Study design
This project began, initially, as a pilot study, which consists of a retrospective part and a prospective follow-up part. This observational ambispective clinical study was approved by the Clinical Research Ethics Committee of the Basque Country (CEIC-E) (Internal Code PI2016088, 07/2016). In addition, it is registered at www.ClinicalTrials.com (n° NCT03352284).
Study population
Patients who met the following inclusion criteria were included in the study:
-
1.
Patients treated in Own Master of Periodontology and Osseointegration in the University of the Basque Country (UPV/EHU)
-
2.
Age > 18 years
-
3.
One single tooth missing in the anterior maxilla (1.5–2.5)
-
4.
Plaque index <20% [15]
-
5.
Bleeding on probing index <20% [16]
-
6.
Periodontally healthy or treated periodontal conditions
-
7.
Is able to fully understand the nature of the proposed surgery and is able to provide signed informed consent
Conversely, patients who presented any of the following exclusion criteria were not included in the study:
-
1.
General contraindications to dental and/or surgical treatment
-
2.
Is taking medications or receiving treatments which have an effect on healing in general (e.g., steroids or large doses of anti-inflammatory drugs)
-
3.
Untreated periodontal conditions
-
4.
Not willing to participate
In this way, a total of 28 patients (16 women and 12 men) with a mean age of 54.1 years [34-67 years] who required dental implants to replace a single tooth in the maxilla were recruited to participate in the study, and all of them were properly informed and signed a written informed consent.
Clinical and radiographic evaluation
All-ceramic one-piece implants (PURE Ceramic Implants Monotype, Institut Straumann AG, Basel, Switzerland) were used.
Before surgery, a clinical and radiographic diagnostic assessment was carried out to choose the appropriate implant for each case. To locate the 3D implant position, the following minimal distances were taken into consideration: minimum 1.5 to 2 mm from the natural adjacent teeth, 1 mm palatal to the ideal point of emergence, and 2 mm apical to the midfacial gingival margin of the final implant prosthesis [17]. A minimum of 1.5 mm to 2 mm thickness of buccal bone was preserved as well. The implant diameter and the length were chosen according to each individual case. These implants had two different abutment heights: 4 and 5.5 mm, and for the selection of the implant, all these considerations (position of natural teeth, width of alveolar ridge and occlusion) were taken into consideration in the planification of the treatment of each patient. Finally, study models were made to manufacture splints for use as surgical guides for each patient.
All surgeries were performed under local anesthesia with articaine (Meganest ® 1:200.000, Clarben, Madrid, Spain). The surgical technique consisted in the elevation of a full-thickness mucoperiosteal flap, both vestibular and palatal, through a mid-crestal incision. After the alveolar bone had been exposed, the drilling sequence was carried out according to the manufacturer’s instructions before the placement of the fixture. In some cases where bone volume was insufficient, dehiscence or fenestrations were treated by the guided bone regeneration technique with xenograft (Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland) and resorbable collagen membrane (Collagene AT®, Centro de Odontoiatria Operativa S.R.L, Podova, Italy). Once the implant had been inserted, a healing cap was placed in almost all cases and the flap was closed and sutured (Fig. 1a–d).
In 18 of the cases (56.3%), an immediate provisional crown was made due to the esthetic demands of the patients. In this case, primary stability with an insertion torque > 30 Ncm was confirmed and a pre-formed polycarbonate crown of the appropriate size was chosen. That crown was overlaid with a self-curing resin (Tab 2000, Kerr, Scafati, Italy) and composite (TPH Spectrum®, Dentsply Sirona, York, Pensilvania, USA) and then polished perfectly. The crown was cemented with Temp-Bond (Temp-Bond™, Kerr, Scafati, Italy), and the occlusion was verified to check that there was no contact during centric or eccentric movements to prevent loading during osseointegration.
Post-operative instructions included amoxicillin 750 mg every 8 h for 8 days, dexketoprofen 25 mg every 8 h for 4 days, and rinsing with chlorhexidine digluconate 0.12% twice a day for 15 days. Sutures were removed after 7 days.
After 6 to 8 weeks of healing and following the manufacturer’s recommendations, final impressions were taken using the corresponding impression cap with a closed tray and VPS impression material of putty (Empress™ 2 Putty Soft, 3M ESPE, Seefeld, Germany) and ultra-light viscosity (Empress™ 2 Ultra-Light Body Quick, 3M ESPE, Seefeld, Germany). Due to the one-piece design of the ceramic implant, all-ceramic zirconia crowns were inserted in all cases. Permanent glass ionomer cement (Ketac Cem™, 3M ESPE, Seefeld, Germany) was used to cement the crowns directly onto the implant abutment. Special attention was paid to remove all remaining cement.
After placement of the definitive prosthesis (T0), we carried out photography, intra-oral radiography, and measurements of probing depth, bleeding on probing, maximum distance from the gingival margin to the incisal edge, and Jemt papilla index, and took these parameters as the baseline from which any changes were evaluated.
In each of the follow-up appointments, 4 (T4), 8 (T8) and 12 months (T12) after the placement of the prosthesis, plaque control was reinforced, whatever supragingival plaque that could be removed was removed, a photograph of the restoration was taken, and the following parameters were recorded by one of the researchers (MV):
-
Probing depth (PD): pocket probing on dental implants was recorded with light force (approximately 0.25N) at six points around the implant.
-
Bleeding on probing (BOP) (at six points around the implant) [16]
-
Suppuration on probing (SOP): local SOP score was recorded as the percentage of total surfaces (six points per implant) that exhibited suppurating on gentle probing with a light force (approximately 0.25N)
-
Plaque index [15]
-
Peri-implant recession (Pi-Rec): the difference between maximum distance from the gingival margin to the incisal edge measured at baseline and 1 year-follow-up, measured on the mid buccal site.
-
Jemt papilla index (JPI) [18]
At the last follow-up appointment, an X-ray was also performed to assess bone changes, namely any loss or gain as measured at the mesial and distal aspect of each implant relative to the baseline measurements at the beginning of the study. The final photograph was used to analyze soft tissue changes, namely peri-implant recession (Pi-Rec) and the state of the papilla according to the Jemt papilla index [18].
All radiographic measurements were taken by the same investigator (RE), at baseline (T0) and at 12 months (T12). Changes in the bone level were measured both mesially and distally of the implant on a periapical X-ray taken with a standardized film holder (Rinn® Flip-Ray Film Holder, Rinn, Dentsply International Inc. Elgin, IL, EEUU). The length of the polished neck of the implant (1.8 mm) served as a reference to calibrate the X-ray before measuring marginal bone loss (MBL) from the neck of the implant to the first bone-implant contact (BIC). A positive value indicated that the first BIC was located above the first thread of the implant, and a negative one indicated that it was located below.
Statistical analysis
The data were analyzed by XM using IBM SPSS software version 22. For descriptive statistics, we used the mean, standard deviation, rank, and percentages. For analytical statistics, the Wilcoxon signed-rank test for related samples was carried out. P values of less than 0.05 were considered statistically significant.