Contact allergies to dental materials in patients.

BACKGROUND: Concerns regarding contact allergies and intolerance reactions to dental materials are widespread among patients. Development of novel dental materials and less frequent amalgam use may alter sensitization profiles in patients with possible contact allergy. OBJECTIVES: To analyse current sensitization patterns to dental materials in patients with suspected contact allergy. METHODS: This retrospective, multicentre analysis from the Information Network of Departments of Dermatology (IVDK) selected participants from 169 834 people tested in 2005-2019 and registered with (i) an affected area of 'mouth' (and 'lips'/'perioral'), (ii) with the dental material in question belonging to one of three groups (dental filling materials, oral implants or dentures or equivalents) and (iii) with patch-testing done in parallel with the German baseline series, (dental) metal series and dental technician series. RESULTS: A total of 2730 of 169 834 tested patients met the inclusion criteria. The patients were predominantly women (81.2%) aged ≥ 40 years (92.8%). The sensitization rates with confirmed allergic contact stomatitis in women (n = 444) were highest for metals (nickel 28.6%, palladium 21.4%, amalgam 10.9%), (meth)acrylates [2-hydroxyethyl methacrylate (HEMA) 4.8%] and the substances propolis (6.8%) and 'balsam of Peru' (11.4%). The most relevant acrylates were HEMA, 2-hydroxypropyl methacrylate, methyl methacrylate, ethylene glycol dimethacrylate and pentaerythritol triacrylate. Few men were diagnosed with allergic contact stomatitis (n = 68); sensitization rates in men were highest for propolis (14.9%) and amalgam (13.6%). CONCLUSIONS: Allergic contact stomatitis to dental materials is rare. Patch testing should not only focus on metals such as nickel, palladium, amalgam and gold, but also (meth)acrylates and the natural substances propolis and 'balsam of Peru'.

Effect of implant type on the stability of cantilever fixed dental prostheses: An in vitro study.

OBJECTIVES: To simulate the replacement of a premolar with an implant-supported cantilever fixed dental prosthesis (ICFDP) and how the fracture load is affected by implant type, positioning within the zirconia blank, and aging protocol. MATERIALS AND METHODS: Seventy-two ICFDPs were designed either within the enamel- or dentin layer of a 4Y-PSZ blank for bone-level and tissue-level titanium-zirconium implants. Fracture load was obtained on the cantilever at baseline (no aging) or after aging in a chewing simulator with the load applied within the implant axis (axial aging) or on the cantilever (12 groups with n = 6). A three-way ANOVA was applied (α = .05). RESULTS: A three-way ANOVA revealed a significant effect on fracture load values of implant type (p = .006) and aging (p < .001) but not for the position within the zirconia blank (p = .847). Fracture load values significantly increased from baseline bone level (608 ± 118 N) and tissue level (880 ± 293 N) when the implants were aged axially, with higher values for tissue level (1065 ± 182 N) than bone level (797 ± 113 N) (p < .001). However, when the force was applied to the cantilever, fracture load values decreased significantly for tissue-level (493 ± 70 N), while values for bone-level implants remained stable (690 ± 135 N). CONCLUSIONS: For ICFDPs, the use of bone-level implants is reasonable as catastrophic failures are likely to be restricted to the restoration, whereas with tissue-level implants, the transmucosal portion of the implant is susceptible to deformation, making repair more difficult.

In vitro pilot study comparing a novel implantoplasty sonic instrumentation protocol with a conventional protocol using burs.

BACKGROUND AND OBJECTIVES: The aim of implantoplasty (IP) is to remove titanium implant layers that have been contaminated and to smoothen the implant surfaces so they retain less plaque. However, existing IP methods are very invasive and reduce implant wall thickness. AIM: To investigate the suitability of novel sonic tips in IP and to compare this novel protocol with conventional abrasive procedures. MATERIALS AND METHODS: Thirty dental implants (Ø 4.1 mm, 10 mm length) were distributed in three groups and investigated according to the protocol of Sivolella et al., with modifications to the instrument's feed rate, the applied contact force, and the speed of implant rotations per minute. The upper third of the implant was processed with a diamond-coated bur (BUR) or novel non-diamond-coated sonic tips (AIRSCALER). After standardized IP, the surfaces were analyzed by tactile profilometry and scanning electron microscopy (SEM). Changes in implant weight, implant material loss, and implant fracture strength were assessed. RESULTS: The mean roughness (Ra , Sa ), implant material loss, and change in implant weight were significantly lower in the AIRSCALER group than in the BUR group, whereas the mean compression resistance values were significantly higher in the AIRSCALER group than in the BUR group. CONCLUSIONS: IP with uncoated sonic tips smoothes the surfaces and reduces structural loss of the implant in the area of microthreads. This new IP method could be of great clinical importance, especially for implants with microthreads and reduced diameter or wall thickness.

