Implant prosthodontics has come a long way

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1 CPD POINTS AVAILABLE Continuing Education credits are available on this article for subscribers by answering the questionnaire at Guided implant surgery - the new standard of care? By David B Dunn, BDS (Hons), FRACDS, FPFA It is important to state quite unequivocally that guided surgery, especially when combined with immediate loading, is no slam dunk and should only be undertaken by clinicians with appropriate training and surgical and restorative experience... Implant prosthodontics has come a long way since the introduction of Brånemark s concepts of osseointegration to the profession at large back in the early 80 s. We have seen a dramatic change in all areas of the application of this biotechnology including the developments in both the macro- and micro-design of implants, with over 300 different implant manufacturers now offering various products. Exciting changes have also occurred in materials science and the use of CAD/CAM manufacturing for both titanium and zirconia abutments along with one-piece, fixed partial-denture substructures. Further, we have evolved from the original two-stage surgical protocols, as described by Brånemark, to the concepts of immediate placement and immediate loading (where indicated). We have witnessed the development of both soft and hard tissue grafting techniques and technologies including guided bone regeneration techniques (GBR) utilising various resorbable and nonresorbable membrane technologies, as well as a variety of both allografts and the xenografts. We have seen block grafts, sinus grafts, distraction osteogenesis, platelet enriched plasma (PRP) and now, the application of bone morphogenic proteins (BMP 2) with various carriers. One of the other significant developments in this field has been the concept of guided surgery with sophisticated, three-dimensional implant planning software programs utilised with either fan beam (CT) or cone beam radiographic scanning technologies. The genesis of guided surgery In 2000, Professor Jacobs of Oral Imaging Cluster, KU Leuven, compared the accuracy of implant placement utilising simple drill guides with manual placement and no guide, or template, with meticulous care, utilising cadavers. The accuracy level, in the X-axis, obtained with implants placed utilising drill guides was 0.92 mm as against manual placement with an error of 3.71 mm. It is important to also note that these implants were placed under ideal conditions with no saliva, blood, tongue or opening issues, etc. In 2002, Professor Daniel van Steenberghe published a paper titled a custom template and definitive prosthesis allowing immediate implant loading in the maxilla: a clinical report in the International Journal of Oral and Maxillofacial Implants. He presented his data on two cadavers and eight human patients utilising LITORIM - Leuven Information Technology-based Oral Rehabilitation by means of Implants. Here he compared the results of the implant positions and axes achieved from the positions planned versus those actually achieved, following the use of computer tomography scanning technology along with a sophisticated three-dimensional software planning program and surgical templates produced from this planning process. This technology formed the basis of what we now know as NobelGuide. He concluded the results indicated nearly a perfect match between the positions and axes of the placed implants and those planned. The error in the 142 Australasian Dental Practice January/February 2009

2 Figure 1a. Pre-treatment OPG. Figure 1b. Simplant Surgi-guide in situ. Figure 1c. OPG at provisional restoration stage. Figure 1d. Completed treatment with Procera custom ceramic abutments and all-porcelain crowns. implant axes was 1.8 with a standard deviation of 1, whilst the error in the implant entry point was 0.8 mm with a standard deviation of 0.3. These results were obviously very encouraging for precision implant prosthodontics. Developments in radiography Historically, when we consider past attempts at improved diagnosis and presurgical planning, we see the application of what now appear as rather crude tools! Initially, OPG s and periapical radiographs were utilised with various clear overlay templates of varying magnifications. Ridge mapping was also undertaken utilising transfer templates and calliper readings in the mouth to enable subsequent modification of study models. Computed tomography (CT) was the next development along with rather basic planning software programs such as Dentascan utilising various forms of simple radiographic templates. At this stage of the development in implant prosthodontics, it must be considered that most of the cases were fully edentulous (and mainly in the mandible) and the emphasis at that time was on function rather than aesthetics. Indeed, early on there was very little sophistication in abutment options and single and partial cases were rarely attempted. Further, more often than not, a team approach philosophy was utilised in implant prosthodontics. This included a restorative dentist or prosthodontist along with an oral surgeon (and later periodontists) undertaking treatment. It would not be unfair to say, at that time, that implants were