This study was conducted at the Oral and Maxillofacial Radiology Department, Faculty of Dentistry, between 2022-09-29 and 2023-02-20 in accordance with the World Medical Association Declaration of Helsinki (of 1975 as revised in 2000). The study protocol was approved by the ethics committee of the university (IR.TBZMED.REC.1401.588) and registered in the Iranian Registry of Clinical Trials (IRCT20220317054321N1).
Participants, eligibility criteria, and settings:
The inclusion criteria were (I) patients requiring extraction of carious mandibular posterior teeth and their replacement with dental implants, and (II) ages over 18 years.
The exclusion criteria were (I) intake of corticosteroids and bisphosphonates, (II) pregnancy or nursing, (III) cigarette smoking and tobacco use, (IV) wearing removable dentures, (V) history of chemotherapy or radiotherapy, and (VI) systemic diseases (such as diabetes mellitus) which would affect wound healing.
The sample consisted of 75 teeth (25 in each group) that were scheduled for extraction and replacement with dental implants.
Interventions:
All patients signed informed consent forms prior to study enrollment, and were then assigned to the following three groups:
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No socket preservation.
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Socket preservation with xenograft material.
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Socket preservation with allograft material.
All patients showed up for implant placement 4 months after surgery.
Surgical extraction technique: The teeth were extracted atraumatically as much as possible by preserving the buccal and lingual cortical bone plates at the Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Tabriz University of Medical Sciences.
After complete debridement of the tooth extraction socket, the width and height of the sockets were clinically measured. After measurements, the tooth socket remained empty with no manipulation to be filled with blood clots in the control group. In the first experimental group, the tooth sockets were filled with Straumann® AlloGraft (Institut Straumann AG, Basel, Switzerland) while in the second experimental group, the tooth sockets were filled with Straumann® XenoGraft (Institut Straumann AG, Basel, Switzerland) along with non-resorbable membranes (Tutapatch, Germany). The flaps were then sutured to preserve the blood clot or the grafted material, and the patients received postoperative instructions. The sutures were removed after 2 weeks, and the patients were recalled after 4 months for implant surgery.
Radiographic assessment: After suture removal and prior to implant surgery, the patients underwent CBCT for preoperative measurements using a 3D CBCT scanner (NewTom SRL, Italy). All CBCT scans were obtained at the Oral and Maxillofacial Radiology Department, Faculty of Dentistry, Tabriz University of Medical Sciences with the exposure settings of (Kvp:110, mA:1.94, S:3.6).
The images were saved in DICOM format. Images with artifacts such as ring artifacts, aliasing artifacts, partial volume effect, and beam hardening artifacts were excluded. The CBCT scans were evaluated by a postgraduate student of oral radiology under the supervision of an oral radiologist. All images were evaluated in the axial section using MaZda software (the Technical University of Lodz, Institute of Electronics, Poland) [20, 21]. Next, the region of interest was selected for evaluation of the GLCM as a circular region at the center of the socket (Fig. 1). The GLCM is a square-shaped matrix in which the number of rows and columns equals the number of grayscale pixels of the image, and can reveal certain features regarding the spatial resolution of images. In other words, this statistical method calculates the distribution of grayscale pixels and shows the number of times the amount of grayscale pixels in the I and J dimensions of a matrix of a 2D image is equal at certain intervals (1, 2, 3, 4 and 5-pixel) and angles (0, 45, 90, and 135 degrees). Using the GLCM function, the following statistical parameters were analyzed: entropy, the sum of the entropy, correlation, contrast, differential (dif.) variance, and inverse difference moment(InvDfMom). These parameters enabled quantitative assessment of tissue characteristics.
Finally, the results obtained from the software were used to compare the homogeneity, contrast, and texture complexity of the hard tissue among the three groups (Table 1).
Table 1. Definition of parameters obtained from the TA technique
Outcomes (primary and secondary):
The main objective of this study was to assess the hard tissue changes following socket preservation with allograft and xenograft materials for dental implantation by TA using CBCT.
Sample size calculation:
The sample size was calculated to be 22 in each group according to previous studies [20, 21, 28] assuming the mean vertical distance (stent-crest) before and after the intervention to be 7.45 + 3.1 vs. 7.7 + 3.1 mm, and 7.69 + 4.2 vs. 7.69 + 4.2 in the intervention and control groups, respectively, type I error of 0.05, and study power of 80%. To increase the accuracy of the results, the sample size was increased by 20% (27 in each group).
Interim analyses and stopping guidelines:
No interim analyses were performed, and no stopping guidelines were established.
Randomization:
Patients were randomly assigned to the groups (25 each) using the random number generator in the SPSS software (version 23; IBM Inc., Armonk NY, USA). Randomization was carried out by a single investigator specially chosen for this task to lessen selection bias. By doing this, the bias was tried to be as minimum as possible.
Blinding:
The CBCT scans were evaluated by a postgraduate resident of oral radiology under the supervision of two professors in the field of oral and maxillofacial radiology. The resident and the professors were blinded to the group allocation of the patients.