Full-arch implant-supported rehabilitations: A prospective study comparing porcelain-veneered zirconia frameworks to monolithic zirconia.

OBJECTIVES: To evaluate the performance of two types of zirconia frameworks. MATERIAL AND METHODS: From 2014 to 2016, in a prospective clinical trial, 150 patients were rehabilitated with 83 and 110 implant-supported, screw-retained, full-arch ceramic-veneered zirconia (PVZ) rehabilitations and monolithic zirconia with porcelain veneering limited to buccal (MZ) rehabilitations, respectively. Patients were consecutively enlisted according to pre-defined inclusion criteria and evaluated on 4 months intervals. A Kaplan-Meier estimator was adopted, and the log-rank test and Wilcoxon test used to test differences in survival and successful function in the two different groups. RESULTS: The average follow-up time (±SD) and implant success rate was 608.80 ± 172.52 days with 99.53% implant success for the PVZ group and 552.63 ± 197.57 days with 99.83% success for the MZ group. According to the Kaplan-Meier estimator, the mean cumulative survival rate at the 2-year follow-up for framework fracture, major chipping, minor chipping, or any of the former combined to occur was 0.99, 0.95, 0.93 and 0.85 for the PVZ group (n = 18) and 0.99, 0.95, 0.95 and 0.89 for the MZ group (n = 15). No significant differences were found between the two groups. CONCLUSIONS: Results suggest zirconia as a suitable material for frameworks in full-arch implant-supported rehabilitations. Both groups presented a low incidence of technical complications. When comparing the two different designs, the MZ group presented a lower technical complication rate, thus presenting itself as a viable alternative for full-arch implant-supported rehabilitations. Further clinical studies with longer follow-ups (5 years) should be performed to evaluate the long-term stability of such rehabilitations.

Fatigue Failure of External Hexagon Connections on Cemented Implant-Supported Crowns.

PURPOSE: To evaluate the probability of survival and failure modes of different external hexagon connection systems restored with anterior cement-retained single-unit crowns. The postulated null hypothesis was that there would be no differences under accelerated life testing. MATERIALS AND METHODS: Fifty-four external hexagon dental implants (∼4 mm diameter) were used for single cement-retained crown replacement and divided into 3 groups: (3i) Full OSSEOTITE, Biomet 3i (n = 18); (OL) OEX P4, Osseolife Implants (n = 18); and (IL) Unihex, Intra-Lock International (n = 18). Abutments were torqued to the implants, and maxillary central incisor crowns were cemented and subjected to step-stress-accelerated life testing in water. Use-level probability Weibull curves and probability of survival for a mission of 100,000 cycles at 200 N (95% 2-sided confidence intervals) were calculated. Stereo and scanning electron microscopes were used for failure inspection. RESULTS: The beta values for 3i, OL, and IL (1.60, 1.69, and 1.23, respectively) indicated that fatigue accelerated the failure of the 3 groups. Reliability for the 3i and OL (41% and 68%, respectively) was not different between each other, but both were significantly lower than IL group (98%). Abutment screw fracture was the failure mode consistently observed in all groups. CONCLUSION: Because the reliability was significantly different between the 3 groups, our postulated null hypothesis was rejected.

Thickness evaluation of articulating papers and foils.

Articulation and occlusion test materials are tools used in daily prosthodontic and restorative procedures that aid the clinicians in the evaluation of adjacent and opposing natural and/or artificial tooth contacts. A precision micrometer (Series 293, Mitutoyo, Japan) with a resolution of 0.001 mm was used to measure the thickness of five articulating papers and six articulation foils. Four of the articulating foils tested presented thicknesses inferior or equal to 21 µm, confirming their adequacy for the evaluation of natural dentitions. Clinicians and researchers should be aware that some labeled and actual papers/foils thicknesses are not in accordance. CLINICAL SIGNIFICANCE: The thickness of articulating papers and foils reported by some manufacturers is not accurate. The information provided in this article may aid clinicians and researchers to better select the most appropriate materials for the evaluation of static and dynamic occlusion.

Scan-layered reconstructions: A pilot study of a nondestructive dental histoanatomical analysis method and digital workflow to create restorations driven by natural dentin and enamel morphology.

