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Symmetric multiquadrant isolated dentin dysplasia (SMIDD), a unique presentation mimicking dentin dysplasia type 1b
Vol. 123 No. 5 May 2017
Symmetric multiquadrant isolated dentin dysplasia (SMIDD), a unique presentation mimicking dentin dysplasia type 1b Hiba Qari, BDS, MS,a Harvey Kessler, DDS, MS,a Nagamani Narayana, DMD,b and Sundaralingam Premaraj, BDS, MS, PhDb Dentin dysplasia (DD) is a rare developmental dentin disorder that causes root malformation. It is divided into radicular DD type 1 (DD-1) and coronal DD type 2 (DD-2). Recently, a new entity causing localized root malformation of permanent first molars that resembles DD-1b has been described as molar-incisor malformation (MIM). We report and compare 4 new cases that exhibit similar clinical, histologic, and radiographic features to the new entity, MIM. We believe MIM and our 4 cases to be the same entity, which is nonhereditary and, because of the isolated but bilaterally symmetric pattern of involvement, may be caused by a short-duration environmental insult that disrupts normal development/function of Hertwig’s epithelial root sheath. We propose the name symmetrical multiquadrant isolated dentin dysplasia as the most appropriate descriptive designation for this unusual but highly distinctive anomaly. (Oral Surg Oral Med Oral Pathol Oral Radiol 2017;123:e164-e169)
Dentinogenesis is the formation of dentin and constitutes the bulk of tooth structure. Dentin is composed of 70% inorganic matrix, 20% organic matrix, and 10% water. The organic portion is composed mainly of collagen type 1 (85%), while the noncollagenous part is made up of various proteins, the most common being dentin sialophosphoprotein.1-3 Dentin dysplasia (DD) is a rare developmental disorder of dentin production. It is reported to be transmitted as an autosomal-dominant trait, affects both primary and permanent teeth, and is found in approximately 1 in 100,000 patients.4-6 Rushton reported that it was first described by Ballschmiede in 1920, but the term dentin dysplasia was coined by Rushton in 1939.7 In 1972 it was divided by Witkop8 into 2 subtypes, radicular DD type 1 (DD-1) and coronal DD type 2 (DD-2). DD-1 was further divided by Shields9 into 4 subtypes (DD-1a, DD-1b, DD-1c, and DD-1d) according to radiographic features. A recent entity that resembles DD-1b was reported by Lee et al. as molar-incisor malformation (MIM).10 It is reported to be localized predominantly to permanent first molars, but deciduous second molars can also be affected on occasion. Two additional cases were reported by Witt et al., and they theorized that the external stimulus could be damage to the vascular supply or infection.11 This new anomaly raises the possibility that even though a definitive cause is still not clear and a genetic mutation cannot be ruled out, a
Texas A&M University College of Dentistry, Dallas, TX, USA. University of Nebraska Medical Center College of Dentistry, Lincoln, NE, USA. Received for publication Aug 26, 2016; returned for revision Nov 18, 2016; accepted for publication Nov 29, 2016. Ó 2016 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2016.11.024 b
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external stimulus could be a factor. The fact that only isolated tooth roots in a bilaterally symmetric pattern are affected is a strong argument that disruption of development of Hertwig’s epithelial root sheath could be the proximate cause of the anomaly. The isolated involvement also suggests that the disruption was of relatively short duration at a critical point in time. Because MIM has radiographic features that, although isolated, are indistinguishable from DD-1b, we believe that MIM and our cases could represent the same entity and be due to a nongenetic, environmental factor. We present 4 additional cases showing this same root malformation. Interestingly, 1 of our cases demonstrates involvement of the permanent second molar teeth with normal-appearing first molar tooth roots, further emphasizing the possibility of an environmentally induced etiology. We propose the new nomenclature of symmetrical multiquadrant isolated dentin dysplasia (SMIDD) for this unusual but highly distinctive tooth root anomaly.
CASE SUMMARIES Case 1 The patient was a healthy 9-year-old Caucasian girl. Dental history was not available. She presented with a chief complaint of pain associated with the molar teeth.
Statement of Clinical Relevance The disease process provides an easily recognizable and distinct radiographic presentation that defines the disease and allows proper recognition and treatment.
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Fig. 1. Case 1. Radiographic and histopathologic findings. A, Panograph shows root malformation isolated to permanent first molars (tooth # 3, 14, 19, and 30) with abnormal root formation and crescent shape pulp chambers. B, Scanning power image of tooth #19 showed a well-developed crown but deficient root development. C, Pulp chamber with pulp stones. Above the pulp chamber normal tubular dentin was present and below the pulp chamber abnormal globular dentin formation was seen (H&E x2). D, Abnormal globular dentin below the pulp chamber (H&E x10).
