MRI susceptibility artefacts caused by orthodontic wire.

OBJECTIVES: To evaluate magnetic susceptibility artefacts produced by orthodontic wires on MRI and the influence of wire properties and MRI image sequences on the magnitude of the artefact. METHODS: Arch form orthodontic wires [four stainless steels (SS), one cobalt chromium (CC) alloy, 13 titanium (Ti) alloys] were embedded in a polyester phantom, and scanned using a 1.5-T superconducting magnet scanner with an eight-channel phased-array coil. All wires were scanned with T1-weighted spin echo (SE) and gradient echo (GRE) sequences according to the American Society for Testing and Materials (ASTM) F2119-07 standard. The phantom also scanned other eight sequences. Artefacts were measured using the ASTM F2119-07 definition and OsiriX software. Artefact volume was analysed according to metal composition, wire length, number of wires, wire thickness, and imaging sequence as factors. RESULTS: With SE/GRE, black/white artefacts volumes from all SS wires were significantly larger than those produced by CC and Ti wires (P < .01). With the GRE, the black artefacts volume was the highest with the SS wires. With the SE, the black artefacts volume was small, whereas white artefacts were noticeable. The cranio-caudal extent of the artefacts was significantly longer with SS wires (P < .01). Although a direct relationship of wire length, number of wires, and wire thickness with artefact volume was noted, these factors did not influence artefact extension in the cranio-caudal direction. CONCLUSIONS: Ferromagnetic/paramagnetic orthodontic wires create artefacts due to local alteration of magnetic field homogeneity. The SS-type wires produced the largest artefacts followed by CC and Ti.

Comparison of 3-D mandibular surfaces generated by MRI and CT.

OBJECTIVE: The purpose of this study was to evaluate the errors of three-dimensional mandibular surfaces generated using magnetic resonance imaging (MRI) when computed tomography (CT) was set as the gold standard. SETTINGS AND SAMPLE POPULATION: Seven patients with orthognathic deformities who had undergone CT and MRI scans were included in the study. MATERIALS AND METHODS: Mandibular surfaces were generated on each CT and MR image by the surface-rendering method. Intra-individual reliability between CT and MRI was statistically tested by the confidence limits of agreement (LOA) for systematic error, 95% confidence interval minimal detectable change (MDC95 ) for random error and intra-class correlation coefficient (ICC). RESULTS: The average total error was 1.6 mm. The greatest MDC95 was observed in the coronoid region in all directions. The other regions showed MDC95 values of < 1.8 mm (transvers direction), 3.5 mm (vertical direction) and 1.7 mm (antero-posterior direction). ICCs showed 'almost perfect' agreement with respect to all regions. CONCLUSION: Random errors were quantified for 3-D rendering of the mandible from MRI data. Although the coronoid region showed the greatest errors, the other regions of the mandibular surfaces generated using MRI were able to be evaluated.

Dental Subphenotypes in Infants With Orofacial Clefts-A Longitudinal Population-Based Retrospective Radiographic Study of the Primary and Secondary Dentitions.

OBJECTIVES: To determine the developmental patterns of primary and secondary dentitions in infants with orofacial clefts. DESIGN: Retrospective, longitudinal, population-based cohort study. MATERIALS: Longitudinal records and radiographs of 192 nonsyndromic Northern European infants with isolated unilateral cleft lip (UCL, n = 111) and isolated cleft palate (CP, n = 81). METHODS: Radiographic assessments of primary and secondary dentition anomalies and dental maturation, by gender and cleft severity for comparisons between the groups and with historical controls. RESULTS: In infants with UCL, the frequencies of dental anomalies were high in both primary (38.7%) and secondary (18.0%) dentitions. Primary and secondary dentition anomalies were not observed in infants with CP and different in the UCL group (P = .003). Risk differences involved primary supernumerary teeth (P = .0001) and talon cusp formation (P = .0001), and secondary tooth agenesis (P = .001) of the maxillary lateral incisor on the side of the cleft lip. Delayed primary and secondary dental maturation occurred in the UCL and CP groups, greater in infants with UCL (P < .0001). Primary and secondary dental maturation featured sexual dimorphism with greater delay in males (UCL, P < .0001; CP, .0001 > P = .001). The effect of cleft severity on dental maturation was significant in infants with UCL (P = .0361) and CP (P = .0175) in the primary but not in the secondary dentition. CONCLUSIONS: There were different dental anomalies in the primary and secondary dentitions in operated infants with UCL and no dental anomalies in unoperated infants with CP. Dental maturation was delayed in infants with UCL and CP with greater delay in males compared to females.