OBJECTIVE: This work aims to present a pilot study of a non-destructive dental histo-anatomical analysis technique as well as to push the boundaries of the presently available restorative workflows for the fabrication of highly customized ceramic restorations. MATERIALS AND METHODS: An extracted human maxillary central incisor was subject to a micro computed tomography scan and the acquired data was transferred into a workstation, reconstructed, segmented, evaluated and later imported into a Computer-Aided Design/Computer-Aided Manufacturing software for the fabrication of a ceramic resin-bonded prosthesis. RESULTS: The obtained prosthesis presented an encouraging optical behavior and was used clinically as final restoration. CONCLUSION: The digitally layered restorative replication of natural tooth morphology presents today as a clear possibility. New clinical and laboratory-fabricated, biologically inspired digital restorative protocols are to be expected in the near future. CLINICAL SIGNIFICANCE: The digitally layered restorative replication of natural tooth morphology presents today as a clear possibility. This pilot study may represent a stimulus for future research and applications of digital imaging as well as digital restorative workflows in service of esthetic dentistry.

Do not let the Spanish "s" misguide you.

The orthographic representation of the "s" in the Spanish language may have three phonetic variations and be associated with other phonological phenomena that add to its unpredictability when used to evaluate the closest speaking space. These are of clinical interest since each of these variations may represent a more or less pronounced difference from what is observed in the English language and patient population. The present article explains the previously mentioned variations and reviews the suggested Spanish terms for evaluation of the closest speaking space.

Volumetric shrinkage and film thickness of cementation materials for veneers: An in vitro 3D microcomputed tomography analysis.

STATEMENT OF PROBLEM: Few studies have investigated the volumetric polymerization shrinkage and film thickness of the different cementation techniques used to cement veneers. PURPOSE: The purpose of this in vitro study was to evaluate the volumetric polymerization shrinkage (VS) and film thickness (FT) of various cementation techniques through 3-dimensional (3D) microcomputed tomography (µCT). MATERIAL AND METHODS: Forty-eight artificial plastic maxillary central incisors with standard preparations for veneers were provided by a mannequin manufacturer (P-Oclusal) and used as testing models with the manufacturer's plastic veneers. They were divided into 8 groups (n=6): RelyX Veneer + Scotchbond Universal (RV+SBU); Variolink Esthetic LC+Adhese Universal (VE+ADU); Filtek Supreme Ultra Flowable + Scotchbond Universal (FF+SBU); IPS Empress Direct Flow + Adhese Universal (IEF+ADU); Filtek Supreme Ultra Universal + Scotchbond Universal (FS+SBU); IPS Empress Direct + Adhese Universal (IED+ADU); Preheated Filtek Supreme Ultra Universal + Scotchbond Universal (PHF+SBU); and Preheated IPS Empress Direct + Adhese Universal (PHI+ADU). Specimens were scanned before and after polymerization using a µCT apparatus (mCT 40; Scanco Medical AG), and the resulting files were imported and analyzed with 3D rendering software to calculate the VS and FT. Collected data from both the VS and FT were submitted to 1-way ANOVA (α=.05). RESULTS: VE+ADU had the lowest volumetric shrinkage (1.03%), which was not significantly different from RV+SBU, FF+SBU or IEF+ADU (P>.05). The highest volumetric shrinkage was observed for FS+SBU (2.44%), which was not significantly different from RV+SBU, IED+ADU, PHF+SBU, or PHI+ADU (P>.05). Group RV+SBU did not differ statistically from the remaining groups (P>.05). Film thickness evaluation revealed the lowest values for RV+SBU, VE+ADU, FF+SBU, and IEF+ADU, with an average between groups of 0.17 mm; these groups were significantly different from FS+SBU, IED+ADU, PHF+SBU, and PHI+ADU (P>.05), with an average of 0.31 mm. CONCLUSIONS: Both the VS and the FT of direct restorative composite resins were higher than those of veneer cements and flowable composite resins, whether preheated or not preheated.

Histomorphological and Histomorphometric Analyses of Grade IV Commercially Pure Titanium and Grade V Ti-6Al-4V Titanium Alloy Implant Substrates: An In Vivo Study in Dogs.

