Comparative radiopacity of ceramics and metals with human and bovine dental tissues

Recent Advances in Quaternary Ammonium Monomers for Dental Applications

Resin-based dental materials have been one of the ideal choices among various materials in the treatment of dental caries. However, resin-based dental materials still have some drawbacks, such as the lack of inherent antibacterial activity. Extensive research has been conducted on the use of novel quaternary ammonium monomers (QAMs) to impart antibacterial activity to dental materials. This review provides a comprehensive overview of the recent advances in quaternary ammonium monomers (QAMs) for dental applications. The current progress and limitations of QAMs are discussed based on the evolution of their structures. The functional diversification and enhancement of QAMs are presented. QAMs have the potential to provide long-term antibacterial activity in dental resin composites, thereby prolonging their service life. However, there is a need to balance antibacterial performance with other material properties and the potential impact on the oral microbiome and general health. Finally, the necessity for further scientific progress in the development of novel quaternary ammonium monomers and the optimization of dental resin formulations is emphasized.

Evaluation of radiopacity of cements used in implant-supported prosthesis by indirect digital radiography: an in-vitro study

In order to help dentists in choosing the right type of cement for implant-based prostheses, the radiopacity of commonly used cements available in the market was investigated by digital radiography with PSP sensor. In the present study, temporary cements of TempBond (Kerr, Germany), TempBond clear (Kerr, Germany), Dycal (Dentsply, USA) and permanent cements of Multilink N (Ivoclar, Brazil), Panavia F 2.0 (Kurrary, Japan), Fuji plus (GC, Japan), RelyX (3M, USA), Durelon (3M, USA) were used. Four pill-like samples with 0.5 mm and 1 mm thickness and 5 mm in diameter inside the silicon index as recommended by the manufacturer were prepared for each cement. Aluminum step wedge (99% aluminum alloy) was used as control. Using digital radiography, cement and aluminum step wedge samples were radiographed. The images of cement tablets were measured by digital radiography using DFW software to check their radiopacity values. Bonferroni test and Mann-Whitney U test were used for comparison of cements. The highest radiopacity between the group of 1 and 0.5 mm thickness was related to Glass ionomer Fujiplus GC (2407±45.99) and TempBond (137.21±22.46) cement, respectively. Whereas, the lowest radiopacity among the groups was related to Clear cement. The difference between the mean radiopacities among the studied groups was statistically significant (p<0.001). Based on the results, among the available cements, Glass ionomer Fujiplus GC and TempBond cement are the most efficient for 1 and 0.5 mm thickness, respectively, and Clear cement is the least efficient cement in both groups in terms of radiopacity.

In situ titanium phosphate formation on a titanium implant as ultrahigh bonding with nano-hydroxyapatite coating for rapid osseointegration

Titanium (Ti) has been widely used as a dental implant material due to its excellent mechanical property and good biocompatibility. However, its poor biological activity severely limits its ability to bond with bony tissues. To ameliorate this situation, a preparation method of ultra-high bonding nano-hydroxyapatite (n-HA) coating on the Ti surface is urgently needed. Here, Ti phosphate/n-HA (TiP-Ca) composite coatings with ultra-high bonding were prepared by a two-step hydrothermal treatment. The TiP coating was first formed in situ on the pure Ti substrate and then n-HA crystals further grew on the TiP surface. The formation mechanism of composite coating and reasons for increased bonding strength were systematically investigated. The results show that the TiP-Ca coating remains stable and exhibits an ultra-high bonding strength with the Ti implant (up to 783.30 ± 207.46 N). An effective solution was designed to address the problems of easy peel off. Cell experiments showed that TiP-Ca could promote the adhesion of MC3T3-E1 and expression of OCN, Runx2, and ALP. In vivo evaluation further confirmed that the TiP-Ca composite coating significantly enhanced osseointegration. The designed coating shows great potential in clinical application of implants.

Reliability and accuracy of intraoral radiography, cone beam CT, and dental MRI for evaluation of peri-implant bone lesions at zirconia implants - an ex vivo feasibility study

OBJECTIVES

To determine the reliability and accuracy of intraoral radiography (IR), cone-beam-computed tomography (CBCT), and dental magnetic resonance imaging (dMRI) in measuring peri‑implant bone defects around single zirconia implants.

