This document discusses mouth preparation for removable partial dentures. It covers oral surgical preparation such as extractions and alveoloplasty. It also discusses conditioning of irritated tissues using salines and massages. Periodontal preparation to reduce pockets and establish healthy gingiva is covered. Preparation of abutment teeth includes creating guiding planes, modifying contours for retention, and preparing rest seats. The goals are to direct forces along tooth axes and prevent damage to abutment teeth.

1. Preparation of the mouth for
Removable partial denture
by
Mohamed al-dkmawy

2. Definition
Mouth preparation are identified as those
procedures that are accomplished to prepare the
mouth for reception of prosthesis.
Renner Boucher

3. When?
• Mouth preparation follows the preliminary diagnosis and the
development of a tentative treatment plan.
• Mouth preparation must be accomplished before the
impression procedures are performed that will produce the
master cast on which the removable partial denture will be
fabricated. (before secondary impression)

4. Mouth preparation includes
procedures in four categories:
A. oral surgical preparation.
B. conditioning of abused and irritated tissues.
C. periodontal preparation.
D. preparation of abutment teeth.

5. Oral Surgical Preparation
All pre-prosthetic surgical treatment for the
removable partial denture patient should be
completed as early as possible.

6. Surgical Preparation include
A. Extractions
Planned extractions should occur early in the
treatment regimen but not
before a careful and thorough
evaluation of each
remaining tooth in the
dental arch is completed

7. Alveoloplasty After Extraction
• When a tooth is hypererupted due to the absence of an
antagonist, bone irregularity is usually observed after its
extraction. This may cause problems for the normal healing
process and abnormality of the alveolar bone, resulting in
obstruction of the placement of a prosthetic restorative
appliance. In such cases, immediately
after extraction of the tooth, recontouring of the bone in the
area must be performed.
photo

9. Surgical Preparation include
B. Removal of Residual Roots
All retained roots or root fragments should be
removed if they are in close proximity to the
tissue surface, or if associated pathologic findings
are evident.

10. Surgical Preparation include
C. Impacted Teeth
• All impacted teeth, including those in edentulous areas, as
well as those adjacent to abutment teeth, should be
considered for removal.
• Asymptomatic impacted teeth in the elderly that are covered
with bone, with no evidence of a pathologic condition, should
be left to preserve the arch morphology.

11. Surgical Preparation include
D. Malposed Teeth
• The loss of individual teeth or groups of teeth may lead to
extrusion, drifting, or combinations of malpositioning of
remaining teeth.
• Orthodontics may be useful in correcting many occlusal
discrepancies, but for some patients, such treatment may not
be practical because of lack of teeth for anchorage of the
orthodontic appliances or for other reasons. In such
situations, individual teeth or groups of teeth and their
supporting alveolar bone can be surgically repositioned.

12. surgically repositioned
• Selective alveolar corticotomy to intrude overerupted molars
• source of research

13. Case restored dentition made
possible by
a combination of endodontics, periodontics, and
fixed and removable partial prosthodontics.

14. Surgical Preparation include
E. Cysts and Odontogenic Tumors
Panoramic roentgenograms of the jaws are recommended to
survey the jaws for unsuspected pathologic conditions.
F. Exostoses and Tori
The existence of abnormal bony enlargements should not be
allowed to compromise the design of the removable partial
Denture.

15. Surgical Preparation include
G. Hyperplastic Tissue
Hyperplastic tissues are seen in the form of fibrous tuberosities,
soft flabby ridges, folds of redundant tissue in the vestibule
or floor of the mouth, and palatal papillomatosis.
photo source

16. Surgical Preparation include
H. Muscle Attachments and Frena
I. Bony Spines and Knife-Edge Ridges
photo source

17. Surgical Preparation include
J. Osseointegrated Devices
These devices offer a significant stabilizing effect on dental
prostheses through a rigid connection to living bone.

18. Conditioning of Abused and
Irritated Tissues
Many removable partial denture patients require some
conditioning of supporting tissues in edentulous areas before
the final impression phase of treatment begins.
Patients who require conditioning treatment often
demonstrate the following symptoms:
1. Inflammation and irritation of the mucosa covering
denture-bearing areas.
2. Distortion of normal anatomic structures, such as
incisive papillae, rugae, and retromolar pads.
3. A burning sensation in residual ridge areas, the tongue,
and the cheeks and lips.

