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Prosthodontic Perspective to All- On-4 ® Concept for Dental Implants



The clinical success and longevity of endosteal dental implants as load bearing abutments are controlled largely by the mechanical setting in which they function. The treatment plan is responsible for the design, number and position of the implants. In biomechanically compromised environment such as poor quality bone, strain to the crestal bone can be reduced by increasing the anterioposterior spread of implants, placement of longer implants and maximizing the number of implants. The All-on-4® concept is one such treatment procedure which enlightens us for its use in the completely edentulous patients and which also leaves behind the routine treatment alternative of conventional dentures with successful outcome in the short term, long term and the retrospective studies that have been done in the past. The area of concern for any treatment alternative lies in the success of the prosthesis and its prosthodontic perspective involving the principles of occlusion. This article reviews the All-on-4® concept and its prosthodontic aspects.
Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19
DOI: 10.7860/JCDR/2014/9648.5020
Review Article
Keywords: All-on-4®, Cantilever prosthesis, Implant occlusal scheme, Multi units
In some cases of the completely edentulous patients, implant
supported prosthesis treatment is almost impossible without
complex techniques such as nerve transposition and grafting in the
posterior maxilla and mandible. A solution for such situations is the
All-on-4® concept. This method advocates tilting distal implants
in edentulous arches which enables us in the placement of longer
implants, improved prosthetic support with shorter cantilever arm,
improved inter implant distance and improved anchorage in the bone
[Table/Fig-1]. The “All-on-4® “treatment concept was developed by
Paulo Malo with straight and angled multi-unit abutments, to provide
edentulous patients with an immediately loaded full arch restoration
with only four implants.
–Two placed vertically in the anterior region and two placed upto an
angle of 45o in the posterior region.
When used in the mandible, tilting of posterior implants makes it
possible to achieve good bone anchorage without interfering with
mental foramina in severely resorbed maxillae, tilted implants are an
alternative to sinus floor augmentation [1].
General considerations
To achieve primary implant stability (35 to 45 Ncm insertion •
Indicated with a minimum bone width of 5mm and minimum •
bone height of 10mm from canine to canine in maxilla and 8mm
in mandible.
If angulation is 30• o or more , the tilted implants can be splinted.
For tilted posterior implants, the distal screw access holes should be •
located at the occlusal face of the first molar, the second premolar,
or the first premolar [2].
Surgical Procedure [Table/Fig-2]
Implants in the maxilla are placed with two distal implants in the
posterior region which are tilted anterior to the maxillary antrum
while in the mandible implants are positioned anterior to the mental
foramen. They should be inserted at an angulation of 30o-45o. The
use of the All-on-4® surgical guide assists in ensuring the placement
of the implants with correct positioning, angulation and emergence.
The guide is placed into a 2mm osteotomy that is made in the
midline position of the maxilla or mandible and the titanium band
is contoured to follow the arc of the opposing arch. The guide also
Dentistry Section
Prosthodontic Perspective to All-
On-4® Concept for Dental Implants
The clinical success and longevity of endosteal dental implants as load bearing abutments are controlled largely by the mechanical
setting in which they function. The treatment plan is responsible for the design, number and position of the implants. In biomechanically
compromised environment such as poor quality bone, strain to the crestal bone can be reduced by increasing the anterioposterior
spread of implants, placement of longer implants and maximizing the number of implants. The All-on-4® concept is one such treatment
procedure which enlightens us for its use in the completely edentulous patients and which also leaves behind the routine treatment
alternative of conventional dentures with successful outcome in the short term, long term and the retrospective studies that have been
done in the past. The area of concern for any treatment alternative lies in the success of the prosthesis and its prosthodontic perspective
involving the principles of occlusion. This article reviews the All-on-4® concept and its prosthodontic aspects.
assists in retracting the tongue in mandibular cases. The vertical
lines on the guide are used as a reference for drilling at the correct
angulation, which should not be greater than 45o. The other guides
that can be used for implant placement are Template, Angulated
pins and Denture [Table/Fig-3a,b].
Straight, 17o multiunit abutments and 30o angulated abutments with
different collar heights are placed onto the implants. These are used
to achieve the correct access allowing relative parallelism and so
that the rigid prosthesis can be seated passively.
Success rate in edentulous maxillae
A retrospective clinical study including 242 patients with 968
immediately loaded implants supporting fixed complete arch
maxillary all-acrylic prosthesis demonstrated a high survival rate 93%
at patient level and 98% at implant level after 5 y of follow up . Recent
studies encouraged the use of All-on-4® concept emphasizing
that when planning a fixed rehabilitation in an edentulous maxillae
using four implants, the quality of bone, the length of implants, the
patient’s habits and the length of expected cantilever should be
considered [3].
Comparison of tilted v/s non tilted implants
If an implant is part of a multi implant supported prosthesis, the spread
of implants and stiffness of the prosthesis will reduce bending of
[Table/Fig-1]: All-on-4® Concept M.Taruna et al., Prosthodontic Perspective to All-On-Four Concept for Dental Implants
Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19 1717
Keywords: All-on-4®, Cantilever prosthesis, Implant occlusal scheme, Multi units
Step 1 Selection Of Case Satisfying The Inclusion Criteria
Step 2 Planning Implant Placement Using All-On-4® Guide(Prefered)
Step 3 Location Of Maxillary Antrum And Mental Foramen With All-On-4® Guide
Step 4 Implant Placement Done Following The Protocols
Rangert 10 mm for a cantilever of 20 mm (2xA-P-spread)for mandibular ISFPs
English ISFPs should be 1.5 times A-P-spread for mandible maxillary ISFP
posterior cantilever should be reduced to 6-8mm due low bone density
Step 1 Open tray impression made with wire and GC resin splinting for improved
Step 2 Final impressions after integration is verified, being splinted with GC resin
and metal.
