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.

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.

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.

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.

Studying the relationships between the outlines of the face, maxillary central incisor, and maxillary arch in Jordanian adults by using Fourier analysis.

STATEMENT OF THE PROBLEM: The outline shapes of the dental arch, face, and tooth are esthetic factors used to determine the proper form of artificial teeth when selected for artificial prostheses. PURPOSE: The purpose of this study was to investigate the quantitative relationships between the outlines of the face, the maxillary central incisor, and the maxillary arch by using Fourier analysis. MATERIAL AND METHODS: Frontal facial photographs and irreversible hydrocolloid impressions of the maxilla were obtained from 200 young, dentate individuals (100 men, 100 women) ages 22 to 28 years. On the resultant casts, standardized photographs were made for the dental arch and the maxillary central incisor. The outlines of the face, dental arch, and tooth were digitally traced and the digitized curved outlines were converted into X-Y coordinates with special software, which, in turn, were imported into Fourier Shape Descriptor software for harmonic analysis. The quantitative outputs of Fourier analyses were analyzed and tested with statistical software to investigate the differences across the shapes of the 3 outlines under study. RESULTS: Facial and tooth outlines were similar for each sex, although the similarity was stronger among the men. By contrast, no relationship was found between tooth and maxillary arch outlines or between face and maxillary arch outlines. CONCLUSIONS: Face and tooth forms were quantitatively related. Therefore, face form may reliably guide the selection of artificial anterior tooth form in complete denture prostheses or any complex anterior restorations.

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.

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.

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 validity, reliability, and time requirement of study model analysis using cone-beam computed tomography-generated virtual study models.

OBJECTIVES: To investigate the validity, reliability, and time spent to perform a full orthodontic study model analysis (SMA) on cone-beam computed tomography (CBCT)-generated dental models (Anatomodels) compared with conventional plaster models and a subset of extracted premolars. SETTING AND SAMPLE POPULATION: A retrospective sample of 30 consecutive patient records with fully erupted permanent dentition, good-quality plaster study models, and CBCT scans. Twenty-two extracted premolars were available from eleven of these patients. MATERIALS AND METHODS: Five evaluators participated in the inter-rater reliability study and one evaluator for the intrarater reliability and validity studies. Agreement was assessed by ICC and cross-tabulations, while mean differences were investigated using paired-sample t-tests and repeated-measures anova. RESULTS: For all three modalities studied, intrarater reliability was excellent, inter-rater reliability was moderate to excellent, validity was poor to moderate, and performing SMA on Anatomodels took twice as long as on plaster. CONCLUSIONS: Study model analysis using CBCT-generated study models was reliable but not always valid and required more time to perform when compared with plaster models.

Coordinate geometry method for capturing and evaluating crown preparation geometry.

STATEMENT OF PROBLEM: A validated universal method requiring no human input is needed to capture and evaluate preparation geometries in a manner that can be used to see the correlation of different parameters. PURPOSE: The purpose of this study was to present a method of capturing and evaluating crown preparation geometry. MATERIAL AND METHODS: One manually machined acrylic resin block and 9 randomly selected preparations for ceramic complete crowns prepared by general dentists were selected and prepared. The specimens were scanned (3D scanner; Nobel Biocare), and buccolingual and mesiodistal cross section images were collected. The images were imported into digitizing software (Engauge Digitizer 4.1) to convert the outlines into x and y coordinates. Six points were chosen by using a set of algorithms, and the resulting parameters were calculated. RESULTS: The acrylic resin block was milled with a 12 degree total occlusal convergence (TOC) instrument producing a 12.83 degree TOC. For the other specimens, average TOC values ranged from 18 degrees to 52 degrees. The mean average margin width was 0.70 mm, and the mean average base dimension was 6.23 mm. The surface area/volume ratio, resistance length, and limiting taper were also calculated. CONCLUSIONS: The method described provides a basis for accurately evaluating preparation geometry without human input.

Mandibular permanent first molars and incisors as predictors of mandibular permanent canine and premolar widths: applicability and consistency of the method.

