What is Sinus Lift?
Sinus Lift is a procedure of which the maxillary sinus membrane is elevated and subantral augmentation is performed with bone graft placement. The end result is the improved bone height in the posterior maxilla which is more favorable for implant placement.
Usually, when tooth is lost, pneumatization (referred to the phenomena which the volumn of sinus cavity increase due to the bone loss at the base of sinus and the sinus membrane relocated to more apical) of the maxillary sinus occurs. The loss of teeth results in alveolalr resorption, decrease in bone width and height, and decrease in bone density. When implant is inserted in this area, the initial implant stability is poor coupling with inadequate bone height for the implant length. This result in implant failure either initially or during loading.
Where is the maxillary sinus and what is its function?
The maxillary sinus is the largest of four paranasal sinus. It appears as a pyramid of four thin, bony walls, the base of which faces the lateral nasal wall and the apex of which extends toward zygomatic bone. The antrum is approximately 34 to 35mm at its base, and the apex extends 23mm toward the zygomatic area. The average volume is 15mL and increases as posterior tooth loss and pneumotization occurs. Bony septa joining medial and lateral walls may complicated the sinus lift procedure as potential for sinus membrane perforation at these areas.
Pathologically, sinusitis has been related often to maxillary or frontal sinus involvement. Other problems identified with lesser encounter includes tumors and malignancy. 60% of squamous cell carcinomas of the paranasal sinuses located in the maxillary sinus, usually in the lower half of the spectrum. Other iatrogenic incidence would be oroantral fistulas as the consequence of the tooth or implant extraction, trauma, or surgical entry into the maxillary sinus. Because of anatomic proximity of the sinus and oral cavity, many oral diseases also extend into the sinus such as periapical, follicular, and odontogenic keratocysts, fibrous dysplasia, ossifying fibromas, and giant cell lesions. Other cystic lesions such as pseudocysts, retention cysts, and/or mucocele may be diagnosed in the area.
- Upper left: maxillary sinus in relation to the skull
- Upper right: close up view of maxillary sinus
- Lower left: maxillary sinus in relation to the teeth, noted the root proximity of posterior teeth to the sinus floor
- Lower right: interior view of maxillary sinus, the lateral wall is carefully section and lift up to see the inside of the sinus cavity. The sinus membrane lines the cavity. Note the ostium where the sinus drainage occurs.
How is the maxillary sinus bone height influence the implant placement process?
Carl Misch subcategorized the implant treatment planing into four approaches bases on bone height in the posterior area:
- Subantral Option 1(SA1), conventional implant placement: there is sufficient available bone height (greater than 12mm) to permit the placement of endosteal implant. No lift required in this category as implant can be placed normally. Bone graft may be used to augment the bone width. In my opinion, whenever bone graft is placed, barrier should be considered as to inhibit connective tissue migration into the area and allow the bone cells to migrate, differentiated, and mature at the bone site.
- Subantral Option 2(SA2), subantral lift and simultaneous implant placement with osteotome lift technique: there is 8mm-12mm available bone height, thus we need probably only 2-3mm more to properly place a 13mm length implant in the area. 13mm or more implant length is preferred due to numerous studies (Hurztler et al) which shows the implant success in relative to length (or surface area). Osteotome lift technique is used of which the implant is tapped and produced a green stick fracture on the sinus floor. Bone graft can be added and further elevates the sinus membrane. (Please select Implant, Osteotome Lift under service menu for more information).
- Subantral Option 3(SA3), sinus membrane elevation with subantral augmentation and simultaneous endosteal implant placement: there is only 5mm-8mm bone height of vertical bone and sufficient width are present between the antral floor and the crest of residual alveolar ridge. A Tatum lateral wall approach is performed just superior to the residual alveolar bone. Green stick fracture introduced in the access window as it is rotating inward and upward and served as the floor of the implant. A mixture of autogenous bone and/or allograft material is placed into the area previously occupied by the sinus cavity. Implant is then placed from the top of the ridge, through the 5mm bone height, and into the graft area. A barrier membrane (please select Guided Tissue Regeneration under services menu) placed at the window opening, and flap closure.