Step 3 All ceramic Zirconia bridge being designed with CAD/CAM technology
Step 4 Use of CAD/CAM zirconia bridge or Titanium framework milled for crown
Step 5 Crowns luted to zirconia framework
Step 6 Implant-supported zirconia bridge framework with individual crowns
[Table/Fig-2]: Surgical technique
[Table/Fig-4]: A-P spread
[Table/Fig-5]: Prosthetic phase
[Table/Fig-6a, b]: Prosthetic phase a resin splinting., b-final prosthesis
[Table/Fig-7a, b]: Simultaneous bilateral point contacts on canine and posterior
teeth and grazing contacts on incisors
the implant [4]. The more distal position of the posterior implant
and the resulting shorter cantilever may have a role in reduction
of stress values in the implant [5]. Strain gauge measurements
performed by Krekmanov showed no significant differences in
forces and bending moments between titled and non tilted implants
[6]. Theoretical models show that an increased prosthetic base, due
to the inclination of implants can reduce the force acting over the
implants. Therefore, from biological point of view, the position of
the neck of the implant can be more important than the inclination
of the implants themselves. Bevilacqua et al., demonstrated that
tilting of the distal implant by 30o in a FFP decreased the level of
stress by 52% and 47.6% in compact bone and cancellous bone
respectively, when compared to vertical implants supporting FFP
with longer cantilevers [7].
Loading of the cantilever on prosthesis can cause a hinging effect
that induces considerable stresses on the implants closest to the
load application [8]. When the distal cantilevers of FFP are excessive
in length, deformation of the framework can result in fracture of the
prosthetic screw, the acrylic resin teeth or even the framework itself
The splinted tilted implants showed lower stresses than the axial
implant with cantilever and the reduction of the stresses generated
with the prosthesis might help reduce maintenance problems of
FFPs v/s those that employ a conventional implant configuration
[10]. When a vertical load was applied to the first premolar of the
tilted implant, the two neighboring implants mostly shared the
load, as the prosthesis was loaded between the mesial and distal
implants load was distributed to both supporting implants through
the prosthesis, the tilted implant configuration did not show over
loading or bending [11].
Stress patterns on implants in prosthesis supported
by four or six implants
A long term study found no significant differences in implant survival
in a comparison of complete maxillary prosthesis supported by
four or six implants. The stress location and distribution patterns
were very similar in both four and six implant models. The cantilever
should be minimized as its presence greatly increases stress on
the distal implant, regardless of whether or not the prosthesis is
supported by four or six implants [12].
Stress patterns around distal angled implants in the
All-on-4® concept configuration
A study analysed the photo elastic strain patterns surrounding distal
implants placed at 0o, 15o, 30o and 45o. There was no remarkable
difference in strain magnitude between models of implants placed
at 0, 15, 30. But increase in strain pattern for 45o angled implants
Angled Abutments
In general, the magnitude of stress and strain for angled abutments
was within or slightly above the physiologic limits. The use of angled
abutments on two tilted implants placed in a curved arch and with
cross-arch splinting might help decrease the stresses around the
distal implants [13].
Loading on the healing bone
Overloading and fracturing happen more readily in healing bone
than in normal bone [14]. Occlusal loading in the period immediately
after placement may be sufficient to cause micro damage in the
bone surrounding the implant, even though the same load will not
do so after healing and adaptation of the bone to the implant. The
All-on-4® concept advocates immediate loading. A slight load on
healing bone shortens healing time rather than prolonging [15].
Immediately loaded implants osseointegrate provided that forces
and implant micromotion are controlled.
Immediate extraction socket placement
The connection of implants may provide a safer transfer of load on
each implant and so the placement in healed or fresh extraction
bone sights may not influence implant survival when rehabilitating
totally edentulous mandibles [16].
From a surgical perspective, the most notable are careful implant
site preparation (including tapping), use of relatively low – torque
producing implants , the preparation of an osseous shelf to level the
alveolar ridge and establish optimum implant sites and the provision
of adequate interocclusal space.
From a prosthetic perspective, the high success rate obtained
with this protocol , including minimal bone loss even with multiple
[Table/Fig-3a,b]: Guides for implant placement., a-guide., b-Template
M.Taruna et al., Prosthodontic Perspective to All-On-Four Concept for Dental Implants
Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19
extractions and bone reduction followed by immediate function is
believed to be as a result of –
• Stable splinting of all four implants with the provisional
immediately after surgery,
• Carefulocculsaladjustmenttoprovidebilateralocculsioninthe
canine and first premolar areas,
• Avoidocclusalcontacttowardthedistaloftheprosthesisand
maximizing the anteroposterior spread [17].
An Anteroposterior spread that minimizes the distal cantilevers
and establishes well distributed four-point stability was probably
contributary to both implant and prosthetic success. The immediate
implant loading and function in the dental extraction setting can be
performed with a high degree of confidence.
A-P-spread and cantilever values [Table/Fig-4]
Rangert provides simple guidelines for controlling occlusal loads on
implants and prosthetic reconstruction- an A-P-spread( distribution
distance between the most anterior and most posterior implants)
of 10 mm was proposed for a cantilever of 20 mm (2xA-P-spread)
for mandibular ISFPs English proposed Anecdotally that a very
reasonable rule of thumb for determining posterior cantilever in
mandibular ISFPs should be 1.5 times A-P-spread. According to
English, this would allow a 10-12 mm posterior cantilever for the
mandible, whereas maxillary ISFP posterior cantilever should be
reduced to 6-8mm due low bone density [18].
