Utilization of rapid antigen tests for screening SARS-CoV-2 prior to dental treatment.

Potential aerosols containing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral particles can be generated during dental treatment. Hence, patient triage is essential to prevent the spread of SARS-CoV-2 in dental clinical settings. The present study described the use of rapid antigen tests for SARS-CoV-2 screening prior to dental treatment in an academic dental clinical setting in Thailand during the pandemic. The opinions of dental personnel toward the use of rapid antigen test screening prior to dental treatment were also assessed. From August 25 to October 3, 2021, dental patients who were expected to receive aerosols generating dental procedures were requested to screen for SARS-CoV-2 using a rapid antigen test before their treatment. A total of 7,618 cases completed the screening process. The average was 212 cases per day. Only five patients (0.07%) were positive for SARS-CoV-2 in the rapid antigen screening tests. All positive cases exhibited mild symptoms. For the questionnaire study, experienced dental personnel frequently and consistently agreed with the use of the rapid antigen test for SARS-CoV-2 screening, which made them feel safer during their patient treatment. However, implementing rapid antigen tests for SARS-CoV-2 may increase the total time spent on a dental appointment. In conclusion, a rapid antigen test could detect the infected individual prior to dental treatment. However, the specificity of rapid antigen tests for SARS-CoV-2 must be taken into account for consideration as a screening process before dental treatment. The enhanced infection control protocols in dental treatment must be consistently implemented.

Procedures Used in Managing SARS-CoV-2 Infected Dental Personnel or Patients: A Case Study From a Thai Dental Hospital.

SARS-CoV-2 can transmit undetected from asymptomatic and pre-symptomatic patients in dental clinics. Triaging dental patients using temperature and questionnaire screening cannot completely exclude asymptomatic SARS-CoV-2 infected individuals. Hence, asymptomatic SARS-CoV-2 infected individuals might visit dental hospitals/clinics seeking dental treatment without knowing that they are infected and might infect others, especially in a pandemic area. Ideally, a nasopharyngeal swab for real-time polymerase chain reaction or rapid antigen screening for dental personnel and patients prior to their appointment should be done. However, the implementation of this approach is impractical in some situations. Here, we describe the procedures for dental hospitals/clinics in case of an asymptomatic SARS-CoV-2 infected individual involved in dental service/treatment and later after testing positive for SARS-CoV-2. Potential closely contacted individuals were traced and classified according to their exposure risk. The recommended course of action is to identify individuals based on their risk and take the risk-appropriate action. We also discuss the implementation of these procedures in a dental setting during the COVID-19 pandemic in our school as a case study.

Texture of composite resins exposed to two- and three-body wear in vitro.

PURPOSE: To analyze on scanning electron microscopy (SEM) pictures from eight composite resins, taken in the centers of the initial, the middle and the terminal thirds of in vitro produced wear tracks morphological features to explain causative mechanisms for the material wear observed under two- and three-body wear. MATERIALS AND METHODS: In vitro wear behavior of eight composite resins, three conventional and five nanofiller containing marketed products was evaluated using a custom-made Zr-ball-on-disk sliding device. The composite specimens were subjected to 50,000 one-way sliding cycles (1.2 Hz, 50 N load), either simulating two-body wear with water as the intermediate medium or three-body wear using aqueous suspensions of polymethyl methacrylate (PMMA) beads and poppy seeds, respectively. Volume loss of the materials was determined in previous study. Representative specimens were selected for inspection by scanning electron microscopy at 500-fold magnification. From each of the 24 wear tracks microphotographs were taken in the central deepest parts of the initial, middle and terminal thirds of the tracks. RESULTS: For most materials morphological differences were detected depending on the location within the wear track. As a rule, the surface deterioration found increased toward the final part of the wear scar. According to common classification in tribology abrasive wear and fatigue wear, or a combination of both mechanisms were found for all materials tested. Wear was dependent both on the testing mode and on the composition of the individual composite resin material. CONCLUSION: The morphological assessment of wear tracks refects the nature of the abrasive and reveals insight into the mechanism generating wear patterns. Morphological details confirmed abrasive and fatigue-related wear as main failure mechanisms. Selection of food-like slurries as third-body media, such as poppy seed suspension is mandatory to simulate wear of composite restorations in occlusal cavities where three-body wear is the dominating determinant of loss of substance and surface deterioration.

Quantitative wear and wear damage analysis of composite resins in vitro.

The aim of this study was to investigate volume loss and worn surfaces' morphologies of eight composite resins: Durafill VS (DUR), Clearfil AP-X (APX), Filtek Z250 (Z250), Filtek Supreme XT (FIL), Kalore (KAL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP). Disc-shaped specimens were fabricated and mounted in a ball-on-disc wear testing machine and abraded in water or with the third-body media, poppy seed slurry and polymethyl methacrylate (PMMA) slurry. Volume loss (n=5) was determined after 50k sliding cycles, and analyzed using two-way ANOVA (α=0.05). The worn surfaces were examined with SEM. Two-way ANOVA suggested significant interaction between composite and wear condition. DUR, KAL and MFL showed low wear in water. DUR, Z250 and FIL showed moderate wear with PMMA slurry, whereas APX, KAL and MFL were deeper abraded. Under the action of poppy seed slurry DUR proved high volume loss. SEM showed that Z250, FIL and MFL were uniformly abraded in water. KAL and MFL with poppy seed were heavily destructed, whereas VED and VEP appeared very smooth. KAL and MFL abraded with PMMA slurry showed many cracks, but VEP remained crack-free and smooth. Volume loss and worn surfaces' morphologies varied with type of composite and third-body media used.

