Implant complications

Preoperative complications

Treatment planning complications
Compromised interdental space
It is important to take accurate measurements of the intertooth space to plan for the appropriate size implant. A minimum intertooth space of 7 mm is required to place a standard 3.75–4.1 mm diameter implant. There are times when the interdental space is too small to place an implant or too large for one implant but too small for two implants. Some studies (Tarnow et al., 2003) have found that the distance between two implants should be at least 3 mm in order to preserve the interdental bone. It is also recommended that there be 1.5 mm between the implant and the tooth to main­ tain bone adjacent to the teeth and 1 mm between the implant and the tooth when using platform‐switched implants (Vela et al., 2012). Inability to perform good oral hygiene, compromised papilla on the adjacent tooth, persistent inflammation, bone loss, and pain may arise when the implants are placed in a compromised intertooth space (Figure 7.1).
It is also important to not only measure the distance between the roots but also at the crowns. The crowns may encroach into the edentulous space and make it difficult to maneuver instruments.

Prevention and management
Proper planning with diagnostic images (e.g., with a radiographic stent made from a diagnostic wax‐up) and study casts can prevent placing an implant in an inadequate space. If there is insufficient space to place a standard‐sized implant, other options should be con­ sidered such as:
1 Insert an implant with a narrower diameter.
2 Place a fixed partial denture instead of an implant.
3 Enlarge the space by orthodontically moving the adjacent teeth. If the distance between the crowns is minimal, reducing the proximal surfaces of the crowns can sometimes create enough space to allow placement of the implant (Greenstein and Cavallaro, 2010, p. 406). This reduction can also flatten the con­ vexity of the proximal surfaces, broaden the contact with the implant‐supported prosthesis, and minimize food impaction.
Malposition of the implant in the esthetic area
Malposition of an implant can lead to compromised esthetics. When teeth are lost in the esthetic zone, there are many factors that the clinician must evaluate (Belser, Bernard, and Buser, 2003):
• Mesiodistal dimension of the edentulous area:
◦ It is more difficult to gain a papilla between two adjacent implants than a natural tooth and an implant. It is not recommended to place a central and lateral implant adjacent to one another.
• Three‐dimensional radiographs of the site:
◦ Cone‐beam scans allow for three‐dimensional radiographic examination of the implant site, which can reveal facial bone thickness, bone density, bone contours, presence of pathology on adjacent teeth, and proximity of adjacent anatomical structures such as nerves, vessels, bony undercuts, and the
proximity of the maxillary sinus and nasal floor. The aforementioned information can allow for more predictable treatment planning and presurgical preparation.
• Neighboring teeth (e.g., tooth dimensions, interproxi­mal bone levels, restorative status, endodontic pathology, form, position, and orientation; periodontal/ endodontic status; length of roots; bone level that will affect papilla fill; and crown‐to‐root ratio):
◦ They help dictate where the implant will be placed.
◦ Does site development need to be done before implant placement?
• Interarch relationships (e.g., vertical dimension of occlusion, interocclusal space, choosing between screw‐retained or cement‐retained implant crown, and necessity of odontoplasty of adjacent or opposing teeth).
• Esthetic parameters (e.g., height of upper smile
line, lower lip line, occlusal plane orientation, dental and facial symmetry, and esthetics of contra­ lateral tooth).
• Patient expectations:
◦ Problems arise when the patient does not have ideal conditions for implant placement (e.g., bone quality) and still has high expectations (Klokkevold, 2006, p. 1182).
• Plaque control.
• Infection at or near the site where the implant will be placed.
• There is a greater chance of postoperative complications.
• Immunocompromised patient (i.e., any general health issue that lowers resistance to infection).
• Are the patient’s anterior teeth triangular or highly scalloped with a thin biotype?
◦ These cases are harder to manage because there is a greater risk of midfacial recession and loss of the interdental papilla.
◦ Phonetic problems may result when the implant prosthesis is made with unusual palatal contours due to malpositioning of the implant (Klokkevold, 2006, p. 1189).

Prevention
A surgical stent and CT scans are essential in the preven­ tion of implant malpositioning (Figure 7.2). A parallel pin can be placed in the osteotomy and an X‐ray taken to ensure proper angulation of the implant after the pilot drill has been used. If a correction is needed, it can be done before further drilling is done.
Thin (≤1 mm) buccal walls are found in most extraction sites in the anterior maxilla (Huynh‐Ba et al., 2010). In most clinical situations, if less than 2 mm of facial bone thickness is predicted, augmentation procedures are necessary to attain sufficient bony contours around the implant (Chen and Buser, 2010, p. 142). Studies have also found that the insertion of a soft tissue graft at the time of immediate implant placement in the esthetic zone can be advantageous (Grunder, 2011).

Implant positioning
Apicocoronally the implant should be placed 1 mm apical to the cementoenamel junction of the adjacent tooth in patients who do not have gingival recession (Table 7.1) or 3 mm apical to the final buccal gingival margin of the implant restoration. If the implant is placed too deep, recession may occur and the gingival harmony may be disrupted. If the implant is too shallow, the metal margin may be visible. Deep implant placement may be caused by the surgeon wanting to ensure he achieves primary stability in immediate loading situations. Studies show that immediately loaded implants are placed 0.3 mm deeper than early loaded implants (Ganeles et al., 2008). The implant should not be placed too facially to pre­ vent soft tissue recession. If the implant is placed too palatally, a ridge‐lap crown would need to be fabricated, which may be difficult for the patient to clean (Chen and Buser, 2010, p. 138). When the occlusion allows, the surgeon should place the implant using the cin­ gulum of the adjacent tooth as a guide, not the incisal edge. It may be prudent to avoid wide‐diameter implants in the esthetic area to reduce the likelihood of recession and allow for a more esthetic emergence profile.

