Single scanning of CBCT and intraoral scanning for guided implantation in terminal dentitions with multi-unit metal restorations: technical note.

When anatomical landmarks are missing or obstructed by metal artefacts, it is challenging to accurately merge cone beam computed tomography (CBCT) and intraoral scanning (IOS) information, and the accuracy of the implant surgical guides would be compromised. This article describes a novel technical note using oral wound dressings and flowable resin as additional new radiopaque fiducial landmarks to design surgical guides for full-arch immediate implant placement. This technical note provided an accurate, convenient, and cost-effective option for the clinician.

Patient-specific 3D printed models for enhanced learning of immediate implant procedures and provisionalization.

INTRODUCTION: This study aimed to describe the fabrication, implementation and evaluation of 3D-printed patient-specific models for unskilled students to enhance learning in immediate implant procedures and provisionalization. MATERIALS AND METHODS: The individualized simulation models were designed and processed based on CT and digital intraoral scanning of a patient. Thirty students performed simulation implant surgery and provisionalized the implant sites on the models and answered questionnaires to assess their perceptions before and after the training. The scores of the questionnaires were analysed using the Wilcoxon signed-rank test. RESULTS: Significant differences before and after training were found in the students' responses. Students reported better results in understanding of surgical procedures, knowledge in prosthetically driven implantology, understanding of minimally invasive tooth extraction, confirming the accuracy of surgical template, usage of the guide rings and usage of the surgical cassette after simulation training. The overall expenditure on the simulation training involving 30 students amounted to 342.5 USD. CONCLUSIONS: The patient-specific and cost-efficient 3D printed models are helpful for students to improve theoretical knowledge and practical skills. Such individualized simulation models have promising application prospects.

Silk fibroin-chitosan aerogel reinforced by nanofibers for enhanced osteogenic differentiation in MC3T3-E1 cells.

Proper bone scaffolds should be biocompatible, mechanically robust and porous for cell migration. Here, pure silk fibroin (SF)- chitosan (CS) aerogel scaffolds reinforced with different amount of SF nanofibers (SF-CS/NF1%, SF-CS/NF2% and SF-CS/NF3%) are prepared for bone regeneration. Surface morphology and composition were analyzed to ensure successful integration of each component. Incorporating 3 % nanofibers endowed the aerogels with a resistance to 3.5 times the compressive stress of the pure SF-CS aerogels. The benefits of nanofibers were also confirmed by the high porosity of 72.3 ± 1.3 %, the regulated pore size and the high-water uptake ratio of 1770.4 ± 156.8 %. Enhanced cell viability of the aerogel scaffolds was verified with Cell Counting Kit-8 (CCK-8) assays, and confocal microscopy and scanning electron microscopy (SEM) images were taken to assess the cell migration and distribution. The cell differentiation on the aerogel scaffolds was evaluated with enzyme-linked immunosorbent assay (ELISA). Significantly higher level of Collagen type I (Col-I), osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) expression was observed on SF-CS/NF3% aerogels. This biocompatible nanofiber-reinforced aerogel scaffold facilitates osteogenic differentiation by rougher surface, enhanced mechanical strength and well-regulated pores. Thus, as-prepared scaffolds may be further applied in bone regeneration field.

Radiopaque fiducial markers as an aid to fabrication of an implant surgical guide for a patient with orthodontic brackets: A dental technique.

Designing implant surgical guides for patients undergoing orthodontics merely by merging data imaging and communications in medicine (DICOM) files generated from cone beam computed tomography (CBCT) images and standard tessellation language (STL) files generated from surface scanners is challenging because of the inaccuracy caused by metal artifacts. The present technique describes a straightforward and effective method of fabricating a surgical guide with the aid of fiducial markers made from cotton swabs and flowable resin. The implant surgical guide is designed by using a software program after the superimposition of digital scan and CBCT data. This chairside technique provides an accurate, convenient, and cost-effective option for the clinician.

A Digital Technique to Manage Restoration of Severely Tilted Adjacent Implants: A Dental Technique.

Implant placement in close proximity with adverse angulations may result in difficulty with impression making. With the lock surface function provided by intraoral scanning software programs, severely tilted adjacent implants can be digitized one by one without interfering with the accuracy of the digital cast. This article presents a straightforward digital impression technique for severely mesiodistally tilted adjacent implants in a clinical case.

