Keywords
zirconia - monotype zirconia implants - soft tissue - cut-back - metal-free restoration
Introduction
The osseointegration process has been widely proven in the literature, although many
implant macro- and micro-topographies were reported.[1]
Wilson and Weber, in 1993, proposed the first timeline classification for implant
placement, splitting them into immediate, recent, delayed and mature placements, depending
on the time between extraction and implant achievement.[2]
Hämmerle et al revised this classification as the previous classification, dividing
immediate implants into four types of scenarios and defining the advantages and disadvantages
of performing the implant at the time corresponding to the respective type.[3]
Many authors considered the alveolar topography, the extraction less-invasivity, and
the implant primary stability the main factors to achieve success.[4]
Despite the surgical technique proposed for immediate implants undergoing improvements
and success rates comparable to those reported for delayed and mature implant placements,
mucositis and peri-implantitis due to metal and/or manufacturing remnants were said
to be relevant.[5]
[6]
[7]
Considering the positive soft tissue responses assessed when ceramic restorations
were used, industry and research focused on developing new materials to address this
issue.[8]
Compared with ceramics for dental prostheses, the increased mechanical properties
of zirconia frameworks allowed the development of this material for dental implant
manufacturing, ideally chosen to treat the esthetic areas or patients with many general
allergies.[9]
Zirconia has an elastic modulus and tensile stress similar to or superior to titanium
as long as the structure's thickness is maintained.[10]
Superficial in vivo and in vitro studies have shown that physicochemical properties
inhibit bacterial adherence to zirconia in the oral cavity.[11]
[12]
The macrogeometry of these devices, as for titanium implants, is provided with two
different possibilities: monophasic, that is, a single piece joining together the
fixture and the abutment and biphasic, where an abutment–fixture connection physically
exists. Monophasic implants have more excellent resistance to mechanical stresses,
allowing them to develop smaller implants than standard ones. The variable abutment's
heights and different geometries make possible the treatment of different scenarios,
even though implant placement should be accurate, to comply with the prosthetic plan
and the available room. Typically, the monophasic implant should be placed with the
neck out of the bone crest at the soft tissue level.[13]
Biphasic implants offer greater surgical and prosthetic versatility and are often
achieved at or above the bone crest. Even though they empower both cemented or screw-retained
restorations, a narrower range of prosthetic solutions makes the main difference compared
with conventional titanium and monophase implants, which can only allow cemented restoration.[14]
[15]
This article illustrates a 3-year follow-up clinical case performed with monophase
implants to replace three teeth.
Case Report
The clinical case concerns treating a healthy Physical Status Classification System
(ASA 1) 48-year-old male patient who needed to replace hopeless teeth 4.4, 4.5, and
4.6 ([Fig. 1A, B]). An orthopanoramic tomography ([Fig. 2]) was taken as the primary analysis, followed by a cone-beam computed tomography
to carry out a three-dimensional assessment of hard tissues and to set a guided prosthetically-driven
implant plan. An intraoral scan was performed using a scanner (Trios, 3 Shape) ([Fig. 3A, B]) and the resulting scans allowed to make a digital wax-up of the future teeth ([Fig. 3C, D]). The prosthetic analysis was performed digitally, and it revealed physiologic prosthetic
rooms except on tooth 4.4, where the antagonist extrusion reduced the vertical dimension.
The guided surgical plan was performed because of the poor versatility of the selected
monophase zirconia implant (Monotype, Straumann). The case assessment addressed the
possibility of immediate implants with delayed bone healing.
Fig. 1 The clinical dental status of the first and the fourth quadrant showing the hopeless
teeth into occlusion (A) and form an occlusal view (B).
Fig. 2 The orthopanoramic tomography was used for a primary assessment of the oral status
revealing the failure of treatments involving teeth 4.4, 4.5, and 4.6.
Fig. 3 An intraoral scan was performed (A, B) to perform a digital wax-up of future prostheses and plan implant placement (C, D) accordingly.
The patient underwent antibiotic prophylaxis with amoxicillin 2000 mg, taken 1 hour
before the surgery and 1000 mg of the same medication 6 hours later.
At the time of intervention, gentle extractions were performed under local anesthesia
(articaine 40mg/adrenaline 1:100.000), maintaining both bone and soft tissues intact.[16] Then, a pilot surgical guide was used to prepare implant sites, trying to respect
the ideal prosthetic plan and utilizing the extra-socket bone ([Fig. 4A]). Then, each implant was placed, whose dimension was 4 × 12mm for the implant body
and 5.5 mm at the abutment side for sites 4.6 and 4.5 ([Fig. 4B]). The reduction in the prosthetic space on 4.4 required using a 4 mm abutment implant.
The final implant insertion torque reached was below 30N, and according to the existing
literature, delayed prosthetic loading was selected.[17] The residual bone gap between the alveolar buccal wall and the implant was filled
with blood clots stabilized with a collagen sponge without any other bone substitute.
The surgical procedure ended with applying a poly-ether-ether-keton healing cup over
each abutment and some single sutures to stabilize gingival margins ([Fig. 4C]). A postoperative X-ray was performed ([Fig. 4D]).
Fig. 4 A pilot surgical stent was printed to guide implant placement (A), performed without erasing the flap (B). Few sutures were applied to improve soft tissue healing faster (C). The intraoral X-ray after 3 months shows the ideal bone healing and osteointegration
(D).