Facial Asymmetry in Nonsyndromic and Muenke Syndrome-Associated Unicoronal Synostosis: A 3-Dimensional Study Based on Facial Surfaces Extracted From CT Scans.

OBJECTIVE: To quantify soft tissue facial asymmetry (FA) in children with nonsyndromic and Muenke syndrome-associated unicoronal synostosis (NS-UCS and MS-UCS), hypothesizing that MS-UCS presents with significantly larger FA than NS-UCS. DESIGN: Retrospective cohort study. PATIENTS AND METHODS: Twenty-one children (mean age: 0.6 years; range: 0.1-1.4 years) were included in the study (NS-UCS = 14; MS-UCS = 7). From presurgical computed tomography scans, facial surfaces were constructed for analysis. A landmark guided atlas was deformed to match each patient's surface, obtaining spatially detailed left-right point correspondence. Facial asymmetry was calculated in each surface point across the face, as the length (mm) of an asymmetry vector, with its Cartesian components providing 3 directions. Mean FA was calculated for the full face, and the forehead, eye, nose, cheek, mouth, and chin regions. RESULTS: For the full face, a significant difference of 2.4 mm (P = .001) was calculated between the 2 groups, predominately in the transverse direction (1.5 mm; P < .001). The forehead and chin regions presented with the largest significant difference, 3.5 mm (P = .002) and 3.2 mm (P < .001), respectively; followed by the eye (2.4 mm; P = .004), cheek (2.2 mm; P = .004), nose (1.7 mm; P = .001), and mouth (1.4 mm; P = .009) regions. The transverse direction presented with the largest significant difference in the forehead, chin, mouth, and nose regions, the sagittal direction in the cheek region, and the vertical direction in the eye region. CONCLUSIONS: Muenke syndrome-associated unicoronal synostosis presented with significantly larger FA in all regions compared to NS-UCS. The largest significant differences were found in the forehead and chin regions, predominantly in the transverse direction.

Description of a family with X-linked oculo-auriculo-vertebral spectrum associated with polyalanine tract expansion in ZIC3.

Oculo-auriculo-vertebral spectrum (OAVS) [MIM:164210], or Goldenhar syndrome, is a developmental disorder associating defects of structures derived from the first and second branchial arches. The genetic origin of OAVS is supported by the description of rare deleterious variants in a few causative genes, and several chromosomal copy number variations. We describe here a large family with eight male members affected by a mild form of the spectrum, mostly auricular defects, harboring a hemizygous ZIC3 variant detected by familial exome sequencing: c.159_161dup p.(Ala55dup), resulting in an expansion of the normal 10 consecutive alanine residues to 11 alanines. Segregation analysis shows its presence in all the affected individuals, with a recessive X-linked transmission. Whole-genome sequencing performed in another affected male allowed to exclude linkage disequilibrium between this ZIC3 variant and another potential pathogenic variant in this family. Furthermore, by screening of a cohort of 274 OAVS patients, we found 1 male patient carrying an expansion of 10 to 12 alanines, a variant previously reported in patient presenting with VACTERL. Loss-of-function variants of ZIC3 are causing heterotaxy or cardiac malformations. These alanine expansion variants could have a different impact on the protein and thereby resulting in a different phenotype within the OAVS/VACTERL.

Delayed maturation and reduced crown width of the permanent first mandibular molar in all subgroups of cleft lip and palate.

