Crestal Sinus Elevation
Earliest description of a transalveolar approach to the sinus floor elevation procedure dates to Tatum (1986). It was later modified by Summers (1994), and since then, numerous iterations have been reported. This chapter will highlight the BAOSFE (bone‐added osteotome sinus floor elevation) technique originally described by Summers.
A transalveolar (aka crestal, transcrestal, vertical, internal) sinus floor elevation is indicated when an implant is planned in the posterior region of the maxilla and there is inadequate residual bone height (RBH) for an adequately sized implant. It provides a conservative alternative to the lateral window (Caldwell‐Luc) approach in that flap reflection is minimal, access is limited to the implant osteotomy, and predictable installation of the implant can usually be obtained concurrent to the procedure (versus a staged approach often encountered with the Caldwell‐Luc technique). Localized elevation of the sinus floor limits unnecessary manipulation of the Schneiderian membrane, thereby mitigating the risk of sinus complications including tears, perforations, and post‐operative infections. Additionally, when compared with the lateral window technique, there is a decrease in post‐surgical morbidity, healing period prior to implant loading, chair time, materials, and overall financial costs to the patient and practitioner alike.
The multi‐center retrospective study by Rosen et al. (1999) reported greater than 95% success rate for implants placed with the BAOSFE technique when the RBH was ≥5 mm. However, when the RBH was ≤4 mm RBH, successful osseointegration decreased to 85.7%. A recent systematic review by Shi et al. (2016), corroborated the results of Del Fabbro’s systematic review, where the cumulative survival rates were significantly lower when the RBH was <5 mm. These results strongly suggest that the transalveolar sinus elevation is most predictable with an RBH ≥5 mm. The decision whether the implant placement would be concurrent to the sinus floor elevation or delayed after subsequent healing would be primarily dependent upon the primary stability of the implant.
Compared with a lateral window approach, the crestal sinus approach is seen to be as successful, if not more. In Del Fabbro’s (2012) systematic review, the researchers found a 97.2% survival rate with follow‐up of six years for the crestal approach compared with 93.7% for lateral window approach. However, as with any procedure, there are some risks and drawbacks. Anatomical variations in patients including the presence of septae at the implant sites, or pneumatization of the sinus following tooth loss are contraindications for the procedure. The technique is “blind” as there is no direct visualization of the sinus floor elevation. This may potentially increase the risk of perforations and complicate its management. Unlike the lateral window approach, the transalveolar sinus approach are usually limited to one to two implant sites and have a mean bone gain of 3.8 mm (Toffler 2004).
The specific type of sinus floor elevation depends on criteria including, but not limited to RBH, marginal bone width sinus anatomy, presence of intact Schneiderian membrane, extent of sites needing rehabilitation, clinician training and experience, and patient‐related factors (medical history, preference, etc.). Practitioners need to consider alternative treatment options and develop patient catered care for each individual’s needs as well as the surgeon’s technical ability. These may include the lateral window approach, the use of osseodensification burs or the placement of short implants.
In additional to the traditional implant surgical set‐up, a number of additional instruments and materials should be at the practitioner’s disposable for the transalveolar approach:
- Drill stops to allow the surgeon to limit the osteotomy to 1 mm short of the sinus floor
- Ball‐tipped probe or blunt depth gauge to confirm the presence of bone or feel the exposed membrane
- Offset osteotomes and mallet to both infracture the sinus floor and pack the grafting material into the sinus cavity
- Biomaterials, such as bone replacement grafts and barriers, to augment the recipient site, to provide a buffer prior to grafting within the osteotomy, or to repair any tears or perforations
In the past, traditional intraoral radiographs and panoramic images have been sufficient to diagnose and treatment plan for a transcrestal sinus floor elevation of limited sites. However, with developments in radiographic technology, cone beam computed tomography would yield the ideal and recommended images to visualize sinus pneumatization, anatomy including septae, rule out any sinus pathology, and confirm residual ridge height.
