The correlation between mineralization degree and bone tissue stiffness in the porcine mandibular condyle.

The aim of this study was to correlate the local tissue mineral density (TMD) with the bone tissue stiffness. It was hypothesized that these variables are positively correlated. Cancellous and cortical bone samples were derived from ten mandibular condyles taken from 5 young and 5 adult female pigs. The bone tissue stiffness was assessed in three directions using nanoindentation. At each of three tested sides 5 indents were made over the width of 5 single bone elements, resulting in a total number of 1500 indents. MicroCT was used to determine the local TMD at the indented sites. The TMD and the bone tissue stiffness were higher in bone from the adult animals than from the young ones, but did not differ between cancellous and cortical bone. In the adult group, both the TMD and the bone tissue stiffness were higher in the center than at the surface of the bone elements. The mean TMD, thus ignoring the local mineral distribution, had a coefficient of determination (R(2)) with the mean bone tissue stiffness of 0.55, p < 0.05, whereas the correlation between local bone tissue stiffness and the concomitant TMD appeared to be weak (R (2) 0.07, p < 0.001). It was concluded that the mineralization degree plays a larger role in bone tissue stiffness in cancellous than in cortical bone. Our data based on bone from the mandibular condyle suggest that the mineralization degree is not a decisive determinant of the local bone tissue stiffness.

The microstructural and biomechanical development of the condylar bone: a review.

BACKGROUND: Bone constantly strives for optimal architecture. Mandibular condyle, which is subjected to various mechanical loads forcing it to be highly adaptive, has a unique structure and a relatively high remodelling rate. Despite the eminent clinical relevance of mandibular condyle, literature on its structural and biomechanical development and on the mechanical role of its mineralized and non-mineralized bone components is scarce. OBJECTIVE: The aim of the present review is to provide a brief introduction to basic bone mechanics and a synopsis of the growth and development of human mandibular condyle. Subsequently, the current ideas on the relationship between the structural and biomechanical properties of bone in general and of mandibular condyle in particular are reviewed. Finally, up-to-date knowledge from fundamental bone research will be blended with the current knowledge relevant to clinical dentistry, above all orthodontics. METHODS: A comprehensive literature study was performed with an emphasis on recent and innovative work focusing on the interaction between microarchitectural and micromechanical properties of bone. CONCLUSIONS: Mandibular condyle is a bone structure with a high bone turnover rate. Mechanical properties of mandibular condyle improve during adolescence and are optimal during adulthood. Local mineralization degree might not be a decisive determinant of the local bone tissue stiffness as was believed hitherto. Bone collagen and its cross links play a role in toughness and tensile strength of bone but not in its compressive properties. Clinical procedures might affect mandibular condyle, which is highly reactive to changes in its mechanical environment.

Relationship between dental anomalies and orthodontic root resorption of upper incisors.

The aim of this study was to examine the potential relationship between the occurrence of orthodontic root resorption and presence of dental anomalies such as tooth agenesis and pipette-shaped roots. Dental anomalies and root resorption were assessed on dental panoramic tomographs (DPT) of 88 subjects, 27 males and 61 females, mean age 28.4 (SD = 11.3 years), selected from orthodontic patients on the basis of the following exclusion criteria: previous fixed appliance treatment, bad quality of the DPTs and no visibility of the periodontal ligament of every tooth, and younger than 15 years of age at the onset of treatment with fixed edgewise appliance lasting at least 18 months. A pipette-shaped root was identified as defined by a drawing. Tooth agenesis was assessed on DPTs and from subjects' dental history. Root resorption was calculated as the difference between the root length before and after treatment, with and without a correction factor (crown length post-treatment/crown length pre-treatment). If one of the four upper incisors showed root resorption of ≥2.3 mm with both formulas, the patient was scored as having root resorption. Chi-square tests indicated that there was no relationship between orthodontic root resorption and agenesis (P = 0.885) nor between orthodontic root resorption and pipette-shaped roots (P = 0.800). There was no relationship between having one of the anomalies and root resorption either (P = 0.750). In the present study, it was not possible to confirm on DPTs a relationship between orthodontic root resorption and dental anomalies, such as agenesis and pipette-shaped roots.

