Esthetic outcomes in orthodontics through digital customization with a lingual appliance system.

BACKGROUND: Contemporary fixed orthodontic appliances are shifting from non-customized pre-adjusted appliances to custom-designed and printed appliances with novel digital setup systems. We are one step closer to precision dentistry and orthodontics using personalized mechanics and custom appliances. However, despite the evidential enhancement and other improvements to fixed appliances, tooth movement is still limited to five degrees of freedom. Opening or closing spaces still requires manually placing elastomeric chains or coil springs. AIM: In this article, we aimed to demonstrate how advancements in CAD/CAM technology, reverse engineering, and digital customization are helping orthodontics constantly evolve, enabling treatment with enhanced esthetics and minimal compliance. The clinical system (InBrace®, Irvine, CA) described in this article uses a patient-specific, digitally designed multiloop NITI wire that delivers friction-free, light, and continuous forces and activates automatically whenever the malocclusion deviates from the digital setup. CONCLUSION: Through digital customization, InBrace allows for automated tooth movement in all six degrees of freedom, including space opening or closure, via programmed non-sliding mechanics. CLINICAL SIGNIFICANCE: Precision orthodontics and personalized treatment have been significant developments in orthodontics recently. This article focuses on how a technologically advanced lingual appliance system could achieve targeted cosmetic results methodically via automation and personalization.

Connecting the dots towards precision orthodontics.

Precision orthodontics entails the use of personalized clinical, biological, social and environmental knowledge of each patient for deep individualized clinical phenotyping and diagnosis combined with the delivery of care using advanced customized devices, technologies and biologics. From its historical origins as a mechanotherapy and materials driven profession, the most recent advances in orthodontics in the past three decades have been propelled by technological innovations including volumetric and surface 3D imaging and printing, advances in software that facilitate the derivation of diagnostic details, enhanced personalization of treatment plans and fabrication of custom appliances. Still, the use of these diagnostic and therapeutic technologies is largely phenotype driven, focusing mainly on facial/skeletal morphology and tooth positions. Future advances in orthodontics will involve comprehensive understanding of an individual's biology through omics, a field of biology that involves large-scale rapid analyses of DNA, mRNA, proteins and other biological regulators from a cell, tissue or organism. Such understanding will define individual biological attributes that will impact diagnosis, treatment decisions, risk assessment and prognostics of therapy. Equally important are the advances in artificial intelligence (AI) and machine learning, and its applications in orthodontics. AI is already being used to perform validation of approaches for diagnostic purposes such as landmark identification, cephalometric tracings, diagnosis of pathologies and facial phenotyping from radiographs and/or photographs. Other areas for future discoveries and utilization of AI will include clinical decision support, precision orthodontics, payer decisions and risk prediction. The synergies between deep 3D phenotyping and advances in materials, omics and AI will propel the technological and omics era towards achieving the goal of delivering optimized and predictable precision orthodontics.

Clinical advances in maxillary skeletal expansion and introduction of a new MARPE concept.

BACKGROUND: Transverse maxillary deficiency, typically characterized by the clinical manifestations of unilateral or bilateral crossbite, is a common orthodontic discrepancy. The primary goal of maxillary expansion should be to obtain a nearly maximum width increase in the basal bone of the constricted maxilla and to avoid the dental expansion of the anchor teeth. The introduction of miniscrew anchorage-supported rapid maxillary expansion (MARPE) devices has helped increase the feasibility of obtaining nonsurgical transverse correction in late adolescents and young adults with optimum orthopedic effects. However, the success rate of MARPE shows a negative correlation with age. Although MARPE offers an effective method for correcting a transverse skeletal deficiency, given the appliance cost and increased risk for complications, it could present challenges for adult patients and practitioners in daily practice. AIMS: In this article, current advances in maxillary skeletal expansion are summarized, and a new MARPE concept is introduced. CONCLUSION: The new MARPE design offers several advantages to other existing methods: (1) it can be installed directly to the patient in the clinical setting with no additional laboratory waiting times. (2) It is purely a bone-borne appliance. (3) The appliance is designed to be placed in the thickest part of the anterior palate to maximize the cortical and trabecular bone support. (4) Allows for bicortical placement of the miniscrews with no perforations in the nasal floor. Finally, (5) offers an esthetic and minimalistic approach to maxillary skeletal expansion in late adolescent and adult patients.