placed where the bone was and not in accordance with a predetermined, restoratively driven treatment plan. Surgical templates were rarely utilised, and if provided, they were used minimally (this may have also been a reflection of the lack of experience of the restorative team member, lack of pre-treatment work-up as well as the crudity of the surgical templates provided). Over the ensuring years, the planning software programs certainly improved in sophistication along with some improvements in the construction of the radiographic and surgical templates. However, the issue remained that the success of even a meticulously planned case was effectively only as good as the surgical templates and these templates had to be manually and arbitrarily interpreted or adjusted (in the case of the modification of a radiographic template) from the information gained from the planning. Furthermore, the surgical templates only provided two-dimensional controls (to a limited extent) and not true three-dimensional placement as well as the fact that the implants were not placed through the guiding templates, again leading to potential for further errors. Aesthetics becomes the focus As implant hardware technologies developed, a dramatic increase in single and partial cases were undertaken. As the profession on the whole became more comfortable with the concept of osseointegration and its applications, aesthetics began to become a more and more powerful concept. Single tooth and partial January/February 2009 Australasian Dental Practice 143

3 fixed denture cases were being undertaken more routinely. The challenge significantly increased when having to replace missing teeth with an implant supported prosthesis that not only was functional and provided long-term predictability, but also one that was highly aesthetic and blended with the surrounding dentition and soft tissues. This became even more so when replacing a single or only a few missing teeth in the aesthetic zone and without symmetry! In order to meet these demanding challenges, and especially those of fulfilling the heightened aesthetic demands of our patients (and ourselves,) we had to be far more precise in both the diagnostic workup and ultimately the three-dimensional implant placement, in strict accordance with the treatment plan. Guided implant placement Today, thankfully, we have excellent tools to assist us in this process and to achieve this end result more easily. There are both static and optical dynamic navigation systems available for guided implant surgery. The dynamic systems are based upon three-dimensional data, with the osteotomy drill displayed live at the time of surgery by infra-red optical correlation of the patients jaw with the drill by the software and displayed on a computer screen in the surgical setting. Guided implant placement with a surgical guide is referred to as a static procedure. By far the most popular guided systems today utilise static procedures. Surgical guides can be produced in a stereo-lithographic process in a manufacturing centre utilising digital data (e.g. NobelGuide and SimPlant) or via a converted radiographic guide into a three-dimensional surgical guide via a special transfer device such as with med 3-D. All systems are based upon backwards planning. All systems allow drilling through the surgical guide; however, a high degree of precision can only be achieved when the entire implant placement procedure, from drilling to placement, is through the surgical guide. In 2007, in an article in the European Journal of Esthetic Dentistry titled Three-dimensional navigation in implant dentistry, authors Marquardt, Witkowski and Strub concluded: it is now possible to predetermine the precise three-dimensional position of the planned implant before the actual implant insertion and to transfer this position to the surgical site... this increases the quality of both the surgical procedure and the restoration. The author considers this as one of the Holy Grails of implant prosthodontics. The goals of guided surgery So what then are the goals of guided surgery? Firstly, and most importantly, to accurately and predicably achieve clinical outcomes transposed from careful diagnostic and pre-surgical planning. This should ideally be applicable to all clinical situations; from single teeth to full arch rehabilitations. It should enable the treatment of difficult sites such as very narrow ridges. It should reduce both the complexity and time of treatment for both patients and clinicians. It ideally should enable the pre-construction of a provisional or final prosthesis. It should ideally enable flapless and open flap procedures for implant placement. It should enable full three-dimensional guidance i.e. depth, mesio-buccal and bucco-lingual angulations. And finally, it should become the medico-legal standard of care in most cases and certainly in more complex cases. Advantages of guided surgery There are obviously many advantages of guided implant surgery and these relate to the main three players in the relationship; most importantly - the patient, the practitioner(s) and the dental technician. For the patient, the author believes that guided surgery (with experienced operators) does offer the ability to achieve the highest level of diagnosis utilising