The potential use of nanozymes as an antibacterial agents in oral infection, periodontitis, and peri-implantitis.

Several studies suggest that oral pathogenic biofilms cause persistent oral infections. Among these is periodontitis, a prevalent condition brought on by plaque biofilm. It can even result in tooth loss. Furthermore, the accumulation of germs around a dental implant may lead to peri-implantitis, which damages the surrounding bone and gum tissue. Furthermore, bacterial biofilm contamination on the implant causes soft tissue irritation and adjacent bone resorption, severely compromising dental health. On decontaminated implant surfaces, however, re-osseointegration cannot be induced by standard biofilm removal techniques such as mechanical cleaning and antiseptic treatment. A family of nanoparticles known as nanozymes (NZs) comprise highly catalytically active multivalent metal components. The most often employed NZs with antibacterial activity are those that have peroxidase (POD) activity, among other types of NZs. Since NZs are less expensive, more easily produced, and more stable than natural enzymes, they hold great promise for use in various applications, including treating microbial infections. NZs have significantly contributed to studying implant success rates and periodontal health maintenance in periodontics and implantology. An extensive analysis of the research on various NZs and their applications in managing oral health conditions, including dental caries, dental pulp disorders, oral ulcers, peri-implantitis, and bacterial infections of the mouth. To combat bacteria, this review concentrates on NZs that imitate the activity of enzymes in implantology and periodontology. With a view to the future, there are several ways that NZs might be used to treat dental disorders antibacterially.

Microstructure, physical and mechanical properties of dental polychromic multilayer zirconia of uniform composition.

The present study aimed to compare the microstructure, physical, and mechanical properties of three commercially available dental polychromatic multilayer zirconia materials of uniform composition: Dima Mill Zirconia ML, VITA YZ/ST Multicolor, and VITA YZ/XT Multicolor (with 3, 4, and 5 mol% Y2 O3 , respectively); thus, the influence of Y2 O3 content on the above properties of the produced materials was experimentally studied. Homogeneous zirconia ceramics with a dense micro- and nanostructure, without pores or defects, were produced after milling the blocks and sintering, which resulted in yttrium-stabilized tetragonal and cubic zirconia. Statistical analysis of the results of measurable magnitudes was performed by the one-way ANOVA test. The increase of Y2 O3 content (from 3 to 5 mol%) favored larger grain and crystallite sizes and a decrease of the values of the mechanical properties; yet, the differences were statistically insignificant. Clinically, these differences are expected to have no impact on their function in the oral cavity, both in terms of their fracture propensity and the damage that can be caused to the opposing teeth. Accordingly, the experimental results qualify the polychromic multilayer zirconia ceramics of uniform composition fabricated by milling technology for use in dental restorations.

Computational analysis of 3D printing: Selecting the better among newly released materials.

Resin-based three-dimensional (3D) printing finds extensive application in the field of dentistry. Although studies of cytotoxicity, mechanical and physical properties have been conducted for newly released 3D printing resins such as Crowntec (Saremco), Temporary Crown Resin (Formlabs) and Crown & Bridge (Nextdent), the resistance of these materials to esterases in saliva has not been demonstrated at the molecular level. Therefore, in this study, the binding affinities and stability of these new 3D printing resins to the catalytic sites of esterases were investigated using molecular docking and molecular mechanics with Poisson-Bolzmann and surface area solvation (MM/PBSA) methods after active pocket screening. Toxicity predictions of the materials were also performed using ProTox-II and Toxtree servers. The materials were analyzed for mutagenicity, cytotoxicity, and carcinogenicity, and LD50 values were predicted from their molecular structures. The results indicated that out of the three novel 3D printing materials, Nexdent exhibited reduced binding affinity to esterases, indicating enhanced resistance to enzymatic degradation and possessing a superior toxicity profile.

