The effects of dietary loading on the transdifferentiation of condylar chondrocytes.

INTRODUCTION: Transdifferentiation of chondrocytes into bone cells explains most condylar growth during prenatal and early postnatal stages, but the mechanisms regulating chondrocyte transdifferentiation during late postnatal growth remain unknown. This study aimed to quantify the effects of dietary loading on chondrocyte-derived osteogenesis during late postnatal condylar growth. METHODS: Two compound mouse lines were used to trace the fate of chondrocyte lineage in vivo. Twelve 3-week-old male Aggrecan-CreERT2 (AcanLineage); R26RTdTomato; 2.3 Col10a1-GFP and twelve 3-week-old male Col10a1-Cre (Col10a1Lineage); R26RTdTomato; 2.3Col1a1-GFP were randomly divided into experimental (soft-food diet, n = 6) and control (hard-food diet, n = 6) groups and kept for 6 weeks. One time, tamoxifen injections were given to AcanLineage mice at 3 weeks. Radiographic, microcomputed tomographic, and histomorphometric analyses were performed. RESULTS: Radiologic analysis showed that mice with a soft-food diet had smaller mandible lengths as well as decreased bone volume and density for their condylar process. Histologically, mice with soft diets had reduced activity in chondrocyte proliferation and maturation compared with the controls. Cell lineage tracing results showed the number of AcanLineage-derived bone cells (293.8 ± 39.8 vs 207.1 ± 44.6; P = 0.005), as well as total bone cells (445.6 ± 31.7 vs 360.7 ± 46.9; P = 0.004), was significantly higher in the hard-diet group than in the soft-diet group, whereas the number of non-AcanLineage-derived bone cells was not significantly different among groups (P = 0.938). Col10a1Lineage mice showed the same trend. CONCLUSIONS: Dietary loading directly affects condyle chondrogenesis and chondrocyte transdifferentiation, which alters the extent of condylar growth and remodeling.

How does arch form and interproximal contact size affect the 3D displacements and rotations of teeth: a finite element analysis.

OBJECTIVE: The objective of this study was to determine how arch form and interproximal contact size displace mandibular teeth subjected to an anterior component of force (ACF). METHODS: Nine finite element models (FEM) of the mandibular arch were developed using Ansys® v. 16.0 software. They were designed to evaluate the effects of three arch forms (triangular, oval, and square) and three contact sizes (point-to-point, 1 mm diameter, and 2 mm diameter). All nine models were subjected to an ACF of 53.8 N (5486 gm). Three-dimensional tooth rotations and displacements of the mandibular teeth were evaluated, from the right first molar to the left first molar. RESULTS: Arch form had a greater effect on tooth movements than contact size. Triangular arches and point-to-point contacts produced the greatest displacements and rotations of teeth. Oval arches with 2 mm wide interproximal contact points showed the greatest stability. The right first premolar showed the greatest displacements in all of the models. CONCLUSIONS: Arch form and contact size affect interproximal tooth stability. Teeth are least stable in narrow arches with point-to-point interproximal contacts, and most stable in wider arches with larger contacts.

Short-term effects of mechanical loading on the transdifferentiation of condylar chondrocytes.

INTRODUCTION: Transdifferentiation of chondrocytes into bone cells explains most of the prenatal and early postnatal condylar growth, but its role during later postnatal growth and the mechanisms regulating transdifferentiation remain unknown. This study aimed to quantify the effects of mechanical loading on chondrocyte-derived osteogenesis during late postnatal condylar growth using a short-term mandibular laterotrusion model. METHODS: Thirty 4-week-old Aggrecan-CreERT2, R26RtdTomato, and 2.3Col1a1-GFP compound mice received tamoxifen injections and were divided into control and experimental groups. Appliances were bonded to shift the mandibles of the experimental mice for 5 days, causing protrusion and retrusion of the right and left condyles, respectively. Radiographic, microcomputed tomographic, and histomorphometric analyses were performed. RESULTS: The experimental and control groups showed substantial transdifferentiation of chondrocytes into bone cells. The experimental mice developed asymmetric mandibles, with the protrusive side significantly longer than the retrusive side. The protrusive condyles showed significantly increased chondrogenesis and greater numbers of chondrocyte-derived osteogenic cells, especially in the posterior third. The opposite effects were seen on the retrusive side. CONCLUSIONS: Transdifferentiation of chondrocytes into bone cells occurs during late postnatal condylar growth. Laterotrusion regulates condylar chondrogenesis and chondrocyte transdifferentiation, which alters the amount and direction of condylar growth. Our study demonstrated that chondrocytes are key players in condylar bone formation and should be the focus of studies to control and further understand condylar growth.

