Outcomes of dental autotransplantation in relation to dental root formation. Systematic review and meta-analysis

Abstract

Introduction

Dental autotransplantation (DAT) is a surgical procedure used to replace hopeless or missing teeth. The technique entails the purposeful extraction of a desired sound tooth, which is then implanted into another alveolar site of the same oral cavity.

Objectives

To analyse the survival rates and success rates of DAT in relation to donor teeth with an incomplete root development (open apex) and complete root formation (closed apex). Additionally, it attempts to evaluate the prognostic components of DAT with infection-related (inflammatory) root resorption, ankylosis, and pulpal necrosis complications.

Materials and methods

An electronic search was conducted using EBSCO MEDLINE Web of Science, Scopus and Cochrane databases from January 2014 until November 2024. The selected articles were chosen within the parameters outlined in the Materials and Statistical Methodology section. The addressed PICO question “does the stage of the donor tooth’s root development affect the long-standing prognosis and clinical outcomes of dental autotransplantation?”.

Results

The final 26 articles featured a total of 2837 transplanted teeth: 2192 donor teeth with an open apex and 645 donor teeth with a closed apex. The overall survival rate was 93.8% in the open apex group and 92.6% in the closed apex group. Success rate was 84.0% in the open apex group and 86.7% in the closed apex group. The rate of infection-related root resorption was 6.3% in the open apex group and 5.9% in the closed apex group. The rate of ankylosis was 4.4% in the open apex group and 6.7% in the closed apex group. The rate of pulp necrosis was 6.4% in the open apex group. No factors were identified as influencing the rate of pulp necrosis; however, the duration of follow-up was significantly associated with the rate (p = 0.057). None of the selected articles reported pulp necrosis rate in the closed apex; thus, no meta-analysis was possible.

Conclusion

DAT is a reliable treatment alternative for the replacement of lost teeth. The procedure yields low complication rates of infection-related root resorption, ankylosis, and pulp necrosis, while achieving high rates of survival and success. It can be accomplished with donor teeth that have an open or closed apex.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-025-01450-0.

Introduction

The replacement of lost or hopeless teeth due to etiological factors such as dental agenesis, tooth loss secondary to trauma, or dental caries remains an outstanding issue in modern dentistry today. Numerous treatment options are available to address this issue, such as removable or fixed prostheses, orthodontics, osseointegrated dental implants (ODIs), and dental autotransplantation (DAT); however, the ideal clinical protocol has yet to be established. DAT is defined by the American Association of Endodontics (AAE) as “the extraction of a tooth from its original site, placing it in an edentulous recipient site, whether it’s a post-extraction socket or a surgically prepared socket, within the same mouth” [1] Fig. 1. The procedure has a rich historical lineage whose foundations were constructed centuries ago, but regrettably have not been well-documented or widely recognised.

Fig. 1.

DAT of an impacted 2.8, transplanted into the 2.6 alveolus with a 3D printed tooth replica of the donor tooth. A Bayonett flap preparation of 2.8 B ostectomy of bone surrounding 2.8 C Odontosection of 2.6 D Simple extraction of 2.6 fragments following odontosection E 3D printed tooth replica insertion into 2.6 alveolus to confirm its new show of the 2.8 F Extraction of 2.8 G Comparison of 3D printed tooth replica of 2.8 with existing 2.8 tooth H Transplantation of 2.8 into 2.6 recipient alveolus I Semi-rigid splint (0.5 mm wire) of the transplanted tooth to adjacent teeth. Conducted on the vestibular surface using resin composite acid etch technique. Peña-Cardelles, J., Ortega-Concepción, D., Moreno-Perez, J., Asensio-Acevedo, R., Sánchez, A., García-Guerrero, I., & Gómez-De-Diego, R. (2021). Third molar autotransplant planning with a tooth replica. A year of follow-up case report Fig. 2a–i. Journal of Clinical and Experimental Dentistry, e75–e80. https://doi.org/10.4317/jced.57066

In child and adolescent patients, the use of ODIs are contraindicated in the replacement of lost or hopeless teeth as the patient’s craniofacial structures are in continual development alongside adjacent tooth germs in the dental arch. According to Sharma et al., the average age for the maxillofacial structure to finish substantial growth is 16–18 years, whilst in males it is 18–21, thus ODIs ideally should not be placed until this time [2]. DAT, therefore, serves as a viable treatment alternative for these patients. In adults, DAT is indicated for exodontia, hypodontia, and relocation of ectopic dental eruptions [3].

DAT has a highly variable success rate, ranging from 0% [4] to 100% [5]. Lunderg et al. reported typical post-operative complications after DAT affecting the survival rate and success rate of the procedure, including both inflammatory (infectious) root resorption and replacement (ankylosis) root resorption and pulp [6]. These factors are contingent on the observation time after the procedure, the surgical protocol and a range of prognosis factors such as patient age; type of donor tooth; recipient alveolar transplant site; splinting procedure; splinting duration; transplanted tooth occlusal seating; the use of 3D printed replicas of the donor tooth; the use of pre-orthodontic force on the donor tooth; and extra oral time [7–10]. Due to insufficient evidence, researchers have been unable to establish the potential connections between these prognosis elements and the long-term success and survival of DAT, thus have been unable to confirm absolute conclusions.

The purpose of this article is to review DAT studies published within the past 10 years which record complications such as root resorption, ankylosis and pulpal necrosis in relation to the stage of root development of the donor tooth. It shall present comprehensive evidence and highlight defective results in the existing literature. The overall appraisal should integrate DAT success and long-term survival rates in relation to fundamental prognostic factors. This increased awareness of DAT will enable dental professionals to counsel patients on when DAT is an appropriate course of treatment, with the goal of expanding its use within the dental community.

Although several systematic reviews and meta-analysis have been conducted in the past regarding the success and survival rate of DAT [11–15], these articles analysed pioneer studies of DAT, with large scale studies conducted throughout the mid to late twentieth century, such as 1974 Slagsvold et al. [16]. This article has assessed the contemporary dental literature of DAT, conducted within the last 10 years, whilst simultaneously illustrating a unique perspective of the potential prognosis factors which can influence the procedure. Modern technologies, such as CBCT and 3D-printed tooth replicas of the donor tooth, as well as pre-orthodontic forces before donor tooth extraction, were not evaluated in some of these previous studies. These factors have been shown to influence the survival rate and success rate of the procedure.

Hypothesis and objectives

H1: The survival rate and success rate of DAT are more likely in donor teeth with an incomplete root formation (open apex) compared to teeth with a complete root formation (closed apex). Furthermore, prognostic factors such as age of patient; type of donor tooth; recipient alveolar site; splinting method; splinting duration; occlusal seating of donor tooth; use of 3D printed replica donor teeth; extra-oral time of the donor tooth; pre-orthodontic force affect the long-term survival and success of the DAT.

N0: The survival rate and success rate are not influenced by the donor tooth’s stage of root development. Prognosis factors such as age of patient, type of donor tooth, recipient alveolar site, splinting method and duration, occlusal seating of donor tooth, use of 3D printed replica donor teeth, extra-oral time of the donor tooth and the pre-orthodontic force do not influence the long-term survival and success of the DAT.

Objectives

General objective

Evaluate the prognostic factors of DAT, including patient age, type of donor tooth, recipient alveolar site, splinting method, splinting duration, occlusal seating of donor tooth, use of 3D printed replica donor teeth, pre-orthodontic force, and extra-oral time.

Specific objective

1. Document the 6-month, 1-, 5-, and 10-year overall survival rates and success rates in DAT with teeth, and identify the root resorption rate, ankylosis rate, and pulpal necrosis rates throughout the included articles.

2. Evaluate the outcome of DAT in relation to transplanted teeth with incomplete root formation (open apex) and complete root formation (closed apex).

Materials and statistical methodology

An electronic search was conducted in established online databases. The search strategy protocol was outlined and performed, followed by article screening, paper selection, and statistical analysis. This systematic review and meta-analysis were completed following the statement of the PRISMA guide (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) [17].

A PICO question was generated:

Population: Patients with a loss of a single individual tooth due to an indication such as tooth agenesis, traumatic tooth loss, tooth decay or periodontal disease.

Intervention: Dental autotransplantation (DAT) involving a donor tooth with incomplete root formation (open apex) in child and adolescent patients.

Comparison: Compared to Dental autotransplantation (DAT), which involves a donor tooth with a complete root formation (closed apex).

Outcome: 1. Primary outcome: evaluation of DAT survival rates 6 months, 1, -5, -10 years after the procedure was completed and success rates. 2. Periodontal outcome of DAT: infection-related root resorption, ankylosis, and pulpal necrosis.

