Bond strength of resin-based restorative materials to fast-setting calcium silicate cement using different resin adhesive systems.

This study assessed the bond strength of resin-based restorative materials to fast-setting calcium silicate cement (Aarhus Uinversity, Denmark) when treated with each of two one-bottle universal adhesive systems. The cement surface (N = 256) was treated with a self-priming adhesive and a self-etch phosphate monomer-containing adhesive with and without etching of the cement surface. Specimens then received either resin composite or compomer restorative materials (n = 32). The bond strength was measured after 1 day and 1500 thermocycles (n = 16). The failure type was visually inspected. The cement-adhesive-restorative material interface was visualized using scanning electron microscopy (SEM). The data were analyzed using multiple linear regression. Restorative material type, resin adhesive system, and thermocycling had a statistically significant effect on the bond strength. Compomer restorative material and self-etch universal adhesive system demonstrated statistically significantly higher bond strength values to fast-setting calcium silicate cement, predominantly exhibiting cement cohesive failure. Etching the cement surface enhanced the bond strength of the self-priming universal adhesive. Thermocycling significantly reduced the bond strength. SEM showed self-etch universal adhesive seemingly diffused over the etched cement surface compared to other groups. Self-etch phosphate monomer-containing universal adhesive and compomer resulted in the highest bond strength to fast-setting calcium silicate cement.

Influence of universal adhesives and silane coupling primer on bonding performance to CAD-CAM resin-based composites: A laboratory investigation.

OBJECTIVE: Obtaining strong resin bonds to computer-aided design and computer-aided manufacturing (CAD-CAM) resin-based composites with dispersed fillers (CCRBCs) poses a challenge. Therefore, this study aimed to assess the effect of three universal adhesives and a two-component silane coupling agent on the shear bond strength to three (CCRBCs). MATERIALS AND METHODS: Eight hundred and sixty-four specimens of Brilliant Crios, Lava Ultimate, and Tetric CAD were polished or grit blasted, bonded with Adhese Universal DC, One Coat 7 Universal (OC7), and Scotchbond Universal Plus Adhesive (SBU) with or without a silane primer. Shear bond strength was measured after 24 h and 10,000 thermocycles. Linear regressions were performed (α = 0.05). RESULTS: After thermocycling, bond strengths were similar for the universal adhesives on polished Brilliant Crios and Lava Ultimate (p ≥ 0.408). Grit blasted Tetric CAD showed no significant differences (p ≥ 0.096). The silane primer had minimal impact on grit blasted Tetric CAD (p ≥ 0.384). The silane primer increased the bond strength of OC7 to Brilliant Crios (p = 0.001) but decreased the adhesion of SBU to Brilliant Crios and Lava Ultimate (p ≤ 0.018). CONCLUSIONS: Bond strength of universal adhesives varied with CCRBC type. The two-component silane coupling agent showed mixed effects on adhesive performance. CLINICAL SIGNIFICANCE: Selecting universal adhesives from the same CCRBC product line does not always guarantee superior bond strength. The efficacy of silane coupling agents differs based on the bonding substrate.

Effect of ionizing radiation on the shear bond strength of two different adhesive systems in primary teeth. in-vitro study.

