The influence of delayed light curing on the degree of conversion and polymerization contraction stress in dual-cured resin luting agents

The aim of the study was to assess the effect of delayed photo-initiation on the polymerization contraction stress (PCS) and degree of conversion (DC) of a dual-cure resin-luting agent. Thirty-five disk (6 mm × 1 mm) samples (n = 10 each group) of dual cure resin luting agent for PCS assessment were fabricated and polymerized using two illuminated quartz rods. Based on the delay in photo-initiation, 30 disks were divided among six groups [group A-0 min (min) delay, group B-2 min, group C-4 min, group D-6 min, group E-8 min and group F-10 min]. A non-photoinitiated group (group G – chemical cure – n = 5) was included as control. The PCS for all specimens was assessed using a Tensometer. For DC evaluation thirty-five specimens were divided into seven groups with delays in photo-initiation (group H-0 min, group I-2 min, group J-4 min, group K-6 min, group L-8 min and group M-10 min, group N-chemical cure). DC was assessed using attenuated total reflectance spectroscopic technique. Statistical comparison among groups was performed using analysis of variance (α = 0.05). The maximum and minimum PCS and DC values with delayed photo-initiation was observed in group-C (3.34 MPa) & group-F (2.44 MPa); and group-M (0.78 MPa) and group-H (0.55 MPa) respectively. Chemically cured samples showed the least PCS (group-G, 1.94) and DC (group-N, 0.53) values in their respective categories. PCS significantly decreased with delayed photo-initiation. A significant increase in DC was noticed when photo-initiation was delayed in the dual cure resin luting agent

COVID-19 Pandemic Driven Knowledge, Attitude, Clinical Practice, Distress Reactions, and Post-Traumatic Growth of Dental Care Providers in Riyadh City, Saudi Arabia: A Cross-Sectional Study

Objective: The present study aimed to assess knowledge, attitude, clinical practices, distress reactions, and post-traumatic growth of dentists during the COVID-19 pandemic in Riyadh City. Methodology: An online questionnaire was developed to assess various dental professionals from both governmental and private sectors during the early COVID-19 outbreak in Riyadh City, Saudi Arabia. The questionnaire was framed to assess the demographic variables, knowledge, attitude, and clinical practices towards handling the COVID-19 pandemic. Furthermore, the general anxiety disorder-7 (GAD-7), worry questionnaire items, short form of post-traumatic growth inventory (PTGI-SF), and life satisfaction questionnaire items were developed to assess the anxiety, worries, post-traumatic growth, and life satisfaction of dental care providers following the traumatic events. Data were analysed using SPSS 22.0 and R environment ver.3.2.2. Continuous measurement results were presented as mean ± SD, and categorical measurements results were presented in number (%). Results: Our study's significant findings revealed that a majority of the dentists were in the age group of 21-30 and practiced general dentistry. The study participants in age groups 51–60 and 41–50 years old showed more liability in perceiving COVID-19 as an extremely dangerous disease than 31–40 and 21–30 age groups. The majority of respondents (63.4%) had an anxiety scale score of greater than 40, followed by 22.8% with scores 20-40 and 13.9% with scores less than 20, respectively. The mean scores for the GAD-7 and the worry items were 8.24 ± 3.21 and 13.92 ± 4.77, respectively. The data showed that most survey participants had adopted moderate post-traumatic changes during the pandemic, as evident by their mean score of 34.17 ± 3.40. The life satisfaction of the participants was neutral, as demonstrated by their mean score of 20.16 ± 4.03. Conclusion: This study’s findings delineated that the COVID-19 pandemic situation has influenced dentists' mental health, with a moderate level of anxiety, and worries among other psychological symptoms. Furthermore, there was adequate knowledge regarding the COVID-19 among dentists; however, the pandemic affected the financial conditions of the respondents. There was a moderate level of post-traumatic growth and neutral life satisfaction of the dental providers

Influence of Toothbrush Abrasion and Surface Treatments on Roughness and Gloss of Polymer-Infiltrated Ceramics

