Superimposition of dental models to determine orthodontic tooth movements : Comparison of different superimposition methods in vitro and in vivo.

PURPOSE: Using a commercial orthodontic treatment planning system, tooth movements were simulated to analyse how precise predefined movements can be determined by three different superimposition methods. Additionally, a retrospective analysis on clinical patient models before and after orthodontic treatment was performed to analyse possible differences in determination of clinical tooth movements with these methods. METHODS: (1) A hexapod system was used to perform the tooth movements in physical maxillary dental models (N = 70). The initial and final situations were scanned, superimpositions executed, movements calculated, and their accuracy compared to the predefined movements was determined. (2) Digital three-dimensional (3D) maxillary dental models representing pre- and postorthodontic treatment situations (N = 100 patients) were superimposed. Selected tooth movements were calculated (N = 3600), and the results of the different superimposition methods were compared pairwise. RESULTS: (1) The experimental study delivered only small location and scale shifts. Furthermore, concordance correlation coefficients above 0.99 for all three methods. This verified that all methods deliver values corresponding well to the predefined movements. (2) The retrospective analysis of the clinically performed orthodontic tooth movements comparing pairwise the three different methods intraindividually also showed small location and scale shifts. Furthermore, concordance correlation coefficients between 0.68 and 0.98 were observed, with only three of them below 0.8. This verified that the applied superimposition methods delivered values sufficiently close to each other. CONCLUSIONS: As the experimental study showed very good agreement between the predefined and determined movements, and as the retrospective clinical study showed that the methods compared pairwise delivered values close to each other for the performed orthodontic tooth movements, it can be concluded that orthodontic tooth movements can be determined adequately correct by each of the examined methods.

Comparative investigation of fully customized lingual bracket systems and conventional labial appliances: Analysis of forces/moments and final tooth positions.

INTRODUCTION: The assessment of forces and moments generated by fully customized lingual appliances and their effectiveness in tooth movement were compared with conventional labial bracket systems, applied to a specific malocclusion model. METHODS: Two fully customized lingual appliances (Incognito [3M Unitek, Monrovia, Calif] and WiN [DW Lingual Systems, Bad Essen, Germany]) and 2 labial bracket systems (Discovery classic and Discovery smart [Dentaurum, Ispringen, Germany]) were examined with nickel-titanium wires of different cross-sections (0.012, 0.014, 0.016, and 0.016 × 0.022-in) and 3 tooth types (canine, lateral incisor, and second premolar). Simulated movement was performed with a wire replacement as soon as forces or moments were no longer effective. RESULTS: Lingual and labial appliances showed statistically significant differences in initial forces and moments when tested with the same cross-section wires. Statistically significant differences between the 2 lingual bracket systems were also registered. Both lingual appliances rotated the premolar less than the conventional labial appliances. CONCLUSIONS: In areas of smaller lingual interbracket distance and higher lingual slot misalignment, the tested lingual multibracket appliances showed higher forces than the labial appliances. The force difference was particularly prominent with vertically oriented lingual slots and rectangular wires. The tested lingual appliances presented difficulties in rotating the premolar.

Vertical and Orovestibular Forces Generated by Beta-Titanium and Stainless-Steel Rectangular Wires in Labial and Fully Customized Lingual Bracket Systems.

This study aimed to investigate the force values exerted from rectangular wires when combined with conventional labial and fully customized lingual appliances under predefined, idealized activation. Fully customized lingual brackets of two brands Incognito™ (3M Unitek, Monrovia, CA, USA) and WIN (DW Lingual Systems, Bad Essen, Germany) and labial brackets of another brand, discovery® MIM and discovery® smart systems (Dentaurum, Ispringen, Germany), were chosen. Stainless-steel and beta-titanium wires of 0.018" × 0.025" were examined. For IncognitoTM, 0.0182" × 0.025" beta-titanium wires were tested. Intrusion/extrusion and orovestibular movements were performed in a range of 0.2 mm, and the forces were recorded for each 0.1 mm of the movement. Mean values and standard deviations were calculated for all measurements, and ANOVA was performed for statistical analysis. Slight differences were observed between the forces generated from beta-titanium and stainless-steel wires. The same wire generated in some cases 5-53% higher forces with the lingual appliance due to the vertical orientation of the long walls during intrusion/extrusion and increased wire stiffness at the anterior region. Beta-titanium and stainless-steel 0.018" × 0.025" wires can generate similar force values during the final stages of the orthodontic therapy; thus, possibly only one of the two alloys could be used in each orthodontic wire sequence.

