The hard and soft tissue deficiency is a limiting factor for the
prosthetic restoration and any surgical attempt to correct the anatomic
foundation needs to be precisely executed for optimal results.
The purpose of this paper is to describe the clinical
steps that are needed to confirm the treatment plan and allow its proper
execution.
Methods
Team work and basic principles are emphasized in a step-by-step
description of clinical methods and techniques.
This clinical report describes the interdisciplinary approach in the
rehabilitation of a partially edentulous patient. The importance of the
transitional restoration which sets the guidelines for the proper
execution of the treatment plan is especially emphasized along with all
the steps that have to be followed.
Results
The clinical report describes the diagnostic arrangement of teeth, the
ridge augmentation based on the diagnostic evaluation of the removable
prosthesis, the implant placement with a surgical guide in the form of
the removable partial denture duplicate and finally the special 2-piece
design of the final fixed prosthesis.
Conclusions
Clinical approach and prosthesis design described above offers a
predictable way to restore partial edentulism with a fixed yet
retrievable prosthesis, restoring soft tissue and teeth and avoiding an
implant supported overdenture.
dental implantsimplant-supported dental prosthesissurgical diagnostic techniqueplanning techniquesdiagnostic techniques and procedures.INTRODUCTION
Dental implants are used widely in clinical dentistry today to restore partial
or complete edentulism [1]. The longevity of the implants and
the supported restoration depend on a great degree of the careful evaluation of
clinical parameters, the proper design of the treatment plan and its precise execution
[2,3]. Modern techniques and new protocols offer predictable solutions
in almost any therapeutic intervention by solving functional problems and achieving
at the same time an aesthetic result. The interdisciplinary approach of the described
clinical report emphasizes the need for "restoration guided" implant rehabilitation
through the preoperative establishment of the final therapeutic goal on the diagnostic
casts [4,5]. The planned restoration must be tested and
either accepted or modified in the clinical environment in order to guide the correct
position of the dental implants which in turn allow their proper restoration.
In the described clinical case the following problems could be identified: the
disturbance of the occlusal plane, the lack of anterior guidance, the reduced vertical
dimension, the reverse smile line, the missing teeth and the unaesthetic appearance.
Both the presence of severe anatomical deficits and a faulty prosthesis were acting
in synergy to create a major problem for the patient who was complaining for limited
function, aesthetics and phonetics.
American College of Prosthodontists (ACP) has developed a classification system
(I-IV) for the partial edentulism based on diagnostic criteria and according to
that the patient described herein presents a Class IV edentulism which is characterized
by severely compromised location and extent of edentulous areas [6].
The diagnosis of the aforementioned clinical findings necessitates the re-establishment
of the missing guidelines through the diagnostic arrangement of artificial teeth
and the clinical testing of provisional restorations that set the framework for
the next clinical level. The hard and soft tissue deficiency is a limiting factor
for the prosthetic restoration and any surgical attempt to correct the anatomic
foundation needs to be precisely executed for optimal results.
The purpose of this paper is to describe the clinical steps that are needed to
confirm the treatment plan and allow its proper execution. Team-work and basic principles
are emphasized in a step-by-step description of clinical methods and techniques.
CASE DESCRIPTION AND RESULTS
The patient was a 40 year old Caucasian male who had lost his maxillary teeth
from the right canine (tooth #13) to left first molar (tooth #26) at the age of
19 due to an accident. He wore a removable partial denture in the maxilla since
that age and sought treatment to improve function and aesthetics. The existing fixed
partial denture in the mandible was extending from the right first premolar (tooth
#44) to the right third molar (tooth #48) and the mandibular left first and second
molars were missing (Figure 1). The patient's past medical history
was negative, he has never been hospitalized, not currently under any medication
and smoking habits were absent.
Intraoral pretreatment situation.
A record base with a wax rim was initially used to record the centric relation
and along with a face-bow transfer of the maxillary cast they were used to ensure
the accurate mounting on the articulator (Figure 2). The conventional
methods and techniques employed in the removable prosthodontics were used to shape
the wax rim and determine the occlusal plane and the vertical dimension of occlusion
(VDO). The clinical trial of the maxillary missing teeth at the determined VDO revealed
their dramatic effect on the improvement of the facial aesthetics but the patient
had to go through a transitional period to assess the proposed treatment plan. For
this reason a maxillary splint in the form of a provisional removable partial denture
(RPD) was delivered to the patient for a period of two months and was accompanied
with a metal reinforced provisional acrylic fixed partial denture extending from
mandibular right first premolar to third molar (Figure 3). No
clinical signs and symptoms for the patient were recorded at the end of the trial
period and the validity of the therapeutic goal was initially confirmed. The treatment
options involved the fabrication of a maxillary RPD or an implant supported fixed
prosthesis. The patient expressed the wish for a fixed metal ceramic restoration
and the treatment plan of implant insertion was initiated. The patient have read
and signed informed consent form.
