Dario Repić

Clinical and microbiological parameters in patients with self-ligating and conventional brackets during early phase of orthodontic treatment.

OBJECTIVE To determine the effect of different bracket designs (conventional brackets and self-ligating brackets) on periodontal clinical parameters and periodontal pathogens in subgingival plaque. MATERIAL AND METHODS The following inclusion criteria were used: requirement of orthodontic treatment plan starting with alignment and leveling, good general health, healthy periodontium, no antibiotic therapy in the previous 6 months before the beginning of the study, and no smoking. The study sample totaled 38 patients (13 male, 25 female; mean age, 14.6 ± 2.0 years). Patients were divided into two groups with random distribution of brackets. Recording of clinical parameters was done before the placement of the orthodontic appliance (T0) and at 6 weeks (T1), 12 weeks (T2), and 18 weeks (T3) after full bonding of orthodontic appliances. Periodontal pathogens of subgingival microflora were detected at T3 using a commercially available polymerase chain reaction test (micro-Dent test) that contains probes for Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Treponema denticola. RESULTS There was a statistically significant higher prevalence of A actinomycetemcomitans in patients with conventional brackets than in patients with self-ligating brackets, but there was no statistically significant difference for other putative periodontal pathogens. The two different types of brackets did not show statistically significant differences in periodontal clinical parameters. CONCLUSION Bracket design does not seem to have a strong influence on periodontal clinical parameters and periodontal pathogens in subgingival plaque. The correlation between some periodontal pathogens and clinical periodontal parameters was weak.

The effect of two different bracket types on the salivary levels of S mutans and S sobrinus in the early phase of orthodontic treatment

OBJECTIVE To determine the difference in the levels of Streptococcus mutans and S sobrinus in stimulated saliva in orthodontic patients with different bracket types (stainless steel and esthetic brackets) using polymerase chain reaction and cultivation method. MATERIALS AND METHODS Thirty-two patients, aged 13 to 30 years, were selected following these criteria: 1) orthodontic treatment indication, 2) systemic health, and 3) no tobacco and antibiotic consummation for three months prior to the commencement of the study. Patients were divided into two groups according to the bracket type; 16 patients formed the conventional bracket group (stainless steel brackets), and 16 patients formed the esthetic bracket group (plastic brackets). The levels of S mutans and S sobrinus in stimulated whole saliva samples were collected prior to fixed orthodontic appliance placement (T1) and 12 weeks after placement (T2), as were the Decayed, Missing, and Filled Surface Index (DMFS) and Oral Hygiene Index-Simplified (OHI-S). Mann-Whitney, Wilcoxon, and chi-square tests were used for statistical analysis. RESULTS Statistical analysis (chi-square test) showed no difference in S mutans and S sobrinus counts among patients with different brackets at either T1 or T2. There was no difference in total bacteria counts after fixed orthodontic appliance placement. CONCLUSION The number of colony-forming units of S mutans and S sobrinus in stimulated saliva samples does not seem to be significantly different between patients with stainless steel brackets and patients with plastic brackets.

Utilization of transgenic models in the evaluation of osteogenic differentiation of embryonic stem cells

Abstract Previous studies reported that embryonic stem cells (ESCs) can be induced to differentiate into cells showing a mature osteoblastic phenotype by culturing them under osteo-inductive conditions. It is probable that osteogenic differentiation requires that ESCs undergo differentiation through an intermediary step involving a mesenchymal lineage precursor. Based on our previous studies indicating that adult mesenchymal progenitor cells express α-smooth muscle actin (αSMA), we have generated ESCs from transgenic mice in which an αSMA promoter directs the expression of red fluorescent protein (RFP) to mesenchymal progenitor cells. To track the transition of ESC-derived MSCs into mature osteoblasts, we have utilized a bone-specific fragment of rat type I collagen promoter driving green fluorescent protein (Col2.3GFP). Following osteogenic induction in ESCs, we have observed expression of alkaline phosphatase (ALP) and subsequent mineralization as detected by von Kossa staining. After 1 week of osteogenic induction, ESCs begin to express αSMARFP. This expression was localized to the peripheral area encircling a typical ESC colony. Nevertheless, these αSMARFP positive cells did not show activation of the Col2.3GFP promoter, even after 7 weeks of osteogenic differentiation in vitro. In contrast, Col2.3GFP expression was detected in vivo, in mineralized areas following teratoma formation. Our results indicate that detection of ALP activity and mineralization of ESCs cultured under osteogenic conditions is not sufficient to demonstrate osteogenic maturation. Our study indicates the utility of the promoter-visual transgene approach to assess the commitment and differentiation of ESCs into the osteoblast lineage.

Oral Health Changes during Early Phase of Orthodontic Treatment

The aim of the study was to assess the influence of fixed orthodontic appliance on Streptococcus (S.) mutans and S. sobrinus counts in orthodontic patients with regard to their previous caries experience (Decayed, Missing and Filled Teeth (DMFT) index) during the first 12 weeks of orthodontic treatment. Twenty-two patients that satisfied inclusion criteria (healthy systemic and periodontal condition, avoidance of antibiotic therapy and antiseptic mouthwashes in the past three months) were included. All clinical measurements took place prior to and 12 weeks after fixed orthodontic appliance placement, in the following order: 1) stimulated saliva flow (SS); 2) Simplified Oral Hygiene Index (OHI-S); and 3) DMFT. The method of polymerase chain reaction (PCR) was used to detect the presence of S. mutans and S. sobrinus at T1 and T2. T-test showed significant increase in DMFT index and SS between T1 and T2. Results also indicated significant improvement in OHI-S index. By use of the PCR method, S. mutans was detected in two patients at T1. At T2, two more patients had S. mutans, but the increase was not statistically significant. Using the same method, S. sobrinus was detected only in two patients at T2. In conclusion, fixed orthodontic appliances did not induce statistically significant changes in caries microflora even in the presence of enhanced oral hygiene habits.