Evaluation of immediately loaded dental implants bioactivated with platelet-rich plasma placed in the mandibular posterior region: A clinico-radiographic study

Abstract

Background and Objectives:

The purpose of the present study was to clinically and radiographically assess the soft and hard tissue changes around the immediately loaded single tooth implants bioactivated with platelet-rich plasma (PRP), placed in the mandibular posterior region.

Materials and Methods:

A total of 11 patients having single tooth edentulous space in the mandibular posterior region were selected. An endosseous implant was placed after clinical and radiographic examination in each selected site using single stage surgical approach. The patients were followed up at 3, 6, 9, and at 12 months of post implant insertion. The patients were subjected to recording of clinical parameters like modified plaque index, modified gingival index, probing depth, and clinical implant mobility scale. Radiographs made at different intervals were subjected to assessment of bone level mesial and distal to each implant using computer assisted image analysis.

Results:

Scores for clinical parameters were minimal and comparable. The probing depth around the implant was measured during the follow-up period and the changes observed were statistically non-significant. None of the implants were clinically mobile during the follow-up period. Radiographically, the peri-implant bone resorption both on mesial and distal sides was within normal limit after one year of immediate loading. Finally, the overall success rate for the immediately loaded bioactivated implant placed in the mandibular posterior region was recorded as 100%.

Interpretation and Conclusion:

The use of platelet-rich plasma may lead to improved early bone apposition around the implant; and thus, results in increased rate of osseointegration. Single stage implant procedure with the adjunctive use of PRP enhances the ability of peri-implant healing tissue to create favorable soft and hard tissue relationships. It also gives the added advantage of psychological boost for the patient by getting fixed replacement of tooth within a short time period.

INTRODUCTION

Ever since the introduction of the concept of osseointegration,[1] implants have gained significant ground in the field of dentistry. Osseointegration, being the main stay in implant dentistry, has been the ultimate goal for the dentists to achieve, and one of the pre-requisites for this to happen is that the immediate milieu around the dental implant must be conducive for proper healing and tissue regeneration. As time evolved, the various protocols stated as pre-requisites by Branemark and co workers have been reevaluated and scrutinized. There has been a marked increase in the understanding of the physiology of bone healing and new discoveries have paved the way for challenging old preset protocols and replace them with new ones. During the time that most implantologists believed that bone healing required the absolute absence of stress, some researchers observed that the complete absence of stress at the bone-implant interface was preventing active osteogenesis and excessive micromovement at the bone-implant interface; thus, inhibiting osteogenesis. These new paradigms led to the genesis of the concept of immediate loading of implants without compromising on the long term prognosis of the therapy, and more recently, implantologists are coming up with computerized navigation to enable accurate planning to improve the predictability of immediately loaded implants.[2]

Three predominant biologic factors emerge in consideration of osseointegration and immediate loading such as factors affecting interfacial bone formation (osteogenesis), peri-implant bone resorption (osteolysis), and micromotion effects on peri-implant osteogenesis. Success further depends on maintaining implant stability during initial healing. Strategies for improving the success of immediate loading may be directed at enhancing osteogenesis, limiting functional loads and micromotions, and controlling the resorption that reduces stability during the healing period.[3]

Platelet-rich plasma (PRP) is an autologous source of various growth factors that is obtained by sequestering and concentrating freshly drawn venous blood. Tayapongsak et al.[4] reported that using autologous fibrin adhesive with cancellous bone enhanced osteoconduction by means of the fibrin network and that it was useful for promoting adhesion. In 1998, Marx et al.[5] wrote about the remarkable clinical benefits of applying autologous concentrated platelet gel (a form of PRP) in Oral and Maxillofacial reconstructive surgery. Platelets release various growth factors, such as platelet-derived growth factor, transforming growth factors-1 and -2 (TGF-1 and -2), vascular endothelial growth factor, basic fibroblast growth factor, and platelet activating factor, which are very important in wound healing.[6]

