Aesthetic Outcomes of Single Tooth Implant-supported Restorations in the Anterior Maxilla With Either White Zirconia or Fluorescent White Zirconia Abutments

This study aims to answer the question whether the use of a fluorescent layer over white zirconia abutments will improve the aesthetic outcomes of implant borne single-tooth restorations when compared to the use of non-layered white zirconia abutments. The study is designed as a parallel, single-centre and double blind clinical trial. Patients in need of a single tooth implant in the maxilla (from right second premolar to left second premolar, both included) with the presence of adjacent natural teeth will be randomly divided into two treatment groups: using white yttria-stabilized zirconia abutment (PYRCA; BioHorizons, Birmingham, EEUU) with immersion in fluorescent liquid (Zirkonzahn, South Tirol, Italy)(test group) or white yttria-stabilized zirconia abutment (PYRCA; BioHorizons, Birmingham, EEUU) without immersion in fluorescent liquid (control group). 1 and 12 months after crown placement, patients will be recalled and subjected to aesthetic, clinical, radiographic and patient centered outcomes.

Dental implants (Tapered internal implants; BioHorizons, Birmingham, EEUU) will be placed in healed residual ridges (minimum of 4 months after tooth extraction) following the manufacturer's recommendations. After connecting healing abutments, the flaps will be sutured around the abutments for non-submerged healing. A standard postoperative protocol will be followed (antibiotics, anti-inflammatory medication and topical application of 0.12% clorhexidine) and fixed or removable provisional restorations will be provided without immediate occlusal function.

After a 3-months of healing, subjects will be allocated to either test or control group. An abutment composed of white yttrium oxide stabilized zirconia abutment (PYRCA; BioHorizons, Birmingham, EEUU) previously immersed in fluorescent liquid (Zirkonzahn, South Tirol, Italy) will be placed in the test group, whether in the control group the same abutment will be used but without fluorescent layer. The selected abutment is machined and designed for use with cemented restorations.

A single experienced restorative dentist using one dental laboratory will carry out all the prosthetic procedures. Single crowns full ceramic will be performed and cemented with RelyX™ Luting Cement.

The subjects will then be advised to comply with their regular dental hygiene and maintenance protocol and committed to return for one month and one-year examinations in order to register all the outcome variables of the study.

Eligibility Criteria:
Inclusion Criteria:- Systemically and periodontally healthy subjects,18 years of age with good plaque control (less than 25% PlI) or subjects with a healthy periodontium if selected from a periodontal maintenance program.

* The presence of a single tooth gap in the anterior maxilla (from tooth number 1.5-2.5) with the presence of natural adjacent dentition. A minimum 4 months healing was required if the tooth had been recently extracted.
* The presence of ≥ 2 mm of keratinized tissue in the alveolar ridge and enough bone availability to insert a Tapered internal implant (BioHorizons, Birmingham, EEUU) without the need of bone augmentation (minimum of 5.5 mm in width and 9 mm in height).
* The opposing dentition should be stable (without removable appliances) and subjects with bruxism were excluded.

Exclusion Criteria:

* In patients with a history of periodontitis, if periodontitis re-occurred (clinical attachment loss ≥ 2 mm), they will be excluded from the study and receive periodontal therapy.

  * During implant placement, the selected subject will be excluded if implants were not positioned in appropriate prosthetic guided positions. Implants needing any hard tissue augmentation will be excluded before the surgery, however if during the surgery any of this procedure is needed due to unforeseen, the patient will also be excluded from the study "a posteriori".
  * Pregnant women at any time of the study will be excluded.
  * Inadequate vestibular depth to place the Spectrophotometer device