Comparative Analysis of the Mechanical Properties and Biocompatibility between CAD/CAM and Conventional Polymers Applied in Prosthetic Dentistry

Modern media often portray CAD/CAM technology as widely utilized in the fabrication of dental prosthetics. This study presents a comparative analysis of the mechanical properties and biocompatibility of CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) polymers and conventional polymers commonly utilized in prosthetic dentistry. With the increasing adoption of CAD/CAM technology in dental laboratories and practices, understanding the differences in material properties is crucial for informed decision-making in prosthodontic treatment planning. Through a narrative review of the literature and empirical data, this study evaluates the mechanical strength, durability, esthetics, and biocompatibility of CAD/CAM polymers in comparison to traditional polymers. Furthermore, it examines the implications of these findings on the clinical outcomes and long-term success of prosthetic restorations. The results provide valuable insights into the advantages and limitations of CAD/CAM polymers, informing clinicians and researchers about their suitability for various dental prosthetic applications. This study underscores the considerable advantages of CAD/CAM polymers over conventional ones in terms of mechanical properties, biocompatibility, and esthetics for prosthetic dentistry. CAD/CAM technology offers improved mechanical strength and durability, potentially enhancing the long-term performance of dental prosthetics, while the biocompatibility of these polymers makes them suitable for a broad patient demographic, reducing the risk of adverse reactions. The practical implications of these findings for dental technicians and dentists are significant, as understanding these material differences enables tailored treatment planning to meet individual patient needs and preferences. Integration of CAD/CAM technology into dental practices can lead to more predictable outcomes and heightened patient satisfaction with prosthetic restorations.

Application of CAD/CAM technologies and materials for prosthetic restoration of severely damaged teeth-clinical cases

In cases of severely damaged teeth with limited coronal tooth structure and remaining hard dental tissues subgingivally, a custom-made post-and-core restoration is required. Teeth with non-circular canal space also require this type of restoration because the build-up with pre-fabricated posts could lead to thick cement layer. The development of CAD/CAM technologies widens the range of the materials that can be used for prosthetic restorations. Along with base dental alloys, newly developed materials may be applied. The aim of the article is to present four clinical cases of severely damaged teeth which utilize different materials and different production techniques for custom post-and-core fabrication. In the first clinical case, a metal post-and-core restoration was fabricated by direct metal laser sintering. In the second clinical case, digital technologies were used to produce a 3D-printed resin prototype for further investing and casting from base metal dental alloy. In the third clinical case, fibre-reinforced composite was used for fabrication of the custom post-and-core by milling. In the fourth clinical case, the restoration is produced by milling of lithium disilicate ceramics IPS emax CAD (Ivoclar Vivadent, Lichtenstein). The bond between the fibre-reinforced composite post-and-core and the hard dental tissues offered possibility to compensate-to some extent-the shape of the preparation which was not optimal. CAD/CAM technologies applied in these clinical cases provided combination of high accuracy of fitting with good stability and individual shape of the restorations. © 2023 Australian Dental Association.

Clinical and laboratory study of corrosion resistance of a base dental alloy for selective laser melting

INTRODUCTION

CAD/CAM technologies are becoming widely used for the production of metal ceramic dental restorations. Powder Co-based alloys are developed for selective laser melting. The corrosion resistance of the dental alloy affects the biocompatibility, functional suitability, and longevity of the prosthetic restoration.

Patch test results in dental staff with dermatitis

BACKGROUND

Dental workers are exposed to allergenic materials in the workplace.

OBJECTIVES

To summarize patch test results in dental staff with work-related dermatitis.

MATERIALS AND METHODS

Cross-sectional study of dental staff with dermatitis was conducted. Symptoms, clinical findings and results from patch tests with 40 dental allergens were summarized.

RESULTS

Of 329 participants, 155 (47.1%) had at least one positive patch reaction. The highest frequency of positive reactions was observed for metals (38.6%), acrylics (7.3%) and additives in acrylic resins (3.6%). One hundred and eighty-five (56.2%) participants were currently symptomatic; in this group, 79 (42.7%) had current dermatitis. Thirty-eight patients had at least one positive patch test considered occupationally related to their current dermatitis.

CONCLUSION

Almost half of the dental staff with dermatitis had at least one positive patch test and approximately 12% had current occupational relevance of the allergens. Our results underscore the importance of patch testing in the evaluation of dental staff with dermatitis.

Clinical Evaluation of Corrosion Resistance, Ion Release, and Biocompatibility of CoCr Alloy for Metal-Ceramic Restorations Produced by CAD/CAM Technologies

BACKGROUND

CAD/CAM technologies facilitate using powder CoCr alloys to produce metal-ceramic dental restorations. However, base alloys may induce oxidative stress in the oral cavity due to corrosion and ion release. This study evaluated resistance to corrosion and release of metal ions from 3D printed CoCr dental alloy and their effect on oral oxidative stress.

