Following tooth loss, alveolar resorption and ongoing pneumatization of the maxillary sinus may lead to vertical bone deficits in the posterior maxilla. This deficit reduces the distance between the maxillary sinus floor and the alveolar process, so that reconstructing the vertical bone height by means of a sinus floor elevation procedure may be a prerequisite for placement of dental implants of the correct dimensions and in the ideal three-dimensional position in order to achieve optimal functional and esthetic treatment outcomes.

Sinus floor elevation is a predictable procedure for vertical bone augmentation in the posterior maxilla that compensates for inadequate bone height. Grafting material is placed into the sinus to increase available bone height and to facilitate the placement of implants of the desired dimensions and in the correct prosthetically driven positions. This module will focus on patient assessment, diagnosis, and treatment planning for sinus floor elevation procedures.

After completing this ITI Academy Module, you should be able to: list the criteria for proper patient selection for sinus floor elevation, describe the radiographic techniques for sinus imaging, discuss the principles of treatment planning for sinus floor elevation cases, and list the surgical techniques for sinus floor elevation.

Careful patient selection is critical to the long-term success of implant treatment in cases requiring sinus floor elevation. To determine a patient's suitability for sinus floor elevation, in-depth knowledge of the anatomy of the maxillary sinus and its adjacent structures is key. The pattern of bone modeling and remodeling that takes place after tooth extraction also must be understood. Furthermore, careful consideration must be given to relevant aspects of the patient's medical history as well as the indications and contraindications for sinus floor elevation procedures.

A thorough review of the patient's medical history is mandatory to identify and assess the aspects relevant to sinus floor elevation procedures. A systematic approach includes an assessment of the patient's general health status, concomitant medication, possible allergies, tobacco and alcohol consumption, and compliance.

The following is a summary of significant medical findings; it is by no means an exhaustive list of all conditions that increase risk for sinus floor elevation. Any medical condition with the potential to compromise bone healing adds risk to the sinus floor elevation procedure. Poorly controlled diabetics, patients who have had radiation treatment that included the maxilla, and those receiving immunosuppressive therapy should not be considered for this treatment. Patients taking medications that affect bone healing such as antiresorptive drugs or those that might cause excessive bleeding should be treated with great caution, and only after full and frank discussions about risks, and only after receiving explicit consent to proceed. Additionally, patients may be taking medications that can interact with other drugs that are to be administered during treatment. These risks must be identified and mitigated.

Patients with allergies are not directly contraindicated, but care should be taken to ensure that medications taken to manage allergy symptoms do not interfere with treatment or interact with drugs given during treatment. Whilst cigarette smoking is not an absolute contraindication for sinus floor elevation surgery, patients must be advised that there are increased risks of implant and graft failure in smokers, and encouraged to cease smoking, or significantly reduce their habit in the lead up to their surgery and during the healing period. Finally, patients that are not able to comply with postoperative instructions should not be considered for SFE procedures.

Sinus floor elevation procedures may be considered if implant placement is indicated by the prosthodontic plan, but there is insufficient bone height to conventionally place implants due to the position or pneumatization of the maxillary sinus. No local or systemic conditions that would compromise bone healing or immune response should be present in candidates for sinus floor elevation. In this clinical case, the maxillary left first molar is missing. A periapical radiograph taken with a steel ball for calibration revealed residual bone height of 7 mm.

Absolute contraindications for sinus floor elevation procedures include patients having undergone high-dose head-and-neck radiotherapy with the field of irradiation including the maxilla, patients receiving high-dose antiresorptive therapy against multiple myeloma or bone metastases from other types of cancer, patients undergoing chemotherapy, and patients with a history of poor compliance, which may be related to substance abuse or psychological or emotional disorders.

Relative general contraindications include diabetic patients with poor glycemic control who should be medically optimized before sinus floor elevation is considered, osteoporotic patients on long-term antiresorptive treatment of greater than 5 years, and smoking.

