Digital impression or plaster cast: two methods of taking impressions in orthodontics

Digital impressions and plaster casts are the two methods used in orthodontics in Divonne-les-Bains to capture the precise shape of teeth. They lead to the same diagnostic objective but offer a very different experience for the patient.

You are about to begin orthodontic treatment in Divonne-les-Bains, and you are wondering which impression-taking method your practitioner will use in 2026. This detailed article explains how intraoral scanning and alginate molding work, the selection criteria, the step-by-step process, and the specific context of orthodontics in Divonne-les-Bains. For all prior exchange with the firm, A clinical consultation remains essential for a personalized opinion.

Why is taking an impression essential before orthodontic treatment?

Taking an impression is the step that allows for the creation of an exact model of the dental arches, an essential basis for orthodontic diagnosis. Without this precise replica, no reliable treatment plan can be developed.

The resulting model, whether plaster or digital, serves three essential purposes. First, it allows the orthodontist to analyze the malocclusion in 3D, outside the patient's mouth, with a perspective impossible to obtain in a direct consultation. Second, it enables the virtual or manual planning of the desired tooth movements. Finally, it serves as the basis for fabricating custom-made appliances: clear aligners, bonded brackets, metal archwires, and retention splints.

This step usually takes place during the initial orthodontic assessment, before the first appliance is fitted. It can be repeated during treatment to adjust a retainer or fabricate a supplementary device. Depending on the’Health Insurance, The treatment of dental malpositions by dentofacial orthopedics is based on a complete diagnosis systematically including the analysis of study models.

How does traditional plaster casting work?

Plaster casting involves using an alginate paste poured into an impression tray inserted in the mouth for 30 to 60 seconds, then replicating it in plaster in the laboratory. This is the historical method of orthodontics, still used today in certain contexts.

What is alginate?

The process in 5 steps

1. Choosing the impression tray

   The practitioner selects the size appropriate for the upper or lower arch, often a perforated model to retain the paste well.

2. Preparing the dough

   Precise dosing of alginate powder with room temperature water. Temperature directly influences setting time.

3. Insertion into the mouth

   The filled impression tray is gently inserted, positioned, and then lightly pressed against the teeth and gums.

4. Setting time

   The material remains in the mouth for 30 to 60 seconds, until it hardens completely. The patient breathes calmly through their nose.

5. Withdrawal and pouring

   Extraction with a quick, sharp movement, quality check, then pouring of the plaster within 10 to 15 minutes to avoid any deformation.

Plaster casting remains a simple and proven tool. It provides a good reproduction of oral contours, more than sufficient for many orthodontic indications: study models, removable appliances, and traditional retainers. Its limitations lie in its sensitivity to time and humidity, as well as the discomfort experienced by some patients, particularly those with a pronounced gag reflex.

How does the 3D digital impression taking process work?

3D digital impressions use a small intraoral camera (optical scanner) that films the teeth in a few minutes, generating a virtual model displayed live on the computer screen. No paste, no impression trays: just a sterile tip passed over the tooth surfaces.

What is an intraoral scanner?

The step-by-step process

The patient sees their dental arches gradually appear in 3D on the screen, often with a colorful or photorealistic rendering. This visual aspect has significant educational value: the orthodontist can immediately point out areas of crowding, tooth rotations, or occlusion problems. In children and adolescents, this interactive dimension contributes to treatment adherence.

«"During consultations, we regularly observe that immediate 3D visualization reassures patients and helps them better understand their dental situation. Children often find the experience almost playful, which completely changes their perception of this step."»

What is optical fingerprinting?

What are the differences in comfort and accuracy for the patient?

Digital impressions eliminate the need for paste in the mouth, significantly reduce the gag reflex, and prevent material deformation, with an accuracy of a few microns. Plaster molds remain reliable but are less comfortable and take longer to send to the laboratory.

Comparison of the two methods

Both techniques share the same diagnostic objective but differ in several respects. Digital impressions require no material in the mouth, only the scanner tip, whereas plaster casting uses alginate paste in an impression tray. Digital scanning is performed progressively, arch by arch, while plaster casting requires uninterrupted exposure for 30 to 60 seconds, which frequently triggers the gag reflex in sensitive patients. Digital accuracy is on the order of microns, while plaster casts remain good but are susceptible to deformation. Finally, the digital file is immediately transmitted to the laboratory and archived permanently, whereas plaster models require physical transport and bulky storage, with increased consumption of single-use materials.

These values illustrate a qualitative trend widely reported in dental literature. They do not replace an individual assessment during a consultation.

The question of accuracy

Precision is a key criterion for successful orthodontic treatment, especially for mass-produced invisible aligners, where each tray must perfectly fit the teeth at a specific stage. Modern intraoral scanners achieve micron-level accuracy across the entire dental arch, which is consistent with the requirements of CAD/CAM (computer-aided design and manufacturing).

Plaster casting remains clinically reliable for most indications, but it has several potential sources of error: bubbles in the alginate, material shrinkage, deformation between shrinkage and pouring, and shrinkage of the plaster itself. Each step can introduce a micro-inaccuracy.

