Leaching and cytotoxicity of bismuth oxide in ProRoot MTA - A laboratory investigation.

AIM: The present study examined the leaching and cytotoxicity of bismuth from ProRoot MTA and aimed to identify whether bismuth leaching was affected by the cement base and the immersion regime used. METHODOLOGY: The leaching profile of bismuth was examined from ProRoot MTA and compared with hydroxyapatite containing 20% bismuth oxide as well as hydroxyapatite and tricalcium silicate to investigate whether bismuth release changed depending on the cement base. Bismuth leaching was determined after 30 and 180 days of ageing immersed in Dulbecco's modified Eagle's medium (DMEM) using mass spectroscopy (ICP-MS). The media were either unchanged or regularly replenished. The pH, surface microstructure and phase changes of aged materials were assessed. Wistar rat femoral bone marrow stromal cells (BMSCs) and cutaneous fibroblasts were isolated, cultured and seeded for cell counting (trypan blue live/dead) after exposure to non-aged, 30- and 180-days-aged samples in regularly replenished DMEM. Aged DMEM in contact with materials was also used to culture BMSCs to investigate the effect of material leachates on the cells. Gene expression analysis was also carried out after direct exposure of cells to non-aged materials. Differences between groups were statistically tested at a significance level of 5%. RESULTS: All materials exhibited alterations after immersion in DMEM and this increased with longer exposure times. The bismuth leached from ProRoot MTA as detected by ICP-MS. Aged ProRoot MTA samples exhibited a black discolouration and surface calcium carbonate deposition. ProRoot MTA influenced cell counts after direct exposure and its 180-days leachates reduced BMSC viability. After direct BMSC contact with non-aged ProRoot MTA an upregulation of metallothionein (MT1 and MT2A) expression and down-regulation of collagen-1a (Col-1a) and bone sialoprotein (BSP) expression was identified. CONCLUSIONS: Bismuth leaching was observed throughout 180-days observation period from all materials containing bismuth oxide. This negatively influenced cell viability and gene expression associated with bismuth exposure. This is the first study to report that metallothionein gene expression was influenced by exposure to ProRoot MTA.

Effect of exposure conditions on chemical properties of materials for surgical endodontic procedures.

This study investigated the role of aging and changes in environmental conditions on selected properties of a prototype radiopacified calcium silicate-based cement (TZ-base) with or without incorporation of silver nanoparticles or bioactive glass, and two commercial materials, Biodentine and intermediate restorative material. Materials were immersed in ultrapure water or fetal bovine serum for 28 days and were characterized with scanning electron microscopy and energy dispersive x-ray analysis. Immersion media were either replaced weekly or not replenished at all and were assessed for alkalinity and calcium release after 1, 7, 14, 21, and 28 days; antibacterial effect against 2-day monospecies biofilms; and cytotoxicity by the 3-(4,5 dimethylthiazolyl-2-yl)-2,5-diphenyl tetrazolium bromide assay after 1, 7, or 28 days. Alkalinity, calcium release, antibacterial activity, and cell cytotoxicity increased over time when the medium was not changed but decreased with medium replenishment. Immersion in fetal bovine serum resulted in lower alkalinity, less bactericidal properties, and lower cytotoxicity of prototype cements and Biodentine than did water immersion. Biodentine and 20% bioactive glass-containing cement had overall lower alkalinity, calcium release, and antibacterial activity than TZ-base, and Biodentine was less cytotoxic than TZ-base. In conclusion, exposure conditions and cement modifications significantly affected materials' leaching properties. Exposure conditions warrant consideration when evaluating cements' clinical properties.

Effectiveness of root canal filling materials and techniques for treatment of apical periodontitis: A systematic review.

