Dental Implant Intraoperative Complications

FIG 5.1 Postextraction socket. (A) With existing pathology. (B) Removal of fibrous and granulation tissue with serrated spoon curette. (C) Walls of extraction site are decorticated with #2 or #4 round bur to initiate regional acceleratory phenomenon (RAP). (D) After complete removal of all bacteria and tissue, implant placement. (E) If the extraction site is compromised, a bone graft procedure is recommended. 

Retained Root Tips in Implant Site

Placement of dental implants into extraction sites that contain retained tooth roots may lead to inflammation and retrograde peri-implantitis. Unfortunately, in some cases, root tips are difficult to diagnosis preoperatively, the condition may go unnoticed until after implant placement.

Etiology

Placement of dental implants, especially after immediate extraction, may lead to undiagnosed retained root tips at the site of implantation. Gray et al, in an animal study, evaluated the intentional placement of dental implants into tooth roots. Histologically, there was no inflammation, and in some of the specimens a calcified material was deposited on the implants. Buser et al also supported the same findings in animal studies. However, implants should never be placed in contact with tooth structure because this may be a source of infection and place the practitioner at risk for possible medicolegal issues.

Prevention

To prevent retained tooth roots, atraumatic and careful extraction of teeth should be completed. Special care should be exercised with multirooted teeth and tooth roots with dilacerations. Preoperative evaluation should include a CT evaluation with the following Hounsfield numbers as a guide (Fig. 5.2):

Air = − 1024 Hu

Water = 0 Hu

Trabecular bone ≅ 200 Hu

Cortical bone ≅ 1500 to 2000 Hu

Tooth structure—Enamel ≅ 3072 Hu

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FIG 5.2 Retained root tips. (A–B) All root tips should ideally be removed prior to bone graft or implant placement. (C) Retained bacteria, granulation tissue, or tooth root may lead to increased morbidity after implant placement. 

Treatment

Prior to Placement.

Root tips should be removed and the site evaluated for implant placement. If an inadequate amount of bone is present, grafting should be completed followed by implant placement at a later date.

After Implant Placement.

If a root tip is discovered after implant placement, the site should be evaluated on a strict recall basis. If any signs of inflammation develop, the implant and root tip should be removed, grafted, with implant placement at a later date (Figs. 5.2 and 5.3).

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FIG 5.3 Evaluation of different densities. (A) Retained root tip. (B) Difference in host bone vs. grafted bone utilizing medical grade CT imaging (Hounsfield units) and showing different bone densities. 

Flapless Surgery

Flapless surgery has become very popular today in implant dentistry. This technique entails no reflection of the crestal soft tissue and placement of the implant through the opening for the osteotomy. The advantages of flapless surgery are: (1) no soft tissue reflection, decreasing the invasiveness of the surgery; (2) minimizes bleeding; (3) reduces inflammation and pain; (4) hard and soft tissue preservation, which maintains vascular supply and soft tissue drape; and (5) no suturing.

Etiology

However, flapless surgery does have disadvantages that may be detrimental to the prognosis of dental implants. These include: (1) inability to assess the bone volume before or during the implant osteotomy and insertion; (2) inability to ascertain perforation of the cortical plates; (3) tissue punches are often used, which may result in decreased keratinized tissue; (4) difficulty in visualizing crestal bone area, resulting in the inability to determine apicocoronal positioning; (5) possibility of overheating the bone and causing thermal damage, especially if a tissue borne surgical template is used; and (6) possibility of soft tissue entrapment into the osteotomy site, which may lead to a retrograde infection (Fig. 5.4).

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FIG 5.4 Flapless surgery. (A) Drill sequence and implant placement after tissue punch. (B) Osteotomy preparation and implant placement through surgical template. (C) Flapless surgery leading to lingual position of implant, with the complication of traumatizing the lingual tissue and vital structures in the mandible. (D) Maxillary anterior flapless surgery leading to implant placed facially, completely out of the bone. (E) Tissue surgical templates should be fixated with bone screws to minimize possibility of malposition. 

Prevention

A thorough preoperative evaluation should be completed including a three-dimensional analysis of the available bone and anatomic variants. Use of cone beam computed tomography (CBCT)–generated surgical templates is recom­mended. Care should be noted in Division B or Division C ridges because ideal placement is difficult.

