Radiological features and treatment of erupting maxillary canines in relation to the occurrence of dental developmental abnormalities.

OBJECTIVE: This study aimed to investigate the radiological features of the permanent canines and the treatment carried out to ensure their eruption relative to certain features involved in Dental Anomaly Patterns (DAP). MATERIAL AND METHODS: The cross-sectional part of this retrospective register--based study focused on 1,315 dental panoramic tomographs (DPTs) of children aged 8.5-10.5 years, while the longitudinal part involved information on the treatment provided for 1,269 canines after the DPTs and on their eruption into the oral cavity. RESULTS: The canines of the DAP children more often showed evidence of early treatment (p = 0.014), with girls having more frequently interceptive treatment (p = 0.004) and boys early headgear (p = 0.022). Delayed dental age was associated with early treatment (OR 3.29, 95% CI 1.08-9.99). Either no or clear overlapping of a canine with the lateral incisor occurred more often in the DAP children, whereas canine inclination did not differ between the groups. The root development stage of the canine was more often either beginning or well advanced in the DAP children. CONCLUSIONS: The children with dental developmental abnormalities more often showed evidence of early treatment for the canines. Monitoring of the erupting canines after the first mixed stage is important to enable timely early treatment.

Features of Dental Anomaly Patterns in Finnish children as seen in panoramic radiographs at the late mixed stage.

OBJECTIVE: To describe the prevalence of the developmental abnormalities involved in Dental Anomaly Patterns (DAP) and investigate their co-occurrence in an age cohort of children with late mixed dentition. MATERIAL AND METHODS: Retrospective, register-based study focused on 1315 panoramic radiographs of children aged 8.5-10.5 years. The features examined were absent teeth, peg-shaped maxillary lateral incisor, delayed dental age, infraocclusion of primary molars, transposition and distal angulation of unerupted mandibular second premolar. RESULTS: Feature involved in DAP was detected in 29.8% of the children, most common being infraocclusion of primary molars (17.5%), followed by absent teeth (8.4%), delayed dental age (7.6%), distal angulation of unerupted mandibular second premolar (7.3%), peg-shaped maxillary lateral incisor (2.4%) and transposition (0.5%). Two DAP features occurred together in 4.7% of children, while three occurred in 0.7%. Infraocclusion (p=.040) and absent teeth (p=.001) occurred more commonly in girls. Phenotypic variations in maxillary lateral incisor more often occurred together (p=.004). Absent teeth, peg-shaped maxillary lateral incisor and delayed dental age more often occurred together (p<.01) as did transposition and absent teeth (p=.016). CONCLUSION: Almost third of the children had dental developmental abnormalities involved in DAP. Absent teeth, peg-shaped lateral incisors and delayed dental age more often occurred together.

Crown heights in the permanent teeth of 47,XXY males and 47,XXX females.

OBJECTIVE: Earlier results based on dental casts and radiographs have shown that additional X and Y chromosomes influence permanent and deciduous tooth crown sizes, with 47,XYY males exhibiting greater crown heights than 46,XY males. We studied here the effect of both X and Y chromosomes on tooth crown heights. MATERIAL AND METHODS: The series consisted of 48 47,XXY males, 22 of their male relatives, and seven 47,XXX females with five female relatives. The population controls consisted of 27 males and 33 females. Measurements of all applicable teeth except for the third molars on both sides of the jaws were made on panoramic radiographs with a sliding digital calliper. RESULTS: Apart from a few teeth, the mean crown heights in the 47,XXY males were greater than those in the male population controls, the differences being statistically significant for one tooth in the maxilla and ten teeth in the mandible. With the exception of two teeth, the 47,XXX females had taller tooth crowns than the female population controls, the differences in the two teeth being statistically significant. The 47,XXY males had greater tooth crown heights than the 47,XXX females, except in one tooth, and the differences were significant in two teeth. The tooth crown heights of the male relatives of the 47,XXY males and the female relatives of the 47,XXX females were close to those in the general population. CONCLUSIONS: The present results demonstrated the effect of additional X and Y chromosomes in increasing crown heights. The differences between the 47,XXY males and 47,XXX females indicated a stronger effect of a Y chromosome on tooth crown height than of an X chromosome.

