Radiomorphometric indices and their relation to alveolar bone loss in completely edentulous Turkish patients: A retrospective study

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March 2009

Radiomorphometric indices and their relation to alveolar bone loss in completely edentulous Turkish patients: A retrospective study Bulem Yüzügüllü, DDS, PhD,a Ayse Gulsahi, DDS, PhD,b and . Pervin Imirzalioglu, DDS, PhDc Baskent University, Faculty of Dentistry, Ankara, Turkey Statement of problem. In edentulous patients, alveolar bone loss is a critical factor that affects denture retention, stability, and masticatory function. In addition to their use for the assessment of bone quality, panoramic radiomorphometric indices have been used to observe signs of bone resorption. Currently, there is no published data on the possible relationships between bone loss, radiomorphometric indices, and edentulism. Purpose. The purpose of this study was to investigate the influence of age and gender on the mandibular cortical index, panoramic mandibular index, and mandibular cortical width, as well as alveolar bone loss and bone height, using panoramic radiographs of patients having been edentulous for more than 2 years. Material and methods. Panoramic radiographs of 94 edentulous patients (41.5% men and 58.5% women) were assessed. In addition to gender and age, the mandibular cortical index (normal cortex, mild or severe erosions on endosteal margin of the mandible), panoramic mandibular index, mandibular cortical width at the mental foramen region, alveolar bone loss, and bone heights of the premolar and molar regions of the mandible were recorded. Statistical comparisons were performed using chi-square, Mann-Whitney U, Kruskal-Wallis, and 2-way ANOVA tests (α=.05). Results. Mild erosions on the endosteal margin of the mandible were more frequently seen in age groups of ≤60, and severe erosions on the endosteal margin of the mandible were more frequently observed in age groups of >60 in women (P<.001). While the mean values of the mandibular cortical width were stable as age increased in men, the mean mandibular cortical width values decreased significantly with age in women (P<.01). The panoramic mandibular index, alveolar bone loss, and bone heights were not affected by age or gender. Conclusions. Severe erosions on the endosteal margin of the mandible are seen more frequently in women over 60 years in age. While mean mandibular cortical width values are stable in men over 60 years, mean mandibular cortical width values decrease significantly in women of the same age group. (J Prosthet Dent 2009;101:160-165)

Clinical Implications

In edentulous patients, the quality of alveolar bone decreases with age and becomes less ideal in women more frequently than in men. Furthermore, women demonstrate less bone quantity with increasing age. These results may have implications on treatment planning, with special regard to reconstructive procedures, subsequent implant treatment, and removable complete dentures. In many phases of prosthetic dentistry, healthy alveolar bone with normal regenerative capacity is essential for a successful treatment outcome.1 Residual ridge resorption is widely rec-

ognized as one of the most important factors affecting denture support, retention, stability, and masticatory function in edentulous patients.2 Reduction of the residual alveolar ridges

could be described as a resorptive atrophy, a physiologic reaction to loss of function and inactivity.3 Due to its progressive nature, the height of the alveolar ridge and basal bone will

Assistant Professor, Department of Prosthodontics. Assistant Professor, Department of Oral Diagnosis and Radiology. c Associate Professor, Department of Prosthodontics. a

b

The Journal of Prosthetic Dentistry

Yüzügüllü et al

decrease,4-7 resulting in alveolar ridge bone loss as great as 1 mm per year in complete denture wearers.8,9 Agerelated mandibular bone loss may be due to general thinning and increased porosity of the mandibular cortex, which is distinct from the change in the size of the mandibular alveolar process in edentulous individuals.4 Resorption is more pronounced during the first few years following the loss of teeth.6,7 Due to the greater tendency toward bone atrophy among women, it would be logical to assume that osseous changes are significantly affected by gender.10-12 According to Mercier,13 the higher incidence of bone atrophy in women should be viewed more in the context of major skeletal differences between the 2 genders, as opposed to the actual hormonal imbalances that predispose women to osteoporosis. However, Lerouxel et al14 demonstrated that reduction of reproductive hormones is associated with a decrease in bone mass in the mandibles of male rats. Bone loss occurs more rapidly in the premolar and molar regions of the edentulous mandible, compared to the anterior region. Therefore, bone resorption of the basal bone is more frequent in this region.13 Previous investigations on the effects of radiomorphometric indices and alveolar bone loss (ABL) have focused primarily on partially or completely dentate women.15-23 Accordingly, it is logical to assume that a possible relationship exists among bone loss, radiomorphometric indices, and edentulism. In the literature, limited data exists with regard to mandibular bone heights in edentulous patients of different genders.24-26 A number of qualitative and quantitative indices, including the mandibular cortical index (MCI), mandibular cortical width (MCW), or panoramic mandibular index (PMI), have been used to assess bone quality and to observe signs of resorption on panoramic radiographs.15-19,25-28 Previous studies have shown that MCW has a

Yüzügüllü et al

significant negative correlation with age.20,21 In light of these observations, the purpose of the study was to assess the influence of age and gender on ABL, MCI, PMI, MCW, and average bone heights in the premolar and molar regions of the mandible using panoramic radiographs of individuals having been edentulous for more than 2 years. Accordingly, the null hypothesis was that ABL and radiomorphometric indices would not change with age and gender in complete edentulism.

MATERIAL AND METHODS Digital panoramic radiographs acquired between 2005-2006 were obtained from the patient records of Baskent University, Faculty of Dentistry, Ankara, Turkey. The study protocol was approved by the Research Committee at Baskent University (project no. D-KA08/09). Inclusion criteria stipulated the selection of high quality, correctly positioned panoramic radiographs of patients having been completely edentulous for more than 2 years. All panoramic images were made with the same digital panoramic radiography unit (PM 2002 EC Proline DIMAX2; Planmeca, Helsinki, Finland). Radiomorphometric indices generally demonstrate a strong negative correlation with age until the sixth decade, when the values begin to fall sharply compared to the mean values of a population.20,26 Therefore, the radiographs were grouped into 2 age groups, ≤60 and >60 years. Gender and age were recorded for each patient. Linear measurements on panoramic images were made using imaging software (Dimaxis; Planmeca, Helsinki, Finland) at a correction for 20% magnification, relatively, to better simulate the clinical situation. Two calibrated, independent observers performed the measurements for MCI, MCW, PMI, ABL, and bone heights. MCI refers to the inferior mandibular cortical thickness, and is categorized

