When patients initially present with a request for dental implant treatment, they do so with teeth that require extraction, or with teeth that have been missing for some time. Although there are similar factors that need to be assessed in these two situations, an additional factor to consider when teeth are present is the ideal time to place the implant after extraction. These considerations are dealt with in a separate module on timing of implant placement after tooth extraction. The focus of this module is surgical assessment of the edentulous site after the teeth have been extracted and the ridge has healed.

The assessment of the edentulous site is an essential step in planning for dental implant therapy and should always be undertaken with the final implant prosthesis in mind. There are specific hard and soft tissue considerations that need to be evaluated in relation to the surgical phase of treatment. The extent of the edentulous space can vary from single-tooth spaces, to short and extended spaces, to fully edentulous jaws. The location of the prosthesis can include either the maxillary or mandibular jaw and regions which are of high esthetic importance. At individual sites, specific anatomical structures need to be identified, and the surgical risks evaluated. The quality and quantity of the soft and hard tissues at the site need to be assessed in relation to the final prosthesis to determine the need for soft tissue and bone augmentation procedures. This module discusses the assessment of the hard and soft tissue characteristics of the edentulous site.

After completing this ITI Academy Module, you should be able to describe the following: the factors needed to assess the soft tissues at the implant site, the factors required to assess the bone at the implant site, the relationship between the planned prosthesis and the implant site, and the factors that determine the need for bone augmentation at the implant site.

The assessment of the soft tissues at the implant recipient site involves a careful clinical examination to analyze the following: The presence of pathological conditions, the periodontal phenotype, also referred to as the gingival or periodontal biotype, and the quantity and quality of the soft tissues.

Several soft tissue pathological conditions may be present at the surgical site, such as manifestations of viral infections or systemic diseases and fungal infections; inflammatory processes and traumatic or non-traumatic ulcers; hyperplasia, tumors, or cancers. Common soft tissue pathoses include oral dermatoses and infections.

When present, oral mucosal lesions should be properly assessed and diagnosed. In this clinical image, an implant prosthesis replaces the maxillary right lateral incisor in a patient with a history of oral lichen planus. A few years after the implant was placed, the patient developed persistent ulcerative lesions at the mucosal margin around the implant consistent with oral lichen planus. Clinicians should be cautious in recommending implant treatment to patients with oral dermatoses, and patients should be advised of the risk that these lesions can develop around implant-supported prostheses.

Infections associated with the proposed implant site and surrounding soft tissues need to be evaluated and treated before considering implant treatment. The adjacent teeth must be evaluated for endodontic and periodontal lesions and existing root fractures. The adjacent root sockets also require evaluation. Infections are frequently associated with bone loss at the potential implant site, often necessitating bone augmentation procedures before implants can be placed. In this patient, implant treatment to replace the missing premolar teeth is being considered. The first premolar site, however, presents with persistent inflammation. A radiograph reveals the presence of retained roots. This needs to be addressed and infection eliminated before implants can be placed.

The periodontal phenotype may be classified as thick, thin, or medium. This determination is made clinically, based on the morphological characteristics of the gingiva. A thin tissue phenotype has thin gingival tissue with less underlying osseous support and less blood supply, and the interdental papillae are long and slender. The tissue is more predisposed to resorption after tooth extraction compared to a thick phenotype.

A thick tissue phenotype has a flatter scallop contour, shorter interdental papillae, and a wide expanse of gingiva. The tissue is more fibrotic and vascularized. The underlying bone tissue is thicker, making the soft tissue more resistant to recession. Treating a soft tissue defect in a thick phenotype is much more predictable than in a thin phenotype.

