Comparison of xenograft and allograft bone graft for oral and maxillofacial surgical preparation prior to dental implantation: A systematic review

2.1 Review development and PICO question

This systematic review was conducted based on these guidelines. In the present systematic review, we applied the PRISMA statement²⁰ and registered a systematic review of the International Prospective Register of Systematic Reviews (PROSPERO) database No. CRD42025641250²¹ This systematic review did not require ethical approval. The research model applied in this study is the PICO model, which stands for Population, Intervention, Comparison, and Outcome, as expounded below. P (Population): Patients in oral and maxillofacial surgery oral implant preparation, (I): xenograft bone graft, (C): allograft bone graft material, O (Outcome): success rate in preparation of site for implant placement using dental implants may include: (e.g. clinical, radiographic, and histologic analysis). There are some guidelines for assessment (for example after four months of treatment, immediately after surgery, three months later, after six months). Clinical Success Rate: Positivity was defined as the absence of issues and osseointegration of the implant. The assessment is that follow-up time was required to set the success level of the program.

Histological Analysis: The measurement included in the present study was as follows (a quantitative percentage of newly formed bone and residual graft particles).

2.2 Eligibility criteria

2.2.1 Inclusion criteria

Human investigations: Any adult patient aged 18 years and above who was chosen for oral and maxillofacial surgery for implant site preparation. In particular, allograft materials have been compared to xenografts. Controlled clinical trials (CCTs). Cohort studies. Case-control studies. Comparative studies. Cohort and case control. For the purpose of the present analysis, we compared only the publications that included the data of the same cohort of patients, and only the manuscript that provided a full and sufficient dataset was considered.

The sources searched only analyzed literature published in the last eight years to ensure that the findings relayed the most current practice in the use of the materials and the identification of findings.

2.2.2 Exclusion criteria

Receiving chemotherapy or radiation therapy, patients with cancer, or heavy smokers of more than ten cigarettes daily. Research conducted on animals or tissues in a culture medium. Animal models and tissue cultures. Systematic reviews of literature comparing the effectiveness of graft materials that will not merit the comparative mention of autografts.

Here, we followed any trial in which the quality assessment pointed out had a high risk of bias, as determined using the Cochrane Risk of Bias Tool or the ROBINS I risk of bias tool.

2.3 Type of Intervention and Comparisons

Studies that compared and contrasted the management of oral and maxillofacial surgery before implantation using xenogeneic, allograft bone grafts in the same patient were included in the study. Because of the lack of research comparing these two forms of blocks directly, studies on ridge and sinus augmentation have also been conducted.

2.4 Data collection

The main measure used to evaluate the performance of allografts compared with xenografts in surgeries related to augmentation of oral and maxillofacial sites prior to implant dentistry was the fate of the graft materials and holding of the implants planted in the augmented areas. The following secondary outcomes were also evaluated: The present study was designed to compare intra- and postoperative success rate of both allografts vs xenografts using the following endpoints: bone gain and resorption in the graft materials, changes in marginal bone levels and histological, clinical and histomorphometric findings. Graft survival was defined as the ability to maintain the graft material at the desired location to achieve implant success during re-entry surgery. For dental implants, only those that did not demonstrate mobility, progressive marginal bone loss, or for which implant failure necessitated removal were considered in the survival analysis.

2.5 Sources & search strategy

An electronic search was conducted in three electronic databases (google scholar, Medline/(PubMed) and Cochrane Database) up to January 2024 using the English language, human studies, and publications published since 2016 as search filters. combined with free terms using Boolean operators without filters or restrictions, as follows: Disagreements were settled through discussion or confrontation with the second reviewer.

The bibliographic data search was performed using several MeSH terms and free-text words that were connected using Operators: AND or OR. PubMed: ((dental implant OR dental implantation) AND (bone graft [xenograft] AND graft [Mesh] AND bone [Mesh] OR bone graft) [Mesh]) [text word [text word]; Filter/library: randomized controlled trial-comparative clinical studies; Date-March 2008-; language: English; human. Combined with free terms using Boolean operators without filters or restrictions, any disputes were resolved through confrontation and discussion between the two reviewers.

The bibliographic search consisted of a combination of MeSH terms and free-text words, combined with operators (AND or OR). The keywords used were as follows: Google Scholar: Dental implant OR dental implantation [Mesh] AND bone graft [xenograft] AND graft [Mesh] AND bone [Mesh] OR bone graft [text word [text word]; filters: RCT-Compared clinical studies; 8 years’ studies; Human studies; and English studies.

Data were derived from general study characteristics, population characteristics, and graft and implant techniques. Any issues that arose were resolved through discussions with all members involved in contributing to the discrepancy.

2.6 Study selection and screening methods

Methods Used in Selecting and Screening of Studies Two reviewers, A. Abushama and N. Alim, conducted a preliminary screening of the articles found using both electronic and manual methods focusing on the titles and abstracts. They then assessed the whole text of the articles that were included or those that did not provide clear information that they should be excluded from the title and abstract.

