An analysis of the effect of mandibular ridge loss in the edentulous patient John W. Unger, DDS,* Charles John C. Gunsolley, DDS, MSC
W. Ellinger,
School of Dentistry, Medical College of Virginia, University of Kentucky, Lexington, Ky.
length
on residual
DDS, MS,b and
Richmond, Va., and College of Dentistry,
The relationship of mandibular length to residual ridge loss was studied in 22 edentulous patients. Tracings made from cephalometric films taken at initial insertion of complete dentures and at 20 years after placement were measured. Mandibular length was determined to have no statistical relationship to the reduction in residual ridge height in either the maxillae or the mandible. In addition, alveolar bone loss in the one jaw had no relationship to the amount of loss in the other jaw. (J PROSTAET DENT 1992;67:827-30.)
T he inevitable
change in the height and contour of the residual ridge affects the success of the most precisely constructed prosthesis. Although residual ridge loss is most often associated with the mandible, the maxillary residual ridge undergoes a similar process of bone loss. The ability to predict which patients are likely to have greater than normal amounts of alveolar bone loss would be significant to all concerned. In the literature, a connection is made between mandibular length and increased levels of maxillary residual ridge loss in the edentulous patient. In addition, residual ridge loss in one jaw was found to have an inverse relationship to the amount of loss in the other jaw.l The purpose of this study was to determine whether increased mandibular length can be linked to residual ridge loss in the completely edentulous patient and further to discover whether a relationship does exist between the residual ridge loss in the maxillae and mandible. LITERATURE
REVIEW
The study of alveolar bone loss in edentulous patients has been undertaken by many investigators.1-10 The variability in loss of residual ridge height is a common feature in all these reports. The reduction in the anterior residual ridge height in the mandible has been determined to be four times the rate of loss found in the maxillae.2 Attempts to correlate the loss in residual ridge height to the patient’s Supported by U. S. Public Health Service Research grant no. R01 009401 from the Department of Health, Education, and Welfare. aAssociate Professor and Chairman, Department of Removable Prosthodontics, School of Dentistry, Medical College of Virginia. bProfessor, Department of Oral Health Practice, School of Dentistry, University of Kentucky. CAssociate Professor and Director, Office of Applied Research, School of Dentistry, Medical College of Virginia. 1011136082
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
morphologic characteristics have been made. Investigation into the possibility of a link between the Frankfort-mandibular plane angle and mandibular residual ridge loss is an example of correlating morphology to reduction in ridge height.“? i2 In Tallgren’s investigation’ of facial morphology and residual ridge loss, 11 patients were studied over a ‘l-year period of wearing complete dentures. The dentures were constructed 2 to 3 months after the extraction of the remaining teeth. Measurements to determine the amount of residual ridge loss were made from cephalometric films. Mandibular length was measured from a point on the condyle to a point on the symphysis. A positive correlation was discovered between the length of the mandible and the reduction in the height of the maxillary anterior residual ridge. Tallgren’ indicated that the orientation of the maxillary occlusal plane and the relationship of the mandibular incisors to the maxillary residual ridge might play a role in explaining this finding. No such correlation was discovered in regard to the loss in height of the mandibular residual ridge. In that study, Tallgren’ found an inverse relationship between the loss of residual ridge in the maxillae and mandible. When marked resorption was present in one jaw, only slight reduction in residual ridge height was seen in the other. The present study was undertaken to discover whether a similar relationship between mandibular length and maxillary residual ridge loss would be seen in a larger patient population studied over a longer period of time and to determine whether any relationship exists between the extent of bone loss in one jaw as compared to the other. METHODS
AND
MATERIAL
Cephalometric films made at the initial placement of complete dentures and at a point 20 years later were available for 22 patients. These patients were part of a study of complete denture patients performed at the University of 827
UNGER,
ELLINGER,
AND
GUNSOLLEY
Maxillary height
Fig. 1. Determination of mandibular length was made by measuring from gonion (Go) to menton (Me) and at a second location from the lowest point on the coronoid notch (CN) to menton (Me).
