Special considerations for implant therapy in diabetic patients

Healing and risk of postoperative infection: The repercussions of diabetes on the healing of soft tissue depend on the degree of glycaemic control in the perioperative period and the existence of chronic vascular complications. Patients with poor metabolic control have their immune defences impaired: granulocytes have altered functionality with modifications in their movement towards the infection site and deterioration in their microbicide activity, with greater predisposition to infection of the wound. In addition, the high concentration of blood-glucose in body fluids encourages the growth of mycotic pathogens such as candida. The microangiopathy arising as a complication of diabetes may compromise the vascularization of the flap, thus delaying healing, and also acting as a gateway for the infection of soft tissue.

Perioperative measures: In view of the studies revised, high levels of glucose in plasma have a negative influence on healing and bone remodelling processes. In order to ensure osseointegration of the implants (understood as the direct bond of the bone with the surface of the implant subjected to functional loading) and to avoid delays in the healing of gum tissue, it is necessary to maintain good glycaemic control before and after surgery. To measure the status of blood-glucose levels in the previous 6–8 weeks, the HbA1c values have to be known (< ?xml:namespace prefix = "mbp" />Table 7.1). A figure of less than 7% for HbA1c is considered a good level of glycaemic control (the normal value for healthy individuals is 3.5–5.5% depending on the laboratory) (Table 7.2). Although there is some controversy over the use of antibiotics in healthy patients, these are recommended for diabetic patients about to be subjected to implant surgery. The antibiotic of choice is amoxicillin (2 g per os 1 h previously), as the pathogens most frequently causing postoperative complications following the placement of implants, are streptococci, Gram-positive anaerobes and Gram-negative anaerobes. Clindamycin may also be used (600 mg per os 1 h previously), azithromycin or clarithromycin (500 mg per os 1 h previously), and first-generation cephalosporins (cephalexin or cefadroxil: 2 g per os 1 h previously) only if the patient has not had any anaphylactic allergic reaction to penicillin. In addition to antibiotic prophylaxis, the use of 0.12% chlorhexidine mouthwash has shown a clear benefit by reducing the failure rates from 13.5% to 4.4% in type 2 diabetics, during a follow-up period of 36 months. This same study observed a reduction of 10.5% in the failure rate when antibiotics were administered preoperatively.

Table 7.1 Showing the relation of glycosylated Hb% with diabetes

Table 7.2 Recommendations to reduce the risk of implant failure in diabetic patients

Conclusion

There is evidence that hyperglycaemia has a negative influence on bone formation and remodelling and reduces osseointegration of implants. Soft tissue is also affected by the microvascular complications deriving from hyperglycaemia – vascularization of the tissue is compromised, healing is delayed and wounds are more predisposed to infection. This entails an increase in the percentage of failures in implant treatment of diabetic patients. The bibliography reviewed recommends good glycaemic control in the perioperative period, in order to improve the survival rates for implants in diabetics. HbA1c figures of less than 7% indicate appropriate glycaemia levels in the preceding 6–8 weeks. Preoperative antibiotic therapy and the use of 0.12% chlorhexidine mouthwash are recommended, as both measures have been shown to reduce the percentage of failures. Although there is a higher risk of failure in diabetic patients, experimental studies have shown that the optimization of glycaemic control improves the degree of osseointegration in implants. Nonetheless, it is necessary to extend the number of prospective studies in humans, in order to clarify the true impact of diabetes on the prognosis for osseointegration.

Hypertension

Hypertensive patients often have the tendency to bleed more than the normal because of high vascular pressure; hence, they should be only operated under controlled blood pressure conditions. A continuous monitoring of the blood pressure is also mandatory during surgical procedures in implantology.

Thyroid disorders

Implant therapy can successfully be given to patients with hypothyroidism but hyperthyroidism is a medical problem which requires attention, as excessive production of the thyroxin hormone results in symptoms like increased pulse rate, nervousness, intolerance to heat, excessive sweating, atrial fibrillation, and congestive heart failure. Patients with hyperthyroidism are also sensitive to catecholamines such as epinephrine in local anaesthesia. When such patients are exposed to catecholamines, coupled with the stress often related to implant surgery, an exacerbation of the symptoms of hyperthyroidism may occur during surgery, resulting in thyrotoxicosis or “thyroid storm”, which is often life-threatening to the patient. The physician’s opinion and the normal range of thyroxin investigation, i.e. the patient who reports normal thyroid function and has had no symptoms of the disease during the preceding 6–8 months, is at low risk and can successfully get the implant surgery done. Patients with hyperthyroidism should receive the implant surgery in a very calm and comfortable operatory environment and if local anaesthesia is used, it should be devoid of adrenalin. Anti-anxiety/sedative drugs should also be avoided in such patients.