into the following 3 groups according to the criteria described by Klemetti et al16: C1: the endosteal margin of the cortex is even and sharp on both sides; C2: the endosteal margin shows semilunar defects (lacunar resorption) and/or seems to form endosteal cortical residues on one or both sides; and C3: the cortical layer forms heavy endosteal cortical residues and is clearly porous. MCW is the measurement of the cortical width at the mental foramen region and is assessed according to the technique described by Ledgerton et al.20 Accordingly, the mental foramen is identified and a line is traced which passes perpendicular to the tangent of the lower border of the mandible and through the center of the mental foramen. The cortical width was measured at this point. The PMI, as described by Benson et al,29 is the ratio of the thickness of the mandibular cortex to the distance between the mental foramen and the inferior mandibular cortex. Alveolar bone loss (ABL) of the mandible is the ratio of the radiographic mandibular total bone height to the height from the center of the mental foramen to the inferior border of the mandible.30 Bone heights from 2 different regions of the mandible (Hp: height in the first premolar region; Hm: height in the first molar region) were measured according to measurement locations described by Güler et al.24 Reliability was assessed using repeated measurements. The oral radiologist served as the main observer, and intraobserver reliability was estimated between measurements. The second observer was a prosthodontist, and interobserver reliability was assessed. For intraobserver and interobserver reliability, MCI classifications were reassessed and the distances were remeasured in all specimens by both observers. The kappa value was calculated for MCI classification, and the intraclass correlation coefficient (ICC) was calculated for MCW, PMI, ABL, and bone heights. Measurements from each examiner were averaged and analyzed.

161

March 2009

Radiomorphometric indices and their relation to alveolar bone loss in completely edentulous Turkish patients: A retrospective study Bulem Yüzügüllü, DDS, PhD,a Ayse Gulsahi, DDS, PhD,b and . Pervin Imirzalioglu, DDS, PhDc Baskent University, Faculty of Dentistry, Ankara, Turkey Statement of problem. In edentulous patients, alveolar bone loss is a critical factor that affects denture retention, stability, and masticatory function. In addition to their use for the assessment of bone quality, panoramic radiomorphometric indices have been used to observe signs of bone resorption. Currently, there is no published data on the possible relationships between bone loss, radiomorphometric indices, and edentulism. Purpose. The purpose of this study was to investigate the influence of age and gender on the mandibular cortical index, panoramic mandibular index, and mandibular cortical width, as well as alveolar bone loss and bone height, using panoramic radiographs of patients having been edentulous for more than 2 years. Material and methods. Panoramic radiographs of 94 edentulous patients (41.5% men and 58.5% women) were assessed. In addition to gender and age, the mandibular cortical index (normal cortex, mild or severe erosions on endosteal margin of the mandible), panoramic mandibular index, mandibular cortical width at the mental foramen region, alveolar bone loss, and bone heights of the premolar and molar regions of the mandible were recorded. Statistical comparisons were performed using chi-square, Mann-Whitney U, Kruskal-Wallis, and 2-way ANOVA tests (α=.05). Results. Mild erosions on the endosteal margin of the mandible were more frequently seen in age groups of ≤60, and severe erosions on the endosteal margin of the mandible were more frequently observed in age groups of >60 in women (P<.001). While the mean values of the mandibular cortical width were stable as age increased in men, the mean mandibular cortical width values decreased significantly with age in women (P<.01). The panoramic mandibular index, alveolar bone loss, and bone heights were not affected by age or gender. Conclusions. Severe erosions on the endosteal margin of the mandible are seen more frequently in women over 60 years in age. While mean mandibular cortical width values are stable in men over 60 years, mean mandibular cortical width values decrease significantly in women of the same age group. (J Prosthet Dent 2009;101:160-165)

Clinical Implications

In edentulous patients, the quality of alveolar bone decreases with age and becomes less ideal in women more frequently than in men. Furthermore, women demonstrate less bone quantity with increasing age. These results may have implications on treatment planning, with special regard to reconstructive procedures, subsequent implant treatment, and removable complete dentures. In many phases of prosthetic dentistry, healthy alveolar bone with normal regenerative capacity is essential for a successful treatment outcome.1 Residual ridge resorption is widely rec-

ognized as one of the most important factors affecting denture support, retention, stability, and masticatory function in edentulous patients.2 Reduction of the residual alveolar ridges

could be described as a resorptive atrophy, a physiologic reaction to loss of function and inactivity.3 Due to its progressive nature, the height of the alveolar ridge and basal bone will

Assistant Professor, Department of Prosthodontics. Assistant Professor, Department of Oral Diagnosis and Radiology. c Associate Professor, Department of Prosthodontics. a

b

The Journal of Prosthetic Dentistry

Yüzügüllü et al

decrease,4-7 resulting in alveolar ridge bone loss as great as 1 mm per year in complete denture wearers.8,9 Agerelated mandibular bone loss may be due to general thinning and increased porosity of the mandibular cortex, which is distinct from the change in the size of the mandibular alveolar process in edentulous individuals.4 Resorption is more pronounced during the first few years following the loss of teeth.6,7 Due to the greater tendency toward bone atrophy among women, it would be logical to assume that osseous changes are significantly affected by gender.10-12 According to Mercier,13 the higher incidence of bone atrophy in women should be viewed more in the context of major skeletal differences between the 2 genders, as opposed to the actual hormonal imbalances that predispose women to osteoporosis. However, Lerouxel et al14 demonstrated that reduction of reproductive hormones is associated with a decrease in bone mass in the mandibles of male rats. Bone loss occurs more rapidly in the premolar and molar regions of the edentulous mandible, compared to the anterior region. Therefore, bone resorption of the basal bone is more frequent in this region.13 Previous investigations on the effects of radiomorphometric indices and alveolar bone loss (ABL) have focused primarily on partially or completely dentate women.15-23 Accordingly, it is logical to assume that a possible relationship exists among bone loss, radiomorphometric indices, and edentulism. In the literature, limited data exists with regard to mandibular bone heights in edentulous patients of different genders.24-26 A number of qualitative and quantitative indices, including the mandibular cortical index (MCI), mandibular cortical width (MCW), or panoramic mandibular index (PMI), have been used to assess bone quality and to observe signs of resorption on panoramic radiographs.15-19,25-28 Previous studies have shown that MCW has a

Yüzügüllü et al

significant negative correlation with age.20,21 In light of these observations, the purpose of the study was to assess the influence of age and gender on ABL, MCI, PMI, MCW, and average bone heights in the premolar and molar regions of the mandible using panoramic radiographs of individuals having been edentulous for more than 2 years. Accordingly, the null hypothesis was that ABL and radiomorphometric indices would not change with age and gender in complete edentulism.

