Journal of Oral and Maxillofacial Surgery

Transcription

1 Journal of Oral and Maxillofacial Surgery Copy of Notification zgf0333 RUSH: Journal of Oral and Maxillofacial Surgery article <# 53000> for proofing by Cabov ===== Dear Author, The proof of your article, to be published by Elsevier in Journal of Oral and Maxillofacial Surgery, is available as a "PDF" file at the following URL: Login: your address Password: ---- The site contains 1 file. You will need to have Adobe Acrobat Reader software to read these files. This is free software and is available for user download at: After accessing the PDF file, please: 1) Carefully proofread the entire article, including any tables, equations, figure legends and references. 2) Ensure that your affiliations and address are correct and complete. 3) Check that any Greek letter, especially "mu", has translated correctly; 4) Verify all scientific notations, drug dosages, and names and locations of manufacturers; 5) Be sure permission has been procured for any reprinted material. 6) Answer all author queries completely. They are listed on the last page of the proof; You may choose to list the corrections (including the replies to any queries) in an and return to me using the "reply" button. Using this option, please refer to the line numbers on the proof. If, for any reason, this is not possible, mark the corrections and any other comments (including replies to questions) on a printout of the PDF file and fax this to Laura Dinkins-White( ) or mail to the address given below. Do not attempt to edit the PDF file (including adding <post-it> type notes). Within 48 hours, please return the following to the address given below: 1) Corrected PDF set of page proofs 2) Print quality hard copy figures for corrections if necessary (we CANNOT accept figures on disk at this stage). If your article contains color illustrations and you would like to receive proofs of these illustrations, please contact us within 48 hours. If you have any problems or questions, please contact me. PLEASE ALWAYS INCLUDE YOUR ARTICLE NUMBER (located in the subject line of this ) WITH ALL CORRESPONDENCE. Sincerely, Laura Dinkins-White Senior Journal Manager Elsevier Science 1600 John F.Kennedy Blvd. Philadelphia, PA Phone: Fax: la.white@elsevier.com

2 AQ: 1 tapraid2/zgf-joms/zgf-joms/zgf00308/zgf0333d08z nandys S 1 1/17/08 Art: J Oral Maxillofac Surg xx:xxx, 2008 Correlation Between the Pattern of Facial Growth and the Position of the Mandibular Third Molar Mario Legović, DDS, PhD,* Izak Legović, DDS, Gordana Brumini, PhD, Irena Vančura, PhD, Tomislav Ćabov, DDS, PhD, Maja Ovesnik, PhD,# Senka Meštrović, PhD,** Martina Šlaj, DDS, Mrsc, and Ana Škrinjarić, DDS Purpose: The purpose of this study was to examine the correlation between variables that determine the position of the third molar (M3) and correlation between the pattern of facial growth and examined variables. Materials and Methods: Material for the study consisted of 130 panoramic radiographs and lateral radiographs of subjects heads (LL) in whom orthodontic therapy had been started. Analysis of the position of the mandibular M3 and its relation to the bone and other teeth were determined by 4 variables: evaluation of the space for both M3, spatial relation between M2 and M3, vertical position of the M3 in relation to the alveolar ridge, and inclination of the germ of the M3. Results: In boys, significant correlation was determined on the right side of the jaw, between retromolar area and the vertical position of M3. Significant correlation was determined in girls, between retromolar area and the vertical position of M3 on both sides, retromolar area and M3 inclination on the left side, and retromolar area and spatial relation of M3 on the right side. Analysis of correlation between facial growth pattern and 4 variables that determinate the position of M3 showed positive correlation only for the lower right M3 inclination in subjects with anterior facial rotation. Conclusion: The present study showed that the amount of retromolar space for the position of the third molar is not a sign of its normal development. No significant differences were determined between the position of M3 and type of facial growth American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg xx:xxx, 