Provisional Restoration Research Articles

One-stage prosthodontically driven jaw reconstruction in patients with benign and malignant pathologies: A 7- to 11-year cohort study.

One stage functional jaw reconstructionis defined as the resection and reconstruction of segmental defects in conjunction with the placement of dental implants in an ideal prosthetic position and loaded with a provisional restoration, during one surgical procedure. The aim of the study is to describe clinical outcomes of patients who underwent one stage functional jaw reconstruction. Patients who underwent one-stage functional jaw reconstruction, from January 2013 to March 2016 were recalled in 2022 and 2023. Planning and execution for the reconstruction utilized either analogue or digital techniques. Outcome parameters recorded were treatment-related outcomes at patient level, implant-related outcomes and patient-reported outcome measures. Eighteen patients underwent one-stage jaw reconstruction with a total of 57 implants. Four patients had maxillary and 14 had mandibular reconstructions. Ten patients underwent postoperative radiotherapy. Ten patients were planned using analogue and eight by digital planning. Three patients had partial flap necrosis, three patients had plate fractures, implant loss was seen in one patient and four patients died during the period. A functional prosthesis was provided in 16 out of the 18 patients. One-stage functional jaw reconstruction is a predictable method for providing rehabilitation with successful outcomes at 7-11 years. However, caution should be exercised when the treatment modality is carried out in patients with malignant pathologies who have undergone radiotherapy.

Comparative Evaluation of Microhardness and Polymerization Shrinkage in Residual Zirconia Reinforced Provisional Restorations: An In Vitro Study.

Aim The aim of this study is to evaluate and compare the microhardness and polymerization shrinkage of polymethyl methacrylate reinforced with residual zirconia. Materials and methods A total of 360 resin samples were fabricated, with dimensions of 12 mm × 12 mm × 3 mm and 12 mm × 8 mm × 6 mm. Zirconia dust (40% by weight) was added to 180 of these samples. The study included four groups: Group A (autopolymerizing acrylic resin), Group H (heat-polymerizing acrylic resin), Group ZA (autopolymerizing acrylic resin with zirconia dust), and Group ZH (heat-polymerizing acrylic resin with zirconia dust). Each group consisted of 90 samples, with 45 samples used for evaluating microhardness and 45 samples for assessing polymerization shrinkage. Results Group ZH exhibited the highest microhardness at 6.06 ± 0.31 GPa. It also recorded the lowest shrinkage values, measuring 52.11 ± 3.21 mm³. Tukey's honestly significant difference test revealed that microhardness was significantly higher in Group ZA (4.53 ± 0.29 GPa) compared to Group A (3.51 ± 0.25 GPa). However, Group H (5.42 ± 0.26 GPa) demonstrated greater hardness than Group ZA. Regarding shrinkage, the addition of zirconia dust resulted in reduced values, with Group ZA (73.93 ± 3.55 mm³) showing less shrinkage compared to Group A (91.9 ± 6.38 mm³). Similarly, Group ZH (52.11 ± 3.21 mm³) had lower shrinkage than Group H (66.71 ± 5.97 mm³). Group A exhibited the highest shrinkage among all the groups. Conclusion Within the limitations of this study, it can be concluded that there is an increase in hardness and a decrease in shrinkage values of the resin with the addition of zirconia dust in heat and autopolymerizing acrylic resin used for the fabrication of provisional restorations. Zirconia-incorporated heat-activated resin showed superior microhardness and decreased shrinkage values. Although the addition of residual zirconia to autopolymerized samples demonstrated better hardness, it was observed that pure heat-polymerized samples showed greater hardness. Reusing computer-aided design and computer-aided manufacturing powder waste can cut down on economic losses and aid in environmental sustainability.

Clinical and radiographic outcomes of a two-piece ceramic implant: one year results from a prospective clinical trial.

