Loading Protocols for the Mandibular Two-Implant Overdenture
Joseph R. Carpentieri, DDS • Dennis P. Tarnow, DDS
Wherever possible, a one-stage
surgical procedure with an early loading protocol (ie, 6 to 8 weeks) is the
recommended technique for the two-implant overdenture. There may be instances
when conventional loading (ie, 12 weeks) might be appropriate as well. A third
“philosophical” variation on early and conventional loading protocols is
immediate loading, in which final abutments are connected and retentive
elements are activated at the time of implant placement. At present, immediate
loading is not appropriate for the
unsplinted two-implant overdenture design.
In recent years, histological and
experimental studies have demonstrated that newer implant surfaces may result
in an increased and earlier bone-to-implant contact than was observed with
conventional loading 12 weeks following implant placement.1-3 Such
findings have led to the growing observance of “early loading” protocols when
more ideal bone quality and quantity, more refined surgical and prosthetic
protocols, and more advanced implant designs are available.
Currently, no consensus exists
defining “early loading.” Studies evaluating early loading have demonstrated
excellent success with a range of early loading from 3 to 8 weeks. Because of
the larger body of research validating the success of early loading at 6 to 8
weeks postoperatively, the authors recommend this somewhat longer period as the
technique of choice, pending additional empirical validation of an even shorter
healing period. At this point, this is the least amount of time that will
result in the highest level of predictability with the least amount of
potential risks. Accordingly, early loading represents a significant paradigm
shift in which the conventional 12-week healing period is dramatically
Indications For Early Loading
Early loading protocols may be
considered when a one-stage surgical protocol has been achieved, which may
include the following critical determinants:
implant placement (eg, no hard or soft tissue grafting);
primary stabilization (eg, absence of micromotion at time of surgery);
quality is Type I or II;
length is a minimum of 10mm; and
surface is osseoconductive.
Technique to Utilize Early Loading
Studies have demonstrated that
patients may be permitted to wear their dentures immediately postsurgically--on
the day of surgery--provided that the denture has been significantly relieved (minimally
3 mm) to provide adequate space for a soft reline material (Figures 1 and 2). The denture is relined and again relieved over the implants to minimize
premature loading forces during this initial period of wound healing (Figures 3-4-5-6-7). During this initial period, follow-up is critical to avoid
excessive loading and micromovement.
This postsurgical restorative
technique (ie, providing a denture on the same day as surgery) is not defined
as early loading (theoretically, it is a load-free period) but, rather, is part
of the early load protocol.
Numerous studies demonstrate that
the early loading of implants splinted or unsplinted (in the mandibular
anterior region), utilized with overdentures at 6 to 8 weeks after implant
placement, is an effective and predictable treatment for the edentulous patient
and is the recommended loading protocol of choice where possible. Practically,
it may be defined when the final connection of matrix and patrix has been
established with the activation of retentive elements or when an implant
restoration is in full function.
A stress-free, nonloaded healing
period of 12 weeks in the mandible and 24 weeks in the maxilla has been
recommended by Brånemark and coworkers as an accepted prerequisite to achieve
bone apposition without interposition of a fibrous scar tissue.4
Following this principle both for submerged and nonsubmerged implants has
resulted in high implant success rates.
Indications for Conventional
Conventional loading protocols
are indicated when the following conditions are present:
quantity is >5 mm;
quality is Type III or IV;
augmentation is necessary;
conditions (eg,diabetes) are present;
history of heavy bruxism exists; or
clinician is less experienced in implant treatment.
Procedure for Conventional
Studies have shown that it is the
excess of micromotion during the healing phase that leads to fibrous
encapsulation and interferes with bone repair during the healing phase
following implant surgery. A threshold of tolerated micromotion has been
documented between 50 µm to
150 µm.5,6 In order not to
exceed this threshold, patients undergoing conventional loading are instructed not to wear the denture for 10-14 days
following implant placement. At the end of this time period, the denture is
relined, relieved, and delivered. This approach may also be indicated for less
experienced clinicians who are uncomfortable controlling these loading forces
during the critical initial healing period.
The conventional loading protocol
is the same whether one-stage or two-stage implant treatment is involved.
The high levels of implant
success and immediate restorations in the anterior mandible reported for more
than two implants and a fixed connection of two or more interforaminal implants
with rigid overdenture connection should
not be extrapolated to the unsplinted two-implant overdenture. Placement of two
implants followed by final abutment connection and activation of the retentive
components has not yet been successfully reported in the evidence-based
literature. An assumption may be made that this prosthetic design and its
non-rigid function may negatively effect wound healing and new woven bone
formation in the first few weeks after surgery.
- Testori T, Del Fabbro, Feldman S, et al. A
multicenter prospective evaluation of 2-months loaded Osseotite implants placed
in the posterior jaws: 3-year follow-ups. Clin Oral Implants Res
- Bornstein MM, Lussi A, Schmid B, et al. Early
loading of nonsubmerged titanium implants with a sandblasted and acid-etched (SLA) surface: 3-year results of a prospective study in
partially edentulous patients. Int J Oral Maxillofac Implants
- Chiapasco M. Early and immediate restoration
and loading of implants in completely edentulous patients. Int J Oral
Maxillofac Implants 2004;19:76-81.
- Brånemark P-I, Hansson BO, Adell R, et al.
Osseointegrated implants in the treatment of the edentulous jaw. Experience
from a 10-year period. Scand J Plast Reconstr Surg 1977;16(Suppl):1-132.
- Soballe K. Hydroxyapatite ceramic coating for
bone implant fixation. Mechanical and histological studies in dogs. Acta Orthop
- Vaillancourt H, Pilliar RM, McCammond D.
Finite element analysis of crestal bone loss around porous-coated dental
implants. J Appl Biomater 1995;6(4):267-282.