Functional characterization of ATF1, GREM2 AND WNT10B variants associated with tooth agenesis.

OBJECTIVE: To determine the functional effects of ATF1, WNT10B and GREM2 gene variants identified in individuals with tooth agenesis (TA). SETTINGS AND SAMPLE POPULATION: Stem cells from human exfoliated deciduous teeth (SHED) were used as an in vitro model system to test the effect of TA-associated variants. MATERIALS AND METHODS: Plasmid constructs containing reference and mutant alleles for ATF1 rs11169552, WNT10B rs833843 and GREM2 rs1414655 variants were transfected into SHED for functional characterization of variants. Allele-specific changes in gene transcription activity, protein expression, cell migration and proliferation, and expression of additional tooth development genes (MSX1, PAX9 and AXIN2) were evaluated. Data analyses were performed using Student's t-test. P-values ≤ .05 were considered statistically significant. RESULTS: Mutant variants resulted in significantly decreased transcriptional activity of respective genes (P < 0.05), although no changes in protein localization were noted. Expression of MSX1 was significantly decreased in ATF1- and GREM2-mutant cells, whereas PAX9 or AXIN2 mRNA expression was not significantly altered. Mutant WNT10B had no significant effect on the expression of additional TA genes. ATF1- and GREM2-mutant cells presented increased cell migration. Cell proliferation was also affected with all three mutant alleles. CONCLUSIONS: Our results demonstrate that ATF1, WNT10B and GREM2 mutant alleles have modulatory effects on gene/protein function that may contribute to TA.

Evaluation of current additive manufacturing systems for orthodontic 3-dimensional printing.

INTRODUCTION: The objective of this research was to evaluate and compare linear and surface accuracy of dental models fabricated using 3 different vat photopolymerization printing units: digital light synthesis (M2 Printer; Carbon, Redwood City, Calif), digital light processing (Juell 3D Flash OC; Park Dental Research, New York, NY), and stereolithography apparatus (Form 2; Formlabs Inc, Somerville, Mass), and a material jetting printing unit: PolyJet (Objet Eden 260VS; Stratasys, Eden Prairie, Minn). METHODS: Maxillary and mandibular dental arches of 20 patients with the American Board of Orthodontics Discrepancy Index scores ranging between 10 and 30 were scanned using an intraoral scanner. Stereolithographic files of each patient were printed via the 3-dimensional (3D) printers and were digitized again using a 3D desktop scanner to enable comparisons with the original scan data. One-sample t test and linear regression analyses were performed. To further graphically examine the accuracy between the different methods, Bland-Altman plots were computed. The level of significance was set at P <0.05. RESULTS: Bland-Altman analysis showed no fixed bias of one approach vs the other, and random errors were detected in all linear accuracy comparisons. When a 0.25 mm tolerance level was deemed acceptable for any positive or negative surface changes, only the models manufactured from digital light processing and PolyJet units showed more than 97% match with the original scans. CONCLUSION: The surface area of 3D printed models did not yield an utterly identical match to the original scan data and was affected by the type of printer. The clinical relevance of the differences observed on the 3D printed dental model surfaces requires application-specific judgments.

Referral patterns of pediatric dentists and general practitioners to orthodontists based on case complexity.

