Electrical and thermal pulp tests are unreliable after a traumatic dental injury, and there may be no response to both tests even if the circulation is restored.^23,24 Therefore, the clinical evaluation of a traumatized tooth requires symptomatic, visual and radiographic assessment. If the tooth becomes necrotic and infected, external inflammatory root resorption may occur, which may result in tooth loss in a short period.²⁵ In teeth with incomplete root formation, circulation survival and revascularization are possible^23,25,26 and highly desirable, not only to maintain an infection-free pulp space but also to allow the tooth to continue to develop and strengthen.

Measuring pulpal blood flow, or PBF, using laser Doppler flowmetry, or LDF, has been described as being a more sensitive technique for evaluating tooth vitality than using conventional methods such as electrical and thermal pulp testing.^27,28 Several authors reported using flowmetric values to demonstrate the reestablishment of vitality in traumatized teeth^27–29 or to show significant blood flow reduction in the maxillary teeth of patients who underwent Le Fort I osteotomy.^30–35 In instances of dental trauma, LDF may be useful in detecting transient ischemic episodes and identifying teeth at risk of developing adverse sequelae such as avascular necrosis and tissue loss.

As longitudinal avulsion type–related LDF PBF data are not available in the literature, we conducted this study to evaluate the efficacy of LDF in diagnosing revascularization of avulsed permanent maxillary central incisors after replantation and splinting.

Laser Doppler flowmetry may be useful in detecting transient ischemic episodes and identifying teeth at risk of developing adverse sequelae.

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS PROCEDURE RESULTS DISCUSSION CONCLUSION REFERENCES

 
Subjects. The study group comprised 17 subjects who were undergoing replantation and splinting after dental trauma. Ten subjects were female, and seven were male; their mean age was 9 years (range, 7 to 10 years). The subjects’ parents or guardians were informed about the study procedure, and we received informed consent from each subject’s parent or guardian. Inclusion criteria were presence of a single maxillary central incisor affected by an avulsion type injury, absence of concomitant dentoalveolar injuries and that trauma had occurred within the past two hours. We treated each of the subjects with a 0.16- by 0.50-inch standard edgewise wire (Leibinger, Mülheim, Germany). We did not collect LDF data if a maxillary incisor was missing or the injured maxillary central incisor had a crown, had received endodontic treatment or had a large restoration.

Splint application. We bonded the splints to the labial aspect of both the lateral and central maxillary incisors. We cut the wire to the desired length and then adapted it to the curvature of the incisors using pliers. We secured the splints with light-curing composite. After placing cotton rolls in the vestibule, we air-dried the incisors. We etched the enamel surface with 37 percent phosphoric acid gel (Totaletch, Ivoclar Vivadent, Ellwangen, Germany) for 30 seconds. We then rinsed off the gel with water from the dental unit and air-dried the etched surfaces. We applied a thin layer of bonding agent (Heliobond, Ivoclar Vivadent) to the etched enamel surface using a microbrush and left it on for 20 seconds before we polymerized it with a light source for another 40 seconds.

Apparatus. We took PBF measurements with a laser Doppler flowmeter (Periflux 4001 Master, Perimed, Järfälla, Sweden). Light with a wavelength of 632.8 nanometers was produced by a 1-milliwatt helium-neon laser within the flowmeter and was transmitted along a flexible fiber-optic conductor inside a specially designed round dental probe that was 2 millimeters in diameter (PeriFlux Probe 416, Perimed).^23,31–33 A fraction of the backscattered light from the tooth was returned to the flowmeter along a pair of afferent optical fibers within the probe. The optical fiber’s diameter was 125 micrometers, and the fiber-to-fiber distance was 500 µm. The flowmeter then processed the amount of Doppler-shifted light that was returned and produced an output signal. The measured voltage is linearly related to the flux of red blood cells (number of cells multiplied by their average velocity) encountered within the tooth and represents a relative PBF measure.

We calibrated the flowmeter before each data collection session. We adjusted the narrow band to read zero voltage when the probe was placed against a motionless object, while we used a commercially available motility standard (Perimed) to calibrate the flowmeter on the wide band to a specific value of 250 perfusion units, or PUs. We activated the artifact filter and collected the PBF data on a wide band setting. Voltage output values were sent from the flowmeter’s RS-232 port at a rate of 32 signals per second to a computer for storage and subsequent analysis.

	PROCEDURE

TOP ABSTRACT MATERIALS AND METHODS PROCEDURE RESULTS DISCUSSION CONCLUSION REFERENCES

 
We took the measurements on the labial aspect of each experimental tooth about 5 mm from the gingival margin. Each subject underwent four measurement sessions: on the day of splint removal (T1), at 12 weeks after splint removal (T2), at 24 weeks after splint removal (T3) and at 36 weeks after splint removal (T4). To ensure accurate and reproducible spatial positioning of the probe at each session, we prepared custom-made clear plastic splints (Bioplast, Scheu-Dental, Iserlohn, Germany) that covered the maxillary teeth and provided appropriately placed holes with a diameter similar to that of the flowmeter probe. At each measurement session, we had the subject rest in a supine position in the dental chair for approximately 10 minutes and then we collected blood flow data for three minutes.

