Biofilm inhibition of denture cleaning tablets and carvacrol on denture bases produced with different techniques.

OBJECTIVES: This study compares the biofilm inhibition effects of denture cleaning tablets, carvacrol, and their combined use against Candida albicans on denture bases produced with different techniques. Additionally, the surface roughness and contact angles of these denture bases were evaluated. MATERIALS AND METHODS: Test samples were prepared from four different denture base materials (cold-polymerized, heat-polymerized, CAD/CAM milling, and 3D-printed). The surface roughness and contact angles of the test samples were measured using a profilometer and goniometer, respectively. For the evaluation of biofilm inhibition, samples were divided into 5 subgroups: Corega and carvacrol, separately and combined treatments, positive (inoculated with C. albicans) and negative control (non-inoculated with C. albicans, only medium). Biofilm mass was determined using the crystal violet method. An additional prepared test sample for each subgroup was examined under scanning electron microscopy (SEM). RESULTS: The surface roughness values of the 3D-printed test samples were found to be statistically higher than the other groups (P < .001). The water contact angle of all test materials was not statistically different from each other (P > .001). Corega and carvacrol, separately and combined, significantly decreased the amount of biofilm on all surfaces (P < .0001). Treatment of corega alone and in combination with carvacrol to the 3D-printed material caused less C. albicans inhibition than the other groups (P < .001; P < .05). CONCLUSIONS: The surface roughness values of all test groups were within the clinically acceptable threshold. Although Corega and carvacrol inhibited C. albicans biofilms, their combined use did not show a synergistic effect. CLINICAL RELEVANCE: Carvacrol may be used as one of the disinfectant agents for denture cleaning due to its biofilm inhibition property.

The impact of different surface treatments on repair bond strength of conventionally, subtractive-, and additive-manufactured denture bases.

OBJECTIVE: This study aimed to examine the shear bond strength (SBS) of repair material to conventionally, subtractive-, and additive-manufactured denture bases after different surface treatments. MATERIALS AND METHODS: Disk-shaped test specimens (N = 300) were prepared from denture base materials produced by one conventional (Procryla), one subtractive (Yamahachi), and one additive (Curo Denture) method. The test specimens were randomly divided into five groups (n = 10) and exposed to a variety of surface treatments-Group A: no surface treatment; Group B: grinding with silicon carbide paper; Group C: sandblasting; Group D: erbium: yttrium-aluminum-garnet laser; and Group E: plasma. Repair was performed with autopolymerizing acrylic resin (Meliodent). Surface roughness analyses were performed with a profilometer. Scanning electron microscopy was used to examine one specimen from each subgroup. SBS was evaluated on a universal testing machine. Failure types were observed under a stereomicroscope. RESULTS: Surface roughness values were significantly higher in all test materials in Group D than in the other groups (p < 0.001). For conventional resin, the SBS values were higher in Group C than in Groups A, D, and E (p < 0.001). For CAD/CAM material, Groups B and C had significantly greater SBS increases compared with Group E (p < 0.001). For 3D material, Group D showed higher SBS than all groups except Group C (p < 0.001). CONCLUSIONS: For SBS, sandblasting was most effective in the conventional group, whereas laser treatment was the most effective in the additive-manufactured group. For the subtractive group, surface treatments other than plasma exhibited similar SBS. CLINICAL SIGNIFICANCE: In repairing fractured prostheses, any degree of roughening suitable for the material content may provide an SBS benefit.

Bacterial adhesion to composite resins produced by additive and subtractive manufacturing.

The aim of this study was to evaluate the surface roughness and contact angle of composite resins produced by CAD/CAM milling and three-dimensional (3D) printing for permanent restorations as well as the adhesion of S. mutans and S. sanguinis bacteria to these composites. Three CAD/CAM milling composite resins (Vita Enamic-VE, Cerasmart-CE, Lava Ultimate-LU) and three 3D printing resins (Varseo Smile Crown plus-VSC, Saremco print Crowntech-SPC, Formlabs 3B Permanent crown-FLP) were selected. Twenty samples were prepared for each group. Using a contact profilometer, the surface roughness was determined, and an optical goniometer was used to quantify the contact angle. To evaluate the bacterial adhesion, composite specimens were immersed in mucin containing artificial saliva. All samples were incubated for 24 h at 37°C in 5% CO2. CFUs were determined by counting colonies after the incubation period. Surface roughness values of test samples were the highest in the Group VSC [0.46 (0.14) µm], whereas the lowest values were found in the Group LU [0.23 (0.05) µm]. There was no statistically significant difference between the groups in contact angle values (p > 0.05). The S. mutans adhesion extent on the Group SPC was statistically higher compared to all other materials with p < 0.05. For S. sanguinis, the lowest bacterial adhesion value was recorded in Group CE (3.00 × 104 CFU/ml) and statistically significant differences were found with Group VE and VSC (p < 0.05). Different digital manufacturing techniques and material compositions can affect the surface roughnesses of composite resins. All composite resin samples have hydrophobic characteristics. Microbial adhesion of the tested composite resins may be varied depending on the bacterial species. S. mutans showed much more adhesion to these materials than S. sanguinis.

The effect of various surface treatments on the repair bond strength of denture bases produced by digital and conventional methods.

There is limited information on the repairability of prostheses produced with digital technology. This study aims to evaluate various surface treatments on flexural bond strength of repaired dentured base resins produced by digital and conventional methods. A total of 360 samples were prepared from one heat-polymerized, one CAD/CAM milled and one 3D printed denture base materials. All of the test samples were subjected to thermocycling (5-55 °C, 5000 cycles) before and after repair with auto-polymerizing acrylic resin. The test samples were divided into five subgroups according to the surface treatment: grinding with silicon carbide (SC), sandblasting with Al2O3 (SB), Er:YAG laser (L), plasma (P) and negative control (NC) group (no treatment). In addition, the positive control (PC) group consisted of intact samples for the flexural strength test. Surface roughness measurements were performed with a profilometer. After repairing the test samples, a universal test device determined the flexural strength values. Both the surface topography and the fractured surfaces of samples were examined by SEM analysis. The elemental composition of the tested samples was analyzed by EDS. Kruskal-Wallis and Mann-Whitney U tests were performed for statistical analysis of data. SB and L surface treatments statistically significantly increased the surface roughness values of all three materials compared to NC subgroups (p < 0.001). The flexural strength values of the PC groups in all three test materials were significantly higher than those of the other groups (p < 0.001). The repair flexural strength values were statistically different between the SC-SB, L-SB, and NC-SB subgroups for the CAD/CAM groups, and the L-SC and L-NC subgroups for the 3D groups (p < 0.001). The surface treatments applied to the CAD/CAM and heat-polymerized groups did not result in a statistically significant difference in the repair flexural strength values compared to the NC groups (p > 0.05). Laser surface treatment has been the most powerful repair method for 3D printing technique. Surface treatments led to similar repair flexural strengths to untreated groups for CAD/CAM milled and heat-polymerized test samples.