To describe the clinical and radiographic performance and survival rate of a new two-piece ceramic implant system after at least 12 months of follow-up. Sixty-five implants were placed and followed up for at least 12 months (12.3 ± 1.5), in 50 patients. The implants were installed both in fresh extraction sockets and in healed sites and received provisional restoration when the clinical insertion torque was greater than 35Ncm. The primary results describe the survival rate of these implants. Clinical performance was evaluated through the evaluation of the Pink Esthetic Score (PES) and the degree of satisfaction of the patients. Bone loss was measured through radiographic measurements of the marginal bone loss in the mesial (MBLM) and distal (MBLD) sites. The survival rate was 98.5%. The average MBLM was 0.24mm (± 0.53) and the MBLD was 0.27mm (± 0.57). A statistical difference was observed only when comparing immediate implants with delayed ones (MBLM - p = 0.046 and MBLD - p = 0.028) and when they received immediate provisionalization or not (MBLM - p = 0.009 and MBLD - p = 0.040). The PES before the intervention (T0) was 13.4 (± 0.8) and the PES at T2 (12-month follow-up) was 12.9 (± 1.5) (p = 1.14). The new two-piece ceramic implant used in the present study showed predictable and reliable results, similar to those found with titanium implants after one year of follow-up. These implants can be used as an alternative to titanium implants in terms of the marginal bone loss and the degree of patient satisfaction.

Evaluation of wear resistance and surface properties of additively manufactured restorative dental materials

ObjectivesTo evaluate the wear resistance of three additively manufactured dental crown materials (NextDent C&B MFH, Saremco print CROWNTEC and Bego VarseoSmile Crown) under two environmental conditions (dry and artificial saliva), two loads (49 N and 70 N) and two surface treatments (polished and glazed). MethodsA total of 120 specimens were divided into 24 groups and tested for wear under two loads (49 N and 70 N), surface treatment (polished or glazed), and environment (dry or submerged in artificial saliva). All samples underwent reciprocating wear testing at 1 Hz using a wear simulator, replicating 48 months of In Vivo conditions with a stainless-steel ball as the antagonist. The coefficient of friction (CoF), surface roughness, volumetric and vertical wear loss were measured and statistically analysed. Confocal microscopy assessed the surface properties of crown materials and the antagonists. ResultsThe NextDent material demonstrated the most homogenous wear, with relatively low vertical and volumetric loss across all groups (p < 0.004). NextDent and Bego materials performed similarly in artificial saliva regardless of the load type (p > 1.000). The CoF remained below 0.3 for all groups. All groups exhibited significant increases in surface roughness after testing, however, this did not correlate with an increase in the CoF. Confocal analysis revealed material deformities due to load and notable scratch marks on the stainless-steel antagonists. ConclusionIt was found that all investigated addtively manufactured materials can be suggested for provisional use. Both vertical loss and volumetric loss results should be included for material evaluation. CoF and surface roughness should be implemented into wear evaluation. Clinical significanceThis study highlights the practical value of additively manufactured dental crown materials, particularly for provisional restorations. However, their extended use requires careful consideration of individual patient needs, emphasising the need for judicious clinical application evaluation.

Mechanical performance of patient-specific prefabricated temporary shell versus laboratory-fabricated CAD/CAM provisional implant-supported single-tooth restorations: Alaboratory study.

To evaluate the mechanical performance of patient-specific prefabricated temporary shell versus laboratory-fabricated CAD/CAM provisional restorations on titanium temporary abutments, with and without thermo-mechanical ageing. Implants with a conical connection were divided into four groups (n = 24) and restored with temporary shell or laboratory-fabricated central or lateral incisor PMMA restorations that were relined or bonded on titanium temporary abutments. The diameter of the central and lateral incisor groups' implants was regular (ϕ 4.3 mm) or narrow (ϕ 3.5 mm), respectively. Half of each group's specimens were subjected to ageing, simultaneous thermocycling (5-55°C) and chewing simulation (120,000 cycles, 50 N, 1.7 Hz) resulting in eight groups in total (n = 12). The aged specimens were evaluated with optical microscopy, and survival and complication rates were determined according to modified USPHS criteria. The non-aged specimens and those that had survived ageing were loaded until failure, whereupon bending moments were calculated. Survival rates after ageing were 100% for all groups. Apart from wear facets (ϕ 2-3 mm) on the palatal restoration surface, no complications were observed. The mean fracture load and bending moments ranged between 597.6-847.1 N and 433.3-550.6 Ncm, respectively, with no significant differences between the eight groups (p = .25; p = .20). As patient-specific temporary shell central and lateral incisor provisional implant-supported restorations are mechanically stable enough to withstand clinical bite forces, even after thermo-mechanical ageing, they may serve as an alternative to laboratory-fabricated provisional restorations.

Effect of Dietary Simulating Solvents on the CAD-CAM Provisional Restorative Materials' Microhardness and Color Stability Properties: An in vitro Study.

