Light microscopic study of periapical lesions associated with asymptomatic apical periodontitis

Herpes simplex virus type 1 in periapical pathoses: Systematic review and meta-analysis

OBJECTIVES

The objective of this systematic review and meta-analysis of observational studies was to assess whether herpes simplex virus type 1 (HSV-1) can infect endodontic periapical lesions.

MATERIALS AND METHODS

Studies with cross-sectional design investigating HSV-1 in periapical tissues of patients with symptomatic and asymptomatic acute and chronic apical periodontitis were searched through MEDLINE, Scopus, Embase, Web of Science, and Google Scholar. Pooled HSV-1 prevalence proportion with 95% confidence interval (95CI) in periapical lesions was assessed with both fixed-effect and random-effects models, with/without adjustment for study quality and publication bias. Result robustness was investigated through sensitivity and subgroup analyses.

RESULTS

Literature search, performed twice, provided 84 items, and eight remained for the meta-analysis; globally, there were 194 patients mostly adults. The pooled HSV-1 prevalence proportions, assessed with various methods, were 6.9% (95CI, 3.8-11.3%, fixed-effect); 6.8% (95CI, 3.6-11.0%, random-effects); 8.1% (95CI, 4.4-14.5%, quality-adjusted); and 4.8% (95CI, 2.0-11.4%; adjusted for small-study effect).

CONCLUSIONS

The results indicated that HSV-1 can colonize the periapical tissues of 3%-11% patients with periapical diseases. Such data do not imply a causative role of HSV-1 in disease development and advancement. Well-designed and large-sized prospective cohort studies should be added in the literature panorama.

Modulation of Matrix Metalloproteinase 14, Tissue Inhibitor of Metalloproteinase 3, Tissue Inhibitor of Metalloproteinase 4, and Inducible Nitric Oxide Synthase in the Development of Periapical Lesions

INTRODUCTION

Periapical cysts and granulomas are chronic lesions caused by an inflammatory immune response against microbial challenge in the root canal. Different cell types, cytokines, and molecules have been associated with periapical lesion formation and expansion. Therefore, because of the chronic inflammatory state of these lesions, the aim of this study was to evaluate the in situ expression of matrix metalloproteinase (MMP)-14 and -19, tissue inhibitor of metalloproteinase (TIMP)-3 and -4, CD68, and inducible nitric oxide synthase (iNOS) in periapical cysts and granulomas.

METHODS

Sixteen cases of periapical cysts and 15 cases of periapical granulomas were analyzed. Ten normal dental pulps were used as the negative control. Immunohistochemistry was performed with anti-MMP-19, anti-MMP-14, anti-TIMP-3, anti-TIMP-4, anti-iNOS, and anti-CD68 antibodies.

RESULTS

The expression of TIMP-3, TIMP-4, iNOS, and CD68 was significantly higher in both the cyst and granuloma groups than in the control group. TIMP-4 was also significantly higher in cases of chronic apical abscess. There was also a significant difference in the expression of MMP-14 between the cyst and control groups. However, there were no differences in the expression of MMP-19 between the 3 groups.

CONCLUSIONS

Our data suggest that the expression of MMP-14, TIMP-3, and TIMP-4 is associated with the development of periapical lesions.

Radicular Cyst: An Update of the Biological Factors Related to Lining Epithelium

INTRODUCTION

Radicular cysts are common lesions in daily dentistry practice. However, the mechanisms related to epithelial lining formation and cavity growth are not fully understood. Therefore, the purpose of this article was to review the biological factors implicated in these process.

METHODS

Literature was selected through a search of PubMed electronic databases matching the following key words in the title or abstract: "cyst" OR "granuloma" OR "abscess" AND "radicular" OR "apical" OR "periapical" AND "epithelium" OR "epithelial" OR "epithelial lining." The PubMed database was searched for articles published between 1975 and 2014. Only English language was applied to the search.

RESULTS

The literature search yielded a total of 187 articles. After duplicate references were discarded, a subsequent search at the title and abstract level revealed 42 articles for full-text reading. The articles were categorized into 5 main subtopics: (1) cell proliferation, cell cycle, and apoptosis; (2) extracellular matrix constituents; (3) inflammatory components; (4) bone metabolic factors and; (5) others. These subtopics described the characteristics of radicular cysts focusing on the epithelial tissue effects.

CONCLUSIONS

Several factors from different sources (epithelial cells, stromal cells, extracellular matrix, and bone matrix) were implicated on apical cyst pathogenesis. Probably a combination of many factors involving an epithelial-stromal interaction is responsible for the sustenance and growth of apical cysts.

Matrix metalloproteinase expression in teeth with apical periodontitis is differentially modulated by the modality of root canal treatment

INTRODUCTION

The objective of this study was to investigate the expression of matrix metalloproteinases (MMPs) in apical periodontitis and during the periapical healing phase after root canal treatment.

METHODS

Apical periodontitis was induced in dog teeth, and root canal treatment was performed in a single visit or by using an additional calcium hydroxide root canal dressing. One hundred eighty days after treatment the presence of inflammation was examined, and tissues were stained to detect bacteria. Bacterial status was correlated to the degree of tissue organization, and to further investigate molecules involved in this process, tissues were stained for MMP-1, MMP-2, MMP-8, and MMP-9. Data were analyzed by using one-way analysis of variance followed by Tukey test or Kruskal-Wallis followed by Dunn test.

RESULTS

Teeth with apical periodontitis that had root canal therapy performed in a single visit presented an intense inflammatory cell infiltrate. Periapical tissue was extremely disorganized, and this was correlated with the presence of bacteria. Higher MMP expression was evident, similar to teeth with untreated apical periodontitis. In contrast, teeth with apical periodontitis submitted to root canal treatment with calcium hydroxide presented a lower inflammatory cell infiltrate. This group had moderately organized connective tissue, lower prevalence of bacteria, and lower number of MMP-positive cells, similar to healthy teeth submitted to treatment.

CONCLUSIONS

Teeth treated with calcium hydroxide root canal dressing exhibited a lower percentage of bacterial contamination, a lower MMP expression, and a more organized extracellular matrix, unlike those treated in a single visit. This suggests that calcium hydroxide might be beneficial in tissue repair processes.

High matrix metalloproteinase activity is a hallmark of periapical granulomas

INTRODUCTION

The inability to distinguish periapical cysts from granulomas before performing root canal treatment leads to uncertainty in treatment outcomes because cysts have lower healing rates. Searching for differential expression of molecules within cysts or granulomas could provide information with regard to the identity of the lesion or suggest mechanistic differences that may form the basis for future therapeutic intervention. Thus, we investigated whether granulomas and cysts exhibit differential expression of extracellular matrix (ECM) molecules.

METHODS

Human periapical granulomas, periapical cysts, and healthy periodontal ligament tissues were used to investigate the differential expression of ECM molecules by microarray analysis. Because matrix metalloproteinases (MMP) showed the highest differential expression in the microarray analysis, MMPs were further examined by in situ zymography and immunohistochemistry. Data were analyzed by using one-way analysis of variance followed by the Tukey test.

RESULTS

We observed that cysts and granulomas differentially expressed several ECM molecules, especially those from the MMP family. Compared with cysts, granulomas exhibited higher MMP enzymatic activity in areas stained for MMP-9. These areas were composed of polymorphonuclear cells (PMNs) in contrast to cysts. Similarly, MMP-13 was expressed by a greater number of cells in granulomas compared with cysts.

CONCLUSION

Our findings indicate that high enzymatic MMP activity in PMNs together with MMP-9 and MMP-13 stained cells could be a molecular signature of granulomas unlike periapical cysts.