Fabrication of a Mandibular Implant-Retained Overdenture Using an Existing Subperiosteal Implant: A Clinical Report

Mahnaz Arshad, Nourin Khoramshahi, Gholamreza Shirani

Full text link: https://pubmed.ncbi.nlm.nih.gov/38571903/

Fabrication of a Mandibular Implant-Retained Overdenture Using an Existing Subperiosteal Implant: A Clinical Report

1. Scientific Reference

• Study Title: Fabrication of a Mandibular Implant-Retained Overdenture Using an Existing Subperiosteal Implant: A Clinical Report
• Authors: Mahnaz Arshad, Nourin Khoramshahi, Gholamreza Shirani
• Journal: Clinical Case Reports
• Year of Publication: 2024
• DOI: 10.1002/ccr3.8662

2. Scientific Background

Managing severe mandibular atrophy remains one of the greatest challenges in implant dentistry and oral and maxillofacial surgery. Progressive alveolar bone resorption following tooth loss can significantly limit the placement of conventional endosseous implants while also increasing the risk of pathological or traumatic mandibular fractures. These anatomical limitations often require alternative reconstructive approaches to restore both function and oral rehabilitation.

Recent advances in digital imaging, three-dimensional planning, CAD/CAM technologies, and additive manufacturing have renewed interest in custom-made subperiosteal implants for patients with advanced bone loss. These patient-specific implants offer a potential treatment option when conventional implant placement or extensive bone grafting is not feasible. This clinical report explores a complex rehabilitation in which a custom subperiosteal implant was initially used to stabilize a mandibular fracture before serving as the foundation for implant-retained prosthetic rehabilitation. Beyond describing a technical solution, the report emphasizes the importance of integrating surgical and prosthetic planning from the earliest stages of treatment.

3. Study Objective

The primary objective of this clinical report was to describe the prosthetic rehabilitation of a completely edentulous patient who had previously received a customized mandibular subperiosteal implant for fracture stabilization. More specifically, the authors aimed to present the management of a prosthetic complication caused by inadequately designed ball abutments that became submerged beneath the peri-implant soft tissues during healing. The report also highlights the importance of interdisciplinary collaboration between oral surgeons and prosthodontists when planning complex implant-supported rehabilitations.

4. Methodology

This publication is a single-patient clinical case report, representing a low level of clinical evidence but providing valuable information regarding an uncommon clinical situation.

The patient was a 64-year-old completely edentulous woman who had worn complete dentures for approximately thirty years, resulting in severe mandibular alveolar bone resorption. Following a fall, she developed a mandibular fracture that subsequently healed in malunion. Due to insufficient bone volume, conventional endosseous implant placement was considered unsuitable, and treatment involved surgical placement of a customized subperiosteal implant to stabilize the fracture.

After healing, the prosthetic phase revealed that the implant’s ball abutments were too short and had become covered by keratinized soft tissue. Surgical exposure was attempted but failed to provide a lasting solution. Consequently, the clinical team designed and fabricated a custom connector that effectively lengthened the abutments, allowing fabrication of a mandibular implant-retained overdenture. The prosthetic workflow included customized impressions, master cast fabrication, a cobalt-chromium framework, and delivery of the definitive overdenture. Clinical follow-up extended over five years.

5. Main Findings

The customized prosthetic solution successfully restored the functionality of the existing subperiosteal implant despite the unfavorable position of the original ball attachments. By incorporating a patient-specific connector, the clinicians were able to elevate the attachment system above the surrounding soft tissue without modifying or replacing the osseointegrated implant.

According to the authors, delivery of the implant-retained overdenture resulted in noticeable improvements in facial appearance and speech. The patient underwent scheduled postoperative evaluations beginning immediately after prosthesis delivery and continuing with annual reviews. Throughout the reported five-year follow-up, no prosthetic or implant-related complications were identified.

The report also emphasizes that this complication was likely preventable. The authors attribute the problem primarily to inadequate preoperative prosthetic planning, including the absence of prosthodontic consultation and the lack of a radiographic stent during implant design. They suggest that these planning deficiencies contributed directly to the insufficient height of the original ball abutments.

6. Clinical Analysis

This case report demonstrates that the long-term success of complex implant rehabilitation depends not only on surgical execution but also on comprehensive prosthetic planning. Although the customized subperiosteal implant successfully stabilized the mandibular fracture, its prosthetic design did not adequately anticipate the requirements of the definitive overdenture. As a result, the ball abutments remained submerged beneath the keratinized mucosa, preventing conventional prosthetic rehabilitation.

The most valuable contribution of this report lies in the management of this unexpected complication. Rather than replacing the implant or performing extensive additional surgery, the clinicians designed a customized connector that effectively extended the ball attachments above the soft tissue level. This patient-specific prosthetic solution preserved the existing implant while allowing successful fabrication of a mandibular implant-retained overdenture. The approach illustrates how individualized prosthetic design can compensate for certain implant design limitations in carefully selected clinical situations.