MATERIAL AND METHODS Digital panoramic radiographs acquired between 2005-2006 were obtained from the patient records of Baskent University, Faculty of Dentistry, Ankara, Turkey. The study protocol was approved by the Research Committee at Baskent University (project no. D-KA08/09). Inclusion criteria stipulated the selection of high quality, correctly positioned panoramic radiographs of patients having been completely edentulous for more than 2 years. All panoramic images were made with the same digital panoramic radiography unit (PM 2002 EC Proline DIMAX2; Planmeca, Helsinki, Finland). Radiomorphometric indices generally demonstrate a strong negative correlation with age until the sixth decade, when the values begin to fall sharply compared to the mean values of a population.20,26 Therefore, the radiographs were grouped into 2 age groups, ≤60 and >60 years. Gender and age were recorded for each patient. Linear measurements on panoramic images were made using imaging software (Dimaxis; Planmeca, Helsinki, Finland) at a correction for 20% magnification, relatively, to better simulate the clinical situation. Two calibrated, independent observers performed the measurements for MCI, MCW, PMI, ABL, and bone heights. MCI refers to the inferior mandibular cortical thickness, and is categorized

into the following 3 groups according to the criteria described by Klemetti et al16: C1: the endosteal margin of the cortex is even and sharp on both sides; C2: the endosteal margin shows semilunar defects (lacunar resorption) and/or seems to form endosteal cortical residues on one or both sides; and C3: the cortical layer forms heavy endosteal cortical residues and is clearly porous. MCW is the measurement of the cortical width at the mental foramen region and is assessed according to the technique described by Ledgerton et al.20 Accordingly, the mental foramen is identified and a line is traced which passes perpendicular to the tangent of the lower border of the mandible and through the center of the mental foramen. The cortical width was measured at this point. The PMI, as described by Benson et al,29 is the ratio of the thickness of the mandibular cortex to the distance between the mental foramen and the inferior mandibular cortex. Alveolar bone loss (ABL) of the mandible is the ratio of the radiographic mandibular total bone height to the height from the center of the mental foramen to the inferior border of the mandible.30 Bone heights from 2 different regions of the mandible (Hp: height in the first premolar region; Hm: height in the first molar region) were measured according to measurement locations described by Güler et al.24 Reliability was assessed using repeated measurements. The oral radiologist served as the main observer, and intraobserver reliability was estimated between measurements. The second observer was a prosthodontist, and interobserver reliability was assessed. For intraobserver and interobserver reliability, MCI classifications were reassessed and the distances were remeasured in all specimens by both observers. The kappa value was calculated for MCI classification, and the intraclass correlation coefficient (ICC) was calculated for MCW, PMI, ABL, and bone heights. Measurements from each examiner were averaged and analyzed.

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Volume 101 Issue 3 MCI classifications were compared according to gender and age groups using the chi-square test at a significance level of α=.05 and α=.001, respectively. The 2-way ANOVA test was used to determine the effect of age and gender on mandibular cortical width, ABL, Hp, and Hm (α=.05). PMI values were compared between age groups and between genders using the Mann-Whitney U test (α=.05).

RESULTS All observations were acceptable and were included in the present study. The kappa values showing both intraobserver and interobserver

agreement were nearly perfect (0.905 and 0.821, respectively) for MCI. For MCW, PMI, ABL, and bone heights, ICC values indicating intraobserver and interobserver agreement were also nearly perfect (0.946 and 0.851; 0.934 and 0.848; 0.925 and 0.896; and 0.912 and 0.889, respectively). Of the 94 patients, 39 (41.5%) were men and 55 (58.5%) were women. Only 2 categories of MCI (C2/56.4% and C3/43.6%) were detected. There was no significant difference within C2 and C3 categories of MCI between age groups in men. Category C2 was more frequently seen in age groups of ≤60, and category C3 was more frequently ob-

served in age groups of >60 in women (P<.001) (Table I). There was no significant difference between either age groups or gender for MCW. However, there was a significant interaction between age and gender. While the mean MCW values did not change as age increased in men, the mean MCW values decreased significantly with age in women [F(degree of freedom) (1.90)=8.34, P<.01] (Fig. 1). PMI was not affected by gender or age (Table II). The descriptive statistics of ABL, Hp, and Hm values, according to age and gender, are presented in Table III. These values were not affected by gender or age. Also, there was not any interaction between age and gender.

Table II. Mean (SD) mandibular cortical width (MCW) (mm) and panoramic mandibular index (PMI) according to age and gender

Gender

Age (Years)

Mean (SD)

Median (Minimum-Maximum)

≤60

4.60 (0.35)

0.26 (0.17-0.48)

>60

4.77 (0.59)

0.26 (0.12-0.55)

≤60

4.75 (0.38)

0.24 (0.12-0.45)

>60

4.18 (0.50)

0.23 (0.12-0.53)

Table III. Mean (SD) alveolar bone loss and bone height values (mm) according to age and gender Gender

Age (Years)

Alveolar Bone Loss

Hp (mm)

Hm (mm)

≤60

2.13 (0.4)

42.10 (19.66)

33.45 (16.56)

>60

1.99 (0.6)

38.02 (12.79)

31.23 (11.82)

≤60

2.06 (0.5)

41.46 (13.86)

35.53 (13.94)

>60

1.96 (0.5)

36.22 (8.62)

30.54 (7.83)

Men

Age (Years)

C2

C3

n

≤60

6 (86%)

1 (14%)

7

>60

21 (66%)

11 (34%)

32

≤60

17 (90%)

2 (10%)

19

>60

9 (25%)

27 (75%)

36

Women

PMI

Women

MCI Classification

Men

MCW (mm)

Men

Table I. Distribution (%) of mandibular cortical index (MCI) classifications (category C2, mild erosions; category C3, severe erosions on endosteal margin of mandible) according to age and gender Gender

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Women

Hp: average bone height in mandibular first premolar region; Hm: average bone height in mandibular first molar region; SD: standard deviation

DISCUSSION 4.80

MCW (mm)

4.60

4.20 Men 4.40

Women

≤60

>60

Age (Years) 1 Interaction between age and gender groups according to mandibular cortical width (MCW).