Distribution of congenitally missing teeth and treatment options for the lower second premolars in patients referred to special care.

OBJECTIVE: The aim was to evaluate the distribution of congenitally missing teeth and the treatment provided for congenitally missing lower second premolars in an eleven-year cohort of patients referred to a publicly funded source of specialist care. MATERIAL AND METHODS: This was a retrospective, register-based cohort study. Search for patients referred to a publicly funded source of specialist care based on ICD10 diagnosis code K00.00 (partial anodontia) and treatment codes EBA00, EBA05, EBA10, EBA12, EBB10 and EBB20 during the period 1.1.2009-27.10.2019 yielded 232 patients (151 females, 81 males), of whom 218, born in 1941-2009, were eligible. Data collected from medical files were presented in the form of descriptive statistics and analysed using Fisher's exact test. RESULTS: The 218 subjects possessed 876 congenitally missing teeth (males 307, females 569) (third molars excluded). The most common missing teeth were upper second premolars and lateral incisors, and lower second premolars and central incisors. No difference in laterality was found. Statistically significant associations were found between the choice of treatment and both the patient's age at referral and the patient's year of birth. Most common treatment for adult patients (age 18-56 years) was placement of an implant (67%), while autotransplantation (11%) was the preferred option for children at the mixed dentition stage (age 9-15 years). CONCLUSIONS: The congenitally missing teeth most commonly involved in referrals of patients to publicly funded specialist care were lower second premolars. The most frequent treatment was insertion of an implant for adults and autotransplantation at the mixed dentition stage.

Profile shape variation and sexual dimorphism amongst middle-aged Northern Europeans.

AIM: To explore profile shape variation in a large population of middle-aged individuals and investigate features of sexual dimorphism. MATERIALS AND METHODS: Facial profile photographs of 1776 individuals (964 females and 812 males; 46 years old), members of the Northern Finland Birth Cohort 1966 (NFBC1966), were uploaded and digitized with Viewbox software. Profile shape was defined with 47 landmarks (4 fixed and 43 sliding semi-landmarks). Digitized images were reoriented and scaled with Procrustes Superimposition, and shape variation was determined with a Principal Component Analysis. RESULTS: More than 90 per cent of profile shape variation was explained by Principal Components (PC) 1-9. PC1, explaining the largest amount of variation (33.1 per cent) described changes in facial convexity, slope of the forehead, lip, and chin protuberance. PC2 (23.1 per cent variation) was more related to vertical changes of the lower facial third and PC3 (11 per cent variation) primarily described changes in lip protrusion and nasal projection. Shape analysis showed a significant difference between the average female and the average male profile shape (P < 0.001); however, this was not evident upon visual observation. The shape variable most associated with sex was PC3 (η 2 = 0.245; P < 0.001), which described changes in lip prominence and in projection of the dorsal nasal surface. An additional discriminant analysis showed that profile shape predicted sex in 76 per cent of males and 79.6 per cent of females. CONCLUSIONS: There is significant sexual dimorphism in facial profile among middle-aged adults. Profile shape variation was associated to changes in lip protrusion, nasal protuberance, and chin projection.

The dental healthcare professionals' competence in mentoring students in the clinical practice.