METHODS

Twenty-four zirconia implants were inserted in bovine ribs with various peri‑implant defect sizes and morphologies. True defect extent was measured without implant in CBCT. Defects were measured twice in IR, CBCT, and dMRI with the inserted implant by three experienced readers. Reliability was assessed by ICC, accuracy by the Friedman test, and post-hoc-Tukey's test.

RESULTS

A comparable good to excellent intra- and inter-reader reliability was observed for all modalities (intra-/inter-rater-CC range for IR; CBCT; dMRI: 0.81-0.91/0.79;0.87-0.97/0.96;0.87-0.95/0.94). Accuracy was generally high, with mean errors below 1 mm in all directions. However, measuring defect depth in the mesiodistal direction was significantly more accurate in dMRI (0.65 ± 0.38 mm) compared to IR (2.71 ± 1.91 mm), and CBCT (1.98 ± 1.97 mm), p-values ≤ 0.0001 respectively ≤ 0.01.

CONCLUSIONS

Osseous defects around zirconia implants can be reliably measured in IR/CBCT/dMRI in the mesiodistal directions. In addition, CBCT and dMRI allow assessment of the buccolingual directions. dMRI provides a comparable accuracy in all directions, except for the mesiodistal defect depth, where it outperforms IR and CBCT.

An engineering perspective of ceramics applied in dental reconstructions

The demands for dental materials continue to grow, driven by the desire to reach a better performance than currently achieved by the available materials. In the dental restorative ceramic field, the structures evolved from the metal-ceramic systems to highly translucent multilayered zirconia, aiming not only for tailored mechanical properties but also for the aesthetics to mimic natural teeth. Ceramics are widely used in prosthetic dentistry due to their attractive clinical properties, including high strength, biocompatibility, chemical stability, and a good combination of optical properties. Metal-ceramics type has always been the golden standard of dental reconstruction. However, this system lacks aesthetic aspects. For this reason, efforts are made to develop materials that met both the mechanical features necessary for the safe performance of the restoration as well as the aesthetic aspects, aiming for a beautiful smile. In this field, glass and high-strength core ceramics have been highly investigated for applications in dental restoration due to their excellent combination of mechanical properties and translucency. However, since these are recent materials when compared with the metal-ceramic system, many studies are still required to guarantee the quality and longevity of these systems. Therefore, a background on available dental materials properties is a starting point to provoke a discussion on the development of potential alternatives to rehabilitate lost hard and soft tissue structures with ceramic-based tooth and implant-supported reconstructions. This review aims to bring the most recent materials research of the two major categories of ceramic restorations: ceramic-metal system and all-ceramic restorations. The practical aspects are herein presented regarding the evolution and development of materials, technologies applications, strength, color, and aesthetics. A trend was observed to use high-strength core ceramics type due to their ability to be manufactured by CAD/CAM technology. In addition, the impacts of COVID-19 on the market of dental restorative ceramics are presented.

Tailoring the monomers to overcome the shortcomings of current dental resin composites - review

Dental resin composites (DRCs) have become the first choice among different restorative materials for direct anterior and posterior restorations in the clinic. Though the properties of DRCs have been improved greatly in recent years, they still have several shortcomings, such as volumetric shrinkage and shrinkage stress, biofilm development, lack of radio-opacity for some specific DRCs, and estrogenicity, which need to be overcome. The resin matrix, composed of different monomers, constitutes the continuous phase and determine the performance of DRCs. Thus, the chemical structure of the monomers plays an important role in modifying the properties of DRCs. Numerous researchers have taken to design and develop novel monomers with specific functions for the purpose of fulfilling the needs in dentistry. In this review, the development of monomers in DRCs were highlighted, especially focusing on strategies aimed at reducing volumetric shrinkage and shrinkage stress, endowing bacteriocidal and antibacterial adhesion activities as well as protein-repelling activity, increasing radio-opacity, and replacing Bis-GMA. The influences of these novel monomers on the properties of DRCs were also discussed.

