Exploring the Crucial Role of Maxillary Sinus in the Success of Dental Implants: A Comprehensive Review

Flap design

The blood supply must be disrupted as little as possible, and the surgical site must be adequately covered while creating the flap for sinus augmentation. The incision is often performed through the keratinized, connected mucosa, either mid-crestal or paracrestal manner. When making the osteotomy and retracting the flap, extra care must be taken to avoid the infraorbital foramen and guard against any harm to the neurovascular bundle.

The optimum osteotomy door shape should resemble the frequently curved internal surface of the maxillary sinus. Radiographic and clinical assessments can help with door-form planning. It can be necessary to thin out the entire sinus lateral wall if it has a thick lateral wall. To reduce the possibility of membrane injury when dealing with rounded corners, it is best to design a wide cranial hinge base. It is advisable to use finger pressure rather than sharp objects while luxating the door. This helps the surgeon prevent any complications and enables them to feel any resistance.^[23]

Schneiderian membrane

During the sinus lift surgery, maintaining the integrity of the thin Schneiderian membrane is crucial to preventing graft material leakage into the sinus and maintaining a sufficient blood supply. Various factors, including smoking, chronic sinusitis, allergies and prior sinus surgery, can affect how the membrane is feeling.

The membrane may appear atrophic, brittle and thin in smokers. On the other side, a thicker membrane might result from allergies and persistent sinusitis. These disorders must be addressed at the preoperative planning stage, as they are considered contraindications to the sinus lift procedure. Previous sinus procedures can also be a contraindication since the preparation of healthy, undamaged mucosal tissue may be hampered by scar tissue.^[24]

A delicate procedure, the separation of the Schneiderian membrane necessitates the use of specialized tools with blades of various shapes and angles. Although the distal side of the sinus may stretch far, the membrane must be entirely removed from the caudal area in order to elevate the sinus. A sinus that is overfilled may develop sinusitis, membrane necrosis and graft loss. When the membrane is separated from the septa and longitudinal rims, navigating the sinus floor’s convolutions and avoiding root tip expressions might be difficult.

In a study by Aimetti et al.,^[25] it was discovered that people with thick and thin gingival tissues, respectively, had sinus mucosa with thicknesses of 1.26 +/– 0.14 mm and 0.61 +/– 0.15 mm. This implies that the thickness of the gingival tissue might be used as a metric to forecast the thickness of the sinus membrane. However, additional study is needed to confirm these preliminary results.

Maxillary sinus septa

A bony division that separates the maxillary sinus into several recesses and smaller accessory sinuses is referred to as an antral septum. The incidence of this typical anatomical variation in the maxillary sinus ranges from 16% to 58% in the general population. Multiple septa are less frequent than a single septum.^[26]

Sinus augmentation treatments can be complicated by the presence of septa, unless they are in the caudal (lower) region of the sinus. A normal augmentation procedure is possible in these circumstances. However, clinicians have a number of alternatives if a septum is located higher than the caudal region. The septum can be partially removed after raising the membrane, or it can be partially removed after creating two trapdoors, a door on one side of the septum (usually the mesial side), or a W-shaped window by following the outlines of the sinus.

Studies have looked at the frequency, distribution, size, shape, orientation and morphology of maxillary sinus septa. For instance, research by Park et al.^[27] using CT scans discovered that 37% of the individuals, or 27.7% of 400 maxillary sinuses, had septa. The anterior region had 22.5% of the septa, the middle region had 45.9%, and the posterior region had 31.5%. The majority of septa (87.6%) were buccopalatal, while only a tiny proportion were sagittal (11.1%) or transverse (1.3%).^[27]

2534 of the 8923 sinuses examined in a meta-analysis by Pommer et al.^[28] that used data from 1995 to 2011 had septa. However, there was a 29% error rate in the diagnosis when panoramic radiographs were employed. The septal height was 7.5 mm on average. In comparison to dentate maxillae, the incidence of septa was substantially higher in atrophic sinuses. The transverse septa made up 87.6% of all septa, whereas sagittal septa made up 11.1% and horizontal septa made up 1.3%. It was uncommon (0.3%) to find a complete septum separating the sinus into two distinct chambers. 4.2% of patients had multiple septa, while 17.2% of patients had bilateral septa.

