Frontiers in Dentistry
Volume:9 Issue: 1, Winter 2012

Stem cells are of great interest for regenerating disturbed tissues and organs. These cells are commonly isolated from the bone marrow, but there has been interest in other tissues in the recent years. In this study, we evaluated the possibility of isolation of stem cells from oral connective tissue and investigated their characteristics. In this experimental study, sampling from the bone marrow and oral connective tissue of a beagle dog was performed under general anesthesia. Bone marrow stem cell isolation was performed according to the established protocols. The samples obtained from oral soft tissue were broken to small pieces and after adding collagenase I, the samples were incubated for 45 minutes in 37°C. Other processes were similar to the processes which were carried out on bone marrow cells. Then cell properties were compared to evaluate if the cells from the connective tissue were stem cells. The cells from the bone marrow and connective tissue had the same morphology. The result of colony forming unit assay was relatively similar. Population doubling time was similar too. In addition, both cell groups differentiated to osteoblasts in osteogenic media. The cells isolated from the oral connective tissue had the characteristics of stem cells, including fibroblastoid morphology, self renewal properties, high proliferation rate and differentiation potential.

Head and neck squamous cell carcinoma, including oral squamous cell carcinoma (OSCC) is the sixth most common cancer in the human population. Despite significant efforts committed in treatment of OSCC the overall survival rate of OSCC has not improved significantly. Activating mutations in the fibroblast growth factor receptor 3 (FGFR3) genes are responsible for some human cancers, including bladder and cervical carcinoma. Despite a high frequency in some benign skin disorders, FGFR3 mutations have not been reported in cutaneous malignancies. Therefore, FGFR3 gene may play a role in epithelial biology and mutations of FGFR3 gene may contribute to the development of OSCC. In this cross-sectional study, DNA was extracted and purified from snap frozen tissue biopsy sections of 20 OSCC cases. Exons 7 and 15 were amplified by polymerase chain reaction (PCR) and sequenced in both directions. In three cases silent mutations were identified in exon 7 (882 T to C) which may be introduced as Single Nucleotide Polymorphism (SNP) and no mutation was identified in exon 15. FGFR3 gene mutation in exon 7 and 15 has no significant role in the development and progression of OSCC. Analyzing other exons or considering other advanced gene mutation assessment techniques may clarify the role of this receptor mutation in OSCC pathogenesis.

Iron deficiency is the most common form of malnutrition in developing countries. Iron containing supplements have been used effectively to solve this problem. In children, because of teeth staining after taking iron drops, parents have the idea that iron drops are the cause of tooth decay; therefore, they limit this vital supplement in their children’s diet. Hereby, we evaluate the histologic effect of iron containing supplements on tooth caries in rice rats with cariogenic or non-cariogenic diet. Twelve rats were selected and divided into four groups for this interventional experimental study. Four different types of dietary regimens were used for four months; group A, cariogenic diet with iron containing supplements; group B, cariogenic diet without iron containing supplements; group C, non-cariogenic diet with iron containing supplements; group D, non-cariogenic diet without iron containing supplements. After sacrificing the rats, 20-micron histological sections of their posterior teeth were prepared using the Ground Section method, then they were studied under polarized light microscopy. In order to compare the progression of caries in different samples, the depth of the lesions in the enamel was measured as three grades I, II and III. The mean grade value of A, B, C and D groups were 1.61, 2.61, 1.37 and 1.80, respectively. Statistical analysis revealed that significantly fewer caries were seen in the group which had received iron containing supplements and cariogenic diet compared with cariogenic diet without iron supplements (p<0.05). Ferrous sulfate reduces the progression of dental caries in the cariogenic dietary regimen.

The purpose of this study was to compare shear bond strength (SBS) of orthodontic brackets bonded to enamel prepared by Er:YAG laser with two different powers and conventional acid-etching. Forty-five human premolars extracted for orthodontic purposes were randomly assigned to three groups based on conditioning Group 1- conventional etching with 37% phosphoric acid; Group 2- irradiation with Er:YAG laser at 1 W; and Group 3- irradiation with Er:YAG laser at 1.5 W. Metal brackets were bonded on prepared enamel using a light-cured composite. All groups were subjected to thermocycling process. Then, the specimens mounted in auto-cure acryle and shear bond strength were measured using a universal testing machine with a crosshead speed of 0.5 mm per second. After debonding, the amount of resin remaining on the teeth was determined using the adhesive remnant index (ARI) scored 1 to 5. One-way analysis of variance was used to compare shear bond strengths and the Kruskal-Wallis test was performed to evaluate differences in the ARI for different etching types. The mean and standard deviation of conventional acid-etch group, 1W laser group and 1.5W laser group was 3.82 ± 1.16, 6.97 ± 3.64 and 6.93 ± 4.87, respectively. The mean SBS obtained with an Er:YAG laser operated at 1W or 1.5W is approximately similar to that of conventional etching. However, the high variability of values in bond strength of irradiated enamel should be considered to find the appropriate parameters for applying Er:YAG laser as a favorable alternative for surface conditioning.