PURPOSE: To evaluate the bone response to grade IV commercially pure titanium (G4) relative to Ti-6Al-4V (G5). MATERIALS AND METHODS: Implant surface topography was characterized by optical interferometry and scanning electron microscopy (SEM). Thirty-six implants (Signo Vinces, n = 18 per group) were installed in the radius of 18 dogs. The animals were killed at 1, 3, and 6 weeks, resulting in 6 implants per group and time in vivo for bone morphology, bone-to-implant contact (BIC), and bone area fraction occupancy (BAFO) evaluation. RESULTS: SEM depicted a more uniform topography of G4 than G5. Surfaces were statistically homogeneous for Sa, Sq, and Sdr. At 1 week, new bone formation was observed within the healing connective tissue in contact with the implant surface. At 3 weeks, new bone in direct contact with the implant surface was observed at all bone regions. At 6 weeks, the healing chambers filled with woven bone depicted an onset of replacement by lamellar bone. No significant effect of substrate was detected. Time presented an effect on BIC and BAFO (P < 0.001). CONCLUSION: Both titanium substrates were biocompatible and osseoconductive at the bone tissue level.

Multidimensional optimization of promising antitumor xanthone derivatives.

A promising antitumor xanthone derivative was optimized following a multidimensional approach that involved the synthesis of 17 analogues, the study of their lipophilicity and solubility, and the evaluation of their growth inhibitory activity on four human tumor cell lines. A new synthetic route for the hit xanthone derivative was also developed and applied for the synthesis of its analogues. Among the used cell lines, the HL-60 showed to be in general more sensitive to the compounds tested, with the most potent compound having a GI50 of 5.1 µM, lower than the hit compound. Lipophilicity was evaluated by the partition coefficient (K(p)) of a solute between buffer and two membrane models, namely liposomes and micelles. The compounds showed a logK(p) between 3 and 5 and the two membrane models showed a good correlation (r(2)=0.916) between each other. Studies concerning relationship between solubility and structure were developed for the hit compound and 5 of its analogues.

Structural and biochemical analysis reveals how ferulic acid improves catalytic efficiency of Humicola grisea xylanase.

Humicola grisea var. thermoidea is an aerobic and thermophilic fungus that secretes the GH11 xylanase HXYN2 in the presence of sugarcane bagasse. In this study, HXYN2 was expressed in Pichia pastoris and characterized biochemically and structurally in the presence of beechwood xylan substrate and ferulic acid (FA). HXYN2 is a thermally stable protein, as indicated by circular dichroism, with greater activity in the range of 40-50 °C and pH 5.0-9.0, with optimal temperature and pH of 50 °C and 6.0, respectively. FA resulted in a 75% increase in enzyme activity and a 2.5-fold increase in catalytic velocity, catalytic efficiency, and catalytic rate constant (kcat), with no alteration in enzyme affinity for the substrate. Fluorescence quenching indicated that FA forms a complex with HXYN2 interacting with solvent-exposed tryptophan residues. The binding constants ranged from moderate (pH 7.0 and 9.0) to strong (pH 4.0) affinity. Isothermal titration calorimetry, structural models and molecular docking suggested that hydrogen bonds and hydrophobic interactions occur in the aglycone region inducing conformational changes in the active site driven by initial and final enthalpy- and entropy processes, respectively. These results indicate a potential for biotechnological application for HXYN2, such as in the bioconversion of plant residues rich in ferulic acid.

COVID-19 Management in Clinical Dental Care. Part I: Epidemiology, Public Health Implications, and Risk Assessment.

Coronavirus disease 2019 (COVID-19), a viral disease declared a pandemic by the World Health Organization (WHO) in March 2020, has posed great changes to many sectors of society across the globe. Its virulence and rapid dissemination have forced the adoption of strict public health measures in most countries, which, collaterally, resulted in economic hardship. This article is the first in a series of 3 that aims to contextualise the clinical impact of COVID-19 for the dental profession. It presents the epidemiological conditions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), namely, its modes of transmission, incubation, and transmissibility period, signs and symptoms, immunity, immunological tests, and risk management in dental care. Individuals in dental care settings are exposed to 3 potential sources of contamination with COVID-19: close interpersonal contacts (<1 m), contact with saliva, and aerosol-generating dental procedures. Thus, a risk management model is propsoed for the provision of dental care depending on the epidemiological setting, the patient's characteristics, and the type of procedures performed in the office environment. Although herd immunity seems difficult to achieve, a significant number of people has been infected throughout the first 9 months of the pandemic and vaccination has been implemented, which means that there will be a growing number of presumable "immune" individuals that might not require many precautions that differ from those before COVID-19. In conclusion, dental care professionals may manage their risk by following the proposed model, which considers the recommendations by local and international health authorities, thus providing a safe environment for both professionals and patients.

