Effects of recombinant human bone morphogenetic protein-2 compared to other biomaterials in the treatment of intrabony defects in periodontitis patients: A systematic review.

BACKGROUND: Bone morphogenetic proteins have a powerful osteoinductive capacity and have been used as a new adjunct to graft materials for bone regeneration. The objectives of this systematic review are to assess the amount of radiographic bone fill, clinical attachment level (CAL) gain, and reduction in pocket depth (PD) in patients with intrabony defects in periodontitis patients following the use of recombinant human bone morphogenetic protein-2 (rhBMP-2).
MATERIALS AND METHODS: Electronic bibliographic databases search of Medline, Science Direct, and Google Scholar was made from January 1980 to December 2017. Studies using rhBMP-2 to treat periodontal intrabony defects of the maxillary or mandibular region with follow-up period of at least 6 months were searched. Two reviewers performed the systematic review using the PRISMA Statement for reporting and the Cochrane risk-of-bias tool was used for quality assessment.
RESULTS: It was found that rhBMP-2 showed statistically significant results with respect to radiographic defect resolution, CAL, and PD reduction at 9 months compared to open-flap debridement but showed statistically significant results only with respect to radiographic bone fill when compared with platelet-rich fibrin at 6 months.
CONCLUSION: The rhBMP-2 may provide a promising alternative to traditional grafting procedures therapy that can enhance periodontal regeneration in patients having intrabony defects. Due to limited human studies, it can be concluded that no definitive evidence exists to ascertain the effectiveness of rhBMP-2 in the treatment of intrabony defects in periodontal diseases.

INTRODUCTION

Tissue engineering constitutes interaction between soluble molecular signals, responding cells with associated cell-surface receptors, and assembly of the extracellular matrix. This concept can be applied to bone regeneration and periodontal regeneration.[1] The human body possesses a persistent capacity to restore itself. The damaged bone can repair itself, so long as it is not of a “critical size.” Specific bone formation substances are needed to activate the nonspecific mesenchymal tissue with the aid of a scaffold.[2] Urist first described bone morphogenetic protein (BMP) by the ability of demineralized bone to induce new cartilage and bone formation at ectopic sites.[34]

BMPs are growth factors such as cytokines or metabolites. “Bone morphogenetic” is derived from the word “morphogenesis” meaning the generation of new bone.[5] They play a crucial role in regulating bone induction and maintenance. These proteins belong to transforming growth factor superfamily of genes with a unique property.[5] They stimulate the formation of newer blood vessels and also aid in the migration, proliferation, and differentiation of the cells of the mesenchyme into chondroblasts and osteoblasts. Primarily, BMP was regarded as growth factors. At present, they are involved in morphogenesis and organogenesis.[5]

Most of the recognized BMP proteins identified are known to induce formation of the bone. Three subfamilies of BMPs are known till date.[5] BMP-1 belongs to metalloproteinases.[4] Almost 80% amino acid sequence homology of molecules are present in BMP-2 and BMP-4. There is a substantial homology between the decapentaplegic peptide and BMP-2 and 4 subfamily, suggesting they are the equivalents of a decapentaplegic peptide gene product. BMP-5, 6, and 7 belonging to the second group show 78% amino acid sequence homology. BMP-3 alone constitutes third group. It is unique from the other BMP subfamily of BMP.[6]

Protein components of bone matrix present as growth and differentiation factors. Expression of these proteins using recombinant technology evidenced new induction of bone matrix. Utilizing the advances in technology in molecular biology and sequence information from the bovine molecular clones attained the coding sequence of human homologs of each BMP. Mammalian cells have the property of self-expression, Implantation of coding gene sequence for each protein into an expression vector and fabricating stable cell lines.[7]

The introduction of recombinant DNA technology led to the development of recombinant human BMP-2 (rhBMP-2). These are available readily as an osteoinductive autograft replacement. Regeneration of new periodontal tissues was reported at a concentration of 1.5 mg/cc.[5]

In vivo animal studies have reported the osteoblastic activity of BMP-2 and the formation of new bone nodules. Clinically, BMP-2 has been tested in orthopedic spinal surgery, cleft alveoli and palate, and irradiated tissue.[8] Regeneration of periodontal tissues necessitates the induction of alveolar bone, cementum, and periodontal ligament. Significant periodontal regeneration was noted in several studies with the use of BMPs. It is important to understand the behavior of this material, biological process, and its effects.