Intrinsically radiopaque biomaterial assortments: a short review on the physical principles, X-ray imageability, and state-of-the-art developments

X-ray attenuation ability, otherwise known as radiopacity of a material, could be indisputably tagged as the central and decisive parameter that produces contrast in an X-ray image. Radiopaque biomaterials are vital in the healthcare sector that helps clinicians to track them unambiguously during pre and post interventional radiological procedures. Medical imaging is one of the most powerful resources in the diagnostic sector that aids improved treatment outcomes for patients. Intrinsically radiopaque biomaterials enable themselves for visual targeting/positioning as well as to monitor their fate and further provide the radiologists with critical insights about the surgical site. Moreover, the emergence of advanced real-time imaging modalities is a boon to the contemporary healthcare systems that allow to perform minimally invasive surgical procedures and thereby reduce the healthcare costs and minimize patient trauma. X-ray based imaging is one such technologically upgraded diagnostic tool with many variants like digital X-ray, computed tomography, digital subtraction angiography, and fluoroscopy. In light of these facts, this review is aimed to briefly consolidate the physical principles of X-ray attenuation by a radiopaque material, measurement of radiopacity, classification of radiopaque biomaterials, and their recent advanced applications.

Artifact expression of polyetheretherketone in cone beam computed tomography: An in vitro study

STATEMENT OF PROBLEM

Dental prosthetic materials can cause artifacts in cone beam computed tomography (CBCT) images, adversely affecting diagnostic quality, although the problem may be less with polyetheretherketone (PEEK). Studies evaluating the artifacts caused by frequently used prosthetic materials are lacking.

PURPOSE

The purpose of this in vitro study was to compare the artifacts in CBCT images caused by PEEK, zirconia, cobalt-chromium (Co-Cr) alloy, and titanium (Ti).

MATERIAL AND METHODS

A polymethylmethacrylate phantom (Ø4.0×4.0 cm) with a central cylindrical aperture (Ø0.5×0.5 cm) was produced. Co-Cr, Ti, zirconia, and PEEK cylinders (0.5×0.5 cm) were manufactured, and CBCT images of the empty phantom (control group) with the test cylinders inside were made 3 times. In all images, the axial sections passing through the middle of the materials were evaluated. Eight regions of interest (ROI) area were determined around the materials (0.5×0.5 cm). The presence of artifacts was evaluated by making gray value standard deviation (SD) calculations in these ROI areas. The average SD values of 8 ROI fields from the 3 CBCT scans were made, and the materials were compared with each other in terms of the presence of artifacts by using 1-way analysis of variance (α=.05).

RESULTS

The difference between the SD values of the control and the PEEK cylinder was not statistically significant (P>.05). The SD values of both the control and PEEK groups were significantly lower than those of the zirconia, Co-Cr, and Ti groups (P<.05).

CONCLUSIONS

Zirconia, Ti, and Co-Cr caused artifacts in CBCT images, but the artifacts with PEEK were similar to those in the control group, suggesting it was the optimal choice in terms of achieving diagnostic quality.

A novel coating layer on zirconia using modified zinc phosphatizing method

Yttria doped ZrO₂ was deposited using an acidic zinc phosphatizing solution and the hydrothermal treatment. The coating was analyzed using a field emission-scanning electron microscope (FE-SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). A piston on three balls (ISO 6872) was used for the measurement of biaxial flexural strength. MC3T3-E1 cells attachment was evaluated by SEM, and cell proliferation were assessed using MTS assay™. SEM images confirmed that the zinc phosphate coating layer was successfully prepared and fully covered the surface. The measured adhesive strength of the coating was 79.11 MPa. In vitro cell study indicated that the coated sample had better cell morphology and proliferation. XRD and EDS analysis revealed that the crystalline coating structure indexed as zinc phosphate (hopeite) and the substrate was assigned as zirconia. The flexural strength test showed that the strength of zirconia before and after hydrothermal treatment was not affected.

Assessment of the efficiency of a pre- versus post-acquisition metal artifact reduction algorithm in the presence of 3 different dental implant materials using multiple CBCT settings: An in vitro study

Purpose

The aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, postacquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings.

Materials and Methods

Titanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor.

Results

The analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either.

Conclusion

This in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

Silicon nitride ceramic for all-ceramic dental restorations

Silicon nitride (Si₃N₄) is one of the promising ceramics for dental restoration due to providing significant benefits during the application. This study aimed to investigate the potential use of Si₃N₄ for all-ceramic dental restorations by characterizing some critical properties as color shade, mechanical resistance, shear-bond strength and radiolucency. For our study, porous Si₃N₄ ceramic was produced by partial sintering process with limited amounts of sintering additives and low temperature. A commercial ZrO₂ ceramic was prepared according to manufacturer's instructions and results were compared with Si₃N₄. Si₃N₄ is an attractive ceramic for dental applications with good mechanical properties even in porous form, it has additional advantages over the conventional ceramics used as restorative material, such as, inherent antibacterial/anti-infective activity, radiolucency, and lower hardness. It is expected that Si₃N₄ will become popular in dental applications as well.