Open tray multi-unit impression copings are placed onto the multi-
unit abutments, which are then splinted with a low shrinkage
autopolymerising resin (GC pattern resin) and wire bars [Table/
Fig-5,6a]. This ensures an accurate transfer without accidental
displacement of the impression copings. An open tray impression is
made with a rigid polyvinyl siloxane material (3M ESPE Imprint Putty)
to capture the positions of the implants and the soft tissues.
Provisional all-acrylic resin prosthesis is then constructed and
issued to the patient within a few hours or overnight. The provisional
prosthesis is torqued to 15Ncm. The patient is reviewed after one
week, at three weeks, three months and then annually.
At the three month appointment, fabrication of the definitive bridge
may be started. The final restorative solution can be a:
1. CAD/CAM designed fixed prosthesis with Zirconia or Titanium
framework. Individual crowns are cemented to the final bridge
2. Fixed prosthesis with CAD/CAM designed Titanium or Zirconia
framework with acrylic veneering [Table/Fig-6b].
3. Fixed prosthesis with cast metal and veneering porcelain.
4. Removable final prosthesis: e.g. milled bar overdenture, MK1
attachment overdenture.
Comparision of superstructure framework
The first patient with fixed complete dentures were provided with
Cr-Co alloy frameworks with resin teeth. This protocol was modified
over time and gold alloy casting was introduced to provide a more
stable occlusion in metal and to allow porcelain veneering of the
framework, however in case like severe bone resorption, large amt
of gold alloy had to be cast. To avoid problems with casting few
non casting approaches such as premachined gold-alloy cylinders
/bars and laser – welded titanium frameworks were introduced.
More recently a new protocol based on using computer numeric-
controlled milling of a solid block of titanium was developed and
is free of the technical challenges involved in previous approaches
Occlusal aspect
Many implant failures can be attributed to improper occlusal design
which can concentrate stresses in the bone and lead to rapid bone
resorption. The goal of any prosthetic procedure must include the
establishment of a functional occlusion [20].
Occlusal Schemes
Occlusal scheme of implant-prosthetic superstructure basic
requirements are
1. Establishment of stable jaw relationships with maximum
intercuspal contacts that are bilaterally identical
2. Establishment of “ freedom in centric” within the overall occlusal
3. Elimination of any interference between the maximum
intercuspal and retruded contact positions
4. Provision of harmonic, free mandibular movements with light
tooth contacts during both lateral and protrusive maneuvers.
Occlusal scheme for immediate loading for All-on-
Four concept
Avoid or minimize length of cantilever .Simultaneous bilateral point
contacts on all teeth, excluding teeth distal to implant emergence.
In lateral movements, group function or guidance with flat linear
pathways and minimal vertical super impositon excluding teeth in
cantilever. In protrusive movements, guidance distributed on all
anterior teeth including canines, with flat linear pathways and minimal
verical super imposition. Even if the implant supported prosthesis is
opposed to a removable full denture, in excursive movements avoid
balancing contacts.
Occlusal scheme for All-on-Four definitive prosthesis
Simultaneous bilateral point contacts on canine and posterior teeth
and grazing contacts on incisors. In lateral movements , canine
guidance opposing natural dentition, group function opposing
posterior implant supported bridge with flat linear pathways and
minimum vertical super imposition [Table/Fig-7a,b]. If the implant
supported prosthesis is opposed to removal, complete denture or
implant supported over denture or a distal extension cast partial
denture leave the most distal tooth slightly out of occlusion and
in excursive movements seek one or more balancing contacts,
planning greater anteroposterior space at the anterior teeth. The
occlusal pattern should have relatively flat cusps i.e. the inclination
of the cuspal planes should be less than the inclinations of the
condylar path.
Complete denture opposing All-on-4• ® concept
Over denture opposing All-on-4• ® concept
Precision attachment opposing All-on-4• ® concept
Cast partial denture opposing All-on-4• ® concept
Distal tooth out of occlusion •
Balancing contacts •
planning greater anteroposterior space at the anterior teeth•
Since the teeth of the distal cantilever are less heavily loaded, the
guiding surfaces of the incisors and canines can be expected
to undergo increasing abrasions with time, therefore eliminate
premature or non working side contacts on the distal cantilever
Advantages of the All-on-4® concept
• Angledposteriorimplantsavoidanatomicalstructures
• Angled posterior implants allow longer implants anchored in
better quality bone
• Reducesposteriorcantilever
• Eliminatesbonegraftsintheendentulousmaxillaandmandible
inmajorityofcases M.Taruna et al., Prosthodontic Perspective to All-On-Four Concept for Dental Implants
Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19 1919
• Highsuccessrates
• Implantswell-spaced,goodbiomechanics,easiertoclean
• Immediatefunctionandaesthetics
• Finalrestorationcanbexedorremovable
• Reducedcostduetolessnumberofimplantsandavoidance
• Goodgeneralhealthandacceptableoralhygiene;
• Sufcientbonefor4implantsofatleast10mminlength;and
• Implantsattainsufcientstabilityforimmediatefunction.
• Freehandarbitrarysurgicalplacementofimplantisnotalways
possible as implant placement is completely prosthetically
• Length of cantilever in the prosthesis cannot be extended
beyond the limit.
• Itisverytechniquesensitiveandrequireselaboratepre-surgical
preparation such as CAD/CAM, surgical splint.
Length of cantilever in the prosthesis cannot be extended beyond
the limit.
