Radiographic assessment of CBCT-guided autotransplantation of a premolar to the maxillary incisor region: A 2‐year prospective split‐mouth study

doi:10.21203/rs.3.rs-4358973/v1

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Radiographic assessment of CBCT-guided autotransplantation of a premolar to the maxillary incisor region: A 2‐year prospective split‐mouth study

https://doi.org/10.21203/rs.3.rs-4358973/v1

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Background: To investigate the 2-year radiographic outcome of cone-beam computed tomography (CBCT)-guided tooth autotransplantation (TAT) of a premolar to the maxillary incisor region in children.

Methods: Eighteen paediatric patients with a missing maxillary incisor were recruited for CBCT-guided premolar transplantation to the maxillary central incisor region (TAT group), neighbouring a healthy contralateral central incisor (control group). Radiological parameters, assessed at 2-year follow-up, included periodontal ligament space (PLS), the outline of lamina dura, the vertical distance between the cementoenamel junction and crestal bone (CEJ-CB), pulp obliteration, radiographic root area (RRA) and length (RRL) and crown-root ratio (CRR).

Results: Positive root growth in 89% of the TAT cases, with an average increase in RRA by 27% compared to the control. Pulp obliteration was observed in 83% of the TAT cases (partial: 55.6%; complete: 27.8%). The average crown-to-root ratio was 0.72 and 1.01 for the control and TAT group, respectively. No significant differences existed between TAT and control concerning PLS (p=0.09), lamina dura (p=0.12), and CEJ-CB distance mesially (p=0.17) or distally (p=0.28).

Conclusions: CBCT-guided TAT might act as a viable treatment option for rehabilitating missing maxillary (centrally) incisor teeth in paediatric patients when osseointegration may not be the preferred option. (Clinical trial center and ethical board University Hospitals, KU Leuven: S55287; ClinicalTrials.gov Identifier: NCT02464202)

tooth autotransplantation

premolars

central incisors

maxilla

intraoral radiography

Managing missing maxillary central incisors in a paediatric population is a challenging task requiring a multidisciplinary treatment approach due to its aesthetic, functional, and psychological implications. Considering dentoalveolar growth in children and adolescents, common treatment strategies for replacing missing incisors, such as an osseointegrated implant or prosthetic rehabilitation, are not favourable. While orthodontic space closure is not always optimal, tooth autotransplantation (TAT) has evolved into a well-established treatment option in children for restoring maxillary anterior region with a transplanted premolar, having an overall success rate of 82–100%¹.

As an autogenic biological approach, TAT offers multiple benefits compared to other treatment modalities, such as increased resistance to occlusal loading and the ability to maintain and stimulate continued growth of the surrounding periodontal bone^2,3,4. Furthermore, the physiological integration of TAT allows a natural feedback pathway through the preserved mechanoreceptive function of the periodontal ligament (PDL)⁵. Literature has shown that the predictability of TAT treatment strongly depends on the survival of periodontal ligament cells during the surgical procedure.

The procedure can be performed at any age and has shown a high success rate in paediatric patients before complete root formation and adult patients with fully formed roots^5,6,7,8,9. Although the success rate of TAT has been well documented^4,7,8,9, its long-term prognosis remains unpredictable due to the complexity of the procedure. It is highly dependent on the treatment protocol and characteristics of both donor tooth and recipient site^4,6,7,10. Previous evidence suggests that TAT has an overall success of 87.6% and 94.4% survival rate in paediatric patients at a follow-up period of 2.6 ± 1.8 years¹¹. However, the majority of the evidence is low, and limited data is available concerning patient-reported outcomes¹².

The conventional TAT surgical approach, with the utilization of only two-dimensional radiography at the treatment planning phase, offers a lower success and survival rate due to a high risk of increased extra-alveolar donor tooth time, periodontal tissue damage and complexity of the surgical procedure depending on the surgeon’s experience¹³. The development of cone-beam computed tomography (CBCT)-guided approaches with low-dose imaging protocols, computer-aided surgical planning, and fabrication of a precise replica of the donor tooth with a three-dimensional (3D) printer has drastically simplified the TAT surgical procedure, reducing the extra-alveolar time of the donor tooth to < 1min by decreasing the number of manipulations, meanwhile preserving the viability of the periodontal ligament and its stem cells¹⁴. This results in a higher success rate, increased predictability of the procedure, and healing pattern¹⁴. Additionally, it allows passive adaptability of TAT at the recipient site, which might facilitate the preservation of the pulp vitality and periodontal ligament stem cells, consequently reducing the risk of necrosis and root resorption ^{14, 15 16, 17}.