The Journal of Prosthetic Dentistry

Yüzügüllü et al

The present study provides new findings on the effects of age and gender on radiomorphometric indices, ABL, and bone heights, all in a group of completely edentulous Turkish individuals. The null hypothesis was rejected, in part, since MCI and MCW changed with age and/or gender in edentulous patients. The study group of patients was not selected on the basis of any radiographic or medical criteria, which would define an individual as “normal” or “osteoporotic.” Thus, the study population represents patients undergoing dental panoramic radiographic examination as part of their routine treatment. Panoramic radiographs of patients who were completely edentulous for less than

Yüzügüllü et al

2 years were excluded, since alveolar bone loss is more pronounced during the first few years after tooth loss.6,7 Previous studies showed that minor anteroposterior shifts and tilts are associated with small variations (less than 2%) in vertical measurements.31,32 In the present study, all measurements were reduced to the original size of the mandibular features, according to the magnification of the panoramic machine used (20%, according to the manufacturer). This compensation allowed for comparison with other studies, because different panoramic machines have different magnification factors. MCI is a simple, qualitative, 3-point index with fairly good reproducibility.18 In the current study, only C2 and C3 categories were observed

in the study group of edentulous patients. This may be attributable to the fact that the group of selected patients was relatively older, in comparison to the age of 30, when the first signs of bone loss start to manifest radiographically.5 Also, the similar number of patients with C2 and C3 categories in this study correlates with the findings of Knezovic-Zlataric et al,1 who stated that this finding may be characteristic of this group of patients, as related to age or time of edentulousness. In accordance with another study,25 parallel to the increase in age of women in the present study, the number of patients with category C3 increased significantly as well, indicating a decrease in bone quality with age. In agreement with the results reported by Ledgerton et

162

Volume 101 Issue 3 MCI classifications were compared according to gender and age groups using the chi-square test at a significance level of α=.05 and α=.001, respectively. The 2-way ANOVA test was used to determine the effect of age and gender on mandibular cortical width, ABL, Hp, and Hm (α=.05). PMI values were compared between age groups and between genders using the Mann-Whitney U test (α=.05).

RESULTS All observations were acceptable and were included in the present study. The kappa values showing both intraobserver and interobserver

agreement were nearly perfect (0.905 and 0.821, respectively) for MCI. For MCW, PMI, ABL, and bone heights, ICC values indicating intraobserver and interobserver agreement were also nearly perfect (0.946 and 0.851; 0.934 and 0.848; 0.925 and 0.896; and 0.912 and 0.889, respectively). Of the 94 patients, 39 (41.5%) were men and 55 (58.5%) were women. Only 2 categories of MCI (C2/56.4% and C3/43.6%) were detected. There was no significant difference within C2 and C3 categories of MCI between age groups in men. Category C2 was more frequently seen in age groups of ≤60, and category C3 was more frequently ob-

served in age groups of >60 in women (P<.001) (Table I). There was no significant difference between either age groups or gender for MCW. However, there was a significant interaction between age and gender. While the mean MCW values did not change as age increased in men, the mean MCW values decreased significantly with age in women [F(degree of freedom) (1.90)=8.34, P<.01] (Fig. 1). PMI was not affected by gender or age (Table II). The descriptive statistics of ABL, Hp, and Hm values, according to age and gender, are presented in Table III. These values were not affected by gender or age. Also, there was not any interaction between age and gender.

Table II. Mean (SD) mandibular cortical width (MCW) (mm) and panoramic mandibular index (PMI) according to age and gender

Gender

Age (Years)

Mean (SD)

Median (Minimum-Maximum)

≤60

4.60 (0.35)

0.26 (0.17-0.48)

>60

4.77 (0.59)

0.26 (0.12-0.55)

≤60

4.75 (0.38)

0.24 (0.12-0.45)

>60

4.18 (0.50)

0.23 (0.12-0.53)

Table III. Mean (SD) alveolar bone loss and bone height values (mm) according to age and gender Gender

Age (Years)

Alveolar Bone Loss

Hp (mm)

Hm (mm)

≤60

2.13 (0.4)

42.10 (19.66)

33.45 (16.56)

>60

1.99 (0.6)

38.02 (12.79)

31.23 (11.82)

≤60

2.06 (0.5)

41.46 (13.86)

35.53 (13.94)

>60

1.96 (0.5)

36.22 (8.62)

30.54 (7.83)

Men

Age (Years)

C2

C3

n

≤60

6 (86%)

1 (14%)

7

>60

21 (66%)

11 (34%)

32

≤60

17 (90%)

2 (10%)

19

>60

9 (25%)

27 (75%)

36

Women

PMI

Women

MCI Classification

Men

MCW (mm)

Men

Table I. Distribution (%) of mandibular cortical index (MCI) classifications (category C2, mild erosions; category C3, severe erosions on endosteal margin of mandible) according to age and gender Gender

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March 2009

Women

Hp: average bone height in mandibular first premolar region; Hm: average bone height in mandibular first molar region; SD: standard deviation

DISCUSSION 4.80

MCW (mm)

4.60

4.20 Men 4.40

Women

≤60

>60

Age (Years) 1 Interaction between age and gender groups according to mandibular cortical width (MCW).

