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rev port estomatol med dent cir maxilofac . 2019;60(4):175-188 185

this implant system lacks prosthodontic flexibility when a Contrary to previous classifications, the rehabilitation
screw-retained full-arch rehabilitation with tilted implants is schemes here proposed are not mainly implant-system depen-
proposed. 54-56 As previously mentioned, tilted implants may dent. This perspective is in agreement with the findings of a
avoid the use of cantilevers in cases where limited bone height recent systematic review, which concluded that there was not
is found in the first molar position of edentulous maxillae and enough available evidence suggesting that any specific im-
mandibles. However, the rehabilitation schemes proposed by plant or implant feature affects the treatment outcome in the
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these authors only consider straight implants. Furthermore, maxilla of fully edentulous patients. Although a similar anal-
and taking into consideration its virtual nature, no intra-sur- ysis is lacking for the mandible, the authors of this paper have
gical modification of the edentulous ridge and no implant adopted the same viewpoint.
loading protocol were mentioned or considered. Possible con- The Maxilla CC classes rehabilitation scheme for a fixed
siderations related to the patients’ clinical history or risk fac- full-arch rehabilitation suggesting six implants in cases of an-
tors influencing the therapeutic option were also not included. terior and posterior bone availability is in accordance with the
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Another classification system suggested a complete arch results of a meta-analysis. When evaluating post-loading
site classification based on four implants, as originally pro- implant failure in edentulous maxillae, in terms of the impact
posed by Bränemark and later developed by Mattsson and of implant number or position, fixed full arches with six or
Krekmanov. 33,34,57 The system proposed by Jensen was based more implants presented favorable results. A low implant fail-
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on implant placement strategies for an immediate loading ure rate of 0.28% was found. A comparison with fixed full-arch
protocol. Based on an anatomically driven implant placement, schemes based on four implants could not be made due to a
areas of high-density bone in the edentulous maxilla and low number of high-quality studies. However, both of the op-
mandible were the key factors for a predictable high insertion tions described are in accordance with the tendency found by
torque. Although accepted, this principle contradicts the cur- Mericske-Stern considering the optimal number of implants
rent biological and prosthodontically driven standard. Regions for cross-arch fixed prosthesis and a minimally invasive, pa-
close to the maxillary sinus and the nasal cavity in the maxil- tient-centered approach. 7,67
la or the inferior border of the mandible, or the inferior alveo- Considering the previously mentioned meta-analysis for
lar nerve, are described as anchors for the apical part of a the edentulous mandible, the post-loading implant failure rate
two-piece implant (NobelActive NobelBiocare ). Once again, in a fixed full-arch rehabilitation with four implants is statis-
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this description is purely based on one implant system and its tically significantly higher when compared to five or more
macrogeometry. Surgical techniques proposing a transverse implants. The CC classes for the edentulous mandible with any
buccal-to-palatal/lingual implant positioning of the distally type of anterior and posterior bone availability – CCI, CCII and
tilted implants in the mandible may represent an increased CIII Option A – are in agreement with these results. Bone aug-
risk of fenestration and hemorrhagic accidents in the first mo- mentation procedures, as proposed in the Mandible CCV Op-
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lar region with a lingual undercut ridge. Although Jensen’s tion B, were not the focus of the meta-analysis. As previously
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description may reflect extensive surgical experience, its ap- mentioned in the deciding factor section of this class, favor-
plication cannot be considered as “user-friendly” or reproduc- able results were found in healthy patients when vertical aug-
ible among clinicians. In addition, it also did not take into mentation procedures were applied. 53
account potential biomechanical risk factors for the patient Although satisfactory results have been obtained with
subjected to the surgical technique. Parafunctional habits, arch both all-on-four, all-on-six and, in some exceptional cases,
size or type, and extension and type of the opposing arch are more than six implants, these full-arch rehabilitation
not addressed as considerations that may modify the rehabil- schemes should not be generalized and blindly matched with
itation scheme. all edentulous cases. Biological considerations such as bone
The limitations identified in both the described classifica- quality and quantity, soft-tissue conditions, medical factors,
tions have opened the field for discussion. Taking into consid- oral hygiene, the biomechanical profile of the type of the op-
eration that patient-related factors potentially interfere with posing jaw, and parafunctional habits should be weighed be-
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treatment planning, should we not develop a patient-centered fore deciding the rehabilitation option. Since there is a lack
classification system for an edentulous maxilla and mandible? of evidence correlating some of these factors with the surviv-
The positive answer to this question was this paper’s rationale. al and success rates of a full-arch rehabilitation, an extrapo-
By achieving this, the authors of this manuscript set a signifi- lation from the available evidence of partial fixed prostheses
cantly relevant path in the integration of these factors into a was considered to be the logical next step. In this regard,
new classification for fixed or removable full-arch rehabilita- several risk factors proposed as modifiers of the CC classes’
tion of edentulous jaws. therapeutic options are identified in the available literature.
For each of the five edentulous classes, fixed and remov- For example, bruxism was mentioned as a predictor for im-
able full-arch rehabilitation schemes were proposed. By pro- plant failure with an odds ratio of 2.71 (95% CI, 1.25, 5.88) in
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viding a broad and flexible spectrum of rehabilitation options, relation to non-bruxers. Mechanical and technical compli-
we are providing a tool where the patient’s particularities and cations with implant-supported prostheses were also found.
needs are taken into account. This viewpoint contrasts with In a different study, based on a sample of 1406 patients, a
the previous “all-on-four” or “all-on-six” dichotomic princi- cluster behavior of dental implant failures with factors such
ple. 59-65 By adding a removable option, we are as well address- as bruxism, poor quality bone, age of patient or smoking were
ing the needs of an increasingly aging population and de- found to exert a harmful effect at an implant level. Some of
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manding economic situations. 2 these risk indicators and others such as diabetes type 1,