Similar clinical characteristics can be observed in longer edentulous spans and fully edentulous sites. These clinical examples exhibit healthy mucosa. The image on the left shows a thin periodontal phenotype with a narrow band of keratinized tissue on the crest of the ridge. In the central image, a wider band of keratinized tissue is present over the ridge in a patient classified as having a medium periodontal phenotype. In the right image, a broad band of keratinized tissue and a thick phenotype is observed. Sites with medium to thick tissue phenotypes are easier to manage surgically than thin phenotype sites. Flap management and overall soft tissue handling are facilitated by having a wider band of keratinized mucosa present in regions with thicker tissue. In contrast, thin phenotype sites are more difficult to manage due to the narrow band of keratinized mucosa, which is often thin and delicate.

Several soft tissue characteristics that describe the quantity and quality of the soft tissues should be evaluated. This includes the volume of soft tissues, the width of keratinized tissue present, soft tissue thickness, and the presence of mucogingival anomalies. These characteristics will now be discussed.

The volume of soft tissue can be readily determined by visual inspection, as seen in this clinical example. The ridge shows signs of narrowing at the crest and a reduction in soft tissue volume. The volume of soft tissue can be an indicator of the volume of bone beneath. A cone beam CT examination of this patient confirms significant resorption of the ridge on the buccal aspect and a lack of buccolingual thickness of bone to place implants.

In some cases, however, the volume of soft tissues does not always reveal the condition of the underlying bone. In this clinical image of a missing maxillary right central incisor, resorption of the ridge from the facial aspect can be seen, but there appears to be adequate soft tissue volume, which in turn could suggest sufficient bone to place an implant. Subsequent cone beam CT examination, however, shows that there is reduced bone width at the crest. With an outline of an implant superimposed, this suggests that an implant can only be placed in conjunction with a bone augmentation procedure.

It is also important to identify the amount of keratinized tissue remaining over the ridge. In the clinical example on the left side, there appears to be more keratinized mucosa remaining compared to the clinical case on the right side. Although the scientific evidence is limited, most clinicians agree that it is desirable to maintain a band of keratinized mucosa around an implant so that the patient can maintain adequate plaque control. Therefore, sites with less keratinized mucosa need to be managed very carefully during surgery so as not to lose the band of keratinized tissue. As mentioned previously, grafting procedures are sometimes necessary to increase the amount of keratinized mucosa present.

Determining tissues thickness by visual assessment may be subjective and difficult. Thus, a more precise method to assess this is bone sounding, which can be applied to single-tooth, partially, or fully edentulous sites. It is performed with a fine needle and a rubber stopper. The thickness of the soft tissues can be recorded with the help of a ruler. Obviously, this procedure must be performed under local anesthesia.

Soft tissue thickness can also be evaluated as part of the radiographic evaluation of the site. Traditionally, it is thought that imaging examinations are limited to analysis of the hard tissues; however, cone beam computed tomography, or CBCT, can also be used to evaluate soft tissues in the edentulous site. Since a three-dimensional scan is often requested for the analysis of the residual bone, the same scan can often be used for the analysis of the soft tissue. As shown in the reformatted radiographic images, the red arrows indicate the buccal mucosa, and the white arrows, the palatal or lingual mucosa. Their thickness can be directly measured with the software from the CT provider or with a ruler in a 1:1 ratio to a printed image.

Another important aspect regarding the soft tissues that must be clinically assessed is the presence of mucogingival anomalies, which may influence the surgical approach and which have the potential to affect the esthetic outcome in areas of esthetic importance. In this clinical image, there is a lot of scarring of the soft tissues due to previous surgery to remove an impacted canine. Scarring such as this complicates surgery, making elevation and mobilization of the flap more difficult. Scarred tissue close to the mucosal margin of the implant can adversely affect esthetic outcomes. In this clinical image, the presence of a large and wide frenal attachment close to the soft tissue margin on the buccal aspect of the mandibular distal implant has resulted in a narrow band of keratinized mucosa, soft tissue pull, and interference with plaque control.

Soft Tissue Assessment, Key Learning Points: Careful assessment of the soft tissues at the implant site and adjacent areas is necessary. The soft tissues must be assessed for the presence of pathology, periodontal phenotype, amount of keratinized attached mucosa, soft tissue thickness, and mucogingival anomalies. Methods to assess the soft tissue include visual inspection, bone sounding, and three-dimensional radiography.