2008 *Professor, Department of Orthodontics, School of Medicine, University of Rijeka, Croatia. Private dental practice, Poreč, Croatia. Department of Computer Science, School of Medicine, University of Rijeka, Croatia. Private dental practice, Rovinj, Croatia. Assistant Professor, Department of Oral and Maxillofacial Surgery, School of Medicine, University of Rijeka, Croatia. #Professor, Department of Orthodontics, School of Medicine, University of Ljubljana, Slovenia. **Professor, Department of Orthodontics, School of Dental Medicine, University of Zagreb, Croatia. Variability of crown and root morphology, 1,2 the large intervals during which mineralization and eruption occur, 3,4 frequent hypodontia 3,5,6 and impaction, 8,9 and the influence on lower arch crowding, are some of the characteristics of mandibular third molars (M3), which have prompted orthodontics and oral surgeons to carry out numerous investigations. Panoramic radiography is used in routine orthodontic and oral surgical diagnostics, and would be of even greater assistance if its analysis enabled prediction of M3 impaction at an early age. However, this is impos- Department of Orthodontics, School of Dental Medicine, University of Zagreb, Croatia. Private dental practice, Poreč, Croatia. Address correspondence and reprint requests to Dr Ćabov: Department of Oral and Maxillofacial Surgery, School of Medicine, University of Rijeka, Tome Strižića 3, Rijeka, Croatia; tomislav.cabov@medri.hr 2008 American Association of Oral and Maxillofacial Surgeons /08/xx0x-0$34.00/0 doi: /j.joms

3 2 FACIAL GROWTH AND POSITION OF MANDIBULAR M sible because of the specificity of development of M3 at 10 to 11 years of age. 13 Impaction of M3 can only be predicted by analysis of the panoramic radiographs after the age of 20 years because up until that age important positional changes take place According to Hattab, 17 such changes are unpredictable. Reliable indicators of M3 eruption, which can be established by analysis of panoramic radiographs are: relation of the retromolar space and mesiodistal crown width of the M3, inclination of the M3 toward the base of the mandible and M2, and variables by which the vertical position of M3 can be determined. 24 Apart from etiologic factors that cause M3 impaction, 18,25,26 it has been established that impaction can be associated with the pattern of facial growth The purpose of this study was to examine the correlation between variables that determine the position of the third molar (retromolar space, spatial relation of the crown of the second molar and the third molar, vertical position of the third molar in relation to the alveolar ridge and inclination of the tooth towards M1) and correlation between the pattern of facial growth and the above variables. Materials and Methods Materials for the study consisted of 130 panoramic radiographs and lateral radiographs (LL) of subjects heads (65 boys, 65 girls) in whom orthodontic therapy had been started. Both radiographs were performed on the same day. The following conditions were necessary for selection of the panoramic radiographs and LL radiograph: the presence of all 4 third molars, absence of hypodontia of the permanent teeth, mineralization of the third molar to at least the sixth stage, according to Nolla, and patients without extraction of permanent teeth or any previous orthodontic procedures. The sixth stage of crown mineralization was necessary for evaluation of the longitudinal axis of the tooth. The age of subjects ranged from 12 to 13 years. Analysis of the position of the mandibular third molar and its relation to the bone and other teeth were determined by means of the following 4 variables: 1. Evaluation of the space for both third molars. Variables were marked (RSR for retromolar space right and RSL for retromolar space left). 