Correlation between the size of released titanium particles and changes in the surface of dental implants during insertion into bone blocks: an in vitro study.

PURPOSE: This study investigated the size and amount of titanium particles immediately released following dental implant insertion into bovine bone blocks and aimed to correlate them with the surface roughness of the implants. METHODS: Twelve bone blocks were prepared from bovine mandibles. Six tapered (group A) and 6 cylindrical (group B) dental implants were inserted into the bone blocks under water irrigation, following the standard drilling protocol. After insertion, the implants were immediately removed from the bone. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy were performed to investigate the released titanium particles and implant surface roughness, respectively. The amount of titanium ions in the irrigation water was measured using inductively coupled plasma mass spectrometry. Dynamic light scattering (DLS) was used to determine the size range of the released titanium particles. RESULTS: The percentages of titanium content on the surface of implants decreased in both groups after implantation into bone blocks. SEM-EDX analysis confirmed the presence of titanium particles embedded in the implanted bone bed. Group B implants showed significantly higher concentrations of titanium ions in the collected water than group A implants (0.868 and 0.565 µg/L, respectively). Group A implants demonstrated high pre-implantation surface roughness, which led to a much greater decrease in post-implantation surface roughness than was observed for group B implants. DLS analysis showed that the titanium particles released from group A implants were within the nano-size range, whereas those released from group B implants were within the micro-size range. CONCLUSIONS: Dental implant placement leads to a decrease in implant surface roughness and the immediate release of titanium particles into the peri-implant bone. Variations in the size range and amount of released particles were correlated with implant surface roughness. This finding has clinical implications and warrants additional in vivo studies.

In vitro immunomodulatory effect of solid versus porous phosphate-based glass microspheres using macrophages.

This study aimed to investigate the immunomodulatory effect of two different forms of phosphate-based glass microspheres (solid and porous), on human macrophages. Human THP-1 monocytes were converted to M0 macrophages after being treated with 100 ng/mL phorbol 12-myristate 13-acetate for 48 h. The differentiated cells were analysed for the CD14 marker using flow cytometry. The adhesion, spreading, and viability of M0 macrophages grown directly or indirectly (extracts) at varying concentrations of solid and porous glass microspheres (GMs) were analysed via phase contrast microscopy, confocal microscopy, and XTT assay. The expression of IL-8, IL-1ß, IL-6, IL-10, TNF-α, and IL-12p70 cytokines was investigated using flow cytometry. The conversion to M0 macrophages was confirmed by their adherent nature, increased granularity, and CD14 expression. The results showed that both solid and porous GMs or extracts favored the attachment, spreading, and proliferation of macrophages in a comparable manner to cells grown in a normal tissue culture medium. Only the higher concentration of porous GMs (10 mg/mL) changed the morphology of M0 macrophages and increased the expression of IL-1ß and IL-8 pro-inflammatory cytokines; this could be related to the fast degradation nature of porous GMs. Of the six cytokines analysed, M0 macrophages grown directly or indirectly with GMs only expressed IL-1ß, IL-10, and IL-8. Accordingly, solid microspheres may have advantages as regenerative agents due to their controlled degradation.

Titanium Particles Modulate Lymphocyte and Macrophage Polarization in Peri-Implant Gingival Tissues.

Titanium dental implants are one of the modalities to replace missing teeth. The release of titanium particles from the implant's surface may modulate the immune cells, resulting in implant failure. However, little is known about the immune microenvironment that plays a role in peri-implant inflammation as a consequence of titanium particles. In this study, the peri-implant gingival tissues were collected from patients with failed implants, successful implants and no implants, and then a whole transcriptome analysis was performed. The gene set enrichment analysis confirmed that macrophage M1/M2 polarization and lymphocyte proliferation were differentially expressed between the study groups. The functional clustering and pathway analysis of the differentially expressed genes between the failed implants and successful implants versus no implants revealed that the immune response pathways were the most common in both comparisons, implying the critical role of infiltrating immune cells in the peri-implant tissues. The H&E and IHC staining confirmed the presence of titanium particles and immune cells in the tissue samples, with an increase in the infiltration of lymphocytes and macrophages in the failed implant samples. The in vitro validation showed a significant increase in the level of IL-1ß, IL-8 and IL-18 expression by macrophages. Our findings showed evidence that titanium particles modulate lymphocyte and macrophage polarization in peri-implant gingival tissues, which can help in the understanding of the imbalance in osteoblast-osteoclast activity and failure of dental implant osseointegration.

