Influence of Different Pigment Incorporation Methods on the Sorption and Solubility of Medical Silicones.

OBJECTIVE: The aim of this study is to verify the influence of three pigment incorporation methods (conventional, mechanical, and industrial) on the sorption and solubility of the MDX4-4210 and A-2186 silicones. MATERIALS AND METHODS: The groups formed were based on the silicones used (A-2186 and MDX4-4210), intrinsic pigments (pink, bronze, and black), and pigment incorporation methods (conventional, mechanical, and industrial). The dimensions of all samples were 45-mm diameter (ø) × 1-mm thickness. Readings were taken initially and after 1,008 hours of aging. STATISTICAL ANALYSIS: Three-way analysis of variance and the Tukey's test were performed (α = 0.05). RESULTS: For sorption and solubility, there was no difference between the incorporation methods for the A-2186 silicone, regardless of the pigment used (p > 0.05). For pink MDX4-4210, the industrial and mechanical methods showed higher values of sorption compared with the conventional method (p < 0.05). For bronze MDX4-4210, the industrial method showed a higher sorption value compared with the conventional and mechanical methods (p < 0.05). For black MDX4-4210, there was no difference between incorporation methods based on sorption (p > 0.05). For pink MDX4-4210, the mechanical method showed a higher solubility value compared with the industrial and conventional methods (p < 0.05). For black MDX4-4210 and bronze MDX4-4210, there was no statistically significant difference between incorporation methods based on solubility (p > 0.05). CONCLUSION: Based on sorption and solubility, for the A-2186 silicone, the conventional, mechanical, and industrial methods of pigment incorporation were equivalent. For the MDX4-4210 silicone, its results of sorption and solubility were varied, and further studies are recommended.

Relation Between Insertion Torque and Implant Stability Quotient: A Clinical Study.

OBJECTIVES: This study aimed to assess the relation between the insertion torque and implant stability quotient (ISQ recorded immediately and 6 months after implant placement). MATERIALS AND METHODS: Twenty-five patients over the age of 18 years were selected for this study. One implant was placed per patient after tooth extraction. All implants had the same size (11.5 × 3.75 mm) and brand (Hexagonal Morse cone, DSP Biomedical). The insertion torque (Ncm) and resonance frequency analysis (ISQ value) (Osstell Mentor) were used to assess the primary stability (on the day of surgery). After 6 months, resonance frequency analysis was used to assess the secondary stability of each implant. STATISTICAL ANALYSIS: The insertion torque data were correlated with ISQ measurements by using Pearson's correlation. The significance level was 5%. RESULTS: There was a positive correlation between insertion torque and initial ISQ (correlation: 0.457; p = 0.022); however, no correlation was found between insertion torque and final ISQ (p = 0.308). CONCLUSION: The present study demonstrated that there is a positive correlation between the insertion torque and the initial ISQ. Therefore, the higher the insertion torque, the higher the initial ISQ (and vice versa).

SARS-CoV-2 and Dentistry-Review.

SARS-CoV-2 (or 2019-nCoV) is the novel Coronavirus that affects humans. It originated in China at the end of 2019 due to the consumption of animals contaminated with this pathogen. SARS-CoV-2 causes the disease known as COVID-19 (coronavirus disease - 2019), and until May 21, 2020, approximately 213 countries and territories had been affected by SARS-CoV-2. The objective of this study was to review the origin and characteristics of this virus (SARS-CoV-2), symptoms and diagnosis of COVID-19, treatment of people with COVID-19, forms of transmission of the SARS-CoV-2, and precautions in dentistry. A literature search on PubMed/Medline was performed on the May 21, 2020, using the keywords (Mesh terms) "COVID-19" or "SARS-CoV-2" or "Coronavirus" associated with "dentistry" or "dental care" or "oral medicine." SARS-CoV-2 articles about the origin and characteristics of this virus (SARS-CoV-2), symptoms and diagnosis of COVID-19, treatment of people with COVID-19, forms of transmission of the SARS-CoV-2, and precautions in dentistry were included. The search was expanded according to necessity. Articles related to precautions in dentistry and SARS-CoV-1 or MERS-CoV were also selected, since precautions used in the dental clinic to avoid these viruses also apply to SARS-CoV-2. In addition, the references cited in the publications of articles included were also considered when appropriate. There was no limit in relation to the year of publication, and only articles written in English were included. In this study, suggestions for the safety of dental professionals were also included. Forty-seven articles and nine websites were included in this review.

Influence of Different Pigmentations and Accelerated Aging on the Hardness and Tear Strength of the A-2186 and MDX4-4210 Silicones.

OBJECTIVE: To evaluate the influence of different pigmentations and accelerated aging on the hardness and tear strength of the A-2186 and MDX4-4210 silicones. MATERIALS AND METHODS: The samples A-2186 and MDX4-4210 were manufactured without and with pigmentations (black, bronze, and pink). For the Shore A hardness test, 80 samples of each silicone were fabricated, and for the tear strength test, 320 samples of each silicone were fabricated. Eight groups were created for each test (n = 10). These tests were performed before and after 252, 504, and 1008 hours of aging. Three-way repeated-measures analysis of variance and the Tukey test were performed (α = 0.05). RESULTS: The A-2186 silicone showed higher hardness and tear strength when compared with the MDX4-4210 silicone (p < 0.05), except in the hardness of the A-2186 and MDX4-4210 groups without pigmentation after 1008 hours (p > 0.05). All hardness values were between 25 and 35 units, regardless of the silicone type, period, and pigmentation (or no pigmentation). In most situations, the hardness of silicones used increased after 252 hours (p < 0.05). The nonpigmented MDX4-4210 group and all A-2186 groups showed an increase in tear strength after 252 hours (p < 0.05). For the nonpigmented MDX4-4210 group, from 252 to 1008 hours, there was no change in tear strength (p > 0.05). All pigmented MDX4-4210 groups showed no change in tear strength from 0 (initial) to 1008 hours of aging (p > 0.05). In all A-2186 groups, from 252 to 504 hours, there was a reduction in tear strength (p < 0.05), and from 504 to 1008 hours, there was an increase in tear strength (p < 0.05), except in the bronze A-2186 group (p > 0.05). CONCLUSION: In most situations, the A-2186 silicone showed significantly higher values of hardness and tear strength than the MDX4-4210 silicone. All hardness values were considered clinically acceptable. Accelerated aging could increase, decrease, or not significantly change the hardness and tear strength of the silicones used. The results of hardness and tear strength suggest that MDX4-4210 was more influenced by the presence of pigmentation after aging.