CE: Accurate Denture Records by Dr. Leif Stromberg

 

How to determine and record tooth position

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Short description
Learn fundamentals for predictable and successful complete dentures! This course focuses on how to determine and record the positions of maxillary anterior teeth in complete dentures. It covers practical concepts and techniques applicable to all types of tissue-supported complete dentures, including digital, implant-retained and traditional analog methods.

Abstract
This course offers practical strategies for achieving predictability and success in fabricating tissue-supported complete dentures. It focuses on overcoming common challenges, such as determining and recording maxillary anterior tooth positions and incisal edge placement for a natural, aesthetic denture dentition. The outdated guideline of positioning denture teeth solely over the remaining alveolar ridge often leads to inadequate outcomes. By incorporating key fundamentals, dentists can optimize patient outcomes for all types of complete dentures.

Learning objectives
After completing this course, readers should be able to:

1. Clinically refine the contours of the maxillary aesthetic wax rim to guide denture teeth positions, including using tools such as the denture gauge and alameter.
2. Create a comfortable, retentive aesthetic wax rim for accurate recordings.
3. Establish an acceptable occlusal plane for the dentures, using tools such as a Fox Plane and Swissedent wax rim former.
4. Mark the dental midline and high lip line on the wax rim.

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Introduction
Achieving predictable success in fabricating tissue-supported complete dentures begins with mastering fundamental principles, including determining and recording appropriate tooth positions. This course highlights practical concepts and techniques applicable to all types of tissue-supported complete dentures, including digital, implant-retained and traditional analog approaches.

Challenges addressed:

• Determining and recording acceptable maxillary anterior tooth positions and arch form.
• Defining incisal edge positions for maxillary anterior teeth.

This course is designed to empower participants with knowledge, skills and confidence to successfully navigate complexities of complete denture fabrication. By the end of the course, participants will be able to use these concepts in their offices to create dentures with greater predictability and success while effectively meeting patient expectations.


Developing a guide for maxillary anterior tooth positioning—the maxillary aesthetic wax rim
Tooth positioning in complete dentures directly impacts patient satisfaction as it affects aesthetics, comfort, facial support, function and phonetics. Contouring and refining the maxillary aesthetic wax rim as a guide for positioning maxillary anterior denture teeth is critical to achieving predictably positive results.

Initial clinical steps: Adjusting the maxillary aesthetic wax rim
The first clinical steps of the records appointment involve adjusting, contouring and refining the maxillary aesthetic wax rim to guide the positioning of the maxillary anterior denture teeth.

Initial adjustments to the baseplate and the maxillary aesthetic wax rim include:

• To ensure accurate records, patient comfort and normal functional movements during the record-making process are essential. The baseplate and wax rim should be smooth, comfortable, stable and retentive. Roughness or instability can distract the patient, causing abnormal movements and function, which may result in inadequate wax rim contours and a faulty guide for tooth positioning. A well-fitted baseplate with a comfortable wax rim facilitates natural movements during adjustments (Fig. 1).
• If additional retention is needed, denture adhesive can be applied, or the baseplate can be relined on the master cast with polyvinyl siloxane (PVS) material. Avoid relining the baseplate in the mouth, as it would not fit precisely back on the master cast, and precise fit is essential. Alternatively, the baseplate can be remade using the master cast and 3D printing to improve fit.
• The initial wax rim contours provided by the laboratory to the dentist should be customized by the laboratory to approximate the final denture’s shape closely. This approach minimizes dentist chair time and enhances treatment predictability by allowing the clinician to efficiently refine the wax rim with minimal adjustments, avoiding significant modifications before finalizing the details. To streamline this process, the dentist should provide the laboratory with specific guidance on the desired wax rim contours. Details of this recommended guidance are covered in part two of this six-part print CE series, “CE2: Making a Great Impression,” available in the June 2024 issue or online at dentaltown.com/CE-LS2.
• The wax rim received from the laboratory should be shaped as closely as possible to the final desired contours. Figure 2 shows a contoured wax rim with adequate lip support and contours and an occlusal plane closely matching the intended final denture contours. In contrast, Figure 3 depicts preformed wax rims that dental laboratories sometimes attach to baseplates without proper contouring, resulting in time-consuming adjustments for the dentist. Figure 4 illustrates a bulky wax rim on a baseplate that lacks appropriate laboratory contouring.

Chairside refinement of the maxillary aesthetic wax rim: Understand the patient’s desires
When designing new dentures, clinicians should understand and consider the patient’s desires and expectations regarding aesthetics, such as lip support and tooth display. However, fully meeting these expectations may not always be possible because of the patient’s anatomy. For example, a patient may have a long or short upper lip relative to their residual alveolar ridge, which can affect the overall tooth display and aesthetics.

