Customized Fiber Post Improves the Bond Strength and Dentinal Penetrability of Resin Cementation System to Root Dentin

SUMMARY Objective: This study aimed to evaluate the effect of fiber post customization on the bond strength (24 hours and 6 months), resin cement thickness, and dentinal penetrability of Adper Scotchbond Multi-Purpose – RelyX ARC (AS-RA), RelyX U200 (R2), and Scotchbond Universal – RelyX Ultimate (SU-RU) cementation systems to root dentin from the cervical-, middle-, and apical-thirds of the post space. Methods: One hundred twenty bovine incisors were endodontically treated. After post space preparation, the roots were divided into six groups, according to the luting protocols (AS–RA, R2, SU– RU) and the type of fiber post [noncustomized post (NC) and customized post (C)]. Customization procedures were peformed using a resin composite (Z350 XT). 24 hours (n=60) or 6 months later (n=60), specimens from the cervical-, middle-, and apical-thirds of the post space were submitted to cementation system thickness measurement, bond strength evaluation, and dentinal penetrability analysis with Confocal Laser Scanning Microscopy (CLSM). Failure mode was classified as adhesive, cohesive, or mixed. Data were submitted to ANOVA and Tukey tests (α=0.05). Results: Cementation protocols with customized fiber posts presented the lowest cementation system thickness, regardless of the cementation system or post space-third (p<0.05), and the highest bond strength values (p<0.05), regardless of the third space (p>0.05), for both periods (24 hours or 6 months). The comparison of push-out bond strength values between 24 hours and 6 months showed a reduction in all groups for the cervical-third (p<0.05). For the middle-third, only noncustomized groups showed reduction (p<0.05). For the apical-third, no reduction was observed (p>0.05). Conclusions: Anatomical customization favored both the bond strength of cements to dentin and the dentinal penetrability, but with lower cementation system thickness, regardless of cement composition and adhesive strategy.

Microhardness evaluation of root dentin after using resin sealer solvents

Background. This study aimed to assess the effects of methyl ethyl ketone (MEK) and ethyl acetate (EA) on dentin microhardness, used as resin sealer solvents. Methods. Eighty halves of single-rooted teeth were randomly divided into four groups to apply MEK, EA, chloroform, or saline solution. Vickers hardness values were measured for three root levels before and after the direct application of solvents for 5 and 15 minutes or a 1-minute application with ultrasonic agitation. The results were analyzed using repeated-measures ANOVA, and adjustments were made for comparisons with Bonferroni tests. Results. The dentin microhardness decreased in all the solvent groups (P<0.05). The changes in microhardness increased with prolonged exposure times, except for the saline solution group. Chloroform exhibited the most significant decrease in value. Furthermore, ultrasonic agitation elicited a more substantial decline in values. Conclusion. MEK and EA might be preferred over chloroform as a solvent for resin sealers because they offer an attenuated decrease in dentin microhardness and do not have gutta-percha-dissolving properties.

Agentes Fluoretados e Cárie Radicular: Uma Revisão de Literatura / Fluoride Agents and Root Caries: A Literature Review

