TWiV 611: Corona and crowns

May 10, 2020

Daniel Griffin provides a weekly clinical update on COVID-19, then Michael Schmidt discusses how dentistry can be safely practiced during a pandemic, followed by answers to listener questions.

Hosts: Vincent Racaniello, Dickson Despommier, Alan Dove, Rich Condit, and Brianne Barker

Guests: Daniel Griffin and Michael Schmidt

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Intro music is by Ronald Jenkees.

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13 comments on “TWiV 611: Corona and crowns

  1. After the lengthy discussion of dentistry environments, please speak to aerosols, ie, construction dust and how the construction industry will be affected.

    With all the discussion on dentistry, spread of Covid 19 will be rampant on construction dust, particularly interior construction.

    Construction labor has to go back to work. How?

    I have asked before. I have not heard any conversations on the twiv’s regarding this topic.

  2. Robert McCown MD May 10, 2020

    I wrote this for my Facebook feed:

    In the news, on the Web, there are articles about the mutations of the SARS-CoV-2 virus, the virus that causes COVID-19. They didn’t ask my opinion about the name, so don’t blame me. I’ll refer to this in this article as “The Virus”.
    I’m not a virus expert, nor am I a scientist. I’m an old Family Medicine doc, I have lots of scientific training but I’m a technician, having spent 40 years going from one examining room to the next. Still, I do have training and have tried to keep up, and in the past couple of months have been studying this Virus at a level I can understand. I’ve listened to virologist podcasts, read popular and scientific articles, and I can get the gist of what these real scientists are saying.
    This is really, really complicated.
    There are two kinds of genetic chemicals involved in biology and evolution, DNA and RNA. We bacteria, plants, and animals have both. Viruses tend to have one or the other, and much less than living things (I’m in the “non-living” camp for viruses, but this is a specious argument.)
    The Virus getting so much attention these days is an RNA virus. It is unusual in that it is pretty big for a virus, with some 30,000 base pairs, rather like the bits and bytes in a computer, the information storage format.
    In general, RNA viruses mutate more often than DNA viruses, although this virus does seem to have some of the proof reading function that most RNA viruses don’t have. There are a couple of different ways for mutations to happen, the differences are not important here.
    Those smart virologists can examine the RNA of The Virus down to amazingly fine detail. In order to explain this in a manner I can understand I will use the analogy of automobiles.
    Go to a car dealership, washing your hands and wearing your face mask so you won’t accidentally infect someone else, and look at the lines of all the pretty, apparently identical cars. Look closely. They are not identical. Within a particular kind of car some are red, some are blue, some are grey. These cars all work the same though, you will drive them the same, they use the same gas etc.
    Look more closely, some have leather seats, some have cloth seats. You can put a blue driver’s door on a red car, it will look funny but it will work just fine. Similarly, you can take a leather covered seat and replace the homologous cloth seat, it will work fine. However, if you try to put a driver’s door on the passenger side or a front seat into the back, it won’t fit. To beat this analogy a little more, if someone in the factory forgot to put in a piston the car won’t run at all.
    The Virus detectives can get to the level of looking at the brand of spark plugs or tires. I, for one, would never notice a difference between tires or spark plugs (until something wears out, of course. Viruses don’t wear out.)
    The big picture is that there is one strain of The Virus, the changes found are like different colors, even mismatched colors, or different brands of spark plugs. There have been some only some 20 amino acid changes in the proteins of The Virus from within the 30,000 base pairs noted since December 2019, when the virus was identified. You won’t find a Ford C-max Hybrid, like I drive, with a Chevy 327 engine in it. If you make that change, it would not be a C-max any more. Somewhere in the mists of time over perhaps millions of Virus generations, which are very short, there were changes that made this critter able to infect humans. The Virus got lucky and found, quite by accident, a new host. There have been literally thousands of changes found in The Virus over the world, and virologists can use these changes to build a family tree. This is how they found that the virus in New York came from Europe while the virus in Seattle came from China, and not from a bio-warfare lab.
    There are concerns. It is conceivable that some mutations may make the virus better able to infect humans than others. This is a worry but has NOT BEEN DEMONSTRATED. Functionally, these are not more deadly than the original Virus, just MAYBE spreads more easily in laboratory data, not demonstrated yet in real people.
    There is no evidence that this is a lab accident or intentionally made virus. There is evidence that this occurred naturally.
    Remember that something like 80% of people who get this Virus will be have no symptoms or relatively minor symptoms. This is what happened with Polio, by the way, when testing for Polio antibody became available in the 1950s it was discovered that most adults had antibodies but had not had symptomatic disease, that is, paralysis.
    Wash your hands, wear your masks. Don’t let the politicians who want to blame somebody (else) for something set your hair on fire. Don’t subscribe or re-post wackadoodle conspiracy theories. If you see an article with a scary title, read it first, and check the source. If it is from the Weekly World News, please don’t post it. If it comes from the CDC ( it is probably more reliable.
    Thank you for your time and attention.

  3. Mary Hollen May 10, 2020

    Vincent Racianello mentioned that all letters sent in would be posted in ‘show notes’. where are ‘show notes’? Thank you.