Assessment of dental anomalies on panoramic radiographs: inter- and intraexaminer agreement.

The presence of dental anomalies has been rated radiographically in a number of studies. However, since the reliability of the assessment of these anomalies has rarely been investigated, the aim of this study was to examine inter- and intraexaminer agreement in identifying morphological dental anomalies, such as tooth agenesis, dilacerated, pipette-shaped, blunt, pointed, and short roots. Pre-treatment panoramic radiographs of 40 patients (13 males and 27 females; mean age 27.7 ± 10.8 years) treated between 1983 and 2008 were selected. Four examiners independently assessed the radiographs twice. For a dilacerated root and agenesis, a definition was given. For pipette-shaped, blunt, or pointed roots, a drawing was shown, and for a short root, a ratio was used to identify the anomaly. Intraexaminer agreement of the assessments of the dental anomalies was presented by Cohen's Kappa and varied between -0.01 for short roots and 1.00 for agenesis. With respect to short roots, three of the examiners did not rate them to be present on at least one measurement occasion. This implies that intraexaminer agreement could not be calculated for these three examiners. Interexaminer agreement for dilacerated roots varied between 0.14 and 0.50, for pipette-shaped roots between -0.01 and 0.33, for blunt roots between 0.05 and 0.32, and for pointed roots between 0.17 and 0.37. All values for agenesis were 1.00. It can be concluded that assessing agenesis on panoramic radiographs is reliable. Rating the presence of dilacerated, pipette-shaped, blunt, pointed, and short roots on panoramic radiographs, however, does not result in a reliable assessment.

The masticatory system under varying functional load. Part 2: Effect of reduced masticatory load on the degree and distribution of mineralization in the rabbit mandible.

A reduction in mechanical loading of the mandible brought about by mastication of soft food is assumed to decrease the remodelling rate of bone, which, in turn, might increase the degree of bone mineralization. The effect of a reduction in masticatory functional load on the degree and distribution of mineralization of mandibular bone was investigated in male juvenile New Zealand White rabbits. The experimental animals (n=8) had been raised on a diet of soft pellets from 8 to 20 weeks of age, while the controls (n=8) had been fed pellets of normal hardness. The degree of mineralization of bone (DMB) was assessed at the attachment sites of various jaw muscles, the condylar head, and the alveolar process. Differences between groups and among sites were tested for statistical significance using a Student's t-test and one-way analysis of variance, respectively. The DMB did not differ significantly between the experimental and control animals at any of the sites assessed. However, in the rabbits that had been fed soft pellets, both cortical bone at the attachment sites of the temporalis and digastric muscles and cortical bone in the alveolar process had a significantly higher DMB than cortical bone at the attachment site of the masseter muscle, while there were no significant differences among these sites in the control animals. The results suggest that a moderate reduction in masticatory functional load does not significantly affect the remodelling rate and the DMB in areas of the mandible that are loaded during mastication but might induce a more heterogeneous mineral distribution.

The masticatory system under varying functional load. Part 1: Structural adaptation of rabbit jaw muscles to reduced masticatory load.

Skeletal muscle fibres can change their myosin heavy-chain (MyHC) isoform and cross-sectional area, which determine their contraction velocity and maximum force generation, respectively, to adapt to varying functional loads. In general, reduced muscle activity induces transition towards faster fibres and a decrease in fibre cross-sectional area. In order to investigate the effect of a reduction in masticatory load on three functionally different jaw muscles, the MyHC composition and the corresponding cross-sectional area of fibres were determined in the superficial masseter, superficial temporalis, and digastric muscles of male juvenile New Zealand White rabbits that had been raised on a soft diet (n=8) from 8 to 20 weeks of age and in those of normal diet controls (n=8). Differences between groups were tested for statistical significance using a Mann-Whitney rank sum test. The proportion and cross-sectional area of fibres co-expressing MyHC-I and MyHC-cardiac alpha were significantly smaller in the masseter muscles of the animals that had been fed soft food than in those of the controls. In contrast, the proportions and cross-sectional areas of the various fibre types in the temporalis and digastric muscles did not differ significantly between the groups. The results suggest that reducing the masticatory load during development affects the contraction velocity and maximum force generation of the jaw-closing muscles that are primarily responsible for force generation during chewing. These muscles adapt structurally to the reduced functional load with changes in the MyHC composition and cross-sectional area mainly within their slow fibre compartment.

