Association between genetic variants in key vitamin-D-pathway genes and external apical root resorption linked to orthodontic treatment.

This study evaluated the association between single-nucleotide polymorphisms (SNPs) in vitamin-D-related genes and the amount of external apical root resorption linked to orthodontic treatment. One hundred and forty-three individuals were assessed. The amount of external apical root resorption of upper central incisors (EARRinc ) and lower first molars (EARRmol ) were evaluated in radiographs. Seven SNPs were genotyped across four genes including the vitamin D receptor [VDR], group-specific component [GC], cytochrome P450 family 27 subfamily B member 1 [CYP27B1], and cytochrome P450 family 24 subfamily A member 1 [CYP24A1]. Linear regressions were implemented to determine allele-effects on external apical root resorption. Individuals carrying the AA genotype in VDR rs2228570 had a 21% higher EARRmol than those having AG and GG genotypes (95% CI: 1.03,1.40). EARRmol in heterozygous rs2228570, was 12% lower than for homozygotes (95%CI: 0.78,0.99). Participants with the CCG haplotype (rs1544410-rs7975232-rs731236) in VDR had an EARRmol 16% lower than those who did not carry this haplotype. Regarding CYP27B1 rs4646536, EARRinc in participants who had at least one G allele was 42% lower than for homozygotes AA (95%CI: 0.37,0.93). Although these results did not remain significant after multiple testing adjustment, potential associations may still be suggested. Further replication studies are needed to confirm or refute these findings.

Effect of ionizing radiation on polymer brackets.

OBJECTIVE: The purpose of this study was to investigate whether the mechanical properties of polymer brackets can be improved without discoloration by electron beam (EB) irradiation applied with a Rhodotron electron accelerator using standard high-energy parameters including a 10 MV acceleration voltage and 100 kGy of energy. We analyzed polymer samples and several commercially available brackets. MATERIALS AND METHODS: The first group included three polymeric base materials (polyoxymethylene, polycarbonate, polyurethane) currently used in various bracket systems. The second group included five bracket types, three of which are on the market (Aesthetik-Line and Brillant by Forestadent; Envision by Ortho Organizers) while the other two were experimental brackets containing urethane dimethacrylate as a monomer matrix and functional silane-treated SiO2 fillers with a filler content of 10 or 40 vol%. Each category included 40 specimens previously irradiated by a commercial provider (Beta-Gamma-Service, Bruchsal, Germany) and another 40 nonirradiated controls. The polymer specimens were analyzed for fracture toughness, Vickers hardness, and wear resistance, and the bracket specimens for Vickers hardness and color stability. The Wilcoxon-Mann-Whitney U test was used for pairwise comparison to identify significant differences (p ≤ 0.05). RESULTS: Significant increases in fracture toughness and Vickers hardness were observed in polycarbonate and polyurethane after EB irradiation, while EB irradiation of polyoxymethylene resulted in a significant decrease in these parameters. The polyurethane samples demonstrated significantly less postirradiation wear. All the commercially available brackets except for Brillant revealed significant increases in Vickers hardness. Significant discoloration was observed in all brackets after irradiation. CONCLUSION: Although our evaluation of polymer brackets revealed considerable improvements in mechanical properties after EB irradiation, this benefit was marred by very obvious discoloration. We cannot therefore recommend industrial scale EB irradiation for any polymer bracket currently on the market.

Effects of mechanical and bacterial stressors on cytokine and growth-factor expression in periodontal ligament cells.