Using existing interim complete dentures as an aid for an interocclusal record to align edentulous intraoral scans for implant-retained overdentures.

This technique describes a workflow to align the maxillary and mandibular edentulous intraoral scans in the computer-aided design and computer-aided manufacturing (CAD-CAM) software program for the fabrication of CAD-CAM implant-retained overdentures. Using the patient's existing and clinically satisfactory interim complete dentures as an aid for the interocclusal record, this technique provides a convenient option for aligning edentulous intraoral scans without the need for an additional clinical appointment, record base, or maxillomandibular tracing device.

Coronavirus disease 2019 (COVID-19): Experiences and protocols from the Department of Prosthodontics at the Wuhan University.

STATEMENT OF PROBLEM: The novel Coronavirus Disease 2019 (COVID-19) is a global pandemic, and many countries and regions are still currently in the midst of the outbreak. This pandemic has caused prosthodontics units to suspend their clinical and educational operations in academia. PURPOSE: The purpose of this article was to review the experiences from the Department of Prosthodontics, Wuhan University School and Hospital of Stomatology (DP-WHUSHS), during the COVID-19 outbreak and the protocols DP-WHUSHS used to resume clinical activities after the outbreak. MATERIAL AND METHODS: The descriptive approach was used in this article to provide a chronological narrative of the experiences and protocols from the DP-WHUSHS during the COVID-19 outbreak and after the outbreak. RESULTS: During the COVID-19 outbreak period, clinical care was provided for patients with dental emergencies by using enhanced grade 2 or grade 3 personal protective equipment (PPE). Teledentistry was used to provide care for patients with nonemergency needs. Online webinars and lectures were conducted for the predoctoral students, residents, and dentists to minimize the interruption in their education and engage the dental community amid the pandemic. Various factors were considered before clinical activities resumed after the outbreak subsided. Additional resources were allocated for facility preparation and management and employee training. New infection control and clinical operation protocols were developed to minimize the health-care-associated infection of airborne transmission diseases. The psychological health and mental wellness of the employees were emphasized. Distance or online education is still under rapid development to provide students and dentists opportunities to advance their knowledge amid the pandemic. CONCLUSIONS: Within the limitation of this descriptive review, the following conclusions were drawn. Patient welfare and emergency needs should be considered amid the pandemic. Enhanced grade 2 or grade 3 PPE should be used during the outbreak. Multifactorial considerations for work resumption after the outbreak included facility preparation and management, training for employees, and clinical operation management. In-person psychological consultation and online mental wellness programs were available to employees to improve their mental wellness. Distance or online education was under rapid development to minimize the interruption in education for the students and to engage the dental community amid a pandemic.

Mesoporous calcium silicate nanoparticles for superficial dental tissue reconstruction, in vitro and in vivo.

The underlying dentin could be exposed to a humid atmosphere filled with bacteria if the covering enamel layer is broken because of external chemical and physical conditions. Accordingly, some diseases like bacterial invasion and dentin hypersensitivity often occur, which impact the daily life of patients. The study is aimed at evaluating the occluding effects of mesoporous calcium silicate nanoparticles (MCSNs) on the dentinal tubules in vitro and in vivo, as well as the antibacterial property and drug delivery ability when loaded with chlorhexidine (CHX) in vitro. MCSNs were synthesized according to the standard protocol. After a series of complimentary evaluations in vitro and in vivo, it was found that MCSNs and CHX-MCSNs could continually form apatite-like enamel layers on the exposed dentinal tubules and significantly reduced dentin permeability both in vitro and in vivo. Besides, MCSN and CHX-MCSN possessed low cytotoxicity in vitro, and only mild pulp inflammation was observed in two MCSNs containing groups in vivo. In addition, MCSN loaded with CHX released CHX sustainably and revealed a significant antibacterial effect against E. faecalis in vitro. Therefore, the results suggest that MCSN could be used as a promising biomaterial to occlude the dentinal tubules and carry antibiotics for avoiding further pulp infection.

Modifications of Poly(Methyl Methacrylate) Cement for Application in Orthopedic Surgery.

