Arch parameters and dental discrepancy (crowding and spacing) in a sample of an Afro-Colombian population.

The aim of this study was to determine the differences in arch length, inter-canine distance, inter-premolar distance, intermolar distance and arch shape between dental discrepancies (crowding and spacing) in a sample of dental casts from the Afro-Colombian population of San Basilio de Palenque. An analytical, cross-sectional study was conducted on a convenience sample of 63 subjects aged 11 to 57years, of Afro-Colombian origin, with full dentition from first molar to first molar, without extensive caries or restorations, and excluding casts with defects due to loss. The differences between arch (upper and lower) variables were analyzed according to dental discrepancies. Plaster models digitalized with a TR1OS3 Mono scanner with exactitude (6.9 ± 0.9 pm) and precision (4.5 ± 0.9 pm) were analyzed with Orthonalyzer software. Statistical analyses were done on SPSS software (Version 20 for Windows) and Real Statistics. Spacing discrepancy of68.25% was found for upper arch and 66.66% for lower arch; crowding discrepancy of 19.04% for upper arch and 20.63% for lower arch, and an adequate ratio of 12.69% for both arches. No statistically significant difference (p>0.05) was found between arch parameters except for inter-premolar distance on the lower arch. The most frequent arch shape in the population was oval for both upper arch, with 76.19%, and lower arch, with 71.42%. Tooth size was larger in males than females but the difference was not statistically significant.

El objetivo de este estudio fue determinar las diferencias en longitud de arco, distancia intercanina, interpremolar, intermolar y la forma de arco entre discrepancias dentales (apiñamiento y espaciamiento), en una muestra de modelos dentales de la población afrocolombiana de San Basilio de Palenque. Se realizó un estudio analítico transversal, en una muestra por conveniencia de 63 sujetos con un rango de edad entre 11 y 57 años, de origen afrocolombiano, quienes tuvieron dentición completa de primer molar a primer molar, sin caries extensas, ni restauraciones; se excluyeron los modelos con defectos por el vaciado. Se analizaron las diferencias entre las variables de los maxilares (superior e inferior) con las discrepancias dentales. Se utilizaron modelos de yeso que fueron digitalizados con el escánerTR1OS3 Mono con una exactitud de (6.9 ± 0.9 pm) y una precisión de (4.5 ± 0.9 pm)y analizados con el software Orthonalyzer. Los análisis estadísticos se llevaron a cabo utilizando el software SPSS (Versión 20 para Windows) y Real Statistics. Se encontró una discrepancia de espaciamiento de un 68,25% para el arco superior y 66,66% en el arco inferior; y una discrepancia de apiñamiento en el arco superior de 19,04% e inferior de 20,63% y una relación adecuada de 12,69% para los dos arcos. No se encontraron diferencias estadísticamente significativas (p>0.05) en los parámetros de arco a excepción de la distancia interpremolar del arco inferior. La forma de arco más frecuente en la población fue ovalada tanto en el arco superior con un 76,19% como en el arco inferior con un 71,42%. En cuanto al tamaño dental, se presentó mayor tamaño en los hombres que en las mujeres, pero este no fue estadísticamente significativo.

Arch parameters and dental discrepancy (crowding and spacing) in a sample of an Afro-Colombian population / Parámetros de arco y discrepancia dental (apiñamiento y espaciamiento) en una muestra de población Afrocolombiana

The aim of this study was to determine the differences in arch length, inter-canine distance, inter-premolar distance, intermolar distance and arch shape between dental discrepancies (crowding and spacing) in a sample of dental casts from the Afro-Colombian population of San Basilio de Palenque. An analytical, cross-sectional study was conducted on a convenience sample of 63 subjects aged 11 to 57years, of Afro-Colombian origin, with full dentition from first molar to first molar, without extensive caries or restorations, and excluding casts with defects due to loss. The differences between arch (upper and lower) variables were analyzed according to dental discrepancies. Plaster models digitalized with a TR1OS3 Mono scanner with exactitude (6.9 ± 0.9 pm) and precision (4.5 ± 0.9 pm) were analyzed with Orthonalyzer software. Statistical analyses were done on SPSS software (Version 20 for Windows) and Real Statistics. Spacing discrepancy of68.25% was found for upper arch and 66.66% for lower arch; crowding discrepancy of 19.04% for upper arch and 20.63% for lower arch, and an adequate ratio of 12.69% for both arches. No statistically significant difference (p>0.05) was found between arch parameters except for inter-premolar distance on the lower arch. The most frequent arch shape in the population was oval for both upper arch, with 76.19%, and lower arch, with 71.42%. Tooth size was larger in males than females but the difference was not statistically significant.

