Synthesis and characterisation of microcapsules for self-healing dental resin composites.

AIM: The purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures. MATERIALS & METHODS: Microcapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently. RESULT: Average diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 µm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%. CONCLUSION: TEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.

The effectiveness of dental water jet in reducing dental plaque and gingival bleeding in orthodontic patients: A systematic review and meta-analysis of randomized clinical trials.

INTRODUCTION: This systematic review and meta-analysis tests the effectiveness of dental water jet (DWJ) with manual toothbrushes (MTB) compared to MTB alone in oral health maintenance in orthodontic patients. METHODS: Four databases were systematically searched: PubMed, Scopus, Web of Science (WoS) and Cochrane Library until 6 January 2022 using a combination of medical subject heading (MeSH) terms and keywords. Randomized clinical trials (RCTs) were only included and critically appraised using the Cochrane Risk of Bias (ROB) tool. The mean difference (MD) effect measure was calculated using the Mantel-Haenszel statistical test (95% confidence interval [CI]) to compare both study groups (p-value < 0.05). RESULTS: After reviewing 5881 studies from a systematic search, six were selected for inclusion, with four involved in the quantitative analysis. The risk of bias was low in two studies, moderate in two studies and high in the remaining two studies. The meta-analysis showed a significant improvement in plaque index and bleeding scores in DWJ + MTB group compared MTB alone group in orthodontic patients with generalized gingivitis (MD = -0.75, 95% CI [-1.29, -0.22], p = 0.006) and (MD = -0.17, 95% CI [-0.27, -0.08], p = 0.0003), respectively. However, no significant improvement was detected between both groups in the gingival index. CONCLUSIONS: The use of DWJ as an adjunctive device in addition to MTB can be an effective strategy for maintaining oral hygiene in orthodontic patients with gingivitis. However, more high-quality RCTs are needed to confirm the findings.

Surface hardness and flexural strength of dual-cured bulk-fill restorative materials after solvent storage.

BACKGROUND: This study aimed to evaluate the surface hardness (VHN) and biaxial flexural strength (BFS) of dual-cured bulk-fill restorative materials after solvent storage. METHODS: Two dual-cured bulk-fill composites (Surefil One® and Activa™ Bioactive), a light-cured bulk-fill composite (Filtek One Bulk-Fill) and a resin-modified glass ionomer (Fuji II LC) were investigated. Surefil One and Activa were used in the dual-cure mode, all materials were handled according to manufacturer's instructions. For VHN determination, 12 specimens were prepared from each material and measured after 1 h (baseline), 1 d, 7 d and 30 d of storage in either water or 75% ethanol-water. For BFS test, 120 specimens were prepared (n = 30/material) and stored in water for either 1, 7 or 30 d before testing. Repeated measures MANOVA, two-way and one-way ANOVA followed by the Tukey post hoc test (p ≤ 0.05) were used to analyze the data. RESULTS: Filtek One had the highest VHN, while Activa had the lowest. All materials exhibited a significant increase in VHN after 1d of storage in water, except for Surefil One. After 30 d of storage, VHN increased significantly in water except for Activa, while ethanol storage caused a significant time-dependent reduction in all tested materials (p ≤ 0.05). Filtek One showed the highest BFS values (p ≤ 0.05). All the materials, except for Fuji II LC, exhibited no significant differences between 1 and 30 d BFS measurements (p > 0.05). CONCLUSIONS: Dual-cured materials had significantly lower VHN and BFS compared to the light-cured bulk-fill material. The low results of Activa VHN and Surefil One BFS, indicate that these materials should not be recommended in posterior stress-bearing areas.

A comprehensive review of resin luting agents: Bonding mechanisms and polymerisation reactions.

The field of dentistry is constantly evolving and increasingly embracing minimally invasive approaches. One such approach, which is bonding to the tooth structure, particularly enamel, has been shown to offer the most predictable outcomes. However, there are instances where significant tooth loss may limit treatment options for a restorative dentist. In these scenarios, indirect restoration might be the preferred treatment option. This literature review provides a comprehensive examination of the currently available resin luting agents and their bonding requirements. It provides valuable insights for dental professionals seeking an in-depth understanding of the current state of the field and the future prospects of dental adhesion.