BACKGROUND: Apical periodontitis (AP) is an inflammatory disease of the apical periodontium as sequelae of pulp death. It is managed by disinfection and filling of the root canal space. OBJECTIVES: The aim of this systematic review was to investigate whether obturation techniques and materials used for root canal filling led to the management of AP. METHODS: A systematic review protocol was written following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist and registered on the international prospective register of systematic reviews (PROSPERO; CRD42021260275) including two populations, interventions, comparisons, outcomes and time (PICOT) for the research questions querying the effectiveness of obturation techniques (PICOT 1) and materials (PICOT 2) for the management of AP. Electronic searches were conducted on PubMed, ScienceDirect, Scopus and Embase search engines. Searches on International Endodontic Journal, Journal of Endodontics, Clinical Oral Investigations, Journal of Dental Research and Journal of Dentistry websites were also conducted, until May 2021. Both primary (tooth survival) and secondary outcomes were evaluated. The risk of bias was assessed by Cochrane RoB2 for the randomized and ROBINS-I for the nonrandomized trials. RESULTS: The search strategy identified 1652 studies, with 1600 excluded on the title and abstract screening, leaving 52 studies for full-text screening. In total, 10 studies met the inclusion criteria. The obturation technique and materials used did not affect the outcome of AP. Vertical compaction resulted in faster resolution of periapical lesions. The oral health-related quality of life of patients treated with lateral condensation exhibited poorer outcomes compared with single matched cone after 6 months of recall. DISCUSSION: The inclusion and exclusion criteria used for this systematic review enabled the capture of all the literature available on the effect of obturation techniques and materials on the outcome of AP. The data were heterogenous, and a number of articles investigating obturation techniques had no information on the materials and techniques used as they looked at the quality of fill. CONCLUSIONS: Included studies did not find any difference between different procedures (PICOT 1) and materials (PICOT 2). The risk of bias was high, thus the findings should be interpreted with caution. REGISTRATION: PROSPERO registration number: CRD42021260275.

Periradicular tissue fluid-derived biomarkers for apical periodontitis: An in vitro methodological and in vivo cross-sectional study.

BACKGROUND: Periradicular tissue fluid (PTF) offers a source of diagnostic, prognostic and predictive biomarkers for endodontic disease. AIMS: (1) To optimize basic parameters for PTF paper point sampling in vitro for subsequent in vivo application. (2) To compare proteomes of PTF from teeth with normal apical tissues (NAT) and asymptomatic apical periodontitis (AAP) using high-throughput panels. METHODOLOGY: (1) To assess volume absorbance, paper points (n = 20) of multiple brands, sizes and sampling durations were inserted into PBS/1%BSA at several depths. Wetted lengths (mm) were measured against standard curves to determine volume absorbance (µL). To assess analyte recovery, paper points (n = 6) loaded with 2 µL recombinant IL-1ß (15.6 ng/mL) were eluted into 250 µL: (i) PBS; (ii) PBS/1% BSA; (iii) PBS/0.1% Tween20; (iv) PBS/0.25 M NaCl. These then underwent: (i) vortexing; (ii) vortexing/centrifugation; (iii) centrifugation; (iv) incubation/vortexing/centrifugation. Sandwich-ELISAs determined analyte recovery (%) against positive controls. (2) Using optimized protocols, PTF was retrieved from permanent teeth with NAT or AAP after accessing root canals. Samples, normalized to total fluid volume (TFV), were analysed to determine proteomic profiles (pg/TFV) of NAT and AAP via O-link Target-48 panel. Correlations between AAP and diagnostic accuracy were explored using principal-component analysis (PCA) and area under receive-operating-characteristic curves (AUC [95% CI]), respectively. Statistical comparisons were made using Mann-Whitney U, anova and post hoc Bonferonni tests (α < .01). RESULTS: (1) UnoDent's 'Classic' points facilitated maximum volume absorbance (p < .05), with no significant differences after 60 s (1.6 µL [1.30-1.73]), 1 mm depth and up to 40/0.02 (2.2 µL [1.98-2.20]). For elution, vortexing (89.3%) and PBS/1% BSA (86.9%) yielded the largest IL-1ß recovery (p < .05). (2) 41 (NAT: 13; AAP: 31) PTF samples proceeded to analysis. The panel detected 18 analytes (CCL-2, -3, -4; CSF-1; CXCL-8, -9; HGF; IL-1ß, -6, -17A, -18; MMP-1, -12; OLR-1; OSM; TNFSF-10, -12; VEGF-A) in ≥75% of AAP samples at statistically higher concentrations (p < .01). CXCL-8, IL-1ß, OLR-1, OSM and TNFSF-12 were strongly correlated to AAP. 'Excellent' diagnostic performance was observed for TNFSF-12 (AUC: 0.94 [95% CI: 0.86-1.00]) and the PCA-derived cluster (AUC: 0.96 [95% CI: 0.89-1.00]). CONCLUSIONS: Optimized PTF sampling parameters were identified in this study. When applied clinically, high-throughput proteomic analyses revealed complex interconnected networks of potential biomarkers. TNFSF-12 discriminated periradicular disease from health the greatest; however, clustering analytes further improved diagnostic accuracy. Additional independent investigations are required to validate these findings.

