Current prospect of dental zirconia recycling: A scoping review.

PURPOSE: This scoping review aimed to identify and discuss the recyclability of dental zirconia residuals along with the factors influencing the properties of dental recycled zirconia. STUDY SELECTION: In vitro studies written in both English and Chinese that evaluated the recyclability of dental zirconia residue were selected. A literature search was conducted in Medline, PubMed, Web of Science, and Cochrane Library databases with no restrictions on the publication year. RESULTS: Sixteen studies were included in this review. Residual dental zirconia can be recycled. Cold isostatic pressing improved the density of recycled zirconia compared with uniaxial pressing. Recycled zirconia powder with fine particles enhanced the performance of recycled zirconia compared with coarse particles. A presintering temperature of 950 to 1100°C was suitable for preparing recycled zirconia presintered bodies. Recycled zirconia may require a higher sintering temperature (≥1500°C) compared with commercially available zirconia. Additionally, recycled zirconia powder can enhance the properties of polymethylmethacrylate as a reinforcing filler and can be combined with alumina powder to obtain an alumina/zirconia composite material. CONCLUSIONS: Despite a limited body of literature, the recycling and reutilization of dental zirconia residuals are feasible and reliable, and can reduce economic and environmental losses. Nevertheless, several factors influence the recycling effect, including the particle size, molding techniques, and sintering parameters. In addition, recycled zirconia powder can act as a reinforcing filler, potentially enhancing the mechanical properties of other materials. To realize commercially viable recycled zirconia materials, further studies are essential to comprehensively explore and understand their recycling performance.

ß-Tricalcium Phosphate as Alveolar Bone Grafting in Cleft Lip/Palate: A Systematic Review.

The aim of this systematic review is to describe and identify the prospects of ß-Tricalcium Phosphate (ß-TCP) as an alveolar bone grafting (ABG) material in cleft lip/palate (CL/P) or alveolar bone cleft defects. A systematic review protocol based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) was drafted. The literature search was conducted using MEDLINE/PubMed, Web of Science/ISI Web of Knowledge, Scopus, and the Cochrane Library, with English as the inclusion criterion and no publication year limits. The keywords yielded a total of 5824 publications. After removing duplicates and non-English articles, there were 3196 suitable articles available for evaluation. Subsequently, 1315 studies remained after reviewing titles and abstracts. Furthermore, 85 full articles were assessed for eligibility. After reading the complete texts of those papers, 20 were eventually selected that matched the inclusion requirements. Thirteen out of the twenty studies included in this systematic review were deemed to have a low risk of bias; one had a high risk of bias; and six had a moderate risk of bias due to not reporting randomization. ß-TCP, when used as an ABG material, is biocompatible, visible, practical, offers a less invasive procedure, and does not interfere with orthodontic treatment. Synthetic ß-TCP for ABG can be an alternative to autologous bone grafts under certain terms and conditions. The efficacy of ß-TCP for ABG in CL/P or alveolar bone cleft defects can be enhanced through a tissue engineering approach that combines ß-TCP with growth factors, mesenchymal stem cells, or other graft materials, along with modifications to ß-TCP's physical properties.

Prevalencia del segundo conducto en dientes anteroinferiores usando Tomografía Computadorizada Cone Beam / Second root canal prevalence in lower anterior teeth using Cone Beam Computed Tomography

Introducción: Es un error común pensar que los dientes anteroinferiores, por lo general, tienen un solo conducto radicular con una sola raíz. Sin embargo, un estudio realizado por Vertucci et. al., (1974), mostraron una alta prevalencia (13%) de dos conductos radiculares en los dientes anteroinferiores, lo que estimuló más investigaciones. Objetivo: El propósito de este estudio fue determinar la prevalencia del segundo conducto radicular en los dientes anteroinferiores en una población nicaragüense, estos fueron detectados por medio de tomografía computadorizada (Cone Beam). Materiales y Métodos: En el estudio se analizaron 293 piezas dentales, de canino a canino de la arcada inferior. Para realizar el análisis se utilizó el software libre Radiant DICOM Viewer 2021.2.2, se realizaron cortes sagitales, axiales y coronales para ver la prevalencia del segundo conducto radicular. Resultados: De las 293 piezas dentarias analizadas se encontró que 259 presentaban un solo conducto que correspondía al 88.4% y 34 dientes presentaban dos conductos que correspondían al 11.6%. De acuerdo con el análisis tomográfico, se encontró que en los cortes axiales y sagitales fue donde se observó la presencia del segundo conducto. Con respecto a la presencia del segundo conducto de acuerdo al tercio del canal radicular se identificó que la mayoría se presentó en el tercio medio (52.94%), seguido por coronal (29.41%) y por último el tercio apical (17.65%). De acuerdo con la clasificación de Vertucci se encontró que se presenta un mayor porcentaje del tipo I con 88.40%, seguido por el tipo III con 4.44%, después el tipo V con 3.41%, y el tipo II con 2.39%. El de menor porcentaje fue el tipo VI con 1.37%, mientras que, en las piezas analizadas, no se encontraron los tipos IV, VII y VIII. Conclusión: Basados en los resultados obtenidos en este estudio, la prevalencia de un segundo conducto en dientes anteroinferiores fue de 11.6%.