Animal and human studies have shown that PRP enhances and accelerates soft tissue repair and bone regeneration. The preparation of PRP applied to an implant surface adheres to metal and might create a new dynamic surface that could potentially show biologic activity. This protein layer consists of a fibrin net embedded with growth factors that covers the whole implant surface and transforms the initial interactions of the implant surface with the surrounding tissues. It also influences cellular attachment, proliferation and differentiation, and bone matrix deposition.[7] Anitua, in 2006, showed that osseointegration of implants was enhanced by coating the implant surface with PRP, which is rich in growth factors, before insertion into the alveolus.[7] Furthermore, in a five-year retrospective study conducted by Anitua et al., the authors suggested that immediate loading of implants bioactivated with platelet, rich in growth factors could be considered as a safe and predictable procedure if strict clinical protocols were followed.[8] Similarly, Nikolidakis and co-workers,[9] observed a significant effect on bone apposition to roughened titanium implants bioactivated with PRP, in the early phase of healing.

Currently, there are very few human studies in the dental literature evaluating the clinical use of PRP in the bioactivation of implant surfaces for enhancement of healing after immediate loading. However, more recently, Garcia et al.,[10] in their study, observed that PRP did not enhance bone formation around acid etched implants; and thus contradicting the results shown by earlier studies. Hence, the purpose of the present study was to investigate the success of bioactivated dental implants after immediate loading.

MATERIALS AND METHODS

Eleven patients (seven male and four female) in the age range of 18-54 years (mean age of 34.45±8.21 years) were selected from the Out Patient Department of Periodontology and Implantology, Bapuji Dental College and Hospital, Davangere. Only those patients, who were found to have missing single tooth in mandibular posterior region with healed edentulous area for atleast six months, were considered. An informed consent was procured from all the patients before starting the treatment, and ethical approval for the study was obtained from the Institutional Ethical Committee.

The inclusion criteria for the patients were as follows: 1) patients having single edentulous space in the mandibular posterior region, 2) adequate bone quantity and quality at the implant site, 3) patients well motivated for implant therapy and maintaining good oral hygiene. Exclusion criteria involved: 1) medically compromised or patients taking any immunosuppressive drugs which may complicate the treatment outcome, 2) infection around the implant site, 3) history of bruxism/parafunctional habits, 4) patients with history of any bleeding disorder or on anti-coagulant therapy.

Preparation of PRP

The patients were subjected to complete hemogram analysis, which includes the platelet count, hemoglobin concentration, bleeding time, clotting time, and total and differential counts. Before starting the surgical procedure, 20 ml venous blood was taken from the anticubital region with a 21 gauge needle syringe and collected in an autoclaved glass container containing the anti-coagulant Calcium Phosphate Dextrose-A.

The tubes were placed into the centrifuge, always ensuring that the tubes are counterbalanced, as per the centrifuge manual. The first centrifugation is for 10 minutes at 2,400 rpm to produce platelet poor plasma (PPP), and then a second centrifugation is performed for 15 minutes at 3600 rpm to concentrate platelets. The result is separation of the whole blood into PPP and buffy coat or the PRP, and erythrocytes.[11] Then for the activation of PRP, human thrombin was prepared by the addition of CaCl₂ and beads into the PPP, as described earlier by Su et al.[12]

Surgical procedure

Following the preparation of the osteotomy site [Figure 1], it was thoroughly irrigated with saline to clear any bone debris that might be present at the site. Just prior to the placement of the implant, it was dipped in activated PRP solution contained in an autoclaved dapen-dish taking care so as to avoid any contact with the walls of the container thus avoiding any contamination of the implant surface, which could be detrimental to successful osseointegration [Figure 2]. Implant was tightened with hand wrench until a good primary stability was achieved [Figure 3]. Finally, the healing abutment was placed over the implant and the flaps were sutured back in place. Patients were given post-operative instructions, and prescribed antibiotics (amoxycillin 500 mg 8 hourly, for five days), and analgesics/anti-inflammatory drugs (ibuprofen 400 mg TDS, for three days).

Figure 1.

Osteotomy site prepared

Figure 2.

Implant being coated with PRP

Figure 3.