Various researches done on the concept and practice of the
rehabilitation has advanced the All-on-4® treatment option from the
skeptical to the predictable with commendable success rates. The
long term results of this technique and the numerous advantages
of immediate loading, the reduced morbidity, the high patient
satisfaction and relatively low costs should be taken into account
when a decision among the alternative treatment options for an
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[3] Paulo Malo, et al. All-on-4® immediate function concept for completely edentulous
maxillae. A clinical report on the medium and long term 5 years outcome, Journal
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[4] Dallenback K, et al. Biomechanics of in-line vs offset implants supporting a partial
prosthesis. J Dent Res.1996;75:183.
[5] Chiara M Bellini, et al. Comparison of tilted versus non-tilted Implant –supported
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[7] BevilacquaH,etal.Threedimensionalniteelementanalysisofloadtransmission
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[11] DuyckJ,VanOostcrwyckH, VanderSlotenJ,et al.Magnitudeand distribution
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[14] Frost HM. Perspectives: Bone’s mechanical usage windows. Bone miner.
[15] Isodro F. Influence of forces on peri, implant bone. Clin Oral Implants Res.
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implants supporting mandibular cross arch fixed prosthesis – 18 month follow up
from a multi centre prospective cohort. Eur J Oral Implantol. 2012;5(3):277-85.
[17] Daniel F Galindo, et al. Immediately loaded Mandibular fixed implant prosthesis
using the All-on-4® protocol. A report of 183 consecutively treated patients
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Bo Rangert, et al. All-on-4® Immediate-Function Concept with Brånemark System
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[19] AmirHKhatami,etal.“All-on-4®”Immediatefunctionconceptandclinicalreport
of treatment of an edentulous mandible with a fixed complete denture and milled
titanium framework. Journal of Prosthodontics.2008;17:47-51.
Schemes of occlusion – Color atlas of dental medicine. Implantology. pg 299-304.
[21] Immediate loading – A new era in oral implantology – chap – 14 –pg 234.
Occlusion in implant supported prosthesis under immediate loading and delayed
1. Professor, Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, India.
2. HODand Professor, Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, India.
3. Professor, Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, India.
4. Reader, Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, India.
5. Postgraduate Student, Department of Prosthodontics, Kamineni Institute of Dental Sciences, Sreepuram, Narketpally, India.
Dr. M.Taruna,
Kamineni Institute of Dental Sciences, Sreepuram, Narketpally-508254, India.
Phone : 9849033670, E-mail :
Date of Submission: Jun 10, 2014
Date of Peer Review: Jul 02, 2014
Date of Acceptance: Aug 26, 2014
Date of Publishing: Oct 20, 2014
... A very popular means of treating edentulism (loss of all teeth) is to prepare the patient's jaw for placement of 4 load-bearing dental implants that carry an overdenture [2]. These implants can either be unsupported -placed individually with no structural connections, or supported -usually with a soldered metal wire or a solid bar that acts as a stirrup that connects all 4 implants together for better distribution of masticatory forces. ...
Two variants of implant-supported overdentures (IODs) were investigated by quantitative computed tomography-assisted finite element method (QCT-FEA) on a patient-specific CTreconstructed model of human maxilla. The analyzed variants are bar-supported (splinted) and unsupported (unsplinted) implant assemblies. The loading was done by a 800 N force slanted by 30° in the buccolingual direction. The results of the analyses show favorable stress distributions for the bar-supported variant.
... For completely toothless patients, the process of delivering an implant-supported prosthesis might be virtually impossible without implementing intricate methods such as nerve relocation and grafting in the molar region of the upper and lower jaw. In such circumstances, the All-on-4 concept provides a practical resolution [4]. Nonetheless, the implant-supported prosthesis can often be rendered unfeasible due to proximity to critical anatomical structures such as the mandibular canal or the maxillary sinus. ...
Full-text available
Edentulism, a condition characterized by the absence of teeth, significantly impacts facial aesthetics, eating efficiency, and speech fluency, thereby diminishing the quality of life. This paper aims to explore the All-On-Four Treatment Concept in Dental Implants, a promising solution to this issue. The All-On-Four approach, though complex, offers a pathway to restore smile and functionality by using four strategically positioned implants to hold a temporary prosthesis. This prosthesis is later replaced by a permanent version after approximately four months. This swift oral restoration technique significantly enhances a patient’s self-confidence and overall life quality. The significance of this treatment lies in its potential to provide a less invasive and more affordable solution for severe jawbone atrophy, where the proximity of critical anatomical structures and compromised bone conditions may hinder other prosthetic solutions. The paper concludes with a discussion on the potential of the All-On-Four treatment to revolutionize dental implant procedures, offering a beacon of hope for individuals suffering from edentulism.
... The all-on-4 concept is an ideal solution that enables using four dental implants placed in the interforaminal region to retain a prosthesis. Paulo Malo provided completely edentulous patients with full arch restoration using only four implants by developing the all-on-4 concept by applying either angled or straight multi-unit abutments (2) . ...
... Entretanto, é necessário dimensões mínimas do processo alveolar na maxila entre a parede mesial dos seios maxilares e entre o surgimento dos nervos Research, Society and Development, v. 12, n. 5, e27512541725, 2023 (CC BY 4.0) | ISSN 2525-3409 | DOI: 5 mentais na mandíbula, pois isso é o que permite assim a colocação dos quatro implantes (Penarrocha-Diago et al., 2017). Em pacientes totalmente edêntulos em casos bastante complexos, essa técnica pode ser uma solução vis às altas taxas de sucesso (Taruna et al., 2014). ...