The aim of this study was to compare the surface roughness and gloss of polymer-infiltrated ceramics after simulated in vitro toothbrushing in different storage mediums. Four polymer- infiltrated ceramics were evaluated, Lava ultimate (LU), Vita enamic (EN), Shofu (SH), and Crystal ultra (CU). The control group was a feldspathic ceramic, Vita Mark II (VM). One hundred and twenty specimens (12 × 14 × 2.5 mm) were prepared using a precision saw. For each material (n = 24), the specimens were allocated into two groups, polished and stained. The specimens of each group were stored (for 7 days) in either citric acid (0.2N) or distilled water. Data for surface gloss (ΔE*SCE-SCI) and roughness (Ra) were evaluated before (baseline) and after simulated toothbrushing. For toothbrushing simulation, a toothpaste slurry containing a toothpaste of 100 relative dentin abrasion (RDA) and 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Data were analyzed using t-test and ANOVA. A p-value of ≤ to 0.05 was considered significant. The highest mean value of surface gloss was identified in CU (stained—water) (4.3 (0.47)) (ΔE*) and EN (stained—acid) (4.3 (1.00)) (ΔE*) specimens, whereas the lowest mean value was shown by SH (stained—acid) (2.04 (0.42)) (ΔE*) samples. The highest mean value of surface roughness was observed in SH (0.40 (0.99)) Ra (stained—acid) whereas the lowest in VM (0.13 (0.039)) Ra (polished— water). A significant difference (p < 0.05) was observed in surface roughness and gloss between the materials with simulated toothbrushing, except in VM and LU, respectively. Therefore, it can be concluded that simulated toothbrushing impacts on surface roughness and gloss, irrespective of the storage medium

Management of the flabby ridge using a modified window technique and polyvinylsiloxane impression material

Flabby ridge is a common clinical finding affecting the alveolar ridges of the mandibular or maxillary arches. The anterior region of maxilla is the most affected area in edentulous patients. Dentures on flabby ridges have compromised stability, support, and retention unless adequate measures for its management are employed. Methods applied for flabby ridge management, include surgical removal and augmentation, special impression techniques, balanced distribution of occlusal loads and implant therapy. Special impressions often involve window technique for static impression of flabby area, which present multiple challenges. The purpose of this technique report is to present a modified window technique for the impression of anterior maxillary flabby tissues for improved and controlled application of polyvinylsiloxane impression material that are routinely available in dental practice. Keywords: Flabby tissue, Fibrous tissue, Window technique, Polyvinylsiloxan

BENS, a novel regulator of bone/cartilage healing

Indiana University-Purdue University Indianapolis (IUPUI)Enhancing osteoblast proliferation, survival, and extracellular matrix protein secretion are potential therapeutic approaches to treat bone fractures and diseases such as osteoporosis. BENS is a traditional medicine used in many countries such as India for thousands of years to treat many diseases including bone diseases. In this study, molecular, cell-based and in vivo approaches were utilized to investigate the effects of BENS on bone and cartilage regeneration. An osteosarcoma cell line (MG63) was incubated in serum free media with and without 0.8 mg/ml of BENS. BENS significantly increased cell survival up to 30 days and these cells retained their ability to proliferate in fresh media with serum. After adding BENS, there were statistically significant decreases in the expression of both anti-apoptotic and pro-apoptotic proteins. An in vivo non-critical size segmental bone defect Xenopus system was used to evaluate the ability of BENS to enhance cartilage formation. After a small segment of the anterior hemisection of the tarsus bone was excised, the frogs were divided into three groups and given subcutaneous injections of either phosphate-buffered saline or BENS once daily for 30 days and then bone/cartilage formation evaluated. The total cartilage area/total section area was significantly increased (2.6 fold) in the BENS treated samples. In an osteoporotic rat model, the anabolic properties of BENS on bone mass were assessed by histomorphometric analyses. Ovariectomized (OVX) rats received daily intraperitoneal injections for 4 weeks. Bone formation rates (BFRs) for the cortical periosteal bone surface of the midshaft tibia were 383.2, 223.9, 308.8, 304.9, and 370.9 µm3/µm2/year, and for the trabecular surface were 82.2, 113, 212.1, 157, and 165 µm3/µm2/year for the sham, OVX, PTH, 3 mg/kg BENS, and 30 mg/kg BENS groups, respectively. BENS increased both trabecular and cortical BFRs. It generated better results on cortical periosteal bone surface than did PTH. Taken together, these findings suggest that BENS promotes osteoblast survival due to its effects on altering the balance between pro-apoptotic and anti-apoptotic proteins. In addition, in vivo studies revealed that BENS enhanced cartilage formation in Xenopus and BFRs in rats. Therefore, BENS may possess anabolic bone/cartilage properties

Repair Bond Strength of Composite Resin to Aged Resin and Glass-Matrix CAD/CAM Ceramic Materials Using Two Different Repair Systems