El objetivo de este estudio fue determinar las diferencias en longitud de arco, distancia intercanina, interpremolar, intermolar y la forma de arco entre discrepancias dentales (apiñamiento y espaciamiento), en una muestra de modelos dentales de la población afrocolombiana de San Basilio de Palenque. Se realizó un estudio analítico transversal, en una muestra por conveniencia de 63 sujetos con un rango de edad entre 11 y 57 años, de origen afrocolombiano, quienes tuvieron dentición completa de primer molar a primer molar, sin caries extensas, ni restauraciones; se excluyeron los modelos con defectos por el vaciado. Se analizaron las diferencias entre las variables de los maxilares (superior e inferior) con las discrepancias dentales. Se utilizaron modelos de yeso que fueron digitalizados con el escánerTR1OS3 Mono con una exactitud de (6.9 ± 0.9 pm) y una precisión de (4.5 ± 0.9 pm)y analizados con el software Orthonalyzer. Los análisis estadísticos se llevaron a cabo utilizando el software SPSS (Versión 20 para Windows) y Real Statistics. Se encontró una discrepancia de espaciamiento de un 68,25% para el arco superior y 66,66% en el arco inferior; y una discrepancia de apiñamiento en el arco superior de 19,04% e inferior de 20,63% y una relación adecuada de 12,69% para los dos arcos. No se encontraron diferencias estadísticamente significativas (p>0.05) en los parámetros de arco a excepción de la distancia interpremolar del arco inferior. La forma de arco más frecuente en la población fue ovalada tanto en el arco superior con un 76,19% como en el arco inferior con un 71,42%. En cuanto al tamaño dental, se presentó mayor tamaño en los hombres que en las mujeres, pero este no fue estadísticamente significativo.

New regression equations for mixed dentition space analysis in Nepalese mongoloids.

BACKGROUND: Mixed dentition space analysis methods using regression equations, namely, Moyers' analysis and Tanaka-Johnston analysis are commonly used around the world. However, the applicability of these analyses among different racial groups have been questioned. The primary objective of this study was to assess the applicability of the Moyers' and Tanaka-Johnston analyses among Nepalese Mongoloids and to develop regression equations for the same population if needed. METHODS: One hundred (50 males and 50 females) pre-treatment study models of the Nepalese Mongoloid patients undergoing orthodontic treatment were retrieved from the archives of the department of Orthodontics. The mesiodistal widths of mandibular incisors and widths of canines and premolars of all 4 quadrants were measured by a single investigator using a digital caliper to the nearest 0.01 mm. Predicted widths of canines and premolars were obtained using standard Moyers' and Tanaka-Johnston analyses and then compared with the measured widths. RESULTS: The measured widths of canines and premolars were significantly different from the predicted widths obtained from Moyers' and Tanaka-Johnston analyses. Strong and positive correlations were found between the sum of mesiodistal widths of mandibular incisors and the sum of mesiodistal widths of canines and premolars in males (0.73 for maxillary arch and 0.68 for mandibular arch) and females (0.64 for maxillary arch and 0.79 for mandibular arch). CONCLUSIONS: The Moyers' and Tanaka-Johnston analyses did not accurately predict the mesiodistal width of unerupted canines and premolars for Nepalese Mongoloid population. Hence, new regression equations have been developed for this population. However, validation studies should be conducted to confirm the applicability and accuracy of these equations.

Mesiodistal and faciolingual diameters of the permanent teeth in a Jordanian population.