Properties of model E-glass fiber composites with varying matrix monomer ratios.

OBJECTIVE: To evaluate properties of fiber-reinforced-composites (FRC) containing Bis-EMA/UDMA monomers but identical dispersed phase (60% wt BaSi glass power +10% wt E-glass fibre). METHODS: A control (Group A), monomer mixture comprising 60% Bis-GMA, 30% TEGDMA, and 10% PMMA (typical FRC monomers) was used. The following monomer mass fractions were mixed: 50% bis-GMA plus 50% of different ratios of Bis-EMA+UDMA to produce consistent formulations (Groups B-E) of workable viscosities was also studied. Flexural strength (FS), fracture toughness (KIC), water sorption (SP), solubility (SL) and hygroscopic expansion (HE) were measured. FS and KIC specimens were stored for 1, 7 d, and 30 d in water at 37 °C. SP/SL specimens were water-immersed for 168d, weighed at intervals, then dried for 84 d at 37 °C. To analyze differences in FS, and KIC, a two-way ANOVA and Tukey post-hoc tests (α = 0.05) were conducted. For SP/SL, and HE, one-way ANOVA with subsequent Tukey post-hoc tests (α = 0.05) were utilized. RESULTS: FS and KIC for groups A, D, E decreased progressively after 1 d. Groups B and C (highest amounts of Bis-EMA) did not decrease significantly. The modified matrix composites performed significantly better than the control group for SP and HE. The control group outperformed the experimental composites only for SL with up to 250% higher SL for group E (6.9 µg/mm) but still below the maximum permissible threshold of 7.5 µg/mm. SIGNIFICANCE: EXPERIMENTAL: composites with highest amounts of Bis-EMA showed improved hydrolytic stability and overall enhancement in several clinically-relevant properties. This makes them potential candidates for alternative matrices to a semi-interpenetrating network in fiber-reinforced composites.

Advanced restorative management of focal microdontia: A brief review and case report.

Focal microdontia is a dental anomaly characterized by the presence of a single abnormally small anterior or posterior tooth. The objective of this article is to provide an updated review of the literature on the advanced restorative management of focal microdontia, and to document a clinical case where the reviewed advanced restorative approaches were applied to treat a young adult presenting with a non-syndromic asymmetrical focal microdontia.We conducted a preliminary examination of the existing literature on the advanced restorative management of focal microdontia. Additionally, we presented a minimally invasive approach to the treatment of an 18-year-old female patient with non-syndromic asymmetrical focal microdontia. The primary advantage of adhesive dentistry is that it can better preserve the structure of smaller teeth. A review of literature reveals a paucity of reports on localized microdontia in the maxillary anterior region of the mouth. However, novel minimally invasive restorative procedures satisfy patients' aesthetic and functional preferences. Well-executed additive diagnostic wax-ups and intraoral mock-ups can serve as a permanent restoration blueprint, providing predictable results for focal dental anomalies in the aesthetic zone. In conclusion, the use of minimally invasive dental approaches in young patients with focal microdontia can result in long-term satisfactory aesthetic outcomes.

Mechanical properties and degree of conversion of resin-based core build-up materials and short fiber-reinforced flowable resin-based composite.

To evaluate the degree of conversion (DC), surface hardness (SH), and flexural strength (FS) of resin-based core build-up materials. Core build-up materials used were: MultiCore Flow (MCF); Activa (ACT); Core-X Flow (CXF); and everX flow (EVX), and DC, SH and FS were measured. An increase of DC was identified for all materials post-cure, except for EVX. The DC change percentage ranged from 5%-33%, and EVX was displayed the greatest DC rate. All materials displayed an SH increase after 30 days and the greatest increase was observed in ACT. At 1 h, the SH of EVX and CXF was different from the other materials. At 30 days, MCF displayed the greatest SH. All materials displayed an increase in their FS after 30 days except for EVX, and ranging 3%-36% were noticed. Differences observed between materials, thus clinician should be acquainted mechanical properties of these materials to ensure the success of the restorations.

