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Principles of Prosthetically Driven Implantology and Implant as the Third Dentition

Index of Contents

Introduction
Definition and concept
Objectives of prosthetically driven implantology
Fundamental principles
4.1 Comprehensive patient assessment
4.2 Begin with the definitive restoration
4.3 Diagnostic wax-up and trial restoration
4.4 Three-dimensional implant positioning
4.5 Bone and soft-tissue considerations
4.6 Biomechanical and occlusal principles
4.7 Selection of implant number, size and distribution
4.8 Emergence profile, abutment and retention design
4.9 Digital planning and surgical guides
4.10 Maintenance-oriented prosthetic design
Consequences of prosthetically unfavourable implant placement
Implant as the “third dentition”
Natural teeth versus implant-supported dentition
Clinical significance
Conclusion
References

1. Introduction

Osseointegrated dental implants have changed prosthodontic treatment from merely replacing missing teeth to restoring oral function, appearance, speech, comfort and patient confidence. Modern implant treatment must not be planned as a surgical procedure alone. The implant is a prosthetic foundation, and its position must permit fabrication of a biologically acceptable, mechanically stable, hygienic and aesthetic restoration.

The contemporary philosophy is therefore prosthetically driven implantology, also called restoration-driven or prosthesis-driven implant planning. The clinician first visualizes the planned definitive restoration, then determines the ideal implant position, and finally performs surgery to achieve that position while respecting anatomical limitations.

In this context, implant-supported restorations are often called the third dentition. The first dentition is primary teeth, the second is permanent teeth, and implant-supported prostheses provide a third opportunity to restore lost teeth. However, implants are not biological replacements identical to natural teeth. They require special biomechanical design, meticulous hygiene and lifelong maintenance.

2. Definition and Concept

Prosthetically driven implantology

Prosthetically driven implantology is the planning and placement of dental implants according to the requirements of the proposed definitive prosthesis, rather than placing an implant solely where bone is available.

The sequence is:

Desired tooth position → planned crown/prosthesis → ideal implant position → assessment of available bone and anatomy → augmentation or modification of treatment plan if required.

This principle ensures that implant placement supports:

Proper tooth position and facial contour
Acceptable emergence profile
Suitable occlusion
Aesthetic gingival architecture
Cleansable contours
Appropriate load distribution
Retrievability and maintenance
Long-term peri-implant tissue health

The ITI consensus literature describes prosthetically driven implant dentistry as the optimal approach and emphasizes detailed pre-treatment planning to obtain a correct three-dimensional implant position in relation to the planned prosthesis. ITI guidance on computer-aided implant surgery

3. Objectives of Prosthetically Driven Implantology

The principal objectives are:

To replace missing teeth in the ideal aesthetic and functional position.
To position implants within available bone without damaging vital structures.
To obtain a restoration with a favourable crown-to-implant relationship.
To establish a stable and cleansable peri-implant soft-tissue contour.
To reduce mechanical complications such as screw loosening, fracture of porcelain, abutment fracture and implant overload.
To provide an occlusal scheme compatible with the reduced proprioception of implants.
To design a prosthesis that is retrievable, repairable and easy for the patient to clean.
To achieve predictable long-term implant survival and prosthesis success.

4. Fundamental Principles

4.1 Comprehensive Patient Assessment

Treatment begins with diagnosis, not implant placement.

A. Medical assessment

The clinician should assess:

Diabetes and glycaemic control
Smoking or tobacco use
Previous head and neck radiotherapy
Immunosuppression
Antiresorptive or antiangiogenic medications
Bleeding disorders and anticoagulant use
History of periodontitis
Parafunction, especially bruxism
Patient expectations, motivation and oral hygiene

The patient must understand that implant treatment involves surgery, cost, maintenance and possible biological or technical complications.

B. Dental assessment

A complete examination includes:

Periodontal condition of adjacent teeth
Caries activity and endodontic status
Occlusion and interarch space
Tooth position and occlusal plane
Ridge form and residual bone volume
Smile line and lip support
Existing restorations and vertical dimension
Temporomandibular joint and parafunctional habits
Oral hygiene ability and plaque control

Untreated periodontal disease, poor plaque control and uncontrolled systemic disease must be managed before implant therapy.

4.2 Begin with the Definitive Restoration

This is the most important principle.

The definitive restoration should be planned before surgery by considering:

Number of teeth to be replaced
Tooth shape, size and position
Facial and palatal/lingual contours
Incisal edge position
Occlusal plane
Vertical dimension of occlusion
Smile line
Phonetics
Type of prosthesis: single crown, fixed partial denture, full-arch fixed prosthesis or overdenture
Retention method: screw-retained or cement-retained

The surgeon should not place an implant where bone happens to be present if this creates a restoration with poor contour, excessive cantilever, unfavourable angulation or inaccessible hygiene.

If adequate bone is not available in the ideal restorative position, the choices include:

Ridge augmentation
Sinus floor elevation
Orthodontic tooth movement
Modification of implant diameter or length
Use of short or tilted implants in selected cases
Alternative prosthetic design
Conventional tooth-supported or removable prosthesis

Thus, bone should be developed for the restoration, not the restoration compromised for the bone, whenever clinically justified.

4.3 Diagnostic Wax-up and Trial Restoration

A diagnostic wax-up is a three-dimensional simulation of the final prosthesis. It may be conventional or digital.