Optical effects of graphene addition on adhesives for orthodontic lingual retainers.

The objective of this study was to determine the effects on the colour of adding increasing concentrations of graphene to orthodontic fixed retainer adhesives and to evaluate changes in optical transmission during light curing and the resultant degree of conversion. Two different types of adhesives commonly used for fixed retainers were investigated: A packable composite (Transbond) and a flowable composite (Transbond Supreme). Graphene was added to the adhesives in three different concentrations (0.01, 0.05, and 0.1 wt%). Adhesives without graphene addition were set as control groups. A Minolta colourimeter was used to measure the colour and translucency parameters. Irradiance transmitted during curing was quantified using MARC Light Collector. Fourier-transform infrared spectroscopy was used to record degree of conversion. Data were statistically analysed with the Student's t-test and one-way ANOVA with Tukey's tests (α = 0.05). The findings showed that incorporating graphene darkened the adhesive colour significantly and reduced translucency. As the graphene concentration reached 0.1 wt%, samples became opaque; yet, no adverse effect on degree of conversion was observed. The addition of graphene reduces optical transmission of lingual retainer adhesives; the effect increases with graphene concentration.

Evaluation of bond strength between zirconia milled ceramic material and veneered dental porcelain.

This study aimed at examining the bond strength between zirconia and ceramic veneer, following the ISO 9693 guidelines. A total of fifty specimens of zirconia/ceramic-veneer system were produced using two commercial zirconias (VITA YZ-HTWhite and Zolid HT+ White, referred to as Group A and Group B, respectively) and a ceramic-veneering material (Zirkonia 750). The microstructure (via x-ray diffraction analysis, XRD and Secondary Electron mode, SEM) and the mechanical properties (via 3-point bending tests) of the two groups were assessed. Then, experiments were conducted according to the ISO 9693 and conventional protocols applied for producing zirconia/ceramic-veneer restorations. Bond strength values, measured by 3-point bending tests, were 34.42 ± 7.60 MPa for Group A and 31.92 ± 6.95 MPa for Group B. SEM observations of the cohesively fractured surfaces (on the porcelain side) and the examination for normality using the Shapiro-Wilk test suggested the use of Weibull statistical analysis. Median strength (σ50%) for Group A and Group B was 34.76 and 32.22 MPa, while the characteristic strength (σ63.2%) was 35.78 and 33.14 MPa, respectively. The Weibull modulus disparity between groups (12.69 and 13.07) was not significant. Bond strength exceeded the ISO 9693 minimum of 20 MPa, suggesting satisfactory strength for clinical use.

Effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials: An in vitro investigation.

The aim of the study was to evaluate the effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials [CERASMART (GC); VITA ENAMIC (VITA Zahnfabrik); Lava Ultimate (3 M)] in comparison to feldspar ceramic (VITABLOCS Mark II, VITA Zahnfabrik) and resin composite materials (ceram.x universal, Dentsply Sirona). Daily brushing and acid exposure were simulated using a brushing apparatus and a solution of 0.5 vol% citric acid. Microhardness, surface roughness, and substance loss were measured at baseline and after simulation of 1 and 3 years of function. All materials showed a decrease in microhardness after 3 years and an increase in surface roughness (Ra) after 1 and 3 years. The Ra increase was statistically significantly lower for the resin-matrix ceramics than for feldspar ceramic and similar to composite material. After 3 years, only feldspar ceramic showed no significant substance loss. In conclusion, resin-matrix ceramics demonstrate reduced roughening compared to feldspar ceramics, potentially improving restoration longevity by preventing plaque buildup, but differences in abrasion resistance suggest the need for further material-specific research. Future research should aim to replicate clinical conditions closely and to transition to in vivo trials.

Chemical analysis of n-propyl gallate used as pre-treatment for resin-dentin bond strength: In vitro study.