the various software planning programs available today, and from this planning, develop a treatment plan with the placement of implants (and ultimately the definitive prosthesis) undertaken predictably and in strict accordance with this treatment plan. In the absence of other variables (the validity of the diagnosis and treatment plan, surgical skill and experience, the skill of the laboratory technician, etc), patients can have more predictable treatment resulting in a higher level of safety and ultimately the desired aesthetic and functional outcome. In many cases, especially in flapless or blind techniques, this can result in decreased swelling, bleeding and discomfort. The number of procedures and hence the time requirement (for the patient) can be decreased significantly and in many instances, costs can also be reduced. For the clinician, the advantages of guided surgery are compelling, especially for the single operator. There are several very sophisticated software planning programs available today, including NobelGuide, SimPlant and med 3-D, to enable excellent diagnosis and treatment planning and from this planning and in accord with it, have surgical templates constructed. However, all systems have their various pros and cons and not all systems achieve the same level of accuracy or control as one another. By far, the most significant advantage for the clinican is the ability to visualise the hard and soft tissue anatomy of their patient and to test their proposed treatment plan, and various options within this plan, prior to any intervention being undertaken. Whilst in most cases it enables the determination of an appropriate treatment plan, in others it may eliminate that patient from initial treatment and determine the need for either or both hard and soft tissue grafting prior to future implant treatment. Further, it enables an appropriate dialogue with the patient, describing their proposed treatment plan in detail, including risk assessment and the ability to outline the options in treatment or identification of any compromising factors. Again, predictability is the key and the ability to minimise unknowns and operator variables is very significant. Whilst there is certainly an increased time requirement in the diagnostic work-up and the computer planning/assessment stage for the clinican, there is a significant potenial for savings in the context of clinical time, which for most, is the critical issue. Difficult cases such as narrow ridges, minimal bone above the inferior alveolar nerve (IAN), nasal or sinus floors, all on four techniques utilising angled distal fixtures to avoid either the maxillary sinus or the IAN, in mandibular cases, closed or blind placement of Zygomaticus implants, narrow mesio-distal spaces with close root proximity and flapless procedures, are but some of the examples where guided surgery is of enormous benefit. The ability to construct a provisional or indeed definitive prosthesis prior to implant 144 Australasian Dental Practice January/February 2009

4 Figure 2a. Pre-treatment OPG. Figure 2b. Pre-treatment-close up. Figure 2c. med3d radiographic template. Figure 2d. Implant placement via med 3D planning and surgical template. Figure 2e. Provisional crowns ready for immediate loading. Figure 2f. NobelGuide radiographic template and index. Figure 2g. NobelGuide surgical template. Figure 2h. NobelGuide surgical template and index. Figure 2i. OPG of provisional restorations utilizing 2 different technologies: Lower LHS placed using med3d; Maxilla placed with NobelGuide F/-OIB. Figure 2j. NobelGuide F/- provisional OIB demonstrating accuracy of placement of implants with access holes through occlusal/palatal surfaces. January/February 2009 Australasian Dental Practice 145

5 Figure 3a. Pre-treatment OPG. Figure 3b. Pre-treatment. Figure 3c. Mid-treatment at approximately 6 months following maxillary tooth removal. Patient is ready for flapless surgical placement of implants. placement and have the confidence that the prosthesis, with appropriate surgical skills, can be placed at the time of surgery is certainly of benefit. However, at this stage, only the NobelGuide system (Nobel Biocare) with true three-dimensional guidance and the placement of the implants through the surgical template including depth control and utilising their specific guided abutment to accommodate any minor discrepancies, can achieve this reality. However, in the author s opinion, most immediately placed restorations should be provisional only and immediate function only utilised when the appropriate criteria have been met. The ability to test the prosthetic design with provisional restorations prior to definitive restorations provides the opportunity to make changes, have tryin procedures, accommodate any soft tissue changes following implant placement and more readily confirm successful osseointegration, prior to embarking on expensive laboratory procedures. Having said that, the ability to have a provisional prosthesis pre-constructed and inserted at the same day of surgery or the next day, is a significant advantage and a great motivator for patients. Figure 3d. NobelGuide radiographic template. Many practitioners, especially with more complex cases, are often caught with increased costs at the laboratory level