Diagnosis and planning of the augmentation procedure
The aim of implant prosthetic rehabilitation is the integration of fixed or removable dental prostheses. Therefore, it is necessary to set up a treatment plan that considers the individual findings according to the result expected by the patient. It is important to define the surgical, prosthetic, and dental technical effort to achieve a functional and esthetic result. The amount of surgical effort required depends on the available bone and soft tissue. This effort is necessary both before and during implant insertion in order to achieve a long-term stable prosthetic result. To achieve an optimal result, detailed planning is as important as a complication-free reconstruction of the atrophied jaw and prosthetically oriented implant placement, which requires proper training in all treatment steps.93
The planning of the position, number, and dimension of the implants represents the essential step for a successful restoration from an esthetic and functional point of view. The prosthetic aspects have to be considered and the available bone evaluated. Today, implants can be inserted from a prosthetic point of view as far as possible using various grafting techniques.81 Nevertheless, it is necessary to take precise account of the anatomical landmarks at the time of implant placement,44 otherwise insufficient bony coverage of the implant surface can lead to complications such as peri-implantitis shortly after the final prosthetic delivery.29 Further restrictions in terms of the functionality of the prosthetic restoration result from implant positions that require a non-physiologic tooth shape with a limited esthetic result (Fig 2-1a to d) or do not allow for sufficient hygiene maintenance (Fig 2-2a to g).94
2.2 Patient consultation
Depending on the patient’s expectations and willingness to cooperate, it is necessary to precisely define the aim of the treatment. Clarify right from the start in detail the various available grafting techniques and their suitability for the specific patient. Also, alternative methods should be considered such as diameter-reduced or ultrashort and tilted implant placement to avoid grafting procedures.69,77 To achieve the best possible patient cooperation and satisfaction, it is not sufficient to only explain the intra- and postoperative surgical risks. Patients need information about the overall treatment duration, costs involved, and possible alternative procedures.77 During the course of clarifying the implant prosthetic treatment requirements and procedures, it may happen that the patient’s original expectations change once the realization sinks in that the time involved, the material costs, the surgical procedure itself or the increased risks of surgery, especially in the presence of systemic disease, are too much for the patient.
Especially in patients with alveolar crest defects, it is important to describe the entire treatment at the beginning. To achieve high patient satisfaction, it is vital to match the patient’s expectations and the necessary treatment steps as closely as possible.8
For the definition of the selected therapy, special attention should be paid to the motivation of the patient in an extensive implant prosthetic treatment in order to achieve good cooperation in the long-lasting and intensive course of therapy. Important information about the patient’s motivation is provided by the cause of the tooth loss and the patient’s attitude toward it (Fig 2-3a and b). The possibilities of the prosthetic design also depend on the awareness of the patient regarding hygiene. Depending on the patient’s oral hygiene status, the choice between fixed, conditionally removable, and removable prostheses should be differentiated.
In addition to the general conditions, the medication, the presence of allergies, the consumption of psychoactive drugs, and the patient’s attitude to antibiotic medication should be surveyed as part of the medical history. In particular, there is a tendency of differentiated patients to reject a postoperative antibiotic medication, which can lead to an increased complication rate, especially when using heterologous grafting materials.
2.3.1 Nicotine consumption
Patients often show early tooth loss due to nicotine use. This situation should be rehabilitated by correspondingly extensive therapies with a fixed prosthesis.52 Tobacco smoke passing through the oral cavity contains a mixture of hazardous substances that has cytotoxic and carcinogenic effects. This leads to a degeneration of the soft tissue, with a reduced perfusion and vascular supply, which, in a similar way to diabetes mellitus, can lead to surgical or long-term complications in implant therapy.46
If patients show complete or partial tooth loss with pronounced or severe alveolar ridge atrophy at the end of the fourth decade of life, an evaluation of the interleukin-1 polymorphism can be made. This is synergistically known in smokers for chronic periodontal disease. At the same time, these patients also have an increased risk of peri-implantitis.11,32 In order to clarify the long-term prognosis, simple swab tests are now commercially available that allow the pain-free diagnosis of an IL-1 mutation by polymerase chain reaction (PCR)-based methods.
In case of heavy nicotine consumption (more than 10 cigarettes per day), the extensive use of xenogenic bone substitute materials in combination with membrane techniques should be avoided, as wound healing complications are more likely to occur due to reduced vascularization and therefore loss of the augmented areas.6
Nicotine use is not a contraindication for bone augmentation, but patients should be aware of the overall increased risk of complications.3 For the surgical procedure, the focus should be on minimally invasive methods such as the tunnel technique or the vestibular incision technique (see Chapter 8 on risks and complications).
2.3.2 General medical findings
Among general medical conditions, diseases with a direct impact on bone metabolism are still the greatest risk group for implant therapy, especially in combination with bone grafting. Most patients in western society do not exercise enough and many of them suffer from degeneration of the skeletal system, especially due to hormonal changes and advanced age. Today, osteoporosis is considered to be one of the most severe diseases, with the risk of life-threatening vertebral body factors35 (Fig 2-4a). Hints that the blood levels of cholecalciferol (vitamin D) is low are soft bone structures in preoperative radiographs or increased bone resorption.19 In such cases, medication is administered, which is specified in three different stages.36 The least risky and most beneficial for implant placement consists of calcium and vitamin D supplements. Newer drug approaches follow the application of strontium preparations, which have a positive effect on bone metabolism, as bone resorption is inhibited, and the formation of new bone is promoted. In such instances, however, negative phenomena can occur in the area of the oral mucosa, which can then lead to peri-implant mucosal changes if the medication continues (Fig 2-4b).