OBJECTIVES: The goal of the study was to examine the effects of a mechanical (orthodontic force simulation by static compressive loading) and a bacterial (endotoxins from a heat-inactivated gram-negative periodontal pathogen) stressor on the expression patterns of factors that are key to regulating osteoclastogenesis and bone remodeling. MATERIALS AND METHODS: Three experimental groups were formed with fifth-passage periodontal ligament (PDL) fibroblasts treated by the static application of compressive force (2 g/cm(2)), heat-inactivated aggregatibacter actinomycetemcomitans (1 × 10(7) cells), or both of these stressors combined. Real-time polymerase chain reaction (RT-PCR) was used to study gene expression of IL-6, IL-8, COX-2, IGF-1, VEGF, and MMP-13 in the 3 groups. Protein levels of COX-2, prostaglandin E2 (PGE(2)), and IL-8 production were quantified using immunoblotting and enzyme-linked immunosorbent assay (ELISA). RESULTS: The mechanical stressor upregulated the genes of COX-2, IL-8, IGF-1, and MMP-13 in PDL fibroblasts and the bacterial stressor upregulated IL-6, IL-8, COX-2 and MMP-13. Both stressors in combination upregulated VEGF and caused COX-2 gene expression to increase further; the latter effect was also detected at the protein level and indirectly via the enhanced production of PGE(2). We noted that the posttranscriptional regulation of IL-8 was induced by the mechanical stressor and influenced by PGE(2). CONCLUSION: While mechanical-stressor application increased the gene expression of COX-2, IL-8, and VEGF in the presence of the bacterial stressor, IL-8 production was posttranscriptionally regulated by the mechanical stressor, whereas COX-2 expression correlated with enhanced production of the inflammatory tissue hormone PGE(2), which exerted a suppressive effect on endotoxin-induced IL-8 production.

The role of hypoxia in orthodontic tooth movement.

Orthodontic forces are known to have various effects on the alveolar process, such as cell deformation, inflammation, and circulatory disturbances. Each of these conditions affecting cell differentiation, cell repair, and cell migration, is driven by numerous molecular and inflammatory mediators. As a result, bone remodeling is induced, facilitating orthodontic tooth movement. However, orthodontic forces not only have cellular effects but also induce vascular changes. Orthodontic forces are known to occlude periodontal ligament vessels on the pressure side of the dental root, decreasing the blood perfusion of the tissue. This condition is accompanied by hypoxia, which is known to either affect cell proliferation or induce apoptosis, depending on the oxygen gradient. Because upregulated tissue proliferation rates are often accompanied by angiogenesis, hypoxia may be assumed to fundamentally contribute to bone remodeling processes during orthodontic treatment.

Student evaluation of problem-based learning in a dental orthodontic curriculum--a pilot study.

OBJECTIVE: The present questionnaire survey investigated student reception of problem-based learning (PBL) in the orthodontic curriculum with regard to acceptance, sense of purpose and motivation, knowledge and understanding, as well as tutorial support. METHODS: Over a period of two terms, we compared two different didactic methods (PBL and short presentations) by randomizing the participants of a course on orthodontic diagnostics into two different groups, who inversed methods after the first term. RESULTS: The two student groups did not show any significant differences with regard to assessments or examination performance. Therefore, acceptance of the PBL concept seems to be mainly associated with the motivation of individuals to use this method. The higher the motivation, the more positive is the attitude towards the PBL concept. Students seem to work more constructively and efficiently with PBL if they can judge the concept meaningful for themselves. CONCLUSION: In consideration of the relevant literature and the present results, PBL can be principally integrated into the dental curriculum as a method of learning. However, student motivation is vital to learning success.

Influence of dental materials on dental MRI.

OBJECTIVES: To investigate the potential influence of standard dental materials on dental MRI (dMRI) by estimating the magnetic susceptibility with the help of the MRI-based geometric distortion method and to classify the materials from the standpoint of dMRI. METHODS: A series of standard dental materials was studied on a 1.5 T MRI system using spin echo and gradient echo pulse sequences and their magnetic susceptibility was estimated using the geometric method. Measurements on samples of dental materials were supported by in vivo examples obtained in dedicated dMRI procedures. RESULTS: The tested materials showed a range of distortion degrees. The following materials were classified as fully compatible materials that can be present even in the tooth of interest: the resin-based sealer AH Plus(®) (Dentsply, Maillefer, Germany), glass ionomer cement, gutta-percha, zirconium dioxide and composites from one of the tested manufacturers. Interestingly, composites provided by the other manufacturer caused relatively strong distortions and were therefore classified as compatible I, along with amalgam, gold alloy, gold-ceramic crowns, titanium alloy and NiTi orthodontic wires. Materials, the magnetic susceptibility of which differed from that of water by more than 200 ppm, were classified as non-compatible materials that should not be present in the patient's mouth for any dMRI applications. They included stainless steel orthodontic appliances and CoCr. CONCLUSIONS: A classification of the materials that complies with the standard grouping of materials according to their magnetic susceptibility was proposed and adopted for the purposes of dMRI. The proposed classification can serve as a guideline in future dMRI research.

