Functional and Aesthetic Rehabilitation With Porcelain Veneers and Attachment-Retained RPD: 40 Months of Follow-Up

AUTHORS

Rodrigo Melim Ferreira, DDS, is a master’s student in the department of dentistry at Ingá University Center-UNINGÁ in Maringá, Brazil. Conflict of Interest Disclosure: None reported.

Thais Patricia dos Santos is an undergraduate student in the department of dentistry at Ingá University Center-UNINGÁ in Maringá, Brazil Conflict of Interest Disclosure: None reported.

Renata de Paula Cortati Rabelo is an undergraduate student in the department of dentistry at Ingá University Center- UNINGÁ in Maringá, Brazil Conflict of Interest Disclosure: None reported.

Aline Akemi Mori, DDS, PhD, is an assistant professor in the department of dentistry at Ingá University Center-UNINGÁ in Maringá, Brazil. Conflict of Interest Disclosure: None reported.

Fernanda Ferruzzi, DDS, PhD, is an assistant professor in the department of dentistry at Ingá University Center-UNINGÁ in Maringá, Brazil. Conflict of Interest Disclosure: None reported.

ABSTRACT

Background: Distal edentulous spaces can be challenging when rehabilitation with dental implants is limited. Attachment-retained removable partial dentures (RPD) work as a therapy that can compensate rotational movements and reduce the number of abutments.

Case description: This clinical report addresses indications, selection and procedures for the rehabilitation of a partially edentulous maxilla, involving laminate veneers, fixed and removable prostheses.

Practical implications: Attachment-retained RPDs provide sufficient retention and improved aesthetics compared to clasp-retained partial dentures. Careful aesthetic and functional planning and periodic follow-up are essential for patients’ satisfaction.

Keywords: Denture, partial, removable, denture precision attachment, dental prosthesis design, dental veneers

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Although complete edentulism is decreasing due to improvement in the oral health of individuals and better understanding of the oral diseases, the proportion of partial edentulism is increasing because life expectancy has risen and more teeth are being retained by this population. [1,2] Dental implants are a conservative and comfortable treatment modality, however, surgical procedures are needed that might increase complexity, time and cost. Removable partial dentures (RPDs) can be indicated to overcome surgical limitations, biomechanical and aesthetic issues related to implants, such as excessive bone resorption, that demand bone augmentation or the need for a flange to provide aesthetics. [1,2] When dental implants and/or conventional fixed dental prostheses (FDPs) are not indicated or not desired by the patient, removable partial dentures are a treatment alternative that can yield excellent clinical results. [2–6]

RPDs can be easily removed, which facilitates oral hygiene and favors the survival of abutment teeth; however, poor retention and stability can result in treatment failure. [5] The retention, aesthetics and biomechanics of RPDs can be improved by means of attachments. [7] Attachments are mechanical devices for the fixation, retention and stabilization of a prosthesis. [8] They consist of two parts that relate to each other in a patrix-matrix system. The matrix is positioned inside or outside the contours of the crown of the abutment teeth, while the patrix is attached to the denture framework or base. [8] The primary indication of attachments is aesthetics because retention arms are not present at the facial surface. [7,9] Biomechanical advantages may be obtained, depending on the type of attachment used, the design and adaptation of the framework and the characteristics of abutment teeth and the edentulous space. [5,10]

Attachments are classified as intracoronal or extracoronal depending on if they are positioned within the contours of the abutment teeth or not. [7,8] They can also be rigid or resilient depending on the material and amount of movement they provide to the prostheses. [7,8] Considerations for attachment selection are based in basic prosthodontic principles, including rotation movements and the possibility of torque on abutment teeth as well as the size and location of the edentulous space. It is important that the removable partial denture framework is closely adapted to the teeth and the edentulous ridge. Attachments should be passive when the prosthesis is in its terminal position.[9,10] In this way, careful planning of the clinical steps is essential to treatment success as well as high-quality impressions, proper axis of insertion and guiding planes and precise laboratory procedures.

This clinical report aims to discuss the fabrication of an attachment-retained free distal extension RPD, fixed prosthodontics and porcelain laminate veneers to meet the aesthetic and functional expectations of a partially edentulous patient.