126.96.36.199 Antiresorptive therapy
To inhibit osteoclast activity, antiresorptive therapy using bisphosphonate or RANKL inhibitors is available.83 The range of increased performance bisphosphonate drugs has increased in the past few decades. In addition, the human RANKL antibody Denosumab (Prolia) was approved in 2010 for the treatment of postmenopausal osteoporosis. As a subcutaneously administered drug, it extends the possibility of individualized osteoporosis medication, also interfering in bone metabolism.87
To reduce the risk of occurrence of osseous disseminations, e.g. in patients with breast and prostate carcinomas and with multiple myeloma, a high dose of bisphosphonates is given. For these tumors, a high rate of new disease (antiresorptive drug-related osteonecrosis of the jaw – ARONJ) is continually observed every year.31 Usually, intravenously administered bisphosphonate therapy, which is used curatively as well as palliatively, means a reduction in the consequences of the oncological disease for these patients, since further metastasis growth in the bone is reduced.31 Since metastasis needs the help of the osteoclasts to remove bone, allowing for their growth, the strong inhibition of the osteoclasts will stop bone resorption: metastasis cannot grow inside the bone any longer.
Due to the change in bone metabolism, a careful dental examination is recommended to perform invasive dentoalveolar surgery prior to medication in order to avoid osteonecrosis in the oral cavity.
Osteoporosis is a disease that shows an increasing prevalence with increasing life expectancy, especially in females. If left untreated, it leads to a significant impairment of the quality of life of those affected. In Germany, a prevalence of 6.3 million people with osteoporosis is assumed, with an incidence of 885,000 new cases per year.35 Bisphosphonate therapy for osteoporosis is administered through a weekly oral intake or a quarterly or yearly intravenous injection that lead to a stabilization of the skeletal system. A short-term intake of bisphosphonates shows no increased risk of osteonecrosis. After an intake of the medication for longer than 3 years, a higher prevalence of osteonecrosis as well as other general medical side effects are evidenced.80 Classic open wound healing is absolutely contraindicated, especially after tooth extraction, due to extremely high risk of infection. In addition, after other dentoalveolar surgery, reduced bone regeneration is observed, and the risk for sequestration of the infected bone can occur31 (Fig 2-5a and b).
In this context, a few years ago, the systemic intake of bisphosphonates for the treatment of oncological disease or in osteoporosis was an absolute contraindication. Clinical experience shows that this contraindication needs to be reevaluated.16,25 Bisphosphonate medication interferes with the physiology of bone metabolism, thereby limiting the function of the osteoclasts responsible for the bone resorption and remodeling processes.89 Accordingly, the indication for techniques that require high osteoclastic activity for the remodeling must especially be reevaluated. In this case, techniques that involve the transplantation of autologous spongiosa are preferable to those that transplant purely cortical bone or xenogeneic bone substitute material that requires higher resorption kinetics to achieve a stable implant site.20
For oncology therapy with regular infusions ranging from a few months to a few years, implant placement should be avoided.31 Even with long-term oral administration or intravenous administration in the form of so-called ‘depot injections’ of these preparations, the critical limit is set at 3 years. To avoid bisphosphonate-induced bone necrosis in patients receiving treatment for osteoporosis, a very strict indication for augmentation and implant therapy is recommended for these patients.31,34
Since the success of implant therapy with bisphosphonate therapy is controversial,42,87 the extent of treatment should be determined on an individual basis, depending on the patient’s health and dental history.
188.8.131.52 Specific antibody therapy
Nowadays, a large number of antibody therapies are successfully used for cancer treatment, even in the advanced stages, and are sometimes administered continually to avoid cancer progression. This can significantly improve the survival rates of these patients. Although these therapies are not without side effects, there are fewer compared with conventional chemotherapy. Therapies include the administration of high-dose cortisone, which is utilized to stabilize the patient. However, even in cases where such treatments are given only for a short period of time, they can negatively influence the prognosis of treated teeth as well as the healing of bone postsurgery due to their intervention in the calcium balance. Therefore, tooth loss that is due to tumor treatment, bone metabolism, and the capacity for wound healing should be clarified specifically, as is the case with patients undergoing antiresorptive therapy.10
184.108.40.206 Albert Schoenberg’s disease
This hereditary osteopathy, known as marble bone disease, shows a massive compression of cancellous bone and medullary spaces of the regular bone tissue caused by a genetic defect of the osteoclast function. Strong bone apposition without sufficiently simultaneous bone resorption compresses the medullary spaces so severely that hardly any vascularization remains possible. The bone then looks extremely white, like marble. Radiologically, the eponymous marble-like change in bone structure is also known as osteopetrosis. It also shows developmental disorders of the teeth, with enamel hypoplasia and crown and root malformations. High-grade sclerosis results in an increased risk of fracture of the entire skeleton, with a poor healing tendency of the bone, so that implant or augmentation therapy is absolutely contraindicated.65 With this condition, single case reports show a high risk of osteomyelitis after implant placement.61
220.127.116.11 Osteitis deformans (Paget’s disease)
This is a chronic generalized or monostotic bone disorder of an unknown cause that occurs predominantly in the 6th and 7th decade of life in males. In contrast to Albert Schoenberg’s disease, the cortical bone is transformed into a fine-meshed cancellous bone, the medullary spaces of which are filled with fibrous tissue.15
In addition to the rheumatic complaints, an increase in the circumference of the skull is characteristic, which in extreme cases presents as Leontiasis ossea (lion face) with a high skull cap, pronounced prominent zygomatic bones, increased eye relief, and distension of the maxilla. Radiologically, brightening and shading occur, resembling a cotton flake structure, and the affected bone is generally thickened. Nowadays, the bisphosphonates described above are usually administered intravenously to stabilize the bone. Due to the altered bone metabolism, a strict indication for implant or augmentation therapy is recommended. The initial case reports show positive treatment outcomes, although there are as yet no long-term studies.75,76,90 If necessary, modeling osteotomies can be performed to improve the prosthetic anchorage on the deformed alveolar process.
