IDRR APRIL -MAY -JUNE 2020 - Flipbook - Page 8
PROSTHODONTICS
It can cause technical complications in arranging the
teeth and gaining a successful occlusal relationship
(Fig 1).
Fig 1.
Subsequent to dental extraction jaw bone gets re
modelled
In normal occlusal relationship, the maxillary teeth
appear overlapping the mandibular teeth. In a
crossbite situation, the overlap gets reversed. In the
case of natural teeth, orthodontic treatment gets the
relationship of crossbite reversed. When a completely
edentulous individual reports for complete dentures,
an assessment of the ridges has to be made prior to
designing the occlusal contacts. Arch width is the
main criterion that decides whether a normal occlusal
relationship or a crossbite relationship has to be
designed for the complete dentures. In dentures,
posterior teeth are positioned more or less over the
crest of the ridges to ensure stability for the dentures
during function. In a crossbite ridge relationship, if the
normal occlusal scheme is employed, either the
maxillary teeth would be positioned far buccal from
the ridge or the mandibular teeth positioned far
lingual to the ridge. Both the situations are unfavourable
for function. Hence specific crossbite setting of posteriors
is attempted. Step by step procedures of one method
of crossbite set up are described here.
1.Arch width of the edentulous cast is assessed by
marking the crestal lines in the posterior region. Width
of both the maxillary and mandibular casts are
assessed to find out the discrepancy (Fig 2,3)
2.Occlusion rims are fabricated according to the arch
form and a provisional jaw relation is registered. This
will give an idea on the future design of the complete
dentures and the occlusal relationship (Fig 4-6)
Fig 2.
For evaluation of the arch width crestal lines are
marked and projected to the land
July-August-September 2019
3.Occlusion rims are removed and crestal lines are
marked on both maxillary and mandibular casts. The
lines are then projected to the heels of the cast. The
gap between the upper and lower lines is measured
and compared against the bucco lingual width of a
premolar tooth. If the gap is more, a crossbite set up is
inevitable. If the gap is less, a conventional set up is
possible (Fig7-9)
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