Purposes of the diagnostic wax-up

Determines ideal tooth position
Establishes incisal edge and occlusal plane
Assesses available restorative space
Guides aesthetic evaluation
Assists in evaluating lip support and phonetics
Helps determine implant number and distribution
Provides the basis for a radiographic and surgical guide
Allows patient communication and informed consent

For an anterior tooth, a diagnostic wax-up helps define:

Incisal edge level
Labial prominence
Midline
Tooth width and length
Gingival zenith
Papillae and contact point location

A provisional restoration is often used to condition peri-implant soft tissue and develop the desired emergence profile.

4.4 Three-Dimensional Implant Positioning

Correct three-dimensional placement is central to successful implant prosthodontics. It involves the implant’s mesiodistal, faciolingual and apicocoronal position, as well as its angulation.

A. Mesiodistal position

The implant should be placed with adequate distance from adjacent natural teeth and implants.

General clinical guidelines commonly used are:

Approximately 1.5 mm or more between an implant and an adjacent tooth
Approximately 3 mm or more between two adjacent implants

This spacing helps preserve interproximal bone and supports papilla formation. The actual position should always be dictated by anatomy, implant diameter, prosthetic design and the planned emergence profile.

Poor mesiodistal placement may lead to:

Loss of papilla
Black triangles
Difficulty in cleaning
Overcontoured crowns
Compromised contact areas
Inadequate restorative material thickness

B. Faciolingual position

The implant should ideally emerge through the centre of the planned crown. In posterior teeth, the implant should generally be aligned with the central fossa or functional cusp zone to transmit forces along the implant’s long axis.

In the aesthetic zone, a facially placed implant can result in:

Thin facial bone
Gingival recession
Grey shine-through of titanium
Long clinical crown
Unfavourable emergence profile
Poor aesthetic outcome

An excessively palatal implant may cause:

Palatal screw access
Bulky restoration
Poor emergence profile
Difficult hygiene
Excessive cantilever from implant axis to facial crown contour

C. Apicocoronal position

Vertical placement affects:

Emergence profile
Crown height
Soft tissue contour
Ability to mask the implant-abutment junction
Screw-access position
Cleansability

A very shallow implant may compromise aesthetics and produce a short, bulky emergence profile. An excessively deep implant can create a deep restoration margin, difficult cement removal, difficult hygiene and increased risk of peri-implant inflammation.

D. Implant angulation

The implant should be positioned as close as possible to the long axis of the planned restoration. Excessive angulation results in off-axis loading and may cause:

Screw loosening
Abutment or prosthetic screw fracture
Porcelain fracture
Increased bending moment
Unfavourable screw-access channel
Need for angled abutments or bulky restorations

In immediate implant placement in the maxillary aesthetic zone, a surgical or computer-guided template and preplanned provisional are recommended to achieve an optimal restoration-driven three-dimensional position. ITI immediate implant consensus

4.5 Bone and Soft-Tissue Considerations

A. Bone quantity and quality

Implant planning requires assessment of:

Ridge height
Ridge width
Ridge angulation
Bone density and quality
Presence of defects
Relation to adjacent roots
Relation to maxillary sinus, nasal cavity, inferior alveolar canal and mental foramen

Cone-beam computed tomography is useful for evaluating three-dimensional bone anatomy and avoiding vital structures. However, radiographic planning must be combined with clinical examination and prosthetic planning.

B. Facial bone and aesthetic zone

The facial bone plate is important for aesthetic stability. A thin facial plate and facial implant placement increase the risk of soft-tissue recession and loss of contour.

Treatment planning should aim to preserve or reconstruct:

Facial bone volume
Papillae
Keratinized mucosa when needed
Gingival scallop
Soft-tissue thickness and emergence contour

C. Soft-tissue phenotype

A thin soft-tissue phenotype is more prone to recession and implant show-through. A thick phenotype generally offers better masking and tissue stability, although it does not compensate for incorrect implant placement.

The prosthesis must support, not compress, the peri-implant mucosa. Overcontoured subgingival restoration may impair plaque removal and promote inflammation.

4.6 Biomechanical and Occlusal Principles

Osseointegrated implants are rigidly attached to bone and lack a periodontal ligament. Therefore, they do not have the shock absorption and tactile feedback of natural teeth.

Biomechanical objectives

Direct forces along the long axis of implants
Reduce lateral forces and bending moments
Avoid excessive cantilevers
Provide sufficient implant number and distribution
Use adequate implant diameter where indicated
Provide proper occlusal contacts
Protect implants in patients with bruxism

Implant-protected occlusion

The concept of implant-protected occlusion aims to reduce overload by controlling force magnitude, direction and distribution.

Important measures include:

Axial loading whenever possible
Reduced cusp inclination in posterior restorations
Narrower occlusal table when indicated
Avoidance of broad flat contacts that produce lateral forces
Elimination of non-working side interferences
Light centric contacts, especially in single implant crowns
Reduced occlusal contacts on implant restorations in heavy parafunction
Minimization of cantilever length
Night guard in selected bruxers

Cantilever

A cantilever magnifies force at the implant-bone interface and at prosthetic components. Its effect depends on:

Length of cantilever
Occlusal force
Arch location
Implant number and distribution
Bone quality
Opposing dentition
Presence of parafunction

Posterior cantilevers should be minimized, especially in full-arch implant-supported fixed prostheses.

