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Dentistry/cavity/root canal after fillings?


hi. how can you get a cavity after a tooth filling? is it because the tooth filling wasn't place in correctly or the tooth was cracked? would this cause your tooth to be extracted? and how can you need a root canal after a tooth fillings? thanks

Dear beth,

Picture a pothole in the street.  The workers fill it with asphalt to level and smooth the road.  Then traffic and weather begins to break up the asphalt "filling".  After some years of wear and temperature change (hot foods to cold ice cream), a filling can begin to break down, and its seal to the tooth surface can open up and begin to allow saliva and food particles to leak into the broken seal.  This is the beginning of re-decay around a filling.  Sometimes a tooth filling may be placed incorrectly, and this can be the cause of re-decay.  If the filling has lasted longer than 2 years before becoming re-decayed, it was probably placed correctly.  Some teeth just do not hold up well due to weak, porous enamel, which allows decay to re-form quickly.  And, of course, lots of sweets and acidy foods will promote re-decay.

A tooth that is cracked is another story.  Cracked tooth can be another cause for re-decay or for needing a root canal and crown.  Some cracked teeth must be extracted because the crack is in a place that makes the tooth unrestorable.

Sometimes when decay is very deep, the bacteria that cause the decay can travel to the nerve of the tooth and begin to cause it to be infected.  You may not feel this infection at first.  But the trauma of removing the decay and replacing it with filling might cause it to become irritated and painful.  Studies have shown that, under the best of conditions, about 3-4% of teeth that are treated will end up needing a root canal.

I hope this answered all your questions.


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Howard Finnk, D.D.S., P.A., CEO


I am a Family, Implant and Cosmetic dentist. I will answer questions on any aspect of dentistry and matters relating to the smile, gums, jaws and lower face. Member American Dental Association, Florida Dental Association, Broward County Dental Association, and Atlantic Coast District Dental Association. I have served as District Council Member of Alpha Omega, as well as serving for one term as its President. I am also a member of The Vedder Honors Society, Broward Dental Research Clinic, and Mount Sinai Hospital Guild. I have served as a Volunteer for Project Dental Health and The Tri-County Dental Health Council.


Having attained over 30 years of clinical experience in private practice in Michigan, in 2001 I was re-certified by taking and passing the Florida State Dental Board Examination. After moving to Florida, I spent nearly 10 years re-honing my skills while working as an Associate Dentist for several large dental groups. In September, 2004, I was appointed Adjunct Clinical Professor at Nova University's College of Dental Medicine. I am certified in placement of Mini Dental Implants, and I am Director of The Florida Implant Center ( On March 1, 2010, at the age of 62, I began all over again by buying a dental practice near my home in the Fort Lauderdale area. As sole owner and Chief Dental Officer of the new Nob Hill Dental Center (, I can now carefully provide dental care to patients who care, all within a caring, joyful environment. Over my career lifetime, I have provided thousands of diagnoses, fillings, crowns, bridges, root canals, periodontal treatments, TMJ therapies, partials, dentures and extractions, and dozens of implants for my patients. The only aspect of dentistry with which I have very little experience is orthodontics.

American Dental Association, Florida Dental Association, Broward County Dental Association, Atlantic Coast District Dental Society, Vedder Honors Society, Broward Dental Research Clinic, Alpha Omega Alumni Association, and American Association of Dental Implantologists. Formerly, American Academy of General Dentistry, Michigan Dental Association, Macomb Dental Society, Detroit District Dental Society, Tri-County Dental Health Council (a charitable dental care organization)

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Bachelor of Arts and Sciences in Psychology from Wayne State University Doctor of Dental Surgery from University of Detroit College of Dentistry Adjunct Clinical Professor, Special Needs Department, Nova Southeastern University College of Dental Medicine, Fort Lauderdale, Florida

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