Implant dentistry has evolved considerably since early treatment protocols in which the positioning of implants was not considered critical to a successful outcome. In this surgically driven approach, implants were placed where there was sufficient bone to support them, and the emphasis was on the functional outcome. This clinical image shows three adjacent implants supporting single crowns. These provided the patient with a good functional outcome, but esthetics at the level of the implant emergence was only a secondary consideration. In modern implant dentistry, the overall esthetic result is of equal or greater importance to the patient. Esthetic results are closely related to a high level of accuracy in the positioning of the supporting dental implants. A second clinical image shows an example of an implant-supported single crown on the upper left central incisor where careful implant positioning has allowed the emergence profile to mimic that of the natural right central incisor. Templates to guide accurate three-dimensional implant placement are critical to achieving such an outcome. This ITI Learning Module will discuss routine use of templates in implant therapy.

Templates assist with implant site assessment, planning, and placement. They represent the desired three-dimensional positioning and features of teeth on the proposed prosthesis. When inserted into the mouth, they relate the desired tooth positions to the intended implant sites. In this manner, they indicate any areas where hard or soft tissue augmentation will be needed. These templates are made to be worn in the patients mouth during certain phases of treatment. One of these stages is the surgical assessment of the implant site. In this clinical image, a template with radiopaque teeth shows the planned positions and outlines of the teeth on the proposed prosthesis. It also demonstrates the extent of missing hard and soft tissue contours that will need to be replaced by grafting during surgery. The template thereby serves as a visual reference for the surgeon to guide augmentation procedures during surgery. Because the teeth are radiopaque, the template is also worn during radiographic assessment of the bone at the proposed implant sites. A surgical template is then used to guide the surgeon during the implant placement procedure, ensuring correct three-dimensional implant positioning and angulation that is consistent with the prosthodontic plan. This clinical image shows a surgical template being used during implant placement. The template restricts the position and angulation of the implant drills to ensure that the implant position is appropriate for the planned crown.

Achieving optimal outcomes in implant dentistry, such as this implant-supported crown replacing the upper left central incisor, requires both meticulous planning and a high level of skill in executing the treatment plan. In this case, an excellent esthetic result is ensured by the accurate placement of the implant in a position to allow natural emergence of the crown. The planning process always starts by defining the prosthodontic needs of the case, that is, the number of teeth that need to be replaced, and where those teeth must be positioned to achieve the best outcomes in esthetics, function, and phonetics. The plan also has to consider what forces the prosthesis will have to manage, and what means will be used to retain the prosthesis to the supporting implants.

Templates transfer a copy of the planned prosthodontic outcome to the patient's mouth to facilitate surgical assessment and planning and to provide guidance to the surgeon on correct implant placement. This ensures that implant positioning is driven by the overall prosthodontic plan and also ensures that implants are placed in the correct three-dimensional positions. These images demonstrate the safety and danger zones for implant positioning in the orofacial, mesiodistal, and apicocoronal dimensions. The green zones indicate safe positions for implant placement. Implant placements that err into the red zones are more likely to have complications.

Incorrect implant placement can lead to problems with esthetics or function. For example, placing implants too close to other implants or to adjacent teeth can lead to loss of the interdental papilla. Placing implants too far to the facial often results in recession, as shown in this clinical example. Here, a patient with a high smile shows the implant collars, which have become exposed due to recession. This issue was identified by Evans and Chen in their paper in 2008. A more serious outcome can result when the implant impinges onto adjacent structures. This radiograph shows a clinical situation where implant placement has resulted in the loss of vitality of an adjacent tooth. In both of these cases, the complications could have been avoided by using carefully planned and well-made templates.

When the patient wears a radiographic template during a computed tomography or cone-beam CT scan, the resulting images allow the surgeon to assess the bone volume available for implant placement and to determine whether grafting will be needed to allow placement of an appropriate implant. In this clinical case, implant-supported crowns are planned to replace the missing lower left second premolar and first and second molars. A diagnostic set-up has determined the necessary tooth positions, and this has been converted into a radiographic template with radiopaque teeth so that the outlines of the planned teeth are visible on radiographs. Channels prepared within each radiopaque tooth show the planned axial inclination of the implants. Reformatted CBCT images show the situation at the first molar site. The axial positioning of the planned implant can be determined from the outline of the channel in the radiopaque tooth. A scaled overlay of the proposed implant, in this site a wide diameter one-piece implant with an endosseous length of 10 millimeters, shows that it can be safely placed in this position, avoiding the inferior alveolar nerve while at the same time achieving an acceptable emergence profile.