Recommended products for the clinical setup for chairside adjustment of the maxillary aesthetic wax rim include:

• Swissedent wax rim former is used to adjust the wax rim length and the occlusal plane (Fig. 5).
• Flat wax paddle for contouring the wax rim (Fig. 6).
• Hard pink baseplate wax.
• Chairside Bunsen burner (Fig. 7).
• LeeMark denture gauge, formerly known as the Alma gauge (Fig. 8). The original Alma gauge is no longer being manufactured. Dentists and laboratories can purchase an upgraded denture gauge from LeeMarkDental.net. I recommend this instrument.
• Alameter (Fig. 9).
• Papillameter.
• Boley gauge.
• Fox Plane (Fig. 21) and tongue blades (Fig. 22).

Information from the patient:

• Photographs of the patient with their natural teeth (Fig. 10).
• Images from magazines or online showing smiles the patient finds appealing.

General guidance for maxillary anterior tooth positioning
The following suggestions and guidelines aid in the chairside refinement of the aesthetic wax rim, serving as a guide for positioning the maxillary anterior teeth.

The LeeMark denture gauge is a valuable tool for determining tooth positions and incisal edge placement relative to anatomical landmarks during denture fabrication.

The denture gauge is highly recommended for complete denture fabrication as it significantly enhances accuracy and efficiency. Clinically, the dentist can use it to evaluate and refine the aesthetic wax rim to achieve the desired final contours. Additionally, it facilitates clear communication with the dental laboratory technician regarding the specific desired contours and dimensions of the wax rim.

For a natural and aesthetic dentition, the incisal edges of maxillary central incisors are typically 8–10 mm anterior to the center of the incisive papilla (Fig. 11). The labial surface of the wax rim should be contoured accordingly, and the denture gauge is particularly useful for obtaining these measurements. However, the skeletal structure of the patient can influence this 8–10 mm distance, requiring adjustments to the guideline (Fig. 12).

The position of the incisive papilla on the palate remains constant, even as alveolar bone resorbs following dental extractions. After the extraction of the maxillary anterior teeth, the alveolar ridge resorbs, resulting in a loss of reference between the ridge and the denture teeth. The guideline of positioning the incisal edges of the maxillary anterior teeth 8–10 mm anterior to the center of the incisal papilla helps restore natural tooth positioning. Figure 13 shows an edentulous maxillary arch with significant alveolar ridge resorption labial to the incisive papilla. This bone loss results in a challenge in determining denture tooth positioning.


Additional guidelines for contouring a maxillary aesthetic wax rim
For the vertical height of the anterior portion of the wax rim, an aesthetic dentition with naturally positioned teeth typically places the incisal edge of the lateral incisor 20–22 mm below the highest level of the labial vestibule above the lateral incisor (Fig. 14). This measurement serves as a reference for positioning the other maxillary anterior teeth.

The alameter is a useful tool for measuring the widest part of the nose at the alae, and this provides a close approximation of the distance between the centers of the labial surfaces of the maxillary canines and the width of the anterior portion of the dental arch at the canines (Fig. 9).

To facilitate tooth positioning that mimics natural anatomy, contour the wax rim to align with the form of the alveolar ridge. As shown in Figure 15, a tapering ridge form suggests a tapering wax rim form from anterior to posterior, guiding the tooth setup to follow this tapering pattern. Other ridge forms include square and ovoid shapes.


Consequences of tooth loss
Following extractions, alveolar ridge resorption occurs in unpredictable patterns. The residual ridge typically does not indicate the optimal positions for denture teeth, and relying solely on the remaining ridge for tooth positioning can result in unacceptable outcomes.

In the anterior maxilla, resorption occurs in a labial-to-lingual direction and upward (apically) (Fig. 17). Therefore, the anterior denture teeth should not be placed directly over the remaining ridge but instead positioned in their natural locations. Typically, the labial surfaces of the maxillary central incisors should be 8–10 mm anterior to the center of the incisive papilla (Fig. 11).

Figure 16 shows a complete natural dentition. Figure 17 illustrates the typical direction of alveolar bone resorption after extractions, as indicated by the arrows. Figure 18 highlights the challenge of positioning denture teeth to replicate the patient’s natural tooth positions. Figure 19 compares the natural position of a central incisor in the alveolar bone (right) to the resorbed bone after extraction (left). As the ridge resorbs, the crest of the alveolar ridge usually moves upward and lingually from its original position. Setting denture teeth directly over the ridge, as illustrated in the left image of Figure 19, would typically be unaesthetic and unnatural.

Figure 20 illustrates a wax rim after clinical contouring and refinement, with the maxillary incisal edge positions indicated by the arrow. When setting the denture teeth, the incisal edges must align with the indicated positions to ensure proper tooth placement. Deviating from these positions can compromise both aesthetics and function, resulting in unpredictable final dentures.