The Journal of Prosthetic Dentistry

Yüzügüllü et al

The present study provides new findings on the effects of age and gender on radiomorphometric indices, ABL, and bone heights, all in a group of completely edentulous Turkish individuals. The null hypothesis was rejected, in part, since MCI and MCW changed with age and/or gender in edentulous patients. The study group of patients was not selected on the basis of any radiographic or medical criteria, which would define an individual as “normal” or “osteoporotic.” Thus, the study population represents patients undergoing dental panoramic radiographic examination as part of their routine treatment. Panoramic radiographs of patients who were completely edentulous for less than

Yüzügüllü et al

2 years were excluded, since alveolar bone loss is more pronounced during the first few years after tooth loss.6,7 Previous studies showed that minor anteroposterior shifts and tilts are associated with small variations (less than 2%) in vertical measurements.31,32 In the present study, all measurements were reduced to the original size of the mandibular features, according to the magnification of the panoramic machine used (20%, according to the manufacturer). This compensation allowed for comparison with other studies, because different panoramic machines have different magnification factors. MCI is a simple, qualitative, 3-point index with fairly good reproducibility.18 In the current study, only C2 and C3 categories were observed

in the study group of edentulous patients. This may be attributable to the fact that the group of selected patients was relatively older, in comparison to the age of 30, when the first signs of bone loss start to manifest radiographically.5 Also, the similar number of patients with C2 and C3 categories in this study correlates with the findings of Knezovic-Zlataric et al,1 who stated that this finding may be characteristic of this group of patients, as related to age or time of edentulousness. In accordance with another study,25 parallel to the increase in age of women in the present study, the number of patients with category C3 increased significantly as well, indicating a decrease in bone quality with age. In agreement with the results reported by Ledgerton et

164

Volume 101 Issue 3 al20 and Dutra et al,26 the results in the current study for the mean values of MCW demonstrate an age-related decrease in women. To date, only a few studies25,26,28 have evaluated the changes in MCW for men. The results by Knezovic-Zlataric et al25 suggest a general decrease for both genders until the age of 75, when the values begin to decrease sharply for women compared to men. Although there was a general, age-related decrease for MCW values in both genders, Dutra et al26 observed higher values for MCW in men. The present study revealed that men showed a stable profile concerning MCW values, irrespective of an increase in age. One advantage in the use of PMI over MCW is that its method of calculation considers differences in magnification associated with different panoramic radiography machines. Thus, unlike other linear indices, it is possible to make a direct comparison of absolute figures with other studies.20 Recent studies on PMI values have been performed primarily on women,20,27,29 and demonstrate PMI values between 0.31-0.38, which are higher than the mean value of 0.23-0.24 found in the present study. These differences may not only be due to ethnic origins, but may arise due to the inclusion of partially edentulous patients, in addition to completely edentulous individuals. The present mean PMI values for edentulous patients agree with those of Gulsahi et al,28 who reported mean PMI values of 0.30, 0.32, and 0.22 for C1, C2, and C3 categories, respectively, in a large, mixed, study population. The pattern of change in mean PMI in relation to the age range also differs from that described by Ledgerton et al.20 The investigators demonstrated a gradual reduction with age until the sixth decade, when its mean value decreased sharply. By contrast, there was no significant difference among the age groups in the present study. Once again, ethnic origin would seem the likeliest reason for differences in age-related patterns of PMI. Bone heights in the first premolar

and molar regions (Hp and Hm) were similar in men and women, in contrast to the findings of Güler et al,24 in which men had greater bone height than women in the same regions of the mandible. In the present study, parameters such as general health, denture wearing habits, nutrition, or medication intake were not included, which may have affected the outcome related to gender. Hp and Hm were also similar between age groups. In general, physiologic and muscular activities decrease with age. Along with progressive residual ridge atrophy, muscular function also decreases in order to protect the bony structures of the residual ridges, especially in the mandible.4,6 It is interesting to note how the atrophic mandible is not characterized solely by resorption phenomena, since, in fact, some parts of the mandible are paradoxically subject to a process of new bone formation.7 This phenomenon may be attributable to the fact that, with the progressive reduction of the alveolar processes and the subsequent involvement of the basal bone, muscular strength is limited to a smaller bone area.7 Also, the reason for similar measurements found between age groups in the posterior mandible may be due to the existence of parafunctional conditions in which muscular hyperactivity may preserve bone from extreme resorption.7 ABL was not affected by age according to gender in the present study. This finding is in agreement with the results of Soikkonen et al,22 who concluded that in both genders, ABL does not increase significantly with age. Surgical procedures, mastication forces transmitted by dentures, and, in general, factors that affect bone metabolism are all involved in determining the rate of residual ridge resorption.23 Given the wide number of factors involved in the atrophic processes of the edentulous mandible, it is difficult to make definitive conclusions regarding the problem of ABL. Also, elderly edentulous patients with a long history of edentulism may have

The Journal of Prosthetic Dentistry

low masticatory force. Therefore, the present study has limitations, and the results may not be applicable to similar groups of middle-aged edentulous patients or patients with a short-term edentulous experience. An extreme reduction in the height of the alveolar process, which in serious situations involves the basal bone,7 is accompanied by an inversion in the morphology of the crest, as well as an increase in the consistency of the cortical walls and vestibular and lingual surfaces.7 The progressive reduction in the height of the mandibular bone presumably results in an increase in the intensity of mechanical stimuli caused by muscular actions along the main load course of the mandibular body,7,23 which might also be one of the reasons for the lack of significant differences among the age groups. Unlike several studies which report that women have more advanced bone loss than men,10,11 the present results, agreeing with those of a previous report,12 indicate that there is no difference between genders. This finding could be attributed to the individual variation in the rate of bone loss and body mass index.12 Besides age, gender, and duration of edentulousness, factors often correlated with residual ridge resorption are facial structure, denture wearing habits, number of dentures worn, oral hygiene and parafunctions, occlusal loading, nutrition, general health, and the use of medication for osteoporosis.9 Due to the restrictions in the selection of parameters, the present data cannot support a statistical model that includes the analysis of all of these variables. As a result, differences in MCI classifications and MCW values in relation to age and gender in this study may have been due to osteoporosis. Further studies incorporating such patients are needed to make more sound conclusions.

were drawn for a Turkish population: 1. Category C3 of the mandibular cortical index, in which the cortical layer forms heavy endosteal cortical residues and is clearly porous, was more frequently seen in women over 60 years in age (P<.001). 2. The values of mean cortical width at the mental foramen region decreased significantly with age in women (P<.01). 3. The ratio of the thickness of the mandibular cortex to the distance between the mental foramen and the inferior mandibular cortex (PMI), alveolar bone loss (ABL) of the mandible, and bone heights were not affected by gender or age.