Where possible, screw-retained crowns are preferred over cemented crowns because they are readily removable for maintenance or repair, and they avoid the complications that can accompany the use of cement. The potential for use of a screw-retained prosthesis is determined, to some degree, by the underlying bone anatomy. In this case, superimposing an implant onto the image shows that it can be placed with an axial inclination that is compatible with a screw-retained crown without the need for significant bone grafting at the time of implant surgery.

Imaging using a radiographic template can assist in assessing the emergence profile of the implant-supported crown. In this example, the ideal contours of the planned prosthesis have been reproduced in radiopaque material and incorporated into the template worn by the patient during the CT scan. The reformatted image demonstrates the relationship of the emergence profile of the planned crown to the underlying bone and soft tissues. It should be noted that one of the limitations of CBCT imaging is the poor soft tissue contrast compared to CT images; since CBCT imaging does not demonstrate the soft tissue volume well, CT imaging is therefore more useful in this regard.

Because radiographic templates are used to visualize the relationship between the proposed prosthesis and the underlying bone anatomy, they can be useful when deciding whether to plan for a fixed or removable prosthesis. In this reformatted CT image, a radiographic marker shows the desired axial position of the implant. An implant outline has been superimposed to assess the available bone dimensions. Diagrammatically, this patient presents with a favorable relationship between the planned tooth position and the underlying bone, allowing the straightforward placement of an implant without the need for bone augmentation.

In another situation, the reformatted CT image shows that the desired axial inclination of the implant is positioned facial to the native bone. A diagrammatic representation of this situation shows the planned tooth position to be well facial of the available bone. A fixed prosthesis will require significant bone augmentation that may require the use of an extraoral donor site, with an associated increased risk of morbidity. Alternatively, a removable prosthesis with a flange may serve as a simpler solution while still maintaining the lip support needed in this case.

Radiographic templates can be transitioned into surgical templates. In this image of a radiographic template for an edentulous patient, their mandibular prosthesis has been duplicated in clear acrylic, and channels have been prepared to indicate the desired implant positions and axial inclinations. These channels can then be filled with a radiopaque material - in this case gutta percha - to make them visible on radiographs. Once the implant positions and angulations have been confirmed, the gutta percha can be removed. The channels are then adapted to guide the surgical placement of the implants.

Surgical templates may be either prescriptive or indicative. Prescriptive templates define the position of implant placement very precisely in all three dimensions and do not allow for any significant modification of the plan. Prior to use, it is therefore important to verify that the template prescribes the exact desired three-dimensional positioning. In this clinical example, a missing molar is planned for replacement with an implant-supported crown. The diagnostic wax-up shows the desired dimensions and outline of the crown. These features are duplicated in a clear acrylic surgical template with a guiding channel that restricts the surgeon to the precise position and angulation dictated by the prosthodontic plan. This results in the final placement of the implant in an optimal position for the planned prosthesis.

Alternatively, the surgical template may be indicative. These templates merely indicate the planned tooth positions, allowing the surgeon to select the best sites based on intraoperative findings. This allows for some modification of the plan during surgery. Mostly, an indicative template tells the surgeon where implants cannot be placed, rather than stipulating their exact positions. Indicative templates have a greater risk of incorrect implant placement and, as such, should only be used by experienced implant surgeons. The template shown here only prevents the surgeon from placing implants that would have undesirable angulations that might result in screw access holes penetrating through the facial aspect of the prosthesis. Virtually all other sites and angulations are allowable although, as a general rule, evenly spaced and parallel implants are desired.

Role of Templates, Key Learning Points: Templates transfer the planned prosthodontic outcome to the patient's mouth, ensuring the correct 3D implant placement. Radiographic templates allow the surgeon to assess available bone and to determine the need for augmentation procedures during or prior to implant placement. Radiographic templates assist prosthetic planning by indicating both the most suitable type of prosthesis as well as the potential for screw retention. Prescriptive surgical templates limit implant placement to a precisely defined position, while indicative templates allow for intraoperative modification of the surgical plan.

There are three basic conditions that templates must meet. First, templates are a representation of the planned definitive prosthesis and should accurately depict the desired three-dimensional features of the teeth. The size, outline, and positioning of the teeth, as well as the planned mucosal emergence profile, should be accurately portrayed. The planned mucosal emergence can guide the surgeon in the assessment, planning, and execution of grafting procedures and can assist in determining the depth of implant placement. If missing hard and soft tissue volumes are to be replaced with a prosthetic component such as a flange, this should also be indicated by the template. This diagnostic set-up shows planned replacements for the two upper left incisor teeth. The wax flange on the diagnostic set-up indicates a need for hard and soft tissue augmentation. The surgical template based on this set-up can be used by the surgeon to assess the case through direct, intraoral visual inspection of the relationship between the template and the residual ridge.