Comparison of obturation quality in natural and replica teeth root-filled using different sealers and techniques.

OBJECTIVES: This study aims to assess the obturation efficacy of sealers placed with different techniques using microcomputed tomography (µCT) and assess the influence of µCT testing parameters on the obturation data obtained. MATERIALS AND METHODS: Incisors and mesial roots of lower molars with standardized root length were scanned using µCT, and one tooth of each type was 3D printed in acrylic. Two obturation techniques (warm vertical and single cone) and 4 sealer types (AH Plus, BioRoot RCS, Totalfill BC, and Bio-C Sealers) were assessed following storage in Hank's balanced salt solution for 3 and 6 months by assessing gap and void volume percentages on both natural and replica incisor and molar roots. The storage solution was analysed to assess calcium ion leaching. The influence of temperature, tooth positioning, and moisture content of the teeth while µCT scanning was also investigated. RESULTS: The obturation quality in the incisor group was the same using both natural teeth and replicas (p > 0.05). No changes in void volume were identified when comparing the same sealer using different obturation techniques. The premixed sealers used in single-cone obturation exhibited high void volume in the 3D printed replicas in the long term. The temperature, positioning, and moisture content of the teeth did not affect the outcome of µCT testing. CONCLUSIONS: BioRoot RCS, Totalfill BC, and Bio-C Sealers are suitable for obturation of both complex and simple root canal systems using different obturation techniques with BioRoot RCS exhibiting the highest calcium ion release. 3D printed acrylic teeth can be used to assess the obturation quality in uncomplicated root canal systems. µCT parameters had no significant effect on the µCT measurement. CLINICAL RELEVANCE: The single-cone obturation technique with hydraulic sealer is a simple technique that can be used for obturation of all root canal systems.

Association between rheumatoid arthritis and pulpal-periapical pathology: a systematic review.

OBJECTIVES: Rheumatoid arthritis (RA) is a debilitating disease where numerous pro-inflammatory cytokines have a proven role in its pathology. These cytokines are also involved in the pathogenesis of apical periodontitis (AP) where they have a pro-inflammatory role and induce bone resorption. Patients with RA may therefore be more prone to develop pulpal-periapical pathology (PPP). This study systematically reviewed the existing literature evaluating the association between RA and PPP. MATERIALS AND METHODS: Studies including human participants with both RA and PPP were included. The search was performed in PubMed, Web of Science, and The Cochrane Library databases using keywords and Medical Subject Headings (MeSH) search terms. The risk of bias was assessed using Newcastle-Ottawa Quality Assessment Scale. The following parameters were extracted and analyzed by the reviewers; author, journal, year, design of the study, diagnostic criteria for periapical pathology, the association between rheumatoid arthritis and periapical pathology, and the evidence level. RESULTS: The search identified 142 records. Inclusion criteria were as follows; studies in the English language, including human participants only, including patients with RA and PPP, cohort studies, cross-sectional studies, clinical trials, and case-control studies. According to the inclusion criteria, 5 studies were included in this systematic review. Three of the five studies reported significant association between RA and PPP. CONCLUSIONS: Existing evidence suggests there may be an association between RA and PPP. CLINICAL RELEVANCE: Clinicians should be aware that RA patients can be more prone to develop PPP which may result in a reduced quality of life.

Physicochemical, mechanical and biological properties of nano-calcium silicate-based cements: a systematic review.

This systematic review evaluated the effects of nano-sized cement particles on the properties of calcium silicate-based cements (CSCs). Using defined keywords, a literature search was conducted to identify studies that investigated properties of nano-calcium silicate-based cements (NCSCs). A total of 17 studies fulfilled the inclusion criteria. Results indicated that NCSC formulations have favourable physical (setting time, pH and solubility), mechanical (push out bond strength, compressive strength and indentation hardness) and biological (bone regeneration and foreign body reaction) properties compared with commonly used CSCs. However, the characterization and verification for the nano-particle size of NCSCs were deficient in some studies. Furthermore, the nanosizing was not limited to the cement particles and a number of additives were present. In conclusion, the evidence available for the properties of CSC particles in the nano-range is deficient-such properties could be a result of additives which may have enhanced the properties of the material.

