Radiopacity of composite dental materials using a digital X-ray system

The aim of this study was to evaluate the radiopacity of 32 current dental composite materials with digital technique. Digital radiographs with CCD sensor along with an aluminum step wedge, 1-mm-thick tooth slice and 1mm thick composite specimen were taken in five different combinations of exposition/voltage. The radiopacity in pixels was determined using Digora 2.6. software. The equivalent in thickness of aluminum for each material was then calculated from the calibration curve. 74.9% of all tested materials in all exposure combinations had radiopacity between 2 mm and 4 mm aluminum equivalent. The radiopacity of composites ranged from 0.61 mm Al (Gradia Direct Anterior) to 4.78 mm Al (Te-Econom). The average radiopacity for enamel and dentine was 2.05 and 1.11 mm Al. The use of digital technique for radiopacity is an easy, reliable, fast and precise way to analyze different dental materials. Most of the tested composite materials fulfill the requested criteria for radiopacity with a few exceptions.     

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.     

Radiopacity of dental restorative materials

Objectives

Radiopacity of dental materials enables clinician to radiographically diagnose secondary caries and marginal defects which are usually located on the proximal gingival margin. The aim of this study was to measure the radiopacity of 33 conventional resin composites, 16 flowable resin composites, and 7 glass ionomer cements and to compare the results with the radiopacity values declared by the manufacturers.

Materials and methods

From each restorative material, six 2-mm-thick disk-shaped specimens were fabricated and eight 2-mm-thick sections of teeth were made and used as reference. The material samples and tooth sections were digitally radiographed together with the aluminum stepwedge. Gray values were obtained from the radiographic images and radiopacity values were calculated and statistically analyzed. Post hoc Tukey’s honestly significant difference test was used to calculate significant differences in radiopacity values between materials and reference dentin and enamel values.

Results

The radiopacity values of all 56 restorative materials were above the dentin reference radiopacity value; however, 4 out of 33 conventional composites and 3 out of 16 flowable resin composites had significantly lower radiopacity than enamel (p?<?0.05). There were up to 1.53 mm eq Al differences between the measured and the manufacturers’ declared radiopacity values of some materials.

Conclusions

Majority of the materials exceed enamel radiopacity and would not hamper radiographic diagnosis of secondary caries. However, manufacturers’ data are not always reliable.

Clinical relevance

Materials with radiopacity lower than enamel might be misinterpreted as secondary enamel caries on radiographic images, especially when applied as initial increment on the proximal gingival margin.     

Radiopacity of glass ionomer dental materials

The radiopacity of glass ionomer dental materials is quite variable. The use of a poorly radiopaque material as a base under other restorative materials can mislead the dentist to a diagnosis of recurrent decay. This study investigates the radiopacity of these materials and proposes a minimal radiopacity under which a material should not be used as a base or liner. All base, liner, and core formulations of glass ionomer under investigation were more radiopaque than dentin. All restorative and luting formulations of glass ionomer under investigation were less radiopaque than dentin and therefore should be avoided as bases or liners.     

Radiopacity of endodontic materials on film and a digital sensor

The purpose of this study was to compare the radiographic appearance of 12 endodontic materials as visualized on either Kodak Ultra-speed D speed film (Eastman Kodak Company, Rochester, NY) or a Gendex eHD digital sensor (Gendex Dental Systems, Milan, Italy). Ten discs of each material were radiographed alongside an aluminum alloy 1100 (Alcoa, Pittsburgh, PA) stepwedge that was used for reference. For every radiograph, the average grayscale value of the material was converted into absorbance notation and compared with that of the reference stepwedge in order to determine the equivalent radiopacity in terms of millimeters of Al 1100 per millimeter of material. Two-way repeated-measures analysis of variance testing detected significant differences with respect to imaging system, material, and the interaction of the two factors (p < 0.001). The difference in a material's radiopacity as measured on the digital sensor compared with film was greater than 10% for 4 of the 12 materials and over 40% for InnoEndo (Heraus Kulzer, Armonk, NY). It was speculated that barium fillers cause this effect.     

Radiopacity of impression materials.

The radiographic densitites of twenty-six impression materials were measured and the values expressed as an equivalent thickness of aluminum. Under simulated clinical conditions, only ten of the materials tested could be consistently distinguished from the bone structure in periapical radiographs. It was far more dificult to detect objects with beveled margins than objects of uniform thickness. The minimum radiopacity of a material which could be detected in the periodontal tissue on a periapical radiograph was estimated.     