Even with the emerging of newly-developed bone substitutes, poly(methyl methacrylate) (PMMA) cement is still a widely-used bone replacing biomaterial in orthopedic surgery with a long history. However, aseptic loosening, infection of the prosthesis and thermal necrosis to surrounding tissue are the common complications of PMMA. Therefore, additives have been incorporated in PMMA cement to target those problems. This chapter summarizes different additives to improve the performance of the PMMA cement, i.e.: (1) bioceramic additives; (2) filler additives; (3) antibacterial additives; (4) porogens; (5) biological agents, and (6) mixed additives. To improve the biological and mechanical performance of PMMA cement, mixed additives aiming to fabricate multifunctional PMMA seem the most suitable choice. Although in vivo animal studies have been conducted, long-term and clinical studies are still needed to evaluate the modifications of multifunctional PMMA cement for matching a specific clinical application.

A versatile and injectable poly(methyl methacrylate) cement functionalized with quaternized chitosan-glycerophosphate/nanosized hydroxyapatite hydrogels.

Injectable polymethylmethacrylate (PMMA) bone cement is alluring because it allows a minimally invasive surgical approach, reducing both the cost of treatment and patient discomfort. However, several documented drawbacks have necessitated the design of a more versatile version with adorable properties for future application. In this study, to amend the bulk behavior of PMMA cement, we synthesized a modified version by combining PMMA with quaternized chitosan (N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride, HTCC)-based hydrogels loaded with nanosized hydroxyapatite (Nano-HA). Then, the physicochemical properties, antimicrobial properties, remineralization capacity and mechanical performance changes under imitated physiological conditions were tested for these cements using a type K thermocouple, scanning electron microscope (SEM), microcomputed tomography (µ-CT), calcium ion test kit and mechanical compression tests. The results demonstrated that the HTCC-GP thermosensitive hydrogel generated interconnected pores, lower the Tmax value, lengthened the working time, developed appropriate mechanical properties and imparted excellent antibacterial activity to the cement. The Nano-HA particles engendered improved biomineralization ability of the cements without adversely influencing the mechanical performance. Hence, these results indicated that the injectable and multifunctional cement resulting from the p-PMMA/HTCC-GP/Nano-HA combination grips rosy prospect for future applications in bone reconstruction.

Effects of different concentrations and exposure time of sodium hypochlorite on the structural, compositional and mechanical properties of human dentin.

This study evaluated the effects of sodium hypochlorite (NaOCl) with different concentrations and exposure time on the structural, compositional and mechanical properties of human dentin in vitro. Sixty dentin slabs were obtained from freshly extracted premolars, randomly distributed into four groups (n=15), and treated with 1%, 5%, 10% NaOCl and distilled water (control group), respectively, for a total of 60 min. Attenuated total reflection infrared (ATR-IR) spectroscopy, Raman spectroscopy and X-ray diffraction (XRD) were carried out before, 10 min and 60 min after the treatment. Scanning electron microscopy (SEM) and flexural strength test were conducted as well. The results showed that dentins experienced morphological alterations in the NaOCl groups, but not in the control group. Two-way repeated-measures analysis of variance revealed that the carbonate:mineral ratio (C:M), Raman relative intensity (RRI), a-axis, c-axis length and full width at half maximum (FWHM) with the increase of time and concentration in the NaOCl groups were not significantly different from those in the control group (P>0.05). Nevertheless, the mineral:matrix ratio (M:M) increased and the flexural strength declined with the increase of concentration and the extension of time in the NaOCl groups (P<0.05). Additionally, it was found that the M:M and the flexural strength remained unchanged after 1% NaOCl treatment (P>0.05), and the morphology changes were unnoticeable within 10 min in 1% NaOCl group. These results indicated that NaOCl has no significant effects on the inorganic mineral of human dentin; but it undermines and eliminates the organic content concentration- and time-dependently, which in turn influences the flexural strength and toughness of dentins. In addition, an irrigation of 1% NaOCl within 10 min can minimize the effects of NaOCl on the structural and mechanical properties of dentin during root canal treatment.

Evaluation of the effectiveness of micro-Raman spectroscopy in monitoring the mineral contents change of human enamel in vitro.