Impact of the endocannabinoid system on murine cranial and alveolar bone phenotype.

PURPOSE: The endocannabionoid signaling system has been demonstrated to be present in the skeleton, with involvement in the regulation of skeletal homeostasis. However, investigations substantiating these findings in cranial and alveolar bones are missing to date. The aim of our study was to investigate a potential impact of the endocannabinoid system on cranial and alveolar bone structures and phenotypes. BASIC PROCEDURES: CB1-/-, CB2-/- and WT mice (n = 5) were scanned via µCT. Reconstructed datasets were processed for analyses. Cranial cephalometric measurements were performed with OnyxCeph3TMsoftware. Alveolar bone densities were determined via mean grey value measurements with Mimics research 18.0. Alveolar bone heights around teeth in upper and lower jaws were morphometrically analyzed. Alveolar osteoclasts were quantified via TRAP staining of paraffin-embedded histologies. Bone-marrow derived macrophages isolated from murine hind legs were analyzed for CD40 and MMR expression via flow cytometry. MAIN FINDINGS: CB2-/- mice exhibited significantly higher bone densities with mean grey values of 138.3 ± 22.6 compared to 121.9 ± 9.3 for WT for upper jaws, and 134.6 ± 22.9 compared to 116.1 ± 12.9 for WT 134.6 ± 22.9. Concurrently, CB2 receptor knockout entailed reduced alveolar bone heights of about 50% compared to WT mice. Antigen-presenting cell marker expression of MMR was significantly diminished in bone-marrow derived macrophages of CB2-/- mice. Cranium dimensions as much as alveolar osteoclasts were unaffected by receptor knockouts.CB1 receptor knockout did not involve statistically significant alterations in the parameters investigated compared to WT mice. PRINCIPAL CONCLUSIONS: The endoncannabinoid system, and particularly CB2 receptor strongly affects murine alveolar bone phenotypes. These observations suggest CB2 as promising target in the modulation of oral bone phenotypes, probably by impact on bone dynamics via osteal immune cells.

Dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents.

PURPOSE: Premolar extraction in orthodontic therapy is common in adolescent patients. Knowledge of the tissue reaction in an extraction site is mainly based on studies with animal and adults. Thus, we aim to describe the time-dependent dimensional changes of the alveolar ridge contour of the premolar extraction site in adolescents. METHODS: Clinical data were obtained from a randomized controlled clinical trial (Universal Trial Number U1111-1132-6655), comparing treatment modalities with orthodontic space closure was initiated after 2-4 weeks (group A) and ≥ 12 weeks after tooth extraction (group B). Dental casts taken before the tooth extraction (T1) and before initiation of the space closure (T2) were digitalized with a 3D scanner and superimposed to analyze the dimensional changes of the alveolar ridge in early and later stage of wound healing. Linear mixed models were used for statistical analysis. RESULTS: Plaster models of 25 patients (mean age 15.2 years, 11 male and 14 female) with 66 extraction sites were enrolled. The average atrophic changes from tooth extraction to the early stage of wound healing (group A, n = 41) were in total 27.5% ± 11.8; labially 31.3% ± 15.1 and orally 23.6% ± 13.4. In group B (n = 25) the average atrophic changes were in total 38.6% ± 12.1; labially 46.2% ± 16.7; orally 31.3% ± 18.9. The atrophic changes between the groups in total (p = 0.031) and at the labial side (p = 0.012) were significant. The jaw affiliation was a significant parameter for all examined areas in regard to all cases (labial p = 0.019; oral p = 0.020; total p = 0.001). Atrophic changes between genders were not statistically different. CONCLUSIONS: Alveolar atrophy increased over time after extraction primarily in the lower jaw at the labial side. The main atrophy occurred in the first healing phase of the extraction socket. Thus, timely coordination is important to preserve sufficient bone levels. The atrophic changes of the alveolar ridge in adolescents parallel those reported for adults.

