Long-term Results of Subperiosteal Implants Combined with Cancellous Bone Grafts

D S Bloomquist

Full text link : https://pubmed.ncbi.nlm.nih.gov/7042938/

Long-term Results of Subperiosteal Implants Combined with Cancellous Bone Grafts

1. Scientific Reference

• Study Title: Long-term Results of Subperiosteal Implants Combined with Cancellous Bone Grafts
• Author: Dale S. Bloomquist
• Journal: Journal of Oral and Maxillofacial Surgery
• Year of Publication: 1982
• DOI: Not specified in the provided document.

2. Scientific Background

Managing patients with advanced mandibular ridge resorption has historically been one of the most challenging situations in oral and maxillofacial surgery. Severe alveolar bone loss compromises denture stability and function, often leaving clinicians with limited reconstructive options. Before the widespread adoption of modern endosseous dental implants, subperiosteal implants represented an alternative for patients whose bone anatomy prevented conventional implant placement.

To improve the biological environment surrounding these implants, a combined approach incorporating cancellous bone and bone marrow grafting was introduced. The rationale was to restore alveolar height while providing additional osseous support beneath the implant framework. Although early reports suggested encouraging outcomes, long-term clinical evidence remained limited. This study was designed to evaluate whether combining subperiosteal implants with cancellous bone grafts could improve long-term clinical performance compared with conventional subperiosteal implant therapy.

3. Study Objective

The primary objective of this investigation was to assess the long-term clinical outcomes of subperiosteal implants placed in combination with cancellous bone and bone marrow grafts in patients with severe mandibular atrophy.

More specifically, the authors sought to determine whether bone grafting could maintain reconstructed alveolar bone, prevent progressive implant settling, reduce framework exposure through the mucosa, and ultimately provide clinical advantages over traditional subperiosteal implant techniques.

4. Methodology

This publication represents a long-term observational case series.

Between 1972 and 1976, 23 subperiosteal implants combined with cancellous bone grafts were placed at the University of Washington. Nineteen patients treated with a modified surgical protocol were available for long-term evaluation after a minimum follow-up period of 4.5 years.

The authors introduced several technical refinements to the original procedure, including reduced surgical exposure during impression taking, increased framework height, harvesting cancellous bone from the posterior iliac crest, and modifications intended to improve soft tissue management around the transmucosal posts.

Clinical examinations and serial radiographic assessments were performed to evaluate implant stability, graft behavior, soft tissue complications, and overall treatment outcomes throughout the follow-up period.

5. Main Findings

The long-term evaluation produced mixed clinical outcomes. Of the 19 patients available for review after at least 4.5 years of follow-up, three implants had already been removed, while three additional cases were considered likely to require removal because of persistent clinical problems. According to the authors, most early failures occurred during the initial phase of the clinical experience and were attributed primarily to technical challenges encountered before modifications to the surgical protocol were introduced.

The most consistent finding was that long-term complications were predominantly associated with the soft tissue interface rather than with mechanical instability of the implant itself. Mobile mucosa surrounding the transmucosal posts created areas that were difficult for patients to clean effectively, promoting chronic inflammation and recurrent infections. Among the reviewed patients, 13 presented with unsatisfactory mucosal conditions around at least one post, 12 experienced at least one infection, 4 developed framework exposure, and 5 exhibited sequestration of a fixation screw. Persistent epulis formation around one or more posts was also reported in three patients.

Radiographic follow-up suggested that the cancellous bone graft was gradually replaced by newly formed bone. The maturation process appeared relatively slow, with the graft resembling native basal bone approximately one year after surgery. Importantly, clinically significant bone loss was not observed except in patients with persistent infection. Although many implants remained mechanically stable throughout follow-up, the authors concluded that the combined procedure did not demonstrate a meaningful long-term advantage over conventional subperiosteal implants.

6. Clinical Analysis

This study provides valuable historical insight into one of the earliest attempts to improve the biological performance of subperiosteal implants through simultaneous bone augmentation. Rather than focusing solely on implant survival, the investigation explored whether increasing mandibular bone volume could address several biological limitations traditionally associated with subperiosteal implant therapy.

One of the most relevant observations concerns graft behavior. Serial radiographic examinations suggested that the cancellous graft underwent progressive replacement by newly formed bone, supporting the concept that the reconstructed ridge could remain relatively stable over time. This finding is clinically important because one of the principal concerns surrounding the technique was the possibility that the graft would eventually resorb, leaving the framework unsupported within soft tissues. Based on the observations reported in this series, the authors found no convincing evidence that this scenario represented the primary cause of failure.

Instead, the study clearly identifies the mucosal–metal interface as the principal biological challenge. Despite satisfactory implant stability in many patients, the emergence of the transmucosal posts through mobile soft tissue frequently resulted in plaque accumulation, chronic inflammation, and recurrent infections. These findings anticipated concepts that have become fundamental in contemporary implant dentistry, where the quality and stability of peri-implant soft tissues are now recognized as essential determinants of long-term treatment success.

The authors also demonstrate how progressive refinements of the surgical protocol appeared to reduce certain complications. Less invasive impression techniques, improved graft harvesting, greater framework elevation, and modifications in flap design all contributed to technical improvements. Nevertheless, none of these changes completely eliminated the soft tissue complications that remained the dominant limitation of the procedure.