Title The prevalence of a second root canal in mandibular anterior teeth using Cone Beam Computed Tomography. Abstract Introduction: It is a common misconception that the mandibular anterior teeth usually have a single root canal with a single root. However, a study by Vertucci et. al., (1974), showed a high prevalence (13%) of two root canals in the lower anterior teeth, which stimulated further investigations. Objective: The purpose of this study was to determine the prevalence of the second root canal in the mandibular anterior teeth in a Nicaraguan population, these were detected by means of computed tomography (Cone Beam). Materials and methods: In the study, 293 teeth were analyzed, from canine to canine of the mandibular teeth. To perform the analysis, the free software Radiant DICOM Viewer 2021.2.2 was used, sagittal, axial and coronal views were made to see the prevalence of the second root canal. Results: Of the 293 teeth analyzed, it was found that 259 had a single root canal corresponding to 88.4%, and 34 teeth had two root canals corresponding to 11.6%. According to the tomographic analysis, it was found that the presence of the second root canal was observed only in the axial and sagittal views. Regarding the presence of the second canal according to the third of the root canal, it was identified that the majority presented in the middle third (52.94%), followed by coronal (29.41%) and finally the apical third (17.65%). According to the Vertucci classification, it was found that there is a higher percentage of type I with 88.40%, followed by type III with 4.44%, then type V with 3.41%, and type II with 2.39%. The one with the lowest percentage was type VI with 1.37%, while in the pieces analyzed, types IV, VII and VIII were not found. Conclusion: Based on the results obtained in this study, the prevalence of a second root canal in lower anterior teeth was 11.6%.

Evaluation of the ergonomic sitting position adopted by dental students while using dental simulators.

Background/purpose: Ergonomics in dentistry encourages the work to be in an organized manner, where a dentist achieves highest performance with maximum comfort and minimum physical and psychological effort. The purpose of this study was to evaluate the ergonomic sitting position of dental students from third, fourth and fifth year undergraduate programs while they prepared teeth 46 and 27 as Black Class I preparation for amalgam using dental simulators. Materials and methods: Ten students were randomly selected from each year for this study. Photos and videos were taken from them to record their sitting position as they performed a Black Class I amalgam preparation in Nissin simulators. Results: It was found that more students had a poor ergonomic sitting position while working in mandibular area (60%, torso and neck angle; 53% knee-angle; 50% elbow-angle). When comparing the average score between maxilla and mandible within students of the same year, fourth year students had a significant difference in their average, with a better performance in maxilla (P ≤ 0.01). They also showed better performance in maxillary area compared to fifth-year students (P ≤ 0.008). The main reasons that the students presented as justification for their bad posture were little work time, lack of knowledge, not knowing how to use indirect vision, and poor comfort. Conclusion: Every undergraduate year had a compromised sitting position, with the exception of fourth-year students when working in maxillary area. No correlation between undergraduate year and performance was found.

Reduction of inflammation in a chronic periodontitis model in rats by TNF-α gene silencing with a topically applied siRNA-loaded calcium phosphate paste.

