Cone beam computed tomography analysis for immediate implant placement in the anterior maxilla based on radial root position: An observational study

Abstract

Aim:

To validate the CBCT classification for immediate implant placement (IIP) given by Howard Gluckman in the local population of Gujarat, India, and additionally evaluate the available bone beyond the tooth apex for IIP in the direction of proposed osteotomy.

Setting and Design:

Cross-sectional Observational study.

Materials and Methods:

A total of 103 cone beam computed tomography (CBCT) scans involving the six maxillary anterior teeth were scrutinized in the radial plane. Each CBCT was divided into six slices (n = 618), which were classified according to Gluckman’s classification, followed by making the osteotomy lines. Six measurements (L, W1, W2, W3, W4, and W5) were made from root to nasal floor. Bone length (L) was measured in the direction of proposed osteotomy, whereas the bone width was measured at five different points along the proposed osteotomy.

Statistical Analysis Used:

Chi-square p value, One-way ANOVA and Post hoc Tukey test.

Results:

As per Gluckman’s classification, it was found that class I showed the highest bone width with the lowest bone length, whereas Class V showed the lowest bone width. The highest bone length was observed in Class IV. The prevalence of different radial root position (RRP) starting from class I to class V was 1%, 75%, 15%, 16%, and 3%, respectively.

Conclusion:

A distinct correlation was found between the anterior root position and the available bone between the root tip and the nasal floor as per Gluckman’s classification.

Clinical Significance:

This study helps in the radiographic evaluation of available bone around the roots of maxillary anterior teeth, which is a critical determining factor for treatment planning in IIP cases. A deep knowledge of RRP, bone morphology, and available alveolar bone beyond the apex provides useful perception to the clinician to plan surgical and grafting procedures to achieve primary stability. This will also help the clinicians to visualize the final prosthetic outcome with respect to the position of access hole.

INTRODUCTION

Analysis of tooth position plays a pivotal role in immediate implant placement (IIP). Maxillary anterior teeth, primarily have thin facial and thick palatal bone which makes the palatal bone thickness a determining factor for implant placement.[1] IIP[2] is the placement of dental implants immediately after the extraction of tooth into the alveolar socket. IIP is gaining favor as a means of tooth replacement as it is a quick and efficient procedure requiring less downtime compared to the conventional technique.[2]

IIP can make the implant treatment procedure a more positive experience for the clinician and the patient.[3,4,5,6,7,8] The placement site is very crucial and has a high impact on determining the position of the access hole and thereby aesthetics as well. Recommendations for IIP specify the ideal anatomic state (thick facial and palatal bone, gingival phenotype, and sufficient amount of bone from root apex to nasal floor) and implant treatment by experienced and trained clinicians.

IIP is a technique-sensitive treatment option and may sometimes cause complications.[9,10] For implant placement, precise use of implant drills governs the success rate of the implant. Alveolar bone perforation or thinning of either the palatal or facial site, incorrectly placed implant, improper emergence, and dehiscence may be caused by incorrect angulation of the drill. In some cases, either the available bone height or width, or both may be deficient leading to poor primary stability during placement of the immediate dental implant.

Bucco-palatal collapse and gingival recession are the most frequent long-term IIP complications, although these may occur with the conventional approach as well.[9,11,12,13] Correct selection of patient, history and intraoral examination, thorough treatment planning, and contemplation of all factors involved is imperative to achieve the ideal success rate for immediate implant treatment and its lifelong aesthetic solidity.[14,15,16]

Factors such as gingival type and contour, facial and palatal bone height and width, amount of available bone at the level of apex and beyond the apex, and also the buccal gap have a significant effect on the outcome of IIP.[9,10,14,16,17,18] Among these factors, extraction socket and alveolar bone dimensions have a pronounced effect on postextraction ridge changes.[7,8,14,18,19,20,21,22] Abundant literature is present evaluating most of these variables, yet information on factors such as tooth root position and available remaining bone after tooth extraction which have a pivotal effect on IIP is scarce.[23,24,25]

Previous studies were solely concerned with the assessment of bone present buccally and palatally to the extraction socket. Gluckman et al.[1] were one of the first people to publish a study concerning the assessment of bone 4 mm beyond apex. The root angulation and root position classification for IIP proposed by Lau et al. evaluated the correlation between the facial and palatal walls of the upper anterior teeth. It also provided clinical guidelines for implant placement.[26] Nevertheless, this double classification system appears complex.