A Radiopaque Nanoparticle-Based Ink Using PolyJet 3D Printing for Medical Applications

The aim of this study was to develop a 3D printable radiopaque ink and successfully print a finished artifact. Radiopaque 3D printing would be hugely beneficial to improve the visibility of medical devices and implants, as well as allowing more realistic phantoms and calibration aids to be produced. Most 3D printing technologies are polymer based. Polymers are naturally radiolucent, allowing X-rays to pass through, showing up as faint dark gray regions on X-ray detectors, as for soft tissues. During this study, a 3D printable ultraviolet (UV) curable resin containing zirconium oxide (ZrO₂) nanoparticles was developed. 5 wt.% ZrO₂ was dispersed in a base resin using a high-shear mixer. Particles remained in suspension for 6-8 h at room temperature, allowing time for 3D printing. A model of a hand including radiopaque bones and a test block demonstrating a range of internal radiopaque features were successfully 3D printed. Radiopacity was demonstrated in the 3D-printed models, and there was good dispersion of ZrO₂ within the resin matrix. The impregnated resin remained UV curable and viscosity was not compromised. In this study, 3D-printed radiopaque features demonstrated clear radiopacity under X-ray and microcomputed tomography imaging.

Customized Therapeutic Surface Coatings for Dental Implants

Dental implants are frequently used to support fixed or removable dental prostheses to replace missing teeth. The clinical success of titanium dental implants is owed to the exceptional biocompatibility and osseointegration with the bone. Therefore, the enhanced therapeutic effectiveness of dental implants had always been preferred. Several concepts for implant coating and local drug delivery had been developed during the last decades. A drug is generally released by diffusion-controlled, solvent-controlled, and chemical controlled methods. Although a range of surface modifications and coatings (antimicrobial, bioactive, therapeutic drugs) have been explored for dental implants, it is still a long way from designing sophisticated therapeutic implant surfaces to achieve the specific needs of dental patients. The present article reviews various interdisciplinary aspects of surface coatings on dental implants from the perspectives of biomaterials, coatings, drug release, and related therapeutic effects. Additionally, the various types of implant coatings, localized drug release from coatings, and how released agents influence the bone–implant surface interface characteristics are discussed. This paper also highlights several strategies for local drug delivery and their limitations in dental implant coatings as some of these concepts are yet to be applied in clinical settings due to the specific requirements of individual patients.

Bioactive glass coating on zirconia by vacuum sol-dipping method

In order to the preparation of biodegradable, bioactive and strongly adhered coating layer to the bioinert zirconia substrate, a bioactive glass (BG) was successfully coated on the zirconia plates. To achieve this goal, the zirconia plates dipped into the 45S5 BG sol in the vacuum chamber (vacuum sol-dipping method) followed by sintering to fabricate a strongly adhered BG coating on the zirconia plates. The parameters such as surface morphology and BG coating coverage ability on the zirconia plates have been assessed before and after coating with 45S5 BG. Phase structure of the BG coating based on the X-ray diffraction (XRD) result could be indexed as Na₄Ca₄(Si₆O₁₈). The interfacial adhesive strength between the zirconia substrate and BG coating layer was higher than the measured adhesive strength (55±7 MPa). The viability results approved the satisfying conclusion for the offered coating method on the zirconia substrates.

Comparative radiopacity of conventional and full-contour Y-TZP ceramics

The purpose of this study was to evaluate the radiopacity of different yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics used in the fabrication of fixed dental prostheses. Disk-shaped specimens (N=120, n=30 per group) were fabricated with thicknesses of 0.3, 0.5, and 1 mm from the following four Y-TZP ceramics: Cercon ht (Degudent) (CZ), Prettau (Zirkonzahn) (ZZ), Alliance (Kuraray Noritake Dental) (NA), and Ice Zirkon (Zirkonzahn) (ICE). The optical densities of each material were measured from radiographic images, and each material (N=1) were characterized by using XRD and SEM. The results were analyzed with oneway analysis of variance and the Tukey-Kramer test (α=0.05). In the case of the ICE and NA specimens, the radiopacity significantly differed with thickness (p<0.05). However, the radiopacities of 0.5- and 0.3-mm-thick CZ and ZZ specimens were not significantly different (p>0.05). Full-contour Y-TZP materials have higher radiopacities than those of the conventional Y-TZP materials in decreased thicknesses.

