Effect of voxel size in cone-beam computed tomography on surface area measurements of dehiscences and fenestrations in the lower anterior buccal region.

OBJECTIVES: This study aims to assess whether different voxel sizes in cone-beam computed tomography (CBCT) affected surface area measurements of dehiscences and fenestrations in the mandibular anterior buccal region. MATERIALS AND METHODS: Nineteen dry human mandibles were scanned with a surface scanner (SS). Wax was attached to the mandibles as a soft tissue equivalent. Three-dimensional digital models were generated with a CBCT unit, with voxel sizes of 0.200 mm (VS200), 0.400 mm (VS400), and 0.600 mm (VS600). The buccal surface areas of the six anterior teeth were measured (in mm2) to evaluate areas of dehiscences and fenestrations. Differences between the CBCT and SS measurements were determined in a linear mixed model analysis. RESULTS: The mean surface area per tooth was 88.3 ± 24.0 mm2, with the SS, and 94.6 ± 26.5 (VS200), 95.1 ± 27.3 (VS400), and 96.0 ± 26.5 (VS600), with CBCT scans. Larger surface areas resulted in larger differences between CBCT and SS measurements (- 0.1 ß, SE = 0.02, p < 0.001). Deviations from SS measurements were larger with VS600, compared to VS200 (1.3 ß, SE = 0.05, P = 0.009). Fenestrations were undetectable with CBCT. CONCLUSIONS: CBCT imaging magnified the surface area of dehiscences in the anterior buccal region of the mandible by 7 to 9%. The larger the voxel size, the larger the deviation from SS measurements. Fenestrations were not detectable with CBCT. CLINICAL RELEVANCE: CBCT is an acceptable tool for measuring dehiscences but not fenestrations. However, CBCT overestimates the size of dehiscences, and the degree of overestimation depends on the actual dehiscence size and CBCT voxel size employed.

Precision of orthodontic cephalometric measurements on ultra low dose-low dose CBCT reconstructed cephalograms.

OBJECTIVES: To analyze differences in variation of orthodontic diagnostic measurements on lateral cephalograms reconstructed from ultra low dose-low dose (ULD-LD) cone beam computed tomography (CBCT) scans (RLC) as compared to variation of measurements on standard lateral cephalograms (SLC), and to determine if it is justifiable to replace a traditional orthodontic image set for an ULD-LD CBCT with a reconstructed lateral cephalogram. MATERIAL AND METHODS: ULD-LD CBCT images and SLCs were made of forty-three dry human skulls. From the ULD-LD CBCT dataset, a lateral cephalogram was reconstructed (RLC). Cephalometric landmarks (13 skeletal and 7 dental) were identified on both SLC and RLC twice in two sessions by two calibrated observers. Thirteen cephalometric variables were calculated. Variations of measurements, expressed as standard deviations of the 4 measurements on SLC and RLC, were analyzed using a paired sample t-test. Differences in the number of observations deviating ≥ 2.0 mm or degrees from the grand mean between SLC and RLC were analyzed using a McNemar test. RESULTS: Mean SDs for 7 out of 13 variables were significantly smaller for SLCs than those for RLCs, but differences were small. For 9 out of 13 variables, there was no significant difference between SLC and RLC for the number of measurements outside the range of 2 mm or degrees. CONCLUSIONS: Based on the lower radiation dose and the small differences in variation in cephalometric measurements on reconstructed LC compared to standard dose LC, ULD-LD CBCT with reconstructed LC should be considered for orthodontic diagnostic purposes. CLINICAL RELEVANCE: ULD-LD CBCT with reconstructed LC should be considered for orthodontic purposes.

Symmetry of palatal shape during the first year of life in healthy infants.

OBJECTIVES: The purpose of this study was to quantify the symmetry of the alveolar process of the maxilla and palate during the first year of life in healthy infants with the help of a semiautomatic segmentation technique. MATERIALS AND METHODS: Maxillary plaster models of seventy healthy babies at 0, 3, 6, 9, and 12 months were collected and digitized. A semiautomatic segmentation tool was used to extract the alveolus and palate. The resulting model was aligned within a reference frame and mirrored on its medial plane. Distance maps were created and analyzed to compare and quantify the differences between the two hemispheres. Additional hemispherical width and area measurements were performed. An ANOVA test with additional post hoc tests was performed to check if the symmetry changed during development. Finally, the results were tested on intra- and interobserver variability. RESULTS: The absolute mean inter-surface distance between the original and mirrored models in each age group ranged between 0.23 and 0.30 mm. Width and area analysis showed a small but significant larger left palatal hemisphere. ANOVA and post hoc tests showed no significant difference in symmetry between groups. Reliability analysis showed no significant differences between observers. CONCLUSIONS: This study showed that in this infant population, only a small degree of palatal asymmetry was present, which can be considered as normal and clinically irrelevant. CLINICAL RELEVANCE: The data from this study can be used in future comparative studies as reference data. Furthermore, modeling of these data can help in predicting the growth pattern, which may lead to improved treatment protocols for children with craniofacial anomalies.