The primary aim of assessing bone at the surgical site is to determine whether there is sufficient bone volume to allow the placement of implants into the correct three-dimensional prosthodontic position. Although a visual assessment of the site can provide an indication of the amount of bone available, a three-dimensional computed tomography examination is regarded as the most accurate method today. The advent of cone beam CT imaging technology has provided dentists with an accessible and accurate radiographic tool. The clinician can be confident that the bony conditions at the time of surgical exposure can be predicted with accuracy beforehand. As this clinical example illustrates, the moderate resorption of the ridge observed in the CBCT image was confirmed after flap reflection.

Bone volume is assessed in three dimensions: mesiodistal, apicocoronal, and buccolingual. Measurements can be made directly from the reformatted images to determine whether there is sufficient bone to place an implant. In the image on the left, the bone width is 5 mm at the crest and increases to 7 to 8 mm towards the mid-portion of the ridge. The apicocoronal height is 11 mm from crest to the superior border of the mandibular canal. This indicates sufficient bone to place a standard 4-mm diameter implant of 8 to 10 mm in length. In contrast, the image on the right shows a significantly resorbed ridge. Although there appears to be adequate height from crest to the mandibular canal, there is insufficient width.

A bone density analysis may be performed preoperatively on radiographs. Two-dimensional radiographic imaging such as periapical or panoramic radiography can give an estimation of the bone density and the cortical thickness. Three-dimensional radiology such as multislice CT and cone beam computed tomography may also be used for preoperative bone density estimations. Bone density is an important consideration when preparing the osteotomy during surgery, as adjustments to the drilling technique and loading protocols may need to be made. The CBCT image on the left shows a mandibular site 10 weeks after tooth extraction, whereas the image on the right shows a long-standing edentulous site in another patient. It can be clearly seen that the image on the right side shows much denser bone than the image on the left.

Anatomical structures can also be identified using cone beam CT imaging. CBCT images provide invaluable information for the clinician, first, in assessing a potential implant site for bone height and proximity to anatomical structures, and second, in planning augmentation procedures. In the image on the left, the maxillary sinus is clearly identified. The thickness of the bone at the crest as well as on the lateral or buccal side can also be seen. A lateral-window sinus floor elevation will be required for implant placement. Cone beam CT imaging can also reveal vascular channels in the bone, hidden concavities in the ridge, retained roots, and other abnormalities. In the image on the right, the mandibular canal, indicated with an arrow, can be clearly identified in this resorbed mandibular ridge.

Proximity of the planned implant position with the roots of adjacent teeth needs to be carefully assessed. In particular, post-orthodontic treatment cases should be evaluated carefully for relapse and convergence of roots of adjacent teeth. Periapical radiographs can be used for this purpose, although care needs to be taken to ensure that the radiographs are taken with a paralleling technique. Fiducial markers made of radiopaque materials can be used. In this radiograph of a maxillary right lateral incisor site, relapse in the retention phase of orthodontic treatment has resulted in convergence of the roots of adjacent teeth. Orthodontic re-treatment was required to increase the space between roots of the teeth.

Serial axial views from cone beam CT scans can provide accurate measurements of the distance between the roots of adjacent teeth. In this example, a developmentally missing maxillary lateral incisor site is being assessed for implant treatment. The periapical radiograph shows a relatively narrow space between the roots of adjacent teeth. An accurate determination of the space between the roots of the teeth cannot be made on this radiograph, as periapical radiographs have a risk of horizontal alignment error. Serial axial views of the site can provide an accurate determination of the space between the roots of the adjacent teeth. In these close-up axial views at different apicocoronal levels, the distance between the adjacent teeth at two levels can be visualized and measured.

The proximal bone crests of teeth adjacent to the edentulous site can be identified on periapical radiographs. The location of the proximal bone crests can also be determined on axial views from CBCT scans. If the proximal bone peaks are receded, there is a risk that surgery to place the implant may be accompanied by recession of the papillae adjacent to the natural teeth. This can have significant consequences in areas of esthetic importance. These clinical images show the use of a periapical radiograph to determine the height of the proximal bone crests adjacent to a maxillary left central incisor site, as indicated by the arrows.