OBJECTIVE: The aim of this study was to evaluate dentists', dental hygienists' and dental assistants' competence in mentoring students and to identify distinct mentor profiles. METHODS: The study employed a cross-sectional design. Data were collected using the Mentors' Competence Instrument (MCI), which includes 45 items structured under seven mentoring competence sub-dimensions. The data were collected during autumn 2017 from dentists, dental hygienists and dental assistants working in the Finnish primary healthcare (n = 1097) using a paper survey, whilst dentists (n = 26) who have completed mentoring education in one university completed an electronic questionnaire. Cases with more than 5% missing data (n = 164) were listwise deleted, whilst the remaining data (n = 933) underwent analysis. K-mean clustering was used to identify significantly different mentor profiles, whilst comparisons of mentoring competence between the identified profiles were performed with Kruskal-Wallis and Mann-Whitney tests. RESULTS: Three distinct mentor profiles (A, B and C) that differed in the level of mentoring competence were identified. The participants in profile A encompassed mostly dental assistants, profile B included mostly dental assistants and dentists, and profile C mainly comprised dentists and dental assistants. Profiles A, B and C differed significantly in terms of education, job title, role of mentor and participation in mentoring education. The largest difference in competence was observed between participants of profiles A and C. Each profile differed significantly from the other two across all seven competence areas. Most of the participants had not previously received any mentoring education. CONCLUSION: There is room for improvement in the competence of dentistry student mentors, especially regarding knowledge of effective mentoring practices, goal-oriented mentoring, mentor characteristics and motivation for mentoring. Every mentor that works with oral healthcare students should receive mentoring training.

Influence of overjet and overbite on soft tissue profile in mature adults: A cross-sectional population study.

INTRODUCTION: The aim of this study was to explore the association of soft tissue profile and severity of overbite and overjet in a large adult population. METHODS: The study population consisted of 1630 adults (age, 46 years; 712 men, 919 women), all part of the Northern Finland Birth Cohort 1966. A clinical examination was performed on all subjects, including recording of overjet and overbite, and digital facial (frontal and profile) photographs were obtained. A multivariate regression model was developed to study the correlation of soft tissue measurements with overjet and overbite, considering the effect of sex. RESULTS: The regression model explained approximately 30% of the variability in overjet in our sample and approximately 22% of the variability in overbite. Overjet was related more significantly to upper and lower anteroposterior lip position, and upper and lower facial height (P <0.05). Overbite showed a stronger association with anteroposterior position of the lower lip, pogonion, and soft tissue B-point (P <0.05). CONCLUSIONS: Soft tissue profile was weakly to moderately correlated with severity of overjet and overbite in the entire sample. However, in subjects with negative overjet (mandibular prognathism), this association was highly significant.

Association of facial sagittal and vertical characteristics with facial aesthetics in the Northern Finland Birth Cohort 1966.

OBJECTIVE: To explore the association of facial sagittal and vertical dimensions with aesthetic assessment by three panel groups. MATERIALS AND METHODS: The study population comprised adult individuals from the Northern Finland Birth Cohort 1966 (NFBC1966). A clinical oral examination including digital facial photographs was performed. The study population was divided into subjects with the lowest and highest values in soft tissue measurements in lower anterior facial height percentage (LAFH%) (60 subjects) and antero-posterior jaw relationship [soft tissue A-point, nasion, and B-point (ANB) angle; 60 subjects] and a control group (30 subjects). Frontal and profile facial photographs were presented to three panel groups: five orthodontists, five dentists, and five laypersons, who evaluated the photographs using the visual analogue scale (VAS). RESULTS: This study showed significant differences in VAS mean scores between the panel groups. Curve estimation revealed a significant quadratic association between aesthetic VAS evaluation and ANB angle for all panel groups. The association between ANB angle and perceived facial attractiveness was highest among orthodontists (R2 = 0.276, P = 0.001 for males; R2 = 0.285, P = 0.001 for females). However, no statistically significant association was found between facial attractiveness and LAFH%. CONCLUSION: Facial sagittal dimensions appeared to influence facial aesthetics more than vertical dimensions in middle-aged adults. In their perception of facial aesthetics, orthodontists were more influenced by antero-posterior jaw relationships than dentists and laypersons. The overall perception of facial attractiveness related to facial dimensions appeared to differ between the panel groups in female and male faces.

Does headgear treatment in young children affect the maxillary canine eruption path?