Treatment

Flapless implant placement should only be completed in the presence of adequate keratinized tissue and sufficient bone quantity and angulation, where root approximation is not an issue. If bone quantity is compromised, the surgical approach should be changed to an exposure (flap) procedure to verify ideal placement and angulation.

Malpositioned Initial Osteotomy Site

In certain initial osteotomies, the initial implant position may not be placed in the ideal location. The osteotomy may need to be repositioned to allow for ideal placement. The use of a Lindemann bur is ideal for the repositioning of an osteotomy because of its side-cutting capabilities. Lindemann burs are side-cutting burs, which allow easy positional change with minimal trauma to the bone.

Etiology

Once the initial osteotomy is prepared, it is assessed for proper position with a direction indicator. If incorrect, the osteotomy site may need to be “stretched” or repositioned to a more ideal location.

Prevention

Use of surgical templates or implant-positioning devices for ideal implant positioning to decrease the possibility of changing the osteotomy position.

Treatment

To horizontally reposition an osteotomy site, the use of conventional drills is difficult because of the end-cutting capabilities of the burs. The use of a side-cutting Lindemann bur will allow for repositioning to a new, corrected site. The new osteotomy position should be deepened so that subsequent end-cutting drills will not reposition back into the original osteotomy site. However, when using the Lindemann bur, always use copious amounts of saline because this bur will generate a significant amount of trauma and heat to the bone7 (Fig. 5.5).

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FIG 5.5 Malpositioned initial osteotomy site (i.e., not equidistant between implants). (A) Implant position too close to center implant. (B) Use of Lindemann bur to move the implant site posteriorly. (C) Side-cutting Lindemann bur. (D) Lindemann bur used to reposition osteotomy site by increasing osteotomy depth to prevent from entering back into original malpositioned site. 

Lack of Keratinized Tissue at Surgical Site

The presence of keratinized tissue is a controversial subject in oral implantology. However, there appear to be greater benefits with having this tissue in relation to an implant when compared to a natural tooth. Some reports indicate the lack of keratinized tissue may contribute to implant failure.8

Etiology

Mobile, nonkeratinized mucosa has been shown to exhibit greater probing depths, which has been confirmed histo­logically. The absence of keratinized mucosa also increases the susceptibility of periimplant regions to plaque-induced destruction.9 Additional studies have shown that mobile mucosa may disrupt the implant-epithelial attachment zone and contribute to an increased risk of inflammation from plaque.10 For larger edentulous ridges, the zone of attached tissue on the facial flap (mandible) provides greater resistance for the sutures against tension of the mentalis muscle in the anterior region and the buccinator muscle in the molar-premolar regions, which often cause incision line opening. As a result, an incision made facial to the attached tissue may cause partial ischemia to some of the crestal tissue. In addition, the incision in unkeratinized facial tissue also severs larger blood vessels, which increases bleeding and decreases vision during surgery, while also potentially complicating final suturing (Fig. 5.6).

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FIG 5.6 (A) Ridge with lack of keratinized tissue. (B) Incision made to the lingual to maintain as much attached tissue on facial as possible. (C) Dermal accelular matrix (e.g., OraCELL [Salvin Dental Specialties, Inc.]) modified with a tissue punch. (D) Dermal matrix placed over implants prior to closure. 

Prevention

A thorough clinical examination to determine the amount of host-attached tissue prior to surgery and the possible implementation of tissue grafting prior to implant placement.

Treatment

For implant sites intended for crown restorations, an evaluation of attached tissue should be done. If insufficient attached tissue is present, tissue augmentation procedures should be completed prior to implant placement. For larger edentulous sites, especially in the mandible, the incision may be modified to maintain the attached tissue in some cases. If the crest of the ridge is above the floor of the mouth, and there exists greater than 3 mm of attached, keratinized gingiva on the crest of the ridge, a full-thickness incision is made, bisecting the attached tissue. If less than 3 mm of attached gingiva exists on the ridge, the full-thickness incision is made more to the lingual so that at least 1.5 mm of the attached tissue is to the facial aspect of the incision line. Additionally, AlloDerm may be used as a membrane and to increase the amount of attached tissue.