Biomechanics of the mandible and growth extension.

BACKGROUND AND OBJECTIVE: One way of determining the direction of growth of the mandible is to consider the temporomandibular joint and movement of the mandible as a four-joint gear system, regarding growth then as an extension of the gear system. Our aim was to examine any correlations between the type of biomechanical growth extension and change in the maxilomandibular relation after Class II therapy. SUBJECTS AND METHODS: A total of 130 lateral cephalograms-before and after orthodontic treatment-were available from 65 adolescent class II patients with open bite or deep bite. The two lateral cephalograms from each patient were superimposed on the occlusal plane. Cephalometric values and the vertical base point deviation were determined from biomechanical analyses, together with three distances and three angles. RESULTS: No correlation between the cephalometric data and distances or angles were observed. Although there were no significant differences in the distances, we did note significant differences in all three angles (p < 0.05). CONCLUSION: If gear system extension during growth is considered, this can be interpreted as meaning that the occlusal plane of those patients with an initially open bite dropped during treatment, but that it rose in patients with an initially deep bite.

Profiling type I collagen gene expression in growing mandibular structures.

We conducted a temporal gene expression analysis with type I collagen in the coronoid process, alveolar process and mandibular angle of the rat. We observed gene expression cross-sectionally across different important physiological time points in the rat postnatal life in order to observe in which developmental stage mandibular development mainly occur. This study indicates prominent type I collagen expression at day 10 postpartum in the mandibular ramus and at day 21 in the alveolar process. These findings correspond well with previously obtained data from proliferation studies in facial bone suggesting that craniofacial growth in the rat occurs mainly between days 10 and 21.

Three-dimensional localization of impacted teeth using magnetic resonance imaging.

Impacted teeth remain embedded in the jawbone beyond the normal eruption time with completed root growth. They can often get infected or damage neighboring teeth. Information about the three-dimensional position of impacted teeth is invaluable in orthodontic diagnosis and treatment planning. The purpose of this prospective study was to assess the feasibility of using magnetic resonance imaging (MRI) for the three-dimensional localization of impacted teeth in children and adults. The study included 39 patients from the pediatric age group with different tooth impactions and seven adults with impacted wisdom teeth. MRI yielded a clear separation between impacted teeth and the surrounding tissue, and the position and angulation of impacted teeth in all three spatial dimensions could be assessed. Compared to conventional radiography, dental MRI provides the advantage of full volumetric morphology accompanied by complete elimination of ionizing radiation, which is particularly relevant for repeated examinations of the pediatric group.

Cortisol daily rhythm in saliva of healthy school children.

AIM: To investigate the daily rhythm of cortisol levels in saliva of school children. SUBJECTS AND METHODS: Probands (10-14 years, both genders) were recruited via personal contact and school visits. Exclusion criteria included hormonal and dental treatments during the trial, pharmaceuticals containing cortisol, or poor oral hygiene. Each volunteer collected 20 saliva samples during one day at defined times starting immediately after waking up and ending at night. Additionally, they completed a sampling diary. Saliva samples were analysed in duplicate using a commercial cortisol luminescence kit. RESULTS: Cortisol concentration in saliva followed a daily rhythm. Within 20 minutes after waking up cortisol reached the highest level of 9.69 (+/-3.89) nmol/L. After 90 minutes cortisol concentration decreased linearly by 50% and stagnated at 4.14 (+/-1.93) nmol/L for 3 to 8 hours. Thereafter, levels decreased gradually reaching almost zero after 14 hours. Overall, no gender-specific differences in saliva cortisol levels were observed except for 3 time points: 3, 10 and 11 hours after waking. CONCLUSION: This study establishes guidelines for a normal secretion pattern, plus explores pain level measurements and their correlation to saliva cortisol levels in this age group.

