Transnasal dental implant placement using PLACATE guidelines

Dr. Dan Holtzclaw describes one of the newest methods of implant treatment

Background

Treatment of severely atrophic maxillae often requires highly advanced procedures such as quad-zygomatic implants^1-3 (Figure 1) or customized subperiosteal implants (Figure 2).^4,5 Quad-zygomatic implant treatment has a long history of success, but requires significant surgical expertise due to limited malar bone availability and propinquity to anatomic structures such as the orbit and infraorbital nerve.⁶ Customized subperiosteal implants, on the other hand, are a promising new treatment option but have limited long-term follow-up data and significant expense.⁷ Transnasal dental implants have recently been introduced as another option for treatment of severely atrophic maxillae, specifically as an alternative to quad-zygomatic implant placement (Figure 3).⁸ Transnasal implants may serve as a replacement for anterosuperior zygomatic implants as they tangentially traverse the interior lateral nasal wall and achieve high insertion torque via 3 mm-5 mm of apical engagement in the confluence of the inferior concha, lateral nasal wall, and frontal process of the maxilla (Figure 4).^8-16

In 2019, the first report on transnasal implants, called the Vanderlim technique, was published in Brazil as an alternative to the quad-zygomatic implant configuration.⁸ In this publication, the authors described using 16 mm–25 mm long implants placed tangentially along the interior of the lateral nasal wall to achieve insertion torque of 40-50 Ncm for immediate loading. In 2021, Almeida published a case report documenting use of an “extra-long transnasal implant” as an alternative to the quad-zygoma,¹⁰ and Vanderlim supported his 2019 publication with a series of 12 cases using “transnasal implants placed using the Vanderlim technique” with follow-up of 2-26 months.⁹ In 2023, Holtzclaw published a textbook with a case series of seven transnasal implant cases performed by himself and other dental implant surgeons.⁶

While there were no transnasal dental implant articles published in 2022, case reports on a handful of patients were published by Oh, et al.,¹² and Sahin¹⁴ in 2023. In this same year, Holtzclaw published an article discussing protocols addressing atrophic maxillae which featured one case of unilateral transnasal implant treatment.¹⁷ In 2024, Sales echoed Holtzclaw’s 2023 publication with a case report on a unilateral transnasal implant in the treatment of an atrophic maxilla¹⁵ while Nunes, et al., published a case series of three patients treated with both unilateral and bilateral transnasal fixtures.¹³ Up to this point, all transnasal publications had been case reports or case series. This changed in late 2024 when Gelpi, et al., published a retrospective multi-center study of 45 transnasal implants placed in patients who underwent surgery between July 2021 and November 2023. In this largest study to date on transnasal implants, the survival rate was 100%, although mean follow-up was relatively short.

Initial guidelines for transnasal dental implant placement as noted in the initial publications by Vanderlim^8,9 and Almeida¹⁰:

1. Minimum bone volume of 3 mm for apical anchorage in the inferior concha and frontal process of the maxilla
2. Minimum bone height of 4 mm between the ridge of the maxilla and the nasal cavity
3. Insufficient premaxillary bone volume for the placement of two conventional implants
4. Insufficient bone volume for the placement of two zygomatic implants in a single malar process
5. Infraorbital nerve position which would be violated by placement of a zygomatic implant
6. Large concavity of the anterior maxillary wall which may facilitate soft tissue recession with placement of a zygomatic implant
7. Avoid placing transnasal implants in wide nasal cavities
8. Avoid tearing the nasal mucosa during elevation

PLACATE guidelines

In 2023, Holtzclaw expanded the guidelines for transnasal dental implant placement with (P)re(LAC)rimal (A)ssesment of (T)ransnasal Implant (E)ngagement — PLACATE. ⁶ Under PLACATE guidelines, appropriate transnasal dental implant candidates must meet the following parameters:

1. Simmen 2 or 3 classification of the nasolacrimal canal
2. Prelacrimal bone width ≥3 mm
3. Subnasal bone height ≥2 mm
4. Vertical measurement from residual subnasal bone, or anticipated anterior alveolar ridge reduction level, to prelacrimal bone engagement point that does not exceed 25 mm

Failure to meet all four PLACATE criteria prevented a patient from being an appropriate transnasal implant candidate.

A recent 2025 retrospective review by Holtzclaw, et al.,¹¹ evaluated anonymized cone beam computer tomography (CBCT) scans from 300 sequential referrals using PLACATE guidelines to determine transnasal dental implant feasibility. In this study, inferior conchae were initially located in the coronal plane, and imaging crosshairs were positioned just superior to this structure in the axial plane. To evaluate the ipsilateral and contralateral transnasal engagement points, imaging crosshairs were next positioned over each concha in the sagittal plane. This prelacrimal engagement point, sometimes referred to as the “Z-Point”,^6,12 was then evaluated according to PLACATE guidelines as follows:

1. Simmen classification19 determined by measurement from the external aspect of the frontal maxilla to the most anterior aspect of the nasolacrimal canal (Figure 5)
2. Mediolateral measurement of prelacrimal bone width (Figure 6)
3. Vertical measurement of subnasal bone height
4. Vertical measurement from subnasal bone to prelacrimal bone engagement point (Figure 7)

The results of this study found that only 30.54% of patients qualified for transnasal dental implants anatomically. The most common disqualification was inadequate prelacrimal bone width which affected 49.71% of patients. Excessive subnasal bone height, which could foster placement of conventional dental implants, eliminated 28.74% of patients. The third most common reason for patient disqualification from transnasal dental implant placement, 22.16% of patients, was Simmen 1 classification which would result in potential violation of the nasolacrimal canal.

