Oral and maxillofacial infections are common health problems worldwide. More than 500 bacterial species are known to constitute normal oral microbiota [1] . Dentalcaries, on the other hand, is considered to be endogenous bacterial disease, caused by oral cavity bacterial flora with have latent pathogenic potential. The disease is a result of creatiton of favorable conditions where by the resistance of the host (the tooth) is reduced and the specific bacterial species multiply, leading to expression in cariogenic types. If caries is not treated, complications occur with repercussions to pulp-periodontal complex [2] .

A number of studies have reported on the microbial composition of necrotic dental pulps, that is in infected root canal, and have indicated the presence of facultative anaerobic bacteria, which are usually present in oral envoirment.Some studies have also shown that obligate anaerobes predominated in infected root canals of teeth and made as up as much as 90% or more of the microbiota [3] [4] .

Pulp diseases and periodontal tissues diseases depend of anatomical, physiological and histological characteristics. The growth and development of orofacial system as a whole, the development and maturation processes of dento-alveolar tissue and involutive processes in primary and young permanent teeth are of great importance for the genesis and development of the dental infections in children [5] . Pulp of the tooth primary is infected and becomes necrotic of its own oral microflora. Conditions in pulpal low to settle inside of if mixed, mostly anaerobic flora.

This polymicrobial community which is part of the root canal has several biological and pathogenic characteristics as antigenicity, mitоgenic characteristics, chemotaxis, histolysis with enzymes and activation of host cells. Microbial invaders in root canal themselves can progress or their products can be spread to the periapical tissue. As response to them, the host activates its defense mechanism which is composed of several type of cells, intercellular substances, antibodies and effectors molecules [6] - [8] .

Etiology and pathogenesis of dental infections in children are the same in the primary (deciduous) teeth and in the permanent teeth, but they differ only by the course of the process because of the specifics in the anatomical and physiological conditions of the jaws and in the organism of the child as a whole, which is still in a phase development. Therefore, according to Caufield et al. [3] , the pathogenesis of dentogenic infections depends on variety of the roots from primary (deciduous) teeth is their formation and absorption, then from the location and closeness of the beginnings of the permanent teeth and their follicles which are well vascularized. Тhe expansion of the pathological process is also affected by the anatomical structure of procesus alveolaris, which is very thin in children and the spongious part of bone is rarer. The predisposition of the child organism to inflammation of bone and bone marrow and to the soft tissues is with special importance. According to some authors, dentin canals of primary (deciduous) teeth are more wider than those in permanent teeth, which contributes to faster spread of caries [9] - [11] . Seow [12] has established that these canals are wider in peripheral dentin at primary teeth than at permanent teeth where the dentin layers are closer to the pulp were almost the same width.

A spredominant pathology which is a consequence of chronic dentogenic infections, are considered those teeth that were with chronic apical paradontitis with fistula, then parulis which is subgingival localized abscess in alveolar bone and who is connected with chronic periapical process of primary tooth through fistulising canal. And the residual roots of primary teeth with apical processes are considered as a relevant factor responsible for the occurrence of dentogenic infections [13] .

For the permanent teeth, on the other hand are chronic apical paradontitis with fistula; fractured teeth with fistula (as a consequence of dental caries or dental trauma); apical paradontitis verified with radiographs; residual gangrenous teeth with periapical processes and fistula;and secondary caries with periapical processes as a result of the failed treatment of dental caries [14] .

The aim of this prospective study was to 1) Investigate the bacterial strains of aerobic and anaerobic bacteria in samples taken from alveoli of freshly extracted teeth of deciduous and permanent dentition with acute and chronic dental infections, and 2) To determine the species of each isolated group of identified bacteria from aerobic and anaerobic microorganisms.

Seventy kids aged 5 - 15 years (36 females, 34 males) were studied prospectively at the University Dental Clincal Center of Kosovo, Department of Pediatric Dentistry in cooperation with Microbiologic Department of Faculty of Medicine. All patients who had clinical and radiological confirmation of their dental infections, followed by extraction of their teeth. Once the tooth was extracted blood and pus sample from the empty alveoli were cultured. The analysis of the sample for bacteria identification was done using the automated system VITEK 2 cards (Biomeriux, France) for the identification of gram positive (ID-GP cards) and gram negative (ID-GN cards).The bacterial suspension through the special pipe transferred prepared blood suspension up to card. Through this pipe, material is transferred from suspension up to card. Cards are also recorded in automated VITEK system. After registration cards are placed in VITEK apparatus for identification of gram―positive bacterium, 24 hour mean.