Kan et al. classified maxillary anterior in a sagittal root position with respect to its osseous housing to aid in treatment planning for IIP.[24] Gluckman et al. viewed maxillary anterior teeth in the radial plane of cone beam computed tomography (CBCT) to evaluate the alveolar bone morphology and radial root position (RRP) of maxillary anterior teeth.[1]

Evaluation of tooth position in the radial plane helps in decision-making with respect to the three-dimensional (3D) position of the implant placement. It has clinical applicability in terms of ideal patient selection, direction of initial osteotomy, and risks and challenges associated with the given case. Recent recommendation for IIP indicates osteotomy preparation into the thick palatal socket wall, leaving space on the buccal side for grafting and better osseogenesis.[14] However, structural limitations come into play, such as root position, inclination and available bone width and height from root apex to nasal floor. Bone available (from the apex of the tooth to the nasal floor) in the direction of proposed osteotomy is a critical factor in achieving optimum primary stability during IIP. Thickness of available buccal bone is also a very critical factor for long-term biomechanical and aesthetic outcomes. A thorough knowledge of the above-mentioned factors (available bone on buccal and palatal site, bone beyond the root apex to nasal floor) would also help a clinician, plan and prepare ahead for IIP and perform soft and hard tissue augmentation procedures if indicated followed by temporization to achieve good harmony between pink and white esthetics.

The importance of buccal bone in IIP is an established fact hence the palatal and apical bone was the primary focus of this investigation because they also contribute to increased bone anchorage and an improved prosthetic outcome. This study also aims to investigate the validity of Howard Gluckman’s classification in the local population of Gujarat, India, and correlate the presence of bone beyond the apex of the tooth to the Gluckman classification. According to the null hypothesis, there would be no difference in the prevalence of the Gluckman classification with that of the local population of Gujarat, and there is no association of the abovementioned classification to the bone present between the root tip and the nasal floor.

MATERIALS AND METHODS

The study was implemented to evaluate the bone available in the direction of the proposed osteotomy along with its inclination as per the Gluckman’s IIP classification. The study was carried out after due approval from the institutional review board and ethical committee (FDS/DDU/EC/11/2022).

This observational study evaluated 103 maxillary anterior CBCTs, each having six maxillary anterior teeth (n = 618) as viewed in the radial plane of cone beam computed tomography (CBCT) scans. The scans were procured from various radiology centers based in Ahmedabad, Gujarat. The sample size for the study was calculated using General power analysis (G power). The power level was set as 95% in order to minimize false negative results. CBCTs of the six maxillary anterior teeth till the nasal floor were included. The inclusion criteria included maxillary CBCT scans of individuals between the ages of 25 and 60 with satisfactory periodontal health. The exclusion criteria involved the presence of apical pathology, fracture of root or tooth, apicoectomy, root resorption, radicular bone resorption, severely malaligned teeth, ongoing orthodontic treatment, or recently treated orthodontic patients’ CBCT, severe scattering and/or distorted image. All CBCTs were chosen randomly and evaluated by a single blind observer to eliminate bias.

In order to maintain standardization, centers using a CBCT machine (CS 9300 premium, Carestream, New York) with a field of view of 17 cm × 6 cm and 17 cm × 11 cm (to have CBCT of maxillary arch), and 90 μm resolution were chosen. The images were analyzed using CS 3D imaging software (v3.8.7, Carestream Health, New York, USA). Participants’ head positions were maintained by ensuring that the Frankfort horizontal plane was parallel to the laser marking of CBCT machine.