There are a number of local factors that increase risk for sinus floor elevation. Local high risk factors include chronic and acute periodontitis, acute sinusitis, and apical periodontitis on teeth adjacent to the maxillary sinus. Such infections must be treated successfully before a sinus floor elevation procedure can proceed. Additionally, apical periodontitis on teeth adjacent to the maxillary sinus must be allowed an adequate healing period between endodontic treatment and sinus floor elevation. A number of factors can be seen as moderate risks. Smoking has been identified in numerous studies as being associated with higher rates of both implant and graft failure and complications, especially in patients with a history of periodontitis. Also, whilst thickening of the sinus membrane as a consequence of chronic infection is not an absolute contraindication, additional care is indicated when performing sinus elevation in such cases. Finally, where the residual bone height is insufficient to obtain adequate primary stability of the implants, a staged approach should be used, with implant placement delayed until the graft has sufficiently healed. As with all risks in implant treatment, a thorough discussion of these risks must be conducted with the patient, advising them of all risks and the consequences of such risks should they arise. Treatment can only proceed when the patient has understood these risks and given their explicit and continuing consent.

Patient Selection, Key Learning Points: Patient evaluation requires thorough knowledge of maxillary sinus anatomy and socket healing. Patients with local or systemic conditions that would compromise bone healing or immune response are not candidates for sinus floor elevation procedures. Local risk factors that must be addressed prior to sinus floor elevation include periodontitis, acute sinusitis, and apical periodontitis in the region of the maxillary sinus. Any risk factors must be discussed with the patient during the informed consent process.

Radiographic imaging is indispensable to determine sinus anatomy and the most appropriate treatment approach. Intraoral and panoramic radiographs should be combined with conventional computed tomography or cone-beam computed tomography. A preoperative CT or CBCT scan is recommended to evaluate the anatomy of the maxillary sinus due to the detailed information it offers. Cone beam CT is preferred as it involves a significantly lower effective radiation dose than conventional multi-slice computer tomography.

Each of these three imaging modalities will have some advantages at the various timepoints in the treatment process. These are outlined in the table onscreen. Conventional periapical radiographs can be used throughout treatment. They have good imaging quality and low exposure dosage, but lack three-dimensional information. Panoramic radiographs can also be used, but have the potential problems of distortion and lower image resolution, and also lack three-dimensional data. CT and CBCT provide three-dimensional information for treatment planning. Bony linear measurements on cross-sectional CBCT images have been shown to be highly accurate and reliable.

The preoperative radiographic evaluation should include an evaluation of the available residual bone height and width of the alveolar ridge in the posterior maxilla, the status of the neighboring teeth, the presence of bony septae in the maxillary sinus, the course of the sinus floor, signs of pathologic conditions in the maxillary sinus, and the course of the posterior superior alveolar artery. In this clinical case, CBCT data has been reformatted to demonstrate cross-sections of the region of interest. Residual bone volume for implant placement is limited, but the region is free from complicating anatomy and the sinus membrane is healthy and of normal thickness.

Radiographic Techniques, Key Learning Points: Radiographic imaging for sinus floor elevation should combine periapical, panoramic, and three-dimensional CT or CBCT images. Key items to assess include residual bone height and width, anatomy of the sinus and adjacent structures, and presence of sinus pathology.

Careful patient selection and treatment planning is critical to the long-term success of implant treatment in cases requiring sinus floor elevation. The number, dimension, and position of implants should be defined based on a prosthetically-driven treatment plan. Also, in sinus floor elevation patients, the bone height is a diagnostic factor of primary importance. When implant therapy is planned in the atrophic posterior maxilla, the three-dimensional interarch relations should be evaluated, and in patients with severe resorption, three-dimensional site development should be considered.