On visual examination, the crowns of the molar teeth appeared clinically normal. A panoramic radiograph revealed atypical permanent first molars in all 4 quadrants (Figure 1A). The affected teeth had bulbous crowns with marked cervical constriction and significant reduction in the size of the pulp chamber, with only a thin, linear, crescent-shaped pulp visible. Root formation was deficient, with shortened tapered roots barely visible in the radiograph. Periodontal defects appeared to be present, associated with the affected teeth. The left first molar teeth appeared to be slightly more severely affected than those on the right side. The left first mandibular permanent molar was extracted and processed for microscopic examination (Figure 1B). Small remnants of enamel matrix were seen in the crown area. The underlying dentin appeared tubular and was otherwise unremarkable. A thin, linear, crescent-shaped pulp was clearly evident. Small pulp stones were present in the pulp tissue (Figure 1C). Apical to the pulp chamber the dentin became irregular and more globular, and the roots appeared shorter than normal (Figure 1D). Case 2 The patient was a 7-year-old boy. He was adopted, therefore any dental history was unavailable. The panoramic radiograph revealed thin, short roots with
small pulp chambers of all first permanent molars (Figure 2A). The deciduous second molar teeth had a somewhat similar pulp morphology, and the distal root formation of these teeth appeared to be deficient. The deciduous upper left and lower right second molars were extracted due to caries; the permanent first molars were retained. Histologic examination of the extracted deciduous teeth revealed residual enamel matrix and underlying normal tubular dentin (Figure 2B). The pulp chamber was very thin in the occlusal-apical dimension. There was a transition from normal tubular dentin into an area of abnormal dentin below the pulp chamber (Figure 2C). Case 3 The patient was a 15-year-old boy who was referred for orthodontic evaluation. Dental history was not available. Dental examination showed normal crown formation with malalignment of upper right premolars, with partial eruption of upper right canine and lateral incisor causing malocclusion. Upper left central incisor was impacted and the crown was poorly visualized in the panoramic radiograph. There was an incidental radiographic finding of poorly developed roots on all 4 permanent first molars with obliteration of pulp chambers. No treatment was planned for the first molar teeth (Figure 3).
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Fig. 2. Case 2. Radiographic and histopathologic findings. A, Panograph reveals normal crown formation and abnormal root formation of permanent first molars tooth # 3, 14, 19, and 30 with short thin roots and narrow pulp chambers. B, Deciduous tooth # 29D (T). Normal tubular dentin formation above the pulp and abnormal dentin formation below the pulp (H&E 2x). C, Prominent cement line separates normal tubular dentin (left) from abnormal globular dentin (right) (H&E x2).
Case 4 The patient was an 11-year-old girl. Dental history was not available. A routine screening panoramic radiograph showed isolated abnormal root development of all permanent second molars with normal crown formation. The maxillary second molars appeared more severely affected than the corresponding mandibular molars. Upper second permanent molars had markedly deficient root development and narrow, crescent-shaped pulp chambers. Lower second permanent molars revealed thin linear pulp chambers with pulp stones and malformed roots. The remaining teeth appeared normal radiographically (Figure 4).
DISCUSSION Root development begins after crown completion approximately 5 days postnatally, when Hertwig’s epithelial root sheath begins to interact with the dental papilla to guide root formation.12,13 Root malformation occurs due to genetic and developmental factors. Hereditary nonsyndromic conditions affecting the dentin of both primary and permanent teeth can be divided into dentinogenesis imperfecta (DI) types 1, 2, and 3, and
DD-1 and DD-2. The classification is determined by the clinical and radiographic appearance.14 DI-1 is due to a mutation in collagen type 1 (COL1 A1, COL1 A2). Similar dental features can be seen with the systemic condition osteogenesis imperfecta.15-17 DI-2, DI-3, and DD-2 are autosomal-dominant diseases with complete penetrance and variable expressivity and with overlapping clinical and radiographic features18,19 because they share the same genetic mutation of dentin sialophosphoprotein, located on chromosome 4.20,21 Current theory, therefore, suggests that DI-2, DI-3, and DD-2 represent a single disease entity with variable severity of expression.22 On the other hand, the cause of DD-1 remains a mystery. Clinically, the condition manifests with normal crown development but deficient root formation. The affected teeth exhibit an increase in mobility, and early exfoliation is common due to short root formation.23 Radiographically, DD-1 is subclassified into 4 types: DD-1a, DD-1b, DD-1c, and DD1d. Type 1a has no pulp chamber or root formation. Type 1b has 1 horizontal, crescent-shaped pulp chamber with minimal root development. Type 1c has 2 horizontal crescents with some root formation. Type 1d is considered the least severe form. It has complete pulp
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Fig. 3. Case 3. Radiographic and clinical findings. Panograph shows isolated dentin disorder of root malformation and pulp obliteration related to permanent first molars tooth # 3, 14, 19, and 30.
