[Unerupted first deciduous molar located higher to the first premolar: a case report]

Tooth eruption is defined as the movement of a tooth from its site of development within the alveolar process to its functional position in the oral cavity. The process of tooth eruption can be divided into different phases: pre-eruptive bone stage, alveolar bone stage, mucosal stage, preocclusal stage, occlusal stage and maturation stage. Any disturbance in these phases can lead to eruptive anomalies. The incidence of unerupted teeth is usually higher among permanent teeth than among deciduous ones. Of the primary teeth reported as unerupted, second deciduous molars are the teeth most frequently involved, followed by primary central incisors. At present almost no coverage is seen about the impaction of the first deciduous molar. In this case, a 4-year-old boy who presented with an impacted left maxillary first deciduous molar came to the Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology. This tooth, located higher to the left maxillary first premolar, was well near to the maxillary sinus. The family and medical histories were noncontributory and his physical findings were within normal limits. The mother was reported as having experienced no illness or other complications and taken no medications during pregnancy. His clinical extraoral examination was noncontributory. His clinical intra-oral examination revealed that the maxillary left first primary molar was not present. No enlargement of the area was apparent visually or on palpation. The remaining primary dentition was well aligned and in good condition. His oral hygiene was good, although there were incipient occlusal carious lesions in the mandibular second primary molars. There was no history or evidence of dental trauma. A diagnosis of a left maxillary first deciduous molar was made on the basis of the clinical and radiographic evidence. Numerous local etiologic factors have been described for impacted teeth. These include anomalous teeth, malposition, fusion with adjacent or supernumerary teeth, odontoma, dentigerous cysts, tumors, underdevelopment of the jaws, keratinized epithelial lining, hereditary conditions, and trauma. In this case, the reason for impaction was not clear. After the comprehensive clinical evaluation, treatment consisted of placement of a space maintainer, the periodic examination was indicated for the follow-up, so that early interventions, such as subsequent surgical intervention and orthodontic traction could be recommended timely to manage orofacial disfigurement and to avoid consequent problems with resultant proper functioning and good periodontal health.

Accuracy and evaluation of a new regression equation in predicting the width of unerupted permanent canines and premolar teeth

AIM

To assess the applicability of two regression equations based on mixed dentition analysis and to propose and evaluate a new regression equation using the mandibular incisors and first permanent molars as predictors in calculating the size of unerupted permanent canines and premolar teeth in school children.

METHODS

Dental study casts of 100 children (50 males and 50 females) aged 11-14 years from schools situated in Moradabad, Uttar Pradesh, India were used. The analysis of Tanaka Johnston, Bernabe Flores-Mir and the proposed equation were tested on the casts.

RESULTS

The analysis of Tanaka Johnston and Bernabe Flores-Mir tended to overestimate the mesio-distal width of the canines and premolars. The proposed equation also overestimated but the mean difference showed a closer approximation with the actual measured values compared to the other two equations.

CONCLUSION

Validating studies with a similar population must be conducted to confirm the applicability and precision of the proposed equation.

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.

New regression equations for mixed dentition space analysis in an Iranian population

AIMS

Prediction of the mesiodistal crown width of unerupted canines and premolars is an important aspect of mixed dentition analysis. The accuracy of Tanaka-Johnston equations, the most commonly method, is questionable when it is applied to different ethnic groups. In this study, we aimed to develop a new regression equation for this prediction in an Iranian population.

MATERIALS AND METHODS

The dental casts of 120 Iranian subjects with complete permanent dentition were selected. Mesiodistal crown widths of teeth were measured with digital caliper. In the first part of the study, the correlation and linear regression equations between four mandibular incisors and the canine-premolars segments of both arches were developed (modified Tanaka-Johnston equation). In the second part, as a new method, correlation and linear regression equations were developed between the sum of mandibular central incisors-maxillary first molars and the canine-premolars segments.

RESULTS

It was found that the correlation coefficients between the sum of mandibular central incisors-maxillary first molars and the maxillary and mandibular canine-premolars segments were higher (r = 0.66, 0.68 respectively) than the one between the four mandibular incisors and the canine-premolars segments (r = 0.58. 0.64).

CONCLUSION

New linear regression equations were derived. In this study, the sum of mandibular central incisors and maxillary first molars was better predictor for unerupted canines and premolars. This novel approach allows the prediction of width of unerupted canines and premolars to take place at earlier age.

CLINICAL SIGNIFICANCE

Using the new method, orthodontists could take advantage of mixed dentition analysis at earlier age. Moreover, to test the derived equations on a larger sample size and in other ethnicities is highly recommended.

Prediction of width of un-erupted incisors, canines and premolars in a Ugandan population: a cross sectional study

BACKGROUND

Accurate prediction of the space forms an important part of an orthodontic assessment in the mixed dentition. However the most commonly used methods of space analysis are based on data developed on Caucasian populations. In order to provide more accurate local data we set out to develop a formula for predicting the widths of un-erupted canines and premolars for a Ugandan population and to compare the predicted widths of the teeth from this formula with those obtained from Moyers' tables, and Tanaka and Johnston's equations.

