Texture Analysis of Hard Tissue Changes after Sinus Lift Surgery with Allograft and Xenograft

In the realm of dental surgery, implants are essential for replacing missing teeth. To facilitate implant placement, techniques such as bone grafting and sinus lifts are utilized to augment the volume of atrophied alveolar bone in candidates for dental implants. Typically, patients undergo a period of recovery following bone grafts before proceeding with implant placement. This study investigates the efficacy of Cone Beam Computed Tomography (CBCT) in measuring the residual bone volume and assessing bone quality after the healing phase. A texture analysis was conducted on CBCT scans from 42 patients requiring maxillary sinus lift reconstruction. These patients were categorized into two groups based on the type of grafting material used: Xenograft or allograft. The study analyzed the distribution of various texture parameters and conducted a Mann-Whitney U test to identify significant statistical differences between the groups. Results indicated non-normal distributions for specific variables such as Area_S(1,0) and S(1,0)SumOfSqs, while others like S(1,0)Entropy displayed normal distributions. The findings revealed no significant statistical differences in the primary outcomes between the xenograft and allograft groups. However, the average values of the gray shades of pixels in the allograft group were statistically significantly higher compared to the xenograft group, suggesting differences in bone texture post-procedure.

Replacing missing teeth has historically been a challenge in dental medicine. For decades, removable dentures were the standard solution, offering a simple but often uncomfortable option for patients due to the mobility of these prostheses. With the advent of dental implants, a more stable and fixed prosthesis became available, significantly reducing discomfort associated with traditional dentures. However, implant stabilization remains particularly challenging in the posterior areas of the upper jaw, where limited bone volume and proximity to the sinus can complicate procedures [1]. Sinus pneumatization following tooth extraction often leads to alveolar bone atrophy, further exacerbating the loss of suitable implant sites [2,3].

Although recent studies suggest that short implants may be effective in areas with reduced bone volume [4,5], sinus bone augmentation has proven to be a reliable method for enhancing implant anchorage. This technique involves the careful elevation of the Schneiderian membrane to avoid perforation and the placement of bone graft material into the newly created space above the sinus [4,6]. Depending on the height of the remaining alveolar bone, implants may be placed simultaneously with bone grafts if sufficient primary stability can be achieved.

Cone Beam Computed Tomography (CBCT) has emerged as a critical tool in this context, enabling precise measurement of residual bone and assessment of the graft site post-procedure [7-10]. This study aims to evaluate the effectiveness of sinus lift augmentations using two different types of graft materials: xenografts and allografts. By examining the transplanted areas and analyzing the outcomes, this research seeks to enhance our understanding of the comparative benefits of these materials in promoting successful dental implantation, thus guiding future clinical practices.

This study was conducted in accordance with the World Medical Association Declaration of Helsinki (of 1975 as revised in 2000) and was approved by the ethics committee of Tabriz University of Medical Sciences. (Institutional Review Board: IR.TBZMED.REC.1400.1023).

42 patients with bone loss in the posterior region of the upper jaw were selected for the sinus lift procedure. CBCT images were divided into 2 categories; using xenograft or allograft material. Texture analysis (TA) was done by MaZda Software (Technical University of Lodz, Institute of Electronics, Poland) on the images obtained in the axial sections (Figure 1). Transplantation was done in all patients by one surgeon using the same protocol. CBCT scans were performed with a Newton 3D scanner (VGI, QR SRL, made in Italy) at the Faculty of Dentistry, Tabriz University of Medical Sciences. Then, all CBCT images were used for DICOM analysis, and images containing artifacts that reduce resolution (such as beam hardening artifacts, partial volume effect, aliasing artifacts, ring artifacts, etc.) were removed. Then the desired ROI will be selected at the center of the examined area of the bone graft sites to evaluate the grey-level co-occurrence Matrix (GLCM). Eleven texture parameters, listed in Table 1, were extracted for each ROI on each slice [11].

GLCM is a square matrix that can show certain features about the spatial resolution of the image. A statistical method is used which is calculated through the distribution of gray shades and it is related to the number of times the amount of gray shade in dimensions i and j of the two-dimensional matrix of the image are equal in the 1-, 2-, 3-, 4- and 5-pixel intervals and at specific angles (0-45-90 and 135 degrees). Finally, the results obtained from the software will be used to compare the contrast, homogeneity, and texture complexity of hard tissue in the three different groups. With the help of the parameters obtained from this technique, it is possible to obtain the average gray levels and the way pixels change, which has the highest diagnostic value in examining healthy and pathological tissue changes [11].

The normality of distribution for our data was assessed using the Kolmogorov-Smirnov test, a non-parametric method suitable for samples of any size. This test was conducted using IBM SPSS software (version 23; IBM Inc., Armonk NY, USA). The timeframe of the study spanned from 2022 to 2023, utilizing current CBCT technology and methodologies.

The Kolmogorov-Smirnov test was used to check the normal distribution of the variables. The test’s significance level, detailed in Table 2, was established at 0.05. Table 2 presents an analysis of eleven factors relating to the selection of texture parameters and their statistical significance across different groups. The results posit that:

A) There was no clear statistical difference between the means of variables S(1,0)AngScMom, S(1,0)Contrast, S(1,0)Correlat, S(1,0)InvDfMom, S(1,0)SumVarnc, S(1,0) 0) (SumEntrp and S(1,0)Entropy) in the two investigated groups (p > 0.05).

B) There was a clear statistical difference between the means of variable S(1,0)SumAverg in the two investigated groups, and the means mentioned in the allograft group were higher than the xenograft group (p < 0.05).

The nature of the materials used in sinus augmentation has evolved in the past decades: initially, autograft was the only possible way for the procedure, which was taken from the ilium, tibia, or chin bone [12-17]. Cortical bone grafting was used for the upper parts of the sinus and trabecular bone grafting was used for the lower parts of the sinus cavity for augmentation. Currently, the complications of autografted bone are well-defined. In this case, the volume of bone autograft to be removed is moderate, and other limitations such as increased morbidity and limited availability are related to it [18]. On the other hand, xenografts and allografts are alternatives with less morbidity rate which eliminate the need for a secondary surgical (donor) site [4,19].

Previous studies on TA such as what Ditmer, et al. performed demonstrated the ability of TA to differentiate tissues Based on the characteristics between lesions of a tumor (high and low-grade tumors), including quantifying changes in surface characteristics [20].

The application of TA is a useful technique to differentiate between normal and abnormal tissues. All these parameters are suitable to characterize the gray-level distribution of regions of interest (ROIs) and accentuate features from images that have usually been missed by the human eye [21,22].

This method can be used to measure the quality of bone in the transplanted areas to determine the radiographic features when the gross structure has completely disappeared.

Our study confirms that texture analysis (TA) of Cone Beam Computed Tomography (CBCT) images effectively evaluates areas augmented with allograft and xenograft materials. Although there were no significant statistical differences between the two groups for most parameters, we observed that the distribution of gray shades of pixels was significantly higher in the allograft group compared to the xenograft group. This finding suggests that allografts may influence bone texture more distinctly, a consideration that could guide material selection in clinical practice.

Ethical approval

This study was conducted in accordance with the World Medical Association Declaration of Helsinki (of 1975 as revised in 2000) and was approved by the ethics committee of Tabriz University of Medical Sciences. (Institutional Review Board: IR.TBZMED.REC.1400.1023).

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