Evaluation of Bone Remodelling After Endodontic Therapy of the Periapecal Lesion

Svrha je istraživanja ocijentit preoblikovanje kosti mjereći površinu osteoida, debljinu osteoida, osteoklasni indeks i broj upalnih stanica nakon dviju različitih endodontskih terapija periapeksnih lezija na psećim zubima. Na 23 donja premolara (37 korijenskih kanala) 6 pasa mješanaca inducirane su periapeksne lezije. U skupini 1, 17 korijenskih kanala instrumentirano je do apeksne delte crown-down tehnikom služeći se ProFile® Ni-Ti rotirajućim instrumentima napunjeno do iste dužine tehnikom Thermafill® i Top Seal® cementom. Ostalih 20 korijenskih kanala (skupina 2) instrumentirani su tehnikom kontrolirane preinstrumentacije do točke određene elektroodontometrijski (električni apeks lokator EED-11, Struja, Zagreb, Hrvatska). Kanali su napunjeni tehnikomThermafill® na dužini 2 mm kraćoj od radne dužine. U objema skupinama dužina punjenja provjerena je radiološki, a pristupni kaviteti ispunjeni amalgamom. Životinje su žrtvovane 35 dana nakon endodontske terapije. Nedemineralizirani rezovi debeli 5-7 mm obojeni su Toluidinskim modrilom. Histomorfometrijski indeksi (površina osteoida, debljina osteoida, osteoklasni indeks i broj upalnih stanica) mjereni su svjetlosnim mikroskopom koristeći se računalnim programom (ISSA, Vams, Zagreb, Hrvatska). Razlike između skupina statistički su znatne za sve mjerene indekse. U skupini 1 površina osteoida je manja (10,34 % ± 11,60), a tako i debljina osteoida (15,62 µm ± 7,41) i broj upalnih stanica (111,39 ± 75,81), dok je osteoklastni indeks viši (111,34 mm - 2 ± 115,46). U skupini 2 površina osteoida je veća (33,21 % ± 21,43), kao i debljina osteoida (16,26 µm ± 6,46) i broj upalnih stanica (137,62 ± 46,34) a osteoklastni je indeks niži (27,00 mm - 2 ± 39,03). Za statističke raščlambe upotrijebljen je Mann-Whitney U test. Rezultati dobiveni mjerenjem morfometrijskih indeksa pokazuju održavanje aktivnosti resorpcije kosti u skupini 1 i brže stvaranje kosti u skupini 2. Veći broj upalnih stanca u skupini 2 vjerojatno je uzrokovan dodatnom traumom periapeksnoga tkiva prigodom preinstrumentacije. Ova trauma ne utječe na remodelaciju kosti.The aim of the study was to evaluate bone remodelling by measuring osteoid surface, osteoid thickness, osteoclast index and inflammatory cell count after two differnet approaches in endodontic therapy of periapecal lesion on dogs’ teeth. After inducing periapecal lesion in 23 mandibular premolars (37 root canals) from six mongrel dogs, 17 root canals were instrumented to the apical delta with crowndown techniwue using ProFile® Ni-Ti rotary instruments and filled to the same length with Thermafill® obturation technique and Top Seal® cement (group 1). The other 20 root canals (group 2) were instrumented using controlled overinstrumentation technique to the point determined ellectronically (electronic apex locator EED-11, Struja, Zagreb, Croatia). Teeth were obturated with Thermafill® at the length 2mm shorter than the working length. Length of obturation was confirmed radiographically and access cavities sealed with amalgam in both groups. The animals were sacrified 35 days after the end of endodontic treatment. Undemineralizad sections 5-7 mm thick were stained with toluidine blue. The histomorphometric indices (oseoid surface, osteoid thickness, osteoclast index and inflammatory cell count) were measured by light microscopy using computer program (ISSA, Vams, Zagreb, Croatia). The difference between grops was statistically significant in all measured indices. In group 1 the osteoid surface was lower (10.34 % ± 11.60) as well as osteiod thickness (15.62 µm ± 7.41) and inflammatory cell count (111.39 ± 75.81) while osteoclast index was higher (111.34 mm - 2 ± 115.46). In group 2 osteoid surface was higher (33.21 % ± 21.43) as well as osteoid thickness (16.26 µm ± 6.46) and inflammatory cell count (137.62 ± 46.34), while osteoclast index was lower (27.00 mm - 2 ± 39.03). Stastistical analysis was performed using Menn-Whitney U Test. Results obtained by measuring histomorphometric indices indicate sustained bone resorption activity in group 1 anf faster bone formation in group 2. The greater number of inflammatory cells in group 2 was probaly caused by additional trauma of periapical tissues during overinstrumentation. This trauma does not interfere with bone remodelling