The fabrication of a dental crown requires a precise partnership between the dentist and a skilled dental laboratory technician. This process is a communication system designed to translate a patient’s unique oral anatomy and aesthetic needs into a custom-made restoration. Success depends on the clarity and completeness of the instructions provided to the technician. The dentist must communicate three distinct types of information to the lab: a formal legal order, the physical dimensions of the prepared tooth, and the detailed specifications for the final crown’s appearance and structure.
The Written Order: The Laboratory Prescription
The foundation of the crown fabrication process is the laboratory prescription, often called a lab slip, which serves as the formal, legal work order. Without this document, the dental laboratory cannot legally begin work on a custom medical device. The prescription is the administrative framework that authorizes the technician to act under the direction of the licensed dentist.
This document must contain mandatory administrative details. These include the full name and license number of the prescribing dentist, the patient’s name or unique case identification number, and the date the order was issued. The expected delivery date is also specified, allowing the lab to manage its schedule and the dentist to communicate an accurate timeline.
Beyond the administrative data, the prescription requires a clear description of the service being ordered, including the specific tooth number and the materials to be used. The dentist’s signature, which can be electronic, validates the order and confirms responsibility for the prescribed work. The formal prescription is retained by both the dentist and the lab for a mandated period, typically four years, for regulatory review.
Essential Clinical Data: Impressions, Scans, and Models
While the lab prescription provides the legal authority, the physical dimensions of the patient’s mouth are conveyed through precise clinical data. This data allows the technician to replicate the prepared tooth, the surrounding teeth, and the opposing arch with accuracy. The goal is to ensure the final crown fits perfectly and aligns correctly with the patient’s bite.
The physical representation of the mouth has historically been captured using traditional impression materials, such as polyvinyl siloxane (PVS), which the lab uses to pour a stone model. This stone model is a three-dimensional duplicate of the patient’s arches, used by the technician to sculpt the restoration. A separate impression of the opposing arch shows how the upper and lower teeth meet, and a bite registration records the exact relationship between the arches when the mouth is closed.
A growing number of dentists now use intraoral scanners, which capture the mouth’s geometry using light and software to create a digital file, typically in STL format. This digital workflow eliminates the need for physical impressions and models, transmitting the data instantly to the lab via a secure portal. Whether physical or digital, the data must clearly capture the preparation margin—the distinct line where the prepared tooth ends—as this boundary is where the final crown must terminate for a proper fit.
Defining the Final Product: Material, Shade, and Contour Instructions
The final set of instructions details the specifications for the crown’s function and aesthetic qualities. Material selection is important, as the dentist must specify the restorative material based on the location, the patient’s chewing forces, and aesthetic demands. For example, materials like Zirconia or lithium disilicate (Emax) are commonly prescribed for their durability and appearance.
Shade matching relies on both objective tools and subjective observation to achieve a natural look. Dentists use standardized shade guides, such as the VITA classical scale, to select the base color, often supplemented by digital photography. These photographs help the technician replicate subtle details like translucency, internal color variations, or specific stains known as custom characterization, ensuring the crown is indistinguishable from natural teeth.
The dentist also provides specific instructions regarding the crown’s contour and the preparation margin design. The margin preparation type, such as a chamfer or a shoulder, is selected based on the restorative material and the amount of tooth structure removed. Notes on the crown’s final shape ensure the technician designs the restoration to match the alignment, size, and surface texture of the adjacent natural teeth.