bovine and swine dentin presented similar radiodensity, and only bovine dentin presented greater similarity to human dentin. Bovine teeth seems to be more similar to human teeth in respect to radiodensity.

Detection of marginal defects of composite restorations with conventional and digital radiographs

The purpose of this study was to determine the validity of detecting approximal imperfections of composite fillings using three intraoral radiographic systems in vitro. Class II composite resin restorations (108) with three radiopacities (264, 306, 443% Al 99.5) of which 27 had marginal openings or overhangs, respectively, were conventionally (Ektaspeed plus) and digitally (Dexis, Digora) radiographed. Images were assessed by 10 observers for the presence of marginal gaps and overhangs, as well as for their need of restorative treatment according to a five-point confidence rating scale. The validity of the observations were expressed as areas under receiver operating characteristic (ROC) curves (Aroc). Repeated measures analysis of variance revealed significant effects of 'radiographic system' and 'diagnostic purpose'. Marginal overhangs (Aroc = 0.90) were significantly easier to diagnose than openings (Aroc = 0.63). Marginal gaps were better detected on conventional and Dexis radiographs than on Digora images. the range of sensitivities and specificities of the treatment decision was 0.53-0.56 and 0.87-0.88, respectively. It was concluded that the validity of detecting marginal defects of composite resin restorations based on radiographs was only slightly affected by the radiographic system being used. The diagnosis of marginal gaps frequently resulted in false-positive and false-negative decisions.

Radiopacity of tantalum oxide nanoparticle filled resins

OBJECTIVES

Radiopacity of composite resins allows radiographic distinction of existing restorations and recurrent caries. Current composites must be supplemented with heavy metal-containing glasses or minerals to achieve a desired radiopacity. The purpose of this study was to evaluate the radiopacity of Tantalum oxide (Ta2O5) filled resins at varying percentage loadings.

METHODS

Methacrylate functionalized Ta2O5 nanoparticles (< 50 nm) in methanol-dissolved or powder forms were mixed into either glycerol dimethacrylate (GDMA) or a bisGMA, TEGDMA, bisEMA mixture (GTE). Specimens were made in a split brass mold (2 x 2 x 15 mm) and compared with an aluminum stepwedge (99.5% pure Al) and a dentin slice of the same thickness. Kodak Ultraspeed periapical X-ray film on a lead plate at a target distance of 45 cm was exposed at 70 kVp and 10 mA, for 0.5 s and processed automatically. Optical density was measured (n = 3) with an RMI Processor Control Densitometer. Radiopacity was calculated as percent relative linear attenuation coefficient (Alpha). ANOVA and Student-Newman-Keuls comparisons were used to determine significance at the 95% confidence level.

RESULTS

Radiopacity increased significantly with Ta2O5 loading (p = 0.001). Ta2O5 nanoparticle filled resins enter the optimal range of diagnostic detectability (alpha = 150-250) at 50 wt.% and approach equivalence with enamel at approximately 70 wt.%.

SIGNIFICANCE

The introduction of tantalum oxide nanoparticle filler has potential as a miscible component of a resin composite to provide radiopacity for microfiller-type restorative materials and to circumvent the need for hydrolysis-prone glass reinforcing fillers.

Aluminium radiopacity standards for dentistry: an international survey

OBJECTIVE

The aims of this study were to determine the appropriate composition and purity limits of aluminium alloy radiopacity standards for dental biomaterials, taking into account the current status in representative laboratories worldwide, and to formalise the calculation procedure for processing radiopacity data.

METHODS

A series of aluminium step-wedges were obtained from academic and industrial research laboratories. These were analysed by energy dispersive X-ray procedures. The set of step-wedges were independently characterised for radiopacity at two University dental schools.

RESULTS

The percentage of aluminium together with the percentages of minor alloying elements (magnesium, manganese, iron and silicon) have been determined as mass percentages. For each centre, the optical density versus step-height for all wedges was judged to fall on a common curve, with the main exception of one step-wedge that was found to contain 4% copper, by mass. A suitable calculation procedure was described explicitly.

CONCLUSION

Of the examined representative step-wedges, all but the aluminium--4% copper material were satisfactory and gave results comparable with wedges of high purity. Limits should therefore be revised for composition of aluminium radiopacity step-wedges or test blocks to a more realistic level of purity. Alloys with more than 0.05% copper or 1.0% iron should be excluded and the aluminium content should be at least 98% by mass. In the calculations deployed for deriving radiopacity as 'equivalent aluminium thicknesses', an appropriate linear regression procedure should be employed and considerable care taken in the evaluation of materials of low or borderline radiopacity, relative to specification limits. The method described is principally suitable for materials with radiopacity greater than 1 mm. For materials with radiopacity less than 1 mm aluminium, thicker specimens (2 mm) should be used.

