Assessment of buccal and lingual alveolar bone width in the posterior region at dentate and edentulous sites: A cone-beam computed tomography study.

BACKGROUND: Alveolar bone dimensions form an important prognostic factor in determining the success of implant treatment outcome. The present study evaluated the buccal and lingual bone width in posterior dentate and edentulous sites using cone-beam computed tomography (CBCT).
MATERIALS AND METHODS: The study included 100 patients, divided equally into two groups, Group A (males) and Group B (females) indicated for implant therapy. CBCT scans were evaluated for the assessment of the thickness of buccal and lingual bone width at four levels, i.e., crestal bone width (CBW), mid root bone width, middle of alveolar bone housing bone width , and most apical portion bone width (APBW). Bone width was measured at three levels in the edentulous region as CBW, bone width 5 mm from crest (CBW-1), and 10 mm from crest (CBW-2).
RESULTS: Gradual increase in bone width was observed from crestal bone at buccal and lingual level (CBW-B and CBW-L) from 1.10 ± 0.29 mm and 1.21 ± 0.34 mm to APBW at buccal and APBW lingual side from 2.82 ± 0.51 mm and 3.43 ± 0.42 mm, respectively. For both the groups, the differences in bone width at three levels were statistically significant, with CBW being significantly higher for Group A than Group B.
CONCLUSION: At edentulous sites, CBW was lesser as compared to the apical levels. The bone width on buccal and lingual sides of dentate sites at the coronal level is minimal compared to the apical level, which has definite implications for implant therapeutics. Copyright:

INTRODUCTION

Restoration of the masticatory apparatus with implant therapy in conditions where extraction of natural teeth is inevitable has been established as an acceptable treatment modality. Clinicians have utilized different approaches such as immediate [1] or early [23] or delayed [4] placement protocols of dental implants depending on the individual situation. The literature is replete with substantial alterations occurring in the soft- and hard-tissue dimensions after extraction of teeth. These alterations are marked in deficiencies in the height and width of alveolar bone, especially on the buccal aspect [56] which may have to be rectified consequently with augmentation procedures, to achieve and maintain osseointegration of the implant. Optimal alveolar bone height, width, volume, and favorable architecture are essential prerequisites for functionally viable and esthetically pleasing dental implant restorations. Considering the above factors, dimensions of the alveolar bone before extraction of the teeth are regarded as important prognostic determinants of the extent of bone resorption postextraction.[78] Precise knowledge about the healing intricacies and their clinical consequences would aid the clinician in the selection of appropriate therapeutic approach.

Various methods have been adopted in the past for assessing the dimensions of alveolar bone including clinical measurements,[9] histological investigations,[10] cephalometric analysis,[11] and subtraction radiography.[7] Since these methods have inherent limitations, currently cone-beam computed tomography (CBCT) has been widely used as a preferred imaging modality in the dental profession,[12] especially for the assessment of bone quality,[13] therapeutic planning of periodontal and implant surgeries,[1415] and evaluating their results.[16] CBCT has been proved to provide high resolution, superior quality images for a detailed evaluation of different parameters with low radiation exposure. The cone-beam system allows a three-dimensional view of the anatomical structure in relation with the teeth and in edentulous sites and provides the operator with a clear indication of the proximity of vital structures to the area of interest. Diagnosing a lingual undercut, thin buccal or lingual cortical plate and an inadequate alveolar bone width with a CBCT has aided in minimizing the impediment in challenging and unconventional cases of restoring edentulous sites.

Preliminary studies have evaluated the influence on esthetics in implant restorations.[317] However, it is felt that there is a paucity of literature on the bone dimensions in the posterior region at dentate sites owing to the region being placed in the nonesthetic zone. However, since these dimensions are important from the functional point of view, the present study was aimed to assess the buccal and lingual bone width of the maxillary and mandibular posterior region at dentate and edentulous sites based on CBCT images.

MATERIALS AND METHODS

The present prospective CBCT observational study included 100 patients referred to the Department of Periodontics and Implantology of our Institute from July 2017 to September 2018 for implant therapy. (Clinical Trials Registry – India, CTRI/2018/04/013368). All the patients were equally divided into two groups based on the gender of the participant. Oral and written information of the study was given to all the participants, and informed consent was obtained from them. The study was initiated after approval of the protocol by the Institutional Ethics Committee as being in accordance with the Helsinki Declaration. A total of 100 patients that met the inclusion criteria of our study were selected from a total of 122 patients with partially edentulous sites. Inclusion criteria of the study were as follows: (i) Periodontally healthy individuals, (ii) Participants with missing maxillary or mandibular premolar/molar, and (iii) Individuals in age range of 20–50 years. Patients exhibiting tooth malalignment, presence of periapical infections were excluded from the study.