4.7 Selection of Implant Number, Size and Distribution

The number and distribution of implants should be determined by the planned prosthesis and loading requirements, not simply by the number of missing teeth.

Factors affecting implant selection

Mesiodistal space
Bone width and height
Prosthetic tooth size
Occlusal load
Arch position
Presence of parafunction
Need for a fixed versus removable prosthesis
Crown-to-implant ratio
Aesthetic demand
Bone quality

Implant distribution

A broad anteroposterior spread improves force distribution in full-arch restorations and reduces cantilever forces. Implants should be strategically positioned to support the planned prosthesis.

For example:

A single missing tooth may be restored with one implant and crown.
Multiple missing teeth may require several implants or an implant-supported fixed partial denture.
The edentulous mandible may be restored with two implants supporting an overdenture or with multiple implants supporting a fixed prosthesis.
The edentulous maxilla often requires more implants or a different design because of poorer bone quality and greater functional demands.

4.8 Emergence Profile, Abutment and Retention Design

A. Emergence profile

The emergence profile is the contour of the restoration as it emerges from the peri-implant mucosa.

An ideal emergence profile should be:

Gradual
Convex but not overcontoured
Aesthetic
Cleansable
Compatible with soft-tissue thickness
Supportive of papillae and gingival contour

Overcontouring increases plaque accumulation and makes oral hygiene difficult. Undercontouring may compromise aesthetics and food deflection.

B. Abutment selection

Abutment selection depends on:

Implant angulation
Soft-tissue height
Interarch space
Aesthetic zone requirements
Need for screw retention
Material selection
Emergence profile
Retrievability

Custom abutments may improve emergence profile and margin placement in selected situations. Angulated screw-channel systems may allow screw retention where implant angulation is slightly unfavourable.

C. Screw-retained versus cement-retained restorations

Screw-retained restorations

Advantages:

Retrievable
No risk of residual cement
Easier repair and maintenance
Useful for immediate provisionalization
Preferred when long-term maintenance is anticipated

Disadvantages:

Screw-access opening may affect aesthetics or occlusion
Technique-sensitive
Requires appropriate implant angulation

Cement-retained restorations

Advantages:

May improve aesthetics where screw access is unfavourable
Can compensate for minor implant angulation
Familiar clinical technique

Disadvantages:

Risk of residual cement
Retrieval may be difficult
Deep margins make cement removal and hygiene difficult

Whenever cement is used, the margin should be accessible and cement should be meticulously removed. Prosthetic design should favour maintenance and peri-implant health.

4.9 Digital Planning and Surgical Guides

Digital implant planning combines:

CBCT data
Intraoral scan or digitized cast
Diagnostic wax-up
Virtual tooth arrangement
Virtual implant placement
Surgical-guide design
Provisional restoration design

This permits planning of implant position based on the future restoration while simultaneously assessing bone availability and anatomical limitations.

Advantages

Improved visualization of anatomy
Prosthetically directed virtual implant planning
Greater precision in difficult sites
Better patient communication
Facilitation of immediate provisionalization
Ability to fabricate static surgical guides

Limitations

Guided surgery is not error-free. Errors may arise from:

Inaccurate CBCT scan
Inaccurate scan matching
Errors in impression or intraoral scan
Guide fabrication defects
Poor guide seating
Sleeve tolerance
Drill deviation
Limited mouth opening
Intraoperative movement of the guide

Therefore, the clinician must verify guide fit clinically and be prepared to modify the procedure if the clinical situation differs from the plan.

4.10 Maintenance-Oriented Prosthetic Design

The restoration should permit both professional and patient-performed plaque control.

A maintenance-friendly implant prosthesis should have:

Cleansable embrasures
Accessible interproximal areas
Smooth polished surfaces
No excessive tissue pressure
Adequate space for interdental brushes, floss or water irrigation devices
Accessible screw channels when possible
Retrievability for repair and periodic assessment
Clearly instructed hygiene methods

Poorly designed prostheses can create plaque-retentive areas and contribute to mucositis and peri-implantitis. Recent consensus-based literature emphasizes that prosthetic configuration should allow self-performed hygiene and that correct prosthetically driven 3D implant positioning helps prevent peri-implant complications. SEPA expert consensus summary

5. Consequences of Prosthetically Unfavourable Implant Placement

Implant osseointegration alone does not equal prosthetic success. An implant may be osseointegrated but still be a prosthetic failure if it is incorrectly positioned.

Unfavourable placement	Likely consequence
Too facial	Recession, thin facial tissue, grey shine-through, poor aesthetics
Too palatal/lingual	Bulky crown, poor emergence profile, palatal screw access, hygiene difficulty
Too mesial or distal	Loss of papilla, poor contact, black triangle, inadequate restorative space
Too shallow	Poor emergence profile, visible metal, aesthetic compromise
Too deep	Deep margin, cement retention, difficult hygiene and retrieval
Excessively angled	Off-axis loading, screw loosening, fracture, poor screw-access location
Inadequate implant spread	Cantilever and overload in full-arch prosthesis
Implant placed without restorative space assessment	Inadequate ceramic thickness, weak prosthesis, poor occlusion

Thus, “implant survival” must be differentiated from “prosthetic success.” A surviving implant with recurrent screw loosening, poor aesthetics, inaccessible hygiene or peri-implant inflammation cannot be considered an ideal treatment outcome.