They were in good general health and had not been treated for any other illness. This research study was approved by the Human Ethic Commitee of the University Dental Clinical Center of Kosova.

A total of 202 bacterial strains were isolated from 70 patients, 122 aerobic specie; 60.5%, and 38% anaerobic specie, 2% was Candida and 0.5% was undifferentiated (Figure 1)

All samples are divided in 3 groups and each group is studied with 2 sub-groups (6 groups all together). The first group were patients with acute and chronic infections, in the second group are studied patients with deciduous and permanent dentition and in the third study research consist in analyzes from blood and pus samples taken from each group.

Of 70 children, 34 (48.5%) of them had dental infection in deciduous teeth and 36 (51.5%) in permanent teeth. While the acute infections dominated in deciduous dentition, in permanent dentition we have the preponderance of chronic apical infections (Table 1 and Figure 2).

In all samples with acute infections, Streptococcus group, mitis and oralis were present in 30%, Str. pyogenes gr. A in 12.9%, and Str.sanguinis in 10%. The other bacteria that are isolated also in streptococcus group are presented in 2.9%.Staphylococcus epidermidis and Kocuria Kristinae in 1.4% (Table 2 and Figure 3).

Of anaerobic bacteria in acute infections the most prevalent bacteria was Actynomyces group Actinomyces mayeri in 18.6%, Actinomyces odontoliticus in 8.6% and Actinomyces naeslundi in 7.1%. Lactobacillus gasseri was isolated in 4.2% and Prevotella, Veilonella and Clostridium Clostridiformis was isolated in 2.9%.The other bacteria were present in 1.4% present in samples (Table 3 and Figure 4).

In chronic infections we have higher percentage of Streptococcus mitis (44.4%) and oralis (41.6%) and Streptococcus sanguinis had the same value as in acute infections (10%).Other aerobes isolated on chronic infections are also from streptococcus group, Streptococcus sanguinis gr “A” and Kocuria rosea with Granulicatela adiacens both in 5.7%. Staphilococus epidermidis, Leuconostoc m. spp. cremoris, Erisypela rhusiopathiae and Serratia marescens are presented only in 2.9% (Table 4 and Figure 5). In patients with chronic infections

Actinomyces mayeri was present in 11.4% and Actynomyces naeslundi in 10.0%, while the Anaerococcus prevoti was present in 7.1% and Lactobacillus gasseri in 5.7%. The other bacteria, Lactobacillus and Biffidobacterium spp. was in 2.9%. Clostridium group and Finegoldia magna were present with 1.4% (Table 5 and Figure 6).

In our study, we have demonstrated that the dental infections in pediatric population (5 - 15 years old) are polymicrobial predominantly anaerobic bacteria over aerobic. This study paves the way for preventives measures that need to me implemented in this group of children. Epidemiological features of dental infections were the object of research by authors from the world's leading research institutes. Caste [14] within period of 1976-79 year investigated bacteriology and treatment of 61 patients with an average age of 15 - 25 years. While Hunt [15] and collaborators studied the microbiological and epidemiological characteristics at a state hospital in the United States, as well as a simple predominance of male (52%), Haimdahl [16] reported management of microbiological data for 58% of patients. Batty (in 1958) [17] isolated Actinomyces odontoliticus in caries samples from patients with advanced caries. Dodson [18] [19] gave demographic data for 113children, finding the existence of a high level of infection in female children (59%) compared with the male (41%) and the average age was 4.5 years.

More evidence suggests that apical periodontitis is a disease in which biofilm has leading role in the etiology. In situ researches which are made using optical and /or electronic microscope allow be identified bacteria that colonize the root canals of primary infected teeth or in the teeth with persistent infection where bacteria are in the form of biofilms that cover root canal walls [12] [13] [20] - [23] . Apical ramifications, lateral canals and isthmuses that connect the mainroot canals are shown to contain bacterial cells that are often formed biofilms. [14] [15] [24] Biofilms which are found on the apical surface of roots (extra radicular biofilms) is assumed to have etiological role in apical period ontitis which occurs after treatment of the roots [16] [17] .

