Introduction
The alteration in alveolar bone dimension (vertical and horizontal) following tooth
loss in the posterior dental arches makes it challenging to accommodate dental implants.
In such situations, clinicians choose to replace the lost teeth using short implants,
tilted implants, zygomatic implants, or conventional implants with sinus augmentation.
Sinus augmentation had a better prognosis compared with all other available procedures
to rehabilitate severely deficient alveolar bones.[1] The sinus augmentation is a well-documented bone augmentation procedure to gain
the vertical height. Studies have proven a high success rate for implants in combination
with sinus elevation. However, with an increasing number of clinicians performing
them and an increasing number of cases, surgical (intraoperative) and postsurgical
complications have also increased. Sinus elevation is considered a relatively invasive
procedure with a low incidence of complications, intraoperatively and postsurgically.
Most complications reported in literature can be avoided by careful and precise presurgical
evaluation of the sinus. The most common type of complication reported with sinus
floor elevation is the perforation of the Schneiderian membrane.[2]
Case selection is the first step toward success for any surgical procedure. The sinus
augmentation is generally indicated in residual ridges with inadequate width to place
implants conventionally or in the atrophic maxilla or when there is a low quality
of available bone. The absolute and relative sinus contraindications are listed in
[Table 1].[3] Uncontrolled systemic conditions, smoking, and preoperative sinus pathologies, if
not appropriately managed, can lead to acute complications postoperatively.[4] A thorough preoperative evaluation of the sinus with adequate knowledge about the
sinus anatomy and its common variations is needed to avoid most complications at any
stage of the procedure. Before the procedure, most of the complications mentioned
above can be avoided by careful evaluation by cone beam computed tomography (CBCT)
and ENT clearance.
Table 1
Contraindications for maxillary sinus augmentation[3]
|
Absolute contraindications
|
Relative contraindications
|
|
1 Posttraumatic/surgical/radiotherapy scarring on the nasal-sinus walls and/or mucosa
lining
|
1 Stenosis of drainage pathways in sinus (septal deviation, presence of Haller cell,
paradox curve of middle turbinate bone, oroantral fistula, etc.)
|
|
2 Recurring or chronic sinusitis with or without polyps
|
2 Acute viral or bacterial or mycotic or allergic rhinosinusitis (functional endoscopy
indicated)
|
|
3 Intolerance to acetylsalicylic acid
|
3 Nonobstructive benign tumors, mucosal cysts, cholesterinic granuloma, antrochoanal
polyp (functional endoscopy required)
|
|
4 Immunological deficiencies
|
|
|
5 Wegener's granulomatosis, sarcoidosis
|
|
|
6 Locally aggressive benign tumors (myxoma, inverted papilloma)
|
|
|
7 Nasal-sinus malignant tumors of the maxillary sinus
|
|
Etiology of Sinus Complications
The etiology of complications is listed in [Table 2]. Apart from the previously mentioned sinus-related contraindications, the contraindications
to implant surgery or periodontal or conventional surgeries will become apparent contraindications
for sinus surgery, for example, systemic conditions like uncontrolled diabetes or
any other immunocompromised conditions. Uncontrolled diabetes has been linked with
increased susceptibility to complications or infections because of the reduced host
response, lowered chemotaxis, and phagocytosis of early responding polymorphonuclear
leukocytes.[5]
[6] During sinus elevation, uncontrolled diabetes may contribute to decreasing graft
turnover, postoperative infection, and cause the incision line opening. Although no
studies have assessed the influence of diabetic control on sinus augmentation, researches
have shown no significant influence on implant outcomes.[7] However, due to the proximity to the maxillary sinus, which can be predisposed to
congestion and irritation, infection in the sinus may be more notable than after routine
implant placement.
Table 2
Classification of complications based on etiology[13]
|
Pre-existing systemic diseases and medications related
|
Anatomy and surgical procedure-related
|
Sinus pathology related
|
Infection-related
|
Prosthetic related
|
|
Uncontrolled diabetes
|
Perforation of membrane
|
Pseudocysts
|
Infection
|
Postoperative temporary prosthesis
|
|
Osteoporosis
|
Sinus septa
|
Retention cysts
|
Swelling/hematoma
|
Implant length and diameter
|
|
Bisphosphonate medication
|
Onlay graft and residual bone height
|
Mucoceles
|
Incision line opening/ wound dehiscence
|
Insufficient number of implants
|
|
Immunocompromised patients
|
Bleeding
|
|
Bone sequestrum/fragments
|
Increased occlusal table
|
|
Cigarette smoking
|
Displacement of implants into sinus
|
|
Sinusitis
|
Nonsplinted implants
|
|
Obliteration of sinus cavity
|
|
Oroantral fistula
|
|
Another condition that should be addressed and managed with attention is osteoporosis
and its associated medicine, that is, bisphosphonate. It was found that patients under
bisphosphonate therapy experienced 40 to 46% implant loss following their induction
into grafted sinuses.[8] To allow for proper healing of the graft following sinus augmentation, prolonging
the healing time before implant placement has been suggested. In the maxilla, 8 months
should be given for graft maturation, whereas in the mandible, at least 6 months is
advised.[9]
Patients with immunocompromised states are often contraindicated for sinus augmentation
because of the impaired wound healing, prospect of infection, and altered bone metabolism.