Me Kentucky, College of Dentistry. A total of 64 patients were involved at the beginning of the Kentucky study, which involved the construction of complete dentures using either a standard or complex technique. All of the patients were edentulous for at least 1 year before beginning the study. Their ages ranged from 30 to 65 years.13 Unlike Tallgren’s study,l mandibular length was not measured from the condyle to the symphysis. It was not possible to accurately locate the superior surface of the condyle because of the superimposition of other anatomic structures and interference from the orientation device of the cephalostat. The measurement of mandibular length was made in two different regions. The distance from gonion (the point on the angle of the jaw that is the most inferiorly, posteriorly, and outwardly directed) to menton (the most inferior point on the mandibular symphysis) was measured. A second measurement from menton to the lowest point on the coronoid notch was also made (Fig. 1). These measurements were made from the films taken at initial placement of the dentures. The height of the maxillary residual ridge was measured at a right angle from a line extending from the anterior nasal spine to posterior nasal spine to the lowest point on the maxillary residual ridge in the midline. The mandibular residual ridge height was measured from menton to the highest point on the residual ridge in the midline (Fig. 2). Measurement of the residual ridge height was made on films taken at initial placement of the dentures and at 20 years after placement. The change in residual ridge height was determined by subtracting the measurement of ridge height at year 20 from the measurement determined at initial placement of the dentures. All measurements were made on tracings of
828
2. Residual ridge height in the maxillae was determined by measuring at a right angle from a line that extended from anterior nasal spine (ANS) to posterior nasal spine (PNS) to the lowest point on the residual ridge in the midline. Mandibular residual ridge height was measured from menton (Me) to the highest point on the mandible in the midline. Fig.
the available films by the same individual to avoid introducing errors. RESULTS The overall goal of this study was to relate the reduction in residual ridge height in the maxillae and mandible to mandibular length. In addition, it was of interest to determine whether there is a significant loss of residual ridge height in each arch and whether reduction in the height of the mandible can be related to reduction in the maxillae. Mandibular length measured from gonion to menton ranged from 57 mm to 82 mm with a mean distance of 72.2 mm. The mandibular length, measured from the low point along the coronoid notch to menton, ranged from 85 mm to 115 mm with a mean distance of 96.2 mm. The total loss of residual ridge height in the mandible was 46 mm, which produced a mean loss per patient of 2.1 mm and a mean loss per year of 0.104 mm. The range of loss in the mandible was from 0 to 5 mm. Residual ridge loss in the maxillae totaled 21 mm and ranged from 0 to 2 mm. The mean loss per patient was 0.9 mm with the mean loss per year of 0.048 mm (Table I). A paired t-test was used to determine whether there was
JUNE
1992
VOLUME
67
NUMBER
6
RESIDUALRIDGRLOSSANDMANDIRULARLENGTH
Table
I.
Measurements in study of 22 endentulous patients
Lth 1 (mm)
Lth 2 (mm)
78 76 71 82 74 57 68 69 74 77
100 94 86 89 90 85 95 94 99 94 85
69 73 66 70 63 73 71 72 79 72 79 76
IP-Mx (mm)
IP-Md (mm)
20-Mx (mm)
20-Md (mm)
Diff-Mx (IP-20)
14 14 17 18 17 15 18 19 22 13
27 26 11 29 15 25 29 29 37 17 20 29 23 27 23 33 26 33 18 31 31 35
13 13 17 17 16 13 17 18 22 12 16 15 19 12 16 20 17
27 26 9 25 11 21 27 28 37 14 18 25 22 22 21 31 25
17 16 20 20 15
30 16 29 29 35
1 1 0 1 1 2 1 1 0 1 0 1 1 1 1 1 2 2 1 1 0 1
16 16 20 13 17 21 19 19 17 21 20 16
111 89 97 97 95 99 100 115 102 96 105
Diff-Md (IP-20) 0 0 2 4 4 4 2 1 0 3 2 4 1 5 2 2 1 3 2 2 2 0
Lth 1, Distance from gonion (Go) to menton (Me); Lth 2, distance from coronoid notch (CN) to menton (Me); IF’-Mzc, height of maxillary residual placement of complete dentures; IP-Md, height of mandibular residual ridge at initial placement of complete dentures; ZO-Mx, height of maxillary 20 years after placement of complete dentures; 2@Md, height of mandibular residual ridge 20 years after placement of complete dentures.