19. Conditioning of Abused and
Irritated Tissues
These conditions are usually associated with ill-fitting or
poorly occluding removable partial dentures. However,
nutritional deficiencies, endocrine imbalances, severe health
problems (diabetes or blood dyscrasias), and bruxism must
be considered in a differential diagnosis.

20. Conditioning of Abused and
Irritated Tissues
underextended bases properly extended
Treatment:
• rinsing the mouth three times a day with a prescribed saline
solution.
• massaging the residual ridge areas, palate, and tongue with a soft
toothbrush.
• removing the prosthesis at night.
• Some inflammatory oral conditions caused by ill-fitting dentures
can be resolved by removing the dentures for extended periods.
• Use of Tissue Conditioning Materials.

21. Tissue Conditioning
Materials
Temporary liner use in dentistry is not new and is known for
many years . Resilient liners which were used previously, were
natural rubbers. In the year 1945,the first synthetic resin made
of plasticized poly vinyl resins were developed and the silicone
rubbers followed in 1958.
Tissue conditioners find several uses: in the speciality of
used in treatment of abused tissues,improve the fit of ill fitting
dentures , retain a temporary obturator , for base-plate
stabilization , to diagnose the outcome of resilient liners ,as
liners in surgical splints, used in trial denture base and are also
used as a functional impression material.
More about tissue conditioning materials

22. Periodontal Preparation
Objective are as follows:
1. Removal and control of all etiologic factors contributing
to periodontal disease along with reduction or elimination
of bleeding on probing.
2. Elimination of, or reduction in, the pocket depth of all
pockets with the establishment of healthy gingival sulci
whenever possible.
3. Establishment of functional atraumatic occlusal relationships
and tooth stability.
4. Development of a personalized plaque control program
and a definitive maintenance schedule.

23. Abutment Teeth Preparation
Objective:-
• direct stress along the axis of the tooth.
• Eliminate interferences by recontouring of teeth.
• Create retention by simple alteration procedures.
• Allow placement and removal of prosthesis without
transmitting wedging types of stress against teeth with which
it comes in contact.

24. CLASSIFICATION OF
ABUTMENT TEETH
The subject of abutment preparations may be
grouped as follows:
• those abutment teeth that require only minor modifications
to their coronal portions.
• those that are to have restorations other than complete
coverage crowns.
• those that are to have crowns (complete coverage).

25. Sequence of Abutment Teeth
preparation
1. Preparation of Guiding Planes
2. Modification of Height of Contour
3. Preparation of Retentive Undercuts
4. Rest seat preparation

26. Preparation Of Guiding Planes
• Two or more vertically parallel surfaces on
abutment teeth and/or fixed dental prostheses
oriented so as to contribute to the direction of
the path of placement and removal of a
removable partial denture, maxillofacial
prosthesis, and overdenture.

27. Advantages Of Guide Surface
And Guide Plate
• Food impaction is prevented.
• Hypertrophy of the soft tissue between the tooth and the
prosthesis is prevented.
• The friction force in these areas supports the retention and
stability of the prosthesis in great proportion.
• Controlling of the movement of the teeth by supporting in
antero-posterior direction.

28. Advantages Of Guide Surface
And Guide Plate
• natural appearance is obtained by full contact of tooth and
RPD without any space in between. Otherwise, the area
between the teeth and the prosthesis will appear as a dark
space, which will cause esthetic problems.

29. Advantages Of Guide Surface
And Guide Plate
• Allows a reciprocating component to maintain
continuous contact with a tooth as the denture
is displaced occlusally.

30. • A reciprocating element must brace the abutment as the
retentive element passes to and from its fully seated position.
• If reciprocation is ineffective, potentially destructive lateral
forces (arrow) will be transferred to the abutment.
• A properly prepared guiding plane permits sustained contact
between the reciprocal element and the abutment and
prevents the application of unopposed lateral forces.

31. Preparation of guiding plan
To Tooth-supported Segments
• Guiding planes should be at least 1/2 to 1/3 of the axial height
of the tooth (generally 2-4mm in height). Use a light sweeping
stroke continuing past the bucco- and the linguo proximal line
angles.

32. Preparation of guiding plan
To free end saddle
• A guiding plane adjacent to a distal extension space is 1.5-2.0
mm in height Reduced height results in decreased contact
with the minor connector and permits greater freedom of
movement for the removable partial denture.
• Hence, potentially damaging forces are minimized.

33. Preparation of Lingual Surfaces
• A properly prepared lingual guiding plane should be 2 to 4 mm
in occlusogingival height and should be located in the middle
third of the clinical crown.

