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Objectives: This article proposes a classification system for partial edentulism according to criteria of patient’s efficiency, sufficiency and functional deficitsMethods: The ABC classification is based on a critical analysis of functional units premolars and molars in antagonism between them. The indispensable diagnostic tools are the visit of patient, diagnostic imaging tests and model analysis in antagonism to each other. Results: Classification proposal. The classification recognizes and classifies three distinct functional levels identifying them with a letter and a standardized color code. Class A (green) represents an anatomical condition that allows bilateral masticatory function; Class B (yellow) identifies bilateral edentulous conditions and represents a condition of functional sufficiency. Class C (red) represents the condition of functional insufficiency.Conclusions: The ABC classification represents a rapid pre-diagnostic tool capable of identifying 3 levels of difficulty of the clinical case: progressively, proceeding from green to red, the clinician can ideally foresee the series of pretreatments and the level of difficulty in prosthetic acceptance of every single individual. The classification is proposed as a general guideline with which to analyze advantages and disadvantages of different therapeutic alternatives, but also as an effective communication tool with the patient.
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Annali di stomatologia
prosthetic acceptance
Classification system for partial edentulism: ABC classification
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MD, DDS, Full Professor ,Department of Surgery, Medicine, Dentistry and Morphological Sciences with Interest in Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy
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prosthetic acceptance
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Classification system for partial edentulism: ABC classification
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                                                                                                                Article


Classification system for partial edentulism:
ABC classification


Sergio Bortolini1, DDS, Associate Professor                   Conclusions: The ABC classification represents a
Andrea Berzaghi1, DDS, PhD                                    rapid pre-diagnostic tool capable of identifying 3
Alessandro Bianchi1, DDS, PhD                                 levels of difficulty of the clinical case: progressively,
Alfredo Natali2, DDS                                          proceeding from green to red, the clinician can ide-
Frugone-Zambra Raul3, DDS, MHSc, DHSc, Professor              ally foresee the series of pretreatments and the level
Mario Barbano4 DDS, MDS Full Professor                        of difficulty in prosthetic acceptance of every single
Jorge Biotti4 DDS, MDS Associate Professor                    individual. The classification is proposed as a gen-
Maurizio Franchi5, MD, DDS, Associate Professor               eral guideline with which to analyze advantages and
Ugo Consolo1, MD, DDS, Full Professor                         disadvantages of different therapeutic alternatives,
                                                              but also as an effective communication tool with the
                                                              patient.
1
    Department of Surgery, Medicine, Dentistry and Mor-
    phological Sciences with Interest in Transplant, Onco-
    logy and Regenerative Medicine, University of Mode-       Keywords: Partial edentulism, masticatory function,
    na and Reggio Emilia, Modena, Italy; sergio.bortolini@    functional unit, prosthetic acceptance.
    unimore.it ; andrea.berzaghi@unimore.it; alessandro.
    bianchi@unimore.it ugo.consolo@unimore.it
2
    DDS, Prosthodontist, private practice in Carpi, Mode-     Introduction
    na, Italy                                                 The functional tooth unit is a concept described by Eich-
3
    Faculty of Dentistry, San Sebastián University, San-      ner, accepted and applied constantly up to the pres-
    tiago, Chile. University Autónoma de Chile, Temu-         ent day. The functional units are a pair of premolars
    co, Chile; raulfrugone@gmail.com                          or molars of intact anatomy in correct inter-arch rela-
4
    School of Dentistry, Universidad Mayor, Santiago, Chi-    tionship1-2. Eichner’s classification of edentulism, in its
    le. mbarbano@gmail.com                                    full version, was born for epidemiological purposes in
5
    Department of Biomedical and Specialty Surgical           the pre-implant era and, although it still represents an
    Sciences, University of Ferrara, Ferrara, Italy; mauri-   effective and appreciated tool, it requires high prosthet-
    zio.franchi@unife.it                                      ic skills to be converted into a clinical method of daily
                                                              work. Furthermore, it has recently been criticized for
Corresponding author:                                         the modest level of scientific evidence it offers2. The
Berzaghi Andrea, andrea.berzaghi@unimore.it                   classification proposal is based on critical analysis of
                                                              functional units in partial edentulism and is the result of
Abstract                                                      the observation of the growth of subjective prosthetic
                                                              dissatisfaction manifested by numerous patients reha-
Objectives: This article proposes a classification            bilitated with removable prosthetic therapy, mainly in
system for partial edentulism according to criteria of        Emilia Romagna, after 2012. In a short time we real-
patient’s efficiency, sufficiency and functional deficits     ized that we had higher prosthetic failure rates with the
                                                              same objective prosthetic parameters; moreover, the
Methods: The ABC classification is based on a crit-
                                                              phenomenon appeared almost independent of the lev-
ical analysis of functional units premolars and mo-
                                                              el of clinical experience of the operators. Patients with
lars in antagonism between them. The indispensable
                                                              prosthetic dissatisfaction or rejection showed common
diagnostic tools are the visit of patient, diagnostic
                                                              characteristics, summarized with typical clinical histo-
imaging tests and model analysis in antagonism to
                                                              ries, identifiable both on the basis of psychosocial pa-
each other.
                                                              rameters and on anatomical indications3-5. In this paper
Results: Classification proposal. The classification          we aim to report the salient points of the classification
recognizes and classifies three distinct functional           system for partial edentulism according to criteria of
levels identifying them with a letter and a standard-         patient’s efficiency, sufficiency and functional deficits
ized color code. Class A (green) represents an an-            with the intention of proposing a useful and immediate
atomical condition that allows bilateral masticatory          tool in defining the complexity of the clinical case and
function; Class B (yellow) identifies bilateral eden-         the predictability in terms of therapeutic success. The
tulous conditions and represents a condition of               result is a simple analysis model, merged into the “The-
functional sufficiency. Class C (red) represents the          ory of Simplified Models” and summarized by the ABC
condition of functional insufficiency.                        classification, described below.