Age-related changes in collagen properties and mineralization in cancellous and cortical bone in the porcine mandibular condyle.

Collagen is an important constituent of bone, and it has been suggested that changes in collagen and mineral properties of bone are interrelated during growth. The aim of this study was to quantify age-related changes in collagen properties and the degree of mineralization of bone (DMB). The DMB in cancellous and cortical bone samples from the mandibular condyle of 35 female pigs aged 0-100 weeks was determined using micro-computed tomography. Subsequently, the amount of collagen and the number of pentosidine (Pen), hydroxylysylpyridinoline (HP), and lysylpyridinoline (LP) cross-links were quantified by means of high-performance liquid chromatography. The amount of collagen increased with age in cancellous bone but remained unchanged in cortical bone. The number of Pen and LP cross-links decreased in both bone types. In contrast, the number of HP cross-links decreased only in cancellous bone. The sum of the number of HP and LP cross-links decreased with age in cancellous bone only. The DMB increased in cancellous and cortical bone. It was concluded that the largest changes in the number of mature collagen cross-links and the mineralization in porcine cancellous and cortical bone take place before the age of 40 weeks. The low number of mature cross-links after this age suggests that the bone turnover rate continues to be high and thereby prevents the development of mature cross-links.

Referral patterns of Dutch general dental practitioners to orthodontic specialists.

General dental practitioners (GDPs) act as gatekeepers for specialist dental care since they generally decide whether, when, and where to refer patients. It is important for orthodontists to understand the factors influencing the referral decision in order to be able to satisfy both the referring dentists and the patients. A specifically designed questionnaire was sent to a random sample of 634 GDPs in The Netherlands. In part A, general characteristics of the GDPs such as gender, years in practice, number of patients in the practice, possibilities to refer to an orthodontist, and number of patients referred to the orthodontist per year were collected. Part B assessed the importance of 20 various factors related to the GDPs' usual referral decision. Intraclass correlation coefficients (ICC) were calculated to assess the relationship in rank scores of the items of the various groups. The response rate was 60 per cent. Most GDPs (38 per cent) had the possibility to refer to three to four orthodontists, 22 per cent could choose between five and six, and 21 per cent could refer to one or two. Most GDPs (55 per cent) actually referred to one to two orthodontic specialists, while 34 per cent choose between three and four orthodontists. The rank order of the items for male and female dentists was nearly equal (ICC = 0.99, P < 0.001). The most important factors governing the choice of an orthodontic treatment provider by GDPs were patient satisfaction, favourable experience in the past, and oral hygiene monitoring by the orthodontist.

The adaptive response of jaw muscles to varying functional demands.

Jaw muscles are versatile entities that are able to adapt their anatomical characteristics, such as size, cross-sectional area, and fibre properties, to altered functional demands. The dynamic nature of muscle fibres allows them to change their phenotype to optimize the required contractile function while minimizing energy use. Changes in these anatomical parameters are associated with changes in neuromuscular activity as the pattern of muscle activation by the central nervous system plays an important role in the modulation of muscle properties. This review summarizes the adaptive response of jaw muscles to various stimuli or perturbations in the orofacial system and addresses general changes in muscles as they adapt, specific adaptive changes in jaw muscles under various physiologic and pathologic conditions, and their adaptive response to non-surgical and surgical therapeutic interventions. Although the jaw muscles are used concertedly in the masticatory system, their adaptive changes are not always uniform and vary with the nature, intensity, and duration of the stimulus. In general, stretch, increases neuromuscular activity, and resistance training result in hypertrophy, elicits increases in mitochondrial content and cross-sectional area of the fibres, and may change the fibre-type composition of the muscle towards a larger percentage of slow-type fibres. In contrast, changes in the opposite direction occur when neuromuscular activity is reduced, the muscle is immobilized in a shortened position, or paralysed. The broad range of stimuli that affect the properties of jaw muscles might help explain the large variability in the anatomical and physiological characteristics found among individuals, muscles, and muscle portions.