Present status and future directions: Hydraulic materials for endodontic use.

BACKGROUND: Hydraulic materials are used in Endodontics due to their hydration characteristics namely the formation of calcium hydroxide when mixing with water and also because of their hydraulic properties. These materials are presented in various consistencies and delivery methods. They are composed primarily of tricalcium and dicalcium silicate, and also include a radiopacifier, additives and an aqueous or a non-aqueous vehicle. Only materials whose primary reaction is with water can be classified as hydraulic. OBJECTIVES: Review of the classification of hydraulic materials by Camilleri and the literature pertaining to specific uses of hydraulic cements in endodontics namely intra-coronal, intra-radicular and extra-radicular. Review of the literature on the material properties linked to specific uses providing the current status of these materials after which future trends and gaps in knowledge could be identified. METHODS: The literature was reviewed using PUBMED, and for each clinical use, the in vitro properties such as physical, chemical, biological and antimicrobial characteristics and clinical data were extracted and evaluated. RESULTS: A large number of publications were retrieved for each clinical use and these were grouped depending on the property type being investigated. CONCLUSIONS: The hydraulic cements have made a difference in clinical outcomes. The main shortcoming is the poor testing methodologies employed which provide very limited information and also inhibits adequate clinical translation. Furthermore, the clinical protocols need to be updated to enable the materials to be employed effectively.

The dentine-sealer interface: Modulation of antimicrobial effects by irrigation.

AIM: Assess whether sodium hypochlorite (NaOCl) or chlorhexidine (CHX) and two irrigation protocols may alter the antibacterial properties of dentine and three endodontic sealers using a novel ex vivo tooth model. METHODOLOGY: Prior to antibacterial testing, the tooth model was validated by means of scanning electron microscopy (SEM) to evaluate the separation between dentine and sealer surfaces. Root blocks prepared from extracted human roots were pre-treated with 17% EDTA + 0.9% saline and subsequently treated with 1% NaOCl (G1), 2% CHX (G2) or no irrigant (G3). Two irrigation protocols were further investigated, "1% NaOCl + 17% EDTA" (P1) and "1% NaOCl + 17% EDTA + 2% CHX" (P2). Following irrigation, the root blocks were either filled with AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS), or left empty. All groups were incubated for 1, 7 and 28 days. Direct contact tests for planktonic E. faecalis and 48 h E. faecalis biofilms were performed at the level of dentine and sealer surfaces. Statistical analysis was performed on the bacterial survival between irrigants (G1, G2 and G3) and between irrigation protocols (P1 and P2); p < .05. RESULTS: The model was considered reproducible as SEM examination of dentine samples indicated consistent separation between dentine and sealer surfaces. Irrigation with CHX (G2) and irrigation protocol P2 enhanced the antibacterial properties of dentine without sealer application as well as dentine in contact with all three sealers tested, especially against planktonic E. faecalis. G2 and P2 also improved the antibacterial effect of AH Plus surfaces for all three incubation times. No irrigation groups (G1, G2) or irrigation protocols (P1, P2) altered the antibacterial properties of BioRoot RCS surfaces against planktonic bacteria or biofilms. Only BioRoot RCS surfaces eliminated the planktonic E. faecalis in all irrigation groups (G1, G2, G3) and protocols (P1, P2) investigated whilst PCS surfaces eliminate E. faecalis in biofilms in all groups up to 7 days. CONCLUSIONS: The tooth model was reproducible. CHX improved the antibacterial activity upon both sealer and dentine surfaces. Amongst sealers, BioRoot RCS was less affected by NaOCl and CHX, and exhibited high antibacterial properties regardless the irrigation applied.

Surface characteristics and bacterial adhesion of endodontic cements.