Annali di Stomatologia 2022; XIII (1-4): 21-26                                                                              21
     Classification system for partial edentulism: ABC classification

     Methods                                                             simplified models: A1: condition of intact dentition in nor-
                                                                         mal occlusion with maximum number of functional units
     The classification system for partial edentulism is based           bilaterally. A2: unilateral intercalated edentulous (premolar
     on a critical analysis of functional units premolars and            or molar) in the absence of occlusal collapse, diastema,
     molars in antagonism between them. Implant-prosthetic               dental migration or passive extrusion of the antagonist
     crowns and fixed prosthetic restorations of natural ele-            elements. A3: unilateral distal molar edentulous. Series
     ments are also considered functional units. No acrylic or           B identifies bilateral edentulous conditions and is distin-
     ceramic tooth of partial or total removable prosthesis can          guished by the yellow color. It represents a condition of
     be assimilated to an occlusal unit. It is conventionally es-        functional sufficiency hierarchically submitted to series A
     tablished that an occlusal unit molar (i.e. a pair of molars in     (Fig.2). The B series is also summarized in three distinct
     antagonism physiological) has value 2 and a premolar has            simplified models: B1: edentulous intercalated with signs
     value 1, while a natural tooth abraded, rotated, ectopic or         of occlusal collapse, mono or bilateral, diastemas, migra-
     summarily rehabilitated with disfigurement of the normal            tions of the border elements or passive extrusions of the
     anatomy, has a value of 0. The third molars, when they              antagonists. B2: bilateral molar edentulous or “shortened
     meet the functional requirements indicated above, are               dental arch” (S.D.A.). B3: bilateral distal edentulous with
     considered similarly to the first and second molars6. Final-        last active functional unit. The C series represents the con-
     ly, it is established that the central incisors, the lateral ones   dition of functional insufficiency, is characterized by the red
     and the canines have a value of 0 in terms of functional            color and represents the condition of maximum risk of PRS
     unit. The diagnostic tools essential to the case study are          (“Prosthesis Rejection Syndrome”). It too identifies three
     the visit of patient, diagnostic imaging tests and the anal-        distinct simplified models, all marked by no functional unit
     ysis of the plaster models in antagonism with each other.           in antagonism (Fig. 3). C1: residual maxillary and / or man-
     The classification recognizes and classifies three distinct         dibular dental elements not in antagonism with each other.
     functional levels, defined as “classes” or “series”, identify-      C2: “Single Denture Syndrome” and related syndromes.
     ing them with a letter and a standardized color code.               C3: total edentulous outcome of one of the previous con-
                                                                         ditions (C1 and C2). ABC identifies, through the study of
                                                                         these nine models, a general guideline, with immediate
     Results
                                                                         visualization of the level of effectiveness and functional
     The first class, coded by the letter A, is marked green in          efficiency; moreover, it allows to advance a forecast of the
     color and identifies the conditions of functional excellence.       evolution of the clinical case, both in anticipation of dental
     The subject in class A by definition presents an anatom-            extractions with the resulting downgrading and in the case
     ical condition that allows bilateral masticatory function           of fixed implant prosthesis to restore the physiological den-
     (Fig. 1). Series A identifies three distinct conditions called      tal formula, with the advantages we know7-10.