Today, many people self-medicate to improve their physical and psychologic wellbeing. These medications are often not declared at the anamnesis, even though they may have an impact on the outcome of implant therapy. How these medications impact implant therapy has not yet been evaluated for all medications, and many patients assume that their medication history is not relevant for the dentist. Patients receiving proton pump inhibitors (PPI) to treat gastritis or serotonin reuptake inhibitors to stabilize depression episodes exhibit higher rates of implant failure.45 In these patients, the duration and number of drugs should be investigated before considering implant treatment.45
For other medications such as glucocorticoids and NSAIDs, conflicting results have been reported regarding their effect on implant treatment outcomes.26 However, due to the risk of serve wound healing disturbances, the possibility of a drug holiday should be checked with the responsible physician regarding long-term or high-dose glucocorticoid treatment.
ASA PS classification
Examples (including, but not limited to)
A normal healthy patient
Healthy, non-smoking, no or minimal alcohol use
A patient with mild systemic disease
Mild diseases only, without substantive functional limitations. Examples include (but are not limited to): current smoker, social drinker of alcohol, pregnancy, obesity, well- controlled DM/HTN, mild lung disease
A patient with severe systemic disease
Substantive functional limitation; one or more moderate to severe diseases. Examples include (but are not limited to): poorly controlled DM or HTN, COPD, morbid obesity (BMI ≥ 40), active hepatitis, alcohol dependence or abuse, implanted pacemaker, moderate reduction of ejection fraction, ESRD undergoing regularly scheduled dialysis, premature infant PCA < 60 weeks, history (> 3 months) of MI, CVA, TIA or CAD/stents
A patient with severe systemic disease that is a constant threat to life
Examples include (but are not limited to): recent (< 3 months) MI, CVA, TIA, or CAD/stents, ongoing cardiac ischemia or severe valve dysfunction, severe reduction of ejection fraction, sepsis, DIC, ARD or ESRD not undergoing regularly scheduled dialysis
A moribund patient who is not expected to survive without the operation
Examples include (but are not limited to): ruptured abdominal/thoracic aneurysm, massive trauma, intracranial bleed with mass effect, ischemic bowel in the face of significant cardiac pathology or multiple organ/system dysfunction
A declared brain-dead patient whose organs are being removed for donor purposes
18.104.22.168 Cardiovascular diseases
Other general medical conditions only represent a contraindication to implant and augmentation therapy if the patient’s life is threatened by the surgical procedure. Intraoperative cardiovascular complications induced by surgical stress should be reduced or even eliminated by perioperative monitoring.13 Depending on their medical insurance system, it is recommended for patients with ASA Class III to receive dentoalveolar treatments as inpatient procedures (Table 2-1).47 If surgical intervention is performed as an outpatient procedure, it must be ensured that postoperative home care is in place. In an infarct event, there is an absolute contraindication for elective implant prosthetic surgery in the first 6 months.
22.214.171.124 Hemorrhagic diathesis
When anticoagulant therapy is required, the risk of extensive intraoperative or postoperative bleeding is relevant (Fig 2-6). Anticoagulant therapies are not an absolute contraindication; however, depending on the indication, the risk of a suspended medication or changeover should be weighed against the associated benefits of planned implant and augmentation therapy.82 When patients declare that they are taking one or more of the so-called blood thinners, it is crucial to find out the exact medication. In case of postoperative bleeding, it is important to know the exact mechanism and, if appropriate, to take into account the specific systemic treatment for the drug (Table 2-2). In some diseases such as atrial fibrillation and coronary artery stenting, double or even triple anticoagulant therapy is recommended.78
A distinction should be made between antiplatelet agents such as ASS or P2Y12-antagonists or plasma disorders (coumarins, heparin). While platelet aggregation inhibitors are essentially prophylactically formulated to prevent arterial thrombi in the event of heart attack risk, the plasmatic drugs, in addition to the prophylactic indication, are primarily used therapeutically in cardiac arrhythmias, heart valve replacement, and deep venous thrombosis. The latest developments are direct oral anticoagulants (DOAC/NOAC), which are classified as thrombin or factor-Xa inhibitors. The extent of anticoagulant therapy can also be partially recognized during the patient examination. If old hematomas are already recognizable on the legs or hands, this indicates that the anticoagulant therapy is very heavily adjusted or uncontrolled.