2.7 Clinical data extraction

Within each study, data extraction was performed by the same two reviewers. In situations where some data were missing or not presented at all in the article, the authors of the specific article were asked for additional information. If questions were raised, data that may form that particular point of the question were omitted until more information was collected.

2.8 Quality assessment and risk of bias

The quality of the study was independently evaluated by two authors of the present publication, A. Abushama and N. Alim, and the risk of bias for RCTs was performed using a revised Cochrane risk of bias for randomized trials tool (RoB 2).²² The parameters included in the tool (RoB2) were as follows: the process of randomization, the degree to which actual care delivered departs from planned care, the amount and nature of missing outcome data, the measure used to assess the outcome, and the choice of outcomes reported. If all parameters were filled with low risk (green), or up to position two if there was an unclear (yellow), the general result was a Low Risk of Bias (green). For results with risk of bias only in one of the criteria (red) and a maximum of two in doubt (yellow), the result was a Moderate Risk of Bias. However, if the alert value was equal to or included two or more high-risk (red) and/or more than two unclear risks (yellow), then the result was a High Risk of bias.

The ROBINS-I tool was used to evaluate the risk of bias in non-randomized studies of interventions.²³ This tool is designed to evaluate seven domains of bias: confounding bias, participant selection bias, intervention classification bias, intervention implementation and receipt bias, attrition bias sample bias, and sources of the reported result in each domain. The study is categorized further into a group of low risk, moderate risk, serious risk, or critical risk of bias. The global estimate of the risk of bias was generally equal to the higher value declared by each domain.

3.1 Study selection

The electronic search provided 330 papers, of which 20 were found from the manual search 350. Of these, 350 were duplicates and triplicates that were excluded, 258 After the prior screening based on the title/abstract, 165 articles were retrieved for full-text review. Finally, 12 of these studies were included in the review; six involved immediate implant, two delayed implant, three ARP, one sinuses. Figure 1 illustrates the search and selection processes. Meta-analysis was not possible because of the variability in the included studies.

Figure 1. PRISMA flow diagram for study identification and selection.

3.2 Study characteristic

Of the 12 included trials, Nine (75%) were conducted at universities.^{4,15,10,24–29} Two studies (16.67%) were conducted by an independent research clinic and another by a clinical author institute research organization,^30,31 and one study (8.33%) did not indicate the location of the study. Mean age: 40,46 years Thus, the Total number of patients was 395. The gender split of participants was 29.9, male and 70.1, female; nonetheless, 50% of the studies failed to report patient sex. The Total number of bone grafts was 58.1% bovine bone blocks and 41.9% allograft bone blocks.

Specificity of surgery was mentioned by 58.3% of the articles, as the surgeries performed included surgeries involving specified zones of the posterior mandibular region, maxillary anterior region, and the premolar region, sinus floor augmentation, anterior maxillary region, single-rooted teeth region, lateral window approach for the maxilla, posterior molar, and preliminary zones. Nevertheless, 41.7% of the studies investigated failed to specify them for surgical sites. A wide variety of bone grafts were used, with some materials: 8.3% used a 10% collagen matrix, 8.3% used a collagen membrane, 8.3% used NBCM and RECXC, and 75% of which the response did not specify which type of membrane they employed.

3.3 Outcome evaluation

Comparing the Gingival Index for FM of the two study subjects at 1 year, we found the following results: allograft 0.86 ± 0.31, and xenograft 0.82 ± 0.12. In the IMP site at 1 year, AL adjusted for Allograft resulted as 0.94 ± 0.21 and xenograft 0.80 ± 0.26 for both groups for the maintenance of gingival health. Probing depth: Consequently, the values in both groups declined over the 1-year period, implying that good implant stability was achieved. Bone resorption: Both groups experienced a mild degree of bone loss around the implant in the mesial and distal areas, although the results were not statistically significant.¹⁵ The average contrast and differential entropy of the allograft and xenograft image pairs were carefully compared, and no significant differences were observed (P > 0.05). Furthermore, the authors could not document a significant difference in the dif variance between xenografts and allografts. Therefore, all other of the following pairing; X-Atl, X-PT, X-Pal, Pt-Atl, Pt-Pal and Atl-Pal had a significantly different outcome (P < 0.05).²⁴ Radiographic evaluation: Preoperatively alveolar bone loss in the crystal region was measured to be -1.85 ± 1. 26 mm in the xenograft area and -1.75 ± 1. 51 mm at the allograft area (P = 0.791). The distance of the regenerated osseous crest at 3 months following tooth extraction and ridge preservation was 1.17 ± 0.83 for the group treated with xenograft and 1.00 ± 1.14 for the group treated with allograft (P = 0.523). In the last re-entry session, the sites with grafted bone differentiated them again at 6 and 8 months postoperative. After the radiographic assessment, the mean bone resorption of the allografts appeared to be slightly greater than that of the xenografts 0.9 ± 0.52 mm after 3 months. Change in bone loss after these months for allografts was raised to 1.83 + 0.42 and for xenografts was 1.37 + 1.12 with no significant difference, P > 0.5³⁰ Clinical comparison The assessment of gingival and plaque indices The gingival and plaque indices in the two groups were compared statistically at three, six, and 12 months of follow-up in the study groups demonstrated no statistical significance (P > 0.05). The mean probing depths and resorption of bone at three, six, and 12 months of follow-up were not statistically significant (P > 0.05) in the intergroup comparison.¹⁰ A clinical and histomorphometric analysis of both groups showed shrinkage of bone dimensions. At mesial, canter and distal sites, the vertical changes in dimension were 20.6, 0.5, and 20.1 mm for the allograft and 21.1, 20.4, and 20.9 mm for the xenograft. The horizontal changes in dimensions were 21.4 mm for the allograft and 22.6 mm for the xenograft. New bone and residual graft material were 25.5610.1% and 33.869.4% at the allograft and 35.3616.8% and 22.2613.4% at the xenograft sites.⁴ Xenograft in the immediate implant site showed excellent osseointegration around the immediate implant site. However, the differences between the groups were not statistically significant.²⁵ A non-significant difference was observed in all parameters at different time intervals (P > 0.05) recorded on the mesial, distal, buccal, and lingual sides.³²