OBJECTIVE: The objectives of this research were to investigate and compare general and pediatric dentists' subjective judgments of orthodontic case complexity and to determine how their perceptions of case complexity influence their decisions to refer the patient to an orthodontist. METHODS: Twenty pediatric dentists and 21 general dentists participated in the study. Pretreatment orthodontic records of 20 patients with a variety of malocclusions and a range of American Board of Orthodontics Discrepancy Index (DI) scores were used. Respondents were asked about their background and training in orthodontics. They were also asked to identify the subjective complexity of each case with the use of a 100-point visual analog scale (VAS) and whether they would refer the patient to an orthodontic specialist. A mixed-model multivariate data analysis was used to evaluate the subjective case complexity with the use of fixed factors such as DI score, type of panel member, experience, annual continuing education rate, and gender. Generalized linear mixed models were used to investigate the referral patterns of the general dentists and pediatric dentists. Level of significance was set at P < 0.05 for all statistical analyses. RESULTS: General dentists appeared to provide more overall orthodontic treatment than pediatric dentists; many general dentists provide limited orthodontic treatment and clear aligner therapy (P < 0.05). The perceived complexity score for cases was not significantly different between the 2 groups (P = 0.82). The association between DI score and perceived complexity was similar in both groups (P = 0.183) and there was a high correlation between DI and VAS score in the sample (r = 0.71; 95% Cl 0.38-0.87). Pediatric dentists had higher referral rates for cases with DI scores both below and above 20. Significant differences were noted between the pediatric and general dentists in the individual case referral decision as evaluated by the DI (P < 0.037) and VAS (P < 0.042) scores. CONCLUSIONS: General dentists provided more orthodontic care than the pediatric dentists. Both groups identified case complexity similarly, with only minor differences, but pediatric dentists had higher referral rates to orthodontic specialists regardless of the initial case complexity.

Specialist training influences the ability to recognise orthodontic case complexity.

General dentists and other dental specialists may be treating orthodontic cases without a proper understanding of the key components of malocclusion. This mini-review aims to identify the discrepancies in recognition of orthodontic case complexity and to give an insight as to why advanced speciality training is a must for the provision of comprehensive orthodontic care.

Further evidence for the role of WNT10A, WNT10B and GREM2 as candidate genes for isolated tooth agenesis.

OBJECTIVE: To investigate the association of single nucleotide variants in the candidate genes WNT10A, WNT10B and GREM2 with isolated tooth agenesis. SETTING AND SAMPLE POPULATION: A total of 435 Caucasian individuals (88 cases with isolated tooth agenesis and 347 unrelated controls) were ascertained at the University of Texas Health Science Center at Houston School of Dentistry. Clinical and radiographic examination by orthodontists confirmed the diagnosis of tooth agenesis. Genetic evaluation excluded syndromic forms of tooth agenesis. MATERIALS AND METHODS: Saliva samples were collected as source of genomic DNA. Fourteen variants in/nearby WNT10A, WNT10B and GREM2 were genotyped to test for association with tooth agenesis. Genotyping was performed using TaqMan chemistry in a real-time polymerase chain reaction assay. Allelic and haplotype frequencies were compared among cases and controls using chi-square tests as implemented in PLINK v.1.06. Bonferroni correction was used and P ≤ 0.004 indicates statistical differences between groups. RESULTS: Significant associations were found between individual SNPs and SNP combinations in WNT10A, WNT10B and GREM2 SNPs with isolated tooth agenesis (P < 0.004). CONCLUSION: Our findings further support a role for variants in WNT10A, WNT10B and GREM2 genes in the aetiology of isolated tooth agenesis. Functional studies are necessary to investigate the biological effects of these gene variants in tooth agenesis phenotypes.

Accuracy of 3-dimensional curvilinear measurements on digital models with intraoral scanners.

INTRODUCTION: Our objectives were to evaluate and compare the digital dental models generated from 2 commercial intraoral scanners with manual measurements when performing 3-dimensional surface measurements along a curved line (curvilinear). METHODS: Dry mandibles (n = 61) with intact dentition were used. The mandibles were digitized using 2 chair-side intraoral scanners: Cadent iTero (Align Technology, San Jose, Calif) and Lythos Digital Impression system (Ormco, Orange, Calif). Digitized 3-dimensional models were converted to individual stereolithography files and used with commercial software to obtain the curvilinear measurements. Manual measurements were carried out directly on the mandibular teeth. Measurements were made on different locations on the dental arch in various directions. One-sample t tests and linear regression analyses were performed. To further graphically examine the accuracy between the different methods, Bland-Altman plots were computed. The level of significance was set at P <0.05. RESULTS: There were no significant differences between any of the paired methods; this indicated a certain level of agreement between the methods tested (P >0.05). Bland-Altman analysis showed no fixed bias of 1 approach vs the other, and random errors were detected in all comparisons. Although the mean biases of the digital models obtained by the iTero and Lythos scanners, when compared with direct caliper measurements, were low, the comparison of the 2 intraoral scanners yielded the lowest mean bias. No comparison displayed statistical significance for the t scores; this indicated the absence of proportional bias in these comparisons. CONCLUSIONS: The intraoral scanners tested in this study produced digital dental models that were comparatively accurate when performing direct surface measurements along a curved line in 3 dimensions.

