The philosophy of a gradual transition to an implant retained prosthesis in
cases of full-mouth or extensive rehabilitation usually involves a staged
treatment concept. In this therapeutic approach, the placement of implants
may sometimes be divided into phases. During a subsequent surgical phase of
treatment, the pre-existing implants can serve as anchors for the surgical
template. Those modified surgical templates help in the precise transferring
of restorative information into the surgical field and guide the optimal
three-dimensional implant positioning.
Methods
This article highlights the rationale of implant-retained surgical templates
and illustrates them through the presentation of two clinical cases. The
templates are duplicates of the provisional restorations and are secured to
the existing implants through the utilization of implant mounts.
Results
This template design in such staged procedures provided stability in the
surgical field and enhanced the accuracy in implant positioning based upon
the planned restoration, thus ensuring predictable treatment outcomes.
Conclusions
Successful rehabilitation lies in the correct sequence of surgical and
prosthetic procedures. Whenever a staged approach of implant placement is
planned, the clinician can effectively use the initially placed implants as
anchors for the surgical template during the second phase of implant
surgery.
Recent advances in implant dentistry have introduced a number of alternative
treatment options for the rehabilitation of partially and completely edentulous
patients [1,2]. In recent years, focus has shifted to a great extent into the
restoration-driven approach for the placement of dental implants through a detailed
pre-surgical planning [3]. However, functional
and aesthetic replacement of multiple missing teeth with implant-supported
restorations remains a complex task and requires a comprehensive treatment
planning.
Traditionally, in clinical situations where a patient presented with advanced
periodontal and/or structural problems to the teeth, the treatment of choice often
involved approaches that focused on extraction of remaining teeth, followed by hard
and soft-tissue regeneration procedures prior to the placement of the dental
implants. These rehabilitations often required a significant amount of healing time
utilizing delayed loading protocols and removable interim restorations during the
transitional period. For many patients this treatment approach was not attractive
due to the consequent impact of an interim removable prosthesis on psychology,
phonetics and mastication. For all the aforementioned reasons, as well as in cases
of patients with thin gingival biotype, in need of extensive surgeries or in
clinical cases where immediate loading is contraindicated, the clinician is forced
to suggest a smoother transition into the fixed implant restorations [4].
This procedure involves serial extraction of selected hopeless teeth and the
placement of implants and/or grafts through a staged approach while utilizing the
remaining teeth to support a fixed interim restoration [5]. An important parameter in this therapeutic approach is the
preservation of natural teeth, whether of fair or questionable prognosis until the
end of the healing process. Upon successful osseointegration of the first series of
implants, the tooth-supported interim restoration is converted to an
implant-supported provisional prosthesis. This procedure allows for the extraction
of the remaining hopeless dentition and subsequent progression to the second phase
of implant rehabilitation [5].
In preparation for the surgery, the duplication of the provisional prosthesis
facilitates the fabrication of a surgical template that will dictate the location
and inclination of the additional implants [6-9]. To achieve optimal accuracy
and effectiveness, the surgical template should be simple in construction, have
sufficient stability and not interfere with the surgeon's access [8,10].
A variety of surgical templates differing in design, cost, and stability have been
described in the literature. They are usually made of thermoplastic sheets or clear
acrylic resin [9,11-14]. In partially
edentulous patients, they cover the occlusal surfaces of the adjacent teeth or rest
on any prepared teeth to gain adequate retention and support [15]. On the contrary, when templates are derived from a
duplication of transitional removable prostheses, their precise repositioning is
extremely difficult after tissue reflection because of a change in the architecture
of the underlying soft tissues that served as the only reference points [15,16].
Serving as the communication tool for transferring to the surgeon the necessary
guidelines for implant placement, it is quite clear that a stable, well-designed
surgical template can improve the accuracy of the surgical implant installation,
thus reducing the duration of surgery [8,21-23].
