Tarek El-Bialy

Frictional Resistance in Self-Ligating Orthodontic Brackets and Conventionally Ligated Brackets

OBJECTIVE To compare the amount of expressed frictional resistance between orthodontic self-ligating brackets and conventionally ligated brackets in vitro as reported in the literature. METHODS Several electronic databases (Medline, PubMed, Embase, Cochrane Library, and Web of Science) were searched without limits. In vitro studies that addressed friction of self-ligating brackets compared with conventionally ligated brackets were selected and reviewed. In addition, a search was performed by going through the reference lists of the selected articles to identify any paper that could have been missed by the electronic searches. RESULTS A total of 70 papers from the electronic database searches and 3 papers from the secondary search were initially obtained. After applying the selection criteria, only 19 papers were included in this review. A wide range of methods were applied. CONCLUSIONS Compared with conventional brackets, self-ligating brackets produce lower friction when coupled with small round archwires in the absence of tipping and/or torque in an ideally aligned arch. Sufficient evidence was not found to claim that with large rectangular wires, in the presence of tipping and/or torque and in arches with considerable malocclusion, self-ligating brackets produce lower friction compared with conventional brackets.

Growth Modification of the Rabbit Mandible Using Therapeutic Ultrasound: Is it Possible to Enhance Functional Appliance Results?

Previous studies have shown that functional appliances can enhance mandibular growth when applied during the active growth period. However, besides patient compliance problems with bulky appliances and prolonged treatment demands, there is contradictory evidence that functional appliances have a significant long-term effect. Is there a method to enhance the growth response and improve the long-term success of functional appliances? Previous studies have also found that therapeutic ultrasound (US) can stimulate cartilage and bone growth. The objective of this study was to evaluate the effect of therapeutic US on condylar and mandibular growth in the rabbit model. Eight growing New Zealand male rabbits were chosen for this study. They received therapeutic US on one side of the mandible for 20 minutes/day for four weeks. Anthropometrical and histological evaluations revealed that US enhances mandibular growth by condylar endochondreal bone growth and consequently mandibular ramus growth. The significant results of this study support conducting a long-term study to evaluate the ultimate stability of the results obtained. Also, they suggest an extended research with a larger sample size and investigating the molecular basis of this stimulatory effect, together with forward posturing splints for optimal macroscopic and microscopic responses.

Anabolic effects of low-intensity pulsed ultrasound on human gingival fibroblasts §

OBJECTIVE Low-intensity pulsed ultrasound (LIPUS) demonstrated anabolic effects on cementoblasts, odontoblasts, and periodontal ligament cells. However, LIPUS effect on human gingival fibroblasts (HGF) remains to be investigated. Therefore, we evaluated the in vitro effects of LIPUS on HGF proliferation and differentiation to test its feasibility for periodontal therapy. DESIGN LIPUS treatment (1.5MHz, 30mW/cm(2)) was applied to HGF in the experimental groups after 24-h of culture (5 or 10min/day for 28 days) and omitted in the control. Changes in HGF activities were evaluated in response to LIPUS treatment in dose-dependent (5 and 10min) and time-dependent (weeks 1-4) manner. The effects of LIPUS on HGF cell viability (MTT), proliferation (total DNA content and growth pattern), alkaline phosphatase (ALP) activity, and gene expression by reverse-transcriptase polymerase chain reaction (RT-PCR) were determined. RESULTS Cell viability remained unchanged after LIPUS treatment during the 4 weeks of treatment as compared to the untreated control group which ensured a safe biological response. Both LIPUS treatments (5-10min/day) did not yield any significant changes in the proliferation, and expression of proliferating cell nuclear antigen (PCNA) and collagen-I (COL-I). Conversely, LIPUS treatment enhanced osteogenic differentiation potential of HGF as determined by significant up-regulation of specific ALP activity and osteopontin (OPN) expression, with optimum effect following 3 weeks of 5min/day LIPUS treatment. CONCLUSION LIPUS treatment at 30mW/cm(2) selectively enhanced HGF differentiation but not proliferation. The ability of LIPUS to enhance HGF differentiation is promising for its application in cell-based periodontal therapy.

Effects of Ultrasound Modes on Mandibular Osteodistraction

Previous studies have shown that therapeutic pulsed ultrasound (pulsed) has superior stimulatory effect on bone fracture healing compared with continuous ultrasound (continuous). Our predictive hypothesis was that pulsed ultrasound can produce better bone formation during mandibular osteodistraction than continuous ultrasound. Thirty-six New Zealand rabbits were divided into 3 groups of 12. Osteodistraction was performed at 3 mm/day for 5 days. Group 1 received pulsed, group 2 received continuous ultrasound, and group 3 was the control group (distraction only). Bone formation was assessed by quantitative bone density (QBD), mechanical testing, and histological examination. In the first 2 wks post-distraction, group 2 showed enhanced bone formation more than group 1 (p < 0.05); however, in the 3rd and 4th wks, group 1 showed more bone formation than group 2 (p < 0.05). Earlier stages of bone healing were enhanced more by continuous, whereas late stages were enhanced more by pulsed, ultrasound. Abbreviations: PULSED, low-intensity pulsed ultrasound; CONTINUOUS, low-intensity continuous ultrasound.

The effect of low intensity pulsed ultrasound in a 3D ex vivo orthodontic model

OBJECTIVES This study investigated the effects of low intensity pulsed ultrasound (LIPUS) on dentoalveolar structures during orthodontic force application using a novel organ culture system. METHODS Mandibles were dissected from 28-day-old male Sprague Dawley rats, sliced into 1.5mm and cultured at 37°C and 5% CO(2), prior to application of a 50g force to each mandible slice. Slices were randomly divided into three groups of control, 5 and 10min LIPUS application and cultured for five days before histological and histomorphometrical analysis. RESULTS Cementum and predentine thickness and subodontoblast and periodontal ligament cell counts were increased in the ultrasound groups, with increases statistically significant in the 10min treated groups. Odontoblasts remained viable during LIPUS exposure and osteoclast activity was increased by LIPUS. CONCLUSIONS LIPUS may influence remodelling of the dentine-pulp complex and associated tissues during orthodontic force application ex vivo.

Effect of Low-Intensity Pulsed Ultrasound on Orthodontically Induced Root Resorption in Beagle Dogs

We investigated the effect of low-intensity pulsed ultrasound (LIPUS) on orthodontically induced inflammatory root resorption in vivo. Ten beagle dogs were treated with an orthodontic appliance to move the mandibular fourth premolars bodily. The orthodontic movement was carried out for 4 wk with a continuous force of 1 N/side; using a split-mouth model, LIPUS was applied daily for 20 min. Fourth premolar and surrounding periodontal tissue were evaluated with micro-computed tomography and hematoxylin and eosin and tartrate-resistant acid phosphatase staining. We calculated the number, volume and distribution of root resorption lacunae and their percentage relative to total root volume, orthodontic tooth movement and periodontal ligament space. There was no significant difference in orthodontic tooth movement between the two sides. LIPUS significantly reduced the number of orthodontically induced inflammatory root resorption initiation areas by 71%, reduced their total volume by 68% and reduced their volume relative to the affected root total volume by 70%. LIPUS induced the formation of a precementum layer, thicker cementum and reparative cellular cementum.

Force levels in complex tooth alignment with conventional and self-ligating brackets

INTRODUCTION The force applied to the teeth is a variable of orthodontic treatment that can be controlled. Poor control of the applied force can lead to adverse biologic effects as well as undesirable tooth movements. The selected archwire-bracket combination is a primary determining factor in the force level applied to a tooth during orthodontic treatment. The aim of this research was to use an experimental biomechanical setup to measure forces generated during complex orthodontic tooth movements with various archwire-bracket combinations. METHODS The materials consisted of 3 types of 0.022-in slot orthodontic brackets: (1) conventional brackets (Victory Series [3M Unitek, Monrovia, Calif] and Mini-Taurus [Rocky Mountain Orthodontics, Denver, Colo]), (2) self-ligating brackets (SmartClip [3M Unitek] and Time3 [American Orthodontics, Shegoygan, Wis]), and (3) a conventional low-friction bracket (Synergy [Rocky Mountain Orthodontics]); and 4 archwire types: (1) 0.012-in stainless steel (3M Unitek), (2) 0.0155-in coaxial (Advanced Orthodontics [Näpflein, Düsseldorf, Germany]), (3) 0.012-in Orthonol (Rocky Mountain Orthodontics), and (4) 0.012-in Thermalloy (Rocky Mountain Orthodontics). Stainless steel ligatures and elastomeric rings were used. The materials were used in different combinations in a simulated malocclusion that represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). RESULTS The lowest forces were measured when the brackets were combined with either the coaxial or the Thermalloy archwires; the forces ranged from 3.4 ± 0.2 to 0.7 ± 0.1 N in the x-axis direction, and from 4.5 ± 0.3 to 0.5 ± 0.1 N in the z-axis direction. The highest forces were measured in combination with stainless steel archwires; the forces ranged from 6.3 ± 0.3 to 3.0 ± 0.1 N in the x-axis direction, and from 6.3 ± 0.3 to 1.7 ± 0.1 N in the z-axis direction. CONCLUSIONS We recommend 0.0155-in coaxial and 0.012-in Thermalloy archwires for leveling and alignment. Elastomeric rings, when used with conventional brackets, increased the force applied to the teeth.

Low-Intensity Pulsed Ultrasound in Dentofacial Tissue Engineering

Oral and maxillofacial diseases affect millions of people worldwide and hence tissue engineering can be considered an interesting and clinically relevant approach to regenerate orofacial tissues after being affected by different diseases. Among several innovations for tissue regeneration, low-intensity pulsed ultrasound (LIPUS) has been used extensively in medicine as a therapeutic, operative, and diagnostic tool. LIPUS is accepted to promote bone fracture repair and regeneration. Furthermore, the effect of LIPUS on soft tissues regeneration has been paid much attention, and many studies have performed to evaluate the potential use of LIPUS to tissue engineering soft tissues. The present article provides an overview about the status of LIPUS stimulation as a tool to be used to enhance regeneration/tissue engineering. This review consists of five parts. Part 1 is a brief introduction of the acoustic description of LIPUS and mechanical action. In Part 2, biological problems in dentofacial tissue engineering are proposed. Part 3 explores biologic mechanisms of LIPUS to cells and tissues in living body. In Part 4, the effectiveness of LIPUS on cell metabolism and tissue regeneration in dentistry are summarized. Finally, Part 5 relates the possibility of clinical application of LIPUS in orthodontics. The present review brings out better understanding of the bioeffect of LIPUS therapy on orofacial tissues which is essential to the successful integration of management remedies for tissue regeneration/engineering. To develop an evidence-based approach to clinical management and treatment of orofacial degenerative diseases using LIPUS, we would like to be in full pursuit of LIPUS biotherapy. Still, there are many challenges for this relatively new strategy, but the up to date achievements using it promises to go far beyond the present possibilities.

Analysis of Orthodontically Induced Root Resorption Using Micro-Computed Tomography (Micro-CT)

OBJECTIVE To establish a protocol for assessing orthodontically induced tooth root resorption (OITRR) in human premolars using micro-computed tomography. MATERIALS AND METHODS Ten extracted maxillary first premolars were obtained from eight healthy adolescent patients; five of these premolars were extracted before any orthodontic movement was applied to them, and the other five premolars were involved in nonextraction orthodontic treatment for 1 year before treatment plan modification lead to extraction treatment. Using reconstructed scanned images, we measured several key resorption lacunae parameters, including the number, volume, and depth on each surface, as well as its extension coronoapically. RESULTS Orthodontic treatment resulted in a significantly greater tooth root resorption lacunae volume, number, maximum depth, and coronoapical extension as well as in areas of dentin demineralization subjacent to the resorption lacunae than in normal premolars. CONCLUSIONS We have established a protocol to evaluate OITRR quantitatively and have provided a method to predict further resorption based on dentine demineralization.

nonsurgical treatment of hemifacial microsomia by therapeutic ultrasound and hybrid functional appliance

Aim: Conventional treatment of patients with hemifacial microsomia involves orthognathic surgery and/or distraction osteogenesis of the mandible. Previous reports showed that low-intensity pulsed ultrasound (LIPUS) enhances mandibular growth in growing rabbits and monkeys. In monkeys, LIPUS enhanced mandibular growth when combined with functional jaw orthopedic appliances. The purpose of this pilot study was to investigate if LIPUS could enhance mandibular growth in children with hemifacial microsomia. Methods: Five children (age range 3–11 years) with hemifacial microsomia were treated with hybrid jaw orthopedic functional appliances and treatment of the affected mandibular condyle by LIPUS for 20 minutes per day. Results: The results showed that after one year of treatment, significant improvement of the underdeveloped side of patients’ faces and mandibles was recognized both clinically and