Regardless of the location or extent of treatment, the planning of implant therapy should always be prosthodontically driven. This ensures that the implant placement will serve the needs of the prostheses and will be compatible with the desired end result. With the aim of achieving an optimal outcome, the prosthodontic planning should include consideration of all relevant prosthodontic factors and an appropriate diagnostic work-up as the basis for the specific planning of implant prostheses and supporting implants.

After completing this ITI Academy Module, you should be able to discuss general prosthodontic planning considerations related to implant therapy, explain the benefits of a diagnostic prosthodontic work-up for implant placement, and outline the specific planning points for implant prostheses and their supporting implants.

Prosthodontic treatment planning is aimed at dental rehabilitation of the patient. The rehabilitation is based on the patient's functional and esthetic needs as required to preserve teeth or to replace them. With the goal of optimal oral health and long-term stability of the final treatment outcome, the patient's basic presenting conditions should be addressed before the prosthodontic planning is commenced. For example, the patient shown in this radiographic image presents with a number of problems and significant active disease. Whilst implant treatment may be part of this patient's rehabilitation, it should be regarded as the final treatment phase once all other aspects have been addressed by the comprehensive treatment plan.

As part of this comprehensive approach, the clinician should review the biological factors that will impact on treatment planning. Biological considerations include failing teeth for various reasons including caries, endodontic issues, trauma, fracture, or resorption as shown in this radiograph. Further biological issues include replacement of congenitally absent teeth as well as replacement of teeth and associated hard and soft tissues lost as a result of trauma or in connection with surgical interventions to correct skeletal deformities or to treat oral and maxillofacial pathology. In all of these situations, implants can provide prosthetic support and retention points that are independent of adjacent teeth. Another specific implant indication is the preservation of residual hard tissues in edentulous jaws where loaded implants preserve bone volume. In this clinical image, the two implants will serve to reduce pressure-induced atrophy in the anterior mandible associated with the prosthesis.

The prosthodontic plan may involve decisions regarding biological factors. These decisions should be made in consultation with the implant surgeon to ensure optimal patient management. Prosthodontic planning for failing teeth includes prescription of minimally traumatic extraction techniques to avoid undue loss of hard and soft tissue and selection of the appropriate time point for implant placement. The clinical situation will determine whether placement is best served by a Type 1 (immediate), Type 2 (early with soft tissue healing), Type 3 (bony infill), or Type 4 (healed site) approach.

Timing of placement in the younger patient needs additional consideration due to the potential for continued growth leading to relative infraocclusion of an implant prosthesis compared with adjacent natural teeth. For the older patient consideration should be given to the level of dexterity and motivation, and in general treatment planning should aim for simpler rather than complex solutions. In the case of congenitally absent teeth the available space for tooth replacement may be unsuitable and may require orthodontic treatment. The orthodontic therapy could also include correction of root angulation of adjacent teeth to allow safe implant placement.

Prosthodontic planning for implant placement should address the identified general prosthodontic indications for treatment as well as the specific indications for implant therapy. In many cases these indications will overlap, but for the purpose of this overview they will be divided into two categories: esthetic and functional. Scrutinizing implant indications in this manner will help to prompt specific planning considerations that should be factored into the prosthodontic implant plan. This also applies to any specific patient wishes and expectations that need to be considered. In this clinical example, the esthetic indication for replacing the maxillary central incisor may be combined with the patient's desire to address the crowded tooth positions and darker shade of the left central incisor. The suboptimal plaque control presents a further professional implant planning consideration.

Lost or already missing teeth give rise to esthetic indications. Missing hard and soft tissue volume and contours add to this concern. Whereas the esthetic implant indication in the left image is limited to replacement of the central incisor, the esthetic concern in the middle image includes both tooth replacement and the need for restoration of lip support. The specific implant indication for the single-tooth implant prosthesis on the left is a one-to-one replacement, whereas implant assistance for a full-arch prosthesis for the patient on the right will need to provide both support and retention for the combined esthetic replacement of teeth and hard and soft tissue volume and contours.