OBJECTIVES: To investigate the effect of inclusion of silver nano-particles (SNP) or bioactive glass (BG) on the surface characteristics and bacterial adhesion of prototype tricalcium silicate (TCS)-based cements alongside two commercial cements, under different aging periods and exposure conditions. MATERIALS AND METHODS: A basic formulation of radio-opacified TCS without (TZ-base) and with additions of SNP (0.5, 1, or 2 mg/ml) or BG (10 or 20%) was used. Biodentine and intermediate restorative material (IRM) served as reference materials. Material disks were immersed in ultrapure water or fetal bovine serum (FBS) for 1, 7, or 28 days. Surface roughness (n = 3), microhardness (n = 9), and wettability (n = 6) were analyzed by standard procedures. Adhesion of Enterococcus faecalis was assessed by fluorescence microscopy (n = 5). Data from these assays were evaluated for normality and comparisons among groups were conducted with statistical procedures (p < 0.05 for significance). RESULTS: The surface morphology of SNP- and BG-containing cements had higher roughness values than TZ-base after 28 days (p < 0.05). No differences in microhardness were observed among prototype cements (p > 0.05). Biodentine presented smooth surface characteristics and the highest hardness values (p < 0.05). The FBS-immersion resulted in surface reactions in prototype materials and Biodentine, depicted with scanning electron microscopy. All 1- and 7-day prototype cements showed negligible bacterial adhesion, while in Biodentine and IRM, noticeable E. faecalis adherence was observed from day 1 (p < 0.05). CONCLUSIONS: Incorporation of SNP or BG did not improve the antibacterial effect of the experimental cement; all 28-day aged materials failed to inhibit bacterial adherence. The measured physical parameters did not appear to be related to the degree of bacterial adhesion. Exposure of TCS-based cements in FBS resulted in surface reactions, which did not affect bacterial adhesion. CLINICAL RELEVANCE: Changes in the surface characteristics of prototype TCS-based cements by inclusion of SNP and BG or exposure to different environments did not affect bacterial adhesion. All experimental materials showed inferior physical properties and higher antibacterial effect than Biodentine.

PRILE 2021 guidelines for reporting laboratory studies in Endodontology: A consensus-based development.

Reproducible, skilfully conducted and unbiased laboratory studies provide new knowledge, which can inform clinical research and eventually translate into better patient care. To help researchers improve the quality and reproducibility of their research prior to a publication peer-review, this paper describes the process that was followed during the development of the Preferred Reporting Items for Laboratory studies in Endodontology (PRILE) 2021 guidelines and which used a well-documented consensus-based methodology. A steering committee was created with eight individuals (PM, RO, OP, IR, JS, EP, JJ and SP), plus the project leaders (PD, VN). The steering committee prepared an initial checklist by combining and adapting items from the modified Consolidated Statement of Reporting Trials checklist for reporting in vitro studies of dental materials and the Clinical and Laboratory Images in Publications principles as well as adding several new items. The steering committee then formed a PRILE Delphi Group (PDG) and PRILE Online Meeting Group (POMG) to provide expert advice and feedback on the initial draft checklist and flowchart. The members of the PDG participated in an online Delphi process to achieve consensus on the items within the PRILE 2021 checklist and the accompanying flowchart for clarity and suitability. The PRILE checklist and flowchart developed by the online Delphi process were discussed further by the POMG. This online meeting was conducted on 12 February 2021 via the Zoom platform. Following this meeting, the steering committee developed a final version of the PRILE 2021 guidelines and flowchart, which was piloted by several authors when writing up a laboratory study for publication. Authors are encouraged to use the PRILE 2021 guidelines and flowchart to improve the clarity, completeness and quality of reports describing laboratory studies in Endodontology. The PRILE 2021 checklist and flowchart are freely available and downloadable from the Preferred Reporting Items for study Designs in Endodontology website (http://pride-endodonticguidelines.org/prile/).

Physicochemical, antimicrobial, and biological properties of White-MTAFlow.