This in vitro study investigated the effects of dietary solvents on the microhardness and color stability of CAD/CAM provisional restorations compared to conventional materials. Disc-shaped specimens (n=200) were fabricated from self-cured acrylic resin, two 3D-printing resins (FormLabs, NextDent), and a milled material (TelioCAD). Randomization assigned specimens (n=10/group) to immersion solutions: artificial saliva, citric acid, heptane, coffee, and tea. Microhardness and color stability were evaluated. One-way and three-way ANOVA with Tukey's post hoc test analyzed the data. Dietary solvents significantly reduced the surface microhardness of all tested materials (p<0.05). Unpolished surfaces exhibited greater color changes compared to polished ones (p<0.05) across all materials. Coffee and tea induced the most substantial reductions in hardness and the most significant color alterations (p<0.05), whereas saliva and citric acid had minimal effects. Milled provisional restorations exhibited superior hardness and color stability. Dietary solvents significantly affected material properties over time, highlighting the importance of material selection for clinical applications.

Influence of Different Build Directions on the Fracture Load and Surface Roughness of Additively Manufactured Three-unit Provisional Restoration and Comparison with Conventional Methods of Provisional Fabrication

Influence of Different Build Directions on the Fracture Load and Surface Roughness of Additively Manufactured Three-unit Provisional Restoration and Comparison with Conventional Methods of Provisional Fabrication

Evaluating Color Stability of Three Different Provisional Crown Materials: A Short Study

Purpose: To evaluate and compare the colour stability of three different provisional restorations using three different pigmented solutions Material and Methods: Total six samples of each material for each group ( Self-cure PMMA, Revotek LC, and CAD-CAM milled ) with the following specifications 2mm occlusal reduction, 1.5 axial reduction, 1mm round chamfer finish line, 6° convergence angle. This prepared tooth will be used as a guide for the metal die. After immersion in a staining solution of synthetic saliva (control), synthetic saliva and tea, synthetic saliva, and turmeric, on the 1st, 7th and 30th-day color measurement was done using a Spectrophotometer. Results: Mean values were compared using one-way analysis of variance (ANOVA) (statistically significant when P &lt; 0.05). Post hoc test using Tukey’s honestly significant difference was employed to identify significant groups (statistically significant when P &lt; 0.05). Repeated measures of ANOVA were performed to analyze the color stability of the different specimens at different periods of storage. Significant groups were identified using the Bonferroni test. Conclusion: Maximum discoloration was seen in synthetic saliva &amp;turmeric solution for all the two materials. CAD-CAM is the best material out of both if the provisional restoration has to be given for a longer duration in the esthetic region.

Custom-Made Composite Shade for Matching an Odd-Shaded Restoration

Objective: This case report aims to present how to fabricate a new restoration to match existing odd-shaded ones. Clinical considerations: A polycarbonate provisional crown was used to produce a cement-retained immediate load provisional restoration over an implant of tooth number #9. Using a color correcting light source, it was noticed that existing restorations had very high value with excess gray hue. XL2 of Premise composite shade tab was the closest match found, and the base shade for the custom-made restoration. Once no shade match was found in commercially available shade guides, there was a demand to produce a custom-made shade to address this case. The facial surface of the provisional crown was prepared as a veneer. Utilizing XL2 Premise composite and adding different amounts of gray color modifier, shade matching was fulfilled by mixing the composite and the color modifier. In this case, five attempts were made to achieve color match. The restoration was polished utilizing Soflex Discs. Provisional crown was in function for 12 weeks. Conclusions: By implementation of the principles of color, restorative materials and characterization kits, the new temporary restoration could match the existing ones using the technique described in this case report.

Biological Effects of PMMA and Composite Resins on Human Gingival Fibroblasts: An In Vitro Comparative Study.