OBJECTIVES: Surgical closure of the cleft damages nerves and blood supply in the area and may possibly negatively influence dental development in children with cleft lip and palate (CLP). Previous studies of the permanent first mandibular molar (M1inf ) in children with unilateral complete CLP found delayed maturation and decreased follicle/crown width before any surgical interventions. This study aimed to investigate if these findings are representative for the total population of individuals born with CLP. SETTING AND SAMPLE POPULATION: A population-based consecutive longitudinal sample of 224 children with clefts: 183 with CLP (66 with complete [47 unilateral, 19 bilateral], 117 with incomplete [70 unilateral, 47 bilateral], and 41 with unilateral incomplete cleft lip (controls), was examined pre- and post-lip closure (at 2 and 22 months of age). MATERIAL AND METHODS: In lateral cephalometric X-rays (obtained as part of a standard treatment protocol), M1inf follicle maturation and follicle/crown width were assessed. Mantel-Haenszel test and Pearson's correlation coefficient R were used to describe relationships. Differences between group means were tested using Wilcoxon rank sum test. Significance level was set to 5%. RESULTS: Follicle maturation was significantly delayed in all groups with CLP compared to that in controls (P < .01). Follicle and crown width were significantly reduced in all CLP groups compared with those in controls (P < .01). Sex did not influence these variables. CONCLUSION: Delayed follicle maturation and decreased follicle/crown/tooth size were found to be part of the congenital traits characterizing individuals with all types of CLP and not a result of surgical iatrogenesis.

Three-dimensional assessment of facial morphology in children and adolescents with juvenile idiopathic arthritis and moderate to severe TMJ involvement using 3D surface scans.

OBJECTIVE: This study aims to (1) assess the facial morphology in juvenile idiopathic arthritis (JIA) subjects with moderate to severe temporomandibular joint (TMJ) involvement using 3D surface scans and (2) compare the facial morphology in these subjects to that in JIA subjects without TMJ involvement. METHODS: Sixty JIA subjects were included and grouped as follows: group 1 (no involvement group), JIA without TMJ involvement; Group 2 (unilateral group), JIA with moderate to severe unilateral TMJ involvement; and group 3 (bilateral group), JIA with bilateral TMJ involvement. Standard orientation of all surfaces was accomplished. The means and variabilities of facial morphology in groups 2 and 3 were assessed and compared with those of group 1 in three dimensions, respectively. RESULTS: Group 2 (unilateral group) exhibited a more retruded and wider chin, shorter mandibular height, and more prominent cheek (2, 2, 5, and 2 mm, on average, respectively) on the affected side and a more retruded and narrower chin and more prominent malar region (4, 3, and 2 mm, on average, respectively) on the unaffected side compared with group 1 (no involvement group) (p < 0.05). Group 3 (bilateral group) exhibited a more retruded chin, shorter mandibular height, more prominent upper cheeks, and narrower perioral region (5, 5, 3, and 2 mm, respectively) compared with group 1 (no involvement group) (p < 0.05). CONCLUSIONS: In JIA subjects with moderate to severe unilateral or bilateral TMJ involvement, the affected side(s) revealed similar facial dysmorphology with reduced mandibular height, chin retrusion, and prominent upper cheek. CLINICAL RELEVANCE: Three-dimensional surface scans can be a non-ionizing indicator of signs of TMJ involvement in JIA subjects.

Spatially Detailed 3D Quantification of Improved Facial Symmetry After Surgery in Children With Unicoronal Synostosis.