Bur “Stuck” in Bone During Osteotomy

Etiology

Often in hard bone (≈D1–D2 bone), if the handpiece is stopped with the surgical drill in the bone, it may be difficult to remove out of the osteotomy. Attempting to remove the bur with the handpiece (either forward or reverse) will result in damage to the handpiece gears (Fig. 5.7).

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FIG 5.7 Bur lodged in the bone. (A) Osteotomy preparation in dense bone may result with internal stress within the prepared site leading to difficulty in bur removal. (B) When bur cannot be removed, do not attempt to use handpiece in reverse direction because this may cause damage to the handpiece. (C) Handpiece disengaged from bur. (D) Bur gently removed with forceps in counterclockwise direction. (E) Bur removed carefully to minimize possibility of fracturing buccal plate. 

Prevention

To avoid this complication, in dense bone small (minimal) increments of bone should be removed at a time. When performing the osteotomy, “bone dancing” should be performed, which will result in less stress to the bone and will allow for ease of widening the osteotomy. Also, by using intermediate burs (more burs close in diameter), smaller amounts of bone are removed at a given time, decreasing the possibility of burs being lodged in the bone (“bur integration”).

Treatment

If a bone drill becomes lodged in the bone during preparation, the hand piece should not be wiggled back and forth to disengage the drill. This may increase the size of the bone preparation, cause injury and necrosis to the bone, or separate the drill above or below the bone. Instead, the drill is disengaged from the handpiece and gently rotated counterclockwise with forceps or rongeurs.

Overpreparation of Final Drill

Etiology

The final drill is the most critical surgical step in the osteotomy preparation. The bone surrounding this drill will be in direct contact with the implant. When the final drill preparation is not precise, the implant-bone region may be irregular with gaps that may decrease initial stability and lead to early implant failure. A decreased initial bone contact of the host bone and dental implant also decreases the percentage of new bone-implant contact formation (Fig. 5.8).

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FIG 5.8 (A) Overpreparation of the osteotomy site that results in mobility and lack of bone implant contact. (B) Irregular osteotomy site showing overpreparation of site. (C) In less dense bone (lack of cortical bone), no crestal bone drill should be used because this will result in lack of stability of the implant. 

Prevention

A constant pressure and angulation is used with the final drill to ensure that a precise, round osteotomy is prepared. The most important factor is the use of the final drill only once to avoid over preparation, most importantly in less dense bone (≈D3–D4). In D4 bone the final bur is often not used to increase bone-implant contact (BIC) around the implant. Additionally, in less dense bone a crestal bone drill should never be used because of increased loss of initial fixation.

Treatment

If overpreparation of the osteotomy site occurs, clinical evaluation should be completed to determine if mobility of the implant exists. If mobility does exist, the following are possible options; however, it is imperative that the final placement of the implant not have any micromovement:

Compress Buccal and Lingual Cortical Plates.

In less dense bone, the buccal and lingual cortical plates can be depressed to reduce movement of the implant. The implant should then be evaluated for micromovement. If movement exists, the implant should be removed.

Remove Implant, Deepen Osteotomy.

The mobile implant may be removed, and the osteotomy deepened so that rigid fixation is obtained. However, care should be exercised to not allow encroachment on any vital structures (e.g., mandibular canal) or compromise the prosthesis by increasing the crown-implant ratio.

Remove Implant, Place Wider Implant.

If sufficient width of bone is present, the implant may be removed and a wider implant placed to obtain rigid fixation. Usually, the osteotomy site does not need to be further prepared for the wider implant. However, a minimum of 1.5 mm of bone should be present on the facial aspect of the ridge after implant placement.

Remove Implant, Graft, Let Heal.

Usually, the ideal technique for a mobile implant, which will lead to decreased implant morbidity, is to remove the mobile implant, graft the site, and allow for sufficient healing prior to implant placement.

Remove Implant, Graft, Replace Implant.

An often-used technique, which has the highest possibility of complications, is removing the mobile implant, replacing the implant, and grafting the areas with little bone contact.

