Correlation Between Peri-Implant Bone Mineral Density and Initial Stability of Implants as Interpreted by Artificial Intelligence Jaw Density Classification

doi:10.21203/rs.3.rs-2295092/v1

Objective: To investigate the correlation between peri-implant BMD and initial stability of implants when combined with the new artificial intelligence classification method of jaw density.

Materials and Methods: 49 patients who received dental implant treatment in the Affiliated Hospital of Stomatological of Fujian Medical University were included. The torque value and implant stability quotient (ISQ) value of the implants after implantation were recorded. Artificial intelligence image segmentation software was used to obtain the distribution of jaw density in implant areas, and the neck, the middle, the bottom and the total bone mineral density (BMD) coefficients of the 1mm region around the implant were calculated by model overlap and image overlap techniques. Then, the correlation betwen ISQ and BMD evaluated by a new jaw density artificial intelligence classification method were investigated.

Results: There was a significant positive correlation between the BMD coefficient of the total, the neck and the middle region around implants and the ISQ value (P < 0.05), but there was no significant correlation between the BMD coefficient of the bottom around implants and the ISQ value (P > 0.05). BMD was significantly higher at the implant site with larger implant torque (P < 0.05).

Conclusions：The results of this study suggest that there is a positive correlation between BMD coefficient and the ISQ. BMD of both the neck and the middle of the implant have a significant positive correlation with the ISQ, while BMD of the bottom of the implant has no significant correlation with ISQ.

Oral implant

Initial stability

Overlap model

Bone mineral density

ISQ value

Clinical research

The formation of strong osseointegration is very important for the success of oral implant. Excessive fretting of the implant during the formation of osseointegration will lead to the formation of fibrous tissue between the implant and the bone, which will affect the healing process of the implant. When the fretting is larger than 100 µi, there is a higher risk of implant failure^[^].

The successful formation of strong osseointegration requires a certain initial stability after implantation^[^]. The initial stability of the implant refers to the mechanical stability formed immediately after implantation. The initial stability of the implant is related to a variety of factors, such as the bone density and quality, the macro- and micro-design of the dental implant, as well as the surgical procedure ^[^][^]

The initial stability of implants can be reflected by many indexes, such as implant insertion torque (IT),implant stability quotient (ISQ), periotest Value (PTV) and so on. It has been reported that the higher the ISQ value, the more stable the implant is, and the implant with ISQ value less than 50 has a higher risk of failure ^[^].It has been proved that the BMD of the implant region is positively correlated with IT and ISQ, which means, the higher the BMD is, the higher the IT and ISQ values are ^[^].Therefore, when making the treatment plan before operation, it is necessary to analyze the BMD of the implant area to predict the primary stability of the implant, and it is also what a reasonable surgical procedure is based on.

BMD are usually evaluated by L&Z classification ^[^] and the HU value of the a 10mm cumular region beneath the alveolar redge of implant area ^[^].However, due to lack of objective criteria of L&Z classification, and the 10mm cumular area under the alveolar ridge can not fully represent the BMD around the implant, and the evaluation of BMD still needs to be improved. Some studies have provided a modification to the measurement of BMD with the use of implant design software to obtain the mean value of HU in the range of 0.5mm ~ 1mm around the virtual implant ^[^][^][^]; however, whether there is a deviation between the real implant used and the virtual implant has not been mentioned. Besides, there is not enough studies to support how the BMD of different parts around the implant, such as the neck and bottom of the implant, affect the ISQ value.

In our previous studies, we have preliminarily established a new BMD grading system based on artificial intelligence ^[^], where we proposed a new classification method of BMD. According to the HU value, the BMD is divided into five grades: 1 grade for HU value > 1000, 2 grade for HU value 700–1000, 3 grade for HU value 400–400, 4 grade for HU value 100–400, and 5 grade for HU value < 100. After the section of CBCT, the system can automatically grade the jaw BMD through artificial intelligence analysis and interpretation(Fig. 1). In this study, we combined the new artificial intelligence bone mineral density grading system with the implant design software to explore the correlation between the neck, middle or bottom of the alveolar bone region that is 1mm around the implant and the ISQ of the implant.