6. Implant as the “Third Dentition”

The term third dentition refers to implant-supported replacement of lost teeth after the loss of primary and permanent dentitions.

First dentition

Deciduous or primary teeth
Temporary dentition
Important in speech, mastication, appearance and preservation of arch space

Second dentition

Permanent teeth
Natural dentition expected to serve through adulthood
Supported by periodontal ligament and alveolar bone

Third dentition

Implant-supported prosthetic rehabilitation replacing lost permanent teeth
May be a single crown, fixed partial denture, full-arch fixed dental prosthesis or implant overdenture
Restores function, appearance, speech and quality of life

The concept is valuable because it communicates that implants offer a further opportunity for oral rehabilitation. However, the phrase must not imply that implants are identical to natural teeth.

7. Natural Teeth versus Implant-Supported Dentition

Feature	Natural tooth	Osseointegrated implant
Attachment to bone	Periodontal ligament	Direct bone-to-implant contact through osseointegration
Mobility	Physiological mobility present	Minimal mobility
Shock absorption	Periodontal ligament dissipates force	No periodontal ligament shock absorption
Proprioception	High tactile sensitivity	Reduced tactile sensitivity
Blood supply	Periodontal ligament and surrounding tissues	Peri-implant soft tissues have comparatively different vascular arrangement
Response to overload	Mobility and adaptive periodontal response possible	Greater risk of mechanical and crestal bone complications if overload persists
Disease	Caries, gingivitis, periodontitis	Peri-implant mucositis and peri-implantitis
Repair potential	Natural biological healing and periodontal adaptation	Cannot regenerate periodontal ligament or enamel; requires prosthetic maintenance

Important implications

Implants do not erupt or orthodontically move like teeth.
Implants have reduced proprioception, so occlusal overload may not be sensed early by the patient.
Implants cannot develop caries, but peri-implant soft tissues remain susceptible to inflammation and bone loss.
Implants require lifelong maintenance, just as natural teeth require preventive care.
A natural tooth should not be extracted merely to place an implant when it has a predictable prognosis. Preservation of natural teeth remains the first priority of prosthodontic and periodontal care.

8. Clinical Significance

The concept of implant as a third dentition has changed the goals of prosthodontics.

A. Single-tooth replacement

An implant-supported crown can avoid preparation of adjacent healthy teeth and preserve the edentulous ridge. It is particularly valuable when the adjacent teeth are intact.

B. Partially edentulous patient

Implants can replace posterior missing teeth without a distal extension removable partial denture. They can also eliminate the need for long-span tooth-supported bridges in selected cases.

C. Completely edentulous patient

Implant overdentures improve retention, stability, chewing efficiency and patient satisfaction. Fixed full-arch implant prostheses can provide a more natural-feeling restoration in selected patients.

D. Psychological and social benefit

A stable implant prosthesis may improve:

Self-confidence
Speech
Social interaction
Comfort during eating
Perceived oral health-related quality of life

E. Requirement for continuing care

Third dentition is not a “fit and forget” treatment. Follow-up should include:

Plaque and bleeding assessment
Peri-implant probing when indicated and performed gently
Evaluation of suppuration, mobility and soft tissue
Radiographic assessment of crestal bone when clinically indicated
Occlusal evaluation
Assessment of screw loosening, fracture, wear and prosthesis fit
Reinforcement of home-care instructions

9. Conclusion

Prosthetically driven implantology is the foundation of predictable implant treatment. The implant must be placed according to the requirements of the final restoration in all three dimensions, while respecting anatomy, bone volume, soft tissue, aesthetics, occlusion and maintenance needs.

The correct sequence is not “place the implant and then make a crown.” It is:

Plan the final prosthesis, determine the ideal implant position, evaluate whether the anatomy permits it, and modify the site or prosthetic plan appropriately.

Dental implants represent a valuable third dentition, restoring missing teeth after loss of the natural permanent dentition. Yet, implants do not replicate all biological features of natural teeth. Their long-term success depends on prosthetically correct positioning, controlled occlusal loading, hygienic restoration design, patient compliance and lifelong supportive care.

10. References

Standard Prosthodontic and Implant Textbooks

Misch CE. Dental Implant Prosthetics. 2nd ed. St. Louis: Elsevier Mosby; 2015.
Zarb GA, Hobkirk J, Eckert SE, Jacob RF. Prosthodontic Treatment for Edentulous Patients: Complete Dentures and Implant-Supported Prostheses. 13th ed. St. Louis: Mosby Elsevier; 2013.
Buser D, Belser UC, Wismeijer D, eds. ITI Treatment Guide: Implant Therapy in the Esthetic Zone. Berlin: Quintessence Publishing.
Carl E. Misch. Contemporary Implant Dentistry. 3rd ed. St. Louis: Mosby Elsevier; 2008.
Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 5th ed. St. Louis: Elsevier; 2016.
Sadowsky SJ, ed. Evidence-Based Implant Treatment Planning and Clinical Protocols. Ames: Wiley-Blackwell; 2017.