INTRODUCTION: Estimating the mesiodistal widths of the mandibular permanent canines and premolars is an essential aspect of mixed dentition analysis. A method is proposed to predict the sum of the mandibular permanent canine and premolar widths based on the sum of the mandibular permanent first molars and incisors. In this study, we aimed to test the applicability and reliability of this method in a population in Belo Horizonte, Minas Gerais, Brazil. The methods of Moyers and of Tanaka and Johnston were also tested. METHODS: The sample consisted of 200 orthodontic study models, obtained from white Brazilian patients (123 female, 77 male). The mesiodistal widths of the teeth were measured with an analog caliper. Paired Student t tests with a significance level of 5% were used to compare the actual and predicted values. RESULTS: No statistically significant differences were found between the predicted and actual values of the sum of the mandibular permanent canine and premolar widths when using the new method. The differences were 0.6 mm for the male sample, 0.5 mm for the female sample, and 0.6 mm for the total sample; the standard deviations were 1.9, 2.1, and 2.2 mm, respectively. However, overestimated predicted values with differences of 1.4 and 1.9 mm (male and female) in the Moyers method and 1.9 and 3.3 mm (male and female) in the Tanaka and Johnston method were found. CONCLUSIONS: The new method is consistent and applicable to the population of Belo Horizonte. The other 2 methods tended to overestimate the actual values of the permanent canines and premolars.

Accuracy and reproducibility of dental replica models reconstructed by different rapid prototyping techniques.

INTRODUCTION: Rapid prototyping is a fast-developing technique that might play a significant role in the eventual replacement of plaster dental models. The aim of this study was to investigate the accuracy and reproducibility of physical dental models reconstructed from digital data by several rapid prototyping techniques. METHODS: Twelve mandibular and maxillary conventional plaster models from randomly chosen subjects were selected and served as the gold standard. The plaster models were scanned to form high-resolution 3-dimensional surface models in .stl files. These files were converted into physical models using 3 rapid prototyping techniques: digital light processing, jetted photopolymer, and 3-dimensional printing. Linear measurements on the plaster models were compared with linear measurements on the rapid prototyping models. One observer measured the height and width of the clinical crowns of all teeth (first molar to first molar) on all models (plaster and replicas) using a digital caliper. All models were measured 5 times with a 2-week interval between measurements. RESULTS: The intraobserver agreement was high (intraclass correlation coefficient >0.94). The mean systematic differences for the measurements of the height of the clinical crowns were -0.02 mm for the jetted photopolymer models, 0.04 mm for the digital light processing models, and 0.25 mm for the 3-dimensional printing models. For the width of the teeth, the mean systematic differences were -0.08 mm for the jetted photopolymer models, -0.05 mm for the digital light processing models, and -0.05 mm for the 3-dimensional printing models. CONCLUSIONS: Dental models reconstructed by the tested rapid prototyping techniques are considered clinically acceptable in terms of accuracy and reproducibility and might be appropriate for selected applications in orthodontics.

Measurement of the buccolingual inclination of teeth: manual technique vs 3-dimensional software.

INTRODUCTION: In this study, we aimed to measure the inclination of teeth on dental casts by a manual technique with the tooth inclination protractor (TIP; MBI, Newport, United Kingdom) and a newly designed 3-dimensional (3D) software program. The correlation of the 2 techniques was evaluated, and the reliability of each technique was assessed separately. METHODS: This study was conducted on 36 dental casts of normal, well-aligned Class I occlusions; we assessed 432 teeth. All casts had a normal Class I occlusion. After determining the facial axis of the clinical crown and the facial axis points on the dental casts, we measured the inclinations of the incisors and posterior teeth up to the first molars in each dental arch relative to Andrews' occlusal plane and the posterior occlusal plane using the TIP. Moreover, the casts were scanned by a structured-light 3D scanner. The inclination of teeth relative to the occlusal plane was determined using the new software. To assess the reliability, measurements of all teeth from 15 casts were repeated twice by the 2 methods. Intraclass correlation coefficient and Dahlberg's formula were used for calculation of correlation and reliability. RESULTS: Overall, the 2 techniques were not significantly different in the measurements of the inclinations of the teeth in both jaws. The ranges of Dahlberg's formula were 3.1° to 5.8° for the maxilla and 3.3° to 5.9° for the mandible. The overall correlation of the 2 techniques according to the intraclass correlation coefficient was 0.91. For calculation of reliability, the intraclass correlation coefficients for the TIP and the 3D method were 0.73 and 0.82, respectively. CONCLUSIONS: The TIP and the 3D software showed a high correlation for measurement of the inclinations of maxillary and mandibular teeth relative to the occlusal plane. Also, the reproducibility of the measurements in each method was high.

