Redesigning the Macrostructure of Dental Implants

INTRODUCTION
Because of the improvement of dental implant surgical protocol, the restorative dentist can restore dental implants immediately with a high degree of patient satisfaction from the outset. However, subsequent tissue recession¹ can result in loss of supporting tissue,² loss of osseointegration, loss of aesthetics, and total failure of treatment.

Redesigned Implant for Immediate Placement
In 2008, a new implant design was introduced that can be used in most clinical situations. The dental implant system, which consists of a dental implant, fixture mount abutment, and abutment screw (Figure 1), is specifically designed for the purpose of immediate impression taking and immediate implant placement. The new design employs several modern concepts, not only to establish high insertion torque and enhance the primary stability, but also to provide multiple applications of an implant fixture mount.³

The implant has a double-margin design (Figure 2) with an anodized⁴ (yellow and magenta) collar that is approximately 1.2 mm in vertical height, designed to improve aesthetics in case of implant exposure or subsequent tissue recession. This collar (Figure 3) provides a mirrorlike surface, much smoother than the machined titanium surface found in the coronal portion of other dental implants, helping to reduce dental plaque deposition and subsequent tissue recession.^4,5 The double-margin design also allows the restorative dentist to change margin location in case of implant exposure or subsequent tissue recession. Most of the rough surfaces cannot be avoided.⁵

Figure 1. Assembly and platform switch design.	Figure 2. The Immediate Dental Implant (IDI) (AIDI Biomedical).
Figure 3. Anodized collar and microthread design.	Figure 4. Mechanical properties of the implant thread.

Figure 5. HA crystal Soluble Blast Media surface.

The dental implant has a platform switching design (Figure 1) that can reduce stress to crestal bone.⁶ A platform switching design can also minimize the loss of crestal bone height. The Immediate Dental Implant (IDI) (AIDI Biomedical) is designed to be placed at bone level. The coronal portion of the implant has a platform switching design, which is intended to maximize the alveolar bone around the collar of the implant and provide soft-tissue support.^7-9

A microthread design (Figure 3), located 1.3 mm apical to the platform, counteracts marginal bone resorption in accordance with Wolff’s law¹⁰ and increases the resistance to shear forces significantly, optimizing implant stability in suboptimal clinical conditions.¹¹ The relocated microthread of the IDI is designed to prevent significant bone destruction found with the unintentional perforation of 2-stage implant thread exposure.²

The body thread (Figure 2) of the IDI is a deeper, single-thread design (a triple-thread design can increase micromotion).^12,13 Further, using an asymmetric thread design increases the apical face angle/decreases coronal face angle (Figure 4) and narrows the implant apex; reducing resistance of dental implant insertion, minimizing site preparation, and maximizing bone preservation. This design allows for gradual expansion of the bone as the implant advances, which is similar to the utilization of osteotome^3,14 to achieve high insertion torque (90 Ncm) and increase initial stability. It is appropriate for immediate dental implant placement and immediate loading with appropriate occlusal loading even when a compromised quality of alveolar bone exists.

A sinolift design (Figure 2), located at the apical end, functions like an osteotome by simultaneously lifting the maxillary sinus and condensing the bone.^14-16

The implant design allows for preparing a narrower-than-typical initial implant osteotomy and placing the implant in a method similar to turning a corkscrew. This allows for gradual expansion of the maxillary alveolar bone and cortical bone of sinus floor as the implant advances to avoid possible complication of rupturing the Schneiderian membrane.^16,17

The surface of these dental implants possesses an implant body that is blasted with a resorbable HA crystal Soluble Blast Media, creating a biocompatible roughness (Figure 5) for osseointegration;^18-20 however, the 1.2-mm neck collar area (Figure 3) remains with its anodized smooth surface.

Several clinical cases will now be presented to illustrate the clinical application of this new implant design.

CASE REPORTS
Case 1
A male patient, age 61 years, was admitted with a horizontal tooth crack on tooth No. 26 (Figures 6 and 7). Clinically, this tooth presented with an inadequate ferrule and a resulting poor prognosis. After discussing the treatment options, the patient elected to have tooth No. 26 extracted with one implant (3.5 x 13.5 mm IDI) to be immediately placed.

Figure 6. Preoperative photo showing fractured tooth No. 26.	Figure 7. Preoperative radiograph of tooth No. 26.
Figure 8. Ball screw and fixture mount abutment utilized as impression coping.	Figure 9. Radiograph of ball screw and fixture mount abutment.
Figure 10. Final restoration, delivered 6 hours after tooth extraction.	Figure 11. Final restoration, delivered 6 hours after tooth extraction.

Figure 12. The 18-month follow-up of tooth No. 26.

Figure 13. The 18-month follow-up radiograph of tooth No. 26.

