Meir Redlich

The effect of mouth breathing versus nasal breathing on dentofacial and craniofacial development in orthodontic patients.

To determine the effect of mouth breathing during childhood on craniofacial and dentofacial development compared to nasal breathing in malocclusion patients treated in the orthodontic clinic.

The effect of different porcelain conditioning techniques on shear bond strength of stainless steel brackets

With the increasing demand for adult orthodontics, a growing need arises to bond attachments to porcelain surfaces. Optimal adhesion to a porcelain surface should allow orthodontic treatment without bond failure but not jeopardize porcelain integrity after debonding. In this study, 90 glazed porcelain facets were divided into three groups according to different conditioning techniques: (1) roughening with a coarse diamond; (2) hydrofluoric acid 8%; (3) microetching with 60 micron aluminum oxide particles. Each group was divided into three groups and stainless steel brackets were then bonded to the conditioned porcelain with three different dental adhesives. The adhesives used were: (1) silane+Right-On; (2) silane+Concise; (3) High-Q-Bond without silane. Four additional facets (three of which conditioned as above and one intact) were analyzed macroscopically and by scanning electron microscopy. Shear bond strength was measured with an Instron universal testing machine and a macroscopic examination of the debonded porcelain surfaces was performed. Results showed that shear bond strength was highly influenced by both conditioning technique and the adhesive. Shear bond strength of the High-Q-Bond groups was significantly lower than both the silane+Right-On and the silane+Concise groups; nevertheless the shear bond strength achieved by High-Q-Bond was enough to sustain full orthodontic treatment duration (except for the group conditioned by roughening with a coarse diamond). Scanning electronic microscopy analysis revealed that diamond roughening and microetching produced only a surface-peeling pattern, whereas hydrofluoric acid conditioning produced an extensive in-depth penetrating pattern. Hydrofluoric acid preparation produced greater shear bond strength than both diamond roughening and microetching. After debonding by means of a shearing force, the percentage of damaged porcelain surfaces in the silane+Concise groups was significantly higher than the silane+Right-On and High-Q-Bond groups.

Comparison of arch forms between Israeli and North American white populations

INTRODUCTION The aim of this study was to evaluate the morphologic differences in the mandibular arches of Egyptian and North American white subjects. METHODS The sample included 94 Egyptian subjects (35 Class I, 32 Class II, and 27 Class III) and 92 white subjects (37 Class I, 29 Class II, and 26 Class III). The subjects were grouped according to arch form types (tapered, ovoid, and square) to compare their frequency distribution between ethnic groups in each Angle classification. The most facial portions of 13 proximal contact areas were digitized on scanned images of mandibular casts to estimate the corresponding clinical bracket point for each tooth. Four linear and 2 proportional measurements were taken. RESULTS In comparing arch dimensions, intermolar width was narrower in Egyptians than in the whites (P = 0.001). There was an even frequency distribution of the 3 arch forms in the Egyptian group. On the other hand, the most frequent arch form was ovoid followed by tapered and square in the white group; the square arch form was significantly less frequent than the tapered and ovoid arch forms (P = 0.029). CONCLUSIONS The arch forms of Egyptians are narrower than those of whites. The distribution of the arch form types in Egyptians showed similar frequency, but the square arch form was less frequent in whites. It is recommended to select narrower archwires from the available variations to suit many Egyptian patients.

Improved orthodontic stainless steel wires coated with inorganic fullerene-like nanoparticles of WS2 impregnated in electroless nickel–phosphorous film

