Long‐term outcome of autogenously transplanted maxillary canines

Abstract The aim of this study was to determine the long‐term outcome of autotransplanted maxillary canines and to investigate the influencing parameters. Seventy‐one patients (84 transplanted canines) volunteered to participate in this study. The mean follow‐up time was 21 years. In case of tooth survival and when patients were found willing for recall, teeth were investigated clinically and radiographically. Transplanted teeth were compared to the contralateral canine and scored with an aesthetic and radiographic index. The survival rate was 67.9%, considering that 27 transplanted teeth were lost before examination. The mean survival time was 15.8 years. Maxillary canine autotransplantation may have a successful outcome up to 21 years after transplantation requiring minimal patient compliance and low financial costs. The survival rate can be considered favorable realizing that autotransplantation is a treatment option in a selected group of cases.

. The traditional treatment options for impacted canines are interceptive removal of the decidiuous canine, surgical exposure with or without orthodontic traction to align the malpositioned tooth, no treatment, autotransplantation of the permanent canine or removal of the permanent canine and prosthetic or restorative treatment.
When surgical exposure and subsequent orthodontic realignment are difficult or impossible due to unfavorable impaction position of a impacted maxillary canine or the patient refuses prolonged orthodontic treatment, autotransplantation is a valuable alternative. Autogenous tooth transplantation can be defined as the surgical movement of a tooth from one position in the mouth to another in the same individual. (Moss, 1968 Jacobs, 2018). The present study aimed to determine the long-term outcome and survival of autotransplanted canines.

| Subjects
In 71 patients, 84 teeth, maxillary canine transplantation had been performed. All these procedures were performed between 1995 and 2002. Equal gender distribution was found (33 male (41 teeth) and 38 female (43 teeth) (Table 1). At the time of transplantation the mean age was 20.7 years (range 10.9-46.3 years), and the mean follow-up period was 21 years (range 19.9-23.9 years). The same surgeon performed all transplantations (CP), following the same protocol. All transplanted teeth reported here were maxillary impacted canines.
Pre-and perioperative parameters were retrieved out of the medical files (Table 2). By observation of previous radiographs (intra-oral and panoramic), the stage of root development at time of transplantation was evaluated with Moorrees et al.'s classification. (Moorrees, Fanning, & Hunt, 1963) All patients were contacted by telephone and survival of the transplanted canine was checked for. In case the transplanted canine was still in situ, patients were invited for a recall visits to the department for further clinical and additional radio graphical analysis. Out of the 47 patients (57 surviving autotransplanted maxillary canines) who were eligible for a recall visit, 23 patients (27 surviving autotransplanted maxillary canines) decided to participate in the presented study. Clinical and radio graphical examination of these 27 autotransplanted maxillary was performed by the same examiner. This involved evaluation of the transplanted canine and the contralateral canine using aesthetic and radiographic indexes as described by . In case of bilateral autotransplantation both teeth were eval-   were further questioned concerning the timing of failure and the current treatment or treatment plan (no plan, resin retained bridge, prosthesis, dental implant with or without bone augmentation procedure).
The study protocol was approved by the Ethics Committee of our Hospital (s number: s53225).

| Surgical procedure
The same surgeon performed all transplantations (CP), following the same protocol. This protocol, including the surgical technique and criteria for endodontic treatment, has been described in the previous study of Gonissen et al ( Figure 1). (Gonnissen et al., 2010) Prior to carrying out the actual surgery a radiographic presurgical analysis was carried out identifying the specific location and donor site characteristics.

| Clinical and radiographic examination
All transplanted teeth that were still in place were eligible for recall and further evaluation. Each patient signed a written informed con-

| Statistical analysis of the results
The ratio between failed and succeeded canines was first compared between different groups by means of a generalized linear model. Subsequently, survival analysis was performed by means of Kaplan-Meier graphs and survival regression for censored normally distributed data. Overall, almost half of the teeth (13 teeth (Figure 2,A). On clinical examination major discolouration was seen in 4 teeth. Minor discoloration was seen in 5 teeth. All other transplanted teeth showed normal color.
16 of the transplanted maxillary canines were scored to have an excellent, 9 with a good, 1 with an acceptable and 1 having a poor aesthetic outcome (Figure 3,4). Two teeth showed extensive recession of the gums (Figure 2,B). Six teeth were found to have a major deviation of the buccolingual inclination when compared to the contralateral maxillary canine.