Mandibular incisor extraction in carefully selected cases as an alternative option to four bicuspid extraction or non extraction treatment has been advocated. The purpose of this study was to determine the degree of improvement in occlusion in patients with Bolton discrepancy treated by one lower incisor extraction using Peer Assessment Rating Index (PAR indexes). Pre and post treatment dental casts of 14 patients treated with one lower incisor extraction were included in the study. Pre and post treatment dental casts were scored with PAR index. 70% reduction in PAR index was considered as high standard improvement. To test the hypothesis that the mean improvement in dental occlusion after one mandibular incisor extraction is at least 70%, one-tail one-sample student t-test was used. The mean improvement in dental occlusion in this group of patients was 78%. Fifty percent of the cases finished with a post treatment PAR score of 2. Spearman correlation coefficient was 0.763 (p<0.01), showing that more severe cases had greater post treatment PAR scores. Mandibular incisor extraction treatment may provide a high standard treatment outcome.

Both anorganic bovine bone (ABB) and β-tricalcium phosphate (β-TCP) are used in clinical practice as bone substitute materials, but there is limited data comparing these two materials in standardized defects.The aim of this study was to histologically evaluate the effectiveness of ABB and β-TCP in the healing of experimentally induced bone defects. Eighteen bone defects were created on the calvaria of six rabbits. In each animal, one defect was left untreated and the other two were filled with ABB and β-TCP. After one month, histological sections were prepared. Type and vitality of newly formed bone, percentage of new bone formation and residual material, thickness of trabeculae, inflammation and foreign body reaction were assessed. The newly formed osseous tissue was vital in all defects and consisted of woven and lamellar bone. Mean percentages of new bone formation were 30.83±14.29%, 16.83±11.07% and 14.00±8.17% in β-TCP, ABB and control groups, respectively and the mean percentages of residual biomaterial were 24.17±14.01% and 36.50±8.43% in β-TCP and ABB groups, respectively. However, the differences were not statistically significant (all ps>0.05). Inflammatory infiltration was statistically higher in β-TCP compared to the control group (p=0.025), but the difference was not significant between β-TCP and ABB groups (p=0.083). Trabeculation thickness and foreign body reaction were not statistically different between β-TCP and ABB groups. β-TCP and ABB were not different with regard to the quantity and quality of newly formed osseous tissue. However, inflammatory infiltration was higher in sites filled with β-TCP.

The purpose of the present randomized clinical trial study was to compare the effectiveness of Bovine Porous Bone Mineral (BPBM) with and without Plasma Rich in Growth Factors (PRGF) in the treatment of mandibular Class II furcation defects. In seven patients, nine pairs of symmetric buccal or lingual mandibular class II furcation defects were treated. In each patient, one defect received BPBM (control) and the other received BPBM/PRGF (test) by random assignment. Clinical measurements were made both at baseline and 6-month evaluation. Similar improvements were observed with both treatment modalities. Significant reductions were gained in the gingival index, probing depth and relative vertical clinical attachment level. Plaque index and gingival recession changes were not significant in both groups. The mean probing depth reductions were 2.67±0.87 mm for the control group and 3.22±1.56 mm for the test group (p<0.001). The mean relative vertical clinical attachment level gains were 1.57±0.96 mm (p<0.001) and 1.65±1.24 mm (p<0.004) in the control and test groups, respectively. In the test group, the relative horizontal clinical attachment level reduced from 5.87±0.96 mm to 4.58±1.02 mm (p<0.02). No significant differences were observed in all clinical parameters 6 months postoperatively between the two groups. The application of a combined technique using BPBM/PRGF, compared to the BPBM alone, resulted in greater healing, although not significant, in the treatment of mandibular class II furcation defects.

