Evaluation of single implants placed in the posterior mandibular area under immediate loading: a prospective study

Abstract

The aim of this study was to evaluate the survival of single dental implants subjected to immediate function. Twelve patients with edentulous areas in the posterior mandible were included in the study. All received at least one regular platform dental implant (3.75 mm × 11 mm or 3.75 mm × 13 mm). Clinical and radiographic parameters were evaluated. The survival rate after 12 months was 83.3%. The implants showed no clinical mobility, had implant stability quotient values (ISQ; Osstell) around 70, bone loss of up to 2 mm, and a probing depth of ≤3 mm. Although the posterior mandible is an area in which the immediate loading of dental implants should be performed with caution, this treatment presented a good success rate in the present study sample.

Oral rehabilitation with dental implants has a high success rate. With the conventional protocol, the implants are loaded 3–6 months after their installation. This is to avoid a fibrotic union between bone and implant, which is the main cause of implant failure.

In implant therapy, the survival rate is often used to describe a situation in which the implants are functional, whether or not they fulfil all of the success criteria. Several parameters are used to define implant success, including stability, the amount of bone loss, and the periodontal probing depth. The probing depth is among the clinical parameters most often used to evaluate peri-implant soft tissue and health. It is considered one of the most accurate methods to detect a peri-implant pathology.

Some studies have compared the immediate loading of implants with delayed loading and have concluded that both techniques are predictable in totally and partially edentulous patients. However, the great majority of studies that have evaluated immediate loading have involved implants placed in the anterior areas of the maxilla and mandible. The aim of the present study was to evaluate immediate loading of single implants placed in the posterior mandible.

Materials and methods

This study was approved by the Ethics Committee of Araraquara Dental School, São Paulo State University (UNESP) and was conducted in accordance with the guidelines of the Declaration of Helsinki. All patients were informed of the study methodology and signed a consent form.

Twelve adult patients who presented tooth loss in the posterior mandible, and for whom osseointegrated implants were indicated, were recruited consecutively into this study; study recruitment took approximately 9 months. The following inclusion criteria were applied: agreement by the patient to participate; having at least one tooth posterior to the edentulous area to be implanted; sufficient bone width for the insertion of a 3.75-mm implant; sufficient bone height to insert an implant of at least 11 mm; no bruxism; no systemic health issue that could compromise the technique; no drug addiction; satisfactory oral hygiene. These patients were evaluated prospectively from inclusion.

All procedures were performed in the ambulatory care setting under local anaesthesia. The patients received antibiotics 1 h before the procedure, either 1 g of oral amoxicillin, or in the case of allergy to amoxicillin, 300 mg of clindamycin. The antibiotic and 0.12% chlorhexidine mouth rinse were prescribed for 7 days postoperatively.

A semilunar incision was used in order to improve papilla formation. The surgical sockets were prepared according to the manufacturer’s guidelines (PROSS Dabi Atlante, São Paulo, Brazil). After implant insertion, a healing abutment was installed to facilitate soft tissue repositioning and 4–0 Vicryl sutures were placed. The implants used were of a cylindrical design with an acid-etched surface treatment, which confers roughness; all implants used had an external hexagon connection ( Fig. 1 ).

Fig. 1
Macroscopic view of the implant system used in this study.

The healing abutment was removed and the transfer casting was done. Provisional crowns were installed within a maximum time frame of 48 h and were kept in infra-occlusion (1 mm) during the first 6 months after surgery.

The evaluation parameters used in this study were the probing depth, implant stability, and peri-implant bone loss. These parameters were assessed immediately after prosthesis installation (T1) and at 3 months (T2), 6 months (T3), and 12 months (T4) postoperatively. All evaluations were done by the same individual and the data were tabulated and registered for later analysis. The parameter evaluation was done by a periodontology specialist dentist (independent observer) and not the surgeon who performed the implant insertion or the dentist who made the crowns.

The peri-implant probing was done according to the technique of Watzek et al., with the use of a Hu-Friedy millimetre probe, in the mesial (M), distal (D), vestibular (V), and lingual (L) faces of the implant.

Implant stability was measured through resonance frequency analysis by magnetic transduction using an Osstell ISQ apparatus (Osstell AB, Göteborg, Sweden) and SmartPeg A3 (Osstell AB, Göteborg, Sweden). For the measurements, the crowns were removed and the SmartPeg A3 was positioned in the implant platform. The Osstell sensor was then positioned perpendicular to the implant axis and the analysis was done in duplicate, in accordance with the manufacturer’s guidelines. The results were calculated from the peak amplitude and expressed in implant stability quotient (ISQ) units, on a scale of 1–100. The value is directly proportional to the stability of the implant.

