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Unsal GS, Turkyilmaz I, Lakhia S. Advantages and limitations of implant surgery with CAD/CAM surgical guides: a literature review. J Clin Exp Dent. 2020; 12:e409-e417 https://doi.org/10.4317/jced.55871
Salem D, Mansour MH. Surgical guides for dental implants; a suggested new classification. J Dent Oral Health. 2019; 6:1-8
Kola MZ, Shah AH, Khalil HS Surgical templates for dental implant positioning; current knowledge and clinical perspectives. Niger J Surg. 2015; 21:1-5 https://doi.org/10.4103/1117-6806.152720
Henprasert P, Dawson DV, El-Kerdani T Comparison of the Accuracy of implant position using surgical guides fabricated by additive and subtractive techniques. J Prosthodont. 2020; 29:534-541 https://doi.org/10.1111/jopr.13161
Reyes A, Turkyilmaz I, Prihoda TJ. Accuracy of surgical guides made from conventional and a combination of digital scanning and rapid prototyping techniques. J Prosthet Dent. 2015; 113:295-303 https://doi.org/10.1016/j.prosdent.2014.09.018
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Misch CE., 3rd edn. : Mosby Elsevier; 2008
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Raico Gallardo YN, da Silva-Olivio IRT, Mukai E Accuracy comparison of guided surgery for dental implants according to the tissue of support: a systematic review and meta-analysis. Clin Oral Implants Res. 2017; 28:602-612 https://doi.org/10.1111/clr.12841
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Implant surgical guides play a crucial role in the success of dental implant treatments. By aiding in diagnosis, treatment planning, and precise positioning of implants, these guides ensure accurate placement in the jaw bone. There are two main types of surgical guides: customized conventional radiographic templates and computer-generated templates. While the former may lack important dimensions and anatomical information, the latter, made using 3D imaging, offer precise planning and efficient implant placement, reducing complications. However, inexperienced dentists must undergo appropriate training and consider critical anatomical structures. In summary, implant surgical guides enhance accuracy and improve the success rate of implant therapy, with the choice depending on patient needs and clinician expertise.
CPD/Clinical Relevance: Implant surgical guides are important in ensuring accurate and successful dental implant treatments.
Article
Dental implants have become a widely used treatment option and good treatment planning is crucial for their success. Proper diagnosis and implant placement are important factors in success of implant prosthetics.1 Failures can occur when the super structure is not considered during pre-operative treatment planning2. According to the Glossary of Prosthodontic Terms, surgical guides assist in diagnosing and treatment planning, as well as correct positioning and angulation of dental implants in the jaw bone.1,3 During surgery the guide can, for example, be placed on the remaining dentition or edentulous space and will therefore offer information about the correct implant placement. Thus, the treatment can be restoratively driven, be planned from the top down and executed from the base up to achieve an excellent prosthetic result.
Consideration of the soft-tissue quality, is also essential for the long-term success of implant therapy. Soft-tissue management is an important factor in the outcome of implant therapy and can be achieved with several techniques such as flap design, grafting or suturing4. When designing the flap, the surgical guide should be considered. During the procedure it is important to ensure that the surgical guide does not crush the soft tissues. When all these factors are taken into consideration during pre-operative treatment planning, implant prosthetics can be achieved with excellent long-term results.
Types of implant surgical guides
Implant surgical guides consist of two components: the guiding cylinders and the contact surface.5 The contact surface will either be in contact with the patient's remaining natural teeth, or their gums or bone. The guiding cylinders support the drills and guide them into an accurate position, which was planned beforehand.
Implant surgical guides can be grouped into three categories according to their supporting surfaces.5 First, a guide can be tooth supported, being placed on the remaining teeth. Secondly, it can be mucosa supported where it is placed directly onto the mucosa (e.g. in edentulous patients). Thirdly, a guide can be bone supported and placed onto the bone after raising a full-thickness mucoperiosteal flap5.
An alternative way of classifying guides is by the way they are used.6 Free guides show the tooth centre point, access guides guide the first drill only, and precision guides guide the whole drilling sequence.6
Surgical guides can also be divided into customized conventional radiographic surgical templates, and computer-generated surgical templates, which have become the treatment of choice7 and are discussed in this article.
In a customized conventional radiographic surgical template, a comprehensive radiographic examination and good diagnosis of the bone are crucial.2 Measurements of the bone cannot be completely accurate because of the magnification factor in radiographs.2 However, this method remains the standard for implant planning.2 To plan implants using this method, the patient wears a radiographic template with metal guide posts of a known dimension. The implant is then planned according to the magnification factor and dimensions of the metal guides.2,8 In addition, during CBCT, patients can wear radiographic guides only that resemble customized guides (Figure 1). These guides can be modified to accurately direct the initial drill during the osteotomy procedure. Figures 2 and 3 show a modified guide used during implant surgery.