This study aimed to evaluate the effect of n-propyl gallate as pre-treatment for resin-dentin bond strength. The dentin pre-treatments evaluated included propyl gallate of concentrations 0.1% (w/v), 1.0% (w/v), and 10.0% (w/v), as well as glutaraldehyde 5.0% (v/v), and distilled water as a control treatment. Dentin specimens were prepared for Fourier Transformed Infrared Spectroscopy (FT-IR) (n = 3/pre-treatment). Pre-treatments were actively applied to dentin blocks before performing the adhesive procedure to composite resin. Microtensile bond strength to dentin (µTBS) (n = 8/pre-treatment) was determined after 24 h and 6 months of storage. Data were submitted to a two-way ANOVA, followed by Tukey's post hoc test. As for FT-IR, propyl gallate 1%-treated specimens presented higher water, carbonate, collagen, and amide absorbance rates compared to other tested groups, while specimens pre-treated with glutaraldehyde and distilled water presented similar absorbance curves. Regarding µTBS, all concentrations of propyl gallate resulted in statistically significant higher bond strength values than distilled water at 24 h. After 6 months of storage, propyl gallate 0.1% was the only group that maintained µTBS over time. Propyl gallate 0.1% might be a suitable dentinal pre-treatment due to being able to present chemical bonds with demineralized dentin and providing resin-dentin bond stability after 6 months of storage.

Evaluation of the Milled and Three-Dimensional Digital Manufacturing, 10-Degree and 20-Degree Preparation Taper, Groove and Box Auxiliary Retentive Features, and Conventional and Resin-Based Provisional Cement Type on the Adhesive Failure Stress of 3 mm Short Provisional Crowns.

BACKGROUND This study evaluated the effects of milling (CADCAM), 3D printing, preparation taper angles (10-degree and 20-degree), auxiliary retentive features (groove and box), and provisional cement types (conventional and resin-based) on the adhesive failure stress of 3-mm short provisional crowns (PC). The research was motivated by the need to understand how digital dentistry technologies impact the retention and durability of provisional crowns. MATERIAL AND METHODS A total of 160 working models (3D-printed) and PCs [80 milled (CopraTemp)/80 printed (Asiga)] were fabricated from two 10- and 20-degree typodont master models and two 20-degree 3D-printed master models (groove and box), simulating a 3 mm high all-ceramic short PC. After provisional cementation with conventional (Kerr TempBond) and resin-based (ProviTemp) cements, 16 subgroups (n=10 each) underwent thermocycling (10 000 cycles; 5-55°C) and pull-off tests on a universal testing machine. Statistical analysis was performed using one-way ANOVA and post hoc Tukey test. RESULTS Conventional cement failed at lower stress for milled (47.68 to 73.54) and printed (48.40 to 77.91) as compared to resin cement for milled (104.2 to 137.27) and printed (184.85 to 328.84), respectively, with significant differences. Increased taper and groove decreased failure load except for the printed PC/resin cement combination. Use of proximal box preparation increased retention significantly. Except for 20-degree taper cemented with conventional cement, the differences in auxiliary retentive features for milled and printed provisional crowns were statistically significant at P≤0.05. CONCLUSIONS 3D-printed PC, resin-based cement, 10-degree taper, and proximal box preparation were associated with higher retention than milled, conventional cements, 20-degree taper, and vertical groove.

The Impact of Repeated Steam Sterilization Cycles on the Efficacy of Chairside Adjustment Kits for Polishing Monolithic Multi-Layered Zirconia Dental Restoration Material.

BACKGROUND Before insertion, chairside adjustment kits are heat sterilized for positioning and polishing dental restorations. This study aimed to evaluate the effects of 2 steam sterilization cycles on the efficacy of polishing highly translucent monolithic zirconia (HTMLZ) dental restoration material. MATERIAL AND METHODS 100 HTMLZ disc-shaped specimens were adjusted (grinding, finishing, polishing) with EVE Diacera kit. Two steam sterilization techniques [standard (Gp S), immediate/flash (Gp (F)] of CAK were further subgrouped based on number of sterilization cycles [cycle 1 (control), cycle 5, 10, 15, and 20 (experimental)] (n=10 each). Each subgroup accordingly was evaluated for average surface roughness (Ra) and root mean square roughness (Rq) using a profilometer. Mean and standard deviation of 5 subgroups were statistically analyzed using one-way ANOVA/post hoc Tukey's test. Scanning electron microscopy complemented Ra, Rq measurements. Statistical differences of P≤0.05 were considered significant. RESULTS HTMLZ specimens in both groups showed increased (Ra/Rq) values after repeated sterilization of EVE Diacera kit, with Gp F showing lesser increase than Gp S (20 cycles). Gp F at 10 cycles and Gp S at 15 cycles showed clinically unacceptable roughness threshold (0.25 µm). Differences between subgroups for Ra and Rq values were significant (P≤0.05) with less differences within groups observed in early cycles (1, 10). Results validate the manufacturer's recommendations of using flash sterilization/10 cycles for EVE Diacera kit. CONCLUSIONS Repeated sterilization reduces efficacy of chairside adjustment kit to produce smooth surfaces on HTMLZ. This study recommends flash sterilization to a maximum of 10 times to get the clinically acceptable results of Ra and Rq.