Regarding the alveolar peri-implant bone, each implant underwent radiological evaluation. Peri-apical radiographs were obtained using the parallel X-ray technique with modified positioners and an individualized bite block made of condensed silicone. After the radiographs had been taken, the silicone block was washed, disinfected, and kept in a freezer to avoid drying. Each patient’s block was stored in a container labelled with the owner’s name for subsequent use in all postoperative evaluations.

All radiographs were taken with a GE 1000 (General Electric) X-ray machine, working on 90 kV, 10 mA, film-focus distance stable at 40 cm, and exposure time of 0.2 s. Speed group F sensitivity film was used (Kodak).

Processing was done automatically by a Dent-X 9000 processor (Philips, USA) inside a dark chamber. After developing, the films were digitized using a table scanner (SnapScan 1236; Agfa, Germany) and the image obtained was saved in JPEG format on the hard disk of a computer. The images were imported into Adobe Photoshop CS-6 software, standardizing the contrast and brightness based on the histogram values of each image. This provides uniformity in grey-scale, facilitating the visualization of the contours of the anatomical structures.

The images were opened one by one in VixWin Pro 1.2c software (Gendex-Dentsply) and magnified until they were of the largest possible size for the screen. The grey section tool was selected to allow the evaluation of the pixel numeric values around the implants – this software differentiates shades of grey according to a numeric value for each pixel inside the digital image. The procedure allows the areas surrounding the implants to be mapped, attributing them numerical values, and making it possible to compare radiographs taken at different time-points postoperative.

The implants were all restored with a screw-retained prosthesis.

The data were considered parametric according to the Kolmogorov–Smirnov test. For comparisons, analysis of variance (ANOVA) was used, followed by the Tukey test; for two-by-two comparisons, the t -test was applied. The STROBE checklist (Strengthening the Reporting of Observational Studies in Epidemiology) was used.

Results

The initial sample consisted of 12 patients. One woman was excluded from the study due to non-attendance on the scheduled follow-up days. However, 12 implants were evaluated because one of the patients received two implants (one on each side of the mandible).

Among the 11 patients included in the study, six were female and five male. The average age was 43 years, ranging from 31 to 60 years. Of the 12 implants inserted, two were lost, giving a survival rate of 83.3%.

The probing depth results are shown in Fig. 2 and Table 1 .

Fig. 2
Probing depth at the different time points. M, mesial face; D, distal face; V, vestibular face; L, lingual face.

Table 1
Probing depth (millimetres) at different time points and locations.
Time point Location Mean ± SD
3 months M 1.1 ± 0.394
D 1.1 ± 0.474
V 1.2 ± 0.483
L 1.0 ± 0.369
6 months M 1.1 ± 0.851
D 1.2 ± 0.825
V 1.5 ± 0.685
L 1.2 ± 0.577
12 months M 1.0 ± 0.577
D 1.1 ± 0.626
V 1.4 ± 0.81
L 0.9 ± 0.459
SD, standard deviation; M, mesial; D, distal; V, vestibular; L, lingual.

The mesial and distal faces were evaluated for bone loss. Bone loss was observed at both sites, with greater loss for the mesial face ( Fig. 3 ). The mesial and distal bone loss values are shown in Table 2 . For the mesial face, a statistically significant difference was found only between the 3-month and 12-month postoperative periods ( P = 0.04); no statistical differences were found for the distal face.

Fig. 3
Bone loss around the implants at the different time points compared to the immediate postoperative evaluation.

Table 2
Bone loss (millimetres) at different time points and locations.
Time point Location Mean ± SD
3 months M 1.54 ± 1.05
D 1.39 ± 0.99
6 months M 1.67 ± 1.13
D 1.56 ± 1.24
12 months M 2.17 ± 0.94
D 1.73 ± 1.01
SD, standard deviation; M, mesial; D, distal.

When evaluating implant stability for the four periods (T1–T4), a reduction in the ISQ values was found in both directions (MD and VL) ( Fig. 4 ). The values found for the VL and MD faces are shown in Table 3 .

Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Evaluation of single implants placed in the posterior mandibular area under immediate loading: a prospective study
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