This study investigated potential variations in polymerisation of light- and dual-cured (LC and DC) resin cements photoactivated through four CAD/CAM restorative materials as a function of substrate thickness. Four CAD/CAM materials [two resin composites CeraSmart (CS) and Grandio Blocs (GB); a polymer infiltrated ceramic Vita Enamic (VE) and a feldspathic ceramic Vita Mark II (VM)], with five thicknesses (0.5, 1, 1.5, 2, and 2.5 mm) were prepared and their optical characteristics measured. 1 mm discs of LC and DC resin cement (Variolink® Esthetic, Ivoclar AG) were photoactivated through each specimen thickness. After 1 h post-cure, polymerisation efficiency was determined by degree of conversion (DC%) and Martens hardness (H_M). Interactions between materials, thicknesses and properties were analysed by linear regressions, two-way ANOVA and one-way ANOVA followed by post hoc multiple comparisons (α = 0.05). All substrates of 0.5- and 1.0-mm thickness transmitted sufficiently high peak irradiances at around 455 nm: (I_t = 588-819 mW/cm²) with translucency parameter TP = 21.14 - 10.7; ranked: CS> GB = VM> VE. However, increasing the substrate thickness (1.5-2.5 mm) reduced energy delivery to the luting cements (4 - 2.8 J/cm²). Consequently, as their thicknesses increased beyond 1.5 mm, H_M of the cement discs differed significantly between the substrates. But there were only slight reduction of DC% in LC cements and DC cement discs were not affected. Photoactivating light-cured Ivocerin™ containing cement through feldspathic ceramics and polymer-infiltrated ceramics achieved greater early hardness results than dual-cured type, irrespective of substrate thickness (0.5 - 2.5 mm). However, only 0.5 and 1 mm-thick resin composites showed similar outcome (LC>DC). Therefore, for cases requiring early hardness development, appropriate cement selection for each substrate material is recommended.

Reinforced polymeric materials are investigated as novel non-metal alternatives for prosthetic frameworks. This study examined the adherence of Streptococcus mutans to three high-performance polymeric (HPP) composites focusing on their microstructural composition, wettability, and surface roughness. Three CAD/CAM HPP composites [two fiber-reinforced composites, CarboCad (CC) and TRINIA (TR), and one ceramic-reinforced polyether ether ketone, DentoPEEK (PK)], were sectioned into ten beam- and ten plate-shaped specimens from each material. Surface properties (n = 10) were analyzed by water wettability and roughness measurements (Ra and Rz). The biofilm adherence was determined by calculating the number of S. mutans through colony-forming units (CFUs). Representative images were obtained using a confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). The data were analyzed using Welch one-way ANOVA and Dunnett T3 post hoc tests. The results showed significant differences in roughness (Ra) across the materials, ranked from highest to lowest as follows: TR, 0.231 µm; CC, 0.194 µm; and PK, 0.161 µm (p = 0.0001). The contact angle averages varied from 51.36° to 91.03°, with PK exhibiting the highest wettability (p = 0.0012). However, S. mutans adherence was markedly reduced in PK (1.96 CFU/mm², p = 0.0001) in comparison to TR and CC (2.86 and 2.98 CFU/mm², respectively). Consequently, the fiber-reinforced composites (CC and TR), despite their low wettability, exhibited greater susceptibility for bacterial adherence than the smoother and more wettable PK, highlighting the substantial impact of their surface roughness and microstructural variability.

This study aimed to investigate the efficacy of 3 bleaching methods on stained polymer-based CAD/CAM blocks in terms of surface roughness, hardness stability, discolouration reduction and susceptibility to re-staining following bleaching. Two-mm-thick slabs (N = 128) were prepared from CeraSmart (CS), Grandio Blocs (GB), Vita Enamic (VE), and direct resin composite GrandioSO (RC). Coffee-stained specimens (n = 8) were subdivided into bleaching (BL) groups: in-office bleaching (OB), home bleaching (HB), whitening mouthwash (MW), and a control group with 14-day storage in water (CL). Measurements of roughness (Ra), Vickers hardness (HV), and colour parameters (ΔE_00, ΔL*, Δb*) were taken before and after BL. Then, all the bleached specimens were re-stained to determine their stain susceptibility. Repeated measures of ANOVA, Pearson's χ² test, and multiple post hoc tests were performed (α = 0.05). HB was more effective in whitening in terms of achieving minimal residual colour (-0.87 to 0.7) and greater resistance to re-staining (0.41 to 0.89). MW resulted in an increased lightness (ΔL*) of all materials (1.96 - 2.30). However, MW increased the roughness of VE (0.8 µm) and RC (0.4 µm), compared to their baseline measurements (0.057 µm and 0.087 µm, respectively, p = 0.003). All the BL treatments resulted in a greater hardness reduction (14.4% to 18.1%) in the RC than in the other materials. The investigated polymer-based materials and modes of bleaching treatment influenced the bleaching efficacy. For CAD/CAM blocks, in-office bleaching and whitening mouthwash reduced the discolouration but adversely affected their roughness and hardness compared to home bleaching. Home bleaching proved to be the least susceptible to re-staining. Knowing how a specific bleaching product affects the colour, roughness and hardness and consequent susceptibility to staining of 4 studied polymer-based materials that represent pre-existing restorations would impact the consideration of bleaching treatment.

Background: There are very few studies comparing dentists' knowledge in relation to their clinical approach despite the existence of a possible gap between what they know and what they do.Aim: To measure the agreement between knowledge and practice methods related to a selected clinical scenario involving the placement of an indirect post in endodontically treated teeth (ETT) among different types of practitioners.Methods: An electronic questionnaire was emailed to members of the Saudi Dental Society. The questionnaire presented a clinical scenario of restoring a posterior ETT with an indirect post, core unit, and crown, followed by specific questions regarding knowledge and practice related to ten different treatment aspects such as who prepares the post space, technique, isolation, time, gap between gutta-percha, and time to cementation of the crown. Each question was presented twice for each aspect, once asking about their practice method and then what they thought was the correct practice (knowledge). The relationship between the participants' responses and their specialty and the agreement between the responses of knowledge and practice for each participant were analyzed by Pearson's chi-square test and Kappa.Results: 203 completed questionnaires were analyzed. Most participants were 30 years old or younger (62.6%), and general dental practitioners (59%). When comparing the knowledge to the practice methods of each participant, nine out of ten aspects were of a "weak" level agreement or below (kappa < 0.59,p < 0.001). Only one aspect demonstrated a "strong" level of agreement (Kappa = 0.804), which was related to the duration of time between obturation and post space preparation in the presence of a periapical lesion. However, this strong agreement in the responses was not aligned with current evidence. There was also a significant difference among the responses of endodontists, restorative dentists and general practitioners in most of the aspects.Conclusion: Overall, there was a weak agreement between what practitioners know and do in most aspects of a selected clinical scenario involving the placement of an indirect post in posterior ETT. Moreover, the participant's specialty influenced their responses regarding both knowledge and clinical practice.