Facial Dehiscence After Implant Placement

After implant placement, it is not uncommon to have facial plate dehiscence on the buccal aspect of the implant. Because bone resorbs from the facial aspect, usually less than 1.5 mm of facial bone is present after final implant placement. Thus, if inadequate bone is present, this may lead to future soft tissue complications and increased implant morbidity.

Etiology

Bony defects at the crest after implant placement will usually result in lack of available bone width at the ridge level (Fig. 5.9) (e.g., a division B ridge that is compromised in width ∼<6 mm).

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FIG 5.9 Facial dehiscence after implant placement. (A) Ideal implant position in relation to ridge. (B) When lingual bone is higher than buccal bone, implant placement will result in a facial bony dehiscence. (C) 3-D image of implant placement in division B bone. (D) Autograft from osteotomy site. (E) Defects packed with autograft. (F) All sites grafted with bone retained within surgical drills prior to closure. 

Prevention

All ridges should be modified to obtain a division A bone (e.g., >6 mm width and >12 mm of bone height) before osteotomy initiation. After implant placement, 1.5 mm of facial bone should be present or the area should be grafted.

Treatment

After implant placement, if there exists less than 1.5 mm of bone on the facial aspect of the ridge, the site may be grafted with autogenous bone (ideally). The autogenous bone may be obtained from fragments gathered from the flutes of the surgical drills during the osteotomy preparation. The consistency of this bone allows for ease of packing, and the graft will have less of a chance of migrating. Allograft bone is not preferred because it tends to migrate easily after placement and is an added expense.

Loss of Facial Plate When Placing an Implant

When placing implants in bone that is compromised in width (∼division B), it is not uncommon to fracture or lose the facial plate of supporting bone. This leads to a compromise in the healing of the implant and the longevity of the implant and prosthesis.

Etiology

Ideally, the width of bone needs to exceed 6.0 mm for placement of a 4.0-mm diameter implant. When compromised width of bone exists, the trauma of the osteotomy or the placement of the implant may fracture or “pop off” the buccal plate. This is most likely the result of the buccal plate being thinner than the lingual plate, which results in the facial plate being more susceptible to fracture (Fig. 5.10).

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FIG 5.10 (A) Facial plate fracture leading to exposure of the implants after placement. (B) Prevention includes grafting site prior to implant placement to restore site to ideal dimensions prior to implant placement. (C–D) Grafting facial aspect of implant with autogenous bone harvested from surgical burs. 

Prevention

Determine the available bone prior to implant placement. If nonideal width of bone is present, site development, including grafting, is indicated to obtain a division A bone. The osteotomy preparation should be in one plane, and care should be exercised to not deviate from the original angulation. If division B bone is present, ridge augmentation is recommended to achieve a division A ridge prior to implant placement.

Treatment

After implant placement, if a fracture or loss of the buccal plate exists, treatment will depend on the extent of the deficit.

Loss of Entire Buccal Plate.

If the entire buccal plate is lost or if mobility of the implant exists, the ideal treatment should include grafting then allowing for sufficient healing before implant placement.

Partial Buccal Plate Still Intact.

If no mobility of the implant is present and the facial plate is partially intact, the facial area can be grafted, ideally with autogenous bone from the osteotomy site (e.g., surgical drill).

Not Altering Surgical Protocol in Poorly Dense Bone

Many studies have shown the greatest risk of surgical failure is observed in the softest bone type (D4), especially when found in the maxilla. To combat this problem, Misch developed a different surgical protocol for the various bone qualities in 1988. The implant design, surgical protocol, healing times, treatment plans, and progressive loading time spans are unique for each bone density type.

Etiology

Fine trabecular (D4) bone has very little density with minimal to no cortical crestal bone. The most common locations for this type of bone are the posterior molar region of the maxilla in a long-term edentulous patient, in an augmented ridge (grafted for height and width with particulate bone or substitutes), or in a sinus graft.

The tactile sense during osteotomy preparation of this bone is similar to stiff, dense Styrofoam or soft balsa wood. The bone trabeculae may be up to 10 times weaker than the cortical bone of D1. The BIC after initial loading is often less than 25%. A CBCT scan with reformatted images of D4 bone has a Hounsfield number (or equivalent) of less than 375 units (Fig. 5.11).