Second, templates need to be readily usable in various phases of clinical assessment and planning. They should be transferrable to the mouth to allow confirmation of esthetics, phonetics, and function. Where needed, the template should include radiographic contrast to allow imaging in two- and three-dimensional radiographic studies. Additionally, they need to be well-fitting, retentive, and stable. Poorly fitting and unstable templates can lead to errors in implant placement. Here, radiopaque teeth have been incorporated into the template to provide contrast in imaging studies. This template is strong enough to be worn by the patient and is well-supported and retained by the acrylic occlusal coverage of surrounding teeth.

Finally, templates guide the surgeon when they place implants and augment hard and soft tissues. These surgical templates must be accurate and retentive and should not impede access to the surgical site. This surgical template reproduces the planned prostheses and incorporates channels to guide the surgical drills. In this image, surgical guide pins are being used to confirm the positions and axial inclinations of the implant osteotomies. This template is well localized and retained by the acrylic coverage of surrounding teeth, and it does not impede surgical access or irrigation of the osteotomy sites. Note that the mucosal margins are clearly indicated, providing guidance to the surgeon in the depth of implant placement and desired position of the final soft tissue contours.

In order to meet these three conditions, templates must be adequately supported and located by the surrounding structures. Where available, teeth provide good support to the template, and they can accurately position the template in three dimensions. Implants also provide highly accurate positioning. Templates can also be supported by mucosa, much in the same way that dentures are mucosa-supported, and by bone. Because mucosa is compressible and allows some movement of the template, and accurate reproduction of bone contours is difficult with most available technology, the accuracy of mucosa- and bone-supported templates can be problematic. In a recent review of the accuracy of templates for guided surgery by Tahmaseb and colleagues, implant- and tooth-supported templates were shown to be the most accurate, followed by mucosa- and bone-supported templates.

To communicate the desired position of the implant to the surgeon, surgical templates must meet certain conditions. They need to remain stable during the surgery to ensure optimal accuracy. Ideally, they should be reasonably rigid to avoid distortion, retentive so that they do not need to be held in place during surgery, and of an open design so as not to impede access to the surgical site. Unfortunately, templates often fall short of these criteria. For example, templates for full-arch implant-retained overdentures are often non-retentive and must be held in place by the surgeon. Vacuum-formed templates can be very retentive but also easily distorted. Care must be exercised when handling this type of template so that the accuracy of implant placement is not affected.

Radiographic templates have requirements similar to surgical templates. They should reproduce the outline of the planned prosthesis and detail the positions and axial inclinations of the planned implants. These templates also need to be capable of accurate placement in the mouth, stable once in position, and not dislodged in occlusion. Additionally, details of the planned prosthesis and implant positions must be visible on radiographic images. This requires some form of radiopaque marker to be incorporated into the template. This can be something as simple as gutta percha markers placed in channels in the template. Templates can also be made using radiopaque teeth. Commercially available radiopaque denture teeth can be used, or radiopaque materials such as barium sulfate can be incorporated into the acrylic when it is mixed.

Construction of a template for an implant-supported prosthesis begins with treatment planning that is based on sound prosthodontic principles. According to the particular clinical case, consideration of occlusion, vertical dimension, and phonetics should be made. Where appropriate, esthetic considerations should also be addressed, including attention to symmetry, proportion, and support for surrounding soft tissues. In extended edentulous spaces in the esthetic zone, lip support is a very important factor, and the need for lip support may dictate the use of a removable prosthesis rather than an FDP. Diagnostic set-ups may also indicate the need for prosthetic soft tissue replacement or bone grafting. This is illustrated in the clinical case shown. The wax flange on this diagnostic set-up indicates a need for hard and soft tissue grafting to achieve an acceptable esthetic result. If grafting is not successful, pink restorative material will need to be incorporated into the prosthesis. This can be somewhat problematic if access for good hygiene is limited, and esthetic concerns may arise if the junction between the prosthetic soft tissue and the patient's mucosa is visible during smiling or function. In cases of multiple tooth loss, it is important to recognize that it is not necessary to replace all missing teeth. Reconstruction to a shortened dental arch may be appropriate, especially in low esthetic risk cases. Planning final tooth positions is covered in the ITI Academy Learning Module on 'Prosthodontic Planning Principles for Implant Placement'.

