▋ An Implant Protocol Designed for Asian Patients

Due to variations in clinical conditions and regional characteristics, Dr. Lee’s protocol differs from the Malo Clinic protocol proposed by Paulo Malo.

A simplified and regionally adapted workflow, termed the Imperial Clinic Surgical Protocol (Fig. 1, 2), was developed specifically for Asian patients.

The key principles include:

Reducing implant failure caused by cantilever forces
Minimizing the need for invasive surgical procedures
Achieving immediate loading with long-term stability while minimizing surgical trauma

If sufficient bone is present in the first molar region, conventional placement of six axial implants remains an option.

▋ Requirement of ≥ 4 mm Crestal Bone Height in Posterior Regions

The use of tilted implants increases the anterior–posterior (A–P) spread and reduces posterior cantilever. Additionally, longer implants allow greater engagement with cortical bone, improving load-bearing capacity.

Beyond the All-on-4 concept, this technique is also useful in partially edentulous posterior regions to avoid sinus augmentation procedures. A 2016 study by Queridinha BM reported a 5-year success rate of 96.7%.

In 2015, Enrico L. Agliardi proposed a classification for trans-sinus tilted implants in partially edentulous posterior maxilla (Fig. 3), recommending:

≥ 4 mm crestal bone height
≥ 4 mm apical bone

Dr. Lee also supports that at least 4 mm of crestal bone height significantly improves success rates.

In full-arch cases with more severe posterior bone deficiency, zygomatic implants should be considered. If patients are reluctant to accept zygomatic implants, trans-sinus tilted implants or pterygoid implants may be used as less invasive alternatives.

▋ Application of Trans-Sinus Tilted Implants

Trans-sinus tilted implants (Fig. 4, 5) are more technique-sensitive than conventional tilted implants.

Achieving adequate primary stability during surgery often allows only one or two attempts, requiring substantial clinical experience.

According to a 2013 study by Paulo Malo, 70 patients underwent All-on-4 treatment with immediate loading, including 83 trans-sinus tilted implants, achieving a 3-year survival rate of 96.3%.

No significant differences were observed in marginal bone resorption among straight implants, conventional tilted implants, and trans-sinus tilted implants.

▋ Guided Surgery vs. Freehand Technique

Guided implant surgery can reduce human error; however:

Tactile feedback is reduced
It is more difficult to detect deviations and adjust intraoperatively
Resistance from the anterior sinus wall may cause the implant to slip into the sinus cavity, leading to loss of primary stability

Therefore, Dr. Lee emphasizes that guided surgery should be performed only after mastering freehand techniques, allowing immediate modification of the surgical strategy when necessary.

▋ Dr. Lee’s Freehand Technique Tips
Tip 1: Create a lateral window and elevate the sinus membrane; use extraction socket angulation or guided reference to determine the correct implant trajectory
Tip 2: Maintain direct visualization to ensure the implant follows the prepared osteotomy and does not slip into the sinus
Tip 3: Understand implant design and prepare the osteotomy according to apical diameter
Tip 4: Graft bone into the sinus; if re-implantation is needed, a wider implant can be placed
Tip 5: Always prepare backup options such as zygomatic or pterygoid implants; in some cases, three implants may be temporarily loaded while awaiting osseointegration

If trans-sinus tilted implants are not suitable or primary stability is compromised, zygomatic or pterygoid implants should be used as rescue strategies.

In selected cases, three stable implants may temporarily support a prosthesis; however, this increases the risk of prosthesis fracture, overload, and reduced patient satisfaction.

▋ Clinical Case Application

The patient was elderly, with a history of treated and stable breast cancer and well-controlled diabetes. She presented with a low smile line and relatively soft bone quality.

Treatment was completed using tilted implants combined with the All-on-4 concept.

▋ Implant Selection

Implant selection is critical for trans-sinus tilted implant applications, particularly for achieving bicortical fixation.

Using Nobel Biocare as an example:

NobelSpeedy Ø4 mm → apical diameter: 2.2 mm
NobelSpeedy Ø5 mm → apical diameter: 2.0 mm

Primary stability can be enhanced through under-preparation of the osteotomy.

In contrast, NobelReplace Conical Connection features a round apex (2.56 mm), requiring larger apical drilling and offering reduced stability. Its maximum length (16 mm) also limits clinical applicability.

Highly aggressive self-tapping implants such as NobelActive can achieve high primary stability but carry the risk of over-cutting and stability loss. Additionally, their neck design may reduce cortical bone engagement (Fig. 6).

▋ Conclusion

Trans-sinus tilted implants demonstrate survival rates comparable to conventional tilted implants while being less invasive than zygomatic implants. They can be effectively integrated into the All-on-4 concept, reducing both surgical morbidity and cost.

However, the technique is highly sensitive and requires:

Backup planning (e.g., zygomatic implants)
Thorough understanding of implant design

If an oroantral communication occurs, a submerged healing approach is recommended before second-stage prosthetic loading to reduce the risk of sinusitis.

In addition to posterior-to-anterior trans-sinus approaches, anterior-to-posterior tilted implants—namely pterygoid implants (Fig. 7)—are another viable option. A 2023 systematic review (10 studies, 911 implants) reported a cumulative success rate of 95.5%.

However, due to proximity to the pterygoid plexus and branches of the maxillary artery, intraoperative bleeding risk is higher. Posterior positioning also complicates oral hygiene and prosthetic procedures.

For these reasons, Dr. Lee does not recommend pterygoid implants as the first-line option for posterior implant support. Further details will be shared in future reports.