Esthetic planning considerations are closely related to visibility of the teeth to be replaced in the smile, which has implications for the number of teeth to be replaced. The visibility of teeth and surrounding soft tissue depends on the level of the lip line in the smile, known as the 'smile line'. The smile line is categorized as high, medium, or low. The left image demonstrates a high smile line with extensive visibility of teeth as well as soft tissues. The middle image shows a removable implant overdenture with visibility of interdental papillae and posterior teeth in relation to a medium smile line. The right image shows a low smile line with almost no visibility of the soft tissue. Even with a low smile line, however, it is clear that replacement of molar teeth could be indicated to meet esthetic demands in a broad smile.

If a patient with crowded teeth has any present or future desire to correct this condition, it is important to explore options for orthodontic treatment before any definitive implant placement is planned. Similarly, if a patient desires correction of excessive spacing this treatment should be discussed first. If the patient desires spacing to be preserved, multiple separate implant-supported prostheses may be indicated. The spacing may also dictate modification of adjacent teeth to improve the esthetic result. In the example shown here, the space for the left central incisor is wider than the right central incisor. The patient can accept a midline diastema or alternatively opt for additive contouring of the right central incisor to balance the respective widths and thereby close the diastema.

In the case of several missing teeth with no contralateral remaining teeth to guide selection of tooth dimensions and characteristics, some other means of reference is needed. For replacement of anterior teeth, older photographs from the patient's dentate past can be very helpful and can provide information about tooth arrangement as well. If a photograph is to be used as a guide to the original dimensions of the teeth, the patient should be facing forward and looking directly at the camera with a wide smile that displays the upper anterior teeth. The width of the original central incisors in real life can be calculated using the equation shown here. If the patient is facing forward and looking directly at the camera, the inter-pupillary distance can be measured in the photo. This distance does not change after the age of 20. By smiling and displaying the upper anterior teeth, the combined width of the two central incisors can be measured on the photo as well. The inter-pupillary distance is then measured in real life. The combined width of the original central incisors can then be calculated by entering the measurements into the equation. Finally, the combined width can be divided by 2 to obtain the width of an individual central incisor.

Older dental casts or extracted teeth are other very useful references for dimensions and characteristics of teeth to be replaced. In the age of digital dentistry, it is sensible to collect data on the patient's full dentition early in life so that this may be used for reference in the future.

However, in the absence of any other useful tooth reference, the literature reports average coronal tooth dimensions that can be taken into consideration, as shown in these tables. If the patient presents with abnormally small or large teeth compared to these reported normal values, width-to-length ratios can be used as a guide to tooth dimensions. For example, the upper central incisor normally has a width-to-length ratio of 0.8.

For planning the definitive esthetics of the implant prosthesis, the white esthetic outcome score can be helpful as well. The score assesses multiple tooth parameters including form, outline, volume, color, surface texture, translucency, and characterizations. These parameters are schematically superimposed on this clinical example. When removed, it can be seen that further attention is needed to mimic the contralateral tooth in terms of outline at the mucosal emergence and color.

The future contours and level of the peri-implant mucosa are another important aspect of planning. The modified pink esthetic outcome score can be used in this process. The score assesses various parameters in comparison to contralateral teeth, including the level of the papillae, curvature of the facial mucosa, level of the facial mucosa, and root convexity as well as soft tissue color and texture. The status of the adjacent teeth and their proximal bone levels are relevant to achieving this. The patient's periodontal phenotype and the underlying thickness and level of facial bone are also relevant. In this clinical example of an implant-supported tooth replacement for the upper right central incisor, the underlying bone ensures support for the mucosal papilla and mid-facial mucosal margin. However, loss of bone on the mesial aspect of the natural right lateral incisor has resulted in recession of the distal papilla in comparison to the contralateral papilla on the left. The periodontal phenotype seen here is classified as thick.