How does arch form and interproximal contact size affect the 3D displacements and rotations of teeth: a finite element analysis

ABSTRACT Objective: The objective of this study was to determine how arch form and interproximal contact size displace mandibular teeth subjected to an anterior component of force (ACF). Methods: Nine finite element models (FEM) of the mandibular arch were developed using Ansys® v. 16.0 software. They were designed to evaluate the effects of three arch forms (triangular, oval, and square) and three contact sizes (point-to-point, 1 mm diameter, and 2 mm diameter). All nine models were subjected to an ACF of 53.8 N (5486 gm). Three-dimensional tooth rotations and displacements of the mandibular teeth were evaluated, from the right first molar to the left first molar. Results: Arch form had a greater effect on tooth movements than contact size. Triangular arches and point-to-point contacts produced the greatest displacements and rotations of teeth. Oval arches with 2 mm wide interproximal contact points showed the greatest stability. The right first premolar showed the greatest displacements in all of the models. Conclusions: Arch form and contact size affect interproximal tooth stability. Teeth are least stable in narrow arches with point-to-point interproximal contacts, and most stable in wider arches with larger contacts.

RESUMO Objetivo: O objetivo deste estudo foi determinar como o formato da arcada e o tamanho do contato interproximal deslocam os dentes inferiores submetidos a um componente anterior de força (CAF). Métodos: Nove modelos de elementos finitos (MEF) da arcada inferior foram desenvolvidos utilizando o software Ansys® v. 16.0. Eles foram projetados para avaliar os efeitos de três formatos de arcada (triangular, oval e quadrado) e três tamanhos de contato interproximal (ponto a ponto, 1 mm de diâmetro e 2 mm de diâmetro). Todos os nove modelos foram submetidos a um CAF de 53,8 N (5486 gm). Foram avaliados tridimensionalmente as rotações dentárias e os deslocamentos dos dentes inferiores, do primeiro molar direito ao primeiro molar esquerdo. Resultados: A forma da arcada teve um efeito maior no movimento dos dentes do que o tamanho do contato interproximal. Arcadas triangulares e contatos ponto a ponto produziram os maiores deslocamentos e rotações dos dentes. Arcadas ovais com pontos de contato interproximal de 2 mm de largura apresentaram maior estabilidade. O primeiro pré-molar direito apresentou os maiores deslocamentos em todos os modelos. Conclusões: O formato da arcada e o tamanho do contato interproximal afetam a estabilidade dos dentes. Os dentes foram menos estáveis nas arcadas estreitas com contatos interproximais ponto a ponto, e mais estáveis nas arcadas mais largas com contatos maiores.

Differences in finished case quality between Invisalign and traditional fixed appliances.

OBJECTIVES: To compare the treatment and posttreatment effects of Invisalign aligners that incorporated SmartForce features and attachments to traditional fixed appliances. MATERIALS AND METHODS: This randomized controlled trial included 66 patients, 32 aligners, and 34 fixed-appliance patients. The median ages of the aligner and braces patients were 26.7 (interquartile range [IQR]: 9.8) and 25.9 (IQR: 16.6) years, respectively. Pretreatment occlusion was assessed using the ABO Discrepancy Index. Posttreatment (T1) and 6-month retention (T2) occlusions were quantified using the ABO Objective Grading System (OGS) scores. RESULTS: The braces group finished treatment significantly (P < .001) earlier (0.4 years) than the aligner group. The median DI scores for the aligner and braces groups were 4.5 and 7.0, respectively, which was a statistically significant (P = .015), but clinically insignificant, difference. There were no statistically significant between-group differences for the total OGS scores or any of the individual component scores at debond (T1) or after 6 months of retention (T2). During the posttreatment period, alignment and overjet worsened significantly in the aligner group, while buccolingual inclinations and occlusal relations improved. Over the same period, alignment worsened in the braces group and buccolingual inclinations improved. There was no statistically significant between-group difference in posttreatment changes of the total OGS scores. CONCLUSIONS: While patients with simple malocclusions require 4.8 months longer treatment times with aligners than traditional braces, the treatment and 6-month posttreatment occlusal outcomes are similar.

