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Dentistry has dramatically improved over the past 50 years, but tooth loss has not been eliminated. According to the American College of Prosthodontics (ACP) website, four of five adults, or 178 million people in the United States, are missing at least one permanent tooth.1 The ACP also reports that in the geriatric population, the ratio of edentulous to non-edentulous persons is 2 to 1, with 23 million people being totally edentulous and 12 million being edentulous in one arch. Even if a cure for periodontal disease—a key contributor to edentulism—is discovered, traumatic injury and parafunctional habits that cause tooth loss will not be eliminated. The current and future need for dental implants is tremendous.
Patients need to understand the importance of maintaining their teeth throughout their life. It has been established that the ability to get adequate nutrition is a determining factor of health in the elderly.2,3 Edentulism is a primary indicator of the ability to get adequate nutrition.4,5 One need only visit a nursing home and look around; up to 80% of the occupants are edentulous, and it is not a coincidence. For most nursing homes, edentulism is a key indicator of the degree of care a resident will require. Lack of teeth results in reduced quality of life6,7; it can also decrease life expectancy.
Implants are becoming an increasingly popular option for meeting the need to treat missing teeth. Dentists recognizing this opportunity can position themselves to provide a valuable service to their patients and support the growth of their practices into the future.
The SAFE Implant Protocol
A solution that can help meet the needs of patients who are missing teeth is known as SAFE (simple, affordable, fast, and esthetic) implants. The author has taken the integration of cone-beam computed tomography (CBCT) and chairside CAD/CAM technologies and organized existing workflows into a more efficient protocol. This protocol simplifies the implant process and reduces chairtime. The protocol is fast, resulting in tooth replacement in as few as three appointments, with total chairtime of less than 2 hours. Since the goal is to deliver a functionally esthetic replacement, treatment starts by designing the final restoration using a ceramic screw-retained crown. The SAFE implant protocol makes it easier to achieve functional natural-looking tooth replacements.
Patient Selection
With the SAFE implant protocol, proper patient selection leads to success. Identifying simple cases is important, particularly for those clinicians just beginning to place implants. The ideal patient is a healthy nonsmoker8 with no systemic disease9 and no periodontal disease.10 The edentulous site should be fully healed, with adequate keratinized tissue and bone volume. Not meeting all criteria does not mean the patient cannot undergo treatment; some criteria can be altered, particularly the keratinized tissue and bone volume. If inadequate, the patient can undergo hard- and/or soft-tissue augmentation.11,12 This can change a complex implant site to a simple one.
Bone Volume Evaluation
CBCT is an accurate tool for evaluating bone volume. Many CBCT scanners include proprietary digital implant planning software. There are also “open platform” software solutions that can be used with any CBCT data file. These are excellent diagnostic and planning tools and serve as the foundation of the SAFE implant protocol. Using the SAFE implant protocol is possible without direct access to a CBCT scanner or a chairside CAD/CAM system, but dentists with access to integrated CBCT-CAD/CAM systems have a simplified workflow, involving three appointments.
Clinical Exam Appointment
The first appointment is diagnostic. The patient’s medical and dental histories are reviewed and a CBCT is exposed, or arranged for if a scanner is not on site. Accurate study models are obtained, and a clinical examination is conducted, particularly looking for signs and symptoms of occlusal disease. A periodontal exam is also completed. If occlusal13,14 or periodontal disease is present, it should be treated before starting implant therapy.
Before completing the clinical exam, the edentulous site is evaluated for adequate volume in facial-lingual and mesial-distal dimensions. The smallest standard implants are 3.0 mm in diameter, but their restorative platform is 3.5 mm, andshould be 1.5 mm from adjacent teeth,15 requiring a minimum mesial-distal dimension of 6.5 mm (3.5 mm + 1.5 mm + 1.5 mm). Accounting for 1 mm of bone facially and lingually,15 plus approximately 1.5 mm of gingiva over each, requires a minimum facial-lingual dimension of 8 mm (3 mm + 1 mm + 1 mm + 1.5 mm + 1.5 mm). The ridge should also be palpated for facial undercuts commonly found apical to the muco-gingival line. These undercuts can affect the position and angulation of implants and should be further evaluated with CBCT.
