## 2 Materials and Methods  
The present prospective study included 72 patients (49 females and 37 males) affected by maxillary lateral incisor agenesis and rehabilitation by means of implant-proshetic restorations. The age of the patients ranged from 19 to 46 years. In 39 patients, the anomaly was unilateral (54.16%), while in 33 subjects it was bilateral (45.8%). All patients were in good general health; 15 were smokers (20.83%), and 6 showed occlusal parafunctionalhabits (8.3%). Patients were provided with a consent form and a written explanation regarding alternative techniques, the nature of the treatment, and associated procedures and risks. The patients were also provided with a consent form to participate in the study. The study was performed by expert prosthodontists of the Department of Fixed Prosthodontics of the University \"Federico II\" of Naples (Italy); an ethical review was stated by the university. The recruitment of patients was carried out between September 2003 and July 2004 according to the common criteria established by the literature for implant-supported prostheses. The following inclusion criteria were adopted [22; 23]:  
* single tooth space(s) with adjacent teeth intact or restored with functionally and aesthetically good restorations;
* the presence of prostheses precluding the addition of the missing tooth;
* patient reluctance of preparation of adjacent teeth;
* patient refusal to wear removable partial dentures. Patients with a history of substance abuse, psychoses, unrealistic aesthetic expectations, inability to undergo minor oral surgical procedures, comprised health of the local site, insufficient bone quality or mouth opening precluding the placement of the implant, inadequate vertical space, or incomplete facial growth and tooth eruption were excluded from the study. Before surgery, the quantity and quality of bone tissue were analyzed by means of clinical examination with Rinn standardized periapical radiographs according to the long cone technique with parallel rays and CT Dental Scan. All patients showed an average bone thickness from the buccal to the lingual side of 6 \(\pm\) 1 mm, an average bone height of \(\pm\)131 mm (from the margin of the alveolar ridge to the floor of the nose), and an edentulous space (measured from the distal side of the central incisor to the mesial aspect of the canine) of \(\pm\)60.5 mm. According to the bone crest height, 105 TII-SLA Narrow Neck implants (Institut Straumann AG, Waldenburg, Switzerland) were used, as reported below:  
* Sixty-one Narrow-Neck implants 3.3 mm \(\times\) 10 mm;
* Twenty-one Narrow-Neck implants 3.3 mm \(\times\) 12 mm;
* Twenty-three Narrow-Neck implants 3.3 mm \(\times\) 14 mm. The clinician performed a crestal incision located slightly on the palatal aspect and extended the incision through the sulcus of the adjacent teeth to both the buccal and palatal aspect of the alveolar ridge to surgically insert implants. Buccal relieving incisions were only performed for 37 patients. A fine tissue elevator was used to elevate the buccal and palatal muco-periostal flaps to ensure low-trauma soft tissue handling. Narrow-Neck protective copings with an internal occlusal screw were employed to cover the implants after the surgery. During the healing time, 48 patients did not wear any temporary restoration, whereas the other 24 patients wore a resin denture tooth supported by a fake orthodontic appliance. Four months after the surgical procedure, the osseeintegrated implants were loaded. In order to take a fixture-level impression, a thin layer of an adhesive specific for polyethers (Polyether Adhesive, 3M ESPE) was spread on custom autopolimerizing acrylic resin trays (SR-Ivolen, Ivoclar, Schaan, Liechtenstein), and impression transfers and polyether materials (Permadyne Penta H,Permadyne Penta L, 3M ESPE, Seefeld, Germany) were used. A dental technician prepared 105 titanium standard hollow abutments (height of 9 mm) and 105 screwed acrylic temporary crowns.