Treatment
Depending on the extent of malpositioning, the implant may need modification of the restoration design. If the implant is severely malpositioned, it is favorable to remove the implant, start over, and inform the patient of the potential need for one or more regenerative procedures to prevent failure of the implant components.
A preparable ceramic abutment can be used in shal­ low placement situations. The ability to modify the crown‐implant margin for subgingival placement can help when there is inadequate soft tissue thickness with a poor emergence profile (Al‐Faraje, 2011, p. 74).
If recession has occurred, a connective tissue graft can be placed. However, once papillae have been lost, there are no predictable methods to regenerate them.

Limited jaw opening
The range of opening is 36 to 60 mm in women and 38 to 65 mm in men without regard to overlap and overbite (Misch, 2008, p. 250). Temporomandibular joint disor­ ders can lead to limited jaw opening. The condyles are not able to move downward and forward the height of the articular eminence and therefore cause limited opening. Trismus causes limited jaw opening due to spasm of the muscles of mastication. Limited opening can complicate or prevent implant placement.

Management
In cases where there is limited jaw opening, tilting the implants mesially allows easier access for the dentist. The dentist may want to use the indirect coping tech­ nique that needs less vertical space (Greenberg and Prein, 2002). If access for screw placement is limited, a cement‐retained implant prosthesis might be indicated (Rosen and Gornitsky, 2004).
Depending on the situation, control of symptoms of temporomandibular disorders with warm compresses, premedication with nonsteroidal anti‐inflammatory drugs, and muscle relaxants may be considered. In the placement of multiple dental implants, one should con­ sider starting with the most posterior implant so as the patient gets tired, the clinician is not “locked” out.
Retained root tips in the implant location
A retained root tip can lead to infection and peri‐ implantitis (Al‐Faraje, 2011) or even implant failure (Figure 7.3). However, it is important to note that a study in baboons found that the unintentional placement of dental implants into retained root fragments did not cause any clinical problems or histological signs of inflam­ mation (Gray and Vernino, 2004). A retained root tip or fragments may also result in poor bone healing, resulting in a fibrous‐osseous defect. This will cause the dentist to abort the implant placement and have the implant placement procedures be delayed by 2–3 months.
Prevention
If a root tip is suspected at a dental implant site, a CT scan should be performed to help determine its location. In many cases an implant can be placed 2–4 months after the root tip has been removed. Sometimes it is pos­ sible to remove the tip and perform the osteotomy in the same procedure (Al‐Faraje, 2011, p. 40).

Management/treatment
The implant site must be monitored for inflammation if
the implant has been placed near a root tip. Factors to consider are as follows:
1 If the root tip has had a previous endodontic procedure or shows sign of a periradicular lesion, it should be extracted, grafted, and replaced.
2 If the root tip is small and does not have a lesion, keep the osteotomy away from it. If the root tip is directly in the way of the osteotomy, remove the root tip and place the implant at the same time (if possible).
3 If the root is too close to the nerve and it can lead to more complications, keep the root tip as it is.

Periodontal considerations

Poor bone quality

Leckholm and Zarb (Brånemark, 1985; (Misch, 2008, p. 647)) classified the jaws according to bone quality and quantity (Table 7.2).
According to the Misch bone density scale, there are five types of bone (Figure 7.4):
Studies show that the greatest implant failure is in areas of the softest bone, especially in the maxilla (Misch, 2008, p. 645). Studies have found that the high­ est risk factor for implant failure is in type 4 bone found in the maxilla (Hutton et al., 1995 and Goiato et al., 2014). Another study found that of the 10% of the 1054 implants placed in type 4 bone, 35% failed (Jaffin and Berman, 1991). However, another study found no difference in survival rates in marginal bone level bet­ ween implants positioned in the bone of various den­ sities after 1 year (Bergkvist et al., 2010).
Possible causes of poor quality of the bone are as follows:
1 Older patients with osteoporosis
2 Denture patients with maxillary resorption

Prevention

Avoid overheating the bone and allow the site to be irrigated. The use of internally irrigated drills can decrease heat.

Treatment

Use of surface‐treated implants was found in a sys­ tematic review to have lower failure rates than machined surface implants (Goiato et al., 2014). Additionally, there is the possibility of overengineering
the case with more implants in type 4 bone. For example, if a case was planned to restore to the maxil­ lary first molar, the clinician can consider placement of an additional implant in the second molar position.

Mucogingival defects around implants
Soft tissue grafting around implants is a controversial topic as depicted in Figure 7.5.
The etiology includes the following (Chu and Tarnow, 2013):
1 Poor implant spatial placement
2 Horizontal biologic width creation
3 Incorrect abutment contour
4 Excessive implant diameter
5 Thin biotype
Soft tissue defects are common in patients with a thin biotype. Figure 7.6 describes the characteristics of a thin biotype.


Prevention
Recognition that a patient has a thin biotype will help the clinician plan for a more gentle extraction that facil­ itates ridge preservation. Immediate implants are not recommended in these patients. Studies showed that sites with a thin gingival biotype had greater changes in facial gingival levels than sites with a thick gingival bio­ type (Kan et al., 2011; Evans and Chen, 2008).
The implant should be placed with the buccal surface 1.5 mm from the dental arch curvature (Chen and Buser, 2010, p. 151). If the implant is placed too far facially, soft tissue grafting cannot remedy the recession.

Treatment
A connective tissue graft with a coronally advanced flap may be used to correct recession on the buccal mucosa. Studies have shown clinically significant improvement, but after 6 months the coverage shrank to a mean of 66% (Burkhardt, Joss, and Lang, 2008). Another option is to remove the suprastructures and bury the implant by advancing the flap. Once healing has occurred, a small opening can be made, and the excess soft tissue can be moved to the buccal when replacing the abutment and crown (Chen and Buser, 2010, p. 150). To maintain the tissues in a healthy and stable position over the long term, the abutment‐crown contour should be flat or even undercontoured (Chu and Tarnow, 2013).
In cases where an immediate implant must be placed in thin biotype situations, a technique combining sub­ epithelial connective tissue graft and immediate implant placement and provisionalization is recommended to gain a more predictable soft tissue contour (Kan, Rungcharassaeng, and Lozada, 2005).