Perceptions of orthodontic case complexity among orthodontists, general practitioners, orthodontic residents, and dental students.

INTRODUCTION: Our aims were to assess the perceptions of orthodontic case complexity among orthodontists, general dentists, orthodontic residents, and dental students and to compare their perceptions with the American Board of Orthodontics Discrepancy Index (DI). METHODS: Orthodontists, general dentists, orthodontic residents, and dental students (n = 343) participated in a Web-based survey. Pretreatment orthodontic records of 29 cases with varying DI scores were obtained. Respondents were asked to evaluate case complexity on a 100-point visual analog scale. Additional information was collected on participants' orthodontic education and orthodontic treatment preferences. Pearson correlation coefficients were used to assess the relationship between the average complexity score and the DI score. Repeated measures analysis with linear mixed models was used to assess the association between the average complexity score and the DI score and whether the association between the 2 scores varied by level of difficulty or panel group. The level of significance for all analyses was set at P <0.05. RESULTS: The results showed that 71.6% of general dentists provided some orthodontic services, with 21.0% providing full fixed appliances and 38.3% providing clear aligners. DI score was significantly associated with complexity perceptions (P = 0.0168). Associations between average complexity and DI score varied significantly by provider group (P = 0.0033), with orthodontists and residents showing the strongest associations. When the DI score was greater than 15, orthodontists and residents perceived cases as more complex than did the other provider groups. CONCLUSIONS: Orthodontists and orthodontic residents had better judgments for evaluating orthodontic case complexity. The high correlation between orthodontic professionals' perceptions and DI scores suggested that additional orthodontic education and training have an influence on the ability to recognize case complexity.

Color Properties of Demineralized Enamel Surfaces Treated with a Resin Infiltration System.

OBJECTIVE: To assess color properties of white spot lesions (WSLs) following resin infiltration treatment in vitro. MATERIALS AND METHOD: WSLs were artificially created on 30 extracted human teeth. Two groups were formed: (a) control, and (b) resin infiltrant group (n = 15, each). Instrumental color measurements were performed using a spectrophotometer and visual color evaluation was performed by three independent evaluators. Color assessment was determined at three time points: baseline (T0), after WSL formation (T1), and after resin infiltrant or control treatment (T2). CIELAB color coordinates were determined and the resultant color difference (ΔE*) was calculated between the time points. Two-way repeated measures analysis of variance (ANOVA) and One-way ANOVA analyses were used to evaluate the color changes. Pearson chi-square analysis was performed to evaluate the visual ratings between treatment and control groups. Level of significance was set p <0.05. RESULTS: After treatment of WSLs there was a significant color change (ΔE*) between treatment and control groups (p <0.05). Resin infiltration group showed a regression of all values toward the pretreatment levels. There was a significant difference in visual evaluation ratings between groups after treatment; treatment group had all surfaces receive a rating of being clinically acceptable, with 73% of these surfaces having no perceptible color difference to adjacent sound enamel. Meanwhile, control group received ratings of all surfaces having a visual color difference that was deemed as unacceptable (p < 0.05). CONCLUSION: In-vitro resin infiltration for the treatment of enamel WSLs produced a significant improvement in color, reverting L*, a*, and b* values back toward baseline values. CLINICAL SIGNIFICANCE: Resin infiltration of enamel white spot lesions on teeth is capable of managing the esthetic problem by reverting the L*, a*, and b* color coordinates back to their baseline values. (J Esthet Restor Dent 28:339-346, 2016).

Accuracy and mechanical properties of orthodontic models printed 3-dimensionally from calcium sulfate before and after various postprinting treatments.

