Temporomandibular dysfunction in adult patients with myotonic dystrophy (DM1).

Myotonic muscle dystrophy is a systemic disease with early engagement of the facial muscles. Our aim was to study dysfunction of the temporomandibular system in patients with 'classic' dystrophia myotonica (DM1) and compare it with TMD patients and healthy controls. The study included 27 referred patients with DM1, 18 women and nine men, aged 30-62 years, and two matched control groups: patients with temporomandibular disorders symptoms (TMD) and healthy controls, both groups were consecutive patients. The patients answered questions regarding facial pain, jaw function and dysfunction. A clinical examination of the temporomandibular system including the occlusion was performed, and the maximum bite force and finger forces were measured. Among the DM1 patients, 33% reported difficulty biting off, and 22% had difficulty chewing, avoiding foods like meat and raw vegetables, and 37% of the DM1 patients scored their pain and discomfort as moderate to fairly severe. Their main complaints were TMJ clicking and locking, difficulty opening wide and tiredness. They had more clinical signs of dysfunction compared with the controls (P < 0·001), but no statistically significant difference to the TMD patients. The maximum bite force in DM1 patients was impaired compared to both the TMD patients and the controls (P < 0·001). Significantly more occlusal interferences were found in DM1 patients and were associated with chewing difficulties (P < 0·001). In conclusion, patients suffering from DM1 had an increased prevalence of TMD symptoms, reported impaired chewing function and had a decreased maximum bite force.

Palatal morphology changes in post-stroke patients measured by geometric morphometrics.

This study aimed to describe longitudinal palatal shape changes in post-stroke patients when compared to a sample of healthy subjects through linear measurements and geometric morphometrics. The 3D palatal scanned models of seven stroke patients having a 1-year post-stroke follow-up were matched with seven control subjects of the same age group (range 50-87 years). Intercanine, intermolar distances and palatal height were measured. 3D images were also analysed through geometric morphometrics to assess changes in the shape of the palate from T0 to T1 (1 year after the stroke). Principal component analysis was used to describe shape morphology changes, and visual colour maps were used to qualitatively assess differences between T0 and T1. No changes were detected nor in linear measures neither in palatal shape in healthy subjects from T0 to T1. The palates of stroke patients showed no linear differences either. However, when visualising shape changes through colour maps, the lateral aspects of the palatal vault were slightly narrower in T1, with respect to T0 in stroke patients. This may be attributed to altered tongue function following the stroke.

Functional changes after early treatment of unilateral posterior cross-bite associated with mandibular shift: a systematic review.

The objective of this systematic review was to investigate whether oral functional asymmetry in children treated for unilateral functional posterior cross-bite disappears after orthodontic treatment with a resulting normalisation of oral functions. A literature search was carried out using PubMed, Web of Science and the Cochrane Library to locate longitudinal studies reporting on clinical oral functional changes, recorded by methods including masseter muscle thickness, bite force, masticatory/chewing cycle or electromyographic masticatory muscle activity, following the treatment of unilateral functional posterior cross-bite. All potential articles were initially screened according to their title and abstract, the full text of selected articles was evaluated, and the final study selection was made based on the pre-defined criteria. Data extraction was subsequently carried out. The initial literature search identified 736 articles, with 12 articles fulfilling pre-defined criteria. Although there was a lack of high-quality prospective studies, based on the available evidence, results suggest that the abnormal masticatory cycle associated with functional posterior unilateral cross-bite tends to normalise following early cross-bite treatment. Masticatory muscle activity shows an increase after early functional unilateral posterior cross-bite treatment, and this activity approaches normal levels. Insufficient evidence was available to conclude on maximal molar bite force or masticatory muscle thickness changes following early treatment of functional unilateral posterior cross-bite. Results should be interpreted with caution due to the lack of high-quality controlled studies. Well-designed prospective studies with large patient samples and long-term follow-up are necessary before making reliable conclusions concerning change in functional asymmetry following unilateral functional posterior cross-bite correction.

Treating Class II malocclusion in children. Vertical skeletal effects of high-pull or low-pull headgear during comprehensive orthodontic treatment and retention.

