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Signs of Occlusal Instability Continued

Due to our recent blog on Signs of Occlusal Instability, we’ve received a great comment from one of our followers.  The reader asked for a more detailed discussion on checking the fremitus, including the differences between operator's finger sensation or occlusal overload in the presence of bone resiliency and how it could vibrate the implant restoration.  We’ve asked Dr. Johnson to elaborate this subject for our readers.

By Dr. Shannon Johnson
Let’s take a closer look at checking for fremitus.  It is no doubt that checking for fremitus is a quick, easy, and low-cost way to evaluate a patient for signs of occlusal instability.
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The operator’s finger should be placed very lightly on the tooth surface.  The necessary pressure is quite similar to taking a patient’s pulse—if you press too hard, you miss it.  Once there, focus your concentration on feeling any movement or vibration when the patient brings his/her teeth together and grinds around.  The best way to learn is to check all patients.  As we begin to feel teeth without fremitus, the ability to diagnose subtle movement and vibrations will improve.  Different operators may possess different finger sensations, but hopefully with the above advice, the clinician will be able to develop this important skill!

Fremitus occurs when the adaptive capacity of the periodontium is overcome by occlusal forces, either acutely or chronically.  In the initial phases of occlusal trauma—the injury phase—there are tensile and compressive forces acting on the tooth at the same time.  These forces can result in changes to the histology of the periodontal ligament.  As long as the reparative capacity for that person exceeds the traumatic forces, the reparative phase begins.  New connective tissue, cementum, and bone are formed.   Additional bone buttresses previously weakened areas.  If the forces are not stopped or the tooth does not migrate out of harm’s way, remodeling of the periodontal structures may occur via the third phase, or adaptive remodeling.  The periodontal ligament is thickened and boney defects may occur.  This is the body’s attempt to prevent chronic trauma from further injuring the periodontal tissues.

All that said, implants do not have a periodontal ligament.  Occlusal forces are directed into the bone.  Bones ability to absorb occlusal stress is significantly lower than the periodontal ligament.  Without a periodontal ligament, there is a tremendous decrease in the physiologic (non pathological) mobility implants exhibit versus natural teeth. 
Research demonstrates that occlusal overloading leads to the vast majority of biomechanical failures including screw loosening, fixture fractures, and implant failure.   A recently (Jan 2013) published study by Nagasawa in the International Journal of Oral & Maxillofacial Implants is the first small animal model study that demonstrates bone loss occurs around overloaded implants in the absence of infection.  Until evidence to the contrary arises, it is my opinion that fremitus on dental implants still represents a sign of occlusal instability and requires further investigation.

Shannon Johnson, DMD is an associate faculty member at the Dawson Academy. She also leads two Dawson Study Clubs and teaches the Core Curriculum. Dr. Johnson owns and operates her practice in Louisville, KY.