Temperature rise in photopolymerized adhesively-bonded resin composite: A thermography study.

OBJECTIVES: To assess visually and quantitatively the contributions of the adhesive layer photopolymerization and the subsequent resin composite increment to spatio-temporal maps of temperature at five different cavity locations, subjected to two irradiance curing protocols: standard and ultra-high. METHODS: Caries-free molars were used to obtain 40, 2 mm thick dentin slices, randomly assigned to groups (n = 5). These slices were incorporated within 3D-printed model cavites, 4 mm deep, restored with Adhese® Universal bonding agent and 2 mm thick Tetric® Powerfill resin composite, and photocured sequentially, as follows: G1: control-empty cavity; G2: adhesive layer; G3 composite layer with no adhesive; and G4 composite layer with adhesive. The main four groups were subdivided based on two curing protocols, exposed either to standard 10 s (1.2 W/cm2) or Ultra high 3 s (3 W/cm2) irradiance modes using a Bluephase PowerCure LCU. Temperature maps were obtained, via a thermal imaging camera, and numerically analyzed at 5 locations. The data were analyzed using two-way ANOVA followed by multiple one-way ANOVA, independent t-tests and Tukey post-hoc tests (α = 0.05). Tmax, ΔT, Tint (integrated area under the curve) and time-to-reach-maximum-temperature were evaluated. RESULTS: Two-way ANOVA showed that there was no significant interaction between light-curing time and location on the measured parameters (p > 0.05), except for the time-to-reach-maximum-temperature (p < 0.05). Curing the adhesive layer alone with the 10 s protocol resulted in a significantly increased pulpal roof temperature compared to 3 s cure (p < 0.05). Independent T-tests between G3 and G4, between 3 s and 10 s, confirmed that the adhesive agent caused no significant increases (p > 0.05) on the measured parameters. The ultra-high light-curing protocol significantly increased ΔT in composite compared to 10 s curing (p < 0.05). SIGNIFICANCE: When the adhesive layer was photocured alone in a cavity, with a 2 mm thick dentin floor, the exothermal release of energy resulted in higher temperatures with a 10 s curing protocol, compared to a 3 s high irradiance. But when subsequently photocuring a 2 mm layer of composite, the resultant temperatures generated at pulpal roof location from the two curing protocols were similar and therefore there was no increased hazard to the dental pulp from the immediately prior adhesive photopolymerization, cured via the ultra-high irradiation protocol.

Bond Strength, Microleakage, Microgaps, and Marginal Adaptation of Self-adhesive Resin Composites to Tooth Substrates with and without Preconditioning with Universal Adhesives.

PURPOSE: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. MATERIALS AND METHODS: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and µTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or µTBS using a universal testing machine at a crosshead speed of 0.5 mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24 h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at α = 0.05. RESULTS: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p < 0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. CONCLUSION: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives.

Biomechanical reinforcement by CAD-CAM materials affects stress distributions of posterior composite bridges: 3D finite element analysis.