OBJECTIVES: To evaluate, in Class II malocclusion children, vertical skeletal changes occurring with high- and low-pull headgear during non-extraction comprehensive orthodontic treatment, and retention. SETTING AND SAMPLE POPULATION: Two groups of thirty Class II malocclusion children (mean age 10.8 years) who had undergone non-extraction comprehensive orthodontic treatment with either high- or low-pull headgear and fixed appliances. MATERIAL AND METHODS: Retrospective longitudinal study, where pre-treatment, post-treatment and at least 2 year post-retention lateral cephalometric radiographs were analyzed. Comparisons were made concerning changes during treatment and retention in high- or low-pull headgear-treated children. Correlation analyses were carried out investigating changes in vertical cephalometric parameters and pre-treatment vertical facial pattern or type of headgear used. RESULTS: During treatment, sagittal relationships improved in all children and remained stable during retention. Vertically, in both high- and low-pull headgear groups, the intermaxillary angle as well as the maxillary and mandibular plane angles did not show statistically significant changes during treatment or retention, and large variation was seen between patients. When pooling the whole patient sample, change in the vertical facial pattern was independent of the pre-treatment vertical facial pattern or type of headgear used. CONCLUSION: When treating Class II malocclusion children non-extraction with high- or low-pull headgear and fixed appliances, changes in vertical skeletal relationships demonstrate wide variation, both during treatment and retention. Dentoalveolar changes brought about by these appliances may not be able to make a predictable difference in vertical skeletal patterns of growing patients.

The Erasmus programme for postgraduate education in orthodontics in Europe: an update of the guidelines.

In 1989, the ERASMUS Bureau of the European Cultural Foundation of the Commission of the European Communities funded the development of a new 3-year curriculum for postgraduate education in orthodontics. The new curriculum was created by directors for orthodontic education representing 15 European countries. The curriculum entitled 'Three years Postgraduate Programme in Orthodontics: the Final Report of the Erasmus Project' was published 1992. In 2012, the 'Network of Erasmus Based European Orthodontic Programmes' developed and approved an updated version of the guidelines. The core programme consists of eight sections: general biological and medical subjects; basic orthodontic subjects; general orthodontic subjects; orthodontic techniques; interdisciplinary subjects; management of health and safety; practice management, administration, and ethics; extramural educational activities. The programme goals and objectives are described and the competencies to be reached are outlined. These guidelines may serve as a baseline for programme development and quality assessment for postgraduate programme directors, national associations, and governmental bodies and could assist future residents when selecting a postgraduate programme.

Reduced masticatory function is related to lower satellite cell numbers in masseter muscle.

The physiology of masseter muscles is known to change in response to functional demands, but the effect on the satellite cell (SC) population is not known. In this study, the hypothesis is tested that a decreased functional demand of the masseter muscle causes a reduction of SCs. To this end, twelve 5-week-old male Sprague-Dawley rats were put on a soft diet (SD, n = 6) or a hard diet (HD, n = 6) and sacrificed after 14 days. Paraffin sections of the superficial masseter and the m. digastricus (control muscle) were stained with haematoxylin and eosin for tissue survey and with anti-myosin heavy chain (MHC) for slow and fast fibres. Frozen sections of both muscles were double-stained for collagen type IV and Pax7. Slow MHC fibres were equally distributed in the m. digastricus but only localized in a small area of the m. masseter. No differences between HD or SD for the m. digastricus were found. The m. masseter had more SCs per fibre in HD than in SD (0.093 ± 0.007 and 0.081 ± 0.008, respectively; P = 0.027). The m. masseter had more fibres per surface area than the m. digastricus in rats with an SD group (758.1 ± 101.6 and 568.4 ± 85.6, P = 0.047) and a HD group (737.7 ± 32.6 and 592.2 ± 82.2; P = 0.007). The m. digastricus had more SCs per fibre than the m. masseter in the SD group (0.094 ± 0.01 and 0.081 ± 0.008; P = 0.039). These results suggest that reduced masseter muscle function is related to a lower number of SCs. Reduced muscle function might decrease microdamage and hence the requirement of SCs in the muscle fibres.

Tooth eruption: altered gene expression in the dental follicle of patients with cleidocranial dysplasia.

