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Journal of Oral Science & Rehabilitation Volume 2 | Issue 2/2016 17 T h r e e - y e a r r e s u l t s o f A l l - o n - 4 i n d a i l y p r a c t i c e Introduction Complete edentulism is associated with de- creasedmasticatoryfunction,aswellasunfavor- able esthetics due to the loss of support for the facialmusculature, decreasedverticaldimension and speech impairment.1–3 The conventional method fortreating edentulous patients is to re- habilitate them with a complete removable den- ture.However,thedenturemustbeadjustedover time to compensate for the progressive tissue changes associatedwith denturewearing.4, 5 Ad- vances in implant dentistry have allowed a shift from a complete removable denture to an im- plant-supported overdenture for the oral reha- bilitation of edentulous patients.6 The McGill consensus statement in 20027, 8 and some inde- pendent studies9–11 state that mandibular two-implant overdentures arethe gold standard for edentulous patients. However, technical and biological complications can occur.12–15 In two pilot retrospective studies, Maló et al. presented a planning protocol for the rehabili- tation of the edentulous mandible and maxilla using four implants (All-on-4, Nobel Biocare, Kloten, Switzerland) to overcome anatomical limitations inthe mandiblethat make it challeng- ing to treat without the use of more complex techniques.16, 17 The two most anterior implants are placed axially, andthe posteriorimplants are placed in an angled positionto maximize implant length and avoid anatomical structures (i.e., the mentalnerveandanteriorborderofthemaxillary sinus). The All-on-4 treatment concept seems to be a safe, effective and efficient surgical and prosthetic procedure on both jaws after ten years in function.18, 19 However, as confirmed in a recent systematic review, few independent uncontrolled prospective and retrospective stu- dies have confirmed these preliminaryresults.20 The purpose ofthis prospective observation- al study was to evaluate the three-year clinical and radiographic outcomes ofimplant-support- ed complete-archfixed dentalprostheses (FDPs) delivered on four implants placed according to the All-on-4 protocol in edentulous or partially edentate patients with a preference for an im- plant-supported restoration.This studyfollowed the Strengthening the Reporting of Observati- onal Studies in Epidemiology guidelines.21 Materials and methods This prospective observational study was de- signed to evaluate patients treated according to the All-on-4 protocol in the mandible or maxilla. The patients were selected and treated in two private centers in Rome and Sassari, between January 2008 and December 2011. The inclusion criteria were a healthy patient aged18yearsorolderatthetimeofimplantplace- ment, ableto give herorhis informed consentfor participation,with a residualalveolarcrest, distal to the first premolar, of ≤ 5 mm in height and ≤4mm in width, assessed by computed tomo- graphy (CT) or scans, and refusal of a conventi- onal bone augmentation procedure; partially edentate patient with hopeless dentition based on multiple risk factors, including endodontic22 and periodontal criteria,23 prosthetic restorabili- ty of the tooth, cost–benefit ratio and patient preference in terms of refusing any major bone augmentation procedures. The exclusion criteria were general medical (American Society ofAnesthesiologists Physical Status Class III orIV) and/orpsychiatric contrain- dications; pregnancy or nursing; any interfering medication, such as steroid therapy or bisphos- phonate therapy; alcohol or drug abuse; heavy smoking (>10 cigarettes/day); radiation therapy to the head or neck region within five years; high or moderate parafunctional activity; untreated periodontitis; poor oral hygiene and motivation, defined as full-mouth bleeding on probing and a full-mouthplaqueindexof≥25%;knownallergic or adverse reactions to the restorative material; and unavailability for regular follow-ups. This investigation was conducted according to the principles embodied in the Declaration of Helsinkiof1975forbiomedicalresearchinvolving human subjects, as amended in 2008. All of pa- tientsweredulyinformedaboutthenatureofthe study and gave their written consent. Before implant placement, all of the patients underwent CT or CBCT scan according to a dou- ble-scan protocol.24 In the case of immediately post-extraction implants, a previously reported two-piece radiographic guide was used for the diagnostic study and for virtual implant plan- ning.25, 26 If the operator decided to wait for hea- ling of the post-extraction socket, the implant sites had to healfor at least three months before radiographic examination (Figs. 1–2). DICOM data of the two sets of scans were transferred to a 3-D software planning program (NobelGuide,NobelBiocare)andmatchedtoeach Volume 2 | Issue 2/201617