Figure 1. Radiographic guide.Figure 2. Tooth-supported modified radiographic surgical guide.Figure 3. Positioning of the first osteotomy drill using a modified radiographic surgical guide.
Fabrication method
There are different ways to fabricate this type of surgical guide. For example, diagnostic casts can be used to make a diagnostic wax-up. Then, a silicon impression of the cast with the wax-up is taken and an acrylic resin is poured over it and cured. Access holes are made in which metal surgical guide posts are placed.2
Another method would be to use a vacuum-formed template. Once the wax-up has been carried out, it is duplicated and a cast then poured. The template is placed over the cast and is vacuum formed. The edentulous space is filled with radiopaque material, such as barium sulphate.2 The surgical guide is then placed in the patient's mouth and a radiograph is taken. From here, the positioning of the implant can be planned. The radiographic guide is then converted into a surgical guide by removing the radiographic material and trimming the acrylic to create space for the surgical drills.
Accuracy
As these types of surgical guides are widely used, they can be seen as fairly accurate. However, they do have limitations. They are made from a 2D-image and are therefore not able to give information about the bucco-lingual or bucco-palatal bone dimension. They also do not take certain anatomical landmarks into account, for example the lingual blood vessels. Furthermore, these templates are made on rigid casts and do not consider the underlying soft tissues or bone topography.2
Despite the limitations, these conventional types of surgical guide have been proven to be more accurate than free-hand implant placements.9 Reyes et al10 stated that they are more accurate than CBCT-scanned surgical guides when placed on tooth surfaces. However, because it is not possible to correlate them with a CBCT scan, it may be more difficult to ideally place implants.10
Computer-generated surgical templates
Computer-generated surgical templates are made using a rapid prototyping technology called stereolithography, which simulates the implant placement in 3D. The templates are placed directly onto the bone and are pre-programmed with the individual depth, angulation, and mesio-distal and buccolingual positioning of the implants.11 The computer-generated or computer-aided design/computer-assisted manufacturing (CAD/CAM) technique applies data from a computed tomography (CT) scan to plan the implant placement according to the anatomical site and planned prothesis.7
Fabrication method
To create a stereolithographic template a radiographic template is needed first. Its fabrication is described above. It is kept in the patient's mouth during a CT scan procedure, so that it can indicate the location of the teeth and gingival tissues.2 A 3D reconstruction of the full dental arches and their relevant structures (e.g. nerves) can be generated by CT planning and imaging software.7 Next, this software transports the pre-surgical plan to the surgical site using stereolithographic drill guides.7 The stereolithographic template is then produced in the laboratory. It is a transparent mould that is designed to replicate the exact position and shape of the dental arches and their related anatomical structures. The template is made of transparent acrylic resin.7 The material is transparent so that the clinician can observe the position of the teeth and gingival tissues.2 Once the template is completed, it is placed in the patient's mouth during the surgery, thus the exact location of the implants can be determined2.
Figure 4. Flow chart for customized conventional radiographic surgical guides.Figure 5. Flow chart for computer-generated surgical guides.Figure 6. Flow chart for orthodontic surgical guides.
Advantages of this technique include the possibility of precisely placing implants while considering the anatomical structures, less invasive surgery due to correct planning and a reduced surgical exposure time.7 Disadvantages include a restriction of the view of the surgical site and tactile control throughout the surgical treatment, a compromised surgical procedure if the patient's mouth opening is insufficient and a chance of harm to vital anatomical structures if the guide was not planned correctly.7
Accuracy
Studies have shown that using computer-generated surgical guides can improve implant placement and allow a true translation of the treatment plan to the surgical site.12–14 They allow the clinician to place the implants accurately and efficiently, thereby reducing the risk of complications.7 Although computer-generated surgical guides can be very precise, they are not entirely accurate. Appropriate training before using these surgical guides is essential.5 Moreover, an adequate amount of space between implants and critical anatomical structures should always be considered.5 Geng et al13 looked at the accuracy of various kinds of CAD/CAM surgical guides. They found that they do enhance the precision of implant placements and that tooth-supported surgical guides may be more accurate than mucosa-supported surgical guides.15 Finally, they discovered that partially guided templates provided the same results as fully guided templates.15 Cunha et al16 analysed the accuracy of computer-guided implant surgery associated with prototyped surgical guides. The null hypothesis of this study was that angular and linear deviations would be similar between the planned and placed implants.16 They found that flapless computer-guided implant surgery with virtual planning showed some angular and linear deviations, but still considered it an acceptably safe and accurate technique.16 These results suggest that raising a flap is beneficial during the treatment, because it provides the clinician with better sight of the surgical area.