Research object

Patients who were diagnosed as dentition defect and intended to receive oral implantation were collected from the Department of Implant, affiliated Hospital of Stomatological of Fujian Medical University from August 2021 to January 2022. According to the inclusion and exclusion criteria, a total of 49 patients with 63 implants were collected, including 27 Straumann BL implant system and 36 NobelReplace PMC implant system. The model distribution is shown in Fig. 2.

Inclusion criteria

(1) Patients with dentition defect (over 18 years old); (2) Healthy periodontal tissue without cyst, tumor, other bone destruction and history of orthodontic orthodontic treatment; (3) Alveolar bone width and height sufficient for routine implantation; (4) Preoperative blood examination showed that the bleeding and coagulation function was normal and the platelet count was normal; (5) The patients had good compliance.

Exclusion criteria

(1) Contraindications for implant surgery; (2) Hematological diseases such as leukemia, aplastic anemia, taking anticoagulants or blood coagulation tests in the past 12 weeks; (3) Insufficient width and height of alveolar bone for implantation or additional bone increment techniques and alveolar bone plate fractures or even deletions are required;(4) Severe periodontitis; (5) Systemic diseases or drug use that may affect soft and hard tissue healing; (6) Uncontrolled systemic diseases such as hypertension and diabetes.

Measurement and recording of intraoperative data (Fig. 3)

Insert torque: the insert torque was recorded as ≥35Ncm or <35Ncm using torque wrench supplied by corresponding surgical kit.
Resonant frequency analysis: the SmartPeg was handled and tightened with a torque of 4-6 Ncm; the measurement probe of the resonant frequency analyzer is kept close to the top of the SmartPeg, and the equipment will display the ISQ value automatically.
Note: ①The same SmartPeg can only be used for the same implant in the same patient.②The measurement probe should be perpendicular to the long axis of SmartPeg, ③The lip (cheek), tongue (palate), mesial and distal sites should be measured respectively for three times, and the results were shown as the average value of each site. ④All measurements were done by the same dentist.

Measurement of bone mineral density in implant area (Fig. 4–6)

Due to the false shadow of implants in CBCT images, which will influence the acquisition of BMD, therefore, in this study, the three-dimensional model of the dentition and implant was constructed in the postoperative CBCT, and the model was overlapped with the preoperative CBCT using the implant design software to obtain the accurate position of the actual implant on the preoperative CBCT, and then, the virtual implant can be placed. According to the length of the implant, the implant is divided into three parts: the neck, the middle and the bottom. The screenshot of the minimum slice thickness (0.2mm) was overlapped with the BMD map obtained by the jaw bone density automatic recognition software, and the proportion of all kinds of bone around the virtual implant in different parts of each layer of CBCT was calculated. The first grade was recorded as P₁, grade 2 as P₂,grade 3 as P₃,grade 4 as P₄,and grade 5 as P₅. In addition, if no bone was found in the area of 1mm around the implant ( the neck for example), it is recorded as the proportion of blank P₀. Because the BMD of grade 1 was the highest and that of grade 5 was the lowest, the score of grade 1 as 5, grade 2 as 4, grade 3 as 3, grade 4 as 2, and grade 5 as 1. According to the proportion of all bone grades, the bone mineral density score was calculated as BDC = 5×P₁ + 4×P₂ + 3×P₃ + 2×P₄ + 1×P₅ + 0×P₀.

Statistical analysis

Use Spss22.0 statistical software to input all clinical data and to establish a database. For the data obeying normal distribution, Pearson test is used for correlation test, t test is used for the difference test of two independent samples, and analysis of variance is used for the difference test of multiple independent samples. the data are expressed as mean ± standard deviation. For the data that do not obey the normal distribution, the correlation test uses Spearman test, the difference test of two independent samples uses Mann-Whitney test, and the difference test of multiple independent samples uses Kruskal-Wallis test. The data is expressed by median and quartile spacing.

Correlation analysis between bone mineral density coefficient around the implant and ISQ

(1)Straumann implant group

The scatter diagrams of ISQ and neck, middle, bottom and total bone mineral density coefficient after implantation in Straumann implant group were shown in Fig. 7.