OBJECTIVES: This 3D finite element analysis study aimed to investigate the effect of reinforcing CAD-CAM bars on stress distribution in various components of a posterior composite bridge. METHODS: A virtual model mimicking the absence of an upper second premolar was created, featuring class II cavity preparations on the proximal surfaces of the adjacent abutment teeth surrounding the edentulous space. Five distinct finite element analysis (FEA) models were generated, each representing a CAD-CAM reinforcing bar material: 3-YTZP (IPS. emax ZirCAD MO; Zr), lithium disilicate (IPS e.max CAD; EX), nano-hybrid resin composite (Grandio Blocs; GB), Fibre-reinforced composite (Trilor; Tri), and polyetheretherketone (PEEK). A veneering resin composite was employed to simulate the replacement of the missing premolar (pontic). In the FEA, an axial force of 600 N and a transverse load of 20 N were applied at the center of the pontic. Subsequently, maximum von Mises (mvM) and maximum principal stresses (σmax) were computed across various components of the generated models. Additionally, shear stresses at the interface between the CAD-CAM bars and the veneering resin composite were determined. RESULTS: CAD-CAM materials with high modulus of elasticity, such as Zr and EX, exhibited the highest mvM stresses and shear stresses while transferring the lowest stress to the veneering resin composite in comparison to other materials. Conversely, PEEK demonstrated the lowest mvM stresses but produced the highest stresses within the veneering resin composite. There was a uniform distribution of mvM stresses in the remaining tooth structure among all groups, except for a noticeable elevation in the molar region of Zr and EX groups. SIGNIFICANCE: Reinforcing CAD-CAM bar materials with a high modulus of elasticity, such as Zr and EX, may result in debonding failures at the connector sites of posterior composite bridges. Conversely, GB, PEEK, and Tri have the potential to cause fracture failures at the connectors rather than debonding.

Effect of Bleaching Agents on Discoloured Resin-Based Composites for Direct Restorations: A Systematic Review.

The purpose of the review was to assess the influence of office and home bleaching on the color durability after staining of resin-based composites (RCs) for direct restorations. A web-based search for possibly relevant scientific papers in the English language between January 2013 and August 2022 was conducted in the databases such as PubMed, Scopus, Cochrane Library, and EMBASE. In-vitro studies that explored the influence of in-office and other bleaching treatments on the discolored RC for direct restorations in extracted human teeth were included. Case studies, case series, animal studies, systematic reviews, and letters to the editor were not considered. A total of 212 articles from a web-based search and 32 studies from a manual search were retrieved. After removal of duplicate records, 181 titles and abstracts were reviewed for eligibility; 92 were chosen for full-text analysis, and nine in-vitro studies matched the inclusion criteria. The two examiners examined the methodological quality of the selected studies independently based on the study design, methodological soundness, and data analysis. Distinct values were assigned to studies evaluating color variations of stained RC subjected to bleaching agents. The methodological quality scores were expressed as a percentage of the highest possible score based on the established scoring system and categorized as indicating a low, moderate, and high level of evidence. The reversal of color alterations following home and office bleaching was found to be dependent on the RC used. Within the limitations of the in-vitro investigations, it was deduced that the bleaching agents were successful in eliminating stains and improving the durability of the color to near baseline values.

The Depth of Cure, Sorption and Solubility of Dual-Cured Bulk-Fill Restorative Materials.

This study aimed to examine depth of cure (DoC), mass change, water sorption and solubility of dual-cured bulk-fill restorative materials (Surfil One and Activa) in comparison with a light-cured bulk-fill composite (Filtek One Bulk-Fill) and a resin-modified glass ionomer (Fuji II LC). Twenty specimens were prepared of each material using stainless steel molds designed with a slot (8 × 4 × 2 mm) and irradiated for either 20 or 40 s. The Vickers hardness (VHN) was measured at every 0.5 mm to assess the DoC after 24 h of storage at 37 °C. The depth of cure was reported as the depth corresponding to 80% of the maximum Vickers hardness. Disc-shaped specimens were prepared of each material (n = 5) to investigate mass change, sorption and solubility after 4 months of water storage. The data were analyzed using a two-way and one-way analysis of variance (ANOVA) followed by the Tukey post hoc test (p ≤ 0.05). Fuji II LC had the greatest DoC while Activa had the lowest. The two different irradiation times did not demonstrate a significant difference in DoC for all dual-cured materials (p > 0.05). Fuji II LC had the highest sorption while Filtek One showed the lowest. Surefil One and Fuji II LC had a negative solubility. This study concluded that dual-cured materials showed different depth of cure values despite having the same setting reaction. Both materials exhibited a high water sorption, which might jeopardize their dimensional stability and effect their clinical performance.

Dental Fiber-Post Systems: An In-Depth Review of Their Evolution, Current Practice and Future Directions.