A prior study suggested a higher survival rate of TAT with a CBCT-guided approach (92%) compared to its conventional counterpart (84%)¹⁴. Previous radiological studies have either compared CBCT-guided TAT with a historical conventional group or solely reported the success and/or survival rate of TAT in a single group without considering the similarities with the contralateral incisor^14,17. To the best of our knowledge, no radiological study exists applying a split-mouth design and comparing the periodontal and endodontic outcomes of the CBCT-guided TAT technique with the contralateral incisor acting as a control in a paediatric population. Such comparative information would allow testing whether CBCT-guided TAT could offer a clinically acceptable outcome comparable to that of a contralateral incisor at a long-term follow-up in children and adolescents.

Therefore, the following study aimed to radiographically assess the periodontal and endodontic outcomes of CBCT-guided TAT of a premolar to the unilateral maxillary central incisor region compared with the contralateral incisor at a 2-year follow-up period.

Sample selection

This split-mouth study was conducted in compliance with the World Medical Association Declaration of Helsinki on medical research. Ethical approval was obtained from the Ethical Review Board of the University Hospitals Leuven (reference number: B322201317710 / S55287). Informed consent was not required for this retrospective study, as patient-specific information was kept anonymous.

A total of 18 patients (15 male, 3 female, age range: 9–12 years, average age: 11 years) who underwent TAT during the period 2007 to 2018 were recruited from the database of patients referred to the Paediatric Dentistry Department, University Hospitals Leuven, Leuven, Belgium. The inclusion criteria consisted of paediatric patients with missing unilateral central incisors who underwent CBCT-guided TAT of a premolar with incomplete root formation to the maxillary central incisor region (TAT group) and the presence of contralateral central incisor (control group). Exclusion criteria were the presence of craniofacial malformations such as cleft lip and/or palate, craniosynostosis, microtia, hemifacial microsomia, and other syndromic diseases.

Two surgeons performed all CBCT-guided TAT surgical procedures under general anaesthesia based on a previously validated surgical protocol^13,14. CBCT-derived 3D printed tooth replicas and surgical guides were fabricated to aid the transplantation procedure (Fig. 1). Intraoral radiographic images were acquired immediately after surgery (baseline) and at 2-year follow-up time-point. The radiographic images were obtained using the paralleling technique, with a direct current (DC) Minray intraoral X-ray tube (Soredex, Tuusula, Finland) having a rectangular collimation and standard size-2 phosphor plate (measuring 31×41 mm) of the Digora system (Soredex, Tuusula, Finland).

Image evaluation

The intraoral images were initially calibrated considering the known dimensions of the phosphor plate using an open access software, Image J version 1.47 (National Institutes of Health, Bethesda, MD, USA). Subsequently, both TAT and contralateral incisor were radiographically assessed based on the following parameters: periodontal ligament space (PLS) and its configuration (wide, narrow or normal) along the complete extension of root, outline of lamina dura, linear distance between cementoenamel junction and crestal bone (CEJ-CB), pulp obliteration, radiographic root area (RRA) and length (RRA) and crown-root ratio (CRR). All measurements were performed by the same evaluator and repeated within a 4-week interval using the abovementioned software.

The evaluated parameters were further allocated into 4 categories for describing the radiographic assessment in context to the clinical outcomes: (1) Periradicular and pulpal health, (2) Root growth, (3) Pattern of TAT root formation and (4) TAT longevity

1. Periradicular and pulpal health was determined based on the following radiographic parameters: PLS, the outline of lamina dura, vertical (linear) distance between CEJ-CB, and pulp obliteration. PLS was classified as absent (not visible), partially present (visible with some interruptions), and present (visible without interruption) with a narrow (not well defined – less than 0.4 mm), normal (around 0.5 mm) or wide (enlarged – more than 1 mm) configuration. Similarly, lamina dura was classified as absent, partially present, and present. Pulp obliteration was categorized as partial, complete, and absent, depending on the distinguishability of the pulp canal lumen.

