Novel software for quantitative evaluation and graphical representation of masticatory efficiency.

Blending of chewing gums of different colours is used in the clinical setting, as a simple and reliable means for the assessment of chewing efficiency. However, the available software is difficult to use in an everyday clinical setting, and there is no possibility of automated classification of the patient's chewing ability in a graph, to facilitate visualisation of the results and to evaluate potential chewing difficulties. The aims of this study were to test the validity of ViewGum - a novel image analysis software for the evaluation of boli derived from a two-colour mixing ability test - and to establish a baseline graph for the representation of the masticatory efficiency in a healthy population. Image analysis demonstrated significant hue variation decrease as the number of chewing cycles increased, indicating a higher degree of colour mixture. Standard deviation of hue (SDHue) was significantly different between all chewing cycles. Regression of the log-transformed values of the medians of SDHue on the number of chewing cycles showed a high statistically significant correlation (r² = 0.94, P < 0.01). ViewGum eliminates drawbacks of previous two-colour chewing gum test methods by the simplicity of its application. The newly developed ViewGum software provides speed, ease of use and immediate extraction of clinically useful conclusions to the already established method of chewing efficiency evaluation and is a valid adjunct for the evaluation of masticatory efficiency with two-colour chewing gum.

Geometric morphometric analysis of craniofacial variation, ontogeny and modularity in a cross-sectional sample of modern humans.

This investigation aimed to quantify craniofacial variation in a sample of modern humans. In all, 187 consecutive orthodontic patients were collected, of which 79 were male (mean age 13.3, SD 3.7, range 7.5-40.8) and 99 were female (mean age 12.3, SD 1.9, range 8.7-19.1). The male and female subgroups were tested for differences in mean shapes and ontogenetic trajectories, and shape variability was characterized using principal component analysis. The hypothesis of modularity was tested for six different modularity scenarios. The results showed that there were subtle but significant differences in the male and female Procrustes mean shapes. Males were significantly larger. Mild sexual ontogenetic allometric divergence was noted. Principal component analysis indicated that, of the four retained biologically interpretable components, the two most important sources of variability were (i) vertical shape variation (i.e. dolichofacial vs. brachyfacial growth patterns) and (ii) sagittal relationships (maxillary prognatism vs. mandibular retrognathism, and vice versa). The mandible and maxilla were found to constitute one module, independent of the skull base. Additionally, we were able to confirm the presence of an anterior and posterior craniofacial columnar module, separated by the pterygomaxillary plane, as proposed by Enlow. These modules can be further subdivided into four sub-modules, involving the posterior skull base, the ethmomaxillary complex, a pharyngeal module, and the anterior part of the jaws.

Pharmacological management of pain during orthodontic treatment: a meta-analysis.

OBJECTIVES: To evaluate the effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs) in managing pain arising from orthodontic interventions, such as archwire or separators placement. DATA SOURCES: Medline and Cochrane databases searched in February 2010 and updated in July 2010 using orthodontics and pain as the search terms. Additional studies located from Google Scholar, Clinical Trials and the reference lists of retrieved articles. STUDY SELECTION: Randomized controlled trials comparing NSAID to placebo using visual analogue scale (VAS) scores. DATA SYNTHESIS: Of the 1127 studies identified through database searches, seven were included for meta-analysis. Treatment effects (Hedges' g using random effects model) and 95% confidence intervals (CI) of the pain VAS scores were evaluated at 2, 6 and 24 h after intervention, during chewing and biting activities. Pain level at 2 h differed between the ibuprofen and placebo groups during biting (95% CI: -0.178 to -0.046), but not during chewing (95% CI: -0.551 to 0.148). At 6 h, the ibuprofen group exhibited lower pain levels during both activities (chewing 95% CI: -0.640 to -0.123, biting 95% CI: -0.857 to -0.172). At 24 h, no statistically significant difference could be detected between ibuprofen and placebo (chewing 95% CI: -0.642 to 0.112, biting 95% CI: -0.836 to 0.048). No statistically significant difference was found between ibuprofen and acetaminophen at any time point. CONCLUSION: Ibuprofen appears to lower orthodontic pain compared to placebo at 2 and 6 h after separators or archwire placement, but not at 24 h, when pain peaks.

Fluctuating molar asymmetry in relation to environmental radioactivity.