The field of dental medicine is constantly evolving and advancing toward minimally invasive techniques. Several studies have demonstrated that bonding to the tooth structure, particularly enamel, yields the most predictable results. In some instances, however, significant tooth loss, pulpal necrosis, or irreversible pulpitis may limit the options available to the restorative dentist. In these cases, placement of a post and core followed by a crown is the preferred treatment option, provided all requirements are met. This literature review provides an overview of the historical development of dental FRC post systems as well as a comprehensive examination of the currently available posts and their bonding requirements. In addition, it offers valuable insights for dental professionals seeking to understand the current state of the field and the prospects of dental FRC post systems.

Surface properties and Streptococcus mutans biofilm adhesion of ion-releasing resin-based composite materials.

OBJECTIVE: To evaluate the adhesion of Streptococcus mutans (S. mutans) and related surface properties of ion-releasing resin-based composite (RBC) restorative materials. METHODS: Two ion-releasing RBCs, Activa (ACT) and Cention-N (CN), were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). Ten disk-shaped specimens were fabricated for each material (n = 40). After standardized surface polishing procedure, the surface properties of the specimens were evaluated using surface roughness measurements by a profilometer and hydrophobicity using water contact angle measurements. To assess bacterial adhesion, the number of S. mutans bacteria was calculated from colony-forming units (CFU). Confocal laser scanning microscope analysis was done for qualitative & quantitative assessment. The data were analyzed using One-way ANOVA followed by Tukey's post-hoc test to compare the mean values of surface roughness, water contact angle and CFU values. To compare the mean dead cell percentage Kruskal-Wallis rank test and Conover test were used. A p-value of ≤ 0.05 was used to report the statistical significance. RESULTS: Z350 and ACT had the smoothest surfaces, followed by CN, and the roughest surface was seen in FUJI-II-LC. The lowest water contact angles were seen in CN, and Z350, and the highest were in ACT. S. mutans counts were the highest in ACT and the lowest in Z350 and CN. CN and Fuji-II-LC registered the highest percentage of dead bacterial cells, while the lowest were in ACT. SIGNIFICANCE: Surface properties did not significantly influence bacterial adhesion. More S. mutans bacteria accumulated on ACT than on the nanofilled composite and on CN. CN had antibacterial effects against Streptococcus mutans biofilms.

Effect of Fibres on Physico-Mechanical Properties of Bulk-Fill Resin Composites.

OBJECTIVE: To measure the flexural strength (FS) of bulk-fill resin composites and assess their long-term water absorption and solubility properties with and without the inclusion of short glass fibres. METHODS: One resin composite, everX Flow with fibres, and four commercially available bulk-fill composites without fibres, namely, PALFIQUE, Activa, SDR Plus, and Filtek Bulk Fill One, were tested. Six specimens (2 × 2 × 25 mm) were fabricated for each material and stored in water for 1 day and 30 days to measure the flexural strength using a three-point bending test. To evaluate water absorption and solubility, circular disks measuring 15 × 2 mm (n = 5) were immersed in water for 60 days, and their weights were recorded periodically. After 60 days, the specimens were dried for an additional 21 days to determine solubility. RESULTS: Flexural strength values ranged from 101.7 to 149.1 MPa. Significant distinctions were observed among the resin composites at the onset of the study (p < 0.05). The highest FS value was identified in everX Flow, while ACT exhibited the lowest (p < 0.05). However, the flexural strength values exhibited a significant decrease with increased storage time (p < 0.05), except for ACT, which demonstrated a noteworthy increase. Concerning water absorption and solubility, ACT displayed the highest absorption, while the range of solubility varied from -0.88 to 5.8 µg/mm3. ACT also had the highest solubility, whereas everX Flow exhibited negative solubility. SIGNIFICANCE: The addition of short fibres, along with potential differences in matrix composition, enhanced the flexural strength of everX Flow. However, the substantial reduction in flexural strength observed in everX Flow and SDR following exposure to water corroborates the manufacturers' recommendation to apply a conventional resin composite cap on these materials.

