Biomedical subjects

Anestis Mavropoulos

Publications and source records attributed to Anestis Mavropoulos.

10 recordsLinked to original sources

PubMed2007

Different responsiveness of alveolar and tibial bone to bone loss stimuli.

UNLABELLED: Mandibular and systemic bone loss are poorly associated. We compared the effect of isocaloric protein undernutrition and/or ovariectomy on BMD and microstructure of mandibular alveolar and proximal tibia sites in adult rats. Mandibular bone was significantly less affected. INTRODUCTION: Whether mandibular bone and axial or peripheral skeleton respond similarly to systemic bone loss remains a subject of controversy. We have previously shown that mechanical loading during mastication influences bone mass and architecture of the mandibular alveolar bone. Isocaloric protein undernutrition and ovariectomy are known to cause bone loss and deterioration of bone microarchitecture at various axial and peripheral skeletal sites. We studied how the mandible, which is subjected to heavy, abrupt, and intermittent forces during mastication, responds to low-protein intake and/or ovariectomy and compared this response to that of the proximal tibia in adult rats. MATERIALS AND METHODS: Forty-four 6-month-old female Sprague-Dawley rats underwent transabdominal ovariectomy (OVX; n=22) or sham operation (n=22) and were pair-fed isocaloric diets containing either 15% or 2.5% casein (sham 15%, n=11; sham 2.5%, n=11; OVX 15%, n=11; and OVX 2.5%, n=11) for 16 weeks. BMD and bone microarchitecture parameters (e.g., bone volume fraction [BV/TV] and trabecular thickness and number) of the mandible and the proximal tibia were measured at the end of the experiment using DXA and microCT. RESULTS: Mandibular alveolar bone was negatively influenced by both protein undernutrition and OVX, but to a significantly lesser extent than the proximal tibia. In sham-operated animals, low-protein intake led to a 17.3% reduction of BV/TV in the mandible and 84.6% in the tibia (p<0.001). In normal protein diet-fed animals, OVX led to a reduction of BV/TV of 4.9% in the mandible but 82% in the tibia (p<0.001). In the mandible, protein undernutrition resulted in thinner trabeculae (p<0.05), whereas OVX led to a reduction of trabecular number (p<0.05). CONCLUSIONS: Mandibular alveolar bone was found to be less sensitive to either protein undernutrition or OVX than the proximal tibia spongiosa. We hypothesize that the mechanical loading of the alveolar process during mastication may protect the alveolar bone from the detrimental effects observed in other skeletal sites, such as the proximal tibia. Morphological and embryological differences between the two skeletal sites might also play a role.

Alveolar Bone Loss↗

PubMed2006

Bracket bond strength dependence on light power density.

OBJECTIVES: In order to reduce curing time for bracket bonding with light-cured composites, manufacturers increase the power density (PD) of light sources. The present study aims at investigating the relationship between PD and shear bond strength (SBS) at short exposure time. METHODS: Stainless steel brackets were bonded to bovine incisors using light-cured adhesive. Six groups of 20 incisors each were exposed to 4s of halogen light with different PD increasing from 500 to 3000 mW/cm(2) in steps of 500 mW/cm(2). Two more groups were exposed to a PD of 3000 mW/cm(2) for 6s (n=15) and 8s (n=19), thus simulating non-available PD of 4500 and 6000 mW/cm(2) for 4s. A halogen lamp with a PD of 1000 mW/cm(2) was used for 40s in the control group (n=15). After storage for 24h at 37 degrees C in water, SBS and adhesive remnant index (ARI) were recorded. RESULTS: SBS was significantly different among groups (ANOVA, p<0.001). SBS comparable to the control group could only be achieved with a PD of at least 3000 mW/cm(2). An exponential model described the relationship between SBS and PD. The best-fit curve based on this model reached 85% of the highest possible SBS at approximately 4000 mW/cm(2). ARI scores showed that higher PD was associated with better adhesion at the bracket/adhesive interface. CONCLUSIONS: Our findings show the SBS dependence on PD, and thus provide a valuable tool for the development of light-curing systems. An exponential model suggests that SBS enters a region of saturation and cannot be improved significantly by further increasing PD.

Adhesiveness↗

PubMed2006

Noncompliance unilateral maxillary molar distalization:.

The aim of this prospective study was the three-dimensional (3-D) analysis of tooth movements after unilateral upper molar distalization by means of a noncompliance intraoral appliance, the Keles slider. This appliance exerts a distalizing force of 150 g at approximately the level of the center of resistance of the upper first molar. Twelve patients (six girls and six boys with a mean age of 13.1 years) with a unilateral Class II molar relationship participated in the study. Dental casts were taken immediately before placement and after removal of the appliance. The casts were digitized using a 3-D surface laser scanner and superimposed on a predefined area of the palate. The average unilateral upper first molar distal movement was 3.1 mm (range: 2.4 to 5.3 mm). Anchorage loss was expressed by a 2.1 mm (range: 0.8 to 3.8 mm) proclination of the central incisors and a 6.1 degrees mesial inclination of the ipsilateral first premolar (range: 1.7 degrees to 12.3 degrees ). There was approximately 1 mm of midline deviation toward the contralateral side and a 1.6 mm (range: 0.8 to 2.3 mm) buccal displacement of the contralateral first premolar. A substantial variation was observed among patients. Noncompliance unilateral upper molar distalization was an efficient treatment approach. There was, however, a substantial anchorage loss. Case selection is strongly recommended because significant anterior crowding, ectopic canines, or spacing can lead to significant anchorage loss.