which were initially unforeseen. Guided surgery, enabling the achievement of the predetermined prosthetic plan, minimises the risks of more complicated technical procedures being required to accommodate issues such as angulation issues, minimal soft tissue dimensions and too close proximity of implants. Figure 3e. NobelGuide model pre-made from planning. Medico legal considerations We live in an increasingly litigious society which raises the question of the medicolegal responsibility of the clinician to use all appropriate diagnostic and surgical aids in undertaking a patient s particular treatment. Guided surgery helps support the practitioner (and indeed ultimately the patient) in two significant ways. Firstly, it demonstrates an intent to initially generate appropriate diagnostic information and to then utilise this information in conjunction with a specific implant planning software program to test the prescription and ultimately define a treatment plan based upon this information. Secondly, it demonstrates an intent to utilise the most precise templating for implant surgical placement to achieve the desired and predetermined treatment plan. Of course, this is but part of the story and indeed problems have and will continue to occur despite the best planning and use of guided surgery and implant software planning technologies, especially in inexperienced hands. Implications for the dental lab For dental technicians, guided surgery has already and will increasingly be of great benefit. Ideally, technicians should be involved in the decision-making phase of treatment planning to provide input on the technical aspects of the proposed treatment. This may include considerations of the restorative design such as cement-on/ cross-pinned or screw retained; whether abutments are utilised and which type; the choice of substructure for the reconstruction (i.e. titanium, chrome cobalt, gold alloy or zirconia); and whether there is a need for prosthetic soft tissue replacement, its design and composition. The dental technician should also be able to provide a firm estimate of the laboratory costs involved and not be faced with the multitude of problems they can often encounter with cases undertaken with manual placement. 146 Australasian Dental Practice January/February 2009

6 Figure 3f. Surgical template and NobelGuide surgical index in situ immediately prior to implant placement. Figure 3g. Surgical template controlling 3D placement at time of flapless surgery. Figure 3h. Tissue fitting surface of provisional F/- OIB utilizing provisional abutments, Figure 3i. Provisional immediate OIB at laboratory stage just prior to placement. Figure 3j. Post-treatment OPG following insertion of provisional F/- OIB. Guided surgery systems There are currently three major guided surgery systems available on the local market today - NobelGuide (Nobel Biocare); SimPlant (Materialise, available through Tomatic) and med 3-D (med 3-D AG available through Alphabond). It is important to state quite unequivocally that guided surgery, especially when combined with immediate loading, is no slam dunk and should only be undertaken by clinicians with appropriate training and surgical and restorative experience. The author firmly believes that at present, these systems are all being advertised and promoted as entry-level technology for inexperienced users with minimal training but this can only lead to complications and most importantly, unhappy patients. This technology is no substitute for experience at either the surgical or prosthodontic level and certainly not the panacea of all ills when it comes to implant treatment! Here is as a brief overview of each: Both SimPlant and med 3-D can utilise most implant makes on the market today, whereas NobelGuide is restricted to Nobel Biocare implants only. All three systems have good to excellent 3-dimensional planning software. All three systems can utilise either CT or cone beam scans NobelGuide and med 3-D utilise raw DICOM data. SimPlant requires DICOM files to be processed for a fee prior to use with the software unless the clinician has invested in the highest level PRO software. Ideally, a double-scan technique (the patient and template are scanned together and then the template scanned separately) is preferable to avoid artefacts in the scans. NobelGuide is the only system utilising a double-scan technique. The radiographic template design is critical as well as it s stabilisation while radiographic imaging is undertaken. The NobelGuide protocol includes the use of an occlusal index to stabilise and maintain the orientation of the radiographic template while scanning procedures are undertaken. The other systems utilise a passively seated template with no stabilisation. All systems are at risk of errors with movements or incorrect positioning of the radiographic template at the time of the scanning procedures. The stabilisation of the surgical template is also critical. In the NobelGuide system, this is achieved utilising anchor pins which are 1.5 mm diameter lateral stabilising pins designed at the planning stage and incorporated into the template. No other system has this feature. This is especially important in unbounded saddles and obviously in fully edentulous situations. SimPlant does have optional 2mm retention screws to stabilize the template at time of surgery. The SimPlant safe system provides true 3-dimensional control and implant placement through the template, however, it is at present restricted to external hex implants only and also to diameters between 3.75 mm and 4.1 mm. The med 3-D system is mainly utilised with a single 2 mm pilot hole sleeve, however, several templates can also be constructed with other diameter sleeves used. Implant placement is not undertaken through the template. SimPlant normally provides three templates with varying diameter sleeves according to practitioner preference. However this can complicate issues with multiple implants of varying diameters. 148 Australasian Dental Practice January/February 2009