The extraction was done and the implant placed, with a newly designed torque wrench being utilized for final torque (80 Ncm) of the dental implant. Immediately after implant placement, final impressions (Heavy Body of EXAMIX NDS [GC America]) were taken using the fixture mount abutment and ball impression screw as impression copings (Figures 8 and 9), and then a provisional abutment was placed. A single screw-retained restoration for tooth No. 26 (Figures 10 and 11) was delivered on the same day, 6 hours after the tooth extraction and dental implant placement.

The 18-month post-delivery check revealed good stability of the dental implant and the restoration (Figure 12). Soft-tissue and osseous-tissue recession was very minimal. The 18-month follow-up radiograph (Figure 13) also revealed less alveolar bone loss of IDI at tooth No. 26 position compared to a competing manufacturer’s 4.3 mm x 13.5 mm dental implant in the tooth No. 27 position; the bone level of this dental implant resorbed to the first thread after 3-year follow-up. The bone level of the IDI placed on tooth No. 26 maintained its bone level near the platform level after 18 months.

Case 2
A 63-year-old male patient presented with edentulous maxillary and mandibular arches (Figure 14) with moderate to severe bone loss. After clinical evaluation, the decision was made to restore this patient with dental implant-supported fixed restorations. The missing alveolar bone would be restored using a pink ceramic.

Figure 14. Edentulous maxilla and mandible.

Figure 15. Full-contour wax-up.

Figure 16. Definitive restoration was delivered about 4 weeks later.

A flapless operation was performed and a total of 16 dental implants were placed on the maxillary and mandibular arches. The final torque measurements for all implants were between 50 Ncm and 85 Ncm. After the abutment screws were removed, ball screws were utilized to secure the fixture mount abutments. Both maxillary and mandibular final vinyl polysiloxane (VPS) impressions were taken immediately after implant placement. Face-bow and centric relation (CR) records were taken immediately after the impressions were done. A full-contour wax-up (Figure 15) was also fabricated for both arches. The definitive restorations (Figure 16) were delivered about 4 weeks later. The postdelivery appointment revealed good stability and aesthetics, and the patient was pleased with the outcome.

Case 3
A 59-year-old female patient presented with a severe resorbed edentulous maxilla (Figure 17). She had worn complete dentures for 25 years. After examination, it was determined that the anterior resorbed maxillary ridge did not have enough alveolar bone to house dental implants.

Figure 17. Resorbed edentulous maxilla.	Figure 18. Nine IDIs placed.

Figure 19. Solid cast working model.

Figure 20. Full-contour wax-up.

Figure 21. Maxillary implant-supported complete restoration.

Figure 22. Final radiograph of the completed case.

A flapless operation was performed. A total of 9 dental implants (Figure 18) were placed in both maxillary posterior areas. Two dental implants were placed at tuberosity area of both sides of the maxilla.

A 6-month healing period was provided for osseous integration. Then, a VPS final impression, face-bow, and CR records were taken. A solid cast was made (Figure 19) and a full-contour wax-up was then carefully made (Figure 20). The vertical dimension of occlusion was increased 1.0 mm in the second molar area to reduce the effect of her Class III malocclusion (due to the resorbed anterior maxillary area). As a result, the resorbed maxilla was restored with an implant-supported fixed complete restoration (Figures 21 and 22) rather than an overdenture. A good aesthetic result was achieved and the patient was very pleased with the outcome.

CONCLUSION
Due to improvements in surgical protocols and dental implant design, such as the recently introduced implant system described and demonstrated in this article, the restorative dentist can immediately place and restore dental implants with predictable outcomes and excellent patient satisfaction.

References

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Mr. Tian, a mechanical and industrial engineer, began his career in dental implant technology and applied his engineering knowledge in the pursuit of improving dental implants and accessories. He currently is the chief engineer and production manager of AIDI Biomedical. He can be reached at jack@aidibiomedical.com.

Disclosure: Mr. Tian is the senior engineer of the IDI Dental Implant System.

Dr. Tseng, DDS, a graduate of New York University College of Dentistry, has more than 20 years of clinical dental therapy and implant experience. He received his MBA at National Taiwan University and is a
member of International College of Dentistry. He is former president of the Taipei Congress of Oral Implantologists (2000-2001);
the Taiwan Association of Oral Healthcare Management (2001-2003); and the Academy of Oral Implantology Taiwan (2007-2009).

Disclosure: Dr. Tseng is an associated partner of the IDI Dental Implant System.

Dr Hung graduated from the advanced prosthodontics program at the University of Southern California (USC) School of Dentistry. He was a part-time faculty member at USC’s School of Dentistry. He is limiting his practice in the fields of prosthodontics, rehabilitation, and implant dentistry. He is the founder of Upland Dental Implant and Orthodontics and AIDI Biomedical. Currently, he is devoted in developing new implant systems. He can be reached at william@aidibiomedical.com.

Disclosure: Dr. Hung is the designer of the IDI Dental Implant System.