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Atualmente diversas são as opções de reabilitação oral em pacientes edêntulos. Uma opção já validada na literatura por diversos estudos e que vem sendo uma alternativa ao uso desses enxertos para reabilitação oral, é o protocolo de reabilitação total implantossuportada denominado All-on-four. Essa técnica, inicialmente divulgada em 2003, vem se mostrando nas duas últimas décadas, uma opção favorável, por ser uma técnica rápida e segura para os pacientes dendentados totais. O objetivo do presente trabalho foi apresentar uma revisão de literatura e um relato de caso clínico, de um paciente com maxila atrófica, utilizando o protocolo All-on-four e reabilitando com prótese implantossuportada. Para esse estudo buscou-se artigos nos bancos de dados PUBMED, Lilacs e Scielo. Foram buscados artigos com os termos implantes dentários, reabilitação oral, planejamento de prótese dentária e protocolo All-on-four, nos idiomas portugues e/ou inglês. Selecionou-se 34 artigos publicados entre os anos de 2003 e 2021. Além disso, relatou-se um caso clínico onde elegeu-se esse tipo de técnica para a reabilitação. O protocolo All-on-four vem avançando na área clínica e de pesquisa, apontando excelentes taxas de sucesso, inúmeras vantagens e alta taxa de aceitação pelos pacientes. O presente caso clínico apontou um protocolo de rápida execução, e com sucesso quanto à estética e função. Conclui-se que essa técnica é um método viável especialmente para mandíbulas edêntulas. Dentro dos limites do presente relato de caso, pode-se concluir que a técnica All-on-four pode ser considerada uma alternativa para reabilitação com implantes.
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Nowadays, the dental implant surgery is a sophisticate and accurate sector with techniques increasingly innovative such as rapid prototyping, guided implant surgery and stem cell-based approaches. An example is certainly the use of multiple implants (4-6), instead of several prosthesis in case of human edentulous condition. The aim of this research is to investigate the mechanical behavior of the All-on-Four technique for different boundary conditions such as the value of load, framework material, type and position of implant. The goal was essentially trying to find out, by the application of structural static Finite Element Analysis (FEM), the best design for this specific treatment. After that, a stress-life fatigue numerical analysis was conducted for the optimal configuration in order to estimate the fatigue life in accordance with both Gerber and Goodman mean stress theory. The coupling involved the implants supported by an arch and a human mandible composed of cortical and cancellous part. After the simulations, it was found that the stress/strain field was very sensitive to the boundary conditions imposed. In particular, the position of the implants and the material framework yielded different responses depending on the implant design. Finally the use of ultrashort implants provided a significant decrease in the developed efforts than the long ones if the first premolar position was assumed. More specific, the stress peaks were in the range 100-225 MPa for the implants, 300-537 MPa for the framework, 50-124 MPa for the cortical bone and 3-35 MPa for the cancellous bone and they were located essentially in the abutment-framework connection as much as in implant neck-bone coupling. The best design saw the presence of ultra-short implant, first premolar position and Co-Cr alloy as framework material. The fatigue test confirmed the stability of the structure even with dynamic loads, but critical spots were present in the framework. In conclusion, the All-on-Four technique is a valid and safe alternative, even in case of ultrashort implants, for human edentulism care.
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The long-term success and predictability of implant-supported restorations largely depends on the biomechanical forces (stresses) acting on implants and the surrounding alveolar bone in the mandible. The aim of our study was to investigate the biomechanical behavior of an edentulous mandible with an implant-supported full bridge on four implants under simulated masticatory forces, in the context of different loading schemes, using a three-dimensional finite element analysis (3D-FEA). A patient-specific 3D finite element model was constructed using pre- and post-implantation computer tomography (CT) images of a patient undergoing implant treatment. Simplified masticatory forces set at 300 N were exerted vertically on the denture in four different simulated load cases (LC1–LC4). Two sets of simulations for different implants and denture materials (S1: titanium and titanium; S2: titanium and cobalt-chromium, respectively) were made. Stress outputs were taken as maximum (Pmax) and minimum principal stress (Pmin) and equivalent stress (Peqv) values. The highest peak Pmax values were observed for LC2 (where the modelled masticatory force excluded the cantilevers of the denture extending behind the terminal implants), both regarding the cortical bone (S1 Pmax: 89.57 MPa, S2 Pmax: 102.98 MPa) and trabecular bone (S1 Pmax: 3.03 MPa, S2 Pmax: 2.62 MPa). Overall, LC1—where masticatory forces covered the entire mesio−distal surface of the denture, including the cantilever—was the most advantageous. Peak Pmax values in the cortical bone and the trabecular bone were 14.97–15.87% and 87.96–94.54% higher in the case of S2, respectively. To ensure the long-term maintenance and longevity of treatment for implant-supported restorations in the mandible, efforts to establish the stresses of the surrounding bone in the physiological range, with the most even stress distribution possible, have paramount importance.
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Edentulism, a prevalent condition among elderly individuals, arises from diverse factors encompassing subpar oral hygiene, dental caries, and periodontal disease. Its ramifications extend beyond the physical realm, permeating into the social and psychological domains. Adverse effects manifest in compromised facial and oral aesthetics, diminished masticatory function, and impaired speech abilities, collectively culminating in a substantial diminishment of patients' quality of life. A spectrum of prosthetic solutions is available for ameliorating the edentulous state, including conventional complete dentures, implant-supported removable prostheses, and implant-supported fixed prostheses. Among these options, the all-on-four paradigm stands as a compelling alternative to conventional implant modalities. This approach entails the strategic placement of four implants-two in the interforaminal region of the mandible and two in the pre-maxillary region in cases of total edentulism. Noteworthy is the configuration wherein the two anterior implants conform to the natural contours of the jaw, while the two posterior implants assume a posterior tilt of 45°. This arrangement confers a trifecta of benefits: robust JOPD HEB implant anchorage, abbreviated cantilever length, and a generous inter-implant distance, collectively fostering a propitious treatment outcome. This study endeavors to delineate the foundational tenets of the all-on-four concept, offering a comprehensive exposition of its merits and demerits. Through meticulous scrutiny, this research aims to provide an incisive assessment of this innovative approach in the rehabilitation of edentulous patients, with the ultimate goal of augmenting the efficacy and refinement of dental prosthetic interventions.