Patients with periodontitis
The topic is controversial. Figure 7.7 describes the opposing viewpoints on this topic.

Management

In patients with aggressive periodontitis, dental implants should be considered in the overall treatment plan (Klokkevold and Nagy, 2006, p. 700). However, there is a possibility of progressive bone loss around implants in regenerated bone in patients treated for aggressive periodontitis (Mendel and Flores‐de‐Jacoby, 2005). Hopeless teeth can be used to develop the site for implant placement. With patients who lack papilla and bone, an orthodontist can use forced eruption to regen­ erate the bone with up to 70% efficacy and soft tissues with up to 60% efficacy (Amato et al., 2012).
The surgeon must consider the following when assessing implant placement in patients with periodontal attachment loss (Rose and Minsk, 2004, p. 621):
1 Loss of attached gingiva
2 Deformities of the osseous structure
3 Poor contour of the soft and hard tissue
4 Change in embrasure space and papilla height

Poor patient compliance
Poor oral hygiene is a major risk factor for implant failure, and it should be addressed prior to dental implant treatment. The oral hygiene of the patient impacts the marginal bone stability around the implant (Quirynen and Teughels, 2003). One of the most important factors for long‐term success is good oral hygiene and mainte­ nance care. Plaque control by the patient with manual or powered toothbrushes as well as professional interven­ tion (oral hygiene instruction and mechanical debride­ ment) has been shown to be effective in reducing clinical signs of inflammation (Jepsen et al., 2015).

Management
Implants should not be an option for patients who appear uncooperative and are not compliant with oral hygiene instructions. If implants have already been placed and the patient is noncompliant, the risks and consequences must be explained to the patient and documented in the chart. Patients must understand and learn how to clean and care for their implants on a daily basis. It is the den­ tist’s responsibility to teach patients effective plaque con­ trol skills. If the skills have been mastered by the patient, but are not routinely practiced, then it is a compliance problem. Periodic maintenance visits are essential to remove plaque subgingivally. Three‐month cleaning recalls are recommended, especially for patients who have difficulties in performing the necessary plaque con­ trol skills (Armitage and Lundgren, 2008, p. 645).

Intraoperative complications

Damage to adjacent teeth
It is devastating when an implant hits an adjacent tooth. It not only compromises the tooth but also the implant. It may be caused by a lack of parallelism or incorrect positioning while inserting the implants (Lamas Pelayo et al., 2008). The adjacent tooth may be devitalized, need endodontic treatment, or even removal (Greenstein and Cavallaro, 2010, p. 405).

Prevention
Meticulous treatment planning with a surgical guide and cone‐beam CT images can help the clinician evaluate the space needed to place the implant. It is important to identify if the roots of adjacent teeth angulate into the space of the planned implant. Furthermore, it is helpful to take periapical radiographs with a guide pin (5 mm depth) during implant placement to ensure that the angulation is correct (Greenstein and Cavallaro, 2010, p. 406).

Treatment
Depending on the amount of damage to the adjacent tooth, the adjacent tooth may have to be adjusted (smoothed, restored), endodontically treated, or removed. The implant will have to be removed and repositioned.

Complications related to flapless surgery
The indications for flapless surgery are the following:
1 Sufficient keratinized mucosa.
2 No bone graft is needed.
3 Good quality and quantity of bone (allow assessment of morphology).
The surgeon must understand the risks and benefits of flapless surgery, depicted in Figure 7.8 (Brodala, 2009).
The flapless technique is “often more demanding than the conventional surgical approach (Brodala, 2009). Therefore, the use of flapless implant placement as a ‘routine’ procedure in daily practice is not recom­ mended.” Another study found the flapless technique had more marginal bone resorption compared with the flap technique (Maló and Nobre, 2008).

Prevention
It is recommended that the surgeon use a surgical guide and three‐dimensional radiographs to prevent unwanted clinical outcomes. The dentist should sound
the bone to verify that the bone in the surgical area is consistently of good quality with no osseous or soft tissue defects. There should be plenty of bone in all three dimensions of the implant because it is easy to cause a dehiscence or fenestration. A good guideline before flapless implant surgery is to have 2 mm of bone around the implant.

Management
There is a possibility that a dehiscence or fenestration may result while drilling. A flap should be raised to cover the defect with guided bone regeneration. The implant may need to be removed or buried when there is an esthetic compromise or when removal of the implant is indicated (Wilson, 2010, p. 353).

Implant hits a vessel
Arteries in danger of being damaged during implant placement are as follows (Al‐Faraje, 2011, p. 44):
1 Greater palatine
2 Nasopalatine/incisive
3 Lingual
4 Sublingual
5 Facial
6 Submental
Arterial damage at the floor of the mouth is usually a result of perforation of the lingual cortical plate.

Prevention
As previously mentioned, three‐dimensional radio­ graphs are essential in planning cases and preventing complications such as bleeding from a vessel following implant placement. The tip of periosteal elevators should always be placed on bone when reflecting flaps.


Management
Overall emergency management of bleeding from a damaged artery during surgery will depend on the skills and experience of the surgeon.
Bleeding from an artery can be managed in several ways (Al‐Faraje, 2011, p. 43):
1 Compression of the vessel
2 Crushing of adjacent bone into the artery to reduce the size of the arterial lumen
3 Electrocautery
4 Hemostatic agents, such as bone wax
It is essential to stop the ongoing procedure, place gauze at the bleeding site, and reassure the patient. It is important to have a trained assistant that won’t make comments to scare the patient. A local anesthetic (e.g., lidocaine) with epinephrine can be used temporarily to stop the bleeding.
Major bleeding from the floor of the mouth is a life‐ threatening situation with difficult access to the sublin­ gual space (Al‐Faraje, 2011, p. 47):
1 Call 911 at the first sign of swelling (possible respiratory compromise).
2 Apply pressure.
3 Explain the situation to the patient.
4 The vessel (if buried) should be ligated with the needle entering the tissue 6 mm away from the vessel on one side and exit 3 mm on the other side.
5 If the vessel can be isolated, close the lumen by plac­ing a knot using sutures.

