Implant-Assisted Unilateral Removable Partial Dentures

Transcription

Continuing Education
Volume 33 No. 1 Page 106
Implant-Assisted
Unilateral Removable
Partial Dentures
Authored by John F. Carpenter, DMD
Upon successful completion of this CE activity 2 CE credit hours will be awarded
Opinions expressed by CE authors are their own and may not reflect those of Dentistry Today. Mention of
specific product names does not infer endorsement by Dentistry Today. Information contained in CE articles and
courses is not a substitute for sound clinical judgment and accepted standards of care. Participants are urged to
contact their state dental boards for continuing education requirements.
Implant-Assisted Unilateral
Removable Partial Dentures
Effective Date: 1/1/2014
Expiration Date: 1/1/2017
Figure 1.
Traditional unilateral
Kennedy Class III
partial. A major
connector is utilized
to connect both
sides of the arch.
Patients often
complain of its
bulkiness.
ABOUT THE AUTHOR
Dr. Carpenter is a full-time practicing
clinician in New Windsor, NY, emphasizing
implant and complex restorative dentistry.
He is an attending in the department of
dental medicine at Westchester Medical
Center in Valhalla, NY, where he works
with the dental residents helping them plan and execute all
phases of dentistry. Dr. Carpenter is a Fellow and a Master in
the AGD, and a Diplomate in the International Congress of
Oral Implantologists. He is a member of numerous dental
associations and serves as a manuscript reviewer for General
Dentistry, AGD’s bimonthly journal. Dr. Carpenter is active in
the Ninth District Dental Association, a component of the New
York State and ADA, where he has served as education
chairman for 2 terms. In addition, Dr. Carpenter has lectured
as well as published articles for several professional journals
on implants and other subjects. He can be reached at
jcarpenter@hvc.rr.com.
speech issues, metal clasps that show, and movement
(instability). Patients often ask: “If I’m only missing teeth on my
left, why does the partial need to go over to my right side?”
This article will review alternatives to the traditional
bilateral RPD. Three cases will be presented that describe
unilateral implant-assisted RPD (IARPD) solutions.
ALTERNATIVE OPTIONS TO THE TRADITIONAL
BILATERAL METAL REMOVABLE PARTIAL DENTURE
Fixed Implant Prosthesis Option
Restoration of unilateral missing posterior teeth with a fixed
implant-supported prosthesis is the most current ideal
option (Figures 2 to 4). The advantages of a fixed implant
restoration are numerous with patients often perceiving
them as actual body parts.
However, possible contraindications include anatomical
challenges, such as proximity to vital structures and lack of
bone. While many of these challenges can be overcome, not
all patients are willing to undergo the additional surgeries and
the time necessary to grow bone. Other disadvantages
include financial limitations and bioengineering challenges,
such as excess interocclusal space.
Disclosure: Dr. Carpenter reports no disclosures.
INTRODUCTION
A unilateral edentulous space (Kennedy Classifications II and
III), in my opinion, is one of the most difficult situations to
restore with a removable partial denture (RPD). The traditional
RPD design to solve this unilateral space is actually bilateral
(Figure 1); rests and clasps placed opposite the edentulous
side are necessary, and a major connector is used to connect
the 2 sides. In the maxilla, the major connector will contact and
cross the palate and in the mandible, cross behind the lower
anterior teeth. While these designs offer good support, stability,
and retention (the 3 keys to removable partial denture design),
many of my patients have been less than happy. The negatives
of such a traditional partial include bulkiness, palatal coverage,
Metal “Nesbit” Unilateral Removable Partial Denture
The “Nesbit” partial is another option. This small, removable
prosthesis is used to replace one to 3 teeth on one side of
the arch. Historically, this has been used only for a Kennedy
Class III edentulous arch (a unilateral posterior space with
anterior and posterior teeth) (Figure 5). The traditional Nesbit
RPD has metal rest seats and clasps that fit around the teeth
on each side of the space.
1
Figures 2 to 4. A posterior fixed-implant restoration. Note the excellent bone width. No bone grafting was necessary to complete this restoration.
recently. A simple modification was all that was necessary to
create an enhanced Nesbit RPD. By adding an implant to
this original traditional Nesbit design, a more stable, supported, and retentive prosthesis is obtained. The danger of
accidental dislodgement has been minimized and the
unfavorable forces on the abutment teeth and the
edentulous ridge have been eliminated.