OBJECTIVE: To assess improvement of soft-tissue facial symmetry in children surgically treated for unicoronal synostosis (UCS) in infancy, to correlate pre- and postsurgical facial asymmetry and to evaluate whether the improvement was visually recognizable. DESIGN: Case-controlled follow-up. PATIENTS/SETTINGS: Eleven Danish children diagnosed with UCS were included, 3 of whom had tested positive for Muenke mutation. Preoperative computed tomography scans and postoperative 3dMD surfaces were available for measurements. A control group of healthy children matched for age and sex was employed. MAIN OUTCOME MEASURES: Pre- and postsurgical facial asymmetry was analyzed using a computerized method capable of objective and spatially detailed quantification in 3-dimension (transverse, vertical, and sagittal directions). Asymmetry was evaluated in the facial region and 6 subregions (forehead, mouth, eyes, nose, cheek, and chin). RESULTS: The largest significant improvement was seen in the sagittal direction of the facial (1.9 mm), forehead (2.0 mm), and cheek (3.4 mm) regions. Small but significant improvements were also seen in the mouth, chin, and eye regions. No significant improvement was seen in the nose region. Significant correlations were found between the pre- and postsurgically calculated facial asymmetry and between calculated asymmetry and clinical validation scores. CONCLUSIONS: All patients presented with improved facial symmetry after surgery and the improvements were visually recognizable. However, only 1 (9.1%) of the 11 patients reached a level of facial asymmetry as low as that seen in the control group. The best outcome was, in general, seen in cases with mild facial asymmetry presurgically.

Tooth formation and eruption - lessons learnt from cleidocranial dysplasia.

The principles of formation, renewal, and eruption of teeth are discussed. Numerous genetic aberrations may affect the formation and eruption of teeth. Cleidocranial dysplasia (CCD), caused by mutations in the runt-related transcription factor 2 (RUNX2) gene, is such a condition. The dental phenotype includes problems in both tooth formation (multiple supernumerary permanent teeth) and tooth eruption (lack of shedding of primary teeth and delayed or arrested eruption of permanent teeth). Clinical studies, animal models, and molecular biology studies have documented that RUNX2 is of paramount importance for osteoblast differentiation, for regression of the dental lamina, and for osteoclastogenesis in the dental follicle and the periodontal ligament. Jensen & Kreiborg, 25 yr ago, proposed a treatment strategy to be applied to patients with CCD, focussing on the importance of early treatment to promote spontaneous eruption of permanent teeth through extraction of primary teeth, surgical removal of supernumerary teeth, and removal of bone covering the first formed permanent teeth at the time when root formation of the permanent teeth has reached half or two-thirds of their final length. This strategy still seems valid and seems to lead to reduction in the burden of care for patients compared with the treatment protocols otherwise recommended.

Parental age in relation to the severity of cleft lip and/or palate.

OBJECTIVE: To investigate parental age in relation to the severity of cleft diagnosis in a population-based consecutive sample of individuals with clefts. SETTING/SAMPLE: Retrospective, consecutive. MATERIAL/METHODS: The sample comprised 545 consecutive cases with nonsyndromic clefts (437 individuals with cleft lip with/without cleft palate [CL ± P] and 106 individuals with isolated cleft palate [CP]) and parental ages recorded. The groups were subdivided according to the extent/severity of cleft. Unilateral clefts were divided according to left/right sidedness. Logistic regression was used to analyse the association between parental age and risk of severe cleft separately for CL ± P and CP, as well as between parental age and risk of right-sided cleft. RESULTS: In CL ± P, the risk of a complete cleft in the offspring increases with maternal age when the paternal age exceeds approximately 29 years. Moreover, the risk is higher when both parents are old than when both parents are young. In CP, no statistically significant results were identified. However, there were clear trends that indicated a similar pattern as that for CL ± P. No association was identified between increased parental age and the sidedness of clefts. CONCLUSIONS: Parental age seems to contribute to cleft severity, as older parents showed a higher risk of having offspring with a complete cleft than younger parents.

Phenotypic subregions within the split-hand/foot malformation 1 locus.