BACKGROUND: Radiotherapy is a treatment modality used for head and neck cancer patients. It has a negative influence on bonding strength of adhesives. Little information is available about the effect of radiotherapy on bonding strength of adhesives in primary teeth. Therefore, this in vitro study aimed to detect the best adhesive system and ideal time to apply restorations in primary irradiated teeth regarding adhesive shear bond strength. METHODS: Dentin samples from primary teeth were randomly assigned to four groups based on restoration application time and radiation exposure, (G1: control, G2: preradiation, G3: 24 h postradiation, and G4: 6 months postradiation) with 20 samples per group. These groups were further divided into 2 subgroups according to the adhesive system used, with 10 samples per subgroup. (1) 3M™ Single Bond Universal Adhesive (SB), (2) 3M AdperSingle Bond 2 (AS). Samples were exposed to gamma radiation from a cobalt-60 machine. One shot of 60 Gy of radiation was delivered. Then samples were subjected to a shear bond strength test. The load was applied until failure and the maximum load was recorded. Numerical data are presented as mean and standard deviation values, then distributed according to Shapiro-Wilk test or Levene's test and analyzed via two-way ANOVA. The significance level was set at p < 0.05 for all tests. Statistical analysis was performed with R statistical analysis software version 4.4.1 for Windows (Team RC, R: A language and environment for statistical computing. R foundation for statistical computing, 2023). RESULTS: Compared with the AS subgroup, the SB subgroup presented significantly greater values (p < 0.001). For SB, there was no significant difference among the G1 and G4 groups (p > 0.001). However, there was a significant difference between G1, G2, and G3 (p < 0.001, P = 0.025, P = 0.265 ns respectively), and G3 presented the lowest values. For AS, there was no significant difference between groups G1 and G4 (p = < 0.001). Compared with the other groups, G3 presented a significant difference (p = 0.265 ns) and the lowest results. CONCLUSION: Restorations performed 24 h after radiation had lower bond strength than those performed six months after radiation. Regardless of the adhesive system used, SB performed better than AS in terms of the shear bond strength.

Influence of geometric dimensions on early failures of adhesively retained composite resin core build-ups.

OBJECTIVE: To determine the influence of the geometric dimensions of core build-ups on early core build-up failure, that is, loss before definitive prosthesis cementation. MATERIALS AND METHODS: Adhesive core build-ups of exclusively vital teeth in 114 participants were evaluated (n materials: 40 Rebilda DC, 38 Multicore Flow, 36 Clearfil DC Core; n teeth: 8 incisors, 54 premolars, 52 molars). Impressions of the abutment teeth were made (1) after removal of insufficient restorations/caries and (2) after core build-up and preparation for a fixed prosthesis. Digitized model surfaces of both situations were aligned (Geomagic Design X) and core build-up volume (VCBU ), remaining hard tissue volume (VAbut ), and size of the adhesive surface (Aadh ) were assessed. The derived measure dCBU  = VCBU /Aadh can be interpreted as mean arithmetic core build-up thickness. Associations between participant or core build-up design characteristics and the occurrence of early failures were statistically evaluated (SPSS v27, α = 0.05). RESULTS: A total of six (5.3%) core build-up failures were registered. Higher participant age, greater core build-up volume VCBU and greater arithmetic uniform thickness dCBU were associated with a greater incidence of failure in bivariate and univariate, however, not in multivariate statistics. CONCLUSIONS: Core build-up volume and thickness were associated with early success or failure. CLINICAL SIGNIFICANCE: In the case of voluminous/thick core build-ups in relation to the adhesive surface, additional measures, such as the preparation of retentive elements to increase the bonding area, might be considered to reduce the risk of early core build-up failure.

Development of Proanthocyanidin-Loaded Mesoporous Silica Nanoparticles for Improving Dental Adhesion.

Dentin biomodification is a promising approach to enhance dental tissue biomechanics and biostability for restorative and reparative therapies. One of the most active dentin tissue biomodifiers is proanthocyanidin (PAC)-rich natural extracts, which are used in the dental bonding procedure in combination with resin-based adhesives (RBAs). This study aimed to investigate the use of mesoporous silica nanoparticles (MSNs) for the sustained delivery of PACs for dentin biomodification as a novel drug-delivery system for dental applications. The effects of the incorporation of MSN functionalized with 3-aminopropyltriethoxysilane (APTES) and loaded with PAC into an experimental RBA were assessed by characterizing the material mechanical properties. In addition, the immediate and long-term bonding performance of an experimental resin-based primer (RBP) containing MSN-APTES loaded with PAC was also evaluated. For that, different formulations of RBA and RBP were prepared containing 20% w/v MSN-APTES loaded with PAC before or after functionalization (MSN-PAC-APTES and MSN-APTES-PAC, respectively). The incorporation of MSN-APTES-PAC did not negatively impact the degree of conversion or the overall mechanical properties of the RBA. However, adding MSN-PAC-APTES resulted in inferior mechanical properties of the experimental RBA. In the adhesion studies, APTES-functionalized MSN was successfully added to an experimental RBP for drug-delivery purposes without compromising the bond strength to the dentin or the failure mode. Interestingly, the sequence of surface functionalization with APTES resulted in differences in the bonding performance, with better long-term results for RBP containing MSN loaded with PAC after functionalization.