The PICO question “does the stage of the donor tooth’s root formation affect the long-term prognosis and clinical outcomes of dental autotransplantation?”.

Eligibility criteria

The selected literature and clinical studies included in this systematic review and meta-analysis had to be in strict accordance with the following criteria Table 1.

Table 1.

Inclusion and Exclusion criteria during the article selection process

Inclusion criteria	Exclusion criteria
Type of Study
Studies published in English, dated between January 2014 and November 2024. The following research formats were included: human studies, retrospective and prospective studies, randomised clinical trials, controlled clinical trials, observational studies, and case series	Animal studies, expert opinion pieces, editorials, case reports, technical reports, questionnaires, and in vitro studies
Type of Candidate
Studies had to examine five or more test candidates. Studies should analyse both genders and not exclude any ethnic background. Studies that feature patients with an ASA grade I or II (American Society of Anaesthesiologists) [18]	Studies including patients with pre-operative systemic health pathologies that fall into category ASA III-VI; pregnant or lactating patients; patients who are taking chronic pharmaceutical medications which could affect DAT outcome, eg) bisphosphonates; patients who have been irradiated in the Head or neck within 1 year of DAT procedure
Type of Intervention
Studies investigating DAT in relation to incomplete or complete root formation of a single tooth, due to tooth agenesis, traumatic tooth loss, tooth decay, or periodontal disease (which has since been treated and resolved)	Studies that evaluate DAT after severe trauma to the craniofacial structure and anterior quadrants of the mouth, which involve deciduous teeth, intentional reimplantation or cryopreservation
Type of Outcome
Studies that report DAT post-operative statistical data. Studies documenting DAT long-term survival rates and success rates with a minimum of 1 year post-completion. Studies that documented DAT complications, including tooth ankylosis, dental root resorption and pulpal necrosis	Studies that do not report any statistical data regarding post-operative survival rates, success rates, prognosis factors or complication rates of DAT

Search strategy and study selection

An electronic search was conducted using EBSCO MEDLINE [19], Web of Science [20], Scopus [21] and the Cochrane databases [22]. The elementary keywords used in the search include “tooth autotransplantation” and “dental autotransplantation”. These keywords were integrated with Boolean operators such as “AND” or “OR” before commencing the advanced electronic search option, Table 2. MeSH terms were utilised in the PubMed [23] search to generate a more appropriate and extensive search among the dental literature Fig. 2.

Table 2.

Rundown of MeSH term searches conducted in specific electronic databases

Database	Search MeSH terms	No. of Articles	Date of Search
EBSCO Medline	Search: (tooth autotransplantation) OR (dental autotransplantation) Filters: in the last 10 years, Full text, English, Humans ((("teeth s"[All Fields] OR "teeths"[All Fields] OR "tooth"[MeSH Terms] OR "tooth"[All Fields] OR "teeth"[All Fields] OR "tooth s"[All Fields] OR "tooths"[All Fields]) AND ("autotransplantion"[All Fields] OR "transplantation, autologous"[MeSH Terms] OR ("transplantation"[All Fields] AND "autologous"[All Fields]) OR "autologous transplantation"[All Fields] OR "autotransplantation"[All Fields] OR "autotransplantations"[All Fields])) OR (("dental health services"[MeSH Terms] OR ("dental"[All Fields] AND "health"[All Fields] AND "services"[All Fields]) OR "dental health services"[All Fields] OR "dental"[All Fields] OR "dentally"[All Fields] OR "dentals"[All Fields]) AND ("autotransplantion"[All Fields] OR "transplantation, autologous"[MeSH Terms] OR ("transplantation"[All Fields] AND "autologous"[All Fields]) OR "autologous transplantation"[All Fields] OR "autotransplantation"[All Fields] OR "autotransplantations"[All Fields]))) AND ((y_10[Filter]) AND (fft[Filter]) AND (humans[Filter]) AND (english[Filter])) Translations: tooth: "teeth's"[All Fields] OR "teeths"[All Fields] OR "tooth"[MeSH Terms] OR "tooth"[All Fields] OR "teeth"[All Fields] OR "tooth's"[All Fields] OR "tooths"[All Fields], autotransplantation: "autotransplantion"[All Fields] OR "transplantation, autologous"[MeSH Terms] OR ("transplantation"[All Fields] AND "autologous"[All Fields]) OR "autologous transplantation"[All Fields] OR "autotransplantation"[All Fields] OR "autotransplantations"[All Fields], dental: "dental health services"[MeSH Terms] OR ("dental"[All Fields] AND "health"[All Fields] AND "services"[All Fields]) OR "dental health services"[All Fields] OR "dental"[All Fields] OR "dentally"[All Fields] OR "dentals"[All Fields], autotransplantation: "autotransplantion"[All Fields] OR "transplantation, autologous"[MeSH Terms] OR ("transplantation"[All Fields] AND "autologous"[All Fields]) OR "autologous transplantation"[All Fields] OR "autotransplantation"[All Fields] OR "autotransplantations"[All Fields]	494	22.11.24
Web of Science	(ALL = (tooth autotransplantation OR dental autotransplantation)) AND 2014 or 2015 or 2016 or 2017 or 2018 or 2019 or 2020 or 2021 or 2023 or 2022 or 2024 (Publication Years), Human studies, and English (Languages)	424	22.11.24
Scopus	(TITLE-ABS-KEY(tooth AND autotransplantation) OR TITLE-ABS-KEY(dental AND autotransplantation) AND ( LIMIT-TO ( SUBJAREA, "BIOC") OR LIMIT-TO ( SUBJAREA, "MEDI") OR LIMIT-TO ( SUBJAREA, "DENT")) AND ( LIMIT-TO ( LANGUAGE, "English"))	144	22.11.24
Cochrane Library	((((tooth autotransplantation OR dental autotransplantation OR Autologous Transplantations OR Transplantations OR Autologous; Autologous Transplantation; Autotransplantation; Autotransplantations; Autografting; Autograftings))))):ti,ab,kw (Word variations have been searched) with Cochrane Library publication date from Jan 2009 to Jan 2024, in Cochrane Protocols, Trials, Clinical Answers, Editorials and Special Collections (Word variations have been searched)	3	22.11.24
Journal of Endodontics (JOE)	(ALL = (tooth autotransplantation OR dental autotransplantation)) 2014 or 2015 or 2016 or 2017 or 2018 or 2019 or 2020 or 2021 or 2023 or 2022 or 2024 (Publication Years), Human studies, and English (Languages)	86	22.11.24
International Journal of Oral and Maxillofacial Surgery	(ALL = (tooth autotransplantation OR dental autotransplantation)) AND ALL = (survival rate OR open apex) and 2014 or 2015 or 2016 or 2017 or 2018 or 2019 or 2020 or 2021 or 2023 or 2022 or 2024 (Publication Years), Human studies, and English (Languages)	13	22.11.24

Fig. 2.

The scheme followed in the selection of articles is based on the PRISMA flowchart. Source: Page MJ, et al. BMJ 2021;372:n71. https://doi.org/10.1136/bmj.n71. This work is licensed under CC BY 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

A filter was applied in EBSCO MEDLINE [19] to include articles published in English between January 2014 and November 2024. When utilising other search databases, the search strings were adapted using the “Polyglot search translator tool” [24, 25]. The definitive search was concluded on 20th November 2024. An identical search was conducted (by HGR) in February 2025 to examine any contemporary articles published after this paper’s analysis had commenced. However, this latest search revealed no new articles which had been published during that time. Numerous search results within the initial parameters, Table 1, remained consistent with the preliminary search conducted in November 2024.

The keywords used in EBSCO MEDLINE [19], Web of Science [20], Scopus [21], and Cochrane databases [22] included: Search: (tooth autotransplantation) OR (dental autotransplantation). Filters: in the last 10 years, Full text, English, Humans Table 2.

Furthermore, a manual search was conducted in November 2024, within dental journals such as “The Journal of Endodontics” [26] and “The International Journal of Oral and Maxillofacial Surgery” [26]. This search utilised the identical keywords searched within the electronic databases mentioned previously, Fig. 2.