Even though several techniques have been reported in the literature for surgical
template stabilization in the form of surgical fixation screws [17], transitional implants [16,18,19], or sequential extraction
of the remaining teeth during implant placement [20], those solutions seem to be rather complicated. Therefore, whenever
a staged rehabilitation is planned, the clinician can effectively use the existing
implants as anchors for the surgical template during the second phase of implant
surgery.
The objective of this paper is to describe the utilization of previously used implant
mounts for the fabrication of stable surgical templates in such staged procedures.
The rationale and design of fixed surgical templates is illustrated through the
presentation of two clinical cases.
CASES DESCRIPTION AND RESULTS
Case 1
A 66-year old patient presented to the clinic with extensive restorations in both
arches. The clinical and radiographic examination revealed caries under the existing
restorations combined with generalized moderate to severe bone loss due to
periodontitis. After the fabrication of diagnostic casts, a wax-up was performed in
accordance with the aesthetic and functional requirements of the case. Given the
severity of dental caries and extensive bone loss, the treatment plan advocated for
the extraction of the majority of the maxillary teeth. Furthermore, the diagnostic
wax-up confirmed a hard-tissue deficit in bucco-lingual dimension resulting in
insufficient ridge width for ideal implant positioning in the anterior maxilla.
Since the patient declined the use of immediate dentures, a two-stage approach for
the extractions and implant placement was planned. After laboratory fabrication of
the provisional restorations, all existing restorations were removed. The extraction
of several hopeless teeth was performed with emphasis on retaining as many abutments
as possible, in a satisfactory antero-posterior distribution and in strategic
locations on the maxillary arch. The provisional restoration was relined, cemented
with provisional cement and served for the evaluation of aesthetic and functional
characteristics.
Following patient's consent, the duplication of the interim prosthesis
facilitated the construction of a tooth-supported combined radiographic-surgical
template. The first phase of surgery included the placement of bone grafts in the
anterior region and four implants at the first premolar and molar sites in the
maxilla. After a period of six-months and complete healing of the graft sites, the
interim restoration was removed and an implant level impression was made, followed
by the construction of a master cast (Figure
1). Additionally, temporary abutments were placed intraorally and the
interim restoration was converted into an implant-supported restoration. Upon
delivery of the interim implant-supported restoration, a new alginate impression was
made.
Master cast with implant analogs in place.
In the laboratory, a vacuform matrix (Invisacryl A, Great Lakes Orthodontics LTD, NY,
USA) was made over the new diagnostic cast. Two implant mounts (Straumann USA,
Andover, MA, USA) were placed on the premolar analogs (Straumann USA, Andover, MA,
USA), and the cast was coated with a liquid separator. Two holes were drilled in the
vacuform matrix to allow it to be properly seated over the implant mounts. The
vacuform matrix was then filled with clear, auto-polymerizing acrylic resin
(Orthodontic Resin, Dentsply Caulk, Milford DE, USA), carefully placed in the cast
and secured with rubber bands (Figure 2). The
acrylic resin was allowed to set in a pressure pot for ten minutes at which point it
was removed and the excess material was trimmed and polished (Figure 3A and 3B). During the second surgery the surgical
template was screw retained to the existing implants after tissue reflection (Figure 4). Maintaining teeth contours in the
surgical template enabled the surgeon to visualize the proposed implant positions
based upon the ideally planned restorative positions.
Vacuform template relined over implant mounts.
A = intaglio view of the template after polishing; B = cameo view of the
template after polishing.
Template retained on implants prior to implant positioning.
Case 2
During the course of treatment, the implant in site #33 was lost due to
peri-implantitis. A master cast was made of the remaining three implants in sites
#36, #43 and #46 (Figure 5). A vacuform
matrix (Invisacryl A, Great Lakes Orthodontics LTD, NY, USA) fabricated from the
original wax-up was relined over two implant mounts (Straumann USA, Andover, MA,
USA) on implant analogs at sites #36 and #43 utilizing clear, auto-polymerizing
acrylic resin (Orthodontic Resin, Dentsply Caulk, Milford DE, USA) (Figure 6). The template was trimmed, polished
and sterilized prior to surgery (Figures 7A and
7B). At the surgical visit, once the tissue was reflected at site #33,
the template was placed onto implants #36 and #43 and provided a clear visualization
of the desired implant position based upon the planned restoration (Figure 8).