Generally, the amount of literature contraindicating sinus augmentation and implant
therapy due to systemic diseases is low.
Cigarette smoking has shown to significantly increase the rate of complications in
dental therapy.[10]
[11] Although the definite mechanism is not clearly understood, the impaired immune response
and vascular changes observed among smokers have been thought to play a significant
role. It was observed that smoking increases the implant failure by ~7.0 to 17.1%,
and it has also been found that smoking significantly increases the failure rate (12.7%)
compared with nonsmokers[12] (4.8%). Smokers also have a significantly higher prevalence of acute infections
at 14.2% than in nonsmokers (2.2%).[13]
The most common complications associated with antral lift are perforation or tear
(60%), infection (21%), bleeding (9%), dislocation of the implant into the sinus,
and rarely benign paroxysmal position vertigo (BPPV).[2] The first mentioned complications are generally encountered intraoperatively, while
the latter two complications are commonly seen postoperatively. Intra and postoperative
complications are listed in [Table 3].[14]
Table 3
Classification of complications based on time of occurance[14]
|
Intraoperative
|
Acute postoperative
|
Chronic postoperative
|
|
Tearing of membrane/ nasal Penetration
|
Pain, swelling, edema, Infection
|
Infection
|
|
Bleeding
|
Acute Sinusitis
|
Chronic sinusitis
|
|
Obstruction of ostium
|
Hemosinus
|
Implant periapical lesion
|
|
Insufficient primary stability
|
Oroantral fistula
|
Postoperative maxillary cyst
|
|
Fenestration/dehiscence
|
Benign paroxysmal positional vertigo
|
|
|
Perforation of alveolar bone
|
Temporary or permanent palatal numbness
|
|
Intraoperative Complications
Membrane Perforation
It is the most frequent type of complication concerning maxillary sinus elevation.
Various factors accentuate the chances of membrane perforation. The tear of the membrane
can occur at any stage of sinus elevation, such as during the lateral wall scoring
or elevation of bony walls or when releasing the membrane.[15] Perforation may also occur when there is a pre-existing perforation, existing, or
previous pathology. Such factors can be eliminated with proper history taking and
systematic evaluation of radiographs. The prognosis of the treatment generally depends
on the amount of membrane tear.[16] It is observed that when the membrane tear is less than 5 mm, the survival rate
of implants is around 97.14%, 5 to 10 mm of tear has a 91.89% of survival rate and
when it is 10 mm or more, the survival rate is around 74.14%.[17] The decision making of implant placement is generally up to the clinician's experience,
but the literature suggests ~90.81% of survival rate when a contemporary approach
is used.[16] So, a careful and wise decision has to be made when perforation occurs. A staged
approach is a safe method as it gives time for the membrane to heal. Classification
of membrane perforations is given in [Table 4].[18]
[19]
Table 4
Classification of membrane perforation[18]
[19]
|
Type of perforation
|
Extent of perforation
|
|
Class I perforation
|
Perforation occurring at any point along the most apical wall of the prepared sinus
window
|
|
Class II perforation
|
Perforations occurring along with the lateral or crestal aspects of the prepared sinus
window
|
|
Class III perforation
|
Perforations occurring at any location within the body of the prepared sinus window
|
Management
It is a well-established fact that membrane perforation is commonly encountered during
direct sinus lift procedures than indirect sinus lift. The access to the membrane
is generally substantial with direct sinus lift than in indirect where it is minimal.
Hence, it becomes evident that management with different approaches is different.