Review and selection of the acquired articles

The acquired articles were filtered based on title, abstract, and full text. The initial stage of screening involved scanning the article titles and then removing those studies that did not qualify under the previously mentioned selection parameters. If one or more identical articles were included, they were eliminated manually. The second stage of screening involved reading the article abstracts and evaluating the introduction, objective, methodology, results, discussion, and conclusion. During the search, if the article’s abstract lacked text and data, a full-text reading of the article was conducted. The third stage of screening involved meticulously reading the article’s full text and peer reviews, allowing the appropriate data to be extracted. A final evaluation was conducted by a secondary author (SMR), leaving a total of 23 selected articles Fig. 2. When disagreements arose between reviewers regarding the inclusion or exclusion of articles, discussions were held to resolve the matter. The degree of inter-examiner agreement regarding the final inclusion/exclusion of articles was assessed using Cohen’s kappa test, following the scale proposed by Landis and Koch. Inter-examiner agreement was considered almost perfect (k = 0.87).

Data extraction

Data extraction was conducted between 22nd November and 20th December 2024. The information gathered from the final article selection was recorded Table 3, Table 4. These tables document how only the appropriate information was generated, strictly following the initial search criteria as previously mentioned. The categories within the table contain the following headings: (1) authors, (2) year of publication, (3) country of study, (4) study design, (5) number of patients (n), (6) number of teeth transplanted (n), (7) mean age of patients (years), (8) type of donor tooth, (9) recipient site recipient site, (10) splinting procedure, (11) splinting duration (weeks), (12) seating position of the transplanted tooth, (13) 3D printed replica of donor tooth, (14) pre-orthodontic force on the donor tooth, (15) extra-oral time, (16) mean follow-up (years) Table 3.

Table 3.

Data Extracted from Final 26 Articles (DAT prognosis factors, characteristics and study design)

Authors	Year of publication	Country of study	Study design	No. of patients (n)	No. of teeth (n)	Age range of patient (years)	Type of donor tooth (n)	Recipient site	Splinting procedure	Splinting duration (weeks)	Occlusion/infra occlusion	3D replica tooth	Pre-orthodontic force	Extra oral time (mins)	Mean follow-up (years)
Incomplete Root Development (Open apex)
Raabe et al. [31]	2021	Switzerland	RET	23	23	12.5 (8–17)	MX: PM1 (4) PM2 (1) M2 (1) M3 (3) MD: C (1) PM1 (1) PM2 (9) M3 (3)	MX: CI (1) C (1) PM1 (3) PM2 (3) MD: PM1 (1) PM2 (11) M1 (2) M2 (1)	TTS, WCS, Suture, Ortho	6.6	Occlusal	NO	No	NR	6.7
Barendregt et al. [32]	2023	Netherlands	RET	NR	1190	14.5 (9.3–20.1)	MX: PM1 (8) PM2 (1145) MD: PM2 (37)	MX: PM1 (11) PM2 (33) M1 (1) MD: PM1 (26) PM2 (1110) M1 (9)	Suture	1	Occlusal	Yes	Yes	NR	2.3
Louropoulou et al. [33]	2024	Netherlands	RET	NR	493	11.8 (8.8–15.9)	MX: PM1 (1) PM2 (403) MD: C PM1 (2) PM2 (87)	MX: CI (441) LI (37) C (11) MD: LI (3) C (1)	Suture	2	Occlusal	Yes	Yes	NR	3.2
Nagori et al. A. [34]	2014	India	PRO	45	45	20 (15–25)	MX: M3 MD: M3	MX: M1 M2 MD: M1 M2	WCS or Suture	WCS: 2 Suture: 1	Infra Occlusion	No	No	Immediate	1.8
Nagori et al. B. [35]	2014	India	PRO	13	13	20 (16–25)	MX: M3 MD: M3	MX: M1 M2 MD: M1 M2	WCS or Suture	WCS: 2 Suture: 1	Infra Occlusion	No	No	Immediate	1.4
Mertens et al. [7]	2014	France	RET	25	25	17 (10–29)	MD: PM2 (10) M3 (15)	MX: LI (10) PM2 (1) M1 (5) MD: PM2 (2) M1 (6) M2 (1)	WCS and Sutures	WCS: 6 Suture: 2	Infra Occlusion	No	No	Immediate	15
van Westerveld et al. [36]	2019	Netherlands	RET	51	74	16.6 (9.3–23.9)	MX: PM1 PM2 M2 M3 MD: PM1 PM2 M2 M3	MX: PM1 PM2 M1 M2 MD: PM1 PM2 M1 M2	Suture	NR	Infra Occlusion	No	No	NR	9.7
Lucas-Taulé et al. [10]	2021	Spain	RET	12	12	NR	MX: M3 MD: M3	MX: M1 M2 MD: M1 M2	WCS and Sutures	2	Occlusal	Yes	No	Immediate	1.6
Michl et al. [37]	2017	Germany	PRO	20	26	13.6 (11–19)	MX: PM2 (6) MD: PM1 (9) PM2 (11)	MX: CI (6) MD: CI (11) LI (4) C (5)	WCS or Ortho	3	NR	No	No	Immediate – 7.4	2.4
de Carvalho et al. [38]	2014	Portugal	RET	21	21	NR	CI, LI, C, PM, M2, M3	CI, LI, C, PM, M1, M2	NR	NR	NR	No	No	NR	7
Verweij et al. [39]	2016	Netherlands	RET	79	111	15.9 (10.1–21.6)	PM (97) M (14)	MX: PM1 PM2 M1 M2 MD: PM1 PM2 M1 M2	WCS and Suture	4	Infra Occlusion	No	No	NR	1.1
Barcellos et al. [40]	2021	Brazil	RET	5	5	11.4 (8–16)	NR	NR	NR	NR	NR	No	NR	NR	9.68
Strbac et al. [41]	2017	Austria	RET	52	66	19.6 (14 -24)	MX: M2 + M3 (20) MD: M2 + M3 (46)	MX + MD: PM (5) M (61)	Suture	NR	Infra Occlusion	No	No	NR	5
EzEldeen et al. [42]	2019	Belgium	PRO	44	50	10.7 (8–13)	MX + MD: PM (50)	MX + MD: CI, LI, PM	WCS and Suture	NR	Infra Occlusion	Yes	No	Immediate  < 1	4.5
Complete Root Development (Closed apex)
Dhar et al. [43]	2022	India	PRO	20	20	41 (21–61)	MD: M3	MD: M1, M2	Erich arch with WCS	4	Infra Occlusion	Yes	No	NR	1
Barendregt et al. [32]	2023	Netherlands	RET	NR	96	35.1 (18.2–65.2)	MX: PM1 (3) PM2 (73) MD: PM1 (6) PM2 (14)	MX: PM1 (6) PM2 (12) M1 (5) MD: PM1 (6) PM2 (46) M1 (19) M2 (2)	Suture	1	Infra Occlusion	Yes	Yes	NR	3.1
Louropoulou et al. [33]	2024	Netherlands	RET	NR	170	29.8 (18–59.7)	MX: PM1 (2) PM2 (113) MD: PM1 (8) PM2 (47)	MX: CI (132) LI (22) C (13) MD: LI (2) C (1)	Suture	2	Infra Occlusion	Yes	Yes	NR	2.8
Wu et al. [44]	2019	China	RET	10	10	30.5 (19–42)	MX: M3 (3) MD: M3 (7)	MX: M1 (1) MD: M1 (3) M2 (6)	WCS + Suture	5	NR	Yes with GBR	NR	NR	2
Xia et al. [45]	2020	China	PRO	27	28	27.6 (20–34)	MX: M3 (11) MD: M3 (17)	MX: M1 (4) M2 (1) MD: M1 (16) M2 (7)	WCS + Suture	1 to 2	Infra Occlusion	Yes	No	2.5 ± 1.3	2
Yu et al. [46]	2017	China	PRO	60	65	37 (19–55)	MX: M3 MD: M3	MX: PM1 PM2 M1 M2 MD: PM1 PM2 M1 M2	Suture (non-absorbable)	2 to 3	NR	No	No	15	9.9
He et al. [47]	2018	China	PRO	8	8	27.5 (23–32)	MX: M3 (4) MD: M3 (4)	MX: M1 (2) MD: M1 (6)	0.25 mm diameter steel wire	4	Occlusal	Yes	No	< 3	2
Maddalone et al. [48]	2022	Italy	RET	60	61	46.5 (17–76)	MX: M3 (15) MD: M3 (46)	MX: M1 (15) MD: M1 (32) M2 (14)	WCS and Sutures	< 4	Infra Occlusion	No	No	15.5	5.5
Shinde et al. [49]	2018	India	PRO	42	42	36 (22–50)	MX: M3 MD: M3	MX: M1 M2 MD: M1 M2	WCS and Sutures	1	Infra Occlusion	No	No	< 18	1
Lucas-Taulé et al. [10]	2021	Spain	RET	24	24	NR	MX: M3 MD: M3	MX: M1 M2 MD: M1 M2	WCS and Sutures	2	Occlusal	Yes	No	NR	1.6
Jang et al. [9]	2016	Korea	RET	96	105	< 45: 82 > 45: 23	MD: M3 (91) Other (14)	INCISORS + PM (12) M1 + M2 (93)	Periodontal dressing and WCS	2	Occlusal	Yes	No	< 15 min: 82 > 15 min: 18	2.9
Grisar et al. [50]	2021	Belgium	PRO	16	16	18 (11–29)	MX C(17)	MX C(17)	WCS, Ortho, Suture	WCS: 2 to 4 Suture: 1	Infra Occlusion	Yes	Yes	5.5 ± 6.8	2.3

Key: AN Anterior tooth, GBR Guided bone regeneration, MD Mandibular, MX Maxillary, NR Not Recorded, PRO Prospective Study, RET Retrospective Study, TTS Titanium Trauma Splint, WCS Wire Composite Splint, CI Central Incisor, LI Lateral Incisor, C Canine, PM1 1st Premolar, PM2 2nd Premolar, M1 1st Molar, M2 2nd Molar, M3 3rd Molar

Table 4.