Xavier SP Found Implant survival rate: FFB (fresh frozen bone allograft) 97.8%, BBM (bovine bone mineral) 100% (P = 0.352) Bone volume and resorption (CT evaluation): FFB group: median resorption rate 31.2% BBM group: median resorption rate 12.22%, significant differences in initial and final bone volumes (P = 0.015) and resorption rates (P = 0.009); histological findings: FFB: residual FFB with empty osteocyte lacunae, new bone formation, and no inflammation BBM: particles in close contact with new bone, osteoclasts present, and no inflammation.²⁶ The mean marginal bone level in xenograft at baseline (13.58 ± 1.09), 3 months (12.64 ± 0.88), 6 months (12.02 ± 1.42), and 12 months (11.20 ± 1.26), respectively. In allograft, the marginal bone level was at baseline (14.22 ± 0.26), 3 months (13.52 ± 1.28), 6 months (13.10 ± 0.32), and 12 months (12.12 ± 1.26), respectively. A statistically significant difference was observed between the two groups. Moreover, there were no statistically significant differences between the groups.

Duration of intergroup comparison of the mean marginal bone level. The mean difference of implant stability in xenograft the implant stability was 188.6 ± 22.5 and in allograft was 191.5 ± 18.2, and there was no statistically significant difference found between the groups²⁷ Changes in ridge width at 6 months were 1.5 mm for AL versus 2.5 mm for BB and 2.3 mm²⁸ Newly formed bone percentage: Allograft: mean 65% (range 22-86%) Xenograft: mean 45% (range 13-67%) Significant difference found between allograft and xenograft (P < 0.05) Remaining graft particles percentage: Allograft: mean 27% (range 7-62%) Xenograft: mean 41% (range 10-79%) Distribution analysis: Only the allograft group showed differences in the distribution of newly formed bone percentage (Shapiro-Wilk test)²⁹ Primary endpoint of Scheyer ET: at 6 months, extraction socket horizontal measures were significantly greater for DBBMC + NBCM (average 1.76 mm greater, P = 0.0256). Secondary and Exploratory endpoints: lingual and buccal vertical bone changes were not significantly different between the two treatment modalities, histomorphometric% new bone and % new bone + graft were not significantly different, but significantly more graft remnants remained for DBBMC at 1 month, incision line gaps were significantly greater and more incision lines remained open for DFDBA + RECXC; higher inflammation at 1 week tended to correlate with lower ridge preservation results; and deeper socket morphologies with thinner bony walls correlated with better ridge preservation. Thirty-seven of the 40 sites had sufficient ridge dimensions for implant placement at six months; the remainder were DFDBA + RECXC sites.³¹

3.4 Risk of bias

The majority of domains in the RoB 2 tool ( Figure 2) were low to moderate, indicating that many of the trials making up the review had reasonable rigor. Nevertheless, some concerns and one high-risk domain suggest certain caveats in the interpretation of the findings. In non-randomized studies, there are apparently more serious issues according to ROBINS-I evaluation ( Figure 3). The most worrisome source of risk for bias in this case is confounding, as confounding threatens the validity of findings in observational studies. These results indicate that there are systematic problems in the design and conduct of the studies; more specifically, the moderate risk of bias in participant selection, data selection, and outcome measurement in the five domains is an indication of this.

Figure 2. Quality assessment of studies using ROB2 for RCT.

Figure 3. Quality risk of bias using ROBINS I for non-randomized clinical trial.