Upon successful and profound anesthesia, appropriate incisions are made and a full‐thickness mucoperiosteal flap is elevated to provide adequate visibility and access to the underlying ridge. Initiate osteotomy according to manufacturer’s recommended protocol under copious sterile irrigation. Osteotomy depth should be approximately 1 mm crestal/occlusal to sinus floor. For example, if the RBH is 6 mm from the alveolar crest to the sinus floor, the depth of the osteotomy should NOT exceed 5 mm. Depth of prepared osteotomy should be verified with ball‐tipped probe. Drill stops would be advantageous to ensure the tip of the drill does not extend further than planned. Continue widening your osteotomy to the final width. In most cases, this will be about 0.5 mm narrower than the final width of the proposed implant fixture. This ensures a wider surface area for the graft and osteotome and minimizes sinus perforations. Add a small amount of hydrated BRG (one scoop of a Miller or Lucas curette). BRG should be filled to no more than ½ the depth of the osteotomy. Using the example of a 5 mm osteotomy depth, graft about 2.5 mm in height.
Next, select the widest osteotome possible to passively fit into your prepared osteotomy. Ensuring proper angulation and finger rests, gently tap the osteotome with the mallet. You should feel a decrease in resistance (or the “break”). Summers (1998) stated that the concave tip of the osteotome traps the BRG and fluids as the instrument is inserted, which in turn, creates a hydraulic force which exerts pressure in all directions (“Pascal’s law”). The BRG within the osteotomy appears to serve as a buffer/cushion for the sinus floor infracture. Important point is to ensure that the osteotome NEVER exceed the initially measured RBH. In this way, you are providing a safety check so that perforation of the sinus secondary to the osteotome extending into the sinus cavity is taken out of the equation. The Valsalva maneuver should be performed to test for any sinus perforations by gently holding the patient’s nostrils and asking to blow through the nose. If air is noted from the osteotomy, it’s a probably indication that there is a sinus perforation and the grafting should be aborted.
Continue the process of grafting, aligning osteotome and gently tapping for about 10 times prior to exposing a radiograph. Ten times is an arbitrary number but adequate to have enough crestal sinus elevation that would be apparent and visible on the radiograph. A “dome” of the BRG should be noted. Generally, 0.5–1 cc of BRG would suffice for a single site. If an implant is to be placed simultaneously, complete your last osteotome crestal tap similarly and do NOT extend the osteotome to the final proposed depth. The final installation of the fixture ensures further displacement of the BRG within the sinus cavity.
If it is determined that this will be a staged transalveolar sinus augmentation, then the procedure should be completed with BRG placed all the way to the most crestal portion of the osteotomy. A barrier may be considered to cover the grafted site. Usually, a four to six month healing period appears to be adequate in time to ensure that proper healing and consolidation of the crestal sinus graft has occurred. At the time of fixture placement, adequate RBH should be present. If further crestal augmentation is necessary, an additional crestal sinus augmentation may be performed with a concurrent implant placement.
Tan et al. (2008) reported the most commonly reported complication was perforation of the sinus membrane, which varied from 0–21.4%, with a mean of 3.8%. Post‐operative infection was observed less than 1% of the time. Attempts can be made to repair the perforation and/or tear with a variety of materials (i.e. resorbable collagen membrane, wound dressings). If the perforation/tear is irreparable or too severe, the procedure should be aborted. Infrequently, complications such as benign paroxysmal positional vertigo and detached retina have been reported.
Post‐surgical medications may include an analgesic or NSAID, an antibiotic, an anti‐bacterial rinse and a nasal decongestant. A routine post‐surgical appointment should be performed within 7–14 days of the procedure. Results from a three‐year multicenter randomized controlled trial demonstrated that short implants (5–6 mm) have demonstrated similar success rates compared with longer implants (10 mm) placed in osteotome‐mediated sites (Gastaldi et al. 2017).