The purpose of this in vitro study was to investigate the efficacy of micro-Raman spectroscopy on detecting mineral content change during the demineralization and de/remineralization cycling process. The enamel samples (n = 55) were randomly divided into three groups and separately treated with demineralization solution (n = 20), de/remineralization cycling solution (n = 30), and distilled water (n = 5). Micro-Raman spectroscopy, microhardness (MHS), and the released calcium ions concentration were performed before and after treatment, respectively. A one-way analysis of variance (ANOVA) with a post hoc Tukey test was used to analyze the results. The Spearman correlation coefficients among the parameters of Raman relative intensity decrease (RRID%), the percentage of MHS loss (PML), and the released calcium ions concentration were also analyzed. In demineralization group, RRID%, PML, and released calcium ions concentration were highly correlated with each other (r = 0.979, p < 0.001; r = 0.984, p < 0.001; and r = 0.983, p < 0.001, respectively). While for the de/remineralization cycling group, there also existed a high correlation between RRID% and PML (r = 0.987, p < 0.001). In conclusion, micro-Raman spectroscopy could effectively monitor the mineral content change, and its efficacy was validated by the measurement of released calcium ions concentration and MHS.

Bone Response to Porous Poly(methyl methacrylate) Cement Loaded with Hydroxyapatite Particles in a Rabbit Mandibular Model.

The aim of the current study was to evaluate bone formation and tissue response to porous poly(methyl methacrylate) (PMMA) cement with or without hydroxyapatite (HA) in a rabbit mandibular model. Therefore, 14 New Zealand White rabbits were randomly divided into two groups of seven according to the designed study end points of 4 and 12 weeks. For each rabbit, two decorticated defects (6 mm in height and 10 mm in width for each) were prepared at both sides of the mandible. Subsequently, the defects were filled with, respectively, porous PMMA and porous PMMA-HA cement. After reaching the designated implantation period, the rabbits were euthanized and the mandibles were retrieved for histological analysis. Results showed that both porous PMMA and porous PMMA-HA supported bone repair. Neither of the bone cements caused significant inflammation to nerve or other surrounding tissues. After implantation of 12 weeks, majority of the porosity was filled with newly formed bone for both cements, which supports the concept that a porous structure within PMMA can enhance bone ingrowth. Histomorphometrical evaluation, using histological grading scales, demonstrated that, at both implantation times, the presence of HA in the PMMA enhanced bone formation. Bone was always in direct contact with the HA particles, while intervening fibrous tissue was present at the PMMA-bone interface. On the basis of results, it was concluded that injectable porous PMMA-HA cement might be a good candidate for craniofacial bone repair, which should be further evaluated in a more clinically relevant large animal model.

Physicochemical properties and mineralization assessment of porous polymethylmethacrylate cement loaded with hydroxyapatite in simulated body fluid.

The aim of this study was to evaluate the effect of carboxymethylcellulose (CMC) as a pore generator and hydroxyapatite (HA) as an osteoconductive agent on the physicochemical properties and in-vitro mineralization ability of porous polymethylmethacrylate (PMMA) cement. To this end, various compositions of PMMA cements, which differed in amount of millimeter-sized hydroxyapatite (HA) particles and CMC hydrogel, were prepared and immersed into simulated body fluid (SBF) for 0, 7, 14, 21 and 28 days. It was demonstrated that the incorporation of CMC hydrogel decreased the maximum temperature of cement to the normal body temperature and prolonged the handling time during polymerization. Further, the amount of CMC was responsible for the creation of porosity and interconnectivity, which in turn determined the final mechanical properties of cements. The loaded HA particles enhanced the potential bioactivity of cement for bone ingrowth. Albeit different amount of HA particles influenced their final exposures on the surface of cured cement, all of the three amounts of HA did not weaken the final mechanical properties of cements. The data here suggests that the HA particle loaded porous PMMA cement can serve as the promising candidate for bone reconstruction.

Physicochemical properties and in vitro mineralization of porous polymethylmethacrylate cement loaded with calcium phosphate particles.

The main goal of this study was to evaluate the effects of incorporation of calcium phosphate (CaP) particles on the physicochemical properties and mineralization capacity of cements in vitro. Herein, two different types of CaP particles were loaded into polymethylmethacrylate (PMMA) cements exhibiting an interconnected porosity created by mixing with carboxymethylcellulose. The incorporation of CaP particles did not influence the maximum polymerization temperature of the porous PMMA, but reduced the porosity and the average pore size. Small CaP particles formed agglomerations within the PMMA pores, whereas big CaP particles were partially embedded in the PMMA matrix and partially exposed to the pores. Both types of CaP particles enhanced the mineralization capacity of PMMA cement without compromising their mechanical properties. The data presented herein suggest that porous PMMA/CaP cements hold strong promise for surgical application in bone reconstruction.