Radiographic image analysis

All the patients were taken up for CBCT scans (Orthophos SL 3D, Dentsply Sirona Extraoral Imaging System, Germany) with a field of view (FOV) of 8 cm × 8 cm. To avoid artifacts due to metallic restorations which may lead to streaking or beam hardening, such teeth were avoided to be placed in the center of FOV. Furthermore, in every patient, the occlusal plane alignment was done horizontally to minimize artifacts on axial CBCT slices.[1819] The teeth immediately adjacent to the edentulous area that is on the mesial and distal aspect of that area were assessed in the scans. For example, measurements of the second premolar and second molar were taken with respect to missing first molar. The scan image analysis was performed with Imaging software (3 DIEMME, Bio-Imaging Technology, Versions 4.2, Figino Serenza [Co], Italy). In sagittal view, a vertical line traced through the major axis (long axis) of the selected tooth was taken as a reference. A horizontal line (E) was traced from buccal to palatal wall at the level of the bone ridges [Figure 1]. The thickness of the buccal and lingual bone walls for dentate sites in the respective coronal scans was measured perpendicular to the long axis of the root at four different levels on the examined teeth [Figure 2].

Figure 1

Arrow showing horizontal line (E) from buccal to palatal wall at level of bone ridges

Figure 2

Arrows showing thickness of buccal bone wall at dentate sites in the coronal scans, measured perpendicular to long axis of the root at four different levels: Alveolar crest (crestal bone width), mid root level (mid root bone width), middle of alveolar bone housing and most apical portion of the tooth bone width at buccal aspect. Similar measurements were performed on the lingual/palatal dentate sites (P)

At the alveolar crest - Crestal bone width buccal (CBW-B) and crestal bone width lingual (CBW-L)

Mid root level - Mid root bone width buccal (MRBW-B) and mid root bone width lingual (MRBW-L)

Middle of the alveolar bone housing buccal (MABHBW-B) and middle of the alveolar bone housing lingual (MABHBW-L)

Most apical portion of the tooth bone width buccal (APBW-B) and apical portion bone width lingual (APBW-L).

At the mesiodistal midpoint of the edentulous site, bone width was measured at the following levels [Figure 3].

Figure 3

Bone width measured at the three different levels for edentulous sites: Crestal bone width, bone width 5 mm from the crest (crestal bone width-1) and bone width 10 mm from the crest (crestal bone width-2)

CBW

Bone width 5 mm from the crest (CBW-1)

Bone width 10 mm from the crest (CBW-2).

All the measurements were recorded by a single examiner (RK) and were repeated after 1 week. The intraclass correlation (ICC) coefficient with the two-way mixed-effects model was obtained for each measurement. The ICC ranged between 0.92 and 0.99 in the groups (P < 0.0001) indicating excellent intra-rater reliability.

Statistical analysis

The statistical data analysis was undertaken using the Statistical Package for the Social Sciences (SPSS Version 22, Armonk, NY: IBM Corp, USA). Descriptive analysis of the acquired data paved way for inferential statistics. Comparison of the mean values of buccal and lingual bone width at different levels for both the groups was performed with one-way Analysis of variance (ANOVA). The comparison between buccal and lingual bone width for males and that for females was done using the paired t-test. A two-way ANOVA was performed for determining the effect of factors such as gender and different levels simultaneously on the dependent variable, i.e., distance on buccal and lingual sides. At the edentulous sites, the difference of mean bone width across different levels was done using one-way ANOVA and among the groups through Tukey's post hoc test.

RESULTS

A total of 100 patients requiring a single posterior tooth implant in an age range of 20–50 years were grouped as Group A - 50 males and Group B - 50 females. Bone width measurements were recorded at the mesial and distal dentate sites and at the edentulous sites at different levels.

Bone width for dentate sites

Bone width for these sites, at different levels for Group A (males) and Group B (females) on the buccal and lingual sides is presented in tabular form [Tables 1 and 2]. The mean bone width for Group A at CBW-B level was 1.13 ± 0.24 mm, which increased steadily to APBW-B level to 2.99 ± 0.51 mm. A similar trend of increase in bone width for Group A at CBW-L level, which was 1.25 ± 0.32 mm was found to be 3.45 ± 0.42 mm at the APBW-L level. In both instances, i.e., on buccal and lingual sides, the differences of bone width between the levels were found to be statistically significant (P < 0.0001). For Group B, the bone width was again seen to follow a similar trend of gradual increase from CBW-B and CBW-L to APBW-B and APBW-L levels. At the CBW-B level, the bone width was recorded as 1.10 ± 0.29 mm which increased to 2.82 ± 0.51 mm at APBW-B level on buccal side and at the CBW-L level, it was 1.21 ± 0.34 mm, which increased to 3.43 ± 0.42 mm. The differences between the bone width at different levels on buccal and lingual sides were found to be statistically significant with P < 0.001 and P < 0.0001, respectively.