OBJECTIVES: This study aimed to provide, for a Jordanian population, the first norms of the faciolingual diameters of the permanent dentition and the mesiodistal diameters of the second molars and to provide and review previously published data on the mesiodistal diameters of the permanent teeth up to the first molars in order to investigate any secular trends. DESIGN: Mesiodistal and faciolingual diameters of the permanent teeth were manually measured on 204 archival pretreatment study casts of adolescents (80 males and 124 females) aged 11-18 years. SPSS (version 16) was used to generate descriptive statistics and investigate the statistically significant differences between right and left sides and between sexes. RESULTS: Males had larger teeth than females, significantly in the mesiodistal dimension and less significantly in the faciolingual dimension. Moreover, in the faciolingual dimension, there was a wider variation in anterior compared with posterior teeth and in males compared with females while the variations were more consistent mesiodistally between anterior and posterior teeth and between sexes. There were some secular trends in the mesiodistal permanent tooth diameters of Jordanians toward a slight reduction and wider variation in tooth size and a slight reduction in sexual dimorphism. CONCLUSIONS: the present study has established the first norms of the faciolingual permanent tooth diameters for a Jordanian population which were consistent with corresponding norms that have been published for few other populations. In addition, the present study has provided norms of the mesiodistal permanent tooth diameters of a Jordanian population that are newer and more complete than the previously published norms. It is anticipated that the new norms presented will be utilized in various clinical disciplines of dentistry, in basic dental research, in forensic odontology and in anthropological research.

Accuracy of four different digital intraoral scanners: effects of the presence of orthodontic brackets and wire.

OBJECTIVE: The objective of this study was to compare the accuracy of four different digital intraoral scanners and the effects of buccal brackets and orthodontic wire. METHODS: For this study, three sets of models (Control model, BKT model with buccal bracket, and WBKT model with buccal bracket and orthodontic wire) were scanned using four different types of intraoral scanners: E4D dentist, iTero, Trios, and Zfx IntraScan. The mesiodistal width of the teeth, intercanine width, and intermolar width measured by four scanners were compared. Three-dimensional (3D) images of the brackets were taken using the four scanners. Data were analyzed with one-way ANOVA, independent t test, and post-hoc Tukey test at a significance level of P < 0.05. RESULTS: When comparing the 3D images with manual measurements using a traditional caliper, iTero and Trios showed the highest accuracy in horizontal measurements.iTero had the lowest values in Devmax-min of maxillary intermolar and intercanine widths (0.16 mm and 0.20 mm, respectively), whereas Trios had the lowest values in Devmax-min of mandibular intermolar and intercanine widths (0.36 mm and 0.14 mm, respectively). The horizontal variables were barely affected by the presence of buccal brackets and orthodontic wire. Comparison of 3D bracket images scanned by the four scanners showed differences in image distortion among the scanners. Bracket characteristics did not affect the 3D bracket images. CONCLUSIONS: The four intraoral scanners used in this study differed in accuracy. However, the results acquired by iTero and Trios were more reliable. Effects of buccal brackets and orthodontic wire on the 3D images taken by intraoral scanners were not clinically significant.

Vertical dimension of occlusion (VDO): cephalometric norms for a Moroccan population.

OBJECTIVES: The purpose of this work was to develop cephalometric standards of the vertical dimension of occlusion (VDO) in Moroccan adults. METHODS: Our data consisted of standardized lateral cephalometric radiographs of 98 students at the Casablanca Faculty of Dentistry. These included 74 women and 24 men aged 18-34 years, who were selected on the basis of a well-proportioned face, acceptable profile, Class I occlusion, minor or no crowding, and no history of orthodontic treatment. Mean values of seven (six angle and one linear) dentoskeletal parameters were determined from lateral cephalometric radiographs. RESULTS: These Moroccans tended to exhibit an opening in the VDO in comparison with the standards of Steiner and Wylie and those of other populations: GoGn/SN: 35.4° ± 5.3°, FMA: 25.6° ± 5.1°, Occ/SN: 19.3° ± 4.7°, Occ/Fr: 9.1° ± 4°, SGn/Fr: 59.2° ± 3.4°, ENA-Xi-Pm: 46.2° ± 4.4°, ENA-Me: 69.7 ± 5.9 mm. CONCLUSION: Moroccans have distinct cephalometric characteristics, which should be used as the reference in future orthodontic and prosthetic treatments.