7 SimPlant turnaround time from the hard model and radiographic template being sent to the production facility in Belgium, is approximately 2 weeks. Med 3-D utilises the fabrication and conversion of the radiographic template to a surgical template. This normally takes approximately one week and is undertaken with a designated local dental laboratory (with the Hexapod device required for conversion). The NobelGuide delivery time from receipt of electronic data to receipt of surgical template is approximately 10 days. NobelGuide can be utilised with either computer-based planning or with modelbased planning. SimPlant requires the model and template to be sent to Belgium for template fabrication, of which 90% to 95% are manufactured. Med 3-D utilises the modification of the radiographic template and is converted in-house by the designated local laboratory. The NobelGuide planning data is sent via the internet with the fabrication of the template by stereo lithographic process in either the US or Sweden. med 3-D utilises implant company drilling/placement armamentarium as per the implant type selected. The operator provides all componentry for use with med 3-D, apart from the sleeves in the template; however, the practitioner needs to account for the guide dimensions with their drilling protocols. SimPlant provides up to three diameters of sleeves in their Surgi-guides, one per guide, but have no depth control for implant placement (apart from their SAFE system, but with restrictions). The SimPlant SAFE system has in its own drilling and implant carrier componentry. A single template is used with interchangeable sleeves. Only two drills are used for 3.75 mm and 4.1 mm diameter external hex implants only. This may cause difficulties in different bone types/densities with the drilling protocol. SimPlant also now has Navigator for the 3i-Biomet implant system and Facilitate for all Astra Osseospeed implants. The Navigator sytem is a rebadged SimPlant that enables the use of the CERTAIN style 3i-Biomet parallel walled, internal connection implants of all diameters. Implants are inserted through the template giving true 3D control. A range of prosthetic abutment options is available for the Certain implants, to enable early/immediate loading. Similar to Navigator, Astra also now has a rebadged SimPlant, called Facilitate. Materialize (SimPlant) can also now produce a NobelGuide template clone compatible with NobelGuide drilling componentry and Guide sleeves. Dentsply will soon be releasing its own guided surgery system, also based on the Materialize platform, for its Friadent range of implants, called Expertease. NobelGuide has a complete system with interchangeable drilling guides (with a single template) specific to the implant type and diameter, including fixture placement through the template and including vertical control of both the implant osteotomy and the implant placement. Further, when the template is ordered, all componentry relevant to the case (including laboratory needs) is assembled and available for order as well, at the same time. This eliminates the problem of ordering errors and componentry being missed. SimPlant and med 3-D templates can be bone, soft tissue or tooth supported and can use flapless or flap techniques. Nobel- Guide is tooth and/or other soft tissue supported and designed primarily for a flapless technique. However, the templates can be utilised with a technique variation for both immediate and flap procedures. The NobelGuide template design utilises extended flanges, which may create difficulties with high lip line smiles and assessing lip support. Patients may also be required to wear a removable prosthesis for approximately six months whilst teeth are removed and healing occurs. Further, some operators are very skilful with immediate placement and immediate loading and thus can reduce treatment time and eliminate the removable prosthesis stage in treatment and may see this step as a hindrance or unnecessary delay. The implant placement sequence and torque utilised is also a critical factor in all systems, with respect to three-dimensional implant placement accuracy and especially with the torquing or tipping of the template with free end saddle or some fully edentulous cases such as with mandibles. All systems enable the treatment of difficult cases such as thin ridges or critical angulation placements. There is a need for approximately 45 to 50 mm of opening for most guided componentry and the need for the corresponding drilling armamentarium. This equates