Assessment of the implant site must also involve identification and diagnosis of any pathologic conditions associated with the underlying bone. The presence of a cyst may result in a lack of bone to stabilize the implant. In this radiograph, the outline of a cyst associated with the recently extracted maxillary right lateral incisor can be seen. There is a risk that the existing bone may be insufficient to stabilize the implant. Further analysis with three-dimensional imaging is indicated. Osteolytic lesions should be investigated to rule out sinister pathology prior to implant treatment planning. In this example, CBCT examination of an edentulous maxillary ridge for implant treatment revealed the presence of an extended osteolytic lesion in the bone. This lesion needs to be investigated to rule out sinister pathology as a first step, before further planning for bone augmentation and implant procedures.

Bone Assessment, Key Learning Points: Careful assessment of the bone at the implant site and adjacent areas is necessary independent of the overlying soft tissue. Bone assessment must include bone volume in three dimensions, adjacent anatomical structures, bone crests of adjacent teeth, and presence of pathologic conditions. Radiographic methods to assess the bone include two- and three-dimensional radiography.

To plan for the correct three-dimensional placement of implants, the assessment of the site must be done with the planned prosthesis in mind. This concept is referred to as prosthodontically driven treatment planning. The need for bone augmentation is identified before treatment begins. These images illustrate an implant in the maxillary left central incisor site that has not been placed with a final prosthesis in mind. The implant position was dictated by the available bone. This resulted in the implant being tilted too far facially, causing recession of the soft tissues. In a prosthodontically driven treatment plan, the need for a bone graft would have been identified before the commencement of treatment and this complication avoided.

Implants must therefore be placed in the correct position in relation to the planned prosthesis. In order to achieve this, it is important to assess the relationship of the planned prosthesis to the bone. This process is greatly assisted by the use of a radiographic template based on a diagnostic wax-up, which is worn by the patient at the time of the CT scan.

The advantages of using a radiographic template during 3D scans are illustrated in the following images. They show that the relationship between the template, bone, and implant long axis can be favorable or unfavorable. In this first CT section, the relationship of the bone, the expected position of the implant-supported prosthesis, and the long axis of the implant, indicated by the white line, is favorable. A similar result is shown in the next image, although a vertical deficiency is visible by the increased distance of the mucosa and bone crest to the radiographic template, which is indicated by the distance between the two arrows. One can also appreciate a narrow crest at the most coronal part.

These principles of prosthodontically driven treatment planning are illustrated in the following clinical case, in which a calibrated image of the planned implant is superimposed on the radiograph so that the need for bone augmentation can be anticipated. The treatment plan for the replacement of this single maxillary central incisor is an implant-supported fixed dental prosthesis. Due to the dimensions of the tooth to be replaced, the prosthodontic plan prescribed an implant with a standard prosthodontic platform. The radiographic image of the site obtained from the cone beam CT examination shows the cross-sectional view of the ridge, which has undergone buccal resorption. Using the superimposed image of an implant that is calibrated to the size of the radiograph, the analysis indicates that a standard diameter implant with a bone level design can be placed in the correct axial position. However, it is likely that the facial bone will be thin and that a fenestration will be created on the buccal aspect of the implant, as indicated by the white arrow. The surgical plan will therefore incorporate the need for a bone augmentation procedure on the buccal aspect of the ridge. The surgeon is then able to plan the appropriate flap design in anticipation of implant placement and simultaneous bone augmentation. The clinical image illustrates the situation with the flap raised and the implant osteotomy completed. As anticipated, the bone on the facial aspect of the implant and the crest is thin, and an apical fenestration has been created.