On the other hand, the phenotype in this clinical image is thin. There is a correlation between the phenotype and the thickness of the facial bone in the alveolar socket, with thin phenotypes tending to have thin facial bone in comparison to thick phenotypes. A thick phenotype generally poses lower esthetic risk since it is usually resistant to recession and can also mask the color of the implant and submucosal metallic components.

The functional indications for prosthodontic treatment are related to the number of teeth to be replaced to meet masticatory and phonetic needs as well as the overall occlusal stability of the dentition. In addition, it is important to prevent positional issues with adjacent and opposing teeth following tooth removal. These issues include supraeruption, tilting, and drifting, which can result in significant alterations to incisal and occlusal planes. It is worth noting that the majority of occlusal changes take place in the first 6 months following extraction. Where there could be risk of positional changes, transitional tooth replacement should always be considered as part of both general and implant-specific prosthodontic planning.

Where several teeth are missing the shortened dental arch concept should be considered. This concept has been proven over many decades of follow-up as adequate to fulfill both functional and esthetic needs and to satisfy oral health-related quality of life. The shortened dental arch is also proven to be more cost effective and to offer similar nutritional status to more extensive tooth replacement solutions. The typical shortened dental arch situation is seen in the left image with ten upper and ten lower teeth and two sets of premolar units in occlusion on each side. A variation is shown on the right with the same number of posterior occluding units; however, this configuration may not offer adequate esthetics.

Other functional considerations are the characteristics of the existing occlusal scheme. The presence of anterior guidance will reduce the risk of unfavorable lateral forces on the planned implant prosthesis. Conversely if the prosthesis forms part of the guidance, the functional demands will rise significantly as will the level of prosthodontic difficulty and risk. Finally, occlusal parafunction is an established risk factor for hardware complications of implant prostheses and their mechanical components, so a number of planning principles should be observed from the outset. These include consideration of splinted prostheses, a retrievable design for repairs, nighttime protection with splints, and avoidance of risky measures such as immediate functional loading of the prosthesis.

Prosthodontic Planning Considerations, Key Learning Points: Prosthodontic planning is based on fulfilling esthetic and functional needs. Biological considerations impact on extraction techniques and timing of implant placement. Esthetic considerations should address missing teeth and soft tissues as well as loss of lip and facial support. The smile line impacts on the number of teeth to be replaced. Correction of crowding and spacing should be considered prior to planning of implant placement. Various strategies can be used to determine the dimensions of missing teeth. Pink and white esthetic outcome scores and the periodontal phenotype aid in planning the definitive esthetics of an implant prosthesis. Functional considerations include prevention of tooth positional issues and unfavorable occlusal forces on the prosthesis.

The purpose of a diagnostic work-up for implant placement is to determine the desired definitive prosthodontic outcome. In turn this will establish a prosthodontically driven plan to guide further surgical requirements such as bone augmentation procedures. It will also disclose the need for additional procedures or a multidisciplinary approach such as preparatory orthodontics to create space for the prosthodontic replacement.

The diagnostic work-up to determine a definitive prosthodontic outcome starts with an evaluation of the prosthodontic space. The prosthodontic space represents the teeth and missing hard and soft tissues to be replaced. The features and dimensions of each given prosthodontic space are unique and are influenced by variations in the features that border the space such as adjacent and opposing tooth positions, contours, and gingival levels as well as the residual ridge morphology.

The first step in evaluation of the prosthodontic space is to ascertain whether there is space for the planned number of teeth. The next step is to determine the need for replacing missing hard and soft tissue volume and whether a diagnostic set-up or wax-up is required to assess and finalize the replacement of teeth and tissues. The denture teeth and wax flange in the right image demonstrate the details of a diagnostic set-up with carefully matched tooth shades and moulds as well as imitation and contouring of the replacement soft tissues to assess missing volume.