An Invitro Evaluation of the Accuracy of Two Electronic Apex Locators to Determine Working Length in the Presence of Various Irrigants.

BACKGROUND: Cleaning and shaping of root canal system requires various irrigating solutions. The question is whether the presence of irrigation solution alters working length determination using apex locators. The purpose of this study was to compare the accuracy of Root ZX and i-Root apex locator for determining working length in the presence of different irrigating solution. MATERIALS AND METHOD: Eighty extracted single rooted human teeth were used. The teeth were sectioned at Cemento Enamel Junction (CEJ) and actual canal length determined. Then, working length measurements were obtained using Root ZX and i-Root apex locator in the presence of irrigating solutions namely 0.9% saline, 3% of sodium hypochlorite (NaOCl), 2% chlorhexidine digluconate(CHX) and 17% Ethylene Diamine Tetra Acetic acid (EDTA). The measurements obtained with Root ZX and i-Root apex locator were compared with actual canal length and subjected to statistical analysis using Post Hoc Test Tukey's Method. RESULTS: This study revealed that both the tested Electronic apex locators (EAL) were able to measure the canal length in the presence of tested irrigating solutions. The presence of irrigating solutions of saline, NaOCl, chlorhexidine and EDTA in the root canal marginally influenced the accuracy of the Root ZX or i-Root (P < 0.36), but with no clinical significance. CONCLUSION: Root ZX and i-Root can be used safely to determine working length in the presence of various irrigants. The content of the root canal did not influence the accuracy while measuring working length using Electronic apex locators (EAL).

Early prediction of maxillary canine impaction.

OBJECTIVES: The aim of this study was to establish prediction criteria for maxillary canine impaction in young patients, based on angular and linear measurements on panoramic radiographs. METHODS: From 828 records having at least 2 panoramic radiographs, both taken between the ages of 7 and 14 years, with a minimum 1-year and maximum 3-year interval (T1 and T2), a training data set consisting of 30 subjects with unilateral canine impaction (12 males and 18 females) was selected. The patients' mean age was 10.1 years [standard deviation (SD) 1.3 years] at T1 and 11.9 years (SD 1.1 years) at T2. The training data set also consisted of 30 maxillary canines from the contralateral sides and an additional 60 normal erupted canines from 30 subjects. Those 30 subjects of a test data set were selected based on displaying bilateral maxillary canine eruption at T2 and being matched for gender and age with the subjects of the training data set [12 males and 18 females; mean age at T1, 10.1 years (SD 1.3 years) and at T2, 11.1 years (SD 1.2 years)]. Angular and linear measurements were performed separately by two observers on the total study sample at T1. Linear measurements were expressed as a multiplication of the maxillary central incisor width at the non-impacted side. RESULTS: Significant differences for linear and angular measurements and radiographic factors were found between the maxillary impacted canine and erupted maxillary canine. The three best-discriminating parameters were canine to first premolar angle, canine cusp to midline distance and canine cusp to maxillary plane distance. These three parameters were combined in a multiple logistic regression model to calculate the probability of impaction, yielding a high area under the curve (AUC) equal to 0.97 (95% confidence interval: 0.94-0.99), with 90% sensitivity and 94% specificity. CONCLUSIONS: Prediction of maxillary canine impaction from a combination of parameters relating to angles and distances measured in panoramic radiographs is weak. However, the final prediction model, based on canine-first premolar angle, canine cusp tip to midline distance and canine cusp tip to maxillary occlusal plane distance, might be useful to discriminate canine impaction for early intervention or regular follow-up.