OBJECTIVE To reduce friction between orthodontic stainless wires and bracket by coating the wire with nickel-phosphorous electroless film impregnated with inorganic fullerene-like nanoparticles of tungsten disulfide (IF-WS(2)) which are potent dry lubricants. METHODS Coating was preformed by inserting stainless steel (SS) wires into electroless solutions of nickel-phosphorus (Ni-P) and IF-WS(2). The coated wires were analyzed by SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectrometer) as well as by tribological tests using a ball-on-flat device. Friction tests simulating archwire functioning of the coated and uncoated wires were carried out by an Instron machine. The adhesion properties of the coated wires after friction were analyzed by a Raman microscope. RESULTS SEM/EDS analysis of the coated wires showed clear impregnation of the IF-WS(2) nanoparticles in the Ni-P matrix. The friction coefficient measured by the ball-on-flat tribometer was significantly reduced (from 0.25 to 0.08). The friction forces as measured with the Instron on the coated wire were reduced by up to 54% (4.00 N+/-0.19 uncoated vs. 1.85 N+/-0.21 coated). Raman spectra showed that even after extensive friction tests the Ni-P with the IF-WS(2) nanoparticles is attached to the underlying stainless steel wire. CONCLUSIONS It is proposed that the wires coated with these nanoparticles might offer a novel opportunity to substantially reduce friction during tooth movement. A few tests undertaken to evaluate the toxicity of the fullerene-like nanoparticles have provided indications that they might be biocompatible.

Gingival response to orthodontic force.

Orthodontic tooth movement is brought about by prolonged application of force on the attachment apparatus. This results in cellular and extracellular changes within the periodontium. As shown in numerous studies, tooth movement is achieved after the remodeling of alveolar bone and the response of the periodontal ligament to the mechanical force. Although gingival changes have also been found to be an important factor in the overall response, the effect of orthodontic tooth movement on the gingiva has been investigated to a lesser extent. Unlike bone and periodontal ligament, which regain their original structure after removal of force, the gingival tissue does not regain its pretreatment structure, a fact on which a hypothesis has been made that tooth relapse after removal of retention may be associated with changes in the gingiva. The present review summarizes available data on the effect of orthodontic force on collagen, elastin, and collagenase in the gingiva and its relevance to understanding the mechanism of tooth relapse.

The response of supraalveolar gingival collagen to orthodontic rotation movement in dogs

An orthodontically rotated tooth relapses toward its pretreatment position. Explanations for this phenomenon have been given after light microscopic studies, according to which it had been assumed that stretched supraalveolar gingival fibers pulled back the tooth and brought about relaxation of the stretched fibers. The rotational relapse, however, can be prevented by supraalveolar fiberotomy of the gingiva around the tooth. This investigation was initiated to reevaluate the validity of the hitherto assumed causes for the relapse, by obtaining ultrastructural data on the response of collagen fibers after orthodontic intervention. Lateral maxillary incisors in the dog were rotated with bonded fixed appliances. The teeth were divided into groups according to different orthodontic procedures. Scanning and transmission electron microscopic analyses were performed on gingival samples after proper processing. Analyses of the untreated control samples showed well-organized, parallel, and densely packed thick bundles of collagen fibers, interconnected with thin fibers. After rotation-followed-by-retention, the gingival fibers were torn, ripped, disorganized, and laterally spaced and of increased diameter. Thus it was concluded that all these patterns are incompatible with stretching. Also, an increased number of elastic fibers were seen in proximity to the torn collagen fibers. After gingival fiberotomy, most fibers resumed the appearance of the organized pattern of large fiber bundles similar to those seen in the controls.

The Effect of Mechanical Force on mRNA Levels of Collagenase, Collagen Type I, and Tissue Inhibitors of Metalloproteinases in Gingivae of Dogs

Orthodontic force causes an injury to and subsequent degradation of the attachment apparatus, thus leading to the transposition of the tooth. The gingiva, however, is compressed and sometimes becomes hypertrophic with tooth movement and often shrinks after treatment. To study the effect of force on the gingiva, we applied orthodontic force in dogs and analyzed gingival tissues 1, 2, 3, 7, 14, and 28 days later as well as after removing the force. The effect of force on mRNA levels of collagen type I (col-I), matrix metalloproteinase-1 (MMP-1), and tissue inhibitors 1 and 2 (TIMPs) genes was analyzed by RT-PCR, and MMP-1 activity was determined by zymography. The results showed that force significantly increased both the mRNA levels of MMP-1 and its interstitial activity. After the removal of force, MMP-1 gene expression was significantly decreased. The results could partly explain the clinically observed shrinkage and adaptation of the gingiva during tooth movement. KEY WORDS: orthodontic force, MMP-1, gene expression.