Adolescent↗

PubMed2006

Validity and reliability of a new edge-based computerized method for identification of cephalometric landmarks.

OBJECTIVE: To evaluate the validity and inter- and intraexaminer reliability when on-screen landmarks are digitized manually or when these are computer-assisted by means of a new cephalometric software feature. MATERIALS AND METHODS: Twenty radiographs were digitized four times by two experienced orthodontists using a manual method and an edge-based algorithm that helps landmark identification by detecting the edges of anatomical structures. RESULTS: The computer-assisted method did not agree with manual digitization in 7 of 13 landmarks and 5 of 10 variables. With a tolerance of 0.5 mm or degrees, the two methods did not agree in cephalometric variables. Intraoperator reliability was improved for B point (x-axis), and Menton (x- and y-axis). It got worse for point A (y-axis). Interoperator reliability was improved for B point (x- and y-axis), Soft Labrale Inferior (x- and y-axis), Soft Pogonion (x-axis), and Menton (y-axis). It decreased for point A (y-axis). Intra- and interoperator reliability got better for only one cephalometric variable under study (SNB). CONCLUSIONS: The edge-locking feature seems to be a promising tool for increasing the reliability of on-screen cephalometric analysis. There seem to be difficulties in locating the appropriate edges when artifacts or soft tissue edges are located near the targeted landmark. The existence of very small, but systematic differences between the two digitization methods manifests the need for further improvement.

Algorithms↗

PubMed2005

Light-curing time reduction with a new high-power halogen lamp.

INTRODUCTION: Orthodontic brackets are routinely bonded with light-cured adhesives. Conventional halogen lights used in bonding have the disadvantage of a long curing time, and the available alternatives (laser and plasma lights) are expensive. Our aim was to investigate the minimum time necessary to bond brackets with a new, relatively low-priced, high-power halogen light. METHODS: Five groups of 15 deciduous bovine incisors were bonded with stainless steel brackets (Mini Diamond Twin, Ormco, Orange, Calif) by using different lamps and curing times. Three of the groups were bonded by using a high-power halogen light (Swiss Master Light, Electro Medical Systems, Nyon, Switzerland) for 2, 3, and 6 seconds, respectively. The fourth group, bonded with a fast halogen light (Optilux 501, Sybron Dental Specialties, Danbury, Conn) for 40 seconds, served as the positive control group. The fifth group, the comparison group, was bonded with a plasma light (Remecure, Remedent, Deurle, Belgium) for 4 seconds. After storage for 24 hours in the dark at 37 degrees C in water, shear bond strength was measured with a universal testing machine. RESULTS: A curing time of 2 seconds with the high-power halogen light negatively affected the bond strength and the probability of bond survival. The adhesive remnant index scores were not significantly different among the groups. Most failures (> 60%) occurred at the bracket base/adhesive interface. CONCLUSIONS: The high-power halogen light seems to be a cost-effective solution to reducing curing time. The recommended curing times to bond stainless steel brackets are 6 seconds and, with caution, even 3 seconds.

Analysis of Variance↗

PubMed2005

Efficiency of noncompliance simultaneous first and second upper molar distalization: a three-dimensional tooth movement analysis.

Objective of this prospective study was the three-dimensional (3D) analysis of tooth movements after the noncompliance simultaneous distalization of the first and second maxillary molars. Ten patients (five girls and five boys; mean age: 13.2 years) with bilateral Class II molar relationships were treated with a noncompliance, fixed intraoral appliance. Upper second molars had already erupted in all cases. Dental casts and lateral cephalometric radiographs were taken immediately before placement and after removal of the appliance. The casts were 3D digitized and superimposed on a predefined area in the palate. The resulting holograms, as well as the cephalometric radiographs, were digitized and analyzed by means of customized cephalometric software. The whole procedure was repeated after a two- to four-week interval to estimate the error of both methods. The cast assessment of 3D sagittal and vertical tooth movements was more reliable than the cephalometric record. The average maxillary first molar distal movement was 2.8 mm. Anchorage loss was expressed by a 1.9-mm proclination of the central incisors. A substantial variation among patients and among the right and left side in the same patient was observed. Noncompliance simultaneous distalization of the first and second maxillary molars can be an efficient treatment option for the correction of Class II molar relationship. However, anchorage loss and individual variation have to be seriously considered. Bilaterally symmetrical effectiveness should not be relied upon.