[Root resorption as a result of orthodontic treatment]. / Wortelresorptie als gevolg van orthodontische behandeling.

Apical root resorption is a biological process induced when orthodontic force is exerted on a tooth and local necrosis of the periodontal ligament occurs. Macrophages remove the necrotic tissue. In this way, differentiating osteoclasts can both attach to the now available dental surface and can then provoke root resorption. There is considerable uncertainty among dental practitioners on how to deal with clinically relevant apical root resorption (bigger/equal 2 mm) during or after orthodontic treatment. To increase understanding and to improve the quality of care, the Dutch Association of Orthodontists has developed a clinical practice guideline. Recommendations have been formulated for the diagnosis of apical root resorption, possible risk factors and treatment management in order to respond adequately to this problem in practice.

Three dimensional maxillary growth modeling in newborns.

OBJECTIVES: The aim of this study was to develop an accurate and intuitive semi-automatic segmentation technique to calculate an average maxillary arch and palatal growth profile for healthy newborns in their first year of life. MATERIALS AND METHODS: Seventy babies born between 1985 and 1988 were included in this study. Each child had five impressions made in the first year after birth that were digitalized. A semi-automatic segmentation tool was developed and used to assess the maxillary dimensions. Finally, random effect models were built to describe the growth and build a simulation population of 10,000 newborns. The segmentation was tested for inter- and intra-observer variability. RESULTS: The Pearson correlation coefficient for each of the variables was between 0.94 and 1.00, indicating high inter-observer agreement. The paired sample t test showed that, except for the tuberosity distance, there were small, but significant differences in the landmark placements between observers. Intra-observer repeatability was high, with Pearson correlation coefficients ranging from 0.87 to 1.00 for all measurements, and the mean differences were not significant. A third or second degree growth curve could be successfully made for each parameter. CONCLUSIONS: These findings indicated this method could be used for objective clinical evaluation of maxillary growth. CLINICAL RELEVANCE: The resulting growth models can be used for growth studies in healthy newborns and for growth and treatment outcome studies in children with cleft lip and palate or other craniofacial anomalies.

Caries preventive measures in orthodontic practice: the development of a clinical practice guideline.

OBJECTIVES: White spot lesions (WSLs) are a side effect of orthodontic treatment, causing esthetic problems and a risk of deeper enamel and dentine lesions. Many strategies have been developed for preventing WSLs, but great variability exists in preventive measures between orthodontists. This study developed statements on which a clinical practice guideline (CPG) can be developed in order to help orthodontists select preventive measures based on the best available evidence. MATERIALS AND METHODS: A nominal group technique (RAND-e modified Delphi procedure) was used. A multidisciplinary expert panel rated 264 practice- and evidence-based statements related to the management of WSLs. To provide panel members with the same knowledge, a total of six articles obtained from a systematic review of the literature were read by the panel in preparation of three consensus rounds. According to the technique, a threshold of 75% of all ratings within any 3-point section of the 9-point scale regarding a specific statement was accepted as consensus. RESULTS: After the first and second consensus rounds, consensus was reached on 37.5 and 31.1% of statements, respectively. For the remaining 31.4% of statements, consensus was reached during a 4-h consensus meeting. CONCLUSIONS: Statements on the management of WSLs derived from a systematic literature review combined with expert opinion were formally integrated toward consensus through a nominal group technique. These statements formed the basis for developing a CPG on the management of WSLs before and during orthodontic treatment.

Transverse dental arch relationship at 9 and 12 years in children with unilateral cleft lip and palate treated with infant orthopedics: a randomized clinical trial (DUTCHCLEFT).