The influence of cephalometrics on orthodontic treatment planning.

Since its introduction, cephalometrics, i.e. cephalometric radiography and analysis, has been used for orthodontic treatment planning. However, the effectiveness of this diagnostic method remains questionable. A randomized crossover study was designed to assess the influence of cephalometrics in orthodontic treatment planning of individual patients. Diagnostic records of 48 subjects (24 males and 24 females aged 11-14 years) were divided in two stratified groups and assigned to one of two combinations: A, dental casts only, and B, dental casts, cephalometric radiographs, and analysis. The records were presented to 10 orthodontic postgraduates and four orthodontists for formulation of orthodontic treatment plans containing a dichotomous decision regarding the use of a functional appliance (FUNC), rapid maxillary expansion (RME), and extraction (EXTR). The combination of FUNC + RME + EXTR was used as the basis of the outcome measure. Agreement on orthodontic treatment planning using all possible comparisons of diagnostic records of individual patients (AB, AA, and BB) was assessed and overall proportions of agreement (OPA) were calculated for orthodontic postgraduates and orthodontists separately. Median OPA were 0.60 (AB), 0.65 (AA), and 0.60 (BB) for orthodontic postgraduates and 0.50 (AB), 0.75 (AA), and 0.50 (BB) for orthodontists. Irrespective of the level of experience, neither consistency of orthodontic treatment planning between both combinations of diagnostic records showed a statistically significant difference (P > 0.05) using Wilcoxon signed rank test nor did consistencies and agreement of orthodontic treatment planning after the addition of cephalometrics. It appears that cephalometrics are not required for orthodontic treatment planning, as they did not influence treatment decisions.

Perception of occlusion, psychological impact of dental esthetics, history of orthodontic treatment and their relation to oral health in naval recruits.

OBJECTIVE: To investigate whether the oral health of young male adults was related to (1) the degree of self-perceived malocclusion, (2) the degree of experienced negative psychosocial impact of dental esthetics, and (3) the history of orthodontic treatment and its duration. MATERIALS AND METHODS: The study subjects were 470 male naval recruits undergoing a routine dental health checkup. They answered the Perception of Occlusion Scale (POS) and Negative Impact of Dental Aesthetics Scale (NIDAS). The Approximal Plaque Index (API), the Sulcus Bleeding Index (SBI), and the number of decayed teeth (DT) and missing teeth (MT) were examined by a staff dentist. Statistical procedures were one-way analyses of variance in the API and SBI and nonparametric Kruskal-Wallis, Mann-Whitney, and chi(2) tests in DT and MT as dependent variables. RESULTS: (1) The subjects ranging within the upper POS quartile scored higher on the SBI (contrast: P = .003) and DT (P = .002) than did those in the lower POS quartiles. (2) In contrast to the subjects reporting minor negative impacts in the NIDAS, those with strong impacts had higher scores on the API and MT (each P < .001). (3) In the subjects with a history of orthodontic treatment lasting 30 months and longer, lower API (P < .05), SBI and DT (each P = .002), and MT (P = .007) scores were found than in the subjects without previous orthodontic treatment. CONCLUSION: The results suggest that self-perceived dental irregularity and negative impact of dental esthetics might affect oral health, whereas previous extensive orthodontic treatment may have favorable effects by improving dental health compliance.

Dentoalveolar compensation in subjects with vertical skeletal dysplasia.