Different bone sesitivity to malformations induced by procarbazine in fetal rats.

The study aimed at to induce cleft-lip-alveolus-palate (CLAP) applying procarbazine in rat fetuses at the 14(th) day of pregnancy, to supply thiocyanate and/or folic acid sufficient for preventive treatment and subsequently to investigate cleft extent in the palatal area as well as bone maturity. In this animal model, female primiparous inbred rats (LEW.1A) were used. The gravid animals were separated into treatment groups: group K (control), group P (procarbazine), group TP (thiocyanate and procarbazine) and group FTP (folic acid, thiocyanate, procarbazine). The results reveal that procarbazine may induce clefts in the palate area. Clefts occurred most frequently in group TP and mainly comprised subtotal clefts of the posterior secondary palate. As for palatal length, group FTP displayed the longest palate which was significantly different only from group K. A different picture was shown for the secondary palate with group TP displaying the shortest values which were significantly different from those in groups K, P, and FTP. Thus, group TP showed the most marked negative changes both for cleft frequency and palatal length as compared to group K and the other groups. The preventive application of either thiocyanate (TP) or thiocaynate and folic acid combined (group FTP) failed to completely prevent cleft formation in the palate area. In conclusion, a preventive effect on palatal clefts and growth inhibition could not be proved for the vitaminoid thiocyanate.

The factors associated with body mass index in adults from the study of health in Pomerania (SHIP-0), Germany.

OBJECTIVE: To investigate the relation between dental status, BMI and systemic diseases and to evaluate the risk factors for having a higher BMI. MATERIALS AND METHODS: Apopulation based cross sectional study of 6248 subjects aged 18-80 years (response of 68.8%, n=4310) was conducted in the Study of Health in Pomerania (SHIP-0). Socio-demographic, medical and oral health information was recorded by 5 dentists at two similarly equipped medical/dental services in the cities of Greifswald and Stralsund. Bivariate statistics, multivariate statistics, linear and logistic regression models were performed to assess the relationship between following covariates: gender, educational level, family status, social activities, income, quality of life (SF-12), smoking, alcohol abuse, diabetes, renal disease, high blood pressure, dental status and high physical activity. RESULTS: Significant risk factors for subjects having a higher BMI were: high blood pressure (OR=2.28), diabetes (OR=2.10), educational level (low: OR=1.49; medium OR=1.27), male (OR=1.32) and former smoker (OR=1.20). whereas young age, being single and being dentate (natural teeth, replaced teeth or fixed teeth) was shown to be protective for having a "high" BMI. CONCLUSION: The most important predictors of BMI were shown to be social and medical factors. Dental factors are most significantly influenced by social factors and also exhibit an important impact on BMI.

Investigations about N-aminopropyl transferases probably involved in biomineralization.

Polyamines are widespread distributed all over in living organisms. In Thalassiosira pseudonana 10 N-aminopropyl transferase like nucleotide sequences exists. It is assumed that these sequences are involved in the biomineralization of the diatom shell. The cDNA of the sequences were cloned, recombinant overexpressed and assayed with decarboxylated S-adenosylmethionine and several radioactive labelled polyamines. However, only a spermidine synthase and a thermospermine synthase were found to be enzymatically active in an in vitro assay. Both enzyme activities could be recognized in the crude extracts of Thalassiosira pseudonana and Cyclotella meneghiana. In further investigations the kinetics of the thermospermine synthase was determined and a site-specific mutagenesis of the bindig cavity of decarboxylated S-adenosylmethionine was carried out.

A novel post-and-core restoration system--results of three years of clinical application of the "Wuerzburg Post".