Data were reconstructed using slices of the radial plane in the cross-sectional direction, perpendicular to the alveolar ridge at 1 mm intervals. The radial plane of each tooth was analyzed in the center of its cross-sectional radial view to evaluate the surrounding alveolar bone, either bucco-palatally or apically and beyond the root apex to the nasal floor. Proposed osteotomy direction was in the middle of the width of bucco-palatal bone and palatally in case of retroclined tooth position.[1] A total of six measurements (L-length, W-width [W1, W2, W3, W4, W5]) from root to nasal floor were taken to evaluate bone available for IIP. Bone length (L) was measured in the direction of proposed osteotomy from entry point in bone to nasal floor. Bone width (W) was measured at five distinct points along the line representing the direction of proposed osteotomy [Table 1].

Table 1.

Five different locations for measuring width along the line of proposed osteotomy

Width	Location
W1	At the entry point of the proposed osteotomy (only palatally)
W2	At root tip
W3	At mid-point of the line of proposed osteotomy
W4	At 2 mm below the nasal floor
W5	At nasal floor

Classification was done for each tooth according to its inclination and RRP within the alveolus as per Gluckman’s classification [Table 2].

Table 2.

Gluckman’s classification for radial tooth root positions and inclinations

Class	Vertical axial inclination, Buccopalatal orientation of tooth in the ridge, thickness of bone wall (s)
Class I	Tooth centrally positioned within ridge Class IA: Thick facial bone wall (>1 mm) Class IB: Thin facial bone wall (<1 mm)
Class II	Tooth retroclined Class IIA: Thick crestal bone Class IIB: thin crestal bone
Class III	Tooth proclined: Typically, thick palatal bone, thin facial crest, thick facial wall apically
Class IV	Tooth facially positioned outside of the bone envelope
Class V	Thin facial and palatal bone walls

CBCTs of all six anteriors were classified according to Gluckman’s classification and all measurements (L, W1, W2, W3, W4, and W5) were assessed. Measurements of all five widths at five different locations (as mentioned above) were perpendicular to the line of the proposed osteotomy [Figure 1]. The data obtained from this study was analyzed using (IBM, NY, USA SPSS Statistics, version 28.0); the One-way ANOVA (Shapiro–Wilk test) to check correlations between the main variables (all six measurements) and Gluckman classification. Chi-square P value was used to check the plausibility of Gluckman’s classification in the population of Gujarat.

Figure 1.

Measurements of length and all width at five different locations

RESULTS

In reference to the classification for RRP, class II pertains to retroclined teeth and it was found to be the most common, accounting for 75% of all teeth (subtype 2A-30%; subtype 2B-35%) whereas Class I (centrally positioned) was found to be just 1%, having the lowest prevalence amongst all classes. The frequency of distribution for each class is shown below [Figure 2].

Figure 2.

Frequency of distribution for each Gluckman’s class

1. The calculated prevalence for each class in the population of Gujarat is shown in Table 3, along with a comparison to Gluckman’s classification. All of Gluckman’s classifications produced nonsignificant findings in the acquired data when compared in Gujarat’s population. The null hypothesis was accepted on the basis of statistical analysis as the P > 0.05 (Chi-square P value), which suggests prevalence was comparable to Gluckman’s classification

2. The measurements for overall bone length and width in five different locations for each maxillary anterior tooth have been recorded [Table 4]. According to the one-way ANOVA test (Comparison of groups), the length (L) and all widths (W1, W2, W3, and W4) except W5 showed variation across all classes. Based on statistical analysis, the null hypothesis was rejected for W1, W2, W3, W4, and L since the P <0.05 [Table 5]. This analysis was done on the mean of the entire sample size for the group. However, in the original full dataset, there were extreme values listed under class IV in W5. This caused the standard deviation of W5 to spike and ANOVA to be nonsignificant. Statistical analysis revealed that the null hypothesis was accepted for W5, since the P > 0.05 [Figure 3 and Table 5]

3. Post hoc analysis using the Tukey HSD test [Table 6] demonstrated that Class V differed significantly from Classes I, IIA, IIB, III, and IV in several measurements, suggesting distinct morphological characteristics in this class

4. Class I had the greatest overall width, while Class V had the smallest. Class IV had the longest length, while Class I had the shortest.