Data Extracted from Final 26 Articles (Selected articles’ survival rate, success rate, and complication rate)

Authors	Overall survival rate (%)	6 months Survival rate (%)	1-year Survival rate (%)	5-year Survival rate (%)	10-year Survival rate (%)	Success rate (%)	Infection-related root resorption (%)	Ankylosis rate (%)	Pulp Necrosis rate (%)
Incomplete Root Development (Open apex)
Raabe et al. [31]	92	100	96	92	NR	69.6	8	0	8
Barendregt et al. [32]	99.7	99.9	99.9	99.7	99.7	99.4	0.2	2.26	NR
Louropoulou et al. [33]	99.8	100	99.8	99.8	99.8	94.3	0.21	0.20	5.28
Nagori et al. A. [34]	95.6	95.6	95.6	NR	NR	86.7	11.1	0	2.2
Nagori et al. B. [35]	92.3	92.3	92.3	NR	NR	92.3	0	0	7.7
Mertens et al. [7]	96	96	96	96	96	61.1	22.2	14.3	16.7
van Westerveld et al. [36]	95.4	100	98.7	97.8	94.6	85.1	9.45	2.7	NR
Lucas-Taulé et al. [10]	90.9	90.9	90.9	NR	NR	81.8	0	0	0
Michl et al. [37]	100	100	100	NR	NR	73	30.8	0	30.8
de Carvalho et al. [38]	75	100	100	100	100	NR	NR	NR	NR
Verweij et al. [39]	87.5	100	100	87.5	NR	82	1.89	6.3	7.2
Barcellos et al. [40]	100	100	100	100	100	NR	NR	0	NR
Strbac et al. [41]	80.3	NR	NR	89.9	80.3	NR	NR	20.8	6.1
EzEldeen et al.; [42]	92	100	100	92	84	86	6	6	NR
Complete Root Development (Closed apex)
Dhar et al. [43]	90	90	90	NR	NR	90	10	5	NR
Barendregt et al. [32]	95.7	100	97.9	97.9	95.8	83.3	0.96	5.3	NR
Louropoulou et al. [33]	96.4	99.4	99.4	99.4	87.5	92.9	0	12.4	NR
Wu et al. [44]	100	100	100	NR	NR	100	0	0	NR
Xia et al. [45]	100	100	100	NR	NR	100	0	0	NR
Yu et al. [46]	90.8	NR	NR	NR	NR	NR	10.8	9.2	NR
He et al. [47]	87.5	100	87.5	NR	NR	87.5	0	12.5	NR
Maddalone et al. [48]	93.4	100	96.7	93.4	NR	90.3	6.6	4.9	NR
Shinde et al. [49]	80.5	80.5	80.5	NR	NR	78	19	2.4	NR
Lucas-Taulé et al. [10]	100	100	100	NR	NR	96	0	4.2	NR
Jang et al. [9]	70	97.4	95.2	80.9	70	70.4	17.1	27.8	NR
Grisar et al. [50]	94.1	94.1	94.1	NR	NR	68	11.8	17.6	NR

The following data sequels were determined (1) survival rate: 6 months, 1-, 5- and 10-year (%), (2) success rate, (%) (infection-related root resorption rate (%), (4) Ankylosis rate (%), (5) pulp necrosis rate (%) Table 4.

During the process of data extraction, the following operational definitions were outlined:

• Survival: The tooth was still present in the recipient alveolus during the follow-up review appointments, with grade 1 or less tooth mobility.

• Success: The transplanted tooth was still in the mouth, with the absence of infection-related root resorption, ankylosis or pulp necrosis. These teeth feature normal mobility with no pathological signs or symptoms.

• Stage of root formation: Before transplantation, the donor tooth had either an open or closed apical foramen.

• Infection-related root resorption: The transplanted tooth presented radiographic indications of infection-related root resorption.

• Ankylosis: the transplanted tooth lacks clinical mobility, with or without ankylosis of the root present in radiographic evaluation.

• Pulp necrosis: these rates were often included and described in the sample articles.

Data synthesis

A meta-analysis was conducted incorporating the data extracted from the 23 eligible articles. This generated a concise summary of each article, allowing comparisons to be made between them. The meta-analysis was conducted to evaluate the prognostic factor of DAT in relation to transplanted teeth, defined in two independent groups: those with incomplete root formation (open apex) and those with complete root formation (closed apex).

The following meta-analyses were conducted:

1. A random-effects model to estimate the overall effect measure (raw rate) for each group (open and closed apex). A restricted maximum likelihood estimator of Heterogeneity will be used. Forest graphs are used to visualise results with 95% confidence intervals. Regarding heterogeneity analysis, Cochran’s Q test was applied. The I² index was also calculated, representing the amount of between-studies variability compared to total variability. Wilson’s correction was applied in articles with rates of 100% or 0% to obtain statistics of variability.

2. Comparison between the open and closed apex groups: Mixed-effects model (meta-regression) with group as the moderator variable. R² was obtained to estimate the amount of between-studies variability explained by the factor.

3. Effect of other factors: Mixed-effects model (meta-regression) with different moderator variables like mean age, involved arch, type of donor and recipient tooth, splinting method, occlusal seating of the transplanted tooth, use of 3D-printed replica donor teeth, extra-oral time of the donor tooth and pre-orthodontic force were estimated. R² was obtained to calculate the amount of between-studies variability explained by the factor.

Forest graphs will be used to visualise results with 95% confidence intervals. Regarding heterogeneity analysis, Cochran’s Q test was applied. The I² index was also calculated, representing the amount of between-studies variability compared to total variability. The Funnel graph has also been used to explore the potential publication bias. Egger’s test was conducted to assess the impact of this type of bias. Wilson’s correction was used to estimate heterogeneity estimators under extreme rates (100% and 0%). The level of significance used in the analysis has been 5% (α = 0.05).

Evaluation of the quality of articles: risk of bias assessment and quality evaluation

All 23 research articles featured a study design of either prospective or retrospective Table 3 thus, the Newcastle–Ottawa Scale (NOS) [27] and QUADAS-2 Scale [28] were used to assess the articles’ quality and risk of bias respectively, Tables S9 and S10. Usage and evaluation of these scales can be found in the discussion section of this article.

Results

The initial electronic search through EBSCO MEDLINE [19], Web of Science [20], Scopus [21], and Cochrane databases [22] generated a total of 1065 articles Fig. 2. EBSCO MEDLINE (n = 494), Web of Science n = 424), Scopus (n = 144), Cochrane (n = 3). Furthermore, a manual search was conducted through selected dental journals, “The Journal of Endodontics” [29] (n = 86), “The International Journal of Oral and Maxillofacial Surgery” [26] (n = 13). This generated a total of 1164 research articles. Then, 527 articles were manually eliminated as they were duplicates. This left 637 articles which were labelled as potential candidates for the systematic review and meta-analysis. During stage two of screening, each article’s title and abstract were carefully considered, evaluating the article’s introduction, objective, methodology, results, discussion, and conclusion, leaving 95 articles remaining. The full text of the 95 articles in which the inclusion and exclusion parameters were applied Table 1, as mentioned in the materials and statistical methodology. A k-value of 0.92 was generated for the inter-examiner agreement between the two authors (HGR and SMR) regarding the inclusion of research articles. Concerning the 1977 Landis and Kock criteria this k-value illustrates an excellent agreement result [30]. This resulted in the 23 research articles used in the systematic review and meta-analysis Tables 3 and 4.