Bone disorders

Patients with bone disorders like osteoporosis, which is usually age-related, present with decrease in bone mass, increased micro-architectural deterioration, and susceptibility to bone fractures. This mostly occurs in the patients after the age of 60 but is very common even at an earlier age in postmenopausal women or women who have the history of ovariectomy, because the lack of oestrogen increases the chances of osteoporosis. A recommended dose of calcium, which can be range from 800 to 1500 mg/day and regular exercise is helpful to maintain the bone mass and increase bone strength. Such patients should thoroughly be investigated and treated before implant therapy.

Patients on bisphosphonates

Bisphosphonates are a group of drugs used to treat pathologies, including Paget’s disease, osteoporosis, multiple myeloma and metastases associated with breast or prostate cancer. Bisphosphonates act on osteoclasts, inhibiting their chemotaxis and lifespan and hence, they inhibit bone resorption and induce osteonecrosis. There are important differences between bisphosphonates administered intravenously or taken orally. Oral administration of bisphosphonates to postmenopausal women to treat osteoporosis is fairly common. Hence, this group of patients should be investigated for bisphosphonate therapy. The American Association of Oral and Maxillofacial Surgeons does not contraindicate dental implant placement in patients who have been taking bisphosphonates orally for under 3 years prior to surgery, but the drug should be stopped for a minimum of 3 months before carrying out implant surgery and should be restarted only after at least 3 months following implant surgery (Table 7.3). Marx et al A blood test, and the serum C-terminal telopeptide (CTX) test on an empty stomach, are recommended to evaluate the risk of osteonecrosis in patients on bisphosphonate therapy for more than 3 years. If values obtained are greater than 150 pg/ml, the implant surgery can be performed with minimum risk and without suspension of medication. When values are lower than 150 pg/ml, medication should be stopped for a period between 4 and 6 months or an alternative treatment option involving other types of prosthesis should be sought. More scientific evidence is required in order to validate CTX testing as the technique for the evaluation of osteonecrosis in these patients. Different studies and clinical trials of implant therapy in patients on bisphosphonate therapy, have found that patients who had taken oral bisphosphonates could successfully be treated with implants. Oral bisphosphonates are stopped 3 months before implant insertion and restarted only after the implant has osseointegrated (3–4 months). As the patients on intravenous bisphosphonates are at high risk of osteonecrosis after implant surgery, other non-surgical prosthetic options should be preferred for such patients.

Liver cirrhosis

The major cause for liver cirrhosis is alcohol consumption. The liver synthesizes clotting factors and detoxifies drugs, hence patients with liver disease show reduced synthesis of the clotting factor (thrombocytopaenia) and prolonged bleeding time during implant surgery. The patients with normal liver function test (SMA, CBC, PTT, and PT) values are at low risk and can be treated as normal patients with basic implant procedures. The physician’s opinion is highly recommended for these patients before performing the implant surgical procedures.

Angina pectoris

It is a form of coronary heart disease, which causes chest pain or cramp of the cardiac muscles because of temporary myocardial ischaemia (low oxygen supply to the cardiac muscles). Atherosclerosis of the coronary vessels is the most common cause of angina pectoris. When treating such patients, the physician’s opinion should be taken before performing implant surgery and nitroglycerin (0.4 mg) tablets should be kept ready in the dental emergency kit. The dental procedure should be done in a stress-free environment and divided into multiple short duration procedures. If the patient complains of chest pain, the procedure should be stopped immediately and the nitroglycerin tablets should be administered sublingually. Local anaesthetics devoid of vasoconstrictors (adrenalin) like xylocard should be used in such patients. Anti-anxiety drugs and prophylactic administration of nitroglycerin tablets are also helpful to reduce the onset of angina in such patients during implant surgery.