Table 3.

Calculated prevalence of Gluckman’s classification in the population of Ahmedabad and their comparison with Gluckman’s results

Final results (%)	Haward Gluckman’s results (%)	χ2 (P)
I - 1	I - 6	0.0588
II A - 30	IIA - 35.2	0.5196
II B - 35	IIB - 41.3	0.4708
III - 15	III - 9.5	0.2665
IV - 16	IV - 7.3	0.0715
V - 3	V - 0.7	0.2318

Table 4.

Measurements for overall bone length and width in five different locations for each maxillary anterior tooth

Class	W1	W2	W3	W4	W5	L
I	4.33	9.95	12.28	12.85	7.95	8.04
II A	3.84	8.63	10.10	11.04	7.18	11.83
II B	3.93	8.86	9.75	10.57	7.51	10.60
III	3.63	7.68	9.33	9.12	6.29	10.64
IV	3.86	7.71	8.74	10.46	6.92	12.5
V	2.18	5.16	6.87	8.09	6.07	9.00

Table 5.

Mean±standard deviation for bone widths (W1–W5) and Length

Class	W1	W2	W3	W4	W5	Length
I	4.33±0.84	9.96±2.14	12.29±1.72	12.86±3.27	7.96±1.64	8.04±1.88
IIA	3.84±0.96	8.64±2.12	10.10±2.37	11.04±3.53	7.19±2.35	11.83±9.68
IIB	3.93±0.89	8.87±2.16	9.76±2.44	10.57±3.20	7.52±7.93	10.60±2.77
III	3.63±1.13	7.69±1.63	9.34±1.99	9.13±2.22	6.30±1.89	10.65±3.36
IV	3.87±2.94	7.72±1.77	8.74±2.14	10.47±3.22	12.88±60.15	12.51±2.60
V	2.18±0.38	5.16±1.31	6.87±1.19	8.09±1.89	6.07±2.23	9.00±3.72
ANOVA P	<0.001	<0.001	<0.001	<0.001	0.456	0.009

Figure 3.

One-way – ANOVA test (Comparison between groups)

Table 6.

Post hoc (Tukey honest significant difference) test for multiple comparisons

I versus J	Mean difference	SE	Significant	95% CI (lower, upper)
For W1
I versus V	2.15333	0.61450	0.007	0.3966–3.9100
IIA versus V	1.66457	0.38439	<0.001	0.5657–2.7635
IIB versus 5	1.75018	0.38205	<0.001	0.6580–2.8424
III versus V	1.45189	0.40013	0.004	0.3080–2.5958
IV versus V	1.68529	0.39656	<0.001	0.5516–2.8190
For W2
I versus III	2.26620	0.69893	0.016	0.2681–4.2643
I versus IV	2.23879	0.69518	0.017	0.2514–4.2262
I versus V	4.79181	0.83301	<0.001	2.4104–7.1732
IIA versus III	0.95021	0.25716	0.003	0.2150–1.6854
IIA versus IV	0.92280	0.24679	0.003	0.2173–1.6283
IIA versus V	3.47582	0.52108	<0.001	1.9862–4.9655
IIB versus III	1.17949	0.25066	<0.001	0.4629–1.8961
IIB versus IV	1.15208	0.24001	<0.001	0.4660–1.8382
IIB versus V	3.70510	0.51790	<0.001	2.2245–5.1857
III versus V	2.52561	0.54241	<0.001	0.9750–4.0762
IV versus V	2.55301	0.53758	<0.001	1.0162–4.0898
For W3
I versus IIB	2.52893	0.77431	0.015	0.3154–4.7425
I versus 3	2.95222	0.79577	0.003	0.6773–5.2272
I versus 4	3.54879	0.79151	<0.001	1.2861–5.8115
I versus 5	5.41389	0.94842	<0.001	2.7026–8.1252
IIA versus IV	1.36153	0.28099	<0.001	0.5583–2.1648
IIA versus V	3.22663	0.59328	<0.001	1.5306–4.9227
IIB versus IV	1.01986	0.27326	0.003	0.2387–1.8010
IIB versus V	2.88495	0.58966	<0.001	1.1993–4.5707
III versus V	2.46167	0.61757	0.001	0.6962–4.2272
IV versus V	1.86510	0.61206	0.029	0.1154–3.6148
For W4
I versus III	3.72844	1.10468	0.010	0.5704–6.8865
I versus V	4.76118	1.31659	0.004	0.9973–8.5250
IIA versus III	1.91544	0.40645	<0.001	0.7535–3.0774
IIA versus V	2.94818	0.82358	0.005	0.5937–5.3026
IIB versus III	1.44524	0.39617	0.004	0.3127–2.5778
IIB versus V	2.47798	0.81856	0.031	0.1379–4.8180
III versus IV	−1.34259	0.45697	0.040	−2.6490–−0.0362