The influence of enamel sandblasting on the shear bond strength and fractography of the bracket-adhesive-enamel complex tested in vitro by the DIN 13990:2017-04 standard.

OBJECTIVES: This study was conducted in order to investigate whether enamel sandblasting as an adjunct or substitute to the acid-etch technique has an effect on the shear bond strength (SBS) and fractography of the bracket-adhesive-enamel complex using the DIN 13990:2017-04 standard. MATERIALS AND METHODS: Upper central incisor brackets (discovery®, Dentaurum, Germany) were bonded using Transbond XT™ (3M Unitek, Germany) on bovine incisors prepared by four different methods (15 samples each): sandblasting with 27 µm Al2O3 at 1.2 bar (s), acid etching with 37.4% phosphoric acid (a), sandblasting with 27 µm Al2O3 at 1.2 bar followed by acid etching (s1a), and sandblasting with 50 µm Al2O3 at 5.7 bar followed by acid etching (s2a). The SBS and adhesive remnant index (ARI) were measured, followed by one-way analysis of variance and Fisher's exact tests at 5%. RESULTS: The SBS in groups s (5.6 ± 2.2 MPa), a (17.1 ± 4.3 MPa), s1a (18.3 ± 4.3 MPa), and s2a (18.5 ± 4.6 MPa) indicated that the s group was significantly inferior to all the other groups (p < 0.001). Likewise, the ARI analysis indicated a different performance of the s group (mostly ARI of 0) compared to the other groups (p < 0.001) and a tendency for different ARI between the a and s1a/s2a groups. CONCLUSIONS: In vitro enamel sandblasting could not substitute acid etching and did not offer improved SBS when used before acid etching, regardless of air pressure and powder granulation. Sandblasting without acid etching produced less residual resin on the tooth after debonding. CLINICAL RELEVANCE: The clinical use of adjunct enamel sandblasting prior to etching to enhance SBS has to be questioned.

Failure patterns of different bracket systems and their influence on treatment duration: A retrospective cohort study.

OBJECTIVES: To compare the failure pattern of four different bracket types and to assess its effect on treatment duration. MATERIALS AND METHODS: A total of 78 white patients (28 male, 50 female) with a mean age of 12.6 years were included in this retrospective cohort study and treated for a mean period of 30.6 months. The patients were treated in a private practice with stainless steel conventionally ligated brackets, ceramic conventionally ligated brackets, stainless steel self-ligating brackets, or nickel-free self-ligating brackets. The loss of at least one bracket during the course of treatment was analyzed with Cox proportional hazards survival analyses and generalized linear regression. RESULTS: The overall bracket failure rate at the tooth level was 14.1% (217 brackets), with significant differences according to tooth type (between 8.0%-23.4%) and bracket type (between 11.2%-20.0%). After taking confounders into account, patients treated with ceramic brackets lost more brackets (hazard ratio = 1.62; 95% confidence interval = 1.14-2.29; P = .007) than patients with stainless steel brackets. On average, treatment time increased by 0.6 months (95% confidence interval = 0.21-1.05; P = .004) for each additional failed bracket. CONCLUSIONS: Bracket failure was more often observed with ceramic brackets and was associated with increased treatment duration.

In vitro biomechanical analysis of torque capabilities of various 0.018″ lingual bracket-wire systems: total torque play and slot size.