INTRODUCTION: Dental models fabricated with 3-dimensional printing technologies are revolutionizing the practice of orthodontics, but they generally comprise polymeric materials that may not be suitable for certain applications, such as soldering appliances. The objective of this study was to investigate the dimensional accuracy and mechanical properties of 3-dimensional printed ceramic-based models before and after various treatments intended to improve their mechanical properties. METHODS: Thirty identical models were printed 3-dimensionally from a calcium sulfate-based substrate and divided into 3 groups for treatment: high heat (250°C for 30 minutes), low heat (150°C for 30 minutes), and Epsom salt treatment. Each model was scanned before and after treatment with a laser scanner, and dimensional stability was analyzed by digital superimpositions using a best-fit algorithm. The models were weighed before and after treatment to evaluate mass changes. Additionally, 3-dimensional printed cylinders treated as described above and an untreated control group were subjected to compressive mechanical testing (n = 11 per group). RESULTS: The Epsom salt treatment group had statistically significant increases in both peak compressive stress and modulus of elasticity when compared with the other treatment groups. All treatment groups had statistically significant changes in mass, with the Epsom salt group gaining mass and the 2 heat-treatment groups losing mass. The low-temperature treatment group had a statistically significantly lower mean average for dimensional deviations (0.026 ± 0.010 mm) than did the other treatment groups (0.069 ± 0.006 and 0.059 ± 0.010 mm for high temperature and Epsom salt, respectively). CONCLUSIONS: Dental models printed 3-dimensionally with calcium sulfate and treated with Epsom salt showed significant improvement in compressive mechanical properties and retained clinically acceptable dimensional stability.

Nonextraction anterior open bite treatment with distalization and intrusion.

This case report describes successful orthodontic retreatment for vertical control with nonextraction orthodontic therapy. A 31-year-old woman complained of anterior open bite and crowding. She had slightly protrusive lips but wanted to correct her malocclusion without extraction. Two palatal temporary skeletal anchorage devices were used for the distalization of the maxillary arch along with posterior intrusion. Mandibular distalization was performed with Class III elastics. The duration of active treatment was 22 months. The plain and efficient mechanics used contributed to the effective distalization of both arches, the intrusion of the maxillary posterior teeth, and favorable profile changes. The results were still stable at the five-year follow-up period.

Comparison of 3-dimensional dental models from different sources: diagnostic accuracy and surface registration analysis.

INTRODUCTION: The aim of this study was to assess the diagnostic accuracy and surface matching characteristics of 3-dimensional digital dental models obtained from various sources. METHODS: Three sets of maxillary and mandibular digital models of 30 subjects were included in this study. Three-dimensional stereolithography model files were obtained from a 3-dimensional laser desktop scanner (Ortho-Insight 3D; Motionview Software, Hixson, Tenn), the emodel system (GeoDigm, Chanhassen, Minn), and cone-beam computerized tomography. Arch-length discrepancy measurements were made on the 3-dimensional digital models and compared with direct caliper measurements. Additionally, stereolithography files from the 3 digital model systems were paired and superimposed using a best-fit algorithm. Average linear differences between the stereolithography shells were computed together with surface correlation amounts at various tolerance levels. Data were evaluated using intraclass correlation coefficients and the Tukey mean difference test. RESULTS: Although all 3 digital model groups displayed good correlation with caliper measurements, the virtual scan models had the highest correlation with the manual method (ICC > 0.95). The Tukey mean difference test showed no consistent bias of one approach vs the others compared with caliper measurements; random errors were detected in all the comparisons. For the estimation of arch-length discrepancy, the mean bias of the scanned virtual models in comparison with caliper measurements (0.24 ± 0.67 mm) was smaller than the mean biases of the emodels and the models generated from cone-beam computed tomography. Additionally, the best surface overlap correlation was observed between the virtual scanned models and the emodels. The mean linear distances between the stereolithography shells of these 2 model systems were 0.14 and 0.13 mm for the maxillary and mandibular arches, respectively. CONCLUSIONS: All 3 digital model systems can provide diagnostic information similar to caliper measurements, with varying degrees of agreement limits. The scanned virtual models had the least mean bias. A strong surface match correlation was observed between the virtual scanned models and the emodels, indicating that these could be used interchangeably.

Diagnostic accuracy of impression-free digital models.