We developed a calcium phosphate-based paste containing siRNA against TNF-α and investigated its anti-inflammatory and bone-healing effects in vitro and in vivo in a rat periodontitis model. The bioactive spherical CaP/PEI/siRNA/SiO2 nanoparticles had a core diameter of 40-90 nm and a positive charge (+23 mV) that facilitated cellular uptake. The TNF- α gene silencing efficiency of the nanoparticles in J774.2 monocytes, gingival-derived cells, and bone marrow-derived cells was 12 ± 2%, 36 ± 8%, and 35 ± 22%, respectively. CaP/PEI/siRNA/SiO2 nanoparticles cancelled the suppression of alkaline phosphatase (ALP) activity in LPS-stimulated bone marrow-derived cells. In vivo, ALP mRNA was up-regulated, TNF-α mRNA was down-regulated, and the amount of released TNF-α was significantly reduced after topical application of the calcium phosphate-based paste containing siRNA-loaded nanoparticles. The number of TNF-α-positive cells in response to CaP/PEI/siRNA/SiO2 nanoparticle application was lower than that observed in the absence of siRNA. Elevated ALP activity and numerous TRAP-positive cells (osteoclasts) were observed in response to the application of all calcium phosphate pastes. These results demonstrate that local application of a paste consisting of siRNA-loaded calcium phosphate nanoparticles successfully induces TNF-α silencing in vitro and in vivo and removes the suppression of ALP activity stimulated by inflammation. STATEMENT OF SIGNIFICANCE: We developed a calcium phosphate-based paste containing nanoparticles loaded with siRNA against TNF-α. The nanoparticles had a core diameter of 40-90 nm and positive charge (+23 mV). The anti-inflammatory and osteoinductive effects of the paste were investigated in vitro and in vivo in a rat periodontitis model. In vitro, the TNF-α gene silencing efficiency of the nanoparticles in J774.2 monocytes, gingival-derived cells, and bone marrow-derived cells was 12 ± 2%, 36 ± 8%, and 35 ± 22%, respectively. The ALP activity of bone marrow-derived cells was recovered. In vivo, TNF-α mRNA was down-regulated and the amount of released TNF-α was significantly reduced, whereas the ALP mRNA was up-regulated. Elevated ALP activity and TRAP-positive cells were observed by immunohistochemistry.

Prolonged release of bone morphogenetic protein-2 in vivo by gene transfection with DNA-functionalized calcium phosphate nanoparticle-loaded collagen scaffolds.

In the combination of scaffolds immersed in growth factor solutions, the release of growth factors mainly depends on scaffold degradation. However, the release of bone morphogenetic protein (BMP)-2 at an appropriate concentration during the stage of tissue regeneration would enhance bone regeneration. To achieve this condition, the present study was performed to investigate the effects of scaffolds combined with gene transfection using non-viral vectors. Nanohydroxyapatite-collagen (nHAC) scaffolds cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or ascorbic acid/copper chloride, and a collagen scaffold (Terdermis®) were prepared, loaded with BMP-2-encoding plasmid DNA-functionalized calcium phosphate nanoparticles (CaP), naked plasmid DNA, or BMP-2 solution, and implanted in rats. The yield of released BMP-2 and its releasing period, respectively, were larger and longer from the scaffolds loaded with CaP than from those incubated with BMP-2 solution. In addition, the alkaline phosphatase activity induced by the CaP-loaded scaffolds was higher. Histological analysis showed that released BMP-2 could be observed on the macrophages or multinuclear giant cells surrounding the nHAC fragments or collagen fibres. TRAP-positive or OCN-positive sites were observed in all groups and a mineralization area was observed in the Terdermis®/CaP sample. The present study demonstrates that gene transfection by scaffold loaded with CaP gene transfer vectors induces a larger yield of BMP-2 for a longer period than by scaffolds loaded with BMP-2 solution or naked plasmid.

Periodontal tactile sensation and occlusal loading condition of autotransplanted teeth: A retrospective pilot study.

PURPOSE: The objectives of this retrospective pilot study were: (1) to examine the occlusal properties (periodontal tactile sensation, occlusal force support ability, dynamic tooth mobility, occlusal force, contact area, preferred chewing side and main occluding area) of autotransplanted teeth with no clinical complications after transplantation (postoperative periods from 1 to 7 years). METHODS: Three groups were formed from 20 subjects (23 teeth in each group): autotransplanted teeth (ATP group), teeth contralateral to the recipient site (control group A), and teeth contralateral to the donor site (control group B). RESULTS: The tactile detection threshold of the ATP group was higher than both the control groups, and the individual occlusal force was significantly lower than control group A. The occlusal force ratio and the occlusal contact area ratio were significantly lower in the ATP group than in both control groups, while the mobility was similar in all groups. Eight out of 20 subjects chose the autotransplanted teeth side as the preferred chewing side. Especially when the recipient site was the first molar, the ATP of these subjects were included in the main occluding area. The pocket depth of the three groups was within the normal range. CONCLUSIONS: These results demonstrate that teeth autotransplantation can achieve a mastication efficiency and periodontal condition similar to normal teeth; however, without proper healing, the periodontal sensation of autotransplanted teeth may be inferior to that of normal teeth (<250).

