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occlusion on implant prostheses, as the occlusal perception
level is higher than that for natural dentition. 1
Further occlusal differences are observed due to the
distinction between natural dentition and implant root
efficiency. Moving posteriorly from the anterior, natural
teeth increase 300 percent in surface area from central
to molars, along with an amplification of the number of
roots present. 6 Although implant structures tend to have a
greater surface area, their increase in width is far less than
that of natural dentition, with most implant systems only
seeing a 25 percent to 50 percent increase from smallest to
largest diameter. 6 As forces are increased in patients with
bruxism, augmentation of bone may be required to allow
for increased area of implantation to provide the mandatory
strength. Lack of periodontal structure, as well as diameter
discrepancy, require precise implant design choice on
behalf of the clinician.
Implant Design
Once osseointegration is achieved, the predominant factor
in implant longevity is maintenance of applied force.
Excessive occlusal pressure must be mitigated or even
avoided by the implant. 8 Strength is directly affected by
the surface diameter created by the thread characteristics,
determining the area available to dissipate force under
increased tension. 6
Patients with bruxism require clinicians to choose the
correct thread characteristics in order to create the most
surface area. The strongest materials often cannot withstand
bruxing, requiring the clinician to plan the final restoration
in a manner that removes it from full occlusion during
maximum intercuspation. Using a sheet of shim stock,
the practitioner positions the implant restoration out of
intercuspation by a minimum of 12 µm during centric
occlusion (Fig. 1). This allows the natural dentition to
absorb and mitigate the pressure through its periodontal
ligaments rather than the implant directing the compressive
forces into the bone.
Protection can also be built into the implant by reducing the
overall diameter and creating a narrow occlusal table of the
restoration so that it rests nearly entirely over the implant,
causing the bite forces to be distributed directly through the
implant itself (Fig. 2). This is important in that it reduces the
cantilever effect, which greatly alleviates the chance of bone
loss. 4 Employing particular design specifications will serve
to increase the likelihood of successful implant treatment.
Occlusal Guards
Effective protection of the implant system can be assisted
greatly by the prescription of a hard occlusal splint. Clinicians
often attempt irreversible occlusal treatments or force
the patient to change their lifestyle in an effort to reduce
bruxism, but custom-made acrylic guards can achieve the
same results. 7 Adjacent dysfunction and pathologic tooth
wear are addressed during the fabrication of the orthotic. 5,9
Achieving mutually protected occlusion within the design of
the guard ensures that the implant prosthesis is not subject
to the negative phenomena exhibited by bruxing patients.
The unconscious pressures exerted in nocturnal bruxism
are spread over the entire arch and lessened, rather than
being absorbed at a single location.
Prescription of a hard occlusal splint begins with the
clinician taking maxillary and mandibular polyvinyl
siloxane impressions. A bite registration is also taken at the
minimum opening needed for splint material fabrication,
with the patient’s temporomandibular joints in the centric
occlusion position according to the clinician’s centric
occlusion registration technique. With the patient in this
Figure 1: Depiction of an implant restoration placed out of intercuspation by 12 µm,
or the thickness of a sheet of shim stock.
Figure 2: Depiction of the direction of occlusal forces on a poorly designed implant
restoration versus those exhibited on natural dentition and a properly designed
implant restoration.
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