Fiber Reinforcement in Prosthetics — When and How to Use It

Fiber in prosthetics solves a specific problem: you need metal-free reinforcement. But — and this is crucial — fiber reinforcement is never an alternative to zirconia or metal. It's a solution for specific clinical situations. At deltalabs., we see it daily: clinicians order fiber-reinforced composite bridges, either to save money or because the patient "doesn't want metal" — and then they're surprised when the bridge breaks in its second year. The problem? Misunderstood intention.

What Is Fiber Reinforcement and Why Do We Need It?

Fiber reinforcement is a layer of fibers (glass, kevlar, polyester) embedded in a composite matrix. The role of the fiber is to interrupt crack propagation. The fiber acts as a "brake" for the network of microdamages within the material.

In laboratory practice, this means:

• Reduced susceptibility to transverse fractures
• Increased structural rigidity (composite + fiber = less deflection under load)
• Ability to build structures without a metal framework

But: fiber does not change the fundamental character of the material. If you have a fiber-reinforced bridge with insufficient wall thickness or improper proportions, fractures will still occur — just a bit later.

Types of Fibers and Specific Laboratory Applications

Glass fiber — always for temporary bridges

Glass prepreg (ready-to-use, resin-impregnated) — everStick, SPLINT-IT, Fiber-Reinforced Resin — is the most common solution.

Practical application:

• Assemble the fiber within a PMMA or bis-acryl framework
• Secure lateral surfaces with composite
• We ship it — the clinician cements it
• Lifespan: 3–6 months (good)

Conditions: where glass fiber works best:

• Temporary bridge during osseointegration of an implant (3–4 months)
• Not too wide (1–2 pontics in the posterior segment)
• Patient does not have bruxism or high occlusal forces
• Aesthetics are important (no metallic show-through)

Problem with glass fiber:

• Fiber damage in the lab (poor modeling) = fractures already in the lab
• Fiber, instead of being a reinforcement → becomes the initiation point for a crack

Fiber ribbon (Ribbond, polyethylene) — periodontal splints

A thin, flexible polyethylene ribbon, adhesively adapted to the lingual surface.

Practical indication:

• Stabilization of a horizontally mobile tooth (patient without endodontic cause does not do this — because it is symptomatic treatment)
• Splint after periodontal treatment (mobile tooth — temporary splint 4–6 weeks)
• Survival: longer than a wire splint (wire bends and breaks; Ribbond is flexible)

Fiber mesh under composite — reconstructions and mock-ups

A quiet but important role. Mesh embedded in the first layer of composite:

• Reduces crack propagation in large reconstructions (post-trauma, extensive crown destruction)
• Composite mock-up for the patient — fiber prevents fractures during design changes

When Fiber Always Makes Sense — And When It Absolutely Doesn't

Fiber: always a good solution:

• Temporary bridge, 1–2 pontics, implantological indications (osseointegration 3–6 months)
• Periodontal splint (mobility threatening tooth loss)
• Composite mock-up for the patient (testing the design before definitive work)
• Post-traumatic reconstruction where most of the tooth structure is lost
• Patient with healthy occlusion, no parafunctions

Fiber: does not make sense (choose zirconia or metal):

• Bridge exceeding 2 pontics (especially in the posterior segment) — excessive load on the fiber
• Bruxism — forces ≥700 N destroy fiber-reinforced composite faster than monolithic zirconia
• Patient with high occlusal forces (>600 N measured by occlusometry) — fiber will fatigue
• Aesthetic work in the smile zone where the patient expects 8+ years of longevity (fiber = 3–5 years max)
• Definitive bridge — if the patient can wait, zirconia or silicate is always better

Strength, Lifespan, and Clinical Reality

Data from the literature clearly show:

What does this mean in practice?

Fiber is a temporary or auxiliary solution. If a patient says "I don't want permanent metal," you respond: "Okay, fiber for 3–4 years, then zirconia." Not: "Fiber will last forever."