Periodontal considerations for adhesive ceramic dental restorations: key points to avoid gingival problems.

The stability and health of the periodontal tissues should be a common goal for all dental care providers with regard to natural or restored teeth as well as implant-supported restorations or any other type of prosthesis. The objective of this study was to address the key aspects to be respected when executing adhesive oral rehabilitations involving ceramic restorations, regardless of their thickness, and to reinforce the importance of each step to ensure the success and longevity of the treatment from a periodontal standpoint. This article reviews the fundamentals of the periodontics that relate directly or indirectly to adhesive ceramic dental restorations, and also addresses their clinical relevance.

Achieving gastroresistance without coating: Formulation of capsule shells from enteric polymers.

Capsules are a widely used oral dosage form due to their simplicity and ease of manufacture. They are equally popular for both pharmaceutical and nutraceutical products and since they do not need extensive formulation development, it is a dosage form of choice for new drugs undergoing animal or clinical trials. In addition to the standard hard-gelatin or cellulose-based vegetarian capsules, functional capsules such as those with built-in gastroresistance would be of great value. In this work, commonly used enteric polymers were investigated for the production of hard-capsules. The polymers used in this study included cellulose derivatives (HPMC AS-LF and HP-55) and acrylic/methacrylic acid derivatives (EUDRAGIT L100 and S100). A range of concentrations of polymers and plasticisers were tested to optimise the formulation for the production of capsule shells with desirable physicochemical and gastroresistance characteristics. Drug release from optimised capsules produced from HPMC AS-LF, HP-55, EUDRAGIT L100 and S100 was shown to be comparable to drug release from corresponding polymer-coated tablets in both compendial and physiological bicarbonate buffer. In summary, herein we report a simple method for producing enteric capsule shells which do not need an additional coating step which, if validated at large scale, can significantly reduce the cost of manufacturing of conventional enteric coated dosage forms. These capsules are also likely to improve the inter-tablet variability in post-gastric drug release inherent in conventional dosage forms due to coating variability.

Comparison of a non-destructive technique using three-dimensional imaging and histoanatomical chemical dissolution for dental morphology analysis.

AIM: The present work aims to compare a digital dental histoanatomical analysis method with chemical enamel dissolution for the study of dental morphology. MATERIAL AND METHODS: Extracted maxillary anterior teeth were scanned under microcomputed tomography (µCT) (µCT 40; Scanco Medical), segmented, and reconstructed three-dimensionally (Amira, version 5.5.2; VSG). Following the digital acquisition of dental morphology, all specimens were acid treated with 5% formic acid for careful dissolution of the enamel layer. Six measurements (three buccopalatal and three mesiodistal) per specimen were performed, both digitally following the µCT scan and physically both before and after enamel dissolution. The obtained measurements were subjected to statistical analysis through concordance coefficient measurements and linear regression. RESULTS: A straight line correlation behavior with no statistically significant difference was found between both methods, with a concordance correlation coefficient of 97%. CONCLUSION: The digital, nondestructive, µCT-layered, three-dimensional reconstruction method presented comparable results to acid-etched enamel dissolution, confirming that both options are reliable for the histoanatomical analysis of enamel and dentin morphologies.

Dental considerations and the role of prosthodontics and maxillofacial prosthetics in facial transplantation.

BACKGROUND: Facial transplantation (FT) is a challenging reconstructive endeavor that requires the expertise of a multidisciplinary team. The specific role of maxillofacial prosthodontists has not yet been reported in detail. METHODS: This review considers the contributions of prosthodontists throughout the FT process, from patient selection and dental evaluation to long-term dental rehabilitation of the transplant patient postoperatively. Moreover, considerations of dental management are evaluated. RESULTS: In the almost 40 FT reported in the literature, the most consistently documented contribution by prosthodontists is the fabrication of a donor mask to maintain donor integrity. Though infrequently reported, prosthodontists have the potential to plan and perform a variety of dental procedures and follow-up plans. CONCLUSIONS: When applicable, facial transplant teams are tasked with providing optimal stomatognathic function and dental occlusion to recipients with severe facial disfigurement. The maxillofacial prosthodontist's contribution is crucial to the long-term dental restoration of the edentulous facial transplant candidate, in addition to the fabrication of the donor mask which fulfills the team's ethical responsibilities. PRACTICAL IMPLICATIONS: Maxillofacial prosthodontists play a pivotal role in facial transplantation, particularly when jaw segments are intended for transplantation.