Evaluation of Retentive Strength of 50 Endodontically-Treated Single-Rooted Mandibular Second Premolars Restored with Cast Post Cores Using 5 Common Luting (Cement) Agents.

BACKGROUND A luting agent is a dental cement used to secure a dental restoration. This study aimed to evaluate retentive strength of 50 endodontically-treated single-rooted mandibular second premolars (extracted) restored using 5 common luting (cement) agents. MATERIAL AND METHODS Fifty single-rooted mandibular second premolars with adequate root length and uniform size/shape were decoronated. After completing endodontic biomechanical preparation and obturation, root canals of all specimens were prepared to receive a cast post core. Depending upon cementation type, CPC specimens were divided in 5 groups (10 each) (Gp): Zinc phosphate (Gp ZP), polycarboxylate (Gp PC), glass ionomer (Gp GI), resin-modified glass ionomer (Gp RGI), and resin cement (Gp RC). Retentive strength was determined using the adhesive failure pull-out test. Mean/standard deviations were calculated for tensile forces (in kilograms) and differences were determined using analysis of variance (ANOVA). Multiple comparison was performed using the t test. A P value of ≤0.05 indicated a statistically significant difference. RESULTS The order of mean tensile strength from higher to lower was Gp RC (21.46) >Gp RGI (18.17) >Gp GI (16.07) >Gp ZP (15.33) >Gp PC (13.63). Differences in retentive strengths between the cements were significant (P≤0.05). Multiple-group comparisons showed that except for Gp ZP and Gp GI, all groups differed significantly from each other. CONCLUSIONS All investigated cements provided optimal retentive strengths, with wide differences between them. Resin cements should be used when CPC removal is not anticipated, while polycarboxylate or zinc phosphate should be used if CPC removal is anticipated.

Shear Bond Strength of Adhesives Placed following Selective Removal of Red-Fluorescing Carious Dentine in vitro.

Red-fluorescing dentine indicates bacterial contamination [Caries Res 2002; 36: 315-319]. We investigated effect of removal of red fluorescent dentine caries on shear bond strength and fracture mode of 4 adhesive approaches. Sixty-five carious teeth and 50 noncarious controls were distributed into 4 groups: Clearfil™ self-etch (CSE), OptiBond™ FL total etch (OTE), Scotchbond™ Universal total etch (STE) and self-etch (SSE). Samples were excited at 405 nm and viewed through 530 nm filter. Carious samples were ground flat exposing strongly red-fluorescing (StrongRF) dentine, on which a composite cylinder was placed, using one of 4 adhesives. After 22 h in water, shear bond strength and fracture mode were analysed. StrongRF was removed; composite cylinders were placed on weakly red-fluorescing (WeakRF) dentine and tested as described above. Finally, red-fluorescing dentine was removed, and composite cylinders were placed on non-fluorescing (NonRF) dentine and tested. Composites were placed at 3 corresponding heights in controls. After 22 h in water, shear bond strength testing and fracture mode analysis were performed. Differences were tested using Mann-Whitney or Wilcoxon tests (p ≤0.05). Median (Q1, Q3) shear bond strength on StrongRF was SSE 14.4 (9.2, 18.2) MPa >CSE 10.2 (6.4, 17.3) MPa >STE 9.1 (6.9, 11.2) MPa >OTE 6.8 (4.0, 10.8) MPa. Shear bond strength increased statistically significantly for all adhesives on WeakRF: SSE 19.8 (13.6, 24.3) MPa >STE 19.5 (12.7, 23.1) MPa >CSE 17.5 (12.0, 22.5) MPa >OTE 15.8 (11.9, 20.9) MPa. Only STE 25.6 (22.4, 29.1) MPa and CSE 22.1 (17.6, 24.6) MPa were significantly different on NonRF compared to WeakRF. For controls tested at corresponding depths, superficial shear bond strength was OTE 18.7 (16.0, 22.1) MPa >STE 18.4 (12.0, 25.9) MPa >CSE 18.1 (12.7, 20.7) MPa >SSE 13.0 (9.6, 17.8) MPa. This was significantly higher compared to StrongRF except for SSE. Central shear bond strength was not significantly different to WeakRF, deep shear bond strength was significantly lower for SSE and CSE but higher for OTE compared to carious. Conclusion: StrongRF dentine should be removed for higher shear bond strength, but WeakRF dentine can often be preserved without compromising adhesive bond strength.