Effect of mold enclosure and chisel design on fatigue bond strength of dental adhesive systems.

To examine the effect of mold enclosure and chisel design on macro shear fatigue bond strengths of dental adhesive systems. The fatigue bond strength testing was conducted with two commercially available dental adhesive systems, (1) OptiBond eXTRa and (2) Scotchbond Universal, for bonding a resin composite (Filtek Supreme Ultra) to both enamel and dentin using a mold enclosure and a non-mold enclosure with a knife-edge and two sized notched-edge chisel assemblies for loading. As a loading reference for the fatigue testing, macro shear bond strengths of the adhesive systems to enamel and dentin were conducted using a mold enclosure and a knife-edge chisel assembly. The shear bond strengths with the mold enclosure using knife-edge chisel assembly did not exhibit a significant difference between the adhesive systems for either enamel or dentin. The fatigue bond strengths of bonded specimens demonstrated significant differences when comparing the mold enclosure and non-mold enclosure, but not between knife-edge and notched-edge chisel assemblies. The fatigue bond strengths of dental adhesive systems demonstrated significantly higher values when using mold-enclosed bonded specimens than a non-mold enclosure, regardless of type of chisel assembly.

Review of nano-technology applications in resin-based restorative materials.

OBJECTIVE: Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles. MATERIALS AND METHODS: A literature review was conducted using PubMed/Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included. RESULTS: A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported. CONCLUSIONS: The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future. CLINICAL SIGNIFICANCE: In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems.

Reconfigurable Dual Peptide Tethered Polymer System Offers a Synergistic Solution for Next Generation Dental Adhesives.

Resin-based composite materials have been widely used in restorative dental materials due to their aesthetic, mechanical, and physical properties. However, they still encounter clinical shortcomings mainly due to recurrent decay that develops at the composite-tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal this interface, but the adhesive seal is inherently defective and readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite-tooth interface and bacterial by-products demineralize the tooth and erode the adhesive. These activities lead to wider and deeper gaps that provide an ideal environment for bacteria to proliferate. This complex degradation process mediated by several biological and environmental factors damages the tooth, destroys the adhesive seal, and ultimately, leads to failure of the composite restoration. This paper describes a co-tethered dual peptide-polymer system to address composite-tooth interface vulnerability. The adhesive system incorporates an antimicrobial peptide to inhibit bacterial attack and a hydroxyapatite-binding peptide to promote remineralization of damaged tooth structure. A designer spacer sequence was incorporated into each peptide sequence to not only provide a conjugation site for methacrylate (MA) monomer but also to retain active peptide conformations and enhance the display of the peptides in the material. The resulting MA-antimicrobial peptides and MA-remineralization peptides were copolymerized into dental adhesives formulations. The results on the adhesive system composed of co-tethered peptides demonstrated both strong metabolic inhibition of S. mutans and localized calcium phosphate remineralization. Overall, the result offers a reconfigurable and tunable peptide-polymer hybrid system as next-generation adhesives to address composite-tooth interface vulnerability.

Ultra-morphological characteristics of dentin surfaces after different preparations and treatments.

Using transmission electron microscopy (TEM), this study investigated the characteristics of smear layers after preparation of dentin surfaces using different methods. In addition, this study analyzed, using scanning electron microscopy (SEM), the interactions of smear layers with the various acidic agents used subsequently to treat the dentin surface. Mid-coronal dentin surfaces were prepared according to one of five instrumentation methods: fracture; grinding with carbide bur; grinding with regular-grit diamond bur; grinding with superfine-grit diamond bur; or grinding with 600-grit silicon carbide (SiC) abrasive paper. Then, each prepared dentin surface was further divided into control (no further treatment) or treatment with one of the following agents: phosphoric acid solution (PAS); phosphoric acid gel (PAG); Clearfil SE Bond 2 Primer (SE2); or Scotchbond Universal Adhesive (SBU). Longitudinal ultra-thin sections were made for TEM observations. Dentin discs, representing each surface preparation and treatment method described above, were created, and the morphology was examined by SEM. The TEM results revealed differences in thickness and denseness of the smear layer, according to the different methods of instrumentation used to prepare the dentin surface. The two forms of phosphoric acid completely removed the smear layer in all groups. Agglomerated silica particles were observed on the top of the collagen layer after etching with PAG. For all dentin surfaces, except for that prepared with SiC, SE2 demonstrated better etching efficacy on different smear layers, whereas SBU provided only superficial interaction.