Implant placed in the prepared osteotomy site

Fabrication of provisional prosthesis

Following suture removal after one week, the healing abutment was removed and transfer coping was attached to the implant. Impression was made using addition silicone impression material with the closed tray technique (indirect impression technique). Implant analog was seated into the coping in the impression and cast was poured. Following this, a provisional prosthesis was fabricated using the heat cure acrylic in such a way that it was kept out of occlusion, with no centric or eccentric contacts [Figure 4]. The provisional prosthesis was cemented with zinc oxide non-eugenol temporary cement within a period of two weeks, following the protocol of immediate loading.[13]

Figure 4.

Provisional prosthesis kept out of occlusion

Fabrication of permanent prosthesis

At the time of recall appointment after three months, after a clinical and radiographic evaluation of the implant, the process of fabrication of definitive prosthesis was taken up. A similar procedure for making the impression was followed as done for the fabrication of provisional restoration. Following this, a wax pattern of the proposed prosthesis was made, which was then subjected to casting procedure to prepare the metal coping. After the fabrication, fit of the metal coping was tried in the patient's mouth. After confirming the adequate fit, porcalein was fired onto the metal coping, and a final, porcalein fused to metal crown was fabricated. The crowns were cemented using glass ionomer cement [Figure 5]. Patients were further reviewed at 6, 9, and 12 months thereafter, for the evaluation of all clinical and radiographic parameters.

Figure 5.

Permanent prosthesis cemented

Clinical parameters

After implant placement, clinical parameters were recorded and evaluated at baseline, 3, 6, 9, and 12 months. The clinical parameters recorded were the modified plaque index,[14] modified gingival index,[15] probing depth around the implant at four sites using the Tissue pressure sensative (TPS) probe,[16] implant mobility according to clinical implant mobility scale,[17] and the absence or presence of any infection around the implant.

Radiographic evaluation

Intra-oral periapical radiographs were taken using the long cone paralleling technique and the bone level was assessed before the implant placement [Figure 6], at the time of implant placement (baseline) [Figure 7], at 3, 6, 9, and 12 months [Figure 8]. The distance from implant shoulder to the first bone-implant contact was measured on the radiographs using computer assisted image analysis, Image J software, which standardizes the measurements and reduces the margin of error.

Figure 6.

Pre-operative IOPA radiograph

Figure 7.

Immediate post-operative IOPA radiograph

Figure 8.

Twelve months post operative IOPA radiograph

RESULTS

In the present study, all patients participated until the end of the study with no clinical dropout reported. All patients showed good compliance in oral hygiene maintenance and following other instructions. No complication was recorded in any of the cases. The one year (12 month) clinical recording and radiographic assessment showed all values within the success criteria; hence, 100% success rate was recorded after the immediate loading of bioactivated implants. Healing, in general, was uneventful with minimal discomfort to all the patients. All the sites maintained excellent peri-implant soft and hard tissue conditions.

After a follow-up period of 12 months, the mean difference in the plaque score and gingival score between the implant and full mouth were 0.01 and 0.03, respectively, which were statistically not significant (P>0.05) [Tables 1 and 2; Figures 9 and 10]. Furthermore, there was no statistically significant difference in the probing depth around the implant after a follow-up of 12 months [Table 3; Figure 11]. None of the implants showed any mobility during the study period. On thorough clinical and radiographic examination during the follow-up visits at regular intervals of 3, 6, 9, and 12 months post insertion of the implant, there was no evidence of any infection around the implant in any of the patients recruited for the study.

Table 1.

Modified plaque index

Table 2.

Modified gingival index

Figure 9.

Mean difference in modified plaque index scores at different intervals

Figure 10.

Mean difference in modified gingival index scores at different intervals

Table 3.

Probing depth

Figure 11.

Mean difference in probing depth at different intervals

The radiographic bone level change was the main response variable used in the present study to evaluate the immediate loading of these self tapping implants, bioactivated with PRP. It forms a very important and viable means of detecting health and stability of bone around the peri-implant hard tissue. Intraoral periapical radiographs taken at baseline, 3, 6, 9, and 12 months using long cone paralleling technique, were subjected to radiographic analysis using Image J software. The distance from the first implant thread to the first bone-implant contact on the mesial and distal sides of the implant was measured, and the values were within the success criteria of immediate loading [Tables 4 and 5; Figure 12].

Table 4.

Radiographic analysis (mesial side)

Table 5.

Radiographic analysis (distal side)

Figure 12.