2. Spatial relation between M2 and M3. Variables were marked SRR for spatial relation right and SRL for spatial relation left. 3. Vertical position of the third molar in relation to the alveolar ridge. Variables were marked VPR for vertical position right and VPL for vertical position left. 4. Inclination of the germ of the third molar. Variables were marked IR for inclination right and IL for inclination left. All the above 4 variables were determined according to the method of Steinhardt et al. 35 Unlike the above authors, who determined the occlusal plane by joining the highest points of the tooth cusp on the panoramic radiographs from P1 to M2, in the present study it was determined by joining the highest points of the crown of the lateral incisor and first molar. For the analysis, the necessary details from the panoramic radiographs were copied onto acetate paper. All the tracings and measurements were carried out on 2 occasions by the same examiner. The distance from the mesial surface of M3 to the distal surface of M1 was measured for determination of the estimated position in the retromolar space of the mandible. Measurement points A and B were obtained by verticals from the mesial surface of M3 and the distal surface of M1 on the occlusal plane. Point C was obtained by lengthening the clamps of points A and B up to the ascending ramus of the mandible. The obtained measurement values, expressed in the formula A.B 100/A C %, determined the estimated retromolar space in both quadrants. The spatial relation of crowns M2 and M3 was determined in both mandibular quadrants. In this respect there are 2 possibilities: the germ of the third molar is far away from M2 or the shadow of the third molar germ and M2 cover each other. For the analysis, data were taken where the shadows of the M3 germ and M2 cover each other. Evaluation of the vertical relation of the position of the M3 in relation to the alveolar process was determined by measuring the distance from the highest point of M3 to the edge of the alveolar process. The value obtained is expressed in percentage relation to the height of the M1 crown. The alveolar process is shown by a line that passes through the cervical edge of M1 (cementoenamel junction). The height of the M1 crown was determined by the distance from the alveolar process to the highest point of the distal M1 cusp through which a parallel is drawn with the line of the alveolar process. The distance from the edge of the alveolar process to the top of the cusp represents the size of B. The size of A is represented by the distance from the highest point on the occlusal surface of M3 to the line of the alveolar process. Depending on whether the highest occlusal point of M3 is below or above the line of the alveolar process, point A can have a positive A1 (above) relation or negative AQ: 2

4 LEGOVIĆ ET AL AQ: 3 AQ: 4 AQ:5-6 AQ:7-8 (A2) (below). The magnitudes are expressed in the formula: A 100/B %. Inclination of the lower third molar germ was determined by the angle between the longitudinal axes of the M1 and M3 crowns. All measurements were performed twice within a period of 15 days. When the 2 measurements differed by more than 1 mm or 1 degree, measurements were repeated. For the analysis, mean values of both measurements were taken for all 4 variables. Data necessary for determination of the type of facial development were copied from the LL radiographs of the head onto acetate paper on which the analysis was carried out. The following were determined: the angle of the flexion of the cranial base (N-S-Ar), joint angle (S-Ar- Go), mandibular angle (Ar-Go-Me), upper (Ar-Go-Nn) and lower (N-Go-Me) segment of the mandibular angle, and the anterior (distance N-Me) and posterior (distance S-Go) facial height. All tracings and measurements were performed by 1 examiner, and all measurements were repeated on 2 occasions. When the results of both measurements differed by more than 1 mm or 1 degree both measurements were repeated. Mean values of both measurements were analyzed. Facial growth was evaluated as: without rotation neutral (relation of posterior to anterior facial height from 62% to 65%, values of Björk s polygon sum of the angles of flexion of the cranial base, joint, and mandibular angle), 396 degrees, angles Ar-Go-Nn 52 to 55 degrees, N-Go-Me 70 to 72 degrees, with anterior rotation (relation of posterior and anterior facial height greater than 65%, values of Björk s polygon and angle N-Go-Me less than normal, and angle Ar-Go-Nn greater than normal), and with posterior rotation (relation of posterior facial height to anterior facial height less than normal, values of Björk s polygon and N-Go-Me angle greater than normal, and Ar-Go-Nn angle less than normal). Differences