Objective: To test whether early headgear (HG) treatment and space conditions in the dental arch affect the eruption pathway of the maxillary canines in young children with mixed dentition. Subjects and methods: Data from two randomized controlled trials studying the effects of early HG treatment were pooled, yielding a study sample comprising 99 children (38 girls and 61 boys, mean age 7.6 years) with Angle Class II occlusion. Fifty-one children were treated with HG and 48 children served as an untreated control group (CG). Digital 3D models and panoramic radiographs were taken before (T0) and after (T1) treatment, and changes in the maxillary canine eruption angle and interdental spaces were measured at T0 and T1. A paired samples t-test was used to assess changes in maxillary canine angulation, and an independent samples t-test was used to evaluate the effect of HG treatment on spacing in the dental arch. Associations between intra-arch space conditions and changes in maxillary canine angulation were estimated with linear regression models. Results: The eruption pattern of the permanent canine was significantly more vertical in the HG group than in the CG. The linear regression models showed a statistically significant association among the intercanine distance, crowding in the anterior part of the maxilla, and changes in the maxillary canine eruption angle. The maxillary canine eruption pattern changed significantly more to a vertical direction in spaced dental arches than in crowded dental arches in the HG group. Conclusion: This study shows that early HG treatment in children with Angle Class II occlusion may change the eruption pattern of permanent maxillary canines to a more vertical direction. This change appears to be related to space conditions in the maxillary arch, especially in the intercanine region, with more effect in children with spaced dental arches than in children with crowded dental arches.

Crown heights in the permanent teeth of 47,XYY males.

OBJECTIVE: The results in human sex chromosome aneuploidies had shown that the extra Y chromosome increases permanent and deciduous tooth crown sizes in the mesiodistal and labiolingual directions. The hypothesis of the study was that the additional Y chromosome increases the permanent tooth crown growth in a vertical dimension. We also aimed to observe possible sex difference in the permanent tooth crown height. MATERIAL AND METHODS: Data on 15 47,XYY males or males with an extra Y chromosome, nine male relatives (five brothers and four fathers) and 45 male and 48 female population controls had been gathered previously for Professor Lassi Alvesalo's KVANTTI Research Project. The measurements from panoramic radiographs were performed of all the applicable teeth, except the third molars on both sides of the jaws with a sliding digital calliper. RESULTS: All the mean tooth crown heights in the 47,XYY males were larger than in the male population controls and the differences were statistically significant in six teeth in the maxilla and 10 teeth in the mandible. Apart from few teeth, the crown heights in the 47,XYY males were larger than in their male relatives, but the difference between these groups was significant only in one tooth. The differences between sexes were statistically significant in eight teeth in the maxilla. CONCLUSIONS: Based on previous investigations and this work, it is evident that the impact of the extra Y chromosome during tooth crown development is holistic, increasing permanent tooth sizes in three dimensions in a balanced manner.

Prevalence of malocclusion traits and orthodontic treatment in a Finnish adult population.

Objective The aim of the study was to examine the prevalence of malocclusion traits and the extent of orthodontic treatment in a Finnish adult population. Materials and methods The study population comprised subjects (n = 1964) from the Northern Finland Birth Cohort 1966 living in the city of Oulu and within 100 km of it. A clinical oral and dental examination with registration of occlusion was carried out in 2012 in connection with a 46-year follow-up survey. Data on previous orthodontic treatment were collected based on a questionnaire. Results In the clinical examination, 39.5% of the subjects had at least one malocclusion trait. The most common malocclusion traits were lateral crossbite (17.9%), overbite ≥ 6 mm (11.7%) and overjet ≥ 6 mm (9.7%). Crossbite on the left premolars, negative overjet and increased overbite were found more frequently in men. The prevalence of malocclusion traits was at the same level in treated and untreated groups. Overall, 18.6% of the subjects had undergone orthodontic treatment. Women showed a significantly higher prevalence of orthodontic treatment. Conclusions The most common malocclusion trait in the present study was lateral crossbite. Significant male dominance in the prevalence of malocclusion was observed, which has not been reported earlier in Finland. Orthodontic treatment of malocclusion traits was more common among females in Northern Finland. This study indicates that orthodontic treatment provided in childhood was, on average, adequate in reducing malocclusion traits to the level observed in the general population.

Genome-wide association study of primary tooth eruption identifies pleiotropic loci associated with height and craniofacial distances.