Diagnostic set-ups and wax-ups offer three-dimensional visualization of the prosthodontic outcome in terms of definitive tooth positions and extent of missing hard and soft tissue contours. They also allow assessment of esthetic and functional aspects and details, and they help to identify further prosthodontic and surgical measures needed to achieve the desired outcome. In the example seen here, the desired esthetic outcome requires specific positioning of the maxillary left central and lateral incisors as well as replacement of the missing associated hard and soft tissue volume and contour.

Diagnostic set-ups and wax-ups also offer the possibility of exploring different options for achieving the desired esthetics and function. In this clinical case, the set-up of three posterior teeth demonstrates the need for elongated necks in keeping with the morphology of the adjacent natural canine. It also demonstrates the need for occlusal modifications as a reflection of the morphology of the mandibular posterior teeth. In a different clinical case, the scope for replacing the existing partial removable dental prostheses, or RDP, with a fixed dental prostheses is confirmed by trying in a diagnostic wax-up, which is shown to offer an acceptable basis for future esthetics.

Diagnostic set-ups and wax-ups are important communication tools. In this clinical example the patient desires replacement of the maxillary right central incisor as well as a more harmonious appearance of the upper incisors overall. The additive wax-up can be transferred for try-in via a vacuum-formed template and use of a temporary prosthesis material. The cast also demonstrates the importance of maintaining the gingival architecture and alveolar process contour for the esthetic harmony of the upper central incisor site. This is an important aspect to address in the planning of the surgical transition from natural tooth to implant-supported prosthesis. The wax-up of this mandibular first molar replacement has a hygienic design with straight, tapered sides and a deliberate mesial space for interproximal hygiene access. Both the try-in of the esthetic proposal and the explanation of the hygienic wax-up allow the patient to assess and give input. Diagnostic set-ups also allow the patient to give informed consent based on realistic expectations of the outcome.

The importance of a realistic set-up for try-in of the planned outcome increases in proportion to the scale of the replacement. When several teeth are to be replaced, testing of proper lip and facial support and visibility when smiling and confirmation of correct tooth positioning for phonetics are essential elements in a prosthodontically driven plan for implant placement. A diagnostic set-up may also become the determining factor in a choice between fixed and removable prostheses. The set-up for the complete dental prosthesis in the top image clearly demonstrates the discrepancy between the residual alveolar ridge and the required tooth position. A removable implant overdenture design will serve this situation better than a fixed dental prosthesis.

The decision between a fixed and removable prosthesis is influenced by the extent of missing hard and soft tissue structures. This is demonstrated in a sequence of schematic illustrations. The first illustration shows a cross section of the anterior maxilla with a natural incisor supporting the upper lip. In the second illustration the tooth has been removed, but the coronal tooth portion is superimposed relative to the volume and contour of the remaining hard and soft tissue at the tooth site. As the relationship of the appropriate coronal position to the underlying hard and soft tissue remains unchanged, an implant-supported fixed dental prosthesis or FDP can be provided without additional procedures. This image depicts a situation in which there is some loss of hard and soft tissue volume from the buccal aspect, and a discrepancy can be seen relative to the white coronal portion. Adjunct augmentation will be required in order to place an implant in a prosthodontically determined position.

In some instances there may be a significant discrepancy between the original position of the coronal tooth portion and the remaining hard and soft tissues. An FDP will require substantial augmentation whereas an implant-supported removable dental prosthesis or RDP will readily compensate for the missing structures through the prosthesis base and flange, thereby avoiding augmentation. An RDP will also allow the implant to be placed in the residual bone.

Once the diagnostic set-up or wax-up has been completed, it can be carried forward into further diagnostic and planning steps for implant placement. For example, the diagnostic set-up can be converted into a radiographic template for three-dimensional imaging. The template shown here has radiopaque teeth that are visible in the cone beam CT images. This allows visualization of the desired definitive tooth positions in relation to the underlying hard tissues. In these cone beam CT images an implant has been superimposed in the prosthodontically determined position, demonstrating the need for hard tissue augmentation on the facial aspect.