between the 4 variables by which the position of M3 and the type of facial development were determined for both genders together. STATISTICAL ANALYSIS OF DATA The data obtained were analyzed by means of the program for statistical analysis of data Statistica 7.1. (StatSoft Inc., Tulsa, OK, USA). Normality of distribution of the variables that determined the position of M3 was tested by Kolmogorov-Smirnov test. For normal distribution as a measure of the central line arithmetic mean (M) was used, and as a measure of dispersion standard deviation (SD). Differences in the values of certain variables between certain types of facial development were determined by one-way analysis of variance and Tukey s post-hoc test. Differences in the frequency of Table 1. MEAN VALUES (M SD) OF MEASURED VARIABLES OF THE ESTIMATED M3 POSITION Variable the occurrence of particular types of facial development, according to gender, were tested by 2 test, as were also differences in the distribution of spatial relations of M2 and M3, according to the type of facial development. Values of P.05 were considered statistically significant. Results Estimated Position of M3 As no significant differences were determined in the measured values between boys and girls, Table 1 shows mean values (M) and standard deviations (SD), measured in all subjects (N 130). With regard to gender, correlation between some variables appears more frequently in girls than in boys (Tables 2,3). In boys, significant correlation was determined only on the right side of the jaw, between RSR and VPR variables (r 0.235; P.023), which suggests that with increase in the retromolar area an increase in the growth index occurs of the vertical position of M3 in relation to the alveolar ridge. Significant correlation was determined in girls between RSL and VPL variables on the left side of the jaw (r 0.247; P.032) and on the right side (r 0.236; P.028). Also, on the left side of the jaw increase (RSL variable) in the retromolar space area was significantly correlated with increase (IL variable) in the angle of inclination (r 0.479; P.001) while between the same variables on the right side of the jaw no significant correlation was determined (r 0.194; P.05). Increase (VPL) in the vertical position of M3 was accompanied by a significant increase (IL variable) in the angle of inclination (r 0.252; P.026). M RSR* RSL* SRR# SRL# VPR* VPL* IR$ IL$ *Values expressed by percent ratio. #Values expressed by proportion. $Values expressed in degrees. Legović et al. Facial Growth and Position of Mandibular M3. J Oral Maxillofac Surg SD T1 T2,3,AQ:9

5 4 FACIAL GROWTH AND POSITION OF MANDIBULAR M T4 T5 T6 Table 2. CORRELATION BETWEEN THE VARIABLES BY WHICH THE POSITION OF M3 IN THE MANDIBLE WAS DETERMINED IN BOYS Left Side Significant negative correlation was determined on the right side between RSR and SRR variables (r 0.366; P.021) which indicates that with the increase in retromolar space the number of M3 covered by M2 decreased, while on the left side of the jaw this significance was not determined (r ; P.05). Dependence of the type of facial growth on the gender of the subject is presented in Table 4. Anterior, posterior, and neutral type of facial growth occurred equally frequently in boys and girls ( ; P.632). Values of the retromolar space (RS variable) determined for anterior, posterior, and neutral facial type were not significantly different in the left mandible (F 0.28; P.759) and right (R 0.58; P.561). The vertical position of M3 in relation to the alveolar ridge (VP variable) did not differ significantly between individual types of facial development on the left side of the mandible (R 1.54; P.219) and on the right side (R 1.00; P.371). No significant differences were determined either in the distribution of the spatial relations of M2 and M3 (SR variable) according to the type of facial development on the left side of the mandible (Table 5) and on the right side (Table 6). No differences were determined between particular types of facial growth in the number of freestanding third molars and third molars covered by the shadows of M2 ( ; P.138). In the anterior, posterior and neutral type of facial growth no significant differences in the number of freestanding third molars and covered third