34. Changing height of contour
when teeth have drifted or tipped these movements produce
distinct changes in the heights of contour. In these situations,
enameloplasty is performed to place partial denture
components in more desirable positions.
Care must be taken not to penetrate the enamel and expose the
underlying dentin. In the event that dentin is
exposed, a restoration must be
placed to protect the tooth.

35. Enhancing retentive undercuts
Under certain conditions, tooth contours may be modified
to enhance an existing undercut or create a conservative
undercut(dimpling).
Depression should be parallel and close to the gingival
margin. The depression should be approximately 4 mm in
mesio- distal length , 1-2 mm in occluso-gingival height
And undercut of 0.010 inches.
4mm 1-2mm

36. Rest Seats
The components of a removable partial denture
that transfer forces down the long axes of the
abutment teeth.
Stewart

37. FUNCTIONS
• Support: Prevent movement of prosthesis toward the tissues.
• Force transfer: To direct the forces of mastication parallel to
the long axis of the abutment tooth.
• Indirect retainer: It is a part of a RPD which assists the
direct retainers in preventing the displacement of distal
extension.
• Serve as a reference point for evaluating the fit of the
framework to the teeth.

38. Types
1. INTRACRONAL RESTS: fit into rest preparations within the
contours of an abutment tooth crown. They may be
precision or semi-precision.
• PRECISION RESTS (prefabricated types) consists of two metal
components manufactured to fit together precisely.
• semi-precision(custom made / laboratory made).

39. Types
2. EXTRA-CRONAL REST: should have the following desirable
characteristics.
• Be rigid.
• Contact the deepest portion of the rest preparation(positive
seat area).
• Form an angle of less than 90° with its minor connector.
• Fill the rest preparation, completing the contours of the tooth,
thus resulting in a smooth metal-to-tooth margin.
• Be capable of rotation within the rest preparation for tooth
tissue supported RPDs.

40. Preparation of Proximal Occlusal
Rest
• It should be as long as it is wide, and the base of the triangular
shape (at the marginal ridge) should be at least 2.5 mm(½ to
2/3 the distance between the facial and lingual cusp tips) for
both molars and premolars.

41. Preparation of Proximal Occlusal
Rest
• The preparation is at least 1.0 mm deep with a slightly deeper
portion 0.5 mm(1.5mm) called the POSITIVE SEAT.

42. EMBRASURE OCCLUSAL
REST
• Its size, shape and dimensions are similar to the proximal
occlusal rest preparation EXCEPT that the flare of the facial
margin is limited by the proximal contact with the adjacent
tooth.
• The embrasure occlusal rest preparation rarely extends
beyond the primary fossa.
• if an embrasure occlusal rest is to be used, the occlusal fossa
of the adjacent tooth is also prepared with an embrasure
occlusal rest preparation UNLESS THERE IS A REASON NOT.

43. TRANSOCCLUSAL RESTS
A transocclusal rest preparation is similar in size and shape to
an embrasure occlusal rest preparation
EXCEPT that the preparation is extended
facially to create space for the rest and
clasp arm to extend onto
the facial surface of the tooth.

44. INCISAL RESTS
Incisal rests are placed on the incisal edges of mandibular
canines and incisors. They are not placed on maxillary canines or
incisors because the minor connector of the rest would interfere
with occlusion and the facial portion of the rest would be very
visible and unaesthetic.
• Mesio-distal dimension of the rest preparation should be 2-2.5
mm and the depth 1.5mm to provide adequate space for a
bulk of metal for the rest.

45. Lingual Rests
• A lingual rest is preferable to an incisal rest because it is
placed closer to the horizontal axis of rotation (tipping axis)
of the abutment and therefore will have less of a tendency to
tip the tooth.
• In addition, lingual rests are more esthetically acceptable than
are incisal rests.

46. Lingual Rests preparation
• Mesio-distal length of the preparation should be a minimum
of 2.5 to 3 mm, labiolingual width about 2 mm, and incisal-
apical depth a minimum of 1.5 mm.
1.5mm
2mm
2.5 to
3 mm

47. References
• files.sld.cu/protesis/files/2018/06/chapter10-rests-and-
preparations.pdf
• McCracken's removable partial prosthodontics 12edi
• www.muhadharaty.com/lecture/20820/ ‫د‬-‫وفاء‬/ preprosthetic-
surgery-pptx