  4. Pat Cho May 11, 2020

    In episode 611 there was a discussion about the air flow requirements for dental offices so I asked a mechanical engineer who designs HVAC systems whether Dental offices had higher air change requirements in the building codes or in The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) guidelines. Here is his response.

    “So here is what ASHRAE has to say about dental offices. Typically they are treated as plain old office spaces. As such the outside air requirement is minimal – 15 cfm per person plus .06 cfm/sqft breathing air. As a practical matter most dental offices employ residential systems so have minimal capability to deal with outside air. To aggravate that situation they can’t handle any level of advanced filtration so seeing any kind of HEPA filtration is hopeless.

    I suspect the best you’d get out of an average system would be to keep everybody in the supply air stream and avoid putting folks immediately downstream of somebody else.

    This situation is thoroughly addressed for medical facilities BTW. High levels of outside air coupled with exhaust allow pressure relationships to be developed that keep people in clean areas. HEPA filtration is employed in those areas where needed.”

    He included the section of the ASHRAE 2015 Handbook ( covering Dental Offices and it mentioned a 1991 study that had found that levels of bioaerosols during and immediately following a procedure can be extremely high. This section also stated that “At this time, only limited information and research are available on the level, nature, or persistence of bioaerosol and particulate contamination in dental facilities. Consider using local exhaust ventilation (possibly recirculating with HEPA filtration) to help capture and control these aerosols, because dental care providers and patients are often close together.”

  5. Richard Cornell May 11, 2020

    Something I can send my dentist.

  6. Colin Wood May 11, 2020

    Hi, Colin speaking from Woking in the UK.
    Panel kept mentioning that SARS-COV-2 is a ‘wimpy virus’. I’m wondering as a mechanical engineer if anyone is looking at mechanical ways in which SARS-COV-2 might be disrupted? For instance if you hit the virus hard against a solid surface (say by doing dentistry in a very high wind) do the spikes break off?

    Great show by the way; I’m learning a lot!


  7. Julia May 11, 2020

    Dear TWIV,

    Thank you as always for being the voice of science and reason. How large are coronaviruses? Could they truly be transmitted via 0.1 um aerosol droplets as suggested by Michael Schmidt?

    -enquiring minds would like to know

  8. scott campbell md, mph May 12, 2020

    Emergency physician from San Francisco who has been tracking Covi since the beginning in our city. Many things made the case fatality rate of 1..7% in SF possible. First, close near daily communication of all emergency physicians (and intensivists) across the acute care grid including a 1 hr weekly call sponsored by the SF Emergency Physicians Association every noon Tuesday (all twivers welcome to join). Secondly, rapid and immediate shelter in place on March 17. Third, a broad health care infrastructure with”universal coverage” of all San Franciscans since early 2000s led by Mayor Newsom. Thirdly, exceptional communication with Gov Newsom and his team as well as Dr Charity Dean at the State of California Dept of Public health at the onset regarding information flow to and from the city. Fourth, a willingness to let the data speak regarding policy decsions and a willingness to work across institutions. And fifth, both enormous luck, resources and time. Thank you

    Scott J Campbell MD, MPH
    Department of Emergency Medicine
    Emergency Medicine Services Liaison to the City of San Francisco
    Kaiser Permanente, San Francisco Medical Center
    President, San Francisco Emergency Physicians Association

  9. William L Ciao May 12, 2020

    I am a retired dentist. I graduated from dental school in 1976. I practiced “wet fingered dentistry” until the AIDS epidemic opened my eyes.
    That triggered a paradigm shift in infection control for us. We also had to modify our practices in the face of bacterial biofilm contamination of our water lines and several other microbial threats.
    I do not have to tackle this one as a practitioner but I been following some of my colleagues discussions of mitigation strategies. There will always be complaints and foot dragging but I am confident my profession will implement effective strategies to mitigate this virus.
    In the past we have absorbed those mitigation costs ourselves. It looks like these costs will be much higher and implementation more difficult. I think a discussion of either insurance or governmental financial support to the practitioners is warranted.

  10. Richard Cornell May 13, 2020

    When Ben Franklin invented the “lighting rod” he took away the belief of God hitting your barn with a light bolt because you did something against God. The church condemned him while at the same time putting one on their church.
    There are those who believe that the warming of the planet more as if it is Gods Will instead it being done by man. Man can not do anything unless God Wills it, so then the melting of the ice caps , flooding of coastal cities is because God Wills it. This virus since it is not made by man then it is Gods way of killing off old folks. The next virus if it is Gods Will need to kill off all those others not so infected now.
    I’m dead now.

  11. Skeptical Chemyst May 18, 2020

    What is astounding to me is how you dealt with the Plandemic in your video. You mention a point by point rebuttal from Big Think as the main thrust of why you don’t need to “spend more time here because it has already been done very well”. You are scientists, why would you allow such a terrible article to stand in for you? Those “seven different points” were mostly rubbish, as anyone with a strong scientific background could readily determine for themselves by simply reading the article and looking at the relevant links embedded in the article, as I did. I encourage your viewers to actually read that article, and then watch the plandemic video and see whose arguments are more persuasive and reputable. Obviously you all are highly reputable yourselves (or some of you are at the very least), and it is therefore a shame that you would allow such a weak argument to stand in for you on this topic.