▋ Introduction

As concluded in the previous article, the success rate of trans-sinus tilted implants is closely related to bone quality and density, as well as implant characteristics. A more conservative approach suggests that a crestal bone height of at least 4 mm is associated with a higher success rate.

If the crestal bone height is less than 4 mm or the bone quality is relatively soft, implants with specific diameters and lengths are required to compensate and improve the success rate.

▋ Case 1: Crestal Bone Height ≈ 3 mm with D4 Bone Quality
Surgical Procedure
A lateral window approach was performed to elevate the sinus membrane.
The implant insertion pathway was confirmed, with direct visualization of the apical opening.
A NobelSpeedy implant (5.0 × 18 mm) was placed, achieving a primary stability of 50 Ncm.
Bone graft material was placed beneath the elevated sinus membrane to promote bone regeneration.
A 30-degree multi-unit abutment (MUA) was installed.
Contingency Strategy
Primary stability 15–25 Ncm:
Consider submerging the implant without immediate loading, and connect the MUA after 4 months of osseointegration.
Primary stability < 15 Ncm:
Immediate conversion to a zygomatic implant is recommended.

Based on risk considerations, the author proposes a Trans-Sinus Tilted Implant Surgical Risk Assessment, in which different rescue strategies are applied according to varying crestal bone heights.

The first-choice implant is the NobelSpeedy system, as it offers lengths up to 25 mm, diameters up to 5 mm, and an apical diameter of only 2 mm—providing a significant advantage in achieving adequate primary stability.

In addition to engaging the piriform aperture, trans-sinus tilted implants may also be anchored in the buccal bone when the canine buttress is sufficiently thick. In such cases, intentional penetration of the buccal wall can be performed to achieve bicortical fixation. This technique is also beneficial for avoiding anterior implant interference.

This approach and its classification were also discussed by Ole T. Jensen (2014).

▋ Case 2: Crestal Bone Height < 3 mm with Postoperative Complication Management in a Heavy Smoker

When a large communication is created during osteotomy for a trans-sinus tilted implant, a conservative submerged approach should be adopted to reduce the risk of acute sinusitis.

In this case, implant failure resulted in a significant oro-antral communication. A buccal advancement flap was ultimately performed to achieve primary closure.

Analysis of Implant Failure
Strong occlusal force and poor patient compliance
Heavy smoking (>10 cigarettes per day)
Implant platform positioned within the sinus cavity, leading to bone resorption and oro-antral communication
Use of conical connection implants, which may transmit greater occlusal forces compared to external hex systems
Implant placed too posteriorly, with thinner bone and excessive angulation
Management and Salvage
Removal of the failed implant and immediate re-placement at a more anterior site with sufficient bone
Repair of the oro-antral communication using a buccal advancement flap
Occlusal adjustment to eliminate loading at the affected site

After five months of osseointegration, definitive prosthetic rehabilitation was initiated. The patient was instructed to wear an occlusal guard.

The full-mouth reconstruction was ultimately completed successfully.