Evaluation of Removal Torque and Internal Surface Alterations in Frictional Morse Taper Connections After Mechanical Loading Associated or Not with Oral Biofilm.

PURPOSE: To evaluate the abutment removal torque and the morphologic aspects of wear in frictional Morse taper connections after axial loading with or without biofilm immersion. MATERIALS AND METHODS: Thirty sets of Morse taper implants and prosthetic abutments were divided into six groups based on the number of mechanical loading cycles and immersion in biofilm derived from human saliva: without load, without biofilm; without load, with biofilm; 100,000 cycles of load, without biofilm; 100,000 cycles of load, with biofilm; 500,000 cycles of load, without biofilm; and 500,000 cycles of load, with biofilm. Mechanical loading was applied at a force of 80 ± 15 N with a frequency of 2 Hz for 100,000 or 500,000 cycles. After removal torque evaluation, the internal surface of the implants was evaluated by scanning electron microscopy and optical profilometer. The results were statistically analyzed at a significance level of P = .05. RESULTS: Overall, the removal torque increased for samples submitted to loading (100,000 cycles of load, without biofilm = 83.8 ± 15.8 Ncm; 100,000 cycles of load, with biofilm = 160.6 ± 16.2 Ncm; 500,000 cycles of load, without biofilm = 147.0 ± 29.3 Ncm; 500,000 cycles of load, with biofilm = 154.5 ± 14.0 Ncm) compared to samples without loading (without load, without biofilm = 23.0 ± 9.4 Ncm; without load, with biofilm = 27.2 ± 7.5 Ncm). The removal torque was not different between groups that received the same number of loading cycles and varied on biofilm exposure (P > .05). However, samples immersed in biofilm showed higher values of removal torque. Surface analysis revealed that the damage on the internal surface of implants was lower in samples not submitted to cyclic mechanical loading (P < .05) independently of immersion in biofilm medium. CONCLUSION: Cyclic mechanical load on the frictional implant-abutment connection of Morse taper implants increased the removal torque of abutments. The findings of this research suggest that the presence of biofilm can potentially increase the removal torque in frictional Morse taper connections, although more studies are recommended to support this affirmation. Oral biofilm did not interfere with the presence of wear areas along the internal surface of Morse taper implants but increased the roughness values.

Literature Review of COVID-19, Pulmonary and Extrapulmonary Disease.

In December 2019 novel coronavirus-Severe Acute Respiratory Syndrome-Corona Virus2 (SARS-CoV2)-originated from Wuhan, China, and spread rapidly around the world. This literature review highlights the dynamic nature of COVID-19 transmission and presentation. Analyzing 59 relevant articles up to May 1st, 2020 reflects that the main reported clinical manifestation of COVID-19 pandemic is fever and respiratory involvement. Also, current literature demonstrates a wide spectrum of different and atypical presentation(s) of COVID-19. The definite route of SARS-CoV2 transmission is respiratory droplets, however, virus nucleic acid has been detected in the stool and urine specimens as well. The severity of symptoms and outcomes of COVID-19 vary based on the patient's medical background, age, sex, and concurrent medical conditions (e.g. pregnancy). This is the first review that classifies all essential points regarding COVID-19 manifestations at a glance to improve the outcome of the patients by a better insight into diagnosis and management.