REFERENCES 1. Zlataric DK, Celebic A. Clinical bone densitometric evaluation of the mandible in removable denture wearers dependent on the morphology of the mandibular cortex. J Prosthet Dent 2003;90:86-91. 2. Hirai T, Ishijima T, Hashikawa Y, Yajima T. Osteoporosis and reduction of residual ridge in edentulous patients. J Prosthet Dent 1993;69:49-56. 3. Knezovic-Ziataric D, Celebic A. Mandibular bone mineral density changes in complete and removable partial denture wearers: a 6-month follow-up study. Int J Prosthodont 2003;16:661-5. 4. Devlin H, Horner K. A study to assess the relative influence of age and edentulousness upon mandibular bone mineral density in female subjects. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:11721. 5. Heersche JN, Bellows CG, Ishida Y. The decrease in bone mass associated with aging and menopause. J Prosthet Dent 1998;79:14-6. 6. Tallgren A. The continuing reduction of the residual alveolar ridges in complete denture wearers: a mixed longitudinal study covering 25 years. J Prosthet Dent 1972;27:12032. 7. Bianchi A, Sanfilippo F. Osteoporosis: the effect on mandibular bone resorption and therapeutic possibilities by means of implant prostheses. Int J Periodontics Restorative Dent 2002;22:231-9. 8. Carlsson GE, Persson G. Morphologic changes of the mandible after extraction and wearing of dentures. A longitudinal, clinical, and x-ray cephalometric study covering 5 years. Odontol Revy 1967;18:2754.

CONCLUSIONS

Within the limitations of the present study, the following conclusions

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9. Devlin H, Ferguson MW. Alveolar ridge resorption and mandibular atrophy. A review of the role of local and systemic factors. Br Dent J 1991;170:101-4. 10.Xie Q, Ainamo A, Tilvis R. Association of residual ridge resorption with systemic factors in home-living elderly subjects. Acta Odontol Scand 1997;55:299-305. 11.Xie Q, Wolf J, Tilvis R, Ainamo A. Resorption of mandibular canal wall in the edentulous aged population. J Prosthet Dent 1997;77:596-600. 12.Carlsson GE, Haraldson T. Fundamental aspects of mandibular atrophy. In: Worthington P, Branemark PI, editors. Advanced osseointegration surgery: applications in the maxillofacial region. Chicago: Quintessence; 1992. p. 109-18. 13.Mercier P. Ridge reconstruction with hydroxylapatite. Part 1. Anatomy of the residual ridge. Oral Surg Oral Med Oral Pathol 1988;65:505-10. 14.Lerouxel E, Libouban H, Moreau MF, Baslé MF, Audran M, Chappard D. Mandibular bone loss in an animal model of male osteoporosis (orchidectomized rat): a radiographic and densitometric study. Osteoporos Int 2004;15:814-9. 15.Horner K, Devlin H. The relationship between mandibular bone mineral density and panoramic radiographic measurements. J Dent 1998;26:337-43. 16.Klemetti E, Kolmakov S, Kröger H. Pantomography in assessment of the osteoporosis risk group. Scand J Dent Res 1994;102:68-72. 17.Taguchi A, Tsuda M, Ohtsuka M, Kodama I, Sanada M, Nakamoto T, et al. Use of dental panoramic radiographs in identifying younger postmenopausal women with osteoporosis. Osteoporos Int 2006;17:38794. 18.Devlin H, Karayianni K, Mitsea A, Jacobs R, Lindh C, van der Stelt P, et al. Diagnosing osteoporosis by using dental panoramic radiographs: the OSTEODENT project. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:821-8. 19.Horner K, Devlin H, Harvey L. Detecting patients with low skeletal bone mass. J Dent 2002;30:171-5. 20.Ledgerton D, Horner K, Devlin H, Worthington H. Radiomorphometric indices of the mandible in a British female population. Dentomaxillofac Radiol 1999;28:17381. 21.Horner K, Devlin H, Alsop CW, Hodgkinson IM, Adams JE. Mandibular bone mineral density as a predictor of skeletal osteoporosis. Br J Radiol 1996;69:1019-25. 22.Soikkonen K, Ainamo A, Xie Q. Height of the residual ridge and radiographic appearance of bony structure in the jaws of clinically edentulous elderly people. J Oral Rehabil 1996;23:470-5. 23.Klemetti E, Kolmakow S. Morphology of the mandibular cortex on panoramic radiographs as an indicator of bone quality. Dentomaxillofac Radiol 1997;26:22-5.

24.Güler AU, Sumer M, Sumer P, Biçer I. The evaluation of vertical heights of maxillary and mandibular bones and the location of anatomic landmarks in panoramic radiographs of edentulous patients for implant dentistry. J Oral Rehabil 2005;32:741-6. 25.Knezovic-Zlataric D, Celebic A, Lazic B, Baucic I, Komar D, Stipetic-Ovcaricek J, et al. Influence of age and gender on radiomorphometric indices of the mandible in removable denture wearers. Coll Antropol 2002;26:259-66. 26.Dutra V, Yang J, Devlin H, Susin C. Radiomorphometric indices and their relation to gender, age, and dental status. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:479-84. 27.Klemetti E, Kolmakov S, Heiskanen P, Vainio P, Lassila V. Panoramic mandibular index and bone mineral densities in postmenopausal women. Oral Surg Oral Med Oral Pathol 1993;75:774-9. 28.Gulsahi A, Yüzügüllü B, Imirzalioglu P, Genç Y. Assessment of panoramic radiomorphometric indices of Turkish patients in different age groups, gender and dental status. Dentomaxillofac Radiol 2008;37:288-92. 29.Benson BW, Prihoda TJ, Glass BJ. Variations in adult cortical bone mass as measured by a panoramic mandibular index. Oral Surg Oral Med Oral Pathol 1991;71:349-56. 30.Ishii K, Taguchi A, Nakamoto T, Ohtsuka M, Sutthiprapaporn P, Tsuda M, et al. Diagnostic efficacy of alveolar bone loss of the mandible for identifying postmenopausal women with femoral osteoporosis. Dentomaxillofac Radiol 2007;36:28-33. 31.Xie Q, Soikkonen K, Wolf J, Mattila K, Gong M, Ainamo A. Effect of head positioning in panoramic radiography on vertical measurements: an in vitro study. Dentomaxillofac Radiol 1996;25:61-6. 32.Batenburg RH, Stellingsma K, Raghoebar GM, Vissink A. Bone height measurements on panoramic radiographs: the effect of shape and position of edentulous mandibles. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:430-5. Corresponding author: Dr Bulem Yüzügüllü Baskent University, Faculty of Dentistry, Department of Prosthodontics 11. sok no:26 06490 Bahcelievler Ankara TURKEY Fax: + 90 312 215 29 62 E-mail: [email protected] Acknowledgements The authors thank Yasemin Genç, DDS, PhD, Ankara University, Faculty of Medicine, Department of Biostatistics, Ankara, Turkey, for the statistical analysis in this investigation. Copyright © 2009 by the Editorial Council for The Journal of Prosthetic Dentistry.