Patients may feel this has the benefit of being singlesided and less bulky. Unfor tunately, a serious risk of
aspiration and swallowing exists due to its small size and
limited retention (Figure 6). This danger can produce
laceration, infection, and requires hospitalization and
surgical intervention.1-3
Flexible Nesbit Unilateral Removable Partial Denture
This is very similar to the metal Nesbit, except new flexible
nylon materials are used (Figure 7). Several material
choices exist (such as Valplast, Flexite, and TCS). The
esthetics are improved, but unfortunately, this is essentially
a tissue-borne prosthesis. The nylon flexible RPD lacks
important elements of the traditional RPD; namely, occlusal
rests and a rigid framework.
Biomechanically, both the metal and flexible unilateral
Nesbits are flawed. The supposed benefit of being singlesided (no bilateral support) creates an unstable prosthesis.
This design does not allow for a broad distribution of force
like the traditional bilateral design that includes indirect
retainers and palatal coverage, etc. Nesbits are subject to
forces during function, resulting in a rocking buccal-lingual
motion.4,5 This creates excessive pressure on the abutment
teeth. The flexible Nesbit also has the added disadvantage
of excessive tissue pressure, causing accelerated bone
loss of the edentulous ridge.
While the Nesbit unilateral RPD addresses the patient’s
desire for a smaller and economical tooth replacement, I
have been reluctant to recommend it. Its inherent
mechanical shortcomings and possible catastrophic risk of
swallowing have precluded its use in my practice until
CASE REPORTS
The following cases will describe unique ways implants can
be used to improve the safety and function of a unilateral
RPD. For the sake of brevity, please understand that each of
these patients underwent a complete evaluation including
dental history, complete radiographs, and oral exam. I feel
passionate that each patient’s treatment diagnosis is unique
and treatment should only be selected after a great deal of
time listening and getting to know our patients. While these 3
patients selected a unilateral IARPD option, others with
similar problems selected a traditional bilateral partial and
others selected a fixed-implant prosthesis.
Case No. 1
A 68-year-old male patient presented with discomfort to
chewing, upper left. An examination disclosed a failing posterior
abutment of a 4-unit fixed bridge (Figure 8). The bridge was
sectioned and No. 15 was extracted atraumatically with
concurrent socket bone grafting.
Treatment options were discussed and included: (1)
implant-supported fixed bridge for Nos. 13, 14, and 15
(sinus grafting would be necessary); (2) bilateral
conventional metal RPD; and (3) unilateral IARPD.
2
Figure 5. A metal “Nesbit” partial. Traditional metal
clasps and rests fit the adjacent abutment teeth.
Figure 6. A radiograph of
a swallowed unilateral
Nesbit partial requiring
surgical intervention.
Figure 7. A nylon flexible Nesbit partial. This offers
improved esthetics but is tissue-borne and will lead to
accelerated ridge destruction.
Figure 8. Panoramic radiograph of patient No. 1. The maxillary upper left posterior bridge is
failing.
Figure 10. Radiograph demonstrating an
anterior ERA attachment and posterior
implant locator attachment. Note the “small
island of bone” that allowed the implant to
be placed without bone augmentation.
Figure 9. Processing of a Micro ERA
attachment (Sterngold).
Figures 11 and 12. Intaglio and intraoral views of implant-assisted removable partial
dentures (IARPD).
(Micro ERA [Sterngold]) to increase retention of the RPD,
and improve esthetics since the buccal clasp on No. 13
would not be needed (Figure 9).
An implant (Legacy [Implant Direct]) was placed in the
small island of bone distally and allowed to heal for 3
months before beginning construction of the prosthesis.
Figures 10 to 12 demonstrate the fabrication of the IARPD.
The patient selected option No. 3. His selection was
based on the avoidance of additional surgery (lateral wall
sinus augmentation). He also declined option No. 2 due to
the fact that it would cross his palate.
A single crown was required for tooth No. 13, since the
bridge was sectioned and the old abutment fit was poor. It
was decided to use a precision extracoronal attachment
3
Figure 15. A LOCATOR abutment (ZEST
Anchors). These abutments are available in
different heights for each implant platform.
IARPDs are a space-sensitive prosthesis so
the correct height must be selected.
Figure 13. “Salvage” case. Attempts at a
fixed-implant prosthesis had failed. Note how
tooth No. 26 is periodontally compromised
and represents a poor quality abutment.