INTRODUCTION: The purpose of this cephalometric study was to investigate vertical dentoalveolar compensation in untreated adults with excessive (long-face) and deficient (short-face) lower anterior face heights. METHODS: Vertical and sagittal base relationships, vertical dentoalveolar dimension in the anterior region of the jaws, incisor inclination, overbite, and overjet were assessed in 112 short-face and 95 long-face subjects. The contribution of skeletal and dentoalveolar components to achieve a normal overbite was assessed by means of regression analysis. For the 2 most important independent variables of the regression equation, the values were calculated that would render an overbite of 2 mm. It was subsequently investigated whether the calculated value fell within the range of the sample. RESULTS: In long-face subjects, overbite was mainly related to lower anterior face height; in short-face subjects, it was mainly related to mandibular anterior alveolar and basal heights. Dentoalveolar compensation occurred in both groups mainly by adaptations in mandibular incisor alveolar and basal heights. Molar height was unrelated to overbite. Cutoff values for achieving a positive overbite were calculated for lower face height and mandibular incisor alveolar and basal heights. CONCLUSIONS: The lower face height mainly determines the overbite in long-face subjects, while in short-face subjects, lower dentoalveolar morphology influences overbite. Lower dentoalveolar compensation can maintain a normal overbite in long-face subjects to a limited extent.

Circadian variation and intermuscular correlation of rabbit jaw muscle activity.

The activation of jaw muscles varies with different tasks and must be coordinated to ensure proper function of the masticatory system. The activation patterns might differ in various muscles or over the time course. In order to evaluate the activation patterns and the intermuscular correlation during normal daily activity the electromyograms (EMG) of the superficial and deep masseter, medial pterygoid and digastric muscles were continuously recorded in rabbits and related to activity levels. Muscle use was assessed as the relative time per hour (duty time) during which predefined levels of the peak-EMG of the day were exceeded. Pearson's correlation of duty times was calculated for 6 muscle pairs at various activity levels. The duty times of the muscles differed significantly at levels exceeding 50% of the peak-EMG. The animals exhibited apparent intraday variations of duty times revealing a circadian covariant pattern of muscle use. These variations, however, were different in each individual animal. The activation of pairs of jaw-closing muscles was more highly correlated than that of pairs consisting of a jaw-closing and a jaw-opening muscle. The mutual dependence of hourly muscle activity among jaw-closers and among jaw-closers and jaw-openers varied with the activity level suggesting that those muscle groups might be independently controlled during non-powerful and powerful motor behaviors.

Glycosylation pattern and cell attachment-inhibiting property of human salivary mucins.

BACKGROUND: Whole human saliva (WHS) and its high molecular weight mucin constituent (Muc) inhibit fibroblast attachment and might influence periodontal and peri-implant wound healing. The aim of this work was to study the potential role of glycosylation of Muc in fibroblast attachment-inhibiting property and to examine in vitro the effect of WHS and Muc on epithelial cell attachment. METHODS: Muc was isolated from WHS by CsCl density gradient ultracentrifugation; covalently immobilized on polystyrene; and subjected to enzymic digestion by N-glycanase, O-glycanase, and sialidase, or chemical desulfation and periodate treatment. Wells of tissue culture microtiter plates were incubated with WHS, Muc, or buffer as control; suspensions of normal human oral keratinocytes, spontaneously immortalized human keratinocytes, or human gingival fibroblasts were applied; and cell attachment determined using methylene blue assay. RESULTS: While enzymic cleavage of N-linked carbohydrates showed no effect, selective removal of O-linked residues and sialic acid as well as desulfation and periodate oxidation resulted in statistically significant reduction of cell attachment-inhibiting property of immobilized Muc. Significantly lower numbers of attached cells of each cell type were found in wells pretreated with WHS or Muc. CONCLUSIONS: Inhibition of cell attachment may be mediated by the carbohydrate residues suggesting specific interactions between the salivary constituent and the cell surface. Exposure of root and implant surfaces to saliva during early wound healing events might influence healing by inhibiting surface colonization by oral keratinocytes and fibroblasts, and enhancing wound repair in the form of long junctional epithelium rather than regeneration.

