Thank you for the presentation. I found it very informative regarding the principles of designing removable partial dentures for patients with defects of the maxilla and mandible.

1. Principles of RPD Design in Patients
with Defects of the Maxilla and
Mandible
John Beumer III DDS, MS
Division of Advanced Prosthodontics,
Biomaterials, and Hospital Dentistry
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2. Principles of RPD design
v Major connectors must be rigid.
v Occlusal rest must direct occlusal forces along the
long axis of the teeth.
v Guide planes are employed to enhance stability and
bracing.
v Retention must be within the limits of physiologic
tolerance of the periodontal ligament.
v Maximum support is gained from the adjacent soft
tissue denture bearing surfaces.
v Designs must consider the needs of cleansibility.

3. Maxillary Defects
Problems complicating RPD design
v Multiple axis of rotation
v Compromised support on the defect side
v Lack of cross arch stabilization because of
the loss of palatal structures on one side
v Long lever arms
v Forces of gravity become more significant

4. Movement of the prosthesis and the
length of the lever arm
v Potential exists for substantial movement as compared to the normal
patients.
v Length of lever arms are much greater than seen in conventional
prosthodontics.
Clinical significance: There is greater risk of overloading abutment
teeth with inappropriate partial denture designs.

5. Preservation of teeth
v RPDdesigns must anticipate and
accommodate the movements of the
prosthesis during function, without exerting
pathologic stresses on the abutment teeth.
Clinical significance: If the RPD designs do not conform
to this idea there is risk that abutment teeth may be
overloaded leading to their premature loss.

6. Multiple axis of rotation
Fulcrum lines are dynamic and once the sites of
occlusal rests are selected, the axis of rotation is
dependent upon the site of load application
Load #1 –
Fulcrum line A - B
Load #2 –
Fulcrum line C - D
Load #3 –
Fulcrum line E - F

7. Abutments adjacent to the defect
These teeth are subject to more vertical and lateral
forces and are more frequently lost than
abutments in other positions. Why?
v The defect offers little support.
v The long lever arms magnify the occlusal forces
Clinical significance: Design and position of rests on these teeth must
direct forces along the long axis of the teeth. In some patients
splinting these teeth to adjacent teeth may be useful; in others it is best
to use these teeth as overdenture abutements.

8. Abutments adjacent to the defect
v Rest position and contour
These rests all have one factor in common – they permit
engagement of the tooth in a “positive” manner and
direct occlusal forces along the long axis of the tooth.

9. Rest position and contours
v Incisal rests are contraindicated on teeth adjacent to
the defect. In this patient the incisal rest on the
cuspid will disengage when an occlusal force is
applied posteriorly

10. Rest position and contours
Anterior teeth
adjacent to the
defect must have
“positive”
cingulum rests.

11. Rest position and contours
v Incisors – Splinting and cingulum rests. We recommend that incisors
adjacent to the defect be splinted together with full veneer crowns and
cingulum rests be developed within their contours.
Note hygiene access

12. Bolus manipulation
v Patients soon learn to confine the bolus on the dentate side but they will
incise on the defect side. Therefore, in most radical maxillectomy
defects, clinically the most significant axis of rotation will be similar to the
C-D axis seen in this defect. However, in this patient the A-B axis is the
most important.

13. Retainers
v “I”
bars are almost always used on the
abutment tooth adjacent to the defect. Why?
vMaximum natural cleansing vMinimal tooth contact
action vExact placement of retention
vPassive functional contact
movement of an extension vMinimal Interference with
prosthesis natural tooth contour
vBetter esthetics

14. Retainers
v “Suprabulge retainers are used posteriorly
Why?
•Better bracing (stability) provided
by this type of retainer.

15. Stability and Bracing
v Lingualplate
v Suprabulge retainers
More bracing is
required in maxillary
resection defects and
so suprabulge
retainers are use on
posterior teeth and
lingual plating is
frequently employed.

16. Support - Palatal shelf area available
One of these patients had a favorable defect and ample palatal
shelf area. The other does not. Partial denture designs can be
conservative for the patient on the left. Little bracing is
required and fewer retainers are necessary. The opposite
would true for patient on the right - more retainers and more
bracing are required.

17. Master Impressions
v Impressions for the RPD framework
v Stock tray with reversible hydrocolloid
v Altered cast impressions of the
defect
v Bordermolding with dental compound
v Wash impression materials
vElastic materials vs thermoplastic wax

18. Clinical procedures
v Impression for the RPD framework
v Physiologic adjustment of partial
denture framework
v Altered cast impressions of the defect
v Centric relation records
v Trial dentures
v Processing
v Delivery and followup

19. Master Impresssions
Impressions for RPD frameworks
A stock tray is used. Periphery wax is used to extend
the tray into the defect and onto the soft palate.
Undercuts on the
medial side of the
defect should be
blocked out.
Otherwise the
residual palatal The completed impression
contours will be records the contours of
distorted upon residual tissues, dentition,
remmoval of the tray. and the defect

20. Master cast and RPD framework

21. Verify and physiologically adjust
the RPD framework
Framework try-in appointment:
a) Verify accuracy of fit
b) Physiologically adjust framework
c) Occlusal adjustment of framework

22. Physiologic adjustment of RPD frameworks
Rouge and chloroform is still the
most effective means. Guide
planes and minor connectors Note where the rouge has
should be carefully evaluated. been rubbed away from
the distal guide plane
(arrow). This area needs
adjustment.
Silicone type indicators
are effective, but much
more expensive.

