One-Tooth One-Time (1T1T): A Straightforward Approach to Replace Missing Teeth in the Posterior Region

Advances in computer-aided design and manufacturing (CAD-CAM) composite materials and chairside CAD-CAM systems offer a new landscape for implant dentistry. Digital workflows are increasingly used, especially for single-unit restorations, and they allow straightforward and cost-effective protocols that improve patient satisfaction.

The efficacy of immediate loading on single implants has been demonstrated.^1,2  Currently, to promote osseointegration, the use of resin-based provisional crowns out of occlusion is recommended for immediate loading. Such protocols require several appointments and a significant contribution of the dentist and the lab technician, which affects overall treatment cost.

On the other hand, CAD-CAM composites, especially polymer-infiltrated ceramic network (PICN), are now competing with ceramics for definitive single-unit restorations, notably because of their better machinability (faster and in lower-thickness milling, with less edge chipping),^3,4  the absence of postmilling firing, and the ease of in-mouth adjustments. In particular, their higher resilience and lower elasticity modulus could indicate them for immediate loading of implants.

Intraoral scanning (IOS) of single-unit implants right after surgery and the chairside manufacturing of a PICN crown would allow delivery of a resilient final tooth on the same day.

The aim of these 2 case reports is to describe, as a technical note, an innovative approach for a straightforward and cost-effective replacement of a single missing tooth in the posterior region, as a proof of concept.

Two patients were consecutively treated according to the same protocols. The first patient was a 40-year-old woman presenting with a single missing tooth No. 30, and the second patient was 47-year-old man missing tooth No. 5. Both were professionally active, in good general health (American Society of Anesthesiologists I), and nonsmokers. The quantity of keratinized tissues was optimal (Figure 1). The cone-beam computerized tomography examinations showed generous bone availability in both cases, and the digital planning allowed the placement of 10- or 12-mm implants of regular diameter (Figure 2).

After local anesthesia, minimally invasive incisions (miniflap) were made above the treatment site, without interfering with the neighboring teeth. The implant placements were carried out according to the standard surgical protocol recommended by the manufacturer; however, the implant bed was slightly underdrilled to ensure excellent primary stability. Then, regular-diameter tissue-level implants (TE, SLAactive, Straumann, Basel, Switzerland) were placed, and 40 N/cm implant stabilities were reached. Twelve- and 10-mm implants were placed in cases 1 and 2, respectively (Figure 3).

Directly after the surgery, Variobase abutments (Straumann) and a Cerec plastic scan body were placed on the implant to allow performance of IOS (Omnicam camera, Cerec System, Sirona, Salzburg, Austria) of the upper and lower jaws as well as bite registration according to manufacturer recommendations (Figure 4). Once the digital impressions were done, healing abutments were placed during the chairside crown manufacturing process.

The implant restoration was designed with Cerec 4 software and manufactured with the Cerec MCXL (Cerec System) using the dedicated PICN block (Vita Enamic IS-16L, Vita Zahnfabrik, Bad Säckingen, Germany; Figure 5). Special attention was given to the restoration's emergence profile, the transgingival part of the crown being designed to put the cervical limit in the ideal position and to guide soft-tissue healing. The crowns were then bonded to the titanium base and stained with a light-cured nano-filled composite coating agent, as described in Figure 6. Before placement, the crowns were cleaned for 2 minutes in 3 consecutive ultrasonic baths (cleaning agent, sterile water, and then 90°C ethanol). The restorations were placed 15 days and 2 hours, respectively, after the surgery. In the first case, a lack of component availability in the practice delayed the placement. The screw-retained crowns were tightened with a torque of 15 N/cm after occlusal contact point adjustments. The access channels were filled with Teflon and temporary filling material (Cavit, 3M ESPE, St Paul, Minn; Figure 7).

Patients were instructed to use chlorhexidine mouth rinse 3 times a day and painkillers if necessary. The sutures were removed after 15 and 7 days, respectively. In the second case, slight unscrewing of the crown occurred after 1 week and was then tightened to 35 N/cm.

Two months after, the patients were recalled to torque the crown to 35 N/cm, if necessary, and to close the screw access channel with a light-cured micro-hybrid composite (Figure 8). Thereafter, clinical and radiographic examinations were done at 6 months and 1 year. Up to the 6-month (tooth No. 5) and 1-year (tooth No. 30) follow-up, the implants and the crowns were nicely integrated, and prosthodontics and biological complications did not occur (Figures 9 and 10).

According to the present case report, the innovative 1T1T protocol displays successful outcomes after a 1-year follow-up. To our knowledge, this is the first case showing implant immediate loading with the final crown in occlusion using a full digital workflow without cast.

However, it is important to emphasize that the case was carefully selected. Besides the good bone quality (type 2), the bone availability allowed placement of regular-diameter tapered implants of 10 and 12 mm in length, respectively, and to reach an excellent primary stability. Besides the choice of implant design, implant surface (SLAactive, Straumann) and the absence of risk factors, such as signs of bruxism or tobacco use, probably contributed to the success of this case.

The choice of a composite restorative material characterized by a higher resilience than ceramic is also a key aspect of the procedure. Currently, 2 types of CAD-CAM composites can be distinguished: dispersed filler and PICN materials.⁵  Because of their specific microstructure resulting from the infiltration of a partially sintered glass-ceramic block secondarily infiltrated by monomers, PICNs exhibit a favorable elasticity modulus, which was shown to be intermediate between that of dentin and enamel, while moduli of other CAD-CAM blocks with dispersed fillers are under that of dentin.⁶  Vita Enamic was also shown to exhibit better bonding properties to resin cement than some other dispersed filler composite materials, which is important for implant restorations cemented on a titanium base.^7–9 

Directly placing the final crown with the ideal emergence profile may be an additional benefit allowing prosthodontically driven soft-tissue healing. Recently, experimental PICNs have been shown to exhibit biocompatibility properties comparable to lithium disilicate and no monomer release, thanks to the original polymerization process involving high temperature and high pressure.^10,11  Those properties can contribute to soft-tissue integration and stability.

Finally, the 1T1T protocol is a cost-effective procedure due to the reduced number of appointments and the absence of lab procedures. This straightforward approach provides immediate results and high patient satisfaction.

This first case combining a full digital workflow, chairside milling, and the delivery of a final screw-retained crown in the PICN within a couple of hours after the surgery is very promising. The technique is straightforward, cost-effective, and highly appreciated by the patient. However, patient selection is probably a key factor for the success of this case, and further clinical research should be done to validate such a protocol in routine practice.

Abbreviations

CAD-CAM:

computer-aided design and manufacturing

IOS:

intraoral scanning

PICN:

polymer-infiltrated ceramic network

The authors declare that they have no conflict of interests. This study was self-funded by the authors and their institutions.