Because it does not obey the normal distribution, the Spearman correlation analysis was used to calculate the correlation between the bone mineral density coefficients of the neck, middle, bottom and perimplant of Straumann implant and ISQ, repectively.

Table 1 Correlation between ISQ and bone mineral density coefficient of each site of Straumann implant group

Site	N	Spearman correlation analysis
Site	N	R	P
Neck	27	0.511	0.006
Middle	27	0.413	0.032
Bottom	27	0.295	0.135
Total	27	0.415	0.031

The results showed that the bone mineral density coefficient in the neck of the implant was significantly and positively correlated with ISQ (R = 0.511, P = 0.006, ＜0.05); the bone mineral density coefficient in the middle of the implant was significantly and positively correlated with ISQ (R = 0.413, P = 0.032, < 0.05); the bone mineral density coefficient at the bottom of the implant was not significantly correlated with ISQ (R = 0.295, P = 0.135, > 0.05); the total bone mineral density coefficient around the implant was significantly and positively correlated with ISQ (R = 0.415, P = 0.031, < 0.05).

(2)Nobel implant group

The scatter diagrams of ISQ and neck, middle, bottom and total bone mineral density coefficient after implantation in Nobel implant group were shown in Fig. 8.

Because it does not obey the normal distribution, the Spearman correlation analysis was used to calculate the correlation between the bone mineral density coefficients of the neck, middle, bottom and periimplant of Nobel implant and ISQ, respectively.

Table 2 Correlation between ISQ and bone mineral density coefficient of each site of Nobel implant group

Site	N	Spearman correlation analysis
Site	N	R	P
Neck	36	0.838	＜0.001
Middle	36	0.635	＜0.001
Bottom	36	0.312	0.064
Total	36	0.689	＜0.001

The results showed that the bone mineral density coefficient in the neck of the implant was significantly and positively correlated with ISQ (R = 0.838, P < 0.05); the bone mineral density coefficient in the middle of the implant was significantly and positively correlated with ISQ (R = 0.635, P < 0.05); the bone mineral density coefficient at the bottom of the implant was not significantly correlated with ISQ (R = 0.312, P = 0.064); and the total bone mineral density coefficient around the implant was significantly and positively correlated with ISQ (R = 0.689, P < 0.001).

Difference of bone mineral density coefficient with different implant torque

(1)Straumann implant group

Table 3 Difference of bone mineral density coefficient(BMDC) in different site of Straumann implant group under different insert torques

Site	IT＜35Ncm	IT≥35Ncm	Mann-Whitney test
Site	N=9	N=18	Z	P
BMDC of neck	2.53(2.03,3.69)	3.83(3.08,3.98)	-2.109	0.035
BMDC of middle	2.71(2.14,4.17)	3.72(2.50,4.16)	-1.183	0.237
BMDC of bottom	3.13(2.82,4.08)	3.30(2.72,4.11)	-0.154	0.877
BMDC of total	2.70(2.35,4.06)	3.87(2.79,4.04)	-1.029	0.304

S-W test showed that the data did not follow the normal distribution. The results of Mann-Whitney U test indicated that the bone mineral density coefficient of neck bone with implant torque ≥ 35Ncm was higher than that of neck bone with implant torque < 35Ncm(2.53,3.83,P = 0.035), and the difference was statistically significant. The bone mineral density coefficients were not significantly different in the middle(2.71,3.72,P = 0.237), the bottom(3.13,3.30,P = 0.877), and the total(2.70,3.87,P = 0.304) bone around implants regarless of the value of implant torque.