Table 1

Bone width across different levels at dentate sites according to buccal and lingual side (Group A-males)

Buccal	CBW-B (mm)	MRBW-B (mm)	MABHBW-B (mm)	APBW-B (mm)	P*
Mean	1.13a	1.34b	1.73c	2.99d	<0.0001 (S)
Median	1.15	1.31	1.72	3.10
SD	0.24	0.30	0.51	0.51
Range	0.08-1.90	0.27-1.99	0.79-3.60	2.01-4.50
Lingual	CBW-L (mm)	MRBW-L (mm)	MABHBW-L (mm)	APBW-L (mm)	P*
Mean	1.25a	1.51b	1.93c	3.45d	<0.0001 (S)
Median	1.23	1.44	1.90	3.33
SD	0.32	0.38	0.57	0.42
Range	0.14-2.34	0.23-2.30	0.87-3.69	2.41-4.62

a,b,c,d Statistically significant difference between mean bone width values as indicated by different superscripts. *P value obtained using one-way ANOVA; Statistically highly significant difference at P<0.0001. CBW – Bone width at the alveolar crest; MRBW – Bone width at mid root level; MABHBW – Bone width at middle of the alveolar bone housing; APBW – Bone width at most apical portion of the tooth; B – Buccal side; L – Lingual side; mm – millimetre; SD – Standard deviation; S – Statistically significant; ANOVA – Analysis of variance; P - value

Table 2

Bone width across different levels at dentate sites according to buccal and lingual side (Group B- females)

Buccal	CBW-B (mm)	MRBW-B (mm)	MABHBW-B (mm)	APBW-B (mm)	P†
Mean	1.10a	1.31b	1.73c	2.82d	<0.001 (S)
Median	1.12	1.29	1.71	2.78
SD	0.29	0.32	0.54	0.51
Range	0.08-2.83	0.18-1.99	0.60-3.60	1.98-4.56
Lingual	CBW-L (mm)	MRBW-L (mm)	MABHBW-L (mm)	APBW-L (mm)	P†
Mean	1.21a	1.50b	1.94c	3.43d	<0.0001 (S)
Median	1.21	1.41	1.90	3.31
SD	0.34	0.41	0.61	0.42
Range	0.14-2.34	0.23-2.32	1.01-3.69	2.38-4.62

a,b,c,d Statistically significant difference between mean bone width values as indicated by different superscripts. † P value obtained using one-way ANOVA; Statistically highly significant difference at P<0.0001. CBW – Bone width at the alveolar crest; MRBW – Bone width at mid root level; MABHBW – Bone width at middle of the alveolar bone housing; APBW – Bone width at most apical portion of the tooth; B – Buccal side; L – Lingual side; mm – millimetre; SD – Standard deviation; S – Statistically significant; ANOVA – Analysis of variance; P - value

On comparison of the bone width for Group A on buccal and lingual sides at CBW, MRBW, MABHBW, and APBW levels, the differences were found to be statistically significant with P < 0.0001 [Table 3]. A similar trend of significant differences was found on the comparison of bone width for Group B patients on buccal and lingual sides at different levels [Table 4]. The gender effect on bone width at all the levels on buccal and lingual sides was found to be statistically significant with P < 0.0001 examined through two-way ANOVA. The model fitness was good as indicated by adjusted R2 of 0.732 on the buccal side and 0.786 on lingual side.