Fig. 4. Case 4. Radiographic findings. Panograph reveals permanent 2nd molars are affected. Normal crown formation, short roots with pulp stones in affected mandibular teeth. Remaining teeth are normal.
chambers, pulp stones, and root formation that resembles DD-2 and is sometimes difficult to distinguish.9,22 In our report, we describe 4 cases that resemble DD-1b with normal crown formation and short roots, but the defects were localized and symmetric instead of having a generalized distribution. In cases 1 and 3, only permanent first molars were affected. In case 2, the defects were isolated to deciduous second molars and permanent first molars, and in case 4, the permanent second molars were affected and the permanent first molars were spared. Other disease processes that produce root anomalies and should be considered in the differential are DI-2, DI-3, DD-2, regional odontodysplasia (ROD), and segmental odontomaxillary dysplasia (SOMD). DI-2, DI-3, and DD-2 have radiographic features similar to
those seen in these cases but are characterized by opalescent, amber-brown teeth. The teeth in the reported cases all had normal clinical appearance.24,25 ROD affects the formation of enamel, dentin, and pulp, in contrast to DD, which only affects dentin. In addition, ROD usually affects several teeth in only 1 quadrant, while in the cases presented here, isolated teeth in multiple quadrants were affected. A radiographic feature of ROD is a ghost-like appearance. Density and thickness of both enamel and dentin are reduced, with large pulp chambers and short roots, features absent in our cases. SOMD is a disorder of the maxilla. Clinically, it presents with unilateral enlargement of the premolar region of the maxilla, causing facial enlargement, bony expansion, and gingival hyperplasia. The radiographic appearance of SOM is an ill-defined radiopacity similar to fibrous dysplasia, but
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also with agenesis or hypoplasia of the premolars in the affected site.26 The features of SOMD were entirely absent in the cases presented here. Recently, several reports have described a new entity characterized by localized and symmetric root malformation in permanent first molars and occasionally involving deciduous second molars, which closely resembles the cases presented here. Defects involving the crowns of the permanent central incisors were also noted, however, and the condition was given the name of molar incisor malformation (MIM) by Lee at el.10 Witt et al.11 also documented 2 similar cases. All cases reported as MIM thus far are similar to, if not the same as, the entity in the 4 cases we report. Our cases all had defective root development in a symmetric pattern isolated to the same teeth in all 4 quadrants of the jaws. However, except for an impacted central incisor tooth in case 3, none of our cases had defects in the incisor crowns. In addition, in our case 4, the second molar teeth were affected rather than the first molars. Even though a specific etiology has yet to be elucidated, the defects being limited to isolated teeth in a symmetric pattern suggests that an external and likely environmental factor could be the cause of the anomaly. We believe our 4 cases are similar to those the other 2 authors think to be an entity separate from DD-1, and suggest that this entity is a localized, nonhereditary variant. Histopathologic evaluation of the extracted teeth in 3 of our cases demonstrated dysplastic dentin replacing the normal tubular dentin in the developing root, roughly equivalent to the histopathologic features seen in the teeth with hereditary DD-1b. However, the classic “streams around boulders” pattern of the hereditary type of DD-1b was absent in our cases. We propose to name this radiographically distinctive dentin disorder symmetrical multiquadrant isolated dentin dysplasia (SMIDD). If it can eventually be proven that an external factor is the cause of the defective root formation, then preventive measures can be instituted that will improve the chances of normal root development and prevent early loss of teeth. For the time being, there is no specific treatment for DD, and the treatment varies from patient to patient, depending on the severity of root malformation. The main goal remains to restore the teeth to proper occlusion for function and esthetics.27,28