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FIG 5.11 Implant placement in less dense bone. (A) D3 to D4 type of poor bone density showing lack of cortical bone and fine trabeculae. (B) Osteotomes to compact the existing bone, increasing bone implant contact, should be used in D3 and D4 bone quality of bone. (C) Implant in D4 type of bone should be countersunk in comparison to better-quality bone (D2). (C, From Misch CE: Contemporary implant dentistry, ed 3, St Louis, 2008, Mosby.)

Prevention

Osteotomy Drills.

The implant surgeon should not prepare D4 bone with rotating drills, which use an extraction technique to remove bone during preparation of the osteotomy. These types of drills in D4 bone will result in distortion of the osteotomy site (enlargement). Ideally, a compaction technique should be used with osteotomes, which expands the bone by compressing the trabecular bone.

Insertion With Handpiece.

The implant should be allowed to self-tap with the use of a slow-speed, high-torque hand piece. A hand wrench is contraindicated because it will widen the osteotomy (i.e., make elliptical) and possibly result in a lack of rigid fixation of the implant. The pressure on the implant during insertion corresponds to the speed of rotation, and the implant proceeds to self-tap the soft bone.

One-Time Placement.

Once inserted, the implant should not be removed and reinserted. Instead, a one-time placement is mandatory because removal of an implant in this bone will lead to less bone at the interface.

Countersink.

The implant is countersunk in this bone if any risk of loading is expected during healing (e.g., under a soft tissue–borne denture). Countersinking the implant below the crest reduces the risk of micromovement during healing in this very soft bone. No countersink drill is used before implant placement because this decreases the density of bone at the crestal area.

Treatment

When a poorer type of bone exists, increased healing times and progressive bone loading should be adhered to. Increased healing time is indicated to allow for more bone to remodel at the surface and to intensify its trabecular pattern. The additional time also allows a more advanced bone mineralization and increased strength. Six or more months of undisturbed healing is suggested. The compression technique for surgery (e.g., osteotomes), the extended healing time, and progressive bone loading protocol allow the remodeling of the poor quality bone into a more organized and load-bearing quality similar to D3 bone before the final prosthetic loading of the implants.

Overheating the Bone

One of the most common complications that has been associated with early implant failure and bone loss is overheating of the bone during osteotomy preparation. This usually is a result of the surgical osteotomy protocol.

Etiology

The amount of heat produced in the bone is directly related to the amount of bone removed by each drill.11 A 3-mm pilot drill has been shown to generate greater heat than a 2-mm pilot drill.12 As a result most manufacturers suggest the first drill be 2 mm or less in diameter. In a similar fashion, the amount of heat generated by successive drills is also directly related to the increase in drill diameter. A 3-mm drill after a 2-mm drill removes 0.5 mm of bone on each side of the drill. A 2.5-mm drill after a 2-mm drill removes only 0.25 mm of bone on each side of the osteotomy. The smaller incremental drill size allows the surgeon to prepare the site faster, with less pressure and less heat. In addition, when large increases in drill diameter are used to prepare bone, the surgeon may inadvertently change the angulation of the drill because the larger drill is removing a greater bone volume and the tactile sense is decreased. As a result, an elliptical osteotomy may be prepared that does not correspond accurately to the round implant diameter. The gradual increase in osteotomy size also reduces the drill chatter at the crestal opening, which can inadvertently chip away pieces of bone on the crest, where complete bony contact is especially desired. The gradual increase in drill diameter also keeps each drill sharper for a longer period, which also reduces the heat generated (Fig. 5.12).

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FIG 5.12 Overheating bone. (A) D1 type of bone: highest amount of bone is present at the interface, which predisposes to heat generation. (B) Area of bone necrosis from overheating around implant (arrow). (C) Devitalized bone (D) and vitalized bone (V). (D) Use copious amount of irrigation during osteotomy preparation to avoid overheating the bone. (E) Caution should be exercised with the use of surgical templates because minimal irrigation enters the osteotomy site and overheating the bone is a common problem. (F) Modification (removal of buccal flange) of the template to allow for increased irrigation (i.e. external irrigation; arrow). (A and C, From Misch CE: Contemporary implant dentistry, ed 3, St Louis, 2008, Mosby.)