The use of temporary resin for provisional restorations is a fundamental step to maintain the position of prepared teeth, to protect the pulpal vitality and the periodontal health as well as the occlusion. The present study aimed at evaluating the biological effects of two resins used in dentistry for temporary restorations, Coldpac (Yates Motloid) and ProTemp 4™ (3M ESPE ™), and their eluates, in an in vitro model of human gingival fibroblasts (hGFs). The activation of the inflammatory pathway NFκB p65/NLRP3/IL-1β induced by the self-curing resin disks was evaluated by real-time PCR, Western blotting and immunofluorescence analysis. The hGFs adhesion on resin disks was investigated by means of inverted light microscopy and scanning electron microscopy (SEM). Our results suggest that hGF cells cultured in adhesion and with eluate derived from ProTemp 4™ (3M ESPE ™) resin evidenced a downregulation in the expression of the inflammatory mediators such as NFκB p65, NLRP3 and IL-1β compared to the cells cultured with Coldpac (Yates Motloid) after 24 h and 1 week of culture. Furthermore, the cells cultured with ProTemp 4™ (3M ESPE ™) after 24 h and 1 week of culture reported a higher cell viability compared to the cells cultured with Coldpac (Yates Motloid), established by MTS cell analysis. Similar results were obtained when hGFs were placed in culture with the eluate derived from ProTemp 4™ (3M ESPE ™) resin which showed a higher cell viability compared to the cells cultured with eluate derived from Coldpac (Yates Motloid). These results highlighted the lower pro-inflammatory action and improved cell biocompatibility of ProTemp 4™ (3M ESPE ™), suggesting a better performance in terms of cells-material interaction.

Impact of Nanoparticle Addition on the Surface and Color Properties of Three-Dimensional (3D) Printed Polymer-Based Provisional Restorations.

This study aimed to evaluate and compare the impact of additives such as ZrO2 and SiO2 nanoparticles (ZrO2NP or SiO2NP) on the hardness, surface roughness, and color stability of 3D printed provisional restorations. Two hundred samples in total were printed using 3D printed resins (ASIGA, and NextDent). Each resin was modified with ZrO2NPs or SiO2NPs in two different concentrations (0.5 wt% and 1 wt%), while one group was kept unmodified (n = 10). Disc-shaped (15 × 2.5 mm) samples were designed and printed in accordance with the manufacturer's recommendation. Printed discs were evaluated for color changes through parameters CIELAB 2000 system (ΔE00), hardness using Vickers hardness test, and surface roughness (Ra) using a noncontact profilometer. After calculating the means and standard deviations, a three-way ANOVA and Tukey post hoc test were performed at α = 0.05. The addition of ZrO2NPs or SiO2NPs to ASIGA and NextDent resins significantly increased the hardness at a given level of concentration (0.5% or 1%) in comparison with pure (p < 0.001), with no significant difference between the two modified groups per resin type (p > 0.05). The highest hardness value was detected in 1% ZrO2NPs with 29.67 ± 2.3. The addition of ZrO2NPs or SiO2NPs had no effect on the Ra (p > 0.05), with 1% ZrO2NPs showing the highest value 0.36 ± 0.04 µm with NextDent resin. ZrO2NPs induced higher color changes (∆E00), ranging from 4.1 to 5.8, while SiO2NPs showed lower values, ranging from 1.01 to 1.85, and the highest mean ∆E00 was observed in the 1% ZrO2NPs group and NextDent resin. The incorporation of ZrO2NPs and SiO2NPs in 3D printed provisional resins increased the hardness without affecting the surface roughness. The optical parameters were significantly affected by ZrO2NPs and less adversely affected by SiO2NPs. Consequently, care must be taken to choose a concentration that will improve the materials' mechanical performance without detracting from their esthetic value.

Effects of various beverages on characteristics of provisional restoration materials.

To investigate the effect of common beverages on four currently used provisional restoration materials: Protemp®4, Integrity®, polymethyl methacrylate(PMMA) block, and acrylic resin. Flowable resin composite is included as a control group. Each material was formed into disks of 10-mm diameter and 4-mm thickness (N = 40) by loading the material into acrylic molds. The exposed surface in the mold was covered using a glass slide to prevent an oxygen inhibition layer, and polymerization then proceeded. The solidified disks were placed in distilled water for 24 h. These samples (n = 8) were then immersed for 14 days in one of four different beverages: water, orange juice, cola, and coffee. Changes in color dimension, hardness, and roughness were observed and then analyzed using two-way repeated analysis of variance. The provisional materials had more obvious changes in all three color dimensions than the flowable resin composite. Integrity showed the biggest changes, followed by acrylic resin and PMMA block, whereas Protemp had the smallest changes. The hardness of all the materials significantly decreased after immersion in any of the beverages for 14 days. There were no changes in surface roughness when the materials were immersed in distilled water. The surface roughness of the PMMA block significantly decreased in orange juice whereas that of Integrity and acrylic resin significantly increased in cola. Different kinds of provisional materials had different degrees of staining due to their composition. Moisture had a significant influence on the hardness of materials, and the acidity of cola significantly roughened the surface of the provisional materials.