Radiopacity of glass ionomer materials

To facilitate the detection of overhangs and defects adjacent to a filling, restorative materials should have a radiographic density higher than or at least similar to that of enamel. In the present study the density of 21 glass ionomer materials was measured and compared with the density of enamel, dentine, amalgam and aluminium. Most materials were more radiopaque than enamel, thereby satisfying the requirements as proposed by several investigators. The materials with lower density were mainly types intended for use in anterior teeth where the entire filling can more easily be examined clinically. They should not be used as a base under approximal fillings in order to avoid a false positive diagnosis of recurrent caries.

Direct digital radiography for the detection of defects in a standard aluminium test object through composite resin restorative materials

While the RVG 32000 (Trophy Radiologie, Vincennes, France) is in wide use for direct digital intraoral radiography in dentistry, there is a dearth of information in the literature concerning the system's sensitivity to small changes in radiographic density consistent with initial and recurrent dental caries. A standardized 7 mm aluminium test block was used as a phantom for perceptibility testing of density changes, both with and without the superimposition of composite resin sheets of various thicknesses. Defects in the block were randomly positioned and varied from 0.1 to 1.5 mm. Thermal prints were used for evaluation. Standard linear images, with no enhancement, were compared with three enhanced modes, standard mode with gradient enhancement (enhanced standard), standard X-function and zoom high resolution (ZHR). Sensitivity improved in the following sequence: standard 0.58 < enhanced standard 0.75 < X-function 0.94 < ZHR 0.95. Accuracy improved in the following sequence: standard 0.45 < enhanced standard 0.58 < X-function 0.73 < ZHR 0.74. Specificity was 1.0 both for X-function and for ZHR. These two modes both proved significantly better (P < 0.05) for the detection of 0.1 mm defects than the other two modes tested. No significant difference was found between X-function and ZHR. As ZHR requires four times the radiation exposure as standard exposures with the X-function, the latter is preferred for the task described in this study.

Studies on radiopaque composites containing ZrO2-SiO2 fillers prepared by the sol-gel process

Radiopacity can facilitate diagnostic observations adjacent to dental composites. To produce radiopaque SiO2-based fillers, ZrO2-SiO2 powders containing up to 45wt% ZrO2 were manufactured by the sol-gel process. The radiopacity of experimental composites containing Bis-GMA+TEGDMA+CQ+DMAEMA monomer mixture (25 wt%) and ZrO2-SiO2 fillers (75 wt%) was evaluated and compared to that of human enamel and two commercial composites with different radiopacity. It became evident that the radiopacity of the experimental composites increased linearly with zirconium content and could match that of the control materials, while the composite containing 15wt% ZrO2-85wt% SiO2 filler possessed radiopacity analogous to that of human enamel. It was demonstrated here that the radiopacity of the composites could be precisely controlled by adjusting the ZrO2 content in ZrO2-SiO2 fillers. These radiopacity-adjustable composites have the potential to be very useful filling materials by enabling dentists to accurately distinguish secondary caries adjacent to the composite restorations.

Dental composites/glass ionomers: the materials

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Digital subtraction radiography in artificial recurrent caries detection

The diagnostic accuracy of digital subtraction radiography in detection of artificial recurrent caries lesions was assessed in this project. The use of digital subtraction radiography has been shown to markedly increase the accuracy of the detection of destruction in the periodontal bone, but the method has not been evaluated in secondary caries detection. Defects of three different sizes, simulating recurrent caries, were sequentially prepared in the interproximal cavity preparation margins of 28 teeth. Two composite restorative materials with different radiographic densities were used as posterior restorations, and a radiograph was obtained of each defect size and restorative material. The radiographs were digitized and subtracted from the reference images, and the conventional radiographs and the subtraction images were evaluated by seven observers. The data were analysed with ROC statistics. Subtraction radiography was found to be superior to conventional radiography in recurrent caries detection, mainly by reducing the false-positive diagnoses. The radiopacity of the restorative material had a significant effect on accuracy with conventional but not with subtraction radiography.

Optimum radiopacity of composite inlay materials and cements

This study evaluated the radiopacity of recently introduced post-cured composite resin inlays and the composite dual-cure resin cements. Composite cement used as a luting material should have a minimal radiopacity of at least the same thickness as aluminum, to help in accurate radiologic discrimination.

Radiographic detection of recurrent carious lesions associated with composite restorations

The greatest potential problem associated with posterior composite restoration is secondary caries detection. It is essential that secondary caries is detected as early as possible to enhance the prognosis for a successful treatment outcome. This laboratory study evaluated the optimum level of radiopacity of composite materials for radiographic detection of secondary carious lesions associated with composite materials. Results indicated that for the radiologic detection of secondary caries, it is sufficient for composite materials to have the same level of radiopacity as enamel.

The radiographic density of composite restorative resins

The radiodensities of enamel, dentin, aluminum, and 14 modern composite resins at thicknesses of 1 to 4 mm were compared. Nine of the 14 composites were radiopaque with respect to that of aluminum. Radiolucent lesions or voids were simulated by cutting grooves 0.5, 1.0, and 2.0 mm deep in aluminum stepwedge blocks, superimposing stepwedges of the radiopaque composites over the blocks, and radiographing the combination. It was found that only five of the nine radiopaque composite materials possessed radiodensities that permitted clear radiographic detection of the smaller defects.