Clinical and radiographic evaluation of recombinant human platelet derived growth factor with beta tricalcium phosphate in the treatment of a periodontal intrabony defect.

The need to increase the predictability of successful periodontal regeneration has led to the use of cell-stimulating proteins in combination with osteoconductive scaffolds and cells based on the principles of tissue engineering. The present case report describes the treatment of an intrabony defect with recombinant human platelet derived growth factor (rhPDGF) + β-tricalcium phosphate (β-TCP). A 25-year-old patient presented with a probing pocket depth of 9 mm mesial to the left maxillary molar. The radiograph revealed an intrabony defect with a depth of 4.23 mm. The defect was treated by open flap debridement and grafting with rhPDGF + β-TCP. On 9 months follow-up, the pocket depth reduced to 3 mm and the defect was completely filled as observed in radiographs and surgical re-entry. A gain in alveolar crest height was also observed.

INTRODUCTION

Periodontal regeneration is defined as the complete replacement of lost periodontal structures, including formation of new cementum with new periodontal ligament (PDL) fibers, bone and gingiva.[1] The intrabony defect provides an ideal environment for the experimental use of novel regenerative techniques. Several treatment protocols have been used to achieve periodontal regeneration in intrabony defects. These have traditionally included scaling, root planing, gingival curettage, various types of flap procedures and bone grafting. However, results from histologic studies suggested that conventional periodontal therapy results in repair, rather than regeneration.[2] The “false” gains in clinical attachment level (CAL) are the result of resolution of inflammation, bone fill, reformation of gingival collagen fibers, and formation of a long junctional epithelium.[3] Although epithelialization may be inhibited/delayed by guided tissue regeneration, inconsistent and varying degrees of cementogenesis were seen at different sites.[4]

The need to increase the predictability of periodontal regeneration has led to the use of cell-stimulating proteins in combination with osteoconductive scaffolds and cells based on the principles of tissue engineering. Recombinant human platelet derived growth factor BB (rhPDGF-BB) has been extensively studied in relation to its contributions to wound healing and periodontal regeneration. The efficacy and safety of rhPDGF-BB + β-tricalcium phosphate (β-TCP) in periodontal osseous defects was tested in large multicenter trials.[56] β-TCP, a purified, multicrystalline porous form of calcium phosphate with a Ca/PO4 ratio similar to natural bone, is an osteoconductive scaffold used widely in reconstructive periodontal surgery.

This case report evaluates the efficacy of rhPDGF with β-TCP in the grafting of an intra-osseous defect, and assesses the bone fill by radiographic means and surgical re-entry.

CASE REPORT

A 25-year-old male patient reported with a chief complaint of food impaction in the left upper back tooth region. On clinical examination, there was a periodontal pocket of 9 mm on the mesial aspect of 26. The buccal aspect of 26 showed a gingival recession (GR) of 1 mm. Radiographic examination revealed an intrabony defect mesial to 26. Informed consent for the surgical procedure was obtained from the patient. The treatment plan comprised of phase 1 therapy followed by surgical therapy (4 weeks after phase one therapy) comprising of open flap debridement and grafting with a combination of β-TCP and rhPDGF.

The clinical parameters, including plaque index (Silness and Loe, 1964)[7] and gingival index (Loe and Silness, 1963)[7] were recorded at baseline, 1, 3, 6, and 9 months while the probing depth, CAL and GR were recorded to the nearest millimeter with a University of North Carolina (UNC)-15 probe at baseline, 6 and 9 months.

The preoperative and postoperative intraoral periapical radiographs were digitized and analyzed using the Image J Software (National Institutes of Health, US). The radiographic parameters included the amount of defect fill, percentage of defect fill and change in alveolar crest height, which were calculated based on the following parameters: Cementoenamel junction (CEJ), base of the defect and alveolar crest.