Myocardial infarction

Myocardial infarction (MI) is a prolonged ischaemia (lack of oxygen supply) that causes injury to the heart. Such patients complain of severe chest pain in the left precordial area during the MI episode, which radiates to the left arm or mandible. The pain is similar to angina pectoris, but more severe and presents symptoms like cyanosis, cold sweat, weakness, nausea or vomiting, and irregular and increased pulse rate, etc. Being a life-threatening medical problem, the implant surgeon besides taking all the precautions as for angina, should take the opinion of a cardiologist before treating such patients. These patients should preferably be treated in hospital where all the emergency management facilities are available.

Subacute bacterial endocarditis (SABE)

It is an infection of the heart valves or the endothelial surfaces of the heart. The microorganisms mainly associated with endocarditis following dental treatment, are streptococci and staphylococci, and less frequently, anaerobes. The risk of bacterial endocarditis increases with the amount of intraoral soft tissue trauma. Improvement of oral hygiene with scaling and root planing, and the administration of prophylactic antibiotics before performing any implant surgical procedure, reduce the onset of subacute bacterial endocarditis after dental surgery, to a large extent (Table 7.4).

Pregnancy

Being an elective procedure, implant surgery should be avoided during pregnancy as the radiographs and medications for the implant procedures may adversely affect the growth of the fetus. Moreover, periodontal diseases are often exacerbated during pregnancy.

Smoking

The lower success rate of endosteal implants in smokers is well documented in literature.¹ Tobacco smoking decreases polymorphonuclear leukocyte activity, resulting in a lower rate of chemotactic migration and reduced phagocytic activity, which contribute to decreased resistance to inflammation and infection and impaired wound-healing potential. Smoking also causes decreased calcium absorption, which weakens bone strength. Slower soft tissue healing, bone graft contamination, etc. are common problems in smokers. The patient should be encouraged to avoid smoking at least for a period of 2–3 weeks postimplant surgery till the soft tissue gets healed.

Oral examination

Detailed oral examination of the patient is paramount for diagnosis and treatment planning for successful implant therapy. The following clinical findings should be examined in detail.

Arch form

The arch form influences the number and positions of the implants required in fixed implant prosthesis for the edentulous maxilla and mandible. Three types of dental arch forms are found in patients.

Square arch: shows minimum facial cantilevered forces; thus minimum number of implants are required to support a full-arch fixed or completely implant-supported removable prosthesis. Only two implants are required at the canine positions to restore the anterior maxillary or mandibular region. Placement of any implant anterior to the canine region is usually not required to restore the full-arch. The full-arch, fixed, implant-supported restoration (12–14 units) can be made possible by placing only six implants (two at canine, two at second premolar, and two at first molar positions) (Fig 7.2A).

Fig 7.2 The arch form should be evaluated during treatment planning for multiple or full-arch implants. (A) The square arch form shows the least facial cantilever, hence requires least number of implants to restore the maxilla or mandible and no implant is usually required anterior to the canine positions. (B) The oval arch form has more facial cantilevering; hence at least one implant should be added anterior to the canine position to restore such arch. (C) The tapering arch form has the maximum facial cantilevering hence requires two additional implants anterior to the canine positions. If 14-unit fixed prosthesis is planned, two more implants should be added at the second molar positions.

Ovoid: shows more facial cantilevered forces on the prosthesis compared to the square arch form, thus one more implant should be added anterior to canines positions (at one of the central incisor positions) to reduce the cantilevered forces on the rest of the implants (Fig 7.2B).

Tapering: has the maximum facial cantilevered forces, thus two more implants should be added anterior to canine positions (one at each central incisor position) to reduce the cantilevered forces on the rest of the implants (Fig 7.2C).

Soft tissue biotype

A thick biotype that contains a thick connective tissue layer under the keratinized attached epithelium is considered to be favourable for implants. The thick biotype makes a tight seal around the implant prosthesis and is more resistant to the recession and peri-implant infections (Fig 7.3A and B). The thick biotype is also helpful in the aesthetic regions to achieve an aesthetic emergence profile and soft tissue drape around the implant prosthesis. It is easy for the implant surgeon to craft the thick soft tissue biotype as required, to achieve optimal aesthetic outcome in the implant prosthesis in the cervical region. If a thin biotype is found at the edentulous region, the implant surgeon should plan for a connective tissue grafting procedure during the implant insertion, or later at the time of implant uncovery, to convert the thin biotype to the thick biotype.