Accuracy, reproducibility, and time efficiency of dental measurements using different technologies.

INTRODUCTION: Historically, orthodontists have taken dental measurements on plaster models. Technological advances now allow orthodontists to take these measurements on digital models. In this study, we aimed to assess the accuracy, reproducibility, and time efficiency of dental measurements taken on 3 types of digital models. METHODS: emodels (GeoDigm, Falcon Heights, Minn), SureSmile models (OraMetrix, Richardson, Tex), and AnatoModels (Anatomage, San Jose, Calif) were made for 30 patients. Mesiodistal tooth-width measurements taken on these digital models were timed and compared with those on the corresponding plaster models, which were used as the gold standard. Accuracy and reproducibility were assessed using the Bland-Altman method. Differences in time efficiency were tested for statistical significance with 1-way analysis of variance. RESULTS: Measurements on SureSmile models were the most accurate, followed by those on emodels and AnatoModels. Measurements taken on SureSmile models were also the most reproducible. Measurements taken on SureSmile models and emodels were significantly faster than those taken on AnatoModels and plaster models. CONCLUSIONS: Tooth-width measurements on digital models can be as accurate as, and might be more reproducible and significantly faster than, those taken on plaster models. Of the models studied, the SureSmile models provided the best combination of accuracy, reproducibility, and time efficiency of measurement.

Digital tooth-based superimposition method for assessment of alveolar bone levels on cone-beam computed tomography images.

INTRODUCTION: Cone-beam computed tomography images have been previously used for evaluation of alveolar bone levels around teeth before, during, and after orthodontic treatment. Protocols described in the literature have been vague, have used unstable landmarks, or have required several software programs, file conversions, or hand tracings, among other factors that could compromise the precision of the measurements. The purposes of this article are to describe a totally digital tooth-based superimposition method for the quantitative assessment of alveolar bone levels and to evaluate its reliability. METHODS: Ultra cone-beam computed tomography images (0.1-mm reconstruction) from 10 subjects were obtained from the data pool of the University of Oklahoma; 80 premolars were measured twice by the same examiner and a third time by a second examiner to determine alveolar bone heights and thicknesses before and more than 6 months after orthodontic treatment using OsiriX (version 3.5.1; Pixeo, Geneva, Switzerland). Intraexaminer and interexaminer reliabilities were evaluated, and Dahlberg's formula was used to calculate the error of the measurements. RESULTS: Cross-sectional and longitudinal evaluations of alveolar bone levels were possible using a digital tooth-based superimposition method. The mean differences for buccal alveolar crest heights and thicknesses were below 0.10 mm for the same examiner and below 0.17 mm for all examiners. The ranges of errors for any measurement were between 0.02 and 0.23 mm for intraexaminer errors, and between 0.06 and 0.29 mm for interexaminer errors. CONCLUSIONS: This protocol can be used for cross-sectional or longitudinal assessment of alveolar bone levels with low interexaminer and intraexaminer errors, and it eliminates the use of less reliable or less stable landmarks and the need for multiple software programs and image printouts. Standardization of the methods for bone assessment in orthodontics is necessary; this method could be the answer to this need.

Influence of simulated apical resorption following orthodontic treatment on working length determination: an in vitro study.