Influence of 38% silver diamine fluoride application on bond stability to enamel and dentin using universal adhesives in self-etch mode.

In order to evaluate the influence of 38% silver diamine fluoride (SDF) application on enamel and dentin bond stability of universal adhesives in self-etch mode, a 38% SDF and three universal adhesives were used in this study. Initial shear bond strength (ISBS), fatigue bond strength (FBS), and shear bond strength of survivors (SBSS) to enamel and dentin of universal adhesives in self-etch mode, with and without SDF application, were determined. SDF was applied to the polished enamel or dentin surface for 1 min, water-rinsed and air-dried for comparison with controls. The universal adhesives were applied to the prepared samples and composite resin was bonded using a mold-enclosed method. Enamel bond stability of universal adhesives with SDF (ISBS: 14.7-20.4 MPa; FBS: 5.5-7.4 MPa and SBSS: 14.4-21.5 MPa) was significantly weaker than those without SDF (ISBS: 28.0-29.2 MPa; FBS: 12.1-15.6 MPa and SBSS: 28.4-34.4 MPa). Dentin bond stability with SDF (ISBS: 14.8-20.9 MPa; FBS: 7.1-8.2 MPa and SBSS: 17.3-21.8 MPa) was also significantly weaker than without SDF (ISBS: 19.3-36.1 MPa; FBS: 11.0-13.7 MPa and SBSS: 22.2-34.6 MPa). The results suggest that SDF application on enamel and dentin reduces the bond stability of universal adhesives in self-etch mode.

Methacrylate perspective in current dental practice.

OBJECTIVE: To provide a current perspective concerning dental personnel sensitivity to methacrylate materials. OVERVIEW: Methacrylate related sensitivity and allergies are currently beyond traditional thoughts concerning denture base resins and methyl methacrylate provisional materials. Methacrylates are now ubiquitous in current dental practice and dental personnel should be aware that dental adhesives contain potent sensitizers that may also cross-sensitize individuals to other methacrylates not experienced. The growing sensitivity to 2-hydroxyethyl methacrylate (HEMA) has been described to be epidemic in nature due to the artificial nail industry with dental patients and dental personnel may be more susceptible to dental methacrylate sensitization. While contact dermatitis remains the most prevalent methacrylate-related clinical presentation, respiratory complications and asthma are increasing associated with methacrylate exposure. While additional personal protective equipment (PPE) is thought to be first protective choice, the National Institute for Occupational Safety and Health (NIOSH) considers PPE overall largely ineffective and should be considered only as a last resort. CONCLUSION: Dental personnel need to be more aware of methacrylate sources and use workplace control measures to limit methacrylate exposures to both dental personnel and patients. CLINICAL SIGNIFICANCE: Sensitivity to methacrylate materials is a growing dental workplace major concern and dental personnel should be aware of both the methacrylate content of current materials and the products that contain ingredients with the most sensitization potential.

In vitro performance of 2-step, total etch adhesives modified by thiourethane additives.

