Sweet Solution: Caramelized Sugar Spacer for Hollow Maxillary Complete Denture

INTRODUCTION

The resorption of the maxillary residual alveolar ridge is a complex biophysical process influenced by multiple factors, including anatomical structure, prosthodontic considerations, metabolic changes, and functional dynamics. This progressive resorption leads to a significant gap between the maxillary and mandibular residual ridges, primarily due to the extensive loss of maxillary denture-bearing tissue. Achieving adequate retention and support in cases of severe ridge resorption presents a significant challenge, particularly when a large restorative space is involved.^[1]

In cases of severe edentulous ridge resorption or extensive maxillofacial defects, the available surface area for denture support, retention, and stability is significantly reduced. This challenge is further exacerbated by an increased inter-ridge space.^[2] One effective strategy to address this issue is reducing the weight of the prosthesis, which has been shown to improve denture stability by minimizing leverage forces. However, fabricating a functional and well-retained prosthesis becomes particularly difficult in patients with severely atrophic maxillae and long lips. Establishing an appropriate occlusal plane in such cases often results in a lengthy and heavy denture, leading to compromised retention and stability due to gravitational pull and unfavorable leverage effects.^[3]

Traditional denture fabrication techniques may produce bulky prostheses, worsening retention and resistance issues. Various methods have been explored to improve the retention and stability of heavy complete dentures, including the use of implants, magnets, modified impression techniques, intramucosal inserts, suction disks, and lightweight denture designs.^[4]

A key approach to reducing prosthesis weight is incorporating a hollow cavity within its structure. Various three-dimensional (3D) spacers, like dental stone,^[5] cellophane-wrapped asbestos,^[6] silicone putty,^[7] gauze with light-body silicone,^[8] modelling clay,^[9] and thermocol,^[10] have been used to create hollow cavities. One method for weight reduction involves placing a solid 3D spacer (e.g., dental stone, silicone putty, or modelling clay) while processing to exclude denture base material from the intended hollow space. Holt et al. introduced a technique where an indexed acrylic resin shim was processed over the residual ridge, after which a spacer was placed, later removed, and the two halves of the prosthesis were bonded using auto-polymerized acrylic resin.^[11]

Two primary techniques for fabricating hollow dentures have been described in the literature: the single-flask and double-flask methods. The single-flask technique involves fabricating the entire prosthesis in one unit within a single polymerization flask.^[12] In contrast, the double-flask method uses two flasks to create the prosthesis in two separate halves, one forming the intaglio surface and the other comprising the polished and occlusal surfaces, before joining them with self- or heat-cured acrylic resin.^[13]

Fattore et al. modified the double-flask technique for obturator fabrication by applying heat-polymerizing acrylic resin over the definitive cast and processing a minimal resin thickness around the teeth using a separate drag.^[14] The two resin portions were later joined with heat-polymerized resin.

O’Sullivan et al. described a modified approach for crafting a hollow maxillary denture, involving the fabrication of a clear matrix of the trial denture base, followed by investment and wax elimination. A 2 mm heat-polymerized acrylic resin shim was then applied to the master cast using a second flask. Silicone putty was placed over the shim, with its thickness estimated using the clear matrix. After this, the initial flask containing the teeth was positioned over the silicone putty and acrylic resin shim, and the processing was completed. The putty was later removed through an opening at the distal end of the denture, which was subsequently sealed using an auto-polymerizing resin. While this technique facilitated spacer thickness estimation, challenges arose during putty removal, particularly in the anterior region of the denture. Additionally, the distal openings had to be adequately sized to allow for putty extraction.^[15]

This article introduces a simple yet precise technique—the lost sugar technique—for fabricating a hollow maxillary complete denture using caramelized sugar as a spacer. This method, implemented through a single-flask approach, ensures accurate spacer placement, easy removal, and a smaller exit hole for spacer extraction.

CASE REPORT

A 75-year-old male patient visited the Department of Prosthodontics, Crown and Bridge, and Oral Implantology at Bhojia Dental College & Hospital, Baddi, Solan, Himachal Pradesh, India, with the chief complaint of looseness in both his upper and lower dentures, requesting their replacement. His medical history revealed that he had been edentulous for 15 years and had been using dentures for the past 14 years.

