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The quality of prosthetic work begins in the dental office. Preparation, scan, bite – these are the input data that define the final outcome. Better data means fewer adjustments.
Insufficient preparation or an incomplete scan are the most common causes of misfits and remakes. Understanding material requirements and the CAD/CAM process helps avoid costly errors.
Each prosthetic material requires a specific minimum thickness to ensure strength and aesthetics. How many millimeters should be left?
The preparation margin line determines marginal seal, gingival aesthetics, and the longevity of the restoration. Which design should you choose?
A multi-unit bridge requires a common path of insertion—without it, the restoration will not seat. How to ensure this clinically?
Insufficient tooth reduction is one of the most common reasons why the laboratory stops production and calls the dentist asking for more reduction. This is not a laboratory problem — it's a preparation problem. Ceramics do not tolerate compromises on dimensions.
The type of preparation margin determines how the technician scans, designs, and perceives the boundary between the tooth and the crown. An illegible margin = the technician interpolates, and every assumption is a potential leakage, misfit, and effort for both the laboratory and you.
A crown that doesn't fully seat, or seats with resistance—this is most often a problem with axial wall taper or undercuts.
A sharp internal line angle in a preparation is an invisible trap. Ceramic designed over a sharp angle creates a stress concentration point there—exactly where the material will fracture under mastication. This is one of the most common reasons for returned cases to the lab: 'the shipment arrived fractured' or 'the patient came in after two months with a fracture.'
Insufficient occlusal reduction is the beginning of problems. The dentist prepares, the lab prepares, but if there's <1.0 mm of clearance on the occlusal surface, the technician only has bad options: making it too thin (risk of fracture) or changing the design during processing (risk of misfit).
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?'.
One of the biggest causes of laboratory errors is an imprecise preparation line on the impression. The laboratory receives an image where the margin of the preparation disappears into the soft tissues — no clear boundary line that the technician could reproduce in CAD. The result: a crown margin that doesn't fit or is too loose.
A veneer is not a small crown. An onlay is not an intermediate solution between a filling and a crown. Each of these restorations requires a different approach to preparation — less invasiveness, but greater precision. Errors in tooth preparation lead to material fractures and restarting the problem.
When you prepare a posterior tooth without a bevel:
When more than 50% of the tooth structure is missing, the crown has nothing to retain to. Thin, unsupported walls will not hold the restoration — even with the best cement. This is a fundamental problem in prosthodontics that must be solved in the dental office, before sending the case to the laboratory.
A root canal post is inserted into the canal at an angle determined by root anatomy — not necessarily perpendicular to the occlusal plane or in line with the path of insertion of adjacent teeth. If you perform a core build-up without correcting the axis, the crown will have to adapt to the incorrect position. This leads to problems in the lab.
A bridge connects two or more abutments. Each independently prepared abutment has its own path of insertion — determined by the angle of preparation. When the paths diverge, the bridge physically cannot seat on all abutments simultaneously. This is not laboratory trickery — it's physics.
A removable partial denture requires precise preparation of abutment teeth — unlike fixed crowns. The absence of guide planes and rest seats leads to one thing: the denture will be unstable, 'rocking,' and clasps will damage the teeth. This is one of the most common causes of patient dissatisfaction and denture failure — and it should be entirely avoidable.
An endodontically treated tooth is structurally weakened—it lacks dentinal fluid, and the pulp chamber may be partially prepared. Without proper prosthetic restoration, the tooth fractures under occlusal load. This is one of the most common mistakes—'treatments failed,' when the cause is selecting the wrong restoration method.
An irregular preparation line is not just an aesthetic issue for the dentist. For the technician, every indistinct margin segment is a point where they must decide—exactly where the boundary between the tooth and the crown lies. Each such guess increases the risk of error.
deltalabs. analyzes every scan for data completeness. If we see a problem – we inform you before we start work, not after.
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