a statistically significant reduction in residual ridge height. Ninety-five percent confidence intervals around the average yearly loss of bone were constructed. Linear regression was used to determine the relationship between residual ridge loss and mandibular length. Statistical significance of the relationship was determined by an f-test. No relationship could be found between the reduction in maxillary and mandibular residual ridge height. Furthermore, no relationship was discovered between loss of residual ridge height in either jaw and mandibular length. There was, however, a significant reduction (p < 0.0001) in residual ridge height in each jaw. Maxillary bone loss had a yearly mean of 0.048 mm with a 95 % confidence interval ranging from 0.035 mm to 0.06 mm. Reduction in mandibular residual ridge height, had a yearly mean of 0.104 mm with a 95 % confidence interval ranging from 0.072 mm to 0.137 mm (Tables II and III).
CLINICAL
IMPLICATIONS
The reduction in the height of the residual ridge is a most significant process, with the mandibular loss generally exceeding that seen in the maxillae. No direct relationship between increased mandibular length and increased residual ridge loss in the anterior maxillae was demonstrated in this study. This must not be interpreted as a suggestion that meticulous attention. to normal prosthodontic principles is not needed to treat edentulous patients. Just the
THEJOURNAL
OFPROSTHE'CIC
DENTISTRY
Table
Paired t-test statistical analysis
II.
t Loss
Table
ridge at initial residual ridge
P
in maxillary
7.78
W. Ellinger,
School of Dentistry, Medical College of Virginia, University of Kentucky, Lexington, Ky.
length
on residual
DDS, MS,b and
Richmond, Va., and College of Dentistry,
The relationship of mandibular length to residual ridge loss was studied in 22 edentulous patients. Tracings made from cephalometric films taken at initial insertion of complete dentures and at 20 years after placement were measured. Mandibular length was determined to have no statistical relationship to the reduction in residual ridge height in either the maxillae or the mandible. In addition, alveolar bone loss in the one jaw had no relationship to the amount of loss in the other jaw. (J PROSTAET DENT 1992;67:827-30.)
T he inevitable
change in the height and contour of the residual ridge affects the success of the most precisely constructed prosthesis. Although residual ridge loss is most often associated with the mandible, the maxillary residual ridge undergoes a similar process of bone loss. The ability to predict which patients are likely to have greater than normal amounts of alveolar bone loss would be significant to all concerned. In the literature, a connection is made between mandibular length and increased levels of maxillary residual ridge loss in the edentulous patient. In addition, residual ridge loss in one jaw was found to have an inverse relationship to the amount of loss in the other jaw.l The purpose of this study was to determine whether increased mandibular length can be linked to residual ridge loss in the completely edentulous patient and further to discover whether a relationship does exist between the residual ridge loss in the maxillae and mandible. LITERATURE
REVIEW
The study of alveolar bone loss in edentulous patients has been undertaken by many investigators.1-10 The variability in loss of residual ridge height is a common feature in all these reports. The reduction in the anterior residual ridge height in the mandible has been determined to be four times the rate of loss found in the maxillae.2 Attempts to correlate the loss in residual ridge height to the patient’s Supported by U. S. Public Health Service Research grant no. R01 009401 from the Department of Health, Education, and Welfare. aAssociate Professor and Chairman, Department of Removable Prosthodontics, School of Dentistry, Medical College of Virginia. bProfessor, Department of Oral Health Practice, School of Dentistry, University of Kentucky. CAssociate Professor and Director, Office of Applied Research, School of Dentistry, Medical College of Virginia. 1011136082
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
