Implant-prosthetic rehabilitation of the atrophic posterior mandible with additively manufactured custom-made subperiosteal implants: a cohort study

1. Scientific Reference

• Full Title: Implant-Prosthetic Rehabilitation of the Atrophic Posterior Mandible with Additively Manufactured Custom-Made Subperiosteal Implants: A Cohort Study
• Authors: Luca Antonio Vaira, Antonio Biglio, Antonio Favro and collaborators.
• Journal: International Journal of Oral and Maxillofacial Surgery
• Year of Publication: 2024
• Volume: 53
• Pages: 533–540
• DOI: 10.1016/j.ijom.2024.01.003

2. Scientific Background

Implant rehabilitation of severely atrophic posterior mandibular regions represents one of the most complex situations in pre-implant surgery. When the residual bone height above the inferior alveolar canal becomes insufficient, conventional solutions generally rely on bone augmentation techniques, the use of short implants, or inferior alveolar nerve lateralization.

However, these approaches present certain limitations. Bone grafting procedures often require multiple surgical interventions and remain associated with non-negligible failure rates. Implants placed in reconstructed sites may also exhibit higher failure rates than those inserted into native bone. As for nerve lateralization, it remains a technically demanding procedure with a risk of persistent neurosensory complications.

The emergence of next-generation custom-made subperiosteal implants, designed through three-dimensional digital planning and additive titanium manufacturing, opens new perspectives for patients presenting severe mandibular atrophy without the need for bone grafting.

3. Study Objective

The objective of this study was to retrospectively evaluate the clinical, radiological, and prosthetic outcomes obtained with custom-made 3D-printed subperiosteal implants for the rehabilitation of severely atrophic posterior mandibular regions.

The authors specifically analyzed:

• surgical safety;
• postoperative complications;
• peri-implant bone stability;
• soft tissue behavior;
• implant maintenance throughout the follow-up period.

4. Methodology

This retrospective cohort study included patients presenting severe posterior mandibular atrophy classified as Cawood and Howell classes V or VI, treated between September 2018 and August 2022 at the Department of Maxillofacial Surgery of the University of Sassari, Italy.

All implants were individually designed based on:

• high-resolution CBCT examinations;
• intraoral digital scans;
• a preliminary digital prosthetic project;
• patient-specific CAD/CAM planning.

The implants were manufactured from Grade V titanium using additive laser melting and subsequently fixed to the mandibular bone using osteosynthesis screws.

The provisional prosthesis was delivered ten days after surgery, while the definitive restoration was placed after six months of tissue healing.

5. Main Results

Study Population

The analysis included:

• 17 patients;
• 30 custom-made subperiosteal implants;
• mean age: 60.4 years;
• mean follow-up: 22.5 months (7 to 53 months).

Surgical Complications

No major intraoperative complications were observed.

The main postoperative side effect was moderate edema, which completely resolved within less than ten days.

Temporary hypoesthesia of the mental nerve territory was observed for six implants located beneath the nerve pathway. All cases recovered spontaneously after an average of 3.2 weeks.

Implant Survival

No implant loss was recorded during the follow-up period.

The implant survival rate observed in this cohort was therefore 100%.

Radiological Results

Regular CBCT examinations showed:

• no implant displacement;
• no screw loosening;
• no significant bone loss beneath the abutments;
• no mobility of the implant structures.

Statistical comparisons between the different follow-up time points revealed no significant variation in the bone-implant interface beneath the prosthetic abutments.

Soft Tissue Condition

No partial or total implant exposure was observed throughout the entire follow-up period.

Bleeding on probing remained low and decreased over time, reflecting good stability of the peri-implant tissues.

6. Clinical Analysis

This study provides particularly interesting data regarding a still poorly documented indication: the use of custom-made subperiosteal implants in posterior mandibular regions.

One of the strengths of the protocol lies in positioning the abutments directly on basal bone, which is considered less susceptible to resorption than residual alveolar bone. This approach aims to limit the progressive bone loss phenomena that historically contributed to the failures of first-generation subperiosteal implants.

The authors also emphasize the importance of several biomechanical principles:

• distancing the implant structure from the incision line;
• positioning fixation screws in areas of maximum mandibular resistance;
• preserving the mental nerve;
• distributing occlusal forces onto the underlying bone.

The complete absence of implant exposure is particularly remarkable considering the history of older subperiosteal implants, whose mucosal complications represented one of the main causes of long-term failure.

7. Clinical Applications

The results of this study mainly concern:

• patients presenting severe posterior mandibular atrophy;
• situations in which short implants are not feasible;
• cases in which bone augmentation is refused or contraindicated;
• patients wishing to limit the number of surgical interventions;
• complex implant-supported rehabilitations assisted by digital technologies.

This approach may represent an interesting alternative when the residual bone height above the inferior alveolar canal is insufficient for conventional implant placement.

8. Level of Evidence and Limitations

This publication corresponds to a single-center retrospective cohort study.

Several limitations must be considered:

• sample size limited to 17 patients;
• absence of a control group;
• absence of randomization;
• follow-up duration still insufficient to evaluate very long-term outcomes;
• inability to determine the optimal implant design.

The authors themselves emphasize the need for large-scale prospective studies to confirm these preliminary results.

9. Key Points

• 17 patients and 30 implants analyzed.
• Implant survival rate of 100%.
• No infections observed during follow-up.
• No implant exposure reported.
• No significant bone loss beneath the abutments.
• Temporary hypoesthesia resolved within a few weeks.
• Provisional prosthetic rehabilitation delivered after 10 days.
• Fully customized design through CAD/CAM and 3D printing.
• Potential alternative to bone grafting in severe mandibular atrophy.

10. Scientific Impact

This study contributes to the contemporary evolution of custom-made subperiosteal implants, whose resurgence is directly linked to advances in three-dimensional imaging, digital design, and additive manufacturing.

Unlike historical devices that suffered from high rates of exposure and implant loss, the new generations appear to offer improved biomechanical and tissue integration through extremely precise anatomical adaptation.

The presented results reinforce the idea that custom-made subperiosteal implants could become a relevant therapeutic solution for certain patients with severe mandibular atrophy when conventional reconstructive options are poorly suited.

11. Editorial Conclusion

This cohort study demonstrates that custom-made mandibular subperiosteal implants manufactured through 3D printing may constitute a reliable solution for the rehabilitation of severely atrophic posterior regions. The observed outcomes are particularly encouraging, with a 100% implant survival rate, absence of implant exposure, and remarkable bone stability throughout follow-up. Although these findings still require long-term validation through controlled prospective studies, they confirm the potential of next-generation subperiosteal implants as a credible alternative to complex bone augmentation procedures in cases of advanced mandibular atrophy.