Radiopacity of elastomeric impression materials

The purpose of this study was to measure and classify the radiopacity of various elastomeric impression materials available on the open market and to compare their appearance in radiographs of the oral tissues. In order to measure and classify their radiopacity, twenty-eight specimens of various materials were placed and exposed on film together with an aluminium stepwedge. A dummy head was used to investigate the radiographic density of the above specimens in comparison with that of simulated oral tissues.     

Radiopacity of glass ionomer materials

summary 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.     

Radiopacity evaluation of Portland and MTA-based cements by digital radiographic system

Objective

The aim of the present study was to evaluate the radiopacity of Portland and MTA-based cements using the Digora TM digital radiographic system.

Material and Methods

The performed tests followed specification number 57 from the American National Standard Institute/American Dental Association (2000) for endodontic sealing materials. The materials were placed in 5 acrylic plates, especially designed for this experiment, along with a graduated aluminum stepwedge varying from 1 to 10 mm in thickness. The set was radiographed at a 30 cm focus-object distance and with 0.2 s exposure time. After the radiographs were taken, the optical laser readings of radiographs were performed by Digora TM system. Five radiographic density readings were performed for each studied material and for each step of the aluminum scale.

Results

White ProRoot MTA (155.99±8.04), gray ProRoot MTA (155.96±16.30) and MTA BIO (143.13±16.94) presented higher radiopacity values (p<0.05), while white non-structural Portland (119.76±22.34), gray Portland (109.71±4.90) and white structural Portland (99.59±12.88) presented lower radiopacity values (p<0.05).

Conclusions

It was concluded that MTA-based cements were the only materials presenting radiopacity within the ANSI/ADA specifications.     

Radiopacity of potential root-end filling materials

ObjectivesIn recent years various root-end filling materials have been suggested for clinical use. The purpose of this study was to assess the radiopacity of some potential materials according to ISO specification 6876.Study designRadiographs were taken of 1-mm thick specimens of eight materials (amalgam, Kalzinol, IRM, Super EBA,Vitrebond, Fuji II LC, Chemfil, gutta-percha); light transmission was assessed densitometrically and related to equivalent thickness of aluminum.ResultsCommercial glass ionomer cements (Vitrebond, Fuji II LC, Chemfil) had radiopacities below the international standard for root canal sealers (<3-mm aluminum); three zinc oxide-eugenol cements (Kalzinol, Super EBA, IRM) had radiopacities equivalent to 5 to 8 mm aluminum; and gutta-percha had a radiopacity equivalent to 6.1-mm aluminum.ConclusionsWe recommend that root-end filling materials should have a radiopacity greater than that for root canal sealers.     

Radiopacity of glass-ionomer/composite resin hybrid materials.

This study visually compared the radiopacity of seven restorative materials (3 resin-modified glass-ionomer cements, 3 polyacid-modified composite resins, and 1 conventional glass-ionomer cement) to a sound tooth structure sample, and an aluminium stepwedge. All hybrid materials were more radiopaque, except for one resin-modified glass-ionomer cement, than both the tooth structure and conventional glass-ionomer cement.     

口腔材料与口腔数字化技术

<正>口腔临床数字化技术日益成熟和普及，对口腔临床诊疗的质量、效率提供了有益支撑，一定程度地降低对临床经验的依赖，可为年轻医生的快速成长提供技术支撑和帮助，助力我国基层口腔诊疗的技术同质化。与此同时，数字化技术辅助下的口腔椅旁诊疗也逐渐成为可能，可减少患者就诊次数，提供更友好的诊疗体验^[1]。随着数字化技术与口腔医学的深入结合，基于数控切削和3D打印技术制作各类口腔假体及辅助治疗装置，已成为口腔医学数字化技术的重要应用领域，应运而生的各种新型“口腔数字化材料”也备受口腔医生关注，成为口腔材料学的重要发展方向之一。     

Radiopacity of direct esthetic restorative materials

This study determined the radiopacity of 21 commercially available direct esthetic restorative materials with reference to an aluminum step wedge and an equivalent thickness of enamel and dentin. A total of 168 samples measuring 6 mm in diameter and 1 mm in thickness, with eight samples of each material, were prepared from restorative materials. Enamel and dentin samples 1-mm thick were also prepared by longitudinally sectioning eight extracted human permanent molars using a microslicing machine. The optical densities of each restorative material, along with one tooth section and an aluminum step wedge were measured from radiographic images using a transmission photodensitometer. The optical density values of the specimens were used to determine the aluminum thickness equivalent values. The data were analyzed with one-way analysis of variance (ANOVA) and Duncan's multiple range tests. The results showed statistically significant differences among materials. Tetric Ceram had the greatest radiopacity value and was higher than enamel. All materials except for the microfilled resin composite Filtek A 110 had radiopacity values greater than dentin and possessed sufficient radiopacity to meet ISO 4049 standard. Significant differences were found among materials of the same composition when compared to enamel.     