METHODS

Metal-ceramic crowns with 3D printed copings from CoCr alloy EOS CobaltChrome SP2 (EOS, Germany) were fabricated for 35 patients. Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the concentration of Co and Cr ions in non-stimulated saliva before prosthetic treatment (BPT), at 2 h and 7 days after the dental treatment (APT2, APT7, respectively). Open circuit potentials (Eocp) were evaluated at APT2 and APT7. Estimating oral oxidative stress, measurements of 8-isoprostaglandin F2-alpha were conducted using liquid chromatography-tandem mass spectrometry (LC-MS/MS) at stages BPT, APT2, and APT7.

RESULTS

Salivary Co level increased at APT2 and decreased to the initial levels at APT7. No statistical difference was found between the levels of 8-isoPGF2-alpha measured, and between the Eocp measurements at APT2 and APT7.

CONCLUSIONS

The studied alloy showed stable corrosion resistance and the metal ion release did not induce oral oxidative stress.

COMPARATIVE SIMULATION TESTINGWITH FUNCTIONAL LOADING OF TWO DENTURE FRAMEWORK MATERIALS – A PILOT STUDY

Introduction:Simulation tests may significantly decrease the cost and time needed for planning and production of prosthetic restorations, providing both computer simulation as part of the refinement process and experimental testing. Aim: Comparative simulation testing with functional loading of two denture framework materials. Materials and methods: Upper model cast denture forbilateral edentulous areas posterior to the natural teeth (Kennedy Class I) was produced on the "Frasaco" phantom model. The denture was scanned by a 3D optical laboratory scanner. The 3D model was transformed into an STL-file and was processed with "Cinema 4D" software before the application of the program "SOLIDWORKS" v.2018. Parameters of two materials – metal alloy I-MG EKO (Interdent, Slovenia) and injection molded resin Bio Dentaplast (Bredent, Germany) were applied. Simulations were performed by equivalent loading according to the Third strength theory (von Mises stress-test) and loading with deformation and shift at constant force 0.1N/mm2 at a maximal number of 159 181 segmented elements of the 3D object. Tests were held upon unilateral loading on the working side, and support was provided by reciprocal clasp arms on the working and non-working side, denture flanges and major connector. Results and discussion: Results showed insignificant differences between the common reflected load of the two tested materials but with different distribution - on the major connector, it was 0.4N for the alloy and 0.87N for the resin, at the flanges – 2.26N and 5.6N respectively, for the clasps – 5.1N and 5.7N. Conclusion: The tested metal alloy is rigid and resistant material which provides distribution of the reflected load between clasp elements and denture saddle, especially distally, while the the tested injection molded material possesses relatively high flexibility and elasticity, which hides a risk for the teeth bearing clasps.

Oxidative Stress in the Oral Cavity before and After Prosthetic Treatment

BACKGROUND: Metal ions emitted from dental alloys may induce oxidative stress leading to numerous pathological changes. Lipid peroxidation may cause disturbance of structure and function of cell membranes, apoptosis, autophagy, and formation of potentially mutagenic compounds. Products of interaction between reactive oxygen species and biomolecules may be used for evaluation of oxidative stress level. AIM: The aim of this study was to evaluate the influence of the prosthetic dental treatment with metal ceramic restorations on the level of oxidative stress in the oral cavity. MATERIALS AND METHODS: Metal ceramic crowns with copings fabricated by direct metal laser sintering were produced for 35 patients. CoCr dental alloy EOS CobaltChrome SP2 (EOS) was used. Non-stimulated and stimulated saliva samples were collected from the patients before and after the prosthetic treatment. For evaluation of oxidative stress concentration of 8-isoPGF2-alpha was measured by liquid chromatography tandem mass spectrometry. For statistical processing, non-parametric Wilcoxon signed-rank test and Mann–Whitney test were applied. RESULTS: The concentration of isoprostane 8-isoPGF2-alpha in non-stimulated saliva was lower 2 h after fixing the crowns compared to the initial level and statistically significant difference was observed. On the 7th day the concentration of isoprostanes remained significantly lower than the initial one. No significant differences were found in isoprostane concentration in stimulated saliva before and after prosthetic treatment. CONCLUSION: Prosthetic dental treatment leads to decrease in oral oxidative stress.

Development and validation of an LC-MS/MS method for determination of 8-iso-prostaglandin F2 alpha in human saliva

Background

Increased formation of reactive oxygen species may be caused by the ion release of the metal alloys used in prosthetic dental restorations due to the corrosion process. As products of lipid peroxidation, isoprostanes can be used as a marker for oxidative stress in the body. There are two significant advantages of using isoprostanes as an oxidative stress marker - presence in all fluids in the body and low reactivity. Saliva provides noninvasive, painless, and cost-effective sample collection and can be used as an alternative testing medium of blood and urine.