Systemic antibiotics and locally applied antimicrobial agents have been suggested to enhance clinical parameters. Patients exhibiting aggressive periodontitis in particular benefit from adjunctive antibiotic therapy. The purpose of this investigation was to evaluate the effect of local antibiotic therapy with metronidazole adjunctively to scaling and root planning (SRP) in the treatment of aggressive periodontitis. Twenty patients diagnosed with aggressive periodontitis were placed in a spilt mouth design. Microbial specimens were taken from the deepest pocket of the teeth. The sites that had positive results of Porphyromonas gingivalis (P.g) were located randomly to receive SRP treatment in the control group and SRP plus metronidazole gel in the test group. Pocket probing depth (PPD), clinical attachment level (CAL) and bleeding on probing (BOP) parameters and numbers of P.g. colony were taken at baseline, 6 weeks and 12 weeks later. All data were collected and analyzed and tested by Wilcoxon and paired t test. The case group patients had significantly better results in BOP, PPD and the number of P.g colony count reduction in comparison with the control group (p<0.05). According to the measurements of CAL, the statistical difference was non significant (p>0.05). In non-surgical periodontal treatment of aggressive periodontits adjunctive metronidazole gel therapy has a better effect on the reduction of porphyromonas gingivalis content of pockets.

Reconstruction methods are an essential prerequisite for functional rehabilitation of the stomatognathic system. Plasma rich in growth factors (PRGF) offers a new and potentially useful adjunct to bone substitute materials in bone reconstructive surgery. This study was carried out to investigate the influence of PRGF and fibrin membrane on regeneration of bony defects with and without deproteinized bovine bone mineral (DBBM) on rabbit calvaria. Twelve New Zealand white rabbits were included in this randomized, blinded, prospective study. Four equal 3.3×6.6 mm cranial bone defects were created and immediately grafted with DBBM, PRGF+DBBM, PRGF+fibrin membrane and no treatment as control. The defects were evaluated with histologic and histomorphometric analysis performed 4 and 8 weeks later. Adding PRGF to DBBM led to increased bone formation as compared with the control group in 4- and 8-week intervals. In DBBM and PRGF+fibrin membrane samples, no significant increase was seen compared to the control group. There was also a significant increase in the rate of biodegradation of DBBM particles with the addition of PRGF in the 8-week interval. Neither noticeable foreign body reaction nor any severe inflammation was seen in each of the specimens evaluated. Under the limitation of this study, adding PRGF to DBBM enhanced osteogenesis in rabbit calvarias. Applying autologous fibrin membrane in the defects was not helpful.

NovaMin, a synthetic mineral composed of calcium, sodium, phosphorous and silica releases deposits of crystalline hydroxyl-carbonate apatite (HCA) structurally similar to tooth mineral composition. The aim of this investigation was to compare the potential remineralization effect of topical NovaMin and Sodium Fluoride gel on caries like lesions in permanent teeth. A total of 60 sound human freshly extracted teeth were subjected to a pH-cycling protocol. Specimens were randomly assigned to one of the two treatment groups with NovaMin contained dentifrice applied to group 1, while group 2 received a dentifrice containing 1.1% neutral Sodium Fluoride. Pastes were applied five times after the samples received a demineralization from an earlier cariogenic challenge. Specimens were then evaluated by a Surface Micro Hardness test (SMH, 25G, 5s). Post-treatment SMH measurements were conducted and Mann Whitney test was employed for statistical analysis. Mean post lesion SMH values were 221.99±26.27 and 224.50±28.64 for the first and second groups, respectively. Post treatment SMH values were 232.52±24.34 for NovaMin and 232.03 ±24.46 for the fluoride group. Two way ANOVA test showed a highly significant difference between the two different treatment protocols (p<0.001). NovaMin dentifrice appears to have a greater effect on remineralization of carious-like lesions when compared to that of fluoride containing dentifrice in permanent teeth.

In this article, three techniques for maxillo-mandibular relationship for Replace- Select implants are described. The use of healing abutments, planning abutments, and Impression copings are presented, and the advantages and disadvantages are discussed.

Primary tooth impaction is a rare finding during the development of primary dentition. Several factors contribute to the impaction of a deciduous tooth. This report describes the diagnosis and treatment of a 10-year-old boy who presented an impacted second primary mandibular molar. This tooth, located inferior to the second premolar together with an odontoma, was positioned superior to the premolar teeth. Treatment consisted of surgical removal of the impacted deciduous tooth and odontoma and placement of a passive lower lingual holding arch. Periodic examination was indicated for follow- up. Early intervention was recommended to manage orofacial disfigurement and to avoid consequent problems.