The radiographic template can then be converted to a surgical template with prosthodontically determined holes to guide the drill during the osteotomy preparation of the implant site. Surgical templates can also be produced directly from the diagnostic set-up or wax-up if there is no need for the additional step of three-dimensional imaging. Surgical templates come in a variety of designs, but their common aim is to facilitate accurate, prosthodontically determined implant placement. Templates should therefore be designed to ensure precise seating on adjacent teeth or soft tissues whilst also offering good visibility and easy drill access. Detailed information on diagnostic wax-ups and radiographic and surgical templates is available in the Learning Module titled 'Additional Diagnostic Investigations'.

Diagnostic Work-up, Key Learning Points: Prosthodontically driven implant placement depends on the desired definitive prosthodontic outcome. Diagnostic wax-ups or set-ups are useful in assessing the replacement of missing teeth as well as missing hard and soft tissues. Diagnostic wax-ups or set-ups help to establish the desired esthetics and function, and they allow for patient input in the decision-making process. They can clarify the need for a removable prosthesis when a fixed prosthesis would require substantial bone augmentation. Diagnostic work-ups can be converted into radiographic and surgical templates to ensure accurate, prosthodontically determined implant placement.

As mentioned in the first Learning Objective, the patient's basic presenting conditions should be addressed prior to prosthodontic planning for implant placement. To be ready for treatment, the patient's acute concerns, symptomatic conditions, and active disease must be appropriately managed first. Etiological factors should be identified and addressed, and the general oral and dental health should be proven stable over a suitable period of time. Three other Learning Modules, 'Patient Social Factors', 'Patient Medical Factors', and 'Patient Dental Factors', provide guidance on evaluating a patient's readiness for treatment.

The other prerequisite to planning of implant prostheses is a thorough, structured assessment that forms the basis for an agreed-upon treatment plan and informed patient consent. The structured assessment should include a comprehensive anamnesis and clinical examination together with any appropriate additional diagnostic investigations. The structured assessment should also lead to determination of case complexity and identification of treatment-modifying factors and risks. The agreed treatment plan should be based on considerations of the dentition as a whole and explain both the general prosthodontic indications and the specific implant indications together with prognosis for the outcome. To ensure informed patient consent the treatment plan must state the intended benefits and possible risks of the treatment and the risks of not undertaking related treatment. The treatment plan should be presented in a clear and neutral manner and, finally, should include discussion of all appropriate treatment options. These prerequisite aspects are covered in more detail in other dedicated ITI Academy Modules, in particular, 'Structured Assessment and Treatment Planning' and 'Treatment Options, Prognosis and Proposal'.

Prosthodontic planning and diagnostic work-up may reveal the need for specific treatment steps. For example, a transitional prosthodontic solution may be needed to replace teeth that are to be extracted or are already missing. Where teeth have been missing for some time, transitional prostheses may serve as diagnostic measures to test tolerance and acceptance of the proposed treatment. An example is seen in this image of a transitional removable dental appliance that is acting as a diagnostic prosthesis. A patient may require provisional rehabilitation to test the prosthodontic parameters identified by the prosthodontic planning and diagnostic work-up. There may also be a need for multidisciplinary input to optimize the prospective implant treatment site.

If the treatment plan involves extraction of teeth, the timing of these extractions should be considered as part of the prosthodontically driven planning. The timing is relevant to the subsequent timing of implant placement. As discussed in the first Learning Objective, there are four recognized types of placement and, depending on the circumstances of each case, one of these may offer specific advantages over the others. It is therefore important to consider this point in the sequencing and timing of the treatment, in conjunction with the implant surgeon. Similarly there are three recognized protocols for functional loading of implant prostheses following placement. These are referred to as immediate (within 1 week of implant placement), early (between 1 and 8 weeks), and conventional loading (after 8 or more weeks). The preferred protocol will have a bearing on the specific prosthesis and implant planning that follows. These topics are covered in detail in the Learning Modules titled 'Timing of Implant Placement After Tooth Extraction' and 'Loading Protocols'.