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O edentulismo é um importante problema de saúde pública que acarreta inúmeras sequelas e reduz de modo significativo a qualidade de vida do paciente, tanto em termos funcionais quanto estéticos. Perdas dentárias do arco superior podem ser acompanhadas de atrofia da maxila, o que dificulta o processo de reabilitação, uma vez que impede a realização de procedimentos que.boa quantidade de massa óssea local. O presente estudo é uma revisão de literatura narrativa que visa descrever o uso da técnica all-on-4 na reabilitação de maxila atrófica em pacientes edêntulos. Assim, uma das abordagens para melhor reabilitação da maxila atrófica desdentada é a técnica all-on-4, procedimento cirúrgico que utiliza quatro implantes para ancoragem de prótese total do arco superior ou inferior. A angulação adequada dos implantes durante a técnica resulta em maior superfície para ancoragem da prótese fixa, que apresenta grande estabilidade e ótimo padrão estético. Trata-se de um procedimento minimamente invasivo e de custo relativamente reduzido que traz resultados satisfatórios na maioria dos casos de edentulismo com atrofia maxilar, com vantagens que incluem previsibilidade, menor tempo de execução do procedimento, redução do cantiléver posterior e elevada estabilidade biomecânica, além do custo reduzido e menor tempo de recuperação. Porém, trata-se de um método de difícil execução que requer bom planejamento e elaboração pré-cirúrgica, além de ser contraindicado em casos de discrasias hematológicas, diabetes, imunossupressão e doenças crônicas. Sua realização é feita em etapas que envolvem seleção do caso; análise da viabilidade de aplicação do protocolo; planejamento do caso; escolha dos locais dos implantes; colocação dos implantes e, por fim, a fase protética. Na grande maioria dos casos os sinais inflamatórios pós-procedimento são reduzidos e a sobrevida dos implantes é longa. Dessa forma, pode-se concluir que a reabilitação de edentulismo com maxila atrófica pela técnica all-on 4 é uma abordagem efetiva que permite que o paciente edêntulo possa recuperar tanto as funções de mastigação, deglutição e fala, como também melhorar o aspecto estético da face.
Objective: This study evaluated the accuracy of different intraoral scanners (IOS) for scanning of implant-supported full arch fixed prosthesis with different implant angulations with and without scanbodies splinting. Materials and methods: Two maxillary models were designed and fabricated to receive an all-on-four implant retained. The models were divided into two groups according to the angulation of the posterior implant (Group 1; 30 and Group 2; 45). Each group was then divided into three subgroups according to the type of IOS used: Subgroup C; Primescan, subgroup T; Trios4, and subgroup M; Medit i600. Then each subgroup was divided into two divisions according to scanning technique; division S: splinted and division N: nonsplinted. Ten scans were made by each scanner for every division. Trueness and precision were analyzed using Geomagic controlX analysis software. Results: Angulation had no significant effect on both the trueness (p = 0.854) and precision (p = 0.347). Splinting had a significant effect on trueness and precision (p < 0.001). Scanner type had a significant effect on trueness (p < 0.001) and precision (p < 0.001). There was no significant difference between trueness of Trios 4 (112.15 ± 12.85) and Primescan (106.75 ± 22.58). However, there was a significant difference when compared to trueness of Medit i600 (158.50 ± 27.65). For the precision results Cerec Primescan showed the highest precision (95.45 ± 33.21). There was a significant difference between the three scanners, precision of Trios4 (109.72 ± 19.24) and Medit i600 (121.21 ± 17.26). Conclusion: Cerec Primescan has higher trueness and precision than Trios 4 and Medit i600 in full arch implants scanning. Splinting the scanbodies improve the accuracy of full arch implants scanning. Clinical significance: Cerec Primescan and 3Shape Trios 4 can be used for scanning of All-on-four implant supported prosthesis when scanbodies are splinted using a modular chain device.