Cell kinetics of mechanically stimulated rat oral epithelia.

OBJECTIVE: To study cell kinetics of rat gingival (GE), sulcular (SE) and junctional (JE) epithelia in the steady-state and after application of mechanical pressure. DESIGN: Elastic bands were inserted between first and second maxillary molars of 8-week-old male rats, which were labelled with H(3) TdR and killed in groups of six to seven animals together with equal-sized groups of labelled control animals at intervals between 1 and 168 h. Autoradiographs were used to determine epithelial cell proliferation on the pressure side of M1 by calculating the percentage of (3)H TdR-labelled cells (PLC) in the basal (BL) and suprabasal (SL) layers of GE, SE and JE and to estimate median cell cycle (MCC) duration of BL cells by plotting mean and median grain counts against time. RESULTS: (3)H TdR-labelled cells were present in SL of SE and JE 1-12h after isotope injection suggesting that the BL might be not the only source of progenitor cells for JE as they might also be derived through migration from adjacent SE. Application of pressure significantly (ANOVA, P<0.05) reduced PLC in BL of GE, SE and JE indicating a decrease of cell proliferation after 1-12h in response to pressure. In steady-state, the MCC durations of BL cells of GE, SE and JE were 39, 14 and 9h, respectively. After application of pressure, they increased significantly (chi(2)-test, P<0.05) to 48, 44 and 34 h, respectively. CONCLUSIONS: Sustained pressure may lead to reduction of proliferative activity of these epithelia inducing slower progression of progenitor cells through the cell cycle.

Higher number of pentosidine cross-links induced by ribose does not alter tissue stiffness of cancellous bone.

The role of mature collagen cross-links, pentosidine (Pen) cross-links in particular, in the micromechanical properties of cancellous bone is unknown. The aim of this study was to examine nonenzymatic glycation effects on tissue stiffness of demineralized and non-demineralized cancellous bone. A total of 60 bone samples were derived from mandibular condyles of six pigs, and assigned to either control or experimental groups. Experimental handling included incubation in phosphate buffered saline alone or with 0.2M ribose at 37°C for 15 days and, in some of the samples, subsequent complete demineralization of the sample surface using 8% EDTA. Before and after experimental handling, bone microarchitecture and tissue mineral density were examined by means of microcomputed tomography. After experimental handling, the collagen content and the number of Pen, hydroxylysylpyridinoline (HP), and lysylpyridinoline (LP) cross-links were estimated using HPLC, and tissue stiffness was assessed by means of nanoindentation. Ribose treatment caused an up to 300-fold increase in the number of Pen cross-links compared to nonribose-incubated controls, but did not affect the number of HP and LP cross-links. This increase in the number of Pen cross-links had no influence on tissue stiffness of both demineralized and nondemineralized bone samples. These findings suggest that Pen cross-links do not play a significant role in bone tissue stiffness.

Covalent RGD modification of the inner pore surface of polycaprolactone scaffolds.

Scaffold production for tissue engineering was demonstrated by means of a hot compression molding technique and subsequent particulate leaching. The utilization of spherical salt particles as the pore-forming agent ensured complete interconnectivity of the porous structure. This method obviated the use of potentially toxic organic solvents. To overcome the inherent non-cell-adhesive properties of the hydrophobic polymer polycaprolactone (PCL) surface activation with a diamine was performed, followed by the covalent immobilization of the adhesion-promoting RGD-peptide. The wet-chemical approach was performed to guarantee modification throughout the entire scaffold structure. The treatment was characterized by means of chemical and physical methods with respect to an exclusive surface modification without altering the bulk properties of the polymer. RGD-modified scaffolds were tested in cell-culture experiments to investigate the initial attachment and the proliferation of three different cell types.

The reliability of assessing rotation of teeth on photographed study casts.