The Wuerzburg Post is a new post-and-core restoration system designed to eliminate the weak parts of post-and-core restorations and the associated problems, respectively. In contrast to conventional posts, the Wuerzburg Post is a short and thick post, which no longer relies on cementation or luting for retention in the root, but on stress-free positive locking, which it achieves by means of a post which can be spread into a predefined and form-congruent undercut cavity. The second key feature is an annular groove which runs in the dentin, girded by a corresponding structure, ensuring regular force transmission and stress dissipation, as opposed to the classic ferrule design. There are two versions: one with a machined core which can be prepared like a classic build-up to support crowns and bridges, and another one with a 2.25 mm ball end to connect to common dies which can be integrated into removable prostheses. As the system utilizes prefabricated parts made from Titanium, a precise fit is ensured, enabling the user to restore teeth quickly and easily. Over the course of the past three years, 129 posts were inserted, most commonly on upper and lower incisors and canines. The main application was restoration of fractured telescopes. During the observation period, five failures were observed. Two of the failiures did not cause significant damage to the tooth, and were subsequently immediately repairable. The survival rate amounts to over 95% after three years under risk.

Conventionally ligated versus self-ligating metal brackets--a comparative study.

The purpose of this study was to compare the frictional properties of four self-ligating metal brackets, Speed, Damon 2, In-Ovation, and Time, with those of three conventionally ligated metal brackets, Time, Victory Twin, and Discovery. The self-ligating Time bracket can also be used as a conventionally ligated bracket. Friction was tested 20 times for each bracket/wire combination using a Zwick testing machine with stainless steel wires in three different wire dimensions (0.017 x 0.025, 0.018 x 0.025, and 0.019 x 0.025 inches). All brackets had a 0.022 inch slot and the prescription of an upper first premolar. The data were statistically analysed with unsigned comparisons of all bracket/wire combinations using the Mann-Whitney U-test and the Games-Howell post hoc test. The results showed almost all brackets to have the lowest frictional force with a wire dimension of 0.018 x 0.025 inch. Friction of the self-ligating brackets using wire with a dimension of 0.018 x 0.025 inches was 45-48 per cent lower than with 0.017 x 0.025 and 0.019 x 0.025 inch wires. Friction of the conventionally ligated brackets showed a 14 per cent or less reduced friction with 0.018 x 0.025 inch wire compared with 0.017 x 0.025 and 0.019 x 0.025 inch wires. The self-ligating metal brackets showed lower frictional forces with a 0.018 x 0.025 inch wire than conventionally ligated brackets, whereas conventionally ligated brackets showed lower friction with 0.017 x 0.025 and 0.019 x 0.025 inch wire. Friction values vary with different bracket/archwire combinations and, therefore, the choice of a bracket system for treatment should consider the correct wire dimension to produce the lowest possible frictional forces.

Development of an improved protocol to analyse gene expression in temporomandibular joint condylar cartilage of rats using DNA microarrays.

PURPOSE: During recent years, gene expression analyses based on DNA chip technologies have allowed for the genome-wide identification of genes potentially associated with growth processes in a variety of organs. The present study aims to identify genes differentially expressed in the growing temporomandibular joint cartilage by means of transcriptome analyses. MATERIAL AND METHODS: In total, the condylar cartilage of 32 rats comprising 4 age groups (newborn, 10 days, 21 days, 8 weeks) were used for analysis. Transcriptome analyses were carried out using Affymetrix Expression Arrays (Rat Genome 230 2.0 Arrays). The availability of high-quality RNA preparations from homogeneous tissue samples is a fundamental precondition of successful transcriptome analyses using DNA arrays. An optimised preparation protocol allowed RNA isolation of sufficient quality which was validated using capillary electrophoresis. RNA collected from 8 test animals of the 4 age groups respectively was mixed in equimolar RNA pools which served for the transcriptome analyses using Affymetrix arrays. RESULTS: Statistical analysis of the gene expression data indicated the existence of genes differentially regulated in the growing temporomandibular cartilage. This evidence, however, requires validation by RT-PCR using individual animals' RNA. Preliminary candidate genes belong, among others, to the groups of matrix-degrading proteases, protease inhibitors and genes involved in cell growth, apoptosis and bone remodelling. CONCLUSION: These differentially expressed genes in TMJ growth identified using DNA array technology may possibly contribute to a better understanding of growth biology and provide an approach to necessary therapy.

Effect of bone conditioning on primary stability of FRIALIT-2 implants.