Teaching dental materials using the personalized system of instruction

Tailoring instruction to the individual needs of students is one approach to ensuring that students with lower scholastic aptitudes obtain the skills and knowledge necessary to function successfully as professionals. This study determined the effects of the personalized system of instruction (PSI) on end-of-course achievement, aptitude-achievement relationships, long-term retention, and course attitudes. The PSI method of instruction was compared to a conventional lecture/laboratory approach for teaching a dental materials course to dental hygiene students. Although there was no significant difference between conventionally taught and PSI students on the end-of-term final examination, lower aptitude students in the PSI class scored significantly higher on the final examination than lower aptitude students in the conventional class. Of students completing a one-year retention examination, those in the PSI class scored significantly higher than students in the conventionally taught class. Student course ratings favored PSI instruction both at the end of the course and at the one-year follow-up interval.     

Radiopacity of 12 visible-light-cured dental composite resins

The radiopacity of 12 VL-cured composite resins was determined with reference to an aluminum step-wedge. Two anterior composites were radiolucent while two anterior and one anterior/posterior composites exhibited the radiopacity equal to, or slightly greater than, that of human enamel. Three posterior and one inlay composites possessed the radiopacity equivalent to, or in tiny excess of, that of human enamel. Three posterior composites had the radiopacity, fairly exceeding that of human enamel. Chemical analyses of the filler particles were carried out with SEM/EDX. It became evident that radiopaque fillers contained at least one radiopaque oxide component such as BaO, ZrO2 and Yb2O3 with varying concentrations. In general, the radiopacity of the composite resin was linearly proportional to the amount of the radiopaque oxide in the filler. It was suggested that ZrO2 was radiopacifier equivalent to, or even stronger than, BaO.     

Penetration of radiopaque dental restorative materials using a novel ultrasound imaging system

PURPOSE: To determine whether a novel ultrasound imaging system could detect 25 microm thick cracks beneath gold, silver amalgam, and porcelain restorations on tooth phantoms. METHODS: Tooth phantoms were constructed using acoustically-matched composite to simulate dentin, with 25 microm thick water-filled cracks located approximately 1 mm inside the simulated dentin. Porcelain and gold restorations were bonded using resinous cement, and an amalgam restoration was attached using mechanical retention. A portion of the gold restoration was left unattached to simulate cement washout. A novel monostatic pulse-echo ultrasound system with a 19 MHz single-element PLZT transducer, custom transmit/receive electronics and signal processing with a Ga-In alloy couplant was used to measure the relative return echo amplitude from restoration surfaces, simulated dentin/restoration interfaces, and cracks. Extracted teeth were also used to demonstrate that the system was capable of detecting cracks in real teeth. RESULTS: Cracks were detected beneath porcelain and amalgam, and within a human molar. Cracks were not detected in simulated dentin beneath gold; however, simulated cement washout directly beneath gold was identified. The ability to detect defects in the phantom was dependent on the acoustic reflection coefficient between interfaces, the attenuation of each material, acoustic clutter within the phantom, and geometry. Gold restorations transmitted minimal acoustic energy due to their large acoustic impedance; however, the ability to distinguish the gold/cement interface from the gold/washout interface indicated that ultrasound can detect density changes immediately below restorations, such as caries, fractures, or debonding. The ability to penetrate resin-composite was also demonstrated.     

Image contrast range for detection of enamel defects using a digital dental imaging system

The purpose of this study was to quantitatively assess the acceptable range of image contrast for the detection of enamel defects by adjusting the contrast and brightness of a digital dental imaging system. Extracted human premolars and molars with enamel defects on the proximal surfaces were mounted in maxillary and mandibular sets on phantoms. The phantoms were individually exposed and processed with a digital dental imaging system from Computed Dental Radiography (CDR, Schick Technologies, Inc., NY, USA). The images were transferred to a personal computer, and the contrast and brightness were determined in the range of ±100 digital digit numbers (DDN) using Adobe Photoshop 4.0.1 J (Adobe Systems Inc., Tokyo, Japan). The 8-bit CRT display used was set at maximum inherent brightness. The relationship between the pixel value and the DDN in contrast at both the enamel and the background on the monitor was used to measure the acceptable image contrast by manipulating contrast and brightness. Six dental radiologists were asked to determine the presence or absence of enamel defects. The detectability was statistically analyzed using Fisher's protected limited standard deviation (PLSD) non-parametric test. When the inherent brightness on an 8-bit CRT display was adjusted to the maximum, there was an acceptable range of image contrast and brightness for the detection of enamel defects with this digital dental imaging system.