| Radiographical index
Radiographical outcome of the transplanted canine was assessed with the autotransplanted maxillary canine radiographical index (AMCRI) (Grisar, Vanpoecke, et al., 2018). Twelve of the transplanted maxillary canines were scored to have an excellent, 3 with a good, 7 with an acceptable and 4 to have a poor radiological outcome ( Figure 2,3,4).
External root resorption was the predominant type of resorption as 9 transplanted teeth showed some sign of external root resorption on 2D and 3D imaging (Figure 4). Three teeth showed apical infection on 2D and 3D imaging. None of the transplanted teeth showed internal root resorption. Four teeth showed signs of ankylosis on 2D and 3D imaging. Three teeth showed apical pathology on 2D and 3D imaging.

| Survival rate
Since 27 transplanted teeth were lost prior to endstage examination, the survival rate was 67.9%. Because of a delayed root channel treatment, 1 transplant was lost 6 months after surgery. Figure 5 represents the Kaplan-Meier risk curve for the overall survival rate over 21 years. The mean survival time was 15.8 years (min 0.5max 23.9; SD 6.6). Figure 6 shows the relation between age at time of transplantation and survival of the transplanted canine (p = 0.0966).
Investigating baseline variables and their influence on final outcome showed a significant correlation between ankylosis of the impacted maxillary canine and failure (p < 0.005). Survival analysis

| Succes rate
The success rate was only calculated for the transplanted teeth that were evaluated on recall visits. In this study was 22 of the 27 surviving transplanted teeth on recall were evaluated as successful after clinical aesthetic and radiological evaluation (Grisar, Claeys, et al., 2018;Grisar, Vanpoecke, et al., 2018).
Patients were questioned using a VAS (visual analogue scale) scoring system consisting of 7 questions: • Q1: judge retrospectively the overall treatment protocol regarding the inherent therapy and the length of treatment?
• Q2: Does the treatment result fulfill the general expectations?
• Q3: Satisfaction with the treatment outcome from a general aesthetic point of view?
• Q4: Satisfaction with the treatment outcome from a general functional point of view?
• Q5: Satisfaction with the treatment outcome regarding color of the tooth?  All patients reported high individual scores (average 8.6, range 6.7-9.6), demonstrating a high long term patient satisfaction. Lower VAS scores were related to lower scores on the maxillary canine aesthetic index (MCAI).    (Grisar, Chaabouni, et al., 2018). However none of the included studies had a follow up longer then 15 years.

| Failed transplantations
A progressive loss of transplanted teeth is to be expected with increasing follow-up time since it has been proven that with increasing time after transplantation, significantly more root resorption can be expected. (Gonnissen et al., 2010) When comparing the outcome rate of this study with the literature, it is important to consider the difference in criteria for success, because there are no common success criteria. This study used established criteria for clinical assessment of transplanted teeth. (Altonen, Haavikko, & Malmström, 1978;Patel et al., 2011;Urbanska & Mumford, 1980) Moreover, the transplanted canine were clinically and radiographically compared with the contralateral canine using previously devel- were enrolled in a non-complex follow-up treatment, such as implant surgery without bone grafting or prosthetic replacement. In almost one third of the cases with a dental implant a separate bone augmentation procedure proved to be necessary ( Figure 8).
In the present study the authors did not consider transient root resorption, ankylosis or endodontic treatment te be a failure. This because even in case of eventual loss of the tooth, autotransplanted teeth may have been retained for considerable lengths of time, providing an aesthetic and functional solution. However, poor aesthetic or radiological outcomes were considerd to be a failure (Grisar, Claeys, et al., 2018b;Grisar, Vanpoecke, et al., 2018c).
Among the surviving teeth, the longest duration was 23. Autotransplantation of impacted maxillary canines may be indicated in selected circumstances, an acceptable long-term survival rate can be expected. Individual success is difficult to predict and patients must be informed of the potential for failure and associated risks before undergoing such a procedure. (Patel et al., 2011) If this is met, a high patient satisfaction can be expected. If the transplanted tooth is lost, replacement can be achieved by means of a dental implant potentially and in addition requiring a bone augmentation procedure.