OBJECTIVE: To examine the intra- and interexaminer reliability of assessing rotation of teeth on photographed study casts. In addition, the reliability parameters of two examiners scoring in mutual consultation were compared with the reliability parameters by one observer. MATERIALS AND METHODS: Standardized photographs of sets of maxillary and mandibular plaster casts of 10 patients before treatment (T1), after treatment (T2), and a long time after retention (T3) were digitized. Tooth rotation was assessed relative to a correct position in the ideal dental arch form. A computer analysis program was used to process the measurements. Two examiners assessed each study cast twice with a washout period of 3 weeks. A third examiner assessed each cast, together with one of the other examiners. The intra- and interexaminer agreements were calculated using intraclass correlation coefficients (ICCs). Wilcoxon signed-rank tests were used to determine significant differences between the intra- and interexaminer reliability coefficients of the three examiners. RESULTS: The ICCs ranged from 0.430 to 0.991. Incisors showed the highest ICCs and molars showed the lowest ICCs. Intraexaminer ICCs of the experienced examiners were significantly higher than those of the examiner with less experience. No significant differences in the reliability between a single examiner and the combination of two examiners were found. CONCLUSION: The method of assessing tooth rotation in the present study has proved to be reproducible, except for the molars. This method can be helpful for clinicians assessing tooth rotation from photographed study casts.

Determination of the relationship between collagen cross-links and the bone-tissue stiffness in the porcine mandibular condyle.

Although bone-tissue stiffness is closely related to the degree to which bone has been mineralized, other determinants are yet to be identified. We, therefore, examined the extent to which the mineralization degree, collagen, and its cross-links are related to bone-tissue stiffness. A total of 50 cancellous and cortical bone samples were derived from the right mandibular condyles of five young and five adult female pigs. The degree of mineralization of bone (DMB) was assessed using micro-computed tomography. Using high-performance liquid chromatography, we quantified the collagen content and the number of cross-links per collagen molecule of two enzymatic cross-links: hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), and one non-enzymatic cross-link: pentosidine (Pen). Nanoindentation was used to assess bone-tissue stiffness in three directions, and multiple linear regressions were used to calculate the correlation between collagen properties and bone-tissue stiffness, with the DMB as first predictor. Whereas the bone-tissue stiffness of cancellous bone did not differ between the three directions of nanoindentation, or between the two age groups, cortical bone-tissue stiffness was higher in the adult tissue. After correction for DMB, the cross-links studied did not increase the explained variance. In the young group, however, LP significantly improved the explained variance in bone-tissue stiffness. Approximately half of the variation in bone-tissue stiffness in cancellous and cortical bone was explained by the DMB and the LP cross-links and thus they cannot be considered the sole determinants of the bone-tissue stiffness.

Oral health-related quality of life and dental esthetics in Amsterdam schoolchildren.

PURPOSE: The purpose of this study was to examine the oral health-related quality of life (OHRQoL) of schoolchildren in Amsterdam, The Netherlands, and to assess the relationship between OHRQoL and self-reported dental esthetics. METHODS: The Child Oral Health Impact Profile (COHIP) was completed by 510 seventh and eighth graders of public primary schools. Subjects also assessed their own dentition with the Esthetic Component of the Index of Orthodontic Treatment Need (AC-IOTN). Gender differences on COHIP subscales and the AC-IOTN were examined using Mann-Whitney U tests. Correlations between the COHIP subscales and the AC-IOTN were assessed with Spearman's rank correlation coefficient. RESULTS: Boys scored significantly lower on the subscales "oral symptoms" and "emotional well-being" than girls. Correlations between OHRQoL and the AC-IOTN were low but significant for boys for the domains "oral symptoms" (0.137) and "emotional well-being" (0.186) and for girls for the domains "functional well-being" (0.148), "emotional well-being" (0.195), and "peer interaction" (0.215). CONCLUSIONS: Dutch schoolchildren in Amsterdam generally reported good oral health-related quality of life. Boys seemed to experience a slightly lower impact of oral symptoms and better emotional well-being than girls. Children's self-perceived dental esthetics did not seem to constitute a relevant variable to explain their level of OHRQoL.