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

Abstract

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.

Full text

Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19
1616
DOI: 10.7860/JCDR/2014/9648.5020
Review Article
Keywords: All-on-4®, Cantilever prosthesis, Implant occlusal scheme, Multi units
Introduction
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 •
torque).
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
ABSTRACT
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
M.TARUNA1, B.CHITTARANJAN2, N.SUDHEER3, SUCHITA TELLA4, MD.ABUSAAD5
[Table/Fig-1]: All-on-4® Concept

www.jcdr.net 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
accuracy
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
cementation
Step 5 Crowns luted to zirconia framework
Step 6 Implant-supported zirconia bridge framework with individual crowns
luted
[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
[9].
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
[13].
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 www.jcdr.net
Journal of Clinical and Diagnostic Research. 2014 Oct, Vol-8(10): ZE16-ZE19
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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
framework.
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
[19].
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
scheme
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
[Table/Fig-7]
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
[21].
DISCUSSION
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

www.jcdr.net 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
ofgraftinginthemajorityofcases.
LIMITATIONS
• 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.
DISADVANTAGES
• Freehandarbitrarysurgicalplacementofimplantisnotalways
possible as implant placement is completely prosthetically
driven.
• 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.
CONCLUSION
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
edentulousjawhastobemade.
REFERENCES
[1] Christopher,et al, Implant rehabilitationintheedentulousjaw:The “All-on-4®
concept” immediate function. Australian dental practice. 2012, page 138-48.
[2] PankajPsingh.ANormanCranin. Atlas of oral implantology. Page 275-81.
[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
of Oral Implantology. Vol. XXXVII/No. Four/2011.
[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
prosthetic designs for the restoration of the edentulous mandible. A biomechanical
study. Int J oral Maxillofacial implants.2009;24:511-12.
[6] Krekmanov L, et al. Tilting of posterior mandibular and maxillary implants of
prosthesis support. Int J Oral maxillofacial implants.2000;15:405-14.
[7] BevilacquaH,etal.Threedimensionalniteelementanalysisofloadtransmission
using different implant inclinations and cantilever lengths. Int J Prosthodont.
2008;21:539-42.
[8] White SN, et al. Effect of cantilever length on stress transfer by implant –
supported prosthesis. J Prosthet Dent. 1994;7:493-99.
[9] Captuto AA, et al. Biomechanics in clinical dentistry. Chicago Quintessance.
1195:64.
[10] Kim KS, Kum YL, Bae JM, Chohw. Biomechanical comparison of axial and tilted
implants for mandibular full arch fixed prosthesis. Int J Oral Maxillofacial Implants.
2011;26:976-84.
[11] DuyckJ,VanOostcrwyckH, VanderSlotenJ,et al.Magnitudeand distribution
of occlusal forces on oral implants supporting fixed prosthesis – An in vivo study.
Clin Oral implants Res.2000;111:465-75.
[12] Guilherme Carvalho Silva, et al. Stress patterns on implants in prostheses
supported by four or six implants. A three dimensional finite element analysis. Int
J Oral Maxillofac Implants.2010;25:239-46.
[13] Tasneem Begg, et al. Stress patterns around distal angled implants in the All-
on-4® concept configuration. Int J Oral Maxillofacial implants. 2009;24:663-71.
[14] Frost HM. Perspectives: Bone’s mechanical usage windows. Bone miner.
1992;9:257-71.
[15] Isodro F. Influence of forces on peri, implant bone. Clin Oral Implants Res.
2006;17:8-18.
[16] Tommaso Grandi, et al. Immediate Loading of four All-on-4® Post-extractive
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
with 1 year of function in definitive prosthesis. Int J Oral Maxillofac Implants.
2012;27:628-33.
[18]
Bo Rangert, et al. All-on-4® Immediate-Function Concept with Brånemark System
Implants for Completely Edentulous Maxillae: A 1-Year Retrospective Clinical Study.
Clinical Implant Dentistry and Related Research. 2005;7(1):S88-94.
[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.
[20]
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
loading.
PARTICULARS OF CONTRIBUTORS:
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.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR:
Dr. M.Taruna,
Kamineni Institute of Dental Sciences, Sreepuram, Narketpally-508254, India.
Phone : 9849033670, E-mail : taruna_e@yahoo.com
FINANCIAL OR OTHER COMPETING INTERESTS: None.
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