Effect of Thickness and Bonding Technique on Fatigue and Fracture Resistance of Feldspathic Ultra-Thin Laminate Veneers.

OBJECTIVES: To evaluate the fatigue and fracture resistance of ultra-thin laminate veneers (UTLV) with two different thicknesses and two different bonding protocols. MATERIALS AND METHODS: A total of 64 flat enamel surfaces were assigned to either 0.2 or 0.4 mm UTLV. The UTLV were further subdivided and assigned to one of two bonding techniques: adhesive resin cement(RC( or preheated restorative resin composite (HC) (n = 16). Eight samples were fatigued with 750,000 mechanical cycles and 8,000 thermal cycles between 5 and 55°C in a chewing simulator, and the failure mode was evaluated using a stereomicroscope and SEM. The other eight samples from each group were loaded to failure in a universal testing machine to test the fracture resistance. Fisher's exact Probability test was used to analyze the fatigue test results, and two-way analysis of variance and Bonferroni's test were used to analyze the fracture resistance test results. RESULTS: The difference in fatigue resistance between failure proportions in different groups was statistically different (p < 0.05). The 0.4-mm-thick UTLV had similar results regardless of the bonding technique, while 0.2-mm-thick UTLV only showed comparable results when cemented with preheated HC. No statistically significant difference was found in fracture resistance between the tested groups (p > 0.05). CONCLUSION: The Bonding technique and the thickness of the UTLV had impacted fatigue resistance but had no significant effect on the fracture resistance. bonding of UTLV with preheated composite increases their fatigue resistance. Different testing approaches delivered different results.

Immunomodulatory effect of IL-1RA in LPS-activated macrophage/dental pulp stem cells co-culture.

AIMS: Lipopolysaccharides (LPS)-activated human dental pulp stem cells (hDPSCs) and macrophage co-cultures showed downregulated TNF-α secretion that is modulated by hDPSCs through IDO axis, whereas the secretory levels of IL-1ß remained unchanged. Therefore, sustained production of IL-1ß could contribute to progressive dental pulp inflammation. However, the role of interleukin-1 receptor antagonist (IL-1RA) in downregulating the secretion of IL-1ß and TNF-α in LPS-activated M0/M1/M2 macrophage and hDPSCs co-culture has not been studied yet. Therefore, the aim of the present study was to determine the immunomodulatory role of blocking IL-1 receptors in DPSCs macrophage co-culture activated with LPS. METHODOLOGY: Human monocytic cell line THP-1 was polarized to M0, M1 and M2 macrophages and co-cultured with hDPSCs. The viability of the co-cultured cells was assessed by apoptosis assay. Co-cultures were activated with LPS followed by the assessment of gene expression and protein levels of IL-1ß and TNF-α with and without IL-1RA blocking via qRT-PCR and cytokine flex assay by flow cytometry. Data from three separate experiments were analysed using one-way anova followed by Tukey's post hoc test and a p-value of <.05 was considered statistically significant. RESULTS: THP-1-derived M0, M1 and M2 macrophages co-cultured with hDPSCs showed spindle and round-shaped cells, with >90% viability when assessed by apoptosis assay. Inflammatory TNF-α and IL-1ß profiles in stimulated co-cultures showed upregulated IL-1ß, whereas TNF-α was downregulated (p < .05). Anti-inflammatory gene expression levels of IL-10 and TGF-ß were downregulated (p < .05). Blocking with IL-1RA resulted in a remarkable decrease in IL-1ß at the gene expression and protein production levels whilst TNF-α levels remained low (p < .05). Levels of anti-inflammatory cytokine IL-10 showed no significant difference. CONCLUSION: Blocking the IL-1 receptor in hDPSCs and macrophage (M0, M1, M2) co-cultures activated with LPS resulted in downregulation of inflammatory cytokines IL-1ß and TNF-α. These findings highlight the immunomodulatory effect of IL-1RA in inflammatory conditions of dental pulp infections.