The relatively rare congenital disorders of blood clotting are known mostly as hemophilia A and B and von Willebrand-Jürgens syndrome. When this disease is present, important factors in the coagulation cascade (mostly factors 8 and 9) are almost absent or ineffective and can have reduced activity that can reach a severe level until < 1%. Depending on the remaining activity of the factor, surgery can be performed by substituting the appropriate factors.41,51
Consultation with the treating physician is recommended in all patients with hemorrhagic diathesis, as unauthorized conversion might present the risk of the complication of lethal thromboembolic. Therefore, it is important to decide with the responsible physician whether a change to subcutaneous heparin injections (‘bridging’) or intermittent paralysis of anticoagulant therapy is necessary. In the case of replacement medication, an uncontrolled change of the medication with the reduction of the dose of the previous therapy can already lead to serious complications. To reduce the risk of a lethal thrombosis, the general opinion today in cases of oral surgery is not to stop any kind of antithrombotic treatment and not to perform any bridging with heparin, even with platelet aggregation inhibitors such as clopidogrel, prasugrel, ticagrelor or ticlopidine. Heavy postoperative bleeding should be controlled with local surgical possibilities such as an atraumatic approach, avoiding cutting important blood vessels, the use of local hemostatic, and good wound closure with the use of compression plates (see Chapter 8 on complications).
126.96.36.199 Diabetes mellitus
While diabetes mellitus type 1, which is caused by absolute insulin deficiency, only shows a prevalence of 0.02% worldwide, the incidence of diabetes mellitus type 2 is rapidly increasing, especially in the social underclasses of industrialized countries. In a few years, a morbidity rate of 10% in these societies is expected.
In these patients, in addition to the risk of a wound-healing disorder after grafting procedures or implant placement, the risk of peri-implantitis also increases.30,70 In the area of the oral cavity, diabetic microangiopathy reduces the regenerative capacity of the oral mucosa, since the nutrition of the tissue is reduced due to damage to the capillaries. This often leads to extensive tissue necrosis with exposure of the augmented area, with partial or complete loss of the augmentation.85
Since the circulation is restricted, the soft tissue seal of the osseointegrated implants, which is otherwise well accepted in endosseous implants, can already be disturbed during superficial bacterial colonization, so that the peri-implant bone is subject to infection. The medical treatment of the disease takes place according to the long-term blood sugar value of the glycohemoglobin or HbA1c, the value of which should be below 6%, which corresponds to a value of 120 mg/dl for the acute blood glucose value. From a value of 8%, the risk of healing complications and periodontal disease increases,80 so that the indication should be carefully checked.54 If, in the further course of the disease there are no signs of any disruption of the long-term blood glucose value, the prognosis for implant restorations is good.29 Some studies show no increased failure rates in patients with diabetes in a two-step approach in case of bone augmentation, with appropriate patient guidance and a good maintenance program.14, 22
188.8.131.52 Other metabolic diseases
The possibilities of implant therapy are limited by other metabolic diseases that directly or indirectly influence bone regeneration. Here, the diseases of the parathyroid gland should be mentioned because, through hyperparathyroidism, a reduced calcium storage in the bone occurs, which leads to osteoporosis.48
The administration of glucocorticoids has become established in several autoimmune diseases today. Cortisone therapy may lead to increased calcium excretion and thus to osteoporosis or a diabetic metabolic condition. This means per se that there are some risks involved in implant treatment in the case of a disturbance of secondary cortical activity (Addison’s disease), but also in long-term treated bronchial asthma, neurodermatitis, autoimmune diseases such as Crohn’s disease, and ulcerative colitis.4,12 However, the decision to undergo implant treatment should be made according to the individual risk profile, taking into consideration the duration and intensity of the cortisone therapy.
2.4 Specific findings
For implant planning, the extra- and intraoral assessment is carried out to best determine the relevant factors for the necessary prosthetic rehabilitation. Not only should the missing teeth and the patient’s desire to restore them be in the foreground of the treatment, but also the functional and esthetic outcome of the entire functioning of the oral system.
