β-Tricalcium Phosphate as Alveolar Bone Grafting in Cleft Lip/Palate: A Systematic Review

The aim of this systematic review is to describe and identify the prospects of β-Tricalcium Phosphate (β-TCP) as an alveolar bone grafting (ABG) material in cleft lip/palate (CL/P) or alveolar bone cleft defects. A systematic review protocol based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) was drafted. The literature search was conducted using MEDLINE/PubMed, Web of Science/ISI Web of Knowledge, Scopus, and the Cochrane Library, with English as the inclusion criterion and no publication year limits. The keywords yielded a total of 5824 publications. After removing duplicates and non-English articles, there were 3196 suitable articles available for evaluation. Subsequently, 1315 studies remained after reviewing titles and abstracts. Furthermore, 85 full articles were assessed for eligibility. After reading the complete texts of those papers, 20 were eventually selected that matched the inclusion requirements. Thirteen out of the twenty studies included in this systematic review were deemed to have a low risk of bias; one had a high risk of bias; and six had a moderate risk of bias due to not reporting randomization. β-TCP, when used as an ABG material, is biocompatible, visible, practical, offers a less invasive procedure, and does not interfere with orthodontic treatment. Synthetic β-TCP for ABG can be an alternative to autologous bone grafts under certain terms and conditions. The efficacy of β-TCP for ABG in CL/P or alveolar bone cleft defects can be enhanced through a tissue engineering approach that combines β-TCP with growth factors, mesenchymal stem cells, or other graft materials, along with modifications to β-TCP’s physical properties.


Introduction
Cleft lip/palate (CL/P) is a major congenital birth defect in the craniofacial structure caused by a defect in palatogenesis during the embryonic phase.CL/P etiology is impacted by genetic, environmental, and a mixture of both factors.CL/P is shown clinically as a cleft in the lip, alveolar bone, palate, and nasal septum.The patients have cosmetic and functional deficiencies [1].CL/P is one of the most frequent orofacial congenital abnormalities worldwide [2].The epidemiology of cleft lip, cleft palate, and cleft lip and palate (CL/P) has been recorded at roughly 1 in 700 births, but it has also been reported at 1 in 500 to 1 in 2500 births in other parts of the world [3,4].The prevalence of CL/P was estimated to be 10.8 million people in 2017, with a disease burden of 652.084 disability-adjusted life years in low-and middle-income countries (94.1%) [5].CL/P is highly common in the Asia area, particularly in Japan, China, and Indonesia, which are high-risk nations for CL/P [6][7][8].
Lifetime costs, loss of productivity, lack of self-confidence due to facial, aesthetic, or cosmetic aspects, increased utilization of mental health services, speech and hearing impairment, prospect of β-TCP as ABG in CL/P has not yet been fully elucidated and remains limited.Therefore, the aim of this systematic review is to describe the regenerative prospect of β-TCP as an ABG material in CL/P based on the existing literature.
is expected to be promising and helpful for clinical results in CL/P therapy.β-TCP materials, followed by xenograft biomaterials, which regrettably still lack established predictability and clinical efficacy, dominate the cranio-maxillofacial market [15].Figure 1 illustrates the possible mechanism of action when β-TCP is used in a tissue engineering approach as an alveolar bone graft in CL/P or an alveolar bone cleft defect.Despite numerous efforts made to investigate the ABG in the field of cranio-maxillofacial medicine, the regenerative prospect of β-TCP as ABG in CL/P has not yet been fully elucidated and remains limited.Therefore, the aim of this systematic review is to describe the regenerative prospect of β-TCP as an ABG material in CL/P based on the existing literature.

Focused Question
Following the Participants, Intervention, Control, and Outcomes (PICO) principle, a focused question was formulated before conducting the literature search according to Preferred Reporting Items for Systematic Reviews and Meta Analyses 2020 (PRISMA 2020).The focused question was 'What is the prospect β-TCP as an ABG material to stimulate the regeneration of CL/P or alveolar bone cleft defects?'.