Lateral Sinus Floor Elevation
The introduction of sinus floor augmentation, which has facilitated the placement of longer implants in the posterior maxilla, has led to an improvement of overall prognosis of maxillary implants. The first paper concerning the treatment of patients with endosseous implants associated with maxillary sinus elevations operations was published in 1980 by Boyne and James. The maxillary sinus was accessed via antrostomy in order to create a “bone window” on the lateral wall which was then delicately pushed and turned inside the antrum. The material used for the graft was generally autogenous bone harvested from the iliac crest and blade implants were inserted in a subsequent operation, some months after the sinus elevation procedure. Since then, this procedure has become a very predictable and well documented one that is an integral part of dental implant treatment.
Insufficient residual alveolar bone height in the posterior maxilla of equal or less than 5 mm may result from alveolar bone resorption following tooth loss, bone loss due to periodontal disease, pneumatization of the maxillary sinus, or a combination of the above.
Wallace and Froum (2003) found the overall of implant survival rate was 91.8% after reviewing 3220 implants placed and Del Fabbro (2004) found it to be 91.49% after reviewing 6913 implants placed in 2046 subjects. More recently, Del Fabbro (2013), found an overall implant survival after a minimum of three years loading was 93.7% and 97.2% for the lateral window and transalveolar approaches, respectively. Of importance is the fact that 80% of failures occurred within the first year and 93.1% of the failures occurred within three years.
Grafting materials range from autogenous bone to allograft to xenograft, to synthetic bone used with or without membrane over the lateral osteotomy. The important points to cover are the vitality of grafted material, survivability of the implants in these grafts, and the amount of remodeling of the grafted material.
In relation to bone vitality, Tarnow et al. (2000) showed that the use of the membrane has affected the vitality of bone from 11.9% vital bone without using membranes versus 25.5% when using membranes in 12 bilateral cases. Further to that, they found a higher survival rate of 100% with membrane versus 92.6% without membrane in 55 placed dental implants over five years.
Later, Froum et al. in (2006) conducted a histomorphometric bi‐lateral study comparing xenograft versus allograft in a 13 bilateral sinus lifts found twice more vital bone with the allograft sinuses and ¼ less residual material as well.
In relation to survivability of the implants in grafted sinuses and of importance, Del Fabbro (2004) correlated the grafting material to the survival rate of dental implant placed in a grafted sinus as follows:
- 1. 87.7% when autogenous bone was used alone.
- 2. 94.88% when combining autogenous with various bone substitutes
- 3. 95.98% when various bone substitute were used alone
which brings us to the amount of residual bone graft. Mordenfeld in a 30 maxillary sinus lifts using a Mixture of Xenograft (DPBB) 80% and 20% autogenous bone did a histomorphometric analysis at 6 months and 11 years and found no statistically significant differences between the length and area of the particles after 11 years compared with those measured after 6 months in the same patients or to pristine particles from the manufacturer.
Later, Danesh‐Sani et al. (2017), in a systematic review evaluating histomorphometric variables, the amount of new bone (NB), residual graft (RG) particles, and soft tissue (ST), related to various grafting materials assess the effect of graft healing time on different histomorphometric outcomes. They found: Autogenous bone (AB) resulted in the highest amount of NB and lowest amount of RG compared with other grafting materials. Based on this meta‐analysis, a significant difference was noticed in the amount of NB formation in grafts with a healing time of >4.5 month when compared with the grafts with less healing time. However, when comparing biopsies taken at 4.5–9 month of healing (average = 6.22 month) to the ones taken at ≥9–13.5 month (average = 10.36 month), no significant difference was noticed in the amount of NB formation of various grafts except allografts that resulted in a significantly higher percentage of NB at 9.5 month of healing. Based on histomorphometric analysis, AB results in the highest amount of NB formation in comparison with the other grafting materials. Bone substitute materials (allografts, alloplastic materials, and xenografts) seem to be good alternatives to autogenous bone and can be considered as grafting materials to avoid disadvantages related to AB, including morbidity rate, limited availability, and high volumetric change. Combining AB with alloplastic materials and xenografts brings no significant advantages regarding NB formation.