Implant hits a nerve
Nerve damage may arise intraoperatively (e.g., during osteotomy preparation or soft tissue manipulation) or postoperatively (e.g., from swelling of adjacent tissues, compression of the nerve). Postoperative nerve damage does not require immediate intervention (Pi‐Anfruns, 2014). There are three types of nerve injuries (Greenstein and Cavallaro, 2010, p. 403):
• Neuropraxia:
◦ The least serious. Sensation returns about 1 month after compression of the nerve. The axon is intact.
• Axonotmesis:
◦ The nerve structure is not altered but there is ischemia, demyelination, and edema. Some sensation may return in 5–11 weeks with improvement within the next 10 months. Some axons may be damaged.
• Neurotmesis:
◦ The nerve is altered (loss of continuity) and no signal can travel through the nerve. A surgery is needed to repair the nerve.
The following are symptoms of nerve injury (Al‐ Faraje, 2011, p. 25):
1 Paresthesia—atypical sensation
2 Hypoesthesia—reduced sensation
3 Hyperesthesia—increased sensation
4 Dysesthesia—painful (unpleasant) sensation
5 Anesthesia—absolute loss of sensation
The inferior alveolar nerve is the most commonly injured nerve (64.4%), followed by the lingual nerve (28.8%) for all types of oral and maxillofacial surgery (Tay and Zuniga, 2007).

More symptoms
1 Pain
2 Biting the cheek or tongue
3 Drooling

Prevention
Preventing nerve damage requires proper planning by the surgeon (i.e., cone‐beam CT and knowledge of the anatomy at the implant site). A three‐dimensional radiograph should be taken when important anatom­ ical structures are in the area of the osteotomy. Drill guards can be used to prevent unwanted deep penetra­ tion in the osteotomy site (Greenstein and Cavallaro, 2010, p. 403).
Lingual nerve: The nerve can be as close as 5 mm apical to the distal lingual line angle of lower second and third molars. It is essential to place the elevator between the lin­ gual plate and the flap. Any damage to the lingual nerve can cause a loss of sensation to the anterior two‐thirds of the ipsilateral half of the tongue (Rateitschak and Wolf, 1995). Incisions should be in the retromolar pad area (occlusal surface), and lingual vertical incisions should not be made distal to the first molar.
Inferior alveolar nerve: The implant should be placed 2 mm above the inferior alveolar canal. The following are some signs of inferior alveolar canal involvement when deciding to extract a tooth and place an implant (Farnad, 2014):
1 Darkening and notching of the root
2 Deflected roots at the region of the canal
3 Narrowing of the root
4 Interruption of the canal outline
5 Diversion of the canal from its normal course
6 Narrowing of the canal outline
Mental nerve: Clinicians should be mindful of the ante­ rior loop of the mental nerve. It can be 3 mm anterior to the mental foramen (Al‐Faraje, 2011, p. 27). The clini­ cian should avoid incisions on the buccal aspect of the lower bicuspid area.
Anterior palatine/nasopalatine nerves: The chance for paresthesia is rare; however, the clinician should avoid incisions in the incisive papilla area and protect the flap with a periosteal elevator when doing surgery.

Management
The following tests need to be done by the dentist after a nerve injury has occurred:
1 Two‐point discrimination.
2 Static light touch.
3 Brush stroke.
4 Vibrational test.
5 A map of the affected site must be drawn.
Patients should get a second opinion within the first 3 weeks of nerve injury. If a patient is numb for greater than 16 weeks, the nerve was likely disrupted and needs to be repaired (Greenstein and Cavallaro, 2010, p. 403) Appropriate scans will be needed and the implant(s) will have to be removed. The patient needs to be care­ fully monitored following removal of the implants (Greenwood and Corbett, 2012). If the surgeon decides to let the implant remain without placing a crown, a traumatic neuroma may form, which can be painful (Greenstein and Cavallaro, 2010, p. 403).

Fractured jaw
The following are symptoms of mandibular fracture after implant placement (Al‐Faraje, 2011, p. 81):
1 Fracture when there has not been trauma
2 Occlusal change
3 Swelling
4 Pain
Some studies found that mandibular fractures occurred 0.05% of the time in mandibles with a height of 10 mm or less, as measured at the mandibular sym­ physis. Other reasons fractures may occur 1 year or more after implant placement include peri‐implantitis and trauma (Soehardi et al., 2011).

Prevention
A cone‐beam scan should be done on patients with atrophic mandibles to be able to determine the quality and quantity of bone at the site. After preparing the osteotomy, a few millimeters of cortical bone should remain on both the lingual and the labial sites (Chrcanovic and Custódio, 2009).
Bone grafting procedures (e.g., block graft or guided bone regeneration) may be done prior to the insertion of the implants to increase the bone strength and volume. Shorter abutments can minimize the stress on the implants, and the surgeon should refrain from excessive tightening of the implant (Al‐Faraje, 2011, p. 81). Wide‐diameter implants should be avoided in an alveolar ridge with significant horizontal resorption.

Treatment
There are a number of considerations that the surgeon must evaluate in deciding to whether remove or retain the implant (Al‐Faraje, 2011, p. 81):
1 The stability of the implant
2 The importance of the implant to the overall treatment plan
3 Presence or absence of infection
4 Mobility of the fractured bone (Greenstein and Cavallaro, 2010, p. 412)
The following are treatment options for fractured mandibles (Soehardi et al., 2011):
1 Closed reduction (immobilization)
2 Rigid fixation using osteosynthesis plates
3 Bone grafts with fixation
4 Occlusal restoration
Complications were found in 48% of the patients who had implant‐associated fractures. These included non­ union, osteomyelitis, screw loosening, plate fracture, and dehiscences with subsequent infections (Soehardi et al., 2011). It is difficult to treat fractures because of the diminished blood supply to the site and the depressed vitality of the bone (Chrcanovic and Custódio, 2009).

