Effect of Double Antibiotic Paste Versus Calcium Hydroxide on RANKL/OPG Levels

Apical periodontitis is an inflammatory disease that occurs as a consequence of the bacterial infection of dental pulp tissue. It represents an inflammatory/immune pathogenesis affecting the periapical tissue including the surrounding bone. This periapical process is primarily initiated by bacterial infection in the necrotic pulp. Its persistence, progression to chronic lesions and destruction of bone structures are a consequence of the inability of host-defense mechanisms to eradicate infection. Periapical lesions are characterized histologically by fibrous and granulated tissue, infiltrated by different inflammatory cells.

Up to now the diagnosis and follow-up of asymptomatic apical periodontitis AAP is based on a clinical radiographic evaluation, however, this reflects the accumulated damage from previous episodes of periodontal tissue destruction. Moreover, the clinical presentation does not reflect the underlying inflammatory response. In accordance, differences in disease severity involve qualitatively and quantitatively different inflammatory responses. Nowadays, the challenge focuses on the necessity of designing innovative non-invasive chair-side point-of-care assessment methods, accounting for the biological profile as a complement to the existing clinical-radiographic assessment to contribute to the early evaluation of treatment outcome.

Rationale for conducting the research:

When dental pulp is infected or inflamed, various inflammatory mediators, including cytokines, chemokines, and neuropeptides, are released by innate and adaptive immune cells. During the development of pulp inflammation, inflammatory mediators result in the formation of apical osteolytic lesions. Bone loss is mainly caused by activated osteoclasts. Various cytokines such as interleukin (IL)-1, IL-11, IL-17, and tumor necrosis factor alpha (TNF-a) stimulate osteoclast progenitor cell differentiation and activation by the osteoprotegerin (OPG)/nuclear factor kappa B ligand (RANKL)/nuclear factor kappa B (RANK) complex.

The molecular mechanisms underlying bone resorption are regulated by the interaction between RANKL and OPG.The interaction between RANKL and RANK is necessary for the differentiation and activation of osteoclasts. This is modulated by OPG, which, in turn, suppresses osteoclast differentiation by preventing the interaction between RANKL and RANK.The production of OPG and RANKL by different cell types is regulated by local and systemic stimuli, including bacterial products, hormones, and inflammatory mediators.Changes in the balance of the mediators determine the progression and severity of bone diseases such as those found in periapical and periodontal lesions.

It has been reported that antibiotics regulate the immune response through modulation of cytokines production. Therefore, the level of cytokines, RANKL, and OPG can also be affected by antibiotics. In the infected root canal system, virulence products, antigens, and microbial cells are the main causes of apical periodontitis. Microorganisms in the root canal system adhere to root canal walls, isthmuses, ledges and commonly formed biofilm communities.The application of antimicrobial intra-canal medication is recommended to eliminate bacteria that could not be removed from the root canal system after instrumentation and irrigation of the root canals.

Calcium hydroxide (Ca (OH)2) is generally preferred in endodontics as an intracanal medicament because of its antimicrobial and biological effects. Because of its solubility, Ca (OH)2 releases calcium and hydroxyl ions slowly providing an alkaline environment in the periapical region.

There has been only a single in vivo study performed to evaluate the effect of Ca (OH)2 combined with ciprofloxacin or ibuprofen on the release of RANKL/OPG in periapical lesions. The aim of the present study is to evaluate the effect of double antibiotic paste when compared to Ca (OH)2, in terms of RANKL and OPG levels in chronic periapical lesions and correlate the results with periapical bone healing findings after a follow up period of one year.