Figure 14. Radiograph of the sole posterior
implant to be utilized to improve the
retention, stability, and support of a small
Nesbit partial.
Figure 16. A blue male is being snapped
into the metal housing with the special
locator tool.
Figures 17 and 18. Final unilateral IARPD with a flexible pink clasp. This was incorporated
into the design to help overcome the patient’s esthetic concerns.
The partial was inserted without the locator attachment to
allow soft-tissue settling. The next day, a LOCATOR abutment
(ZEST Anchors) was torqued into the implant and the metal
housing processed into the intaglio side of the partial.
consuming sinus surgery with its associated morbidity was
complied with.
5. Implant placement in these type of cases is simple:
location is less demanding than with fixed restorations and
there is no need for large/long implants. The IARPD design
allows for a combination of tissue and implant support,
hence the forces are much less on the implant.
Case No. 1 Highlights
1. Most extracoronal attachments used to support a
precision RPD require 2 splinted crown abutments to
prevent excess force on the teeth. The posterior implant
with locator attachment eliminated the need for a second
crown on No. 12.
2. Please note that No. 12 does have a definitive rest
seat and lingual bracing arm. This is traditional RPD design
and will limit harmful lateral and vertical movement in
function (Figure 12).
3. Esthetics was addressed since no buccal clasp will
show in a broad smile.
4. The patient’s desire to avoid complicated, time-
Case No. 2
This case is what I call a “salvage” case. A 50-year-old female
who was formerly treated by a periodontist presented to our
office for a second opinion. Two implants had been placed in
the lower right quadrant and a fixed implant-supported
prosthesis was planned. However, the implant in the No. 27
position had failed 2 times and the patient refused another
implant surgery (Figures 13 and 14). The posterior implant
(Biomet 3i) had osseointegrated.
Complications to treatment included: she was angry
4
with her former periodontist; tooth No. 26 was very weak
periodontally and had a +2 mobility; she did not want any
metal to show; and her finances were limited. She
requested a fixed bridge from Nos. 26 to 29. I explained that
tooth No. 26 was too weak to be used as a fixed-bridge
abutment, and that connecting natural teeth to implants is
not without complications.
After much deliberation, it was decided to fabricate a
unilateral IARPD by placing a locator attachment on the
osseointegrated implant (Figure 15). This would help
provide stability, support, and retention for a unilateral
partial. A metal framework was used with a mesial-occlusal
rest seat, guide plane, and circumferential clasp on No. 30.
Anteriorly, No. 26 received a metal lingual apron for bracing
and a flexible pink buccal retentive arm (Figures 16 to 18).
This case was definitely a compromise, but resulted in a
happy patient.
Figure 19.
Preoperative
radiographic view of
a failing long-span
fixed bridge.
Figure 20. Bone
resorption and
resulting excessive
interarch space.
1. Problem solving patient’s expectations (a fixed bridge
was not appropriate in this situation).
2. Adding a flexible pink clasp eased the patient’s
esthetic concerns, but a lingual bracing arm helped with the
stability of a weak tooth (Figure 18).
3. This treatment was very cost-effective, a major
concern of this patient.
Figure 21. An
implant was placed
after the socket
grafting healed. Note
the lack of bone
vertical height
anterior to the site.
This site was the
only area where
adequate height and
width could be
obtained for implant
placement without
bone augmentation.
Case No. 3
This 55-year-old male had been a patient for some time. At
each recall, I would see an extremely long fixed bridge
(Nos. 17 to 23) that was failing (Figure 19). The posterior
abutment was loose and recurrent decay was developing.
Never really having a good solution to his looming problem,
I dreaded the day when treatment would become
necessary. My initial thoughts regarding treatment options
included: (1) a new fixed bridge (an option with which I was
uncomfortable); (2) two new anterior crowns and a bilateral
RPD (where to place the rests and clasps on the opposite
side concerned me); and (3) a fixed implant-supported
bridge for Nos. 18 to 21 and separate anterior crowns Nos.
22 and 23. (Concerns included proximity to the mandibular
nerve, excessive interarch space [Figure 20], the
unpredictability and cost of vertical bone augmentation.)
Figure 22. Doubleabutted crowns
(Nos. 22 and 23)
with an ERA
extracoronal
attachment
(Sterngold). This
was necessary in
this situation to
resist lateral
movement of the
IARPD.
