Wayne J. Sampson

Craniofacial reference plane variation and natural head position

Commonly used craniofacial reference planes such as Frankfort Horizontal (FH) and sella-nasion have shortcomings, including their variable interindividual orientation when related to true horizontal (HOR). Therefore, the aim of this study was to evaluate the potential usefulness of a range of craniofacial reference planes to HOR, including those which have not been investigated previously: the Krogman-Walker (KW) line, the neutral horizontal axis, the foramen magnum line, and the posterior maxillary plane. A sample of 57 (38 female, 19 males) consecutive, pre-treatment orthodontic subjects aged 12-18 years were photographically recorded in a standing mirror-guided natural head position (NHP). Cephalograms taken at the same time were traced, orientated to a plumb line (true vertical) transferred from the photograph, and measured. Descriptive statistical analysis including means and standard deviations (SDs) were used to describe average orientation and variability. Thirty-nine of these subjects were photographically recorded 2 months later to test the reproducibility of NHP. The results showed that the variability of the 11 selected craniofacial reference planes related to HOR was generally high. The planes illustrating the lowest variability to HOR were FH and the KW line with SDs of 4.6 and 4.7 degrees, respectively. These, however, showed approximately double the variation in NHP reproducibility (mean square error 2.1 degree). The KW line and palatal plane were also on average orientated closest to HOR. Therefore, the KW line and palatal plane are potential substitutes for the commonly used reference planes in the absence of a reliable NHP. However, NHP still represents a more valid craniofacial reference system than the investigated reference planes.

Prediction of dental arch development: An assessment of Pont's index in three human populations

Ponts Index was established by Pont in 1909 to predict maxillary dental arch width from the sum of the mesiodistal diameters of the four maxillary incisors. The usefulness of Ponts Index is controversial and, as there has been a recent resurgence of interest in its clinical use for establishing dental arch development objectives particularly by nonspecialists, reassessment of the Index in different human populations was considered worthwhile. This study aimed to evaluate Ponts Index in untreated, noncrowded samples of Australian Aborigines (n = 80), Indonesians (N = 60), and white subjects (N = 60). Measurements were obtained directly from plaster casts; they included mesiodistal crown diameters of the four maxillary incisors, as well as intercanine, interpremolar and intermolar maxillary arch widths as specified by Pont. A series of double determinations confirmed the reliability of the method. Considerable individual variability was noted in each population with regard to the difference between observed values and Ponts estimates, ranging from -5.9 mm to +6.2 mm (interpremolar width) and -6.1 mm to +12.7 mm (intermolar width). No person displayed the ideal arch dimensions predicted by the Index, but values were within +/- 1.0 mm for 17.5% of the Indonesian sample, 20.6% of the Aboriginal sample, and 30.8% of the white sample. Dental arch width was generally underestimated by the Index in Indonesians who tended to display relatively small tooth size and large arch width. A more even distribution of estimates was noted in Australian Aborigines and white subjects, with the Aborigines showing large tooth size and broad dental arches, and the white subjects displaying smaller tooth size and narrow arches. Correlation coefficients computed between observed and expected values were low in all three populations studied (range r = 0.01 to r = 0.56). Although the concept of a simple index with predictive ability is very appealing to some clinicians, the results of this study have highlighted the marked variation in values of Ponts Index for persons with apparently good occlusions, representing three different human populations. Tooth size variation was poorly correlated with arch width variation, with persons often being over or under Ponts estimation due to variation in tooth dimension, particularly in the size of the maxillary lateral incisor. It is concluded that Ponts Index is unlikely to be a useful clinical predictor of dental arch width and the index should not be used as a guide to dental arch development in contemporary populations.

Prediction of mandibular incisor and canine crowding changes in the mixed dentition

To test the hypothesis that preeruptive tooth positions and dental arch parameters might forecast crowding changes, a sample of 47 aboriginal children (26 males, 21 females) was selected stringently on the basis of Class 1 characteristics and an untreated dentition unaffected by caries or attrition. Crowding scores, radiographic relationships of 765E, and dental arch dimensions were evaluated for the mixed dentition (Stage 1, 8.91 +/- 1.05 years) and earliest emergence of the permanent dentition (Stage 2, 12.48 +/- 0.97 years). Changes between the stages were calculated and the sample was divided into two groups, according to an increase (Group 1) or decrease (Group 2) in incisor and canine crowding. Multivariate and multiple regression analyses were used to identify predictors (Stage 1 radiographic and dental arch parameters) of incisor and canine crowding behavior. Dental arch form and tooth size were important factors in measuring the amount of incisor or canine crowding at Stage 1 and Stage 2. Neither the radiographic nor the dental arch predictors proved useful in forecasting crowding changes. Group 2 dental arches tended to be initially narrower, shallower, and more crowded; however, they showed greater molar and canine width expansion and lessened arch depth reduction than Group 1 cases. Many cases showed a reduction in canine crowding from mixed to permanent dentition. This appeared to be largely independent of the observed incisor crowding. Sexual, racial, and individual variations in dentofacial pattern reinforce the need to carefully consider interceptive extraction or space-regaining therapy for each patient because of the unpredictability of crowding behavior during the transition from mixed to permanent dentition.

