Release of Osteogenic Markers in Immediately and Non-loaded Dental Implants

The aim of this study was to compare the release of the osteoprotegerin (OPG), transforming growth factors (TGF-α), osteocalcin (OCN), osteopontin (OPN), and parathyroid hormone (PTH) during osseointegration of dental implants with and without immediate loading. Forty patients were selected and randomly divided into: Group IM - implant and prosthesis placement within 72 hours; and Group NL - implant insertion and no prosthesis placement during 120 days. Peri-implant crevicular fluid (PICF) was collected immediately after implant insertion and with 7, 15, 30, 60, 90, and 120 days after surgery and were evaluated levels of OPG, TGF-α, OCN, OPN and PTH using Luminex assay. Clinical aspects (Sulcus bleeding and peri-implant probing depth) were also assessed. The data were compared using the ANOVA/Tukey and Friedman/Mann-Whitney tests (α=5%).

This was a prospective, parallel and controlled clinical-laboratory trial. The population evaluated in this study was selected at the Graduate Clinic in Dental Implantology - UNIP-SP.

The selected patients were randomly allocated (by a computer generated list) into:

Group IM - (n = 20) - patients who received placement of implants and prosthesis within a period of 3 days, characterizing immediate loading implants protocol; Group NL - (n = 20) - patients who received single-stage dental implants with no placement of dental prostheses within a period of 4 months, characterizing non-loading implants;

The surgeries, as well as all postoperative follow-up, were performed at the dental clinic of UNIP-SP. Surgical areas were anesthetized (2% mepivacaine with 1:100,000 epinephrine) and mucoperiosteal incisions in the alveolar ridge mucosa were made. The surgical sequence follow the protocol described by the implant company supplier of implants (SIN - São Paulo, SP, BR). In all cases, for maxilla rehabilitation, 6 implants were installed, while, for mandible, 5 were used. Soft-tissue was sutured with simple interrupted sutures using absorbable polygalactin 910 suture. Postoperative care were: amoxicillin 500 mg (8-8 hours/7 days); sodic dipyrone 500mg (6-6 hours/3 days); 0.12% Chlorhexidine mouthwash (12-12 hours/10 days).

The patients in the IM Group received Brånemark full arch prosthesis within 3 days after the implant. All prosthesis used straight mini-abutments (SIN, São Paulo, SP) and received occlusal adjustment and a monthly clinical monitoring (including modified bleeding on probing and peri-implant probing depth).

Evaluation of osteogenic markers The collection of peri-implant crevicular fluid (PICF) was performed immediately after implant insertion (Baseline) and after 7, 15, 30, 60, 90 and 120 days. The site to be collected was dried and isolated with sterile gauze. PICF was collected at four sites per implant using absorbent paper strips (Periopaper, Oralflow, Smithtown, New York). The volume of fluid was measured immediately with the aid of Periotron (Oraflow, Smithtown, New York) and conditioned at 400uL of PBS buffer + 0.05% Tween and then frozen at -80°C.

The levels of the peri-implant osteogenic markers (OPG, OCN, OPN, TGF-α, and PTH) were determined using the LUMINEX/Magpix system (HBN1A-51K and HCCBP1MAG-58K, Millipore Corporation, Billerica, MA, USA). The samples were analyzed individually and the levels were estimated using a 5-parameter polynomial curve in the Xponent® software (Millipore Corporation, Billerica, MA). The concentration values were expressed in pg/ml.

Statistical Analysis The null hypothesis considered in the study was the absence of difference in the peri-implant osteogenic markers concentration between the different loading protocols. For data analysis, the statistical program was used (SAS release 9.1, 2003, SAS Institute Inc., Cary, NC, USA). The demographic and clinical data were compared between the groups using Student's t-test (age), and Fisher's Exact test (gender and site of implants). The data on the levels of osteogenic markers were first analyzed for homogeneity using the Shapiro-Wilk test, which indicated non-normal distribution. Thus, the nonparametric tests - Friedman for intragroup and Mann-Whitney for intergroup analysis, were performed. All the analysis considered α=5%.

Eligibility Criteria:
Inclusion Criteria:

* patients with mandibular and/or maxillary edentulous arch indicated for rehabilitation with dental implants
* extractions had to occur at least 4 months prior to treatment
* good oral hygiene (plaque index \< 20%) (Ainamo \& Bay, 1975)
* age between 18-65 years

Exclusion Criteria:

* presence of systemic disease (including diabetes, arthritis, hypothyroidism, osteoporosis, etc) or use of medication (six months prior to the study) that contraindicated placement or alter implants osseointegration
* use of anti-inflammatory three months before surgery
* patients submitted to bone grafts in the site selected for the implant
* pregnant or breastfeeding women
* smokers or ex-smokers