The unilateral IARPD gave me an option with which I
felt comfortable. The patient agreed, so the failing fixed
bridge was sectioned and tooth No. 17 was extracted with
5
concurrent bone grafting. Three months
later, an implant was placed at site No. 17,
utilizing single-stage surgery (Figure 21).
The prosthesis construction was begun 4
months later and went smoothly. An extra
coronal ERA attachment was utilized for its
retention, esthetics, and stress-breaking
features. After insertion and one day of
tissue settling, a locator attachment was
Figures 23 and 24. Postoperative photos. A locator abutment was torqued into the posterior
utilized for the distal implant abutment implant
and an ERA and LOCATOR attachment were processed, creating a secure
prosthesis.
(Figures 22 to 24).
An esthetic and functional prosthesis was created,
resulting in a satisfied patient.
1. Optimal esthetics were achieved with no display of
metal; however, still note the lingual plate providing stability
behind the double-abutted anterior abutments (Figure 23).
2. Splinted double anterior abutments were utilized in
this case since both teeth needed new crowns and because
the long edentulous space justified the splinting to resist
movement of the RPD during function (Figure 22).
3. Selection of the best implant site: Site No. 17 was
chosen because of its residual height and width. Teeth Nos.
18 to 21 had been missing for 20+ years and resorption
made these sites a poor choice (Figures 21 and 22).
4. The large interocclusal space makes this case a
classic indication for a RPD and not a fixed-implant
prosthesis (Figure 20). The crown height space is excessive.
A fixed-implant prosthesis would create a vertical cantilever
magnifying stress to the prosthesis and implants.
Figure 25.
A diagram
demonstrating the
damaging leverage
forces a RPD can
transmit to the
abutment teeth.
Figure 26. By
adding an implant,
an IARPD is
created. This design
helps neutralize the
damaging forces to
the abutment teeth
and increases
retention, support,
and stability.
Damaging forces to
the ridge by the
RPD are also
mitigated; hence,
bone is preserved.
DISCUSSION
complicated cases.
The use of RPD enhanced by the addition of implants
has been a major growth area of my practice. Demographic
studies show an increase in the number of baby boomers
who have maintained many of their own teeth.6-8 Years ago,
this age group was often fully edentulous but is now
partially edentulous.
Many of the problems with conventional RPDs can be
overcome with the placement of one or more strategically
positioned implants. Enhanced RPDs have been described
in the literature under the following names: IARPD,9 implant-
Each of these patients could have pursued a fixed-implant
reconstruction, yet each declined this option. It has been
my experience when discussing the option of fixed-implant
restorations requiring extensive bone grafting that the
patient often selects an alternative treatment option. Patients often choose the less challenging removable option.
Many reasons exist, including: (1) financial limitations; (2)
patients are often emotionally unable to commit to the
additional bone augmentation surgery with associated
morbidity; and (3) the time commitment of more
6
associated with a unilateral partial were eliminated. Secure
retention was also obtained reducing the risk of swallowing
and allowing for a smaller, less bulky, RPD design.
Table. Advantages of Implant-Assisted
Removable Partial Dentures
l
Improved comfort and confidence
REFERENCES
l
Patients who formerly were unable to wear
conventional removable partial dentures (RPD) are
often able to wear an implant-assisted RPD
l
Enhanced retention, support, and stability
l
Improved esthetics if clasps can be eliminated
l
Preservation of bone
1.
Toshima T, Morita M, Sadanaga N, et al. Surgical removal of
a denture with sharp clasps impacted in the cervicothoracic
esophagus: report of three cases. Surg Today.
2011;41:1275-1279.
2. Brunello DL, Mandikos MN. A denture swallowed. Case
report. Aust Dent J. 1995;40: 349-351.
3. Gallas M, Blanco M, Martinez-Ares D, et al. Unnoticed
swallowing of a unilateral removable partial denture.
Gerodontology. 2012;29:e1198-e1200.
4. Schneid T, Mattie P. Mechanical principles associated with
removable partial dentures. In: Phoenix RD, Cagna DR,
DeFreest CF. Stewart’s Clinical Removable Partial
Prosthodontics. 4th ed. Hanover Park, IL: Quintessence
Publishing; 2008:101-102.
5. Preiskel HW. Distal extention prosthesis. In: Precision
Attachments in Prosthodontics: The Application of
Intracoronal and Extracoronal Attachments, Volume 1.