In silico assessment of biocompatibility and toxicity: molecular docking and dynamics simulation of PMMA-based dental materials for interim prosthetic restorations.

AIM: This study aimed to comprehensively assess the biocompatibility and toxicity profiles of poly(methyl methacrylate) (PMMA) and its monomeric unit, methyl methacrylate (MMA), crucial components in dental materials for interim prosthetic restorations. METHODOLOGY: Molecular docking was employed to predict the binding affinities, energetics, and steric features of MMA and PMMA with selected receptors involved in bone metabolism and tissue development, including RANKL, Fibronectin, BMP9, NOTCH2, and other related receptors. The HADDOCK standalone version was utilized for docking calculations, employing a Lamarckian genetic algorithm to explore the conformational space of ligand-receptor interactions. Furthermore, molecular dynamics (MD) simulations over 100 nanoseconds were conducted using the GROMACS package to evaluate dynamic actions and structural stability. The LigandScout was utilized for pharmacophore modeling, which employs a shape-based screening approach to identify potential ligand binding sites on protein targets. RESULTS: The molecular docking studies elucidated promising interactions between PMMA and MMA with key biomolecular targets relevant to dental applications. MD simulation results provided strong evidence supporting the structural stability of PMMA complexes over time. Pharmacophore modeling highlighted the significance of carbonyl and hydroxyl groups as pharmacophoric features, indicating compounds with favorable biocompatibility profiles. CONCLUSION: This study underscores the potential of PMMA in dental applications, emphasizing its structural stability, molecular interactions, and safety considerations. These findings lay a foundation for future advancements in dental biomaterials, guiding the design and optimization of materials for enhanced biocompatibility. Future directions include experimental validation of computational findings and the development of PMMA-based dental materials with improved biocompatibility and clinical performance.

Optimizing alkaline hydrothermal treatment for biomimetic smart metallic orthopedic and dental implants.

Orthopedic and dental implant failure continues to be a significant concern due to localized bacterial infections. Previous studies have attempted to improve implant surfaces by modifying their texture and roughness or coating them with antibiotics to enhance antibacterial properties for implant longevity. However, these approaches have demonstrated limited effectiveness. In this study, we attempted to engineer the titanium (Ti) alloy surface biomimetically at the nanometer scale, inspired by the cicada wing nanostructure using alkaline hydrothermal treatment (AHT) to simultaneously confer antibacterial properties and support the adhesion and proliferation of mammalian cells. The two modified Ti surfaces were developed using a 4 h and 8 h AHT process in 1 N NaOH at 230 °C, followed by a 2-hour post-calcination at 600 °C. We found that the control plates showed a relatively smooth surface, while the treatment groups (4 h & 8 h AHT) displayed nanoflower structures containing randomly distributed nano-spikes. The results demonstrated a statistically significant decrease in the contact angle of the treatment groups, which increased wettability characteristics. The 8 h AHT group exhibited the highest wettability and significant increase in roughness 0.72 ± 0.08 µm (P < 0.05), leading to more osteoblast cell attachment, reduced cytotoxicity effects, and enhanced relative survivability. The alkaline phosphatase activity measured in all different groups indicated that the 8 h AHT group exhibited the highest activity, suggesting that the surface roughness and wettability of the treatment groups may have facilitated cell adhesion and attachment and subsequently increased secretion of extracellular matrix. Overall, the findings indicate that biomimetic nanotextured surfaces created by the AHT process have the potential to be translated as implant coatings to enhance bone regeneration and implant integration.