BACKGROUND: Primary stability is crucial to implants used for orthodontic anchorage. Bone condensing to enhance primary stability is controversial. MATERIAL AND METHODS: Fourteen Frialit-2-stepped screw and cylinder implants were placed in the median palatine sutures of 22 cadaveric human heads. In half of both types, the implant bed was prepared using a Frialit Bone Condenser. Primary implant stability was evaluated using non-invasive resonance frequency analysis. Moreover, the bone-implant contact area was examined histomorphometrically and radiographically. RESULTS: Bone condensing yielded a slightly, yet not significantly increased implant stability quotient compared with a conventional technique. In spongy bone, a significant histomorphometric increase of bone-implant contact (P<0.0001) and a significant increase of radiographic density was revealed for both implant types, while no significant changes were observed within the compact area. CONCLUSION: The study shows that bone condensing yields an improved histologic implant-bone contact only in spongy bone, which was paralleled by radiographic-densitometric findings.

Frictional properties of aesthetic brackets.

The purpose of this study was to compare the frictional properties of two self-ligating aesthetic brackets, Opal (Ultradent Products) and Oyster (Gestenco Int.), with those of four conventionally ligated aesthetic brackets, Transcend (3M Unitek), Inspire (Ormco), Allure (GAC Int.), and Image (Gestenco Int.). Friction was tested with different wire dimensions and qualities [stainless steel (SS) wire 0.017 x 0.025 inches; SS 0.019 x 0.025 inches; TMA 0.019 x 0.025 inches] using a Zwick testing machine. All brackets had a 0.022-inch slot and the prescription of an upper first premolar of the Roth system (tip: 0 degrees, torque: -7 degree). Each bracket/archwire combination was tested 10 times and each test was performed with a new bracket/wire sample that was pulled through twice. Additionally, two sets of 30 Opal brackets each were aged with an ageing machine under standardized conditions for 9-10 and 18-20 months, respectively. Friction of the aged brackets was tested with identical wire dimensions and qualities using the same testing procedure. All data were statistically analysed with unsigned comparisons of all bracket/wire combinations using GLM and the Games-Howell post hoc test. The results showed Opal brackets to have the lowest frictional forces for all wire dimensions and qualities. Furthermore, friction was lower at a significant level (P

Ritually induced growth disturbances and deformities of the orofacial system--a contribution to cranial morphogenesis.

Numerous ritual acts involving the skull result in orofacial changes. The present study focuses on ritual acts of Brazilian Zoé Indians. A distinct deformation effect of the ritual act (wearing a lip-plug) on the morphology of the orofacial system is demonstrated and documented using jaw models. The studies show that the lip-plug significantly influences tooth position and jaw growth. While the maxilla displays palatal displacement of the lateral incisors and elevation of the palate, retraction occurs in the mandible depending upon plug size. Additionally, both the plug and the nutritional habits of the Indians induce marked abrasion of all teeth. Moreover, it is shown that the duration of lip-plug wear is an essential determinant of sustained orofacial changes.

Evaluation of disparities in physical development and dental age of two specific groups of boys.

AIM: The aim of the study was to investigate potential differences between the physical development and the dental age in two groups of male pupils from two schools with different socio-economic profiles in the city of Torun (Poland). MATERIALS AND METHODS: A total number of 286 school boys (age: 9-12 years) was examined: Group A consisted of 104 pupils of a private school (mean age: 10.36-/+0.1 years), group B were 182 normally intellectually developed, non-handicapped pupils (10.59-/+0.1 years) of a therapeutic school for children with specific learning difficulties like dyslexia, dysgraphy, ADHD or severe speech disorders. The parameters of the physical development (body height, body weight) and the dental age assessed by eruption were evaluated based on a biological frame of reference and percentile charts. RESULTS: The two groups showed distinct disparities in physical and dental development: the mean values of body height were significantly higher in group A than group B (p<0.02). In addition, differences in percentile distributions of body height, body mass and dental age showed statistical significance (p<0.001, 0.01 and 0.01, respectively). The relationship between body height/body mass and dental age was not statistically significant (p>0.3). CONCLUSION: The pronounced disparities concerning physical and dental development within boys of different socio-demographic background should be taken into account by health professionals. No correlation was found between physical and dental development.