A second example illustrates the importance of relating the surgical site to the planned prosthesis, in this case with the use of a radiographic template as part of the assessment and treatment-planning process. This step allows the available bone volume to be assessed at the planned implant sites. The preliminary plan was for implant placement in the second premolar and second molar sites for construction of a 3-unit fixed dental prosthesis. A radiographic template was constructed from a diagnostic setup. The scans taken with the radiographic template in the patient's mouth confirmed the lack of bone volume on the buccal aspect of the ridge in the region of the second molar, as indicated by the blue arrow. As the patient was unwilling to undergo a bone grafting procedure to augment the buccal side of the ridge in this region, the prosthodontic plan was modified to replace only two teeth, the mandibular right second premolar and first molar. CBCT sections of the first molar region show that these sites had sufficient bone volume to permit the placement of implants without the need for grafting.

Dental implants must also be placed in the correct relationship to adjacent teeth. The correct position of the implant shoulder needs to be achieved in three dimensions: orofacial, apicocoronal, and mesiodistal. This principle is demonstrated in these three diagrams. The green region or "safety zone" is where the shoulder of the implant should be placed for optimum results. If implants are placed in the red or "danger zone", there is a risk of esthetic and biological complications.

As already mentioned, the space of the edentulous site should also be assessed clinically when choosing the implant to be placed. This is particularly important for single or partially edentulous areas, where there is a mesiodistal limitation of the space and implants of the appropriate dimensions should be carefully selected. As a general principle, a minimum of 1.5 mm of space should be maintained between the necks of adjacent teeth and the shoulder of the implant. Maintaining this gap will minimize risk of resorption of the proximal bone on the adjacent teeth and recession of the papilla. In single tooth sites, both the mesiodistal space and tooth to be replaced should be taken into consideration; together, they aid in the selection of reduced, regular, or wide diameter implants. In this clinical image, a missing lateral incisor is to be replaced by a dental implant. Since there is limited mesiodistal space and the tooth dimension is small, a reduced diameter implant is the best choice, leaving enough room for the distal and mesial papillae.

When multiple implants are being planned to restore an extended edentulous space, it is important that a minimum 3-mm space be maintained between adjacent implants. This will minimize the risk of unwanted resorption of the bone between the implants. The overall space available must be carefully analyzed in relation to the number of implants planned, the dimensions of each implant, and a need to maintain sufficient interimplant space as well as a minimum 1.5-mm gap between implants and the adjacent teeth. This diagram illustrates these principles when replacing two missing teeth with two implants. The overall mesiodistal space available is therefore the sum of the diameter of the implants at their widest part, the distance of 3 mm between the two implants, and the distance of 1.5 mm mesial and distal to the adjacent natural teeth.

The number and positions of the implants can vary according to several other factors, such as bone volume availability, type of prosthesis, access for maintenance and homecare, and esthetics. The decision on the number, position, and diameter of the implants to be placed needs to be carefully considered and should be guided principally by the prosthodontic treatment plan. This clinical case illustrates an occlusal view of an edentulous space in the maxillary anterior region, where the four incisor teeth are missing. The mesiodistal space will impact the selection of implant diameter and number as well as the position of the implants.

Relationship of Planned Prosthesis to the Implant Site, Key Learning Points: Implants must be placed in the correct three-dimensional position in relation to the planned prosthesis. Radiographic templates should be used to relate the planned prosthesis to the implant site. Implants must be placed in the correct three-dimensional position in relation to adjacent teeth. A minimum distance of 1.5 mm should be maintained between the implant and an adjacent tooth. A minimum distance of 3 mm should be maintained between adjacent implants.

Once the position of the planned prosthesis is properly related to the underlying bone and adjacent teeth, it is then possible to determine whether there is sufficient bone volume to allow the implant be placed in the correct position and whether bone augmentation is required as part of the implant treatment. It is important to observe that the thickness of the bone walls in both the facial and lingual or palatal aspects should be at least 1 mm, after an implant is selected for a given site. If this thickness is not available, a reduced diameter implant could be selected, provided that the implant can still be placed in the correct prosthodontic position and that the implant has sufficient biomechanical properties to withstand the anticipated occlusal forces at the site. If it is anticipated that there will be insufficient thickness of the bone walls or absence of bone when the implant of the appropriate dimensions is selected, the site should be grafted to augment the bone.