Methods

This study presents the development and validation of a sample LC-MS/MS method to quantify 8-isoprostaglandin F2-a in human saliva using salt-out assisted liquid-liquid extraction (SALLE).

Results

The selected sample preparation procedure optimized chromatographic separation and mass detection provided high recovery and sensitivity of the analysis. The calibration curve was obtained in the predefined range 25-329 ng/L with R2 larger than 0.995. Normalized matrix varied between 89.7 % and 113.5%. The method showed sufficient accuracy and precision - accuracy in the range 89.7 %-113.9 %, and precision between 2.3% and 5.4%.

Conclusions

The proposed method is validated according to current EMA/FDA industrial guidance for bioanalysis and offers an appropriate level of sensitivity and sufficient accuracy and precision.

Metal Ion Emission and Corrosion Resistance of 3D-Printed Dental Alloy

Background: Prosthetic rehabilitation requires application of materials with different chemical, mechanical and biological properties which must provide longevity, esthetics, and safe use. Corrosion resistance and metal ion emission are the major factors defining biocompatibility of base dental alloys. Digitalization in Dentistry leads to development of new materials suitable for CAD/CAM technologies. Cobalt-chromium powder alloys are used for additive manufacturing of PFM crowns. The aim of this study is to evaluate corrosion resistance and metal ion emission of Cobalt-chromium dental alloy for 3D printing. Materials and methods: 35 metal copings were designed using digital files of intraoral scans of 35 patients. CoCr dental alloy EOS CobaltChrome SP2 (EOS, Germany) was used to produce the copings by DMLS (direct laser metal sintering). Tests for presence of free Cobalt ions were conducted at several stages of the production process. Open circuit potential measurements were conducted 2 hours, 24 hours, and 7 days after placing the copings in artificial saliva. Metal ion emission was assessed by inductively coupled plasma mass spectrometry (ICP–MS) after 24 hour- and 7 day-period of stay in the solution. Results: Tests for free Cobalt ions were positive at all stages during production of the metal copings. Eocp measurements showed high corrosion resistance which increased in time. ICP-MS showed significantly higher amount of cobalt and chromium ions after 7-day period of stay compared to 24-hour period. Conclusion: Studied alloy showed high corrosion resistance at in vitro conditions. Detected ion emission requires further investigations on the biological properties.

EXPERIMENTAL SETTING FOR TESTING THE BOND STRENGTH BETWEEN METAL ALLOY AND PEEK

Purpose: The aim of the article is to present an experimental setting for bending strength testing of metal specimens covered with PEEK. Materials and methods: Three groups of metal specimens made of cobalt chromium alloy are produced using the lost wax technique: group 1 – specimens with a smooth metal surface; group 2 – sand blasted metal surface; group 3 - sand blasted metal surface with retention crystals. The shape and size of the specimens are designed to correspond to the retentive elements of the apparatus for micro tension and micro pressure LMT 100. PEEK is pressed over the specimens, and after thermal cycling, the bond between metal alloy and PEEK is studied using bending strength three-point micro testing. Results and discussion: The experimental setting is focused on the type of specific contact surface between the two materials. The design corresponds to the requirements of apparatus LMT 100 and allows the production of a big number of specimens. Because of the thermal regime of BioHPP pressing, it is impossible to add groups of specimens using contemporary adhesives on the metal surface. Conclusion: Created specimens allow strength investigation by three-point bending micro testing. The experimental setting provides the production of a big number of specimens with the same shape and size.

The impact of dental metal restorations on the oral oxidative stress level

Background

Dental materials may influence the equilibrium between production and destruction of free radicals, thus creating conditions for developing of local or general oxidative stress. Metal ions, emitted from base dental alloys, may cause changes in cell structures and functions. Isoprostane concentration may indicate possible cell damage, caused by free radicals, and can be used for evaluation of the oxidative stress level. The aim of this study was to compare the level of 8-isoPGF2-alpha in saliva in patients with and without metal dental restorations.

Material and Methods

35 patients were divided in two groups according to the presence or absence of metal dental objects. Non-stimulated and stimulated saliva samples were collected. The concentration of 8-isoPGF2-alpha was measured by liquid chromatography tandem mass spectrometry. For statistical analysis non-parametric Mann-Whitney test, Kruskal Wallis test, and Wilcoxon signed-rank test were applied.

Results

There was a significant difference in the concentration of 8-isoPGF2-alpha between the samples of non-stimulated and stimulated saliva. The concentration of 8-isoPGF2-alpha in non-stimulated saliva in patients with metal dental restorations was significantly higher than the one in the group of patients without metal objects.

Conclusions

The presence of metal dental restorations increases the concentration of 8-isoPGF2-alpha in non-stimulated saliva. Key words:Saliva, dental metal restorations, oxidative stress.