After 10 days of healing, the sutures were removed. The healing time was set in 2
months, and after an X-ray was taken to confirm osteointegration, the prosthetic phase
started. In the first appointment, the silicon conventional impression was performed
after applying snap-on transfer over each abutment. The different colors of coping
codified the different heights of the abutment ([Fig. 5A, B]). After the technician poured the plaster cast with implant analogues embedded,
an extraoral optical scan was performed to start the definitive zirconia crown planning
with a digital workflow ([Fig. 5C, D]). The final crowns, due to the monotype implant used, were cemented, and their digital
design provided a final cut-back of the zirconia core to stratify the final ceramic
layer of the crowns to obtain the best esthetic result ([Fig. 6A, B]). The decision to perform single crowns was set to comply with the patient's request.
Fig. 5 After 2 months of healing, color-coded snap-on transfers were used to take a conventional
impression of the implants (A, B). A plaster cast was poured using implant analogues, and definitive crown digital
modelling was performed (C, D).
Fig. 6 The computer-aided design project included a 360-degree cut-back of the zirconia
framework to stratify a thin ceramic layer (A, B).
At the second and last appointment, the crowns were tried, the occlusion was checked,
and finally, they were definitively cemented ([Fig. 7A, B]) with radiopaque resin cement to be able to verify any submucosal excess, as demonstrated
by the final X-ray. The implants integrated well with the surrounding soft tissues,
and the bone crest remained stable. The proposed implant clinical case report satisfied
the patient's request regarding the reported experience and outcome. Three years after
finalization, an examination was performed to assess clinical and radiographic assessment
([Fig. 7C, D]). The obtained result fulfilled the objective clinical needs, perfectly integrating
the prosthetic crowns with soft tissues and bone crest stability.
Fig. 7 The definitive single crown restorations were cemented (A, B) with radiopaque cement to check for any submucosal excess. A 3-year follow-up visit
and X-ray confirmed the perfect integration of the implant-supported crowns (C, D) and the soft tissue stability.
Discussion
The well-described surgical technique for placing immediate titanium implants has
also been applied to achieve zirconia implants, even in the case of monophasic ones.[1] It should be remarked that the tooth extraction procedure should be performed, leaving
the bone crest and the bone septum intact in case of premolar and molar sites to increase
the chances of stabilizing the implant with final insertion torque values between
35 and 50N.[16]
Various studies assessed the osseointegration outcome at scanning electron microscopy,
showing comparable results to those obtained using titanium implants.[18] As reported by workgroup four at the 2017 world workshop on the classification of
periodontal and peri-implant diseases and conditions, a tremendous biological potential
is expressed by zirconia's implant higher biocompatibility at the soft tissue level
due to the less bacterial adhesion to implant neck surface, resulting in a lower inflammatory
risk and consequently less peri-implantitis risk.[6]
[19] Much research is focused on analyzing soft tissue response, prosthetic integration,
and comparison between implant materials to determine the most biological one, which
can preserve the integrity of the peri-implant soft tissue barrier.[20]
Fretwurst et al, in a recent randomized and controlled clinical trial on advanced
peri-implantitis on both titanium and zirconia implants, showed a lack of difference
in the clinical behavior, and he stated that beyond the material used for implant
fabrication, different peri-implant cellular compositions can be dependent on the
patient immunity itself.[21] A limitation of the monotype implant described in this clinical report is the cementation
of the overhanging crown: it can represent a risk for biological stability because
it incorporates a chance of leaving some cement remnants in the peri-implant sulcus,
which can lead the soft tissues to become inflamed and infected. Zirconia implants
have also demonstrated positive soft tissue responses due to their lower bacterial
adhesion to the implant neck surface, reducing the risk of inflammation and peri-implantitis.
However, it is essential to note that the cementation of overhanging crowns on zirconia
implants can pose a risk of leaving cement remnants in the peri-implant sulcus, potentially
leading to soft tissue inflammation and infection. Using a rubber dam or retractor
cords during cementation is recommended to minimize this risk. The case report illustrated
zirconia implants' benefits regarding biocompatibility, esthetic outcomes, and biomechanical/occlusal
stability.[22]
[23]
[24]
[25]
Furthermore, the treatment duration was optimized, and the clinical and esthetic results
after 3 years were promising. The patient's expectations regarding requests and results
were met, making zirconia implants a viable option for treating partial edentulism.
Zirconia implants represent a valid alternative to titanium for treating partial edentulism,
offering favorable soft tissue biocompatibility and esthetic results. The reported
case demonstrated successful osseointegration and excellent soft tissue integration
with zirconia implants. However, caution should be exercised during cementation to
minimize the risk of peri-implant complications. Further research and long-term studies
are warranted to continue evaluating the performance and biocompatibility of zirconia
implants compared with traditional titanium implants in different clinical scenarios.
Fi-Index Tool
This manuscript has been checked with the Fi-index tool and obtained a score of 0.03
for the complete author list on 04/08/2023, according to SCOPUS.[26]
[27] The Fi-index tool aims to ensure the quality of the reference list and limit any
autocitations.
Conclusions
The reported clinical case shows a modern way to treat partial edentulism with biological
and esthetic-oriented treatment. At the same time, the duration of the treatment has
been optimized, and the result after 3 years seems promising for both clinical and
esthetic response.
Finally, from the patient's view, the result meets its expectations both from the
requests and results side.
