Anamaria Matichescu

The nanoscale surface topography and microhardness of additive and subtractive dental polymers were evaluated following exposure to environmental challenges. The study examined two 3D-printed resins (Saremco and Voco) and two milled CAD/CAM blocks (Vita Enamic and Tetric). Specimens were allocated to control or experimental groups and subjected to hydrothermal ageing (thermocycling), in vitro mechanical wear, or a combined protocol involving wear followed by thermal ageing. Surface microtopography was analysed both quantitatively and qualitatively using atomic force microscopy (AFM), while structural stability was assessed through surface microhardness testing. Statistical significance was determined using matrix comparisons (p < 0.05). Milled monolithic blocks demonstrated a dense, uniform baseline topography, whereas 3D-printed resins exhibited structural heterogeneity attributed to their layer-by-layer photocuring process. Saremco maintained polymer network stability under thermal stress (p = 0.1878), while Voco was highly susceptible to hydrothermal swelling and early matrix plasticization (p = 0.0084). The combined protocol of wear and thermal ageing resulted in advanced structural breakdown in all groups (p < 0.001). Industrial subtractive blocks exhibited greater resistance to oral environmental stresses. The ceramic framework of Vita Enamic limited polymer domain collapse, whereas Tetric experienced accelerated inter-layer delamination and embrittlement. The combined protocol of wear followed by thermal ageing resulted in significant and uniform degradation of surface microhardness and topographic roughness in all tested groups. Nevertheless, the additively manufactured resins demonstrated substantial structural integrity and exhibited low volumetric wear rates.

The optical stability and aesthetic performance of dental polymers are critical for the longevity of restorative treatments. This study aims to evaluate the influence of different polymerisation conditions and maintenance protocols—specifically the use of charcoal pastes and brushes—on the Whiteness Index for Dentistry (WID) of polymer samples. Four groups of polymer samples (Optiprint Lumina, Dentona, AG) were prepared under various conditions: Group I (Standard: 7 min, 22 °C), Group II (Thermal: 7 min, 60 °C), Group III (Extended: 20 min, 22 °C), and Group IV (Glycerin barrier: 7 min, 22 °C). The protocol consisted of brushing with standard or carbon-infused toothpastes and brushes for a period of 2 min. Between brushing, the samples were stored in artificial saliva at 37 °C to simulate the oral environment. The samples were divided into groups. The first group was brushed with a standard paste and a standard brush; the second group was brushed with a simple paste and a carbon brush; the third group was brushed with carbon paste and a standard brush; and the fourth group was brushed with carbon paste and a carbon brush. Changes in the Whiteness Index for Dentistry (WID) were recorded and analysed statistically using a paired t-test and Pearson correlation. Results: All groups showed a statistically significant increase in the WID (p = 0.0191). Group IV (glycerin barrier + carbon paste/brush) exhibited the highest increase, with a WID = 2.0, demonstrating a synergistic effect between oxygen inhibition control and activated charcoal. In contrast, Group II (thermal polymerisation) showed the highest chromatic stability (ΔWID = 0.6), remaining below the Whiteness Perceptibility Threshold (WPT = 0.72). No significant correlation was found between polymerisation time and WID changes (r = 0.087, p = 0.913), indicating that temperature and surface treatment are the primary drivers of optical modification. Conclusions: The heat parameter did not reveal a significant difference in the optical properties. Furthermore, the combination of a glycerin barrier and carbon-based hygiene products maximises the whitening effect while remaining within the Whiteness Acceptability Threshold (WAT < 2.60), providing valuable insights for both material processing and patient maintenance protocols.

In order to provide clinically significant evidence on the long-term functional performance of CAD/CAM provisional materials, especially 3D-printed and milled resins, accurate tribologically in vitro wear tests that integrate wear parameters and surface topography analysis are necessary. The goal of the study was to assess the wear resistance of several CAM-obtained dental crown materials and the relationship between wear and the manufacturing process, distinctive postprocessing, microhardness, microroughness, and surface topography. A standardized ball-on-flat tribological protocol was applied to (n = 70) CAD/CAM-fabricated PMMA specimens (four 3D-printed groups with distinct post-processing protocols (Optiprint) and three milled materials (TelioCAD, Shaded PMMA, Copra Temp Symphony)) to quantify wear parameters micro- and nanoroughness (Ra, Rz, Sa, Sy), and Vickers microhardness, followed by comprehensive statistical analysis (t-tests, Pearson correlations) to elucidate material- and process-dependent differences in wear behaviour. Nanoroughness was carried using atomic force microscopy evaluation. Wear testing showed that most materials, particularly the 3D-printed groups, developed limited wear, whereas the milled materials evolved toward groove-dominated wear topographies. Wear statistics showed that the printed resins consistently had an advantage, meaning that the degree and rate of wear are significantly influenced by the manufacturing process. Hardness has a central role in governing the wear performance of interim resin materials, while nanoroughness acts as a secondary factor. Optimised post-processing of printed materials, particularly a prolonged post-curing period, yields a beneficial combination of low wear and specific topography, thereby providing a significant clinical advantage.