OBJECTIVE: A long-term evaluation to assess the transverse dental arch relationships at 9 and 12 years of age in unilateral cleft lip and palate treated with or without infant orthopedics (IO). The hypothesis is that IO has no effect on the transverse dental arch relationship. MATERIAL AND METHODS: A prospective two-arm randomized controlled trial (DUTCHCLEFT) in three academic cleft palate centers (Amsterdam, Nijmegen and Rotterdam, the Netherlands). Fifty-four children with complete unilateral cleft lip and palate and no other malformations were enrolled in this evaluation. One group wore passive maxillary plates (IO+) during the first year of life, and the other group did not (IO-). Until the age of 1.5, all other interventions were the same. Hard palate was closed simultaneously with bone grafting according to protocol of all teams. Orthodontic treatment was performed when indicated. The transverse dental arch relationship was assessed on dental casts using the modified Huddart/Bodenham score to measure the maxillary arch constriction at 9 and 12 years of age. RESULTS: No significant differences were found between the IO+ and IO- groups. Differences between the centers increased from 9 to 12 years of age. CONCLUSIONS: Transverse dental arch relationships at 9 and 12 years of age do not differ between children with UCLP treated with or without IO. CLINICAL RELEVANCE: There is no orthodontic need to perform IO as applied in this study in children with UCLP.

[Interdisciplinary orthodontic surgical treatment of children with cleft lip and palate from 9 to 20 years of age]. / Interdisciplinaire orthodontisch-chirurgische behandeling van schisis van 9 tot 20 jaar.

Cleft lip and palate is a common congenital malformation with a prevalence of 1:600 newborns. Children with orofacial clefts are treated by an interdisciplinary team of specialists while parents and child play a key role in their own care process. The orthodontic and facial orthopedic treatment of a child with a cleft takes many years. Children often get bored of the long treatment and this can cause problems with compliance and oral hygiene. Therefore it is advisable to distinguish 5 well-defined stages in the orthodontic treatment and to attempt to have some 'orthodontics free' time in between. The 3 orthodontic treatment phases between the age of 9 and 20 years consist of orthodontic treatment concerning the closing of the cleft with a bone transplant, the treatment of the permanent dentition and, finally, a possible combined orthodontic surgical treatment at the end of the period of growth. Good interdisciplinary collaboration among the different dental disciplines is essential in this regard.

[Tooth eruption disturbances and syndromes]. / Eruptiestoornissen en syndromen.

In the tooth eruption mechanism, various disturbances can appear as a result of gene mutations, a consequence of which can be that tooth eruption does not occur. There are 5 syndromes which involve the complete failure of several or even all teeth to erupt, specifically: cleidocranial dysplasia, Gardner's syndrome, osteopetrosis, mucopolysaccharidosis and GAPO syndrome. Some are very rare and will seldom be encountered in a dental practice, but they show how vulnerable the tooth eruption mechanism is. Dentists are generally the ones who identify a tooth eruption problem in a patient. Since syndromes can be associated with other disorders, additional investigation by a clinical geneticist is always important when a syndrome is suspected.

Geometric morphometric analysis of craniofacial variation, ontogeny and modularity in a cross-sectional sample of modern humans.

This investigation aimed to quantify craniofacial variation in a sample of modern humans. In all, 187 consecutive orthodontic patients were collected, of which 79 were male (mean age 13.3, SD 3.7, range 7.5-40.8) and 99 were female (mean age 12.3, SD 1.9, range 8.7-19.1). The male and female subgroups were tested for differences in mean shapes and ontogenetic trajectories, and shape variability was characterized using principal component analysis. The hypothesis of modularity was tested for six different modularity scenarios. The results showed that there were subtle but significant differences in the male and female Procrustes mean shapes. Males were significantly larger. Mild sexual ontogenetic allometric divergence was noted. Principal component analysis indicated that, of the four retained biologically interpretable components, the two most important sources of variability were (i) vertical shape variation (i.e. dolichofacial vs. brachyfacial growth patterns) and (ii) sagittal relationships (maxillary prognatism vs. mandibular retrognathism, and vice versa). The mandible and maxilla were found to constitute one module, independent of the skull base. Additionally, we were able to confirm the presence of an anterior and posterior craniofacial columnar module, separated by the pterygomaxillary plane, as proposed by Enlow. These modules can be further subdivided into four sub-modules, involving the posterior skull base, the ethmomaxillary complex, a pharyngeal module, and the anterior part of the jaws.

Skin and oral mucosa equivalents: construction and performance.