molars were determined ( ; P.236). Inclination of the axis of the third molar towards the longitudinal axis of M3 (I variable) did not differ significantly between certain types of facial development for the left side of the mandible (P.311). However, significant difference was determined for the right side of the mandible (P.040; Table 7). The angle of M3 inclination for anterior type of facial growth was significantly greater than the angle of inclination determined for posterior type of facial growth (P.037) although not greater than the angle determined for neutral type of facial growth (P.562). Discussion Right Side SRL VPL IL SRR VPR IR RSL RSR * SRL SRR VPL VPR 0.77 *Indicates statistically significant correlation coefficient. According to numerous investigations, 16,19-22 the most important variable by which it is possible to predict impaction of M3 by analyzing the panoramic radiographs is the retromolar space. In this study, the anterior point of the ramus was used as the posterior point for its determination. Behbehani et al 33 consider that the retromolar space can be determined more precisely when Ricketts Xi point is used as the posterior point. In their opinion, the anterior edge of the ramus is difficult to determine. These authors 33 performed their measurements on lateral radiographs of the head. According to Ledyard, 36 the amount of the retromolar space is already defined at the age of 14 years. According to Steinhardt et al, 35 increase in the Table 3. CORRELATION BETWEEN THE VARIABLES BY WHICH THE POSITION OF M3 IN THE MANDIBLE WAS DETERMINED IN GIRLS Left Side Right Side SRL VPL IL SRR VPR IR RSL * 0.479* RSR 0.366* 0.236* SRL SRR VPL 0.252* VPR *Indicates statistically significant correlation coefficient. T

6 LEGOVIĆ ET AL Table 4. DEPENDENCE OF THE TYPE OF FACIAL GROWTH ON GENDER Gender Type of Facial Growth Anterior Posterior Neutral Total N % N % N % N % Boys Girls P.632 area of this segment can be expected up to the development of M3, when one third of its root has been mineralized. For normal eruption of M3, the retromolar space must be greater than the mesiodistal crown width of the M3. 16,37 Its amount is defined by the longitudinal growth of the mandible, direction of condylar growth, and direction of tooth eruption. 24,28,33 In this study, the amount of retromolar space was determined by the percent relation of the distance from the distal surface of the M1 crown to the mesial plane of the M3 crown to the distance from the distal plane of the M1 crown to the most anterior point of the ascending ramus of the mandible. It was determined that the index on both sides and for both genders was approximately 100, which indicates marked reduction of the retromolar space. Only results of around 50% to 60% would indicate a satisfactory relation of the retromolar space and mesiodistal crown width of M3. With regard to the spatial relation of M3 and M2, it was established that 25% of the right and 32% of the left shadows of the M3 germ were covered by M2. Steinhardt et al 35 found greater changes in these relations after completion of M3 crown mineralization. In most cases, Richardson 38 found an average space between the M3 germ and M2 of 1 mm. The author considered that the amount of this space and its significance for the occurrence of M3 impaction is not clear. 13 Some authors found significant changes in the spatial relations of unerupted M3 and M2 even after the age of 20 years. 14,15 The vertical position of M3 is determined by the percentage relation of the distance of the occlusal surfaces of M1 and M3 to the neck/cervix of M1. The results of this study for both genders and in both quadrants show that the occlusal surface of M3 is on average 2 heights of the M1 crown away from the occlusal plane. Steinhardt et al 35 state that the occlusal surface of M3 is furthest away from the occlusal plane during the stage of complete crown mineralization. If during transition from the third to the fourth stage M3 continues to maintain a deep position, future impaction is indicated, which has been shown by some authors. 