In Vitro Cytotoxicity and Mineralization Potential of an Endodontic Bioceramic Material.

OBJECTIVE: The interest in bioceramic materials has been steadily growing for different applications in endodontics. With the continued introduction of new bioceramic-based materials into the market, it is of great importance to assess the biocompatibility before providing recommendations on their clinical use. This study evaluated the in vitro cytotoxicity and mineralization potential of two consistencies of unset premixed bioceramic material (TotalFill BC RRM putty and TotalFill BC sealer) compared with an epoxy resin-based sealer (AH Plus) on osteoblast cells. MATERIALS AND METHODS: Overall, 100% extracts were obtained by weighing 0.1 g of each material in 1 mL of cell culture media. Primary human osteoblast (HOB) cells (n = 4) were treated with different concentrations (100, 50, 25, 12.50, and 6.25%) of each extract. XTT assay and Alizarin Red S staining were used to evaluate the cytotoxic effect and the biomineralization potential, respectively. STATISTICAL ANALYSIS: Data were analyzed by one-way analysis of variance followed by Tukey's post hoc tests. RESULTS: The cytotoxicity assay after 24 h treatment showed that all materials at high concentrations of the extract (100 and 50%) were toxic to HOB (p < 0.001). On the contrary to TotalFill BC RRM Putty, AH Plus and TotalFill BC sealer were toxic at 25% concentration. However, at 12.5% concentration and lower, all materials were nontoxic. The mineralization potential analyzed after 7 and 14 days showed that TotalFill BC material-treated cells could deposit mineralized nodules in the normal and osteogenic medium unlike AH plus-treated cells. CONCLUSION: At low concentrations, TotalFill BC materials showed higher biocompatibility to HOB cells than AH Plus, enhanced the viability of the cells, maintained their typical morphology, and induced the formation of mineralized nodules. Despite the encouraging data, clinical trials are needed to identify the effect of this material on the long-term outcome of endodontic treatment.

Synthesis and Biocompatibility Evaluation of PCL Electrospun Membranes Coated with MTA/HA for Potential Application in Dental Pulp Capping.

This study aimed to develop polycaprolactone (PCL) electrospun membranes coated with mineral trioxide aggregate/hydroxyapatite (MTA/HA) as a potential material for dental pulp capping. Initially, the PCL membrane was prepared by an electrospinning process, which was further surface coated with MTA (labeled as PCLMTA) and HA (labeled as PCLHA). The physico-chemical characterization of the fabricated membranes was carried out using field emission scanning electron microscopy (FE-SEM)/Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy, and contact angle analysis. The biocompatibility of the human dental pulp stem cells (hDPSCs) on the fabricated membranes was checked by XTT assay, and the hDPSCs adhesion and spreading were assessed by FE-SEM and confocal microscopy. The wound healing ability of hDPSCs in response to different electrospun membrane extracts was examined by scratch assay. The surface morphology analysis of the membranes by FE-SEM demonstrated a uniform nanofibrous texture with an average fiber diameter of 594 ± 124 nm for PCL, 517 ± 159 nm for PCLHA, and 490 ± 162 nm for PCLMTA. The elemental analysis of the PCLHA membrane indicated the presence of calcium and phosphorous elements related to HA, whereas the PCLMTA membrane showed the presence of calcium and silicate, related to MTA. The presence of MTA and HA in the PCL membranes was also confirmed by Raman spectroscopy. The water contact analysis demonstrated the hydrophobic nature of the membranes. The results indicated that PCL, PCLHA, and PCLMTA membranes were biocompatible, while PCLMTA exhibited better cell adhesion, spreading, and migration.