Speed and clinical follow-up

From a logistical standpoint, digital transmission is a game-changer. A plaster impression requires physical transport to the dental laboratory, often by mail or courier, which can take several days. A digital file is transmitted with a single click, significantly reducing the manufacturing time for aligners or other dental appliances.

How is the orthodontic treatment process organized in Divonne-les-Bains?

Divonne-les-Bains benefits from strong population growth due to its proximity to Geneva, with a mixed French and cross-border patient base that is driving the orthodontic practice to invest in the latest technologies. Digital impression taking is part of this ongoing modernization of the practice.

A territory with a unique demographic profile

According to the’Insee, The Pays de Gex urban area has surpassed 100,000 inhabitants in recent years, driven by the attractiveness of cross-border employment in Switzerland. According to the figures reported by RTS, Geneva had nearly 115,000 cross-border workers in 2024, a significant portion of whom reside in the Ain region.

This dual French and Swiss cultural heritage has a direct impact on the orthodontic practice: patients expect a level of technology consistent with the standards observed in Geneva or Nyon. The use of an intraoral scanner is part of this requirement.

A healthcare pathway specifically for cross-border workers

For patients who work in Switzerland and reside in France, the healthcare pathway has significant differences regarding health insurance coverage (LAMal, French insurance, supplemental insurance). Our dedicated article details this in detail. the organization of orthodontic follow-up and care for border patients between France and Switzerland, along with the administrative procedures to anticipate before starting treatment.

Ongoing modernization of the office

The shift to digital technology isn't unique to Divonne-les-Bains; it affects the entire orthodontic profession in France. However, it's accelerating in areas where patients are accustomed to high standards. This trend benefits patients of all ages: children find the experience less anxiety-inducing, teenagers are more engaged thanks to 3D visualization, and adults value speed and precision.

Digital impression or plaster cast: which method should you choose depending on your situation?

The choice between digital impressions and plaster casts depends on the type of treatment planned, the equipment available in the dental practice, and the patient's individual preferences. No method is universally superior: each has its indications and limitations.

Some concrete scenarios

What remains unchanged regardless of the method

• A complete clinical examination precedes any impression taking.
• After validation of the treatment plan, an active follow-up phase takes place with regular appointments and adjustments to the device, before the final retention is fitted.
• A detailed treatment estimate is provided to the patient before treatment begins.
• Prior agreement from the Health Insurance remains mandatory for children eligible for reimbursement.
• The retention of patient data complies with the obligations of medical confidentiality and the GDPR.
• Orthodontic treatment is a long-term process, with regular consultations.

Cost, reimbursement and ethical framework: what you need to know

Taking impressions, whether digital or traditional, is generally included in the overall fee for the orthodontic assessment or the six-month treatment period. It is not billed separately in most practices.

Covered by Health Insurance

According to the’Health Insurance, Orthodontic treatments are covered for children under 16 (with the possibility of an exceptional extension until the end of the current semester), based on the agreed-upon rates, provided prior approval is obtained from the health insurance fund. The use of an intraoral scanner rather than a plaster cast does not change the basis for this reimbursement: the covered procedure is the overall orthodontic treatment, not the impression technique.

To delve deeper into the specific issue of finances for adults, our detailed article addresses the budget for adult orthodontic treatment in Ain, near Switzerland, with the rules for reimbursement from Health Insurance and supplementary insurance.

A strict ethical framework

The orthodontic profession is regulated by the National Council of the Order of Dental Surgeons and by the provisions of the Public Health Code. Practices may not present technology as a selling point: it is a tool to aid diagnosis, not a service in itself. Fees are set freely by the practitioner, with a mandatory prior estimate provided as soon as the amount exceeds the regulatory threshold.

Digital data storage and security

3D files generated by an intraoral scan are considered health data under applicable regulations. As such, they are stored securely, in compliance with medical confidentiality and the GDPR, with strictly controlled access. The patient may request access to their file at any time.

What to do in case of an emergency during treatment?

Once the impression has been taken and treatment has begun, certain situations may require a prompt consultation: a loose bracket, a wire that is scratching the cheek, a damaged retainer, or unusual pain. The dental office remains the first point of contact.

Outside of office hours, our dedicated article details simple steps to know in case of’discomfort related to orthodontic appliances while waiting for the next appointment. For any situation of’orthodontic emergency, Contact with the firm is preferable.

About the author: Nicolas Barrière

Dr. Nicolas Barrière is an orthodontist, a qualified specialist in dentofacial orthopedics, a former hospital intern, and the founder of his practice in Divonne-les-Bains. He treats children, adolescents, and adults with orthodontic treatments (invisible aligners, lingual orthodontics), paying particular attention to the care of patients living near the French-Swiss border.

Areas of expertise: Orthodontics, Dentofacial orthopedics, Invisible aligners, Lingual orthodontics, Children's orthodontics, Adult orthodontics, Orthognathic surgery and medical-surgical orthodontics, Sleep apnea (OSA), Retention and relapse management.

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