Background: The purpose of this study was to measure and compare the strain levels in the peri-implant bone as generated by the blade-like implant (BLI) and the screw-type implant (STI) with two different internal connections (hexagonal and conical) and with a 1:1 and 2:1 crown/implant (C/I) ratio. Methods: The implants (BLI and STI) were placed into sawbones according to the manufacturer’s protocol. Two strain gauges, horizontal and vertical to the implant axis, were placed around each implant on the bone surface 1 mm from the cervical part. Each implant was loaded by a material testing machine at a force of 100 N. Micro-strains (με) generated in the surrounding bone were measured by a strain gauge and recorded. Results: Recorded micro-strains were not significant in both the insertion and loading phases (p < 0.0625). The average recorded micro-strain values were lower in the horizontal dimension of STI with hexagonal connection when the C/I ratio was 2:1 compared with BLI, 210 με and 443 με, respectively. Conclusion: Within the limitations of this study, implant design, implant-abutment connection and C/I ratio did not influence strain values in bone and there is no statistically significant effect of these parameters on bone.

A wide variety of titanium (Ti) alloy dental implant systems are available and as a result, choosing the correct system has become a challenge. Cleanliness of the dental implant surface affects osseointegration but surface cleanliness may be jeopardized during manufacturing. The purpose of this study was to assess the cleanliness of three implant systems. Fifteen implants per system were examined with scanning electron microscopy to identify and count foreign particles. Particle chemical composition analysis was performed with energy-dispersive X-ray spectroscopy. Particles were categorized according to size and location. Particles on the outer and inner threads were quantitatively compared. A second scan was performed after exposing the implants to room air for 10 min. Carbon, among other elements, was found on the surface of all implant groups. Zimmer Biomet dental implants had higher particle numbers than other brands. Cortex and Keystone dental implants showed similar distribution patterns. The outer surface had higher particle numbers. Cortex dental implants were the cleanest. The change in particle numbers after exposure was not significant (p > 0.05). Conclusion: Most of the implants studied were contaminated. Particle distribution patterns vary with the manufacturer. The wider and outer areas of the implant have a higher probability of contamination.

Introduction: Olfactory and gustatory chemosensory dysfunctions are very prevalent in COVID-19 infection, our aim is to further explore chemosensory recovery among these patients.Methods: This is a cross-sectional follow-up study, which serves as a sequel to a study by Biadsee, et al. Among the previous study population of 128 non-hospitalized patients, who were tested positive for COVID-19 by reverse transcription-polymerase chain reaction (RT-PCR). Ninety-seven patients participated in a telephone survey designed for this study. Recovery of olfactory and gustatory functions were defined when a score is greater or equal to that reported before the disease. Persistent hyposmia and hypogeusia were defined as lower scores reported during follow-up, compared with scores before the disease. Results: A total of 43 men and 54 women were included. Mean age was 37 years (range 18-73). Mean follow-up was 59.2 days (range 21-83). At follow-up, 72 (74.2%) patients reported normalization of gustatory function and 63 (64.9%) reported normalization of olfactory function. No patient reported nasal obstruction at follow-up. Recovery of olfactory function was positively correlated with gustatory recovery (p=0.003). Twenty-three (23.7%) reported persistent xerostomia. Women who reported persistent xerostomia had higher rates of olfactory and gustatory dysfunction (p=0.006 and p=0.008, respectively) than those who did not. Olfactory and gustatory disorders as initial symptoms were negative prognostic factors for recovery. Conclusion: Olfactory and/or gustatory dysfunction as a presenting symptom of COVID-19 infection may be a negative prognostic factor for full recovery of olfactory and gustatory function.

Purpose To estimate the effects of the thermal cycling (TC) process on the metal surfaces of Locators, as well as retention loss, and the correlation between them. Materials and methods Twenty‐five new Locator R‐Tx were included in the study. Four areas were marked on each Locators’ patrix metal surface and scanned using a confocal scanner (μsurf explorer; NanoFocus). Three surface roughness parameters were measured in the scans: Sa (average distance of peaks from the central plain of the area), Vmp (volume of the peaks in the area), and Spc (mean curvature of the peaks describing the degree of their sharpness). Retention test was performed using Instron® 4500 compression tension tensile tester at a speed of 10 mm/min. The retention tests were done using a working model made of two acrylic blocks in which the Locator system parts were inserted. The surface parameters measurements and the retention tests were performed 2 times, once before and once after TC. The Locators were subjected to 15,000 TC cycles by investing them into 2 tubs with different water temperatures, 55°C and 5°C. During each 60‐second cycle, the Locators were submerged in each tub for 20 seconds, with a 10 second transition time between the tubs. The post‐TC retention and surface parameters measurements were compared with those prior to TC and the prior to TC measurements served as controls. Changes in parameters before and after TC were analyzed by a two‐way ANOVA nested model with random intercept and slope by restricted maximum likelihood method. Correlation between retention and surface parameters was quantified and examined using Kendall's correlation test. The findings were considered statistically significant if p < 0.05. Results There was a significant decrease in retention of 16.6N at the second retention test (p < 0.001). A significant statistical decrease in surface parameters were measured after TC process, Sa and Vmp (18 ×10–3 μm, p = 0.041 and 0.94 ×10–3 1/μm, p = 0.001, respectively). A significant statistical increase in Spc of 6.4 ×10–3 μm3/μm2 (p = 0.023) was noticed. The correlation between retention decreases and surface changes was not statistically significant. Conclusion The TC process causes a substantial reduction in retention to the Locator system over time. In addition, TC causes significant but minor changes to the Locator surface area. Most of the changes are in the horizontal dimension.

Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/ computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 µm aluminum oxide particles (SA) and aging; group B, sandblasted with 30 µm silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/ min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

The effects of different heights of ti-base abutments on the color of anterior screw-retained zirconia restorations fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technologies may affect the optical clinical outcome. The purpose of this study was to measure and compare the color parameters of zirconia crowns in different shades on ti-base abutments. Identical specimens (N = 160) were milled to restore the screw-retained central maxillary incisor crown, using 5% mol yttria zirconia (5Y-TZP). The specimens were designed using computer design software to match 3.5 mm and 5.5-mm ti-base abutments and milled using one CAD-CAM technology. Specimens were divided into four main groups depending on zirconia shade (A1/0, A2/3, A3.5/4 and B2/3) and then assigned to two subgroups according to ti-base height. Color measurements in the CIELab coordinates were made using a spectrophotometer under room-light conditions. Color difference (ΔE*) values were calculated using the CIE76 and CIEDE2000 formula. Within the group of A0/1 and A2/3, for 5.5 mm abutment height, a significant difference was found between the means of colors ∆E00 and ∆Eab (p < 0.01). Using a 5.5 mm-height ti-base abutment may produce a clinically unacceptable outcome (ΔEab > 2) in A1/0 and A2/3 color groups.

A marginal fit of all-ceramic crowns is a prerequisite for the long-term clinical success of a dental restoration. Few in vivo studies have investigated the effect of the film thickness of various luting agents on vertical discrepancy. This in vivo study evaluated the influence of three luting cements on the occlusal vertical discrepancy of milled crowns using a complete digital workflow. Forty-three patients treated in a students’ clinic in Tel-Aviv University with 45 single posterior digitally prepared monolithic crowns were included in the study. The crowns were randomly divided into three groups using different resin luting agents: self-adhesive resin cement, resin-modified glass ionomer cement and adhesive resin cement. The crowns were intra-orally scanned before and after cementation. The two standard tessellation language (STL) files for each crown were superimposed using digital software, and between four and six measurements were made at the occlusal surface to demonstrate the occlusal and marginal discrepancies. One-way ANOVA (α = 0.05) was used. The vertical occlusal discrepancy ranged from 2 to 38 μm. The mean vertical discrepancy values were (µm): self-adhesive resin = 12.93 ± 4.74, resin-modified glass ionomer = 19.05 ± 4.60 and adhesive resin = 13.69 ± 5.17. There were significant differences between resin-modified and self-adhesive cement groups (p = 0.004), and between resin-modified and adhesive resin cement groups (p = 0.013). Distal marginal ridge measurements were significantly different between resin-modified glass ionomer cement and self-adhesive resin cement group (p < 0.001) and the adhesive resin cement group (p = 0.021). There were no significant differences between the discrepancy values at the two measurement points in the self-adhesive cement group (p = 0.377), nor the resin-modified glass ionomer group (p = 0.388), or the adhesive resin cement group (p = 0.905). The cementation procedure with various resin cements results in occlusal vertical discrepancies within standard clinical acceptability. Resin-modified glass ionomer cement produced more vertical discrepancy than adhesive and self-adhesive resin cements did.

Background: The purpose of the study was to evaluate the changes of light reflection% on two materials (monolithic zirconia and lithium disilicate) after using two external staining kits following by thermocycling. Methods: Specimens were sectioned from monolithic zirconia (n = 60) and lithium disilicate (n = 60) then divided into six groups (n = 20). Two different types of external staining kits were used and applied to the specimens. The light reflection% was measured before staining, after staining and after thermocycling using a spectrophotometer. Results: The light reflection% of zirconia was significantly higher compared to lithium disilicate at the beginning of the study (p = 0.005), after staining with kit 1 (p = 0.005) and kit 2 (p = 0.005) and after thermocycling (p = 0.005). For both materials, the light reflection% was lower after staining with Kit 1 compared to kit 2 (p < 0.043). After thermocycling, the light reflection% of lithium disilicate increased (p = 0.027) and was unchanged with Zirconia (p = 0.527). Conclusions: There is a difference between the materials regarding light reflection% as the monolithic zirconia showed higher light reflection% comparing lithium disilicate throughout the entire experiment. For lithium disilicate, we recommend using kit 1 as we found that, after thermocycling, the light reflection% of kit 2 was increased.