These patients need to be placed on a soft diet and trained to limit jaw movements (Al‐Faraje, 2011, p. 81).

Implant fracture
Implant fracture may occur during implant surgery or postoperatively. Studies have shown that the incidence of implant fractures in an implant‐supported fixed partial denture after 5 years is 0.4% (Pjetursson et al., 2004). The incidence of implant fracture in a combined tooth/implant‐supported fixed partial denture is 0.9% after 5 years (Lang et al., 2004a and 2004b).
Causes of implant fracture postoperatively include the following (Gealh et al., 2011):
1 Bone loss around an implant can lead to fracture of the implant (below the abutment screw).
2 Design of the material: the crown’s infrastructure made of nonprecious metal alloy.
3 Trauma (e.g., more with ceramic implants) (Spiekerman, 1995).
4 Nonpassive fit of the prosthetic structure—misfit or distortion.
5 Physiological or biomechanical overload (e.g., bruxism, clenching, or cantilevers).
6 Repeated gold screw or abutment loosening (Eckert and Salinas, 2010, p. 102).
Causes of implant fracture during surgery include the following:
1 Implant design: Small‐diameter internal hex implants may not be able to withstand the torque applied when placed in dense bone (Al‐Faraje, 2011, p. 83).
2 Dense bone was not tapped before placement of the implant.
Implant fracture is relatively uncommon. Studies have found 0.2% of 4045 implants had fractures in 5 years of service (Balshi, 1996). All patients with a frac­ tured implant had parafunctional habits. The partially edentulous jaw encounters implant fractures more fre­ quently than edentulous patients (Eckert and Salinas, 2010, p. 108).

Prevention
Patients with parafunctional habits should be given an occlusal guard to be worn at night. The surgeon may recommend a greater number and a wider diameter of implants to distribute the force to prevent implant frac­ ture. It is also important for the surgeon to adjust lateral forces when screw loosening is encountered (Eckert and Salinas, 2010, p. 104).

Treatment
In most cases both fragments of a fractured implant will have to be removed with a trephine drill. However, if there is still adequate threads available, reversal tools can be used. If the implant is not to be replaced, the apical fragment may remain to prevent further bone loss (Spiekerman, 1995). The supraosseous portion may be ground down so it is flush with the osseous level. However, the fractured implant may become infected, and the patient must be monitored.

Surgical trauma

Overheating the bone can cause bone resorption and physiological damage to the bone.

Prevention
1 Studies have shown that the maximum drill speed of 2000 rpm with copious sterile saline irrigation should be used to prevent overheating. The threshold for bone damage is 47°C for 1 min (Eriksson and Albrektsson, 1984).
2 Sharp drills should always be utilized. In type 1 bone, the surgeon should use a drill 1–3 times, and about 10 times in type 2 bone. The surgeon can use the drill about 40 times in type 3 bone and 100 or more times with type 4 bone (Al‐Faraje, 2011, p. 49).
3 The surgeon should use an in‐and‐out motion with the handpiece when preparing the osteotomy site to allow the irrigation to reach the bur’s cutting edges.
Signs and symptoms (Piatelli et al., 1998)
1 No regeneration of bone around the implant
2 Bone sequestra
3 Necrotic bone and bacteria around the implant
4 Inflammatory response in the area between the implant and the bone
5 No organization of the peri‐implant bone clot
6 Presence of mature and compact bone around the implant
Treatment
The implant and necrotic bone needs to be removed. The patient may need antibiotics and pain medication if an infection is present. A new implant may be placed with a bone graft in 3–4 months (Al‐Faraje, 2011, p. 50).

Compression necrosis

Compression necrosis is the overcompression of the adjacent bone during implant placement. An undersizedosteotomy can cause compression necrosis. Areas of dense bone have a higher risk for this complication. Compression necrosis occurs within the first month, and the histology will show inflamed granulation tissue and nonviable bone sequestra with bacterial coloniza­ tion (Bashutski, D’Silva, and Wang, 2009).
An initial torque of 20 N cm is ideal to achieve osseo­ integration. However, a higher torque of 30–45 N cm (bone necrosis may occur at higher torques in type 1 or 2 bone) is recommended for immediate loaded implants because of the stress they encounter from the provi­ sional prosthesis (Al‐Faraje, 2011, p. 85).

Prevention

1 Use drill in the correct order.
2 Use tapping drills in dense bone.
3 Before the implant is just short of its placement, a hand ratchet is recommended to have better control over the level of torque.

Broken instruments

Although it is rare for an instrument to break, it is possible and is a serious complication. Instruments are constantly sharpened and sterilized, and this can lead to fractures.

Treatment and management

If small fragments cannot be located, radiographs are necessary. There are special magnetic instruments that can attract the fragment and allow for retrieval. If there is a chance that the fragment has been aspirated, a chest radiograph is necessary. If the fragment was swallowed, periodic monitoring of feces is vital to make sure it passes through the digestive system.

Postoperative complications

Peri‐implant mucositis
Peri‐implant mucositis is the presence of inflammation in the soft tissue surrounding a dental implant without signs of any loss of supporting bone (Figure 7.9). This is a treatable and reversible plaque‐induced inflammatory condition. A systematic review found that peri‐implant mucositis arises in approximately 63.4% of the subjects and in 30.7% of the implants. Peri‐implantitis was discov­ ered in 18.8% of subjects and in 9.6% of implant sites. The incidence of peri‐implant disease is higher in smokers (36.3%) compared to nonsmokers (Atieh et al., 2013). Maintenance therapy reduces the rate of peri‐implant disease (Atieh et al., 2013). In a 5‐year systematic study, 6.3% of the implants had bone loss exceeding 2 mm over the 5‐year observation period, and peri‐implantitis and soft tissue complications occurred adjacent to 9.7% of the implant‐supported single crowns (Jung et al., 2008).