Accuracy in relation to the tissue of support
Bone-supported surgical guides offer the advantage of direct contact with the bone, providing good stability during implant placement. This type of guide can be especially beneficial in cases where teeth are not present for support. By using bone-supported guides, clinicians can ensure precise positioning of implants in areas with limited anatomical landmarks. However, a systematic review and meta-analysis comparing the accuracy of surgical guides according to the tissue of support found a statistically higher accuracy for mucosa-supported guides than bone-supported guides.17 Similarly, they found better results for tooth-supported guides than bone-supported guides.17 This indicates a more accurate use of surgical guides in dentate patients compared to edentulous patients. The dentition may be used as a reference point and thus offering better precision. In contrast to these findings, Turbush et al18 found no statistical differences in accuracy between mucosa-, tooth- and bone-supported surgical guides. In edentulous patients, mucosa-supported guides are commonly used. D'haese et al19 found a clinically acceptable accuracy for mucosa-supported guides. Nevertheless, the mobility of the mucosa negatively affected guide stability and led to a greater deviation in the implant position.19
Figure 7. Positioning of the first osteotomy drill using a modified radiographic surgical guide (different angle).Figure 8. X-ray control of parallel pin after initial osteotomy.Figure 9. Final implant position.
Cost comparison
When considering the cost of surgical guides, customized conventional radiographic surgical templates may be more cost effective compared with computer-generated surgical templates. Customized templates require materials for impression taking, acrylic resin and metal guide posts, which are relatively inexpensive. In contrast, computer-generated templates involve the use of advanced technology, such as CBCT scans and stereolithography, which can be more costly. However, the costs associated with computer-generated surgical guides decreases per implant when multiple implants are placed simultaneously, and the time and effort required for the procedure workflow also decreases per unit.20 Overall, this may justify the additional expense.
Training requirements
Effective use of customized conventional radiographic surgical templates may require training in diagnostic imaging, impression taking and template fabrication techniques. On the other hand, clinicians using computer-generated surgical templates should be trained in CAD/CAM technology and software to create and use the 3D-guided templates effectively. Specific training requirements may vary, and it is therefore advised to consult with the manufacturer prior to first use.
Dynamic navigation systems
Dynamic navigation systems, such as X-guide (Nobel Biocare, Switzerland), offer real-time guidance and tracking during implant surgery. These systems combine computer technology with intra-oral scanning to dynamically adjust the surgical plan based on real-time data. While surgical guides offer pre-planned implant placement, dynamic navigation systems offer continuous feedback and adjustment throughout the surgical procedure, potentially improving outcomes in complex cases. Block et al21 found similarly good outcomes in terms of accuracy when comparing dynamic navigation systems to static guides. Further, they discovered a better accuracy in dynamic navigation systems over freehand implant placements.21 A systematic review and meta-analysis from 2021 supports these findings. Again, the accuracy of dynamic navigation systems and static computer-generated guides was similar, while dynamic navigation provided enhanced accuracy compared to conventional freehand implant placement.22
Implant surgical guides in orthodontics
Implant surgical guides can also be used in orthodontic treatment. Even though orthodontic mini-implants demand a less complicated surgical procedure, it is still crucial to place them in the correct position, because the risk of root perforation is high.23 The fabrication of these surgical guides is similar to the ones used in implant surgery. A cast is made and is waxed around the implant holes and occlusal areas.23 The areas are then isolated and cold-cure acrylic resin is applied and polymerized.23 The surgical guide is placed into the patient's mouth and the guide's drill holes are used for the osteotomy. The difference in orthodontics is that the guide holes for the mini-implants are placed buccally rather than the ridge.
Conclusion
In cases of sufficient bone volume and anatomical orientation, a surgical guide may not be needed. If these parameters are not given the use of a surgical guide can be beneficial.
The customized conventional radiographic surgical templates are a reliable method for planning implants. Nevertheless, they have some limitations and further research is still required for refining accuracy and developing more efficient methods for their fabrication.
Computer-generated surgical guides provide a great advantage in implant surgery planning in terms of accuracy and translation of the treatment plan. However, when using such advanced tools, inexperienced dentists should require proper training and must always consider the relationship between implants and critical anatomical structures.
The effect of full and partial surgical guides on the peri-implant soft tissue was examined in a Cochrane split-mouth clinical study in 2020. Forty-eight implants placed in 12 patients with either a partial or full surgical guidance showed no statistical differences in plaque index, gingival index, probing depth, probing attachment level, implant stability, bone level or bone density.24 The results of this study suggest that the use of partial or full surgical guides is not associated with any major differences in soft tissue outcomes around implants. Still, further studies are needed to confirm these results.
In conclusion, surgical guides have the potential to offer significant accuracy in implant placement and can be beneficial in cases where bone volume and anatomical orientation are not ideal. Therefore, they give clinicians the opportunity to place implants in areas where the implant–bone interface may be maximized and the prosthetic result is optimized.7 The peri-implant tissues are expected to be in good condition. Experienced practitioners must consider the benefits, drawbacks and limitations of each method before choosing the most suitable technology for their patient.