The maxillary sinuses are bilateral bony cavities in the maxilla, containing an air space volume of approximately 15 cc each, lined by pseudostratified columnar epithelium. The maxillary sinus is located in the body of the maxilla and is the largest of the pneumatic paranasal chambers.
It has the shape of a pyramid:
- – Apex: extends into zygomatic process of maxilla
- – Base or medial wall makes part of lateral wall of the nasal cavity
- – 4 walls:
- a. anterior similar to the maxilla anterior wall
- b. posterior corresponds to the infratemporal surface of maxilla
- c. inferior or floor corresponds to alveolar process
- d. superior or roof is the orbital surface of the maxilla
- The majority of maxillary sinuses have their floors at varying distances below the level of the floor of the nasal fossa. The maxillary sinus communicates with the nasal fossa through the ostium maxillare, which is the Ostium of maxillary sinus using the middle nasal concha.
- The ostium also communicates with the ethmoidale cells thru infundibulum ethmoidale.
A healthy sinus is self‐maintained by postural drainage and actions of the cilicated epithelial lining, which propels bacteria toward the ostium. It also produces mucous with lysozyrnes and immnoglobulins. The rich vascularity of the sinus membrane helps to maintain it in a healthy state by facilitating lymphocyte and immunoglobulin access to the membrane and the sinus cavity. The healthy sinus contains its own flora, of which Haemophilus is the most common species.
Other than the descriptive anatomy of the sinus, there are two important landmarks:
- A. Vascularizations
Vascularization of the lateral maxilla is supplied by branches of the posterior superior alveolar artery (PSAA) and the infraorbital artery (IOA) that form an anastomosis in the bony lateral antral wall, which also supplies the Schneiderian membrane. Both arteries had an average diameter of 1.6 mm.
Solar et al. (1999), in 18 maxillary specimens, they found the PSSA divide itself in two intra‐osseous anastomosis connecting with the IOA, the Internal intra‐osseous anastomosis (IA) and the external intra‐osseous anastomosis (EA) that lounges in the external wall. The mean distance between the alveolar ridge and the external intraosseous‐anastomosis was 23 mm.
The blood supply of the graft periphery is provided by the Schneiderian membrane, intraosseous vascular bundles, and the center of the graft from the endosseous anastomosis; thus the bony window should be as small as possible.
- B. Septae
Bornstein is a study that included 294 maxillary sinuses in 212 patients (126 women and 86 men) with a mean age of 53.8 years. Sinus septa were present in 141 patients (66.5%) and in 166 of 294 sinuses (56.5%). The most common orientation of the septa was coronal (61.8%), 7.6% were oriented axially, and 3.6% were aligned sagittally. Most septa were located on the floor of the maxillary sinus (58.6%), commonly (60.7%) in the region of the first and second molars.
Another important fact that he found in his study that can be of great relevance, is the maxillary sinuses were diagnosed in 36.4% of cases as healthy and without thickening of the sinus membrane. Sex was a significant variable in the health of the maxillary sinus; 57.7% of the sinuses in women and 72.3% in men were diagnosed as pathologic.
- Presurgical cone beam computed tomography (CBCT) scans to disclose sinus pathology and difficult anatomy
- Round diamond burs
- Specially designed hand instruments for lateral sinus elevation
- Piezoelectric surgery with sinus specific inserts
- Materials to control bleeding (electrocautery, local with 1 : 50 000 epinephrine, bone wax)
- Biomaterials, such as bone replacement grafts and barrier membranes, to graft the sinus cavity, or to repair any tears or perforations of the sinus membrane