Clinical signs
1 Inflammation
2 Bleeding on probing (BOP)
3 Suppuration
4 Pockets that are greater than 4 mm

Possible etiology
1 Bacteria: The bacteria associated with gingivitis resemble the bacteria associated with mucositis (Lang, Wilson, and Corbet, 2000; Pontoriero et al., 1994).
2 The sites that facilitate bacterial colonization and retention are the implant‐abutment junction and the implant surfaces (Fletcher, 2014). Furthermore, switching abutments between companies result in greater risk for poor fit.
3 Excess or residual cement (Wilson, 2009).
4 Lack of keratinized gingiva (Block et al., 1996).
A consensus report (Lindhe and Meyle, 2008) found the following risk indicators:
1 Poor oral hygiene
2 A history of periodontitis
3 Diabetes
4 Smoking

Prevention
Oral hygiene by the professional and patient is required to minimize the bacterial load. The sooner peri‐implant mucositis is diagnosed, the sooner treatment can be ren­ dered. Peri‐implant mucositis can be treated nonsurgi­ cally. Because of the problem of decontamination of the roughened, threaded surfaces of exposed implants, peri‐ implantitis is more difficult to treat (Khammissa et al., 2012). Maintenance care should be conducted routinely based on the patient’s susceptibility.

Management
Oral hygiene must be reviewed with the patient. Figure 7.10 describes the cumulative interceptive sup­ portive therapy protocol for treating peri‐implant muco­ sitis and peri‐implantitis.
The main goals are as follows:
1 Disrupt the colonization of the plaque biofilm.
2 Dilute the bacterial load.
3 Detoxify the implant surface by mechanical and che­ motherapeutic means (e.g., curettes, ultrasonics, abrasives, lasers, saline, citric acid, and chlorhexidine) (Fletcher, 2014).
Studies have found mechanical nonsurgical therapy and antimicrobial mouth rinses effective in the treatment of peri‐implant mucositis lesions. However, in peri‐implantitis lesions nonsurgical therapy was inef­ fective (Renvert, Roos‐Jansåker, and Claffey, 2008).

Mechanical debridement (protocol A)
1 Curette: Must be soft because metal curettes can severely damage the implant surface. Carbon fiber curettes are sturdy enough to remove calculus yet they do not harm the implant surface (Eckert and Salinas, 2010, p. 104).
2 Ultrasonic scalers: Can cause a rough surface that attracts plaque (Rapley et al., 1990); however, other studies found positive results for ultrasonic scalers with a nonmetal tip on polished and sand blasted, large grit, acid‐etched surface (Louropoulou, Slot, and Van der Weijden, 2014).
3 Lasers: Some studies find them advantageous over con­ ventional treatment and some studies do not (Kreisler et al., 2003). A review article found no significant difference (in BOP, probing depth reduction of clinical attachment levels, or bone fill) between saline‐soaked pellets at 12 and 24 months of follow‐up and the use of the Er:YAG laser (Valderrama and Wilson, 2013).
4 Air abrasives: Studies have shown it to be a viable treatment option in vitro for implant surface cleaning in peri‐implantitis treatment (Tastepe et al., 2012).
 5 Titanium brush: This brush is composed of a stainless steel shaft with titanium bristles that is inserted into an implant machine handpiece. It is recommended to protect the inner connection of the implant before debridement with a cover screw or healing abutment. It is for single patient use only. Studies have found it to be gentler to the implant surface and more effec­ tive in plaque removing capacity than steel curettes (John, Becker, and Schwarz, 2014). Randomized controlled studies are needed to further evaluate the efficacy of titanium brushes.

Chemotherapeutic (antiseptic protocol B) (Fletcher, 2014)
1 Chlorhexidine: It has high substantivity but it is not effective intracrevicularly. Studies have found no difference between patients receiving chlorhexi­ dine irrigation and another group of patients receiving no treatment for 8 weeks (Lavigne et al., 1994). Another study found the supplement of chlorhexidine (irrigation and gel) to mechanical debridement did not improve the effects as com­ pared to mechanical debridement alone (Porras et al., 2002).
2 0.25% sodium hypochlorite irrigation: Irrigation with 0.25% NaOCl results in an 80‐fold decrease in bacte­ rial endotoxin compared to water and reduces gingival inflammation and supragingival biofilm
accumulation (De Nardo et al., 2012). This solution does not corrode titanium.
3 Citric acid: A review article found that citric acid is effective at decreasing the amount of lipopolysac­ charide present on machined surface and hydroxy­ apatite‐coated implants, but not on titanium plasma‐sprayed implants (Valderrama and Wilson, 2013). Another study found citric acid conditioning of a peri‐implantitis‐affected surface improves nanohydroxyapatite‐blended clot adhesion to the titanium implant surfaces (Gamal, Abdel‐Ghaffar, and Iacono, 2013). More randomly controlled studies are needed to evaluate the clinical signifi­ cance of citric acid.

Antibiotic protocol C
1 Minocycline microspheres are a bioabsorbable locally applied antibiotic. It has been found to improve bleeding scores and mean probing depth (from 5.0 to 4.1 mm) around peri‐implant infections (Renvert et al., 2004 and Salvi et al., 2007).
2 Systemic antibiotics: Systemic administration of anti­ biotics has been shown to decrease the subgingival bacterial load and target the anaerobic segment in patients with peri‐implantitis when used in conjunction with mechanical debridement (Mombelli and Lang, 1992; Renvert, Roos‐Jansåker, and Claffey, 2008). However, systemic antibiotics do not remove biofilms, and it is unlikely that they are sufficient interventions for peri‐implant disease.
If the patient has 4 mm pocket with BOP or 5 mm pockets with or without BOP, sodium hypochlorite irrigation in conjunction with debridement is recom­ mended. If there is no resolution after 3 months, the treatment is repeated and minocycline microspheres are used and the restoration is removed and cleansed (remove plaque, detoxify the platform, and screw opening) (Lang et al., 2004a, 2004b; Fletcher, 2014). The patient is encouraged to use antiseptic mouthwash and triclosan toothpaste at home. Studies have shown reductions in plaque index, gingival index, and bleeding index in the peri‐implant gingival tissues (Ciancio et al., 1995; Sreenivasan et al., 2011), although long‐term studies on the treatment of peri‐implant dis­ ease are needed.