Fabrication of Novel Pre-Polymerized BisGMA/Silica Nanocomposites: Physio-Mechanical Considerations.

Resin composite mimics tooth tissues both in structure and properties, and thus, they can withstand high biting force and the harsh environmental conditions of the mouth. Various inorganic nano- and micro-fillers are commonly used to enhance these composites' properties. In this study, we adopted a novel approach by using pre-polymerized bisphenol A-glycidyl methacrylate (BisGMA) ground particles (XL-BisGMA) as fillers in a BisGMA/triethylene glycol dimethacrylate (TEGDMA) resin system in combination with SiO2 nanoparticles. The BisGMA/TEGDMA/SiO2 mixture was filled with various concentrations of XL-BisGMA (0, 2.5, 5, and 10 wt.%). The XL-BisGMA added composites were evaluated for viscosity, degree of conversion (DC), microhardness, and thermal properties. The results demonstrated that the addition of a lower concentration of XL-BisGMA particles (2.5 wt.%) significantly reduced (p ≤ 0.05) the complex viscosity from 374.6 (Pa·s) to 170.84. (Pa·s). Similarly, DC was also increased significantly (p ≤ 0.05) by the addition of 2.5 wt.% XL-BisGMA, with the pristine composite showing a DC of (62.19 ± 3.2%) increased to (69.10 ± 3.4%). Moreover, the decomposition temperature has been increased from 410 °C for the pristine composite (BT-SB0) to 450 °C for the composite with 10 wt.% of XL-BisGMA (BT-SB10). The microhardness has also been significantly reduced (p ≤ 0.05) from 47.44 HV for the pristine composite (BT-SB0) to 29.91 HV for the composite with 2.5 wt.% of XL-BisGMA (BT-SB2.5). These results suggest that a XL-BisGMA could be used to a certain percentage as a promising filler in combination with inorganic fillers to enhance the DC and flow properties of the corresponding resin-based dental composites.

No-Cap Flowable Bulk-Fill Composite: Physico-Mechanical Assessment.

(1) Background: A newer class of flowable bulk-fill resin-based composite (BF-RBC) materials requires no capping layer (Palfique Bulk flow, PaBF, Tokuyama Dental, Tokyo, Japan). The objective of this study was to assess the flexural strength, microhardness, surface roughness, and color stability of PaBF compared to two BF-RBCs with different consistencies. (2) Methods: PaBF, SDR Flow composite (SDRf: Charlotte, NC, USA) and One Bulk fill (OneBF: 3M, St. Paul, MN, USA) were evaluated for flexural strength with a universal testing machine, surface microhardness using a pyramidal Vickers indenter, and surface roughness using a high-resolution three-dimensional non-contact optical profiler, a and clinical spectrophotometer to measure the color stability of each BF-RBC material. (3) Results: OneBF presented statistically higher flexural strength and microhardness than PaBF or SDRf. Both PaBF and SDRf presented significantly less surface roughness compared with OneBF. Water storage significantly reduced the flexural strength and increased the surface roughness of all tested materials. Only SDRf showed significant color change after water storage. (4) Conclusions: The physico-mechanical properties of PaBF do not support its use without a capping layer in the stress bearing areas. PaBF showed less flexural strength compared with OneBF. Therefore, its use should be limited to a small restoration with minimal occlusal stresses.

Influence of Eugenol and Its Novel Methacrylated Derivative on the Polymerization Degree of Resin-Based Composites.