2.4.1 Genetic findings
Current development in the field of human genetics is providing an increasing amount of information about genetic developmental disorders. For the development of teeth and the periodontal ligament, ectodermal disorders are mainly relevant.17 In ectodermal dysplasia, disorders occur on multiple structures that develop from the outer cotyledon. In addition to the hair, nails, and skin, the teeth are also affected. Only very few teeth are present (oligodontia or hypodontia) in the first and the second dentition (mostly canines), in combination with some rudimentary teeth (Fig 2-7a to c). In oligodontia, the existing teeth are often microdontic, so that the prosthetic value is limited. Due to the development-related lack of teeth, the alveolar ridge is also underdeveloped in volume (Fig 2-7d), but the existing structures compensate for the missing bone supply with a dense bone quality. When planning a restoration, special attention must be paid to the existing available space and the growth pattern, so that pretreatment often requires many years of cooperation with the attending orthodontist (Fig 2-7e to n).64
In the very rare autosomal recessive inherited Papillon-Lefèvre syndrome, the periodontal findings show severe periodontitis, leading to early loss of primary teeth usually up to the 4th year of life, and permanent teeth up to the 14th year. This exceptional periodontal disease presents a pronounced atrophy of the alveolar processes, which requires augmentative pretreatment.86
2.4.2 Extraoral examination
When assessing the extraoral findings, the position of the maxilla and mandible in relation to each other should be evaluated. Due to the differing development of the position of the alveolar ridge due to the centrifugally oriented atrophy in the mandible and the centripetally oriented course in the maxilla, a pronounced prognathic position of the mandible can occur, especially in edentulous patients. The necessary grafting procedures in these cases do not only restore the vertical jaw relation but also determine the position of the alveolar ridge for the new prosthetic restoration. Due to the loss of the vertical dimension in cases of severe atrophy, the extraoral profile often shows a sunken upper lip or a reduced dimension of the lower third of the face; symptoms of this are often angular cheilitis and Candida albicans infection at the corners of the lips. A pronounced mental crease is a clinical sign.
When planning the type of dental prosthesis in the maxilla, the shape of the upper lip influences the decision about whether a fixed or removable prosthesis can be incorporated. Since even extensive augmentation procedures cannot restore the entire alveolar process, either long crowns or crowns with an attached gingiva through the use of pink ceramic or resin should be delivered. Due to the change in tension of the peri-oral soft tissue with age, the problem is less relevant for elderly patients. For younger patients with a short upper lip, this can lead to unacceptable esthetic results, in which case a removable prosthesis should be provided. In the presence of a long upper lip, the final choice between a fixed (Fig 2-8a to c) or removable restoration should be made during the esthetic try-in with the patient.
Patients with less-pronounced atrophy but with long-term partial edentulousness with loss of vertical dimension often have functional complaints with the temporomandibular joints (TMJs). Allegedly asymptomatic findings then show a lack of acceptance after complete restoration of the support zones and optimization of the chewing behavior. After the now optimally reconstructed oral system, the risk exists for the manifestation of oromandibular dysfunctions. In these patients, early functional therapy should be initiated to assess any risk factors prior to the start of the final rehabilitation. In many cases, functional therapy could be started during the healing periods between the grafting procedures. In this way, one can avoid a situation where, in the further course of treatment, the symptoms of an oromandibular dysfunction are erroneously assigned as a concomitant or side effect of the grafting and implant treatment. If functional therapy cannot be successfully performed due to the reduced dental system and vertical dimension, the treatment procedure should be extended through the use of an implant-supported provisional for a period of time. With the aid of the provisional dental prosthesis, functional disorders could be detected before the final superstructure is fabricated, and necessary adjustments to the bite position could be performed.
2.4.3 Intraoral examination
In addition to a pressure point in the area of the masticatory muscles, deviations from the mouth opening pathway as well as clicking and rubbing in the region of the TMJs appear as signs of functional disorders. Especially in partially edentulous jaws, it is important to evaluate the vertical dimension preoperatively. Suspected atrophy, which is compensated for by augmentation in the horizontal and vertical dimensions, can result in a prosthetic complication with a deficient prosthetic restoration or one that is difficult to perform because there is insufficient vertical dimension after augmentation. Accordingly, it is necessary to assess the elongation of the antagonist teeth and the need for correction in the antagonist jaw in case of loss of the vertical dimension before the surgical procedures (Fig 2-9a).
Especially in patients with a generalized aplasia, there is a tendency for a deep bite and the retention of the primary teeth. As a result, the alveolar process does not develop according to age. In the treatment plan of such cases, a bite raising should be considered in addition to the reconstruction of the alveolar ridge by grafting procedures (Fig 2-9b to j).
184.108.40.206 Soft tissue findings
Soft tissue quality and quantity are important criteria for a successful bone grafting procedure. A thin soft tissue biotype as well as scar tissue represent a high risk of tissue necrosis, with exposure of the grafted bone. Especially after several surgeries and in cases of previous surgical procedure failures, bad vascularized scar tissue occurs on the soft tissue. Particularly, in infection cases with augmentation procedures using biomaterials, the xenogenic bone substitute material remains in the connective tissue, making a flap preparation very difficult and significantly reducing the vascularity of the tissue (Fig 2-10a to c). Therefore, in the case of severe scars, it is advisable to improve the quality of the soft tissue through the removal of all biomaterial from the soft tissue and subsequent grafting of the palatal connective tissue at least 2 months prior to the hard tissue augmentation. The use of a tunneling technique in case of vertical bone augmentation will reduce the risk of tissue necrosis and bone exposure (see Chapter 3 on the soft tissue).
The soft tissue situation may also be limited by increased nicotine consumption. Also, systemic diseases that affect the blood circulation such as unadjusted diabetes mellitus with HbA1c values above 8% can lead to wound healing disturbances.80 Therefore, it is important to evaluate the structure of the soft tissue in the planned surgical site in order to take into consideration the number and course of any previous surgery or internal medical factors. Inflammatory symptoms should be treated as part of a systematic periodontal treatment prior to bone augmentation.
