Morphometric analysis of palatal rugae in different malocclusions.

OBJECTIVES: Studies of the association between palatal rugae (PR) and malocclusion are scarce. While unstable following treatment such as rapid maxillary expansion, we hypothesized that PR differ among malocclusions because of genetic determination but also different environmental conditions during development. Our goal was to assess the possible association between PR morphometric measurements and both sagittal and vertical characteristics of malocclusion. METHODS: Maxillary pretreatment dental casts of 243 nongrowing individuals (115 males, 128 females, age 25.5 ± 7.5 years) were laser scanned (Perceptron ScanWorks® V5, Hallam VIC, Australia); angular and linear measurements of the first three PR were recorded in transverse and anteroposterior directions. Cephalometric measurements were obtained from corresponding digitized lateral cephalograms. Statistics included analyses of variance to compare PR measurements among sagittal (class I, class II divisions 1 and 2, class III) and vertical (hypodivergent, normodivergent, hyperdivergent) malocclusion groups and the Pearson correlations among PR dimensions and cephalometric measurements. RESULTS: PR measurements were statistically different between malocclusions, especially with respect to vertical patterns. A majority of transverse and anteroposterior rugae measurements were greatest in class II division 2 subjects. PR were more anteriorly directed in hypodivergent than hyperdivergent groups; the transverse separation between opposing rugae points was smaller. Correlations were generally low. CONCLUSIONS: The findings suggest the possibility for PR to adapt to environmental effects in developing malocclusions, mostly in the class II division 2 phenotype. This premise reinforces the need to explore in longitudinal studies the long-term environmental influences on rugae superimposed on their genetically determined morphological pattern.

Potential and limitations of orthodontic biomechanics: recognizing the gaps between knowledge and practice.

The perennial goals of efficient biomechanics are to obtain more controlled and faster movement and using more discrete appliances. The most recent technological advances have buttressed these goals. Temporary anchorage devices have revolutionized orthodontic practice and loom as a solid cornerstone of orthodontic science, along with the use of light forces, facilitated by "smart" archwires for optimal tooth movement. Accelerated tooth movement with decortication has been successful because of decreasing the resistance of cortical bone but micro-osteoperforation has not matched the same results. Clear aligners and preprogrammed regular or lingual appliances reflect the importance of three-dimensional technology in appliance design based on treatment outcome. These mechanical developments have inched the science closer to the traditional goals, but advances lack regarding their enhancement by biomaterials in a system where the physical stimulus is exerted on the teeth but the expression of tooth displacement is through the biological processes within the surrounding tissues. In this article, present tenets, applications, and advances are explored along with the gaps between knowledge and practice and the possibilities to bridge them. Anchorage control remains the major widely used development but slower is the development of faster noninvasive treatment.

Chin-throat anatomy: Normal relations and changes following orthognathic surgery and growth modification.

OBJECTIVES: To determine if a new facial line (T), tangent to the throat, intersects the mandibular border in anterior (ANT) and posterior (POST) parts in proportions varying with facial configuration, and to evaluate the association between chin projection and throat inclination and the potential for the T-line to reflect this association. MATERIALS AND METHODS: Measurements on profile photographs and cephalograms of 135 adults (aged 18-50 years)-45 each of Class I, II, and III (CI, CII, CIII) malocclusions-included ANT and POST, chin-throat (CTA), and mento-cervical (MCA) angles. Pre- and posttreatment measurements were compared in two subgroups (n = 25 each) of CII and CIII orthognathic surgery patients and in CII, division 1 early-treatment patients (n = 63). Statistics included analysis of variance and t-test for group differences, and Pearson correlation for associations among variables. RESULTS: ANT was nearly equal to POST in CI (50.99%) and CIII (51.86%) subjects and shorter in CII (36.01%) subjects. CTA and MCA were greater in CII profiles and smaller in CIII profiles. Significant differences (P < .0001) were observed for ANT, POST, CTA, and MCA between Classes I/II and II/III and for MCA between Classes II/III (P = .016). High correlations were noted between ANT and CTA in Classes I (r = -0.83), II (r = -0.73), and III (r = -0.68). In surgically treated patients, posttreatment measurements approached CI values. In the early-treatment group, ANT increased but remained smaller than POST; CTA decreased by nearly 13%. CONCLUSIONS: Chin-throat relations and chin extension are associated and require routine assessment in terms of diagnosis and treatment outcome. A practical tool to assess chin-throat relationship, the T-line bisects the mandibular body nearly equally in Class I faces.