Table 3

Comparison of bone width between buccal and lingual side of dentate sites according to levels (Group A- males)

At each level	Buccal		Lingual		P‡
	Mean	SD	Mean	SD
CBW (mm)	1.13	0.24	1.25	0.32	<0.0001 (S)
MRBW (mm)	1.34	0.30	1.51	0.38	<0.0001 (S)
MABHBW (mm)	1.73	0.51	1.93	0.57	<0.0001 (S)
APBW (mm)	2.99	0.51	3.45	0.42	<0.0001 (S)

‡ P value obtained using paired t-test; Statistically highly significant difference at P<0.0001. CBW – Bone width at the alveolar crest; MRBW – Bone width at mid root level; MABHBW – Bone width at middle of the alveolar bone housing; APBW – Bone width at most apical portion of the tooth; mm – millimeter; SD – Standard deviation; S – Statistically significant; P - value

Table 4

Comparison of bone width between buccal and lingual side of dentate sites according to levels (Group B- females)

At each level	Buccal		Lingual		P§
	Mean	SD	Mean	SD
CBW (mm)	1.10	0.29	1.21	0.34	<0.0001 (S)
MRBW (mm)	1.31	0.32	1.50	0.41	<0.0001 (S)
MABHBW (mm)	1.73	0.54	1.94	0.61	<0.0001 (S)
APBW (mm)	2.82	0.51	3.43	0.42	<0.0001 (S)

§ P value obtained using paired t-test; Statistically highly significant difference at P<0.0001. CBW – Bone width at the alveolar crest; MRBW – Bone width at mid root level; MABHBW – Bone width at middle of the alveolar bone housing; APBW – Bone width at most apical portion of the tooth; mm – millimeter; SD – Standard deviation; S – Statistically significant; P - value

Bone width for edentulous sites

For Groups A and B, the differences in mean values of bone width were significant across the CBW, CBW-1 and CBW-2 levels as indicated by P < 0.0001 [Table 5]. The paired analysis revealed a statistically significant difference between mean bone width values as indicated by different superscripts [Tables 1, 2 and 5]. However, for Group A at CBW level, the mean bone width was significantly higher than that for Group B, whereas at CBW-1 and CBW-2 levels, the differences in bone width were statistically insignificant.

Table 5

Descriptive statistics at each level of edentulous sites according to gender

Gender	CBW (mm)		CBW-1 (mm)		CBW-2 (mm)		Pk
	Mean	SD	Mean	SD	Mean	SD
Male	4.50a	1.53	9.57b	2.29	11.30c	2.43	<0.0001 (S)
Female	3.71a	1.31	9.06b	2.22	10.47c	2.50	<0.0001 (S)
P¶	0.007 (S)		0.263		0.093

k P value obtained using One-way ANOVA.

a,b,c Statistically significant difference between mean bone width values as indicated by different superscripts.

¶ Obtained using independent t-test; statistically highly significant difference at P<0.0001. CBW – Crestal bone width; CBW-1 – Bone width 5 mm from the crest; CBW-2 – Bone width 10 mm from the crest; mm – Millimeter; SD – Standard deviation; S – Statistically significant; P - value

Two-way ANOVA was performed for determining the effect of factors such as gender and level simultaneously on the dependent variable, i.e., buccal bone width [Table 6]. The gender effect was statistically significant with P < 0.001. Furthermore, the effect due to levels was statistically significant with P < 0.0001. The interaction effect between gender and levels was statistically significant with P = 0.002. Similar test was performed with regard to the lingual bone width [Table 6]. The gender effect on the dependent variable was statistically insignificant; however, the effect due to levels was statistically significant with P < 0.0001. The interaction effect was insignificant.

Table 6

Tests of between-subjects effects- dependent variable: Buccal and lingual side

Buccal side
Source	Type III Sum of square	DF	Mean square	F	P
Corrected model	1152.950#	7.00	164.707	936.508	<0.0001 (S)
Intercept	7495.720	1.00	7495.720	42619.872	<0.0001 (S)
Gender	2.003	1.00	2.003	11.388	0.001 (S)
Level	1148.294	3.00	382.765	2176.360	<0.0001 (S)
Gender versus level	2.653	3.00	0.884	5.029	0.002 (S)
Error	420.690	2392.00	0.176
Total	9069.361	2400
Corrected total	1573.641	2399
Lingual side
Corrected model	1748.672**	7.0	249.8	1260.74	<0.0001 (S)
Intercept	9862.340	1.0	9862.3	49773.241	<0.0001 (S)
Gender	0.118	1.0	0.118	0.597	0.439
Level	1748.339	3.0	582.78	2941.172	<0.0001 (S)
Gender versus level	0.215	3.0	0.072	0.361	0.781
Error	473.964	2392	0.198
Total	12084.976	2400
Corrected total	2222.636	2399

# R2=0.733 (Adjusted R2=0.732); **R2=0.787 (Adjusted R2=0.786); Gender effect statistically significant with P<0.0001; Effect due to points statistically significant with P<0.002. DF – Degrees of freedom; F – F statistics; S – Statistically significant; P - value

DISCUSSION

Specific knowledge about the alveolar bone dimensions is a pre-requisite for the successful placement of dental implants and their maintenance thereafter. Over the years, it has been established that the presence of adequate bone height and width is vital for long-term stability of sound and proportionate gingival margins surrounding implant restorations.[2021] The bone height has been thought to influence the gingival margin, while the bone width affects the facial convexity.[17] Previous investigations have evaluated the total bone width at dentate sites or at edentulous areas. It is felt that inadequate data is available in the literature pertaining to the important anatomical structures along with buccal and lingual bone width at dentate sites in the posterior region.