METHODS

Dental casts were prepared using mandibular and maxillary arch impressions of 220 children (85 boys/135 girls) aged 12-17 years recruited from schools in Kampala, Uganda. The mesio-distal width of the mandibular incisors, mandibular and maxillary canines and premolars were measured with a pair of digital calipers. Based on regression analysis, predictive equations were derived and the findings were compared with those presented in Moyers' probability tables, and Tanaka and Johnston's equations.

RESULTS

There were no statistically significant differences between the tooth widths predicted by our equations and those from Moyers' probability tables at the 65th and 75th percentile probabilities for the girls and at 75th level in boys in the mandibular arch. While in the maxillary arch no statistically significant differences at the 75th and 95th levels were noted in girls. There were statistically significant differences between predicted tooth sizes using equations from the present study and those predicted from the Tanaka and Johnston regression equations.

CONCLUSIONS

In this Ugandan population, Moyers' probability tables could be used to predict tooth widths at specific percentile probabilities, but generally, Tanaka and Johnston technique tends to overestimate the tooth widths.

Applicability of two methods of mixed dentition analysis in a contemporary Indian population sample

AIM

More than 10 years experience in implementing the Tanaka Johnston and Moyers methods has shown that they overestimate the sizes of unerupted canines and premolars when used in populations other than the Caucasian. This study was designed to assess the applicability of the two most commonly used methods of mixed dentition analysis and to attempt to derive a more accurate and precise formula to predict the sizes of the unerupted premolars and canines in a sample of Indian population.

MATERIALS AND METHODS

The sample included 200 study models (100 male, 100 female). Tanaka Johnston's and Moyer's equations were applied to this sample and the mean differences between the actual and estimated tooth widths were determined. New regression equations were derived using lower first molars and incisors as the predictors.

RESULTS

The mean difference between the actual and estimated values of canines and premolars using Tanaka Johnston's and Moyers methods were clinically and statistically significant. Therefore new regression equations were derived taking lower first molars and incisors as the predictors for both sexes. On validation, these equations were found to be accurate and precise for this population.

CONCLUSION

It is recommended to use these equations as a method of mixed dentition analysis for the Indian population.

Regression equations for predicting the size of unerupted canines and premolars in an Iranian population: a pilot study

AIM

The aim of this pilot study was to evaluate equations for predicting the size of unerupted canines and premolars during the mixed dentition period in an Iranian population.

METHODS AND MATERIALS

This cross-sectional analysis was performed on 106 subjects (52 girls, 54 boys, aged 13-15 years). Data were obtained from dental cast by making direct measurements of the maximum mesiodistal widths of all mandibular and maxillary incisors, canines, premolars, and first molars with an electronic digital sliding caliper, with an accuracy of ± 0.02 mm and repeatability of ± 0.01 mm. The results were statistically analyzed using Student t tests, Pearson product-moment coefficients, and ANOVA tests. Correlation coefficients (r) and error variance of estimates were determined using a significance level of p<0.05.

RESULTS

No significant differences were found between the mesiodistal tooth widths of males and females in this Iranian population. The highest correlation was between the sum of the mesiodistal width of canines and premolars in the maxilla with the mesiodistal width of the mandibular first molars and maxillary central incisors (r = 0.742). A moderate correlation was obtained in the mandible (r = 0.665). Approximations were developed to predict the size of the unerupted canines and premolars in both jaws (in the maxilla, Y = 0.740X + 14.271, or the simplified formula, Y = 3/4X + 14; for the mandibular arch, Y = 0.658X + 16.353, or the simplified formula, Y = 2/3 X + 16).

CONCLUSION

The strongest correlation was found for the sum of the mesiodistal width of canines and premolars in the maxilla with the mesiodistal width of the mandibular first molars and maxillary central incisors in the maxillary analysis (r = 0.742). A moderate correlation was found in the mandible for the sum of the mesiodistal width of canines and premolars with the mesiodistal width of the mandibular first molars and maxillary central incisors (r = 0.665).

CLINICAL SIGNIFICANCE

The simplified equations proposed for the maxillary arch (Y = 3/4 X + 14) and for the mandibular arch (Y = 2/3 X + 16) offer an easy and practical way to predict the size of unerupted canines and premolars in the maxillary and mandibular arches of Iranian children.

Comparative evaluation of the group of teeth with the best prediction value in the mixed dentition analysis

AIM

Mixed dentition analysis allows the prediction of the tooth width of non erupted permanent canines and premolars (SPCP). It is an essential factor in treatment planning since it could predict a tooth-size to arch-length discrepancy. The aim of this study was to determine which group of permanent teeth presented the best prediction capability for the width sums of the unerupted canine and premolars in an Italian sample.