Zirconia in dental implantology: A review

Background:

Titanium has been the most popular material of choice for dental implantology over the past few decades. Its properties have been found to be most suitable for the success of implant treatment. But recently, zirconia is slowly emerging as one of the materials which might replace the gold standard of dental implant, i.e., titanium.

Materials and Methods:

Literature was searched to retrieve information about zirconia dental implant and studies were critically analyzed. PubMed database was searched for information about zirconia dental implant regarding mechanical properties, osseointegration, surface roughness, biocompatibility, and soft tissue health around it. The literature search was limited to English language articles published from 1975 to 2015.

Results:

A total of 45 papers met the inclusion criteria for this review, among the relevant search in the database.

Conclusion:

Literature search showed that some of the properties of zirconia seem to be suitable for making it an ideal dental implant, such as biocompatibility, osseointegration, favourable soft tissue response and aesthetics due to light transmission and its color. At the same time, some studies also point out its drawbacks. It was also found that most of the studies on zirconia dental implants are short-term studies and there is a need for more long-term clinical trials to prove that zirconia is worth enough to replace titanium as a biomaterial in dental implantology.

The Temperature Dependence of Micro-Leakage between Restorative and Pulp Capping Materials by Cu Diffusion

We used the Cu ions for the leakage analysis between pulp capping and restorative materials. Theoretically, Cu has more advantages than Ag ions due to their smaller radii (r_Cu²⁺=73 pm and r_Ag²⁺=94 pm), lower mass density (d_Cu=8.96 g/cm³ and d_Ag=10.49 g/cm³) and higher radio opacity which can be more useful by X-ray or EDX detectors, cheaper price and more abundance in planet when compared with Ag element which is generally used in the leakage studies. The micro leakage between dental restorations and pulp capping materials has been determined by using Micro Computed Tomography, Scanning Electron Microscopy and EDX analysis. It is found that the leakage has temperature dependent mechanism which increases with the increasing temperature. As a result, using Cu solution for leakage studies in dentine is an effective and easy method which can be used in dental science.

In vitro assessment of artifacts induced by titanium, titanium-zirconium and zirconium dioxide implants in cone-beam computed tomography

AIM

The aim of this study was to test whether or not the intensity of artifacts around implants in cone-beam computed tomography (CBCT) differs between titanium, titanium-zirconium and zirconium dioxide implants.

MATERIALS AND METHODS

Twenty models of a human mandible, each containing one implant in the single-tooth gap position 45, were cast in dental stone. Five test models were produced for each of the following implant types: titanium 4.1 mm diameter (Ti4.1 ), titanium 3.3 mm diameter (Ti3.3 ), titanium-zirconium 3.3 mm diameter (TiZr3.3 ) and zirconium dioxide 3.5-4.5 mm diameter (ZrO3.5-4.5 ) implants. For control purposes, three models without implants were produced. Each model was scanned using a CBCT device. Gray values (GV) were recorded at eight circumferential positions around the implants at 0.5 mm, 1 mm and 2 mm from the implant surface (GVT est ). GV were assessed in the corresponding volumes of interest (VOI) in the control models without implants (GVC ontrol ). Differences of gray values (ΔGV) between GVT est and GVC ontrol were calculated as percentages. One-way ANOVA and post hoc tests were applied to detect differences between implant types.

RESULTS

Mean ΔGV for ZrO3.5-4.5 presented the highest absolute values, generally followed by TiZr3.3 , Ti4.1 and Ti3.3 implants. The differences of ΔGV between ZrO3.5-4.5 and the remaining groups were statistically significant in the majority of the VOI (P ≤ 0.0167). ΔGV for TiZr3.3 , Ti4.1 and Ti3.3 implants did not differ significantly in the most VOI. For all implant types, ΔGV showed positive values buccally, mesio-buccally, lingually and disto-lingually, whereas negative values were detected mesially and distally.

CONCLUSIONS

Zirconium dioxide implants generate significantly more artifacts as compared to titanium and titanium-zirconium implants. The intensity of artifacts around zirconium dioxide implants exhibited in average the threefold in comparison with titanium implants.