According to a review by Rossetti et al.,^[29] the use of a removable prosthesis in the past was a risk factor for posterior maxillary resorption, with flabby tissues being linked to the degree of resorption. The incidence of septa was likewise higher in atrophic maxillae. Compared to male patients, female patients typically had reduced medullary connection and quantity.

It is crucial to remember that these conclusions may not be applicable to all situations because they are based on research done with particular groups.

Sinus volume and dimensions

Using CT images, Kirmeier et al.’s study ^[30] showed the accuracy and repeatability of a semi-automatic virtual volumetric analysis technique for calculating maxillary sinus volume. The method’s validation revealed a mean relative error of 0.364%, demonstrating that CT scans are a trustworthy source for determining a patient’s maxillary sinus volume.

CT scans were used by Jun et al.^[31] to assess how age and gender affected changes in maxillary sinus volume. They discovered that the development of the maxillary sinuses lasts until the third decade in men and the second decade in women. Males and females were found to have considerably varying maxillary sinus volumes, with young adults having significantly different mean maxillary sinus volumes between the sexes. The scientists came to a conclusion that maxillary sinus procedures carried out before the sinus’ complete growth might have a negative effect on it, and this fact should be taken into account before surgery.

In the study by Kawarai et al.,^[32] CT scans were employed to measure the size of the maxillary sinus and other paranasal cavities in a sample of healthy Japanese participants. They discovered that males and females had different volumes for the maxillary sinus, with males having somewhat greater volumes than females.

In “normal” children and those with bilateral chronic sinusitis, the maxillary sinus volume was measured using CT scans by Ikeda et al.^[33] The outcomes were contrasted with those of patients who were adults. Inflammation widened the ethmoid infundibulum and middle meatus in kids with bilateral chronic sinusitis that impeded maxillary sinus pneumatization.

These studies demonstrate the value of CT scans in determining the volume of the maxillary sinus, comprehending its patterns of development, and recognizing potential surgical consequences.

Augmentation materials

A variety of grafting materials, including autografts, xenografts, allografts and alloplastic grafts, may be used during sinus elevation treatments. Due to its osteogenetic, osteoinductive, and osteoconductive qualities, autogenous bone, taken from the patient’s own body, is regarded as the gold standard graft material for sinus augmentation. The need for a second surgical site, which can result in donor site morbidity and complications,^[34] is its primary downside.

• 1.

  Autografts: The best type of graft material is autogenous bone, which is taken from the patient’s own body. It has characteristics that are osteogenetic, osteoinductive and osteoconductive. However, the requirement for a second surgical site may result in morbidity and problems at the donor site.

• 2.

  Allografts: Allogeneic graft materials are sourced from tissue banks and are available as mineralized or demineralized bone. Demineralized bone contains bone morphogenetic protein that stimulates osteoinduction. Cost and potential disease transmission risks are concerns associated with allografts.

• 3.

  Xenografts: One kind of often-used xenograft material is deproteinized bovine bone, such as Bio-Oss. It has osteoconductivity and can be applied either on its own or in conjunction with other grafting materials. Bio-Oss goes through a process to get rid of the organic material while keeping the bone structure.

• 4.

  Alloplastic grafts: Alloplastic grafting materials, such as hydroxyapatite-based products like calcium phosphate ceramics, provide synthetic scaffolds for bone formation. They are easy to use and relatively less expensive compared to harvesting bone.

• 5.

  Mesenchymal stem cells (MSCs): Recent studies have investigated the use of MSCs in the augmentation of the maxillary sinus. Early research has produced encouraging findings that point to the possible advantages of cell-based strategies. To prove their efficacy, more randomized controlled trials are required.^[35]

The choice of grafting material depends on various factors, including availability, patient-specific considerations, surgical technique and desired outcomes. Surgeons carefully consider these factors to determine the most suitable graft material for each case.

Postoperative instructions

It is critical to give the patient written and verbal postoperative instructions after sinus augmentation surgery. Several areas of care and precaution must be covered in these guidelines:^[36]

• 1.

  Application of ice and pressure: Apply ice packs to reduce swelling and apply gentle pressure to control bleeding.

• 2.

  Elevation of the head: Keep the head elevated, especially when lying down, to minimize swelling and promote drainage.

• 3.

  Rest: Avoid strenuous activities and get plenty of rest to facilitate healing.

• 4.

  Smoking cessation: It is highly recommended to discontinue smoking before, during, and after the procedure to promote healing and reduce complications.