In either of the cases, verifying membrane integrity plays an important role. Endoscopic
examination of the sinus is the gold standard, while there are few other procedures
such as Valsalva maneuver, microscopic examination, and sterile saline washings. It
is perceived that implants' success rate is generally high in nonperforated areas
(100%) to perforated areas (69.56%).[16] By using any of the techniques mentioned earlier, the amount of perforation has
to be determined. The amount of perforation directly correlates with the prognosis
of implants to be placed. Small perforations (1–2 mm) generally do not need any attention;
they heal by themselves. However, when perforations are large, surgery is deemed an
absolute contraindication and should plan a staged approach.[20] Nevertheless, some authors suggest a contemporary approach even with perforation
with higher failure rates. Large membrane perforations have to be managed using a
lateral approach only. The basic principle of treating perforations is to isolate
the membrane from the surrounding tissues or graft particles. When perforations are
below 5 mm, the membrane can be sutured, or a resorbable membrane can be placed between
the membrane and the bone graft. If the perforation is between 5 and 10 mm, the resorbable
membrane is used, and a small part of the lamellar bone from the sinus window is utilized
to reinforce the reconstruction before placing the grafting material. Large perforations
or perforations >10 mm are managed in either of three ways: (1) Covered with the lamellar
bone of the sinus window, (2) covered with a pedicled buccal fat pad, (3) by the placement
of a bone block graft harvested from intraoral sites. Platelet-rich fibrin was also
used successfully instead of collagen membrane in treating membrane tears because
of its cost-effectiveness and ease of manipulation.[16] Nevertheless, when the implant depth inside the maxillary sinus is higher (> 2 mm),
the sinus membrane does not repair immediately, and debris concentrates on the exposed
surfaces of the implants that were not covered by native bone inside the sinus cavity,
which could lead to sinusitis.[21] This might lead to bone graft failure, which might eventually lead to the implant's
failure. Membrane perforations generally do not lead to chronic postoperative complications.
Bleeding
The infraorbital and posterior superior alveolar artery runs in and out of the maxillary
sinus lateral wall, forming an extraosseous and intraosseous anastomosis. For the
intraosseous branch, it has been stated that straight type branching is present in
75% of cases, and U-shaped branching is seen in ~25% of cases. It is to be perceived
that only a part of intraosseous branching is seen in CBCT; it is possible to predict
blood vessels' paths, which again is a part of the pre-surgical evaluation. The intraosseous
branch can be approximately located in the CBCT from fixed landmarks. The distance
from cementoenamel junction of posterior maxilla to vessel ranges from 15.2 to 34.6
mm with an average of 21.1 to 26.9 mm. The distance of vessels from the maxillary
sinus's inferior border ranges from 2.5 to 19.4 mm with an average of 9.4 to 10.3
mm.[22] Assigning the above-mentioned measurements into clinical practice, it is safe to
place the windows' borders as low as possible, therefore lessening the chances of
encountering the intraosseous branch.
Management
As with the bleeding at other sites, pressure must be applied at the bleeding site,
and the patient should be advised to lift his head. When there is no pulse rhythm
in the intraosseous branch, bleeding can be controlled with gauze packing. If bleeding
does not stop, electrocoagulation, laser, or hemostat can be used to control bleeding.
As a last resort, bone rongeur can crush the bone at the site, hence controlling bleeding.
A high-speed handpiece can be fitted with a diamond bur and applied to the bleeding
site without irrigation to control bleeding. Bone wax is also useful in the management
of bleeding.[23]
Postoperative Complications
Acute Complications
Acute complications generally occur within 24 hours to few weeks of surgery. Typical
symptoms include foul odor, migraine type of headache, midfacial discomfort, pressure
with head position, tenderness, and nasal obstruction. In the case of sinus infection,
purulent nasal exudate is seen in addition to the symptoms mentioned above. For the
management of sinus infection or sinusitis, antibiotics should be prescribed for 2
weeks along with nasal decongestant, antihistamines, analgesics, and patients should
be encouraged to inhale steam to eliminate the excess secretions. The antibiotic of
choice for sinus infection is Augmentin (500 mg amoxicillin and 125 mg of clavulanic
acid). If the symptoms are not relieved by medication or the patient develops symptoms
spontaneously, a surgical approach must be initiated. A small incision is placed on
the lateral wall, and the flap is elevated, and bur is used to pierce the wall. Generally,
an 18-gauze syringe is used to aspirate the contents inside the cavity. After instructing
the patient to hold his breath, normal saline or saline solution with antibiotics
is introduced into the maxillary sinus, and aspiration is executed again. If saline
leaks out of the patient's mouth or nose, the patient should be advised to sit in
an upright position. Suturing is generally unnecessary, and the procedure should be
repeated regularly, which might require patients to visit the clinic every day until
symptoms are relieved. If symptoms do not get relived, patients have to be referred
to ENT specialists, and the patient might have to undergo functional endoscopic sinus
surgery.[23]
BPPV may occur while using a mallet in the osteotome technique to elevate the sinus.
This occurs when otoliths in the utricular macula are detached by the impact of malleting
and move each time the patient changes position, causing dizziness. The patient should
be informed about the risk of BPPV before surgery if osteotome is planned. It generally
occurs in patients above 50 years, and incidence increases with age. Epley maneuver
has to be performed when symptoms of BPPV occur. It is a method of changing the patient's
position and head direction, causing displaced otoliths to come back to the original
position.[24]
Chronic Complications
Implant periapical lesion is one complication that is encountered apart from the complications
mentioned above, which is rare. It occurs due to excessive heat generated during the
drilling procedure. This can be controlled by using an adequate amount of chilled
saline for irrigation. An internal irrigation drill can prevent a temperature rise
inside the bone, but it is difficult to clean and disinfect since the tube is narrow.