Master cast with implant mounts in place.
Vacuform template relined over implant mounts.
A = intaglio view of the template after polishing; B = cameo view of the
template after polishing.
Template retained on implants prior to implant positioning.
DISCUSSION
Fixed provisional prostheses are preferred by most patients because of their improved
aesthetics, stability and ease of use. Preserving teeth with poor or questionable
prognosis to support a fixed provisional restoration helps to avoid excessive
loading of the grafted sites and ensures an uneventful healing process. Furthermore,
both the patient and the clinician may avoid the additional appointments that are
necessary for subsequent relines and any other modifications needed in case of
interim removable prostheses [5].
This paper describes the use of a surgical template design that allows precise
implant installation in two stages. Initial implant placement includes the use of a
surgical guide that is tooth-supported, whereas second phase implant surgery
utilizes an implant-supported one. This template may also resemble the diagnostic
wax-up or the provisional restoration, thus giving similar accuracy and helping to
achieve a satisfactory final result. Other advantages include ease of manufacture
and low cost, while using materials, techniques and equipment that are usually
available in the office or lab.
The incorporation of stable anchoring elements into the template presented herein,
allows its use in multiple ways. The master cast containing the first phase implant
analogs can be used to fabricate the final provisional restoration. When additional
implants are installed, this pre-fabricated provisional restoration can be modified
to take advantage of the additional support and provide immediate loading if needed.
After the necessary time for osseointegration has elapsed and the restorative phase
commences, this surgical template can be further modified to a registration template
to help the clinician fast and accurately mount the final working cast in the
articulator.
Alternative retention devices (other than implant mounts) can be utilized such as
positioning indicators (Straumann USA, Andover, MA, USA) (Figure 9) or impression components. Their stability and design
allow for unrestricted tissue reflection, adequate irrigation of the region and
enhance the predictability of the implant position and inclination and therefore
preventing the injury of adjacent anatomical structures (teeth, sinus, mandibular
canal) [9]. In addition to the corresponding
accuracy due to the existence of reference points (restoration contours, cervical
outline), the surgical procedure is also accelerated, with a positive impact on the
post-operative healing. Also, the parts used for the anchoring of surgical guides
provide reference points for the inclination of the previously placed implants.
Finally, they assist in the uncovering procedure as they indicate the positions of
implantation, thus contributing to a less traumatic procedure. The only drawbacks to
this technique are the additional laboratory time required for the fabrication of a
new template and the necessary construction of a new final working cast at the
completion of the healing phase.
Template fabricated with position aids.
As long as the successful implant rehabilitation relies on being restoration-driven,
the precise design of surgical templates will continue to be a prerequisite for
predictable results. The dentist who chooses to invest in diagnosis, planning and
construction of the surgical template will be redeemed with similar success in the
final restoration and patient satisfaction [9]. There is not a single template design that fulfils the requirements of
all treatment plans and clinical cases. In general, each surgical guide reflects a
rational combination of basic prosthetic rules, the individual prosthetic needs and
the surgeon's preference. It should be mentioned that the application of various
types of surgical templates that are used in routine dental practice, require a
certain learning curve in order to ensure maximum effectiveness.
CONCLUSIONS
The staged approach enables a smooth transition to implant restorations in advanced
clinical cases. Implant placement during sequential surgical phases can be enhanced
utilizing surgical guides anchored in pre-existing implants. The utilization of
implant mounts presents a practical and cost-effective method for the fabrication of
an implant-retained template in a simplified manner. The surgical guide's stable
fixation ensures the accuracy in implant positioning based upon the planned
restoration.
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS
The authors report no conflicts of interest related to this study.