OBJECTIVE: Fluctuating dental asymmetry is considered a sensitive indicator of environmental stress. We used fluctuating asymmetry of teeth in Greek children to assess the effect of the Chernobyl accident to the Greek population, which received relatively large radiation exposure compared to other European countries. DESIGN: Sixty dental casts were divided into two groups according to date of birth prior to or after the Chernobyl accident. The intercuspal distances of the mandibular first permanent molars were measured with digital calipers. We followed the data analysis procedure proposed by Palmer and Strobeck (2003). RESULTS: Fluctuating asymmetry was found at levels above measurement error in all traits except for the buccal measurement. Overall, there were no significant differences in the fluctuating asymmetry between the two groups, after removal of outliers. CONCLUSIONS: These results suggest that environmental radioactivity from the Chernobyl incident did not significantly affect the symmetry of lower permanent molar intercuspal distances in the specific population, even though increased levels of radionuclides have been reported in teeth and other tissues.

A cephalometric morphometric study of the sella turcica.

The purpose of this study was to use quantitative methods to measure the size and shape of the sella turcica and thus establish normative reference standards that could assist in a more objective evaluation and detection of pathological conditions. Standardized lateral cephalograms of 184 healthy Greeks (91 males and 93 females) were used. The age range was between 6 and 17 years. Conventional measurements included three different heights of the sella turcica (anterior, posterior, median), its length, and width, measured in relation to the Frankfort reference line. In addition, the area of sella turcica was calculated. Morphometric methods were used to assess shape. The tracings were superimposed using the Procrustes method, and the average shape was computed. Principal component analysis (PCA) was used to assess shape variability. The data were correlated with centroid size, age, and gender. Unpaired t-tests were used to determine gender differences. Sella height anteriorly was the only variable found to be significantly different between the genders, being larger in females by 0.5 mm. Linear and area measurements were found to be significantly correlated with age, but all correlations were low (r(2) below 8 per cent). Sella turcica shape, as described by PCA, was different between males and females, mainly at the posterior aspect of the sella outline. However, although there was an extensive overlap between the genders, and differences were minimal. Age was not found to be correlated with the shape coefficients, although, in the female group, the first principal component of shape was marginally not significant. Allometry was observed in both genders, the sella showing a tendency towards a flatter and wider shape with increase in size. The results of this study constitute quantitative reference data that could be used for objective evaluation of sella shape.

Activator versus cervical headgear: superimpositional cephalometric comparison.

Clinical trials comparing activator and headgear treatment have shown comparable effectiveness in the total result achieved, but the mechanism of correction is still uncertain. Most studies have used conventional cephalometric methods to evaluate treatment effects, and this might be a factor for the inconclusive results. The aim of this retrospective investigation was to compare the effects of activator and cervical headgear treatment with a superimpositional cephalometric method that could discern between vertical and horizontal effects as well as skeletal, dental, and rotational treatment results. The sample consisted of 2 groups of Class II Division 1 patients, treated without extraction by the same clinician (22 patients were treated with a modified activator-type functional appliance, and 30 patients were treated with a combination of cervical headgear and fixed edgewise appliances). Lateral cephalometric radiographs taken at the beginning of treatment and after Class II molar correction were evaluated conventionally and with a superimpositional method. Regarding the conventional cephalometric measurements, the only difference in the anteroposterior dimension between the 2 treatment modalities was the significantly reduced SNA angle in the headgear group. Both appliances appeared to produce minimal changes in FMA and GoGn-SN angles, and there were no statistically significant differences between the treatment groups. Regional superimpositions showed differences in the movement of molars: the maxillary molar was found to move more posteriorly and inferiorly in the headgear group. Conversely, the mandibular molar was found to move toward the occlusal plane more in the activator group. Assessment of mandibular skeletal changes showed that the mandible moved anteriorly by approximately 1 mm more in the activator than in the headgear group. The overall effect of the 2 appliances was found to be clinically comparable. However, the individual components of change showed differences characteristic of each appliance.

Significance of the soft tissue profile on facial esthetics.