Diagnostic set-ups are often useful in extended edentulous spaces, or cases in which intraoral try-in of tooth positions is needed to verify esthetic or phonetic outcomes. In this clinical case, implant-supported crowns are planned to replace the missing upper left incisor teeth. A trial set-up is completed and tested intraorally to confirm the occlusion, phonetics, and patient acceptance of the planned esthetic result. This step also confirms the need for soft tissue augmentation to replace missing ridge contours. Once the final tooth positions have been determined, the diagnostic set-up can be translated into a radiographic template and/or final surgical template, which is seen here in use. The wax-up or set-up can also be used as a pattern for removable or implant-supported provisional prostheses.

Templates need to ensure safe spacing between teeth and implants. The implant shoulder should not be any closer than 1.5 mm from the surface of the tooth root. This ensures an adequate thickness of hard and soft tissues in this region for health. Similarly, implant shoulders should be at least 3 mm apart.

Virtual planning software can be used to plan cases and to develop surgical templates. Software merges three-dimensional radiographic images with intraoral scans of the existing teeth or scans of dental casts. The resulting virtual model can then be used to plan the definitive positions of the prosthetic teeth and implants. Finally, these planned outcomes can be used in computer-aided design (or CAD) software to design the surgical template, which can then be manufactured using computer-aided manufacturing (or CAM) techniques such as milling or 3D printing. If needed, a printed copy of the diagnostic set-up can also be made for intraoral try-in.

Ideal Properties of Templates, Key Learning Points: Templates are based on final tooth positions that are planned according to prosthodontic principles and spacing guidelines between teeth and implants. Templates should indicate the mucosal emergence of the planned prosthesis as well as any planned replacement of missing hard and soft tissue volume. Templates should be rigid, retentive, and stable; surgical templates should also allow unimpeded access to the implant site. Templates supported by teeth or implants result in the most accurate implant placement. These same principles can be applied in a digital planning environment using virtual models and CAD/CAM techniques.

Many types of templates are promoted and marketed. It may therefore be difficult for the clinician to decide which type of template to use - that is, which type is best for the particular clinical case being treated. The best means of assessing a template type is to measure how well it meets the desired design criteria. Is it an accurate representation of the planned prosthesis? Can it be used intraorally? Is it stable and retentive? Does it allow for the addition of radiographic contrast so that it can be used for imaging purposes? Finally, how accurately does it prescribe the surgical placement of the implants, and is it compatible with surgical access and irrigation of the osteotomy sites? It is helpful to develop a simple checklist so that any proposed template type can be compared to these criteria. For simplicity, a template will either 'Yes', meet, 'No', not meet, or 'Maybe', partially meet each of these requirements. In the following slides, each of the general template types and means of manufacture will be measured against this checklist.

When should one use a prescriptive rather than an indicative template? Indicative templates give the surgeon much greater freedom to decide on the best sites for implant placement. Because these templates tend to dictate only where the implants should not go, they tend to be useful only in situations where the position and axial orientation of the implant are not critical. As such, they tend to be best suited to fully edentulous cases in which rehabilitations such as mandibular hybrid prostheses or overdentures are planned. Prescriptive templates, on the other hand, provide maximum guidance during implant positioning, restricting implant placement to prosthodontically suitable positions only. As such, guided surgery techniques are the classic indication for a prescriptive template. Unfortunately, prescriptive templates give the surgeon very little opportunity to modify the surgical plan if circumstances do not allow for an implant to be placed in the desired site. Prescriptive templates are best for cases where the position of the implant is critical to achieving the desired esthetic or functional outcome.

When compared against the design criteria checklist, indicative templates meet some criteria but fall short of ideal in other areas. They can be made to be an accurate representation of the planned prosthesis and are readily used intraorally. Additionally, they normally do not impede surgical access. However, stability and retention can be difficult in the situations in which they are normally used, and this type of template is rarely used for radiographic assessment. Their greatest shortcoming, however, is that these templates rely heavily on the skill of the surgeon to decide the positions and axial orientation of the implants placed. As such, these are barely an improvement over not using a surgical template at all.

Prescriptive templates, on the other hand, can be constructed so that they meet all of the design criteria that are on the checklist. The degree to which they do meet these criteria is mainly determined by the way in which they are made, rather than the way they are classified.