Important Articles and Consensus Sources

Belser UC, Mericske-Stern R, Bernard JP, Taylor TD. Prosthetic management of the partially dentate patient with fixed implant restorations. Clinical Oral Implants Research. 2000;11(Suppl 1):126-145. PMID: 11168262.
Higginbottom F, Belser U, Jones JD, et al. Prosthetic management of implants in the esthetic zone. International Journal of Oral and Maxillofacial Implants. 2004;19(Suppl):62-72. PMID: 15635946.
Mericske-Stern R. Prosthetic considerations. Australian Dental Journal. 2008;53(Suppl 1):S49-S59. PMID: 18498586.
Katsoulis J, Pazera P, Mericske-Stern R. Prosthetically driven, computer-guided implant planning for the edentulous maxilla: a model study. Clinical Implant Dentistry and Related Research. 2009;11(3):238-245.
Tahmaseb A, Wu V, Wismeijer D, Coucke W, Evans C. The accuracy of static computer-aided implant surgery: a systematic review and meta-analysis. Clinical Oral Implants Research. 2018;29(Suppl 16):416-435.
Gowd MS, Shankar T, Ranjan R, Singh S. Prosthetic consideration in implant-supported prosthesis: a review of literature. Journal of International Society of Preventive and Community Dentistry. 2017;7(1):1-7. PMID: 28713760.

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Principles of Prosthetically Driven Implantology and Implant as the Third Dentition

Index of Contents

Introduction
Definition
Objectives
Principle of restoration-driven treatment planning
Preoperative assessment and diagnosis
Diagnostic wax-up, provisionalization and surgical template
Three-dimensional implant positioning
Hard- and soft-tissue principles
Prosthetic and biomechanical principles
Occlusal principles
Implant number, size, distribution and cantilever
Retention, abutment and emergence-profile design
Digital planning and guided implant surgery
Consequences of incorrect implant positioning
Implant as the third dentition
Natural dentition versus implant dentition
Maintenance and long-term follow-up
Conclusion
References

1. Introduction

Dental implants are an established method for restoring partially and completely edentulous patients. Osseointegration provides a stable foundation for a crown, fixed dental prosthesis, overdenture or full-arch restoration. However, implant survival alone is not the goal. A clinically successful implant must support a restoration that is aesthetic, functional, cleansable, mechanically stable and maintainable.

Modern implant therapy is based on the principle that the implant is placed to support the planned prosthesis. Therefore, the final restoration should be planned first and the implant should then be positioned accordingly. This is known as prosthetically driven implantology, restoration-driven implantology, or backward planning.

2. Definition

Prosthetically driven implantology is the placement of an implant in an ideal three-dimensional position determined by the requirements of the proposed definitive prosthesis, while respecting available bone, soft tissue and vital anatomical structures.

The sequence of treatment is:

Final prosthetic plan → ideal tooth position → ideal implant position → surgical plan.

Thus, implants should not be placed merely where bone is available. If the ideal implant position is not supported by sufficient bone, the clinician should consider augmentation, altered implant selection, changed prosthetic design, or an alternative treatment.

The ITI consensus material states that detailed pretreatment planning is required to establish a correct three-dimensional implant position relative to the planned restoration. ITI review on guided implant surgery

3. Objectives of Prosthetically Driven Implantology

The objectives are to:

Restore missing teeth in an ideal aesthetic and functional position.
Place implants in a position that permits proper crown contour and emergence profile.
Achieve favourable axial loading and reduce lateral forces.
Preserve peri-implant hard and soft tissues.
Facilitate oral hygiene and professional maintenance.
Minimize technical complications such as screw loosening, ceramic fracture and abutment fracture.
Obtain an acceptable occlusal scheme.
Provide a retrievable and repairable prosthesis.
Improve long-term implant and prosthesis success.

4. Principle of Restoration-Driven Treatment Planning

The restoration must be designed before implant placement. The clinician should determine:

Number and position of teeth to be replaced
Tooth width, length, shape and shade
Incisal edge position
Occlusal plane
Vertical dimension of occlusion
Interocclusal restorative space
Smile line and lip support
Gingival zenith and papillae
Type of definitive prosthesis
Crown contour and emergence profile
Screw-retained or cement-retained restoration
Occlusal contacts and opposing dentition

The desired final crown position dictates the required implant position. The implant should ideally emerge through the central portion of the planned crown and permit a restoration with adequate material thickness, normal contours and cleansability.

The following maxim should be remembered:

Do not make the crown fit an incorrectly placed implant. Place the implant to fit the planned crown.

5. Preoperative Assessment and Diagnosis

Thorough diagnosis is mandatory before implant treatment.

A. Medical evaluation

The clinician should assess:

Diabetes and its control
Smoking and tobacco use
Immunosuppression
Head and neck radiotherapy
Antiresorptive and antiangiogenic medications
Bleeding risk and anticoagulant therapy
History of periodontal disease
Bruxism and parafunction
Patient expectations and financial considerations
Ability and willingness to attend maintenance visits

B. Dental evaluation

The clinical examination should include:

Periodontal status of remaining teeth
Caries and endodontic status
Occlusal analysis
Interarch space
Ridge width, height and contour
Facial profile and lip support
Smile line
Adjacent tooth position and root angulation
Oral hygiene status
Existing prostheses and restorations
Temporomandibular joint and muscle evaluation

C. Radiographic examination

Radiographic assessment may include:

Periapical radiographs
Panoramic radiograph
Cone-beam computed tomography, when indicated

CBCT helps assess bone volume, ridge angulation, sinus position, inferior alveolar canal, mental foramen and root proximity. It should be interpreted in conjunction with the planned prosthesis, not in isolation.