In the present study, the buccal and lingual bone width at dentate sites mesial and distal to the edentulous site was measured at four different levels, i.e., CBW-B and CBW-L, MRBW-B and MRBW-L, MABHBW-B and MABHBW-L and APBW-B and APBW-L, across the entire root length. The purpose of such measurements was the fact that it is proposed that the coronal levels of alveolar bone have greater implications on the final esthetics and function of implant restorations due to the bone resorption occurring in postextraction healing phase.[22] However, the apical extent of such resorptive changes have not been estimated as yet, and such a comprehensive information would enable the clinician to assess these structures as diagnostic predictors in implant planning and therapeutics.

It was observed that the bone width on buccal and lingual sides increased steadily from coronal most levels, i.e., CBW-B and CBW-L to APBW-B and APBW-L, which in fact is a similar finding to that obtained by Braut et al.[17] However, in the present study, we evaluated the bone width in posterior region in contrast to the anterior region evaluated by the authors. An additional and interesting finding of our study was the feature of minimal difference of bone width between coronal most two levels, i.e., CBW-B and MRBW-B and CBW-L and MRBW-L, thereby indicating that the mid-root levels of alveolar bone would be susceptible for resorption postextraction as compared to the mid alveolar bone housing and apical levels. From the MABHBW-B and MABHBW-L levels, there was a considerable increase in the bone width which makes these areas of the alveolar housing more resistant to resorption.

It was also revealed that the lingual bone width measurement was considerably higher at all the levels in both the groups when compared to the buccal bone width, which could be considered as one of the major reasons for minimal resorption occurring on the lingual aspects after extraction of teeth. A similar finding was reported by Braut et al.,[8] wherein the authors ascribed the thick lingual bone width to the pronounced lingual inclinations of the alveolar process. Even on the lingual aspects, the bone width followed the trend of a steady increase from coronal most level to the apical most level. Implant angulation also becomes predominantly important to ensure proper distribution of shear forces on the bone.[23] Thus, placing an implant at an ideal prosthesis-driven location becomes utmost important. Lingual undercuts are common finding in the posterior region that can cause hindrance in the implant positioning. Thus, a clinician needs to be vigilant about the presence of these undercuts in the mandibular lingual cortical plates, which may be a reason for lingual perforation during implant placement.[24] Fortunately, only 10% of these lingual undercuts were categorized as potentially influential for perforations of cortical plate.[25]

On comparison of the bone width between Group A (males) and Group B (females) on the buccal side, the mean values for Group A were consistently more than Group B expect at the MABHBW-B levels where the values were equal. On the lingual side, the mean bone width values for Group A and Group B were almost similar, thereby indicating the minimal influence of gender.

At the edentulous sites, the mean bone width values at different levels, i.e., CBW, CBW-1, and CBW-2 were consistently higher in Group A when compared to Group B. For both the groups, the differences in bone width at CBW, CBW-1 and CBW-2 were found to be statistically significant. The mean values of bone width were similar to those reported by Braut et al.[25] and Katranji et al.[26] One of the highlights of the present study is the measurements of bone width which was done at the center of the mesiodistal edentulous site, which is more vulnerable for bone resorption after tooth extraction. The study also highlights the difference in the bone width dimensions between males and females.

However, there are a few limitations to the present study wherein the maxillary and mandibular site dimensions were clubbed together. For edentulous sites, the resorption extent could differ among the maxillary and mandibular areas, their anatomic and histologic makeup of alveolar bone at such sites. Second, age was not considered as an influential factor for variations in bone dimensions.

CONCLUSION

For achieving successful and longer stability of dental implants a precise pre-operative analysis with CBCT cannot be overemphasized. The bone width on the buccal and lingual side of dentate sites at the coronal level is minimal and vulnerable for resorption. The dimensions of such dentate sites may be considered as useful indicators for need of bone augmentation procedures after extraction. Furthermore, such dimensions can influence the decision with regard to placement of immediate or early dental implants in individual cases. Further studies with larger sample size are desirable to better understand and substantiate these observations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.