Why Overdentures?
Implant-Retained Overdentures as Prosthetic Solutions for the 21st Century
Dr. Stefan Holst
Despite
the fact that patients considering implant treatment tend to contemplate a
fixed restoration first, numerous studies have proven that implant-retained
overdentures can also significantly improve masticatory function and, at the
same time, fulfill patients’ expectations and demands.1-3
An
awareness of the need to restore aesthetic appearance is not limited to the
partially edentulous. Indeed, it is of great importance to fully edentulous
patients as well.2,4
The
most conspicuous aesthetic impairment these patients have to face affects extraoral
appearances. Substantial atrophy of the alveolar ridge requires extensive
support of the peri-oral musculature if facial harmony is to be reestablished.2,3
While
this can be achieved technically with a fixed restoration, the resulting design
of the prosthesis may significantly impair hygiene accessibility. It is
important to differentiate between two different types of removable
restorations. The implant-retained, mucosa-supported overdenture is mostly
supported by two interforaminal implants with various anchoring mechanisms such
as round or Dolder bars, ball or magnetic, or other extracoronal attachments.3,5
An
alternative to the resilient treatment modality can be found in the
implant-supported removable prosthesis, which is a rigidly anchored prostheses
purely supported by implants (four or more fixtures).6 The
implant-supported removable prosthesis is stabilized on extended
(CAD/CAM-milled) bars, which prevent rotational movements of the prosthesis.7
The
advantage of this retention and support design is that the restoration is
comparable to a fixed prosthesis. It provides for a stable occlusal plane and
prosthesis position when functional forces are applied.6
Factors to Consider
Repair
options and maintenance needs are additional factors that need to be taken into
consideration when decisions are being made about the design and retention
mechanism of a superstructure.2,3 The most frequently reported technical
complication identified for implant-retained, mucosa-supported restorations is
loosening of the retentive mechanism (e.g., wear of matrices) requiring the
replacement of components.8
However,
the introduction of CAD/CAM-milled, high-precision bar elements for
implant-supported removable prostheses has resulted in a significant reduction
in the need for post-insertion maintenance.7 This also holds true
for the rigid anchoring of implant overdentures by telescopic attachments.
Clinical studies have demonstrated high implant success rates concomitant with
only a minor degree of prosthodontic maintenance effort.
In
general, both fixed and fixed-removable implant restorations are viable
treatment options for edentulous patients (Table).1-3 Clinical
long-term outcome is comparable if patient-specific characteristics are taken
into account during treatment planning and execution.
Decisive
factors for either solution include the patient’s age and expressed
expectations, the amount of missing hard and soft tissue, the manual skills of
the patient and his or her financial situation.2,3
*Clinical Associate Professor, Friedrich-Alexander-University,
and Associate Editor of the journal
Quintessence International.
Adapted with permission from Nobel
Biocare News Vol. 14, No.2, 2012.
References:
1. Feine JS, Carolsson GE, Awad MA, et al. The McGill consensus statement on
overdentures. Mandibular two-implant overdentures as first choice standard of
care for edentulous patients. Montreal,
Quebec, May 24-25, 2002; Int J
Maxillofac Impl 2002;17(4):601-602.
2. Feine JS, Carolsson GE. Implant Overdentures: The Standard of Care
for Edentulous Patients. Carol Stream,
IL: Quintessence Publishing,
2003.
3. Carpentieri JR, Tarnow
DP. The Mandibular Two-Implant Overdenture: First-Choice Standard of Care for
the Edentulous Denture Patient. Mahwah,
NJ: Montage Media Corporation,
2007.
4. Fiske J, Davis
DM, Frances C, Gelbier S. The emotional impact of tooth loss in edentulous
people. Brit Dent J 1998;184(2):90-93.
5. Gotfredson K, Holm B. Implant-supported mandibular overdentures
retained with ball or bar attachments: A randomized 5-year study. Int J Prosthodont 2000;13(2):125-130.
6. Malo P, de Araújo Nobre M, Lopes A, et al. A longitudinal study of the
survival of All-on-4 implants in the mandible with up
to 10 years of follow-up. J Am Dent Assoc 2011;142(3):310-320.
7. Drago C, Sadarriaga RL, Domagala
D, Almasri R. Volumetric
determination of the amount of misfit in CAD/CAM and cast implant frameworks: a multicenter
laboratory study. Int J Oral Maxillofac Impl 2010;25(5):920-929.
8. Fromentin O, Lassauzay C, Nader SA,
et al. Wear of matrix overdenture attachments after one to eight years of
clinical use. J Prosthet Dent 2012;107(3):191-198.
Tables
Table 1: Evaluating Benefits and Limitations of the Removable, Implant-Retained Overdenture
Pros | Cons |
+ Re-establishing facial harmony through ideal
support of peri-oral musculature + Simple hygiene maintenance for the patient
(accessibility of intraoral retentive elements and extraoral cleaning of the
denture) + Cost-efficient treatment solution without compromising
maximum precision of fit and material quality when utilizing
milled titanium bars + No need for removal of retaining structure (i.e.,
a bar) for hygiene recall appointments + Setting of retentive forces can be adjusted to
patient demands/capabilities (low friction — maximum friction) + Reduced number of implants + Fast and easy repair and long-term adjustment
potential + Transfer of an implant-supported removable
prosthesis to an implant-retained mucosa-supported overdenture if manual
skills for hygiene maintenance diminish | – Patient’s demands and expectations for a fixed
solution on dental implants – Renewal of plastic/metallic attachment matrices in
the implant-retained mucosa-supported overdenture – Potential psychological impact – Technical demands to manufacture frameworks for
implant-supported removable prosthesis – Space required for primary and secondary support
structures |