6. Diagnostic Wax-up, Provisionalization and Surgical Template

A. Diagnostic wax-up

A diagnostic wax-up is a three-dimensional representation of the desired final restoration. It may be made conventionally on casts or digitally.

Uses of a diagnostic wax-up

Establishes tooth position and occlusal plane
Assesses available restorative space
Helps evaluate aesthetic outcome
Determines implant number and distribution
Assists in planning emergence profile
Facilitates patient communication
Forms the basis for radiographic and surgical guides
Identifies the need for bone or soft-tissue augmentation

B. Provisional restoration

A provisional restoration has several functions:

Maintains appearance and function during healing
Guides peri-implant soft-tissue healing
Develops the desired emergence profile
Assesses phonetics and aesthetics
Helps establish appropriate occlusion
Enables patient acceptance of the planned restoration

In the aesthetic zone, a properly contoured provisional crown can be used to shape the peri-implant mucosa gradually.

C. Surgical template

A surgical template transfers the planned restoration and implant position to the mouth. It may be:

Conventional acrylic template
Vacuum-formed template
Radiographic guide
CAD-CAM static surgical guide
Dynamic navigation-assisted guidance system

Templates help control implant position in the mesiodistal, faciolingual and apicocoronal dimensions. The ITI emphasizes that templates are an integral part of prosthetically driven implant placement. ITI guidance on surgical templates

7. Three-Dimensional Implant Positioning

Correct implant position must be assessed in three planes.

A. Mesiodistal position

The implant should be positioned to permit:

Adequate distance from adjacent tooth roots
Preservation of interproximal bone
Papilla support
Proper proximal contact areas
Cleansable embrasures
Appropriate crown width and contour

As a practical guide, an implant is generally kept approximately:

1.5 mm or more from an adjacent natural tooth
3 mm or more between adjacent implants

These are clinical guidelines, not substitutes for individualized planning.

Incorrect mesiodistal placement may lead to:

Loss of papilla
Black triangles
Improper contact point
Overcontoured crown
Difficulty in hygiene maintenance
Root damage to an adjacent tooth

B. Faciolingual or oropalatal position

The implant should emerge through the central part of the proposed crown. In posterior teeth, the implant should generally be placed beneath the central fossa or central load-bearing zone.

Implant placed too facially

This may cause:

Thin or absent facial bone
Gingival recession
Grey show-through of implant components
Long clinical crown
Poor soft-tissue aesthetics
Difficult restoration contour

Implant placed too palatally or lingually

This may cause:

Excessively bulky facial crown contour
Unfavourable screw access
Palatal or lingual overcontour
Food stagnation
Difficulty in cleaning
Non-axial loading

Correct orofacial positioning is especially important in the maxillary anterior aesthetic zone.

C. Apicocoronal position

The vertical position of the implant determines:

Crown height
Emergence profile
Gingival margin location
Ability to mask implant components
Access for cement removal
Cleansability
Screw-access position

Implant placed too coronally

Consequences include:

Poor emergence profile
Visible implant shoulder or metal
Insufficient space for soft tissue
Aesthetic compromise

Implant placed too apically

Consequences include:

Excessive crown height
Deep restoration margin
Difficulty in cement removal
Difficulty in maintaining hygiene
Increased risk of residual cement-related inflammation
Difficult access for repair or retrieval

D. Implant angulation

Ideally, the long axis of the implant should correspond closely with the long axis of the proposed restoration.

Excessive angulation may cause:

Off-axis loading
Increased bending moment
Screw loosening
Abutment fracture
Ceramic fracture
Unfavourable screw-access opening
Need for angled abutments
Overcontoured restoration

Correct three-dimensional implant position is considered essential for aesthetics and long-term peri-implant tissue stability. ITI consensus on esthetics

8. Hard- and Soft-Tissue Principles

A. Bone volume

The implant should be surrounded by sufficient bone for stability and long-term tissue support. Assessment should include:

Ridge height
Ridge width
Ridge angulation
Bone density
Presence of dehiscence or fenestration
Relationship to vital anatomical structures

Where bone is insufficient in the ideal prosthetic position, possible treatment options include:

Guided bone regeneration
Ridge split or ridge expansion
Block grafting
Sinus floor elevation
Short implants in selected cases
Tilted implants in selected full-arch cases
Alternative prosthesis design

B. Facial bone and aesthetic zone

The facial bone plate is important for soft-tissue contour. Excessively facial implant placement or inadequate facial bone volume increases the risk of recession and aesthetic failure.

C. Soft-tissue phenotype

A thick soft-tissue phenotype is generally more resistant to recession and can better mask underlying implant components. Nevertheless, thick tissue cannot compensate for poor implant position.

The restoration should support the peri-implant mucosa gently. It should not compress the tissue or have a bulky subgingival contour.

9. Prosthetic and Biomechanical Principles

An implant has direct bone contact and lacks a periodontal ligament. Therefore, it has limited shock absorption and reduced tactile sensitivity compared with a natural tooth.