The efficacy of fluoride varnish vs a filled resin sealant for preventing white spot lesions during orthodontic treatment.

OBJECTIVES: To compare the efficacy of casein phosphopeptide (CPP)-amorphous calcium phosphate (ACP) MI Varnish (GC America, Inc, Alsip, IL) and ProSeal (Reliance Orthodontic Products, Itasca, IL) sealant in preventing the development of white spot lesions (WSLs) in orthodontic patients. MATERIALS AND METHODS: This prospective randomized clinical trial included 40 orthodontic patients 12-17 years of age. One group had sealants placed on their anterior maxillary teeth, with reapplications every 3 months. The other group had MI Varnish applied every 4-6 weeks. WSL formation and oral hygiene were evaluated at the initial appointment before bonding (T1) and 12 months later (T2). Standardized digital photographs were analyzed using the enamel decalcification index (EDI). Statistical comparisons were made using independent and paired-sample t-tests as well as chi-square tests. RESULTS: In this trial, 43% of patients and 15% of teeth developed new WSLs. Lateral incisors showed the highest incidence of decalcification and WSL formation. WSL formation and EDI score increases during treatment were significantly greater in the gingival region than in the mesial, distal, or incisal regions. Of the EDI scores at T2, 93.8% were 0 and 5.5% were 1. Poor oral hygiene at T2 showed a high positive predictive value (76%) for the development of WSLs. There were no statistically significant between-group differences for the development of WSLs. CONCLUSIONS: MI Varnish and ProSeal sealant provided similar levels of protection during the first 12 months of fixed orthodontic treatment. The severity of the WSLs that developed was minimal. WSLs were most likely to develop on lateral incisors and in the gingival regions of teeth, especially among patients with poorer oral hygiene.

Short-term skeletal and dentoalveolar effects of overexpansion.

OBJECTIVES: To evaluate whether the amount of rapid maxillary expansion differentially affects the skeletal and dentoalveolar changes that occur. MATERIALS AND METHODS: This randomized controlled trial included 23 patients who had rapid maxillary expansion (RME). Subjects were randomly assigned to a conventional expansion control group (n = 12) or an overexpansion group (n = 11), who started treatment at 13.2 ± 1.5 and 13.8 ± 1 years of age, respectively. Cone beam computed tomography scans (11 cm) were obtained prior to rapid maxillary expander (RME) delivery and approximately 3.7 months later. Initial hand-wrist radiographs were used to determine the participants' skeletal maturity. RESULTS: The RME screws were activated 5.6 ± 1.2 mm and 10.1 ± 0.6 mm in the conventional and overexpansion groups, respectively. Overexpansion produced significantly greater expansion of the nasal cavity (2.1X-2.5X), maxillary base (2.3X), buccal alveolar crest (1.4X), and greater palatine foramina (1.9X). Significantly greater intermolar width increases (1.8X) and molar inclination (2.8X) changes were also produced. The nasal cavity and maxillary base expanded 23%-32% as much as the screws were activated. Skeletal expansion was positively correlated with RME screw activation (R = 0.61 to 0.70) and negatively correlated (R = -0.56 to -0.64) with the patients' skeletal maturation indicators (SMIs). Together, screw activation and the patients' SMI scores explained 48%-66% of the variation in skeletal expansion. CONCLUSIONS: This pilot study shows that overexpansion produces greater changes than conventional expansion, with greater skeletal effects among less mature patients.

How different time intervals between repeated applications of CPP-ACP fluoride varnish effect smooth surface enamel demineralization?