MATERIALS AND METHODS

A total of 150 subjects with complete permanent dentition were selected. Their dental casts were measured to 0.01 mm with a digital caliper. Pearson correlation and T-test were used for the statistical analysis.

RESULTS/STATISTICS

The combination of the sums of the four lower incisors and the first upper molars showed the best prediction capability for the SPCP in the Italian sample. Moreover new regression equations were formulated including sex and arch as additional predictor variables. In 80% of the cases estimated differences between the predicted and the actual values were smaller than 1 mm.

CONCLUSION

It can be concluded that the new regression equations proposed seemed to show good accuracy.

Mixed-dentition analysis in a Turkish population

OBJECTIVE

To study the reliability of the Tanaka-Johnston mixed-dentition analysis in Turkish individuals and develop a new population-adjusted regression equation for predicting the size of unerupted canines and premolars. The new regression equations were tested to establish their validity in Turkish children.

METHODS

The mesiodistal dimensions of teeth on study casts of 12- to 14-year-old Turkish children were measured. The actual tooth measurements were then compared with predicted values using the Tanaka-Johnston equation. Subsequently, the new regression equations were tested in a group of 50 individuals to determine their validity.

RESULTS

The Tanaka-Johnston regression equations overestimated the actual mesiodistal widths of permanent canines and premolars. With the new regression equations, no statistically significant differences were observed between actual and predicted widths.

CONCLUSION

The Tanaka-Johnston prediction method is not accurate when applied to a Turkish population. The new equations are reliable for predicting the width of unerupted canines and premolars in Turkish individuals.

A comparison of methods for predicting the size of unerupted permanent canines and premolars

The aim of this study was to examine the reliability of eight methods for determining the mesio-distal crown diameters (MDD) of the permanent canines and premolars (C, P(1), and P(2)). The study models of 120 children (60 boys and 60 girls) aged from 14 to 18 years treated in orthodontic clinics were measured using Seipel's method, with callipers accurate to 0.01 mm. The correlation coefficients were determined between the MDD of C, P(1), and P(2) measured on the study models and the sums calculated using various other methods. The correlation coefficients derived by comparison with the methods of Moyers, Tanka and Johnston, Droschl et al., Legović and Hauz, and Berendonk-Nawrath showed a tendency to over-estimate the MDD of C, P(1), and P(2), while the regression methods of Gross and Hasund, Bachmann, and Tränkmann et al. under-estimated the values. Bachmann's method appeared to give the most reliable results.

A new, accurate and fast digital method to predict unerupted tooth size

The sum of the lower incisor tooth width has been proposed as the best predictor for calculating unerupted canine and premolar mesiodistal tooth sizes. The aims of this study were to develop a new, fast, and accurate computerized method to predict unerupted mesiodistal tooth sizes and to determine which reference tooth or combination of reference teeth was the best predictor for canines and premolars in a Spanish sample. The dental casts of 100 Spanish adolescents with permanent dentition were measured to the nearest 0.05 mm with a two-dimensional computerized system. The goal was to predict unerupted canine and premolar mesiodistal tooth sizes using the sizes of the upper central incisor, upper and lower first molar, or a combination of these as a reference and using a specific mesiodistal tooth-size table. The results showed that the Digital Method proposed was very accurate in predicting unerupted canine and premolar tooth size. The combination of the sums of the permanent upper central incisor and the lower first molar was the best predictor for canines and premolars in this sample. Upper arch teeth were better predicted than lower arch teeth. The upper lateral incisor provided the worst predictions.

Mixed dentition space analysis in a Jordanian population: comparison of two methods

AIMS

To test the reliability of the Moyers charts and the Tanaka and Johnston equations in Jordanians and to derive coefficients of correlation between the combined mesiodistal widths of the four permanent mandibular incisors and the combined widths of the canine and premolars of the maxillary and mandibular quadrants.

METHODS

The dental models of the dentition of 130 male and 96 female Jordanian subjects (age range is 14-16 years) with complete permanent dentition were randomly selected. The mesiodistal width of the four permanent mandibular incisors, maxillary and mandibular canines, and premolar teeth were measured using a vernier gauge caliper to the nearest 0.1 mm. The actual teeth measurements were then compared with the predicted values derived from the Tanaka and Johnston equations and Moyers probability tables. Correlation and linear regression analyses were performed between the predicted and actual tooth size for Jordanian children and standard regression equations were developed.

RESULTS

Except for the maxillary arch in male subjects, Tanaka and Johnston regression equations underestimated the mesiodistal widths of permanent canines and premolars. On the other hand, there were no statistically significant differences between actual mesiodistal widths of canines and premolars and the predicted widths from Moyers charts at the 65% and 75% level for the lower and upper arches in male subjects and at the 85% level for the upper and lower arches in female subjects. For the newly developed regression equations, the correlation coefficients between the sum of the mandibular four incisors and the sum of the canine and premolars were 0.60 (for lower) and 0.51 (for upper) in male subjects and 0.59 and 0.64, respectively, in female subjects.