Split-hand/foot malformation 1 (SHFM1) is caused by chromosomal aberrations involving the region 7q21.3, DLX5 mutation, and dysregulation of DLX5/DLX6 expression by long-range position effects. SHFM1 can be isolated or syndromic with incomplete penetrance and a highly variable clinical expression, possibly influenced by sex and imprinting. We report on a new family with five affected individuals with syndromic SHFM1 that includes split-hand/foot malformations, hearing loss, and craniofacial anomalies, and an inv(7)(q21.3q35) present both in the proband and her affected son. The proximal inversion breakpoint, identified by next generation mate-pair sequencing, truncates the SHFM1 locus within the regulatory region of DLX5/6 expression. Through genotype-phenotype correlations of 100 patients with molecularly characterized chromosomal aberrations from 32 SHFM1 families, our findings suggest three phenotypic subregions within the SHFM1 locus associated with (1) isolated SHFM, (2) SHFM and hearing loss, and (3) SHFM, hearing loss, and craniofacial anomalies, respectively (ranked for increasing proximity to DLX5/6), and encompassing previously reported tissue-specific enhancers for DLX5/6. This uniquely well-characterized cohort of SHFM1 patients allowed us to systematically analyze the recently suggested hypothesis of skewed transmission and to confirm a higher penetrance in males vs. females in a subgroup of patients with isolated SHFM.

Facial Asymmetry in Children with Unicoronal Synostosis Who Have Undergone Craniofacial Reconstruction in Infancy.

OBJECTIVE: Quantitatively assess 3D spatially detailed soft-tissue facial asymmetry in children who had undergone craniofacial reconstruction for Unicoronal Synostosis (UCS), and compare the facial asymmetry to control patients. It was hypothesized that there would be no significant differences in the facial asymmetry between the groups. DESIGN: Clinical, retrospective follow-up study. Methodological study. SETTING: Primary care center. PATIENTS/PARTICIPANTS: Twenty-two children with UCS were selected after review of records. INCLUSION CRITERIA: isolated UCS; surgically treated for UCS within the first 19 months of life, without secondary reconstruction; and DNA analysis for the Muenke mutation. An age- and sex-matched control group was employed. INTERVENTIONS: The UCS group had undergone bilateral craniotomy of the frontal bone with unilateral supraorbital rim advancement. MAIN OUTCOME MEASURE(S): Using 3D surface scanning, a detailed map of 3D asymmetry presenting the amount of asymmetry in the sagittal, vertical, and transverse directions was calculated for six facial subregions. RESULTS: The facial asymmetry in the UCS group was significantly larger than in the control group for all regions, to the largest extent in the sagittal direction (level of significance: 5%). The regions with the most pronounced asymmetry were cheeks (mean: 5.45 mm; SD: 1.83 mm), forehead (mean: 5.00 mm; SD: 1.57 mm), and eyes (mean: 4.26 mm; SD: 1.44 mm). CONCLUSIONS: Ninety percent of the UCS patients in the study had significant facial asymmetry throughout the facial area. The study demonstrates a methodology of facial asymmetry quantification well suited for soft-tissue surgical outcome evaluations and long-term follow-up studies in patients with craniofacial anomalies.

Facial morphology in children and adolescents with juvenile idiopathic arthritis and moderate to severe temporomandibular joint involvement.

INTRODUCTION: The aims of this study were to (1) assess lateral facial morphology in children and adolescents with juvenile idiopathic arthritis and moderate to severe temporomandibular joint (TMJ) involvement, (2) compare the lateral facial morphology of these subjects with and without TMJ involvement using cephalograms and 3-dimensional (3D) facial photographs, and (3) compare and correlate the results of the 3D photographic and cephalometric analyses. METHODS: Sixty patients with juvenile idiopathic arthritis were included and grouped as follows: group 1, juvenile idiopathic arthritis patients without TMJ involvement; group 2, juvenile idiopathic arthritis patients with moderate to severe unilateral TMJ involvement; and group 3, juvenile idiopathic arthritis patients with moderate to severe bilateral TMJ involvement. Lateral cephalograms were used to assess and compare lateral facial morphologies between the groups. Lateral projections of oriented 3D photographs were superimposed on the lateral cephalograms. The results of the lateral 3D photographic analysis were correlated with those of lateral cephalometric analysis. RESULTS: Group 3 showed the most severe growth disturbances, including more retrognathic mandible and retruded chin, steep occlusal and mandibular planes, and more hyperdivergent type (P <0.01). Group 2 showed similar growth disturbances, but to a lesser extent than did group 3. Photographic variables were significantly correlated with the soft tissue and skeletal variables of cephalograms (0.5 < r < 0.9; P <0.001). CONCLUSIONS: Subjects with juvenile idiopathic arthritis and unilateral or bilateral moderate to severe TMJ involvement had significant growth disturbances. Early intervention is recommended for these patients to prevent unfavorable facial development. Furthermore, with proper orientation, 3D photographs can be used as an alternative to conventional lateral cephalograms and 2-dimensional photographs.