Centric relation recording at the determined vertical dimension.
Provisional maxillary removable partial denture.
The patient should go through a surgical phase to augment the maxillary ridge
and render it suitable for implant insertion. Computed tomography assessment revealed
bone deficiency in height and width (Figure 4). In order to better
evaluate the amount of bone and the shape that it had to be given, a presurgical
evaluation was performed in the following way: the arrangement of the denture teeth
was duplicated and stabilized on the cast with wax without any base plate. Removal
of the denture teeth and processing of the remaining stabilizing wax "ridge" in
clear acrylic provided a solid duplicate of the bony graft (Figures
5678). This solid duplicate allowed for the exact dimensions of the bone graft
which was harvested from the area of mandibular symphysis. Reconstruction of the
edentulous maxilla was planned on a horizontal and vertical plane. A cortical bone
graft was removed from the donor site between the mental foramina and divided in
two uneven pieces. All the cancellous bone up to the lingual cortical plate was
removed using osteotomes and surgical curettes. The donor side was refilled with
a xenograft (Bio-Oss, Geistlich, Wolhusen, Switzerland) and was covered with a collagen
type resorbable membrane (Bio-Gide, Geistlich, Wolhusen, Switzerland). The flaps
over the donor side were sutured in a two layer fashion using resorbable sutures.
The recipient deficient areas of the maxilla were properly prepared and the two
cortical bone grafts were stabilized using bone screws. The larger cortical block
was placed on the left side and the smaller one on the right side. All the empty
spaces around the grafts were filled with a mixture of autogenous bone graft and
a xenograft (Bio-Oss Geistlich, Wolhusen, Switzerland), in an effort to shape the
reconstructed maxilla according to the solid duplicate of the "wax" ridge. Non-resorbable
membranes (Gore-Tex, Gore, Elkton MD, USA) covered the grafted sites and were stabilized
with pins, 1.2 mm in diameter. At the same time a maxillary sinus augmentation operation
using lateral window approach was performed and the area was filled using a mixture
of autogenous bone graft and xenogenic grafting material (Bio-Oss, Geistlich, Wolhusen,
Switzerland). Special attention was given to the tension free closure of the flaps.
Therefore after the proper wound margins adaptation the surgical area was sutured
using 4-0 Vicryl resorbable sutures (Ethicon, W. Somerville, NJ, USA). The procedure
was performed under local anaesthesia with intravenous sedation and the postoperative
period was uneventful. The RPD was relined with a tissue conditioning material Visco-gel
(Dentsply, Konstanz, Germany) every 2 weeks for the entire healing period, to reduce
pressure effects on the grafted site.
Presurgical computed tomography of the maxilla.
Duplicate of the confirmed teeth arrangement in relation to the anterior maxillary ridge presurgically.
Removable partial denture teeth arrangement is transferred with a silicone key on a duplicate of the maxillary working cast and stabilized with wax only.
Processing of the "wax ridge" in clear acrylic.
Evaluation of clear acrylic allowed better estimation of the bone graft quantity and shape.
After 5 months, the non-resorbable membrane on the right side was exposed. Since
there were no signs of infection and this happened almost at the end of the sixth
month healing period, it was decided not to remove the membrane at that time, but
to wait for an additional month while evaluating the grafting procedure with a new
computed tomography and the clear duplicate of diagnostic teeth arrangement (Figures
9,10). At that time, there were no signs of numbness of the
lower anterior teeth or the lip. The patient was instructed in proper oral hygiene
and when the healing period of 6 months was completed, a new impression of the augmented
maxilla was made and the previously used diagnostic arrangement of denture teeth
was adapted to the new tissue surface with wax and stabilized with a palatal base
plate. Clinical trial in the patient's mouth (Figure 11) confirmed
the correct position of the teeth and its duplication in heat cured clear acrylic
provided a radiographic template (Figure 12). Radiopaque markers
were inserted in the palatal or occlusal surfaces of all missing teeth and a computed
tomography was performed. The analysis of the tomograms, the evaluation
of the grafted ridge and the consideration of the final prosthesis design, set the
guidelines for implant position modifications and led to the fabrication of the
surgical guide for implant placement.
Upon completion of the preoperative work up the patient underwent the second
surgical procedure. The screws, the pins and the non-resorbable membranes were removed
from the grafted sites and five Bränemark System implants (Nobel Biocare AB, Göteborg,
Sweden) were inserted in the maxillary edentulous segment and four implants bilaterally
in the mandible (Figure 13). All implants were submerged and
the surgery was performed under local anaesthesia with intravenous sedation. The
postoperative period was uneventful. The second stage surgery was performed five
months later and all implants were osseointegrated.