CONCLUSION A new entity of localized root deformity related to permanent first molars, deciduous second molars, and permanent central incisors has been reported by Lee et al. as MIM. Involvement of the incisor teeth was not evident in our cases. It has been speculated that this anomaly is due to an external stimulus, which would
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explain its localized nature. We propose the name SMIDD and believe that this is within the spectrum of MIM and represents a localized nonhereditary variant. More studies are needed to investigate external factors that may be the cause. We would like to thank John Fullinwider for helping us on numerous occasions with editing and endnotes. REFERENCES 1. Hart PS, Hart TC. Disorders of human dentin. Cells Tissues Organs. 2007;186:70-77. 2. Luukko K, Kettunen P. Coordination of tooth morphogenesis and neuronal development through tissue interactions: lessons from mouse models. Exp Cell Res. 2014;325:72-77. 3. MacDougall M, Dong J, Acevedo AC. Molecular basis of human dentin diseases. Am J Med Genet A. 2006;140:2536-2546. 4. Cherkaoui Jaouad I, El Alloussi M, Laarabi FZ, Bouhouche A, Ameziane R, Sefiani A. Inhabitual autosomal recessive form of dentin dysplasia type I in a large consanguineous Moroccan family. Eur J Med Genet. 2013;56:442-444. 5. Munoz-Guerra MF, Naval-Gias L, Escorial V, Sastre-Perez J. Dentin dysplasia type I treated with onlay bone grafting, sinus augmentation, and osseointegrated implants. Implant Dent. 2006;15:248-253. 6. Ozer S, Ozden B, Otan Ozden F, Gunduz K. Dentinal dysplasia type I: a case report with a 6-year followup. Case Rep Dent. 2013;2013:659084. 7. Rushton MA. A case of anidrotic ectodermal dysplasia showing extensive dental defect. Proc R Soc Med. 1934;27:725-727. 8. Witkop CJ Jr. Hereditary defects of dentin. Dent Clin North Am. 1975;19:25-45. 9. Shields ED, Bixler D, el-Kafrawy AM. A proposed classification for heritable human dentine defects with a description of a new entity. Arch Oral Biol. 1973;18:543-553. 10. Lee HS, Kim SH, Kim SO, et al. A new type of dental anomaly: molar-incisor malformation (MIM). Oral Surg Pral Med Oral Pathol Oral Radiol. 2014;118:101-109.e3. 11. Witt CV, Hirt T, Rutz G, Luder HU. Root malformation associated with a cervical mineralized diaphragm: a distinct form of tooth abnormality? Oral Surg Oral Med Oral Pathol Oral Radiol. 2014;117:e311-e319. 12. Huang XF, Chai Y. Molecular regulatory mechanism of tooth root development. Int J Oral Sci. 2012;4:177-181. 13. Kumakami-Sakano M, Otsu K, Fujiwara N, Harada H. Regulatory mechanisms of Hertwig’s epithelial root sheath formation and anomaly correlated with root length. Exp Cell Res. 2014;325:78-82. 14. Lee SK, Lee KE, Jeon D, et al. A novel mutation in the DSPP gene associated with dentinogenesis imperfecta type II. J Dent Res. 2009;88:51-55. 15. Barron MJ, McDonnell ST, Mackie I, Dixon MJ. Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia. Orphanet J Rare Dis. 2008;3:31. 16. Wang SK, Chan HC, Makovey I, Simmer JP, Hu JC. Novel PAX9 and COL1 A2 missense mutations causing tooth agenesis and OI/DGI without skeletal abnormalities. PLOS One. 2012;7: e51533. 17. Zhang X, Chen L, Liu J, et al. A novel DSPP mutation is associated with type II dentinogenesis imperfecta in a Chinese family. BMC Med Genet. 2007;8:52. 18. Kim JW, Hu JC, Lee JI, et al. Mutational hot spot in the DSPP gene causing dentinogenesis imperfecta type II. Hum Genet. 2005;116:186-191.
OOOO Volume 123, Number 5 19. Li L, Shu Y, Lou B, Wu H. Candidate-gene exclusion in a family with inherited non-syndromic dental disorders. Gene. 2012;511: 420-426. 20. Kim JW, Simmer JP. Hereditary dentin defects. J Dent Res. 2007;86:392-399. 21. McKnight DA, Suzanne Hart P, Hart TC, et al. A comprehensive analysis of normal variation and disease-causing mutations in the human DSPP gene. Hum Mutat. 2008;29:1392-1404. 22. Neville BW, Damm DD, Allen CM, Chi AC. Oral and Maxillofacial Pathology. 4th ed. St. Louis, MO: Elsevier; 2016. 23. Pintor A, Alexandria A, Marques A, Abrahao A, Guedes F, Primo L. Histological and ultrastructure analysis of dentin dysplasia type I in primary teeth: a case report. Ultrastruc Pathol. 2015:1-5. 24. de La Dure-Molla M, Philippe Fournier B, Berdal A. Isolated dentinogenesis imperfecta and dentin dysplasia: revision of the classification. Eur J Hum Genet. 2015;23:445-451. 25. McKnight DA, Simmer JP, Hart PS, Hart TC, Fisher LW. Overlapping DSPP mutations cause dentin dysplasia and dentinogenesis imperfecta. J Dent Res. 2008;87:1108-1111.