Effect of in-office bleaching agents on the color changes of stained ceromers and direct composite resins.

PURPOSE: To evaluate the effect of two in-office bleaching agents on the color changes of two ceromers (Ceramage and Adoro SR) and one direct composite resin (Gradia Direct Anterior) after staining by tea and coffee. MATERIALS AND METHODS: Twenty-four disk-shaped specimens were fabricated for each resin material and randomly divided into three groups (n = 8). The specimens were immersed in tea, coffee or deionized water, respectively, for 7 days. Each group was then equally divided into two sub-groups (n = 4), which were subjected to two in-office bleaching agents (BEYOND and Opalescence Boost), respectively. The color of the specimens was measured by a spectrophotometer at baseline, after staining and after bleaching. The color differences (ΔE values) between baseline and after treatments were calculated. RESULTS: Statistical analysis indicated that the staining solution had significant influence on the color change of resin composites tested (p < 0.001). The discolorations of resin composites were perceptible after immersing in tea or coffee solutions (ΔE>2.0). There was no statistically significant difference between BEYOND and Opalescence Boost in stains removal from discolored resins (p = 0.550). The color changes in ΔE value between baseline and after bleaching were less than 2.0 for all resin composite groups. CONCLUSIONS: Tea solution produces severe discoloration of three resin composites tested. The two in-office bleaching agents can effectively remove the stains from two ceromers and one direct composite resin tested in this study.

Compositional, structural and mechanical comparisons of normal enamel and hypomaturation enamel.

Hypomaturation amelogenesis imperfecta is a hereditary disorder of the enamel that severely influences the function, aesthetics and psychosocial well-being of patients. In this study, we performed a thorough comparison of normal and hypomaturation enamel through a series of systematical tests on human permanent molars to understand the biomineralization process during pathological amelogenesis. The results of microcomputed tomography, scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, microzone X-ray diffraction, thermal gravimetric analysis, energy diffraction spectrum and Vickers microhardness testing together show dramatic contrasts between hypomaturation enamel and normal enamel in terms of their hierarchical structures, spectral features, crystallographic characteristics, thermodynamic behavior, mineral distribution and mechanical property. Our current study highlights the importance of the organic matrix during the amelogenesis process. It is found that the retention of the organic matrix will influence the quantity, quality and distribution of mineral crystals, which will further demolish the hierarchical architecture of the enamel and affect the related mechanical property. In addition, the high carbonate content in hypomaturation enamel influences the crystallinity, crystal size and solubility of hydroxyapatite crystals. These results deepen our understanding of hypomaturation enamel biomineralization during amelogenesis, explain the clinical manifestations of hypomaturation enamel, provide fundamental evidence to help dentists choose optimal therapeutic strategies and lead to improved biofabrication and gene therapies.

In vitro evaluation of halogen light-activated vs chemically activated in-office bleaching systems.

OBJECTIVES: To compare the tooth whitening efficacy, temperature and HP concentration changes induced by halogen light-activated and chemically activated in-office bleaching systems. MATERIALS AND METHODS: Twenty-four extracted premolars were randomly divided into two groups (n = 12): Group BL (35% HP with halogen light activation) and Group OP (38% HP with chemical activation). Tooth color was measured by a spectrophotometer according to the CIE L*a*b* color space system. Temperatures of bleaching gels and pulp chambers during the bleaching process were monitored and recorded by a digital multimeter with K-type thermocouple. HP concentrations were tested before and after treatments by iodometry. ANOVA and paired t-test were used for statistical analyses at the significance of p < 0.05. RESULTS: Tooth whitening resulted in the increase of ΔL* and ΔE and reduction of Δb*. Paired t-tests revealed groups BL had greater ΔE than group OP, however, there was no statistically significant difference in ΔE between them after 3 weeks post-treatment. Maximal temperature rise (ΔT) was found only in group BL, showing the increment of 2.55 and 2.02°C for bleaching gels and pulp chambers, respectively. HP concentrations were higher than baseline values for group OP (p < 0.001) rather than group BL. CONCLUSIONS: Halogen light and chemically activated in-office bleaching systems were both effective for tooth whitening, but halogen light activation could improve the immediate whitening effect. In contrast, chemical activation was a more conservative method due to the little temperature rise in pulp chambers.