OBJECTIVES: Thio-urethane oligomeric additives have been shown to improve the mechanical properties of dental composites and resin cements. To try to harness those same properties in dental adhesives, in this study, these oligomers (TU) were added to the matrix and/or as filler functionalization of experimental adhesives, and the effects on conversion and mechanical properties were analyzed. METHODS: BisGMA and HEMA (60/40 wt%) were used as the monomer matrix, made polymerizable by the addition of 0.2 wt% 2,2-dimethoxy-2- phenylacetophenone. 2,6-di-tert-butyl-4-methylphenol was added at 0.5 wt% as the inhibitor. This material was used as the unfilled control (BH). TU oligomers were added at 20 wt % to the matrix (BH+20%TU, unfilled) and/or used as filler functionalization (TF, 10 wt%). Fillers functionalized with methacrylate (MF, 10 wt%) served as the control. The experimental adhesives groups containing fillers were: BH+10%MF; BH+10%TF; BH+20%TU+10%MF; BH+20%TU+10%TF. Flexural properties were tested in three-point bending (wet and dry). Polymerization kinetics was followed in real-time in near-IR. Water Sorption/Solubility (WS/SL, ISO 4049) and Viscosity (rotational rheometry) were also evaluated. For Microtensile bond strength 40 vol% ethanol was added to adhesives, which was applied onto sound dentin from third human molars. The data were analyzed with one-way ANOVA and Tukey post-hoc test, and test t for the comparison between storage time of the microtensile bond strength test (alpha = 0.05). RESULTS: There was no significant difference between groups when yield strength (YS) and flexural modulus (FM) were evaluated in dry conditions. After water storage, all the groups containing TU in the matrix showed statistically lower YS/FM values. This was true in spite of the statistically higher conversion for those same groups. The maximum rate of polymerization (Rpmax) was higher for BH+10%TF and no significant difference was found for the groups BH and BH+10% MF. The lowest Rpmax values were found for BH+20%TU+10%TF and BH+20%TU. BH+20%TU+10%TF showed the highest viscosity values followed by BH+20%TU+10%MF and BH+20%TU, with statistically significant difference between them. For the microtensile bond strength test at 24h (p = 0.13) and 6 months (p = 0.11) and WS/SL (p > 0.05), no significant difference was found among groups. The storage time (24 h and 6 months) did not affect the microtensile bond strength results. CONCLUSION: In spite of improving the conversion, the addition of TU in the matrix reduced the mechanical properties of the adhesives tested after water storage. This did not affect the bond strength at 24 h or 6 months.

Modifying Adhesive Materials to Improve the Longevity of Resinous Restorations.

Dental caries is a common disease on a global scale. Resin composites are the most popular materials to restore caries by bonding to tooth tissues via adhesives. However, multiple factors, such as microleakage and recurrent caries, impair the durability of resinous restorations. Various innovative methods have been applied to develop adhesives with particular functions to tackle these problems, such as incorporating matrix metalloproteinase inhibitors, antibacterial or remineralizing agents into bonding systems, as well as improving the mechanical/chemical properties of adhesives, even combining these methods. This review will sum up the latest achievements in this field.

Can universal adhesive systems bond to zirconia?

OBJECTIVE: To measure the bond strength to zirconia subjected to different surface treatments of universal bonding agents. MATERIALS AND METHODS: Eighty blocks of zirconia were obtained by CAD/CAM milling. The blocks were embedded into PVC tubes, polished sequentially with increasing granulation sandpapers and divided into two groups according to surface treatment: polished or grit-blasted with alumina particles. Each group was then subdivided by bonding agent employed: Z-Prime Plus (control); Scotchbond Universal; All Bond Universal; and Z-Prime Plus + All Bond Universal. Cylindrical composite resin build-ups were constructed atop the blocks using a two-part metal die. Specimens were stored for 24 hours and subjected to microshear bond strength testing. Statistical analyses were performed by means of the F-test (ANOVA), Student's t and Tukey's test. After sputter coating, zirconia surfaces and adhesive interfaces were analyzed by scanning electron microscopy (SEM). RESULTS: Bond strength was superior for grit-blasted zirconia. In specimens with this surface treatment, there were no significant differences between experimental groups. On SEM, blasted surfaces exhibited areas of micromechanical retention and adhesive interfaces exhibited areas of zirconia-adhesive interlocking. CONCLUSION: Universal adhesive systems were able to bond to zirconia. The interlocking promoted by grit-blasting enhanced bond strength. CLINICAL SIGNIFICANCE: Universal adhesive systems simplify bonding to zirconia and enable intraoral repair of fractures.

Effect of Light Cure Methods for Intermediate Adhesive Layer on Microleakage of Sealants. An in Vitro Study.