CASE REPORT Qari et al. e169 26. Azevedo RS, da Silveira LJ, Moliterno LF, Miranda AM, de Almeida OP, Pires FR. Segmental odontomaxillary dysplasia: report of a case emphasizing histopathological, immunohistochemical and scanning electron microscopic features. J Oral Sci. 2013;55:259-262. 27. Sahoo SR, Aggarwal S. Dentin dysplasia type 1d: a rare case. Indian J Dent Res. 2014;25:832-834. 28. Singh A, Gupta S, Yuwanati MB, Mhaske S. Dentin dysplasia type I. BMJ Case Rep. 2013;2013. Reprint requests: Hiba Qari, BDS, MS Texas A&M University College of Dentistry 3302 Gaston Avenue Room 214 Dallas TX 75246 USA [email protected]
Symmetric multiquadrant isolated dentin dysplasia (SMIDD), a unique presentation mimicking dentin dysplasia type 1b Hiba Qari, BDS, MS,a Harvey Kessler, DDS, MS,a Nagamani Narayana, DMD,b and Sundaralingam Premaraj, BDS, MS, PhDb Dentin dysplasia (DD) is a rare developmental dentin disorder that causes root malformation. It is divided into radicular DD type 1 (DD-1) and coronal DD type 2 (DD-2). Recently, a new entity causing localized root malformation of permanent first molars that resembles DD-1b has been described as molar-incisor malformation (MIM). We report and compare 4 new cases that exhibit similar clinical, histologic, and radiographic features to the new entity, MIM. We believe MIM and our 4 cases to be the same entity, which is nonhereditary and, because of the isolated but bilaterally symmetric pattern of involvement, may be caused by a short-duration environmental insult that disrupts normal development/function of Hertwig’s epithelial root sheath. We propose the name symmetrical multiquadrant isolated dentin dysplasia as the most appropriate descriptive designation for this unusual but highly distinctive anomaly. (Oral Surg Oral Med Oral Pathol Oral Radiol 2017;123:e164-e169)
Dentinogenesis is the formation of dentin and constitutes the bulk of tooth structure. Dentin is composed of 70% inorganic matrix, 20% organic matrix, and 10% water. The organic portion is composed mainly of collagen type 1 (85%), while the noncollagenous part is made up of various proteins, the most common being dentin sialophosphoprotein.1-3 Dentin dysplasia (DD) is a rare developmental disorder of dentin production. It is reported to be transmitted as an autosomal-dominant trait, affects both primary and permanent teeth, and is found in approximately 1 in 100,000 patients.4-6 Rushton reported that it was first described by Ballschmiede in 1920, but the term dentin dysplasia was coined by Rushton in 1939.7 In 1972 it was divided by Witkop8 into 2 subtypes, radicular DD type 1 (DD-1) and coronal DD type 2 (DD-2). DD-1 was further divided by Shields9 into 4 subtypes (DD-1a, DD-1b, DD-1c, and DD-1d) according to radiographic features. A recent entity that resembles DD-1b was reported by Lee et al. as molar-incisor malformation (MIM).10 It is reported to be localized predominantly to permanent first molars, but deciduous second molars can also be affected on occasion. Two additional cases were reported by Witt et al., and they theorized that the external stimulus could be damage to the vascular supply or infection.11 This new anomaly raises the possibility that even though a definitive cause is still not clear and a genetic mutation cannot be ruled out, a
Texas A&M University College of Dentistry, Dallas, TX, USA. University of Nebraska Medical Center College of Dentistry, Lincoln, NE, USA. Received for publication Aug 26, 2016; returned for revision Nov 18, 2016; accepted for publication Nov 29, 2016. Ó 2016 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2016.11.024 b
e164
external stimulus could be a factor. The fact that only isolated tooth roots in a bilaterally symmetric pattern are affected is a strong argument that disruption of development of Hertwig’s epithelial root sheath could be the proximate cause of the anomaly. The isolated involvement also suggests that the disruption was of relatively short duration at a critical point in time. Because MIM has radiographic features that, although isolated, are indistinguishable from DD-1b, we believe that MIM and our cases could represent the same entity and be due to a nongenetic, environmental factor. We present 4 additional cases showing this same root malformation. Interestingly, 1 of our cases demonstrates involvement of the permanent second molar teeth with normal-appearing first molar tooth roots, further emphasizing the possibility of an environmentally induced etiology. We propose the new nomenclature of symmetrical multiquadrant isolated dentin dysplasia (SMIDD) for this unusual but highly distinctive tooth root anomaly.
CASE SUMMARIES Case 1 The patient was a healthy 9-year-old Caucasian girl. Dental history was not available. She presented with a chief complaint of pain associated with the molar teeth.