Inactivation of IL11 signaling causes craniosynostosis, delayed tooth eruption, and supernumerary teeth.

Craniosynostosis and supernumerary teeth most often occur as isolated developmental anomalies, but they are also separately manifested in several malformation syndromes. Here, we describe a human syndrome featuring craniosynostosis, maxillary hypoplasia, delayed tooth eruption, and supernumerary teeth. We performed homozygosity mapping in three unrelated consanguineous Pakistani families and localized the syndrome to a region in chromosome 9. Mutational analysis of candidate genes in the region revealed that all affected children harbored homozygous missense mutations (c.662C>G [p.Pro221Arg], c.734C>G [p.Ser245Cys], or c.886C>T [p.Arg296Trp]) in IL11RA (encoding interleukin 11 receptor, alpha) on chromosome 9p13.3. In addition, a homozygous nonsense mutation, c.475C>T (p.Gln159X), and a homozygous duplication, c.916_924dup (p.Thr306_Ser308dup), were observed in two north European families. In cell-transfection experiments, the p.Arg296Trp mutation rendered the receptor unable to mediate the IL11 signal, indicating that the mutation causes loss of IL11RA function. We also observed disturbed cranial growth and suture activity in the Il11ra null mutant mice, in which reduced size and remodeling of limb bones has been previously described. We conclude that IL11 signaling is essential for the normal development of craniofacial bones and teeth and that its function is to restrict suture fusion and tooth number. The results open up the possibility of modulation of IL11 signaling for the treatment of craniosynostosis.

MR appearance of a rare ameloblastic fibroma with formation of dental hard tissues with histopathologic correlation: a case report.

An ameloblastic fibroma with formation of dental hard tissues, which the classical name is ameloblastic fibro-odontoma (AFO), is a rare type of mixed odontogenic tumor. An 8-year-old boy was diagnosed with AFO, with an inhomogeneous high signal within the lesion shown by T2-weighted magnetic resonance imaging (MRI). Computed tomography (CT) imaging revealed a unilocular low CT value area of 24 × 19 × 26 mm with buccolingual bony expansion and cortical bone thinning on the left side of the mandible including the crown of the mandibular left second molar. In addition, multiple calcified bodies were detected within the lesion, one of which had a CT value of approximately 2200 HU, equivalent to that of enamel. MRI indicated the lesion to be sized 24 × 19 × 25 mm along with buccolingual bony expansion in the left side of the mandible. Additionally, the lesion showed an internal inhomogeneous high signal, while a portion had an especially high signal in T2-weighted images. That particularly high signal area coincided with the nodular growth area of mucus-rich mesenchymal components without the epithelial component in histopathology findings. The particularly high signal revealed by T2-weighted imaging could be attributed to the mucus-rich component. MRI was found useful for revealing differences in the internal histopathological properties of an AFO in our patient.

Spring-assisted cranioplasty for bicoronal synostosis.

BACKGROUND: Numerous surgical techniques for cranial reconstruction of patients with bicoronal synostosis have been suggested. The outcome is, however, still often suboptimal. METHODS: Since 2005, we have, at the Craniofacial Unit, Sahlgrenska University Hospital, Gothenburg, used a standardized surgical technique with advancement and remodeling of the forehead combined with spring distraction of the occipital area. The aim of the current study was to evaluate this operative technique. Eighteen consecutive patients (9 boys and 9 girls) with bicoronal synostosis operated on using this technique were identified. Sixteen patients had syndromic bicoronal synostosis, and 2 had nonsyndromic bicoronal synostosis. Cephalic index was obtained from three-dimensional computed tomography scans, and photographs were analyzed for aesthetic evaluation. RESULTS: The preoperative calvarial shape was hyperbrachycephalic in all subjects. Postoperatively, the calvarial shape was, in general, much closer to the norm. The reduction in the mean cephalic index from the preoperative stage (94) to the 3-year follow-up (82) was statistically significant (P < 0.0001). The mean duration of surgery was 155 (SD, 32) minutes, with a mean perioperative bleeding of 237 (SD, 95) mL. The mean hospital stay was 6.3 (SD, 1.5) days, of which the mean intensive care unit stay was 1.6 (SD, 1.2) days. In 2 patients, one of the springs had to be reinserted because of postoperative dislocation. No other major complications were observed. CONCLUSIONS: Spring-assisted cranioplasty for bicoronal synostosis is a safe technique, is less invasive than many other cranioplasties, and results in marked improvement in the calvarial shape.