Numerous animal studies have been evaluated the efficacy of BMPs for periodontal regeneration, bone augmentation for the placement of implants, and maxillary sinus augmentation.[91011] The rhBMP-2 allied with a collagen foam carrier in intrabony defects in dogs have proven an increase in the rate of bone formation without side effects such as ankyloses or apical bone resorption.[1213] Further, rhBMP-2 showed limited vertical ridge augmentation before implant therapy in dogs.[14] However, the biological activity of this material is not fully predictable clinically. Most studies reported a low rated and are mainly case series or reports with no control groups. Thus, significant results have been obtained from preliminary data from clinical and preclinical reports. However, definitive conclusions can be drawn particularly in long-term evaluation. Till date, investigators failed to establish a clinical protocol for osseous induction or augmentation during implant therapy owing mainly due to limited number of studies.[15] Thus, the aim of this research is to assess the amount of bone fill, reduction in probing depth, and gain in clinical attachment level (CAL) in periodontitis patients with intrabony defects following application of rhBMP-2.

MATERIALS AND METHODS

This systematic review was based on the PRISMA statement (www.prismastatement.org). The concept of the study was first registered in the “PROSPERO” International prospective register of systematic reviews (Available from http://www.crd.york.ac.uk/PROSPERO/display_record.php? ID=CRD42017075054). Use of rh-BMP2 in the surgical intervention for the treatment of intrabony defects (1, 2, or 3-walled) for periodontal regeneration was compared to other surgical treatment utilizing growth factors, alloplastic, allogeneic grafts, and xenografts.

The randomized and nonrandomized controlled trials (RCTs) were selected. Patients who were diagnosed to have periodontitis with intrabony defects along with an interproximal probing depth ≥5 mm after Phase-I therapy in asymptomatic teeth were included in the study. Furthermore, patients who were systemically healthy having an age of 18 years or more with no contraindications to periodontal therapy were incorporated in the study. Animal studies, in vitro studies, literature reviews, case reports, laboratory studies, and clinical treatment guidelines were excluded from the study.

Outcome measures

Patients with clinical outcome at least 6-month follow-up showing pocket depth (PD) reduction and CAL gain in the involved site and radiographic resolution of original defect of intrabony defects in periodontitis patients were analyzed.

Search methods for identification of studies

The literature searches involved PubMed (Medline), Science Direct, clinical trial registry, Google Scholar, and manual searching through other sources. A total of 3673 studies from January 1980 to December 2017 which were in English language only were included in the study. The electronic search was performed on December 29, 2017, by two researchers (RM and KA) independently using medical subject headings used by the National Library of Medicine. The keywords which were used in various combinations in the search parameters are as follows:

”BMPs,” “BMP,” “rhBMP-2” “BMP-2,” “BMP-2” “recombinant bone morphogenic protein-2”

”Intrabony defect,” “bone defect,” “bony defect”

”Periodontal regeneration”

”Maxillary,” “maxilla,” “mandibular,” “mandible.”

The summary of study searches is given in Figure 1.

Figure 1

PRISMA flow diagram (2009). n – Number of studies

Data collection and analysis

The relevant data of included publications were collected in data extractions files. Before actual scoring, the rating forms were tested by all reviewers. Each reviewer first decided on a study's eligibility for inclusion in the systematic review based on the reported parameters. The data reported from the included studies were summarized based on clinical and radiographic outcomes in the follow-up period. Two examiners evaluated titles, abstracts, and full text, and if there was a diverging opinion, the disagreement among examiners was reexamined in decisions were made unanimously.

RESULTS

This systematic review presents finding on 48 samples who were participants in two individual RCTs with the intended outcome of establishing the effectiveness of the use of rhBMP-2 in the treatment of intrabony defects in periodontitis patients.[1617]

The studies which were excluded consisted of animal studies and in vitro studies and studies related to BMP pool. Out of 1061 studies searched, only two studies met the inclusion criteria of including the human intrabony defects in chronic periodontitis.[1617] Both studies were a RCT with at least 6-month follow-up. One study utilized a split-mouth study design.[17] The authors were contacted to obtain the necessary information, but no replies were received. Both studies were published in nonspecialty dental journals.

