Direct-To Screw Classification

Full arch implant dentistry has the option of coping-free restorations—a system to deal with debonding, costly remakes and a few other key reasonings — using “Direct-To-MUA” workflows that deliver true monolithic prosthetics with high accuracy and durability. This shift has made screw mechanics central to restorative success, yet the growing variety of screw designs on the market has created confusion around which system to use and when. Stay tuned for our publications detailing all the reasons to make the screw choice.

This page presents an introduction to a modern classification of the Direct-To-MUA screws built around four core mechanical design philosophies:

• Flat bottom compression — straightforward downward clamping force
• Frictional wedging — tapered engagement for lateral retention
• Cradle-based vertical capture — controlled vertical seating
• Locking anti-rotational mechanics — axial load with rotational stability

The goal: give clinicians, designers, and manufacturers a shared vocabulary for selecting the right screw for each workflow.

Type 1 — Flat Compression Mechanics 

Compression screws remain the closest link to the classic MUA restorative screw. They use a flat bottom surface that presses vertically onto a defined, right angle seating ledge. The force generated is purely vertical without lateral pull or outward pressure. Their preload behavior is inherently passive. They do not correct misalignment but instead apply a clamping force to secure a properly fabricated prosthesis to the MUA. 

Type 2 – Wedge Screw (Friction Locking Mechanics)

Type 2 screws introduce fundamentally different mechanical behavior. Instead of relying solely on vertical compression, the screw generates simultaneous outward and downward engagement, pressing against the internal walls of the prosthesis. This creates a rigid mechanical lock that resists rotation, micromovement, and vertical displacement. 

Wedge mechanics are ideal in immediate load situations and in resin or milled PMMA restorations, particularly when bone quality, implant distribution, or arch stability is less than ideal. They provide levels of mechanical resistance that simple compression screws cannot. 

Type 2b Wedge Long | Force = Out

Long wedge screws maximize locking behavior through extended taper engagement. They deliver the highest stability and are particularly valuable in high–force, immediate–load conditions. However, they introduce greater lateral pressure and therefore require thicker walls and extremely precise machining. When used appropriately, Type 2b screws provide unmatched rigidity. 

Type 3 – Cradle Screws (Vertical Capture Mechanics)

Cradle screws differ entirely from both compression and wedge systems. Instead of wedging or compressing the prosthesis, the screw engages a rounded or U–shaped channel that captures the seating surface vertically. This prevents lift off while distributing forces across a broad, rounded surface. The screw settles into position rather than forcing the prosthesis into alignment, making it exceptionally forgiving on provisional materials while remaining effective for selected definitive applications. 

Type 4 – Locking Screws (Anti Rotational Mechanics)

Type 4 screws introduce a distinct philosophy. They are designed not only to retain the prosthesis but to resist reverse rotation and loosening, addressing the inherent limitations of low torque, non–elongation screw mechanics. This classification incorporates screws that integrate a specific anatomical or mechanical anti rotational feature purposefully engineered to prevent thread back out.