Surgical technique

At the start of the surgical procedure, the patient was asked to rinse with 0.2% chlorhexidine for 1 min. This was followed by the administration of local anesthesia (2% xylocaine with 1:80,000 adrenaline). Crevicular incisions were given on facial and lingual/palatal sides [Figure 1] and full-thickness mucoperiosteal flaps were reflected, taking care that the interdental papillary tissue was retained as much as possible. After the reflection of the flap [Figure 2], thorough surgical debridement of the 3-wall osseous defect was performed using Gracey curettes. The roots were planed thoroughly. The surgical site was irrigated with 0.9% normal saline. Direct measurements of the osseous defect were taken with the UNC-15 probe [Figure 3]. The flap was partially presutured with 3-0 braided silk before the placement of the graft. The required quantity of β-TCP bone graft was transferred to the dappen dish, saturated with rhPDGF suspended in sodium acetate buffer and left for 10 min to facilitate binding of the rhPDGF-BB protein with β-TCP particles [Figure 4]. The required quantity of the graft was delivered in increments into the osseous defect and slightly compressed with light pressure using the discoid end of a cumine scaler. The material was loosely packed from the base of the defect to the approximate level of the crest of the remaining osseous walls [Figure 5]. Finally, the presutured mucoperiosteal flaps were repositioned and secured with interrupted sutures. The surgical area was protected and covered using noneugenol periodontal dressing (COE-PAK, GC Asia Dental).

Figure 1

Crevicular incision

Figure 2

Infrabony defect

Figure 3

Actual defect depth

Figure 4

Mixing β-tricalcium phosphate with recombinant human platelet derived growth factor

Figure 5

Defect filled with graft

Postoperative instructions

Antibiotics (500 mg amoxicillin thrice daily) and analgesics (100 mg aceclofenac and 500 mg paracetamol twice daily) were prescribed for 5 days postoperatively. The patient was instructed to rinse with 10 ml of 0.2% chlorhexidine mouthwash twice daily for a week. One week after surgery, the dressing and the sutures were removed. Oral hygiene instructions were reinforced.

The patient was recalled at 1, 3, 6, and 9 months postsurgery for assessment of the patient's oral hygiene and for clinical and radiographic examination.

Surgical re-entry at 9 months comprised of sulcular incisions and mucoperiosteal flap elevation just enough to expose the previously treated defect area to assess defect fill and alveolar crest height [Figure 6]. The flaps were replaced and sutured subsequently.

Figure 6

Surgical re-entry

RESULTS

At baseline, the plaque index score and gingival index score were 1.4 and 1.2, respectively. At 1 month postsurgery, the plaque index score and gingival index score reduced to 0.4 and 0.2, respectively and a good oral hygiene was maintained throughout the follow-up period. The probing pocket depth reduced from 9 mm at baseline to 4 mm at 6 months and 3 mm at 9 months. There was no increase in GR at the treatment site.

Radiographic measurements [Figure 7] recorded included:[8]

Figure 7

Arithmetic determinations for radiographic measurements

A0: Distance from CEJ to base of the defect (initial) = 6.93 mm.

A6: Distance from CEJ to base of the defect (6 months postsurgery) = 3.94 mm.

A9: Distance from CEJ to base of the defect (9 months postsurgery) = 2.58 mm.

B0: Distance from CEJ to the crest of alveolar bone (initial) = 2.70 mm.

B6: Distance from CEJ to the crest of alveolar bone (6 months postsurgery) = 2.49 mm.

B9: Distance from CEJ to the crest of alveolar bone (9 months postsurgery) = 2.58 mm.

C0: Initial distance from the alveolar crest to the base of the defect (A0 − B0) = 4.23 mm.

C6: 6 months postsurgery distance from the alveolar crest to the base of the defect.

(A6–B6) = 1.45 mm.

C9: 9 months postsurgery distance from the alveolar crest to the base of the defect.

(A9-B9) = 0 mm.

From the above measurements and arithmetic determinations, the following values were assessed:

Amount of defect fill at 6 months (in mm) − D6 = A0 − A6 = 2.99 mm.

Amount of defect fill at 9 months (in mm) − D9 = A0 − A9 = 4.35 mm.

Percentage of defect fill at 6 months = D6× 100/C0 = 70.68%.

Percentage of defect fill at 9 months = D9× 100/C0 = 102.83%.

Change in alveolar crest height (mm) = E6 (at 6 months) = B0 − B6 = 0.21 mm.

Change in alveolar crest height (mm) = E9 (at 9 months) = B0 − B9 = 0.12 mm.

Clinically, the sites appeared healthy, firm and with good adaptation to the underlying tissues.

Surgical re-entry revealed that the intrabony defect fill was approximately 5 mm. The alveolar crest coincided with the base of the defect indicating complete bone fill.

DISCUSSION

This case report evaluated the efficacy of rhPDGF with β-TCP in the grafting of an intra-osseous defect.