OBJECTIVES: To evaluate the preventive effects of different time intervals between repeated applications of the CPP-ACP fluoride varnish on enamel demineralization. METHODS: Human teeth were sectioned and randomly allocated to three groups: 4-week, 6-week, and 12-week (N = 22/group). Baseline images of the enamel surfaces were obtained using the FluoreCam recording the area, intensity, and impact of baseline enamel demineralization. All groups received fluoride varnish applications at the beginning of the experiment. The varnish was reapplied every 4 or 6 weeks in the 4-week and 6-week groups, respectively. Following each application, the groups underwent thermo-cycling, tooth brushing and pH cycling to simulate the time effect. After 12 weeks, the enamel surfaces were reimaged using the FluoreCam. Within and between-group differences in the area, intensity and impact of demineralization were evaluated. RESULTS: At baseline, there were no significant between-group differences for area, intensity, or impact. Statistically significant (p<0.001) enamel demineralization occurred over time within each group. There were significant between-group differences in the changes that occurred in area (P = 0.004), impact (P = 0.022), but not intensity. The 12-week had significantly larger areas of demineralization than the 6-week (P = 0.041) and 4-week (P = 0.001) groups. Changes in impact was significantly (P = 0.007) greater in the 12-week group than 4-week group, but not greater than the 6-week group. There were no statistically significant differences between 4- and 6-week groups in the changes of area, intensity, or impact. CONCLUSION: Reapplication of the CPP-ACP fluoride varnish every 4-6 weeks, is more effective in reducing enamel demineralization compared to every 12 weeks.

A predictive model of "favorable" and "unfavorable" anteroposterior skeletal relations among Class Is and Class IIs.

OBJECTIVES: To validate the use of the sagittal distance between ANS and Pg (ANSPg) as a measure of favorable and unfavorable anteroposterior skeletal relations and to identify multivariate cephalometric measures that could be used to predict favorable and unfavorable relations at 15 years of age. MATERIALS AND METHODS: This longitudinal study included 226 untreated adolescents evaluated at 10 and 15 years of age. Patients were grouped as "favorable" or "unfavorable" based on the ANSPg (measured parallel to S-N -7°) at 15 years of age (ANSPg15). ANSPg15 was validated based on its correlation with changes in ANSPg between 10 and 15 years of age, as well as its relationships with established measures of growth potential. Multiple regression and discriminant analyses were performed to predict ANSPg15 from measures at 10 years of age. RESULTS: ANSPg15 and the change in ANSPg between 10 and 15 years of age were significantly correlated (R= -0.661; P ≤ .001), with 77% of patients in whom relationships improved (ie, distance decreased) exhibiting favorable relationships at 15 years of age. Established measures of growth potential were significantly (P < .001) correlated with ANSPg15 and showed significant differences between patients with favorable and unfavorable relations. Multiple regression showed that the Y-axis, ANS-N-Pg, and symphyseal angle measured at 10 years explained approximately 60% (R = 0.78) of the variation in ANSPg15. Based on these three variables, discriminant function correctly predicted favorable or unfavorable relations of ANSPg15 77% of the time. CONCLUSIONS: ANSPg15 was a valid measure for determining favorable and unfavorable anteroposterior skeletal relationships that could be predicted with moderately high levels of accuracy.

Correlation between adolescent orthodontic quality of life and ABO Discrepancy Index in an orthodontic treatment-seeking population: A cross-sectional study.

OBJECTIVE: To evaluate the association between adolescents' orthodontic quality of life before initiating orthodontic treatment and their objective case complexity as measured by the American Board of Orthodontics' Discrepancy Index (DI). DESIGN AND SETTING: A single-centre, cross-sectional survey study. METHODS: The Orthodontic Quality of Life Assessment Survey (OQoLAS) was administered to 240 adolescents (aged 11-14 years) during their record-gathering appointment. After completion of the survey, a DI score was calculated for each patient based on pretreatment measurements. Pearson correlation coefficients, r, were used to assess the association of DI scores with OQoLAS total and subdomain scores. A multiple linear regression of OQoLAS total scores adjusting for age, gender and DI scores was conducted. RESULTS: The study did not find a strong correlation between OQoLAS and DI scores (r = 0.10; P = 0.6497). On average, the OQoLAS scores (functional, emotional and social subdomains of OQoLAS) were slightly higher among girls than among boys but there was no statistical difference for total OQoLAS score between boys and girls (42.4 vs. 45.4, P = 0.2005). However, there was a significant difference in oral health perception rating between boys and girls, with girls being more likely to rate their oral health positively (adjusted P = 0.0226). The total DI scores of boys with respect to girls were not statistically different (P = 0.4256). The components of the DI that showed highest score were for cephalometric measures, followed by overjet; and the lowest scores were for lateral open bite and buccal posterior crossbite. The measure of association analysis did not show any strong correlation between the OQoLAS (total score and subdomain scores), and DI score or any of its components. CONCLUSION: Malocclusion severity was not found to be correlated with orthodontic quality of life in adolescents aged 11-14 years seeking orthodontic treatment.