Search Strategies
A systematic review protocol based on PRISMA 2020 was drafted.In addition, reporting was based on the PRISMA 2020 checklist [16,17].In addition, the systematic review was recorded in the international platform for registering systematic reviews and meta-analysis protocols (INPLASY) with registration number INPLASY202380113.

Eligibility Criteria
The following categories of articles were included in this review: original articles that focused on the methodology of using β-TCP as an ABG material in animal models or humans to regenerate CL/P or alveolar bone cleft defects.Open access (accessed through the Graduate School of Dentistry, Tohoku University's IP address) of full-text articles relevant to β-TCP ABG for CL/P or alveolar bone cleft defect were used as inclusion criteria.Reviews, short communications, editorial notes, processes, and recommendations were not considered and excluded.All types of experimental and observational studies in English were included.Nevertheless, no duplicate studies were included in the analysis.Adults or children of any gender or age are acceptable study subjects, as are any other objects of in vivo research.CL/P, alveolar cleft defect, β-TCP, and ABG, as well as any additional therapies involving tissue engineering, were included in the research as study factors or exposures.Bone regeneration, bone repair, bone volume, dentistry, bone remodeling, and any other measure of bone regeneration in CL/P were among the outcomes of the research examined.Articles in languages other than English, letters to the editor, and all types of reviews and commentaries were excluded.There were no restrictions on the year of publication, but only full papers could be accessed for free.The most recent search was conducted in June 2023.

Study Selection and Data Extraction
The three reviewers (A.P.N., H.Y., and J.C.) independently conducted electronic literature searches and selected the studies.Any disagreements were resolved by discussion or by consulting a second reviewer (J.R.V.S., G.H.) [16,17].The reviewers (A.P.N., H.Y., and J.C.) worked to duplicate screening, extract, and recapitulate data using a standardized form in Microsoft Excel that had been validated prior to use [18].Data was primarily extracted using the PICO protocol (Participants: patients (for clinical studies) or animals (for in vivo studies); Intervention: β-TCP ABG; Controls: autograft, xenograft, no treatment, or other regenerative materials; Outcomes: bone regeneration or bone remodeling of CL/P or alveolar bone cleft defects; Data relevant to methodology, sample size, duration of the studies, and the investigations carried out were extracted from each study.Results from the animal (in vivo) and human clinical studies were tabulated in the table using predetermined data collection forms by the two investigators independently [19].

Quality Assessment of Studies
Depending on the type, each study was assessed individually and independently by investigators.It was decided that for the quality assessment of any randomized clinical trials, the Consolidated Standards of Reporting Trials (CONSORT) would be used.The Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines were selected for animal studies.Any disagreements were solved by discussion between investigators.

Risk-of-Bias Assessment
The risk of bias evaluation was carried out in accordance with a technique derived from prior systematic reviews [16,17,20].This assessment evaluated the description of several quality assessment parameters, including a well-defined β-TCP as an ABG process, standardized sample or subject preparation, randomization of samples or subjects, tests conducted by a single blinded operator, a clear test method specification, and comprehensive reporting of results.The article was labeled "Y" for a given parameter if the authors reported it and "N" if the information could not be located.The articles were classified as having a high, medium, or low risk of bias based on the number of "Y" elements included (1-2, 3-4, or 5-6).

Statistical Methods
Microsoft Office Excel (2010, Microsoft, Chicago, IL, USA) was used for descriptive statistics.Due to the heterogeneity of the papers, a pairwise meta-analysis could not be performed.

Study Selection, Data Extraction, and Quality Assessment
The keywords yielded a total of 5824 articles published, with 90 papers from Scopus, 6 papers from PubMed, 4510 papers from the Web of Science, and 1218 papers from the Cochrane Library, respectively.The 3196 suitable articles to evaluate after removing duplicates and languages We had 1315 studies left after doing title and abstract reading.Eighty-five full articles were assessed for eligibility.They read the complete texts of those papers and eventually chose 20 that matched the inclusion requirements.The reviewers (A.P.N., H.Y., and J.C.) independently performed critical evaluations utilizing JBI critical evaluation tools.Figure 2 depicts the flow diagram of the study selection process.A summary of descriptive characteristics of the articles included in this study is shown in Table 2 about animal model experiment.In addition, summary of descriptive characteristics of articles included in human clinical studies shown in Table 3.Average defect volume, bone formation ratio (%), bone volume (mm 3 ), and bone formation ratio (%) were not significantly different between groups.