     Figure 1. Series A, green color. Functional excellence. Small intercalated or distal unilateral edentulism. No signs of occlusal
     collapse. Simultaneous bilateral or alternating unilateral chewing. It requires urgent compensation therapy. Minimal clinical
     difficulty even for inexperienced operators.




22                                                                                          Annali di Stomatologia 2022; XIII (1-4): 21-26
S. Bortolini et al.




Figure 2. Series B, yellow color. Functional Sufficiency. Long-standing intercalated or distal mono or bilateral edentulism attrib-
utable to occlusal collapse outcomes. Ipsilateral chewing. Medium prosthetic difficulty.




                                                           C1



                                                           C2



                                                           C3



Figure 3. Series C, red color. Functional deficit. No intermaxillary relationship preserved. Non-acceptance syndrome of remov-
able prosthesis for the patient who has never been a prosthesis wearer. The dentate patient with complete loss of occlusal
anatomy should also be considered as series C (e.g. extreme bruxist). Maximum difficulty even for experienced operators.




Annali di Stomatologia 2022; XIII (1-4): 21-26                                                                                        23
     Classification system for partial edentulism: ABC classification

     Discussion                                                         Syndrome” seem to have a value predictive of the phe-
                                                                        nomenon. Furthermore, these cases have some pecu-
     The ABC classification allows to perform some clinical             liarities: when treated with fixed implant prostheses,
     considerations of general value such as: a rapid diag-             such as conventional Implant Bridge or Toronto Bridge,
     nostic semiotic analysis of the oral cavity of a partially         they concentrate most of the technical complications in
     edentulous patient; an intuitive biomechanical reason-             the short-medium term, highlighted as fractures or de-
     ing on the patient’s preferred chewing side, by looking            tachment of replacement teeth, chipping or loosening
     for signs of parafunction; educates the clinician to read          of the screws8-10. In these cases it seems prudent to
     the clinical and radiographic changes of a patient who             adopt some precautions, such as adequate provision-
     has undergone tooth extractions not compensated by                 al times and the promotion of a rehabilitation process
     prosthetic replacements in accordance with the mod-                that includes personalized oral physiatry instructions,
     els reported in literature, allowing to advance prog-              to be continued even after the delivery of the definitive
     nostic hypotheses for the prediction of medium-long                prostheses21-23. It is therefore clear that the dentist’s
     term complications; offers a clear, simple and effective           work in prosthetic rehabilitation should not be limited
     communication tool with the patient; analyzes the anat-            to measurement mathematics of bone volumes, to the
     omy according to guidelines common to all operators                positioning of dental implants or to the delivery of the
     in the sector (dentists, dental hygienists, dental tech-           prosthetic restoration in the hope that the patient gets
     nicians) and validates some psychosocial aspects of                used to it by himself. An additional effort is needed
     chronic edentulism; proposes a census of the classic               for the recovery of neuromuscular coordination and
     syndromes of edentulism and an immediate differential              self-image that neuroscience has described as “over-
     analysis relating to the most common complications                 coming of acquired paralysis”24. In all this reasoning,
     reported in the literature; it allows an immediate data            the operator is required to have a cultural background
     collection, suitable for a first visit screening and cata-         in the neurological, physiological and physiatric fields
     logable in any clinical record using a dental alert formu-         which seems to push prosthetic dentistry towards oral
     la about the difficulties of accepting conventional pros-          medicine.
     theses. The moment of incorporation of a removable
     prosthesis is the result of a complex combination of
     factors and recognizes subjective, objective and psy-              Conclusions
     chosocial aspects11-13. The literature has analyzed this