Fig 7.3 (A) Thin biotype, more prone to recession and muscle pull, (B) thick biotype, more resistant to recession.

Width of keratinized soft tissue

A thick band of keratinized soft tissue is paramount around the future implant prosthesis to make it resistant to peri-implant infections. The clinician should evaluate and plan to achieve at least 3 mm of attached keratinized thick marginal soft tissue collar around the implant prosthesis. If a non-keratinized thin and mobile soft tissue is found at the implant site, he/she should plan for soft tissue grafting procedure at the time of implant uncovery, to generate new thick and keratinized soft tissue around the implant prosthesis (Fig 7.4A and B).

Fig 7.4 (A and B) A thick band of keratinized soft tissue regenerated with soft tissue grafting during implant uncovery to minimize the chances of soft tissue recession and peri-implantitis.

Papilla at the implant site (intact or flattened)

The careful evaluation of the presence or absence of papilla should be made during treatment planning for the implant in the aesthetic region. If the papillae are intact, the papilla preservation incision is preferred for the implant placement (Fig 7.5A–D).

Fig 7.5 Care should be taken to preserve intact papilla in the regions of high aesthetics. (A and B) Papilla preservation incision should be planned in such cases to maintain the papillae for future implant prosthesis. (C and D) Flattened papilla.

Periodontal health of adjacent teeth

The teeth adjacent to the edentulous region should be checked for any deep soft tissue pocket, or any periodontal defect with active purulent discharge. Often infection in the adjacent teeth can infect the inserted implant; therefore, all the periodontal problems of the adjacent teeth should thoroughly be diagnosed and treated before implant insertion (Fig 7.6A–C).

Fig 7.6 (A) Tooth adjacent to the future implant site showing deep periodontal pocket with purulent discharge through a sinus. The infected pocket is treated first with scaling, curettage and antibiotics until it healed and showed no active infection. (B and C) The healed periodontal osseous defect is exposed, cleaned, irrigated with antibiotics and grafted simultaneous to implant placement at the adjacent site.

Opposing and adjacent teeth at occlusal position

The teeth adjacent to and opposing the edentulous site should be examined for any supra eruption inclinations, mesial drifting, etc. for prosthetically guided implant insertion (Fig 7.7A–C). Prosthetic planning before implant insertion avoids future problems like unaesthetic prosthesis, recurrent dislodgement of prosthesis, implant component fractures, fractured prosthesis, loosening of the connection screw, implant body fracture, crestal bone resorption, implant failure, etc. after implant is loaded/in function. These problems usually arise because of offset occlusal forces and extreme angulation of the implant prosthesis with the implant axis.

Fig 7.7 (A) Supra-erupted opposing tooth not only result in reduced inter-arch space but also cause undue forces over the implant prosthesis during lateral excursive movements. (B and C) The drifting of adjacent teeth results in reduced mesiodistal dimensions for the implant prosthesis.

Tobacco chewing

Tobacco chewing is often associated with poor oral hygiene and periodontal problems in the remaining teeth. Oral prophylaxis should be done before performing implant therapy and the patient should be encouraged to avoid tobacco chewing and adopt oral hygiene maintenance before placement of implants. Tobacco chewing also causes peri-implantitis in the restored implants; hence the patient should be instructed to avoid tobacco chewing for long-term survival of the implants (Fig 7.8A and B).

Fig 7.8 (A) Implants if inserted in the patient with the tobacco chewing habit result in (B) recurrent soft tissue infections under the implant prosthesis.

Bruxism

The problem of bruxism should be treated before placing implants, to avoid post loading problems, such as the early wearing of the prosthesis, ceramic fractures, component fractures, crestal bone resorption, etc. (Fig 7.9A–D).

Fig 7.9 (A to D) Full mouth rehabilitation using multiple implants done for a patient who has worn out all the teeth; if proper measures are not taken to treat the bruxism, it may result in wearing out or fracture of the implant prosthesis or its components.

History of diseased or lost teeth

The history of tooth loss can be very informative to evaluate the bony tissue present at the planned implant site. The traumatic loss of a tooth often leads to the fracture of the thin facial cortical plate. Either reduced buccolingual bone dimensions or a large osseous defect can be found in such cases, when the bony ridge is exposed for implant insertion (Fig 7.10A–D). The patient, while giving the history of tooth loss because of periodontal infections, usually also presents the osseous defects which need to be grafted before or at the time of implant insertion (Fig 7.11A and B). Teeth with periapical radiolucency or history of apicoectomy often show a medium to large osseous defect at the periapical region during the implant placement (Fig 7.12A and B). For such cases the dentist should plan for bone augmentation procedures during or before the implant placement.