Alveolar cleft repair with autologous BMMNCs and β-TCP
granules was radiographically similar to using ICBG.

Assessment of the Risk of Bias and Quality
The reviewers read the complete texts of those papers and eventually selected 20 studies that met the inclusion criteria.Thirteen of the twenty studies included in this systematic review had a low risk of bias, one had a high risk of bias, and six had moderate bias.Most of the studies did not report the randomization, which is considered a potential source of bias (Table 4).

Qualitative Analysis
Most of the studies included in this systematic review were experimental studies using animal models of alveolar bone cleft defects that were representative of CL/P patients.There were fourteen studies using an alveolar bone cleft defect animal model.Six studies used dogs [24][25][26]29,31,34], five studies used rats [21,22,27,28,33], two studies used goats [30,32], and only one study used rabbits [23].Only one research study claimed that the rat's palatine fissure was an acceptable location for the bone substitute implant application of bone graft materials to replicate the human alveolar cleft in animal model studies of CL/P.In addition, the palatine fissure is a congenital bone abnormality comparable to the alveolar cleft abnormalities seen in people [27].Nevertheless, the rest of the studies were successfully established and reported the research outcome for the alveolar bone cleft defect animal models.A preliminary or pre-clinical study using an animal model as a representative of CL/P conditions in patients is important before the clinical application of the proposed ABG in the clinical setting.
On the other hand, there were several studies of β-TCP application in CL/P patients in a clinical setting, such as five articles of case-control clinical studies [25,32,37,38,40] and one article of a retrospective cohort study [35].Most clinical setting studies of CL/P focused on unilateral alveolar cleft [25,[36][37][38]40].However, only one study used the unilateral or bilateral cleft patients as the study participant in the retrospective study setting [35].The most frequent prevalence of CL/P type in patients was unilateral alveolar cleft.Out of the 20 articles included in this systematic review, 6 articles also investigated the potential impact of alveolar bone graft (ABG) application on orthodontic treatment [21,[28][29][30][31]36,40].β-TCP is a more biocompatible alternative to autogenous bone transplantation for orthodontic tooth movement in alveolar bone cleft abnormalities [29].Other earlier research has found that the use of β-TCP does not impair orthodontic treatment [30,31,40].
Some studies suggested β-TCP, which is a bioceramic, as an ABG material for bone regeneration in CL/P or alveolar bone cleft defects.Notwithstanding this, β-TCP alone cannot substitute for autologous ABG [21].The result of a previous study found a lower bone volume (BV) and bone mineral density (BMD) after β-TCP application compared to autologous ABG [27].β-TCP may be able to overcome its lack of osteoinductive and osteoconductive qualities after undergoing many physical changes or the inclusion of certain stem cells or growth factors.There are several modifications of β-TCP as the alternative ABG, such as the combination of rhBMP2 in a β-TCP scaffold [35], AMSCs seeded in β-TCP [22,24], BMSCs or BMMNSCs combined with β-TCP granules [26,31,34,37], β-TCP in microporous [25,32,36], composite xenogeneic dentin with β-TCP [23], the mixture of autologous ABG in β-TCP granules [32,38,40], combination of HA-β-TCP [28], col/β-TCP scaffolds, and PLLA/PCL scaffolds [33].Even though autografts are the best option for bone regeneration, tissue-engineered β-TCP might be a viable alternative, particularly if autografts are hard to come by or there is donor site morbidity [39].Thus, it may decrease the surgical pain and the number of hospital stay days [37].