2. Root growth: It was assessed based on a previously validated methodology that used RRA to calculate the root growth¹⁸. The equation was as follows:

$$\:\left(\frac{\text{R}\text{R}\text{A}\:\text{O}\text{F}\:\text{T}\text{A}\text{T}\:\text{A}\text{T}\:2\text{Y}\text{E}\text{A}\text{R}}{\text{R}\text{R}\text{A}\:\text{O}\text{F}\:\text{C}\text{O}\text{N}\text{T}\text{R}\text{O}\text{L}\:\text{A}\text{T}\:2\text{Y}\text{E}\text{A}\text{R}}\text{*}100\right)-\:\left(\frac{\:\text{R}\text{R}\text{A}\:\text{O}\text{F}\:\text{T}\text{A}\text{T}\:\text{i}\text{m}\text{m}\text{e}\text{d}\text{i}\text{a}\text{t}\text{e}\text{l}\text{y}\:\text{a}\text{f}\text{t}\text{e}\text{r}\:\text{s}\text{u}\text{r}\text{g}\text{e}\text{r}\text{y}}{\text{R}\text{R}\text{A}\:\text{O}\text{F}\:\text{C}\text{O}\text{N}\text{T}\text{R}\text{O}\text{L}\:\text{i}\text{m}\text{m}\text{e}\text{d}\text{i}\text{a}\text{t}\text{e}\text{l}\text{y}\:\text{a}\text{f}\text{t}\text{e}\text{r}\:\text{s}\text{u}\text{r}\text{g}\text{e}\text{r}\text{y}}\text{*}100\right)$$

3. Pattern of TAT root formation: It was assessed using the RRL and was categorized into 3 groups (G1, G2, and G3) based on the difference between TAT and control at follow-up. The equation was as follows:

$$\:\frac{\:\text{C}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l}\:\text{r}\text{o}\text{o}\text{t}\:\text{l}\text{e}\text{n}\text{g}\text{t}\text{h}-\:\text{T}\text{A}\text{T}\:\text{r}\text{o}\text{o}\text{t}\:\text{l}\text{e}\text{n}\text{g}\text{t}\text{h}}{\text{C}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l}\:\text{r}\text{o}\text{o}\text{t}\:\text{l}\text{e}\text{n}\text{g}\text{t}\text{h}}\text{*}100$$

G1: When the root length difference between the TAT and control was 10% or less.

G2: When the difference was 11–25%.

G3: When the difference was greater than 25% with an unfavourable CRR of more than the minimally acceptable ratio of 1:1.

4. TAT longevity: It was assessed by calculating the CRR. A minimum ratio of 1:1 was considered acceptable, as suggested by Shillingburg et al.¹⁹

Statistical analysis

Data were analysed using statistical software S-Plus 8.0 for Linux (TIBCO, Palo Alto, California, USA). The percentage values were used for descriptive analysis. The difference between the TAT and control group was assessed using binary variables as clustering factors. The normality of the data was checked using a normal quantile plot of residual values. A paired t-test was applied for continuous variables to calculate the differences between the TAT and control groups.

At the 2-year follow-up, all TAT procedures were successful. The TAT group showed a normal PLS in 53.7% of the cases, whereas 22% and 24.1% of cases presented with a widened and narrow space, respectively (Table 1). Pulp obliteration was observed in 83% of the TAT cases (partial: 55.6%; complete: 27.8%). All teeth in the control group had a normal PLS without any pulp obliteration. No significant difference existed between TAT and their control concerning the PLS (p = 0.09), lamina dura outline (p = 0.12), and linear distance between CEJ and CB mesially (p = 0.17) and distally (p = 0.29) (Table 2).

At the 2-year follow-up, the average increase in the TAT RRA was 82%, with a rise of 27% compared to the control group, and 89% of the roots showed a positive root growth. A 77% increase in TAT RRL was observed, with a difference of 10% or less for five cases (27%) compared to the control. The difference mentioned above of 10% or less was defined as an incisor-like root formation pattern (Fig. 2). Additionally, 17% of the cases in the TAT group presented with a favourable RRL difference of > 10% and < = 25%, while 56% showed a difference of > 25% compared to their control. The average CRR was 1.01 and 0.72 for the TAT and control groups, respectively.

Table 1. Absolute value and significance (p-value) of tooth autotransplantation (TAT) and control in relation to the periodontal ligament space and Lamina dura outline.

Table 2. Average/Standard Deviation (SD) and significance (p-value) of tooth autotransplantation (TAT) and control in relation to the distance between CEJ-CB at mesial and distal region.

