A Paradigm Shift in Guided Bone Regeneration: Crestal Approach to Sinus Lift Procedures

A paradigm shift is underway in sinus lift procedures, that challenges the conventional wisdom that once deemed it a foolproof technique with predictable outcomes: “the low window sinus lift” . Dr. Luigi Canullo, a leading authority in implant dentistry, has emerged as a proponent for revisiting the crestal approach, advocating for a deeper understanding of the underlying biology and clinical nuances. In a recent live webinar, Dr. Canullo shed light on the intricacies of this surgical technique, prompting a reconsideration of established practices.

In this blog post, we’ll explore his perspectives on the crestal approach, the key biological considerations, and recommended techniques, tools, and materials.

Early Perspectives on Sinus Lift Procedures^1-3

In the early days of sinus lift procedures, there was a prevailing perception that it was a relatively straightforward technique. Bone regeneration was seen as a simple mathematical equation based on two variables: the correct approach and the use of correct materials. The recommendation was^1,2:

• For cases with a vertical bone height of 8 millimeters: The crestal approach was suggested along with immediate implant insertion and an expected four to six months of healing^1,2.
•  For cases with a vertical bone height of 4 to 8 millimeters: The lateral approach was preferred with an immediate implant insertion and an expected six months of healing^1,2.
• For cases with a vertical bone height of less than 3 to 4 millimeters: The lateral approach with a delayed implant insertion was suggested six to nine months after the bone graft insertion and restored after an additional six months^1,2.

The strongly suggested graft material was bovine bone matrices³.

However, Dr. Canullo challenges this oversimplified approach to sinus lift procedures, emphasizing the necessity for precision and expertise. He asserts that the perception of sinus lifts as straightforward techniques overlooks the intricate biological dynamics at play. According to Dr. Canullo, relying solely on a formulaic approach neglects the multifaceted nature of the procedure, which involves various biological factors. He argues for a more nuanced understanding, urging clinicians to consider the complexity and variability inherent in the crestal approach.

Key Biological Considerations

According to Dr. Canullo, the successful regeneration of bone tissue is contingent upon several key biological considerations, each playing a critical role in the overall outcome of the procedure. Notably, his conclusions focus on a vertical bone height of less than six to seven millimeters⁴, based on a preponderance of literature supporting the efficacy of implants ranging from four to six millimeters.

Buccal-Palatal Measurement

The success of bone regeneration is closely linked to the width of the horizontal measurement of the lateral-medial dimensions⁵. This measurement, which should be taken 10 millimeters away from the bone crest, serves as an indicator of regenerative potential. When this width measures less than 12 millimeters, it suggests a high likelihood of successful bone regeneration. Conversely, widths wider than 12 millimeters⁵ indicate a lower regenerative potential.

This relationship is attributed to the contact between the basal bone and the graft material. Insufficient contact between these elements can compromise the integration process, which may result in implant failure^6-7. Therefore, ensuring adequate contact is crucial for optimizing the outcomes of bone regeneration procedures ^6-7.

Sinus Membrane Integrity

The Schneiderian membrane consists of multiple layers including the epithelium, lamina propria, and periosteum. Typically, it measures between one and three millimeters in width, rarely exceeding this range. Individuals who smoke often have thinner and more delicate mucosa layers.⁸

For the success of the sinus lift procedure, the sinus membrane must remain intact without any tears. A preserved periosteum indicates higher-quality regeneration compared to cases where the periosteum is torn.⁹

Research indicates that wider membranes are associated with a lower risk of perforation. Thin mucosa is prone to perforation in 41% of cases, whereas thicker mucosa perforates only 18% of the time.¹⁰

 Upon inserting graft material into narrow sinuses, there is increased pressure, leading to the possibility of complete detachment. However, with wider sinuses, there is a high risk of inserting the graft material without detachment from the sinus elevator, leading to an over-compression of the mucosa and a fracture of the mucosa itself.^11,12

Minimizing Tearing

Dr. Canullo has several recommendations for how to minimize tearing, including:

• Minimizing the inflammatory response of the mucosa with antibiotic coverage and or anti-inflammatory drugs¹³
• Using micro-instruments to avoid tension during manual sinus membrane elevation¹⁴
• After elevating the sinus mucosa, inserting a thin layer of collagen or PRP, to prevent any potential mucosa microtearing from allowing graft material contamination.^{15, 16}
• Using a spongey material like OSSIX^TM Bone, which also helps avoid pushing the graft material into the sinus cavity and has been demonstrated to provide bone regeneration^17,18.

Surgical Technique

Let’s explore Dr. Canullo’s recommendations for each step of performing the crestal approach.

1. Digital planning: Dr. Canullo strongly advocates for the use of digital planning, which provides crucial insights into implant placement and bone dimensions. This technology aids in determining the precise location for implant insertion and assessing the vertical bone width, essential for navigating the sinus membranes effectively.
2. Approaching the bone by raising the flap
3. Approaching the membrane by creating a bone perforation
4. Membrane elevation: Dr. Canullo recommends a minimally invasive approach involving a slight palatal incision. This technique reduces post-operative discomfort while enabling the gentle placement of surgical guides. Specific burs designed to minimize mucosal invasion should be utilized to decorticalize the sinus floor, followed by the use of rounded burs to prepare the osteotomy site for micro-elevators. Micro-elevators are crucial for gently detaching the membrane without causing mucosal tears¹⁹.
5. Membrane rescue: The use of a collagen or PRP membrane provides an effective solution for reinforcement and repair²⁰.
6. Graft insertion: OSSIX^TM Bone should be meticulously prepared into small pieces and carefully inserted into the osteotomy site. Gentle manipulation with a plugger ensures proper graft placement within the sinus cavity. Finally, implant insertion proceeds cautiously to avoid exerting excess pressure on the graft material or membrane.

Conclusion

In summary, Dr. Canullo offers several valuable insights into optimizing sinus lift procedures:

• Biologically Rethink the Crestal Approach: Dr. Canullo advocates for a nuanced understanding of the crestal approach to sinus lifts, emphasizing the importance of considering biological factors.
• Ensure Graft Material Contact with Bone: Direct contact between graft material and bone is paramount for successful regeneration.
• Utilize Appropriate Tools: Selecting the right tools for elevation and graft insertion is crucial.

Dr. Luigi received financial support from Dentsply Sirona

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