This study evaluates the repair bond strength of resin-matrix and glass-matrix CAD/CAM ceramic materials based on two repair systems. Thirty specimens measuring 2.5 mm in thickness were prepared from Crystal Ultra (CU), Vita Enamic (EN), Lava Ultimate (LU), Cerasmart (CS), and Vitablocs Mark II (VM2) materials and aged for 5000 thermal cycles. Specimens were randomly allocated into three groups: control, Monobond-S (MS) primer, and Monobond Etch & Prime (MEP). Composite resin (Tetric N Ceram) (5 mm in diameter and 2 mm thick) was packed and light-cured onto treated specimen surfaces. Subsequently, the specimens’ shear bond strength (SBS) was evaluated, and failure modes was recorded. Statistical analysis was performed using factorial ANOVA and Tukey’s post hoc tests (a = 0.05). The factorial ANOVA revealed significant interactions between the material type and repair system, which was significant (p < 0.01). The highest and lowest SBS were obtained for CU (27.09 ± 1.11) and VM2 (4.30 ± 0.59) in MS and control groups, respectively. In all the groups, CU demonstrated higher SBS, whereas VM2 demonstrated lower SBS. There were no significant differences in SBS between EN and LU, and CS and CU in all the study groups (p > 0.05). The Monobond-S repair system provided non-significantly higher SBS compared to the MEP systems, except for VM2 and LU materials. The new resin-matrix CAD/CAM material demonstrated the highest SBS compared to the other materials for both conventional and MEP repair systems. Both repair systems showed clinically acceptable bond strength and allowed for successful repair of the resin-matrix ceramic materials

Correction: Alnafaiy et al. Repair Bond Strength of Composite Resin to Aged Resin and Glass-Matrix CAD/CAM Ceramic Materials Using Two Different Repair Systems. Coatings 2021, 11, 1331

The authors wishe to make the following corrections to this paper [...

Assessment of the influence of gender and skin color on the preference of tooth shade in Saudi population

Aim: The aim of the study was to evaluate the influence of gender and skin color on the preference of different teeth shades in general population. Materials and methods: Two standardized frontal smile photographs of male and female subjects were manipulated using photoshop to represent 4 skin colors [(type II, III, IV, and V) (Fitzpatrick scale)]. The teeth shades under each skin color were digitally manipulated to represent one of 6 teeth shades (BL1, BL2, BL3, BL4, B1 and A1). A questionnaire assessed demographic characteristics (age, nationality, gender, education level, occupation, and income) along with the satisfaction of their smiles. Male and female set of pictures with combination of skin colors and teeth shades were presented and participants were asked to select the most esthetically pleasing teeth shade with regard to gender and skin color. Cross-tabulations and chi-squared tests were used to perform the statistical analyses (α = 0.05). Results: Three hundred and thirty-six (60.4% male; 39.6% female) individuals participated in the study. The difference in the preferred teeth shades was significant among the male and female photographs across all skin colors (p < 0.05). Lighter teeth shades were preferred among female subjects compared to male subjects with the same skin color. In addition, lighter teeth shades were preferred among subjects with a lighter skin color and vice versa (p < 0.05). Conclusion: Gender and skin color influences the perception of teeth shades among general population. Therefore, lighter tooth shades (BL1, BL2) for lighter skin color and comparatively darker tooth shades (BL4, B1, A1) for darker skin individuals should be prescribed as these are perceived as natural among Saudi population. Keywords: Skin color, Teeth shade, Color perception, Gender, Ag

BIAXIAL FLEXURAL STRENGTH AND HARDNESS OF RESIN-MATRIX CERAMIC CAD/CAM MATERIALS

This study evaluated the biaxial flexural strength (BFS) and hardness of four resin-matrix ceramic CAD/CAM materials namely, Vita Enamic (EN), Lava Ultimate (LU), Cerasmart (CS), Crystal Ultra (CU) and one glass-matrix ceramic material, Vitablocs Mark II (VM2). Disc-shaped specimens (12 mm in diameter and 1.2mm in thickness) were prepared from the CAD/CAM materials and were accordingly allocated into two groups. One group was used for baseline measurements and the other group was subjected to ageing by thermal-cycling (TC) for 10,000 cycles. The BFS and hardness was evaluated by a universal testing machine and a Vickers hardness tester, respectively. A two-way ANOVA, one-way ANOVA with Tukeys post hoc test, and Students t-test (=0.05) were used to analyse the data (α=0.05). The highest and lowest BFS was seen in CS and VM2 and the difference in the BFS among the materials was statistically significant (p˂0.05). The comparison between the baseline and TC groups showed significant difference in the BFS for EN (p ˂0.001), LU (p˂0.001), and CS (p˂0.012) but no difference was seen for VM2 (p= 0.238) and CU (p˂0.159). The Vickers hardness number (VHN) ranking of the materials for the baseline and TC specimens, was VM2˃EN˃LU˃CS˃CU and VM2˃EN˃LU˃CU˃CS, respectively. Following the TC, all the materials showed a significantly lower VHN (p ˂ 0.05) except for VM2 (p= 0.727). The CS material had the highest BFS among the baseline and TC groups; however, it had the lowest hardness among the materials in the baseline group and had comparable values to CU after the TC. Ageing by thermal-cycling significantly lowered the BFS of the CAD/CAM materials except for VM2 and CU, and lowered the hardness of the resin-matrix ceramic materials