- Subantral Option 4(SA4), sinus membrane elevation and subantral augmentation with no implant placement: there is 4mm or less of bone height and thus there is not enough surface area for anchorage and stabilization of the implant. In this case, Tatum lateral wall approached is performed just superior to the residual alveolar bone.Green stick fracture introduced in the access window as it is rotating inward and upward and served as the floor of the implant. A mixture of autogenous bone and/or allograft material is placed into the area previously occupied by the sinus cavity. Implant will be placed at 8 to 12 months later as the new bone is allowed to migrate, differentiate, and mature.
What are the contraindication to the sinus lift procedure?
Any sign of sinusitis will delay the surgical appointment. If the patient shows any sign of nasal congestion, sinusitis, rhinitis, or upper respiratory tract disease, the surgery should be postponed until the situation resolves. Patient should be aware of sinus drainage, or any kind of health problem leading to inflammation of sinus membrane (fever, cold, flu, allergy, drainage, polypse). Moreover, patient must not have UNCONTROLLED diabetes because high glucose level in the blood will cause delayed wound healing and immunocompromise problem. Controlled diabetic patient should have no problem in healing as their glucose level is kept in check (70-111).
What are the pre-op medications to be prescribed prior to undergo the sinus lift procedure?
The following medication are prescribed by Dr. Bui, D.D.S., M.S., at the preop appointment prior to sinus lift procedure. In summary, they are antibiotics, anti-inflammatory, analgesic, and antihistamine. Other operator may choose a different brand of medication but the therapeutic actions should be the same.
- Antibiotics: Amoxicillin 500mg, taken i tab three times a day for seven days, starting one day before surgery. In the event of patient allergic to penicillin, clindamycin 300mg is used, with i tab taken four times a day for ten days.
- Analgesic: Darvocet N-100, taken i tab every 6 hrs for pain, starting one hour before surgery. Other medications may be prescribed are Lortab, and Vicodin. Lodine 400mg can be prescribed if the patient does not prefer narcotic analgesic medication.
- Anti-inflammatory: Dexamethasone 1.5 mg, 9mg the first morning of surgery, 6mg the next morning, and 3 mg the third day. The total dosage is 18mg for three days. In the event that the tab dosage is .74mg, the number of tab is adjusted to equal to the amount preferred.
- Antihistamine: Claritin 10mg, i tab daily for 10 days.
What are other effects we found in lifting the sinus membrane?
First of all, the lifting of sinus membrane will improve the bone height to favorably placing endosteal implant. Secondly, in many case, it restore the floor of the sinus to the normal physiologic level before the tooth is lost. Moreover, in the people with prolonged tooth loss and severe pneumotization of sinus, he or she may have suffered poor drainage problem. These patients complaint that when they lie down, the excessive drainage occurs. This contributes to the halitosis, bad taste in the mouth, and in extreme case, soft tissue polypses occur in the sinus cavity due to prolonged irritation of sinus membrane leading to granulomatous tissue formation. Many of our patient expressed that they breath better after the sinus lift and the drainage problem is much improved. The explanation for the improvement of drainage is the relocation of the floor of sinus to the level close to the ostium where the drainage occurs.
What happen if the sinus membrane is perforated during the sinus lift?
The sinus membrane is a very thin membrane (similar to our skin when it peels after sun burn) therefore perforation may happen during the surgery. If it does happen, the surgery should be closed up and reentered in 2-3months. It happened to me once before, and I used Attribsorb membrane to close the communication (the term described there is a hole connecting the sinus cavity to the oral cavity) and also graft the bone width prior to flap closure. Attribsorb is a flowable polymeric barrier that composed of poly (DL-lactide)(PLA) dissolved in N-methyl-2-pyrrolidone(NMP). It isolated the regenerative site fom the adjacent gingival connective tissue and epithelium, since the site needed to be reentered to place the implant. Below is the case of sinus perforation that I discussed above. Instead of just close up and wait, I opt to graft the adjacent site and augmented the bone width. It never hurts to have more bone width because increasing implant width can be placed and that means increase the surface area of osseointegration.