OBJECTIVES: To determine the total torque play of various rectangular titanium molybdenum alloy (TMA)/stainless steel (SS) wires in various 0.018″ upper incisor lingual brackets and slot size measurements. METHODS: TMA (0.0175″ × 0.0175″, 0.0170″ × 0.025″, 0.0182″ × 0.0182″, 0.0182″ × 0.025″) and SS wires (0.016″ × 0.022″, 0.016″ × 0.024″, 0.018″ × 0.025″) were twisted in standard (Hiro, Incognito™, Joy®, Kurz 7th generation, STb™: fixation with elastic modules) and self-ligating brackets (Evolution SLT®, In-Ovation® L MTM: closed ligation mechanism) from -20 degrees to +20 degrees with a custom-made machine. The total torque play was calculated by extrapolating the linear portion of the twist/moment curves to the x-axis and adding the absolute negative and positive angle values at the intercepts. The bracket slot height was measured before and after the experiments with a series of pin gauges with round profile. RESULTS: Brackets in ascending order for total torque play with the most slot-filling wire TMA 0.0182″ × 0.025″: Evolution SLT® (0 degree ± 0 degree), Incognito™ (2.2 degrees ±1.1 degrees), Hiro (5.1 degrees ±3.0 degrees), In-Ovation® L MTM (6.3 degrees ±2.2 degrees), STb™ (6.6 degrees ±1.8 degrees), Kurz 7th generation (7.1 degrees ±0.8 degrees), and Joy® (12.0 degrees ±0.8 degrees). Wires in ascending order for total torque play with the most precise slot Incognito™: TMA 0.0182″ × 0.025″ (2.2 degrees ±1.1 degrees), TMA 0.0182″ × 0.0182″ (2.4 degrees ±0.9 degrees), SS 0.018″ × 0.025″ (5.5 degrees ±1.0 degrees), TMA 0.0170″ × 0.025″ (9.4 degrees ±1.8 degrees), TMA 0.0175″ × 0.0175″ (13.0 degrees ±1.5 degrees), SS 0.016″ × 0.024″ (16.1 degrees ±1.4 degrees), SS 0.016″ × 0.022″ (17.8 degrees ±1.0 degrees); differences between some of the experimental groups were not statistically significant. Bracket slot dimensions in ascending order: Evolution SLT® (less than 0.452mm), Incognito™ (0.460mm ±0.002mm), In-Ovation® L MTM (0.469mm ±0.001mm), Hiro (0.469mm ±0.010mm), STb™ (0.471mm ±0.002mm), Kurz 7th generation (0.473mm ±0.002mm), and Joy® (greater than 0.498mm). LIMITATIONS: The applied method must be questioned when used with brackets with incomplete slot walls (Evolution SLT®). Slot measurement with pin gauges may not register bracket wing deformation. CONCLUSIONS: All brackets showed a differing slot size from the nominal 0.018″ (0.457mm). Incognito™ presented the most precise and Joy® the widest slot. The main wires for the retraction phase SS 0.016″ × 0.022″/SS 0.016″ × 0.024″ showed poor torque control. Among the finishing TMA wires, TMA 0.0175″ × 0.0175″ exhibited the highest and TMA 0.0182″ × 0.0182″/TMA 0.0182″ × 0.025″ the smallest torque play. SIGNIFICANCE: The manufacturers could profit from this investigation towards optimization of the dimensional precision of their products. The orthodontist must be aware of the torque play of the wire-bracket combinations to be able to plan and individualize the appliance by third order customization.

Nonsyndromic cleft lip with or without cleft palate: Increased burden of rare variants within Gremlin-1, a component of the bone morphogenetic protein 4 pathway.

BACKGROUND: The genes Gremlin-1 (GREM1) and Noggin (NOG) are components of the bone morphogenetic protein 4 pathway, which has been implicated in craniofacial development. Both genes map to recently identified susceptibility loci (chromosomal region 15q13, 17q22) for nonsyndromic cleft lip with or without cleft palate (nsCL/P). The aim of the present study was to determine whether rare variants in either gene are implicated in nsCL/P etiology. METHODS: The complete coding regions, untranslated regions, and splice sites of GREM1 and NOG were sequenced in 96 nsCL/P patients and 96 controls of Central European ethnicity. Three burden and four nonburden tests were performed. Statistically significant results were followed up in a second case-control sample (n = 96, respectively). For rare variants observed in cases, segregation analyses were performed. RESULTS: In NOG, four rare sequence variants (minor allele frequency < 1%) were identified. Here, burden and nonburden analyses generated nonsignificant results. In GREM1, 33 variants were identified, 15 of which were rare. Of these, five were novel. Significant p-values were generated in three nonburden analyses. Segregation analyses revealed incomplete penetrance for all variants investigated. CONCLUSION: Our study did not provide support for NOG being the causal gene at 17q22. However, the observation of a significant excess of rare variants in GREM1 supports the hypothesis that this is the causal gene at chr. 15q13. Because no single causal variant was identified, future sequencing analyses of GREM1 should involve larger samples and the investigation of regulatory elements.