Two- and three-body wear of composite resins.

OBJECTIVE: The aim of the present study was to investigate two- and three-body wear of microfilled, micro-hybrid and nano-hybrid composite resins using a ball-on-disc sliding device. METHODS: One microfilled (Durafill VS), one micro-hybrid (Filtek Z250), one hybrid (Clearfil AP-X), one nanofilled (Filtek Supreme XT), and two nano-hybrid (MI Flow, Venus Diamond) composite resins were examined. The composites were filled in a cylindrical cavity, and light polymerized. After storage in 37°C distilled water for 7days, all specimens were tested with a custom-made ball-on-disc sliding device with a zirconia ball as antagonist (50N loads, 1.2Hz, 10,000 cycles) immersed in water, poppy seed slurry and polymethyl methacrylate slurry, respectively. Maximum wear depth and volume loss of worn surfaces were quantified by a digital CCD microscope and analyzed with two-way analysis of variance. RESULTS: The interactions between composite resin and condition of their maximum wear depth and volume loss were significant (p<0.01). The abrasive wear produced at three-body loading with poppy seed slurry was very large for the microfilled composite, and small for all other composites tested. In contrast, two-body wear of the microfilled composite, and one nano-hybrid composite was very low. SIGNIFICANCE: The ball-on-disc sliding device used is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration, either in the two- or the three-body wear mode. All tested materials except for the microfilled composite showed low surface wear when exposed to poppy seed as the third-body medium.

Quantification of in vitro produced wear sites on composite resins using contact profilometry and CCD microscopy: a methodological investigation.

BACKGROUND: Although attritive and abrasive wear of recent composite resins has been substantially reduced, in vitro wear testing with reasonably simulating devices and quantitative determination of resulting wear is still needed. Three-dimensional scanning methods are frequently used for this purpose. The aim of this trial was to compare maximum depth of wear and volume loss of composite samples, evaluated with a contact profilometer and a non-contact CCD camera imaging system, respectively. METHOD: Twenty-three random composite specimens with wear traces produced in a ball-on-disc sliding device, using poppy seed slurry and PMMA suspension as third-body media, were evaluated with the contact profilometer (TalyScan 150, Taylor Hobson LTD, Leicester, UK) and with the digital CCD microscope (VHX1000, KEYENCE, Osaka, Japan). The target parameters were maximum depth of the wear and volume loss.Results - The individual time of measurement needed with the non-contact CCD method was almost three hours less than that with the contact method. Both, maximum depth of wear and volume loss data, recorded with the two methods were linearly correlated (r(2) > 0.97; p < 0.01). CONCLUSION: The contact scanning method and the non-contact CCD method are equally suitable for determination of maximum depth of wear and volume loss of abraded composite resins.

Comparative evaluation of mechanical characteristics of nanofiller containing resin composites.

PURPOSE: To determine basic mechanical characteristics of six commercially available nanofiller containing resin composites compared to a microhybrid and a microfilled reference material. The tested hypothesis was that there are no differences in mechanical properties between the materials. METHODS: Durafill VS (DUR) and Filtek Z250 (Z250) were used as microfilled and microhybrid references. The nanofiller containing products were: Filtek Supreme XT (FIL), Grandio (GRA), Kalore (KAL), MI Flow (MIF), Tetric EvoCeram (TET), and Venus Diamond (VED). The following material characteristics were determined after 24 hours water storage (n = 6): Flexural strength and modulus (FM), yield stress (0.02%), tensile strength and modulus (TM), diametral tensile strength, Knoop hardness (KHN), and fracture toughness (KIC). RESULTS: The microfilled composite DUR consistently showed the lowest values for each property investigated. The group of nanofiller containing products could be subdivided into two groups: the nanohybrid products GRA and VED and the nanofilled FIL with higher values, on the one hand, and the flowable MIF, and the prepolymer containing composites KAL and TET, on the other. The mechanical performance of the microhybrid reference material Z250 was overall slightly better or in line with the nanohybrid and nanofilled materials. Stringent linear relationships were found between KHN and the moduli FM and TM, respectively (r > 0.95). Linear relations between the other materialvalues investigated were moderate to high.

In vitro wear resistance, hardness and elastic modulus of artificial denture teeth.

In this study, the wear resistance, hardness, elastic modulus, and the correlations between them of artificial denture teeth at the sub-enamel layer were examined. Four types of tested artificial denture teeth consisted of 3 conventional acrylic resin teeth (Cosmo HXL, Major Dent, and Yamahachi FX), 1 high cross-linked acrylic resin teeth (Trubyte Bioform IPN), 2 composite resin teeth (SR Orthosit PE, and Yamahachi PX), and 1 porcelain teeth (ACE Teeth). The two-body wear test was performed using a custom made pin on disc apparatus. Volume and weight loss were measured. Hardness and elastic modulus were also assessed by using a nanoindentation system. The results suggested wear resistance varied among the denture tooth materials. Wear resistance of high cross-linked acrylic resin teeth was the lowest. A definite relation between wear resistance and mechanical properties of materials could not be found in this study.