The main biomechanical goals are:

Direct occlusal forces along the long axis of implants
Minimize lateral and oblique forces
Avoid excessive cantilever
Provide suitable implant number and distribution
Use suitable implant diameter and length where indicated
Maintain a favourable crown-to-implant relationship
Select appropriate prosthetic materials and framework design
Control parafunctional loading

Biomechanical consequences of poor planning

Poor implant position can create a non-axial crown-implant relationship. This increases bending stresses and may result in:

Screw loosening
Screw fracture
Abutment fracture
Framework fracture
Chipping or fracture of veneering ceramic
Crestal bone loss
Implant overload

A well-planned implant-supported restoration distributes forces predictably and reduces complications.

10. Occlusal Principles

The objective is to develop an implant-protected occlusion.

Principles

Direct forces along the implant long axis.
Reduce cusp inclination when excessive lateral loading is anticipated.
Reduce the occlusal table in selected posterior restorations.
Avoid non-working side interferences.
Minimize cantilever contacts.
Avoid excessive eccentric contacts on implant-supported crowns.
Consider lighter contacts in maximum intercuspation for a single implant crown, particularly adjacent to natural teeth.
Provide mutually protected or group-function occlusion according to the remaining dentition and clinical situation.
Use an occlusal splint in selected patients with bruxism.

Because implants lack periodontal proprioception, patients may not detect excessive forces as early as they might with natural teeth.

11. Implant Number, Size, Distribution and Cantilever

The number of implants is not necessarily equal to the number of missing teeth. Implant selection depends on:

Bone availability
Type of definitive prosthesis
Occlusal load
Opposing dentition
Arch location
Crown dimensions
Bone quality
Presence of parafunction
Aesthetic requirement
Need for fixed or removable rehabilitation

Implant distribution

A wide anteroposterior spread improves force distribution in full-arch restorations and reduces cantilever effect. Implants should be strategically distributed to support the planned prosthesis.

Cantilever

A cantilever acts as a lever and magnifies forces on the supporting implants and prosthetic components. Its influence is greater with:

Long cantilever length
High occlusal force
Poor bone quality
Few implants
Short anteroposterior implant spread
Bruxism
Opposing natural dentition

Therefore, cantilevers should be minimized, especially in fixed full-arch implant restorations.

12. Retention, Abutment and Emergence-Profile Design

A. Emergence profile

The emergence profile is the contour of the restoration from the implant platform through the peri-implant mucosa to the visible crown.

An ideal emergence profile should be:

Gradual
Aesthetic
Cleansable
Compatible with tissue thickness
Free of excessive pressure on the mucosa
Supportive of soft-tissue contour

An overcontoured restoration is plaque-retentive and makes hygiene difficult. An undercontoured restoration can compromise appearance and food deflection.

B. Abutment selection

Abutment selection depends on:

Implant angulation
Soft-tissue height
Available interocclusal space
Aesthetic requirements
Need for screw retention
Position of restoration margin
Emergence profile
Material requirement

Custom abutments may be useful where precise emergence profile or margin placement is required.

C. Screw-retained restoration

Advantages

Retrievable
No risk of residual cement
Easier repair and maintenance
Useful for immediate provisionalization
Favours long-term review

Disadvantages

Screw-access opening may affect aesthetics or occlusion
Requires reasonably favourable implant angulation
Technique-sensitive

D. Cement-retained restoration

Advantages

May provide better aesthetics where the screw channel would emerge facially
Can compensate for minor implant angulation problems
Familiar technique for many clinicians

Disadvantages

Risk of excess cement
Difficult retrievability
Deep margins are difficult to clean
Residual cement may contribute to peri-implant mucositis or peri-implantitis

Whenever possible, the restoration should be designed for retrievability and maintenance.

13. Digital Planning and Guided Implant Surgery

Digital workflow integrates:

CBCT data
Intraoral scanning or digitized study casts
Virtual diagnostic wax-up
Digital smile design where appropriate
Virtual implant placement
Surgical guide fabrication
CAD-CAM provisional and definitive restorations

Advantages

Improves visualization of anatomy
Permits restoration-driven virtual planning
Helps determine implant angulation and depth
Improves communication between surgeon, prosthodontist and laboratory
Facilitates immediate provisionalization in selected cases
Allows fabrication of static surgical templates

Limitations

Guided surgery does not eliminate errors. Deviations may occur due to:

Inaccurate imaging
Improper guide seating
Scan matching errors
Manufacturing tolerance
Sleeve and drill tolerance
Patient movement
Inadequate fixation of the guide
Limited mouth opening

Therefore, surgical guides should be verified clinically, and the clinician must understand their limitations.

14. Consequences of Incorrect Implant Positioning

Incorrect implant position	Consequences
Too facial	Recession, thin facial tissue, implant show-through, poor aesthetics
Too palatal/lingual	Bulky crown, poor emergence profile, poor hygiene access
Too shallow	Visible implant components, poor emergence profile
Too deep	Deep margin, residual cement, poor access and hygiene
Too mesial/distal	Loss of papilla, black triangle, poor proximal contour
Excessively angled	Non-axial loading, screw loosening, fracture, poor screw channel
Inadequate implant spread	Excess cantilever and mechanical overload
Poor restorative space	Weak prosthesis, inadequate material thickness, poor occlusion

An implant can remain osseointegrated yet be a prosthetic failure. Therefore, implant survival should not be confused with complete treatment success.

15. Implant as the Third Dentition

The term third dentition describes implant-supported replacement of teeth after the loss of the natural permanent dentition.