morphologic characteristics have been made. Investigation into the possibility of a link between the Frankfort-mandibular plane angle and mandibular residual ridge loss is an example of correlating morphology to reduction in ridge height.“? i2 In Tallgren’s investigation’ of facial morphology and residual ridge loss, 11 patients were studied over a ‘l-year period of wearing complete dentures. The dentures were constructed 2 to 3 months after the extraction of the remaining teeth. Measurements to determine the amount of residual ridge loss were made from cephalometric films. Mandibular length was measured from a point on the condyle to a point on the symphysis. A positive correlation was discovered between the length of the mandible and the reduction in the height of the maxillary anterior residual ridge. Tallgren’ indicated that the orientation of the maxillary occlusal plane and the relationship of the mandibular incisors to the maxillary residual ridge might play a role in explaining this finding. No such correlation was discovered in regard to the loss in height of the mandibular residual ridge. In that study, Tallgren’ found an inverse relationship between the loss of residual ridge in the maxillae and mandible. When marked resorption was present in one jaw, only slight reduction in residual ridge height was seen in the other. The present study was undertaken to discover whether a similar relationship between mandibular length and maxillary residual ridge loss would be seen in a larger patient population studied over a longer period of time and to determine whether any relationship exists between the extent of bone loss in one jaw as compared to the other. METHODS
AND
MATERIAL
Cephalometric films made at the initial placement of complete dentures and at a point 20 years later were available for 22 patients. These patients were part of a study of complete denture patients performed at the University of 827
UNGER,
ELLINGER,
AND
GUNSOLLEY
Maxillary height
Fig. 1. Determination of mandibular length was made by measuring from gonion (Go) to menton (Me) and at a second location from the lowest point on the coronoid notch (CN) to menton (Me).
Me Kentucky, College of Dentistry. A total of 64 patients were involved at the beginning of the Kentucky study, which involved the construction of complete dentures using either a standard or complex technique. All of the patients were edentulous for at least 1 year before beginning the study. Their ages ranged from 30 to 65 years.13 Unlike Tallgren’s study,l mandibular length was not measured from the condyle to the symphysis. It was not possible to accurately locate the superior surface of the condyle because of the superimposition of other anatomic structures and interference from the orientation device of the cephalostat. The measurement of mandibular length was made in two different regions. The distance from gonion (the point on the angle of the jaw that is the most inferiorly, posteriorly, and outwardly directed) to menton (the most inferior point on the mandibular symphysis) was measured. A second measurement from menton to the lowest point on the coronoid notch was also made (Fig. 1). These measurements were made from the films taken at initial placement of the dentures. The height of the maxillary residual ridge was measured at a right angle from a line extending from the anterior nasal spine to posterior nasal spine to the lowest point on the maxillary residual ridge in the midline. The mandibular residual ridge height was measured from menton to the highest point on the residual ridge in the midline (Fig. 2). Measurement of the residual ridge height was made on films taken at initial placement of the dentures and at 20 years after placement. The change in residual ridge height was determined by subtracting the measurement of ridge height at year 20 from the measurement determined at initial placement of the dentures. All measurements were made on tracings of
828
2. Residual ridge height in the maxillae was determined by measuring at a right angle from a line that extended from anterior nasal spine (ANS) to posterior nasal spine (PNS) to the lowest point on the residual ridge in the midline. Mandibular residual ridge height was measured from menton (Me) to the highest point on the mandible in the midline. Fig.