Resumo: A cárie radicular é uma patologia progressiva e dinâmica que ocorre na interface biofilme e cemento/dentina radicular, com maior taxa de prevalência na população idosa. O uso profissional de agentes fluoretados consiste na intervenção minimamente invasiva, capaz de prevenir e inativar as Lesões de Cárie Radicular (LCRs). Desta forma, o presente estudo objetivou identificar os diferentes agentes terapêuticos fluoretados de uso profissional que agem na inativação/paralisação da cárie radicular. Para tanto, foi realizado levantamento bibliográfico dos últimos cinco anos por meio de análise criteriosa de artigos científicos. Os idiomas foram, predominantemente o português, inglês e espanhol. Como critérios de inclusão foi considerado os trabalhos relacionados com o objetivo do presente estudo, estudos disponíveis na integra, artigos publicados entre 2016 e 2021, sendo descartados artigos que não estavam em consonância com o objetivo deste estudo, teses e dissertações. Conclui-se que o Diamino Fluoreto de Prata (DFP) é o agente fluoretado que apresentou maior eficácia na prevenção e paralização das LCRs. Contudo, sugere-se que mais estudos sejam realizados, com foco na intervenção minimamente invasiva, que tragam protocolos clínicos de atendimento adequado ao tratamento da cárie radicular Palavras-chave: Cárie; Cárie radicular; Agentes fluoretados.Abstract: Root caries is a progressive and dynamic pathology that occurs at the biofilm and cementum/root dentin interface, with a higher prevalence rate in the elderly population. The professional use of fluoridated agents is a minimally invasive intervention capable of preventing and inactivating Root Caries Lesions (CRLs). Thus, the present study aimed to identify the different fluoride therapeutic agents for professional use that act in the inactivation/paralysis of root caries. Therefore, a bibliographic survey of the last five years was performed through a careful analysis of scientific articles. The languages were predominantly Portuguese, English and Spanish. As inclusion criteria, works related to the objective of this study were considered, studies available in full, articles published between 2016 and 2021, and articles that were not in line with the objective of this study, theses and dissertations were discarded. It is concluded that Silver Diamino Fluoride (DFP) is the fluoridated agent that showed the greatest effectiveness in preventing and paralyzing CSFs. However, it is suggested that more studies be carried out, focusing on minimally invasive intervention, which bring clinical protocols for adequate care for the treatment of root caries. Keywords: Caries; Root caries; Fluoridated agents.

Comparative Evaluation of the Effect of Different Endodontic Irrigation Protocols on the Microhardness of Root Canal Dentin: An In Vitro Study

Aim and Objective The present in vitro study was done to comparatively evaluate the effect of different endodontic irrigation protocols on the microhardness at coronal, middle, and apical levels of root canal dentin. Method The total sample size for the study was 100. Each sample consisted of a longitudinally sectioned half of a root of a single-rooted tooth, which was then embedded in acrylic resin. The prepared samples were divided randomly into five groups of twenty samples each. Each group was treated with its respective irrigant to be tested. Group I was the control—the specimens were treated with distilled water. The specimens in group II were treated with sodium hypochlorite (NaOCl), followed by ethylenediamine tetra-acetic acid (EDTA). Specimens in group III were treated with NaOCl, followed by CHX. Specimens in group IV were treated with NaOCl, followed by hydroxyethylidene bisphosphonate (HEBP), and specimens in group V were treated with NaOCl, followed by propolis. Following this, all the samples were placed on the Vickers microhardness tester, and the results were tabulated and statistically analyzed to determine the irrigant solutions' effect on the microhardness of root dentin at coronal, middle, and apical third. Results Intergroup comparison of various irrigants showed that 18% HEBP showed the least reduction in the microhardness values of root canal dentin, and 17% EDTA caused the maximum decrease in microhardness values with a significant difference. When the baseline values were compared with the values after the use of experimental solutions in all the groups, it was observed that the microhardness gradually decreased from coronal to apical third of root dentin. Conclusion On the basis of the results obtained, it can be concluded that weak chelators such as 18% HEBP do not affect the microhardness considerably, and that they can be used in future in place of strong chelators, that is, EDTA, which make root dentin weak by more microhardness reduction.

Protocols for Mechanical Cleaning of the Post Space on the Bond Strength Between Root Dentin and Cementation System