Intraoral examination revealed a narrow, constricted, U-shaped, flat palatal vault, along with severely resorbed maxillary and mandibular ridges. The proposed treatment plan included fabricating a hollow maxillary complete denture and a conventional mandibular complete denture. Due to the significant ridge resorption and increased inter-ridge distance, this approach was chosen to optimize overall denture function.

Fabrication technique

The fabrication of the hollow maxillary complete denture followed these steps:

1. Impressions: Primary impressions of the maxilla and mandible were made, followed by border moulding using green-stick compound. A final impression was then taken with zinc oxide eugenol impression paste.

2. Maxillomandibular relationship & try-in procedure: The maxillomandibular relationship was recorded using wax occlusal rims and transferred to an articulator. Artificial teeth were then arranged, followed by the try-in procedure [Figure 1]. After the try-in procedure, an impression of the try-in was made using irreversible hydrocolloid impression material. A cast was then fabricated, and a vacuum-formed sheet template was created on the cast. This template was subsequently placed over the duplicated cast [Figure 2] to aid in evaluating the space required for hollowing as well as for the acrylic resin.

3. Wax-up and processing: Following the try-in procedure, the wax-up was completed, and the dentures were prepared for processing. The mandibular denture was processed using the conventional technique.

Special steps for hollow maxillary complete denture fabrication

• 4.

  Flasking and dewaxing: The maxillary trial denture was conventionally flasked and dewaxed [Figure 3].

• 5.

  Creating the hollow space: An impression of the master cast was made using laboratory putty, and a shim of putty was created to allow even distribution of sugar crystals. The sugar crystals were caramelized by heating over a flame and then poured into one end of the denture, allowing them to harden [Figure 4].

• 6.

  Trimming the sugar layer: Any excessive caramelized sugar was carefully trimmed, ensuring that a uniform layer of acrylic resin could be maintained on both the buccal and palatal surfaces.

• 7.

  Processing the denture: A separating medium was applied to both sides of the flask, and after polymerization, the denture was deflasked, trimmed, and polished.

• 8.

  Hollowing process: The denture was immersed in water for 48 hours to dissolve the sugar, and any remaining sugar residues were flushed out using a forceful water jet through holes in the flange area.

• 9.

  Sealing the hollow space: The access holes were sealed with autopolymerizing polymethyl methacrylate, and the denture’s hollow nature was confirmed by placing it in water [Figure 5].

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Figure 1:

Try-in procedure.

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Figure 2:

Vacuum-formed sheet template for space evaluation.

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Figure 3:

Flasking and dewaxing procedure.

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Figure 4:

Caramelization of sugar crystals in a shim of putty.

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Figure 5:

Hollow maxillary complete denture.

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DISCUSSION

Severe resorption of the maxillary or mandibular ridge leads to a reduced denture-bearing area, negatively affecting the retention, stability, and support of complete dentures. As resorption progresses, the residual ridge becomes increasingly narrow and constricted, resulting in diminished supporting tissue and greater interarch space between the maxillary and mandibular residual ridges. These anatomical changes make it more challenging for dentures to distribute masticatory forces effectively.^[16]

A widely accepted notion in prosthodontics is that heavier dentures, whether maxillary or mandibular, tend to impair their load-bearing capacity.^[17] Although some suggest that increased weight in mandibular dentures may enhance retention due to gravitational forces, this perspective remains controversial. The overall impact of denture weight on prosthetic retention continues to be debated.^[18]

Managing large maxillofacial defects or severe residual ridge resorption with extensive denture base material presents a significant challenge for prosthodontists. Heavier dentures not only compromise retention but also cause considerable discomfort for patients. Various approaches have been explored to enhance retention and stability in such cases, including utilizing undercuts, modifying impression techniques, incorporating magnets, and employing dental implants.

One of the most effective strategies for reducing denture weight while maintaining function is the fabrication of hollow dentures. This technique has historically involved the use of solid three-dimensional spacers, such as dental stone, cellophane-wrapped asbestos, silicone putty, or modelling clay, during laboratory processing. These spacers are later removed, creating a hollow space within the denture base. This innovative approach effectively addresses the challenges posed by excessive denture weight, improving both patient comfort and prosthesis retention.

