Interproximal Separation: Why 0.3 mm Determines the Quality of the Contact Point

When preparing a crown, you often prepare the adjacent tooth almost directly on its surface. Then the lab technician faces a problem: lack of access to the interproximal space. The result: a contact point made "by feel" — not clinically optimal, the patient feels something is off, and the restoration returns to you with the question "can the contact point be changed?". deltalabs. sees this regularly — preparations without separation are the most common cause of contact point inaccuracies. But it's completely unique — a minimum of 0.3 mm interproximal clearance changes everything.

Problem: Teeth Too Close Together — Lack of Space for Design

During single crown preparation, your bur approaches the adjacent tooth. Standard practice leaves ~0.2 mm to its surface — this is practically no access for the laboratory. What happens in the lab:

The technician captures the geometry of the preparation and the adjacent tooth
In the CAD software, they see: the prepared crown and the adjacent tooth's outline — but the gap is minimal
To place the contact point, they must work "on the edge" — no margin for error
The contact point ends up either too prominent (patient feels "it's tight"), or too weak (restoration loosens)

Consequences of lack of separation:

Inaccurate contact point — inaccurately positioned, not sufficiently "stable" for the adjacent tooth
Difficult restoration execution — the technician spent hours "cleaning" this space, compensating
Unstable chewing — when the patient chews, the proximal contact is weak — teeth move
Proneness to proximal caries — weak contact point = bacteria pass between teeth = caries
Gingival recession — long-term — lack of proper soft tissue support
Return to the dentist — patient returns with "something isn't right"

The Role of Separation in Design — Access = Precision

Interproximal separation is simply a gap between the prepared tooth and the adjacent one. It doesn't hurt, it's not visible, but it changes the possibilities for the laboratory. Proper interproximal clearance (minimum 0.3 mm, ideal 0.5–0.8 mm) gives the laboratory:

What you gain	Practical consequences
Space for design	The technician clearly sees the contour of the adjacent tooth, designs the contact point anatomically — not "blindly"
Ease of production	No working at the edge of accuracy — the margin of error is safe
Longevity of the restoration	Well-placed contact point = lower risk of caries, recession, instability
Patient effect	A contact point that "is there" (supports teeth), and the patient doesn't feel it — this is the standard
Speed of execution	No need for corrections, problem-solving — work proceeds smoothly

deltalabs. practice: Every single crown preparation without separation requires additional verification, increasing the chance of inaccuracy. Crowns with separation — no such problems.

Practical Separation Methods — Anyone Can Do It

Separation is not a complicated procedure. You have several options — all effective:

1. Abrasive strip before preparation

The simplest solution:

Take a regular dental floss or abrasive strip
Several passes through the contact point of the adjacent tooth (mesial–distal)
Just 30 seconds is enough
Creates a minimal but sufficient gap

Advantages: no additional tools, quick, safe Disadvantages: need to remember to do it

2. Separating wedges

Classic approach:

Insert a separating wedge on the side of the adjacent tooth (from the distal side of anteriors, from the distal of posteriors)
Prepare the tooth — wedges protect the adjacent tooth and automatically create a gap
After preparation — remove the wedges

Advantages: protects the adjacent tooth, creates a gap throughout the process, reversible Disadvantages: requires skill for safe placement, risk of gingival trauma (if done incorrectly)

3. Dedicated separation systems

For clinics with higher volume:

Mechanical devices for separation (e.g., orthodontic separators, special instruments)
Ensure precise dimensions

Advantages: precision, speed, repeatability Disadvantages: cost of equipment, unnecessary for fewer cases

Practical rule

Even 0.3 mm is enough. You don't need to create a giant gap — minimal separation is sufficient for the lab to have access. deltalabs. practice shows — all high-quality crowns have separation.