Eficácia entre dois localizadores apicais eletrônicos testados no nível do forame e ultrapassando e retornando ao forame / Effectiveness between two electronic apex locators tested at foramen level and passing through and returning to the foramen

Introdução: O localizador apical eletrônico é uma ferramenta que facilita o tratamento endodôntico. O objetivo do presente estudo foi avaliar, in vitro, a precisão de dois localizadores apicais usados de duas maneiras distintas. Material e métodos: As medidas reais de 20 molares inferiores extraídos de humanos foram determinadas, posicionando-se os instrumentos até o forame, auxiliados por um microscópio clínico com 20x de aumento. As medidas foram realizadas com um paquímetro. Feito isso, os dentes foram montados em uma plataforma de polietileno, posicionada dentro de uma cuba plástica contendo gelatina preparada com soro fisiológico e, então, as medidas eram realizadas com os localizadores Novapex e Root ZX, posicionando os instrumentos na posição zero ou passando com o instrumento além do zero e voltando a essa posição. Para a análise dos resultados foi usada a diferença das duas medidas (real do dente e obtida pelo aparelho). Resultados: Os dados das raízes distais e mesiais foram submetidos à análise estatística. Na raiz distal o teste Anova mostrou diferença significante entre os grupos (p<0,01) e o teste de Tukey demonstrou diferença entre os valores do Novapex passando e do Root ZX na posição zero. Na raiz mesial, o teste Anova não mostrou diferença significante entre os grupos (p>0,01). Conclusão: Conclui-se que quando se usou a técnica de ir até o zero, o aparelho Novapex mostrou-se mais preciso, porém na técnica de passar e retornar ao zero, o aparelho mais preciso foi o Root ZX (AU)

Introduction: The electronic apex locator is a tool that facilitates endodontic treatment. The aim of this study was to evaluate in vitro the accuracy of two apex locators used in two different ways. Methods: Real measurements of 20 lower molars extracted from human were determined by positioning the instruments until the foramen aided by a 20x clinical microscope. The measurements were taken with a caliper. After this, the teeth were mounted on a polyethylene platform, positioned inside a plastic tub containing gelatin prepared with saline and the measures were carried out with the locators Novapex and Root ZX positioning instruments in zero or passing with the instrument beyond zero and returning to this position. The difference between the two measurements (real tooth and obtained by the device) were used for results analysis. Results: Data from the distal and mesial roots were subjected to statistical analysis. In the distal root, ANOVA showed significant difference between groups (p <0.01) and Tukey's test showed difference between the Novapex values ​when passing and Root ZX in zero. At the mesial root, ANOVA showed no significant difference between groups (p> 0.01). Conclusion: It was concluded that when using the technique positioning instruments in zero the Novapex was more accurate, however when the technique was to pass and to return to zero, the most accurate device was the Root ZX (AU)

Development and Evaluation of an Endodontic Simulation Model for Dental Students.

The aims of this study were to develop an endodontic simulation model able to implement the electronic method of working length determination (electronic apex locators, EALs) in a dental school, to evaluate the practicality of this tool for dental students, and to compare the accuracy of working length measurements achieved by the EAL and the radiographic method. A new simulation model was constructed by embedding extracted human teeth in a self-cured resin, along with a conductive medium. After radiographic and electronic working length determinations, root canal instrumentation was performed by students at a dental school in Austria according to the working lengths obtained from the EAL. Subsequently, root apices (n=44) were longitudinally sectioned using a diamond coated bur. Measurements of the distance between the anatomical root apex (ARA) and the apical constriction (AC) as well as between ARA and the ascertained apical point of endodontic instrumentation were performed using digital photography and a 3D computer-assisted design software. The distance between ARA and the radiologic (ARA-R) or electrometric (ARA-EL) readings of the apical point of endodontic instrumentation was compared with the actual distance ARA-AC. The accuracy of both methods was determined. The difference between the actual distance ARA-AC and the targeted radiological distance was statistically significant (p=0.0001), as was the measured distance between ARA-R and ARA-EL (p=0.016). The electronic method seems to be more precisely referring to the AC (R(2)=0.0198) than the radiographic method (R(2)=0.0019). These results suggest that the endodontic simulation model described in this study can be successfully used in preclinical dental education.

Reliability and validity of intraoral and extraoral scanners.