Intrauterine Hormone Effects on Tooth Dimensions

The human dentition is a complex adaptive system that is influenced by genetic, epigenetic, and environmental factors. Within this system, is sexual dimorphism related to the growth promotion of the Y chromosome, or to hormonal influences, or both? This study is the first to investigate both primary and permanent tooth sizes in females from opposite-sex dizygotic (DZOS) twin pairs compared with females from dizygotic same-sex (DZSS) and monozygotic (MZ) twin pairs to indicate the influence of intrauterine male hormone, including the initial testosterone surge, on dental development. Serial dental models of the primary, mixed, and permanent dentitions of 134 females from DZOS, DZSS, and MZ twins were examined. Mesiodistal, buccolingual, crown height, and intercuspal dimensions of all primary teeth and selected permanent teeth were determined by image analysis. Univariate and multivariate analyses showed statistically significantly larger crown size in DZOS females in both dentitions, with the crown height dimensions displaying the greatest increase in size. These findings strongly support the Twin Testosterone Transfer (TTT) hypothesis. We propose that the growth-promoting effects of the Y chromosome and intrauterine male hormone levels influence different tooth dimensions and contribute differentially to the sexual dimorphism of human teeth.

An evaluation of head position and craniofacial reference line variation

Natural head position (NHP) is the usual, balanced position of the head which is adopted for viewing the horizon or an object at eye level. Determination of NHP is useful when reconstructing facial form in art, forensics, orthodontic diagnosis and treatment planning for surgical management of craniofacial dysmorphic conditions. When NHP is uncertain, correction such as orientation to Frankfurt horizontal (FH) has been advocated. However, FH angulation varies between individuals and is subject to landmark identification error. Previous studies have measured FH and other craniofacial planes in relation to the true horizontal (HOR) with subjects in NHP and have found similar variation to that found with FH. This study measured craniofacial planes in 40 Aboriginal Australians (20 male, 20 female, aged 17 years or greater) from lateral cephalographs and compared its results with classical previous studies. Four planes, the neutral horizontal axis (NHA), FH, Krogman-Walker line (KW line), and palatal plane (P plane) demonstrated near parallelism and averaged between -1 degrees and -2 degrees from HOR. The combined use of NHA, FH, KW line, and P plane enables more effective corrected head position (CHP).

General health-related quality of life and oral health impact among Australians with cleft compared with population norms; age and gender differences.

Objective To evaluate general health-related quality of life (HRQoL) and oral health impact among adults treated for cleft to determine age and gender differences, and to compare against population norms. Design Cross-sectional prospective study. Participants/Setting Nonsyndromic cleft patients treated by the Australian Craniofacial Unit from 1975 to 2009 were recruited (n = 112). Response rate was 79% (n = 88). Main outcome measures HRQoL was measured by the Short Form (SF)-36 questionnaire. Oral health impact was measured by the Oral Health Impact Profile (OHIP)-14 questionnaire. State-based and national norms were used for comparative purposes. Results There were no significant age or sex differences in the cleft samples SF-36 and OHIP-14 scores. When compared against South Australian 2002 state-level norms, cleft participants scored higher on physical function and physical role function but lower on vitality and mental health. The prevalence of having experienced one or more of OHIP–14 items “fairly often” or “very often” was 2.7 times higher than national-level estimates, while extent was 2.8 times and severity 1.7 times higher. Conclusions The oral health impact among cleft patients included in our study was poor compared with population-level estimates. The HRQoL showed mixed results, with the vitality and mental health components being poorer in the cleft group compared with population-level estimates. These results indicate that treatment for orofacial clefting does not entirely remove the factors contributing to poor HRQoL and oral health.