OBJECTIVES: The dental follicle plays an important role in tooth eruption by providing key regulators of osteogenesis and bone resorption. Patients with cleidocranial dysplasia (CCD) exhibit delayed tooth eruption in combination with increased bone density in the maxilla and mandible, suggesting disturbances in bone remodeling. The aim of this study was to determine the expression of genes relevant for tooth eruption and bone remodeling in the dental follicles of patients with CCD and normal subjects. MATERIAL AND METHODS: Thirteen dental follicles were isolated from five unrelated patients with CCD, and fourteen dental follicles were obtained from 10 healthy individuals. All teeth were in the intraosseous phase of eruption. The expression of RANK, RANKL, OPG, and CSF-1 was determined by quantitative RT-PCR. RESULTS: In patients with CCD, the mRNA levels of RANK, OPG, and CSF-1 were significantly elevated compared with the control group. Accordingly, the ratios of RANKL/OPG and RANKL/RANK mRNAs were significantly decreased in patients with CCD. CONCLUSION: The observed alterations in the expression and ratios of the aforementioned factors in the dental follicle of CCD individuals suggest a disturbed paracrine signaling for bone remodeling that could be responsible for the impaired tooth eruption seen in these patients.

Predictive value of molar bite force on Class II functional appliance treatment outcomes.

Sagittal intermaxillary changes brought about by functional appliances show large inter-individual variation. One factor that may in part explain these differences is the masticatory musculature and its functional capacity. The aims of this study were to investigate changes in maximal molar bite force during functional appliance treatment and to assess the influence of pre-treatment maximal molar bite force on treatment outcomes with functional appliances used in Class II malocclusion children. Twenty-five children (17 males and 8 females), aged 9-13 years, with a Class II malocclusion and increased overjet were treated with functional appliances for 1-2 years. Dental casts, lateral cephalograms, maximal molar bite force, and finger force measurements were performed before (T1) and after (T2) treatment. These same measurements were also performed 1-2 years before treatment (T0); the intermediate period before starting treatment served as the control. Multiple regression analyses were used to determine possible correlations between initial maximal molar bite force and dental or cephalometric changes during treatment. Maximal molar bite force, which increased pre-treatment (T0-T1), decreased during functional appliance treatment (T1-T2). Children with a weaker T1 maximal molar bite force showed a larger overjet reduction, greater improvement in molar relationship, greater reduction in ANB angle, and greater augmentation in SNB angle from T1 to T2. Treatment of children with Class II malocclusions with functional appliances seems to lead to more favourable treatment outcomes in those with a weaker maximal molar bite force. This was observed both as regards improvements in dental sagittal relationships, namely overjet and molar Class, as well as skeletal changes due to a decrease in ANB and an increase in SNB angles.

Exploring quantitative methods for evaluation of lip function.

The objective was to explore quantitative methods for the measurement of lip mobility and lip force and to relate these to qualitative assessments of lip function. Fifty healthy adults (mean age 45 years) and 23 adults with diagnoses affecting the facial muscles (mean age 37 years) participated in the study. Diagnoses were Möbius syndrome (n=5), Facioscapulohumeral muscular dystrophy (n=6) and Myotonic dystrophy type 1 (n=12). A system for computerised 3D analysis of lip mobility and a lip force meter were tested, and the results were related to results from qualitative assessments of lip mobility, speech (articulation), eating ability and saliva control. Facial expressions studied were open mouth smile and lip pucker. Normative data and cut-off values for adults on lip mobility and lip force were proposed, and the diagnostic value of these thresholds was tested. The proposed cut-off values could identify all inviduals with moderate or severe impairment of lip mobility but not always the milder cases. There were significant correlations between the results from quantitative measurements and qualitative assessments. The examined instruments for measuring lip function were found to be reliable with an acceptable measuring error. The combination of quantitative and qualitative ways to evaluate lip function made it possible to show the strong relation between lip contraction, lip force, eating ability and saliva control. The same combination of assessments can be used in the future to study if oral motor exercises aimed at improving lip mobility and strength could have a positive effect on lip function.

Quantitative assessment of facial muscle impairment in patients with hemispheric stroke.

Facial weakness is frequently observed in patients with hemispheric stroke. Most reports refer to qualitative assessment. The aim was to quantify the upper and lower facial muscle function in patients with hemispheric stroke. Three different facial expressions (forced smile, posed smile and maximum eyebrow lift) and facial rest position were mapped using a 3D video system. Twenty-seven patients with hemispheric stroke (PG) and 22 controls (CG) were recruited. Facial asymmetry was expressed as absolute side differences between four corresponding distances. In PG, a longer distance was found from inner canthus to oral commissure (dist1) on the impaired side in all investigated poses (PG non-affected-affected side: range of all poses 1·18 ± 4·45 to 1·80 ± 2·37 mm; CG right-left side: range -0·69 ± 1·55 to -0·43 ± 1·39 mm, Mann-Whitney tests: 0·0002 < P < 0·0423). In addition, the ratio of the impaired to the non-affected side was different in PG for dist1 in rest and eyebrow lift (Wilcoxon tests: 0·0011 < P < 0·0288). CG showed asymmetries in rest and forced smile (Wilcoxon tests: P = 0·0392 and P = 0·0424). Furthermore, dist1 in PG showed higher variances than in CG (F-tests: 0·0001 < P < 0·0445) except for the relative dist1 at rest (F-test: P = 0·0533). The distance between inner eyebrow corner and inner canthus showed no side difference in both groups during eyebrow lift (n.s.); nevertheless, two patients showed distinct asymmetries. The employed 3D video system proved sensitive in assessing facial muscle function. The results confirm and quantify that the lower facial muscles are more affected by hemispheric stroke than the upper ones and show that the measured distances were more variable in post-stroke patients than in control subjects.