In esthetic areas, it is recommended that the bone on the facial aspect of implants be at least 2 mm thick. This is to ensure adequate support of the overlying mucosa, which is important for esthetic outcomes, and minimizes the risk of soft tissue recession over time. The latest ITI Consensus Conference recommendation is to achieve 2 mm of bone facial to the implant in esthetic areas.

Bone grafting to augment an implant site may be undertaken as a simultaneous or a staged procedure. As a guiding principle, simultaneous implant placement and bone augmentation can be performed predictably if the implant is positioned within the envelope of bone. This means that when the implant is placed in the correct prosthodontically determined position, at least two bone walls enclose the implant. The bone walls assist in stabilizing particulate grafts and provide bone progenitor cells that promote bone regeneration. If the clinician can predict that the implant will not lie within the bone envelope after placement, a simultaneous implant placement and treatment of the defect should not be performed. The outcome is unpredictable, and the defect should be treated as a staged procedure. In other words, the graft - usually an autogenous cortical block graft - is placed to augment the volume of bone as a first step, followed by the placement of an implant as a second procedure once the graft has consolidated.

In this clinical image, the implant has been placed in the maxillary central incisor site in the correct three-dimensional position. The dehiscence of the facial bone requires augmentation. Because the implant lies within the bone envelope due to the presence of bone on the mesial and distal surfaces, simultaneous bone augmentation can be undertaken with a predictable outcome. In contrast, in this posterior mandibular site a planned implant would not lie within the bone envelope. Simultaneous bone augmentation with particulate grafts is unpredictable. The site should be grafted first to augment the ridge before the placement of the implant.

Need for Bone Augmentation, Key Learning Points: The need for bone augmentation is assessed by relating the implant prosthesis to the implant site. A minimum thickness of bone of 1 mm must be maintained on the buccal and lingual sides of the implant. In esthetic areas, a minimum thickness of bone of 2 mm should be maintained on the facial aspect of the implant. If the anticipated position of the implant is within the bone and bone deficiencies are present, implant placement and simultaneous bone augmentation may be performed. On the other hand, if the anticipated position of the implant is outside the bone envelope, a staged bone augmentation and implant placement protocol is recommended.

Surgical Assessment of the Implant Site, Module Summary: Careful assessment of the soft tissues at the implant site and adjacent areas is necessary. The soft tissues must be assessed for the presence of pathology, periodontal phenotype, amount of keratinized attached mucosa, soft tissue thickness, and mucogingival anomalies. Methods to assess the soft tissue include visual inspection, bone sounding, and three-dimensional CT scans. Careful assessment of the bone at the implant site and adjacent areas is necessary independent of the overlying soft tissue. Bone assessment must include bone volume in three dimensions, adjacent anatomical structures, bone crests of adjacent teeth, and presence of pathologic conditions. Radiographic methods to assess the bone include two-dimensional and three-dimensional radiography.

Implants must be placed in the correct three-dimensional position in relation to the planned prosthesis. Radiographic templates should be used to relate the planned prosthesis to the implant site. Implants must be placed in the correct three-dimensional position in relation to adjacent teeth. A minimum distance of 1.5 mm should be maintained between the implant and an adjacent tooth. A minimum distance of 3 mm should be maintained between adjacent implants.

The need for bone augmentation is assessed by relating the implant prosthesis to the implant site. A minimum thickness of bone of 1 mm must be maintained on the buccal and lingual sides of the implant. In esthetic areas, a minimum thickness of bone of 2 mm should be maintained on the facial aspect of the implant. If the anticipated position of the implant is within the bone and bone deficiencies are present, implant placement and simultaneous bone augmentation may be performed. On the other hand, if the anticipated position of the implant is not within the bone envelope, a staged bone augmentation and implant placement protocol is recommended.