INTRODUCTION: Impression-free techniques might eliminate the potential shortcomings of digital dental models. Chairside scanners offer the advantage of obtaining digital dental models directly from the patient without the need for dental impressions. The aim of this study was to evaluate the accuracy of 3-dimensional digital models acquired from a chairside intraoral scanner compared with both manual and cone-beam computed tomography measurements of the same dental anatomy. METHODS: The study sample comprised 60 dry skulls. Each skull had the maxillary and mandibular arches scanned with a Cadent iTero scanner (Align Technology, San Jose, Calif) and had a cone-beam computed tomography scan taken with a CS 9300 unit (Carestream Health, Atlanta, Ga). Linear measurements in all 3 dimensions of the space in each dental arch together with tooth-size arch-length analysis for both the maxillary and mandibular arches were carried out manually on the dry skulls with calipers and digitally on the scanned 3-dimensional models and cone-beam computed tomography images. Intraclass correlation (ICC) analysis was performed for all variables tested in the study groups, with the manual measurements on the dry skulls as the gold standard. The Bland-Altman analysis was also applied to the data to graphically display the agreement of the diagnostic measurements obtained from these methods. RESULTS: Measurements from the iTero models demonstrated near-perfect agreement (ICC, 0.91-0.99) with the caliper measurements. Cone-beam computed tomography measurements had moderate to high levels of agreement (ICC, 0.65-0.99) compared with the caliper measurements. CONCLUSIONS: Direct digital acquisition of the dental arches with a chairside scanner provided almost 1-to-1 diagnostic information of the investigated anatomy and was superior to the cone-beam computed tomography measurements.

Evaluation of Dental Root Development Regarding Maxillary Canine Eruption Status after Secondary Alveolar Bone Grafting in Patients with Cleft Lip and Palate.

In children born with cleft lip and palate, the timing of the secondary alveolar bone graft (SABG) is crucial to its success; this involves estimating the eruption of the permanent maxillary canine. Altered dental eruption in this patient group gives impetus to the identification of dental developmental factors concerning maxillary canine eruption, which may steer the clinical decision of SABG timing. Records of over nine hundred patients who received SABG with pre- and post-operative cone beam computed tomography (CBCT) scans were analyzed for inclusion and divided into two groups (erupting or non-erupting canine after SABG). Roots of the maxillary canines and premolars were segmented from the cementoenamel junction then linear and volumetric measurements were performed. The pre- and post-operative root length and volume differences were calculated and compared statistically using independent sample tests and paired t-tests. No statistically significant differences were found in the volume change (%), or reciprocal of mean root length in the erupted and unerupted groups in the canine, first premolar, or second premolar roots except for an association between the post-operative dental root length of the canine and the maxillary canine eruption status. Therefore, assessment of root development from pre-treatment CBCT scans was not deemed worthy from a diagnostic perspective.

Relapse of orthodontically corrected deepbites in accordance with growth pattern.

INTRODUCTION: A common orthodontic problem is a deep overbite malocclusion. Because of its high relapse tendency, it is also one of the most challenging problems to treat. To minimize relapse, the morphologic characteristics of patients need to be considered. The aim of this study was to compare deepbite relapse in 3 groups of patients categorized by vertical growth type. METHODS: The total sample included 60 patients treated at the University of Washington in Seattle, all with initial overbites greater than 50%. Data were collected from casts and cephalometric radiographs at 3 time points: pretreatment, posttreatment, and 10 years postretention. A mixed-effects model (analysis of variance) and post-hoc t tests were used for the statistical evaluations. RESULTS: The high-angle subjects showed the least deepbite relapse (0.1 ± 1.1 mm), whereas the low-angle (1.2 ± 0.9 mm) and the normal-angle (1.4 ± 1.3 mm) subjects had statistically significant relapses P <0.001. This overbite relapse might be partially due to changes in the mandibular and interincisal angles, which were also observed in these 2 groups. CONCLUSIONS: High-angle subjects tend to relapse less in overbite than do low-angle and normal-angle subjects in the long term.

Surface analysis of study models generated from OrthoCAD and cone-beam computed tomography imaging.