Masseter muscle thickness and treatment outcomes in children with Class II division 1 malocclusion.

AIM: To investigate if treatment outcome in patients with Class II division 1 malocclusion treated by a variety of approaches is affected by masticatory muscle capacity. MATERIALS: Seventy-four children with Class II division 1 malocclusion were included in the present study. These were divided into 54 children (10.4 ± 1.6 years of age) treated with fixed appliances including headgear and/or Class II intermaxillary elastics, 12 children (9.9 ± 1.9 years of age) treated with functional appliances and 8 children treated with fixed appliances and other means of treatment. Ultrasonographic masseter muscle thickness measurements were taken before treatment, while lateral cephalograms were taken before and after treatment. STATISTICS: Multivariate linear regression analysis was used to assess the association between masseter muscle thickness and treatment outcomes, as well as the gonial angle and treatment outcomes. CONCLUSION: In children with Class II division 1 malocclusion treated by means other than functional appliances, treatment outcome is not associated with masseter thickness. This may be the case since the application of intermaxillary forces and torque application may offset the functional component in tooth movement. Outcomes following functional appliance treatment may be partly determined by the masticatory muscles. During functional treatment, children with a weaker masticatory system show greater dentoalveolar compensation. This is however not maintained during the second phase of fixed appliance treatment.

Overeruption of periodontally affected unopposed molars in adult rats.

BACKGROUND AND OBJECTIVE: In clinical practice, anterior teeth with periodontal disease exhibiting signs of overeruption are occasionally encountered. However, the influence of periodontitis on unopposed teeth needs to be further elucidated. This study investigated, in rats, the overeruption pattern of unopposed mandibular molars with experimentally induced periodontitis. MATERIAL AND METHODS: Sixty adult male rats were divided equally into four groups. In two groups, periodontitis was induced by a silk thread placed around the cervix of the right mandibular molar. In two groups with and without experimentally induced periodontitis, the crowns of the right maxillary molars were reduced occlusally by grinding to simulate unopposed teeth. After 4 wk, the animals were killed and scanned using micro-computed tomography to measure the vertical position of molars and the buccal and lingual alveolar bone levels. RESULTS: There were no significant differences in the overeruption of opposed molars with and without periodontitis. However, the alveolar bone level of opposed molars with periodontitis was lower than that of healthy molars. Healthy unopposed molars were extruded when compared to molars with an antagonist. The alveolar bone level of healthy unopposed molars was not influenced by molar overeruption. Unopposed molars with periodontitis exhibited significantly larger extrusion than healthy unopposed molars. The lingual alveolar bone level of unopposed molars with periodontitis was lower than that of other healthy and periodontally affected teeth. CONCLUSION: The loss of antagonist causes overeruption of the unopposed tooth, which becomes more prominent in the presence of periodontitis.

Masseter muscle thickness as a predictive variable in treatment outcome of the twin-block appliance and masseteric thickness changes during treatment.

OBJECTIVES: To estimate the association of initial masseter muscle thickness with treatment outcomes using functional appliances and the effect of treatment on masseter muscle thickness. MATERIAL AND METHODS: Twenty-two children, aged 8-12, with skeletal and dental class II relationships and increased overjet were treated with twin-block appliances for 9-17 months, until a class I molar relationship and decreased overjet was achieved. Dental casts, lateral cephalograms, and ultrasonographic measurements of the masseter muscle were performed before and after treatment. Twenty-two children, aged 8-12, without immediate need for orthodontic treatment, served as controls. They were observed for 11-17 months, and ultrasonographic masseter muscle measurements were taken before and after the observation period. RESULTS: Masseter muscles in treated children were thinner at the end of treatment, while untreated controls showed an increase in thickness. Treated children with thinner pre-treatment muscles showed greater mandibular incisor proclination, distalisation of maxillary molars, and posterior displacement of the cephalometric A point during treatment. CONCLUSION: Treatment of a dental class II relationship with functional appliances leads to mild atrophy of the masticatory muscles, possibly because of their decreased functional activity. The initial condition of the muscles may be associated with mandibular incisor proclination, and the position of maxillary first molars and A point.

