I wholeheartedly agree that proper research and a "fair forum," along with well-defined diagnoses, would go a long way toward resolving the differences that seem to cloud the TMD issue.
I agree with Dr. Hoopin-garner that occlusal prematurities do not cause bruxism. However, I believe working and balancing interferences starts a chain reaction that can cause muscular hyperactivity, which leads to excess force on teeth, bone, ligaments and temporo-mandibular joints as well as muscle fatigue and pain. That excess force is either mitigated by or exacerbated by host resistance and adaptability, behavior issues and a variety of other factors such as bruxism.
Some of the original research demonstrating that occlusal discrepancies directly affect muscle activity was done by Ramfjord almost 40 years ago. Muscular activity has been repeatedly linked to occlusion.
Dr. Sig Ramfjord’s EMG studies showed that a meticulous occlusal equilibration quelled disharmonious muscle activity patterns. When the teeth can be brought together with no deflection from centric relation to centric occlusion, muscle activity is harmonious (
Ramfjord SP. Dysfunctional temporomandibular joint and muscle pain. J Prosthet Dent 1961;11[3-4]:353–74[Medline]
).
Williamson and Lundquist proved that posterior disclusion is a solid scientific tenet. They showed the relationship between decreased muscle activity/EMG activity and anterior guidance (
Williamson EH, Lundquist DO. Anterior guidance: its effect on electromyographic activity of the temporal and masseter muscles. J Prosthet Dent 1983;49[6]:816–23[Medline]
).
Further, the following research also addresses the correlation between occlusal and muscular disharmonies:
Riise C, Sheikholeslam A. The influence of experimental interfering occlusal contacts on the postural activity of the anterior temporal and masseter muscles in young adults. J Oral Rehabil 1982;9(5):419–25.[Medline]
Belser UC, Hannam AG. The influence of altered working-side occlusal guidance on masticatory muscles and related jaw movement. J Prosthet Dent 1985;53(3):406–13.[Medline]
Kirveskari P, Le Bell Y, Salonen M, Forssell H, Grans L. Effect of elimination of occlusal interferences on signs and symptoms of craniomandibular disorder in young adults. J Oral Rehabil 1989;16(1):21–6.[Medline]
Kerstein RB, Farrell S. Treatment of myofascial pain-dysfunction syndrome with occlusal equilibration. J Prosthet Dent 1990;63(6):695–700.[Medline]
These studies represent just the tip of the scientific iceberg. I am surprised that Dr. Hoopin-garner has no knowledge of this research, particularly in light of the fact that he provides comprehensive dentistry and cran-iomandibular orthopedics.
It is extremely difficult to stay abreast of the dental literature. It is also complicated by our tendency to look for simple cause-and-effect relationships rather than multifactorial answers that more closely fit the multifactorial nature of "TMD."
It is not a single disease. There is no single cause nor can there be a single solution. Our challenge is to specifically diagnose our patients’ problems, understand the causes of the problems as well as possible, and then treat them appropriately and specifically.
In my opinion, the majority of problems seen in general practice can be definitely diagnosed as occlusomuscle disharmonies. Fortunately, occlusal equilibration provides a direct solution for most of these clinical challenges. Unfortunately, occlusal equilibration is extremely exacting.
Many of us tend to base our opinions and clinical practices on the teaching and expertise of respected mentors and educators. The ongoing controversy surrounding TMD is a healthy one if we open-mindedly examine those teachings along with the clinical research available and avoid the exclusionary thinking that tends to stifle us all.