In the case of oral mucosal changes, these should first be clarified, as a leukoplakia must be assessed as precancerous.95 A soft tissue change, which is judged inconspicuous during tooth extraction, may recur after superficial removal, as it may be an epulis gigantocellularis.74
220.127.116.11 Dental findings
Pretreatment in the field of cariology, endodontics, and periodontics should be provided to the extent that the medium-term maintenance of the natural abutment is guaranteed. Where the abutment teeth have a limited prognosis, what must be carefully considered is whether the remaining teeth should be used for anchoring the prosthesis in the interim phase. Alternatively, a corresponding increase in patient comfort can be achieved by an immediate restoration on temporary or permanent implants.
If the cause of tooth loss is periodontal disease, the simple hygienic ability of a prosthetic superstructure should insure against it to some extent in the future, as it has been proven that a higher risk of peri-implantitis is present in edentulous patients.84
In the case of a deep bite, a possible vertical reconstruction should be evaluated by functional bite plane treatment before starting the grafting procedures. This can prevent further complications during the prosthetic restoration. After determination of the ideal vertical height, the amount of vertical reconstruction should follow in such a way as to avoid a limited maxillomandibular relationship. A simulation of the prosthetic result using a wax-up may assist decision making, especially after traumatic looseness of the teeth and bone, which creates an open bite situation that complicates the finding of an adequate solution (Fig 2-11a to c).
18.104.22.168 Structure of the bone
The bone quality of the regenerated area is generally classified as reduced, especially when using biomaterials (xenogenic or allografts). By applying the 3D technique with an intraoral bone transplant, iliac crest reconstruction using monocortical strips, and compressed cancellous bone or distraction osteogenesis, a vital and stable bone bed can be achieved that corresponds to a bone class of D2 or D3. Depending on the bone quality, it is important that dysfunctions are detected early to prevent possible overloading of the implant site due to bruxism.
Determining the bone volume is suitable as an initial and immediately available means to so-called bone mapping. The height of the soft tissue situation is determined with a pointed needle and a rubber stopper. By transferring these measured values to a saw-cut model, the existing bone volume can then be measured (Fig 2-12a and b). This kind of diagnostic measuring is rarely used today due to the increased use of digital diagnostic methods such as cone beam computed tomography (CBCT). The use of appropriately modified calipers has not proven to be successful in clinical practice and therefore they are only of historical significance today.
2.4.4 Radiologic findings
In the context of implant therapy, especially in the atrophic jaw, radiologic diagnosis provides the essential information for deciding on the possibilities and scope of the necessary therapy and ensuring the treatment result. Radiologic diagnosis delivers the relevant information for the protection of the anatomical structures in the surgical field. In addition to the purely volumetric assessment of the jaw, the bone structure is also evaluated.
Due to chronic infections, especially after multiple endodontic treatments with revisions of the root fillings, apical root resections or any other infection, sclerotic changes in the jawbone can be seen. As a rule, these are not relevant for further implant therapy because the body’s own immune system has healed the infection through the inflammatory process; in fact, it sometimes repairs more than necessary through new bone apposition. This increases the bone density and the possibility of achieving high primary implant stability. On the other hand, increased bone density makes implant bed preparation more difficult, and in case of insufficient cooling can increase the risk of burning the bone. In rare cases, a more or less pronounced local osteomyelitis may be present.
Osteomyelitis sclerosans Garré is an infectious bacterial chronic event that is sustained by a persistent infection or by itself. Microbiologically, bacterial growth can rarely be detected by an intraoperative swab test. If there is anamnestic evidence of a persistent bony inflammation with symptoms, it is recommended to consider a CBCT (Fig 2-13) or a skeletal scintigraphy to exclude chronic subacute processes.
22.214.171.124 Radiologic techniques
For therapeutic planning, all radiologic procedures in dentistry are now applied on an indication-related basis depending on the different forms of implant prosthetic therapy, from single tooth replacement after traumatic tooth loss to maxillary ridge reconstruction in severely atrophied jaws.
The use of periapical radiographs is particularly recommended to obtain clearer detail of the teeth, bone, and implants. This kind of diagnostic technique is especially recommended for the determination of bone loss around implants or teeth and for the detection of caries (Fig 2-14a and b). In case of planning a bone augmentation, especially if using vertical bone augmentation techniques, periapical radiographs are recommended to detect bone structures covering the neighboring teeth. This information is very important, since vertical bone grafting is limited to the bone level of the neighboring teeth.
When using traditional periapical radiographs, the parallel technique is metrically more accurate than the half-angle technique.73 The use of a holder system for the parallel technique allows for secure positioning, so that a true-to-size and precise image recording can be achieved. Nevertheless, this may lead to deviations or distortions. Therefore, length determination should be verified by an earlier (already created) panoramic radiograph or CBCT in order to achieve an accurate length determination for implant planning.
Use of the dental status for extensive planning has not proven to be successful because the spatial relationships can only be insufficiently detected and there is the risk of an incorrect assessment of the vertical dimension due to deviations in the projection technique. Limited information regarding bone quality can be determined by a periapical radiograph.
Implant therapy is long term and requires appropriate follow-up assessments to evaluate the individual risk of peri-implantitis. Therefore, in addition to the initial diagnosis for the planning of the surgical procedure, the documentation of findings for the completion of the prosthetic restoration is also important. It is essential that these are available later on in the course of treatment. Especially for the evaluation of the crestal bone level of the individual implants, periapical radiographs still show the highest information density today. Digital archiving allows for a comparison of several images on the screen to assess, for example, the development of the peri-implant bone level.