Facial aesthetics and perceived need for further treatment among adults with repaired cleft as assessed by cleft team professionals and laypersons

The objectives of this study were to compare the ratings of professionals and laypeople with and without a cleft regarding the facial aesthetics of adult patients previously treated for orofacial clefting. The necessity for further treatment, as perceived by the respective groups, is also compared. The design of the study was a cross-sectional study. Professionals (two plastic surgeons, one dentist, one orthodontist, and one psychologist) and laypeople (one male and one female adult without a cleft and one male and one female adult with a cleft) were recruited to rate photographs of 80 non-syndromic cleft patients treated by the Australian Craniofacial Unit from 1975 to 2009. Facial aesthetics were measured by a visual analogue scale (VAS; 0-100 mm). High values indicated good aesthetics. Necessity for further treatment was also measured by a VAS (0-100 mm). High values indicated high perceived need for further treatment. The professionals rated facial aesthetics significantly lower and had a lower perception of need for further treatment than the raters with and without a cleft. The laypeople with a cleft rated facial aesthetics significantly higher and had a lower perceived need for further treatment than laypeople without a cleft. The non-surgical professionals rated facial aesthetics significantly lower and had a lower perceived need for further treatment than the surgical professionals. Differences exist in the facial aesthetics ratings and perceived need for further surgery between professionals and laypeople with and without a cleft. This should be considered when managing cleft treatment expectations.

Evidence for endothelial junctions acting as a fluid flux pathway in tensioned periodontal ligament

A continuous tension load of 1.0 N applied to the rat maxillary first molar for 30 min led to a significant increase (p < 0.05) in the mean number of junctions/microns of endothelial perimeter. The mean number of junctions/microns was compared with the mean number of tissue channels/microns 2 as previously reported by fitting linear and quadratic equations. An increase in the mean number of junctions/microns was associated with an increase in mean number of tissue channels/microns 2 (p < 0.01) in control and experimental periodontal ligament. Significant increases in the mean number of junctions/microns occurred in the middle-third zone for venous capillaries (p < 0.01) and in the tooth-third zone for postcapillary-sized venules (p < 0.001). It is concluded that the endothelial junctions of venous capillaries and postcapillary-sized venules provide significant pathways for fluid transport across the tensioned walls of the microvascular bed of the periodontal ligament.

Immunohistochemical detection of nerve growth factor and its receptors in the rat periodontal ligament during tooth movement

OBJECTIVES Nerve growth factor (NGF) and its receptors, p75 and tyrosine receptor kinase A (Trk A), have been shown to increase following trauma. The aims of this study were to examine changes in the detection of NGF and its receptors during orthodontic tooth movement in the rat, and the effects of anti-NGF on these changes. DESIGN Orthodontic separators were placed between the right maxillary first and second molars of Sprague-Dawley rats which were equally divided into two groups. Animals from the second group were injected with anti-NGF. The left sides served as controls, and animals were sacrificed at 0, 3, 7 and 14 days. RESULTS Results of immunohistochemical localisation for p75, Trk A, calcitonin gene-related peptide (CGRP) and NGF showed staining intensity increased at day 3, with a peak at day 7 and decreasing intensity at day 14. Anti-NGF injected animals showed reduced staining at all observation periods. CONCLUSION Data suggest that orthodontic injury induces NGF production, leading to sprouting and invasion by CGRP-positive nerve fibers and that injection of anti-NGF reduces NGF tissue levels and prevents innervation by CGRP-positive fibers.

Microvascular Luminal Volume Changes in Aged Mouse Periodontal Ligament

Data for the microvascular bed in the aged periodontal ligament have not been established. This investigation tested the hypothesis that the luminal microvascular volume decreased in the aged ligament. Mice 35 days old and one year old were vascular-perfused and the mandibular first molar periodontal ligament processed for electron microscopy. Tissue quadrats from each circumferential third ligament region were recorded at 150-μm intervals from the alveolar crest to the apex for randomized sampling of blood vessel lumina. The data were analyzed with a generalized linear model at the p < 0.01 level for the interaction of the aging effect with differences across regions. Stereological parameters were established for vessel lumen volume, and for surface and length densities. Mean ligament width decreased from 119.9 ± 16.94 (μm ± SE) in young mice to 60.0 ± 10.58 (μm ± SE) in aged mice. The luminal volume of 8.63 ± 1.37 (% ± SE) in young ligament increased to 9.83 ± 2.14 (% ± SE) in aged ligament. Collecting venules and the combined group of arterio-venous anastomoses with terminal arterioles showed a two-fold increase in luminal volume density (p < 0.01). In aged ligament, regional shifts affected the microvascular bed distribution, but these changes were not consistent across regions, or with depth. The average cross-sectional tissue area served per capillary decreased from 2117 μm2 to 1451 μm 2 for young and old. Average ligament thickness served per capillary dropped from 52.5 μm to 27.5 μm. These reductions in average diffusion distances indicated a change in the quality of the diffusion barrier with age.