SE: Standard error, CI: Confidence interval

DISCUSSION

IIP requires an evaluation of several factors, including bone thickness, tooth and root position, and inclination. It requires a CBCT evaluation of the alveolar bone or the desired peripheral area of the residual alveolar socket. The initial osteotomy direction and optimal implant placement are determined by the alignment of the root with the alveolar bone and nasal floor.

The thickness of the buccal wall maintains the convexity of the alveolar process.[16] Chappuis et al. conducted a study of the front maxillary region to assess and contrast the aesthetic result and vertical bone loss of the midfacial bone wall following implant placement in the extraction socket and healed ridges.[7] According to Chappuis et al., a maxillary anterior tooth with 1 mm or less labial bone wall thickness exhibits 7.5 mm of vertical bone loss at the midfacial bone wall.

A study conducted by Botticelli et al. evaluated the likelihood of a marginal gap occurring following IIP in an extraction socket.[22] It was concluded that the thickness of the facial bone wall is directly related to ridge alterations after IIP. To get long-term optimal esthetic results, it is essential to control these elements.[14,16,23]

Kinaia et al. evaluated crestal bone changes around immediately placed implants and found less crestal bone level loss (CBL loss) around IIP as compared to implant placement in healed bone.[5]

3D CBCT scans were used in the current study to evaluate the condition of the bone and its suitability for IIP in the direction of the proposed osteotomy according to Gluckman’s classification, as well as to validate and elaborate the classification provided by Gluckman in the local population of Gujarat, India. According to Gluckman classification, the scans were utilized to analyze the inclination and position of the tooth and root. The findings showed that the labial bone thickness was thin (1 mm) in 84% of the maxillary anterior teeth. El Nahass and Naiem found that in 86% of cases, maxillary anterior had <1 mm of bone in the labial crestal region.[18] In 80%of cases, the maxillary anterior teeth had thin labial bone, according to Wang et al.[25] In contrast, 69% of cases were described by Chappuis et al. as having thin labial bone in the midfacial point of the maxillary anterior teeth.[7] The conclusions drawn from the above studies coincide with the results of the current investigation.

Since 83% to 92% of all anterior teeth in the maxillary arch had labial bone <1 mm between the crest and mid-root point, Gluckman asserted that palatal bone is primarily responsible for implant stability.[1,27,28] Huynh-Ba et al. claimed that at least 2 mm of buccal bone is necessary for implant stability, but only specific sites in the area of the anterior maxilla teeth exhibit this clinical scenario.[8,29] Various studies have been done concerning about buccal bone only, but very few cases of maxillary anterior showed sufficient thickness of the buccal bone. Therefore, more research discussing the palatal wall and apical bone of the extraction socket is required in order to have more space for initial osteotomy and high primary stability.