Na18F accumulates on the compressive side of peri-implant bone under immediate loading.

This study aimed to examine the dynamic change in bone metabolism by immediate loading in several sites around implants using high-resolution Na18F-PET scan. Two titanium implants (Ø 1.2 mm) were inserted parallel to each other in the right tibiae of Wistar rats (n = 4). The left tibia was set as control side. One day after insertion, closed coil springs of 4.0 N were attached to the expose superior portions of the implants to apply a continuous mechanical stress. The rats with fluorine-18 (18F) ion (5 mCi/rat) intravenously injected were scanned by PET scanner at 4, 7, 14, 28 days after load application. Round region of interests (ROIs) were set around the distal implant of the right tibia (loaded side) and same site (control) of the left tibia. Furthermore, four rectangular ROIs were set at the superior and inferior parts of traction side (mesial) and opposite side (distal) of the distal implant. Longitudinal dynamic changes in bone metabolism were evaluated by examination of the accumulation count of 18F ion at each ROI. The uptake values of ROIs (loaded side) initially increased until 7 days, and they gradually decreased from the peak level to the pre-loading level despite a static force being applied to the implants. In cancellous bone, the uptake values at the superior part of traction side and inferior part of opposite side showed significantly high value compared with those at other parts. In conclusion, immediate loading to the implant initially enhanced bone metabolism around it, especially at the part with compressive stress. Peri-implant bone metabolism varies according to different loading conditions.

Amiloride-enhanced gene transfection of octa-arginine functionalized calcium phosphate nanoparticles.

Nanoparticles represent promising gene delivery systems in biomedicine to facilitate prolonged gene expression with low toxicity compared to viral vectors. Specifically, nanoparticles of calcium phosphate (nCaP), the main inorganic component of human bone, exhibit high biocompatibility and good biodegradability and have been reported to have high affinity for protein or DNA, having thus been used as gene transfer vectors. On the other hand, Octa-arginine (R8), which has a high permeability to cell membrane, has been reported to improve intracellular delivery systems. Here, we present an optimized method for nCaP-mediated gene delivery using an octa-arginine (R8)-functionalized nCaP vector containing a marker or functional gene construct. nCaP particle size was between 220-580 nm in diameter and all R8-functionalized nCaPs carried a positive charge. R8 concentration significantly improved nCaP transfection efficiency with high cell compatibility in human mesenchymal stem cells (hMSC) and human osteoblasts (hOB) in particular, suggesting nCaPs as a good option for non-viral vector gene delivery. Furthermore, pre-treatment with different endocytosis inhibitors identified that the endocytic pathway differed among cell lines and functionalized nanoparticles, with amiloride increasing transfection efficiency of R8-functionalized nCaPs in hMSC and hOB.

Gene transfection of human mesenchymal stem cells with a nano-hydroxyapatite-collagen scaffold containing DNA-functionalized calcium phosphate nanoparticles.

This study aimed to fabricate a growth factor-releasing biodegradable scaffold for tissue regeneration. We prepared multishell calcium phosphate (CaP) nanoparticles functionalized with DNA, polyethyleneimine (PEI), protamine and octa-arginine (R8) and compared their respective transfection activity and cell viability measures using human mesenchymal stem cells. DNA-protamine complexes improved the transfection efficiency of CaP nanoparticles with the exception of those functionalized with R8. These complexes also greatly reduced the cytotoxicity of PEI. In addition, we also fabricated DNA-protamine-functionalized CaP nanoparticle-loaded nano-hydroxyapatite-collagen scaffolds and investigated their gene transfection efficiencies. These experiments showed that the scaffolds were associated with moderate hMSC cell viability and were capable of releasing the BMP-2 protein into hMSCs following gene transfection. In particular, the scaffold loaded with protamine-containing CaP nanoparticles showed the highest cell viability and transfection efficiency in hMSCs; thus, it might be suitable to serve as an efficient growth factor-releasing scaffold.