Twin and family studies indicate that the timing of primary tooth eruption is highly heritable, with estimates typically exceeding 80%. To identify variants involved in primary tooth eruption, we performed a population-based genome-wide association study of 'age at first tooth' and 'number of teeth' using 5998 and 6609 individuals, respectively, from the Avon Longitudinal Study of Parents and Children (ALSPAC) and 5403 individuals from the 1966 Northern Finland Birth Cohort (NFBC1966). We tested 2 446 724 SNPs imputed in both studies. Analyses were controlled for the effect of gestational age, sex and age of measurement. Results from the two studies were combined using fixed effects inverse variance meta-analysis. We identified a total of 15 independent loci, with 10 loci reaching genome-wide significance (P < 5 × 10(-8)) for 'age at first tooth' and 11 loci for 'number of teeth'. Together, these associations explain 6.06% of the variation in 'age of first tooth' and 4.76% of the variation in 'number of teeth'. The identified loci included eight previously unidentified loci, some containing genes known to play a role in tooth and other developmental pathways, including an SNP in the protein-coding region of BMP4 (rs17563, P = 9.080 × 10(-17)). Three of these loci, containing the genes HMGA2, AJUBA and ADK, also showed evidence of association with craniofacial distances, particularly those indexing facial width. Our results suggest that the genome-wide association approach is a powerful strategy for detecting variants involved in tooth eruption, and potentially craniofacial growth and more generally organ development.

Molar morphology and the expression of Carabelli's trait in 45,X females.

OBJECTIVES: The purpose of this study was to observe the expression of Carabelli's trait in maxillary first (M1) and second (M2) permanent molars in relation to tooth crown size and cusp number and to consider the role of the shortage of sex chromosome material in these features during tooth crown development. METHODS: The data were derived from dental casts belonging to the KVANTTI Research Project on sex chromosome abnormalities headed by Professor Lassi Alvesalo in Finland. The subjects comprised 86 45,X females, 51 first-degree female relatives, and 150 population control females. Carabelli's trait was divided into three grades and cusp number was classified into two classes in Dahlberg's P12 and P9. The tooth crown diameters were measured with a sliding digital caliper. RESULTS: M1 in the 45,X females expressed a lower frequency of Carabelli's trait (19.8%) than in the female relatives (37.2%, P < 0.05). There was also a higher frequency of the three-cusp pattern (11.1%) than in the female relatives (2.4%, P = 0.055) or the control females (1.3%, P < 0.001). The expression of Carabelli's trait in M2 was of the same magnitude in the 45,X females and normal controls and was related to tooth crown size, whereas its expression in M1 of the 45,X females was associated with the cusp number rather than the tooth crown size. CONCLUSIONS: The shortage of one X chromosome in females has an influence on the morphology of the lingual cingulum region of the maxillary first permanent molar during tooth crown development.

Root resorptions related to ectopic and normal eruption of maxillary canine teeth - A 3D study.

OBJECTIVE: To assess the incidence and severity of root resorption of maxillary incisors caused by ectopically and normally erupting maxillary canines and to analyse factors influencing root resorption of incisors using cone beam computed tomography. SUBJECTS AND METHODS: The study sample comprised 59 patients with a total of 80 canines. Forty-six of the canines, in 37 patients, were defined as ectopic and 34 canines, in 22 patients, were defined as normal. The severity of root resorptions were analysed according to studies by Ericson and Kurol. Multiple logistics regression was used to evaluate the association between various factors and root resorptions. RESULTS: The prevalence of root resorptions was significantly higher in the ectopic canine group, 11.0% of the central incisors and 67.6% of the lateral incisors in comparison to 0% and 36.2% in the normal erupting group. Most resorptions were defined as 'slight' and were located in the middle third of the root. There was a statistically significant relationship between canines located mesial to the midline of the lateral incisor and root resorption on the maxillary incisors. CONCLUSION: The present results show that root resorption of maxillary lateral incisors was common in patients referred to CBCT imaging due to maxillary canine eruption disturbances. Although significantly more frequent in patients with ectopically erupting canines, lateral incisor resorption was also found in association with approximately every third of the normally erupting canines. The best predictor for root resorption seemed to be location of the canine mesial in relation to the midline of the lateral incisor root.