OBJECTIVES: To evaluate a new material containing tantalum oxide as an alternative radiopacifier, and a water-based gel for hydration, in comparison with two calcium silicate-based cement: ProRoot MTA and Biodentine. MATERIALS AND METHODS: ProRoot MTA (Dentsply), Biodentine (Septodont), and a new hydraulic calcium silicate cement White-MTAFlow (Ultradent) (in 'thin' consistency) were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The interaction with dentin was also assessed using SEM and EDS. Physical and chemical properties radiopacity, setting time, linear flow, volumetric central filling, and lateral flow, pH, and volume change were investigated together with the color luminosity (L) and color change (ΔE). The agar diffusion and direct contact antimicrobial activity, and methylthiazolyldiphenyl-tetrazolium-bromide (MTT) cytotoxicity using human fibroblast cells were also evaluated. Data were statistically analyzed at a 5% significance level. RESULTS: All materials were composed of tricalcium and dicalcium silicate but had different radiopacifiers, and calcium hydroxide (portlandite) deposition was detected in XRD analysis. White-MTAFlow exhibited radiopacity values in accordance with ISO standard, and the longest setting time. The water-based gel provided the highest linear flow, a comparable cavity central filling, and the highest groove-lateral flow in the volumetric flow analysis. White-MTAFlow exhibited an alkalinity reduction, and Biodentine, a progressive increase of pH values after 28 days. However, similar volume loss for White-MTAFlow was assessed in comparison to Biodentine after the 28-day immersion. White-MTAFlow showed the highest L value (91.5), and ProRoot MTA the lowest (78.1) due to dentin staining caused by bismuth migration. None of the materials exhibited inhibition halos against the tested bacteria, and similar turbidity values were obtained after 48 h in direct contact with E. faecalis, indicating an upregulation to bacterial growth. White-MTAFlow showed MTT cytocompatibility similarly to the control group. CONCLUSIONS: White-MTAFlow in 'thin' consistency presents comparable physicochemical, biological, and antimicrobial properties to ProRoot MTA and Biodentine, and does not cause color alteration in dentin. CLINICAL RELEVANCE: White-MTAFlow is a suitable material for use as reparative endodontic cement. Further studies considering its biocompatibility are necessary.

Physical, chemical, and biological properties of white MTA with additions of AlF3.

OBJECTIVES: Addition of aluminum fluoride (AlF3) to MTA was tested to inhibit dental discoloration. MATERIALS AND METHODS: MTA Angelus with 0, 5, 15, and 45% AlF3 were tested. The set cements were characterized using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. Radiopacity and setting time were analyzed according to ANSI/ADA 57 and ASTM C266-08. Volume change was evaluated using volumetric micro-CT analysis. The pH and calcium ion release were assessed after 3 and 24 h and 28 days. Dental discoloration in contact with the cements was assessed after 24 h and 28 and 90 days of contact with bovine and human dentine. Tissue reaction to subcutaneous implantation in rats was examined after 30 and 60 days. RESULTS: AlF3 altered the microstructure of MTA. The addition of 5% AlF3 did not significantly alter the radiopacity, setting time, and volume change (p > 0.05). pH and calcium ion release significantly increased with addition of AlF3 (p > 0.05). All the tested proportions of AlF3 prevented the dental darkening verified for MTA Angelus in bovine and human teeth. AlF3 did not interfere in inflammatory response of MTA in all periods of analysis; otherwise, lower amounts showed less intense inflammatory infiltrate. CLINICAL RELEVANCE: AlF3 prevents destabilization of bismuth oxide and consequent tooth darkening, frequently verified in clinical practice when using white MTA. CONCLUSIONS: The use of 5% of AlF3 in combination to MTA resulted in a cement that did not result in dental discoloration and did not affect significantly physical, chemical, and biological properties.

Influence of ultrasonic agitation on bond strength, marginal adaptation, and tooth discoloration provided by three coronary barrier endodontic materials.

OBJECTIVES: The effect of ultrasonic agitation (UA) on bond strength and adaptation of cervical plugs prepared with MTA Angelus (MTA), MTA Repair HP (MTAHP), and Biodentine (BIO) was evaluated. Dentin discoloration caused by the materials/treatment was also assessed. MATERIALS AND METHODS: Seventy-two single rooted teeth were divided into six groups depending on the materials/treatment. After cervical plug preparation, dentin discs were excised for the push-out test; additional discs were analyzed under the confocal microscope to determine adaptation (gaps occurrence). For dentin discoloration analysis (ΔE), blocks of bovine incisors had cavities prepared and filled with the materials/treatment (from 7 to 180 days). RESULTS: Both bond strength and adaptation were positively influenced by UA (P < 0.05). Comparison between materials showed an advantage for BIO when compared to MTAHP (P < 0.05). The best and worst results were provided by BIO/UA (12.66 MPa and 1.87%) and MTAHP (2.54 MPa and 28.58%), respectively. For ΔE, significant differences were observed throughout the periods. Just the MTA without UA exhibited noticeable discoloration at 180 days (P < 0.05). CONCLUSIONS: UA favored a better adaptation of the materials to the dentin root, resulting in higher bond strength and adaptation of the materials to the root canal walls. Moreover, UA reduced MTA discoloration, keeping it imperceptible over the period evaluated. CLINICAL RELEVANCE: The better adaptation and higher bond strength provided by UA can be considered clinically relevant due to the importance of maintaining blood clot integrity and the possible esthetic compromise provided by reparative materials when used as coronary barrier in regenerative procedures.