A total of 48 participants were included in the review. The age range was 25–55 years. Table 1 provides detailed information of studies included in this review. Table 2 summarizes qualitative assessment of the included studies was done using the Cochrane tool. Figure 2 summarizes the overall risk of bias assessed by RoB tool 2.0 for randomized studies.

Table 1

Description of included studies

Studies	Allocation group	Study design	Patient groups	Treatment groups	Outcome	Results (test v/s control)	Summary
Vandana et al. 2016	Randomized double-blind	Controlled trial	Intrabony defects in patients with chronic periodontitis (n=32)	rhBMP-2 v/s open flap debridement	Probing Pocket depth	Baseline6.90±0.85 v/s 7.08±0.95 9 months4.40±0.60 v/s 5.23±1.23	Favorable to test (P<0.05)
					CAL	Baseline5.55±1.05 v/s 5.39±1.26 9 months3.65±1.14 v/s 4.08±1.25	Favorable to test (P<0.05)
					Radiographic Bone fill	9 months60.1±15.8 v/s 21.9±22.2	Favorable to test (P<0.001)
Vandana et al. 2017	Randomized	Split mouth controlled clinical trial	Intrabony defects in patients with chronic periodontitis (n=32)	rhBMP-2 v/s autologous platelet rich fibrin	Probing Pocket depth	Baseline6.8±0.87 v/s 7.9±1.26 months5.45±0.61 v/s 3.4±0.8	Favorable to control (P=0.026)
					CAL	Baseline5.55±1.02 v/s 5.7±0.956 months4.3±0.9 v/s 2.4±0.52	Not significant (P=0.122)
					Radiographic Bone fill	6 months41.1±19.2 v/s 26.75±6.03	Favorable to test (P=0.002)

rhBMP-2 – Recombinant human bone morphogenetic protein-2; CAL – Clinical attachment level; PD – Pocket depth; n – Study sample, P – Significance at 0.05 level

Table 2

Assessment of risk of bias in included studies

Domain	Vandana KL et al. 2016		Vandana KL et al. 2017
	Type of bias	Justification	Type of bias	Justification
Bias arising from the randomization process	Low	Randomized double-masked study, however, method of randomization not stated clearly	Low	Randomization was done using computer-generated tables. All patients were allocated to four groups
Bias due to deviations from intended interventions	Low	Not reported or no clear information	Low	No clear information. Some investigators were aware of the participants during follow-up cases but were masked
Bias due to missing outcome data	Low	No attrition reported. All patients were assessed for outcome	Low	No loss of patients reported. All patients were included in outcome assessment
Bias in the measurement of the outcome	Some concerns	The same examiner masked to the procedure category performed all measurements	Some concerns	Examiners masked to the procedure, both participant and observer were blinded
Bias in selection of the reported result	Low	All intended outcome were reported and assessed	Low	All intended outcomes were reported
Overall bias	Low		Low

Figure 2

Overall assessment of risk of bias in included studies

DISCUSSION

Regeneration of periodontal tissues involves the new cementum, bone, and periodontal ligament. Several methods have been suggested to achieve this goal.[12] BMPs, (BMP-2 and BMP-7), transforming growth factor beta, insulin-like growth factors I and II, platelet-derived growth factor, fibroblast growth factors, and vascular endothelial growth factor have been suggested for use in bone tissue engineering.[181920] BMPs were primarily shown to induce ectopic bone growth in vivo. They are known to enhance chondrogenesis and osteogenesis.[721] In vertebrates, ossification occurs by either intramembranous or endochondral mechanisms. BMPs such as BMP-2 and 4 trigger phenotypes of chondroblasts and osteoblasts resulting in the formation of cartilage and bone.[22] The interaction between the heterodimeric complex of serine/threonine kinase transmembrane receptors leads to BMP signal transduction.[2324] Current research is concentrating on the development of an efficient carrier system for these BMPs and the exploitation of methods to promote the efficacy of bone-forming activity in BMPs.