However, it is comfortable and practical to perform irrigation at the drilling site
using a syringe.[24]
Chronic sinusitis is generally seen in patients with oversized turbinates and septal
deviation. This can be avoided by careful and systemic presurgical evaluation of sinus,
and it is thought to be a contraindication of sinus augmentation. Sinus membrane thickening
is also thought to be a prerequisite for postoperative chronic sinusitis. Patients
with a history of sinusitis have higher chances of postoperative complications. Hence,
patients have to undergo a nasal–endoscopic evaluation to rule out the presence of
obstructive phenomena. Idiopathic neuralgia of maxilla is a rare finding that occurs
postoperatively.
Prosthetic Complications
Though these are also a cause for complications, these have been discussed separately.
Though they do not cause complications immediately, they certainly hamper or alter
the long-term survival and/or success of the implants. Proper presurgical prosthetic
planning is required for implants' success before placing implants with or without
sinus elevation procedure. Emphasis has to be given for prosthetically driven placement
of implants. Bone grafting and sinus elevation should follow the prosthodontic design.
Postoperative temporary restoration plays a significant role in shaping soft tissue
and securing the grafted particles around the implant. The caution has to be taken
not to load these prostheses. Partial or full dentures can cause excessive pressure
at the augmented site, if not relieved properly. This excessive pressure may lead
to dehiscence, soft tissue complications, and failure of the graft. Dislocation of
the implant into the antrum can also occur, as mentioned above.
The posterior maxilla is ten times less dense than the posterior mandible.[25] Restorations planned in these regions must maintain proper biomechanics to maintain
health and avoid unfavorable crestal bone loss. Osseointegration in such low-density
areas is less predictable than the denser areas in mandible.[26] Hence, to maximize the bone–implant contact, large-diameter implants are chosen
than longer implants, as they have shown better results. Increasing the number of
implants in the posterior maxilla has a better long-term success rate. Splinting of
implants should be considered whenever possible, as they have better stress distribution
than nonsplinted ones.[27] Generally, a reduced occlusal table is preferred, eliminating excursive and nonworking
contacts, which reduces the strain on the bone. If appropriate principles are not
followed, implant displacement into the sinus will increase drastically, leading to
complex surgical procedures.[28] Retrieval of displaced implants from the antrum generally requires endoscopy or
Cadwell-Luc approach. Emphasis has to be given to reduce the bending movements on
implants as far as possible. It was determined that decreased bending of implants
could be accomplished with prosthetically driven implant placement, narrow occlusal
surfaces, splinted implants, and occlusal contacts that provide for axial loading,
thus reducing the offset forces.[13]
Clinical recommendations to limit intra- and postoperative complications are as follows3:
-
Thorough evaluation of the medical history of the patient.
-
Preoperative computed tomography scan to evaluate sinus anatomy and identify preexisting
pathology.
-
Proper patient selection stressing a healthy maxillary sinus.
-
A smoking-cessation protocol is always recommended and, especially in the case of
heavy smokers (≥15 cigarettes a day), this should be evaluated with caution
-
Resolution of periodontal and/or endodontic diseases.
-
Adequate antibiotic prophylaxis
-
Achieve full-mouth plaque score and full-mouth bleeding score of < 15% before planning
for surgery. In the case of provisional crowns, it is advisable to remove the temporary
crowns and disinfect the abutments with an antiseptic solution.
-
Preoperative disinfection of the skin with an antiseptic solution and mouth rinses
with chlorhexidine.
-
Use of sterile draping and infection-control protocol.
-
Keep the incisions distant from the antrostomy.
-
Prevent salivary contamination of bone graft and/or other biomaterials.
-
Intra- and postoperative control of the hemostasis.
-
Prevention of bone overheating.
-
Use of two different sets of surgical instruments: one for the flap-elevation phase
and the other for the grafting.
-
Rinsing the operative field with sterile saline solution.
-
Managing the surgical time as short as possible.
-
Postsurgical oral rinses with chlorhexidine.
-
Correct postoperative drug therapy.
-
Preplanned check-ups: weekly for the first month and monthly for the following 3 months
Conclusion
Prevention is better than cure. Managing complications is a tenacious process that
is physically, psychologically, and financially draining for patients. Hence, it is
better to avoid complications as much as possible. This can be accomplished by a thorough
understanding of the sinus's anatomy, the patient's medical status, presurgical evaluation
of the sinus, and precise planning of surgery along with proper communication with
the patient.