The authors also highlight an important lesson regarding digital implant planning. Modern technologies—including three-dimensional imaging, CAD/CAM design, and additive manufacturing—can significantly improve treatment accuracy, but their success depends on interdisciplinary communication. In this case, the absence of prosthodontic involvement during implant planning and the lack of a radiographic stent contributed to a design that did not adequately accommodate future prosthetic rehabilitation. The report therefore reinforces the importance of integrating surgical, prosthetic, and digital workflows from the earliest planning stages.

Although the reported five-year outcome is encouraging, the findings should be interpreted with caution. As a single clinical case, the report cannot establish the predictability or long-term performance of this approach in broader patient populations. Instead, it provides an informative example of clinical problem-solving that may guide practitioners facing similar complications with customized subperiosteal implants.

7. Clinical Applications

The clinical observations presented in this report are particularly relevant for the rehabilitation of completely edentulous patients with severe mandibular bone atrophy, especially when conventional endosseous implant placement is not feasible. They also illustrate the potential role of customized subperiosteal implants in managing complex mandibular reconstruction following fracture in compromised alveolar bone.

Beyond the specific technical solution, this report underscores the importance of comprehensive treatment planning in implant dentistry. Digital planning, customized implant design, and close collaboration between oral surgeons, prosthodontists, and dental technicians appear essential to minimize prosthetic complications and optimize long-term rehabilitation. While the described connector represents a successful solution in this individual patient, further clinical evidence is required before similar approaches can be considered broadly applicable.

8. Level of Evidence, Limitations, and Transparency

This publication is a single-patient clinical case report, representing a low level of scientific evidence. Although case reports cannot establish treatment efficacy or generate clinical recommendations, they provide valuable documentation of rare clinical situations, unexpected complications, and innovative technical solutions.

The strength of the evidence is limited by the inclusion of only one patient, with no control group, statistical analysis, or comparison with alternative treatment approaches. Consequently, the reported outcomes cannot be generalized beyond this individual case. Nevertheless, the five-year clinical follow-up offers meaningful insight into the medium-term stability of the customized prosthetic solution.

The authors report no financial or non-financial conflicts of interest related to this publication and state that no external funding was received for the study. Commercial materials mentioned in the report are identified solely for clinical documentation purposes. Written informed consent was obtained from the patient, and the authors indicate that study data are available upon request.

9. Key Study Highlights

• Study design: Clinical case report.
• Level of evidence: Low (single-patient case report).
• Study population: One 64-year-old completely edentulous woman with severe mandibular atrophy and a mandibular fracture.
• Number of patients: 1.
• Number of implants: One customized mandibular subperiosteal implant.
• Follow-up period: 5 years.
• Primary outcome evaluated: Feasibility of fabricating an implant-retained mandibular overdenture after prosthetic complications associated with a previously placed customized subperiosteal implant.
• Main finding: A custom-designed connector successfully extended the submerged ball abutments, allowing fabrication of a stable mandibular implant-retained overdenture without reported complications during the five-year follow-up.
• Scientific conclusion: This clinical report demonstrates that customized prosthetic components may successfully compensate for design limitations of an existing subperiosteal implant while emphasizing the importance of comprehensive preoperative surgical and prosthetic planning.
• Main limitations: Single-patient report, absence of a control group, no comparative analysis, and findings that cannot be generalized to larger patient populations.

10. Scientific Impact

This publication contributes to the growing body of literature supporting the contemporary use of custom-made subperiosteal implants in highly challenging clinical situations involving severe mandibular bone resorption. Rather than introducing a new implant system, the report provides practical insight into managing an uncommon prosthetic complication after successful surgical treatment.

Its principal scientific contribution is the demonstration that individualized prosthetic engineering can preserve a functioning customized implant even when the original prosthetic design proves inadequate. The case also reinforces a broader concept increasingly recognized in digital implant dentistry: successful rehabilitation depends on integrating prosthetic objectives into the earliest phases of surgical planning. Digital workflows, three-dimensional imaging, and additive manufacturing offer significant advantages, but their full potential can only be realized through coordinated interdisciplinary treatment planning.

Although this report does not provide evidence sufficient to validate a new treatment protocol, it documents a reproducible clinical workflow that may assist clinicians confronted with similar complications. It also identifies an area where additional clinical research—including larger case series and prospective studies—would help clarify the predictability and long-term performance of customized prosthetic modifications for subperiosteal implant rehabilitation.

11. Editorial Conclusion

This clinical case illustrates how a customized prosthetic solution can successfully overcome an unforeseen complication associated with a patient-specific subperiosteal implant while preserving the original surgical reconstruction. Beyond the technical aspects of the rehabilitation, the report highlights the critical importance of multidisciplinary collaboration and comprehensive digital treatment planning in complex implant dentistry. Although the favorable five-year outcome is encouraging, the conclusions should be interpreted within the limitations of a single case report, and further clinical evidence is needed before broader clinical recommendations can be established.