Anestis Mavropoulos

Different Responsiveness of Alveolar and Tibial Bone to Bone Loss Stimuli

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.

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.

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.

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.

Do masticatory functional changes influence the mandibular morphology in adult rats

OBJECTIVE This study aimed to investigate the effect of masticatory functional changes on the lateral view morphology of the mandible in adult rats. DESIGN Sixty 21-day-old male Sprague-Dawley rats were divided into two groups. Sixteen received ordinary (hard) food during the whole experimental period (normal group). The remaining 44 received a soft diet during 21 weeks to develop a hypofunctional masticatory system. Then, the now adult animals were divided into two equal groups: one continued on a soft diet (hypofunctional group), and the other changed to an ordinary diet with the aim of functionally rehabilitating their masticatory system (rehabilitation group). After another 6 weeks all animals were sacrificed and their left mandible was dissected, photographed and customised cephalometric software was used to perform morphometric measurements. RESULTS The area of the mandible was smaller in the hypofunctional compared to the normal group. Interestingly, the alveolar process was shorter in the normal group. Morphometric analysis revealed significant differences such as the area of the angular process and the inclination of the condylar process. The rehabilitation group was only marginally different compared to the hypofunctional group, although a general tendency to approach (catch-up) the normal group was observed, and one morphometric variable (condylar base inclination) was indeed significantly different. CONCLUSIONS Morphometric analysis revealed only marginal changes of the adult rat mandibular morphology during a 6-week period of masticatory function rehabilitation. However, the observed catch-up tendency might suggest that a longer rehabilitation period may have significant effect on mandibular morphology.

Rehabilitation of masticatory function improves the alveolar bone architecture of the mandible in adult rats

Masticatory functional changes have been shown to influence the quantity and quality of the alveolar bone during growth. This study was designed to investigate the effect of masticatory function rehabilitation on the morphology and the trabecular architecture of the mandibular alveolar bone after cessation of growth. Forty-four Sprague-Dawley male rats received soft diet in order to develop masticatory muscle hypofunction. After 21 weeks, after cessation of growth, the animals were divided into two groups: the first group continued receiving soft diet for six more weeks (hypofunction group), while the second group changed to ordinary (hard) diet with the aim to restore a normal masticatory function (rehabilitation group). A third group of 16 male rats (normal group) received ordinary (hard) diet during the whole experimental period and served as control. Micro-tomographic histomorphometry was used to evaluate the architecture of the mandibular alveolar bone (e.g. bone volume fraction, trabecular thickness, trabecular separation, etc.) at the end of the experiment (27 weeks). The height and width of the alveolar process were measured as well. The alveolar process trabecular bone volume fraction (BV/TV) was lower for the animals of the hypofunctional group as compared to those of the normal (p<0.01) and the rehabilitation (p<0.05) groups. Despite the significant improvement observed in the rehabilitation group, their BV/TV was lower in comparison to the normal group (p<0.05) at the end of this experiment. All the other micro-tomographic parameters followed the same pattern of change between groups; values of the rehabilitation group were between the values of the two other groups, differing significantly from both of them. The alveolar process was significantly shorter in the normal group in comparison to both the hypofunctional and rehabilitation groups (p<0.05). On the other hand, both the normal and rehabilitation groups were had a wider alveolar process than the hypofunctional group (p<0.05). Both alveolar height and width were significantly correlated with all micro-tomographic parameters under study. The rehabilitation of masticatory function led to a significant improvement of alveolar bone architecture in adult rats, although the negative effects of hypofunction were not totally reversed during the period under study.

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

Abstract.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°. 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° 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.Zusammenfassung.Ziel:Beurteilung der dentoalveolären, skelettalen und Weichteil-Veränderungen nach Anwendung einer modifizierten, intraoralen, gering kooperationsabhängigen Apparatur zur simultanen Distalisation der ersten und zweiten oberen Molaren.Probanden und Methode:Die Untersuchungsgruppe bestand aus 14 Patienten (Durchschnittsalter 13,4 Jahre), die alle von einer Person behandelt wurden. Bei allen Fällen war nach einer durchschnittlichen Behandlungsdauer von 16,5 Wochen die Klasse- II-Molaren-Beziehung bilateral in eine Klasse I korrigiert. Die kephalometrische Analyse erfolgte anhand von Fernröntgenseitenbildern der Patienten, die vor und direkt nach der Behandlung mit der Apparatur angefertigt wurden. Die durchschnittliche Distalisation des ersten Molaren betrug 1,4 mm bei gleichzeitiger Distalkippung um 6,8°. Die Veränderung in der vertikalen Molarenposition war nicht signifikant. Die Verankerungseinheit konnte die reziproke nach mesial gerichtete Kraft der aktivierten Spiralfeder nicht vollständig auffangen. Die zweiten Prämolaren wurden um 2,6 mm nach mesial bewegt und um 4,1° gekippt, ohne dass eine signifikante Extrusion auftrat. Der Overjet nahm um 0,9 mm zu, und der Overbite verringerte sich um 1,0 mm.Ergebnisse:Diese Studie zeigte, dass die Anwendung der vorgestellten intraoralen Apparatur eine effektive und verlässliche Methode zur simultanen Distalisierung erster und zweiter Molaren ist, ohne auf die Mitarbeit des Patienten angewiesen zu sein. Die Wirkung der Apparatur ist primär auf die dentoalveolären Strukturen beschränkt. Die Mesialbewegung und die leichte Protrusion der Verankerungseinheit müssen während der intraoralen Distalisation kritisch beobachtet werden.

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.

Normal masticatory function partially protects the rat mandibular bone from estrogen-deficiency induced osteoporosis

BACKGROUND/AIM In a previous study we showed that mandibular alveolar (trabecular) bone appears to be less sensitive to estrogen deficiency than the proximal tibia spongiosa. We hypothesized that the mechanical loading of the alveolar process during mastication may protect the alveolar bone from the detrimental effects observed in other skeletal sites. To test this hypothesis we compared the effect of ovariectomy on the mandibular alveolar bone and the proximal tibia spongiosa of rats fed either a normal (hard) or a soft diet. METHODS Forty six-month-old female Sprague-Dawley rats underwent trans-abdominal ovariectomy (OVX) or sham operation (SHAM). Half of the animals received their food in the usual form of pellets (hard consistency), while the other half received a soft, porridge-like, isocaloric diet of identical composition (soft consistency). Micro-computed tomographic histomorphometry was used to evaluate the trabecular micro-architecture. A two-factor analysis of variance was used to test for effects and interaction of ovariectomy and/or soft diet. RESULTS OVX had a significantly negative effect on the proximal tibia spongiosa (all parameters under study except trabecular thickness; p<0.001) and on the mandibular alveolar bone (trabecular number and spacing; p<0.05). Soft diet led to a further decrease of mandibular BV/TV (p<0.01), trabecular thickness (p<0.05) and number (p<0.05), as well as increase of separation (p<0.001). A significant interaction was observed between OVX and soft diet concerning the mandibular BV/TV, as well as trabecular thickness and spacing (p<0.05). CONCLUSION Normal (hard) diet limited significantly the negative effects of estrogen deficiency on mandibular alveolar bone micro-architecture four months after ovariectomy.

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.