Chapter 5 Developmental Disorders

1. Chapter 5 Developmental Disorders

2. Outline Embryonic Development of the Face, Oral Cavity, and Teeth Developmental Soft Tissue Abnormalities Developmental Cysts Developmental Abnormalities of Teeth

3. Developmental Disorders (pg. 156) A failure during the process of cell division and differentiation into various tissues and structures Some may be identified clinically, by radiographic examination, biopsy, or histologic examination.

4. Developmental Disorders (cont.) (pg. 156) Inherited disorder Caused by an abnormality in genetic makeup Congenital disorder Present at birth May be inherited or developmental The cause of most congenital abnormalities is unknown.

5. Embryonic Development of the Face, Oral Cavity, and Teeth Face Oral and Nasal Cavities Teeth

6. Face (pgs. 156-157) During the third week, ectoderm infolds to form the stomodeum, the primitive oral cavity. The frontal process is above and the first branchial arch is below. The first branchial arch divides into two maxillary processes and the mandibular process.

7. Face (cont.)

8. Face (cont.) Two pits develop on the frontal process. They divide the frontal process into three parts. The median nasal process The right lateral nasal process The left lateral nasal process The median nasal process grows downward between the maxillary processes to form the globular process. This will form the philtrum.

9. Oral and Nasal Cavities (pg. 157) Premaxilla Forms from the globular process Lateral palatine processes Form from the maxillary process The lateral palatine processes fuse with the premaxilla, creating a Y-shaped pattern. The body of the tongue develops from the first branchial arch. The base of the tongue forms from the second and third branchial arches.

10. Teeth (pgs. 157-158) Odontogenesis Takes place in about the fifth week of life Involves ectoderm and ectomesenchyme Begins with formation of a band of ectoderm in each jaw called the primary dental lamina Ten small knoblike proliferations develop on the primary dental lamina in each jaw. Each extends into underlying mesenchyme.

11. Teeth (cont.)

12. Teeth (cont.) The tooth germ has three parts. The enamel organ Produces enamel The dental papilla Forms the dental pulp The dental sac or follicle The follicle provides cells that form cementum, the periodontal ligament, and alveolar bone. Cementum is formed after the crown is complete.

13. Developmental Soft Tissue Abnormalities (pgs. 158-159) Ankyloglossia Commissural Lip Pits Lingual Thyroid

14. Ankyloglossia (pg. 158) An extensive adhesion of the tongue to the floor of the mouth Due to the complete or partial fusion of the lingual frenum Some patients may have no adverse effects, while others may have difficulty with speech. It may just involve mucosa, or it may be muscular and thick. Treatment Frenectomy This works nicely with a laser.

15. Ankyloglossia (cont.)

16. Commissural Lip Pits (pgs. 158-159) Epithelium-lined blind tracts located at the corners of the mouth (commissure) May be shallow or several millimeters deep. Congenital lip pits may also be observed near the midline of the vermilion border. Treatment None

17. Commissural Lip Pits (cont.)

18. Lingual Thyroid (pg. 159) A small mass of thyroid tissue located on the tongue Results from the failure of the primitive thyroid tissue to migrate from its developmental location in the area of foramen cecum on the posterior portion of the tongue to its normal position in the neck

19. Lingual Thyroid (cont.) Appears as a smooth nodular mass posterior to circumvallate papillae at the base of the tongue. TreatmentS It may be removed if it is obstructive, providing the patient has other functioning thyroid tissue.

20. Developmental Cysts Odontogenic Cysts NonodontogenicS Cysts Pseudocysts

21. Developmental Cysts (cont.) (pg. 159) (Box 5-1) An abnormal fluid-filled epithelium-lined sac or cavity Found throughout the body, including the head and neck region

22. Developmental Cysts (cont.) Developmental cysts are classified as to whether they are odontogenic or nonodontogenic. They are also classified according to location, cause, origin of the epithelial cells, and histologic appearance.

23. Developmental Cysts (cont.) They can cause expansion of bone. Intraosseous cysts Occur within bone Extraosseous cysts Occur in soft tissue Cysts within bone generally appear as well-circumscribed radiolucencies. They may appear as unilocular or multilocular.

24. Odontogenic Cysts Dentigerous Cyst Eruption Cyst Primordial Cyst Odontogenic Keratocyst Calcifying Odontogenic Cyst Lateral Periodontal Cyst and Gingival Cyst

25. Dentigerous Cyst (Follicular Cyst) (pgs. 159-160) Forms around the crown of an unerupted or developing tooth The epithelial lining originates from the reduced enamel epithelium after the crown has formed and calcified. Most commonly around the crown of an unerupted or impacted third molar

26. Dentigerous Cyst (Follicular Cyst) (cont.)

27. Dentigerous Cyst (pgs. 160-161) Radiographic A well-defined, unilocular radiolucency around the crown of an unerupted or impacted tooth Histologic The lumen is most characteristically lined with cuboidal epithelium surrounded by a wall of connective tissue. Treatment Removal of the cyst There is some risk of cystic transformation into a neoplasm.