Discussion

A total of 2799 transplanted teeth were documented: 2154 donor teeth with an incomplete root development (open apex) [7, 10, 31–42] and 645 donor teeth with a complete root formation (closed apex) [9, 10, 32, 33, 43–50] Table 3. Utilising the three meta-analysis models mentioned in the materials and statistical methodology chapter, the DAT survival rate, success rate, infection-related root resorption rate, ankylosis rate, and pulp necrosis rate Table 4 were compared to 9 well-documented prognostic factors [8, 13, 14].

Although several systematic review and meta-analysis’s have been conducted regarding the success and survival rate of DAT, these articles analysed the origins of DAT with large scale studies conducted throughout the mid to late twentieth century, such as 1974 Slagsvold et al. [16]. This meta-analysis assesses contemporary dental literature regarding DAT conducted within the last 10 years, whilst simultaneously illustrating a unique perspective of the potential prognosis factors which can influence the procedure. Modern technologies, such as CBCT and 3D printed tooth replicas of the donor tooth, pre-orthodontic forces before donor tooth extraction were not evaluated in these previous studies.

General objective

All articles of the open apex group [10, 31–42], apart from [7] involved transplantation of teeth from both the maxilla and mandible Table 3. Therefore, no analysis was possible on the effect of the donor tooth’s arch. However, the closed apex group articles [43, 50] exclusively analysed DAT in the mandible and maxilla, respectively Table 3. The meta-analysis indicates statistical significance, where if both jaws were involved in the donor tooth’s arch, survival rate and success rate increased with p-values of 0.003 Table 6 and 0.046 Table 8 respectively, compared to only the mandible. Sugai et al. explored why this might be the case when using donor teeth from the mandible. The researchers put forward that extracting and preparing teeth from the mandible is more strenuous than that of the maxilla, as it features an increased bone density. The denser alveolar bone of the mandible increases the probability of a traumatic extraction of the donor tooth, thus potentially damaging the vital PDL of the donor tooth, which is fundamental to the success of the DAT [51].

Table 6.

Results of simple meta-regressions of the Overall Survival rate by independent factors and covariates in the Closed apex group: Beta coefficient, standard error (SE), 95% confidence interval, z test (p-value), R2 index

	Beta	SE	p-value	95%CI Beta	R2
AGE	0.000	0.002	0.944	− 0.004–0.005	0.0%
DONOR’S ARCH
Only mandible (ref.)	0
Both	0.167	0.057	0.003**	0.055–0.278	58.5%
DONOR´S ANTERIOR (yes)	–	–	–	–	–
DONOR’S PM (yes)	0.006	0.035	0.870	− 0.063–0.074	0.0%
DONOR’S M (yes)	− 0.042	0.064	0.519	− 0.167–0.085	0.519
RECIPIENT’S ARCH	–	–	–	–	–
RECIPIENT´S ANTERIOR (yes)	− 0.079	0.061	0.196	− 0.199–0.041	7.43%
RECIPIENT’S PM (yes)	− 0.093	0.058	0.104	− 0.206–0.019	16.7%
RECIPIENT’S M (yes)	− 0.035	0.076	0.643	− 0.185–0.114	0.0%
WCS	− 0.016	0.062	0.791	− 0.138–0.105	0.0%
SUTURE	0.158	0.051	0.002**	0.059–0.257	61.5%
ORTHO	− 0.019	0.073	0.798	− 0.161–0.124	0.0%
SPLINTING DURATION	0.010	0.025	0.698	− 0.039–0.059	0.0%
OCCLUSAL	− 0.092	0.073	0.205	− 0.234–0.050	8.94%
REPLICA 3D	0.013	0.066	0.842	− 0.117–0.144	0.0%
PRE ORTHO	0.050	0.067	0.451	− 0.081–0.181	0.0%
IMMEDIATE	− 0.023	0.079	0.775	− 0.177–0.132	0.0%
FOLLOW UP	0.002	0.012	0.876	− 0.022–0.025	0.0%

Table 8.

Results of simple meta-regressions of the Success rate by independent factors and covariates in the Closed group: Beta coefficient, standard error (SE), 95% confidence interval, z test (p-value), R2 index

	Beta	SE	p-value	95%CI Beta	R2
AGE	− 0.004	0.004	0.390	− 0.012–0.005	17.7%
DONOR’S ARCH	–	–	–	–	–
Only mandible (ref.)	0
Both	0.146	0.073	0.046*	0.002–0.289	36.7%
DONOR´S ANTERIOR (yes)	–	–	–	–	–
DONOR’S PM (yes)	− 0.009	0.070	0.902	− 0.146–0.128	0.0%
DONOR’S M (yes)	0.030	0.077	0.697	− 0.121–0.181	0.0%
RECIPIENT’S ARCH	–	–	–	–	–
RECIPIENT´S ANTERIOR (yes)	− 0.093	0.074	0.206	− 0.238–0.051	0.0%
RECIPIENT’S PM (yes)	− 0.124	0.067	0.066	− 0.256–0.008	32.2%
RECIPIENT’S M (yes)	0.016	0.093	0.863	− 0.166–0.198	0.0%
WCS	− 0.019	0.077	0.800	− 0.170–0.131	0.0%
Suture	0.109	0.071	0.126	− 0.031–0.249	26.5%
Ortho	− 0.072	0.088	0.418	− 0.246–0.102	0.0%
Splinting duration	0.009	0.029	0.753	− 0.047–0.065	0.0%
Occlusal	− 0.018	0.079	0.819	− 0.172–0.137	0.0%
Replica 3d	0.082	0.084	0.329	− 0.083–0.246	1.42%
Pre ortho	− 0.014	0.078	0.861	− 0.167–0.139	0.0%
Immediate	0.109	0.089	0.223	− 0.066–0.284	5.72%
Follow up	− 0.019	0.028	0.483	− 0.073–0.035	0.0%

Moreover, if molars were the donor teeth in the open apex group, their survival rate would be reduced by 8% compared to teeth from the anterior or premolar positions Table 5. No statistical significance in survival rates was found in the type of donor tooth survival from teeth with a closed apex Table 6. Andreasen et al. suggested that molars have a lower survival rate compared to anterior or premolar-positioned teeth due to the number of roots molars possess. The increased surface area of molars generates a more fragile root structure with a thinner PDL protective layer. Furthermore, the surgical extraction procedure for molar teeth is more complex than for anterior and premolar teeth, making atraumatic extraction during the transplantation period even more challenging. Traumatic extraction of the donor tooth will result in either major or minor damage to the PDL, increasing the risk of future complications after transplantation [8]. The meta-analysis produced similar results when analysing the success rate of DAT concerning the type of donor tooth, where no statistical significance was reported in both the open apex Table 7 and closed apex group Table 8. This is amongst the consensus in the dental literature, supported by other researchers [8, 52, 53].

Table 5.

Results of simple meta-regressions of the Overall Survival rate by independent factors and covariates in the Open apex group: Beta coefficient, standard error (SE), 95% confidence interval, z test (p-value), R2 index

	Beta	SE	p-value	95%CI Beta	R2
AGE	− 0.009	0.005	0.099	− 0.020–0.002	23.8%
DONOR’S ARCH
Only mandible (ref.)
Both
DONOR´S ANTERIOR (yes)	0.013	0.044	0.773	− 0.073–0.098	0.0%
Donor’s PM (yes)	0.063	0.039	0.112	− 0.015–0.140	23.3%
Donor’s M (yes)	− 0.080	0.028	0.005**	− 0.135–0.024	53.6%
RECIPIENT’S ARCH
RECIPIENT´S ANTERIOR (yes)	0.032	0.037	0.375	− 0.039–0.104	0.84%
RECIPIENT’S PM (yes)	− 0.057	0.035	0.106	− 0.127–0.012	13.4%
RECIPIENT’S M (yes)	− 0.058	0.038	0.124	− 0.132–0.016	10.2%
WCS	− 0.011	0.039	0.785	− 0.088–0.067	0.0%
Suture	–	–	–	–	–
Ortho	0.032	0.054	0.558	− 0.075–0.138	0.0%
Splinting duration	− 0.010	0.007	0.145	− 0.024–0.004	0.0%
Occlusal	0.067	0.033	0.045*	0.002–0.133	41.6%
Replica 3d	0.052	0.036	0.144	− 0.018–0.122	19.8%
Pre ortho	0.080	0.037	0.032*	0.007–0.153	36.4%
Immediate
Follow up	0.000	0.005	0.996	− 0.009–0.009	0.0%

Table 7.