Stability of immediately loaded 3 mm long miniscrew implants: a feasibility study.

INTRODUCTION: Shorter miniscrew implants (MSIs) are needed to make orthodontics more effective and efficient. OBJECTIVE: To evaluate the stability, insertion torque, removal torque and pain associated with 3 mm long MSIs placed in humans by a novice clinician. METHODS: 82 MSIs were placed in the buccal maxillae of 26 adults. Pairs of adjacent implants were immediately loaded with 100g. Subjects were recalled after 1, 3, 5, and 8 weeks to verify stability and complete questionnaires pertaining to MSI-related pain and discomfort. RESULTS: The overall failure rate was 32.9%. The anterior and posterior MSIs failed 35.7% and 30.0% of the time, respectively. Excluding the 10 MSIs (12.2%) that were traumatically dislodged, the failure rates in the anterior and posterior sites were 30.1% and 15.2%, respectively; the overall primary failure rate was 23.6%. Failures were significantly (p= 0.010) greater (46.3% vs 19.5%) among the first 41 MSIs than the last 41 MSIs that were placed. Excluding the traumatically lost MSIs, the failures occurred on or before day 42. Subjects experienced very low pain (2.2% of maximum) and discomfort (5.5% of maximum) during the first week only. CONCLUSIONS: Shorter 3 mm MSIs placed by a novice operator are highly likely to fail. However, failure rates can be substantially decreased over time with the placement of more MSIs. Pain and discomfort experienced after placing 3 mm MSIs is minimal and temporary.

The quality of etched enamel in different regions and tooth types and its significance in bonding and the development of white spot lesions.

OBJECTIVES: To quantify differences in the etch quality of enamel within and between human teeth, which has not previously been attempted. MATERIALS AND METHODS: The buccal right and left halves of 27 extracted human teeth were randomly allocated to scanning electron microscopy (SEM) or micro-computed tomography (µCT) for evaluation. The buccal surfaces were pumiced, etched with 37% phosphoric acid gel etchant for 15 seconds, rinsed, and air dried. Each tooth was divided into three regions (incisal, middle, and cervical) and viewed after etching at 1200× magnification with SEM. The µCT scans were taken before and after etching to calculate apparent and material mineral densities. RESULTS: SEM showed greater aprismatic enamel and poorer etch quality (ie, significantly less percentage enamel) for the posterior than anterior teeth and for the cervical region than for the incisal and middle regions of all teeth. Although there were no density differences prior to etching, µCT demonstrated that etching increased material density significantly more for the anterior than posterior teeth. Prior to etching, the enamel in the cervical regions was significantly less dense than the enamel in the middle or incisal regions. Etching significantly increased the material density of all three regions, which decreased initial regional differences. After etching, the apparent density of the cervical region remained significantly lower than the densities of the other two regions. CONCLUSIONS: Based on SEM and µCT, there is greater aprismatic enamel and inferior etch quality in the cervical regions of all tooth types and is clinically significant in explaining the failure of sealant retention and the propensity for white spot lesions.

Keys to Class II correction: A comparison of 2 extraction protocols.