Case Report

A 67-year-old woman presented at a private dental clinic for rehabilitation of edentulous bilateral posterior spaces in the maxilla (from first premolar to second molars) and replacement of provisional crowns on the canines and lateral incisors to improve aesthetics. She wore a conventional RPD and was unhappy with the appearance of the clasps (FIGURE 1). At clinical examination, the maxillary right canine and both lateral incisors were treated endodontically and restored with metal post and cores. The maxillary left canine was vital and prepared for a full crown restoration. Central incisors presented with facial composite resin restorations with marginal discoloration that did not match the shade of the unprepared tooth structure (FIGURE 2). The patient had been treated previously with extraction of the remaining five mandibular teeth and an implant-supported full arch metalacrylic fixed dental prostheses. Treatment with dental implants was planned for the maxillary edentulous spaces; however, the cone beam computerized tomography showed insufficient bone height and width in the edentulous area, requiring bone augmentation procedures for implant placement. The patient desired to keep the six remaining teeth in the maxilla and rejected the treatment plan that included bone augmentation surgery due to the extended time of the treatment. Considering the therapeutic options, the proposed treatment plan was to restore the central incisors with porcelain laminate veneers and lateral incisors and canines with a splinted metal-ceramic FPD that would support an attachment-retained RPD to replace posterior edentulous spaces.

Treatment was started by mounting diagnostic casts on a semi-adjustable articulator (A7 Plus, Bio-Art, São Carlos, Brazil), the maxillary cast was oriented by a facebow record (Elite, Bio-Art) and occlusal relationship was recorded with a wax rim. Acrylic teeth were positioned over an acrylic base in the edentulous areas and a preoperative wax try-in was performed over the anterior teeth for an aesthetic and functional clinical evaluation. A mock-up in bis-acrylic resin (Structur 3, VOCO GmbH, Cuxhaven, Germany) was positioned over the anterior teeth and the position of the artificial teeth was clinically evaluated. This is a key step that allows the patient and the dentist to predict the final result and determine achievable treatment goals.

After the patient’s approval, the prepared anterior teeth were refined and polished. An impression using acrylic copings and low-viscosity polyether (Impregum, 3M ESPE, St Paul, Minn.) was taken (FIGURE 3A). Splinted FPDs were waxed and recontoured with the aid of a dental surveyor to determine the most suitable path of insertion and removal of the RPD. A combination of attachments was planned: semi-precision rigid intracoronal attachments (interlock type) and rigid extracoronal semi-precision attachments (SR 3.0, CNG, São Paulo, Brazil). The intracoronal attachments were contoured during waxing of the FDPs’ metal structures between the lateral incisors and the canines. The rigid attachments consisted of prefabricated acrylic patterns (patrix) positioned at the distal surface of canines and cast with the FDP framework, and metallic retainers (matrix) were embedded in the acrylic base of the RPD. Rest seats and guiding planes for reciprocal clasps were designed to guide insertion and removal. The FPDs’ frameworks were cast in a cobalt-chromium alloy (FIGURE 4).

The FPDs’ framework’s shape and fit were clinically examined and bite registration was performed with acrylic resin (Pattern, Kota, Cotia, Brazil). Maxillary central incisors received chamfer veneer preparations according to biomechanical and aesthetic principles. The shade of the teeth was determined with photographs and the aid of the shade guide of the selected ceramic system (FIGURE 5). A full-arch impression was taken using retraction cords (Ultrapak, Ultradent, South Jordan, Utah) and polyvinyl siloxane (Express XT, 3M ESPE) (FIGURE 3B) to obtain a definitive cast for fabrication of ceramic veneers for the central incisors and porcelain application for the FPD frameworks. The same feldspathic ceramic (IPS d.Sign, IvoclarVivadent AG, Schann, Switzerland) was used to ensure the different prosthetic options would match in shade (the desired final shade was A2, Ivoclar shade guide).