Biocompatibility and bioactive potential of NeoPUTTY calcium silicate-based cement: An in vivo study in rats.

AIM: To evaluate the inflammatory reaction and the ability to induce mineralization activity of a new repair material, NeoPUTTY (NPutty; NuSmile, USA), in comparison with Bio-C Repair (BC; Angelus, Brazil) and MTA Repair HP (MTA HP; Angelus, Brazil). METHODOLOGY: Polyethylene tubes were filled with materials or kept empty (control group, CG) and implanted in subcutaneous tissue of rats for 7, 15, 30, and 60 days (n = 6/group). Capsule thickness, number of inflammatory cells (ICs), fibroblasts, collagen content, and von Kossa analysis were performed. Unstained sections were evaluated under polarized light and by immunohistochemistry for osteocalcin (OCN). Data were submitted to two-way anova followed by Tukey's test (p ≤ .05), except for OCN. OCN data were submitted to Kruskal-Wallis and Dunn and Friedman post hoc tests followed by the Nemenyi test at a significance level of 5%. RESULTS: At 7, 15, and 30 days, thick capsules containing numerous ICs were seen around the materials. At 60 days, a moderate inflammatory reaction was observed for NPutty, BC while MTA HP presented thin capsules with moderate inflammatory cells. In all periods, NPutty specimens contained the highest values of ICs (p < .05). From 7 to 60 days, the number of ICs reduced significantly while an increase in the number of fibroblasts and birefringent collagen content was observed. At 7 and 15 days, no significant difference was observed in the immunoexpression of OCN (p > .05). At 30 and 60 days, NPutty showed the lowest values of OCN (p < .05). At 60 days, a similar immunoexpression was observed for BC and MTA HP (p > .05). In all time intervals, capsules around NPutty, BC, and MTA HP showed von Kossa-positive and birefringent structures. CONCLUSIONS: Despite the greater inflammatory reaction promoted by NeoPutty than BC and MTA HP, the reduction in the thickness of capsules, the increase in the number of fibroblasts, and the reduction in the number of ICs indicate that this bioceramic material is biocompatible Furthermore, NeoPutty presents the ability to induce mineralization activity.

Intracanal removal and apical extrusion of filling material after retreatment using rotary or reciprocating instruments: A new approach using human cadavers.

AIM: This study compared intracanal removal of filling as well as the frequency and volume of extruded material after retreatment with either HyFlex or Reciproc instruments in mandibular teeth from cadavers. METHODOLOGY: The root canals of 14 pairs of contralateral single-rooted teeth in mandibles of cadavers were instrumented with Reciproc R40 and filled using lateral compaction. The mandibles were scanned in a micro-computed tomographic (micro-CT) device before and after retreatment procedures. The contralateral teeth were assigned to two groups (n = 14) according to the retreatment protocol using either HyFlex or Reciproc instrument systems. In the HyFlex group, the HyFlex Remover instrument was worked 3 mm short of the working length (WL), followed by HyFlex CM 40.04 and 50.04 at the WL. In the Reciproc group, the R50 instrument was worked up at the coronal two thirds, followed by two more cycles until the WL was reached. Pre- and post-operative micro-CT images were analysed for extrusion and intracanal removal of filling material. RESULTS: After retreatment, extrusion of filling material occurred in 11 (78%) and 14 (100%) teeth from HyFlex and Reciproc groups respectively (p > .05). A similar volume of extruded material was observed after retreatment with both systems (p > .05). A significant decrease in the intracanal filling volume was verified after retreatment with both tested systems (p < .05). However, residual filling material was found in all root canals, regardless of the system. The amount of filling material removed (HyFlex = 80.8%; Reciproc = 65.9%) and the operation time was similar between systems (p > .05). CONCLUSIONS: A high frequency of filling material extrusion was observed after retreatment with the two systems in a cadaver model, with no significant difference between them. Both protocols obtained similar efficacy in filling material removal procedures, although none completely cleaned the canals.

Multimethod analysis of large- and low-tapered single file reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow.