Mean bone loss on mesial and distal side of implant at different intervals

DISCUSSION

This investigation involved a method of placing bioactivated implants in the mandibular posterior region and subsequently loading them immediately. During the last few decades, several authors have reported that root-form implants may osseointegrate, even though they reside above the bone and through the soft tissue during early bone remodeling. This surgical approach, which eliminates the need for second-stage implant uncovering surgery, has been called a one-stage or non-submerged implant procedure. As a result, the discomfort, surgical time, and healing problems associated with second-stage surgery are eliminated. In addition, the soft tissue is already mature before fabrication of the final prosthesis. The main advantage of immediate implant loading is the significantly shortened time interval between implant surgery and prosthetic rehabilitation.[18] In the protocols of immediate loading, the patients do not undergo the emotional and functional stress of being edentulous.

Wound healing, in particular, bone regeneration, requires an orchestrated sequence of biological events that are regulated by multiple factors, and this process of bone healing is all the more crucial to enhance the long term prognosis of immediately loaded implants. Therefore, PRP as a candidate delivery system for growth and differentiation factors is of interest for two reasons: (1) it is of autologous origin; thus posing no risk for transmission of diseases and (2) it naturally contains growth factors that play an active role in bone formation.[19] Early studies have focused on PRP application to bone graft material, showing that it leads to earlier bone regeneration and soft tissue healing.[5]

Immediate loading of implant is taught with its own risks. The early healing period is very crucial for the success of the implant and one of the important factors to be considered is the bone implant contact (BIC) during this period. Various authors have tried to improve this BIC so as to improve the long term prognosis of implant therapy, by the way of constantly changing the nature of various implant surfaces and have achieved variable success with each of these modifications. One of the novel methods that can be employed in this context is by the way of coating the implant surface with autologous PRP. Studies have shown that topical PRP application enhances bone regeneration at implant host sites in the posterior mandible during early healing. Local PRP administered during dental implant placement, is a relatively simple method to enhance early BIC.[20] The minimal bone loss observed on both the mesial and distal sides around the immediately loaded implants were similar to the earlier observations made by Glauser et al.[21] Calandriello et al.[22] Abboud et al.[23] and Donati et al.[24] in their respective studies. Thus, this mode of therapy can go a long way in enhancing the long term success of immediately loaded dental implants in the posterior mandibular region which probably takes the maximum masticatory loads.

This high (100%) success rate of these bioactivated and immediately loaded implants can be attributed to the following factors playing their roles directly or indirectly in the present study: 1) careful case selection which is one of the pre-requisites for the success of immediate loaded implant, was thoroughly taken care in this study; 2) computed tomography (CT scans) were taken for all the cases for the accurate assessment of bone quality and quantity and to determine the adequate size of the implant to be placed; 3) another important factor, which might have played a very important role, is the good primary stability while placing the implants, which can be considered as the single most important factor in achieving the excellent success with immediate loading; 4) also, by excluding the patients having compromised systemic health or with occlusal discrepancies, might have improved the survival of these implants.

In the present study, the bioactivation of the implant surface with PRP might have played its additional role in achieving these excellent results. The excellent soft tissue healing achieved around the implant site can also be attributed to the established positive effect of PRP in soft tissue healing. The coating of PRP has two important properties that may contribute to optimizing and accelerating the osseointegration process; i) the osteoconductive properties attributed to fibrin and ii) the recognized osteoinductive activities of the growth factors.[6] Thus, the use of PRP can result in greater bone to implant contact (BIC) and greater peri-implant bone volume during the initial healing period. However, in the later stages, the direct influence of PRP may fade away and the physiological mechanism of bone formation will continue to work on an accelerated level.

A recent systematic review and meta-analysis[25] has shown that, in the present scenario, better results have been obtained with conventional loading of especially single tooth implants and ‘caution’ should be the appropriate word while considering immediate loading of single tooth implants. Therefore, we propose that when evaluating a patient for immediate loading protocol, the use of this novel technique of coating the implant with PRP can go a long way in improving the prognosis of the treatment. Preparation of PRP is a relatively simple and fast technique and a plethora of advantages can be derived from its use. This new method can certainly initiate a new revolution in this fast growing science and technology of oral implantology.