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Computed tomography of the maxilla in edentulous patients
dental radiology Edrtor:
JOHN W. PREECE, D.D.S. American Academy of Dental Radiolog) Department of Dental Diagnostic Sciences School of Dentistq, The University of Texas Health Science Center at San Antonio 7703 Floyd Curl Dr. San Antonio, Texas 78284
Computed tomography of the maxilla in edentulous patients Normal anatomy H. Engstriim and P. Svendsen, Giiteborg, Sweden DEPARTMENTS RADIOLOGY,
OF DIAGNOSTIC UNIVERSITY
RADIOLOGY,
SAHLGRENSKA
SJUKHUSET
AND ORAL
OF GijTEBORG
Computerized transverse axial scanning of the head is the method of choice for evaluation of pathologic conditions of the brain and midface’region. At times the maxilla is visualized as an additional finding. If the alveolar ridge is edentulous, the image may vary and it is important to be aware of some normal anatomic variations. The CT image of this region provides a good three-dimensional view of the alveolar ridge as well as of the surrounding structures and may, therefore, give the oral surgeon additional useful information.
A lthough there are many reports concerning visualization of the midface region by computed tomography (CT),’ we know of no previous study dealing with the normal anatomy of the maxilla in edentulous patients. There are certain advantages with the CT technique:: the differentiation between soft tissue and bone, the estimation of the bone density, the absence of superimposed bone structures, and selective enlargement are all of great value. During computed tomography of the head, the maxilla is occasionally visualized. It is therefore important to interpret findings in this region of the skull correctly and to be aware of the normal appearance and the quality of the bone. The aim of this investigation was to evaluate the appearance of normal edentulous alveolar ridges by means of computed tomography (CT). MATERIAL
AND METHODS
Ten edentulous patients referred for CT examination of the brain were included in the study; none of the patients had a history of pathosis associatedwith 0030-422018 I I 110557 + 04$CO.40/0 0 198 I The C. V. Mosby Co
Fig. 1. Levels of the transversesectionsshown in the following figures.
557
558
Engstriim and Svenhen
Oral Surg. November.
1981
Fig. 2. Transverse scans.A, Level of middle maxillary sinus. B, Level of lower maxillary sinus. C, Level of lower maxillary sinus. D, Level of superior alveolar ridge. Normal anaromy: I, Nasal septum. 2, Inferior
turbinate. 3, Maxillary sinus. 4, Nasopharynx. 5, Chvus. 6, Zygomatic. 7. Condyle. 8, Lateral pterygold muscle. 9, Pterygoid plates. IO, Masseter muscle. II, Soft palate. 12, Ramus of mandible 13, Oral cavity 14, Superior alveolar ridge. 1.5,Parotid gland. the oral cavity. The examination was performed with an EM1 CT 1010 Head Scanner using high definition. Narrow slices (5 mm.) parallel to the orbitomeatal line were obtained through the inferior part of the maxillary sinuses and the alveolar ridge (Fig. 1). RESULTS AND DISCUSSION
The CT image in patients with edentulous maxillae were studied. The results confirmed that it is important for the practicing dentist and the oral
surgeon to be aware of the normal anatomy in the midface region (Fig. 2, A-D) and especially the image of the edentulous maxilla. A small but broad alveolar ridge is shown in Fig. 3, A; a thicker but narrower ridge is illustrated in Figure 3. B. Large, highly pneumatized maxillary sinuses are evident as a decreased area of attenuation in the posterior parts of the alveolar ridge, as shown in Fig. 4. The gttenuation produced by a dentulous patient without metal restorations (Fig. 5) is much higher as compared to an edentulous maxilla.
Volume 52 Number
Computed tomography of maxilla in edentulous patients 559
5
Fig. 3. Transverse scans at the level of the superior alveolar ridge. A, Small alveolar ridge. B, Broader alveolar ridge. The reduced attenuation in the posterior parts of the alveolar ridge is due to the maxillary sinuses and should not be misinterpreted as a pathologic condition.
Fig. 4. Transverse scan at the level of the superior alveolar ridge. Note large maxillary sinuses with pneumatization of the tuberosity.
Fig. 5. Transverse scan through the lower part of a dentulous maxilla without metal fillings.
