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- Prior to any/all restorative treatment, verify occlusion, periodontal
probing, and tooth vitality.
- Prior to beginning the case, verify VDO and stable centric stops.
Excluding endo mishaps and perio, most failures in major cases result
from decreased VDO and improper occlusion that stress anterior teeth
to breakage or leave insufficent room for restorative materials. Therefore,
full mouth occlusal adjustment to stable centric and excursions prior
to restorative is a must.
- Both neuromuscular and Dawson-type occlusions share many common factors.
The initial point of contact is either on a neuromuscular arc (N.M.)
or in a hinged-arc, condyle-superior manipulated position (Dawson) and
many individuals can function from either. From this position, one needs
good centric stops on the posterior teeth at a good VDO on the arc of
closure, then anterior guidance on multiple teeth with immediate disclusion
of the posteriors. Posteriors should not touch in protrusive or lateral
excursions else the mandibular closing muscles will be activated, overstressing
all teeth.
- In right (working) excursions: ideal is cuspid guidance or group function
with no left side (balancing) interferences. In left (working) excursions:
ideal is cuspid guidance or group function with no right side (balancing)
interferences.
- With Dawson-type manipulated centric, use gentle condyle-seating pressure.
The slope of the anterior fossa will distalize the condyle if excessive
seating pressure is employed.
- With neuromuscular occlusion, employ the myomonitor (low frequency
T.E.N.S.) to determine arc of closure, or use the standing Willie-May
swallow technique.
- Establish proper vertical dimension of occlusion (VDO) initially.
To allow room for C&B materials, partial clasps, partial frameworks,
attachments, etc., a good starting guide is a Shimbashi number (max
centrals CEJ to mandibular centrals CEJ) of 18 – 20mm.
- ERA attachments are good, simple, reliable attachments but require
adequate clearance for the housing. If necessary, establish adequate
VDO with occlusal buildups prior to initiating final restorative.
- For UCP/LCP cases, saddle-lock clasp designs can give the patient
hidden clasps without the increased cost of crowns and precision attachments.
The clasps must encircle greater than 180 degrees around the tooth.
Giving an abutment tooth a mesial slice (hidden to the lingual) with
a slight mesial groove is advantageous.
- Impressions: never use a triple tray. Up to 60% of all lab remakes
result from triple-tray-related distortion. Few patients can hold a
uni-lateral bite static; most will slide to the side of the impression
while it is setting and cause distortion.
- To maximize impression accuracy and minimize distortion of pour-ups:
- Impressions with posterior preps should be boxed up prior to being poured.
- Delicate margins and interproximal areas should be stabilized with light body impression material delicately painted on these areas. Thin, delicate, multiple layers should be applied as necessary; invert the impression while setting.
- The weight of the die-stone can distort the thin impression areas
and they may not recover through the thickness and weight of the
stone mix; look for and remove or stabilize thin marginal areas
that can fold over.
- If retraction cord is required for the impression it will likely
be needed for isolation prior to seating the restoration to avoid contamination
of the cement.
- Chlorhexidene gluconate (peridex, etc.) should often be used prior
to preparation; and usually between preparation and seating of crown
and bridge.
- Not all patients lend themselves to full porcelain restorations;
choose these cases carefully. Full gold and gold occlusals provide great
durabiltity and great forgiveness; they are the closest alternative
to the natural occlusion. In any case, stable occlusion is the key.
- Take care of your patients first, the profession second, and yourself third. Your rewards will come.
Respectfully Submitted,
Bob Finkel