At the end of the follow-up sessions, we assessed revascularization both clinically and radiographically. Our criteria for diagnosing a vital tooth were the absence of clinical symptoms, the absence of periapical radiolucency and a positive response to sensitivity testing. We diagnosed a nonvital tooth if there was progressive gray discoloration of the crown, a reaction to percussion, a periapical radiolucency and an unresponsiveness to sensitivity testing.^36–38 The clinical diagnostic procedures we used included sensitivity testing with carbon dioxide ice, percussion and mobility testing with a calibrated instrument (Periotest, Medizintechnik Gulden, Bensheim, Germany), and evaluation of crowns for the presence of color changes.³⁸ The radiographic examination of the anterior region consisted of one occlusal film and three periapical exposures, in which the central beam was directed between the lateral and central incisors and between the central incisors.³⁸ We found that seven of the 17 avulsed teeth were vital while 10 teeth were nonvital.

To eliminate background signals and thus isolate the signal from the pulp, we had to eliminate reflected signals from the surrounding periodontal structures. At each session, we used five vital control teeth and five nonvital control teeth to assess the background signal. In 10 subjects, when we took measurements for an avulsed and splinted permanent maxillary incisor, we selected the respective contralateral homologous tooth as a control. The five vital control teeth remained vital during the follow-up.

Using the control data as a template, a single evaluator (H.S.) assessed the 17 teeth as vital or nonvital. He considered the teeth to be vital if the flowmetric signals at T2 were similar to those of the positive controls or if a continuous increase of PBF value occurred from T1 to T2. He considered the teeth to be nonvital if the flowmetric signals at T2 were similar to those of the negative controls or if the PBF value decreased dramatically from T1 to T2. He then correlated the assessments with the vitality statuses that were determined clinically and radiographically at T4.

Data analysis. We calculated the mean PUs for each recording site during each session by averaging each of the PUs collected for three minutes, or 180 seconds. We excluded PUs that registered as movement artifacts from this average. We used univariate analysis of variance, or ANOVA, for repeated measurements to test for statistically significant differences between session-related variations in PBF measurements. Statistical significance was set at P < .05. We used the SPSS X package (SPSS, Chicago) for all statistical analyses.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS PROCEDURE RESULTS DISCUSSION CONCLUSION REFERENCES

 
The LDF data we collected for the five vital control teeth demonstrated that the mean PBF values from T1 to T2 were almost the same (range, 9.9 to 10.4 PUs; mean, 10.2 PUs ± 1.4 standard deviation, or SD). The PBF values showed heartbeat-synchronous oscillations. The LDF recordings from the five negative controls showed an average PBF value of 4.1 PUs ± 1.1 SD at T1, and they stayed at almost the same level until the end of follow-up sessions (range, 3.8 to 4.4 PUs; mean, 4.0 PUs ± 1.1 SD). The heartbeat-synchronous oscillations were irregular and low in amplitude. After the LDF values of the surrounding tissue (negative controls) had been subtracted from the PBF values (positive controls), the net PBF values of the vital control teeth showed that the mean PBF measured was 60.8 percent (range, 56.4–63.5 percent) of the original values.

After subtracting the net PBF value of surrounding tissue (negative controls), the net PBF values of the vital teeth ranged from 1.5 to 10.0 PUs. Of the seven teeth we evaluated as vital at T4, five had a net PBF value of between 50 percent and 71.4. percent of the original value at T2. Two teeth had a net PBF value of 33.3 percent and 14.3 percent of the original value, respectively. Thus, in all vital teeth (100 percent), we saw a net PBF value that was distinctly different from that of the nonvital teeth (Table 1).

Using LDF, we correctly assessed tooth vitality in all teeth 88.2 percent of the time. Among the successfully revascularized teeth, we assessed 100 percent (seven of seven) correctly, and among the nonvital teeth, we assessed 80 percent (eight of 10) correctly.

ANOVA for repeated measurements demonstrated that in teeth we confirmed were revascularized, there was a significant increase in PBF value from T1 to T2 (P < .05), T3 to T4 (P < .05) and T1 to T4 (P < .01). In teeth we confirmed were nonvital, the only significant differences were between T3 and T4 (P < .01) and T1 and T4 (P < .05) (Table 2).