Crown heights in the permanent teeth of 45,X and 45,X/46,XX females.

OBJECTIVE: Previous results regarding human sex chromosome aneuploidies have shown that the X and Y chromosomes affect tooth size and morphology. This study looked for the effect of sex chromosome deficiency on permanent tooth crown heights. MATERIALS AND METHODS: The material, from the Finnish KVANTTI Research Project, consisted of 97 45,X females and 15 45,X/46,XX females. The controls were 32 sisters and 28 mothers of the 45,X females, eight sisters and two mothers of the 45,X/46,XX females and 35 female population controls. Crown heights of all the available teeth except third molars on both sides of the jaws were measured from panoramic radiographs with a digital calliper according to the defined procedure. RESULTS: The tooth crown heights were significantly smaller in the 45,X females than in the female population controls, except for the incisors and one canine in the maxilla, whereas the tooth crown heights of the 45,X/46,XX females were close to those of the normal control females. The differences between the 45,X and 45,X/46,XX females were statistically significant, excluding the upper incisor area and a few teeth in the mandible. CONCLUSIONS: The effect of the sex chromosome deficiency on permanent tooth crown height is due to the magnitude of lacking sex chromosome material. The present results regarding the 45,X females are parallel to previous findings in Turner patients regarding reduced mesiodistal and labiolingual dimensions and tooth crown heights in the permanent dentition.

Genome-wide association study reveals multiple loci associated with primary tooth development during infancy.

Tooth development is a highly heritable process which relates to other growth and developmental processes, and which interacts with the development of the entire craniofacial complex. Abnormalities of tooth development are common, with tooth agenesis being the most common developmental anomaly in humans. We performed a genome-wide association study of time to first tooth eruption and number of teeth at one year in 4,564 individuals from the 1966 Northern Finland Birth Cohort (NFBC1966) and 1,518 individuals from the Avon Longitudinal Study of Parents and Children (ALSPAC). We identified 5 loci at P<5x10(-8), and 5 with suggestive association (P<5x10(-6)). The loci included several genes with links to tooth and other organ development (KCNJ2, EDA, HOXB2, RAD51L1, IGF2BP1, HMGA2, MSRB3). Genes at four of the identified loci are implicated in the development of cancer. A variant within the HOXB gene cluster associated with occlusion defects requiring orthodontic treatment by age 31 years.

Root lengths in the permanent teeth of 45,X females.

OBJECTIVE: Studies in permanent and deciduous tooth crowns and permanent tooth roots in individuals with sex chromosome anomalies and in their relatives have given proof that the X chromosome affects enamel formation, root length and crown and root morphology. The present research studies the effects of sex chromosome deficiency on the development of permanent tooth root. MATERIALS AND METHODS: This research investigated tooth root lengths in a group of 97 45,X females. As controls there were 32 sisters and 28 mothers of the 45,X females, 45 female and 42 male population controls and 15 45,X/46,XX females from the KVANTTI research project. Tooth root lengths on both sides of the jaws were measured from panoramic radiographs in each acceptable instance. RESULTS: The results showed significantly shorter tooth root lengths in the 45,X females than in the female and male controls in all teeth measured, whereas in the female relatives tooth root lengths were shifted towards the aneuploids in relation to that in the general population. The tooth root lengths in the 45,X females differed more from those found in their sisters than in their mothers. CONCLUSIONS: These results with the large pure sample size of the whole dentitions in patients with monosomy X confirm the earlier findings of short tooth roots in 45,X females. The fact that in most instances there were no significant differences in tooth root lengths between 45,X and 45,X/46,XX females comes close to the earlier findings regarding mesio-distal tooth crown sizes.

Effectiveness of mentoring education on health care professionals´ mentoring competence: A systematic review.