Discussion
The objective of alveolar cleft repair is to reconstruct bone volume and quality to match the original anatomy.The accompanying soft-tissue attachment of the oral and nasal mucosa is specific to these cleft abnormalities [21].This systematic review aimed to provide a summary of existing research on the regeneration possibility of β-TCP as ABG in cleft lip and palate patients or alveolar bone cleft defect animal models, assessing the success or failure of these interventions.Overall, the findings of this comprehensive analysis show that the use of β-TCP as ABG improves the regeneration of alveolar bone cleft defects in CL/P humans or animal models (in vivo) [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40].
Nevertheless, a downside of β-TCP alone cannot substitute the golden standard of ABG, which is autologous bone graft [27].Autologous bone remains the gold standard for cleft repair.However, autografts have certain drawbacks, including restricted bone supply, the requirement for an extra donor site, the accompanying postoperative morbidity (pain, hematoma, and delayed ambulation), and an intrinsic sensitivity to resorption in the long run [21].Therefore, different tissue-engineered bone replacements have been proven to be effective options for encouraging bone fusion and minimizing donor site morbidity.The β-TCP is a bioceramic, a synthetic ABG described, and has been recognized to be an alternative to autologous or xenograft ABG, which is acceptable in numerous terms and situations [25].β-TCP with tissue engineering modification eliminates the limits of autologous bone grafts, such as limited donor supply and donor site morbidity, and minimizes the patient's surgical stress, which may be connected to a decreased operating time and hospital stay duration reported [23].
Regarding the post-operative or post-treatment examination of newly produced bone or bone regeneration, the majority of the included research employed CBCT for clinical investigations and micro-CT or HPA for in vivo studies.We found that five studies used CBCT to examine bone regeneration in post-operative CL/P patients, and four studies used conventional dental occlusal radiographs [26,29,31,40].CBCT scans provide a reduced radiation dosage and a limited scanning time (10-70 s), and they allow doctors to scan a small region for a specific diagnosis with fewer picture artifacts [43][44][45].Orofacial cleft patients require a 3D study for the right diagnosis as they present with numerous medical disorders, including bone graft operations, impacted teeth, or supernumerary teeth.This is the reason why CBCT is advised for orofacial cleft patients by the European Academy of Dental and Maxillofacial Radiology [46].Therefore, additional research should employ CBCT as an evaluation technique to quantify newly produced bone, especially in clinical situations.Thus, the registration of the protocol is encouraged and will strengthen its robustness in subsequent studies.Although systematic reviews are regarded as the most solid evidence, the research included in each systematic review also has a related bias.The methodological variability includes discrepancies in the trial locations, a lack of a priori acceptable sample size estimates, the kind of sample included (e.g., type of cleft, age groups), intervention protocols, bone measuring techniques, and follow-up timeframes.Other factors may alter the analysis of primary outcomes as they affect bone remodeling, notably the location of teeth on the bone graft, the cleft defect's breadth, and the volume of grafted bone [47].
The most apparent source of autologous ABG would be the iliac crest bone, which may be retrieved by a surgical procedure with a risk of morbidity, such as infection.However, employing this option in every circumstance would not be practicable, and a synthetic ABG such β-TCP would be more sensible [21,26,30,39].In the research evaluated, there were various constraints that may have biased outcomes.With the information currently available from in vivo and clinical studies, the overall effect summary of β-TCP as ABG for CL/P or alveolar bone cleft defect cannot be determined.Furthermore, these findings should be regarded with caution since clinical and in vivo methodological heterogeneity might alter the extent of the statistical heterogeneity revealed.This systematic review found multiple heterogeneity variables, such as the number of participants or samples, kind of cleft defect, different treatment, timing of outcome, and intervention design.In the present review, we noticed that six of the studies did not apply any type of randomization [24,35,36,[38][39][40].A lack of randomization may have altered the direction of results due to examiners' bias.
The primary results may also be altered by the clinician's skill and the study group's scientific competency.Secondarily, most selected studies were classified as having poor or middling overall quality, which may lower confidence in the findings [47].Moreover, the included studies might overstate the impact of the findings due to the inclusion of numerous publications from a single research project or by ignoring studies in other languages.In this systematic review, the majority of the studies employed a small sample size.In addition, varied and diverse criteria for CL/P patient selection could have had an impact on the estimated efficacy of β-TCP as an ABG material.Nevertheless, there is no gold standard for alveolar bone cleft defect size in animal models.Because of the variability in the techniques, measurements, and findings, it was not possible to perform a meta-analysis in this systematic review.A systematic review without meta-analysis may carry a substantial risk of bias.This was likely the most significant shortcoming of our review, as the mean overall effectiveness of β-TCP could not be calculated.Future studies should conduct blinded RCTs to control various sources of bias, such as the randomization technique, assessment equipment, and follow-up timeframes.Moreover, the cost-benefit analysis of these β-TCP to be employed in tissue engineering procedures for regeneration strategies in the ABG of CL/P is advocated as it plays a vital role in healthcare regulation.