Regenerative or resective therapy (protocol D)

Once the infection has been controlled and treatment modalities A, B, and C have been tried, surgery can be considered. Regenerative therapy or resective therapy may be done based on the morphologic characteristics and size of the defect (Lang and Tonetti, 2010, p. 129).

- Regenerative
1 Biologic mediators (e.g., enamel matrix derivative and platelet‐derived growth factor): Their effects are debatable, but studies have shown that grown factors have positive effects on implant osseointegration (Qu et al., 2011; Froum, Froum, and Rosen, 2012).
2 The defect configuration may have a big impact on the ability to regenerate the defect. Circumferential intrabony defects seem to be favorable in conjunction with a natural bone mineral and a collagen mem­ brane. Defects with a buccal dehiscence (e.g., circum­ ferential or semicircumferential) are not favorable (Schwartz et al., 2010).

- Resective therapy It is important to inform the patient that resective therapy, especially in the esthetic area, may lead to a poor esthetic outcome. It has been shown that the percentage of implants that turned out to be healthy subsequent to treatment (pocket reduction and bone recontouring) was higher for those with minimal initial bone loss (2–4 mm bone loss as evaluated during surgery) compared with the implants with a bone loss of  ≥ 5 mm (74% vs. 40%) (Serino and Turri, 2011).


- Combined resective and regenerative approach Implantoplasty, the removal of the suprabony implant threads affected by peri‐implantitis, has been shown to be successful in combination with deproteinized bovine bone mineral and a collagen membrane. Regenerative and resective treatment of peri‐implant defects produced positive outcomes in terms of radiographic defect bone fill and probing depth reduction after 12 months (Matarasso et al., 2014).
Another study found that resective therapy with implantoplasty had a positive influence on the survival of oral implants involved with inflammatory processes (Romeo et al., 2005).

Peri‐implantitis

Peri‐implantitis is a destructive inflammatory reaction affecting the soft and hard tissues, and it can result from peri‐implant mucositis. Bleeding, suppuration, and loss of osseointegration of the coronal part of the implant, by increased probing depth, are some features of peri‐ implantitis. Treatment is not predictable for peri‐ implantitis (Khammissa et al., 2012). The risk factors for periodontitis and peri‐implantitis are similar. The pro­ gression from mucositis to peri‐implantitis follows a very similar path of events as the progression of gingivitis to periodontitis. However, peri‐implantitis has episodes of rapid progression and can be more pronounced than in cases of chronic periodontitis (Heitz‐Mayfield and Lang, 2010). In most cases peri‐implantitis‐associated bone loss is characterized by a nonlinear progression, with the rate of loss increasing over time (Fransson et al., 2010). Some of the differences between peri‐implantitis and periodon­ titis are described in Table 7.3 (Figure 7.11). 

Risk factors

1 Genetics:
◦ Gene polymorphisms: It has been shown that there is a potential link between IL‐1 genotype and peri‐ implantitis (Dereka et al., 2012).
2 Poor oral hygiene:
◦ Studies show that bacteria can be transmitted from the periodontal pocket to the peri‐implant region (Sumida et al., 2002). Periodontitis‐enhancing factors such as poor oral hygiene and smoking also increase the risk for peri‐implantitis (Quirynen, De Soete, and van Steenberghe, 2002).
3 History of periodontal disease:
◦ Compared with periodontally healthy patients, subjects with a history of chronic periodontitis may
exhibit significantly greater peri‐implant marginal bone loss, long‐term increases in probing depths, and incidence of peri‐implantitis (Karoussis, Kotsovilis, and Fourmousis, 2007; Heitz‐Mayfield and Lang, 2010). Peri‐implantitis was a more frequent finding in patients with a history of periodontal disease and excess cement (Linkevicius et al., 2012).
4 Smoking:
◦ Smokers exhibit greater probing depth and pus around implants compared to nonsmokers (Fransson, Wennström, and Berglundh, 2008).
5 Diabetes:
◦ There is evidence that diabetes is associated with peri‐implantitis (Daubert et al., 2015). Diabetes is con­ sidered a risk indicator for peri‐implantitis (Lindhe and Meyle, 2008).

Etiology
1 Bacteria: Peri‐implant mucositis can develop into peri‐implantitis if it is not treated early. Bacteria can be a factor in the following situations:
i) Contamination of the implant before placement (Al‐Faraje, 2011, p. 108).
ii) Preexisting bacteria at the time of surgery (e.g., bacteria from a previous infection) causing a retro­ grade infection (Quirynen et al., 2005).
iii) Fit of restoration: The gap should be minimal bet­ ween the implant and the prosthesis.
2 Excess cement: Excess dental cement has been associ­ ated with signs of peri‐implant disease. Studies have found that signs of inflammation were absent in 74% of implants after the removal of excess cement (Wilson, 2009).
3 Implant malpositioning: The deeper the position of the implant margin, the greater the amount of cement was found. Cement excess should not be evaluated using dental radiographs (i.e., it is not a reliable method) (Linkevicius et al., 2013).
4 Local factors: Overcontouring the restoration can make plaque control difficult and lead to accumulation of plaque.
Figure 7.12 describes the advantages and disadvan­ tages of cement‐retained restorations. 