Influence of different immediate dentin sealing strategies on bond strength of indirect resin nanoceramic restorations.

In this study, we evaluated the effect of four different strategies for bonding a CAD/CAM resin nanoceramic restoration (Lava Ultimate, 3M) to the dentin surface using a universal adhesive (Scotch Bond Universal, 3M) and adhesive resin cement (RelyX Ultimate, 3M) on the shear bond strength (SBS) and failure mode. The strategies comprised: (i) immediate sealing, immediate bonding; (ii) immediate sealing, bonding after 2weeks with provisional restoration; (iii) immediate sealing with flowable resin composite reinforcement and bonding after 2weeks with provisional restoration; and (iv) no immediate sealing, and bonding after 2weeks with provisional restoration. After bonding, all the specimens were thermocycled, shear tests were performed using a universal testing machine, and failure modes were determined using stereomicroscope and scanning electron microscopy. The highest mean SBS was recorded with immediate sealing, immediate bonding strategy. Most adhesive failures with exposed dentinal tubules were noted in specimens exposed to bonding after 2weeks with no immediate sealing, which was associated with the lowest SBS. Mixed failures predominated in all immediate dentin sealing groups. Immediate sealing with universal adhesives improves SBS, particularly in the single-visit approach, which has shown significantly better performance, whereas the provisional phase has a negative effect.

Comparative Evaluation of Flexural Strength and Microhardness of Two Different Ceramic Reinforced 3-D Printed Resins with Cad-cam Milled and Conventional Tooth Coloured Heat Cured Polymethylmethacrylate Resins as Long-term Provisional Restorative Materials” – An in Vitro Study

Background: Long-term provisional restorations play a crucial role in complex clinical scenarios, Implant-supported prostheses, full-mouth rehabilitation cases &amp; Maxillofacial Prosthodontics. Understanding the mechan-ical properties such as flexural strength and microhardness of newer commercially available provision-al restorative materials is necessary to select an optimum material for long-term provisional fixed den-tal prosthesis. This Research study was conducted to evaluate and compare the Flexural Strength and Microhardness of Two Different Ceramic-reinforced 3-D Printed Resins with CAD-CAM Milled and Conventional Tooth Coloured Heat Cured Polymethylmethacrylate Resins as Long-Term Provisional Restorative Materials. Methods: Twenty-one specimens of dimensions 25 mm × 2 mm × 2 mm (ADA-ANSI specification #27) were fabricated each using: Group A (Control group)-Conventional tooth colored heat cured polymethyl-methacrylate resin (DPI Heat cure tooth moulding powder), Group B-CAD-CAM milled resin, Group C- Ceramic reinforced polymer 3-D printed resin (Temporary CB resin) and Group D- Ceramic rein-forced polymer 3-D printed resin (Permanent CB resin). Flexural strength and microhardness were measured and the values obtained were evaluated. Results: The measured mean flexural strength values (Mega Pascals) were 39.41 (Group A), 153 (Group B), 124.91 (Group C), and 136.50 (Group D). The measured mean microhardness values (Knoop hardness number) were 37.9 (Group A), 40.5 (Group B), 34.67 (Group C), and 43.88 (Group D). The difference in flexural strength and microhardness values of the three groups was statistically significant according to the analysis of variance (ANOVA) as well as the intergroup comparison done using Tukey’s honest significant difference (HSD) Post Hoc test (P &lt; 0.05). Conclusions: Flexural strength with higher values in Group B were noted and the Microhardness test showed higher values in Group D.

The Impact of Gastric Juice on the Surface Roughness of Surface Sealant-Treated Provisional Restorations.