CONCLUSIONS

(1) Tanaka and Johnston prediction method was not accurate when applied to a Jordanian population. (2) Moyers method for prediction can be used for Jordanian children at different probability levels for male and female subjects.

Prediction of lower permanent canine and premolars width by correlation methods

The aim of this study was to determine linear regression equations to estimate the widths of unerupted lower permanent canines and premolars using measurements obtained from 45 degrees oblique teleradiographs. The sample consisted of 30 white Caucasian patients orthodontically treated at the Faculty of Dentistry, Universidade Federal do Rio de Janeiro. The records for each patient included a 45 degrees oblique teleradiograph (left side) in the mixed dentition period and a dental cast of the permanent dentition. Pearson's test was applied between each lower canine, first and second premolars measured on the radiograph, and the sum of their actual widths measured on the dental cast. The strongest correlation occurred for the first premolars for one side (.82) and both sides (.84). One linear regression equation was determined to estimate the widths of un-erupted lower canine and premolars of both sides from a single measurement of the first premolar.

Are the lower incisors the best predictors for the unerupted canine and premolars sums? an analysis of a Peruvian sample

The lower permanent incisor tooth width sum has been proposed as the best predictor for the tooth width sums of the unerupted canine and premolars (SPCP) for populations from different ethnic origins. Only two previous studies have refuted it. The purpose of the present study was to determine which sum or combination of sums of permanent tooth widths presented the best prediction capability for the SPCP in a Peruvian sample, to calculate a specific linear regression equation for this population, and to evaluate the clinical significance. A total of 150 children with complete permanent dentitions were selected. Fifty more children were used as a validation sample for the application of a multiple linear regression equation (MLRE). They did not present clinically visible dental caries or proximal restorations and no active or previous orthodontic treatment. Their dental casts were measured to 0.1 mm with a sliding caliper with a Vernier scale. Three-way analysis of variance, Pearson Correlation Test, Fisher Z values and a MLRE were used for the statistical analysis. The combination of the sums of permanent upper and lower central incisors and upper first molars was the best predictor for the SPCP in this sample. A MLRE was calculated including sex and arch as additional predictor variables. The MLRE determination coefficient was 60% with a standard error of 0.8 mm. This new MLRE underestimates (less than 1 mm discrepancy) the actual SPCP in only 7% of the cases on the basis of a validation sample.

Mixed dentition analysis in a Moroccan population

The aims of this study were to produce odontometric data for a Moroccan population, to test Tanaka and Johnston and Moyers methods, to derive regression equations and elaborate a specific orthodontic prediction table for Moroccan children. 50 dental casts of Moroccan students (25 males, 25 females, mean age 22.6 years sd 1.35) were used to perform measurements of the greatest mesiodistal widths of all mandibular and maxillary canines and premolars and mandibular incisors with an orthodontic calliper. Significant sexual dimorphism was found in tooth sizes (p = .001). The study revealed close relationships between the total mesiodistal widths of the mandibular permanent incisors and that of the maxillary and mandibular canines and premolars. The correlation coefficients (r) and the coefficient of determination (R2) were better sexes combined for the maxilla (r = 0.60 ; R2 = 0.36 ) and for the mandible (r = 0.61 ; R2= 0.37). The regression equations elaborated for males and females were used as a basis for establishing an orthodontic prediction table for Moroccan children.

Appraising number and clinical significance of regression equations to predict unerupted canines and premolars

A sound statistical or clinical reason for proposing several single linear regression equations (SLRE) for predicting unerupted canine and premolar tooth-width sums is needed. The purpose of this study was to develop a methodology to evaluate the number and the clinical significance of SLRE required. A 6-step methodology is presented that permits evaluating the number and the clinical significance of SLRE required for predicting unerupted canine and premolar tooth-width sums. It is important not only to evaluate the statistical need for specific SLRE in different populations, but also to state the clinical significance of their differences against commonly used SLRE.

Prediction of the size of un-erupted permanent cuspids and bicuspids in a Saudi sample: a pilot study

The purpose of this study was to produce an estimated equation for the prediction of unerupted cuspids and bicuspids for the Saudi population. In this study, dental casts of 65 Saudi subjects (37 males and 28 females) were used. The subjects' age ranged from 18 to 25 years. The mesiodistal width of all permanent teeth was measured. The data was subjected to regression analysis. Results showed the Tanaka and Johnston equations overestimate the predicted tooth width of the un-erupted cuspids and bicuspids in Saudis. Results showed the predicted tooth width of Saudis (males and females) is closer to the 50% level of confidence in Moyer's chart. Multiple regression equations were estimated including the sex factor. Accordingly, two equations were estimated for the prediction of the tooth width of the un-erupted cuspids and bicuspids for the Saudi males and females. Based on the results, it can be concluded the 50% data is more accurate than the commonly used percentage Moyer's table (75%) when both sexes are combined. Further studies are needed to confirm the findings of this study.