     complexity in detail and all dentists have experienced             The ABC classification represents a rapid pre-diagnos-
     the frustration of some cases in which high levels of              tic tool capable of identifying 3 levels of difficulty of the
     satisfaction are not achieved despite the procedures               clinical case: progressively, proceeding from green to
     being consistent with the state of the art, while in oth-          red, the clinician can ideally foresee the series of pre-
     er cases mobile prostheses highly incongruous for the              treatments and the level of difficulty in prosthetic ac-
     dentist are considered excellent by patients11-13. These           ceptance of every single individual (Fig. 4). The clas-
     are obviously problems of poor acceptance of the res-              sification system represents a didactic screening tool
     toration in the first case and over-acceptance in the              without epidemiological purposes. It also constitutes
     second. The phenomenon has been widely described                   an alert approach on some frequently observed clinical
     and recognizes a psychosocial origin. The clinician                scenarios, potentially insidious in prognostic terms. It
     must therefore be able to read the patient from an an-             represents an invitation to the analysis and census of
     atomical but also a psychological point of view, and               some classic syndromes of partial edentulism and of-
     must have a clear picture of the predisposing, favoring            fers some prognostic and biomechanical insights that
     and triggering conditions of prosthetic rejection11,14,15.         can be useful to all categories related to dentistry, from
     This diagnostic sensitivity, which recognizes in clinical          dental hygienist to dental technician. The concept of dy-
     experience some antidotes to prosthetic refusal, it can            namic edentulism and the medium-long term tendency
     be supported in terms of communication with the eden-              to concentrate the worsening of the clinical conditions
     tulous patient by a few rules proposed by the ABC clas-            of the oral cavity on the non-working side of the pa-
     sification. It is clear, a fact widely reported in the liter-      tient, invites the clinician to re-evaluate the concept of
     ature, that implant-supported prosthesis can represent             prevention of occlusal collapse. The dental extractions
     a valid therapy for this “inability to adapt to the prosthe-       of the posterior sectors not compensated by the re-
     sis”. The study of some peculiar models of edentulism              placement of the lost elements are the real key factor of
     (the so-called partial edentulous syndromes described              the reasoning proposed by the ABC classification. The
     in the early decades of the 1900s) seems particularly              techniques to compensate for edentulism can be differ-
     indicative in identifying subjects at risk of dissatisfac-         ent, from orthodontics to fixed prostheses to implantolo-
     tion or prosthetic rejection7-10. The explanations of this         gy, and the differential diagnosis is left to the clinician’s
     phenomenon are not completely known, but it is evi-                decision. Fixed prosthetic therapy for edentulous gaps,
     dent that removable prostheses have non-negotiable                 performed according to the state of the art, is the most
     limits, which makes them particularly disadvantageous              effective prevention tool we have. The ABC classifica-
     in some categories of patients compared to fixed pros-             tion has proved to be a tool simple but effective work in
     theses16-20. In our clinical experience, some anatomi-             communication with patient and in the pre-diagnosis of
     cal and clinical conditions such as “Kelly’s Syndrome”,            partial edentulism in a particular context of social den-
     the “Single Denture Syndrome”, “Combination-like                   tistry that it has followed by the 2012 Emilia Romagna
     Syndromes”, the “Eagle’s Syndrome” or the “Ernest’s                earthquake.




24                                                                                        Annali di Stomatologia 2022; XIII (1-4): 21-26
S. Bortolini et al.




Figure 4. Chronology of the progression of partial edentulism not prosthetically compensated. From left to right, excellence,
sufficiency and functional deficits. Implantology represents the tool to be able to reverse the direction of the arrow, offering the
operator the possibility of deciding at which functional level to rehabilitate the patient.




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