Fig 7.10 (A and B) The traumatic loss of teeth often results in loss of thin facial cortical plate. (C and D) The area should be grafted using bone regeneration material and implant inserted in the new bone dimensions after 4 months.

Fig 7.11 (A and B) A large osseous defect can be seen after the extraction of a periodontally compromised tooth.

Fig 7.12 (A and B) Teeth with periapical radiolucency or history of apicoectomy often show a medium to large osseous defect during implant placement. For such cases, the dentist should plan bone augmentation during or before implant placement.

Diagnostic (panoramic/periapical) radiographs

Panoramic and periapical radiographs are very useful diagnostic tools to evaluate the edentulous bony ridge and its surrounding structures. These radiographs give ideas about any root remnant, mesiodistal dimensions of the edentulous space, bone height available to insert implant, any root curvature of adjacent teeth, any bone defect, any periodontal or periapical lesion with the adjacent teeth and the position and route of vital structures in the area, like mental foramina, mandibular canal, maxillary sinus floor, nasal floor, etc. However, when the dentist is planning implant therapy, he/she should always keep in mind that the panoramic radiograph may show 10–30% magnification of hard tissue structures. Whereas, depending on the cone angulation of the radiographic machine, the periapical radiographs show variable amounts of magnification. When planning with these radiographs, a radiographic template with the small metal balls placed above the ridge crest, should be used to calibrate image magnification. If the panoramic radiograph of the patient shows bone dimensions that are more than required, the implant surgeon, to be on the safer side, may plan for the ideal implant size by reducing the radiographic dimensions by 25%. For example, if the panoramic radiograph shows 20 mm bone height above the mandibular canal, it should be reduced by 25% (maximum possible magnification percentage); thus the actual bone height may be 15 mm. Further, leaving 3 mm bone above the canal as a safety guard to avoid nerve injury, the dentist should place only 12 mm long implants. For tight edentulous spaces and limited bone height the bone dimensions can be exactly calibrated using the small metal balls in the radiographic template (e.g. if the metal ball with actual diameter 3 mm is used and shows 4 mm diameter in the radiograph, that means the radiograph is showing 25% magnification). Other disadvantages of these radiographs are that they do not give any idea about bone width and bone density.

Impressions and diagnostic cast preparation

Impression of both the arches should be made using alginate impression material and bite registration should be recorded using an appropriate bite material. Upper and lower diagnostic casts must be articulated in occlusion (for partially edentulous patients) or in centric relation (for completely edentulous patients). These diagnostic casts are used:

Clinical pictures of the edentulous area

These are used to record:

All these features, which are recorded along with clinical pictures, can be very helpful for treatment planning, as the implant dentist can correlate the hard tissue (bone) situations, which are recorded with the radiographs and CT scan, with the type and amount of soft tissue recorded with the clinical pictures.

Bone mapping

Bone mapping is done to evaluate the buccolingual bone dimensions at the edentulous site, which cannot be recorded with the radiograph. There are different ways of doing bone mapping but the easiest way is using a bone calliper. A surface anaesthetic or a small amount of local infiltration is given at the implant site and the bone calliper tips are pierced through the buccal and lingual soft tissue to reach the underlying bone. The bone calliper shows the reading on its scale. This procedure can be repeated at 2 to 3 points along the ridge height to evaluate the bone width at different points along the bony ridge (Fig 7.13A and B). One can record the bone width dimensions and plan the approximate diameter of the implant which can be used at the particular site. Bone mapping may not give accurate bone dimensions, hence the flaps should be elevated to expose the bony ridge for direct visualization and accurate implant placement. CT planning is considered to be more accurate and the dentist can bypass bone mapping procedure if he/she is doing CT planning for the implant treatment.

Fig 7.13 (A) Bone mapping calliper (Salvin Dental Specialities, USA). (B) Surface anaesthetic is applied at the site and the buccolingual bone dimensions at different points along the ridge height is measured using the bone calliper. Its sharp and pointed pins punch through the soft tissue to reach the underlying bone and its scale shows the ridge width present at the particular edentulous ridge site.

