An interim prosthesis is a temporary dental restoration used while determining the effectiveness of a treatment plan or design of a definitive prosthesis. It must satisfy patient and dentist needs by protecting pulp, maintaining oral health, and establishing proper occlusion. Interim restorations can be custom made using impressions or prefabricated shells that are later adjusted. The direct technique forms the restoration directly in the mouth while indirect techniques use models to improve fit and reduce risks.

1. PRESENTED BY- MAHAK RALLI
FINAL YEAR

2.  An interim prosthesis is a fixed or removable
dental prosthesis, or maxillofacial prosthesis,
designed to enhance aesthetics, stabilization
and/or function for a limited period of time,
after which it is to be replaced by a definitive
dental or maxillofacial prosthesis. Often such
prosthesis are used in determination of the
therapeutic effectiveness of a specific
treatment plan or the form and function of the
planned for definitive prostheis.

3.  The word interim means established for the time
being, pending a permanent arrangement.
 Even though a definitive restoration may be placed
as quickly as 2 weeks after tooth preparation, the
interim fixed restoration must satisfy important needs
of the patient and dentist.
 Whatever the intended length of time of treatment,
an interim restoration must be adequate to maintain
patient health.
 It should not be casually fabricated on the basis of an
expected short term of use.

4. ESTHETIC
Easily contourable
Colour compatibility
Translucency
Color stability
MECHANICAL
Resist functional
loads
Resist removal
forces
Maintain
interabutment
alignment
BIOLOGIC
Protect pulp
Maintain
periodontal
health Occlusal
compatibility
Maintain tooth
position
Protect against
fracture

5. Pulp protection : an interim fixed
restoration must seal and insulate the
prepared tooth surface from oral
environment to prevent sensitivity and
further irritation to the pulp.
Periodontal health : to facilitate plaque
removal, an interim fixed restoration must
have good marginal fit, proper contour and
a smooth surface, specially when crown
margin is placed apical to gingival margin.

6. Occlusal compatibility and tooth position:
the interim restoration should establish or
maintain proper contacts with adjacent and
opposing teeth. Inadequate contacts allow
supra eruption and horizontal movement.
Prevention of enamel fracture : interim
fixed restoration should protect teeth
weakened by crown preparation.

9. Function :
• Greatest stress in an interim fixed
restoration occurs during chewing.
• Breakage occur more frequently in partial-
coverage restorations and fixed partial
dentures
• Greater strength is achieved by reducing
the depth and sharpness of the
embrasures.

10.  Displacement :
• Displacement is best prevented through
proper tooth preparation and an interim
restoration with a closely adapted internal
surface.
• Excessive space between the restoration and
tooth places greater demands on the luting
agent, which has lower strength and cannot
tolerate added force.
• Unlined preformed crowns should be avoided.

11. Removal for reuse:
• Interim restorations often need to be
reused and so should not be damaged
when removed from the teeth.
• If cement is sufficiently weak and
restoration has been well fabricated, it
does not break upon removal.

13.  The temporary must have adequate contours, color, translucency and
texture.
 This is especially important in anterior teeth. Because acrylic tends to
darken and discolor over an extended period of time, a different
provisional restorative material may need to be selected if the temporary
is to be worn for a long period.
 A smooth polished surface is important for esthetics as well as plaque
removal.
 Crispin and Caputo studied the color stability of provisional materials.
 They found that methyl methacrylate materials exhibited least darkening,
followed by ethyl methacrylate and vinyl-ethyl methacrylate materials.
 They also reported that increases in surface roughness induced
increases in material darkening and pressure polymerizing did not
influence discoloration relative to air polymerizing.

14. All the procedures that are followed to
prepare an interim restoration include a
common formation of mould cavity into
which plastic material is poured or packed.
Mold cavity is created by two correlated
parts : the external contour of the crown
known as External Surface Form (ESF)
and the prepared tooth surface and the
edentulous ridge (when present) known as
the Tissue Surface Form (TSF).

15. There are two categories : Custom and
Preformed.
CUSTOM
A custom is a negative reproduction of either
the patient’s teeth before preparation or a
modified diagnostic cast.
PREFORMED
Various preformed “crowns are available
commercially.

16. Maybe directly obtained with any
impression material (irreversible
hydrocolloid and silicone are convenient)
Easy accurate reseating done by trimming
the thin areas of impression material (inter
proximally or gingival margin)

18. Baseplate wax can be used
as it is more convenient and
economical

19. These prefabricated crown rarely satisfy
the requirements of a interim restoration,
but they can be thought of as ESFs rather
than as finished restorations and must be
lined with autopolymerising resin.
Most crown forms need modifications-
internal relief, axial re-contouring, occlusal
adjustment- in addition to lining procedure.

