(Replace) 11.esthetics, rotational path, attachments

Esthetics, Use of Attachments and
Rotational Path RPD’s
John Beumer III DDS, MS
Division of Advanced Prosthodontics
UCLA School of Dentistry
and
Eugene King DDS
Section of Dental Oncology
MD Anderson Hospital and Tumor Institute
This program of instruction is protected by copyright ©. No portion of this
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Esthetics, Use of Attachments and
rotational path RPD’s

“I” bar vs circumferential clasp

Circumferential clasp on the cuspid

Esthetics
“I” bars vs circumferential

Esthetics

v Low smile line
v Cuspid –lateral splinted
v Occlusion
v Anterior guidance
v Posterior – Lingualized with
centric only contact

Esthetics – I” bars
5 year post delivery followup.

vNote low smile line
vWidened major connector
vPositive cingulum rests
vOcclusion
vAnterior guidance using the
cuspids
vLingualized posterior
occlusion with
centric only contact

Esthetics – “I” Bars

v Extension Base RPD opposing implant supported
fixed hybrid prosthesis
v Occlusion
v Anterior guidance with the anterior teeth
v Posterior occlusion-lingualized with centric only contact

RPD Attachments
Advantages:
v Elimination of visible clasp arms

Disadvantages:
v Additional expense
v Increased frequency of
adjustment and failure
v Increased technical expertise
required
v Unpredictable or unfavorable
distribution of forces

Attachment Classification
Rigid attachments
v No movement is possible between the
parts. Used in situations where the
abutment teeth fully support the occlusal
forces (tooth borne RPD’s and fixed
partial dentures)

Resilient attachments
v Allows movement to take place between
the parts, thus providing stress-breaking.
An example is the ERA attachment

Attachments - Resilient
ERA attachment – Extra-coronal resilient attachment
The ERA
attachment
permits the RPD
to be displaced
into the
edentulous
extension area
by up to .4 mm


Plastic burnout pattern Metal housing

ERA attachment

Requirements for use
vSplinted abutments
vRest distant from the attachment
vClose followup to consider relines

ERA Attachment

ERA ERA + splinting

Photoelastic analysis - Evaluating the following:
vSplintedvs unsplinted
vRest vs no rest
vRest position

Berg and Caputo et al


ERA ERA+splinting

Summary and conclusions
vAttachment best used when:
v Adjacent teeth splinted
v Positive rests
v Light retention (white and orange attachment)


v Splinting the abutments helps
distribute the forces
v Positive rests away from the
extension area helps direct the
forces vertically onto the
abutment and into the
edentulous bearing surfaces
v Less wear of ERA attachment

Overlay denture attachments
Advantages
v Improved esthetics
v Maintain support
v More favorable biomechanics - Improved crown-
root ratio

Overlay denture attachments
Problems
v Copings become loose
v Attachment wear, loss & breakage
v Alveolar resorption
v Overdenture breakage
v Pt. maintenance problems
v Pt. oral hygiene problems

This patient is status post partial palatectomy for a benign tumor of the
left hard palate. The left tuberosity remains and it contains a third molar

Use the surveyor to prepare the path of
insertion for the attachments

Note the bracing arm through the proximal of #5 and #6. It is
non- retentive but keeps the RPD framework from being
displaced lingually in this region and with the cingulum rest on
#8, keeps the framework centered over the ERA attachment.

Bracing
arm
Rest

ERA
attachment
Cingulum
rest


Bracing arm
The two central incisors have
been splinted together. A
cingulum rest is positioned on
the mesial side of #8. The ERA High smile
attachment is incorporated
within the crown of #9.

Note the bracing arm.


High smile
Note the attachment associated with third molar. This serves as an occlusal
stop and has a retentive attachment incorporated within. The ERA should not
be used unless a positive occlusal stop is present on the defect side,
either from a tooth or an implant.