BACKGROUND: Different types of educational approaches are needed to build a mentor's competence in guiding students during clinical practice; this education should be provided in an interprofessional setting. OBJECTIVES: The objective of this review was to evaluate how effective mentoring education interventions are at improving mentoring competence among health care professionals. DESIGN: A systematic review. DATA SOURCES: A systematic search was conducted across five electronic databases: CINAHL, PubMed, ProQuest, Scopus, and Medic. The search did not have any time limitations and included original studies published in English, Finnish or Swedish. REVIEW METHODS: JBI critical appraisal tools for quasi-experimental studies and randomized controlled trials were used to assess the quality of the selected studies. The eligibility of potentially relevant studies was assessed by two independent researchers based on title, abstract, and full text, along with overall methodological quality. The study findings were synthesized using data tabulation and narrative analysis. RESULTS: A total of two randomized controlled trials and six quasi-experimental studies were included in the review. The described mentoring education interventions were carried out in university hospitals, central hospitals, tertiary care centers, and other health service settings. All of the described educational interventions involved the pedagogical method of blended learning, while three studies also involved web-based learning. The presented educational interventions included versatile pedagogical frameworks, e.g., interactive practical training sessions, teaching workshops, and technology-mediated interactions. One study contained a control group. CONCLUSION: This systematic review can provide insight and evidence-based that can be used to design effective mentoring education. Further research is needed and would ideally include randomized controlled trials and quasi-experimental studies with reference groups; this type of research could further elucidate which aspects of mentoring education are most important for improving the guidance skills of health care professionals.

Incisor Occlusion Affects Profile Shape Variation in Middle-Aged Adults.

BACKGROUND: The aim of this study was to assess the effect of overjet and overbite on profile shape in middle-aged individuals. METHODS: The study population comprised 1754 46-year-old individuals, members of the 1966 Northern Finland Birth Cohort. Their profile images were digitized using 48 landmarks and semi-landmarks. The subsequent landmark coordinates were then transformed to shape coordinates through Procrustes Superimposition, and final data were reduced into Principal Components (PCs) of shape. Overjet and overbite values were measured manually, during a clinical examination. A multivariate regression model was developed to evaluate the effect of overjet and overbite on profile shape. RESULTS: The first nine PCs described more than 90% of profile shape variation in the sample and were used as the shape variables in all subsequent analyses. Overjet predicted 21.3% of profile shape in the entire sample (η2overjet = 0.213; p < 0.001), while the effect of overbite was weaker (η2overbite = 0.138; p < 0.001). In males, the equivalent effects were 22.6% for overjet and 14% for overbite, and in females, 25.5% and 13.5%, respectively. CONCLUSION: Incisor occlusion has a noteworthy effect on profile shape in middle-aged adults. Its impact becomes more significant taking into consideration the large variety of genetic and environmental factors affecting soft tissue profile.

Root length in the permanent teeth of women with an additional X chromosome (47,XXX females).

OBJECTIVE: Previous studies have demonstrated differential effects of the X and Y chromosomes on dental development. The expression of sexual dimorphism in terms of tooth size, shape, number and developmental timing has been explained especially by Y chromosome influence. The Y chromosome promotes enamel, crown and root dentin development. The X chromosome has an effect on enamel deposition. The aim of this research is to study the influence of the extra X chromosome on the development of permanent tooth root length. MATERIAL AND METHODS: The study subjects (all of whom were from the Kvantti Dental Research Project) were seven 47,XXX females, five female relatives and 51 and 52 population control men and women, respectively. Measurements were made from panoramic radiographs on available permanent teeth by a digital calliper according to established procedures. RESULTS: The results showed that the maxillary root lengths of the 47,XXX females were of the same magnitude as those in normal women, but the mandibular root lengths were longer in 47,XXX females than in normal men or women. CONCLUSIONS: Increased enamel thickness in the teeth of 47,XXX females is apparently caused by the active enamel gene in all X chromosomes having no increased influence on crown dentin formation. These results in 47,XXX females indicate an increase in root dentin development, at least in the mandible, which together with the data on crown formation reflects a continuous long-lasting effect of the X chromosome on dental development.