Autotransplantation of premolars for rehabilitation of the congenitally missing or traumatically lost maxillary incisors has become a predictable treatment approach in paediatric patients¹⁴. The technique offers an optimal adaptation, immediate replacement of the missing tooth, preservation of periodontal tissue, and normal response to orthodontic forces, which are of vital importance in young and growing patients for whom dental implants are generally contraindicated^5,7. Another additional benefit is its potential to induce bone formation and remodel the alveolar process to its normal morphology, which could accommodate an implant without the need for bone grafting if TAT failure occurs at a later stage. The application of CBCT-guided approaches has drastically improved the TAT success rate with predictable outcomes¹⁴.

The periradicular area of transplanted teeth had a normal appearance with optimal healing comparable to that of the contralateral control, which was also consistent with previous studies evaluating clinical and radiological outcomes following conventional TAT^6,26,27,28. The findings of the current study suggested that CBCT-guided TAT showed periodontal radiographic similarities comparable to that of the contralateral control tooth, which was in agreement with the previous studies following conventional TAT treatment approaches^3,6,20–23. However, unlike the earlier evidence, all the cases recruited in the present study only involved autotransplantation of premolars with incomplete root formation and the results cannot be extrapolated to the teeth with fully developed roots where the survival and success rate is lower with a higher complication rate^24,25.

The majority of TAT cases showed either partial (55.6%) or complete (27.8%) pulp obliteration without any pathoses. A clinician should not be alarmed if obliteration is observed, as it is a regular and expected finding following the TAT procedure. The obliterated pulp might revitalize usually at follow-up, and a good prognosis has been confirmed by previous long-term follow-up studies^{3,6,8,20,21,22}. Additionally, no notable difference existed based on the distance between CEJ and CB. These positive findings indicate that CBCT-guided TAT might act as a reasonable treatment approach for the restoration of missing central incisors with a considerable potential for marginal periodontal attachment.

Although the roots of the translated teeth continued to grow, they mostly remained shorter than the contralateral central incisor. The “incisor-like root formation pattern of growth” was defined as the TAT having an RRL difference of 10% or less compared to the control, which was only observed in 28% of the cases. The reasoning behind why certain teeth continued growth to reach the so-called incisor-like root formation while others observed a shorter length is still unknown, and future studies are required to identify the influential factors. Furthermore, even though TAT roots were shorter, the CRR remained within the minimal acceptable limit of 1:1¹⁹, thereby ensuring a good prognosis.

The study had certain limitations. Firstly, the sample size was limited, considering the strict inclusion criteria concerning the CBCT-based TAT procedure in the presence of a contralateral healthy central incisor. Secondly, the study only included premolars with partial root formation, and the reported findings cannot be generalized to mature teeth. Further studies with a larger sample size and longer clinical and radiological follow-ups are required to assess the influential factors that might impact the outcome of CBCT-guided TAT.

CBCT-guided TAT might act as a viable treatment option for rehabilitation of missing maxillary (centrally) incisor teeth in children and adolescents. The radiographic similarities between the transplanted premolar and contralateral incisor, with the possibility of achieving an incisor-like growth pattern, point towards a favourable clinical outcome with successful periodontal attachment.

CBCT

cone-beam computed tomography

TAT

tooth autotransplantation

PLS

periodontal ligament space

CEJ

cementoenamel junction

crestal bone

RRA

radiographic root area

RRL

radiographic root length

CRR

Ethics statement: The study was carried out in accordance with the principles described in the Declaration of Helsinki on experimentation with human beings and was approved by the Ethical Committee of the University Hospitals Leuven (B322201317710 / S55287).

Availability of data and materials: The datasets generated and/or analysed during the current study are not publicly available due to patient privacy but are available from the corresponding author on reasonable request and after ethical approval.

Competing interest: The authors deny any conflicts of interest related to this study.

Statement of funding source: Supported by the Research Council of KU Leuven grant numbers (C24/18/068).

Consent to participate declaration: All participants (parents or legal guardians) have given their consent to undergo surgery and take part in the study (ethical approval number S55287).

Authors' contributions: TA, ME, KV contributed to conception, design, data acquisition, analysis and interpretation, drafted and critically revised the manuscript; MC, GVG, JW, RJ, contributed to conception, design, data acquisition, and interpretation, drafted and critically revised the manuscript. All authors gave final approval and agreed to be accountable for all aspects of the work.

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No competing interests reported.

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Radiographic assessment of CBCT-guided autotransplantation of a premolar to the maxillary incisor region: A 2‐year prospective split‐mouth study

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Abstract

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Background

Methods

Sample selection

Statistical analysis

Results

Discussion

Conclusion

Abbreviations

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References

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