16,21 One of the reliable indicators of M3 eruption is its inclination. It can be determined by the angle of the longitudinal axes of M2 and M3, or the angle of the occlusal surface of the M3 mandibular base. 20,33 According to Steinhardt et al, 31 changes in the inclination of M3 can be expected until complete mineralization of the M3 crown. Richardson 39 determined the inclination of M3 by the angle of the occlusal surface of the M3 mandibular base, and confirmed intensive changes in these relations between the ages of 10 and 11 years. The angle, whose values varied from 11 to 83 degrees (mean 38 degrees) in the aforementioned interval, changed from 20 to 42.5 degrees (average 11.2 degrees). In the same interval, the position of M3 changed from 1 to 14.5 mm (mean 5.4 mm). The author did not find correlation between these changes and the dimensions of the tooth and jaw. According to Shiller, 14 inclinational changes of the mandibular third molar can occur after the age of 20 years, and according to Nance et al 15 even after the age of 26 years, and Venta et al, 40,41 after the age of 32 years and 38 years, respectively. According to Behbehani et al, 33 inadequate correction of M3 inclination is one of the more important reasons for its impaction. In the present study, inclination of M3 was determined by the angle of the longitudinal axes of M1 and Table 5. DISTRIBUTION OF SPATIAL RELATIONS OF M2 AND M3 ACCORDING TO THE TYPE OF FACIAL DEVELOPMENT ON THE LEFT SIDE OF THE MANDIBLE Spatial Relation M2 and M3 Type of Facial Growth Anterior Posterior Neutral Total N % N % N % N % Freestanding third molar Covered shadow P AQ: 10

7 6 FACIAL GROWTH AND POSITION OF MANDIBULAR M Table 6. DISTRIBUTION OF SPATIAL RELATIONS OF M2 AND M3 ACCORDING TO THE TYPE OF FACIAL GROWTH ON THE RIGHT SIDE OF THE MANDIBLE Spatial Relation M2 and M3 M3. Average values were and degrees. These results are much higher than those obtained by Haavikko et al. 42 They studied changes in the inclinational angle between M3 and M2 from 13.5 to 19 years. The average value of the angle at 13.5 years was 23 degrees and at 19 years was 13.9 degrees. A small inclinational angle in the early stages of M3 development is a sign of its eruption. It was anticipated that the results of the study would indicate the existence of correlation between the analyzed variables, as indicated in some results. 43 Correlation was particularly expected between the variables retromolar space and the 3 remaining variables. Namely, with greater retromolar space the third molar had the possibility of normal eruption, vertically and sagittally, and the possibility of development behind M2. Artun et al 34 maintain that every increase in the retromolar space reduces the possibility of impaction by 29%. In boys, positive correlation was determined only between the retromolar space right and the vertical position of M3. In girls, positive correlation was determined between the retromolar space and vertical position of M3 on both sides. Negative correlation was determined in girls between the retromolar space and spatial relation of M3 to M2. This was expected because with the greater retromolar space the number of M2 covered M3 germs is less. In girls, positive correlation was determined on the left side of the dental arch between the retromolar space and M3 Type of Facial Growth Anterior Posterior Neutral Total N % N % N % N % Freestanding third molar Covered shadow P.236 Table 7. DISTRIBUTION OF THE INCLINATION OF THE AXIS OF THE THIRD MOLAR WITH REGARD TO THE TYPE OF FACIAL GROWTH Type of Facial Growth inclination, and between the vertical position and inclination of M3. These results confirm the findings of other authors, who consider that positional changes and eruption of M3 are unpredictable phenomena 15 and that differences with regard to gender can be anticipated. 