During resorption of the alveolar ridge the absorbed bone is often replaced by hyperplastic soft tissue. This might explain the reduced attenuation observed in Fig. 3. It is beyond the scope of this report to analyze all the different types of residual ridges; however, it is important to bear in mind the great individual variations that occur in regard to ridge form and alveolar resorption. The total
individual and between different parts of the ridge in the same person. The ridges may be knife edged or well rounded,5 and the images will therefore appear different. Maxillary sinuses tend to enlarge when the teeth are removed,4 and difficulties may arise in the interpretation of the premolar and molar regions. A decreased attenuation might be misinterpreted as a pathologic condition, such as infection or malignant
amount of bone resorbed varies from individual
to
560 Engstrtim and Svendsen
Oral Surg. November.
bone destruction. Metal restorations also produce undesirable artifacts.” It is well know that the CT technique used today gives rise to artifacts, and it is essential to be alert and recognize these undesirable imaging characteristics. A standardized examination technique is important to minimize artifact formation, and proper position of the head is critical. Without a standardized or consistent head position, the image of the maxillary alveolar ridge will vary. For example. if the degree of ridge resorption is uniform but the patient tips his head forward or backward too much, the image of the alveolar ridge will appear sharply depicted in either the anterior or the posterior region only. In order to standardize the technique further. the tongue should be pressed against the hard palate to decreasethe possibility of overswing.” which is a machine artifact that occurs when one is examining different materials close to each other with highly different attenuation. In conclusion, it is important to be familiar with the normal anatomy of the edentulous maxilla as it is visualized by the CT technique. Of equal importance is a thorough understanding of how the image will vary within normal limitations as a result of the degree of atrophy. variations in the anatomic con-
198 I
figuration of the surrounding structures and the edentulous ridges, and differences in head position. REFERENCES
I. Hessehnk, J. R.. New. P. F. J, Davis. K R.. Weber. A L..
2.
3.
4.
5. 6.
Roberson. G. H.. and ‘Taveras, J. M : Computed Tomography of the Paranasal Sinuses and Face. Part I. Normal Anatomy. J. Comput Assist. Tomogr. 2: 701-706. 1978 Ames. J. R.. Johnson. R. P.. and Stevens, E. A.: Computerized Tomography m Oral and Maxillofacial Surgery. J Oral Surg. 38: 145-149. 1980. Svendsen, P. Quiding, L.. and Landahl. I.. Blackout and Other Artefacts in Computed Tomography Caused by Fillings in the Teeth. Neuroradiology 19: 229-234, 1980. Stafne. E C. J.. and Gibtlisco. A. .I Oral Roentgenographic Dtagnosts. ed. 4, Philadelphia. 1975. W.B. Saunders Company. pp. 101-102. Atwood. D. A : Reductron of Restdual Rtdges: A MaJor Oral Disease Entrty. J. Prosthet. Dent. 26: 226-279. 1971 Gado. M . and Phelps. M.: The Pertpheral Zone of Increased Density m Cramal Computed Tomography. Radrology 117: 71.74. 197s
Reprint requests IO: Dr. Helene Engstrom Department of Oral Radiology Faculty of Odontology Universrty of G(iteborg Box 330 70 S-400 33 Gbteborg. Sweden
JOHN W. PREECE, D.D.S. American Academy of Dental Radiolog) Department of Dental Diagnostic Sciences School of Dentistq, The University of Texas Health Science Center at San Antonio 7703 Floyd Curl Dr. San Antonio, Texas 78284
Computed tomography of the maxilla in edentulous patients Normal anatomy H. Engstriim and P. Svendsen, Giiteborg, Sweden DEPARTMENTS RADIOLOGY,
OF DIAGNOSTIC UNIVERSITY
RADIOLOGY,
SAHLGRENSKA
SJUKHUSET
AND ORAL
OF GijTEBORG
Computerized transverse axial scanning of the head is the method of choice for evaluation of pathologic conditions of the brain and midface’region. At times the maxilla is visualized as an additional finding. If the alveolar ridge is edentulous, the image may vary and it is important to be aware of some normal anatomic variations. The CT image of this region provides a good three-dimensional view of the alveolar ridge as well as of the surrounding structures and may, therefore, give the oral surgeon additional useful information.
A lthough there are many reports concerning visualization of the midface region by computed tomography (CT),’ we know of no previous study dealing with the normal anatomy of the maxilla in edentulous patients. There are certain advantages with the CT technique:: the differentiation between soft tissue and bone, the estimation of the bone density, the absence of superimposed bone structures, and selective enlargement are all of great value. During computed tomography of the head, the maxilla is occasionally visualized. It is therefore important to interpret findings in this region of the skull correctly and to be aware of the normal appearance and the quality of the bone. The aim of this investigation was to evaluate the appearance of normal edentulous alveolar ridges by means of computed tomography (CT). MATERIAL
AND METHODS
Ten edentulous patients referred for CT examination of the brain were included in the study; none of the patients had a history of pathosis associatedwith 0030-422018 I I 110557 + 04$CO.40/0 0 198 I The C. V. Mosby Co
Fig. 1. Levels of the transversesectionsshown in the following figures.
557
558
Engstriim and Svenhen
Oral Surg. November.