Gastroesophageal reflux disease causes gastric acid to enter the oral cavity, leading to mucosal changes and deterioration of dental hard tissues and materials. The purpose of this in vitro study was to evaluate the impact of gastric juice on the surface roughness of two types of acrylics used in provisional restorations. Acrytemp ® and Temdent acrylic resin discs (10 × 2 mm) totaling 80 were manufactured and divided into eight groups (n = 10). Groups were prepared as follows: Group 1 (Temdent + Universal Polish) (control), Group 2 (Temdent + Universal Polish + Biscover LV), Group 3 (Temdent + Universal Polish + Resin Glaze), Group 4 (Temdent + Universal Polish + Fortify Plus), Group 5 (Acrytemp + Universal Polish) (control), Group 6 (Acrytemp + Universal Polish + Biscover LV), Group 7 (Acrytemp + Universal Polish + Resin Glaze), and Group 8 (Acrytemp + Universal Polish + Fortify Plus). The resin discs were immersed in distilled water for 24 h and in gastric juice (pH = 2) for additional 24 h. The initial and final roughness values of samples were measured and analyzed with non-parametric statistics including Mann-Whitney U-test for pairwise comparison, Kruskall Wallis test for comparing more than two groups, and Wilcoxon signed rank test for within-group comparison (P < 0.05). Surface roughness did not differ significantly between control groups. It notably increased for all samples with surface sealants, both initially and after gastric juice immersion (P < 0.05). Surface sealants noticeably increased the roughness of two types of acrylic resins. After immersing in gastric juice, Group 4 (Temdent + Universal Polish + Fortify Plus) showed the highest roughness, while the untreated control groups remained the smoothest.

Restoration of Teeth with Severely Compromised Tooth Structure using Digital Planning Combined with Orthodontic Magnetic Extrusion—A Report of 2 Cases

This report outlines 2 digitally planned cases in which the teeth underwent magnetic extrusion to preserve the supracrestal tissue attachment and regain the ferrule, followed by their restoration. Case 1: A 42-year-old man with the chief concern of a fractured right maxillary second premolar. Following the completion of root canal treatment, the remaining tooth structure was insufficient to create a ferrule for tooth restoration. For this scenario, a rapid magnetic extrusion technique was performed on tooth #4 to obtain an approximate 3-mm ferrule. The condition of both the dentition and the restorative margin was acceptable 18 months following treatment. Case 2: A 62-year-old man with the chief complaint of mobility on both sides of the maxillary arch in relation to a tooth-supported fixed partial denture (FPD). Following removal of the FPD, multiple extractions were carried out and tooth #6 was subjected to magnetic extrusion in 3 stages to a maximum of 4 mm to obtain a ferrule. At the 18-month and 3-year follow-up appointments, the tooth had no symptoms and the gingiva around the restorations had optimal architecture and margins. The 3-dimensional digital planning was helpful in precisely positioning the magnets within the tooth and the provisional restorations to facilitate axial extrusion. The extruded teeth were restored with zirconia crowns in both cases. The beneficial outcomes observed from these cases provides evidence that the integration of digital planning and magnetic extrusion holds promise as a method for reconstructing teeth with crowns that are significantly compromised.

Fracture Strength of Six-Unit Anterior Fixed Provisional Restorations Fabricated Using Various Dental CAD/CAM Systems.

This study compares the fracture strengths of long-span fixed provisional restorations fabricated via digital additive and subtractive methods to those fabricated via conventional heat-processing techniques. A six-unit anterior partial restoration was designed as an anatomical and morphologic structure using a dental CAD/CAM system. The provisional restorations (N = 40) of four different fabrication methods (n = 10 per group) were used for the failure loading test: stereolithography apparatus (SLA), liquid crystal display (LCD), milling (MIL), and heat-processed temporary (HPT). The specimens were subjected to a maximum load-to-fracture test using a universal testing machine, and the representative fracture patterns were observed. Statistical analysis was performed using Shapiro-Wilk, Kruskal-Wallis, Mann-Whitney U, and Bonferroni post hoc tests (P < .05). The four groups showed significant differences in fracture strength according to the materials and manufacturing methods used (P < .001, except between SLA and HPT groups). The fracture strengths of MIL and LCD digitally fabricated groups were significantly higher than that of the HPT group (P < .001). The subtractive method is ideal for fabricating long-span fixed provisional restorations for long-term use. Additionally, LCD additive manufacturing technology could soon be a good alternative for restorations.

Effect of Food-Simulating Liquids on the Mechanical Properties of 3D-Printed Provisional Restoration Materials.