Cleidocranial dysplasia : Molecular genetic analysis and phenotypic-based description of a middle European patient group

Cleidocranial dysplasia (CCD) (OMIM 119600) is a rare dysplasia of osseous and dental tissue. Characteristic features are typical facial and dental appearance plus morphologic anomalies. RUNX2 (OMIM 600211), the responsible gene for CCD, is considered to be a master gene for bone development and bone homeostasis. This study describes the genotype–phenotype correlation based on craniofacial features involving an interdisciplinary approach. Our patient cohort consisted of 31 CCD patients from 20 families; five patients from two families were unavailable for clinical examination. Since CCD mostly affects the craniofacial region, phenotypic characterization of each individual focused on craniofacial and dental aspects. After recording patient medical and family history, the phenotypic data was analyzed using homogeneity analysis (HOMALS), a statistical procedure for data reduction in categorical data analysis. The coding sequence of the RUNX2 gene was analyzed using PCR, direct sequencing, and restriction endonuclease digestion. Eight unpublished and four known heterozygous mutations in a total of 14/20 index patients (70%) were identified. In total, we detected 7 missense mutations, 5 frameshift mutations, and 2 nonsense mutations in 14 index patients (35%, 25%, 10%, respectively). The overall CCD phenotype varied from mild to fullblown expression. Using HOMALS, we were able to discriminate four groups of patients showing significant differences in phenotypic expressivity, thereby simplifying the grouping of our large patient cohort into clear distinguishable entities. Analysis of the mutation patterns revealed that mutational frequency and types of mutations found can be attributed to the genes structure and function.

Tensile bond strength of ceramic brackets bonded to porcelain facets

The number of adults requesting orthodontic treatment is constantly growing, with a resultant increase in the need to bond brackets to porcelain restorations. Because adults often favor more esthetic ceramic brackets, it is important to evaluate the bond strength of ceramic to porcelain restorations and the integrity of the porcelain surface after debonding. Eighty porcelain facets, resembling mandibular incisors, were used. The surfaces were conditioned by either hydrofluoric acid or microetching. Mandibular incisor ceramic brackets were bonded with 1 of 2 adhesives: Ideal 1 without silane or Right-On with silane. Debonding was performed with a tensile force on a universal testing machine. The mode of bond failure was determined macroscopically, and the integrity of the porcelain facets was evaluated microscopically. The results showed that the type of porcelain conditioning technique affects the tensile bond strength of both adhesives. Conditioning with hydrofluoric acid resulted in significantly higher bond strength (Ideal 1, 7.7 +/- 3.0; Right-On, 7.1 +/- 2.6) than conditioning by microetching (Ideal 1, 4.1 +/- 2.3; Right-On, 3.8 +/- 2.4; P <.05). The mode of bond failure was mainly adhesive, and the porcelain facets were not damaged during debonding. This study shows that both Ideal 1 and Right-On are suitable for bonding ceramic brackets to porcelain restorations, if the porcelain has been conditioned with hydrofluoric acid.

Medical applications of inorganic fullerene-like nanoparticles

Nanoparticles of layered compounds, like MoS2 and WS2, having hollow closed-cage structures and known as fullerene-like (IF) and inorganic nanotubes (INT), are synthesized in macroscopic amounts. They were found to have superior tribological properties and can serve as solid-state additives to different lubrication fluids. More recently, metallic films incorporating the IF nanoparticles were prepared via wet deposition methods and also by physical vapor deposition techniques. The incorporation of the nanoparticles endows such coatings self-lubricating behavior, i.e. low friction and wear, which is highly desirable for variety of applications. The current feature article provides a short overview of the progress in the materials synthesis of IF and INT phases. Subsequently, a progress report of the various efforts to apply such coatings to medical devices and drug delivery is described.