Prevention of coronal discoloration induced by regenerative endodontic treatment in an ex vivo model.

OBJECTIVES: The aim of this study was to assess the effect of sealing the pulp chamber walls with a dentin-bonding agent (DBA) on prevention of discoloration induced by regenerative endodontic procedures (REPs) in an ex vivo model. MATERIALS AND METHODS: Ninety-six bovine incisors were prepared and randomly divided into two groups. In one group, the pulp chamber walls were sealed with DBA before placement of triple antibiotic paste (TAP) containing minocycline inside the root canals, but in the other group, DBA was not applied. After 4 weeks, the root canals were filled with human blood and each group was then randomly divided into four subgroups (n = 12) according to the endodontic cements placed over the blood clot (ProRoot MTA, OrthoMTA, RetroMTA, or Biodentine). The color changes (∆E) were measured at different steps. The data were analyzed using t test and two-way ANOVA. RESULTS: The specimens in which dentinal walls of pulp chamber were sealed with DBA showed significantly less coronal discoloration at each step of regenerative treatment (p < 0.001). However, application of DBA did not completely prevent the clinically perceptible coronal color change. Sealing the blood clot with different endodontic cements did not result in significant difference in coronal discoloration (p > 0.05). CONCLUSIONS: Sealing the pulp chamber walls before insertion of TAP decreased coronal discoloration following REP using different endodontic cements but did not prevent it. CLINICAL RELEVANCE: Discoloration of teeth undergoing REPs is an unfavorable outcome. Considering the significant contribution of TAP containing minocycline to the coronal tooth discoloration even after sealing the pulp chamber walls, the revision of current guidelines in relation to the use of TAP with minocycline might need to be revised.

Doxycycline and Autogenous Bone in Repair of Critical-Size Defects.

PURPOSE: The association of doxycycline (DOX) and autogenous bone on repair of critical-size defects was evaluated. MATERIALS AND METHODS: Fifty albino rats were divided into 5 groups (n = 10). A 5-mm diameter defect was treated with: control (CO)-blood clot; DOX in Natrosol (NAT)-10% gel; NAT-gel; particulate autogenous bone (PAB); and PAB + DOX - PAB associated with 10% DOX gel. The animals were euthanized at 4 and 8 weeks postoperatively. Histomorphometric analysis was performed to assess the percentage of new bone in the defect area. Statistical analysis of the results was performed using analysis of variance and the Tukey test (P < 0.05). RESULTS: The results showed that new bone formation was limited to the margins of the defect. At 4 and 8 weeks, the group PAB + DOX showed higher bone formation (38.59% and 47.86%, respectively), with statistical difference in comparison with the CO (19.52%) at 4 weeks and CO (18.80%), DOX (22.05%), and NAT (15.89%) at 8 weeks (P < 0.05). CONCLUSIONS: The association of 10% DOX with autogenous bone significantly improved bone healing in critical-size defects.

Surface Microstructural Changes and Release of Ions from Dental Metal Alloy Removable Prostheses in Patients Suffering from Acid Reflux.

PURPOSE: To investigate the surface microstructural changes and the release of ions from metal alloys used in removable dental prostheses and the potential effects of acidic reflux found in patients suffering from gastroesophageal reflux disease (GERD). MATERIALS AND METHODS: Thirty-seven (37) patients were recruited. Data were gathered through a questionnaire and clinical examination. Samples of metal alloy from the dentures and patient's saliva were collected. GERD was confirmed using the GerdQ questionnaire. Denture samples were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), while salivary samples were tested for trace metal ions using inductively coupled plasma (ICP). RESULTS: Characterization of denture samples revealed the presence of nickel, cobalt, and chromium. Nickel-chromium exhibited an etched surface appearance, while cobalt-chromium exhibited no noticeable surface microstructural changes. Higher mean salivary levels of chromium and cobalt in patients wearing any metal alloy-based denture and of chromium and nickel in patients wearing Ni-Cr prostheses were found to be significant. No differences were found in salivary metal ion levels of patients suffering from GERD. CONCLUSIONS: Nickel-chromium alloy is prone to acid etching in the oral cavity, while cobalt-chromium alloy appears to be more resistant. Cobalt, chromium, and nickel are leached in saliva of patients using cast removable prostheses. The impact of gastric acid on metal ion release from dental metal alloys deserves further investigations. CLINICAL SIGNIFICANCE: This preliminary study suggests that metal-based removable prostheses leach trace metal ions in saliva. Nickel-chromium-based dentures exhibit an etched appearance unrelated to GERD.