Conclusions
The following findings may be drawn from this systematic review:

•
β-TCP as an ABG material is biocompatible, more visible and practical, offers a less invasive procedure, and does not interfere with orthodontic treatment.

•
β-TCP as a synthetic ABG material can be the alternative to autologous bone grafts with several terms and conditions, such as if autografts are hard to come by, there is donor site morbidity, and the size of the defect restricts the size of the autograft.

•
The enhancement of osteoinductive and osteoconductive abilities for improvement of β-TCP efficacy for ABG in CL/P or alveolar bone cleft defects can be achieved via a

Figure 1 .
Figure 1.Illustration mechanism of action possibility β-TCP was used in a tissue engineering approach as an alveolar bone transplant in CL/P or an alveolar bone cleft defect (illustration image created with BioRender: Scientific Image and Illustration Software (https://www.biorender.comaccessed on 30 June 2023) and alveolar bone cleft defect image from Texas Children's Hospital (www.texaschildrens.orgaccessed on 30 June 2023).

Figure 1 .
Figure 1.Illustration mechanism of action possibility β-TCP was used in a tissue engineering approach as an alveolar bone transplant in CL/P or an alveolar bone cleft defect (illustration image created with BioRender: Scientific Image and Illustration Software (https://www.biorender.comaccessed on 30 June 2023) and alveolar bone cleft defect image from Texas Children's Hospital (www.texaschildrens.orgaccessed on 30 June 2023).
ALL = (β-tricalcium phosphate)) OR TS = (β-TCP)) OR TS = (bone graft)) OR TS = (bone grafting)) OR TS = (alveolar bone graft)) AND TS = (alveolar bone cleft)) OR TS = (cleft palate) Refined By: Open Access.Click to remove this refine from your search.Document Types: Article.Click to remove this refine from your search.Open Access: All Open Access.Click to remove this refine from your search.Languages: English.Cochrane Library β-tricalcium phosphate OR β-TCP OR bone graft OR bone grafting OR alveolar bone graft AND alveolar bone cleft OR cleft palate in Title Abstract Keyword-in Trials, Clinical Answers (Word variations have been searched)

Figure 2 .
Figure 2. Flow diagram of PRISMA 2020 in the study selection process.Figure 2. Flow diagram of PRISMA 2020 in the study selection process.

Figure 2 .
Figure 2. Flow diagram of PRISMA 2020 in the study selection process.Figure 2. Flow diagram of PRISMA 2020 in the study selection process.

Table 1 .
Databases and search strategies of this study.
Scopus β-tricalcium AND phosphate OR β-TCP or bone graft OR bone grafting OR alveolar AND bone AND graft AND alveolar AND bone AND cleft OR cleft AND palate AND (LIMIT-TO (PUBSTAGE, "final")) AND (LIMIT-TO (OA, "all")) AND (LIMIT-TO (DOCTYPE, "ar")) AND (LIMIT-TO (LANGUAGE, "English")) AND (LIMIT-TO (SRCTYPE, "j")) PubMed β-tricalcium phosphate OR β-TCP OR bone graft OR bone grafting OR biomaterial OR alveolar bone graft AND alveolar bone cleft AND cleft palate Filters applied: Free full text, Clinical Trial, Randomized Controlled Trial, English, Exclude preprints, MEDLINE.

Table 2 .
Summary of descriptive characteristics of articles included in animal model experiments.

Table 3 .
Summary of descriptive characteristics of articles included in human clinical studies.

Table 4 .
Individual studies are prone to bias.JBI critical appraisal for prevalence data studies.