Statement of Clinical Relevance The disease process provides an easily recognizable and distinct radiographic presentation that defines the disease and allows proper recognition and treatment.
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Fig. 1. Case 1. Radiographic and histopathologic findings. A, Panograph shows root malformation isolated to permanent first molars (tooth # 3, 14, 19, and 30) with abnormal root formation and crescent shape pulp chambers. B, Scanning power image of tooth #19 showed a well-developed crown but deficient root development. C, Pulp chamber with pulp stones. Above the pulp chamber normal tubular dentin was present and below the pulp chamber abnormal globular dentin formation was seen (H&E x2). D, Abnormal globular dentin below the pulp chamber (H&E x10).
On visual examination, the crowns of the molar teeth appeared clinically normal. A panoramic radiograph revealed atypical permanent first molars in all 4 quadrants (Figure 1A). The affected teeth had bulbous crowns with marked cervical constriction and significant reduction in the size of the pulp chamber, with only a thin, linear, crescent-shaped pulp visible. Root formation was deficient, with shortened tapered roots barely visible in the radiograph. Periodontal defects appeared to be present, associated with the affected teeth. The left first molar teeth appeared to be slightly more severely affected than those on the right side. The left first mandibular permanent molar was extracted and processed for microscopic examination (Figure 1B). Small remnants of enamel matrix were seen in the crown area. The underlying dentin appeared tubular and was otherwise unremarkable. A thin, linear, crescent-shaped pulp was clearly evident. Small pulp stones were present in the pulp tissue (Figure 1C). Apical to the pulp chamber the dentin became irregular and more globular, and the roots appeared shorter than normal (Figure 1D). Case 2 The patient was a 7-year-old boy. He was adopted, therefore any dental history was unavailable. The panoramic radiograph revealed thin, short roots with
small pulp chambers of all first permanent molars (Figure 2A). The deciduous second molar teeth had a somewhat similar pulp morphology, and the distal root formation of these teeth appeared to be deficient. The deciduous upper left and lower right second molars were extracted due to caries; the permanent first molars were retained. Histologic examination of the extracted deciduous teeth revealed residual enamel matrix and underlying normal tubular dentin (Figure 2B). The pulp chamber was very thin in the occlusal-apical dimension. There was a transition from normal tubular dentin into an area of abnormal dentin below the pulp chamber (Figure 2C). Case 3 The patient was a 15-year-old boy who was referred for orthodontic evaluation. Dental history was not available. Dental examination showed normal crown formation with malalignment of upper right premolars, with partial eruption of upper right canine and lateral incisor causing malocclusion. Upper left central incisor was impacted and the crown was poorly visualized in the panoramic radiograph. There was an incidental radiographic finding of poorly developed roots on all 4 permanent first molars with obliteration of pulp chambers. No treatment was planned for the first molar teeth (Figure 3).
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Fig. 2. Case 2. Radiographic and histopathologic findings. A, Panograph reveals normal crown formation and abnormal root formation of permanent first molars tooth # 3, 14, 19, and 30 with short thin roots and narrow pulp chambers. B, Deciduous tooth # 29D (T). Normal tubular dentin formation above the pulp and abnormal dentin formation below the pulp (H&E 2x). C, Prominent cement line separates normal tubular dentin (left) from abnormal globular dentin (right) (H&E x2).
Case 4 The patient was an 11-year-old girl. Dental history was not available. A routine screening panoramic radiograph showed isolated abnormal root development of all permanent second molars with normal crown formation. The maxillary second molars appeared more severely affected than the corresponding mandibular molars. Upper second permanent molars had markedly deficient root development and narrow, crescent-shaped pulp chambers. Lower second permanent molars revealed thin linear pulp chambers with pulp stones and malformed roots. The remaining teeth appeared normal radiographically (Figure 4).