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Volume 101 Issue 3 al20 and Dutra et al,26 the results in the current study for the mean values of MCW demonstrate an age-related decrease in women. To date, only a few studies25,26,28 have evaluated the changes in MCW for men. The results by Knezovic-Zlataric et al25 suggest a general decrease for both genders until the age of 75, when the values begin to decrease sharply for women compared to men. Although there was a general, age-related decrease for MCW values in both genders, Dutra et al26 observed higher values for MCW in men. The present study revealed that men showed a stable profile concerning MCW values, irrespective of an increase in age. One advantage in the use of PMI over MCW is that its method of calculation considers differences in magnification associated with different panoramic radiography machines. Thus, unlike other linear indices, it is possible to make a direct comparison of absolute figures with other studies.20 Recent studies on PMI values have been performed primarily on women,20,27,29 and demonstrate PMI values between 0.31-0.38, which are higher than the mean value of 0.23-0.24 found in the present study. These differences may not only be due to ethnic origins, but may arise due to the inclusion of partially edentulous patients, in addition to completely edentulous individuals. The present mean PMI values for edentulous patients agree with those of Gulsahi et al,28 who reported mean PMI values of 0.30, 0.32, and 0.22 for C1, C2, and C3 categories, respectively, in a large, mixed, study population. The pattern of change in mean PMI in relation to the age range also differs from that described by Ledgerton et al.20 The investigators demonstrated a gradual reduction with age until the sixth decade, when its mean value decreased sharply. By contrast, there was no significant difference among the age groups in the present study. Once again, ethnic origin would seem the likeliest reason for differences in age-related patterns of PMI. Bone heights in the first premolar

and molar regions (Hp and Hm) were similar in men and women, in contrast to the findings of Güler et al,24 in which men had greater bone height than women in the same regions of the mandible. In the present study, parameters such as general health, denture wearing habits, nutrition, or medication intake were not included, which may have affected the outcome related to gender. Hp and Hm were also similar between age groups. In general, physiologic and muscular activities decrease with age. Along with progressive residual ridge atrophy, muscular function also decreases in order to protect the bony structures of the residual ridges, especially in the mandible.4,6 It is interesting to note how the atrophic mandible is not characterized solely by resorption phenomena, since, in fact, some parts of the mandible are paradoxically subject to a process of new bone formation.7 This phenomenon may be attributable to the fact that, with the progressive reduction of the alveolar processes and the subsequent involvement of the basal bone, muscular strength is limited to a smaller bone area.7 Also, the reason for similar measurements found between age groups in the posterior mandible may be due to the existence of parafunctional conditions in which muscular hyperactivity may preserve bone from extreme resorption.7 ABL was not affected by age according to gender in the present study. This finding is in agreement with the results of Soikkonen et al,22 who concluded that in both genders, ABL does not increase significantly with age. Surgical procedures, mastication forces transmitted by dentures, and, in general, factors that affect bone metabolism are all involved in determining the rate of residual ridge resorption.23 Given the wide number of factors involved in the atrophic processes of the edentulous mandible, it is difficult to make definitive conclusions regarding the problem of ABL. Also, elderly edentulous patients with a long history of edentulism may have

The Journal of Prosthetic Dentistry

low masticatory force. Therefore, the present study has limitations, and the results may not be applicable to similar groups of middle-aged edentulous patients or patients with a short-term edentulous experience. An extreme reduction in the height of the alveolar process, which in serious situations involves the basal bone,7 is accompanied by an inversion in the morphology of the crest, as well as an increase in the consistency of the cortical walls and vestibular and lingual surfaces.7 The progressive reduction in the height of the mandibular bone presumably results in an increase in the intensity of mechanical stimuli caused by muscular actions along the main load course of the mandibular body,7,23 which might also be one of the reasons for the lack of significant differences among the age groups. Unlike several studies which report that women have more advanced bone loss than men,10,11 the present results, agreeing with those of a previous report,12 indicate that there is no difference between genders. This finding could be attributed to the individual variation in the rate of bone loss and body mass index.12 Besides age, gender, and duration of edentulousness, factors often correlated with residual ridge resorption are facial structure, denture wearing habits, number of dentures worn, oral hygiene and parafunctions, occlusal loading, nutrition, general health, and the use of medication for osteoporosis.9 Due to the restrictions in the selection of parameters, the present data cannot support a statistical model that includes the analysis of all of these variables. As a result, differences in MCI classifications and MCW values in relation to age and gender in this study may have been due to osteoporosis. Further studies incorporating such patients are needed to make more sound conclusions.

were drawn for a Turkish population: 1. Category C3 of the mandibular cortical index, in which the cortical layer forms heavy endosteal cortical residues and is clearly porous, was more frequently seen in women over 60 years in age (P<.001). 2. The values of mean cortical width at the mental foramen region decreased significantly with age in women (P<.01). 3. The ratio of the thickness of the mandibular cortex to the distance between the mental foramen and the inferior mandibular cortex (PMI), alveolar bone loss (ABL) of the mandible, and bone heights were not affected by gender or age.

REFERENCES 1. Zlataric DK, Celebic A. Clinical bone densitometric evaluation of the mandible in removable denture wearers dependent on the morphology of the mandibular cortex. J Prosthet Dent 2003;90:86-91. 2. Hirai T, Ishijima T, Hashikawa Y, Yajima T. Osteoporosis and reduction of residual ridge in edentulous patients. J Prosthet Dent 1993;69:49-56. 3. Knezovic-Ziataric D, Celebic A. Mandibular bone mineral density changes in complete and removable partial denture wearers: a 6-month follow-up study. Int J Prosthodont 2003;16:661-5. 4. Devlin H, Horner K. A study to assess the relative influence of age and edentulousness upon mandibular bone mineral density in female subjects. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:11721. 5. Heersche JN, Bellows CG, Ishida Y. The decrease in bone mass associated with aging and menopause. J Prosthet Dent 1998;79:14-6. 6. Tallgren A. The continuing reduction of the residual alveolar ridges in complete denture wearers: a mixed longitudinal study covering 25 years. J Prosthet Dent 1972;27:12032. 7. Bianchi A, Sanfilippo F. Osteoporosis: the effect on mandibular bone resorption and therapeutic possibilities by means of implant prostheses. Int J Periodontics Restorative Dent 2002;22:231-9. 8. Carlsson GE, Persson G. Morphologic changes of the mandible after extraction and wearing of dentures. A longitudinal, clinical, and x-ray cephalometric study covering 5 years. Odontol Revy 1967;18:2754.