The aim of this work was to assess the limiting rate of eugenol (Eg) and eugenyl-glycidyl methacrylate (EgGMA) at which the ideal degree of conversion (DC) of resin composites is achieved. For this, two series of experimental composites, containing, besides reinforcing silica and a photo-initiator system, either EgGMA or Eg molecules at 0-6.8 wt% per resin matrix, principally consisting of urethane dimethacrylate (50 wt% per composite), were prepared and denoted as UGx and UEx, where x refers to the EgGMA or Eg wt% in the composite, respectively. Disc-shaped specimens (5 × 1 mm) were fabricated, photocured for 60 s, and analyzed for their Fourier transform infrared spectra before and after curing. The results revealed concentration-dependent DC, increased from 56.70% (control; UG0 = UE0) to 63.87% and 65.06% for UG3.4 and UE0.4, respectively, then dramatically decreased with the concentration increase. The insufficiency in DC due to EgGMA and Eg incorporation, i.e., DC below the suggested clinical limit (>55%), was observed beyond UG3.4 and UE0.8. The mechanism behind such inhibition is still not fully determined; however, radicals generated by Eg may drive its free radical polymerization inhibitory activity, while the steric hindrance and reactivity of EgGMA express its traced effect at high percentages. Therefore, while Eg is a severe inhibitor for radical polymerization, EgGMA is safer and can be used to benefit resin-based composites when used at a low percentage per resin.

Gelatin-Chitosan Hydrogel Biological, Antimicrobial and Mechanical Properties for Dental Applications.

Chitosan, a natural polysaccharide sourced from crustaceans and insects, is often used with hydrogels in wound care. Evaluating its cytotoxicity and antimicrobial properties is crucial for its potential use in dentistry. OBJECTIVE: To investigate the mechanical properties of gelatin hydrogels based on decaethylated chitosan and antimicrobial activity against Streptococcus mutans and their biological effects with stem cells from apical papilla (SCAPs). MATERIAL AND METHODS: Gelatin-chitosan hydrogels were synthesized at concentrations of 0%, 0.2% and 0.5%. Enzymatic and hydrolytic degradation, along with swelling capacity, was assessed. Fourier transform infrared spectroscopy (FTIR) analysis was employed to characterize the hydrogels. The interaction between hydrogels and SCAPs was examined through initial adhesion and cell proliferation at 24 and 48 h, using the Thiazolyl Blue Tetrazolium Bromide (MTT assay). The antimicrobial effect was evaluated using agar diffusion and a microdilution test against S. mutans. Uniaxial tensile strength (UTS) was also measured to assess the mechanical properties of the hydrogels. RESULTS: The hydrogels underwent hydrolytic and enzymatic degradation at 30, 220, 300 min and 15, 25, 30 min, respectively. Significantly, (p < 0.01) swelling capacity occurred at 20, 40, 30 min, respectively. Gelatin-chitosan hydrogels' functional groups were confirmed using vibrational pattern analysis. SCAPs proliferation corresponded to 24 h = 73 ± 2%, 82 ± 2%, 61 ± 6% and 48 h = 83 ± 11%, 86 ± 2%, 44 ± 2%, respectively. The bacterial survival of hydrogel interaction was found to be 96 ± 1%, 17 ± 1.5% (p < 0.01) and 1 ± 0.5% (p < 0.01), respectively. UTS showed enhanced (p < 0.05) mechanical properties with chitosan presence. CONCLUSION: Gelatin-chitosan hydrogels displayed favorable degradation, swelling capacity, mild dose-dependent cytotoxicity, significant proliferation with stem cells from apical papilla (SCAPs), substantial antimicrobial effects against S. mutans and enhanced mechanical properties. These findings highlight their potential applications as postoperative care dressings.

Short fiber-reinforced resin-based composites (SFRCs); Current status and future perspectives.

One technique for placing of resin-based composite for large posterior cavities is the use of short fiber-reinforced resin-based composite (SFRC) to replace dentin in a biomimetic approach. As endurance under mastication cycles is a significant consideration in the clinical success of resin-based composite posterior restorations, the use of SFRC as a base material may prevent restorative fracture due to the fibers' effectiveness in stopping cracks. This review article specifies the characteristics of SFRC and describes the major underlying mechanisms of short fiber reinforcement for resin-based composite. Insights are further taken from laboratory studies used to define the short fiber-related properties of resin-based composite and the performance of currently available materials, focusing on aspects that are relevant to the reinforcement of resin-based composite. Finally, future standpoints on the development of SFRCs with nano fibers and different resin monomers, and their role in digital dentistry, are discussed.