Application of BMP-2 and 7 in experimental-induced periodontal defects demonstrated a significant regeneration of periodontal tissues in animals.[910] Further, these BMPs induced differentiation of chondroblasts and osteoblasts and new bone and cementum formation.[1213] However, in an in vivo study, the addition of a pool of bovine BMPs did not provide clinical benefits to guided tissue regeneration in the treatment of intraosseous defects.[25]

Young animals are most commonly used in animal models, making the clinical significance of these results very restricted. Furthermore, growth factors in humans are metabolized at different rates to their animal counterpart. When rhBMPs are used in higher mammals, a single BMP, currently either BMP-2 or BMP-7, is preferred. It is used in a pharmacological dose rather than a physiological dose.[11]

In both studies, Altis OBM™ (Altis Biologics Pvt. Ltd., South Africa) was used as osseous grafting material in periodontitis. It comprised BMP (3–12 mg), porcine bone collagen, and bone gelatin. It is available as a lyophilized powder in a sterile syringe. This bone graft substitute is a bioresorbable, osteoinductive nature and also provides scaffolding effect. At this dose, no adverse effects were reported in both studies.[1617]

This systematic review is aimed to find the efficacy of rhBMP-2 in the treatment of human intrabony defects in periodontitis patients. In one study, only open-flap debridement (OFD) was used as a control.[16] In another split-mouth study, two separate controls were used to compare rhBMP-2 with platelet-rich fibrin (PRF) in chronic periodontitis patients.[17]

Pocket depth

According to Vandana et al., the PD reduced significantly within both groups from baseline to 6 and 9 months. The PD reduction was not significant between the groups at 6 months (P = 0.95). At 9 months, the PD was significantly reduced from 6.90 ± 0.85 mm to 4.40 ± 0.60 mm in the BMP group as compared to OFD (P < 0.05).[16] In the study by Vandana and Prakash, the mean PD reduction was significantly greater (P = 0.025) in PRF-treated sites (4.5 ± 0.35 mm) as compared to rhBMP-2-treated sites (1.3 ± 0.78 mm) at 6 months (P = 0.026).[17] Both studies reported contradictory findings. At present, it is not possible to conclude the effect of rhBMP-2 in terms of reduction of PD.

Clinical attachment levels

Contradictory findings were reported in included studies. The improvement in CAL was highly significant within these groups from baseline to 6 and 9 months. The difference in CAL improvement was not significant at 6 months between these groups. However, at 9 months, there was approximately 2-mm improvement of CAL (P < 0.05).[16] Another study also reported no differences (P = 0.12) in CAL gains when rhBMP-2-treated sites were compared to PRF.[17]

Radiographic defect resolution

Both studies reported significant radiographic resolution of intrabony defect at 6 and 9 months. There was a significant amount of radiographic bone fill in the rhBMP-2 group than in the OFD group at 6 months (P < 0.002) and 9 months (P < 0.001). The initial defect depth of 2.87 ± 1.03 mm was significantly reduced to 1.73 ± 0.98 mm (P < 0.001) at 6 months, which further reduced to 1.02 ± 0.7 mm (P < 0.001) at 9 months. Similarly, the original radiographic defect in rhBMP-2-treated sites was significantly gain of 60.1% ±15.8% compared to OFD sites (21.9% ± 22.2%).[16] In another study, the rhBMp-2 sites showed defect resolution of 41.1 ± 19.2 compared to 26.75 ± 6.03 in PRF-treated sites at 6 months (P = 0.0019).[17]

The predictability of bone graft in the treatment of intrabony defect depends on the depth of the osseous defect (i.e., shallow vs. deep or wide vs. narrow) and also morphology of osseous walls. Both studies were lacking in defining the type of intrabony defects. The meta-analysis was not carried out due to the lack of studies and also had the same experimental group. Further studies should be carried out using rhBMP-2 in the intrabony defects. The studies should have a larger sample size and longer follow-up duration so that the generalizability is possible. The physiologic dose of rhBMP-2 should be investigated for greater periodontal regeneration.

CONCLUSIONS

The rhBMP-2, as bone grafting biomaterial, has shown preliminary evidence that it carries a potential to treat the intrabony defects and therefore should be considered for further clinical evaluation. Significant reduction in CAL and radiographic defect resolution were obtained at 6 and 9 months without change in PD reduction in rhBMP-2 after 9 months. Due to the limited human studies, it can be concluded that no conclusive evidence exist to ascertain the effectiveness of rhBMP-2 in the treatment of intrabony defects in periodontal disease. The generalizability of rhBMP-2 still remains uncertain due to lack of data and hence requires more studies for better analysis and conclusion derivation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.