33 In this study, the aim was also to examine the correlation between facial growth and 4 variables by which the position of M3 can be determined. Broadbent 29 reported that facial dimensions of growth are slower in subjects with M3 impaction compared with those in whom M3 is in occlusion. Richardson 39 found no correlation between the changes in M3 position and mandibular growth from the ages of 10 to 15 years. With regard to growth in length of the mandible and the risk of impaction, Björk et al 30 and Capelli 32 allege that there is less chance of impaction with greater mandibular length. Behbehani et al 32 consider that the length of the mandible during the occurrence of impaction is marginal. Apart from reduced length of the mandible and wide ramus, Capelli 32 also attributes the vertical direction of facial growth as an increased risk of impaction. Björk et al 30,31 consider that eruption of M3 is associated with the amount of retromolar space. It is directly connected with the direction of condylar development, which determines resorption of the anterior border of the ramus. Dominant vertical growth of the condyle is connected with reduced resorption of the anterior edge of the ramus and anterior rotation of the mandible. If, on the other hand, the condyle grows more posteriorly, then resorption of the anterior border of the ramus is greater and the mandible rotates posteriorly. Similar results were obtained by Behbehani et al 33 and Artun et al. 34 They determined great risk of M3 impaction in the case of greater magnitude of the ar- Pg/MP angle and smaller magnitudes of the gonial and MP/SN angles. In this study correlation was analyzed between variables by which the position of the lower M3 and type of facial development are determined. It was found that the angle of inclination of the lower right M3 was significantly greater in subjects with anterior facial rotation. No correlation was determined between the Inclination N M SD Anterior F 3.31 Posterior Neutral P.040* *Post-hoc test determined significant difference in the angle of inclination between anterior and posterior type of growth. Legović et al. Facial Growth and Position of Mandibular M3. J Oral Maxillofac Surg AQ: 11

8 LEGOVIĆ ET AL AQ: 12 remaining variables and the type of facial growth. The reason for this could be that changes associated with the growth of the lower M3 could be expected even after the age of 20 years. Characteristically, the development of the lower M3 in contrast to other teeth is not in any correlation with somatic, skeletal, or sexual development. Compared with other teeth, this tooth has great autonomy with regard to development. 44 The amount of retromolar space for the position of the third molar is not a sign of its normal development in subjects older than 12 and 13 years. No significant differences were determined between the position of M3 and type of facial growth. Uncited Reference This section comprises reference that occur in the reference list but not in the body of the text. Please position each reference in the text or delete it. Any reference not dealt with will be retained in this section: 7. Acknowledgment Supported by Croatian Ministry of Science, Education and Sports, grant nos and References 1. Schulze Ch: Anomalien und Missbildungen der menschlichen Zähne. Berlin, Chicago, Sao Paolo, Tokyo, Quintesenz, 1987, pp Kalay J: Dental Anthropology. Zagreb, JAZU, 1974, pp Bishara SE, Andreasen G: Third molars: A review. Am J Orthod 83:131, Daito M, Tanaka T, Hieda T: Clinical observation on the development of third molars. J Osaka Dent Univ 26:91, Graber TM, Swain BF: Orthodontics, current principles and techniques. St. Louis, MO, 1985, p Hotz R: Orthodontie in der täglichen Praxis. Stuttgart, Wien, Hans Huber Verlag, 1970, p Sonnabend E: Zur Unterzahl der Zähne insbesondere der 3 Molaren. Dtsch Zahn Mund Kieferheilk 46:34, Vasir NS, Robinson RJ: The mandibular third molar and late crowding of the mandibular incisors - A review. Br J Orthod 18:59, Van der Linden W, Cleaton-Jones P, Lownie M: Diseases and lesions associated with third molars. Review of 1001 cases. Oral Surg Oral Med Oral Pathol Oral Radio Endod 79:142, Richardson ME: Late lower arch crowding: Facial growth or forward drift? Eur J Orthod 1:219, Richardson ME: Late lower arch crowding. The role of facial morphology. Angle Orthod 56:244, Niedzielska I: Third molar influence on dental arch crowding. Eur J Orthod 27:518, Richardson ME: The etiology and prediction of mandibular third molar impaction. Angle Orthod 47:165, Shiller WR: Positional changes in mesio-angular impacted mandibular third molar during a year. J Am Dent Assoc 99:460, Nance PE, White RP Jr, Offenbacher S, et al: Change in third molar angulation and position in young adults and follow-up periodontal pathology. J Oral Maxillofac Surg 64:424, Venta I, Murtommaa M, Turtola L, et al: Assessing the eruption of lower third molars on the basis of radiographic features. Br J Oral Maxillofac Surg 29:259, Hattab FN: Positional changes and eruption of impacted mandibular third molars in young adults. A radiographic 4-years follow-up study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 84:604, Richetts RM, Turley S, Chaconas S, et al: Third molar enucleation: diagnosis and technique. J Calif Dent Assoc 4:52, Ganss C, Hochban W, Kielbassa AM, et al: Prognosis of third molar eruption. Oral Surg Oral Med Oral Pathol 76:688, Hattab FN, Alhaija ES: Radiographic evaluation of mandibular third molar eruption space. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 88:285, Tsai HH: Factors associated with mandibular third molar eruption and impaction. J Clin Pediatr Dent 30:109, Niedzielska I, Drugacz J, Kus N, et al: Panoramic radiographic predictors of mandibular third molar eruption. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 102:154, Badawi FJ, Levy JC, Yazbeck C, et al: Eruption of third molars: relationship to inclination of adjacent molars. Am J Orthod Dentofac Orthop 25:200, Kaplan RG: Some factors related to mandibular third molar impaction. Angle Orthod 45:153, Richardson ME: Late lower crowding in relation to primary crowding. Angle Orthod 52:301, Burns FN, Kerr WJS: The impacted lower third molar and its relationship to tooth size and arch form. Eur J Orthod 8:254, Björk A, Skiller V: Facial development and tooth eruption. An implant study at the age of puberty. Am J Orthod 62:339, Richardson ME: Lower third molar space. Angle Orthod 57: 155, Broadbent BH: The influence of third molar on the alignment of the teeth. Am J Orthod Oral Surg 29:312, Björk A, Jensen E, Palling M: Mandibular growth and third molar impaction. Acta Odont Scand 14:231, Björk A: Variations in the growth pattern of the human mandible: Longitudinal radiographic study by the implant method. J Dent Res 42:400, Capelli J Jr: Mandibular growth and third molar impaction in extraction cases. Angle Orthod 61:223, Behbehani F, Artun J, Thalib L: Prediction of mandibular thirdmolar impaction in adolescent orthodontic patients. Am J Orthod Dentofacial Orthop 130:47, Artun J, Behbehani F, Thalib L: Prediction of maxillary third molar impaction in adolescent orthodontic patients. Angle Orthod 75:904, Steinhardt J, Mertins J, Mertins H: Röntgenologische Befunde zur Keimlage und zum Durchbruch der dritten Molaren. Forschr Kieferorthop 49:152, Ledyard BC: A study of the mandibular third molar area. Am J Orthod 39:366, Dausch-Neumann D: Welche Rolle spielt der Eckzahn für den tertiären Engstand? Fortschr Kieferorthop 49:48, Richardson ME: The early development position of the lower third molar relative to certain jaw dimensions. Angle Orthod 40:226, Richardson ME: Development of the lower third molar from years. Angle Orthod 43:191, Venta I, Turtola L, Ylipaavalniemi P: Radiographic follow-up of impacted third molars from age 20 to 32 years. Int J Oral Maxillofac Surg 30:54, Venta I, Ylipaavalniemi P, Turtola L: Clinical outcome of third molars in adults followed during 18 years. J Oral Maxillofac Surg 62:182, Haavikko K, Altonen M, Mattila K: Predicting angulational development and eruption of the lower third molar. Angle Orthod 48:39, Mollaoglu N, Cetiner S, Gungor K: Patterns of third molar impaction in a group of volunteers in Turkey. Clin Oral Invest 6:109, Garn SM, Lewis AB, Bonne B: Third molar formation and its development course. Angle Orthod 32:270,

9 JOBNAME: AUTHOR QUERIES PAGE: 1 SESS: 1 OUTPUT: Thu Jan 17 09:41: /tapraid2/zgf joms/zgf joms/zgf00308/zgf0333d08z AUTHOR QUERIES AUTHOR PLEASE ANSWER ALL QUERIES 1 AQ1 Cite reference 7 in numerical order in the text. Please see uncited reference paragraph. AQ2 Please confirm that formula reads correctly. AQ3 ar-go-n changed to Ar-Go-Nn here, correct? AQ4 n-go-m changed to N-Go-Me here, OK? AQ5 n-go-m changed to N-Go-Me here, OK? AQ6 ar-go-n changed to Ar-Go-Nn here, OK? AQ7 n-go-m changed to N-Go-Me here, OK? AQ8 ag-go-n changed to Ar-Go-Nn here, OK? AQ9 Table 2: Explanation of * copied from Table 3 and added to bottom of table, OK? If not, please explain what * indicates in this table. AQ10 Venti changed to Venta per reference list. AQ11 Ref 32 is not Behbehani et al. Make changes as necessary. AQ12 Conclusion head deleted per journal style.