Masseter muscle thickness in hospitalised stroke patients.

The aim of the study was to investigate the thickness of the masseter muscles in stroke patients when compared to a control group (CG). Hospitalised stroke patients (18 men, 13 women; age 69.0 +/- 12.7 years) were compared to a CG (13 men, 11 women; age 68.8 +/- 10.8 years) composed to correspond to in age, gender and dental state. The thickness of the masseter muscle was recorded by means of a real-time ultrasound scanner on both sides, twice under contraction and twice in relaxed condition. In the stroke patients, the thickness of the masseter muscle of the affected side (aff) was smaller than the one of the non-affected side (non-aff) both, under contraction (aff 13.1 +/- 2.4 mm; non-aff 13.8 +/- 2.3 mm, P

Professionals' and laypersons' appreciation of various options for Class III surgical correction.

SUMMARY: The objectives of this study were to evaluate the assessments of maxillofacial surgeons, orthodontists, and laypersons on the predicted aesthetic outcome of various surgical options in Class III correction and the associations between certain initial cephalometric values and the judges' preferred option. Pre-surgical lateral headfilms and coloured profile photographs of 18 skeletal Class III Caucasian adult patients (10 males and 8 females) with a mean age of 24.5 years were used. The headfilms were hand traced and digitized. Conventional cephalometric analysis was performed. Computerized predictions of three surgical options, mandibular setback, Le Fort I advancement, and bimaxillary surgery, were made. For each case, the pre-surgical profile photograph with the three predictions was presented on a printed page. The questionnaire was sent to 51 maxillofacial surgeons (response rate 45.1 per cent), 78 orthodontists (response rate 71.8 per cent), and 61 laypersons (response rate 100 per cent) to aesthetically evaluate the pre-surgical photographs and the surgical predictions by placing a mark along a 10-graded visual analogue scale (VAS) using a standard profile for calibration. Confidence interval was calculated for each patient. An independent samples t-test was used to detect initial cephalometric values associated with the judges' preferred option and analysis of variance/Tukey's honestly significant differences to evaluate differences between judges. Intra-observer reliability was assessed with a paired t-test. All treatment predictions led to improved scoring of facial aesthetics with the exception of the setback option for three patients. For 14 patients, general agreement for the preferred option existed between the three groups of judges. Laypersons tended to give lower improvement scores than professionals. Overjet, nasofacial, and nasomental angles were important in decision making between the mandibular setback and Le Fort I options (the more negative the overjet, the larger the nasofacial angle, the smaller the nasomental angle, the greater the preference for the Le Fort I option). Wits appraisal seemed to be important in decision making between the mandibular setback and bimaxillary options (the more negative the Wits appraisal, the greater the preference for the latter option).

Orthodontists' and laypersons' aesthetic assessment of Class III subjects referred for orthognathic surgery.

This study was undertaken to compare laypersons' and professionals' perception of soft tissue profiles of Class III adults, and to evaluate which cephalometric variables are likely to influence the profile assessment score (PAS). Lateral headfilms and coloured profile photographs of 18 skeletal Class III Caucasian adult patients (10 males, 8 females with a mean age of 24.5 years) prior to surgery, and nine adult Caucasian patients (four males, five females with a mean age of 27.4 years) with a dental Class I occlusion and no major skeletal discrepancy were included in the study. The headfilms were hand traced and digitized. Various cephalometric variables were calculated by computer software. Each printed profile photograph was evaluated aesthetically by 18 laypersons and 18 orthodontists using a 10-graded visual analogue scale (VAS) and a standard profile for calibration. Intra-observer reliability was tested and no significant error was found. Paired and unpaired t-tests were used to compare the scores. The association between various cephalometric variables and the PAS was tested. In general, compared with orthodontists, laypersons were less critical in their evaluation of the Class III profiles (+0.3 grade on the VAS) as well as the reference profiles (+0.7). The reference profiles were found to be more attractive than the Class III profiles by both laypersons and orthodontists (+2.3 grades). The degree of facial concavity had a negatively predictive value for the orthodontists' and laypersons' evaluations. The degree of facial concavity together with the steepness of the mandibular plane were negatively predictive factors for the PAS given by the orthodontists.