First dentition

Primary or deciduous teeth
Functions in mastication, speech, aesthetics and maintenance of arch space

Second dentition

Permanent natural teeth
Supported by periodontal ligament
Intended to serve throughout adult life

Third dentition

Implant-supported restorations replacing lost permanent teeth
May consist of a single crown, fixed dental prosthesis, implant overdenture or full-arch fixed prosthesis
Restores chewing, speech, appearance, comfort and confidence

The phrase is useful because implants offer a further opportunity for oral rehabilitation. However, it must not imply that an implant is biologically identical to a natural tooth.

16. Natural Dentition versus Implant Dentition

Feature	Natural tooth	Dental implant
Attachment	Periodontal ligament	Osseointegration
Mobility	Physiological mobility present	Very limited mobility
Shock absorption	Present due to periodontal ligament	Absent
Proprioception	Well developed	Reduced
Eruption and movement	Can erupt and move orthodontically	Does not erupt or orthodontically move
Disease	Caries, gingivitis, periodontitis	Peri-implant mucositis and peri-implantitis
Biological repair	Some adaptive capacity	No periodontal ligament regeneration
Maintenance	Home care and periodic review	Lifelong home care and periodic professional maintenance

Important points

Implants cannot develop dental caries, but they can develop peri-implant disease.
Implants do not have a periodontal ligament and are therefore less able to absorb occlusal forces.
Implants cannot undergo orthodontic movement like natural teeth.
A restorable natural tooth should generally be preserved rather than extracted merely to replace it with an implant.
Implant prostheses require lifelong maintenance.

17. Maintenance and Long-Term Follow-Up

Implant-supported restorations are not “fit-and-forget” treatments. Regular supportive implant care is essential.

At follow-up visits, assess:

Plaque and bleeding around implants
Soft-tissue inflammation
Suppuration
Probing depth and peri-implant tissue condition
Implant mobility
Occlusion and parafunctional wear
Screw loosening or prosthesis fracture
Prosthesis fit and retrievability
Radiographic crestal bone level when indicated
Patient’s home-care methods

The patient should be instructed in the use of:

Soft toothbrush
Interdental brushes
Implant floss or superfloss where appropriate
Water irrigation devices where suitable
Regular professional maintenance

Maintenance-friendly prosthesis design and good patient plaque control are key determinants of long-term peri-implant health.

18. Conclusion

Prosthetically driven implantology is the basis of predictable implant rehabilitation. The clinician should plan the definitive restoration first and use it to determine the ideal three-dimensional implant position. Surgical placement must be coordinated with prosthetic requirements, bone volume, soft tissue, occlusion, aesthetics and future maintenance.

The principle can be summarized as:

Plan the restoration first, place the implant second, and modify the site when required.

Implants represent a valuable third dentition for patients who have lost natural teeth. Nevertheless, they are not substitutes that equal natural teeth in every biological respect. Their success depends on appropriate case selection, restoration-driven planning, correct surgery, sound prosthetic design, controlled occlusion, plaque control and lifelong maintenance.

19. References

Standard Prosthodontic and Implant Textbooks

Misch CE. Dental Implant Prosthetics. 2nd ed. St. Louis: Elsevier Mosby; 2015.
Misch CE. Contemporary Implant Dentistry. 3rd ed. St. Louis: Mosby Elsevier; 2008.
Zarb GA, Hobkirk J, Eckert SE, Jacob RF. Prosthodontic Treatment for Edentulous Patients: Complete Dentures and Implant-Supported Prostheses. 13th ed. St. Louis: Mosby Elsevier; 2013.
Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 5th ed. St. Louis: Elsevier; 2016.
Buser D, Belser UC, Wismeijer D, eds. ITI Treatment Guide: Implant Therapy in the Esthetic Zone. Berlin: Quintessence Publishing.
Sadowsky SJ, ed. Evidence-Based Implant Treatment Planning and Clinical Protocols. Ames: Wiley-Blackwell; 2017.

Articles and Consensus Documents

Belser UC, Mericske-Stern R, Bernard JP, Taylor TD. Prosthetic management of the partially dentate patient with fixed implant restorations. Clinical Oral Implants Research. 2000;11(Suppl 1):126-145. PMID: 11168262.
Higginbottom F, Belser U, Jones JD, et al. Prosthetic management of implants in the esthetic zone. International Journal of Oral and Maxillofacial Implants. 2004;19(Suppl):62-72. PMID: 15635946.
Mericske-Stern R. Prosthetic considerations. Australian Dental Journal. 2008;53(Suppl 1):S49-S59. PMID: 18498586.
Katsoulis J, Pazera P, Mericske-Stern R. Prosthetically driven, computer-guided implant planning for the edentulous maxilla: a model study. Clinical Implant Dentistry and Related Research. 2009;11(3):238-245.
Tahmaseb A, Wu V, Wismeijer D, Coucke W, Evans C. The accuracy of static computer-aided implant surgery: a systematic review and meta-analysis. Clinical Oral Implants Research. 2018;29(Suppl 16):416-435.
Gowd MS, Shankar T, Ranjan R, Singh S. Prosthetic consideration in implant-supported prosthesis: a review of literature. Journal of International Society of Preventive and Community Dentistry. 2017;7(1):1-7. PMID: 28713760.

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