BACKGROUND: This study evaluated the reliability and validity of one extraoral [Ortho Insight 3D™ (Motionview Software, Hixson, TN/USA)] and two intraoral [ITero™ (Align Technologies, San Jose, CA/USA) and Lythos™ (Ormco Corp., Orange, CA/USA)] scanners. METHODS: Fifteen dry human mandibles were scanned twice with each of the scanners, and digital models were generated. Five measurements were made on the dry mandibles and on each of the generated models, including intermolar width, intercanine width, posterior arch length, premolar crown diameter, and canine height. Systematic and random errors were evaluated based on replicate analyses. Differences were assessed using paired Student's t tests. RESULTS: Replicate analyses showed statistically significant systematic errors for only one measure (intermolar width measured from Ortho Insight 3D scans). Measurements taken from all three scanners were highly reliable, with intraclass correlations ranging from .926 to .999. Method errors were all less than 0.25 mm (averaged ≈ 0.12 mm). Posterior arch length and canine height were significantly smaller when measured on the Ortho Insight 3D scans than when measured on the dry mandibles and significantly smaller than when measured from the ITero and Lythos models. CONCLUSIONS: While all three scanners produced reliable measures, Ortho Insight 3D systematically underestimated arch length and canine height.

Impact on perceived root resorption based on the amount of incisal inclination as determined from conventional panoramic radiography.

INTRODUCTION: Our objective was to measure the impact on perceived root resorption based on the amount of anteroposterior incisal inclination as determined in vitro from conventional panoramic radiography. METHODS: A rapid prototyping model was created to mimic different maxillary and mandibular incisal anteroposterior inclinations. Two titanium beads were placed on the incisors at the apical and incisal edges. Panoramic radiographs were obtained, with the incisors changing relative inclination by 10° increments. The length was measured from the midpoint of the bead on the incisal edge to the midpoint of the bead on the apical edge. By using a length of wire of known size, this value was compared in all images to correct for image magnification. RESULTS: Changes to mandibular incisor anteroposterior inclinations, as either a theoretical proclination or retroclination, resulted in an increase of "apparent" root resorption on a panoramic radiograph. When the maxillary incisors were significantly and severely retroclined, they appeared larger than expected. When the maxillary incisors were mildly retroclined, the length was roughly similar to the theoretical model. When the maxillary incisors were mildly proclined, they appeared shorter than expected. CONCLUSIONS: The foreshortening or forelengthening of incisor root lengths because of incisor inclination vs root resorption cannot be reliably evaluated from panoramic images. The proposed theoretical model helps to understand the direction of the changes produced by the magnification factor. More severe scenarios where either the maxillary or the mandibular teeth are outside the focal trough have not been fully evaluated. The clinical impact of these changes is likely to be questionable.

MIXED DENTITION SPACE ANALYSIS OF A SOUTHERN ITALIAN POPULATION: NEW REGRESSION EQUATIONS FOR UNERUPTED TEETH.

Mixed dentition analysis forms a critical aspect of early orthodontic treatment. In fact an accurate space analysis is one of the important criteria in determining whether the treatment plan may involve serial extraction, guidance of eruption, space maintenance, space regaining or just periodic observation of the patients. The aim of the present study was to calculate linear regression equations in mixed dentition space analysis, measuring 230 dental casts mesiodistal tooth widths, obtained from southern Italian patients (118 females, 112 males, mean age 15±3 years). Student’s t-test or Wilcoxon test for independent and paired samples were used to determine right/left side and male/female differences. On the basis of the sum of the mesiodistal diameters of the 4 mandibular incisors as predictors for the sum of the widths of the canines and premolars in the mandibular mixed dentition, a new linear regression equation was found: y = 0.613x+7.294 (r= 0.701) for both genders in a southern Italian population. To better estimate the size of leeway space, a new regression equation was found to calculate the mesiodistal size of the second premolar using the sum of the four mandibular incisors, canine and first premolar as a predictor. The equation is y = 0.241x+1.224 (r= 0.732). In conclusion, new regression equations were derived for a southern Italian population.

Three-dimensional assessment of teeth first-, second- and third-order position in Caucasian and African subjects with ideal occlusion.