Classification

Table 7.4 describes another classification system of peri‐implantitis based on the severity of the disease. A combination of probing depth, extent of radiographic
bone loss around the implant, and BOP and/or suppuration is used to classify the severity of peri‐ implantitis (Froum and Rosen, 2012).

Management
Figure 7.10 describes the protocol for management of peri‐implantitis. Patients need to be instructed on proper oral hygiene techniques similar to methods used on natural dentition. It is imperative that the excess cement be removed and the implant surface detoxified. If regeneration is deemed necessary, it can be done with a soft tissue graft if there is a mucogin­ gival defect. Some studies have found that in most cases, nonsurgical therapy achieved similar results to those of more complex therapies (Byrne, 2012) (Figure 7.13).

Postoperative bleeding
Please see postoperative bleeding in the periodontal chapter.

Bone growth over the cover screw at second‐stage surgery
This complication may occur for several reasons (Al‐Faraje, 2011, p. 106):
1 The implant is placed below the crestal bone.
2 Second‐stage implant surgery is done after 8 months or longer.
It is imperative that the surgeon use extreme caution when removing bone to prevent damage to the platform of the implant.

Treatment/management
Always make sure the top of the implant is protected by placing the cover screw on top of the fixture. A bone mill or small chisels may be used to remove the
bony overgrowth (Al‐Faraje, 2011, p. 106). A radio­ graph should be taken to make sure there is no space between the healing abutment and the fixture/ platform.

Loss of a posterior implant in an all‐on‐four prosthesis
There are a number of risk factors that may cause a pos­ terior implant to fail. According to Parel and Phillips (2011), these include the following:
1 Opposing natural dentition: Both existing opposing natural mandibular dentition (80%) and poor bone density (85%) presented the highest percentages of all failure scenarios.
2 Poor bone density (e.g., the posterior maxilla).
3 Male patient: Men are three times more likely to experience a primary implant failure.
4 Bruxism: About half of the failures in this study had a bruxing component. However, in none of these individuals was bruxing the only contributing factor.
5 Smoking: Patient compliance with smoking cessation can have a potentially significant role in the incidence of primary failures.
6 Bone volume: The evaluation of bone volume and bone density with a CAT scan was identified as impor­ tant in planning maxillary implant therapy.
7 Cantilevers: Implants placed in the premolar–molar cantilever region are subjected to higher occlusal loads, even when the distal extension cantilever length was reduced in the provisional prosthesis.

Prevention
If the patient has one or more risk factors listed ear­ lier, additional implants or delayed loading should be used. Because implants are more likely to fail in the maxillary arch, one or two additional implants can be placed. A pterygoid implant can also be placed to engage the pterygoid process without bone augmen­ tation (Parel and Phillips, 2011). It is also important for the surgeon to limit the amount of cantilevers, stagger the implants (e.g., implants should not be placed in a straight line), use a wider diameter implant in molar sites, and see the patient more frequently for postoperative checks (Goodacre and Kattadiyil, 2010, p. 183). Patients who have a history of bruxism should use an occlusal guard.

Treatment/management
The failed implant should be removed and a replacement implant placed after adequate bony healing, approxi­ mately 6 months (Wang et al., 2015). The replacement implant should not have any load placed on it until the surgeon deems that it is osseointegrated.

Implant mobility
Implant failure is defined as the state where the implant is no longer integrated after placement. Failure may occur early (i.e., before osseointegration and usually during the first year) or late (i.e., during and after the restorative treatment) (Rosenberg et al., 2010, p. 111). Primary stability at the time of implant placement is necessary to ensure successful osseointe­ gration. One meta‐analysis found the failure rate at 7.7% over a 5‐year period (bone graft excluded) (Esposito et al., 1998). Another study (Berglundh, Persson, and Klinge, 2002) found implant failure of 2–3% when the implant was in function and a 2–3% failure rate of implants supporting fixed reconstruc­ tions. Patients with overdentures had a 5% failure rate during a 5‐year period. No evident differences in implant survival were found between the different implant systems (Eckert et al., 2005).

Possible causes of implant mobility
1 Infection
2 Host factors (smoking, autoimmune disorders)
3 Occlusion and loading
4 Poor bone quality
5 Poor prosthetic design (Rosenberg et al., 2010, p. 111)
6 Inability of the surgeon to achieve primary stability
7 Trauma to the tissue (pressure necrosis and overheat­ ing of the bone) (Rosenberg et al., 2010, p. 112)
8 Prior history of periodontitis
Table 7.5 describes the characteristics associated with an infectious or traumatic cause of mobility.

Prevention
The cause of the failure must be diagnosed and addressed as soon as possible to make every effort to reverse the complication (Rosenberg et al., 2010, p. 111). It is imperative that the surgeon plan the case thoroughly (e.g., cone‐beam imaging, mounted study casts with diagnostic wax‐ups, and review of systemic and local risk factors).

Treatment
When the implant is found to be mobile, it needs to be removed. If there is adequate bone and minimal infection, an immediate implant may be an option (after thorough degranulation). A wider diameter implant with possible bone grafting may be necessary and antibiotics prescribed (Rosenberg et al., 2010, p. 116). Studies have (Machtei et al., 2008) found a survival rate of 83.5% for implants placed in previously failed sites. This is a much lower survival rate compared to implants placed in pristine sites.

Dental changes of adjacent natural teeth relative to the implant crown
When teeth and implants coexist and subtle adult cra­ niofacial growth occurs, complications may occur. Throughout adulthood there is tooth drifting and change in arch length. The continuous eruption of the adjacent anterior teeth can cause great risk of a less favorable esthetic and/or functional implant outcome. The placement of an implant in patients with a normal facial profile should be postponed until growth has concluded. For patients with a long or short face type, further growth, particularly the continuous eruption of adjacent teeth, creates a crucial risk even after the age of 20 years (Heij et al., 2006). When changes in tooth posi­ tion relative to implant restorations secondary to long‐ term adult growth happens, they can cause complications that are difficult to treat (Daftary et al., 2013).