Occlusion
v Right side – Anterior guidance
v Left side – Mutually protected occlusion

Magnetic Attachments
Advantages :
v Ease of insertion and removal
v Simple laboratory work &
economic cost
v Reduced lateral forces
v No leverage
v No fragile parts for fracture
v No activation necessary
v Do not need special equipment
(parallelometer etc)
v Easy to maintain oral hygiene

Applications
v Retained roots
v Implants
v Maxillofacial Prosthetic Applications

Maxillofacial applications

Inappropriate use of attachments

v Insufficient vertical movement allowed
v Cantilever forces delivered to the abutments
v Result
v High rate of periodontal breakdown and abutment tooth fracture


v Result
v High rate of periodontal breakdown and fracture of the
abutment teeth

Nonresilient Attachments in Extension Based RPD’s

v No vertical movement permitted
v Result
v High rate of periodontal breakdown and fracture


v Result
v High rate of periodontal breakdown and fracture of the abutment
teeth


v Result
v High rate of periodontal breakdown and fracture of the abutment teeth

Kennedy Class IV RPD’s
Rotational Path of Insertion RPD’s


v One portion is inserted first permitting rigid portions of the
RPD (proximal plates) to engage undercuts
v The prosthesis is then rotated into position
v In the posterior quadrants limited to tooth borne RPD’s
v Most often used to restore anterior extension defects where
use of attachments or clasps is unfavorable


Advantage
v Elimination of unesthetic retainers (clasp arms)
v The clasp arms are replaced by rigid retainers
v These rigid retainers engage undercuts and consist of
a positive rest and a minor connector (proximal plate)


Caution
v Little tolerance for error. It requires a high level of
sophistication on the part of both the dentist and the lab
technician
v Requires well prepared positive rests seats. May require
restorations to develop an acceptable rest seat
v Undercuts in posterior rest seats will prevent proper seating


v They can also be used
to restore Kennedy
Class III RPD’s with
missing posterior teeth
v Disadvantage
v Bracing from guide
planes is compromised

Treatment planning
v Patientpresents with moderate periodontal
bone loss with recent loss of the incisors
v Options
v Fixed partial denture
v Implant supported fixed partial denture
v Rotational path of insertion RPD

Treatment planning
v Options
v Fixed partial denture – Problems
v Length of span
v Amount of tooth reduction for PFM’s
v Long pontics – Compromised esthetic result

Treatment planning
v Patient presents with moderate periodontal
v Options
v Implant supported fixed partial denture – Problems
v Difficult to predictably restore vertical and horizontal
boney contours with grafting

Treatment planning
v Options
v Rotational path of insertion RPD -Best solution
v Minimal reduction of tooth structure
v Best esthetic result
v Least costly


Tentative RPD design

Surveying the cast
v Identify
the cast orientation that results in at least a .
25 mm undercut on each of the anterior abutments

Surveying the cast
v Tilt cast to determine initial path of insertion.

Surveying the cast
v Verify that at this cast inclination, proper rests can be
developed consistent with the initial path of insertion.
v The rests must not be undercut in relation to the path
of insertion

v Prepare the anterior and posterior rests.
v The rests must be positive
v Beware of excessive buccal inclination of the maxillary
molars. The rests must be positive but should not be
undercut in relation to the path of insertion

v Fabricatethe RPD casting and verify the
adaptation

Completed RPD
Important factors for long term success
v Positive rests
v Survey for appropriate undercuts and proper rotational
path of insertion


v In this patient circular
concave rests were
used on the cuspids
v Guidance in lateral
excursion provided by
the cuspids and
premolars

v Cingulum rests prepared on the cuspids
v Positive rests prepared on the distal side of
the molars

v Positive rests on the cuspids and the molars
v Lingual “I” bars used for reciprocation and
encirclement of the molars
v Guidance in lateral excursion provide by the
cuspids and premolars

v Cingulum rest prepared on the cuspid
v Positive rest on the premolar and molars

v Guidance provided by the cuspid and lateral
incisor on the left the premolar and molar on the
right

Lateral Rotational Path on Insertion
v Patient presents status post anterior mandibular
resection
v The posterior segments of mandible are rotated
to the lingual

v Retention provided by the lingual surfaces of the
right molars and the “I” bar on the left
v Reciprocation and encirclement for the right
molar provided by the trans-occlusal rest

v Trial
denture
v Completed RPD is inserted right to left

v Surveying the cast. Note the lingual
undercuts

v Completed RPD with lingual retention
v Insertion path is from right to left

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(Replace) 11.esthetics, rotational path, attachments

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