Investigation of Acrylic Resin Disinfection Using Chemicals and Ultrasound.

PURPOSE: Dental prosthetic and orthodontic appliances are transported from the clinic to the laboratory for additions and repairs. These appliances, containing microbes from the oral flora, are a high risk for cross-contamination. The aim of this study was to evaluate the effect of chemical and ultrasound disinfection against two in vitro biofilms and an in vivo formed biofilm grown on unprepared and polished polymethyl methacrylate (PMMA) surfaces. MATERIALS AND METHODS: Rough and polished self-curing PMMA surfaces were infected with strains of both Candida albicans and Streptococcus oralis. After incubation, the samples were treated with different disinfection methods, including ultrasound treatment for both 15 and 30 seconds, and immersion in glutaraldehyde and alcohol-based chemical disinfectants (MD520 and Minuten, respectively). The disinfecting efficacy was assessed by colony forming units (CFU) analysis and by scanning electron microscopy (SEM). Furthermore the adequacy of bacterial elimination of application of 30-second ultrasound and MD520 was assessed on PMMA retrieved from ten volunteers by CFU analyses. ANOVA with p = 0.05 followed by the Tukey post hoc test and the Student t-test was used to analyze the data. RESULTS: The ultrasound treatment for 30 seconds, MD520, and Minuten were the most effective disinfectant methods as they reduced the microbial counts compared to the control (p < 0.05) as shown in the in vitro analyses. S. oralis adhered more to rough acrylic resin surfaces (p < 0.05). Ultrasound treatment was the most effective way to reduce microbial counts on PMMA exposed to oral flora (p = 0.043). CONCLUSION: Ultrasound treatment for 30 seconds was effective against C. albicans, S. oralis, and the oral flora as shown by testing microbial growth on agar plates and SEM.

Effect of polishing procedures and hydrothermal aging on wear characteristics and phase transformation of zirconium dioxide.

STATEMENT OF PROBLEM: Yttria-stabilized zirconia used for the fabrication of crowns and fixed prostheses may require intraoral adjustments after placement and cementation. Grinding and polishing methods may result in changes in the surface characteristics of zirconia. PURPOSE: The purpose of this in vitro study was to assess the effect of polishing procedures on surface roughness, topographical and phase changes of zirconia, and wear of the opposing dentition. MATERIAL AND METHODS: Presintered and precut yttria-stabilized zirconia specimens (10×10×1 mm) were divided into 4 groups (control, Intensiv, Shofu, 3M ESPE) depending on the polishing method used to prepare the specimens. All tests were carried out in triplicate. The specimens were polished depending on the polishing regimen, while the control was left untreated. The specimens were thermocycled for 3000 cycles, with a temperature range of 5°C to 55°C. The surface roughness, elemental, and phase changes caused by polishing before and after thermocycling were assessed with surface profilometry, energy-dispersive spectroscopy, and x-ray diffraction analysis. The wear on antagonist steatite balls was also measured after mastication simulation. Statistical analysis was performed using 1-way ANOVA and the Tukey post hoc test to perform multiple comparison tests (α=.05). RESULTS: The polishing procedures increased surface roughness (Ra) of yttria-stabilized zirconia from 0.52 for the control specimen to 0.73 for Intensiv, 0.70 for Shofu, and 0.70 for 3M ESPE (P<.05), which was reduced by thermocycling to 0.44 (control), 0.58 (Intensiv), and 0.58 (Shofu) (P<.001), while roughness remained unchanged for 3M ESPE specimens (0.75; P=.452). The deposition of aluminum when using Shofu abrasives and nickel in Intensiv was demonstrated. Phase changes were observed on the zirconia surface with formation of the monoclinic phase in all polishing methods. Specimen aging enhanced the surface phase changes and also induced compressive stresses in zirconia polished with Intensiv. The different polishing protocols did not affect the wear to the antagonist (P>.05). CONCLUSIONS: Polishing zirconia increased surface roughness and led to surface phase changes, but wear to the antagonist was not affected.