Very few studies have been made for the microbiological flora of the root canals at primary teeth. In re- searches of Pazelli [24] made in a total of 20 primary teeth with necrotic pulp in the region of furcation in the teeth and/or periapical regions, anaerobic microorganisms were selected in 100% of the samples, black-pig- mented bacilli in 30%,aerobic microorganisms in 60%, streptococci 85%, Gram-negative aerobicrods 15% and staphylococci were not quantified. Streptococcus mutans was found in 6 root canals (30%), from which 5 canals were with Streptococcus mutans and 1 canal was with Streptococcus mutans and Streptococcus sobrinus. It was then concluded that in the root canals of deciduous teeth with necrotic pulp and periapical lesions, the infection is polymicrobial with predominance of anaerobic microorganisms.

Until 1970 the most common bacterial group isolated with culture from root canals of permanent teeth was Streptococcus viridians (alpha haemolytic streptococcus).Then, with the development of strictly anaerobic cultural techniques, the concept of endodontic infections has changed since anaerobic microorganisms, which were rarely isolated, were identified as predominant endodontic microorganisms in the flora of permanent teeth with necrotic pulp and periapical lesions [12] [16] .

Studies by William [25] from 1970 have pointed out that the most common bacterial group isolated with cultivation from root canals of permanent teeth were Streptococcus viridians (alpha haemolytic streptococcus).

Oguntebi et al. also find that Streptococcus mitis are the predominant bacteria in isolate samples taken in periapical abscesses [26] .

Sakaguchi [25] et al. believe that the development of anaerobic cultural techniques and the concept of endodontic infections are changed, and because of that, the anaerobic microorganisms which were rarely isolated microorganisms were predominant microorganisms in the flora at permanent teeth with necrotic pulp and periapical lesions. Very few studies have been performed on the microbiological flora in the root canals from primary teeth, but should be noted that the presence of Streptococcus mutans in the root canals of primary teeth was not found previoulsy.

Hegde and Pallavi also isolate Streptococcus mutans in 100% of sample [27] . According to Brook from of aspiration in 12 children with per apical abscesses he isolated 67% anaerobes and the others were aerobic and facultative aerobic [28] .

Marsh and Largent [29] found that the most frequent microorganisms in the root canals of deciduous teeth with necrotic pulp and periapical lesions were Streptococcus salivarius. Da Silva (2010) [30] found polymicrobial infections in primary teeth, mostly anaerobic microorganisms. J. F. Siqueira (2003) [31] isolated Bacteroidetes, Firmicutes, Actinobacteria, fusobacteria and Proteo bacteria (with DNA and Spirochaetes and Deferribacteres) and Pazelli et al. (2009) [24] detected anaerobic microorganisms and types of streptococci in root canals with necrotic pulp at primary teeth. Аccording to Gill. I, Skali C (2009) [32] the most common pathogenic actors of these infections in permanent teeth were Bacteroides, Fusobacteria, peptococci, peptostreptococci and streptococcus viridans group while Léa Assed Bezerra (2010) [30] isolated aerobic MO, streptococci, Gram- negative aerobic rods and Streptococcus mutans and Streptococcus sobrinus. Ashok [33] in their investigations revealed the presence of Gram positive cocci(Peptococcus and Peptostreptococcus), Grampositive bacilli (Lactobacillus, Bifidobacterium, Propionobacterium and Eubacterium), Gram negativecocci (Veillonella parvula) and aerobic bacteria, ferences staphylococci, streptococci, E. coli, K. pneumonia, P. aeruginosa and Candida albicans.

Because of the low level of dental education and the lack of a preventive system inclusive of children in all school levels, appearance of dental infections is relatively frequent pathology in our young population. So, prevention of caries and its complications will greatly reduce the appearance of dental infections.

Our study in 70 children ages 5 - 15 years old has demonstrated that the dental infections in pediatric population are polymicrobial predominantly anaerobic bacteria over aerobic. This study paves the way for preventives measures that need to me implemented in this group of children.