Mixed dentition analysis in a Senegalese population: elaboration of prediction tables

Estimating the size of unerupted teeth is an essential aspect of orthodontic diagnosis and treatment planning in the mixed dentition. Three main methods have been used to estimate the mesiodistal crown widths of unerupted canines and premolars: direct measurements on radiographs; calculations from prediction equations and tables; and a combination of radiographic measurements and prediction tables. Because there are clear racial differences in tooth sizes, the objectives of this study were to produce odontometric data, correlation coefficients between the combined mesiodistal widths of the permanent mandibular incisors and the canine and premolars for each quadrant, and prediction tables with the regression equations, specifically for Senegalese children. Fifty black Senegalese students (25 women, 25 men, mean age 23.50 years) were selected from the University Cheikh Anta Diop in Dakar, Senegal. The mesiodistal crown diameters of the permanent teeth were measured with calipers. Significant sexual dimorphism was found in tooth sizes. The correlation coefficients between the total mesiodistal width of the mandibular permanent incisors and that of the maxillary and mandibular canines and premolars were found to be 0.53 and 0.70, respectively. The standard error of the estimate was better (0.66) for women in the maxilla, and the r(2) values ranged from 0.46 to 0.57 for both sexes. Prediction tables were prepared. The accuracy of the prediction tables should be tested in a larger sample including more ethnic groups.

Prediction of mesiodistal canine and premolar tooth width in a sample of Peruvian adolescents

OBJECTIVES

To compare the predicted tooth width measurements of permanent canine and premolars from Tanaka-Johnston regression equations and Moyers probability tables with the in situ measurements in a sample of Peruvian adolescents.

DESIGN

Cross-sectional.

SETTING AND SAMPLE POPULATION

Trujillo, Peru; 248 dental casts were measured using a sliding caliper with a Vernier scale rounded to 0.1 mm.

RESULTS

Tanaka-Johnston regression equations were not precise, except for the upper arch in the male sample. For females, the Moyers 95th percentile in the upper arch and the 65th percentile in the lower arch predicted the sum precisely. For males, the Moyers 65th percentile for the lower arch predicted the sum precisely, but none of the Moyers percentiles provided precise prediction in the upper arch.

CONCLUSIONS

Using tooth width prediction methods from a different racial origin could create an under- or overestimation of the actual combined canine and premolar tooth width, although their clinical significance is disputable.

Development of a novel mouse osteoclast culture system including cells of mandibular body and erupting teeth

Osteoclasts are multinucleated cells with the specialized function of resorbing calcified tissues. These cells develop from hemopoietic cells of the monocyte-macrophage lineage with the support of osteoblasts/stromal cells. Tooth eruption is a vertical movement of teeth via creation of an eruption pathway in and through the alveolar bone. The precise cellular and molecular determinants of tooth eruption are not yet clear, and a cell culture system that can reproduce the activity of osteoclast formation during tooth eruption is expected to be a useful tool to clarify the mechanism of eruption pathway formation. To this end, mandibular bodies, including incisors and molars, were isolated from 9- to 11-day-old mice undergoing active tooth eruption. Primary cells were obtained from mandibular bodies by enzymatic digestion and cultured in alphaMEM containing 15% FBS without any cytokine or growth factor or hormone in the culture (AFT culture, for alveolar bone, dental follicle, and tooth). A progressive increase in the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclastic cells was observed in AFT culture. The osteoclastic cells generated were immunopositive for cathepsin K and calcitonin receptor, and formed resorption pits when cultured on dentine slices. Parathyroid hormone-related protein (PTHrP), expressed by the enamel organ of tooth, is reported to be an essential factor in creation of the eruption pathway. To verify this point, cells were isolated from mandibular bodies from which all teeth and dental follicles had been removed and cultured similarly (A culture, for alveolar bone). Osteoclastic cells were not formed and PTHrP production was hardly detected in the medium of A culture, in contrast to the high level of PTHrP in AFT culture. Since our previous study demonstrated that neonatal homozygous PTHrP-knockout mice show impaired osteoclastogenesis around tooth germs, AFT culture was performed by using this sample to examine whether this culture system can reproduce the status of osteoclastogenesis observed in vivo. The result showed that none of the osteoclastic cells were generated from cells of homozygous mice. We here report a novel mouse osteoclast culture system that reproduces the activity of osteoclast formation around erupting teeth without addition of any cytokine or growth factor or hormone to the medium. Histological examination of various transgenic and mutant mice now offers valuable findings on studies of tooth eruption and the present culture system using these animals would be a powerful tool in clarifying the cellular and molecular mechanisms of eruption pathway formation.