Radiographic template fabrication

An ideal provisional prosthesis is fabricated for the edentulous site by setting the teeth in position and in correct occlusion with the opposing dentition or prosthesis. Either radiopaque teeth are used in the template or a radiopaque material like gutta-percha or self-cure resin mixed with radiopaque barium sulphate is filled in the template at the prosthetically accurate, desired implant sites. This template is accurately seated in the patient’s mouth and the patient is sent for the dental radiographs and/or dental CT scan. The radiopaque teeth or the radiopaque material filled at the implant site is clearly visible in the dental radiograph or dental CT scan. With reference to these radiopaque sites, which represent the ideal implant positions and three-dimensional orientations for the accurate future prosthesis, the implants with ideal dimensions, positions, and angulations are planned, executed, and placed accurately for the future prosthesis (‘prosthetically guided implant insertion’).

Template for radiograph

As described earlier in this chapter, radiographs show some degree of magnification; thus the template with calibrated metal balls should be used in radiographic planning of the implant case, to exactly calculate the percentage of magnification in the radiographic image (Fig 7.14A–E).

Fig 7.14 (A) Clinical view of missing mandibular second molar. An impression is made and a diagnostic cast is prepared. (B) A metal ball is fixed at the planned implant site on the diagnostic cast, using a glue and (C) a vacuum form tray is adapted over the same. (D) The vacuum form tray carrying the metal ball is seated in the patient’s mouth and (E) a radiograph is taken which shows the metal ball as the round white image. Now the diameter of real ball and its white image in radiograph is measured and calibrated to calculate the exact magnification that the radiograph shows. For example, if the diameter of the real ball is 3 mm and its radiographic image shows 4 mm, there is 25% magnification in the radiograph. Thus if the radiograph is showing 16 mm available bone height from crest to mandibular canal for the implant placement, the actual bone height could be only 12 mm (25% less than the radiographic bone height); therefore, the maximum length of the implant that can be inserted is 10 mm (leaving 2 mm as the safety margin from the mandibular canal).

Template for dental CT

Using the metal ball in the CT scan template results in the scattering of CT images. Moreover, the dental CT scan does not show any magnification, so ball calibration is also not required; hence any non–metallic, radiopaque material like gutta-percha or self-cure acrylic mixed with barium sulphate can be used in the template to evaluate and plan the desired edentulous ridge sites for three-dimensionally accurate implant placements (Figs 7.15 and 7.16).

Fig 7.15 (A) The vacuum form tray is fabricated over the gutta-percha placed on the top of the ridge of the diagnostic cast. (B) The patient is sent for the dental CT scan with the vacuum form tray seated in the mouth. (C–F) The gutta-percha balls can be seen in the CT images as a white opaque image, and they are used as the reference point to plan the dimensions and angulation of the implant for the prosthesis.

Fig 7.16 (A) Patient’s denture teeth are drilled at the ideal implant sites and holes filled with the heated gutta-percha. The patient is sent for radiograph and dental CT scan with the denture in the mouth. (B) The panoramic radiograph, and (C and D) 3D and cross-sectional views of the dental CT scan show the radiopaque GP points. (E) The implants are inserted at the desired site which shows the adequate bone dimensions and are also ideal for the implant prosthesis.

CT planning

With advancements in diagnostic tools, many implant dentists now prefer to evaluate bone quality and measure three-dimensional ridge dimensions accurately with the help of the dental CT scan (Dentascan). Some implant simulation softwares (Nobel Guide, Implant 3D, etc.) are also available in the market, which can create beautiful axial, panoramic, cross-sections and three-dimensional views of the jawbone using the raw dental CT files (Fig 7.18A–E). They have features for accurate simulation of the implant, graft, and prosthesis. The dental CT scan gives an idea about:

Fig 7.18 (A) CT images created with 3D implant planning software showing panoramic view, (B) axial view, (C and D) cross-sectional views and (E) 3D view with implant simulation, traced nerves, osseous defects and radiographic template.

Surgical guide fabrication

As previously mentioned, implant insertion should be guided by the planned future prosthesis. Thus the use of the surgical guide is paramount for the ideal implant insertion. Depending on the technique, there are different ways to fabricate the surgical guide.