Journal of Oral Implantology June 2013 - (Page 406)
LETTER TO THE EDITOR
Dear Editor,
Over the past few years at our annual American
Academy of Implant Dentistry meetings, I have
witnessed many beautiful implant reconstructions,
only to have the presenters conclude with, ‘‘And of
course, we designed our prosthesis to ensure
implant-protected occlusion.’’ Such prophecies are
derived from the concept of mutually protected
articulation (MPA)—an occlusal scheme in which the
anterior teeth disengage the posterior teeth in all
mandibular excursive movements, and the posterior
teeth prevent excessive contact of the anterior teeth
in maximum intercuspation. Unfortunately, this may
not be true.
I question the credibility of MPA simply because
it is illogical. This is old dogma based on incorrect
reasoning, so relying on these fallacious assumptions jeopardizes the longevity of any implant
reconstruction.
The first question to ask is, ‘‘Protection from
what?’’ Certainly not from the normal/natural functions of the stomatognathic system, such as talking,
eating, and swallowing (which range from 40 to 60
lb/in2), but instead proposed protection from the
parafunctional compressions of clenching and/or
grinding of one’s teeth. These functions create
pressure that ranges from 400 to 600 lb/in2. The
entire definition of MPA describes a state of
protectionism from clenching and/or grinding, yet it
does not say that. When the definition says that the
posterior teeth, in intercuspation, protect the anterior
teeth, it does not describe why the posterior teeth are
in a position of intercuspation. Is it because they are
in a normal swallowing closure (60 lb) or are they in a
clench mode (600 lb)? In addition, MPA does not
consider damage to the posterior teeth and alveolar
bone while clenching. Further, what if the patient’s
parafunctional habit is to not clench in MIP, but
instead to clench their anterior teeth? Now what?
When the definition of MPA states that the anterior
teeth disengage the posterior teeth in all mandibular
excursive movements, again, the definition does not
state the reason for the excursions. Is it because the
mandible is going into a nonharmful exercise or is the
patient grinding his or her teeth? What about damage
DOI: 10.1563/AAID-JOI-D-13-00066
406
Vol. XXXIX /No. Three / 2013
to the anterior teeth or implants if the patient is
grinding during this pathologic exercise?
The concept of MPA is not logical and it is
harmful. It does not address patients who have
Class II and III jaw relationships. It also imparts a
false sense of security for Class I relationships. If
protection from parafunction is the objective, it is
not provided by directing untoward forces to
designated teeth to bear harmful loading; instead,
it is obtained by preventive measures.
The confusion regarding occlusion has been a
major distraction, removing the primary focus from
the far more serious problem of clenching and/or
grinding. However, this remains a highly avoidable
situation. Protection from parafunction is obtained
by three easy steps:
1. Tell the patient everything you know about
clenching and grinding. If the problem is
clenching during waking hours, it remains the
patient’s responsibility to self-monitor and control it. Anterior guards should not be worn during
waking hours. Soft guards may encourage
clenching. Patients need to adopt that old adage,
‘‘Lips together; teeth apart.’’
2. Design implant prostheses so vertical loading is
ensured upon closure. Occlusal contacts should
be confined to the tips of the functional cusps.
Incline planes should not touch. The patient’s
remaining teeth should be evaluated to determine whether an equilibration might be beneficial. Patients should be discouraged from going
into lateral excursions.
3. If the patient is grinding and/or clenching while
sleeping, a guard is warranted.
For additional information on occlusion, see
McCoy.1
Gene McCoy, DDS
Gene McCoy, DDS, Inc, San Francisco, Calif.
REFERENCE
1. McCoy G. Occlusion confusion. Guest editorial. General
Dentistry. January/February 2013. Academy of General Dentistry
website. http://www.agd.org/media/121050/si_324.pdf. Accessed
April 1, 2013.
http://www.agd.org/media/121050/si_324.pdf
Table of Contents for the Digital Edition of Journal of Oral Implantology June 2013
Congratulations to Duke Heller, DDS, MS—Pioneer, Teacher, and Mentor
In Vitro Analysis of Resistance to Cyclic Load and Preload Distribution of Two Implant/ Abutment Screwed Connections
Mandibular Implant-Supported Overdenture: An In Vitro Comparison of Ball, Bar, and Magnetic Attachments
An Exploratory Study on Assessment of Gingival Biotype and Crown Dimensions as Predictors for Implant Esthetics Comparing Caucasian and Indian Subjects
A New Approach to the All-on-Four Treatment Concept Using Narrow Platform NobelActive Implants
Regular and Switching Platform: Bone Stress Analysis With Varying Implant Diameter
Comparison Between Immediate and Delayed Laser-Treated Implants Surface With Switching Platform: A Clinical Retrospective Study
Effect of a Multiporous Beta–Tricalicum Phosphate on Bone Density Around Dental Implants Inserted Into Fresh Extraction Sockets
The Effect of Varying Implant Position in Immediately Loaded Implant-Supported Mandibular Overdentures
Bone Regeneration Around Immediate Implants Utilizing a Dense Polytetrafluoroethylene Membrane Without Primary Closure: A Report of 3 Cases
Socket Preservation and Sinus Augmentation Using a Medical Grade Calcium Sulfate Hemihydrate and Mineralized Irradiated Cancellous Bone Allograft Composite
Implant Placement and Immediate Loading With Fixed Restorations in Augmented Sockets. Five-Year Results. A Case Report
Immediate Placement and Provisionalization With Buccal Plate Preservation: A Case Report of a New Technique
Clinical Importance of Recipient Site Characteristics for Vertical Ridge Augmentation: A Systematic Review of Literature and Proposal of a Classification
Postextraction Implant in Sites With Endodontic Infection as an Alternative to Endodontic Retreatment: A Review of Literature
Letter to the Editor
Journal of Oral Implantology June 2013
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