Probing pocket depth reduction may be the most important objective for overall treatment outcome as it directly influences the clinicians ability to instrument a treated area during the maintenance appointments and also aids in patients home care as shallow pockets can be well maintained. CAL is considered an ideal clinical measure to evaluate periodontal regenerative therapies. Pocket depth reduced from 9 mm to 4 mm at 6 months and to 3 mm at 9 months. The CAL reduced from 11 mm at baseline to 5 mm at 6 months and 4 mm at 9 months. Apart from reduction in inflammation, formation of long junctional epithelium, shrinkage of the pocket wall and reattachment of collagen fibers, the attachment gain could be due to the PDGF-induced chemotaxis (directed cell migration) and cell proliferation of osteoblasts, PDL fibroblasts and cementoblasts, as demonstrated in histologic studies.[910]

At baseline, the defect depth was 4.23 mm [Figure 8]. The radiographic defect fill was 2.99 mm at 6 months [Figure 9]. At 9 months, the defect fill was 4.35 mm as per radiographic analysis and 5 mm as per surgical re-entry measurement [Figure 10]. Radiographic assessment of alveolar bone fill often underestimates actual bone fill measured clinically. Thus, surgical re-entry was also done in the present study. A 70.68% defect fill was observed at 6 months while a 102.83% fill was observed at 9 months. This implied that regeneration was seen coronal to the level of the original alveolar crest. Normally, after periodontal surgery, there is remodeling of alveolar bone leading to crestal resorption. The defect resolution occurs by defect fill as well as a change in alveolar crest height. However, in this case, at the end of 9 months, the alveolar crest height increased by 0.12 mm. This finding is in accordance with previous histologic studies,[910] where regeneration (new bone, cementum and PDL) was seen coronal to the original osseous crest.

Figure 8

Preoperative radiograph

Figure 9

Six months postoperative radiograph

Figure 10

Nine months postoperative radiograph

Bone autografts have been referred to as the “gold standard” in osseous grafting procedures because they are generally believed to provide the best results of the available materials - presumably because of the presence of conductive bone trabeculae, cells, and signaling molecules (e.g. growth factors). However, their use is often contraindicated because of the insufficient availability of intraoral graft material, frequency of postoperative pain at the donor site, and increased potential for postsurgical complications related to the graft harvest site. Equally important, even in autografts, the number of viable osteoprogenitor cells may be small and the amount of growth factors limited, especially in smokers, diabetics, osteoporotic patients and geriatric patients.[11]

Due to these limitations, periodontal therapies aimed at regenerating the periodontium have for many years used nonviable, osteoconductive matrices. These mostly inert, physical matrices, including allogenic, xenogenic, and synthetic graft materials function primarily by passively guiding, or conducting, cell migration through the matrix, eventually leading to “repair” of the defect. These may be used alone, in combination with autogenous graft or in combination with other passive materials such as barrier membranes designed to act as a physical guide for cells involved in the repair and regeneration process. While these options are useful for maintaining space and a framework for tissue deposition, results obtained with passive therapeutic matrices may be variable, depending upon their inherent physical and chemical properties as well as the patients’ healing response.

Use of rhPDGF + β-TCP serves as a biomimetic approach to regeneration combining the three elements of tissue engineering i.e. osteoconductive scaffolds, the patient's own progenitor cells for osteoblasts and fibroblasts in vivo, and potent signaling molecules that are capable of stimulating cellular events associated with periodontal regeneration i.e. chemotaxis, proliferation, angiogenesis, cellular differentiation, and production of extracellular matrix. Recently, Nevins et al. provided results from a 36-month extension study of a multicenter, randomized, controlled clinical trial[5] evaluating the effect and long-term stability of PDGF-BB treatment in patients with localized severe periodontal osseous defects. rhPDGF-BB + β-TCP was shown to result in significantly greater clinical and radiographic improvements, from baseline throughout the 36-month observation period, in moderate-severe 2- and 3-wall infrabony defects when compared with β-TCP alone.[12] Darby et al., in a systematic review found that use of rhPDGF-BB led to greater percentage bone fill of ≈40% compared to the osseoconductive control, β-TCP.[13]

Although histologic evaluation is the only reliable method to determine the true efficacy of periodontal regenerative therapy, because of ethical considerations and patient management limitations, no histologic evidence was obtained in this study to establish proof of periodontal regeneration.

CONCLUSION

Within the limits of this study, it can be concluded that the use of rhPDGF + β-TCP leads to significant improvements in clinical as well as radiographic parameters. Recombinant human platelet-derived growth factor, with its well established effects on hard- and soft-tissue cells, may thus have the potential to overcome the limitations of the conventional bone grafts and barrier membranes.