Vertical relapse after orthodontic and orthognathic surgical treatment in a patient with myotonic dystrophy.

Patients with myotonic dystrophy (MD), a neuromuscular multisystem disease characterised by progressive muscular weakness, often present with an anterior open bite associated with excessive facial vertical development. These aberrations in vertical craniofacial growth may be due to the reduced function of the masticatory muscles and the lowered position of the tongue. Well-planned and executed treatment of these patients, with orthodontics and orthognathic surgery, can provide satisfactory results. The long-term stability of these treatment results however remains undocumented. This paper describes a case of severe anterior open bite in a patient with MD treated with orthodontics and orthognathic surgery, with an acceptable post-treatment result. Long-term follow-up however revealed a highly unstable outcome. Reasons for this include the continued overeruption of posterior teeth due to the weakened masticatory musculature, mandibular posture, or problems with TMJ adaptation and remodeling. Possible ways to minimise this instability are discussed, namely lifelong skeletal retention or postponing treatment until a later age.

Notch Coordinates Periodontal Ligament Maturation through Regulating Lamin A.

Tooth eruption is a continuous biological process with dynamic changes at cellular and tissue levels, particularly within the periodontal ligament (PDL). Occlusion completion is a significant physiological landmark of dentition establishment. However, the importance of the involvement of molecular networks engaging in occlusion establishment on the final PDL maturation is still largely unknown. In this study, using rat and mouse molar teeth and a human PDL cell line for RNAseq and proteomic analysis, we systematically screened the key molecular links in regulating PDL maturation before and after occlusion establishment. We discovered Notch, a key molecular pathway in regulating stem cell fate and differentiation, is a major player in the event. Intercepting the Notch pathway by deleting its key canonical transcriptional factor, RBP-Jkappa, using a conditional knockout strategy in the mice delayed PDL maturation. We also identified that Lamin A, a cell nuclear lamina member, is a unique marker of PDL maturation, and its expression is under the control of Notch signaling. Our study therefore provides a deep insight of how PDL maturation is regulated at the molecular level, and we expect the outcomes to be applied for a better understanding of the molecular regulation networks in physiological conditions such as tooth eruption and movement and also for periodontal diseases.

Influence of Age and Tooth Loss on Masticatory Muscles Characteristics: A Population Based MR Imaging Study.

BACKGROUND: Aging is associated with a decline in masticatory muscles mass and performance. The present study aims to examine the differences in the cross-sectional areas of the masseter, medial and lateral pterygoid muscles in relation to age and the present dental status in a population-based magnetic resonance imaging study. METHODS: This cross sectional study involved 747 subjects aged between 30-89 years (344 male, 403 female) who underwent both a whole body MRI and a full oral examination. The cross-sectional areas of the masseter, medial and lateral pterygoid muscles were measured from MRI images using the software Osirix. Dental and prosthetic status data from the oral examination were classified according to Eichner index. The method of generalized least squares, also called growth curve model, was used to examine the associations between the cross-sectional areas, age and tooth status. RESULTS: The cross-sectional area of the lateral pterygoid muscle decreased substantially with age in women but did not depend on age in men. The medial pterygoid muscle depended on age but an effect modification by gender was uncertain. Masseter muscle was weakly associated with age but strongly associated with the number of teeth in both genders. CONCLUSIONS: Our findings suggest that age has a heterogeneous effect on masticatory muscles. This indicates that age related changes to the masticatory muscles are muscle specific and are not consistent between the different muscles.

[Bone anchorage in orthodontics. A review]. / Botverankering in de orthodontie. Een overzicht.

The achievement of absolute anchorage in orthodontics overcoming the reaction forces and moments has been problematic for a long time. This was caused on the one hand by the limitations of the devices available and on the other hand by the dependence on patient cooperation. The introduction of bone anchorage systems changed the traditional way of thinking on orthodontic anchorage. Whereas the application of anchor systems, such as palatal implants and onplants, has specific indications, bone screws with or without plates seem to have the potential of being used on a routine basis. However, appropriate data for more complete understanding of the biological and biomechanical background of this concept of orthodontic anchorage are still lacking. Furthermore, studies on the effectiveness of these systems when compared to the traditional orthodontic anchorage and based on large groups of patients are not available. Well-designed prospective clinical trials substantiating the evidence-based use of these devices are needed.