(2)Nobel implant group

Table 4 Difference of bone mineral density coefficient(BMDC) in different site of Nobel implant group under different insert torques

Site	IT＜35Ncm	IT≥35Ncm	Mann-Whitney test
Site	N=11	N=25	Z	P
BMDC of neck	2.23(1.98,2.38)	3.21(2.67,3.94)	-4.173	＜0.001
BMDC of middle	2.40(2.00,2.72)	3.30(2.55,3.80)	-2.421	0.015
BMDC of bottom	2.51(2.06,3.34)	3.07(2.56,3.57)	-0.944	0.345
BMDC of total	2.30(2.06,2.85)	3.18(2.66,3.64)	-2.799	0.005

S-W test showed that the data did not follow the normal distribution. The results of Mann-Whitney U test indicated that the neck bone mineral density coefficient (2.23, 3.21; P < 0.001), the middle bone mineral density coefficient (2.4, 3.3; P = 0.015) and total bone mineral density coefficient (2.3, 3.18; P = 0.005) in the implant torque ≥ 35Ncm group were higher than those in the implant torque < 35Ncm group, and the difference was statistically significant. There was no statistical difference in bone mineral density coefficient at the bottom in two groups (2.51, 3.07; P = 0.345).

Correlation between ISQ value and bone mineral density

The correlation between ISQ value and jaw bone mineral density is controversial. Reshma et al^[^] pointed out that the sites with higher bone density (such as mandibular anterior teeth and mandibular posterior teeth) showed higher primary stability, and that the higher the HU value is, the higher the initial stability of the implant has. However, the results of Huang et al^[^] point out that bone mineral density is not a factor affecting the ISQ value of initial implant stability for reasons that in addition to the density and quality of bone in implant area, initial stability of implant is also affected by the process of implant cavity preparation, the type of implants used, and treatment of surface and geometric design of implants ^[^]. Strub and other scholars also point out that the initial stability of the implant is the result the compression of the local bone in the implant area, which is related to the mechanical interlocking between bone and implants, and the quantity and quality of local bone and other factors^[^]. Therefore, in the following studies, the bone mineral density of the implant site has been proved to affect the ISQ value proportionally, that is, the higher the local bone mineral density, the higher the ISQ value after the implant^[^][^].

In this study, the correlation between ISQ and jaw bone mineral density was analyzed, and there was a moderately significant correlation between ISQ and the total bone mineral density coefficient around the implant, which was consistent with the results of other studies. In an in vivo study, Merheb et al^[^] found that there was a certain correlation between bone cortical thickness, HU value and ISQ value in different regions, and Periotest, and suggested that implant stability can be predicted according to preoperative imaging parameters. In a study of MustafaFaisalJ et al.^[^], there is a significant correlation between the HU value around the implant from the preoperative CBCT obtained with the use of implant design software and the ISQ value recorded the after implantation. Consistent with this view, Salimov et al^[^] also pointed out that there was a significant correlation between bone mineral density (BMD) obtained from CBCT and ISQ among all clinical variables. It is obvious that the consideration of the BMD of the implant area before operation is helpful to evaluate and predict the initial stability of the implant^[^].

In addition, in this study, the area around the implant was divided into three regions: neck, middle and bottom, in order to explore the correlation between ISQ and bone mineral density coefficient in different parts of bone around the implant. As the maximum torque and ISQ are largely affected by the lateral force, the areas above the collar and below the bottom of the implant are not measured^[^]. In both the Straumann implant group and the Nobel implant group, there was a strong correlation between ISQ and the bone mineral density coefficient around implant neck, and there was no significant correlation between the bone mineral density coefficient around the bottom of the implant and the ISQ value. In accordiance with our results, Chatvaratthana et al^[^] also observed a strong correlation between ISQ and the thickness of the apical cortical bone around the apical region of 19 implants obtained from 16 patients, and the cortical bone thickness of the buccal or lingual side at 3mm below the alveolar crest also showed a correlation with ISQ. However, no correlation was observed at the bone cortical thickness farther away below the alveolar ridge (6mm-9mm). This phenomenon may be due to the fact that the bone at the bottom of the implant has little effect on the stability of the implant. An early in vitro study also showed that ISQ decreased significantly when the loosening of the implant neck increased ^[^]. One can reach a conclusion that there is a greater correlation between the BMD around the neck of the implant and the ISQ value after implantation, which means, the higher the bone mineral density of the implant neck, the higher the initial stability ISQ value of the implant. It is suggested that the BMD of the neck should be considered during process of implantation. When there is a high BMD, the tapping or neck shaping operation should be taken in the process of cavity preparation to facilitate implantation. On the other hand, when the bone mineral density of the neck is too low, the difference between the diameter of implant cavity and the implant should be amplified to improve the stability of the implant.