INTRODUCTION: The purpose of this research was to determine the accuracy of digital models generated by cone-beam computed tomography and compare it with that of OrthoCAD models (Cadent, Carlstadt, NJ) for orthodontic diagnosis and treatment planning by using surface area analysis. MATERIALS: Two sets of maxillary and mandibular digital models of 30 subjects were obtained. The models were made from impressions scanned with OrthoCAD and by conversion of related cone-beam computed tomography files. Each patient's matched pairs of maxillary and mandibular models were superimposed by using a software program and a best-fit algorithm; surface-to-surface analysis was then performed. The average linear differences between the 2 files at all points on the surfaces were measured, and tolerance levels of 0.25, 0.5, 0.75, 1.0, 1.25, and 1.5 mm were set to determine the surface correlation amounts between the 2 files. Additionally, 6 linear measurements from predetermined landmarks were also measured and analyzed. RESULTS: The average maxillary model linear difference was 0.28 to 0.60 mm, whereas the average mandibular model linear difference ranged between 0.34 and 0.61 mm. Greater than a 90% surface correlation was obtained on average at 1.00 mm in the maxillary models and at 1.25 mm in the mandibular models. The mean differences obtained from the linear measurements of the maxillary and mandibular models were 0.071 and 0.018 mm, respectively. CONCLUSIONS: Surface-to-surface analysis of OrthoCAD and digital models generated by cone-beam computed tomography pointed to a fair overlap between the protocols. The accuracy of digital models generated by cone-beam computed tomography is adequate for initial diagnosis and treatment planning in orthodontics.

Digital analysis of staining properties of clear aesthetic brackets.

OBJECTIVE: To analyse the staining properties of clear orthodontic brackets using a digital analysis. DESIGN: In vitro, laboratory study MATERIAL AND METHODS: A total of 500 tooth-coloured brackets from 10 brands (five ceramic and five plastic) were investigated. The cumulative discolouring effect of staining agents (tea, coffee, curry and red wine) were analysed at two consumption levels: light and heavy, based on a 6-month period of exposure. Study group brackets were immersed in the agents consecutively at 37°C. The control group was only exposed to artificial saliva. Samples were analysed digitally to obtain L*, a* and b* (lightness, red-green and yellow-blue) colour readings. Using these values, total colour change (ΔE*) at each level was also calculated. Three-way analysis of variance (ANOVA) test was used for statistical comparisons. RESULTS: L* and b* colour parameters showed significant differences (P<0·001) between different bracket groups, consumption levels and the type of exposure. However, the a* value only differed between bracket groups (P<0·001). According to the ΔE* values, ceramic brackets had less colour change than plastic brackets at the end of phase 1 for both the study and control groups. However, as consumption time increased, the rate of colour change decreased for the plastic brackets. In general, ceramic brackets demonstrated much more resistance to staining agents than plastic brackets. CONCLUSIONS: Both plastic and ceramic brackets showed changes in colour when exposed to heavy consumption of staining agents, with plastic brackets being the most affected.

Do long-term changes in relative maxillary arch width affect buccal-corridor ratios in extraction and nonextraction treatment?

INTRODUCTION: Our aims were to evaluate long-term maxillary arch width changes in orthodontic patients treated with and without premolar extractions and to provide a potential link to the buccal-corridor ratios. METHODS: Dental casts of 34 extraction and 32 nonextraction orthodontic patients with Class I malocclusions were digitized and evaluated before treatment (T1), at posttreatment (T2), and at postretention (T3). The mean postretention times for the extraction and the nonextraction groups were 5 years 2 months and 4 years 10 months, respectively. Specific arch width measurements were made on the anatomic y-axis of the casts between the most labial aspects of the anatomic dental arch immediately distal to the incisive papilla, the farthest point posteriorly of the conjunction of the third lateral and medial rugae on the midpalatal raphe and at an individually constant distance from the incisive papilla. Arch width changes were calculated and compared statistically to determine whether the dental arches were narrower after extraction treatment and at postretention. RESULTS: All maxillary arch width measurements remained virtually stable after extraction therapy and at the postretention follow-up. Significant increases were recorded for all maxillary arch width measurements in the nonextraction group after treatment (mean changes, 1.37-2.05 mm). Posterior arch width measurements decreased significantly between T2 and T3 (mean change, 0.5 mm). Mean changes between T1 and T2 were significant between the 2 groups for all measurements (P <0.05). Only the mean change in posterior arch width was significant between the 2 groups in the postretention period (P <0.05). CONCLUSIONS: Extraction treatment did not result in narrower maxillary dental arches, whereas nonextraction treatment slightly expanded the dental arch.