In Vitro Enamel Remineralization Efficacy of Calcium Silicate-Sodium Phosphate-Fluoride Salts versus NovaMin Bioactive Glass, Following Tooth Whitening.

OBJECTIVES: This study aimed to evaluate the effect of in-office bleaching on the enamel surface and the efficacy of calcium silicate-sodium phosphate-fluoride salt (CS) and NovaMin bioactive glass (NM) dentifrice in remineralizing bleached enamel. MATERIALS AND METHODS: Forty extracted premolars were sectioned mesio-distally, and the facial and lingual enamel were flattened and polished. The samples were equally divided into nonbleached and bleached with 38% hydrogen peroxide (HP). Each group was further divided according to the remineralization protocol (n = 10); no remineralization treatment (nontreated), CS, or NM, applied for 3 minutes two times/day for 7 days, or CS combined with NR-5 boosting serum (CS+NR-5) applied for 3 minutes once/day for 3 days. The average Knoop hardness number (KHN) and surface roughness (utilizing atomic force microscopy) were measured. Surface topography/elemental analysis was analyzed by using scanning electron microscopy/energy dispersive X-ray analysis. All the tests were performed at baseline, after bleaching, and following each remineralization protocol. Data were statistically analyzed by two-way analysis of variance and Bonferroni post hoc multiple comparison tests (α = 0.05). RESULTS: HP significantly reduced KHN and increased roughness (p < 0.05). All remineralization materials increased the hardness and reduced the surface roughness after bleaching except NM, which demonstrated significantly increased roughness (p < 0.05). Ca/P ratio decreased after bleaching (p < 0.05), and following treatment, CS and CS+NR-5 exhibited higher remineralization capacity in comparison to NM (p < 0.05). CONCLUSION: Although none of the material tested was able to reverse the negative effect of high-concentration in-office HP on enamel completely, the remineralization efficacy of CS and CS+NR-5 was superior to that of NM.

Adhesive luting to hybrid ceramic and resin composite CAD/CAM Blocks:Er:YAG Laser versus chemical etching and micro-abrasion pretreatment.

PURPOSE: To evaluate the effect of Er:YAG laser on the roughness, surface topography, and bond strength to resin luting cement based on chemical and micro-abrasion pretreatments of different computer-aided design/computer-aided manufacturing materials. METHODS: A polymer-infiltrated-ceramic-network (PICN) material (Vita Enamic, VE), three indirect resin composite (Cerasmart, CS; Shofu HC, SH; Lava Ultimate, LU), and one lithium disilicate ceramic (IPS e.max CAD, EM) blocks were subjected to one of the following pretreatments: no treatment (NC ), Er:YAG etching with one of two powers (either 3 or 6 W), hydrofluoric acid (HF) etching, self-etching ceramic primer (ME), or micro-abrasion (MA). The shear bond strength (SBS) of resin luting cement to pretreated materials was tested. Surface roughness was measured via atomic force microscopy, and surface topography was analyzed via scanning electron microscopy. Two-way analysis of variance, Tukey post-hoc test, and Pearson correlation were applied. RESULTS: Etching EM and VE with HF or the ME resulted in the highest SBS values in their groups (P < 0.05). LU, SH, VE, and CS indicated similar SBS values when treated with 3 W, 6 W, and MA. The highest surface roughness (Sa ) values were obtained for the LU, CS, and VE groups when treated with 6 W, whereas the lowest Sa values were obtained for CS when treated with the ME and EM when treated with the ME or 3 W. Only SH and CS indicated a significant correlation between surface rough ness and bond strength. CONCLUSIONS: Er:YAG laser etching is comparable to micro-abrasion when treating resin composite blocks and may induce fewer surface cracks. HF etching remains the gold standard for the treatment of glass-based ceramics and PICNs.