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS PROCEDURE RESULTS DISCUSSION CONCLUSION REFERENCES

Traumatic avulsion involves displacement of the tooth out of the alveolar socket. It constitutes 0.5 to 16 percent of all traumatic injuries to permanent anterior teeth,⁴⁰ it usually involves the maxillary anterior teeth, and it is more common in the primary dentition than the permanent dentition.² Tooth avulsion is a very complex wound and involves disruption of the marginal gingival seal, alveolar bone, periodontal ligament fibers, cementum and the neurovascular supply to the pulp.³⁸ Complications after replantation include ankylosis, pulp necrosis, pulp obliteration, external root resorption and loss of marginal bone support.^19,20,41 The most significant prognostic factor for pulpal healing appears to be the stage of root formation at the time of injury and the period between trauma and treatment.^42–45 In teeth with incomplete root formation, blood vessels may pass through the apical foramen, allowing revascularization and normal root formation to occur. Treatment outcome, however, may depend not only on the root formation stage and time elapsed between trauma and treatment, but also on other factors such as the presence of contamination, the type and condition of storage medium, concomitant dentoalveolar injuries and the type of dental trauma splint.^46,47 Further investigation is necessary to answer the question about which additional trauma-related features may have to be defined as "diagnostic for disorder," namely with significant elevated risk of developing adverse sequelae.

We conducted this study to evaluate the efficacy of LDF in diagnosing revascularization of avulsed permanent maxillary central incisors after replantation and splinting. The data indicate that an accurate LDF reading can be established at the 12-week follow-up appointment, which is much earlier than would be expected from standard sensitivity tests. The method of measuring PBF values is a well-established physical assessment of pulpal sensitivity and may be used as a diagnostic tool in dental traumatology. It also may be a useful tool in monitoring PBF in splinted teeth to optimize the splinting time and to detect early changes in PBF in replanted avulsed teeth. A dog model has been used to demonstrate revascularization,^48–51 and the ability of LDF to differentiate vital from nonvital pulp has been demonstrated.^27,28,52 In our study, LDF readings were found to be highly accurate in differentiating a revascularized tooth from a tooth with necrotic pulp, and an accurate LDF reading of pulpal revascularization could be established about 30 days after reimplantation. In addition, we found a continued increase in blood supply with pulpal blood anastomoses after 30 days, an observation that corresponds to the report that PBF values continued to increase from four weeks to 12 weeks after reimplantation.⁴⁸ Therefore, it appears that the LDF assessment for human teeth should be performed for the first time about 30 days after trauma and be continued intermittently for three months.

An accurate laser Doppler flowmetry reading can be established at the 12-week follow-up appointment.

The risk of developing pulp necrosis increases with the extent of the injury to the pulp and periodontal ligament and in teeth with complete root formation.^37,42 With regard to the high incidence of pulp necrosis,^38,53 prophylactic extirpation of the pulp has been recommended to prevent other complications from arising from the pulp necrosis.^54,55 The best outcome for the posttraumatized incisor, however, is to revascularize and to continue normal root development in immature incisors. Therefore, LDF may be used to monitor incisors during the immediate posttrauma phase, and it may help identify revascularization long before it may be detected using traditional sensitivity tests.

This study confirms that LDF signals obtained from human teeth do not reveal the blood flow solely from the pulp but also reflect blood flow from the surrounding periodontal tissue.^56–60 The teeth in the control groups clearly demonstrated that these background readings need to be taken into account. It has been proposed that the reflected signals from nonpulpal tissues in humans be minimized with the use of opaque black rubber dams.^58,60 LDF can be used to assess the degree and duration of dental trauma-related ischemic episodes, and identify patients who are at risk of developing adverse sequelae such as avascular necrosis and tissue loss. Avulsion of an incisor is a common traumatic injury in the permanent dentition. Attention should be given to the pulp tissue and periodontal structures, owing to the high frequency of complications after this type of injury. In addition, complications may be unpredictable, and the treatment can become complex. Therefore, the treatment has to be adaptable to address any complications that may arise. The outcomes of replantation may vary and may not be predictable from the appearance or extent of injury sustained clinically.

In our study, we did not evaluate the validity of the revascularization by comparing it with the histologic condition of the pulp. Instead, we make our diagnoses on the basis of the clinical and radiographic parameters of vital and nonvital teeth. These findings, however, may be difficult to interpret or even may be misleading. From previous studies, there appears to be a general agreement that single signs such as loss of pulpal sensitivity,^23,36,61 coronal dicoloration³⁶ or development of periapical radiolucency³⁷ are not enough to justify a diagnosis of pulp necrosis. Even the concomitant presence of the these classic signs of pulp necrosis may be followed by pulpal repair.³⁷ Further studies are needed to assess the validity of posttraumatic PBF measurements taken by LDF by comparing them with histologic tooth pulp changes and by determining how well PBF diagnoses can predict course and response to treatments in clinical trials.

	CONCLUSION

TOP ABSTRACT MATERIALS AND METHODS PROCEDURE RESULTS DISCUSSION CONCLUSION REFERENCES

 
The results of this study suggest that LDF accurately diagnoses revascularization of avulsed permanent maxillary central incisors after replantation and splinting. Further studies are needed to assess the validity of posttraumatic revascularization by comparing it with histologic tooth pulp changes. LDF may become useful in detecting revascularization much earlier than standard sensitivity tests.