Nonsyndromic cleft lip with or without cleft palate in arab populations: genetic analysis of 15 risk loci in a novel case-control sample recruited in Yemen.

BACKGROUND: Nonsyndromic orofacial clefting (nsOFC) is among the most common of all congenital disorders and has a genetically complex etiology. Based on embryological and epidemiological data, the phenotype can be differentiated into nonsyndromic cleft lip with or without cleft palate (nsCL/P) and nonsyndromic cleft palate only, with nsCL/P being the most frequent form. Recent genetic research, predominantly performed in populations from Europe and Asia, has identified numerous genetic susceptibility loci for nsCL/P. As only few data are available concerning genetic susceptibility to nsCL/P in Arab populations, we investigated a newly recruited nsOFC sample from Yemen. METHODS: For each of the 15 currently known nsCL/P risk loci, the top single-nucleotide polymorphism (plus nine back-up variants) were genotyped in 242 nsCL/P cases and 420 healthy controls. RESULTS: Single-marker association analysis revealed significant associations for four loci (8q24, 9q22, 10q25, 13q31). The strongest association was for the European high risk locus at 8q24 (Pcorrected = 5.09 × 10(-4) ; heterozygous odds ratio = 1.74 (1.22-2.47), homozygous odds ratio = 2.47 (1.55-3.93). Five additional loci (1q32.2, 3q12, 8q21, 17q22, 20q12) showed nominal significance that did not withstand correction for multiple testing. Although the six remaining loci (1p22, 1p36, 2p21, 3p11, 15q22, 17p13) failed to reach nominal significance, the risk alleles were in the same direction as in the discovery studies. CONCLUSION: The results suggest that four of the 15 analyzed nsCL/P risk loci which were identified in European and Asian ethnicities significantly confer risk for nsCL/P in Arab populations.

The influence of cyclic shear fatigue on the bracket-adhesive-enamel complex: an in vitro study.

OBJECTIVES: To describe the effect of fatigue on the strength of the bracket-adhesive-enamel complex and characterize the fatigue behavior of the materials tested. METHODS: Upper central incisor brackets (Discovery(®), Dentaurum) were bonded with a light-curing (Transbond XT™, 3M Unitek) and a chemically-curing adhesive (Concise™, 3M Unitek) on bovine teeth embedded in cylindrical resign bases and stored in water at 37(±2)°C for 24 (±2)h. The first 15 specimens were tested with a universal testing machine ZMART.PRO(®) (Zwick GmbH & Co. KG, Ulm, Germany) for ultimate shear bond strength according to the DIN-13990-2-standard. The remaining three groups of 20 specimens underwent fatigue staircase testing of 100, 1000 and 3000 cycles at 1Hz with a self-made testing machine. The survived specimens were subjected to shear strength testing. RESULTS: The fatigued specimens showed decreased shear strength with both adhesives at all cycle levels. The shear strength after fatigue for 100, 1000 and 3000 cycles was in the Concise™-groups 34.8%, 59.0%, 47.3% and in the Transbond™ XT-groups 33.6%, 23.1%, 27.3% relative to the ultimate shear strength. The fatigue life of the Concise™-groups decreased with increasing stress and Transbond™ XT showed lower fatigue ratio with no obvious trend. The specimens bonded with Transbond™ XT showed typically favorable fracture modes in contrary to Concise™. SIGNIFICANCE: Fatigue of the bracket-adhesive-enamel complex decreased its shear strength. The staircase method can provide a standardized experimental protocol for fatigue studies, however testing at various cycle numbers is recommended.

Genome-wide meta-analyses of nonsyndromic cleft lip with or without cleft palate identify six new risk loci.

We have conducted the first meta-analyses for nonsyndromic cleft lip with or without cleft palate (NSCL/P) using data from the two largest genome-wide association studies published to date. We confirmed associations with all previously identified loci and identified six additional susceptibility regions (1p36, 2p21, 3p11.1, 8q21.3, 13q31.1 and 15q22). Analysis of phenotypic variability identified the first specific genetic risk factor for NSCLP (nonsyndromic cleft lip plus palate) (rs8001641; P(NSCLP) = 6.51 × 10(-11); homozygote relative risk = 2.41, 95% confidence interval (CI) 1.84-3.16).