AIM: External apical root resorption (EARR) is a common complication that may occur during and after orthodontic treatment. In case of need of endodontic therapy for a tooth with EARR, it has not been clarified yet which benefits can be derived by the use of electronic apex locators (EALs). The present study aimed to assess the accuracy of EALs on extracted teeth before and after simulation of EARR subsequent to orthodontic treatment. MATERIALS AND METHODS: Standard access cavities were prepared on 64 single-rooted teeth. After working length (CWL) determination, specimens were embedded in an alginate mass, connected to two EALs (Apit, Osada, Tokyo, Japan; Root ZX, Morita Corp., Tokyo, Japan) and the electronic working length (EWL) was measured. The apical portion of the specimens was then modified to simulate EARR, and the EWL was determined again. The discrepancy between CWL and EWL was regarded as statistical unit. Collected data underwent statistical analysis by means of non-parametric tests (p < 0.05). RESULTS: Within a range of ± 0.5 and ± 1.0 mm from CWL, the accuracies were 79.7% and 98.4% (Apit/intact tooth); 82.8% and 96.9% (Apit/simulated EARR); 81.3% and 98.4% (Root ZX/intact tooth); 76.6% and 96.9% (Root ZX/simulated EARR). No statistically significant differences in relation to device or apical condition emerged (p > 0.05). CONCLUSION: The two considered EALs showed similar accuracy, which was not affected by the EARR simulation. The use of EALs in the treatment of teeth with EARR following orthodontic treatment may be useful.

Accuracy of three different apex locators and visual exam in primary teeth with and without root resorption in vitro.

AIM: The aim of this study was to evaluate the accuracy and reliability of three apex locators (EndoMaster, Raypex, DentaPort ZX) and visual assessment in primary molar teeth in vitro. MATERIALS AND METHODS: Twenty-four extracted human primary molar teeth with and without root resorption were used in this study. After endodontic access preparation, root canal length was visually measured by means of a K file; then the teeth were embedded into alginate and the roots were measured again by mans of the three apex locators. The results were collected in SPSS 15.0 and statistical evaluations were completed by one-way ANOVA and Kruksal-Wallis test. RESULTS: The measurements closest to the visually determined length were obtained with EndoMaster. No statistically significant differences were found between visual and apex locators lengths (p>0.05). CONCLUSION: Within the limitations of this study, the use of apex locators would be useful in the endodontic treatment of primary teeth.

Interarch tooth size relationship of Indian population: does Bolton's analysis apply?

BACKGROUND: Orthodontists have several methods to detect inter arch-tooth size discrepancies in patients presenting for orthodontic treatment. Many methods such as Pont's analysis, Nance and Carey's analysis, Peck and Peck ratio, Bolton's analysis are commonly used methods. A thorough search of literature reveals a paucity of reliable data on the mesiodistal dimensions of the crowns of the permanent dentition of Indian population. Without information about the size of individual tooth and groups of teeth for Indian population, it is difficult for the clinician to make an adequate diagnosis and treatment plan and to carry out a plan of therapy. AIM: To determine the size of individual permanent tooth and the sex differences, with tooth size ratios according to Bolton's formula and to evaluate the reliability of Bolton's norms (Anterior/ Posterior) in Indian population. MATERIALS AND METHODS: One hundred and twenty cases in which an excellent occlusion was naturally existent with the mean age of 22 years (18-27 years) were selected in the study. The casts were prepared after taking alginate impression of maxillary and mandibular arches and pouring them immediately with dental stone. A sliding Digital Vernier calliper used to measure the teeth. The ratios of the mean of mesiodistal dimensions of types of teeth were computed. RESULTS: The mean overall ratio for the Indian population is found to be 92.11 with a standard deviation of 2.12. The values ranged from 86.50-97.13 and the median is 92.16. The mean anterior ratio for the Indian population is found to be 78.14 with a standard deviation of 2.59. CONCLUSION: Bolton's original data does not represent Indian population. In our study greater size variability was found in maxillary teeth as compared with mandibular teeth except mandibular first molar. Our study indicated that population-specific standards are necessary for clinical assessments. Significant differences were shown for the overall ratio and anterior ratio for both sexes as compared to Bolton's ratio.