The prosthodontic plan may indicate a need for a provisional implant-supported prosthesis. A common indication is testing of the prosthodontic parameters of esthetics and function - including occlusal design - before the definitive prosthesis is constructed. Another indication is to observe peri-implant health and the patient's ability to maintain adequate oral hygiene for daily removal of biofilm. Provisional implant prostheses are also indicated for peri-implant soft tissue management to develop optimal mucosal emergence and architecture for the definitive prosthesis.

The decision of whether to opt for a fixed or removable prosthesis was discussed in the previous Learning Objective. This decision is usually determined by the number of missing teeth and extent of missing hard and soft tissue volume to be replaced. This choice is also affected by esthetic, functional, and biological considerations such as facial support, speech, and access for cleaning. The design is further affected by the selection of single-unit or multi-unit fixed dental prostheses in short and extended spaces or one-piece or segmented prostheses for full-arch reconstructions.

The choice of retention for fixed dental prostheses is usually limited to screw retained or cemented, whereas removable dental prostheses have several different retention options. Discussion should include the prosthesis material and method of manufacture, including CAD/CAM options, as well as the need for a pink component.

The abutment selection is determined by the planned prosthesis and its type of retention. This general rule applies to both fixed and removable dental prostheses as shown in these two clinical images. The need for anti-rotation will impact abutment selection for single-unit prostheses, cemented multi-unit prostheses, and full-arch one-piece prostheses. A further factor is the scope for flexibility of the prosthodontic platform on the abutment, which guides the choice of a custom abutment rather than a standard prefabricated abutment. Finally, selection of abutment material is guided by esthetic and functional demands based on the prosthesis type, anterior or posterior location, and need for strength in the presence of, for example, parafunction.

The configuration of implants should be prosthodontically driven by the diagnostic work-up together with the planned type of prosthesis and corresponding planned abutment. These parameters will determine the type, number, positions, and dimensions of the implant or implants to be placed. In the correct implant position, the axis of the implant should be such that it emerges through the cingulum of the planned anterior prosthesis and the central fossa of a posterior prosthesis. There are also specific principles for spacing between implants and teeth and between adjacent implants. Recommended minimum spacing in the mesiodistal dimension as shown in this schematic is 1.5 millimeters between implants and teeth and 3 millimeters between adjacent implants. Further information on this topic can be found in the Learning Module titled 'Implant Configurations for Fixed Dental Prostheses'.

Specific Planning Points, Key Learning Points: Prosthodontic planning must be preceded by a comprehensive assessment and clinical examination and treatment of the patient's basic presenting conditions. Transitional or provisional prostheses may be needed for further diagnosis or to provide soft tissue management. Timing of extractions, implant placement, and implant loading are interdependent and relevant to the overall planning. Prosthesis design factors include fixed or removable, type of retention, and abutment selection. The prosthesis design and abutment selection are two of the factors that dictate the selection and configuration of implants.

Prosthodontic Planning Principles for Implant Placement, Module Summary: Implant planning should be prosthodontically driven to ensure that implant placement is compatible with a desired end result that fulfills esthetic and functional needs. Missing teeth and soft tissues and the resulting loss of lip and facial support are esthetic considerations in implant planning. In addition to determining the number and position of teeth to be replaced, the pink and white esthetic scores and periodontal phenotype should be used in planning the esthetics of the implant prosthesis. Tooth positional issues and unfavorable occlusal forces on the prosthesis are functional considerations in implant planning.

Diagnostic wax-ups are useful in establishing the desired esthetics and function of the implant prosthesis, and they allow the patient to play a greater role in the treatment-planning process. Diagnostic wax-ups can be converted into radiographic and surgical templates to ensure precise, prosthodontically determined implant placement. Implant planning further includes consideration of transitional or provisional prostheses; timing of extractions and implant placement and loading; and overall prosthesis design and abutment selection. The prosthesis design and abutments are key factors in determining the selection and configuration of implants.