Relationship between implant torque and BMD

Since the torque wrench cannot display the detailed torque value, the torque in this study is divided into ≥ 35Ncm group and < 35Ncm group, which is also recommended by some scholars as an alternative recording method ^[^].The results showed that the bone density coefficient around the neck of implants with torque ≥ 35Ncm was significantly higher than that of implants with torque < 35Ncm in both Straumann implants and Nobel implants. This finding was consistent with results from other studies. In a clinical study, Hakim et al.^[22] calculated the correlation between obtained HU value of the implant area abtained from CBCT and implant torque or other indicators. The results showed that the implant torque was significantly correlated with the HU value of the implant area. In an in vitro study, Comuzzi et al.^[^] used polyurethane foam blocks at two densities, 10 pounds fer cubic foot (10 PCF) and 20PCF, and the implant torque and ISQ value were significantly higher in 20 PCF blocks than those in the 10PCF bone blocks. Besides, in the present study, the bone mineral density coefficients are different in the middle and total bone around the implants from two companies. The significant diference of bone mineral density coefficients of the middle and total of Nobel implants between two implant torque groups may be due to the different geometric design of the two groups of implants, which makes it easier for the conical Nobel PMC implant to show higher torque than the columnar Straumann BL implant under the same bone conditions. Comuzzi et al.^[^]also found that the stability of conical implants is higher than that of columnar implants in low-density bone.

In this study, ISQ and IT were significantly and positively correlated with the bone mineral density coefficient, indicating that bone mineral density coefficient can surve as a reliable index for the evaluation of actual bone quality and can also be used as a parameter to predict the initial stability. However, pathological studies are needed to confirm the accuracy of bone mineral density coefficient, and accuracy of how to predict the bone mineral density coefficient more accurately still needs further study.

Within the limitation of this study,the following conclusions were drawn.

1. The bone mineral density coefficient was positively correlated with the initial stability of the implants.

2. Bone mineral density coefficient of the neck and middle bone around the implant had significantly positive correlation with the stability of the implant, while bone mineral density coefficient at the bottom of the implant had no significant correlation with the initial stability of the implant.

3. The new artificial intelligence bone mineral density identification software could present the bone mineral density distribution in the intended implant area more accurately, thus, providing a reliable reference for the prediction of initial stability of implants.

Ethics approval This study was performed in line with the principles of the Declaration of Helsinki.Approval was granted by the Ethics Committee of Biomedical Research of the Afliated Stomatological Hospital of Fujian Medical University (Date 8.9.2021/No.60).

Competing interests The authors declare no competing interests.

Author contribution Conceptualization: L.L, Y.X, J.C, W.H, D.W; methodology: L.L,Y.X, L.Z, J.G, Y,L; formal analysis and investigation: L.L, Y.X, J.G; writing—review and editing: L.L, Y.X; supervision: all authors.

Funding This work was supported by the Medical Innovation Program of Fujian Health and Family Planning Commission (No. 2021CXA035) and Fuzhou Major Science and Technology “Revealing the List and Taking Command” Project (2021-ZD-286).

Availability of data and materials Not applicable.

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No competing interests reported.

Correlation Between Peri-Implant Bone Mineral Density and Initial Stability of Implants as Interpreted by Artificial Intelligence Jaw Density Classification

Status:

Version 1

Abstract

Figures

Introduction

Materials And Methods

Research object

Inclusion criteria

Exclusion criteria

Measurement and recording of intraoperative data (Fig. 3)

Measurement of bone mineral density in implant area (Fig. 4–6)

Statistical analysis

Results

Correlation analysis between bone mineral density coefficient around the implant and ISQ

(1)Straumann implant group

(2)Nobel implant group

Difference of bone mineral density coefficient with different implant torque

(1)Straumann implant group

(2)Nobel implant group

Discussion

Correlation between ISQ value and bone mineral density

Relationship between implant torque and BMD

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1