Full Mouth Rehabilitation with All-on-Six Endosseous Implants with Upper and Lower Arch - A Case Report

ABSTRACT

This article reports the full mouth rehabilitation of a 59-year-old male patient with completely edentulous upper and lower arches using the All-on-Six endosseous implant technique. The treatment involved placing six implants in both the upper and lower arches, followed by the placement of temporary dentures during the osseointegration period. After 15 weeks, impressions of the implants were taken using additional silicone (VPS). The final prosthesis, consisting of a Direct Metal Laser Sintering (DMLS) framework with Zirconia crowns, was designed to ensure optimal aesthetics and function. This case underscores the importance of meticulous diagnosis, planning, and treatment in the successful rehabilitation of implant-supported dentures.

INTRODUCTION

Edentulism is considered a major health problem as it affects the overall health of the patient.[1,2,3] Traditionally, complete dentures were the only treatment option available for edentulous patients.[4] The lack of prosthesis retention and stability, coupled with poor masticatory efficiency, led to dissatisfaction among denture patients, prompting them to seek alternative therapies.[5,6] The advent of implants and implant prostheses has positively impacted the quality of life, and with the widespread adoption of dental implants, the rehabilitation of completely edentulous arches has become quite common. Long-term clinical studies have shown that this type of restoration can be successful for many years. Current standards in implant dentistry aim to provide prosthetic restorations with the finest aesthetic and functional outcomes.

Full arch rehabilitation can be achieved using either fixed prostheses or removable overdenture prostheses. For fixed dental prostheses, a minimum of four implants is recommended.[3,4,5] Fixed dental implant prostheses may be either cement-retained or screw-retained. Screw-retained prostheses are retrievable and require less vertical restorative space compared to cement-retained prostheses.[6,7] Before planning implant restoration, it is critical to assess the patient’s medical and dental history to ensure there are no contraindications to the placement of dental implants.

CASE PRESENTATION

A 59-year-old male presented to the Department of Prosthetic Dentistry with the primary complaint of an inability to chew. He had a history of total teeth extraction three months prior, resulting in complete edentulism. The patient, who had no medical issues and was not on any medication, sought a fixed dental prosthesis. Clinical examination confirmed the complete absence of teeth in both the upper and lower arches, with no muscle or TMJ problems. After evaluation, the “All-on-Four”’ or “‘All-on-Six”’ treatment concepts were proposed as the most suitable options. The patient was informed about the possibility of implant placement with immediate loading, and alternative treatment options included conventional complete full dentures and overdentures on implants.

The preliminary impressions were made using an impression compound, followed by the fabrication of primary casts and trays. Final impressions were taken with zinc oxide eugenol, and bone dimensions were assessed using CBCT imaging. Preoperative imaging, including OPG with the denture placed with gutta-percha at the planned implant sites, was employed for precise diagnosis. The patient received antibiotic prophylaxis and chlorhexidine mouthwash one hour before surgery. Local anesthesia was administered, and various nerve blocks were applied. Using complete dentures as a guide, a mid-crestal incision was made, and a mucoperiosteal flap was raised. Six implants were placed in both arches using a specific drilling sequence, with implant stability exceeding 45 N/cm². Multiunit abutments were placed, followed by temporary cylinders and dentures. Postoperative panoramic radiographs were taken to verify the placement.

Three months later, the patient returned for the second stage of prosthetic rehabilitation. Temporary dentures were removed, and implant sites were checked for complete healing. Open tray impression copings were used for the final impression, which was made with the addition of silicone putty and a light body using a single-step technique. A Direct Metal Laser Sintering (DMLS) bar was employed as a verification jig, and Sheffield’s test was conducted to ensure passivity. Occlusion rims were used for jaw relation records, and a Co-Cr metal Malo framework was fabricated and verified. The final prosthesis, designed in Exocad software and milled in monolithic zirconia, was bonded to the DMLS base and clinically verified for passive fitting. The final restoration, realized in Zirconia Ceramics, considered aesthetic and functional factors, ensuring proper occlusal contacts, anterior guidance, and minimized shear forces to enhance the longevity and functionality of the implant system [Figures 1-3].

Figure 1.

Sequential drilling in the patient done

Figure 3.

OPG after final prosthesis placement

Figure 2.

Final prosthesis in patient’s mouth

DISCUSSION

The All-on-Four therapy is a significant advancement in dental prosthetics, particularly for patients with complete edentulism and limited bone volume. It offers several advantages, including lower costs, shorter treatment intervals, improved quality of life, and reduced patient morbidity.[1,8] This technique utilizes four implants to support fixed dentures, making it a viable option for restoring edentulous jaws. While the All-on-Four technique boasts an implant success rate of up to 99%, the prosthetic survivorship is slightly lower due to issues such as porcelain crown failure, prosthetic fractures, screw loosening, and distal cantilevers.[2,4] To overcome these disadvantages, the All-on-Six prostheses were developed, providing better prosthesis support and improved stress distribution over a larger area.[3,4]

The All-on-Six approach was designed to maximize the use of available bone in the jaw, expedite functional restoration, and eliminate the need for additional regenerative procedures, which can increase treatment costs.[5] By avoiding cantilevers, the All-on-Six concept reduces the risk of biomechanical complications like prosthetic screw loosening and implant overload. Studies, such as the one by Hassan and colleagues, have shown that the All-on-Six implant concept is superior to the All-on-Four, particularly for atrophied maxillae, demonstrating better clinical and radiological outcomes.[6] In this case, the patient underwent implant placement following the prosthodontic plan, with six-unit implant abutments and immediate loading of temporary dentures without cantilevers, ensuring high survival rates and reducing biomechanical risks.[7]

Various prosthetic options are available for All-on-Four or All-on-Six implant full-mouth rehabilitation. These include fixed complete dentures, metal frameworks with individual crowns, zirconia frameworks with porcelain overlays, full contour zirconia, and multiple implant-supported bridges. Each option has its advantages and disadvantages. Fixed complete dentures are cost-effective but require significant restorative space and wear faster. Metal frameworks with individual crowns offer a natural look but have a higher risk of fracture. Zirconia frameworks with porcelain overlays provide excellent aesthetics and strength but are challenging to repair if damaged. Advances in digital manufacturing techniques like DMLS have improved the accuracy and fit of these restorations, offering promising results for crowns and fixed partial dentures.[4,5,6,7] In this patient, a staged approach using zirconia restorations was chosen to meet the patient’s esthetic desires and functional needs, avoiding removable prostheses and ensuring long-term success.

CONCLUSION

The All-on-Six concept in dental implantology offers a stable and resistant solution for complete tooth replacement, allowing patients to chew and speak comfortably. It simplifies treatment by reducing the need for complex procedures and associated costs while providing satisfactory aesthetic results tailored to the patient’s natural look. Additionally, it shortens the healing process, enabling immediate installation of the fixed prosthesis and minimizing the period without teeth.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.