Research has shown that reducing denture weight, either using a hollow denture design or by modifying the occlusal plane, can help preserve the residual alveolar ridge.^[19] The hollow denture technique offers dual benefits: enhanced retention and stability, as well as improved patient comfort. When managing severely resorbed ridges, additional considerations include ensuring broad coverage of the denture base within functional limits, reducing the number of teeth, narrowing the buccolingual width of artificial teeth, optimizing tooth morphology, avoiding inclined planes, providing adequate tongue space, and maintaining proper interocclusal distance.^[20]

The primary advantages of hollow dentures lie in their significantly lighter weight, which reduces the excessive load on residual alveolar ridges. By minimizing stress on the underlying bone and improving overall comfort, hollow dentures provide a comprehensive solution for patients with severe ridge resorption.^[21] This technique serves as a valuable tool in prosthodontics, offering both anatomical preservation and enhanced patient satisfaction.

Hollow dentures have been widely recognized for their ability to reduce the weight of prostheses, particularly for maxillary complete dentures where excessive bulk can compromise retention and patient comfort. Various techniques have been developed to fabricate hollow dentures, including the lost salt technique and different 3D spacers. Each of these methods presents specific challenges and benefits, which merit discussion to optimize clinical outcomes.

The lost salt technique is one of the most commonly employed methods to create a hollow space within dentures.^[22] It involves placing salt particles within the denture base during processing and subsequently dissolving them in water to leave behind a hollow cavity. While the lost salt technique remains a cost-effective and simple method, its unpredictable nature and potential drawbacks necessitate consideration of more advanced methods. The issues associated with the lost salt technique have been presented in Table 1.

The various 3D spacers have been presented in Table 2. This table summarizes the different 3D spacers used in hollow denture fabrication, highlighting their key advantages and disadvantages. These spacers help overcome the limitations of traditional techniques by providing better control over the hollow cavity’s shape, dimensions, and weight reduction, thereby enhancing both patient comfort and overall denture quality.^[23,24]

The use of 3D-printed hollow cores and acrylic spacers offers superior control, strength, and consistency, making them preferable for long-term clinical performance.^[25] However, the choice of technique should be guided by available resources, patient-specific needs, and laboratory expertise to ensure an optimal balance between weight reduction, durability, and prosthetic function. Future research should focus on optimizing 3D printing applications, investigating novel biocompatible materials for spacers, and developing automated workflows to enhance precision in hollow denture fabrication.^[26]

While the lost salt technique is common in hollow denture fabrication, it often struggles to contain the salt in a defined space. In contrast, caramelized sugar offers clear advantages. Once set, it hardens and maintains its shape during packing, allowing precise placement and easy retrieval.^[27] As a heat-labile spacer, sugar is cost-effective and practical, melting during curing and easily flushed out post-curing without compromising denture integrity. Unlike traditional materials, caramelized sugar becomes a viscous liquid when heated, solidifies without distortion, and remains stable during processing. It is easy to handle, non-fracturing, and dissolves completely in water, leaving a clean, well-defined hollow cavity.^[28]

A crucial precaution in this technique involves maintaining appropriate dimensions for the sugar-pumice mix to ensure it does not occupy the space intended for acrylic resin. To achieve this, a vacuum-formed sheet is used to verify uniform resin distribution, and multiple trial closures are conducted to establish a consistent space for the acrylic.^[29]

However, one potential drawback of this technique is that it can be time-consuming, requiring careful handling of the sugar to achieve and maintain the precise temperature necessary for caramelization.^[30] Success depends on the clinician’s skill and precision throughout the process. Attention to detail is essential to ensure optimal results.

CONCLUSION

The rehabilitation of severely resorbed ridges presents a significant challenge for prosthodontists. While treatment options such as overdentures, implant-retained overdentures, and ridge augmentation are available, many patients affected by severe ridge resorption are geriatric individuals with multiple systemic conditions. In such cases, conventional complete dentures remain a practical and effective solution. Optimizing the impression technique to maximize the denture-bearing area and selecting a denture design that enhances patient comfort and acceptance are key considerations in the rehabilitation process.

Denture weight plays a crucial role in treatment planning, particularly for elderly patients with compromised systemic health. Lightweight dentures are advantageous as they help minimize excessive functional forces, thereby preserving the integrity of the already compromised underlying tissues and bone. Reducing the weight of the prosthesis enhances patient comfort and contributes to maintaining oral health.

The described technique for fabricating a hollow maxillary denture offers a straightforward and effective solution to this challenge. This method allows precise control over the creation of a hollow space, enabling easy material placement and retrieval. By incorporating this approach, clinicians can provide a customized and comfortable prosthetic solution for patients experiencing severe ridge resorption, ultimately improving their overall quality of life.