1. Why would maxillary sinus augmentation be required?
- Tooth loss results in bone loss. In the maxilla, the bone loss is greater and more rapid than in the mandible. Therefore, when there are missing teeth in the posterior maxilla, there is commonly a lack of bone and space to allow for implant placement – in these circumstances a maxillary sinus augmentation procedure may be required.
- Maxillary sinus augmentation surgery is one of the most common pre-prosthetic surgeries performed in dentistry today (Woo et al 2004).
- However, sinus augmentation is not the only option in such situations. Other options may include block grafts and angled implants but these have several disadvantages. For example, it is difficult to maintain optimal oral hygiene around angled implants, making them more prone to peri-implant disease.
2. What is the basic anatomy of the maxillary sinus and why is this relevant?
- The maxillary sinus is quadrangular (has 4 sides) pyramid. 2.5-3.5 cm wide, 3.5-4.5 cm high and 12-15 cm3 Its extension anteriorly is variable. It is important to assess this prior to performing any surgery so we understand the area we are dealing with.
- The sinus cavity may be divided into the physiological superior section and the inferior surgical section.
- The anterior inferior wall will be the surgical site. If you lose teeth and bone, we need to be aware that this wall may be thin and close to the infra-orbital foramen and vascular bundle. The base of the sinus and bony walls will also vary in thickness.
- Other structures which may impact on your surgical technique are the ostium (must not be blocked) and septa (these may be deceptive on a DPT and need to be managed carefully during surgery).
- The sinus membrane is a bilaminar ciliated pseudostratified ciliated epithelium on the sinus side and periosteum on the bone side. It is elastic can be very thin (0.13 mm) but variable. If there has been recurrent colds, apical pathology associated with teeth etc. then this chronic inflammation can cause thickening of the membrane.
- The blood supply to the maxillary sinus is from the internal maxillary anterior.
- It is important to realise that all the sinuses – maxilla, frontal, ethmoid, sphenoid – are connected. This is relevant surgically as an infection in one sinus can travel to the others.
3. What pathology is associated with the sinus and why is this important to consider?
- Antral pathology includes sinusitis and less commonly tumours (e.g. ameloblastoma).
- Sinusitis is a common condition that may be acute/chronic/recurrent and is due to chronic irritation which may be bacterial, viral or fungal in origin. Symptoms include congestion, discharge, post-nasal drip and coughs which are worse at night. Treatment for sinusitis may include: humidifier, spray, steam inhalations and antimicrobial treatment. Note: if the infection is fungal in origin, this may require referral to an ENT surgeon.
- It is important to check scans to make sure there is no significant pathology prior to the surgical procedure as sinus augmentation in cases with pathology will be unsuccessful.
4. Who devised the maxillary sinus augmentation procedure?
- Hilt Tatum devised and developed the technique in 1976.
- It was published by Boyne & James in 1980.
- Prof Manuel Chanavaz published the first long-term study.
5. What pre-surgical assessment is required?
- It is important to check for any contraindications to this procedure, which will include candidates not suitable for surgery (previous radiotherapy, healing problems etc), pathology associated with the sinus and smokers.
- A clinical assessment considering the teeth present, the condition of the dentition, periodontal status, vertical height and degree of posterior support is important.
- Radiographs such an intra-oral periapicals and DPTs may be taken but the view of choice is a CAT scan. iCAT is relatively inexpensive but the 3D modelling tool is not ideal. Morita provides a more detailed view but the inside of the sinus is not as clear. Simplant software is excellent to visualise the full inside of the sinus.
- On the CAT scan assessment, check the thickness of buccal wall, width/height of alveolar ridge, thickness of lining, teeth and roots, shape and position of septa, anterior extension of sinus and defects of alveolar bone.
6. What approaches are available for sinus augmentation?
- There are 2 approaches – internal lift OR the lateral window technique. For the internal lift technique you drill a hole in the sinus wall, the sinus floor is felt for and an osteome used to push the floor up, this up-fractures the sinus floor and an implant can then be placed. Dr Sidi prefers using the lateral window technique.
- Implant placement may be completed at the same time as augmentation (simultaneous approach) or a delayed approach can be taken where the grafting is carried out prior to placing the implant (when there is insufficient bone to stabilise the implant – usually less than 4 mm of bone).
7. What are the basic steps for the lateral window technique?
- Incision along the crestal ridge but more palatally. The relieving ncisions should be at least 1 dental unit either side of the planned osteotomy.
- A window is created in the bone using a straight handpiece with a round-ended surgical fissure bur. A periosteal elevator is used to lift the bone away. If the lining is elevated with the bone is place, it is more likely to tear.
- Raising the sinus lining – the membrane should be separated from the bone using angled instruments, always start distally to reduce the chances of tearing the membrane. Push the lining ahead of the curette and elevate all the way to the medial wall (this wall provides source of osteogenic cells for repopulation of graft). If there are septa, cut 2 windows and start distally. Septa can be thin and sharp; these usually run bucco-palatally but very rarley can also run in a transverse direction.
- After the space has been created, bone graft (e.g. bovine bone) is packed into the cavity.
- Replace the window cover with a collagen membrane and place two layers of suture.
8. What are the common risks of this procedure and what post-op instructions should be given?
- Swelling and bruising is predictable and common for a week.
- Nose bleeds can occur and this is related to the pressure in the sinus (advise no nose blowing for 2 weeks and maintain an upright posture when possible).
- No heavy sports should be carried out for at least a week.
- Post-op infections are not common but can be treated with a combination of antimicrobials.
9. What are the basic additional steps for simultaneous implant placement?
- Lift the membrane up to the medial bone.
- Place a plastic backing first to protect the sinus membrane from the drill.
- Place the implant after having filled the inner part of the sinus cavity.
- The rest of the cavity should be filled with graft and covered with the bone window and a collagen membrane.
10. What are the likely complications of this procedure and how can they be managed?
- Tears – likely site is the anterior section due to access difficulties – extending osteotomy as close as possible to the mesial wall reduces the likelihood of a tear. If there is a tear, don’t panic and continue to elevate the sinus extensively all around the tear until it is completely isolated and you can see the lining all the way round it. If it tears further, increase the size of the window to expose more of membrane and continue to elevate it. Close with a collagen membrane. If the tear is very small, the elasticity of membrane will close over the tear. If this is still unsuccessfully – suture the membrane (6.0 vicryl internal mattress suture- Hilt Tatum technique) either to close the tear margins or suture one margin to the boney wall and close over with a collagen membrane. If not possible to suture then you may consider using a ‘sock’ – this is large piece of collagen membrane sutured together with vicryl, it is tried into the cavity and then filled with BioOss and slid back in. A pin may be used to hold it in position and a collagen membrane is placed on top. A collagen capsule is similar – can purchase from Osseous Technologies of America in various sizes. Note: you can often see movement of the sinus lining on breathing – this does not mean there is no tear so the whole lining needs to be inspected carefully prior to grafting.
- Bleeding – apply pressure, LA with adrenaline socked in surgical gauze, electro-cautery.
- Nerve damage – this is extremely rare if the case is planned satisfactorily.