Background: The objective of this study was to determine the effect of an adhesive layer and its photopolymerization on the microleakage of sealants. Study design: 0.5mm-deep standardized fissurectomies were performed on extracted molars (n = 72). Teeth were randomly assigned to 3 different sealant materials (n = 24/group). Teeth were further divided to receive sealants with or without an adhesive layer. Each sealant with adhesive was also divided into two groups: adhesive was light-cured separately or light cured together with the sealant. Following thermocycling, microleakage was assessed using dye penetration and image analysis. Data was analyzed using ANOVA and Tukey's studentized ranged HSD tests. Results: Microleakage was not affected by type of sealant material (p>0.05) but was significantly influenced by application (p<0.05). Overall, placement of sealants without adhesive displayed greater microleakage than sealants with uncured adhesive (p<0.05). Within individual sealant types, this difference was only significant for Ultraseal XT (p<0.05). Sealants bonded with and without prior light curing did not show a significant difference in levels of leakage (Tukey's Studentized Range Test, p>0.05). Conclusion: An adhesive layer should be placed beneath sealants, but whether it should be light cured or left uncured before sealant placement varies by the sealant type.

Determining Optimal Fluorescent Agent Concentrations in Dental Adhesive Resins for Imaging the Tooth/Restoration Interface.

Fluorescent dyes like Rhodamine B (RB) have been used to identify the spatial distribution of adhesive restorative materials in the tooth/restoration interface. Potential effects of the addition of RB to dental adhesives were addressed in the past, but no further information is available on how to determine suitable concentrations of RB in these bonding agents for imaging in the confocal laser scanning microscope. This study provides systematical strategies for adding RB to viscous dental adhesive resins, focusing on the determination of the lowest range of dye concentrations necessary to achieve an acceptable image of the dentin/adhesive interface. It was demonstrated that optimized images of the resin distribution in dentin can be produced with 0.1-0.02 mg/mL of RB in the (tested) adhesives. Our approaches took into account aspects related to the dye concentration, photophysical parameters in different host media, specimen composition and morphology to develop a rational use of the fluorescent agent with the resin-based materials. Information gained from this work can help optimize labeling methods using dispersions of low-molecular-weight dyes in different monomer blend systems.

Effect of desensitizing agents on the microtensile bond strength of two-step etch-and-rinse adhesives to dentin.

Desensitizers can be used to control postoperative sensitivity in adhesive restorations. The aim of this study was to evaluate the effect of desensitizing agents on the bond strength of two-step etch-and-rinse adhesive systems to dentin. Forty-two human molars were sectioned to obtain 3-mm-thick dentin discs. The discs were divided into three groups (n = 14 in each) - no-treatment control group (CT), and oxalic acid [BisBlock (BB)] and calcium phosphate [Desensibilize Nano-P (NP)] desensitizers - before the application of two adhesive systems [Adper Single Bond Plus (SB) and One-Step Plus (OSP)]. A nanoparticle composite resin was used to create a 3-mm-thick build-up. The specimens were stored in distilled water for 24 h before a microtensile bond-strength test was performed. The failure modes were determined using a stereomicroscope at 100 × magnification. Specimens were sectioned perpendicular to the interface for scanning electron microscopy analyses. The CT-SB group exhibited the highest bond strength, differing significantly from BB-SB and BB-OSP groups. Mixed failures were prevalent for all groups. Scanning electron microscopy revealed a continuous hybrid layer and resin tags in all groups. Dentin bond strength of etch-and-rinse adhesive systems was reduced by an oxalic acid desensitizer but was not affected by a calcium phosphate-containing desensitizer.

Influence of light-curing distance on degree of conversion and cytotoxicity of etch-and-rinse and self-etch adhesives.