BACKGROUND: The aim of this study was to provide an updated version of Andrews' seminal study by exploiting 3D software to analyse the tip, torque and in-out values of two groups of different racial and ethnic background. METHODS: The analysis was conducted on one Caucasian group (30 individuals) and one of African origin (29). All subjects were adult, in normal occlusion and had no previous history of orthodontic treatment. Rhinoceros™ 3D modelling software was used to identify anatomical reference points, planes and axes and to make the appropriate measurements. RESULTS: Compared to Andrews' measurements, we found more positive coronal tip values in both African and Caucasian subjects, while the torque values we measured tended to be less negative in the posterior sectors than those reported by Andrews. We measured greater tip values in the lower jaw of Caucasian with respect to African subjects, particularly in the middle sectors. CONCLUSIONS: Race and ethnicity have a strong influence on values of tip, torque and in-out. This is translated as a more positive tip in Caucasian subjects and a more positive torque in those of African descent (greater proclination of the incisors). Finally, with respect to the values reported by Andrews, we found a tendency to more positive mean tip (except for at the upper second molars and lower incisors) and less negative torque in the posterior sectors.

Evaluation of crown-root angulation of lateral incisors adjacent to palatally impacted canines.

BACKGROUND: The objective of this study is to explore differences in crown-to-root angulation between lateral incisors adjacent to palatally impacted canines (PICs) and lateral incisors adjacent to normally erupted canines (NECs). METHODS: Orthodontic records of 100 subjects (51 with PICs and 49 with NECs) were reviewed. Crown-to-root angulations of all lateral incisors were measured manually on the final panoramic radiographs. Also, three experienced orthodontists were asked to visually inspect the morphology of the lateral incisors on the panoramic radiographs. A mixed model was used to test the difference in crown-to-root angulation of the lateral incisor between the experimental and the control groups. The association between the examiners' observations and the presence of a canine impaction was assessed by means of a chi-square test. All analyses were performed at the 0.05 level of statistical significance. RESULTS: A significant (p = 0.009) difference of 2.3° in crown-to-root angulation was found between groups. Also, 66.7% of the lateral incisors that were identified as "abnormal" by the panel of orthodontists were adjacent to a PIC. A percentage of 65.2 of lateral incisors that were identified as "normal" were located adjacent to NECs. CONCLUSIONS: The root of lateral incisors adjacent to PICs is angulated more mesially compared to lateral incisors adjacent to NECs. In addition, clinicians are somewhat able to predict if a canine is palatally impacted by visually observing the crown-to-root angulation of the adjacent lateral incisor. Evaluating the crown-to-root angulation of a lateral incisor on a panoramic image might facilitate an early diagnosis of palatally impacted canines.

Maxillary arch perimeter prediction using Ramanujan's equation for the ellipse.

INTRODUCTION: The prediction of arch perimeter gained when expanding the arch or proclining the anterior incisors is particularly important in the decision of tooth extraction vs nonextraction therapy for orthodontic treatment. METHODS: Correlation of the measured perimeter of the maxillary dental arch and the calculated perimeter applying Ramanujan's equation for the perimeter of an ellipse was evaluated with 30 diagnostic casts of untreated maxillary dental arches. Both linear and circumferential measurements were made directly on the midbuccal surface of these maxillary arches. RESULTS: Ramanujan's equation had a high level of correlation when comparing the measured perimeter of the maxillary dental arch and the calculated perimeter with the 0.01 level (1.2% error) using a 2-tailed t test. The results were applied to Ramanujan's equation to predict maxillary arch perimeter gained by expansion or proclination of the incisors. CONCLUSIONS: The ellipse is an accurate geometric model of the maxillary arch form. The average amounts of maxillary arch perimeter gained were 0.73 mm per millimeter of intermolar expansion and 1.66 mm per millimeter of incisor protrusion.

How to test validity in orthodontic research: a mixed dentition analysis example.

INTRODUCTION: The data used to test the validity of a prediction method should be different from the data used to generate the prediction model. In this study, we explored whether an independent data set is mandatory for testing the validity of a new prediction method and how validity can be tested without independent new data. METHODS: Several validation methods were compared in an example using the data from a mixed dentition analysis with a regression model. The validation errors of real mixed dentition analysis data and simulation data were analyzed for increasingly large data sets. RESULTS: The validation results of both the real and the simulation studies demonstrated that the leave-1-out cross-validation method had the smallest errors. The largest errors occurred in the traditional simple validation method. The differences between the validation methods diminished as the sample size increased. CONCLUSIONS: The leave-1-out cross-validation method seems to be an optimal validation method for improving the prediction accuracy in a data set with limited sample sizes.