Results of simple meta-regressions of the Success rate by independent factors and covariates in the Open group: Beta coefficient, standard error (SE), 95% confidence interval, z test (p-value), R2 index

	Beta	SE	p-value	95%CI Beta	R2
AGE	− 0.003	0.013	0.832	− 0.027–0.022	0.0%
DONOR’S ARCH	–	–	–	–	–
DONOR´S ANTERIOR (yes)	− 0.007	0.073	0.923	− 0.149–0.135	0.0%
DONOR’S PM (yes)	− 0.013	0.093	0.887	− 0.196–0.169	0.0%
DONOR’S M (yes)	− 0.085	0.060	0.155	− 0.201–0.032	12.7%
RECIPIENT’S ARCH	–	–	–	–	–
RECIPIENT´S ANTERIOR (yes)	− 0.079	0.063	0.207	− 0.202–0.044	0.0%
RECIPIENT’S PM (yes)	− 0.007	0.067	0.920	− 0.138–0.124	0.0%
RECIPIENT’S M (yes)	− 0.009	0.068	0.900	− 0.142–0.125	0.0%
WCS	− 0.142	0.047	0.003**	− 0.235– − 0.049	64.4%
Suture	–	–	–	–	–
Ortho	− 0.158	0.091	0.083	− 0.337–0.021	27.2%
Splinting duration	− 0.060	0.007	< 0.001***	− 0.072– − 0.047	100%
Occlusal	0.095	0.056	0.092	− 0.016–0.206	44.6%
Replica 3D	0.144	0.037	< 0.001***	0.072–0.216	77.1%
Pre ortho	0.153	0.033	< 0.001***	0.090–0.217	88.8%
Immediate	–	–	–	–	–
Follow up	− 0.014	0.007	0.047*	− 0.028– − 0.001	28.1%

All articles in the open apex group [7, 10, 31–42] involved placement of the recipient tooth in both arches Table 3 therefore, no meta-analysis was possible for this variable Tables 5 and 7. When analysing whether the type of recipient alveolar socket in the maxilla or mandible affects the survival rate and success rate in the closed apex group, no significant effects were observed Tables 6 and 8. However, if the receiving alveolar site were in the premolar region, the success rate of said tooth would decrease compared to the anterior or molar region Table 8. These small disparities in the results can partly be explained by the type of donor tooth which are eligible to be transplanted in these areas. Teeth from the anterior and premolar region would be exclusively transplanted in the incisor and canine alveolus, whilst only molars would be transplanted into a premolar site. As mentioned previously, the results from this meta-analysis indicate that molars with an open apex as donor teeth statistically have a reduced survival rate by 8% Table 5. Molar anatomy statistically exhibits a higher variation compared to anterior and premolar teeth, meaning the amount of bone preparation required in the recipient alveolar site will vary drastically for each case [54]. This could partly explain the high heterogeneity of the data extracted from the selected articles.

Stabilisation methods found in the selected articles included semi-rigid splints in the form of wire composite splints (WCS) or orthodontic wire, titanium trauma splints (TTS), periodontal dressings and sutures Table 3. Articles [9, 31] were the only studies to include TTS and periodontal dressings; therefore, they could not be analysed in this meta-analysis. In the open apex group [7, 10, 31–42], the type of splinting procedure had little effect on the survival rate of DAT Table 5. In comparison, if sutures were used in the closed apex group [9, 10, 32, 33, 43–50], the survival rate of this group would increase by 15.8% when juxtaposed to the absence of sutures (p-value 0.002) Table 6. Semi-rigid splints in the open and closed apex group had little statistical significance to the survival rate of the tooth Tables 5 and 6. These results are similar to the Bauss et al. study regarding the splinting method of DAT. The researchers concluded that sutures provide more physiological and functional mobility to the transplanted tooth when compared to a rigid wire splint. This contributes to the healing of the PDL and periodontal structures through increased vascularisation, thus reducing rates of complications post procedure, as seen in the rigid wire splint group. Bauss et al. concluded that rigid wire splints should be avoided to stabilise transplanted teeth as they reduce pulpal and periodontal healing whilst increasing the risk of ankylosis of the transplanted tooth. This article follows the consensus of the dental literature on the matter [55]. However, this study did not provide a detailed comparison of the efficacy of semi-rigid splints and sutures, and very little has been published regarding these variables and long-term survival rates of DAT. Therefore, more research should be conducted to confirm these results.

The open and closed apex groups concluded that the splinting duration had no statistically significant effect on the survival rate of DAT (p-value 0.145) and (p-value 0.698), respectively. The open apex group [7, 10, 31–42] recorded statistical significance on the success rate, where a longer splinting duration reduces the success rate (p-value < 0.001) Table 7. Every additional week of additional splinting reduces the success rate by 6%. No statistical significance could be found in the closed apex group [9, 10, 32, 33, 43–50] regarding splinting duration and success rate Table 8. Therefore, the results of this meta-analysis conclude that sutures are the preferred method of tooth stabilisation to ensure the best survival and success rates of DAT, which should stabilise the tooth for the shortest time possible (no more than 1–2 weeks). This conclusion is also consistent with the previous study mentioned by Bauss et al. where sutures stabilised the transplanted tooth for only 7 days. This study produces a DAT success rate of 92.9% with sutures as the stabilisation method, observed for a mean period of 3.4 years of 42 transplanted teeth [55]. The PDL’s anatomy mainly consists of Sharpey’s fibres; fibroblasts; Mallassez epithelial islands; cementoblasts; osteoblasts; and osteoclasts. Andreasen et al. explains that collagen types 1 and 3 begin to amalgamate the detached PDL just 1 week after avulsion or transplantation. This is brought about primarily through fibroblast proliferation, which creates the preliminary stabilisation of the tooth. After 2 weeks post-avulsion or transplantation, regeneration of the collagen principal PDL fibres has reached a stage where over 2/3rds of the fibres’ mechanical strength has returned [56]. This therefore supports that splinting with sutures past 2 weeks is redundant and has now been shown to cause adverse effects on the tooth’s success rate.

The meta-analysis indicates that in the open apex group [7, 10, 31–42], when the transplanted tooth’s cusps or incisal edge was seated on the occlusal plane, the tooth’s survival rate increased by 6.7% Table 5 and its success rate also by 9.5% Table 7. However, the data produced no evidence that the occlusal seating of the transplanted tooth had any effect on the survival rate or success in the closed apex group [9, 10, 32, 33, 43–50] Tables 6 and 8. This article’s conclusion presents conflicting evidence when compared to other authors, such as Kakde et al. The researchers suggest transplanting the donor tooth in an infra-occlusal position to avoid occlusal trauma immediately following the procedure [57]. To date, there have not been any systematic reviews or meta-analyses discussing this variable; thus, calls for more research are warranted. What this article and the dental literature can agree on is that after DAT, occlusal interference and premature contacts with the antagonist arch must be avoided. This is to improve the stress distribution of forces from inhalation, phonation and mastication acting on the tooth. The forces can be directed evenly through the dentine, lamina dura and trabecular bone structures, reducing the risk of periodontal pathology and ultimately the failure of the tooth. Thus, regular follow-ups with the patient post-surgery should be conducted to assess the occlusal position and state of the tooth periodically. Later, if the treatment deems necessary, functional and aesthetic treatments can be performed on the transplanted tooth to improve its occlusal contact with the antagonist arch, for example, preparing the crown to accompany an onlay, overlay or crown fixed prosthesis [58–60].

Only 13 articles [9, 10, 32, 33, 42–45, 47, 50] reported using CBCT 3D printed replica donor teeth in their DAT protocol Fig. 1g. This meta-analysis concluded that these 3D printed replica teeth had no effect on the long-term survival rate in the open apex and closed group Tables 5, and 6. However, it did significantly increase the success rate of the open apex group, reducing the prevalence of tooth complications in short-term follow-ups (p-value < 0.001) Table 7. As CBCT 3D printed replica teeth are still a relatively new technology, there have been very few long-term studies which evaluate their effectiveness in DAT open apex and closed apex groups. Verweij et al. explored the current dental literature to evaluate the relationship between 3D printed replica teeth and the success rate of DAT. The researchers documented similar success rates of 80.0–91.1% in this study; however, they concluded that further long-term analysis is needed [61]. The primary use of this tooth replica was to conform the recipient alveolar site into a complementary shape of the donor tooth. This, therefore, avoids unnecessary damage to the donor tooth’s PDL through unwarranted mechanical trauma during the confirmation process and reshaping the donor tooth’s anatomy for it to sit correctly in the receiving alveolar socket. Furthermore, the 3D printed replica reduces the extra-oral time of the donor tooth whilst outside of its alveolus, reducing potential necrosis of the PDL cells [62]. The PDL of the donor tooth has the highest chance of maintaining its vitality and form during the transplantation procedure, thereby creating the best possible environmental conditions for the treatment’s long-term success.