the available films by the same individual to avoid introducing errors. RESULTS The overall goal of this study was to relate the reduction in residual ridge height in the maxillae and mandible to mandibular length. In addition, it was of interest to determine whether there is a significant loss of residual ridge height in each arch and whether reduction in the height of the mandible can be related to reduction in the maxillae. Mandibular length measured from gonion to menton ranged from 57 mm to 82 mm with a mean distance of 72.2 mm. The mandibular length, measured from the low point along the coronoid notch to menton, ranged from 85 mm to 115 mm with a mean distance of 96.2 mm. The total loss of residual ridge height in the mandible was 46 mm, which produced a mean loss per patient of 2.1 mm and a mean loss per year of 0.104 mm. The range of loss in the mandible was from 0 to 5 mm. Residual ridge loss in the maxillae totaled 21 mm and ranged from 0 to 2 mm. The mean loss per patient was 0.9 mm with the mean loss per year of 0.048 mm (Table I). A paired t-test was used to determine whether there was
JUNE
1992
VOLUME
67
NUMBER
6
RESIDUALRIDGRLOSSANDMANDIRULARLENGTH
Table
I.
Measurements in study of 22 endentulous patients
Lth 1 (mm)
Lth 2 (mm)
78 76 71 82 74 57 68 69 74 77
100 94 86 89 90 85 95 94 99 94 85
69 73 66 70 63 73 71 72 79 72 79 76
IP-Mx (mm)
IP-Md (mm)
20-Mx (mm)
20-Md (mm)
Diff-Mx (IP-20)
14 14 17 18 17 15 18 19 22 13
27 26 11 29 15 25 29 29 37 17 20 29 23 27 23 33 26 33 18 31 31 35
13 13 17 17 16 13 17 18 22 12 16 15 19 12 16 20 17
27 26 9 25 11 21 27 28 37 14 18 25 22 22 21 31 25
17 16 20 20 15
30 16 29 29 35
1 1 0 1 1 2 1 1 0 1 0 1 1 1 1 1 2 2 1 1 0 1
16 16 20 13 17 21 19 19 17 21 20 16
111 89 97 97 95 99 100 115 102 96 105
Diff-Md (IP-20) 0 0 2 4 4 4 2 1 0 3 2 4 1 5 2 2 1 3 2 2 2 0
Lth 1, Distance from gonion (Go) to menton (Me); Lth 2, distance from coronoid notch (CN) to menton (Me); IF’-Mzc, height of maxillary residual placement of complete dentures; IP-Md, height of mandibular residual ridge at initial placement of complete dentures; ZO-Mx, height of maxillary 20 years after placement of complete dentures; 2@Md, height of mandibular residual ridge 20 years after placement of complete dentures.
a statistically significant reduction in residual ridge height. Ninety-five percent confidence intervals around the average yearly loss of bone were constructed. Linear regression was used to determine the relationship between residual ridge loss and mandibular length. Statistical significance of the relationship was determined by an f-test. No relationship could be found between the reduction in maxillary and mandibular residual ridge height. Furthermore, no relationship was discovered between loss of residual ridge height in either jaw and mandibular length. There was, however, a significant reduction (p < 0.0001) in residual ridge height in each jaw. Maxillary bone loss had a yearly mean of 0.048 mm with a 95 % confidence interval ranging from 0.035 mm to 0.06 mm. Reduction in mandibular residual ridge height, had a yearly mean of 0.104 mm with a 95 % confidence interval ranging from 0.072 mm to 0.137 mm (Tables II and III).
CLINICAL
IMPLICATIONS
The reduction in the height of the residual ridge is a most significant process, with the mandibular loss generally exceeding that seen in the maxillae. No direct relationship between increased mandibular length and increased residual ridge loss in the anterior maxillae was demonstrated in this study. This must not be interpreted as a suggestion that meticulous attention. to normal prosthodontic principles is not needed to treat edentulous patients. Just the
THEJOURNAL
OFPROSTHE'CIC
DENTISTRY
Table
Paired t-test statistical analysis
II.
t Loss
Table
ridge at initial residual ridge
P
in maxillary
7.78