SUMMARY Objective: To evaluate the effects of mechanical versus chemical cleaning protocols for cleaning the root dentin surface before cementation of fiberglass posts for their effect on the bond strength, failure mode, and dentinal penetration of the cementing agent using an etch-and-rinse adhesive system on dentin prepared to receive a fiberglass post. Methods: Forty roots of bovine teeth were endodontically treated and prepared for fiber post cementation. The specimens were randomized into 4 groups of 10: Control group (CO) - irrigation with 2.5% NaOCl; DW group- irrigation with distilled water; RB group - rotating brush for cleaning root canals, and CUI group - continuous ultrasonic irrigation. The fiberglass posts were cemented, and the specimens were immersed in distilled water for 6 months. A push-out test was performed on the cervical, middle, and apical thirds of the samples. Dentinal penetration of the cementing agent and the fracture pattern were evaluated by laser confocal microscopy. Statistical analysis was performed using analysis of variance (ANOVA) and post hoc Tukey tests (α=0.05). Results: The RB and CUI groups showed significantly higher bond strength values when compared to the Control and DW groups (p&lt;0.05). In addition, in the control and DW groups, the apical third presented lower bond strength values when compared to middle and cervical thirds. Conclusion: While DW showed the highest incidence of adhesive type failure, CUI resulted in the highest dentinal penetration of the cementing agent (p&lt;0.05). RB and CUI resulted in the highest bond strength between cementation system and root dentin. In addition, CUI favored greater dentinal penetration of fiberglass post cementing agent.

Anti-Demineralization Effects of Dental Adhesive-Composites on Enamel–Root Dentin Junction

Oral biofilm reactor (OBR) and pH cycling (pHC) artificial caries model were employed to evaluate the anti-demineralization effects of four composite filling systems on enamel–root dentin junction. Sixty-four enamel–root dentin blocks (6 mm × 6 mm × 2 mm) each with a cylindrical cavity were randomly assigned to the pHC and OBR group, then four subgroups (n = 8) and filled with either the Beautifil II (BEF, SPRG-filler-containing) or Estelite (EST) composite after the adhesive (either Single Bond Universal (SBU) or FL Bond II (FL, SPRG-filler-containing)). The demineralization lesions of filling interface were examined by micro-computerized tomography (μCT) and swept-source-optical coherence tomography (SS-OCT). According to the degree of interface damage, the caries lesions were sorted into four types: Type A and B (no attachment loss); Type C and D (attachment loss). EST/SBU showed the worst demineralization lesion and attachment loss (100% Type D), while BEF/FL exhibited the shallowest lesion depth (p < 0.05, 145 ± 45 μm on enamel, 275 ± 35 μm on root dentin) and no attachment loss (75% Type A and 25% Type B). Using FL adhesive alone does not effectively reduce enamel demineralization. BEF plays a leading role in acid resistance. The combination of BEF and FL showed a cumulative synergistic effect on anti-demineralization.

PD-1 Suppresses the Osteogenic and Odontogenic Differentiation of Stem Cells From Dental Apical Papilla via Targeting SHP2/NF-κB axis

BackgroundStem cells from the apical papilla (SCAPs) are important for tooth root development and regeneration of root dentin. Here, we examined the expression of programmed cell death protein-1 (PD-1) in SCAPs and investigated the effect of PD-1 on odontogenic and osteogenic differentiation and the relationship between PD-1 and cell differentiation and SHP2/NF-κB signals.MethodsSCAPs were obtained culture in the related medium. The proliferation ability was evaluated by cell counting kit 8 and 5‐ethynyl‐20‐deoxyuridine (EdU) assay. Alkaline phosphatase (ALP) activity assay, ALP staining, western blot, real-time RT-PCR, Alizarin Red S staining, and immunofluorescence staining were performed to explore the osteo/odontogenic potential and the involvement of SHP2/NF-κB pathways. Besides, we transplanted SCAPs component into mouse calvaria defects to evaluate osteogenesis in vivo. ResultsWe found that human SCAPs expressed PD-1 for the first time. PD-1 knockdown enhanced the osteo/odontogenic differentiation of SCAPs by suppressing SHP2 pathway and activating NF-κB pathway. Overexpression of PD-1 inhibited the osteogenesis and odontogenesis of SCAPs via activation of SHP2 signal and inhibition of NF-κB pathway. ConclusionPD-1 activated SHP2 signal to block NF-κB signal and then played a vital role in osteo/odontogenic differentiation of SCAPs.