to approximately 10 mm of increased drill lengths to normal. This may restrict use of this technology in certain cases. However, with SimPlant, the vertical dimensions of the template/sleeves can be changed especially in difficult vertical spaces such as posterior situations. The Navigator system uses integrated depth stops of various dimensions according to planning whilst the Facilitate system uses disposable drills on a case by case basis with integrated depth stops or standard drills. NobelGuide utilizes built-in drill stops with its tapered range of implants, with adjustable drill stops for it s parallel walled implant options. There is a difficulty with partially edentulous cases with narrow mesio-distal dimensions to enable room for the template and drill sleeve componentry. This may readily be seen in lower anterior cases or alternatively, in maxillary central/lateral situations. There is a tendency to drill to prescription rather than appreciate the feel of the bone density in the osteotomy preparation, often leading to over preparation and hence loss of primary stability, especially in inexperienced hands. Again, this is relevant to all systems and especially NobelGuide and SimPlant Safe (including Navigator and Facilitate). In the placement of implants through the template, there is also a tendency to over torque the implants, effectively compromising primary stability by pulling the implant through the bone on tightening. Again, this is specific to systems where the implants are placed through the template, i.e. NobelGuide and SimPlant Safe (including Navigator and Facilitate). The use of a flapless approach in treatment potentially loses some attached soft tissue dimension and this may be especially relevant and difficult to control in mandibular cases. However, with appropriate planning and controls, a flapless approach, in indicated cases, offers greater predictability, minimal soft tissue changes and considerably less discomfort for the patient. 150 Australasian Dental Practice January/February 2009

8 Figure 4a. Pre-treatment-occlusal view. Figure 4b. NobelGuide maxillary working cast constructed from planning. Figure 4c. Maxilla with implants in situ, as per planning. Figure 4d. Provisional P/- OIB with reduced cantilever extensions demonstrating ideal implant positioning. Figure 4e. Provisional P/- OIB- tissue fitting surface. Figure 4f. Provisional P/- OIB insitu, immediately following implant placement. Figure 4g. Procera Zirconia definitive P/- OIB-tissue fitting surface. Figure 4h. Procera Zirconia definitive P/- OIB- occlusal view. Figure 4i. OPG -Procera Zirconia definitive P/- OIB, in situ. SimPlant Surgi-guides and Safe system (including Navigator and Facilitate), as well as med 3-D, require a pick-up impression/registration of a prefabricated prosthesis and then a laboratory step to complete the prosthesis. Facilitate has some provisional abutment componentry enabling early/immediate loading. NobelGuide has a guided abutment which along with the ability to place the implant through the template, enables the insertion of the provisional (or indeed definitive restoration) at the time of implant placement, to achieve true immediate loading. However, in the author s opinion, in the majority of cases, a preconstructed provisional prosthesis can be simply picked up with temporary or definitive abutments and added to the prosthesis in a simple laboratory procedure, on the same day or overnight at worst. This will provide for the most accurate solution as well as improved health of the epithelial cuff around the abutment. There are no five-year multicentre studies published on guided implant surgery available as yet. Henry P J et al, published a 94.1% survival in partially edentulous cases which compares favourably with his multicentre partially edentulous jaw study (Henry, Tolman, Bolender-Quintessence Int. 1993). Most importantly, all three systems enable the use of the planning software as a planning tool only, all the way through to the construction and use of surgical templates constructed from the computerised treatment plan. Conclusion Guided surgery is one of the great advancements in implant prosthodontic therapy over the last five years. Most importantly, it has enabled dramatically improved diagnosis and treatment planning prior to patient intervention. Critically, it has enabled the ability to construct surgical templates to achieve accurate, 3-dimensional implant placement in accord with the designated treatment plan. Further, it has facilitated the pre-construction of a provisional (if not definitive) prosthesis utilising an immediate loading protocol (where indicated). Whilst this technology is not applicable in all cases, it is certainly of the utmost benefit in diagnosis and treatment planning and especially in those more complex and difficult cases. About the author Dr David B Dunn is the principal of The Macquarie Street Centre for Aesthetic, Implant and Reconstructive Dentistry, in Sydney, a referral-based practice restricted to prosthodontics. He lectures both locally and internationally and is part of the gide Faculty for Dental Education in conjunction with UCLA University. He has been published in several International Journals. January/February 2009 Australasian Dental Practice 151