To evaluate the effect of food-simulating liquids (FSLs) on the mechanical properties of provisional restoration materials fabricated by 3D printing, milling, and traditional fabricating methods. The bar specimens were fabricated with traditional, milling, and 3D-printing methods according to ISO 10477 specifications. Each group of specimens was randomly subdivided into four groups to be immersed in various FSLs: distilled water (control group), n-heptane, 50% ethyl alcohol, and 0.02 mol/L citric acid for 7 days at room temperature (n = 19 per group). The Knoop hardness (KHN) was evaluated, and the specimens were subjected to a three-point bending (3PB) test to evaluate flexural strength (FS) and flexural modulus (FM). One-way ANOVA and Tukey tests were used to analyze the data. Fabrication methods had a significant effect on the mechanical properties of the materials being tested. FSLs had no effect on the FS and FM of materials being tested. The 50% ethyl alcohol solution significantly decreased the hardness of traditional group specimens, and the n-heptane and 50% ethyl alcohol solutions increased the hardness of the 3D-printed specimens significantly (P ≤ .05). Scanning electron microscopy (SEM) revealed that while traditional and milling group specimens showed a ductile fracture type, 3D-printed specimens showed a brittle fracture type. Production methods affected the mechanical properties of provisional restoration materials. Immersion in 50% ethyl alcohol solution decreased the KHN of the traditional specimens. FSLs had no negative effect on the mechanical properties of the milled and 3D-printed specimens.

Flexural strength of 3D-printed nanocomposite provisional resins: Impact of SiO2 and ZrO2 nanoparticles and printing orientations in vitro.

The aim of this study was to investigate and compare the influence of zirconium dioxide nanoparticles (ZrO2 NPs) and silicon dioxide nanoparticles (SiO2 NPs) addition and printing orientation on the flexural strength (FS) of provisional three-dimensional (3D) printing resins undergoing thermal cycling (TC). Three dimensional-printed resin (NextDent C&B MFH) was used to fabricate 300bar-shaped specimens (25×2×2mm3 ). The ZrO2 NPs and SiO2 NPs specimens were divided into two groups, then subdivided into three groups, based on the nanoparticle concentration (i.e., 0 wt% (original group), 0.5 wt%, and 1 wt%). Each concentration was printed in three printing orientations (0°, 45°, and 90°). The printed specimens were exposed to 5000 cycles of TC, followed by a three-point bending test to assess the FS. Fracture surface analysis was conducted by using a scanning electron microscope (SEM). For data analysis, ANOVA and Tukey's post hoc were utilized (α = 0.05). Compared to the original material, the addition of ZrO2 NPs and SiO2 NPs had a significantly positive impact on the FS, (P > 0.001). After TC, the FS of the original group decreased significantly and had the lowest value. The highest FS value was observed in 1% ZrO2 NPs at 0°. Regardless of the nanoparticle concentration, the 0° orientation consistently showed a higher FS, compared to the 45° and 90° orientations. At all orientations (i.e., 0°, 45°, and 90°), the FS significantly increased with the addition of NPs, compared with that of the original material (P > 0.001). TC had a significantly negative effect on the FS of the unmodified groups. However, no significant differences existed in FS among the modified groups after TC. The addition of SiO2 NPs and ZrO2 NPs increased the FS of the 3D-printed provisional resin. Regardless of the nanoparticle concentration, the 0° orientation had the higher FS. TC had an effect on the original resin, whereas it had no significant effect on the nanoparticle-modified resins. In clinical practice, 3D-printed provisional nanocomposite resins printed at the 0° orientation could be recommended for long-term dental provisional restorations.

Fracture strength of 3-units fixed partial dentures fabricated with metal-ceramic, graphene doped PMMA and PMMA before and after ageing: An in-vitro study

ObjectivesTo evaluate the fracture strength and linear elongation at break of three-units fixed partial dentures (FPDs) fabricated with traditional and new materials for fixed prosthodontics before and after ageing. MethodsSixty models of three-units FPDs were fabricated and cemented onto a Co-Cr model simulating the replacement of a maxillary second premolar. The samples were randomly divided into 3 groups: metal-ceramic (MCR), graphene-doped polymethylmethacrylate (PMMA-GR) and polymethylmethacrylate (PMMA). Half of the samples were directly subjected to fracture test, while the remaining half underwent an ageing process and then a fracture loading test using an electrodynamic testing machine. Fracture load and elongation at break values were taken and statistically analysed. ResultsSignificant differences were detected between the different materials (p<0.05). All groups showed a reduction of the fracture load and elongation at break values after ageing, but not statistically significant, except for PMMA group (p = 2.012e-19) (p = 3.8e-11). ConclusionsMCR and PMMA-GR three-units FPDs showed higher fracture strength and lower elongation at break compared to PMMA. MCR and PMMA-GR had higher resistance to ageing processes compared to PMMA. Clinical significancePMMA-GR could be considered a material for long-term provisional restorations as its mechanical behaviour and ageing resistance are more like MCR than PMMA.