Purpose: This in vitro study was to assess the effects of using different cements and titanium copings design on the retention of the implant-supported fixed dental prostheses (IFDPs) using a pull-out test. Materials and methods: Fifty zirconia (ZirCAD; Ivoclar Vivadent) and 20 prepolymerized denture acrylic resin (AvaDent) rectangular (36 mm × 12 mm × 8 mm) specimens were milled to mimic the lower left segmental portion of the All-on-Four IFDPs. Cylindrical titanium copings (Variobase; Straumann) (V) were used in 2 prepolymerized denture acrylic resin groups (n = 10) while conical titanium copings (Straumann) (C) were used as a control group for zirconia with 4 groups using cylindrical titanium copings. Before cementation, the outer surfaces of all titanium copings and intaglio bonding surface of prosthetic specimens were airborne-particle abraded. All specimens were cemented following the manufacturer recommendations and instructions according to the experimental design. After artificial aging (5000 cycles of 5°C-55°C, dwelling time 20 sec; 150 N, 1.5 Hz in a 37°C water bath), all specimens were subjected to retention force testing using a pull-out test using a universal testing machine and a custom fixture with a crosshead speed 5 mm/min. Mode of failure were classified (Type 1, 2, or 3). Retention force values were analyzed by the t-test for the prepolymerized denture acrylic resin specimen groups, and 1-way ANOVA and the Tukey test for the zirconia groups at α = 0.05. Results: Mean and standard deviation retention force values varied from 101.1±67.1 to 509.0 ±65.2 N for the prepolymerized denture acrylic resin specimen groups. The zirconia groups ranged from 572.8 ±274.7 to 1416.1 ±258.0 N. There is no statistically significant difference in retention force values between V and C specimens cementing to Zirconia with Panavia SA cement (Kuraray Noritake) (p = 0.587). The retention forces and failure modes were influenced by the cement used (p < 0.05). Modes of failure were predominantly Type 2 (Mixed failure) and Type 1 (Adhesive fracture from prosthetic materials) except for the quick-set resin group (Type 3, Adhesive failure from coping). Conclusions: When bonding IFDPs onto titanium copings, quick-set resin provided significantly higher retention force for prepolymerized denture acrylic resin prostheses. Conical and cylindrical titanium copings performed similarly when cemented to Zirconia with Panavia SA cement under the same protocol. The stability of the bonded interface and retention forces between zirconia prostheses and titanium copings varied from the cement used. This article is protected by copyright. All rights reserved.
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Aim: To evaluate the outcome of immediately loaded mandibular cross-arch prostheses according to the 'all-on-4' concept supported by implants placed in fresh extraction sockets up to 18 months after loading. Materials and methods: In total, 47 patients with a mean age of 62.3 years (range 52 to 78) were rehabilitated with an immediately loaded fixed cross-arch prosthesis supported by four post-extractive implants. A total of 188 implants were inserted. Patients received a provisional fixed dental prosthesis with a metal framework within 48 hours after surgery and a permanent one 6 months later. The patients were evaluated clinically and radiographically at implant placement and at 6-, 12- and 18-month follow-up examinations. Results: At the 18-month follow-up, no implant failed and all restorations were stable. Peri-implant bone levels amounted to 0.31 ± 0.12 mm after 6 months, 0.58 ± 0.112 mm after 12 months and 0.7 ± 0.107 mm after 18 months. No significant differences in bone loss were found between axially placed and tilted implants at the 6-month (0.06 mm; P = 0.115), the 12-month (0.12 mm; P = 0.062) and the 18-month follow-up (0.08 mm; P = 0.146). Three patients had a fracture of the provisional restoration, but all of the definitive prostheses remained stable throughout the study period without any complications. Conclusions: Within the limits of this study, it can be suggested that immediately loaded mandibular cross-arch fixed dental prostheses can be supported by four post-extractive implants, however larger and longer follow-ups are needed.
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Background: Immediate implant function has become an accepted treatment modality for fixed restorations in totally edentulous mandibles, whereas experience from immediate function in the edentulous maxilla is limited. Purpose: The purpose of this study was to report on the medium- and long-term outcomes of a protocol for immediate function of four implants (All-on-4™, Nobel Biocare AB, Göteborg, Sweden) supporting a fixed prosthesis in the completely edentulous maxilla. Materials and Methods: This retrospective clinical study included 242 patients with 968 immediately loaded implants (Brånemark System® TiUnite™, Nobelspeedy™, Nobel Biocare AB) supporting fixed complete-arch maxillary all-acrylic prostheses. A specially designed surgical guide was used to facilitate implant positioning and tilting of the posterior implants to achieve good bone anchorage and large interimplant distance for good prosthetic support. Follow-up examinations were performed at 6 months, 1 year, and thereafter every 6 months. Radiographic assessment of the marginal bone level was performed after 3 and 5 years in function. Survival was estimated at patient level and implant level using the Kaplan–Meier product limit estimation with 95% confidence intervals. Results: Nineteen immediately loaded implants were lost in seventeen patients, giving a 5-year survival rate estimation of 93% and 98% at patient and implant level, respectively. The survival rate of the prosthesis was 100%. The marginal bone level was, on average, 1.52 mm (standard deviation [SD] 0.3 mm) and 1.95 mm (SD 0.4 mm) from the implant/abutment junction after 3 and 5 years, respectively. Conclusion: The high survival rates at patient and implant level indicates that the immediate-function concept for completely edentulous maxillae using the present protocol is viable in the medium- and long-term outcomes.
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Using the three-dimensional finite element method (FEM), this study compared the biomechanical behavior of the "All-on-Four" system with that of a six-implant-supported maxillary prosthesis with tilted distal implants. The von Mises stresses induced on the implants under different loading simulations were localized and quantified. Three-dimensional models representing maxillae restored with an "All-on-Four" and with a six-implant-supported prosthesis were developed in three-dimensional design software and then transferred into FEM software. The models were subjected to four different loading simulations (full mouth biting, canine disclusion, load on a cantilever, load in the absence of a cantilever). The maximum von Mises stresses were localized and quantified for comparison. In both models, in all loading simulations, the peak stress points were always located on the neck of the distal tilted implant. The von Mises stress values were higher in the "All-on-Four" model (7% to 29%, higher, depending on the simulation). In the presence of a cantilever, the maximum von Mises stress values increased by about 100% in both models. The stress locations and distribution patterns were similar in the two models. The addition of implants resulted in a reduction of the maximum von Mises stress values. The cantilever greatly increased the stress.