This study investigated how fabrication method (milling versus 3D printing) affects the water sorption and solubility of PMMA dental materials, and how surface characteristics affect hydrolytic stability. Fifty-six PMMA samples were divided into three groups fabricated from CAD/CAM milled discs (Group A: I–III) and four groups from 3D-printed resin (Group B: IV–VII), each subjected to distinct postprocessing protocols. Water sorption (wsp) and solubility (wsl) were measured after immersion in distilled water at 37 °C for 24, 48, and 72 h, and 7 and 14 days. Surface topography and nanoroughness were assessed using atomic force microscopy (AFM). Statistical descriptive analyses were followed by correlation analyses. Milled PMMA demonstrated significantly lower water sorption and negative solubility (mass loss), indicating material dissolution. In contrast, 3D-printed PMMA showed higher water sorption and positive solubility (mass gain), reflecting water incorporation and polymer swelling. The kinetic profiles differed: milled PMMA displayed a monophasic absorption curve, while 3D-printed PMMA exhibited a biphasic pattern with accelerated water uptake after 72 h. AFM analysis revealed that 3D-printed surfaces had significantly greater nanoroughness than milled surfaces. Strong positive correlations were observed between surface roughness parameters (Sa, Sy) and water sorption capacity. The fabrication method was found to influence the hydrolytic stability of PMMA dental materials. Milled PMMA demonstrated superior stability, with lower water uptake, smoother surfaces, and lower leaching solubility. In contrast, 3D-printed PMMA exhibited increased surface roughness and water sorption, attributed to its layered microstructure and nanoporosity. Surface topography emerged as a strong predictor of wsl, related to hydrolytic degradation. For clinical applications, milled PMMA is recommended for long-term use requiring durability, whereas 3D-printed PMMA may be appropriate for short-term applications with optimised postprocessing.

The continuous development and promotion of dental ceramic materials for computer-assisted design (CAD)/computer-assisted manufacturing (CAM) technologies have led to significant advancements in dentistry. Due to their excellent mechanical and aesthetic properties, biocompatibility, chemical stability or aging behavior in the oral environment, the new generations of zirconia for monolithic dental restorations, processed using CAD/CAM subtractive technologies, offer multiple prospects in prosthetic applications. Yttria-stabilized tetragonal zirconia (3Y-TZP) contains 3 mol% Y₂O₃ and exhibit opacity but high strength and fracture toughness. To obtain a material with high translucency and also resistant, the crystal structure of the conventional material was modified. The increase in the yttria content to 4 or 5 mol% and of the cubic phase to 15 to over 50% results in two polycrystalline zirconia (4Y- and 5Y-TZP) with superior aesthetics at the expense of mechanical properties. These compositional differences are decisive and influence the individual characteristics of each dental zirconia system. Alongside factors as the processing and sintering method or surface treatment, they have an impact on clinical properties such as surface roughness, toughness/microhardness, translucency and resistance to the aging process. In this context, the present study aims to summarize and update the data regarding the classification, mechanical and optical properties, applications, and future perspectives in the use of monolithic translucent zirconia. It provides clinicians with information to find a balance between aesthetics and strength, to preserve properties of material over time, and to extend the lifespan of dental restorations, for the benefit of patients.

Background and aim. This study evaluates and compares three types of thermoplastic resins used for flexible, removable partial dentures, focusing on their microhardness and surface roughness. Methods. Thirty samples with a thickness of 2 mm were obtained from thermoplastic resins and were tested after 24 hours of immersion in distilled water. The samples were obtained from injected resin cartridges of three thermoplastic resins with different degrees of flexibility. Two-way ANOVA and Tukey tests were performed to compare the samples. A Pearson correlation was calculated between the two parameters, surface roughness and Vickers microhardness. Results. After statistical analysis, significant differences were found between the two resins’ surface roughness. Regarding Vickers microhardness, one of the resins with the lowest flexibility range exhibited higher microhardness values. Conclusions. Surface roughness values for the three resins were below 0.2 microns. Microhardness test revealed significant differences between Flaxiacryl and Flexifast samples (p<.05).