The clinician is better equipped to make recommendations about treatment planning and strategy for implant placement with knowledge about the tooth’s position in the radial plane and the amount of available bone. When planning, root location and inclination in the radial plane also offer direction with respect to the standard osteotomy direction and the amount of bone that is present along the proposed osteotomy site (suggested by Gluckman). There are just two studies that have classified the tooth inclination of maxillary anterior teeth, despite the possibility that these parameters are essential for patient selection.[1,24,26]

Evaluation of the width and length of the bone that is available in the direction of the proposed osteotomy location in accordance with Gluckman’s classification helps the clinician to include any overlooked anatomic variations. This further enhances the preparation procedures.

Gluckman et al. also measured thickness of bone 4 mm beyond the apex, in the long axis of the tooth. According to him, at least 10 mm bone is required beyond the apex for primary stability of the implant. Most central incisors (61%) and lateral incisors (63%) had sufficient bone length beyond the apex (10 mm) whereas canines (33%) had bone length between 5 and 10 mm, and 38% had 10 mm.[1] However, this study also evaluated the bone length in the direction of proposed osteotomy which plays a crucial role in the retention of the implant. In the current study, all classes showed the highest width at W3. The highest width was seen in class I (12.28 mm) and the lowest in Class IV (6.68 mm) among the five classes. Sufficient bone on the buccal and palatal site (in case of class I, IIA, IIB) will provide more space to change the path of osteotomy to have an access hole in a favorable site. It is possible to achieve stability in classes I and II by altering the osteotomy path more palatally, which will maintain the buccal bone and engage more bone palatally. That will result in reduced crestal resorption. Class III and class IV showed less width <10 mm (class 3–9.33 mm, class 4–8.74 mm). Under such a situation, additional bone augmentation procedures must be performed in order to place an implant, and the only way to achieve primary stability is to engage more bone apically. Class V tooth root position is a contraindication to IIP as it showed less facial and palatal bone as well as bone beyond the apex to provide primary stability.[1]

According to various studies, the average patient will experience 50% alveolar ridge resorption following extraction and a vertical labial bone wall loss of 7.5 mm in the esthetic zone.[7,21]

Wilson et al. demonstrated that <1.5 mm horizontal bony defects do not require membranes to achieve histologic osseointegration.[30] Therefore, IIP should only be considered where there is enough bone to support the implant and should be limited to three or four-walled socket defects and limited circumferential defects to achieve stability and retention. According to this study, class I shows the highest width and lowest length, whereas class IV and class V show the highest length and lowest thickness of bone. Based on available bone, the direction of osteotomy, grafting procedures, primary stability, osteogenesis and bone resorption pattern, and prosthetic and esthetic outcome can be pre-evaluated for anterior IIP.

Research is still needed to fully understand the role of the alveolar bone that is present along the osteotomy to the nasal floor line, its relationship to the position of the radial root, the inclination of the tooth, the postextraction behavior of the socket, and circumferential bone and defect. Regarding accessible bone thickness and length in the direction of the proposed osteotomy, there may be a gender-specific correlation. For more relevant results, additional research should be conducted with a wider dataset that includes gender and ethnic factors.

CONCLUSION

Based on the findings and limitations of this study, it can be concluded that:

When compared with Gluckman’s classification, results for width and length differed in each class except width at nasal floor (W5). Class I was found to have the highest width and lowest length, whereas the lowest width and highest length were seen in class V and class IV, respectively.

A positive correlation exists between anterior tooth position and available bone between the root tip to nasal floor. The width and length of available bone beyond the apex vary in each class of RRP. Gluckman’s classification showed a positive association when applied to the population of Ahmedabad, Gujarat.

The majority of maxillary anterior teeth have a thin facial bone, which could counteract the benefits of IIP if these hard tissues are not properly managed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.