DISCUSSION Root development begins after crown completion approximately 5 days postnatally, when Hertwig’s epithelial root sheath begins to interact with the dental papilla to guide root formation.12,13 Root malformation occurs due to genetic and developmental factors. Hereditary nonsyndromic conditions affecting the dentin of both primary and permanent teeth can be divided into dentinogenesis imperfecta (DI) types 1, 2, and 3, and
DD-1 and DD-2. The classification is determined by the clinical and radiographic appearance.14 DI-1 is due to a mutation in collagen type 1 (COL1 A1, COL1 A2). Similar dental features can be seen with the systemic condition osteogenesis imperfecta.15-17 DI-2, DI-3, and DD-2 are autosomal-dominant diseases with complete penetrance and variable expressivity and with overlapping clinical and radiographic features18,19 because they share the same genetic mutation of dentin sialophosphoprotein, located on chromosome 4.20,21 Current theory, therefore, suggests that DI-2, DI-3, and DD-2 represent a single disease entity with variable severity of expression.22 On the other hand, the cause of DD-1 remains a mystery. Clinically, the condition manifests with normal crown development but deficient root formation. The affected teeth exhibit an increase in mobility, and early exfoliation is common due to short root formation.23 Radiographically, DD-1 is subclassified into 4 types: DD-1a, DD-1b, DD-1c, and DD1d. Type 1a has no pulp chamber or root formation. Type 1b has 1 horizontal, crescent-shaped pulp chamber with minimal root development. Type 1c has 2 horizontal crescents with some root formation. Type 1d is considered the least severe form. It has complete pulp
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Fig. 3. Case 3. Radiographic and clinical findings. Panograph shows isolated dentin disorder of root malformation and pulp obliteration related to permanent first molars tooth # 3, 14, 19, and 30.
Fig. 4. Case 4. Radiographic findings. Panograph reveals permanent 2nd molars are affected. Normal crown formation, short roots with pulp stones in affected mandibular teeth. Remaining teeth are normal.
chambers, pulp stones, and root formation that resembles DD-2 and is sometimes difficult to distinguish.9,22 In our report, we describe 4 cases that resemble DD-1b with normal crown formation and short roots, but the defects were localized and symmetric instead of having a generalized distribution. In cases 1 and 3, only permanent first molars were affected. In case 2, the defects were isolated to deciduous second molars and permanent first molars, and in case 4, the permanent second molars were affected and the permanent first molars were spared. Other disease processes that produce root anomalies and should be considered in the differential are DI-2, DI-3, DD-2, regional odontodysplasia (ROD), and segmental odontomaxillary dysplasia (SOMD). DI-2, DI-3, and DD-2 have radiographic features similar to
those seen in these cases but are characterized by opalescent, amber-brown teeth. The teeth in the reported cases all had normal clinical appearance.24,25 ROD affects the formation of enamel, dentin, and pulp, in contrast to DD, which only affects dentin. In addition, ROD usually affects several teeth in only 1 quadrant, while in the cases presented here, isolated teeth in multiple quadrants were affected. A radiographic feature of ROD is a ghost-like appearance. Density and thickness of both enamel and dentin are reduced, with large pulp chambers and short roots, features absent in our cases. SOMD is a disorder of the maxilla. Clinically, it presents with unilateral enlargement of the premolar region of the maxilla, causing facial enlargement, bony expansion, and gingival hyperplasia. The radiographic appearance of SOM is an ill-defined radiopacity similar to fibrous dysplasia, but
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also with agenesis or hypoplasia of the premolars in the affected site.26 The features of SOMD were entirely absent in the cases presented here. Recently, several reports have described a new entity characterized by localized and symmetric root malformation in permanent first molars and occasionally involving deciduous second molars, which closely resembles the cases presented here. Defects involving the crowns of the permanent central incisors were also noted, however, and the condition was given the name of molar incisor malformation (MIM) by Lee at el.10 Witt et al.11 also documented 2 similar cases. All cases reported as MIM thus far are similar to, if not the same as, the entity in the 4 cases we report. Our cases all had defective root development in a symmetric pattern isolated to the same teeth in all 4 quadrants of the jaws. However, except for an impacted central incisor tooth in case 3, none of our cases had defects in the incisor crowns. In addition, in our case 4, the second molar teeth were affected rather than the first molars. Even though a specific etiology has yet to be elucidated, the defects being limited to isolated teeth in a symmetric pattern suggests that an external and likely environmental factor could be the cause of the anomaly. We believe our 4 cases are similar to those the other 2 authors think