Another noteworthy aspect of the paper is the authors’ balanced interpretation of their own results. Although many patients expressed high levels of satisfaction because of improved denture retention and masticatory function, the investigators avoided overstating the clinical value of the technique. They concluded that their findings did not support a clear superiority over conventional subperiosteal implants and acknowledged that alternative reconstructive procedures were becoming increasingly attractive for patients with severely atrophic mandibles. This cautious interpretation strengthens the scientific credibility of the study and highlights the importance of long-term clinical follow-up before adopting new surgical protocols.

7. Clinical Applications

The findings of this study are particularly relevant to the management of patients with severe mandibular atrophy, a condition that historically limited the effectiveness of conventional prosthetic rehabilitation. At the time the study was conducted, combining a subperiosteal implant with cancellous bone grafting represented an attempt to restore alveolar ridge height while improving denture support and protecting exposed neurovascular structures.

Although this surgical approach has largely been replaced by contemporary implant protocols and advanced bone reconstruction techniques, the study continues to offer valuable lessons for modern implant dentistry. Its observations emphasize that successful implant rehabilitation depends not only on achieving adequate bone support but also on establishing healthy and stable peri-implant soft tissues. The high frequency of complications associated with the transmucosal posts illustrates how biological factors can ultimately determine long-term treatment outcomes, even when implant stability is maintained.

From a contemporary perspective, this article serves primarily as an important historical reference documenting the evolution of implant rehabilitation strategies for edentulous patients with advanced alveolar bone loss. It also reinforces the importance of meticulous surgical planning, careful soft tissue management, and long-term maintenance protocols in complex implant-supported prosthetic rehabilitation.

8. Level of Evidence, Limitations, and Transparency

This publication should be classified as a retrospective observational case series with long-term follow-up, representing a low level of clinical evidence when compared with randomized controlled trials or prospective comparative studies.

Several methodological limitations should be considered when interpreting the findings. The investigation included a relatively small number of patients and lacked a control group treated with an alternative surgical approach. In addition, the surgical protocol evolved throughout the study period as technical modifications were introduced, making direct comparison among all treated cases more difficult. The authors also acknowledge that radiographic assessment of bone remodeling was relatively limited, reducing the precision of quantitative evaluation.

Importantly, the discussion remains appropriately balanced. Rather than advocating widespread adoption of the technique, the investigators conclude that their experience neither clearly supports nor definitively discourages its use. No conflicts of interest, commercial affiliations, or industry sponsorship are reported in the information provided.

9. Key Study Highlights

• Study design: Retrospective observational case series with long-term follow-up.
• Level of evidence: Low.
• Study population: Patients with severe mandibular alveolar resorption.
• Number of implants: 23 combined subperiosteal implants with cancellous bone grafts.
• Patients evaluated: 19.
• Minimum follow-up: 4.5 years.
• Primary outcome: Long-term clinical performance of subperiosteal implants combined with cancellous bone and bone marrow grafting.
• Principal findings: Bone grafts appeared to undergo gradual replacement by new bone, while complications involving peri-implant soft tissues remained the most common clinical problem.
• Most frequent complication: Infection and unfavorable soft tissue conditions surrounding the transmucosal posts.
• Scientific conclusion: The combined grafting approach produced outcomes comparable to conventional subperiosteal implants but did not demonstrate a significant long-term clinical advantage.
• Main limitations: Small sample size, absence of a control group, protocol modifications during the study period, and limited methodological strength.

10. Scientific Impact

This publication represents one of the earliest long-term clinical evaluations of combining subperiosteal implants with cancellous bone grafting for the rehabilitation of severely resorbed mandibles. Beyond documenting clinical outcomes, the study provides an important critical assessment of a surgical concept that sought to overcome the biological limitations of traditional subperiosteal implant therapy.

The findings suggest that although bone augmentation successfully contributed to maintaining reconstructed alveolar volume, it did not eliminate the biological complications associated with the transmucosal implant design. By identifying soft tissue management—rather than osseous support—as the principal determinant of long-term complications, the study helped shift scientific attention toward peri-implant tissue biology, an area that has become central to contemporary implant dentistry.

Equally important is the authors’ conservative interpretation of their results. Rather than presenting the technique as a definitive solution, they openly acknowledge its limitations and describe their gradual transition toward alternative reconstructive procedures. This balanced perspective enhances the credibility of the study and illustrates the value of rigorous long-term follow-up in evaluating innovative surgical techniques before they become widely adopted.

11. Editorial Conclusion

Bloomquist’s study remains an important historical contribution to the development of implant dentistry and oral reconstructive surgery. Its long-term observations demonstrate that combining cancellous bone grafts with subperiosteal implants can preserve reconstructed bone architecture, yet this advantage alone is insufficient to overcome the biological challenges associated with transmucosal implant components. The study ultimately highlights that successful implant rehabilitation requires more than mechanical stability, emphasizing the critical role of healthy peri-implant soft tissues in achieving durable clinical outcomes. Although contemporary implantology has evolved considerably since this work was published, its findings continue to provide valuable insight into the biological principles that underpin modern implant-supported rehabilitation.