Figure 1: Ceramic bridge cemented, note integrity of occlusal surfaces.
Figure 2: X-ray control (Mandibular nerve has been lateralized.)
Figure 3: "Envelope" flap dissected with opthalmologic scalpel.
Figure 4: Final esthetic result.
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Clinical Evaluation of the Spline Interface
Philippe Russe, DDS
The connection between an implant and a prosthesis was accomplished, for years,
by the interlocking of different types of polygons, mainly hexagons and octogons.
The frequency of screw loosening varied, according to different authors, between
6 and 38%. This prompted Sulzer Calcitek Inc. to develop a new method of connection
between an implant and a prosthesis: The Spline® System. This new interface
is composed of six one-millimeter-high projections [splines] providing stabilization
of the prosthesis by slip fitting. After conducting promising in vitro and in vivo
studies, Sulzer Calcitek was interested in collecting the clinical documentation
and observations from practitioners experienced with implants. Specifically, it
was important to address the surgical and prosthetic ergonomy, as well as, ease
of use in treating patients with this new system.
Starting in July 1995 in the Odontology Department of the Rheims Hospital, led by
Doctors Jean Schittly and Philippe Russe, 114 patients received implants, 75 females
and 39 males, 16 to 77 years old for whom there were no local or general contra-indications.
The Evaluation:
Surgical Perspective
Equipment
It appeared desirable that a small diameter (approx. 2mm) Twist drill be added to
the surgical kit. This allows engagement of the opposite cortical plate at a sharp
angle, as well as the use of surgical stents with drilling tubes. The ergonomy and
the rapidity of surgical placement of the Spline Twist™ implants have been
greatly improved by both the availability of a new surgical kit, including the 5
mm drills, as well as the new SNAP™ Delivery System.
Method
In the presence of a narrow ridge or a removable partial prosthesis, the drilling
depth was increased by one millimeter to bring the healing screw of the implant
flush with the bone level. The first uncovered cases showed the need for a specific
reopening (bone contouring) tool for this procedure. Sulzer Calcitek quickly responded,
developing specially adapted trephines.
Results
226 implants were placed in 114 patients. All versions of the Spline implants were
utilized, with a majority of HA cylinders in the first year and mainly Twist MTX™
in the most recent cases. 12 implants of the trial were exposed during the healing
period, revealing limited bone loss. Bone loss mainly occurred with partially edentulous
patients with Applegate-Kennedy Class I or II situation or in the mandibular symphysis
region. None of the implants required additional surgery (graft or membrane ) and
no implants have been lost up to now. All 160 implants exposed out of 226 have been
osseointegrated.
The Evaluation:
Prosthetic Perspective
Equipment
The prosthetic components available have been very satisfactory in the clinic and
in the laboratory. The prefabricated posts include a peripheral shoulder of a width
compatible with the esthetic and mechanical requirements of prosthetic elements
having an esthetic function. Some cases required the use of the Direct Gold coping
to optimize the emergence profile of anterior restorations. Temporary abutments
are now available, allowing soft tissue contouring during the provisional crown
stage.
Method
For a single tooth replacement or small reconstructions the protocol adopted was
that of repositioned impression post and implant analog. In case of multiple units,
impression with the open tray technique and impression posts assembled with resin
was preferred. This technique seemed best suited to the precision fit of the Spline
interface. Screw holes situated on the occlusal table of the constructions were
not considered compatible with the stabilization of the occlusion and the degree
of esthetic requirements of our patients (Figures 1-2 ). Esthetic constructions
were cemented onto screwed-through bridges as an alternative to a cemented prosthesis
on straight or angulated abutments. The use of a very limited number of tools for
the prosthetic phase, a single screwdriver, for example to carry out most of the
cemented prosthesis cases, is a great advantage, especially for our referring dentists.
Results
The geometry of the interface and its 1 mm high projections presents numerous clinical
advantages :
• Tactile sensation of engagement of components is greatly improved, especially
comparing to the 0.7 millimeter external hexagons.
• The stability of the prosthetic components on the Spline allows the installation
of the screw at a second stage.
• Chairside time-saving by cutting out the X-ray control of the seating of
the abutments.
The Evaluation:
Esthetic Perspective
To achieve an optimal result on the esthetic level, a few treatment planning options
have been defined:
• In case of insufficient bone volume, bony reconstruction took place five
months before implant placement, using autogenous cortical grafts, taken from the
symphysis or the lateral buccal plate of the mandible.
• In every possible case, placement of implants in the anterior region without
any buccal vertical incision, a crestal incision extended to the adjacent sulci
giving access to the bone.
• Reopening of the implants according to the rolled flap technique, modified
to be respectful of papilla architecture and carried out with ophtalmologic scalpels
(Figure 3-4).
• Fused ceramic on the titanium abutments to conciliate the presence of cosmetic
material in the implant sulcus with the situation, slightly sub-gingival, of the
prosthetic joint.
Conclusion:
To date, all implants placed have osseointegrated and no screw fracture or screw
loosening has occured for the first 160 implants of the evaluation, with a feedback
of four years for the first implants to a few weeks for the latest. This result
is extremely encouraging considering that previously most authors reported those
problems during the first year of implant loading.
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