At the next clinical appointment, laminate veneers and FPDs were examined for fit, shade match and aesthetics. The feldspathic laminate veneers were prepared for adhesive bonding with 5% hydrofluoric acid for 60 seconds, rinsed and treated with 37% phosphoric acid for 30 seconds to remove residues from the hydrofluoric acid etching that could jeopardize the bond strength to the resin materials. A silane coupling agent was actively applied to the intaglio surface for 20 seconds and left to react for 60 seconds. Modified rubber dam isolation was performed and a conventional total-etch adhesive technique was carried out. Most of the margins were located in the enamel, thus central incisors were etched with 37% phosphoric acid for 30 seconds. In cervical areas with exposed dentin, acid etch was performed for 15 seconds followed by application of a primer (Adper Scotchbond Multi-Purpose, 3M ESPE). Veneers received a layer of hydrophobic adhesive (Adper Scotchbond Multi-Purpose, 3M ESPE) and composite resin shade A2 (Z100, 3M ESPE) thermally modified in a composite warmer (Calset, AdDent, Danbury, Conn.). After removal of excess composite, 60 seconds of polymerization time was carried out for each tooth.

An acrylic custom tray was made and border molding with impression compound (Kerr, Brea, Calif.) was performed in the edentulous area. Metal ceramic crowns were set in position and an impression was taken with medium viscosity polyether (Impregum, 3M ESPE) in order to transfer the position of the RPD and obtain a selected pressure impression of the edentulous areas (FIGURE 3C). The definitive cast was used for waxing and casting the framework in a cobaltchromium alloy over the metal-ceramic FPDs (FIGURE 6) and also for processing the acrylic portion of the RPD.

Afterward, the relationship between the RPD framework and the FPDs was clinically evaluated. Occlusal relationship and aesthetic arrangement of the acrylic teeth (Pala, Kulzer GmbH, Hanau, Germany) were positioned over the RPD framework with wax and evaluated. Finally, the RPD was processed and its gingival portion was characterized using an acrylic resin staining system (STG Tomaz Gomes, Vipi, Pirassununga, Brazil). The passive seating of the RPD was checked prior to cementation of the FPDs; subsequently, the patient was asked about any pressure, pain or discomfort during the final insertion of the RPD.

FPDs were cemented with resin self-adhesive cement (RelyX U200, 3M ESPE). The RPD was adapted, an occlusal adjustment was performed and the patient was instructed not to remove the prosthesis for the next 24 hours to allow the final set of the cement. The next day, the RPD was removed and the cervical areas around the FPDs were carefully inspected for excess cement. The adjusted occlusal surfaces were polished.

Occlusion, hygiene and comfort were checked in the seven- (FIGURE 7) and 30- day follow-up appointments. The patient was taught how to clean and take care of the prosthesis and was instructed to return every six months. During the 40 months of followup, the patient had no complaints and there was no need for repair or rebase. The patient reported improvement in masticatory function and satisfactory aesthetics after rehabilitation treatment (FIGURE 8).

Discussion

In this clinical report, porcelain laminate veneers, metal ceramic FPDs and an attachment-retained RPD were proposed to rehabilitate a patient with a Kennedy Class I edentulous maxilla. This treatment provided retention, comfort and aesthetics with no need for surgical procedures.

Although the main advantage of attachments is aesthetics, they may also provide some increase in retention and comfort, considering that they are independent of the size and shape of the abutment tooth and present less volume. [7,9,10] The main negative aspect of attachments is the need for placing full crowns on the abutment teeth, which requires removal of tooth structure and also increases the treatment’s complexity and cost. [7] In this case, an attachmentretained RPD was considered as the first nonsurgical option, as the abutment teeth had already been endodontically treated and/or prepared prior to the patient seeking definitive treatment. [9,11]