INTRODUCTION: The purpose of this study was to evaluate the effects of 2 extraction patterns on incisor and molar movements in patients with growing Class II Division 1. METHODS: The sample included 54 patients 10-17 years of age treated by 2 private practice orthodontists using Tweed directional force mechanics, 4 premolar extractions, J-hook headgears, and Class II elastics or Saif springs. The sample was divided on the basis of having maxillary and mandibular first premolars (4/4) or maxillary first and mandibular second premolars (4/5) extracted. Each group included 27 patients. Treatment lasted 2.8 ± 0.60 years and 2.6 ± 0.54 years for the 4/4 and 4/5 groups, respectively. Pretreatment (T1) and posttreatment lateral cephalograms and dental casts were evaluated. Cranial base, mandibular, and maxillary superimpositions were performed to quantify tooth movements and displacements. RESULTS: There were no statistically significant T1 between-group differences in crowding or in the SNA, SNB, ANB, and MPA angles. Analyses of covariance, controlling for statistically significant (P <0.05) differences in T1 mandibular incisor position, showed that mandibular first premolars extractions produced greater (1.6 mm) mandibular incisor retraction than second premolar extractions. The mandibular first molars were protracted significantly more (0.7 mm) after the second premolar than the first premolar extractions. Within-group changes of the MPA, between-group differences in the changes in MPA, and the amount of vertical eruption of the maxillary and mandibular molars were not significantly different between the 2 extraction patterns. CONCLUSIONS: Extraction of mandibular second premolars enhances Class II molar correction, with greater mesial first molar movement and less distal incisor movement. Neither extraction pattern has an effect on the MPA or the vertical dimension (ie, there was no "wedge effect").

Stability of immediately loaded 3 mm long miniscrew implants: a feasibility study

ABSTRACT Introduction: Shorter miniscrew implants (MSIs) are needed to make orthodontics more effective and efficient. Objective: To evaluate the stability, insertion torque, removal torque and pain associated with 3 mm long MSIs placed in humans by a novice clinician. Methods: 82 MSIs were placed in the buccal maxillae of 26 adults. Pairs of adjacent implants were immediately loaded with 100g. Subjects were recalled after 1, 3, 5, and 8 weeks to verify stability and complete questionnaires pertaining to MSI-related pain and discomfort. Results: The overall failure rate was 32.9%. The anterior and posterior MSIs failed 35.7% and 30.0% of the time, respectively. Excluding the 10 MSIs (12.2%) that were traumatically dislodged, the failure rates in the anterior and posterior sites were 30.1% and 15.2%, respectively; the overall primary failure rate was 23.6%. Failures were significantly (p= 0.010) greater (46.3% vs 19.5%) among the first 41 MSIs than the last 41 MSIs that were placed. Excluding the traumatically lost MSIs, the failures occurred on or before day 42. Subjects experienced very low pain (2.2% of maximum) and discomfort (5.5% of maximum) during the first week only. Conclusions: Shorter 3 mm MSIs placed by a novice operator are highly likely to fail. However, failure rates can be substantially decreased over time with the placement of more MSIs. Pain and discomfort experienced after placing 3 mm MSIs is minimal and temporary.

RESUMO Introdução: Mini-implantes (MIs) mais curtos são necessários para uma Ortodontia mais eficiente e efetiva. Objetivo: Avaliar a estabilidade, torque de inserção e de remoção e dor associada a MIs de 3mm instalados em humanos por um ortodontista principiante. Métodos: 82 MIs foram instalados na região vestibular da arcada superior de 26 adultos. Pares de mini-implantes adjacente receberam carga imediata de 100g. Após 1, 3, 5 e 8 semanas, os pacientes foram reavaliados para verificar a estabilidade e preencher um questionário sobre a dor e o desconforto relacionados aos MIs. Resultados: A taxa geral de falhas foi de 32,9%, sendo de 35,7% para os MIs anteriores e 30% para os MIs posteriores. Excluindo os 10 MIs que foram perdidos por trauma (12,2%), a taxa de falha nas regiões anterior e posterior foram de 30,1% e 15,2%, respectivamente e ocorreram no 420 dia ou antes. A taxa geral de falha primária foi de 23,6%. A taxa de falha foi significativamente maior (p=0,010) nos primeiros 41 MIs do que nos 41 últimos (46,3% vs. 19,5%). As experiências relacionadas à dor foram baixas (2,2% máximo), assim como ao desconforto (5,5% máximo) durante a primeira semana. Conclusão: MIs de 3mm instalados por um novato são mais propensos a falhas. Porém, as taxas de falha podem diminuir substancialmente com a instalação de mais MIs com o decorrer do tempo. A dor e o desconforto após a instalação desses dispositivos são mínimos e temporários.

Effects of transverse bodily movements of maxillary premolars on the surrounding hard tissue.