BACKGROUND: The degree of conversion (DC) of resin based materials depends, beside other factors, on the light-intensity applied during light curing. A lower DC might be correlated with an increased cytotoxicity of the respective materials. Therefore, aim of the present study was to investigate the influence of the distance between light-curing tip and adhesives on their cytotoxicity and degree of conversion (DC). METHODS: For the cytotoxicity assay, a total of 98 bovine dentine samples were prepared, distributed to seven groups (G1-G7; n = 14) and treated as follows: G1: untreated; G2-G4: OptiBond FL; G5-G7: OptiBond All-In-One. Adhesives were light-cured (1200 mW/cm(2)) at 1 mm (G2;G5), 4 mm (G3;G6) or 7 mm (G4;G7) distance. Samples were stored in culture media for 24 h and extracts were added to cell cultures (dental pulp cells and gingival fibroblasts) for a further 24 h. Finally, released lactate dehydrogenase activity (LDH) was photometrically determined, as measure for the cytotoxic effects of the extracts. The cytotoxicity assay was performed three times. Additionally, the DC of the adhesives was determined by FTIR spectroscopy. DC measurements were performed five times. RESULTS: For both cell types, no significant difference of LDH release was observed between untreated control group (G1) and treated groups G2-G7 (p > 0.05, respectively), between the groups treated with same adhesive and light-cured at different distance (p > 0.05, respectively), as well as between groups treated with different adhesives and light-cured at the same distance (p > 0.05, respectively). Within the respective adhesive, no significant difference in the DC was observed when light-cured at different distance (p > 0.05, respectively), while OptiBond FL showed significantly higher DCs compared to OptiBond All-In-One when light-cured at same distances (p < 0.05, respectively). CONCLUSIONS: The distance between light-curing tip and adhesive surface does not significantly influence either the cytotoxicity or the DC of the tested adhesives.

Thirty-year follow-up of a TMD case treated based on the neuromuscular concept.

AIM: Occlusal therapy is employed to alleviate the symptoms of a temporomandibular disorder (TMD) at times. However, the long-term effect of occlusal therapy in the masticatory system is not well understood. This case study aims to present a 30-year follow-up of a TMD case. METHODOLOGY: The patient developed TMD with intermittent closed lock of the left temporomandibular joint (TMJ). Chief complaints included trismus, pain, and noise of the left TMJ during function. The patient's occlusal disharmony was assessed with use of electronic instruments and corrected based on the neuromuscular concept. A minimum-invasive and reversible approach using adhesive occlusal restorations was used. RESULTS: The jaw movement and masticatory muscle activity assessed at the 7- and 23-year follow-ups revealed that the established occlusion was well adapted, and re-established the patient's functional occlusion system. The patient has been free from TMD symptoms with the corrected occlusion for 30 years. CONCLUSIONS: Occlusal reconstruction based on the neuromuscular concept can be stably integrated into the patient's functional occlusion system.

Assessment of 10-MDP and GPDM monomers on viability and inflammatory response in human dental pulp stem cells.

OBJECTIVES: to assess the cytotoxicity of the following functional monomers used in dental adhesives: 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) and glycerol phosphate dimethacrylate (GPDM), and their effect on cytokine release from human dental pulp stem cells (hDPSCs). METHODS: The hDPSCs cells were isolated from the dental pulp of extracted human third molars. The functional monomers, 10-MDP and GPDM, were diluted in dimethyl sulfoxide (DMSO) at concentrations ranging from 1 to 4 mM. Cells not exposed to the compounds served as controls. The hDPSCs were seeded into 96-well plates and incubated for 48 h. Subsequently, the cells were exposed to 10-MDP and GPDM for 24 h. Then, the culture medium was removed, the mitochondrial metabolism was evaluated using the MTT assay, while cell death analyzed by flow cytometry. Cytokine release (IL-1ß, IL-6, IL-8, IL-10, TNF-α) was analyzed by the MAGPIX. The data were analyzed using one-way ANOVA and Tukey's test. RESULTS: 10-MDP demonstrated significant toxicity to hDPSCs, reaching the IC50 at 3 mM. However, its impact on cytokine release was minimal, resulting only in IL-6 and IL-8 levels. GPDM exhibited lower toxicity, even at 4 mM, but induced an increase in IL-1ß release and a reduction in IL-6, IL-8, and IL-10 levels, with no effect on TNF-α. Despite the MTT assay results indicating cytotoxicity, the cell death was low for both functional monomers. SIGNIFICANCE: 10-MDP exhibited significant toxicity to hDPSCs, unlike GPDM, however, both monomers resulted in minimal cell death. 10-MDP had a minor impact on cytokine release, whereas GPDM demonstrated a potential to trigger an inflammatory reaction, particularly in the short term.