The panoramic radiograph is an overview, giving general information on the dentition and bone volume and allowing the localization of anatomically sensitive structures such as the inferior alveolar nerve, sinus floor, and nose. Panoramic radiographs show an enlargement of 15% to 25% of the anatomical structures; this varies between the different company brands and also depends on the positioning of the patient during the scan. In the case of implant planning in the proximity of anatomically relevant structures, a reference ball is positioned per segment in order to obtain the most accurate metric analysis possible in the surgical field (Fig 2-14c). With the aid of tomography, rough information regarding the bone quality is provided. Additional devices also provide transversal layers of the planned operating area, first made possible by the Scanora device.5 However, since these layers have to be controlled individually, no data can be created for further processing in planning and surgical guide software. One of the latest developments is panoramic imaging using the multilayer technique. During a standard scan, about 4000 raw images are stored, which also allows for a repeated reconstruction to change the position of the skull or the size of the panoramic curve. Due to the multiple slices, the visualization of the bone structures is improved, which offers more information about the expected bone quality.
For planning implants in routine cases or in cases with moderate atrophy, the panoramic overview provides very good information about the positional relationships, so that usually no further radiologic diagnosis for implant positioning is necessary.
In the semi-axial skull radiograph pa (posterior– anterior beam direction), the skull is partially imaged and, when correctly positioned, allows for the superimposed representation of the zygomatic bone and the maxillary sinus. This image allows for the evaluation of the transverse extent of the antrum. In addition, in a side-by-side comparison, it provides information on the presence of foreign bodies or any sinus pathology. The image is taken at maximum mouth opening, whereby the horizontally guided central x-ray beam enters about 10 cm above the external occipital protuberance and leaves the skull at the spina nasalis (Fig 2-15).
Lateral skull imaging with a laterocentral beam through the sellar region is used at a distance of > 1.5 m as a lateral cephalogram, essentially for cephalometry in orthodontic treatment. For implant planning, this image can impart important information about the sagittal position of the maxilla and mandible as well as the inclination of the incisors and the orientation of the anterior ridge. By showing the contour of the removable prosthesis with tin foil, the degree of atrophy in relation to the necessary prosthetic reconstruction can be determined.
When bone harvesting from the chin is planned, this type of radiograph is useful to preoperatively determine the form and volume of the bone in the symphysis area as well as the amount of bone healing that occurs postoperatively (Fig 2-16a to c).
In medical hard tissue diagnosis, computer tomography (CT) is the gold standard for three-dimensional (3D) imaging. Medical CT offers 3D imaging that allows for a distortion-free, metrically correct spatial diagnosis and planning, including the anatomical structures. If the CT scan is performed with a radiopaque setup of the prosthetic wax-up, the implant planning can even be performed from a prosthetic point of view. In CT, the x-ray beam is picked up by a line-shaped detector, the layers being obtained by rotating the radiation source and the detector around the patient. In the initial CT, the patient is pushed further through the gantry, so that the number of slices and the distance of the scan determine its resolution.39
Today, a continuous feed generates a 3D volume on spiral CTs, which is then visualized in layers. Various protocols exist for performing a low-dose scan to reduce the primary dose.91 For medical indications, the visualization of hard- and low-contrast structures (soft tissue) is important. Therefore, a high energy is necessary, which limits it for routine use in the dental office.
Due to the scattered radiation caused by metallic prosthetic structures, it is important to position the patient carefully, depending on whether one is scanning the maxilla or mandible, so that the jaw can be aligned parallel to the beam path. If the patient is not properly positioned, metal scattering may limit the diagnostic value of the image in determining anatomical structures. Extensive prosthetic restorative reconstructions, such as a fixed partial prosthesis made of zirconia ceramic, may impair the diagnostic accuracy due to scattered radiation. By altering the gantry inclination of the spiral CT scan, the direction of the metal scatter can be changed, resulting in the improved usability of the scan. However, this requires a well-trained radiologist who is familiar with dental details. Due to the high initial cost and the fact that a radiologist is required to take the scan, this diagnostic tool is offered exclusively in centers for radiology (Fig 2-17a and b).
In addition to the reconstructions in the classical radiologic layers, special dental CT reconstructions are also possible, which offer sections perpendicular to a panoramic curve (Fig 2-17c to h). For dental diagnostics, the images are exported in DICOM format so that they can be read in the various viewing and planning software.1 In addition to a precise representation of the bony structures, the spiral CT is particularly distinguished in the imaging of soft tissue (Fig 2-18a to e). Although radiation exposure has been reduced in modern devices, the spiral CT still presents a higher radiation exposure compared with digital volume tomography devices (CBCT).56
Cone beam computed tomography
In addition to spiral CT, CBCT has been available to the dentist for more than 20 years as a continuative method of radiologic imaging.59 Today, devices from various manufacturers are offered that enable a 3D diagnosis in the oral and maxillofacial area.66 Since CBCT devices are much cheaper than CT devices, they have become increasingly common in dental practices oriented toward implantology.