Finally, the amount of attached gingiva is evaluated. There is disagreement regarding the need for attached gingiva around implants,16,17 but the generally accepted minimum is 2 mm.18,19 A zone of 3 mm is recommended by this protocol for esthetics. A simple method of evaluation is to place a periodontal probe against the cementoenamel junctions of the adjacent teeth. At the midpoint between the adjacent teeth, the buccal aspect of the implant should exit 2 mm lingual to the probe. Therefore, if attached gingiva extends 1 mm facial to the probe, there should be adequate keratinized tissue. If the minimum requirements of bone volume and attached gingiva are not met, ridge augmentation and/or soft-tissue grafting are needed prior to implant placement. If the minimum requirements are met, digital impressions of both arches are obtained before dismissing the patient.
Treatment Planning
Once the patient is dismissed, the real work begins. During this phase, the details of surgery, temporization, and final restoration are precisely planned. Attention to detail at this time results in reduced chairtime for the patient throughout the remainder of treatment.
The first step is to design the desired restoration. If designed with CAD/CAM design software (Figure 1), the restoration will need to be saved in a file type that is compatible with the implant-planning software being used. If using an analog wax-up, the waxed up model will have to be scanned with either a laboratory scanner or a chairside CAD/CAM scanner and saved in a compatible file type.
Once the desired restorative outcome is in a digital format, the patient’s CBCT scan is opened in the implant-planning software. If the edentulous space is in the posterior mandible, the inferior alveolar nerve bundle (IANB) is traced so that it is highlighted and avoided by the planned implant (Figure 2). Now, the patient’s digital restoration can be imported. Once imported, most software requires the user to identify corresponding landmarks on the digitized model and on the CBCT to merge the two data sets. It is best to avoid using teeth with crowns or large restorations as landmarks, because they cause distortions in CBCT scans and may result in inaccuracies in data set merges. Once complete, merge accuracy is verified by the user and is either confirmed or reset.
The software can now plan ideal implant placement based on the proposed restoration. The tooth being replaced will need to be identified, along with the implant brand/line, diameter, and length. Once the software digitally positions the implant, it can be repositioned, its length and width changed, and the implant line can also be changed.
Implant Diameter and Length
An important part of the planning process is knowing the implant diameter that should be used for each tooth. For mandibular incisors and maxillary lateral incisors, 3.0- to 3.5-mm implants should be used. For maxillary central incisors and maxillary and mandibular canines and bicuspids, 4.3- to 4.5-mm implants are indicated. For molars, 5.0- to 6.0-mm implants are typically appropriate.
Bone type may also affect implant diameter. Alveolar bone is categorized as type I-IV based on density due to cortical bone thickness and trabecular bone volume.Cortical bone provides primary mechanical stability to the implant, and trabecular bone provides vascularity necessary for integration. An implant’s diameter should allow for anchorage in the buccal and lingual plates while remaining 1.5 mm from adjacent teeth. The software allows the setting of a 1.5-mm “safety zone” line around the implant to aid in setting the implant diameter and position to best harmonize within the space. In addition to diameter, the ideal length also needs to be determined.
A good starting point for implant length is 13 mm. In the mandible, the IANB should be avoided by 2 mm to reduce paresthesia risk.20,21 A 2-mm safety zone line combined with the highlighted IANB helps visualize implant proximity. In the maxilla, the sinus floor and nasal floor can be used to provide primary stability. The implant should not penetrate these more than 2 mm unless a longer implant is required in the posterior and a sinus lift is planned to accommodate this. In determining implant length, angulation also needs consideration.
Implant Angulation and Depth
Implant angulation should result in occlusal forces being directed down the implant’s long axis. Therefore, the center of the implant and the resulting restoration’s screw-access hole should exit through the central fossa of posterior teeth and be directed toward the opposing tooth’s working cusp.21 The SAFE implant protocol goal is a screw-retained crown; therefore, anterior implants should exit through the cingulum. At this point, the implant’s relationship to the facial concavity of the maxilla should be evaluated. If penetration of the buccal plate cannot be avoided, ridge augmentation is necessary prior to implant placement. Lastly, implant depth is set.
Two factors affect implant depth: distance to the proximal contact and surrounding the implant with 1 mm of bone. The implant platform should be 5 mm or less from the proximal contact for proper papilla formation.21,22 Accounting for prosthetic components, the distance to the occlusal surface should be approximately 7 mm (5 mm abutment + 2 mm ceramic). If placing the restorative platform at the osseous crest does not provide this space, it is necessary to remove bone so the implant can be submerged to proper depth. However, if placing the platform 7 mm from the restorative surface does not result in surrounding the implant with 1 mm of bone, a decision must be made. The deficiency will usually be on the facial. The practitioner must either submerge the implant until there is sufficient bone surrounding it, or if this places the implant too deeply, augment the ridge prior to implant placement. Current guided regeneration techniques can predictably gain up to 5.5 mm horizontally23 and 10 mm to 12 mm vertically.24 Once the implant platform is set, the final apical length of the implant can be adjusted and the digital plan is complete (Figure 3).
Digital planning only takes a few minutes. Once completed, the plan can be sent electronically from within the software to a laboratory for production of a surgical guide. Depending on the laboratory, the guide can be made and returned in 2 to 10 days. The surgical appointment can be made, and the final planning steps can be completed.
Provisional Restoration
Before the surgical appointment, a provisional restoration can be made if an immediate load situation is anticipated. This is accomplished by retrofitting an implant analog into the patient’s model using the surgical guide. The analog is mounted on a guided implant mount and placed in the surgical guide. The guide is seated on the model after having removed stone to accommodate the analog. Stone is then flowed around the analog and allowed to set (Figure 4). To ensure that the implant ends up in the same position intraorally, an index of the implant mount in the guide on the model is made with polyvinyl siloxane (PVS) bite registration material (Figure 5). Next, a temporary abutment is placed on the analog, and a CAD/CAM crown is designed with a screw-access hole. The crown is bonded to the abutment and the provisional is complete. Alternately, an acrylic crown shell with a hole through it can be adapted over the temporary abutment.
Surgical Appointment
The surgical appointment is quick and efficient due to the planning of the surgical guide. Standard surgical protocol is adhered to as with any implant surgery. Once the patient is prepared and anesthesia is achieved, the implant manufacturer’s drilling protocol is followed for preparing the osteotomy. The SAFE implant protocol involves flapless implant placement, because soft-tissue deficiencies were identified and addressed before implant placement. It is not unusual for implant preparation and placement to take 15 minutes or less. Once the implant has been placed and verified radiographically, it can be scanned with chairside CAD/CAM to make the final restoration.
To scan the implant, an appropriate scan post is attached to the implant, and a scan body is placed onto the scan post. The scan posts and scan bodies are specific to the chairside CAD/CAM system being used. Implant manufacturers as well as a few large commercial laboratories are developing generic versions of these. The shape on the top of the scan body provides the design software information regarding the depth, angulation, and timing of the implant platform. Both arches and the patient’s bite can now be scanned. Finally, a healing abutment or provisional is placed on the implant, postoperative instructions are given, and the patient is released.