Case report

An 80-year-old male with a relatively clean medical history was referred for full-arch immediately loaded maxillary implant treatment. The patient had been previously treated with maxillary dental implants in a traditional All-on-X approach. The referring clinician noted that the patient’s bone was extremely “soft” and that insertion torque for most of the implants was very low. Although these implants were not immediately loaded, they ultimately failed and created large oroantral communications. While the communications were ultimately closed, extremely large defects resulted in the floor and walls of the maxillary sinuses (Figure 8). CBCT analysis revealed a significantly thickened left Schneiderian membrane and occluded osteomeatal complex. The patient was referred to ENT for a Functional Endoscopic Sinus Surgery (FESS) procedure. Upon healing, a new CBCT was taken and evaluated for potential treatment.

Due to the atrophic nature of the maxilla, treatment following the PATZi protocol was planned.^6,17,20 CBCT evaluation revealed pterygomaxillary bone appropriate for pterygoid implants allowing for posterior arch support and cantilever elimination. The zygomas were of adequate height and width to accommodate multiple zygomatic implant fixtures bilaterally. PLACATE guidelines were used to evaluate the patient for potential treatment with transnasal implants. With Simmen 3 nasolacrimal canal classification, ≥ 3 mm of prelacrimal bone, ≥2 mm subnasal bone, and ≤ 25 mm to the Z-point, the patient satisfied all PLACATE parameters. Accordingly, a treatment plan of bilateral pterygoid, single zygomatic, and transnasal implants was agreed upon.

Following the induction of general anesthesia, extraoral and intraoral local anesthesia was applied. To avoid exposing the large subantral bony defects, mini-flaps were elevated at the pterygoid landing areas to expose the hamular notch. The pterygoid fossa was identified via probing, and pterygoid implant placement ensued. Following the PATZi protocol, bilateral pterygoid implants were placed first and both achieved insertion torque between 45+ Ncm.

Following PATZi, anterior support was sought next. As such, the nasal mucosa was elevated to expose the floor of the nasal cavity and the bone of the inferior conchae. A pair of 25 mm transnasal implants were placed, and each achieved high insertion torque of 45+ Ncm (Figures 9-11). Continuing with the PATZi protocol and treatment plan, 42.5 mm long zygomatic implants were placed in both zygomas. The zygomatic implants were placed using an extrasinus approach and both achieved insertion torque of 45+Ncm. Buccal fat pedicles were advanced bilaterally to cover extrasinus portions of the zygomatic implants, and flap closure was achieved with 4-0 chromic gut suture. The patient was immediately temporized with a screw-retained transitional bridge (Figure 12), and a final zirconia restoration was delivered after 8 months of healing (Figure 13).

Discussion

With fewer than 200 published cases and less than 7 years of follow-up, transnasal dental implants are one of the newest styles of treatment in implant dentistry. The limited number of studies which have evaluated this treatment have generally found transnasal implants to be of diameters ranging from 3.5 mm to 4.2 mm and lengths of 20 mm-25 mm.^6,8-16 Having multicortical anchorage points in subnasal and prelacrimal bones, transnasal implants have been found to have high insertion torques appropriate for immediate loading.^6,8-16 A unique feature of transnasal dental implants is that the midbody of the fixture remains exposed in the nasal cavity. Regarding exposed transnasal implant threads in the nasal cavity, there is currently no consensus on the need for grafting.

Although transnasal implants can be placed under direct visualization, their proximity to certain antatomic structures requires intimate anatomic knowledge and surgical skill. Iatrogenic damage to Kesselbach’s complex may result in excessive hemorrhaging while tearing of the nasal mucosa may lead to oronasal fistulae.6 Careless mucoperiosteal flap elevation can result in damage to the infraorbital nerve, and poor placement of transnasal implant fixtures may lead to dacryostenosis, epiphora, and dacryocystitis.6 Fortunately, to date, published studies have shown few complications with transnasal dental implants and few failures.

Conclusion

When anatomic conditions are appropriate, transnasal dental implants are a promising alternative to anterosuperior zygomatic implant fixtures in quad-zygo treatment. While continually emerging updates such as PLACATE guidelines are improving the safety and predictability of transnasal dental implants, more studies with longer follow-up times are needed to confirm the reliability of this relatively new treatment.