Prevention

Intermediate Drills.

Some manufacturers do not utilize an intermediate drill in their drilling protocol. However, a decrease in the heat and trauma generated is found with the intermediate drill. Gradual increases in drill diameter reduce the amount of pressure and heat transmitted to the bone, especially in the presence of dense and thick cortical bone.

Copious Amounts of Saline.

Along with external irrigation from the surgical drills, increased irrigation may be obtained by using internal irrigation (through the surgical bur) or with supplemental irrigation via a syringe.

Bone Dance.

The bone-dancing technique was introduced by Misch in 1988 to reduce the amount of heat generation. When preparing the osteotomy, small increments of bone should be removed, and by using the up-and-down motion of the drill, irrigation may enter the osteotomy site easier.

Use of Sharp, New Drills.

Drills that are dull will increase heat generation, causing the possibility of no bone integration. On average, surgical drills should be replaced approximately every 20 to 30 autoclave cycles.

Drill Speed.

Sharawy and Misch have shown that the drill speed in hard, dense bone should be approximately 2000 to 2500 RPM. Osteotomy preparation at higher speeds with sharp drills elicits less risk of osseous damage and a decreased amount of devitalized zone adjacent to the implant.12 Yeniyol et al have shown that drilling at very slow speeds results in a higher degree of bone fragmentation.13

Surgical Templates.

Surgical templates often result in overheating of the bone because of the decreased space between the guide tubes in the template and the drill size. Ideally, the template should be modified to open up the facial aspect of the template so supplemental irrigation may be utilized.

Treatment

If known excess heat generation occurs during implant placement, ideally the implant should be removed, regional acceleratory phenomenon (RAP) initiated, and the site grafted for future implant placement. If bone width is available after sufficient RAP is completed, a wider implant may be placed.

Implant Pressure Necrosis

A possible cause of early implant failure is pressure necrosis. Overcompression of the crestal bone has been shown to be a contributing factor in implant failure.14 It is postulated that excessive tightening of the implant creates compression forces within the crestal bone around the implant. This may impair the microcirculation and lead to bone resorption.

Etiology

Pressure necrosis from implant placement may increase the devital zone of bone around the implant or even cause short-term neurosensory impairment when the implant site is in the vicinity of the mandibular canal. This most often occurs where there exists a cortical component of bone in the crestal region (∼D1–D2 bone). If a crestal bone drill is not used in higher bone density with a cortical component, excess stress will be generated upon insertion of the implant, which will lead to a devitalized zone (Fig. 5.13).

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FIG 5.13 Pressure necrosis. (A) Normal implant placement level to the ridge. (B) To decrease pressure necrosis in highly dense bone (~D1), the implant is unthreaded ≈1 mm after insertion. 

Prevention

Torque.

The implant should not be tightened into the osteotomy, such as a nut onto a bolt. A torque value up to 35 N/cm is considered safe with most threaded implant designs.

Crestal Bone Bur.

Because most implants have a wider crest module (wider diameter of the neck of implant in comparison to implant body), greater stress can be concentrated upon placement in D1 and D2 types of bone. To decrease crestal pressure, the implant may be placed to ideal position, then backed off approximately 1 mm to avoid pressure necrosis.

Treatment

Ideally, the thickness of crestal bone and bone quality type should be ascertained prior to implant osteotomy preparation. This is easily evaluated on a CBCT radiographic examination. If a large cortical component of bone is present and the implant placed is known to contain excess pressure, the implant should be removed and the crestal bone modified. The implant should be then reinserted.

Bone Spreading Complications

Bone spreading has become a popular surgical technique to expand the available bone width prior to implant placement. Since Tatum developed the bone spreading technique in the early 1970s, the expansion technique has been primarily used in regions of division B bone to increase the bony width. However, the easiest edentulous ridges to expand are division A bone volume with associated D3 or D4 bone densities. The narrower the bone, the greater the risk of fracture of the facial plate. The softer the trabecular bone quality, the lower the elastic modulus and the greater the viscoelastic nature of the ridge. Therefore, the less dense the bone, the easier and more predictable the bone expansion. There exist three main complications that may occur during bone spreading.