Hanover Park, IL: Quintessence Publishing; 1984:120-124.
6. Douglass CW, Shih A, Ostry L. Will there be a need for
complete dentures in the United States in 2020? J Prosthet
Dent. 2002;87:5-8.
7. Douglass CW, Watson AJ. Future needs for fixed and
removable partial dentures in the United States. J Prosthet
Dent. 2002;87:9-14.
8. Wöstmann B, Budtz-Jørgensen E, Jepson N, et al. Indications
for removable partial dentures: a literature review. Int J
Prosthodont. 2005;18:139-145.
9. Schneid T, Mattie P. Implant-assisted removable partial
dentures. In: Phoenix RD, Cagna DR, DeFreest CF.
Stewart’s Clinical Removable Partial Prosthodontics. 4th ed.
Hanover Park, IL: Quintessence Publishing; 2008:259-277.
10. Chikunov I, Doan P, Vahidi F. Implant-retained partial
overdenture with resilient attachments. J Prosthodont.
2008;17:141-148.
11. Ohkubo C, Kobayashi M, Suzuki Y, et al. Effect of implant
support on distal-extension removable partial dentures: in
vivo assessment. Int J Oral Maxillofac Implants.
2008;23:1095-1101.
12. Carpenter J. The retrofit of an existing removable partial
denture with implants: a case report. Implant Practice US.
2010;3:10-16.
l
Better distribution of forces and elimination of
damaging leverage to natural abutment teeth
l
Psychological advantage to patient of preserving
compromised natural teeth that are not suitable to use
as abutments to support a RPD
l
An increase in chewing force
l
A contingency plan where implant placement may be
staged and this prosthesis can be used as an interim
option
retained par tial overdentures,10 and implant-supported
removable partial dentures.11 There are many advantages
to IARPD versus conventional RPD12 (Table).
Figures 25 and 26 help demonstrate how the placement
of an implant neutralizes the unfavorable torqueing forces
which RPDs place on abutment teeth.
CLOSING COMMENTS
While simple in theory, IARPD treatment requires a
comprehensive understanding of implant therapy and
mastery of removable prosthodontic fundamentals. As with
all dental treatment, a complete diagnosis must first be
completed. Special considerations include evaluation of
atypical anatomy, and measuring intra- and interarch
spaces. A good understanding of RPD design concepts is
a prerequisite for successful treatment.
This article demonstrates a different use of the IARPD
concept. The unilateral posterior edentulous space is one of
the most difficult situations to treat with a RPD. By placing
one strategic implant, each of these patients was able to
receive a unilateral Nesbit IARPD. The destructive forces
7
POST EXAMINATION INFORMATION
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this educational activity you must complete the program
post examination and answer 6 out of 8 questions correctly.
1. In the author’s opinion, restoration of unilateral
missing posterior teeth with a fixed implantsupported prosthesis is the most current ideal
option.
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a. True
b. False
2. The “Nesbit” partial is another option. This small,
removable prosthesis is used to replace 3 to 4 on
one side of the arch.
a. True
b. False
3. Biomechanically, both the metal and flexible
unilateral “Nesbits” are flawed.
a. True
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Use this page to review the questions and mark your
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b. False
4. The flexible “Nesbit” does not cause excessive tissue
pressure that normally would result in accelerated bone
loss of the edentulous ridge.
a. True
b. False
5. Most extra coronal attachments used to support a
precision removable partial denture (RPD) require 2
splinted crown abutments to prevent excess force on
the teeth.
a. True
b. False
6. The implant-assisted removable partial dentures
(IARPD) design allows for a combination of tissue
and implant support, hence the forces are much less
on the implant.
General Program Information:
Online users may log in to dentalcetoday.com any time in
the future to access previously purchased programs and
view or print letters of completion and results.
a. True
b. False
7. Demographic studies show an increase in the
number of baby boomers who have maintained many
of their own teeth.
a. True
This CE activity was not developed in accordance with
AGD PACE or ADA CERP standards.
CEUs for this activity will not be accepted by the AGD
for MAGD/FAGD credit.
b. False
8. Enhanced RPDs have been described in the literature
under the following names: IARPD. In the closing
comments, the author clearly states that a good
understanding of RPD design concepts is not
required for successful treatment.
a. True
8
b. False
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Implant-Assisted Unilateral Removable Partial Dentures

Transcription

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