Three-dimensional analysis of the pulp cavity on surface models of molar teeth, using X-ray micro-computed tomography.

AIM: The purpose of this study was to investigate the scanning and segmentation precision of surface models of molars for the detection of small volumes, such as the reduced pulp cavity; formation of mineral deposits; detection of narrow root canals and to improve the clinical and morphological understanding of the number of root canals and their configuration. METHODS: Eighteen human molars were scanned using X-ray micro-computed tomography. The reconstruction of the surface models had a precision of <1 voxel, using three-dimensional software and quantitative color mapping. In order to relate the measurements to changes over time the size of the pulp chambers was classified in two well-defined groups. RESULTS: The mineral deposits were more evenly distributed in small pulp chambers than in large, but complete root canal calcification was never observed. No difference was observed in the material with respect to the presence of intra-radicular connections. In upper molars, a second mesiobuccal canal (mb(2)) frequency of 91% was found. The difference in length between the first mesiobuccal canal (mb(1)) and mb(2) was <1 mm. The number of root canals could be related to the number of root cones. CONCLUSION: In summary, three-dimensional surface models were made with a high precision; an increased accumulation of mineral deposits was noted in molars with small pulp chambers and combined with the consistent pattern of intra-radicular connections, the potential endodontic treatment complexity is underlined in such cases. Finally, an improved understanding of root canal prevalence was reached, when merging well-defined definitions on root morphology and clinical classification systems.

Pattern of traumatic dental injuries in the permanent dentition among children, adolescents, and adults.

BACKGROUND: Traumatic dental injuries (TDI) comprise six types of luxation and seven types of tooth fractures. The risk of pulp necrosis is increased in teeth with combination injuries where fractures and luxations occur concomitantly. AIM: To report and compare the distributions of luxations and fracture types among children, adolescents, and adults, and to analyze the distribution and prevalence of combination injuries. MATERIAL AND METHOD: The study group included 4754 patients (3186 men and 1568 women) with 10 166 traumatized permanent incisors treated at Copenhagen University Hospital, Rigshospitalet. Differences in the distributions of trauma types among age groups (children <12 years, adolescents 12-20 years, and adults >20 years) and distributions of concomitant crown fractures for each luxation type were analyzed with the Chi-square test. RESULTS: A total of 7464 teeth (73.4%) had suffered a luxation injury and 5914 teeth (58.2%) a fracture. The overall most frequent injuries were crown fractures without pulp exposure (34.9%), concussions (24.2%), and subluxations (22.2%). The relative frequency of crown fractures without pulp exposure decreased across age groups (children 45.2%, adolescents 36.5%, adults 26.3%, P < 0.001), whereas the relative frequencies of other injury types increased across age groups : crown-root fractures (children 1.8%, adolescents 6.3%, adults 9.2%, P < 0.001), root fractures (children 2.5%, adolescents 4.6%, adults 8.7%, P < 0.001), and lateral luxations (children 5.7%, adolescents 10.9%, adults 13.0%, P < 0.001). One-third of the traumatized teeth (n = 3212) had sustained a combination of a fracture and a luxation injury. The luxation types most frequently presenting with a concomitant crown fracture were concussion (57.9%), intrusion (47.2%), and subluxation (33.4%) (P < 0.001). CONCLUSION: The majority of TDI were minor injuries. The relative frequencies of injury types varied among age groups. Combination injuries were observed in one-third of the traumatized teeth and occurred most frequently in teeth with concussion, intrusion, and subluxation.