Alternatives to sinus floor elevation should always be considered when planning treatment cases for implants in the posterior maxilla. In some situations short implants - that is, those with lengths 6 mm or less - can be used. A recent systematic review by Papaspyridakos and co-workers found that short implants had overall survival that was similar to longer implants, but the studies on short implants were prone to greater variability in results, suggesting that short implants might be a somewhat less predictable solution. Short implants might be an alternative that can be used where patients are not comfortable with alternative treatments, but only after appropriate informed consent is obtained. In a recent systematic review, Lin and Eckert found that intentionally tilted implants had survival rates similar to axially placed implants when used to support full-arch fixed dental prostheses. As such, they pose an acceptable alternative to sinus elevation in these cases. Finally, zygomatic implants may be considered in appropriate cases. When combined with other axially placed implants to support a full-arch fixed prosthesis, Chrcanovic and co-workers found that these implants have similar survival to conventional implants. It should be noted that there is little evidence on the relative benefits and risks of these procedures when compared with each other, and with sinus elevation surgery.

The atrophic posterior maxilla can be categorized in four groups. Into group one fall patients who present with an expanded sinus cavity with limited bone height for implant placement. Due to ideal interarch relations, there is no need for procedures other than sinus floor elevation. In most cases, augmentation can be accomplished using locally harvested autogenous bone chips in combination with a bone substitute material.

Finally, group four consists of patients who present with an expanded sinus cavity with extreme vertical atrophy, insufficient bone width, and a large vertical intermaxillary distance. In this group of patients, sinus floor elevation in combination with horizontal and vertical ridge augmentation with a block graft is necessary. The extremely atrophic edentulous maxilla may require bone grafts from extraoral sources such as the iliac crest.

Treatment Planning, Key Learning Points: Planning for sinus floor elevation procedures should be based on prosthetically driven implant positions. Bone height is the primary diagnostic factor for sinus floor elevation patients; ridge morphology and interarch relations should also be considered. A classification system of the atrophic posterior maxilla can be used to guide the surgical approach to achieve ideal bone volume and interarch relations.

Although not always achievable, the following treatment objectives should apply in the edentulous posterior maxilla when a sinus floor elevation procedure is planned: Occlusion should extend at least to the first molar, surgery should be performed on an outpatient basis under local anesthesia, bone should be harvested from intraoral donor sites, and simultaneous implant placement should be planned, provided that primary implant stability can be achieved.

Depending on the residual bone height and the sinus floor anatomy, two techniques are applied for sinus floor elevation. In the lateral window technique a window is prepared in the lateral sinus wall, and the sinus membrane is then lifted to allow placement of the augmentation material into the maxillary sinus. This can include simultaneous implant placement if sufficient primary stability of the implant can be achieved.

Using the transcrestal technique, the sinus floor is elevated through the prepared implant bed. This requires in-fracturing of the sinus floor using an osteotome so that the augmentation material can be introduced into the space beneath the sinus membrane. In this technique, implant placement is needed to help maintain the volume of the graft. Therefore, sufficient residual bone height to ensure good primary stability is the essential criterion for selecting this method. Most guidelines recommend that a minimum of 6 mm of residual bone height is needed to use the transcrestal approach for sinus floor elevation. In-depth information on the indications as well as step-by-step descriptions of these two surgical techniques will be provided in separate Learning Modules dedicated to each technique.

Surgical Techniques, Key Learning Points: Sinus floor elevation is achieved with either the lateral window or transcrestal technique. With the lateral window technique, simultaneous implant placement is possible if primary stability can be achieved. The transcrestal technique requires simultaneous implant placement to maintain the graft material.

Principles of Sinus Floor Elevation, Module Summary: Implant placement in combination with sinus floor elevation is an evidence-based and predictable treatment method with high implant survival rates. The aim of sinus floor elevation procedures is to reconstruct vertical bone height in the edentulous posterior maxilla to facilitate primary implant stability as well as long-term functionally stable treatment outcomes. Careful patient selection is key for the long-term success of implant therapy in cases requiring sinus floor elevation. Resorption of the posterior maxilla will proceed three-dimensionally, often resulting in limited bone volume in the horizontal as well as the vertical plane. For radiological assessment, a preoperative CBCT scan is recommended to evaluate the anatomy of the maxillary sinus. Depending on the residual bone height and the sinus floor anatomy, sinus floor elevation is facilitated either via the alveolar crest or a bony window in the lateral sinus wall.