Splintering of Facial Plate

Etiology.

The most common complication of bone spreading, especially in division B bone that is D2 quality, is splitting the facial plate during the procedure. Once this occurs the surgeon must decide whether to continue, place the implant, and perform a barrier membrane layered bone graft, or abort the procedure and place only a bone graft (Fig. 5.14).

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FIG 5.14 Bone spreading complications. (A) Facial dehiscence after implant healing. (B) Autogenous and allograft bone graft with tent screws. (C) Barrier membrane is placed (e.g., accelular dermal matrix). (D) A second complication occurs with the bone grafting being too facial leading to a facial plate fracture, incision is made slightly lingual to center of ridge. (E) Osteotomy is made lingual to center of ridge. (F) Bone spread maintaining buccal plate. (G) Care should be exercised to minimize compromising facial plate thickness. (H) Implant placement with maintaining buccal plate intact. 
Prevention.

Make sure there exists sufficient bone for bone spreading and good surgical technique. A common misconception is that division C minus width (C−w) ridges may be spread with simultaneous implant placement. This often results in fracturing the facial plate. Bone spreading should be restricted to division A and B ridges.

Treatment.

The implant may be inserted when the following factors are positive: (1) the implant is rigid at the proper depth, (2) the implant is in a favorable angulation, and (3) the facial plate is farther facial than the implant (it is fractured, but expanded). Under these conditions the barrier membrane layered graft procedure will predictably restore the facial bone, and the implant is not compromised. If one of these three factors is negative, it is more prudent to remove the implant, harvest additional autograft, and perform the bone graft without the implant in situ.

Dehiscence

Etiology.

Another complication of bone spreading is the dehiscence of the labial plate after healing and bone remodeling around the implant. This results from insufficient bone quantity preoperatively. Because of its modulus of elasticity the expansion of the labial plate is not beyond the point of permanent deformation, and the bone does not fracture. It will attempt to rebound to its original size during remodeling. As a result, during bone remodeling the bone does not heal in its expanded position, instead returning to its initial narrow dimension, and the implant fenestrates the labial plate. When bone expansion is performed at implant placement, a stage II uncovery with reflection of the facial soft tissue is advantageous to evaluate the facial plate.

Prevention.

To decrease the possibility of bone dehiscence after bone spreading, the technique should be restricted to division A and B ridges.

Treatment.

When a dehiscence is observed, a barrier membrane with layered graft approach is indicated to restore the facial plate. Because the implant is integrated to the remaining bone, the implant may be progressively loaded after a 3- to 4-month period, rather than waiting 6 to 9 months, as with augmentation by barrier grafts alone.

Poor Position

Etiology.

The third complication of bone expansion is a poor final implant position, usually more facial than ideal. The thicker palatal cortical plate tends to push the osteotomes to the facial; if the implant surgeon is unaware of this malpositioning, the end result will be an implant that is too facial and will be problematic esthetically and functionally.

Prevention.

Constant attention of angulation and modification of the palatal bone with side-cutting drills (Lindemann drills) is necessary to prevent this problem.

Treatment.

The final prosthesis should not be compromised for the advantage of placing the implant during the surgery. Bone augmentation and reentry 6 months postoperatively often improve the implant position and, as a result, the final restoration.

Inability to Determine True Location of Mental Foramen on CBCT

If the true position of the mental foramen cannot be determined from the CBCT, reflection of the foramen is recommended to determine the exact position.

Etiology

Although rare, sometimes it is difficult to determine the exact location of the mental foramen or if an anterior loop exists from a CBCT. Because of the possible consequences of placing an implant too close to the mental foramen, care must be exercised to prevent impingement.

Prevention

A CBCT evaluation utilizing the cross-sectional and 3-D images should be used to clearly identify the mental foramen. In some cases, the brightness and contrast will need to be altered to depict the mental foramen.

Treatment

The primary incision is extended anterior and posterior with releases to minimize stretching of the tissue so the foramen may be identified. The location of the foramen is variable, depending on age, ethnic background, amount of resorption, and skeletal relationship. Initially, the periosteum is reflected off the residual crest, and a moist surgical sponge can be used to wipe the periosteum off the dense labial cortical plate to identify the superior aspect of the foramen. After the superior aspect of the foramen is identified, the tissue is reflected anterior and posterior to confirm the exact location of the foramen (Fig. 5.15).