Adolescent↗

PubMed2005

Masticatory demands induce region-specific changes in mandibular bone density in growing rats.

This study investigates the structural adaptation of the mandibular bone when subjected to different masticatory functional and mechanical demands during growth. The effect of two experimental factors, the insertion of a bite block and the alteration of food consistency, on the bone mineral density (BMD) of the mandible was investigated in growing rats. Fifty-two male albino rats were divided into two equal groups, fed with either the standard hard diet or soft diet, at the age of four weeks. After two weeks, half the animals in both groups had their upper molars fitted with an upper posterior bite block. The remaining animals served as a control. Region-specific BMD of the mandible was subsequently measured using dual-energy X-ray absorptiometry (DXA). Soft diet and the consequent reduction of the forces applied to the mandible during mastication resulted in the reduction of BMD in all regions under study. The insertion of the bite-opening appliance (bite block) and the resulting stretching of the soft tissues led to the application of a continuous light force on the lower molars, which was associated with a significant increase of the BMD in the part of the alveolar process just below the root apices. These results raise the question of whether orthodontic treatment with similar appliances may have some, previously unsuspected, short- or long-term effects on the mandibular bone during growth and whether their effects depend on the individual soft-tissue characteristics.

Absorptiometry, Photon↗

PubMed2004

Cephalometric changes following simultaneous first and second maxillary molar distalization using a non-compliance intraoral appliance.

AIM: The aim of this prospective study was to evaluate the dentoalveolar, skeletal and soft tissue changes induced by a modified minimal-compliance intraoral appliance following the simultaneous distalization of first and second maxillary molars. SUBJECTS AND METHODS: The study sample consisted of 14 patients with a mean age of 13.4 years treated by one clinician. In all cases a bilateral Class II molar relationship was corrected to Class I in a mean treatment period of 16.5 weeks. Lateral cephalometric analysis of the sample was based on the radiographs taken before and immediately after treatment with the appliance. The mean maxillary first molar distal movement was 1.4 mm, accompanied by a mean distal tipping of 6.8 degrees. The vertical change in molar position was insignificant. The anchorage unit was unable to completely resist the reciprocal mesial force of the activated coil spring. The second premolars were moved mesially by a mean 2.6 mm and tipped by a mean 4.1 degrees without significant extrusion. The mean increase in overjet was 0.9 mm, and the mean decrease in overbite 1.0 mm. RESULTS: The results of this study have shown that the presented intraoral appliance is an effective and reliable means of distalizing first and second maxillary molars simultaneously without the need for patient compliance. Appliance effects are limited primarily to the dentoalveolar structures. Mesial movement and slight protrusion of the anchorage unit have to be taken seriously into consideration during intraoral distalization.

Activator Appliances↗

PubMed2004

Morphometric analysis of the mandible in growing rats with different masticatory functional demands: adaptation to an upper posterior bite block.

Functional appliances displace the mandible forward and/or downward, causing a stretching of the orofacial soft tissues, muscles included. The resulting forces are directly or indirectly transmitted to the underlying dento-skeletal tissues. The hypothesis underlying the present investigation was that the insertion of a bite-opening appliance influences the lateral morphology of the rat mandible during growth, and that, moreover, this influence depends on the masticatory functional demands. One-hundred and four 4-wk-old male albino rats were divided into two groups, fed a hard and soft diet, respectively. After 2 wk, half of the animals in each experimental group were fitted with upper posterior blocks, and 4 wk later they were killed. Their left hemi-mandibles were transilluminated, photographed under magnification, and digitized on screen. A total of 170 points were used to draw the lateral outline of the mandible. In addition to the inhibitory effect on the height of the dento-alveolar process, the upper bite block resulted in significant changes in the condyle inclination, the length of the coronoid process, and the occlusal plane inclination. Masticatory functional demands influenced this adaptation in an additive way. The results raise the question of whether orthodontic treatment with posterior bite blocks might have different effects on the mandible, depending on the characteristics of the orofacial soft tissues.

Adaptation, Physiological↗

PubMed2003

Orthodontic literature: an overview of the last 2 decades.

The aim of this study was to explore the orthodontic literature in the most important orthodontic and other dental and medical journals from 1981 to 2000. The most commonly used medical bibliographic database, MEDLINE, was used. In addition, some journals were hand searched to estimate the error of the method. Despite some indexing inconsistencies, MEDLINE was found to be a powerful and relatively accurate tool for use in bibliometric studies. About 16,000 articles with orthodontic interest were published during this period. The number of orthodontic articles written in English rose during this period, but almost half of them (45%) were published in nonorthodontic journals. Articles in the orthodontic journals are focusing more and more on diagnosis and treatment evaluation as the need for high-quality evidence becomes obvious, while other topics, such as new techniques and new materials, are losing ground. Many high-quality studies with orthodontic interest are published in nonorthodontic journals with a high Impact Factor, remaining more or less out of reach for most orthodontists.

Abstracting and Indexing↗