• 5.

  Prevent negative pressure: During the first week following surgery, prevent negative pressure in the sinuses by not blowing your nose or sipping from a straw. Sneezing with the mouth open is advised.

• 6.

  Exercise caution when examining the surgical site by not pulling back the lips to reveal the incision line.

• 7.

  Expected symptoms: Let the patient know about typical postoperative side effects such as bleeding, discomfort, oedema, bruising and the presence of tiny bone fragments or granules.

• 8.

  Medication compliance: As directed by the surgeon, take all recommended medications, including anti-inflammatory drugs, antibiotics and nasal decongestants.

By providing clear and comprehensive instructions, patients can properly care for themselves after surgery and contribute to successful healing and recovery.

Implant success rate, survival rate and risk evaluation

The outcome of implantation in maxillary sinus augmentation can be influenced by various factors.^[37]

• 1.

  Surgical technique: The choice of surgical approach (lateral or crestal) and the tools used (piezoelectric surgery or rotary diamond burs) can impact the outcome of maxillary sinus augmentation. The lateral window technique has shown greater bone height gain, but both techniques have similar implant success rates.

• 2.

  Site factors: Bone anatomy and the presence of septa in the sinus can influence the success of implantation. A careful evaluation of these factors are necessary for determining the appropriate surgical approach and technique.

• 3.

  Timing of implantation: Implants can be placed simultaneously with sinus augmentation or in a delayed fashion. The timing of functional loading (immediate or delayed) also affects the outcome. Proper consideration of these factors are important for achieving successful results.

• 4.

  Bone grafting materials: The choice of grafting material can impact implant survival rates. Particulate grafts have shown higher survival rates compared to block grafts. The use of autogenous bone or a combination of autogenous and other graft materials does not significantly affect implant survival.

• 5.

  Barrier membrane: The use of a barrier membrane with rough-surfaced implants in the lateral window approach has shown favorable outcomes.

• 6.

  Implant-related factors: The type, length and width of the implant surface can affect the survival and success rates of implants inserted into grafted sinuses. Compared to machine-surfaced implants, rough-surfaced implants typically have higher survival rates.

• 7.

  Patient-related variables: Systemic disorders (such as bone diseases, diabetes and dental hygiene) and patient-related factors (such as smoking, parafunctional occlusion and oral hygiene) can all have an impact on the effectiveness of implantation. For best results, these aspects need to be carefully evaluated and managed.

To completely understand the impact of these parameters on the success and survival rates of implants inserted after sinus augmentation, more research is necessary, as different studies may report diverse outcomes.

Complications

Complications can arise during or after sinus augmentation procedures.^[38]

• 1.

  Schneiderian membrane perforation: This is the most common surgical complication, occurring in 7–35% of cases. Perforations are more likely to occur at sharp edges and ridges, such as spines or maxillary sinus septa. Small perforations may not require further management, but larger perforations in unfavorable areas must be closed and covered to prevent graft loss. Techniques such as using a resorbable membrane and surgical adhesive can be employed for closure. In cases of very large perforations, further sinus lifts may need to be postponed.

• 2.

  Prevalence of sinus membrane perforations: Studies have reported varying prevalence rates of sinus membrane perforations, with sizes ranging from less than 5 mm to larger than 10 mm.

• 3.

  Bleeding: Bleeding from small vessels in the exposed membrane can usually be controlled spontaneously or with light gauze pressure. Care must be taken to avoid massive bleeding due to arterial anastomoses of the alveolar antral artery. Precautions during osteotomy should be taken to avoid damage to these vessels.

• 4.

  Implant migration into the maxillary sinus: This is a potential complication that may occur at different stages, including several days post-implantation, during abutment connection surgery or even years later. Prompt removal of the migrated implant is necessary once diagnosed.

• 5.

  Pre-existing antral pathologies: Procedures for sinus augmentation might be complicated by conditions including rhinosinusitis, odontogenic sinus disorders, pseudocysts, retention cysts and mucoceles. Before beginning sinus augmentation, it is crucial to recognize and treat these disorders appropriately.

It is crucial to carefully plan the treatment, select suitable patients and adhere to appropriate techniques to minimize the risk of complications during sinus augmentation procedures. Additionally, regular follow-up and prompt management of any complications that may arise are essential for achieving successful outcomes.