The purpose of this study was to evaluate a specific protocol using four implants to support immediately loaded fixed prostheses to restore edentulous and partially edentulous mandibles and report on the outcome after 1 year of function with the definitive prostheses. A retrospective study was conducted of all patients who were treated between June 2008 and December 2010 with fixed prostheses that were loaded immediately after placement of implants. The provisional prostheses were later replaced with computer-aided design/computer-assisted manufacture titanium frames supporting acrylic resin and denture teeth in the definitive prosthesis. All patients were followed for a minimum of 12 months and were assessed for implant survival and prosthetic performance, with descriptive statistics utilized to demonstrate results. One hundred eighty-three consecutive patients received immediately loaded axial and tilted implants according to the defined protocol. One implant failed, resulting in a 99.86% implant success rate. There were two catastrophic prosthetic failures (fracture of the titanium framework), for a 98.9% prosthetic success rate. Three patients (1.6%) presented with fracture of a prosthetic mandibular incisor tooth. No prosthetic screw loosening or fractures were seen. Radiographic evaluation revealed no major bone loss around dental implants. Based on this retrospective study, the following conclusions can be drawn: (1) this technique appears to provide a highly predictable implant performance; (2) it is necessary to critically evaluate framework design, especially around the connectors for cantilever extensions around the most distal implants; and (3) minor complications related to acrylic resin tooth fracture may be anticipated during the early phases of prosthetic treatment.
Controversy exists regarding the "All-on-Four" concept for a mandibular full-arch fixed prosthesis. The purpose of this study was to examine photoelastically the effect of the inclination of the two distal implants according to the All-on-Four concept on the stress distribution within the supporting structure. Two photoelastic models of a human edentulous mandible were fabricated. Each model had four screw-type implants embedded in the interforaminal area. The two distal implants were placed axially in one model and tilted 30 degrees distally in the other model. Two cantilevered acrylic resin prostheses, which used angulated abutments for the distal tilted implants and straight abutments for the axial implants, were fabricated and delivered. Vertical loads of 13 kg were applied at three loading points on the prosthesis: the central fossa of the first molar, the distal fossa of the first premolar, and the distal fossa of the second premolar. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. Whereas all cantilever loadings concentrated the stresses at the distal crest of the distal implant sites in both models, the posterior tilting of distal implants splinted in a full-arch fixed prosthesis did not increase the stresses in bone around the distal implants versus the axial-implant model. Within the limitations of this photoelastic stress analysis, the use of tilted implants reduced the maximum stress in the distal crestal bone of the distal implant by approximately 17% relative to the axial implants.
The All-on-Four concept advocates immediate loading and the placement of distal implants at an angle. The purpose of this study was to do a qualitative descriptive analysis of stress patterns around the distal angled implant of the All-on-Four concept. Four photoelastic acrylic resin models, each with four implants simulating the All-on-Four configuration, were prepared. The two central implants were placed vertically and parallel in each model, and the distal implant on each side was placed at an increasing angle (0, 15, 30, and 45 degrees) in each model. The four implants were splinted by means of a cast metal bar. The photoelastic models were placed between two parallel anvils. Pairs of abutments were systematically subjected to a load by suspending 5-, 10-, and 15-kg weights from one of the anvils. Photoelastic analysis was accomplished using a circular polariscope. The fringe patterns produced in the photoelastic resin for each implant and load were photographed with a digital camera. Fringe concentrations and the highest fringe order were recorded and described for the apical, central, and coronal regions of the distal angled implant for each load scenario. For the implants placed at 15- and 30-degree angles, little difference in stress patterns was observed between the central straight implant and the distal angled implant. For every load scenario and for all angulations, the lowest fringe order was recorded at the central region of the implant. The highest fringe order for the apical region was always higher than the highest fringe order for the coronal region of the implant. Markedly increased isochromatic fringe concentrations were observed in model 4, which had the distal implants placed at a 45-degree angle. Peri-implant bone surrounding the 45-degree-angled distal abutment may be more prone to occlusal overload than bone surrounding implants with lesser tilts.
The purpose of the study was to evaluate, using finite element analysis, the stress patterns induced in cortical bone by three distinct implant-supported prosthetic designs. The first two models consisted of a prosthesis supported by four implants, the distal two of which were tilted, with different cantilever lengths (5 mm and 15 mm). The third design consisted of a prosthesis supported by five conventionally placed implants and a 15-mm cantilever. In the tilted model with 5-mm cantilever and in the nontilted model, the maximum value of compressive stress (-18 MPa) was found near the cervical area of the distal implant. Higher values for compressive stress were predicted near the cervical area of the distal implant in the tilted model with a 15-mm cantilever, as compared to the tilted model with the 5-mm cantilever. For the tilted model with the 5-mm cantilever, peak values of tensile stress were predicted near the cervical area of both the distal (1.25 MPa) and the mesial implants (2.5 MPa). For the nontilted model, the peak value was found near the cervical area of the in-between implant (5 MPa). For the tilted model with 15-mm cantilever, tensile stress values were higher than in the tilted model with 5-mm cantilever. No significant difference in stress patterns between the tilted 5-mm and the nontilted 15-mm configuration was predicted. The tilted configuration with a 15-mm cantilever was found to induce higher stress values than the tilted configuration with a 5-mm cantilever.
Many clinical studies have reported high survival rates for tilted implants. However, tilted implants transmit increased stress to bone when compared to vertically placed implants. Theoretical (computer-based), laboratory, and clinical studies are warranted to effectively address this issue. In this study, a 3-dimensional finite element analysis was performed to analyze the stress values surrounding tilted versus vertical implants. The results revealed laboratory and biomechanical evidence that distal tilting of implants, splinted in full fixed prostheses without cantilevers, reduced the amount of stress generated around the peri-implant bone when compared to the levels of stress seen in peri-implant bone with vertical implants and cantilevered segments in similar full fixed prostheses.