Novel Esthetic Technique for Restoring Dental Implant Access Holes

1. Introduction

Good dental implant outcomes require not only functionality, but also excellent esthetics [1]. The special mechanism of fastening the superstructure to the implant body via abutment screws, which is unique to implant superstructures, protects the implant body from damage caused by excessive occlusal forces [2]. Additionally, the risk of local infection caused by biofilm adhesion is reduced by the ability to remove the implant for cleaning. However, even in the molar region, dark access holes undermine esthetics, compromising the patient’s expected treatment outcome [3]. Although this problem can be solved by cementing the superstructure, the development of peri-implantitis induced by residual cement is a problem [4,5], and discussion of the ideal superstructure fabrication and management method is ongoing [6,7]. To meet the conflicting requirements of esthetics, functionality, and removability, we have devised a new method of restoring implant superstructures – the inlay covering esthetic technique – in which the conventional superstructure fabrication process is augmented with an inlay body covering the access hole of the crown. We undertook a case in which the inlay was fabricated using computer-aided design / computer-aided manufacture and then cemented, and good results were obtained. Here, we report the fabrication method and progress.

2. Technique

A 72-year-old female patient visited our hospital for treatment of severe periodontitis (Figure 1a, b, c). After initial periodontal treatment, implants (Straumann^®® Bone Level SLActive^®® Φ4.1×10, Straumann, Basel, Switzerland) were placed in the mandibular molar region (#46). The surgery was performed in a two-stage procedure, and an acrylic resin provisional crown was placed. Because there were no problems with occlusal function and the peri-implant mucosa was stable, a precise impression was taken (Figure 2).

Step A: Fabrication of Superstructure (Main Body)

The screw-retained superstructure with highly translucent partially stabilized zirconia discs (Sakura Zr. Disk ML, Straumann Japan, Tokyo, Japan) was fabricated by computer-aided design / computer-aided manufacture (D2000, 3Shape, Copenhagen, Denmark). After milling, the inlay cavity was prepared by a dental technician in a semi-sintered state for easy grinding, and then sintering was performed (Figure 3a, b, c).

Step B: Scanning of the Main Body and Fabrication of the Inlay Body

The superstructure was then scanned with a laboratory scanner, and the inlay body was fabricated separately (Figure 4a, b, c).

Step C: Completion of the Superstructure Components

All components were characterized and the superstructure was completed (Figure 5).

Step D: Completion of the Superstructure Components

After the abutment screws were tightened to the torque indicated by the manufacturer, the inlay body was luted with glass polyaluminate cement (IP Temp Cement, Shofu, Kyoto, Japan) (Figure 6). The left molars (#35, 36) were also fabricated using the same technique (Figure 7a,b,c,d), and maintenance treatment was started (Figure 8a,b,c,d).

3. Discussion

This method is a simple way to esthetically seal the access hole by fabricating a zirconia crown and inlay with excellent mechanical strength and minimal negative impact on peri-implant tissue [8]. This method also has an advantage in that the inlay body is easily removed for maintenance and, even if the inlay body is damaged, it can be easily remanufactured using the data from the scanning process [9]. It also has the biological advantage of maintaining healthy peri-implant tissue because it avoids the problem of residual cement in the subgingival area as in the conventional cement retention method. Additionally, the restriction of the implant placement direction is reduced, allowing a wider range of indications. However, a small inlay body may impair retentive force and resistance, and may easily drop out of the cavity. Therefore, the direction of transmission of occlusal force should be taken into account when designing the crown shape [10]. The esthetic restorative technique presented here is most suitable for molars with a wide occlusal surface because of the importance of the stability of the inlay body. Application of this technique to canine and anterior teeth is a subject for future study.

4. Conclusion

The process of implant superstructure fabrication introduced in this paper resolves all of the previous problems related to esthetics, functionality, and cleanability. This novel restorative technique compensates for the shortcomings of conventional screw-retained and cement-retained superstructures, and will lead to improved outcomes for dental implant treatment and contribute to improvement in oral quality of life.