CONCLUSIONS

Within the limitations of the present study, the following conclusions

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9. Devlin H, Ferguson MW. Alveolar ridge resorption and mandibular atrophy. A review of the role of local and systemic factors. Br Dent J 1991;170:101-4. 10.Xie Q, Ainamo A, Tilvis R. Association of residual ridge resorption with systemic factors in home-living elderly subjects. Acta Odontol Scand 1997;55:299-305. 11.Xie Q, Wolf J, Tilvis R, Ainamo A. Resorption of mandibular canal wall in the edentulous aged population. J Prosthet Dent 1997;77:596-600. 12.Carlsson GE, Haraldson T. Fundamental aspects of mandibular atrophy. In: Worthington P, Branemark PI, editors. Advanced osseointegration surgery: applications in the maxillofacial region. Chicago: Quintessence; 1992. p. 109-18. 13.Mercier P. Ridge reconstruction with hydroxylapatite. Part 1. Anatomy of the residual ridge. Oral Surg Oral Med Oral Pathol 1988;65:505-10. 14.Lerouxel E, Libouban H, Moreau MF, Baslé MF, Audran M, Chappard D. Mandibular bone loss in an animal model of male osteoporosis (orchidectomized rat): a radiographic and densitometric study. Osteoporos Int 2004;15:814-9. 15.Horner K, Devlin H. The relationship between mandibular bone mineral density and panoramic radiographic measurements. J Dent 1998;26:337-43. 16.Klemetti E, Kolmakov S, Kröger H. Pantomography in assessment of the osteoporosis risk group. Scand J Dent Res 1994;102:68-72. 17.Taguchi A, Tsuda M, Ohtsuka M, Kodama I, Sanada M, Nakamoto T, et al. Use of dental panoramic radiographs in identifying younger postmenopausal women with osteoporosis. Osteoporos Int 2006;17:38794. 18.Devlin H, Karayianni K, Mitsea A, Jacobs R, Lindh C, van der Stelt P, et al. Diagnosing osteoporosis by using dental panoramic radiographs: the OSTEODENT project. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:821-8. 19.Horner K, Devlin H, Harvey L. Detecting patients with low skeletal bone mass. J Dent 2002;30:171-5. 20.Ledgerton D, Horner K, Devlin H, Worthington H. Radiomorphometric indices of the mandible in a British female population. Dentomaxillofac Radiol 1999;28:17381. 21.Horner K, Devlin H, Alsop CW, Hodgkinson IM, Adams JE. Mandibular bone mineral density as a predictor of skeletal osteoporosis. Br J Radiol 1996;69:1019-25. 22.Soikkonen K, Ainamo A, Xie Q. Height of the residual ridge and radiographic appearance of bony structure in the jaws of clinically edentulous elderly people. J Oral Rehabil 1996;23:470-5. 23.Klemetti E, Kolmakow S. Morphology of the mandibular cortex on panoramic radiographs as an indicator of bone quality. Dentomaxillofac Radiol 1997;26:22-5.

24.Güler AU, Sumer M, Sumer P, Biçer I. The evaluation of vertical heights of maxillary and mandibular bones and the location of anatomic landmarks in panoramic radiographs of edentulous patients for implant dentistry. J Oral Rehabil 2005;32:741-6. 25.Knezovic-Zlataric D, Celebic A, Lazic B, Baucic I, Komar D, Stipetic-Ovcaricek J, et al. Influence of age and gender on radiomorphometric indices of the mandible in removable denture wearers. Coll Antropol 2002;26:259-66. 26.Dutra V, Yang J, Devlin H, Susin C. Radiomorphometric indices and their relation to gender, age, and dental status. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:479-84. 27.Klemetti E, Kolmakov S, Heiskanen P, Vainio P, Lassila V. Panoramic mandibular index and bone mineral densities in postmenopausal women. Oral Surg Oral Med Oral Pathol 1993;75:774-9. 28.Gulsahi A, Yüzügüllü B, Imirzalioglu P, Genç Y. Assessment of panoramic radiomorphometric indices of Turkish patients in different age groups, gender and dental status. Dentomaxillofac Radiol 2008;37:288-92. 29.Benson BW, Prihoda TJ, Glass BJ. Variations in adult cortical bone mass as measured by a panoramic mandibular index. Oral Surg Oral Med Oral Pathol 1991;71:349-56. 30.Ishii K, Taguchi A, Nakamoto T, Ohtsuka M, Sutthiprapaporn P, Tsuda M, et al. Diagnostic efficacy of alveolar bone loss of the mandible for identifying postmenopausal women with femoral osteoporosis. Dentomaxillofac Radiol 2007;36:28-33. 31.Xie Q, Soikkonen K, Wolf J, Mattila K, Gong M, Ainamo A. Effect of head positioning in panoramic radiography on vertical measurements: an in vitro study. Dentomaxillofac Radiol 1996;25:61-6. 32.Batenburg RH, Stellingsma K, Raghoebar GM, Vissink A. Bone height measurements on panoramic radiographs: the effect of shape and position of edentulous mandibles. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:430-5. Corresponding author: Dr Bulem Yüzügüllü Baskent University, Faculty of Dentistry, Department of Prosthodontics 11. sok no:26 06490 Bahcelievler Ankara TURKEY Fax: + 90 312 215 29 62 E-mail: [email protected] Acknowledgements The authors thank Yasemin Genç, DDS, PhD, Ankara University, Faculty of Medicine, Department of Biostatistics, Ankara, Turkey, for the statistical analysis in this investigation. Copyright © 2009 by the Editorial Council for The Journal of Prosthetic Dentistry.