Rethinking Implant Planning in the Posterior Maxilla: Why Prosthodontics Should Lead the Way
When Implant Planning Is More Than Just Bone and Surgery
Dental implant treatment in the posterior maxilla is widely known as one of the most challenging areas in implant dentistry. Limited bone volume, poor bone quality, and the presence of the maxillary sinus often complicate both surgical and restorative decisions.
Traditionally, implant planning in this region has focused heavily on surgical factors such as bone height, sinus augmentation, and implant placement techniques. However, this approach may overlook a crucial question:
What kind of prosthesis are we actually trying to deliver?
In their recent article published in the British Dental Journal, King and Schofield argue that implant planning in the posterior maxilla should be restoratively driven first, not surgically driven.
Why the Posterior Maxilla Is Prosthodontically Complex
Unlike other regions of the mouth, the posterior maxilla presents a unique biomechanical environment. After tooth loss, the alveolar bone resorbs both vertically and horizontally, often creating excessive crown height space and unfavorable implant positions.
These changes can lead to:
Increased crown-to-implant ratios
Non-axial loading of implants
Higher stress concentration at the crestal bone
Greater risk of technical and biological complications
Implants, unlike natural teeth, lack a periodontal ligament. This means occlusal forces are transferred directly to the implant–bone interface, making prosthodontic design choices especially critical.
What the Authors Propose: The Posterior Maxilla Prosthodontic Index (PMPI)
To address this gap in planning, the authors introduce a new classification system: the Posterior Maxilla Prosthodontic Index (PMPI).
Rather than focusing primarily on surgical difficulty, PMPI evaluates prosthodontic complexity based on three key clinical parameters:
1. Crown Ridge Position (CRP)
Assesses horizontal bone resorption and how far the ideal tooth position lies from the residual ridge.
2. Inter-Arch Distance (IAD)
Evaluates vertical space between the ridge and opposing dentition, which directly influences crown height and prosthesis design.
3. Crown-to-Implant Ratio (C:I)
Examines how crown length compares to implant length, a critical determinant of biomechanical load and lever-arm forces.
By combining these three factors, clinicians can categorize cases as simple, moderate, or complex from a prosthodontic perspective before deciding on implant position, angulation, or augmentation procedures.
Balancing Biomechanics and Clinical Reality
The article also explores how prosthodontic decisions affect force distribution around implants, especially in grafted maxillary sinuses.
Key insights include:
Non-axial loading can generate significantly higher stress than axial forces
Long clinical crowns act as lever arms, increasing crestal bone stress
Splinting implants can improve stress distribution
Wide-diameter implants may offer biomechanical advantages in the posterior maxilla
Interestingly, while laboratory studies suggest higher risks with unfavorable crown-to-implant ratios or cantilevers, current clinical evidence does not consistently show increased marginal bone loss. This highlights the ongoing gap between in vitro research and long-term clinical outcomes.
Implications for Daily Clinical Practice
One of the strongest messages from this paper is that implant success in the posterior maxilla is not determined by surgery alone.
Effective treatment planning should begin with:
Diagnostic wax-ups or digital tooth set-ups
Clear visualization of the ideal prosthodontic outcome
Early assessment of prosthesis height, occlusion, and cleansability
In many cases, accepting a removable prosthesis or modifying the restorative plan—may be more predictable than forcing a fixed solution with high biomechanical risk.
A Shift Toward Truly Restoratively Driven Implant Planning
King and Schofield’s work challenges clinicians to rethink how implant cases in the posterior maxilla are approached. By prioritizing prosthodontic assessment and introducing the PMPI, this paper provides a structured framework to improve communication, decision-making, and long-term outcomes.
Ultimately, the message is clear:
Successful implant treatment starts with the restoration in mind not the drill.
Original Article Reference
King EM, Schofield J.
Restoratively driven planning for implants in the posterior maxilla – Part 2: implant planning, biomechanics and prosthodontic planning: a proposed prosthodontic complexity index.
British Dental Journal. 2023;235(9):695–701.
DOI: 10.1038/s41415-023-6440-2