The next "sacred cow" is my favorite because I love materials. It is about PVS for bite registration. This is the most useless material ever made. Let say we took a bite with PVS and it is very accurate, and then what? The lab is pouring stone models which are eventually bigger than the actual size of the mouth (due to stone expansion). That means that the PVS bite will never fit over the stone models. If I compare to wax bite then the wax is much superior for that task since it is plastic and slight pressure expands the wax bite that the model will fit. Doesn't make any sense to buy an expansive material, mixing tips and cartridges when the best thing that can be done is putting it in the garbage. The only reasonable use of PVS bite registration material is for digital intra oral scanning, in such a case there are no dimensional differences between the model and the bite.
I’m dedicating this blog to various topics and not necessarily to the dental ones. Some of the stories I’ve heard from my teachers other from my friends and colleagues, some of them are scientific and the other may be less. Well, this time I’m going to write about the “Sacred Cows” in dentistry. Sacred cow is something considered (perhaps unreasonably) immune from question or criticism. Some of these cows were sacred in the past but some of them are presently sacred and probably will be in the future.
Sacred Cow #1
Taking the dentures out at night.
Q: Is it harmful to wear your upper denture 24/7? I have done so for 30 years and never thought it was bad. Recently, my son got an upper denture, and his dentist told him he should take it out at night. It was very uncomfortable when I tried to do that once, though. If you do think I should be taking it out, can you recommend how to ease this discomfort?
— Laverna, Oklahoma
In 1843, the American Charles Goodyear discovered how to make flexible rubber, named vulcanite, which he made from India rubber (caoutchouc). In 1851, his brother, Nelson, patented an improved manufacturing process to produce hard rubber. Vulcanite found instant use in the fabrication of denture bases world-wide and quickly replaced previously-used materials as it was cheaper. Ivory dentures cost 25 guineas (a year's wages for a housemaid). By comparison, a set of vulcanite dentures cost six guineas. By luck, vulcanite dentures also became available just after the introduction of anaesthesia. People who had preferred toothache to the pain of extraction were prepared to have their rotten teeth removed, creating a demand for the new vulcanite dentures. For the first time in history false teeth were no longer a luxury only the rich could afford and were available to the middle classes.
In 1864 in the USA, the Goodyear Dental Vulcanite Company was founded and every dentist had to obtain an expensive licence to use the material and was charged a royalty for each denture made. The Goodyear patents ran for 25 years finally expiring in 1881 when dental vulcanite came into general use world-wide. In the UK in 1881, vulcanite dentures dropped in price to £5, (a week’s wages for a labourer). Vulcanite dentures were the first functional, durable and affordable dentures, marking a great advance in dental treatment for the masses. By that time the awareness to bacterial endo carditis raised including the connection between the decay and the beta hemolytic streptococcus. That led to preventive massive extractions of the complete dentition and restoration with Vulcanite removable dentures. This was practiced until in 1945 the mass production of the penicillin began. The problem with the vulcanite dentures was their rough surface and the remains of the sulphur that was causing sever stomatitis and oral cancer. At that point the dental practitioners were completely desperate and the only thing that they could suggest to their clients is to take the dentures of when they go to sleep. By the time when the Methyl methacrylate replaced the Vulcanite in spite of being a very hygienic material and even being considered as an anti – carcinogen and approved for implants (not dental) still the dentists keep advising the patient to take the denture out at night. Well only because 80 years ago there were vulcanite carcinogen dentures we still keep suggesting our clients to take out the dentures at night. Think about it!