21. Has the most natural
appearance
Available in single
shade
Available for incisor,
canine and premolar
teeth
Polycarbonate crown forms are more
tolerable, selected to establish contact areas

22.  Cellulose acetate crown
form consists of thin,
soft, and transparent
material.
 Sizes and shape can be
selected from a mold
guide.
 The crown form is trimmed
and festooned to fit the preparation without
impingement on the soft tissue.
 Available in all tooth types

23.  Suitable for
posterior teeth
 Have anatomical
shaped occlusal
and axial surface.
 Care must be taken
during try in
verification to avoid
fracture of their
delicate margins
 As it is highly ductile , it allows easy
contouring

24. Tin Silver preformed crowns are available
for posterior teeth.
This alloy is very soft and the margin of
the crown can be flexed prior to seating
with a swaging block.
This produces a close marginal fit after the
shell is trimmed with a bur.
These should also be lined with acrylic
resin to provide good internal adaptation
and retention of the temporary

25. Used in children with
extensively damaged
primary teeth
They cannot be
altered with resin
 These crowns can be
easily re-contoured
using pliers
Indicated for long term interim restorations.

26. Two categories : indirect
direct
A third category: indirect-direct

27.  The technique involves fabrication of the interim
restoration outside the mouth.
 There is no contact of free monomer with the
prepared teeth or gingival which might cause
tissue damage and an allergic reaction or
sensitization. The technique avoids subjecting
prepared tooth to the heat evolved from the
polymerizing resin. Indirect technique produces
restoration with a superior marginal fit and as an
auxiliary is involved in fabricating the restoration
in the lab, it frees the patient and dentist for
considerable amount of time

28.  Principal disadvantage of the technique
includes increased chair side time and
increased number of intermediate steps. It
is a tedious task to perform if there is
inadequacy of assistants or the laboratory
facilities. In addition, the technique
involves use and possible damage of
diagnostic casts

29. (1) On the diagnostic cast, place a selected acrylic
tooth on the area of the missing tooth, and seal it with
the carding wax.
(2) Following this, a silicone putty index is made
involving at least one tooth each beyond the abutment
teeth.
(3) Prepare the patient’s teeth in the usual manner.
(4) Make a sectional impression of the prepared teeth
and the adjacent structures and pour a check cast.

30. (5) Lubricate the check cast with a petroleum
jelly or any suitable separating media, mix the
provisional restorative material, and place it in
the tissue surface of the index and seat it on the
check cast.
(6) Try in the preformed restoration for its fit on
the cast and intraorally.
(7) Reline the temporary restoration to perfect
the internal fit.
(8)Finish, polish, and cement the restoration

32. The technique produces a custom made
preformed external surface form of the
restoration but the internal tissue surface
form if formed by the underprepared
diagnostic casts

33.  With the combination indirect-direct technique,
chair time can be reduced, since the
provisional shell is fabricated before the
patient’s appointment.
 Enhanced control over restoration contours
minimizes the time required for chair side
adjustments.
 Smaller amount of acrylic resin will polymerize
in contact with the prepared abutment,
resulting in decreased heat generation,
chemical exposure, and polymerization
shrinkage compared to the direct technique

34. The disadvantage of this procedure is the
potential need of a laboratory phase before
tooth preparation and the adjustments that
are frequently needed to seat the shell
completely on the prepared tooth.

35. (1) Pour an accurate pretreatment diagnostic cast from
an impression of the unprepared teeth. For FPDs, wax
a pontic into the edentulous area of the study cast, and
modify with wax to obtain ideal contours, contacts, and
occlusion.
(2) Lightly lubricate the modified diagnostic cast, and
make an impression using a high-viscosity elastomeric
impression material. To provide an adequate bulk of
material at the margins of the provisional, trim the
sharp edge on the elastomeric over impression that
represents the gingival crevice with a round bur to allow
for extra bulk of resin material in this area. The silicone
putty index is made involving at least on tooth each
beyond the abutment teeth.

36. (3)Remove the acrylic tooth and prepare the
abutments on mounted diagnostic casts. (The
diagnostic cast preparations should be more
conservative than the eventual tooth preparation
and should follow precisely the gingival margins
(4) Lubricate the prepared diagnostic cast with a
petroleum jelly or any suitable separating media,
mix the provisional restorative material, and place
it in the tissue surface of the index and reseat it
on the prepared diagnostic casts.

37. (5) After the acrylic resin has polymerized, finish
the restoration. The provisional restoration should
be paper thin and correctly contoured, and it
should precisely follow the gingival margins on the
cast
(6)Prepare the patient’s teeth in the usual manner
(to the gingival margins).
(7)Try in the preformed restoration. (If the amount
of tooth reduction is adequate, the provisional
restoration will show optimal marginal fit with no
need for adjustment.)

38. (8)Reline the temporary restoration to
perfect the internal fit.
(9)Finish, polish, and cement the restoration

40. In the direct technique, patient’s prepared
teeth and the gingival tissues directly
provide the tissue surface form eliminating
all the intermediate laboratory procedures
This is convenient when assistant training
and the office laboratory facilities are
inadequate for efficiently producing an
indirect restoration

41. However the direct technique has
significant disadvantages like potential
tissue trauma from the polymerizing resin
and inherently poorer marginal fit.
Therefore, the routine use of directly
formed interim restoration is not
recommended when indirect techniques
are feasible.

42. (1)Before the tooth preparation, place an acrylic tooth
in place of the missing tooth and make an alginate
impression or a putty index.
(2)Prepare the patient’s teeth in the usual manner.
(3)Lubricate the prepared teeth and the adjacent
gingival margins with petroleum jelly, and reseat the
index or the alginate impression with provisional
restorative material in the dough stage on the tissue
surface of the impression.
(4)Remove and reseat the restoration until it sets.
(5)Finish, polish, and cement the restoration