The soft tissue profile has been studied extensively in orthodontics, primarily from lateral cephalometric radiographs, under the assumption that the form of the soft tissue outline largely determines the esthetics of the whole face. The purpose of this study was to assess the relative contribution of the shape of the soft tissue profile outline on the attractiveness of the face, as seen from the profile view. Pretreatment color profile facial photographs of 20 female patients were used. The photographs were scanned, and the soft tissue outlines were digitized. The average outline of the 20 original photographs was then calculated and used as a template for modifying the photographs with computer warping methods. This resulted in 20 warped photographs, all with the same soft tissue outline. Three additional photographs were constructed with 1 face-the composite average of the 20 original photographs-and 3 hairstyles from 3 of the original pictures. The photographs were printed and presented to 10 laypersons and 10 orthodontists for scoring. Scoring was performed on 2 occasions separated by at least 1 week. On the first occasion, the original photographs of 10 of the patients and the warped photographs of the other 10 patients were shown. At the next session, the remaining 10 original and 10 warped photographs were shown. The 3 composite photographs were interspersed with the 20 pictures shown to the judges in each scoring session. Judges were asked to score facial attractiveness on a scale of 0 to 10. The judges were unaware of both the computer modification of the photographs and the purpose of the study. Good agreement was noted between the judges, although the orthodontists tended to be more influenced by the profile outline than did the laypersons. The 3 averaged composite photographs were consistently given the highest scores. The modified photographs were given higher scores than their original counterparts, showing that facial attractiveness is influenced by soft tissue outline form. However, the score improvement was not sufficient to reach the level of the composite images, especially for faces initially judged as being unattractive. This shows that factors other than profile outline shape may be more influential in facial esthetics.

Acquisition of 3-dimensional shapes from images.

Advances in computer vision have started to infiltrate the specialty of orthodontics. During the past few years, a number of new products have appeared that are capable of extracting the 3-dimensional (3-D) structure of an object just by "looking." Examples include laser scanners for creating 3-D models of the face, and hand-held scanners for creating virtual models of the teeth. Such noninvasive methods will surely evolve rapidly and be applied to a multitude of diagnostic and therapeutic modalities, changing the way we think and practice. This article introduces the basic principles behind such technology so that we can better appreciate its advantages, limitations and possibilities. From the large number of methods for acquiring 3-D shapes from images, 4 were selected and are described below. For more comprehensive coverage, see the book by Klette et al (1).

Intermaxillary forces during activator treatment.

The mode of action of the activator appliance is still unclear. Apart from a possible mandibular growth enhancing effect, some investigators believe that orthopedic forces may be applied to the maxilla, contributing to Class II correction by inhibition of maxillary growth. In addition, orthodontic forces may arise that produce dentoalveolar changes. The purpose of this study was to measure the magnitude of anteroposterior intermaxillary forces during wear of the activator appliance. Ten consecutive patients with Class II dental and skeletal relationships were treated with a modified activator appliance. The appliance had maxillary and mandibular segments that could be detached from each other during the measuring session. A force transducer was placed at the anterior part of the maxillary segment, and the anteroposterior force exerted by the mandibular segment was measured. Measurements were taken in the upright and reclined position at every patient visit for a period of 6 months. Results indicated that intermaxillary forces were generally in the orthodontic range (median values of 100 gf at the upright position and 123 gf at the reclined position). A wide variation in force levels was noted, both between patients and for the same patient during the experimental period. No statistically significant change in force levels was observed during the 6 month period and no difference was noted between upright and reclined posture.

Cephalometric analysis of changes in occlusal relationship.

One of the main problems in assessing the mode of action of various treatment modalities is the method of measuring the treatment change. The purpose of the present study was to develop a cephalometric method that would permit a detailed evaluation of the individual growth processes (skeletal and dental) that contribute to the overall change in occlusal relationship. The change in molar relationship was resolved in five components, i.e. translation of the maxilla, of the upper molar, of the mandible, of the lower molar, and rotation of the mandible. These movements were recorded using regional superimposition of various structures, with the aid of a computer program. Derotation of the mandible was performed to remove any confounding effects of total mandibular rotation on the interpretation of the measurements. The results show that assessment of treatment effects can be carried out by comparison of the five resulting vectors.

Ideal arch force systems: a center-of-resistance perspective.

The analysis of force systems from an ideal arch has shown that the ratio of the moments produced by a straight wire connecting two malaligned brackets depends on the ratio of the angulations of the brackets to the interbracket axis. Although this result permits assessment of the relative forces and moments, prediction of future tooth movement requires knowledge of the position of center of resistance as well. In this study, the forces and moments produced by a straight portion of an arch wire were transferred from the brackets to the center of resistance. The purpose was to compare the force system at the brackets to the force system at the center of resistance and to assess whether bracket geometry can be applied to predict initial tooth movement. A computer model was used to simulate two teeth connected by a straight portion of wire. Forces and moments were calculated with the use of equations derived from elementary beam theory. The results show that the force system at the center of resistance may be of an entirely different "geometry" type than that at the bracket. Factors that influence the force system include the interbracket distance, the angulation of the teeth, the length of the tooth root, and the width of the bracket.