Templates can be made using a number of techniques and materials. Each of these have strengths and weaknesses that will determine the cases in which they may be appropriately used. The most commonly used techniques are vacuum forming of thermoplastic sheets, traditional acrylic resin technology, and computer-aided design and manufacturing systems such as 3D printers and computer numerical control or CNC milling machines that mill or print templates from suitable resin materials.

Vacuum-formed templates are easily made and used, and at a relatively low cost. However, these templates tend to be flexible and can distort when in use. While they do indicate the position of the screw access aperture in the prosthesis, vacuum-formed templates can result in undesirable angulation of the implant because their limited thickness does not accurately guide the drill. This limits indications for their use to single tooth and short-span FDP applications in the hands of an experienced surgeon.

Templates made using a vacuum forming process are easily and inexpensively made but tend to fall short of ideal when assessed against the design criteria. Although stable and retentive in the mouth, these tend not to be an accurate representation of the planned prosthesis, as they tend to be slightly over-sized due to the thickness of the material. Adding radiographic contrast is possible, but doing so is an inconvenient additional process. However, their use as surgical templates is the primary source of their failings. Managing flaps and irrigating around some of these templates can be awkward, and the accuracy of these templates is limited. In fact, vacuum-formed templates are best classified as indicative templates, as they do not significantly restrict the axial inclination of the implant, which is totally in the control of the surgeon.

Templates made using traditional prosthetic techniques and acrylic resin technology have a wide range of applications. They are not overly expensive, and they can be made to try in the patient's mouth to verify occlusal outcomes, phonetics, and esthetics. Additionally, where radiographic templates are needed, commercially made radiopaque denture teeth can be added, or the acrylic material can be mixed with a radiopaque compound such as barium sulfate to make it more readily visible on radiographs. These systems do, however, require some specialized skills and equipment, which adds cost to their manufacture. Also, it is difficult, although not impossible, to interface this manufacturing technique to virtual planning software and guided surgery applications. Due to the flexibility of this technique, it can be used in virtually all situations.

CAD/CAM techniques were designed to be used in guided surgery cases where their accuracy is beneficial. These are mostly complex surgical cases where very precise placement is needed to avoid adjacent teeth or other important anatomical structures, or where limited bone volume is available for implant placement. However, these techniques rely on expensive technologies such as CBCT imaging and digital scanners as well as 3D printers or milling machines, and this can increase costs. While this manufacturing technique can be used for all applications, its reliance on expensive infrastructure may limit its application. This system was created to make templates for guided surgeries, and this is where it is best used.

Digital technologies are also very flexible and can be used in such a way as to meet most of the design criteria. Their only failing relates to the moderate difficulty in making radiographic templates with these technologies; however, CAD/CAM techniques are rarely applied to the fabrication of radiographic templates. Typically, the digital assessment and planning software either does not use radiographic templates at all, using other means to depict the dimensions and outline of the planned prosthetic teeth, or uses conventionally fabricated radiographic templates to capture images that are then used in virtually planning the surgery and making the surgical template.

It is important to note that digitally planned and guided surgery has potential benefits, but these benefits need to be weighed against potential dangers. A recent systematic review by Tahmaseb and colleagues showed that, while average potential errors are relatively low, maximum errors can be significant. Certainly, the average angular error illustrated has the potential to impact on clinical outcomes. Error is mostly related to the potential for templates to move during use and is therefore dependent on the structures that support and stabilize the template. In this regard, implants and teeth provide the most stable support for these surgical templates. An understanding of the potential for error in this technology is needed, and care must be taken to allow adequate safety margins when using this technology for planning or in clinical situations.

Advantages and Disadvantages of Template Types, Key Learning Points: Indicative templates provide the surgeon with minimal guidance when placing the implant, while prescriptive templates are very restrictive during creation of the implant osteotomy. Due to their flexibility, vacuum-formed templates are best used in single tooth or short-span situations. Traditional acrylic resin templates can be used in a broad range of applications and can also be adapted into radiographic templates. Although highly accurate, templates made with CAD/CAM technology are costly and therefore best suited when guided surgery is indicated.

Radiographic and Surgical Templates, Module Summary: Templates are an integrated part of prosthodontically driven implant placement. In the planning phase, templates reveal any need for hard and soft tissue augmentation procedures and indicate the most appropriate type of prosthesis. In the surgical phase, templates ensure correct implant placement in three dimensions. The clinician should select the type of template based on the clinical case, with indicative or vacuum-formed templates being used by experienced surgeons only, CAD/CAM templates being reserved for guided surgery cases, and acrylic resin templates suiting most other indications.