In CBCT, the patient is usually positioned standing or sitting (only a few devices require a horizontal position similar to that used for spiral CT). The radiologic beam is cone shaped so that the radiation source moves on one level around the patient (Fig 2-19a and b). The volume is then reconstructed from 200 to over 500 single images. The applied energy and the resolution of the detector determine the quality of information, with the volume size and resolution of the recording. Depending on the detector technology, the field of view, the radiation exposure with a continuous or pulsed beam, and the filters used, a large variation of the effective dose is possible (between 3 µSv and about 800 µSv).
Due to the specific target of CBCT – the high contrast imaging of bone – the soft tissue structures can only be evaluated to a limited extent. The disadvantage of reduced soft tissue visualization is compensated for by appropriately designed prosthetic planning templates or additionally placed cotton rolls to separate the soft tissue of the alveolar crest from the tongue or floor of the mouth (Fig 2-19c). The diagnostic validity could be optimized by special reconstruction algorithms, so that the same diagnostic value is available when compared with CT.59 In particular, the automatic reconstruction of the known panoramic layer from the 3D volume allows for the usual dental radiologic diagnosis.97
126.96.36.199 Indications for 3D diagnostics
When using any radiologic technique, the benefit and risk of ionizing exposure should be calculated.1,2 Therefore, depending on the type of device, whether spiral CT or CBCT, with or without image intensifier technology, the indication can be limited or passed on.21,72 Before a CBCT scan is taken, a clinical examination and evaluation of the available radiograph images is necessary to ensure that the patient will have a diagnostic or therapeutic benefit greater than the potential hazard from radiation exposure. It should also be considered that the risk of radiation hazard in children is three times greater than in adults, although most patients requiring bone graft surgery are over 50 years of age, at which age the relative risk decreases to 30% to 50% compared with a 30-year-old patient.23
It has been shown that in more than 40% of patients, a mostly asymptomatic change in the maxillary sinus mucosa (e.g. swelling, mucocele) is present. The prevalence of at least one septum is 46.8% per patient67 (Fig 2-19d). Three-dimensional diagnostics can be used to explore areas of undercut on the lingual side of the mandible that are not detectable on a panoramic radiograph (Fig 2-19e). This avoids lingual perforations during implant bed preparation (Fig 2-19f).
The evaluation of the retromolar triangle has shown that the thickness of the buccal cortical structure is approximately 3 to 4 mm. The location of the mandibular canal in moderately atrophied jaws is usually > 10 mm under the alveolar crest, so that sufficient bone is normally available for the harvesting procedure. However, it was also found that in 10.2% of cases, the nerve was very superficial to the buccal site, with very close contact with the vestibular cortical bone plate, which requires a very careful approach for bone harvesting.63
Simulation of the prosthetic setup
Depending on the number of remaining teeth and the software used to accomplish implant planning, the prosthetic setup for implant placement can be performed using a radiologic template, or digitally by matching computer-assisted design/computer-assisted manufacturing (CAD/CAM) data.68 With this digital technique, it is possible to find the ideal position and direction of the implants in a simple way in relation to the ideal position of the implants and to fix them in a surgical guide (Fig 2-20a to m). If necessary, the bone can be reconstructed in different directions according to the surgical guide.
Construction parameters for a 3D radiographic template
If the implant insertion is planned simultaneously with the grafting procedure and with the software utilizing a reference plate, it is recommended to convert the prosthetic setup into a radiologic template. To obtain information about the planned crown position, it is necessary to implement radiopaque structures in the template. This can be done by gutta-percha pins, which represent the ideal axes of the implant abutments. With this approach, no specific software is necessary for the implant planning. After the analysis of the position and the axis of the future implant, the dental technician will replace the corrected position of the guttapercha pin through a hole for the pilot bur.
More orientation is given if the crowns are converted into barium sulfate resin. For the best possible information, the crowns should rest on the soft tissue with the natural anatomical profile. This allows the determination of the thickness of the soft tissue during the scan. For the exact determination of the position, it is important that the crowns are separated at the mucosal level and partly reduced to the diameter of the putative root (Fig 2-21). If a mucosa-supported surgical guide has to be used, a different doping with barium sulphate is recommended for the template base and the setup teeth in order to visualize the soft tissue, so that the soft tissue contours and the prosthetic orientation are reproduced in the image. Depending on the software, a double scan of the patient with the prosthetic setup and the setup alone is sometimes recommended.27 Both scans are matched to give the best visualization of the prosthetic setup for the orientation of the implants and the amount of grafting.
2.5 Choice of grafting technique
The grafting procedure is determined by various factors such as the extent of the bone atrophy, the number of implants necessary for the long-term support of the prosthetic restoration, the maxillomandibular distance, the antagonist dentition, and the soft tissue situation.
2.5.1 Bone atrophy
Bone grafting procedures are usually not necessary in the presence of a bone volume of > 10 mm vertically and > 7 mm horizontally; however, sometimes due to the soft tissue situation or the planned prosthetic restoration an alveolar crest reconstruction may be required.
The decision regarding which grafting procedure to recommend in a specific clinical situation depends naturally on the defect morphology and the anatomical conditions.
If the bone width is partly or completely insufficient, without vertical bone loss in the esthetic region and a remaining vertical bone height of > 10 mm in the other regions, the following procedures are recommended: