Comparison of an imaging software and manual prediction of soft tissue changes after orthognathic surgery.

OBJECTIVE: Accurate prediction of the surgical outcome is important in treating dentofacial deformities. Visualized treatment objectives usually involve manual surgical simulation based on tracing of cephalometric radiographs. Recent technical advancements have led to the use of computer assisted imaging systems in treatment planning for orthognathic surgical cases. The purpose of this study was to examine and compare the ability and reliability of digitization using Dolphin Imaging Software with traditional manual techniques and to compare orthognathic prediction with actual outcomes. MATERIALS AND METHODS: Forty patients consisting of 35 women and 5 men (32 class III and 8 class II) with no previous surgery were evaluated by manual tracing and indirect digitization using Dolphin Imaging Software. Reliability of each method was assessed then the two techniques were compared using paired t test. RESULT: The nasal tip presented the least predicted error and higher reliability. The least accurate regions in vertical plane were subnasal and upper lip, and subnasal and pogonion in horizontal plane. There were no statistically significant differences between the predictions of groups with and without genioplasty. CONCLUSION: Computer-generated image prediction was suitable for patient education and communication. However, efforts are still needed to improve accuracy and reliability of the prediction program and to include changes in soft tissue tension and muscle strain.

Force-degradation pattern of six different orthodontic elastomeric chains.

OBJECTIVE: An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs) claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams. MATERIALS AND METHODS: In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (American Orthodontics, GAC and Ortho-Technology). Each brand was divided into two groups with respect to their claimed characteristics (with or without memory). Each sample was stretched to twice its original length and kept constant in 37°C distilled water. Force-extension diagrams were drawn by universal testing machine at 0,1,8,24,72 hours and 1, 2, 4-week intervals. Additionally, the amounts of elongation required to deliver 200 g force were calculated. To compare the results, ANOVA and Tukey tests were performed. RESULTS: Force-decay rate was significantly different between traditional and memory chains (p<0.05). For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4 weeeks. The memory chains demonstrated more constant force and retained 60% of the force. The maximum amount of elongation required to deliver 200 g force belonged to American Orthodontics memory chains (61.9% after 24hr) and the minimum to Ortho-Technology ECs (23.4% initially). CONCLUSION: Memory chains exhibited superior mechanical properties compared to traditional ones. For delivering the same force, memory chains required more elongation. Memory chains of GAC and American Orthodontics showed better characteristics among all chains.

Fabrication and evaluation of a noncompliant molar distalizing appliance: bonded molar distalizer.

OBJECTIVE: Attempts to treat class II malocclusions without extraction in non-compliant patients have led to utilization of intraoral molar distalizing appliances. The purpose of this study was to investigate dental and skeletal effects of Bonded Molar Distalizer (BMD) which is a simple molar distalizing appliance. MATERIALS AND METHODS: Sixteen patients (12 girls, four boys) with bilateral half-cusp class II molar relationship, erupted permanent second molars and normal or vertical growth pattern were selected for bilateral distalization of maxillary molars via BMD. The screws were activated every other day, alternately. Lateral cephalograms and study models were obtained before treatment and after 11 weeks activation of the appliance. RESULTS: Significant amounts of molar distalization, molar distal tipping and anchorage loss were observed. The mean maxillary first molar distal movement was 1.22±0.936 mm with a distal tipping of 2.97±3.74 degrees in 11 weeks. The rate of distal movement was 0.48 mm per month. Reciprocal mesial movement of the first premolars was 2.26±1.12 mm with a mesial tipping of 4.25±3.12 degrees. Maxillary incisors moved 3.55±1.46 mm and tipped 9.87±5.03 degrees mesially. Lower anterior face height (LAFH) decreased 1.28±1.36 mm. CONCLUSION: BMD is appropriate for distalizing maxillary molars, especially in patients with critical LAFH, although significant amounts of anchorage loss occur using this appliance.

Software design for smile analysis.

INTRODUCTION: Esthetics and attractiveness of the smile is one of the major demands in contemporary orthodontic treatment. In order to improve a smile design, it is necessary to record "posed smile" as an intentional, non-pressure, static, natural and reproducible smile. The record then should be analyzed to determine its characteristics. In this study, we intended to design and introduce a software to analyze the smile rapidly and precisely in order to produce an attractive smile for the patients. MATERIALS AND METHODS: For this purpose, a practical study was performed to design multimedia software "Smile Analysis" which can receive patients' photographs and videographs. After giving records to the software, the operator should mark the points and lines which are displayed on the system's guide and also define the correct scale for each image. Thirty-three variables are measured by the software and displayed on the report page. Reliability of measurements in both image and video was significantly high (α=0.7-1). RESULTS: In order to evaluate intra- operator and inter-operator reliability, five cases were selected randomly. Statistical analysis showed that calculations performed in smile analysis software were both valid and highly reliable (for both video and photo). CONCLUSION: The results obtained from smile analysis could be used in diagnosis, treatment planning and evaluation of the treatment progress.

Neural recording front-end designs for fully implantable neuroscience applications and neural prosthetic microsystems.

An implantable neural recording front-end has been designed in two versions. The first is a multi-channel signal-conditioning ASIC for use with any neural recording probe technology. This ASIC was implemented in a commercial 0.5 mum CMOS process, includes 16 parallel amplifier channels, and measures 2.3 mm2 The amplifiers have a gain of 59.5 dB, a high cutoff frequency at 9.1 kHz and consume 75 microW per channel. The low cutoff frequency is independently tunable on each channel to accept or reject field potentials. This chip is small enough to be chronically packaged for experiments in awake behaving animals or it can be integrated into a fully implantable neural recording microsystem. The second version of the front-end is a neural recording probe with integrated signal conditioning circuitry on the back-end implemented in a 3 microm CMOS process. This version dissipates 142 microW and includes 64 to 8 site selection, 8 per-channel amplifiers each having a gain of 50.2 dB, a tunable low cutoff frequency, and a 7 kHz upper cutoff frequency. Real-time site impedance and circuit testing has been integrated in this design.