ⅠINTRODUCTION

Root canal endodontic therapy is an important dental procedure to survive the diseased tooth involved with pulp damage and pulpitis. In these days the endodontic treatment was frequently performed using different root canal irrigation materials. Among the different root canal irrigation materials the calcium oxide-based materials gave good biological result with strong bactericidal effect¹⁾ compared to the washing and sterilizing solutions containing sodium hypochloride, chlorhexidine⁴⁾, etc.

Recently, Calcipex II has been developed as calcium hydroxide-based water soluble paste by adding a certain penetrating agent, i.e., micro-resin granules, barium sulphate, etc. (The precise data were not provided by the company) It has been widely used for root canal irrigation to prevent bacterial infection. But when Calcipex II was overfilled and spilled into periapical tissue, it was reported that chronic granulomatous lesion could occur due to the foreign body reaction to the fine granular polymer resin materials of Calcipex II^2,3,5) (described as Calcipex II granules in this study). However, the Calcipex II granules were very small in size, about 1 μm in diameter. They are usually round and partly translucent, so that they looked as brown to black spots in the ordinary light microscopic observation. And some Calcipex II granules were engulfed by macrophages, but rarely degraded in the cytoplasms of macrophage, and finally resulted in the apoptosis of involved macrophages. Consequently, the Calcipex II granules were gradually dispersed deeply into connective tissue, and then the microscopic detection of Calcipex II granule became difficult and took a long time even in the high magnification view.

So far we pathologically observed many cases of Calcipex II granules-induced periapical granulomatous lesions, and took a lot of time to find out the Calcipex II granules in the necrotic and granulomatous periapical lesion in order to diagnosis the Calcipex II granule-induced granuloma differentially from other inflammatory lesions. In this study we demonstrated that the Calcipex II granules in granulomatous lesion of peri-implantitis showed bright birefringence in the polarizing microscope observation, and discussed the diagnostic usage of the bright birefringence for the resin granule-related diseases after endodontic treatment.

ⅡCASE REPORT

A 30 years old female patient was complained of dull pain in left mandibular first molar area, where the first molar was replaced by a dental implant. In the dental treatment history, the left mandibular first molar was involved with severe dental caries and progressed into acute pulpitis, and followed by root canal endodontic treatment using Calcipex II root canal irrigation one and half years ago. But the tooth was continuously painful with increased mobility, so that the tooth was extracted and subsequently replaced by dental implant one year ago. But recently she felt dull pain around the implant (#36) area, and also difficulty in mastication due to severe mobility of the implant. Under the clinical diagnosis of severe peri-implantitis, the implant was removed and the associated granulomatous lesion was examined pathologically.

The biopsy specimen (OS2016-40) was referred to the Department of Oral Pathology, Gangneung-Wonju National University Dental Hospital (GWNUDH). The usage of biopsy specimens filed in the Department of Oral Pathology, GWNUDH was approved by our institutional review board (IRB2015-07). The specimen was fixed with 10% PBS-buffered formalin solution, embedded with paraffin, and microsectioned in 4 μm thickness. The microsections were routinely stained with hematoxylin and eosin, and observed under ordinary light microscope and also under polarizing microscope.

Microscopic observation disclosed a granulomatous lesion diffusely infiltrated with chronic inflammatory cells. The granulomatous lesion was diffusely fibrosed with the heavy deposition of collagen bundles, but was distributed with tiny capillaries. Therefore, the granuloma showed no feature of regeneration but became agitated and sclerosed. Throughout the inflammatory lesion fine granular materials were found, and then they were usually scattered, and focally aggregated. The granular materials were small round particles, measuring about 1 μm in diameter, and were brownish and partly translucent. With the dental history of endodontic treatment at left mandibular first molar (#36) by using Calcipex II root canal irrigation materials one and half years ago, these fine granular materials were defined to be derived from the overfilled Calcipex II granules. These findings were also identical to the previous observation of Calcipex II-related diseases, i.e., periapical granuloma³⁾ and maxillary sinusitis²⁾.

In the ordinary microscope observation in hematoxylin and eosin stain the Calcipex II granules were sometimes difficult to be found out in chronic granulomatous lesions (Fig. 1 A1, B1, and C1), because they are somehow similar to bacterial cocci or tissue debris. But with the properties of bright birefringence of resin polymer, the Calcipex II granules can be easily detected in the chronic ganulomatous lesion under the polarizing microscope (Fig. 1 A2, B2, and C2).

ⅢDISCUSSION

Although the endodontic treatment is a beneficial method to survive or to prolong the life of diseased tooth, there is an array of potential factors that influence the outcome of endodontic treatment, success is most significantly dependent upon the elimination of root canal infection present when treatment starts and the prevention of contamination during treatment⁶⁾. Different techniques have been introduced to improve the efficiency of root canal dressing by using calcium hydroxide-based materials, i.e., Calcipex II. These days Calcipex II is widely used due to its good penetrating property deeply into accessory canals as well as strong bactericidal effect. The Calcipex II materials have to be removed through aqueous irrigation, but the removal is sometimes incomplete⁷⁾, and some of Calcipex II materials are overfilled and spilled into periapical tissue.

As Calcipex II materials contain micro beads composed of polymer resin, which are recognized as foreign bodies by antigen present cells, Calcipex II granules remained in periapical tissue can induce inflammatory reaction via recruiting tissue macrophages. And more Calcipex II granules are hardly resorbed by phagocytosis of macrophages, rather the unresorbed Calcipex II granules finally destroy the macrophages via the signaling of apoptosis. Therefore, Calcipex II granules are gradually dispersed and continuously elicit inflammatory reaction. Besides the reported cases of Calcipex II-related inflammatory disease^2,3,5), there are many cases of periapical granuloma, periapical abscess, periapical cyst, regional osteomyelitis, and peri-implantitis which have to be confirmed for the diagnosis of Calcipex II granule-induced foreign body granuloma in our Departments.

In the present study we firstly found that the polymer resin of Calcipex II granules showed bright birefringence under the polarizing light. This bright birefringence of Calcipex II granules is arisen from the relatively homogenous and translucent materials of polymer resin, and quite comparable to various spots of bacterial cocci and degenerating tissue debris in chronic granulomatous lesion. Not only the aggregated Calcipex II granules but also the scattered ones were easily detected as bright spots in dark field view under the polarizing microscope. Therefore, it is suggested that the Calcipex II granule-induced foreign body granuloma lesions have to be observed under polarizing microscope to detect bright birefringence of Calcipex II granules for the differential diagnosis from ordinary infected periapical/periodontal granuloma.

Additionally, because the different root canal filling materials which are composed of homogenous and semi-translucent beads, i.e., different polymer resins, also produce characteristic birefringence under the polarizing light, it is also suggested that the periapical diseases caused by overfilled root canal filling materials composed of polymer resin beads are able to be diagnosed differentially by detecting the characteristic birefringence in the polarizing microscope observation.