Distal extension removable prostheses are challenging because they are supported by both hard and soft tissues. The main concern when designing an RPD is minimizing distal rotation and torque of the abutment teeth during function. [8,9] In the present case report, intracoronal attachments positioned at the canines would favor stress distribution in the long axis of the tooth; nevertheless, they require extensive preparation that would probably demand endodontic treatment of the left canine. Thus, extracoronal attachments were planned for both canines to allow symmetric forces distribution in this Kennedy Class I RPD. Extracoronal attachments, however, represent a lever arm that could increase torque forces in abutment teeth. To reduce these forces, it is recommended to place rigid extracoronal attachments over splinted crowns and ensure that forces are distributed to the residual ridge by means of a well-fitted extended denture base, as performed in this case. [8,10,12] Intracoronal attachments between canines and lateral incisors were designed to provide the most stability possible, reducing distal movement and torque in the abutment teeth that might occur. Although there are no guidelines on the exact number of retainers that should be designed for an RPD, the authors believe that additional intracoronal attachments could act as highly functional indirect retainers in an attempt to compensate the reduced number of abutment teeth. Guiding planes were also designed to increase the contact area of the framework and abutment teeth and guide insertion and removal, contributing to bracing and stability of the abutment teeth. [9,10]

When a combination of FPD and RPD is planned, metal-ceramic prostheses are recommended for both short- and longspan reconstructions because they have high success rates in the long term, and the attachments can be cast or welded to the metal structure. [13,14] Considering the main complaint of this patient was aesthetics, the central incisors received laminate veneers assuming a pleasant shape, shade and size to fulfill the patient’s expectations. This restorative option requires minimal preparation and presents excellent longterm results and patient satisfaction. [15]

Oral rehabilitation with combined FPD and attachment-retained RPD, however, is more complex. Thus, the clinical steps must be carefully planned to prevent any minor distortions that could culminate in misfit of the RPD. [11,16] In the present case, three different impressions were performed to produce different working casts (FIGURE 3). The first provided a working cast for the fabrication of the FPDs’ metal framework. Later, the second cast allowed the fabrication of laminate veneers and ceramic veneering of the FPDs using the same feldspathic ceramic to ensure color match. Considering that forces must be widely distributed to all available tissues in distal extension RPDs, the denture base should be extended to cover all of the residual ridge within the limitation of functional muscle movements. [9,10] The third impression transferred the position of the FPDs and provided an accurate reproduction of the edentulous area. Even minimal errors during impression and cementation of the FPDs might compromise the seating of the RPD. [11] However, in this case, the accurate impressions resulted in excellent clinical fit and only occlusal adjustments were necessary.

Although some controversy may arise with the use of attachments in Class I RPDs, in particular, the influence on stress distribution and the consequences to abutment teeth, there were no complications reported for soft tissues and abutment teeth. In a multicenter randomized clinical trial, Walter et al. [6] evaluated tooth loss in patients wearing attachment-retained RPDs or no removable prostheses or FPD with a distal cantilever in the second premolar (shortened dental arch (SDA) concept) after 10 years. The authors concluded that attachment-retained RPDs are not capable of causing tooth loss at a higher rate than the SDA concept. [6] A systematic review on the clinical performance of RDPs concluded that attachments are unsuitable for Kennedy’s Class II; however, for attachment-retained Class I RPDs, failure rates vary from 11% to 30% and are comparable to conventional RPDs. [5] The possibility of retention loss attributed to the attachments’ wear is a concern. If repairs or replacements are necessary, the procedure might be technically difficult. [16–18] In the present report, no complications were reported and no repair was needed. Although the wear by attrition might occur, clinical studies show these prostheses seem to be less prone to repair and technical complications than conventional clasp-retained RPDs. [5,18] In fact, the attachments provide additional comfort and confidence to patients because treatment failure due to nonwearing is reported for conventional RPDs, but not for attachment-retained RPDs. [5]

Summary

In the present clinical report, oral rehabilitation with removable prosthesis is a conservative therapeutic modality for distal extension edentulous space with excellent clinical results in the short term. Using a combination of intra- and extracoronal attachments as retentive devices provided an RPD with retention and stability. By eliminating conventional facial retention arms, the overall treatment with laminate veneers, FPDs and an attachment-retained RPD provided the patient a highly aesthetic result.

ACKNOWLEDGMENT The authors thank Frank Kaiser, dental technician, for superbly performing all laboratory procedures involved in this case.

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THE CORRESPONDING AUTHOR, Fernanda Ferruzzi, DDS, PhD, can be reached at Fer.ferruzzi@gmail.com.