Download So the steps of preparation for posterior resin bonded bridge are

Cons sheet 17 part 2
22/2/2016
- Occlusal rest with three degree :provide a positive stop for the restoration and
horizontal dysplasia
So the steps of preparation for posterior resin bonded bridge are :
1- Removal of proximal undercut
2- Continue the rest of the preparation with preserving the contour of the lingual
margin
3- Then prepare two occlusal rests and try to always keep your preparation within
enamel.
Now after finishing the preparation you should make an accurate impression,
the margins are critical for resin bonded restoration as for the conventional
bridge. So the it is fine to make the finish line equi gingival or supra gingival
(not necessary to make it sub gingival)
So u take the impression first with heavy putty, then u record the details with
light body silicon , and then provide the temporary occlusal stopper.
The design of the anterior restoration :
Its is very important that u who draw the design not the technetium so that u
can make the outlines to the wings to avoid as much as I can the palatal
surface. you just involve the proximal, also the incisal finish line should be
away from the incisal edge about 2-3 mm to avoid any aesthetic problem with
the incisal edge translucency ., the gingival finish line should be 1 mm above
the gingiva, then I send it to the technician to do the wax pattern according to
the design I drew.
The preparation should extend labially and to the centre of the proximal
surfaces to optimise aesthetics in the anterior region as far for using porcelain
bonding .
Now when we start doing the metal we should outline the metal extend but
for the anterior region we replace the metal with porcelain and extend the
wings to achieve the rub around .
in maxillary arch:
The concept of maximum coverage is limited by the translucency and thickness
near the incisal edge of teeth
For mandibular anterior teeth the surface area is much less than in maxillary
arch and the rub around design is more difficult to achieve in the its virtually
impossible in many periodontal situation to achieve adequate retention
without using the proximal grooves.
Cons sheet 17 part 2
22/2/2016
Preparation of mandibular anterior teeth is similar to that of maxillary incisors
although its enamel thickness is 50% less than the maxillary incisors , that’s
why the preparation should be more conservative.
 In the doctor own words as a summary:
first of all we have to create space for the retainers if at least 0.5 mm
interocclusal space is not available, if there is contact “as shown by the
articulating paper” with the opposing we reduce it but we keep the reduction
within enamel .
the 2nd step is creating parallel proximal walls to reduce the proximal undercuts ,
(distal of central and mesial of canine if we’re preparing a RBB to replace a missing
upper lateral), we have to remove any undercut, and we create a mini chamfer
finish line palatally, then we continue cutting to end the preparation in the middle
of the contact point, because we want our wrap around to cover around the tooth
as much as we can.
3rd step is to create cingulum rest, we make it on the most prominent part of the
cingulum, it will act as a vertical stopper where the restoration will end during
cementation , after casting, the fitting surface of the wings will have projections in
the area of rests and grooves, which guides the positive seating of the restoration
during cementation and prevents further seating more gingivally, so they work as
stoppers and increase the resistance form.
Now design of the posterior restoration:
As for anterior the framework must extend beyond the distobuccally and
mesiobuccally line angles of the respected abutments.
the goals of preparation on posterior abutment teeth are mainly to:
1- provide parallel walls between the abutments
2- maintain the buccolingual curvature.
3- lower the height of contour to within 1mm of the crest of the gingiva, to eliminate
the proximal undercuts.
Lingual reduction on mandibular posterior teeth, especially the molars, requires
lowering the height of contour to provide maximum surface area of contact with the
wings, and due to the normal lingual inclination require more enamel reduction.
Cons sheet 17 part 2
22/2/2016
Two occlusal rests, are required to support the lingual arm of the retainer at both
ends, and eliminate the potential for flexing of that arm, they also provide additional
surface area, occlusal rest with 3 degrees tapered walls provide a positive seat and
stop for the restoration and limit horizontal displacement.