Applicability of the Tanaka-Johnston and Moyers mixed dentition analyses in Northeast Han Chinese.

OBJECTIVES: To assess applicability of the Tanaka-Johnston and Moyers prediction methods in a Han ethnic group from Northeast China and to develop prediction equations for this same population. DESIGN: Cross-sectional study. SETTING: Department of Orthodontics, School of Stomatology, Jiamusi University, Heilongjiang, China. PARTICIPANTS: A total of 130 subjects (65 male and 65 female) aged 16-21 years from a Han ethnic group of Northeast China were recruited from dental students and patients seeking orthodontic treatment. Ethnicity was verified by questionnaire. MATERIAL AND METHODS: Mesio-distal tooth width was measured using Digital Vernier calipers. Predicted values were obtained from the Tanaka-Johnston and Moyers methods in both arches were compared with the actual measured widths. Based on regression analysis, prediction equations were developed. RESULTS: Tanaka-Johnston equations were not precise, except for the upper arch in males. However, the Moyers 85th percentile in the upper arch and 75th percentile in the lower arch predicted the sum precisely in males. For females, the Moyers 75th percentile predicted the sum precisely for the upper arch, but none of the Moyers percentiles predicted in the lower arch. CONCLUSIONS: Both the Tanaka-Johnston and Moyers method may not be applied universally without question. Hence, it may be safer to develop regression equations for specific populations. Validating studies must be conducted to confirm the precision of these newly developed regression equations.

The effect of residual calcium hydroxide on the accuracy of a contemporary electronic apex locator.

OBJECTIVE: The aim of this study was to evaluate the effect of residual calcium hydroxide [Ca(OH)2] on the accuracy of an electronic apex locator (EAL). MATERIALS AND METHODS: Working lengths (WLs) of 56 extracted maxillary incisors were determined initially by two different methods. The first method used the 'APEX' reading of the EAL as a reference point, 0.5 mm was subtracted and recorded as WL0. The second method used the '0.5' reading and the score was recorded as WL0.5 without subtraction. The roots were prepared to WL0 and divided randomly into three experimental groups (n = 16) (1 mm in group A, 2 mm in group B and 4 mm in group C) and a control (n = 8). Specimens in all experimental groups were filled with Ca(OH)2 paste. Following its removal, WLs were re-determined with the same methods. RESULTS: In group C, pre/post WLs were significantly different (p < 0.05). No significant difference was observed between the other experimental groups and the control group. CONCLUSION: Accuracy of EAL decreased proportionally with the amount of paste remaining at the ±0.5-mm tolerance level. Ca(OH)2 paste remnants may cause incorrect EAL readings.

Influence of tooth length on the accuracy of the Root ZX electronic apical foramen locator: an ex vivo study.

OBJECTIVE: Electronic apical foramen locators are now widely used to determine working length. This study was designed to determine whether tooth length influenced the accuracy of the Root ZX device. MATERIALS AND METHODS: Forty extracted maxillary canine teeth with a length range of 27-29 mm were selected. Access cavities were prepared and coronal flaring of canals performed. The teeth were mounted in self-polymerizing acrylic resin to facilitate horizontal sectioning except for the apical 3-4-mm portion of the root and embedded in alginate as the electronic medium. Electronic measurements were taken at the major foramen, 'zero' reading using the Root ZX and compared with the actual root canal length. The teeth were sectioned 3 mm from the coronal reference point to create a second group with shorter length; these reductions in the length continued six times in all to create seven groups of 40 specimens each. The actual and electronic lengths of specimens in each group were measured. Data were analyzed by Pearson's correlation coefficient. RESULTS: Identical measurements between the actual and electronic root canal length from the longest to the shortest groups were 12.5%, 10.0%, 20.0%, 27.5%, 37.5%, 35.0% and 45.0%, respectively. There was a mild negative correlation between the precise measurements of the Root ZX and root canal lengths in the seven groups (r = -0.964, p < 0.001). CONCLUSION: Under the conditions of the study, the Root ZX device was more accurate in shorter teeth compared to longer ones.