This meta-analysis indicates that when orthodontic force is applied to donor teeth with an open apex [7, 10, 31–42] before transplantation, the tooth’s survival rate increased by 8.0% (p-value 0.032) Table 5, and success rate increased by 15.3% (p-value < 0.001) Table 7. Data from the closed apex group [9, 10, 32, 33, 43–50] still reported increased survival rates and success rates, but these results were marginal in comparison to the open apex group [7, 10, 31–42] Table 6 and 8. According to Cho et al., the pre-application of orthodontic forces to the donor tooth creates a mechanical stimulus in the periodontium, causing the PDL to loosen and increase its overall width through fibroblast proliferation. This slackening action of the PDL eases the trauma caused by the extraction process in DAT, whilst simultaneously improving its adaptability once transplanted into the recipient alveolus. The results showed an increase in the long-term survival rate of DAT and a decrease in the prevalence of replacement-related root resorption (ankylosis) during the Healing process after DAT. The study suggests that if the operator and patient decide this is relevant for their case, this should be conducted for a minimum of 4 weeks before the DAT procedure [63].

All research articles in the open apex group [7, 10, 31–42] involved an immediate extra-oral time, except for [37]. Consequently, no meta-analysis was possible when evaluating this variable with the donor tooth’s survival rate or success rate Tables 5 and 7. This was also apparent in the closed apex group, which generated statistically insignificant results for both the survival rate and success rate [9, 10, 32, 33, 43–50] Tables 6 and 8. According to Andreasen et al. both the PDL and dental pulp tissues will be afflicted with considerable damage during the extra-oral time of the tooth from its alveolus. In this instance, the healing response of an avulsed or transplanted tooth will be significantly influenced by root surface contamination; stage of the tooth root development; extra-oral handling; length of time the tooth remains out of its alveolus; and the medium in which the tooth is stored during its extra-oral exposure [64]. All articles note it is imperative to keep the extra-oral time as minimal as possible to ensure the highest long-term survival rate and success rate of the transplanted tooth. As mentioned previously, the use of CBCT 3D-printed tooth replicas Fig. 1g has significantly helped shorten the extra-oral time of donor teeth during the transplant period, reducing the need to keep the donor tooth within an extra-oral storage medium such as Hanks Balanced Salt Solution (HBSS).

Specific objective

The average survival rate in the open apex group was 93.8 ± 1.8% [7, 10, 31–42] Fig. 3 in comparison to 92.6 ± 2.8% Fig. 3 in the closed apex group [9, 10, 32, 33, 43–50]. Therefore, the relationship between the tooth’s survival rate and grade of root formation is similar to what we would expect by chance Fig. 4. The survival rate Heterogeneity in the open apex group was estimated as very high at 98.6% which is consistent with a set of papers reporting success rates in the range 75–100%. This is similar to the closed apex group at 89.6%, consistent with a set of papers reporting success rates in the range 68–100%. Articles [38, 41] were the most heterogeneous studies in the open apex group, and article [9] in the closed apex group, all found outside the normal range in the Galbraith plot. Articles [38, 41] were listed as “possible risk of bias” in the QUADAS-2 scale Table S10 and article [38] was only scored as a “fair quality” study in the Newcastle–Ottawa Scale Table S9 with a total score of 4, whilst articles [9, 41] scored “high quality” study results with 6 and 8 respectively.

Fig. 3.

Forest Graph Analysis Overall Survival Rate Comparison between Incomplete Root Development (Open Apex) Group and Complete Root Development (Closed Apex) Group. The open apex group mean survival rate was estimated at 93.8 ± 1.8%., the closed apex group mean survival rate was estimated at 92.6 ± 2.8%

Fig. 4.

Funnel’s Plot Analysis Overall Survival Rate Comparison between Incomplete Root Development (Open Apex) Group and Complete Root Development (Closed Apex) Group

The survival rate at 6 months and 1 year post DAT procedure was reported in 24 out of the 26 selected research articles, with an average of 97.7% for the open apex group [7, 10, 31–42], and 94.0% for the closed apex group Table 4. Only 14 articles reported survival rates at 5 years post DAT [7, 9, 31, 32, 32, 33, 33, 36, 38–42, 48] Table 4. The average 5-year survival rate of the open apex group was 95.2% and 92.9% in the closed apex group. Finally, 8 articles [7, 9, 32, 32, 33, 33, 36, 38, 40–42] group documented the 10-year survival rate. The average 10-year survival rate of the open apex group was 94.0% and 83.8% in the closed apex group Table 4. Astonishingly, the 10-year survival rates in both the open and closed apex groups can remain equally high, while the highest prevalence of failures occurs within the first year post-DAT. This data suggests that teeth that undergo DAT and survive over 1 year post-procedure have a promising long-term prognosis in terms of survival rate. These results are consistent with a meta-analysis conducted by Rohof et al. who recorded survival rates of 97.4% at 1-year, 97.8% at 5-years, and 96.3% at 10-years of transplanted teeth with an open apex [15]. Moreover, a meta-analysis conducted by Huang et al., analysing the survival and success rates of DAT with a closed apex, documented similar data on survival rates post-DAT of 93.6% at 1 year. Unfortunately, due to the limited number of published articles available in the dental literature, they were unable to document a 5-year or 10-year survival rate for these teeth [13]. Recently, Czochrowska et al. published a longitudinal study in 2013, which monitored DAT teeth over a 17–41-year period, with an average follow-up of 26.4 years for each patient. The study demonstrated a significant long-term success rate, ranging from 79 to 90% in both open apex and closed apex groups [65].

The success rate of the open apex group was 84.0 ± 3.1% [7, 10, 31–42] Fig. 5, and 86.7 ± 3.3% in the closed apex group Fig. 5. Statistically, these studies show no significant differences between the open and closed apex groups (p = 0.539); thus, the relationship between success and the stage of root formation is similar to what we would expect by chance. The Heterogeneity of the open apex group was estimated to be very high at 95.4%, while that of the closed apex group was quite high at 83.2%. Still, it was not associated with any specific author. These results are notably lower compared to a meta-analysis conducted by Rohof et al., who reported a success rate of 96.6% for transplanted teeth with an open apex in 23 articles [15]. Furthermore, the meta-analysis conducted by Huang et al. recorded an overall success rate of 91.7% of transplanted teeth with a closed apex [13]. As with the limitations produced in this meta-analysis, both research groups found a lack of continuity in the definition of success among the included articles.

Fig. 5.

Forest Graph Analysis Success Rate Comparison between Incomplete Root Development (Open Apex) Group and Complete Root Development (Closed Apex) Group. The mean success rate of the open apex group was estimated at 84.0 ± 3.1%, the closed apex group 86.7 ± 3.3%

The rate of infection-related root resorption after DAT was 6.3% ± 2.0% Table 4 in the open apex group and 5.9% ± 2.0% [7, 10, 31–42] Table 4 in the closed apex group [9, 10, 32, 33, 43–50]. Again, there was no statistical significance between these groups (p = 0.878), which indicates that the differences would be expected by chance. The Heterogeneity of the open apex group was estimated as very high at 98.9%, where article [60] escapes the upper boundary of Galbraith’s plot because its rate was extremely high, with a Heterogeneity of 30.8%. This study [60] received a score of 5 out of 8, a “fair quality study according to the Newcastle–Ottawa Scale (NOS) Table S9 and a result of “potential bias” according to the QUADAS-2 scale Table S10, which could explain its extremely high Heterogeneity. The closed apex group was estimated to be quite high at 88.5%; however, it was not associated with any author. A total of 18 research articles were analysed by Rohof et al., reporting a similar result in 2.9% of teeth with incomplete root formation (open apex) [15]. Furthermore, Huang et al. reported an average rate of 6.96% of infection-related (inflammatory) root resorption in donor teeth with a closed apex throughout 11 selected research articles [13]. We can conclude that the rate of infection-related root resorption is very low regarding both the open and closed apex groups.