AIM: To compare eight large- and low-tapered heat-treated reciprocating instruments regarding their design, metallurgy, mechanical properties, and irrigation flow through an in silico model. METHODOLOGY: A total of 472 new 25-mm E-Flex Rex (25/.04 and 25/.06), Excalibur (25/.05), Procodile (25/.06), Reciproc Blue R25 (25/.08v), WaveOne Gold Primary (25/.07v), and Univy Sense (25/.04 and 25/.06) instruments were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy (energy-dispersive X-ray spectroscopy and differential scanning calorimetry), and mechanical performance (cyclic fatigue, torsional resistance, cutting ability, bending and buckling resistance). Computational fluid dynamics assessment was also conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparations. Kruskal-Wallis and one-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Instruments presented variations in blade numbers, helical angles, and tip designs, with all featuring non-active tips, symmetrical blades, and equiatomic nickel-titanium ratios. Cross-sectional designs exhibited an S-shaped geometry, except for WaveOne Gold. Univy 25/.04 and Reciproc Blue displayed the smallest and largest core diameters at D3. Univy 25/.04 and E-Flex Rec 25/.04 demonstrated the longest time to fracture (p < .05). Reciproc Blue and Univy 25/.04 exhibited the highest and lowest torque to fracture, respectively (p < .05). Univy 25/.04 and Reciproc Blue had the highest rotation angles, whilst E-Flex Rec 25/.06 showed the lowest angle (p < .05). The better cutting ability was observed with E-Flex Rec 25/.06, Procodile, Excalibur, and Reciproc Blue (p > .05). Reciproc R25 and E-Flex Rec showed the highest buckling resistance values (p < .05), with WaveOne Gold being the least flexible instrument. The impact of instruments' size and taper on wall shear stress and apical pressure did not follow a distinct pattern, although Univy 25/.04 and E-Flex Rec 25/.06 yielded the highest and lowest values for both parameters, respectively. CONCLUSIONS: Low-tapered reciprocating instruments exhibit increased flexibility, higher time to fracture, and greater angles of rotation, coupled with reduced maximum bending loads and buckling strength compared to large-tapered instruments. Nevertheless, low-tapered systems also exhibit lower maximum torque to fracture and inferior cutting ability, contributing to a narrower apical canal enlargement that may compromise the penetration of irrigants in that region.

Mechanical and biological properties of polymer materials for oral appliances produced with additive 3D printing and subtractive CAD-CAM techniques compared to conventional methods: a systematic review and meta-analysis.

OBJECTIVES: The aim of this review was to analyze mechanical and biological properties of resin materials used with subtractive or additive techniques for oral appliances fabrication and compare them to those conventionally manufactured. MATERIALS AND METHODS: The protocol was registered online at Open Science Framework (OSF) registries ( https://osf.io/h5es3 ) and the study was based on the preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P). An electronic search was conducted on MEDLINE (via PubMed), Scopus, and Web of Science from 1 February 2022 to 1 May 2022. INCLUSION CRITERIA: in vitro and in vivo studies published in the last 10 years, with CAD-CAM or 3D printed resins for occlusal splints. Data considered homogenous were subjected to meta-analysis (95% confidence interval [CI]; α = 0.05) with Stata17 statistical software. Since all variables were continuous, the Hedge g measure was calculated. A fixed-effects model was used for I2 = 0%, while statistical analysis was conducted using a random-effects model with I2 > 0%. RESULTS: 13 studies were included after full-text reading. The mechanical properties most studied were wear, flexural strength, surface hardness and surface roughness, while only 1 study investigated biological properties, performing the XTT viability assay. For the meta-analysis, only surface roughness, volume loss, and flexural strength were selected. Considering surface roughness, the subtractive specimen had a lower average value compared to traditional ones (Hedge's g with 95% CI = -1.25[ -1.84, - 0.66]). No significant difference was detected in terms of volume loss (P > 0.05) between the groups (Hedge's g with 95% CI = -0.01 [-2.71, - 2.68]). While flexural strength was higher in the control group (Hedge's g with 95% CI = 2.32 [0.10-4.53]). CONCLUSION: 3D printed materials showed properties comparable to conventional resins, while milled splint materials have not shown better mechanical performance compared with conventional heat-cured acrylic resin. Polyetheretherketone (PEEK) have great potential and needs to be further investigated. Biological tests on oral cell populations are needed to confirm the long-term biocompatibility of these materials. CLINICAL RELEVANCE: The use of "mixed splints" combining different materials needs to be improved and evaluated in future research to take full advantage of different characteristics and properties.