28. Dentigerous Cyst (cont.)

29. Eruption Cyst (pg. 160) Similar to a dentigerous cyst Found in the soft tissue around the crown of an erupting tooth Treatment None

30. Primordial Cyst (pgs. 160-161) Develops in the place of a tooth Most commonly in place of a third molar Most often seen in young adults and discovered on radiographic examination

31. Primordial Cyst

32. Primordial Cyst (cont.) Histologic The lumen is lined by stratified squamous epithelium surrounded by parallel bundles of collagen fibers. It may prove to be an odontogenic keratocyst or a lateral periodontal cyst. Treatment Surgical removal The risk of recurrence depends on the diagnosis.

33. Odontogenic Keratocyst (OKC) (pgs. 161-163) Characterized by histologic appearance and frequent recurrence The lumen of the cyst contains perakeratin. Most often seen in the mandibular third molar region Can move teeth and cause resorption

34. Odontogenic Keratocyst (pgs. 161-162) Histologic The lumen is lined by epithelium that is 8 to 10 cell layers thick and surfaced by parakeratin. Radiographic Frequently appears as a well-defined, multilocular, radiolucent lesion

35. Odontogenic Keratocyst (cont.) (pgs. 161-162) Treatment Due to a high recurrence rate, surgical excision and osseous curettage are recommended.

36. Calcifying Odontogenic Cyst (COC) (pg. 163) A nonaggressive, cystic lesion lined by odontogenic epithelium Closely resembles an ameloblastoma Has a characteristic feature called ghost cells

37. Lateral Periodontal Cyst and Gingival Cyst (pgs. 163-164) Most often seen in the mandibular cuspid and premolar area An asymptomatic, unilocular or multilocular radiolucent lesion on the lateral surface of a tooth root Found most often in males

38. Lateral Periodontal Cyst and Gingival Cyst (cont.) (pgs. 163-164) Histologic A gingival cyst has the same type of lining, but is located in the soft tissue. A thin band of stratified squamous epithelium lines the cyst Treatment Surgical excision

39. Lateral Periodontal Cyst and Gingival Cyst (cont.)

40. Nonodontogenic Cysts Nasopalatine Canal Cyst Median Palatine Cyst Globulomaxillary Cyst Median Mandibular Cyst Nasolabial Cyst Branchial Cleft Cyst (Lymphoepithelial Cyst) Epidermal Cyst Dermoid Cyst and Benign Cystic Teratoma Thyroglossal Tract Cyst

41. Nasopalatine Canal Cyst (Incisive Canal Cyst) (pg. 164) Located within the nasopalatine canal or the incisive papilla Most commonly seen in men between 40 and 60 years old Usually asymptomatic May see a small, pink bulge near the apices and between the roots of the maxillary central incisors on the lingual surface

42. Nasopalatine Canal Cyst (pg. 164) Radiographic A well-defined, radiolucent lesion May be oval or heart-shaped Histologic Lined by epithelium varying from stratified squamous to pseudostratified ciliated columnar epithelium Treatment Surgical excision

43. Nasopalatine Canal Cyst (cont.)

44. Median Palatine Cyst (pgs. 164-165) A well-defined, unilocular radiolucency Located in the midline of the hard palate Histologic Lined with stratified, squamous epithelium surrounded by dense fibrous connective tissue Treatment Surgical removal

45. Median Palatine Cyst (cont.)

46. Globulomaxillary Cyst (pg. 165) A well-defined, pear-shaped radiolucency found between the roots of the maxillary lateral incisor and cuspid Was once thought to be a fissural cyst, now believed to be of odontogenic epithelial origin Treatment Surgical removal

47. Globulomaxillary Cyst (cont.)

48. Median Mandibular Cyst (pg. 165) A rare lesion located in the midline of the mandible Lined with squamous epithelium Radiographic A well-defined radiolucency below the apices of mandibular incisors Treatment Surgical removal

49. Nasolabial Cyst (pgs. 165-166) A soft tissue cyst Thought to originate from the lower anterior portion of the nasolacrimal duct Observed in adults from 40 to 50 years of age 4:1 ratio in favor of females

50. Nasolabial Cyst (cont.) (pgs. 165-166) Clinical An expansion or swelling in the mucobuccal fold in the area of the maxillary canine and the floor of the nose Histologic Lined with pseudostratified, ciliated columnar epithelium and multiple goblet cells Treatment Surgical excisions