Tooth display
With the patient’s facial muscles relaxed and the lips slightly apart at rest, adjust the length of the wax rim to achieve an appropriate tooth display. The length can be modified in relation to the upper lip as needed. An aesthetically pleasing tooth display typically shows 1–2 mm of the central incisors when the upper lip is relaxed (Fig. 2). However, this may not always be achievable in patients with lips that are excessively long or excessively short in relation to the alveolar ridge. The wax rim should be carefully contoured to indicate the desired positions of the incisal edges.

Additionally, the guideline previously referenced (Fig. 14) regarding the length of the wax rim—and, consequently, the tooth positions—should be considered. This guideline specifies a length of 20–22 mm below the highest level of the labial vestibule above the lateral incisor. Incorporating it into the adjustments can enhance the outcome.


Establishing an acceptable occlusal plane
The Swissedent wax rim former (Fig. 5) is a reliable tool for creating an acceptable occlusal plane that is parallel to the horizon, the patient’s interpupillary line and Camper’s Plane (the ala-tragus line).

The occlusal plane of the maxillary wax rim can be evaluated using a Fox Plane and tongue blade (Fig. 21, 22). An aesthetically pleasing occlusal plane is typically parallel to both the horizon and interpupillary line. Even a slight cant of the occlusal plane can appear highly unaesthetic.


Further refinement of the aesthetic wax rim after establishing the occlusal plane and incisal edge positions
1. Evaluate facial aesthetics: With the maxillary wax rim seated in the mouth, assess the overall facial aesthetics. Determine if modifications to the wax rim contours would create a more pleasing appearance, focusing on lip support, tooth display and occlusal plane alignment. Make appropriate adjustments to achieve a more pleasing and natural result.

2. Mark the anticipated dental midline clearly on the wax rim (this midline will be verified at the important wax try-in appointment): There is no exact midline for the face and teeth, as each side of the face and dental arch is unique. The dental midline refers to the vertical labial embrasure between the two maxillary central incisors. To determine an appropriate dental midline for a patient, assess multiple anatomical landmarks typically located along the midline of the patient’s face, neck and intraoral structures.

A string or piece of dental floss can be used as a visual guide to align and mark the dental midline on the wax rim (Fig. 23) relative to the midline landmarks. Midline references include:

• The midline ridge of the hard palate (palatine raphe) that runs from the incisive papilla to the posterior part of the hard palate (Fig. 24).
• Incisive papilla (Fig. 24).
• Maxillary anterior frenum.
• Midline of the nose (Fig. 23).
• Midline of the chin (Fig. 23).
• Midpoint of the glabella (the area of skin between the eyebrows and above the nose) (Fig. 23).
• Middle of the philtrum of the lip (the vertical groove in the center of the upper lip) (Fig. 23).
• General center of the outline of the face and neck (Fig. 23).
• Adam’s apple (a projection at the front of the neck formed by the thyroid cartilage of the larynx, often prominent in men) (Fig. 23).

Careful use of these references helps ensure a dental midline that complements the patient’s facial symmetry.

3. Marking the high lip line (smile line) to guide tooth selection and positioning: The high lip line records the upper lip’s upward movement limit during smiling and speaking, indicating the amount of denture teeth and gingivae that will be visible in a full smile. To clearly mark the high lip line:

• Engage the patient: Ask the patient to smile broadly while lifting their upper lip as much as possible and pronouncing the letter “E.”
• Mark the high lip line: Use a sharp instrument, such as a small wax spatula, to scribe a line across the wax rim at the highest point reached by the upper lip. Ensure the line follows the natural contour of the lip and is clearly marked.
• Verify accuracy: Have the patient repeat the process of smiling and raising their lip to confirm the accuracy of the marked line.
• This mark is a valuable guide for selecting and positioning denture teeth to achieve an aesthetic and natural appearance.

4. Avoid showing the patient the wax rim while it is in their mouth to prevent any concerns about aesthetics.


Review of the sequence of steps
This section outlines the order of steps for contouring the maxillary aesthetic wax rim:

1. Adjust the baseplate and aesthetic wax rim for adequate retention and patient comfort.
2. Contour the wax rim to indicate natural tooth positions and provide aesthetic lip support, ensuring alignment with the alveolar ridge arch form, and defining the arch width from canine to canine.
3. Determine and record the length of the anterior portion of the wax rim and incisal edge positions. Evaluate the tooth display and adjust as necessary.
4. Establish an acceptable occlusal plane.
5. Clearly mark the dental midline and high lip line on the wax rim.

This systematic approach to creating a guide for the denture tooth positions addresses common procedural challenges and emphasizes the importance of patient-specific customization for achieving predictable results.

By observing and studying the natural positions of teeth in relation to the alveolar ridge as illustrated in Figures 15–19, dentists can more effectively and accurately visualize and determine optimal positions for denture teeth during clinical procedures. Once the aesthetic wax rim has been refined, the next step of the records appointment is to determine and record vertical dimension of occlusion and centric relation for the patient. Details of this step will be covered in Part 3B of this six-part series.

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