The skin and the oral mucosa act as a barrier against the external environment. Loss of this barrier function causes dehydration and a high risk of infection. For the treatment of extensive skin wounds such as in severe burns, autologous skin for transplantation is often not available in sufficient amounts. Reconstructions in the oral cavity, as required after tumor resections or cleft palate repair, are often complicated by similar problems. In the last two decades, the field of tissue engineering has provided new solutions to these problems. Techniques have been developed for the culture of epithelial grafts, dermal substitutes, and the combination of these two to a 'functional' skin or mucosa equivalent. The present review focuses on developments in the field of tissue engineering of skin and oral mucosa. The performance of different types of engineered grafts in animal models and clinical studies is discussed. Recent developments such as the use of epithelial stem cells, and gene therapy with transduced skin grafts are also discussed.

Rate of orthodontic tooth movement after changing the force magnitude: an experimental study in beagle dogs.

OBJECTIVES: To study a possible dose-response relation between force magnitude and rate of orthodontic tooth movement by altering forces during bodily orthodontic tooth movement. SETTING AND SAMPLE POPULATION: Eight young adult beagle dogs were used. The experiments were carried out in the Central Animal Facility, and all analyses were conducted in the Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Centre. MATERIALS AND METHODS: Orthodontic appliances were placed exerting a reciprocal force on the mandibular second premolars and first molars. A force of 10 or 300 cN was randomly assigned to each side of the dogs. After 22 weeks, all forces were changed to 600 cN. Based on intra-oral measurements, tooth movement rates were calculated. RESULTS: The premolars showed no difference in the rates of tooth movement with 10 or 300 cN. Replacing 10 for 600 cN increased the rate, but replacing 300 for 600 cN did not. Molars moved faster with 300 than with 10 cN, and changing both forces to 600 cN increased the rate of tooth movement. Data from all teeth were pooled considering their relative root surfaces, and a logarithmic relation was found between force and rate of tooth movement. CONCLUSIONS: Only in the very low force range, a positive dose-response relation exists, while in higher force ranges, no such relation could be established.

Prenatal ultrasound diagnosis in 51 cases of holoprosencephaly: craniofacial anatomy, associated malformations, and genetics.

OBJECTIVE: To analyze the prenatal ultrasound findings of the craniofacial and extracephalic anatomy, the postnatal pathological findings, and the genetic anomalies in 51 cases of holoprosencephaly (HPE). MATERIALS AND METHODS: Between 1990 and 2005, a collective of 51 fetuses with tentative ultrasound diagnosis of HPE was recruited at two tertiary referral centers for prenatal ultrasound diagnostics via the Pia Fetal Database (GEMedical Systems, Webling, Germany). Cephalic as well as extracephalic anomalies were investigated, and all cases were subdivided into the subgroups lobar, a lobar, and semilobar HPE. In addition to the ultrasound investigation, 45 fetuses were analyzed for genetic anomalies and 21 fetuses underwent an autopsy. RESULTS: The average age at diagnosis was 21.9 weeks of gestation. There was a greater number of female fetuses, with an overall ratio of 2.67:1. In 61% of all cases, there was a reduction of growth in comparison with healthy fetuses of the same age. Within the second trimenon, the cephalic anomalies became evident when investigating the diameter of the fetal head (second trimenon: 71%below the fifth percentile; third trimenon: 92% below the fifth percentile). In 82%of the cases, extracephalic anomalies were diagnosed additionally. In 63%, the diagnosis of holoprosencephaly led to a termination of pregnancy. Ten percent of the fetuses were born alive. In 81% of the cases, the diagnosis of HPE was confirmed postnatally. The remaining 19% showed other severe cephalic and extracephalic anomalies. Chromosomal anomalies were detected in 79% of the fetuses, most frequently trisomy 13 (59%). DISCUSSION: Because of recent advances in the development and improvement of high-resolution ultrasound, early diagnosis of congenital anomalies such as HPE is now possible. In this study, which represents the largest collection of prenatally diagnosed HPE reported in the literature to date, the average age at diagnosis was earlier than in other studies. The ultrasound devices of today provide excellent images of the fetus that allow an exact diagnosis of craniomaxillofacial anomalies as well as extracephalic anomalies. Apart from a very few cases, the diagnosis of HPE is incompatible with life.

[Prevention of white spots during orthodontic treatment with fixed appliances]. / Wittevleklaesies tijdens orthodontische behandeling: preventief beleid.