Regression equations for determining mesiodistal crown diameters of canines and premolars

In this study, regression equations (prediction equations) were established for the purpose of accurately predicting the widths of the crowns of unerupted canines (C) and premolars (P1 and P2) on the basis of the measured mesiodistal diameter (MDD) and vestibulooral diameter (VOD) of the crowns of the erupted central and lateral incisors (I1, I2) and first permanent molars (M1). On the plaster casts of 120 subjects (60 boys and 60 girls), MDD and VOD of the crowns of I1, I2, C, both P1 and P2, and M1 on both sides in both jaws were measured twice, with a time distance between measurements. Gradual regression equations were derived on the basis of the measurement results, by which the sums of the widths of crowns of C, P1, and P2 can be predicted using three to five predictors. The coefficients of multiple correlations regarding the sex and the jaw varied from 0.79 to 0.85.

Structure and microstructure of coronary dentin in non-erupted human deciduous incisor teeth

The dentin structure of non-erupted human deciduous mandibular and maxillary central and lateral incisor teeth was studied employing light and scanning electron microscopy. For light microscopy, nitric-acid-demineralized and ground sections were used. The sections were stained by hematoxylin-eosin, picrosirius and azo-carmine methods, and ground specimens were prepared using a carborundum disk mounted in a handpiece. For SEM study, teeth were frozen in liquid nitrogen and fractured at longitudinal and transversal directions. Structurally, demineralization and ground methods revealed tubules with primary and secondary curvatures, canaliculi, giant tubules, interglobular dentin, predentin, and intertubular dentin. Scanning electron microscopy showed three-dimensional aspects of dentinal tubules, canaliculi, peritubular dentin, intertubular dentin, and predentin. This study contributes to knowledge about dentin morphology showing characteristics of teeth not yet submitted to mastication stress.

New regression equations for predicting the size of unerupted canines and premolars in a contemporary population

The determination of a tooth-size to arch-length discrepancy in the mixed dentition requires an accurate prediction of the mesiodistal widths of the unerupted permanent teeth. This is an essential factor in treatment planning. The aim of this study was to validate Tanaka and Johnston's analysis on 600 Syrian patients aged 14-22 years. Tanaka and Johnston's tables, equations, and approximations were modified in order to improve the accuracy of the prediction. The correlation coefficients found between the size of the permanent mandibular central incisors and maxillary first molars (31, 41, 16, and 26) and the maxillary and mandibular canines and premolars were high (r = .72 and .74, respectively). New, more accurate prediction tables applicable at earlier ages, and new regression equations were constructed. In addition, new easier approximations were developed to allow the prediction of the size of the unerupted maxillary canines and premolars by adding 6 mm to the half-widths of teeth 31, 41, 16, and 26. The analogous prediction of the size of the unerupted mandibular canines and premolars was obtained by adding 5.5 mm to the half-widths of same teeth, 31, 41, 16, and 26.

Prediction of coronal size of third molars by factor and multiple regression analyses

Factor analysis and multiple regression analysis were made to establish a method for the prediction of the unerupted third molar size. The samples were dental casts of 138 adults (69 women and 69 men) who had all their teeth from the central incisor to the third molar, at least in one side of each maxillary and mandibular dentition. Mesiodistal and buccolingual tooth crown sizes were measured with sliding calipers. Five factors were selected from the factor analysis on the tooth crown sizes. Multiple regression analysis with the third molar as the dependent variable was carried out. Independent variables were selected on the basis of the factors obtained from the factor analysis. Two kinds of multiple regression equations were obtained (the first molar was used as an independent variable in one equation and the second molar was used in the other). The accuracy of the prediction was highest when the lateral incisor, the second premolar, and the second molar were used as independent variables in the maxillary dentition, and the central incisor, the first premolar, and the second molar in the mandibular dentition. The mean of the absolute values of the differences between the predicted values and the actual values was 0.5 mm in the maxillary third molar, and 0.42 mm in the mandibular third molar.

Mixed dentition analysis: a review of methods and their accuracy

Methods that have been proposed for mixed dentition analysis are reviewed. Prediction of the space required in the dental arch for unerupted permanent canines and premolars has been based either on the correlation between the mesio-distal widths of these teeth and of erupted mandibular incisors, or on measurements of the unerupted teeth on radiographs. Studies comparing the different methods have shown that the method of Hixon & Oldfather (1958), as refined by Staley & Kerber (1980), is the most accurate.

Prediction of the size of unerupted canines and premolars in a Saudi Arab population

The estimation of the size of unerupted permanent teeth is an essential aspect in treatment planning in the mixed dentition. The commonly used prediction methods of Moyers and Tanaka and Johnston are based on data from a sample of children of Northern European descent. The accuracy of these methods when applied to a different population is questionable. When we applied the Moyers probability tables to a limited sample of a Saudi Arab population, we found that the 35% level was a more accurate determinant than the commonly used 75% confidence level. Likewise, the prediction equations of Tanaka and Johnston overestimated the size of buccal segments in this population. The data illustrate the limitations of these methods when applied to a sample population of other than European descent. From this data, two linear regression equations were developed for tooth size prediction in Saudi Arab children.