Postsurgical computed tomography of the maxilla.
Duplicate of the confirmed teeth arrangement in relation to the anterior maxillary ridge postsurgically.
Removable partial denture teeth arrangement is transferred to the augmented maxilla with a record base for the evaluation of teeth position and soft tissue deficiency.
Radiographic template.
Implants inserted in the maxilla and mandible.
Implant impression was followed by fabrication and mounting of the working casts
which allowed the final evaluation of implant inclination, interocclusal space and
amount of soft tissue deficiency that had to be built into the final prosthesis.
Two modified temporary cylinders were attached to the implants and allowed the clinical
try-in of the initial teeth set-up (Figure 14). The correct teeth
position was confirmed again and a silicon key was then fabricated to guarantee
the exact reproduction in porcelain. Metal framework was tried in for passivity,
followed by bisque bake check and the final glazed prosthesis was made in two segments:
1) a primary base with built-in metal abutments veneered with pink composite (GC
Gradia Gum, GC, Tokyo, Japan) and 2) a secondary PFM prosthesis apically covered
with pink porcelain that was cemented to the primary base with temporary cement
and secured with a small occlusal screw (Figures 15-17). Restoration
of the mandible with fixed prostheses, in conjunction with maxillary restoration
allowed for correction of occlusal plane and improvement of function and aesthetics.
Clinical trial placement stabilized on maxillary implants.
Screw-retained infrastructure veneered with pink composite.
Intaglio surface of cement retained superstructure. The hole for the set screw is visible.
Intraoral view of final prosthesis.
DISCUSSION
This clinical report emphasizes the importance of presurgical planning for the
complex implant rehabilitation, presenting the correct application of clinical methods
usually employed in the treatment of complete edentulism. Analysis of teeth and
base of the transitional removable prosthesis gave the opportunity to evaluate separately
the position of the teeth and the hard and soft tissue deficiency. The surgical
guide presented herein allowed the exact harvesting and the correct shaping of the
grafting material generating the bone substrate for the implant placement at a later
time.
Autologous bone grafts are the gold standard for the restoration of atrophic
mandible and maxilla and implant placement is more predictable when it takes place
secondarily after 6 - 9 months [7]. There are various extraoral
or intraoral donor sites for the bone graft. In this clinical case, the amount of
necessary bone graft dictated by the ridge wax duplicate could be adequately replaced
using an intraoral block graft instead of necessitating extraoral graft harvesting.
Besides the area of the mandibular symphysis another possible intraoral donor site
is the ramus and the external oblique line of the mandible. We decided not to operate
and intervene in an area that implants were planned to be inserted later. Although
resorption of onlay grafts occurs at various rates depending on the donor site and
the technique employed, the success rate of the implants inserted secondarily is
not affected; and vice versa implant failure does not imply failure of
the bone graft [8].
According to the literature, if there is an exposure of a non-resorbable membrane,
various amounts of bone loss are expected in the reconstructed area. In this clinical
report, exposure of the membrane happened at the end of the healing period and was
not an influencing factor [9,10]. Rather, the atrophy of the maxilla
was so extreme initially and difficult to be compensated precisely and predictably,
that ended in a small hard and soft tissue deficiency at the initiation of the prosthetic
restoration phase. Such clinical situations can be restored with a removable or
fixed prosthesis. However, in augmented bone, fixed restorations present higher
success rates compared to removable prostheses [11,12].
The advantages of a two segment fixed prosthesis have been described in the past
with various designs and retention configurations [13-15]. Dividing
the prosthesis into two pieces allows for better control of metal distortion during
porcelain application and almost eliminates the occlusal disturbance of the screws'
exit. The palatal set screw incorporated into the prosthesis further enhances the
confidence of cement retention yet allowing retrievability. With the two piece framework
design the primary base acts as a splint for the maxillary implants dissipating
the functional loading in a more favourable and protective pattern into the grafted
bone [16]. The veneering of the primary base with pink resin
allows easier modification and repair of the emergence profile of the prosthesis
in the event of tissue resorption. Restoration of the mandibular edentulous spaces
that was performed at the same time, allowed the occlusal plane correction, posterior
support and improved function and aesthetics.
CONCLUSIONS
Clinical approach and prosthesis design described above offers a predictable
way to restore partial edentulism with a fixed yet retrievable prosthesis, restoring
soft tissue and teeth and avoiding an implant supported overdenture.
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS
The authors report no conflicts of interest related to this study.