1981
Fig. 2. Transverse scans.A, Level of middle maxillary sinus. B, Level of lower maxillary sinus. C, Level of lower maxillary sinus. D, Level of superior alveolar ridge. Normal anaromy: I, Nasal septum. 2, Inferior
turbinate. 3, Maxillary sinus. 4, Nasopharynx. 5, Chvus. 6, Zygomatic. 7. Condyle. 8, Lateral pterygold muscle. 9, Pterygoid plates. IO, Masseter muscle. II, Soft palate. 12, Ramus of mandible 13, Oral cavity 14, Superior alveolar ridge. 1.5,Parotid gland. the oral cavity. The examination was performed with an EM1 CT 1010 Head Scanner using high definition. Narrow slices (5 mm.) parallel to the orbitomeatal line were obtained through the inferior part of the maxillary sinuses and the alveolar ridge (Fig. 1). RESULTS AND DISCUSSION
The CT image in patients with edentulous maxillae were studied. The results confirmed that it is important for the practicing dentist and the oral
surgeon to be aware of the normal anatomy in the midface region (Fig. 2, A-D) and especially the image of the edentulous maxilla. A small but broad alveolar ridge is shown in Fig. 3, A; a thicker but narrower ridge is illustrated in Figure 3. B. Large, highly pneumatized maxillary sinuses are evident as a decreased area of attenuation in the posterior parts of the alveolar ridge, as shown in Fig. 4. The gttenuation produced by a dentulous patient without metal restorations (Fig. 5) is much higher as compared to an edentulous maxilla.
Volume 52 Number
Computed tomography of maxilla in edentulous patients 559
5
Fig. 3. Transverse scans at the level of the superior alveolar ridge. A, Small alveolar ridge. B, Broader alveolar ridge. The reduced attenuation in the posterior parts of the alveolar ridge is due to the maxillary sinuses and should not be misinterpreted as a pathologic condition.
Fig. 4. Transverse scan at the level of the superior alveolar ridge. Note large maxillary sinuses with pneumatization of the tuberosity.
Fig. 5. Transverse scan through the lower part of a dentulous maxilla without metal fillings.
During resorption of the alveolar ridge the absorbed bone is often replaced by hyperplastic soft tissue. This might explain the reduced attenuation observed in Fig. 3. It is beyond the scope of this report to analyze all the different types of residual ridges; however, it is important to bear in mind the great individual variations that occur in regard to ridge form and alveolar resorption. The total
individual and between different parts of the ridge in the same person. The ridges may be knife edged or well rounded,5 and the images will therefore appear different. Maxillary sinuses tend to enlarge when the teeth are removed,4 and difficulties may arise in the interpretation of the premolar and molar regions. A decreased attenuation might be misinterpreted as a pathologic condition, such as infection or malignant
amount of bone resorbed varies from individual
to
560 Engstrtim and Svendsen
Oral Surg. November.
bone destruction. Metal restorations also produce undesirable artifacts.” It is well know that the CT technique used today gives rise to artifacts, and it is essential to be alert and recognize these undesirable imaging characteristics. A standardized examination technique is important to minimize artifact formation, and proper position of the head is critical. Without a standardized or consistent head position, the image of the maxillary alveolar ridge will vary. For example. if the degree of ridge resorption is uniform but the patient tips his head forward or backward too much, the image of the alveolar ridge will appear sharply depicted in either the anterior or the posterior region only. In order to standardize the technique further. the tongue should be pressed against the hard palate to decreasethe possibility of overswing.” which is a machine artifact that occurs when one is examining different materials close to each other with highly different attenuation. In conclusion, it is important to be familiar with the normal anatomy of the edentulous maxilla as it is visualized by the CT technique. Of equal importance is a thorough understanding of how the image will vary within normal limitations as a result of the degree of atrophy. variations in the anatomic con-
198 I
figuration of the surrounding structures and the edentulous ridges, and differences in head position. REFERENCES
I. Hessehnk, J. R.. New. P. F. J, Davis. K R.. Weber. A L..
2.
3.
4.
5. 6.
Roberson. G. H.. and ‘Taveras, J. M : Computed Tomography of the Paranasal Sinuses and Face. Part I. Normal Anatomy. J. Comput Assist. Tomogr. 2: 701-706. 1978 Ames. J. R.. Johnson. R. P.. and Stevens, E. A.: Computerized Tomography m Oral and Maxillofacial Surgery. J Oral Surg. 38: 145-149. 1980. Svendsen, P. Quiding, L.. and Landahl. I.. Blackout and Other Artefacts in Computed Tomography Caused by Fillings in the Teeth. Neuroradiology 19: 229-234, 1980. Stafne. E C. J.. and Gibtlisco. A. .I Oral Roentgenographic Dtagnosts. ed. 4, Philadelphia. 1975. W.B. Saunders Company. pp. 101-102. Atwood. D. A : Reductron of Restdual Rtdges: A MaJor Oral Disease Entrty. J. Prosthet. Dent. 26: 226-279. 1971 Gado. M . and Phelps. M.: The Pertpheral Zone of Increased Density m Cramal Computed Tomography. Radrology 117: 71.74. 197s
Reprint requests IO: Dr. Helene Engstrom Department of Oral Radiology Faculty of Odontology Universrty of G(iteborg Box 330 70 S-400 33 Gbteborg. Sweden