Organic content in occlusal groove-fossa-system in unerupted 3rd mandibular molars: a light and electron microscopic study

A method is described by means of which organic content in fissure areas of 12 unerupted 3rd mandibular molars can be prepared for studies in the light microscope (LM) and in the transmission electron microscope (TEM). Thus, LM and TEM examinations revealed that the organic content throughout the fissure in bone-covered and in mucosa-covered 3rd molars with uncompleted root formation consists of cells belonging to the enamel organ in late or in postmaturative stages. In mucosa-covered teeth with completed root formation it was only possible to identify enamel organ cells at the entrance of the fissure. Deeper parts were occupied by degenerative cells, polymorphonuclear cells and unidentified material. The results indicate that ameloblasts in fissures do not transform to stratified squamous epithelium but gradually degenerate towards terminal stages and remain as such, as the tooth emerges into the oral cavity.

Prediction of mandibular incisor and canine crowding changes in the mixed dentition

To test the hypothesis that preeruptive tooth positions and dental arch parameters might forecast crowding changes, a sample of 47 aboriginal children (26 males, 21 females) was selected stringently on the basis of Class 1 characteristics and an untreated dentition unaffected by caries or attrition. Crowding scores, radiographic relationships of 765E, and dental arch dimensions were evaluated for the mixed dentition (Stage 1, 8.91 +/- 1.05 years) and earliest emergence of the permanent dentition (Stage 2, 12.48 +/- 0.97 years). Changes between the stages were calculated and the sample was divided into two groups, according to an increase (Group 1) or decrease (Group 2) in incisor and canine crowding. Multivariate and multiple regression analyses were used to identify predictors (Stage 1 radiographic and dental arch parameters) of incisor and canine crowding behavior. Dental arch form and tooth size were important factors in measuring the amount of incisor or canine crowding at Stage 1 and Stage 2. Neither the radiographic nor the dental arch predictors proved useful in forecasting crowding changes. Group 2 dental arches tended to be initially narrower, shallower, and more crowded; however, they showed greater molar and canine width expansion and lessened arch depth reduction than Group 1 cases. Many cases showed a reduction in canine crowding from mixed to permanent dentition. This appeared to be largely independent of the observed incisor crowding. Sexual, racial, and individual variations in dentofacial pattern reinforce the need to carefully consider interceptive extraction or space-regaining therapy for each patient because of the unpredictability of crowding behavior during the transition from mixed to permanent dentition.

Age-specific angulation of unerupted human third molar teeth in a cross-sectional sample

For males aged 18 to 21, the angulation of unerupted third molars was unrelated to age. A counterbalancing loss of data resulting from tooth eruption and extraction accounted for this null finding. The value of age-specific angulation in determining whether a tooth will eventually erupt may be limited.

Histochemical study of giant tubule content in dentin of unerupted cow incisors

Incisal dentin of mandible cow incisors was studied by incident light. The material consisted of 12 intact permanent unerupted incisors from 2-yr-old cows removed immediately after bleeding. These specimens were kept in an isotonic EDTA-sucrose solution to be decalcified while maintaining vitality of cellular components. Three of the specimens were successfully dissected in a mesiodistal plane, exposing the giant tubule lumens and their content. By the use of NBT, a compound reduced by the dehydrogenase enzymes of the electron transport in the inner mitochondrial membrane, it was concluded that the giant tubules contained vital cells. The giant tubules were also shown to communicate with the incisal part of the pulp cavity by wide openings.

Prediction of the widths of unerupted canines and premolars

The purpose of this study was to develop, with simple linear regression analysis, equations that could accurately predict the mesiodistal widths of unerupted canines and premolars in both arches of the mixed dentition patient. Clinically useful prediction equations were developed and tested on a sample of orthodontic patients. Performance of the equations in patients was satisfactory. Charts and suggestions for completing a tooth size-arch length analysis in the patient with a mixed dentition were discussed.

Three-dimensional replicas of pit and fissure morphology in human teeth

Nuva Seal replicas of pits and fissures from surgically removed unerupted human third molars and premolars, and from erupted premolars extracted for orthodontic reasons, were examined in the scanning electron microscope. The results confirm that the morphology on occlusal surfaces of third molars is extremely variable with numerous pits of considerable length positioned at various angles relative to the fissures. In contrast, the morphology of unerupted and erupted premolars is simpler with fewer and shorter pits positioned perpendicular to the fissure. It is pointed out that fine details of the morphology are lost when reconstructions of the occlusal morphology are made from serial ground sections. However, such reconstructions seem to be less reliable in third molars than in premolars.