Orthodontic treatment with fixed appliances involves a significant risk of enamel demineralization. The aim of this study was three-fold: to gain insight into a) the preventive measures which are applied as standard practice in The Netherlands in orthodontics, b) when the use of fluoride rinses is initiated, and c) which concentrations and frequencies of use are recommended. A questionnaire was sent to all orthodontists in private practice in The Netherlands. Completed questionnaires were returned by 154 of the orthodontists (response rate 81%). A basic practice protocol for preventing demineralization was used at the start of treatment by 93%. The majority (90%) recommended to use fluoride rinse once daily. They generally (85%) recommended to do this in the evening immediately after toothbrushing. The authors recommend rinsing at another moment than after tooth brushing, in order to increase the number of fluoride moments during the day, which enhances the effectiveness of this measure in preventing caries.

[Unilateral surgically assisted rapid maxillary expansion using a transpalatal distractor]. / Unilaterale chirurgisch ondersteunde expansie van de bovenkaak door transpalatinale distractor.

A 46-year-old woman was referred for orthodontic surgery consultation because ofa retrognathic maxilla, unilateral cross bite and functional, aesthetic and speech problems. The maxilla was widened unilaterally by unilateral surgically assisted rapid maxillary expansion with a bone-borne transpalatal distractor. During post-operative orthodontic treatment, a temporary anchorage device was administered. With the help of composite veneers, crowns and a removable partial denture, a functionally and aesthetically satisfying result was achieved.

Matrix metalloproteinase inhibitors reduce collagen gel contraction and alpha-smooth muscle actin expression by periodontal ligament cells.

BACKGROUND AND OBJECTIVE: Orthodontic tooth movement requires remodeling of the periodontal tissues. The matrix metalloproteinases (MMPs) degrade the extracellular matrix components of the periodontal ligament, while the tissue inhibitors of metalloproteinases (TIMPs) control their activity. Synthetic MMP inhibitors have been developed to inhibit MMP activity. In this study, periodontal ligament cells in contracting collagen gels served as a model for enhanced periodontal remodeling. The effect of MMP inhibitors on gel contraction and on MMP and TIMP expression was analyzed. MATERIAL AND METHODS: Human periodontal ligament cells were cultured in three-dimensional collagen gels and incubated with the MMP inhibitors BB94, CMT-3, doxycycline and Ilomastat. Gel contraction was determined using consecutive photographs. The relative amounts of MMPs and TIMPs were analyzed using substrate zymography and mRNA expression using quantitative polyermase chain reaction. RESULTS: All MMP inhibitors reduced MMP activity to about 20% of the control activity. They all reduced contraction, but CMT-3 and doxycycline had the strongest effect. These inhibitors also reduced MMP-2, MMP-3 and alpha-smooth muscle actin mRNA expression. The expression of MMP-1 mRNA seemed to be increased by CMT-3. No effects were found on the amounts of MMPs and TIMPs. CONCLUSION: Synthetic MMP inhibitors strongly reduced gel contraction by periodontal ligament cells. This was primarily caused by an inhibitory effect on MMP activity, which reduces matrix remodeling. In addition, alpha-smooth muscle actin expression was reduced by CMT-3 and doxycycline, which limits the contractile activity of the fibroblasts.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in gingival crevicular fluid during orthodontic tooth movement.

Orthodontic tooth movement requires extensive re-modelling of the periodontium. Matrix metalloproteinases (MMPs) degrade the extracellular matrix during re-modelling, while their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The aim of this study was to investigate differences in MMP and TIMP levels in the gingival crevicular fluid (GCF) at the resorption and apposition sides of orthodontically moved teeth, and to compare these with control teeth. GCF samples were collected from eight orthodontic patients wearing fixed appliances with superelastic nickel-titanium coil springs. The samples were analysed by gelatin zymography, which allows detection of both active and latent MMPs, and reverse zymography for analysis of TIMPs. Western blotting was performed to confirm the identity of MMPs. The data were analysed using either the one-way analysis of variance or the Kruskal-Wallis test. In general, higher levels of MMPs and TIMPs were found at both the resorption and apposition sides compared with the control teeth. Remarkably, partially active MMP-1 was found in GCF from both the resorption and the apposition side but was barely present at the control teeth. TIMP-1 was strongly increased at the apposition side. Gelatinases were mainly present at the resorption side, while gelatinolytic fragments were exclusively detected at the apposition side. MMP-9, which is known to be involved in bone degradation, and a 48 kDa gelatinase were increased at the resorption side. The small increase in TIMP-1 at the resorption side might stimulate bone resorption, whereas the large increase at the apposition side reduces bone resorption. The analysis of MMPs and TIMPs may contribute to the improvement of orthodontic treatment regimens.