Aim of the study is to compare three different thermoplastic resins used for flexible removable dentures based on their wear behavior. Materials and methods 24 samples with a thickness of 2 mm were obtained using injected thermoplastic resins. The wear test was performed for half an hour with a force of 30 N using a stainless steel and a zirconia sphere. Two environments were selected for this study, a dry and a wet one with one lubricant that simulates the saliva. Statistical analysis was carried out using one one-way ANOVA test. Image J program was used to calculate the radius for every wear mark with an optical microscope. Results revealed changes for every material, the zirconia sphere in a dry environment and for the stainless steel sphere after applying lubricants. After half an hour there was no statisitically significant weight loss among the samples (p≤.05), but there were changes in their surface in the optical microscopy. Conclusions: Zirconia produced clearer wear marks on the resin samples compared to the stainless steel ball. The glycerine- lubricant icreases the wear when using a stainless steel sphere.

The aim of the study was to assess the surface characteristics of clear thermoplastic materials related to artificial ageing, based on quantitative criteria and to select the most relevant multiscale roughness parameter. Materials and methods: Three commercially available thermoplastic PETG materials were chosen for the study: Crystal (C), Duran (D), and Erkodur (E). They were subjected to artificial ageing by saliva immersion and hydrothermal ageing, in order to simulate 14 days of intraoral use. Topographic characterizations of the surfaces were generated and multiscale roughness parameters were measured. Statistical analyses were performed. Results: During artificial ageing, while micro-roughness decrease, nano-roughness increase. Statistical tests highlighted significant differences between the behaviour of the materials involved into the study. Conclusions: The surface characteristics of PETG clear thermoplastic materials are sensitive to artificial ageing. Nano-roughness parameters are responsible for the increased materials surface roughness.

Introduction: The most common allergens in prosthetic materials are acrylates and metals. Allergy to acrylates and methacrylates is a rare cause of stomatitis, because dentures contain acrylate in polymerized, non-sensitizing form. Background and Objectives: This study aims to report the management of the case of a patient allergic to different materials, which requires prosthetic treatment. Materials and Methods: A 65-year-old woman requested a complete prosthetic rehabilitation. The difficulty of the treatment was to choose the type of prostheses according to the allergies presented by the patient. Results: The removable partial denture, made of Biodentaplast (Bredent, Germany), a combination of classic acrylic and elastic prosthesis, satisfies both aesthetically and functionally. During the evaluation and control at 6 and 12 months, it was found the good preservation of the restorations, the normal appearance of the oral cavity structures and the functionality of the prostheses Conclusions: For the success of the treatment it is important to know the medical and dental history of the patient in establishing the prosthetic treatment plan. The peculiarity of this case lies in the fact that the patient's allergies determine the change of the prosthetic treatment plan, in the sense that a simple fixed pros-thesis becomes a mobile prosthesis made of materials chosen in accordance with the patient's condition.

(1) Background: The intra-oral behavior of clear thermoplastic dental materials can be influenced by various intrinsic and extrinsic factors. Aim: The purpose of this in vitro study was to evaluate the optical properties, color changes and whiteness variations of four thermoplastic polymers used for dental appliances, in a simulated oral environment. (2) Methods: Customized thermoformed specimens of four PETG thermoplastics were selected and investigated in this study: Leone [L], Duran [D], Erkodur [E] and Crystal [C]. The thermoplastic samples were divided into three groups related to pH values (neutral, acidic and basic). A period of 14 days was simulated. Five stages resulted: I. dessicated specimens; II. hydrated in artificial saliva; III. subsequent desiccated; IV. artificial aged; V. further dessicated. Optical CIE L*a*b* coordinates were determined and optical properties, like TP (translucency), OP (opalescence) values, color differences ΔE-NBS, white indexes in dentistry WI_D and white index differences ΔWI_D were calculated for all stages of the study, for each group of the materials. Statistical analyses were performed. (3) Results: Optical properties of PETG clear thermoplastic materials, like TP and OP, increase in a simulated oral environment and the changes become significant after artificial aging. Related to pH values, the optical behavior between the materials is significantly different. During artificial aging, the tested materials behave significantly differently in terms of optical properties. (4) Conclusions: After the simulated period of 14 days, TP and OP values increase, with a migration of the color towards red and yellow. Color changes in some cases even reach the level of extremely marked. Whiteness increases, and the differences are mostly perceptible, but partially exceed the limit of acceptability.