The rate of ankylosis after DAT was 4.4% ± 1.7% in the open apex group Table 4 [7, 10, 31–42] and 6.7% ± 2.3% Table 4 in the closed apex group [9, 10, 32, 33, 43–50]. These results are marginal and showed no statistical significance between the two groups (p = 0.425), indicating the relationship is likely expected by chance. The Heterogeneity of the open apex group was estimated as very high at 89.4%, where article [41] escaped the upper boundary of Galbraith’s plot with a Heterogeneity of 20.8%. This study received a score of only 4 out of 8, only a “fair quality study according to the Newcastle–Ottawa Scale (NOS), which may explain the statistical significance of the results Table S9.

The closed apex group reported a Heterogeneity of quite high at 79.3% and was especially affected by results from article [9], which exceeded the upper boundary of heterogeneity in the Galbraith’s plot. None of the selected articles in the open apex or closed apex group revealed signs of bias according to Egger’s test. The results from this article are consistent with previously completed systematic reviews and meta-analyses Rohof et al. reported an ankylosis rate of 2.0% in donor teeth with an open apex in 19 individual studies [15]. Furthermore, the systematic review and meta-analysis conducted by Huang et al. reported an ankylosis rate of 5.64% amongst 12 research studies [13]. Although both results from these authors are marginally lower than the results produced by this MA, it is not far outside the area of uncertainty.

The rate of pulp necrosis after DAT was documented by only a small number of authors in the open apex group. Most articles only referenced pulp necrosis in their narration or did not provide specific data. Amongst the remaining articles, the open apex group rate of pulp necrosis was 6.4 ± 1.5% [7, 10, 31, 33–35, 37, 39, 41] Table 4. The Heterogeneity in the open apex group was estimated as moderately high at 61%, yet significant (p = 0.018). All articles in this group were recorded within predicted limits except for the article [37] Table 4. This article was classified as “fair quality” in the Newcastle–Ottawa scale (NOS) Table S9, scoring 5 out of 8, and labelled as having a “high risk of bias” in the QUADAS-2 scale Table S10. This could explain why the pulp necrosis rate is so dissimilar to the remaining articles in the open apex group. It must be noted that the surgical protocol varied drastically in articles [9, 32, 43–49]. These authors anticipated the increased risk of post-operative pulp necrosis; thus, a conventional pulpectomy 1–2 weeks post-procedure was conducted. This, therefore, meant the pulp necrosis rate was not recorded in these studies.

The data produced from this article are consistent with results reported in the meta-analysis conducted by Rohof et al. reporting a pulp necrosis rate of 3.3% in donor teeth with an open apex [15]. According to Andreasen et al. "the frequency of pulpal healing and pulpal necrosis appears to be closely related to the stage of root development during the time of transplantation". Their study documented the transplantation of 370 premolars and demonstrated that donor teeth with an open apex had a rate of pulpal Healing of 96% compared to 15% with a closed apex [8]. Further studies are needed to investigate the placement and timing of root canal therapy after DAT surgery, particularly regarding the pulp necrosis rate following transplantation in both open- and closed-apex donor teeth. The data obtained regarding this variable should therefore be examined with extreme caution.

Study limitations

The study design of the selected articles included non-randomised clinical studies. To best analyse the long-term survival and prognosis factors of DAT, randomised controlled studies would offer the highest validity and reliability. However, due to the surgical nature of DAT, this study design would be inconceivable and unethical to conduct single-or double-blind studies.

The heterogeneity of the selected articles illustrates the discernible limitations of this analysis, whilst highlighting their potential bias. It must be noted that a high heterogeneity was consistent in both the open and closed apex throughout the entire study parameters. Study design, variable follow-up period, prognostic factors and study duration all contribute to this. Furthermore, there is a notable disparity between the open and closed apex group sample sizes, with the open apex group being approximately four times larger. This imbalance could skew the comparative analysis between the two groups, thus affecting the strength and generalizability of the conclusions drawn in this research. Articles [7, 10, 31, 34, 35, 37, 38, 43–45, 47, 50] feature small sample sizes bellow 30, which tended to show a higher "risk of bias" in the QUADAS-2 scale Table S10 and low scores in the Newcastle Ottawa scale (NOS) Table S9. These articles mentioned previously were classified only as "fair quality" study designs. Articles [44, 45] only scored 3 out of 8 on the Newcastle Ottawa scale (NOS) Table S9, which is on the extreme limit before categories as a "poor quality" study. Thus, these results should be interpreted with caution, and future studies should ideally be conducted with greater sample sizes.

Moreover, the documentation of the developmental root stage in the open apex group was not consistent throughout the selected research articles. Moorree’s root development stage methodology [66] was a standard unit system in research articles [31–34, 37] to assess the maturity of the developing tooth. However, other articles, such as [35], did not document further details for the specific developmental stage of the donor tooth. This meant a continuous representation across all the articles was not possible, so for the systematic reviews and meta-analyses, the two variable groups had to be simplified into open apex and closed apex. Thus, further research into the effects on the stage of root development of the donor tooth on the long-term survival and success rates after DAT should be conducted.

Finally, throughout the articles, there is a lack of continuity in their definitions of specific criteria. The definition of success, particularly for different age groups, such as young adolescents and mature adults, was a significant issue.

Risk of bias evaluation

The Newcastle–Ottawa scale (NOS) evaluates the quality of the selected research articles included in the meta-analysis (MA). This quality assessment methodology was applied to both retrospective and prospective studies. Articles [7, 9, 32–36, 38, 39, 42, 48] achieved a high score between 8 and 6, therefore labelled as "good quality" studies. Moreover, studies [10, 31, 37, 40, 41, 43–47, 49, 50] featured scores of 5–3, thus categorised as "fair studies", therefore no articles were labelled as "poor studies" in the meta-analysis Table S9 [27]. Articles [7, 10, 31, 35, 37, 44, 47, 50] with small sample sizes produced data where it was more common to find negative values (predicted success rates by model were superior to actual values). This suggests a level of bias and should be examined with extreme caution Fig. 6.

Fig. 6.

Funnel’s Plot Analysis Success Rate Comparison between Incomplete Root Development (Open Apex) Group and Complete Root Development (Closed Apex) Group

Study quality evaluation

The QUADAS-2 scale showcases the level of bias risk for the selected research articles included in the meta-analysis. This quality assessment methodology was applied to both retrospective and prospective studies. Out of the 23 studies, 9 [9, 32, 33, 36, 39, 42, 48] were listed as having a "Low risk of Bias", whilst articles [7, 10, 31, 34, 35, 37, 38, 40, 41, 43–47, 49, 50] were listed as having "possible risk of bias" due to a lack of clarity or possible risk of bias within the article Table S10 [28].

Conclusion

General objective

• DAT features a multitude of prognostic factors which affect the treatment’s outcome. A strict surgical protocol is needed to achieve high long-term survival and success rates, as well as a sufficient follow-up period to monitor for potential complications.

Specific objective

• DAT using donor teeth with incomplete root formation (open apex) and complete root formation (closed apex) is regarded as a favourable and predictable treatment option for replacing lost teeth. Success rate was 84.0% in the open apex group and 86.7% in the closed apex group—no significant differences between groups (p = 0.539). Well-documented complications in DAT, such as infection-related root resorption and tooth ankylosis, remain very low in both the open and closed apex groups, with no significant difference observed between them. The pulp necrosis rate in the open apex group is reported to be low; however, further long-term studies should be conducted to evaluate the pulp necrosis rate of DAT using teeth with a closed apex. Follow-up examinations at 1, 5, and 10 years, in both the open and closed apex groups, produced high survival and success rates, with a marginally higher result in the open apex group. Overall survival rate was 93.8% in the open apex group and 92.6% in the closed apex group—no significant differences between groups (p = 0.833).

Author contributions

Conceptualization, H.R. and S.M.R.; methodology, H.R..; software, S.M.R.; validation, T.H.A., M.F.M.; formal analysis, H.R., S.M.R., T.H.A. and M.F.M.; investigation, H.R.; resources, H.R.; data curation, H.R.; writing—original draft preparation, H.R.; writing—review and editing, H.R., S.M.R. and T.H.A.; visualization, H.R.; supervision, S.M.R. and T.H.A.; project administration, S.M.R., T.H.A. and M.F.M; funding acquisition, U.C.V.. All authors have read and agreed to the published version of the manuscript.

Funding

This systematic review and meta-analysis were self-funded by the authors and the Universidad Católica de Valencia San Vicente Mártir. Review 1: pulp necrosis rate change to NR, remove this from the abstract, discussion and results in the closed apex group.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Approval from the Research Ethics Committee (CEI) was not indicated for this type of study.

Informed consent

This is an observational study analysing retrospective and prospective articles where candidate information remained anonymous. Thus, this research does not require formal consent from the candidates of the selected articles.

Competing interests

The authors declare no competing interests.