INTRODUCTION: This experimental study was designed to (1) produce buccal translation of maxillary premolars and (2) evaluate the effects on the buccal alveolar bone. METHODS: A randomized split-mouth study was designed based on 7 adult male beagle dogs. The experimental side received a custom cantilever appliance fabricated to produce a translatory force through the maxillary second premolar's center of resistance. The contralateral second premolar received no appliance and served as the control. The premolars underwent 6-7 weeks of buccal translation, followed by 3 weeks of fixed retention. Biweekly tooth movements were evaluated using intraoral and radiographic measurements. Pretreatment and posttreatment models were measured to assess tipping. Three-dimensional microscopic tomography was used to quantify the amount and density of buccal bone. Bone formation and turnover were assessed using fluorescent labeling, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and bone sialoprotein immunostaining. RESULTS: The applied force (100 g of force) translated (1.4 mm) and minimally tipped (4°) the experimental teeth. Lateral translation produced dehiscences at the mesial and distal roots, with 2.0 mm and 2.2 mm loss of vertical bone height, respectively. Bone thickness decreased significantly (P < 0.05) at the apical (∼0.4 mm), midroot (∼0.4 mm), and coronal (∼0.2 mm) levels. Fluorescent imaging, hematoxylin and eosin staining, and immunostaining for bone sialoprotein all showed new bone formation extending along the entire periosteal surface of the second premolar's buccal plate. Tartrate-resistant acid phosphatase staining demonstrated greater osteoclastic activity on the experimental than that of control sections. CONCLUSIONS: New buccal bone forms on the periosteal surface during and after tooth translation, but the amount of bone that forms is less than the amount of bone loss, resulting in a net decrease in buccal bone thickness and a loss of crestal bone.

Is there a relationship between dental crowding and the size of the maxillary or mandibular apical base?

OBJECTIVE: To determine whether apical base size is related to dental crowding. MATERIALS AND METHODS: Digital scans of dental casts were taken of 75 untreated Class I adults to measure maxillary and mandibular tooth size, dental arch perimeters, intermolar widths, and intercanine widths. Cone beam computed tomography (CBCT) images were used to measure the apical base of the maxilla and mandible, including the total cross-sectional area, five basal arch perimeters and five basal arch widths. Principal components factor analyses were performed to evaluate the relationships between the apical base size and tooth-size-arch-length discrepancies (TSALD). RESULTS: The dental arch and maxillary apical base measures were significantly larger in males than females. There were only limited sex differences in mandibular apical base size. The dental arch measurements were smaller in subjects with greater upper and lower TSALD. Maxillary and mandibular apical base dimensions were positively interrelated. Low-to-moderate correlations were found between the size of the maxillary apical base and TSALD. The size of the mandibular apical base was not related to upper or lower TSALD. Tooth size showed little to no relationship with TSALD. CONCLUSIONS: Although maxillary apical base size is related to maxillary and mandibular crowding in subjects with Class I malocclusion, mandibular apical base size is not.

A preliminary 3-D comparison of rapid and slow maxillary expansion in children: A randomized clinical trial.

BACKGROUND: This study compared the effects of rapid maxillary expansion (RME) and slow maxillary expansion (SME) using cone-beam computed tomography (CBCT). AIM: To evaluate the skeletal and dentoalveolar effects produced by two different maxillary expansion protocols. DESIGN: Eligibility criteria included maxillary transverse deficiencies in children (mean age, 8.18 years old), randomly assigned to either RME or SME. At the outcome analysis phase, a sample of 29 subjects were analysed (RME group, N = 16 and SME group, N = 13). CBCT scans taken before expansion and 6 months later were evaluated. Five posterior and 6 anterior transverse measurements were made at different vertical levels. Treatment changes were analysed using paired t tests; independent t tests were used to compare the two groups. RESULTS: There were statistically significant (P<.05) increases in maxillary width at the skeletal, alveolar, and dental levels for both groups, with significantly smaller increases at the more superior than inferior levels. The RME group exhibited statistically larger width increases than the SME group for all measures except interorbital width, anterior alveolar process width, and intercanine width. The group differences were greater for anterior than posterior apical base widths. CONCLUSIONS: Rapid maxillary expansion produced greater orthopaedic effects than slow maxillary expansion, with the greatest effects occurring in the anterior apical base.

Risk assessments in orthodontic patients developing white spot lesions.