23. Physiologic adjustment of partial denture frameworks
Another framework. Note
the areas in need of
adjustment (arrows).
Adjustments are made with
a high speed air rotor.

24. Completed RPD with Obturator
Speech and swallowing are restored to normal and mastication
can be accomplished effectively on the unresected side.

25. Completed RPD with Obturator

26. a
c d
Completed RPD -
Obturator

27. Completed RPD - Obturator

28. Completed RPD - Obturators

29. Completed RPD - Obturator

30. Completed RPD - Obturators

31. Completed RPD - Obturators

32. Completed RPD - Obturators

33. c
Completed RPD -
Obturators

34. Mandibulectomy Defects
Problems regarding RPD design
v Compromised support
v Unilateral forces of occlusion
v Angular path of closure tends to displace the
prosthesis laterally towards the defect side.
v Frontal plane rotation

35. RPD design – Lateral discontinuity defects
vStability (bracing), resistance to displacement towards the
resected side as a consequence of the angular path of closure,
is enhanced by the lingual plate and the “I” bar.
vBracing can be enhanced by adding an extra retainer to
engage the first premolar. This retainer should not be in an
undercut.

36. RPD design – Lateral discontinuity defects
Support is maximized by covering the retromolar pad
and extending onto the buccal shelf. These
extensions are best refined with an altered cast
impression.

37. RPD designs Lateral discontinuity defects
Double “I” bars and the
polished surface of the
denture on the nonresected
side prevent the prosthesis
from being displaced laterally
towards the defect side
during mastication.

38. RPD designs - Lateral discontinuity defects
v Physiologic adjustment
Numerous studies have shown that occlusal forces
are distributed more favorably to abutment teeth when
RPD castings are physiologically adjusted.

39. RPD designs – Lateral discontinuity defects
Altered cast impressions
l Note the contours of the polished lingual surface.
The lingual flange on the resected side enhances
stability. Maximal development of this extension, plus
an accurate imprint of the imprint of the tongue on the
polished surface should be made when making the
altered cast impression.

40. Patient is status post composite resection for a
carcinoma of the right tonsil.
The tonsillar bed was reconstructed with a myocutaneous
flap. Tongue bulk and mobility were close to normal.
The remaining anterior teeth were restored with PFM’s with
cingulum rests. The premolar was also restored with a PFM
and a rest was placed on the mesial.

41. Altered cast impressions were made
Occlusion: Cusp angles of the maxilla are flattened and the central fossa
rounded out. The mandibular buccal cusps engage the central fossa of
the maxillary teeth – a variation of the “lingualized” concept.

42. Completed and inserted restoration
Note flattened cusp angles
and rounded central fossa
Note the
frontal plane
rotation

43. Restored lateral defects
Partial denture design – Lateral defects
where continuity has been retained or
restored
Note the multiple axis of Patients tend to use the
rotation. The axis depends dentate side for
upon the point of load mastication.
application.

44. Bracing
Patients with unilateral
dentition and large
edentulous spaces such
as in this case, require
additional bracing. Here,
in addition to the bracing
effect of the proximal
plates on the 2nd molar
and the 1st premolar,
bracing is provided by
plating the lingual
surfaces of the remaining
dentition.

45. Restored lateral defects
Purpose of the
prosthesis
l Lip support and esthetics
l Prevent maxillary teeth
from supererupting

46. Restored lateral discontinuity
defects

47. Restored lateral discontinuity defects

48. Completed RPD

49. Anterior defects
Continuity was restored
with a free graft.
Continuity was maintained and a skin graft
Continuity was retained and the used to resurface the exposed mandible
wound was closed primarily in these two patients
The primary deficiency is the lack of support in the anterior extension
area. The anterior extension of the prosthesis restores lip contours,
and lip seal rather than facilitating mastication.

50. Anterior defects
l Partial denture design – Anterior defects
Axis of rotation

51. Anterior defects
Note distal rests and mesial guide planes

52. l Completed prosthesis. Its primary benefit is
Lack of support anteriorly.

53. a b c
d
l Completed RPD

54. Principles of RPD design
v Occlusal rest must direct occlusal forces along the
long axis of the teeth.
v Major connectors must be rigid.
v Guide planes are employed to enhance stability and
bracing.
v Retention must be within the limits of physiologic
tolerance of the periodontal ligament.
v Maximum support is gained from the adjacent soft
tissue denture bearing surfaces.
v Designs must consider the needs of cleansibility.

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