Combination injuries 2. The risk of pulp necrosis in permanent teeth with subluxation injuries and concomitant crown fractures.

BACKGROUND: The reported risk of pulp necrosis (PN) is generally low in teeth with subluxation injuries. A concomitant crown fracture may increase the risk of PN in such teeth. AIM: To analyse the influence of a concomitant trauma-related infraction, enamel-, enamel-dentin- or enamel-dentin-pulp fracture on the risk of PN in permanent teeth with subluxation injury. MATERIAL AND METHODS: The study included 404 permanent incisors with subluxation injury from 289 patients (188 male, 101 female). Of these teeth, 137 had also suffered a concomitant crown fracture. All the teeth were examined and treated according to a standardized protocol. STATISTICAL ANALYSIS: The risk of PN was analysed separately for teeth with immature and mature root development by the Kaplan-Meier method, the log-rank test and Cox regression analysis. The level of significance was set at 5%. Risk factors included in the analysis were gender, patient age, crown fracture type, mobility and response to an electric pulp test (EPT) at the initial examination. RESULTS: Teeth with immature root development: The risk of PN was increased in teeth with a concomitant enamel fracture (log-rank test: P = 0.002), enamel-dentin fracture (log-rank test: P < 0.0001), enamel-dentin-pulp fracture (log-rank test: P < 0.0001) and in teeth with no response to EPT at the initial examination [hazard ratio: 21 (95% confidence interval, CI: 2.5-172.5), P = 0.005]. Teeth with mature root development: the risk of PN was increased in teeth with an enamel-dentin fracture [hazard ratio: 12.2 (95% CI: 5.0-29.8), P < 0.0001], infraction [hazard ratio: 5.1 (95% CI: 1.2-21.4) P = 0.04] and in teeth with no response to EPT at the initial examination [hazard ratio: 8 (95% CI: 3.3-19.5), P < 0.0001]. CONCLUSION: A concomitant crown fracture and no response to EPT at the initial examination may be used to identify teeth at increased risk of PN following subluxation injury.

Combination injuries 1. The risk of pulp necrosis in permanent teeth with concussion injuries and concomitant crown fractures.

BACKGROUND: The reported risk of pulp necrosis (PN) is low in teeth with concussion injuries. A concomitant crown fracture may affect the risk of PN. AIM: To analyze the influence of a crown fracture (with and without pulp exposure) on the risk of PN in teeth with concussion injury. MATERIAL: The study included 469 permanent incisors with concussion from 358 patients (226 male, 132 female). Among these, 292 had a concomitant crown fracture (70 with and 222 without pulp exposure). All teeth were examined and treated according to standardized protocol. STATISTICAL ANALYSIS: The risk of PN was analyzed by the Kaplan-Meier method and Cox regression. Risk factors included in the analysis: gender, age, stage of root development, type of crown fracture, and response to electric pulp test (EPT) at the initial examination. The level of significance was set at 5%. RESULTS: The risk of PN was low in teeth with immature root development [1.1%, 95% confidence intervals (CI): 0-3.4]. The following factors significantly increased the risk of PN in teeth with mature root development: crown fracture without pulp exposure [hazard ratio 4.1 (95% CI: 1.4-11.9), P = 0.01] and no response to EPT at the initial examination [hazard ratio 30.7 (95% CI: 7.7-121), P < 0.0001]. The overall risk of PN increased from 3.5% (95% CI: 0.2-6.8) to 11.0% (95% CI: 5.2-16.7) when a concomitant crown fracture without pulp exposure was present. If the tooth had both a crown fracture and gave no response to EPT, the risk further increased to 55.0% (95% CI: 34.3-75.8). CONCLUSION: No response to EPT at the initial examination or a concomitant crown fracture significantly increased the risk of PN in teeth with concussion injury and mature root development. If both risk factors were present there was a synergetic effect.