The influence of adhesives and the base structure of metal brackets on shear bond strength.

OBJECTIVE: The objective of this study was to investigate the shear bond strength of compound made of tooth enamel, adhesive, and brackets for certain material combinations according to the DIN 13990-2 standard. MATERIALS AND METHODS: We examined a combination of the following materials on permanent bovine incisors: (1) adhesives: Light Bond™ and Phase II® (both produced by Reliance Orthodontic Products, Itasca, IL, USA), Transbond XT™ (3M Unitek, Monrovia, CA, USA), (2) brackets: Carriere®, Euro Midi Classic, Midi Low Friction (all from Ortho Organizers, Carlsbad, CA, USA). The discovery® bracket (Dentaurum, Ispringen, Germany) served as the reference. According to the DIN standard, the teeth were embedded, adhesive was applied and they were then put into storage. This was followed by shear tests in a material testing machine with the shear force acting directly on the bracket base in the occlusal-gingival direction. Finally, the Adhesive Remnant Index was determined. RESULTS: We observed the greatest shear bond strength (mean value) from the combination of Carriere® and Transbond XT™ (17.4 N/mm(2)), and the lowest from the combination of Euro Midi Classic and Phase II® (12.8 N/mm(2)). There were significant differences in the various material combinations. The values obtained from the measurements of discovery® together with Transbond XT™ agreed very well with the results of previous investigations. CONCLUSION: The combinations of brackets and adhesives investigated in this study according to DIN standard 13990-2 provided a satisfactory result for clinical use.

Treatment of an impacted dilacerated maxillary central incisor.

The diagnosis of an impacted incisor with dilaceration refers to a dental deformity characterized by an angulation between the crown and the root, causing noneruption of the incisor. In the past, surgical extraction was the first choice in treating severely dilacerated incisors. The purpose of this case report was to present the correction of a horizontally impacted and dilacerated central incisor through 2-stage crown exposure surgery combined with continuous-force orthodontic traction. The tooth was successfully moved into its proper position. The treatment is discussed, and the orthodontic implications are considered, with a review of the current literature on this topic.

The significance of RUNX2 in postnatal development of the mandibular condyle.

OBJECTIVE: RUNX2, in the Runt gene family, is one of the most important transcription factors in the development of the skeletal system. Research in recent decades has shown that this factor plays a major role in the development, growth and maturation of bone and cartilage. It is also important in tooth development, mechanotransduction and angiogenesis, and plays a significant role in various pathological processes, i.e. tumor metastasization. Mutations in the RUNX2 gene correlate with the cleidocranial dysplasia (CCD) syndrome, important to dentistry, particularly orthodontics because of its dental and orofacial symptoms. Current research on experimentally-induced mouse mutants enables us to study the etiology and pathogenesis of these malformations at the cellular and molecular biological level. This study's aim is to provide an overview of the RUNX2 gene's function especially in skeletal development, and to summarize our research efforts to date, which has focused on investigating the influence of RUNX2 on mandibular growth, which is slightly or not at all altered in many CCD patients. MATERIALS AND METHODS: Immunohistochemical analyses were conducted to reveal RUNX2 in the condylar cartilage of normal mice and of heterozygous RUNX2 knockout mice in early and late growth phases; we also performed radiographic and cephalometric analyses. RESULTS: We observed that RUNX2 is involved in normal condylar growth in the mouse and probably plays a significant role in osteogenesis and angiogenesis. The RUNX2 also has a biomechanical correlation in relation to cartilage compartmentalization. At the protein level, we noted no differences in the occurrence and distribution of RUNX2 in the condyle, except for a short phase during the 4th and 6th postnatal weeks, so that one allele might suffice for largely normal growth; other biological factors may have compensatory effects. However, we did observe small changes in a few cephalometric parameters concerning the mandibles of heterozygous knockout animals. We discuss potential correlations to our findings by relating them to the most current knowledge about the RUNX2 biology.