AIM: To determine whether caries risk factors, including cariogenic bacterial levels and salivary function, can be used to identify orthodontic patients who develop white spot lesions (WSL). METHODS: This prospective case-control study comprised 50 patients 11-17 years of age, including 25 controls and 25 cases who developed new WSL during treatment. WSL, oral hygiene and fluorosis were evaluated from intraoral photographs. The biofilm was assessed with bacterial cultures and adenosine triphosphate (ATP) bioluminescence. Salivary analyses were performed to determine the pH of saliva and flow rates. A survey was used to assess snacking frequency, oral hygiene and fluoride utilization. RESULTS: There were no between-group pretreatment differences in WSL. Cases reported eating sugary foods significantly more often than the controls. There was a significant decline in oral hygiene during treatment, with no significant between-group difference. There also were no statistically significant between-group differences in the amount of saliva, buffer, ATP bioluminescence and bacterial levels. Both groups showed lower than normal buffer capacity and high bacterial levels. CONCLUSION: Cases had greater sugar intake between meals than controls. ATP bioluminescence, Streptococcus mutans levels with Saliva Check Mutans, and salivary factors do not identify patients who develop WSL.

The prevalence of clinically meaningful malocclusion among US adults.

OBJECTIVE: The primary purpose of this study was to statistically evaluate age, ethnic and sex differences in the prevalence of clinically meaningful malocclusions among adults. SETTING AND SAMPLE POPULATION: A random sample of 8804 untreated US adults between 17 and 46 years of age was selected from the Third National Health and Nutrition Examination Survey data. MATERIALS & METHODS: Three ethnic (non-Hispanic White, non-Hispanic Black and Mexican Americans) and three age (17-26, 27-36 and 37-46 years) groups were evaluated. Subjects with and without clinically meaningful malocclusions were categorized based on the established cut-off values. Chi-square analyses were performed to determine differences in prevalence. RESULTS: The prevalence of clinically meaningful mandibular incisor irregularity, overjet and overbite increased significantly (P < 0.05) with age, while posterior crossbite decreased. There were statistically significant ethnic differences in the prevalence of incisor irregularity, overbite, overjet, open bite and reverse overjet. Males had a significantly higher prevalence of clinically meaningful mandibular incisor irregularity, overbite, open bite and reverse overjet than females. One-third of US adults exhibited no clinically meaningful malocclusions. CONCLUSIONS: There are age, ethnic and sex differences in the prevalence of clinically meaningful malocclusions that characterize approximately two-thirds of untreated US adults.

Localizing the osseous boundaries of micro-osteoperforations.

INTRODUCTION: The aim of this work was to determine how far the effects of micro-osteoperforations (MOPs) extend within bone by quantifying the damage caused and the short-term bony adaptations that occur in and around the injury site. METHODS: With the use of a split-mouth design, 34 MOPs (Propel) were randomly placed in the mandibular furcal bone of 13 beagle dogs either 2 or 4 weeks before killing them. The control side received no treatment. Vickers hardness microindentation, microscopic computed tomography, and histologic analyses were performed to evaluate the bone surrounding the MOPs. RESULTS: Microfractures produced during insertion extended ∼0.6 mm from the MOP sites. Cortical and trabecular bone were significantly less dense on the experimental than on the control side up to 4.2 mm from the edge of the MOP, but side differences were small (<5%) beyond 1.5 mm from the MOP. Experimental cortical bone was significantly softer than the control bone up to 0.8 mm from the MOP after 2 weeks of healing, and up to 0.5 mm from the MOP after 4 weeks of healing. Hematoxylin and eosin stained sections of cortical and trabecular bone showed small areas of woven bone within the MOP sites after 2 weeks, and acellular areas of bone extending ∼0.5 mm from the MOP. After 4 weeks of healing, there were greater amounts of woven bone, as well as early signs of lamellar bone, in and around the MOP sites. Markedly increased TRAP activity extending up to 2.5 mm from the MOP was evident after 2 weeks, but not after 4 weeks. Vital fluorescence staining showed diffuse bone deposition on the experimental side up to 1.5 mm from the MOP margin. CONCLUSIONS: When MOPs are performed in beagle dogs, demineralization is transient and healing of the injured area, as well as remineralization of bone affected by MOP placement, begins during the first 2 weeks. Although the transient effects extend farther, the principal effects extend only ∼1.5 mm from the MOP site.