to be an entity separate from DD-1, and suggest that this entity is a localized, nonhereditary variant. Histopathologic evaluation of the extracted teeth in 3 of our cases demonstrated dysplastic dentin replacing the normal tubular dentin in the developing root, roughly equivalent to the histopathologic features seen in the teeth with hereditary DD-1b. However, the classic “streams around boulders” pattern of the hereditary type of DD-1b was absent in our cases. We propose to name this radiographically distinctive dentin disorder symmetrical multiquadrant isolated dentin dysplasia (SMIDD). If it can eventually be proven that an external factor is the cause of the defective root formation, then preventive measures can be instituted that will improve the chances of normal root development and prevent early loss of teeth. For the time being, there is no specific treatment for DD, and the treatment varies from patient to patient, depending on the severity of root malformation. The main goal remains to restore the teeth to proper occlusion for function and esthetics.27,28
CONCLUSION A new entity of localized root deformity related to permanent first molars, deciduous second molars, and permanent central incisors has been reported by Lee et al. as MIM. Involvement of the incisor teeth was not evident in our cases. It has been speculated that this anomaly is due to an external stimulus, which would
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explain its localized nature. We propose the name SMIDD and believe that this is within the spectrum of MIM and represents a localized nonhereditary variant. More studies are needed to investigate external factors that may be the cause. We would like to thank John Fullinwider for helping us on numerous occasions with editing and endnotes. REFERENCES 1. Hart PS, Hart TC. Disorders of human dentin. Cells Tissues Organs. 2007;186:70-77. 2. Luukko K, Kettunen P. Coordination of tooth morphogenesis and neuronal development through tissue interactions: lessons from mouse models. Exp Cell Res. 2014;325:72-77. 3. MacDougall M, Dong J, Acevedo AC. Molecular basis of human dentin diseases. Am J Med Genet A. 2006;140:2536-2546. 4. Cherkaoui Jaouad I, El Alloussi M, Laarabi FZ, Bouhouche A, Ameziane R, Sefiani A. Inhabitual autosomal recessive form of dentin dysplasia type I in a large consanguineous Moroccan family. Eur J Med Genet. 2013;56:442-444. 5. Munoz-Guerra MF, Naval-Gias L, Escorial V, Sastre-Perez J. Dentin dysplasia type I treated with onlay bone grafting, sinus augmentation, and osseointegrated implants. Implant Dent. 2006;15:248-253. 6. Ozer S, Ozden B, Otan Ozden F, Gunduz K. Dentinal dysplasia type I: a case report with a 6-year followup. Case Rep Dent. 2013;2013:659084. 7. Rushton MA. A case of anidrotic ectodermal dysplasia showing extensive dental defect. Proc R Soc Med. 1934;27:725-727. 8. Witkop CJ Jr. Hereditary defects of dentin. Dent Clin North Am. 1975;19:25-45. 9. Shields ED, Bixler D, el-Kafrawy AM. A proposed classification for heritable human dentine defects with a description of a new entity. Arch Oral Biol. 1973;18:543-553. 10. Lee HS, Kim SH, Kim SO, et al. A new type of dental anomaly: molar-incisor malformation (MIM). Oral Surg Pral Med Oral Pathol Oral Radiol. 2014;118:101-109.e3. 11. Witt CV, Hirt T, Rutz G, Luder HU. Root malformation associated with a cervical mineralized diaphragm: a distinct form of tooth abnormality? Oral Surg Oral Med Oral Pathol Oral Radiol. 2014;117:e311-e319. 12. Huang XF, Chai Y. Molecular regulatory mechanism of tooth root development. Int J Oral Sci. 2012;4:177-181. 13. Kumakami-Sakano M, Otsu K, Fujiwara N, Harada H. Regulatory mechanisms of Hertwig’s epithelial root sheath formation and anomaly correlated with root length. Exp Cell Res. 2014;325:78-82. 14. Lee SK, Lee KE, Jeon D, et al. A novel mutation in the DSPP gene associated with dentinogenesis imperfecta type II. J Dent Res. 2009;88:51-55. 15. Barron MJ, McDonnell ST, Mackie I, Dixon MJ. Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia. Orphanet J Rare Dis. 2008;3:31. 16. Wang SK, Chan HC, Makovey I, Simmer JP, Hu JC. Novel PAX9 and COL1 A2 missense mutations causing tooth agenesis and OI/DGI without skeletal abnormalities. PLOS One. 2012;7: e51533. 17. Zhang X, Chen L, Liu J, et al. A novel DSPP mutation is associated with type II dentinogenesis imperfecta in a Chinese family. BMC Med Genet. 2007;8:52. 18. Kim JW, Hu JC, Lee JI, et al. Mutational hot spot in the DSPP gene causing dentinogenesis imperfecta type II. Hum Genet. 2005;116:186-191.
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CASE REPORT Qari et al. e169 26. Azevedo RS, da Silveira LJ, Moliterno LF, Miranda AM, de Almeida OP, Pires FR. Segmental odontomaxillary dysplasia: report of a case emphasizing histopathological, immunohistochemical and scanning electron microscopic features. J Oral Sci. 2013;55:259-262. 27. Sahoo SR, Aggarwal S. Dentin dysplasia type 1d: a rare case. Indian J Dent Res. 2014;25:832-834. 28. Singh A, Gupta S, Yuwanati MB, Mhaske S. Dentin dysplasia type I. BMJ Case Rep. 2013;2013. Reprint requests: Hiba Qari, BDS, MS Texas A&M University College of Dentistry 3302 Gaston Avenue Room 214 Dallas TX 75246 USA [email protected]