Comments on the porosity of human tooth enamel

The porous nature of surface and sub-surface enamel undergoing the final stages of maturation has been observed on unerupted, partly-erupted, and fully-erupted human teeth, using polarized light microscopy, microradiography, and scanning electron microscopy. Maturation deficiency of developmental origin can be distinguished from early carious lesions with polarized light by the absence of a well-circumscribed "dark" zone.

Reliability and validity of lower third molar space-assessment techniques

Present techniques for predicting eruption or impaction of lower third molars are based on measurements of the space between the second molar and the ramus. This study was designed to investigate the reliability and validity of radiographic techniques often used for assessing this space. Rotational tomograms (O.P.G.s) yielded the best estimates of the Space Width Ratio (found by dividing the space available by the mesiodistal width of the lower third molar) as measured directly on dried skulls. Estimates for lateral cephalograms were unreliable. The use of Xi point to lower second molar for assessing the space for lower third molars is not supported.

A revision of the Hixon and Oldfather mixed-dentition prediction method

A revision of the Hixon and Oldfather prediction method was undertaken with measurements obtained from persons who participated in the Iowa Facial Growth Study, the same group of subjects used originally by Hixon and Oldfather to develop their prediction equation. A significantly improved prediction equation was developed. A graph was made for clinical use in the prediction of mandibular canine and premolar widths in mixed-dentition patients.

A nonextraction approach to crowded dentitions in young children: early recognition and treatment

A total of 22 cases that were diagnosed as having space discrepancy problems in the deciduous and early mixed dentitions showed that treatment by early expansion therapy with Crozat appliances had eliminated the need for extraction of deciduous canines or permanent premolars.

The eruption tendency and changes of direction of impacted teeth following surgical exposure

Surgical exposure may be an integral part of orthodontic treatment of impacted teeth. In some cases the surgical procedure alone results in eruption and alignment of such teeth. The nature of the mechanism that starts concomitantly with the removal of covering tissues is not known. The aim of this investigation was to study factors associated with eruption as well as the eruption route of impacted and unerupted teeth following surgical exposure. The material consisted of 542 impacted teeth in 389 patients. The findings given strong support to the hypothesis that forces within surrounding tissues act upon the exposed crown in such a way as to direct it toward the area where the tissues were removed.

Late third molar genesis: its significance in orthodontic treatment

(1) Third molar genesis may occur up to the age of sixteen years, although the possibility of their appearance after the age of twelve years is reduced. (2) When third molar genesis is delayed beyond the age of ten years, the possibility of all four third molars developing is reduced by about fifty percent. (3) The intraindividual variability in stage of development of third molars increase when genesis is delayed beyond ten years of age. (4) There is no significant difference in size of early and late developing third molars.

The sequelae of surgical exposure of unerupted teeth

The late effects of surgical exposure of unerupted teeth were analyzed. Of 121 teeth, 62 had only the crowns exposed; additional traction was applied to 31 teeth and 28 were repositioned. Postoperative observation time ranged from eight months to 13 years. One hundred and eleven teeth assumed their position in the arch and were deemed successfully treated; ten teeth failed to erupt. Of the successfully treated teeth, 23% showed biological aberrations such as obliteration of the pulp, dwarfed roots, and denervation. These pathophysiologic changes, alone or in combination, were commensurate with the amount of trauma inflicted on the teeth. Teeth that wer repositioned showed the most change, whereas teeth that only had crowns exposed showed the least change.

Prediction of lower canine and premolar widths in the mixed dentition

The purpose of this investigation was to determine whether, with multiple regression analysis, a more accurate method than is now available for predicting the widths of unerupted mandibular canines and premolars of mixed-dentition patients could be developed. Regression analyses were performed on data derived from 83 Caucasian subjects (42 males and 41 females) who participated in the Iowa Growth Study. Measurements were taken on plaster casts of the mandibular incisors, canines, premolars, and first molars. Measurements of the mandibular canines, premolars, and first molars were obtained from periapical radiographs taken with a long-cone technique. Newly developed regression equations for each sex had the highest correlation coefficients and smallest absolute errors of estimate when compared to previously published methods. The new equations and previous prediction methods were tested on a sample of 55 orthodontic patients (23 males and 32 females). The newly developed equations were also the most accurate method of prediction in the orthodontic patient sample.

Application of analysis of crowding and spacing of the teeth

Spacing or crowding of the teeth is measured and analyzed to assist in decisions regarding the maintenance of teeth in their existing positions or their movement to improved positions. Numerical guides always should incorporate a gray zone in which decisions cannot be made without additional information. In the stage of mixed dentition, estimates of the size of unerupted teeth are more accurate than estimates of future spacing or crowding because the perimeter of the arch does not diminish the same amount in all cases. Instead, it appears to be related to the amount of crowding in the mixed dentition. Determination of the amount of crowding or spacing must always be accompanied by consideration of molar, canine, and incisor relationships. In addition, the effect of the dentition on lip posture should also be evaluated.