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FIG 5.15 Mental foramen reflection. (A) When reflecting the mental foramen, a 3-D CBCT image is used to determine position in reference to an adjacent tooth (arrows). Reflection should be initiated anteriorly and posteriorly (green arrows) to allow for access to the foramen. (B) Full-thickness reflection exposing the superior aspect of the mental foramen. (C) Mental foramen exposure (blue arrow). 

Incisive Foramen Implant Placement Complications

The incisive foramen region, rather than a central incisor site, may also be used to insert an endosteal implant, especially when an overdenture is the intended final prosthesis.15 The incisive canal ranges in length from 4 to 26 mm and is directly related to the height of bone in the premaxilla. As alveolus height is resorbed, the canal reduces in length; therefore division A, B, and C−w bone have greater canal length than division C−h and D. The incisive canal has an average axis of 70 degrees with a range of 57.0 to 89.5 degrees from the horizontal plane.16 This structure contains terminal branches of the nasopalatine nerve, the greater palatine artery, and a short mucosal canal (i.e., Stensen duct). A vertical projection above the incisive canal along the nasal floor is called the premaxillary wing. The nasal process of the premaxilla rises 2 to 3 mm above the nasal floor. As a result, when 7 to 11 mm of bone is present below the nasal floor, a large osteotome may create a greenstick fracture in this process above the foramen and permit the placement of a 9- to 14-mm implant. The foramen is usually 4 to 6 mm in diameter at the crest and narrows down to 4 mm at the apex. Implants inserted at the same time as the soft tissue is curetted are usually 5 to 6 mm in diameter.

Prevention/Treatment

There exist many possible complications with incisive foramen implants.

The first surgical complication of an incisive foramen implant is the result of an implant that is too small for the foramen and not properly fixated. The implant may be inadvertently pushed through the incisive canal and into the nares proper. Because the patient is lying on their back during the surgery, the implant may fall back into the soft palate, then into the trachea or esophagus. If the implant disappears from the oral site, the patient’s head should be turned to the side immediately, then down and forward. A nasal speculum and tissue forceps may then be used to recover the implant.

A second surgical complication may include bleeding from the incisive foramen. Although this complication is very rare, it is possible. When reflection of the palatal tissue off the incisive canal is associated with arterial bleeding, a blunt bone tap (mirror handle) may be placed over the canal and a mallet used to hit the instrument firmly, crushing the bone over the artery. After several minutes the procedure may continue, and the implant insertion will obdurate the site and arrest the bleeding.

The short-term complication of an incisive foramen implant is associated with enucleation of the soft tissue from the foramen. Although the author has not witnessed this complication, neurologic impairment of the soft tissues in the anterior palate may exist. This may lead to paresthesia to the soft tissue or a dysesthesia, with a report of a burning/painful sensation. It is logical to include this risk in an informed consent. If it should occur, removal of the implant for dysesthesia is warranted, whereas paresthesia of the palate most likely is a condition the patient can tolerate without significant issues. In many cases the patient will regain neurosensory feeling from collateral innervation.

A long-term complication that has been observed twice by the author is the regeneration of the soft tissue in the incisive canal, resulting in bone loss around the implant. When the implant is removed and the soft tissue biopsied, nerve fibers can be seen reinvading the site. This most likely occurs because the implant was too small for the size of the foramen, and the soft tissue can reform around the implant. Treatment of this complication includes removing the implant and, if necessary for the treatment plan, regrafting and/or reimplantation (Fig. 5.16).

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FIG 5.16 Incisive foramen implant failure. (A) Bone loss and probing depths resulting from not removing all soft tissue from the incisive foramen implant. (B) Removal of implant with trephine bur. (C) Implant removed with soft tissue interface. (D) Histologic examination of the soft tissue around the implant reveals the contents of the incisive canal are reforming around the implant. (E) Histologic examination demonstrates nerve fibers in the soft tissue around the implant. 
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Jan 12, 2018 | Posted by in Implantology | Comments Off on Dental Implant Intraoperative Complications
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