Final Restoration Design
The implant is allowed to integrate, during which time the final restoration is designed. Ceramic screw-retained crowns are the restoration of choice for the SAFE implant protocol because they allow for tissue contouring and are esthetic. Besides being retrievable, they also eliminate cement sepsis caused by subgingival cement, a leading cause of post-restorative implant failure.25
Ivoclar Vivadent (www.ivoclarvivadent.com) makes an IPS e.max® abutment block with a pre-milled screw access hole that fits precisely over a Sirona TiBase. Sirona also makes an inCoris Meso block that is a zirconia block with the same pre-milled hole. There are other companies that make TiBase abutments, but they are not manufactured to fit the Ivoclar or Sirona blocks. In the author’s opinion, these materials simplify the fabrication process of screw-retained implant crowns. Once designed and milled, the restoration is processed in a porcelain furnace and bonded to the TiBase with an appropriate cement (Figure 6). If chairside CAD/CAM is not available, a fixture-level PVS impression is taken after integration is confirmed and sent to a lab for fabrication of the final restoration.
Restoration Delivery Appointment
The third and final step in the protocol is delivery of the restoration. Once integration is confirmed, the healing abutment or provisional restoration is removed and the final restoration is tried in. After proximal contacts are adjusted and seating of the restoration is verified radiographically, the occlusion is checked and adjusted. The prosthetic screw is torqued to the manufacturer’s specification, and the screw-access hole is closed by placing a piece of Teflon tape into the hole to protect the screw and filling the hole with composite. Properly done, the access hole is almost imperceptible (Figure 7). The tooth replacement is now complete.
The Question of Affordability
Despite the need, dental implants have been underused in the United States. Although up to 178 million people are missing teeth, the American Academy of Implant Dentistry (AAID) reports only 5.5 million implants have been placed by dentists in the United States.26 This may be due in part to the fact that, according to the AAID, only 10% of dentists place implants. There is also the perception that implants are too expensive. There are situations in which a single tooth implant can cost $5,000 or more. The increasingly popular All-on-4® (Nobel Biocare, www.nobelbiocare.com) treatment—which uses four or more implants to support an immediately-loaded full-arch prosthesis—can cost $25,000 to $45,000 per arch. It is also true that dental plans are covering implant services and are driving down contracted fees. It is not unusual to see a patient whose dental plan has a contracted fee for an implant of $1,500 and pays 50%.
As patients consider the perceived expense of implants, it is imperative to also help them understand the “costs” of non-treatment. Not replacing a missing tooth can lead to drifting of surrounding teeth, which can result in increased risk of tooth decay and periodontal disease due to increased difficulty in cleaning malpositioned teeth. Patients may also experience shifting in their bite, causing functional changes. These changes may result in temporomandibular disorder signs and symptoms as well as wear or fracture of other teeth. Ultimately, a lack of treatment can lead to additional tooth loss.
The focus of the SAFE implant protocol is providing functional esthetic restorations in a predictable, safe manner. This can be accomplished in as few as three appointments, with total chairtime amounting to less than 2 hours. SAFE implants also provide the opportunity for cost savings. With the incorporation of integrated CBCT and chairside CAD/CAM, the cost of providing this treatment can be kept around $895 (eg, surgical guide, $350; implant, $325; interim abutment, $50; TiBase, $100; 2 ceramic blocks, $70). The cost of treating an implant traditionally can vary from approximately $825 to $1025 (implant, $325; interim abutment, $50; stock abutment and crown, $450, or custom abutment and crown, $650, or screw-retained crown, $500). The cost of traditional implant treatment can differ due to variable lab fees and the cost of different implant brands. Additional cost savings can be realized through reduced chairtime of approximately 1 hour with the protocol. This saved hour can then be used to treat additional patients.
Conclusion
SAFE implants provide a workflow that allows the functional and esthetic replacement of a missing tooth with an implant and screw-retained crown in a predictable manner. It allows for increased patient convenience by reducing the number of appointments and total chairtime. The use of integrated CBCT and chairside CAD/CAM can enhance the process and help reduce costs, making implants a treatment option that is obtainable by more patients.
References
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About the Author
Gregory Scott Sauer, DDS
Eldorado Smiles and Orthodontics
Frisco, Texas
Implant Subject Matter Expert and Faculty
PDS Institute
Irvine, California
