The effect of short-term tooth intrusion on human pulpal blood flow measured by laser Doppler flowmetry

Macrophage M2 polarization promotes pulpal inflammation resolution during orthodontic tooth movement

Mechanical force induces hypoxia in the pulpal area by compressing the apical blood vessels of the pulp, triggering pulpal inflammation during orthodontic tooth movement. However, this inflammation tends to be restorable. Macrophages are recognized as pivotal immunoreactive cells in the dental pulp. Whether they are involved in the resolution of pulpal inflammation in orthodontic teeth remains unclear. In this study, we investigated macrophage polarization and its effects during orthodontic tooth movement. It was demonstrated that macrophages within the dental pulp polarized to M2 type and actively participated in the process of pulpal inflammation resolution. Inflammatory reactions were generated and vascularization occurred in the pulp during orthodontic tooth movement. Macrophages in orthodontic pulp show a tendency to polarize towards M2 type as a result of pulpal hypoxia. Furthermore, by blocking M2 polarization, we found that macrophage M2 polarization inhibits dental pulp-secreting inflammatory factors and enhances VEGF production. In conclusion, our findings suggest that macrophages promote pulpal inflammation resolution by enhancing M2 polarization and maintaining dental health during orthodontic tooth movement.

The effect of orthodontic tooth movement on the sensitivity of dental pulp: A systematic review and meta-analysis

Objectives

Orthodontic tooth movement (OTM) is a process that's initiated by orthodontic forces. As a consequence, the forces could restrict pulpal blood supply, possibly affecting dental pulp. The study aimed to review the available evidence on the short and long-term effects of orthodontic tooth movement on dental pulp sensitivity and to identify clinically relevant risk factors.

Sources

PubMed, Embase, Scopus, and Web of Science were searched for papers from 1990 to the end of December 2021.

Study selection

The studies that evaluated dental pulp sensitivity of teeth undergoing OTM were included in the systematic review. Randomized, nonrandomized and case-controlled studies were included in the analysis. Risk of bias in each study was assessed using the ROBINS-I tool.

Data

The systematic search yielded an initial sample of 1110 studies, 17 were included in qualitative analysis. Most studies were classified as moderate risk of bias, however only limited long-term evidence with a higher risk of bias exists. Electric pulp test (EPT) sensitivity threshold during active OTM was increased by 4.25 SD (P < 0.001) and the relative risk (RR) of pulpal non-sensitivity was 13.27 (P < 0.001) higher compared to pre-orthodontic baseline status. Significant differences were between subgroups associated with the type of OTM. A positive relationship between pulpal non-sensitivity and mean patient age was discovered (P = 0.041). After OTM the risk of pulpal non-sensitivity remained 5.76 times higher (P < 0.001) in the long term.

Conclusions

Evidence showed that OTM could affect dental pulp sensitivity. The type of OTM and patients' age were identified as clinically relevant risk factors.

Clinical significance

Orthodontic tooth movement negatively impacts the sensitivity of dental pulp during active treatment and to a lesser degree in the long term. Pulpal sensitivity tests during active OTM should therefore be interpreted with caution. Data indicates younger patients have a lower risk of negative pulpal sensitivity during orthodontic treatment.

Adverse effects of orthodontic forces on dental pulp. Appearance and character. A systematic review

OBJECTIVE

To comprehensively assess recent data on the effects of orthodontic forces on the dental pulp and to critically evaluate, whether any of the changes are permanent.

MATERIALS AND METHODS

Articles published between 2/2009 and 2/2022 were searched electronically on the PubMed, EMBASE and SCOPUS databases. The initial search retrieved 780 publications and, applying the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 33 relevant articles were identified. Twenty articles fulfilled the requirements for high (n = 1) or moderate (n = 19) methodological quality and were included. All assessments were made independently by three researchers.

RESULTS

Orthodontic forces appeared to cause a reduction in pulpal blood flow and a reduction in tooth sensibility, as indicated by increased response thresholds and increased amounts of negative responses to tooth sensibility tests. In addition, there were increases in the expression or activity levels of enzymes and neuropeptides associated with hypoxia and inflammation. Fibrotic tissue formation in the pulp was also reported.

CONCLUSIONS

Except for some histological and morphological alterations, the observed pulpal changes were in most cases only temporary, appearing within days of initiating the treatment and usually lasting for weeks. There were no clear signs of permanent damage.

Pulp blood flow changes in maxillary and mandibular anterior teeth after orthodontic retraction: a prospective study

Background

Previous studies of pulpal blood flow (PBF) changes in anterior teeth have been limited in the early phase of orthodontic treatment; less is known about the blood supply of anterior teeth in bimaxillary protrusion patients after orthodontic retraction.

Methods

Fifty bimaxillary protrusion patients (25 orthodontic patients ready for debonding and 25 non-orthodontic patients) were selected as study participants. The PBF of maxillary and mandibular anterior teeth were measured using laser Doppler flowmetry. For orthodontic patients, the PBF was measured at 1 day (T1), 1 month (T2), and 3 months (T3) after fixed appliance removal. Non-orthodontic patient PBF was measured as a control. Cone-beam computed tomography (CBCT) examinations before and after orthodontic treatment were performed for orthodontic patients to measure the root resorption. The anterior teeth in orthodontic group were further divided into subgroups according to root resorption and patient age.

Results

At T1 and T3, PBF changes did not differ significantly between the orthodontic and non-orthodontic groups. Maxillary lateral incisor, maxillary central incisor, and mandibular lateral incisor PBFs at T2 were significantly higher in the orthodontic group (P = 0.048, P = 0.04, and P = 0.021). No significant difference in PBF was found between the root resorption and non-resorption subgroups at any time point. Adolescent patients showed a higher PBF in the maxillary lateral incisor at T2 (12.23 ± 3.48) relative to that at T1 (9.10 ± 3.76) and T3 (9.81 ± 2.80) with statistically significant difference (P = 0.020).

Conclusion

For bimaxillary protrusion patients with four premolars extraction, PBF in the maxillary anterior teeth increased transiently after orthodontic appliance removal and then returned to non-orthodontic levels 3 months later. This effect was more pronounced in adolescents. The PBF of anterior teeth after orthodontic retraction may not be influenced by root resorption.

Association between Orthodontic Force and Dental Pulp Changes: A Systematic Review of Clinical and Radiographic Outcomes

INTRODUCTION

Orthodontic force triggers a sequence of biological responses that can affect dental pulp. The aim of this study was to systematically evaluate the clinical and radiographic findings of orthodontic force application on dental pulp.

METHODS

Two reviewers comprehensively and systematically searched 6 electronic databases (Latin American and Caribbean Health Sciences [LILACS], Embase, Cochrane Library, MEDLINE/PubMed, Scopus, and Web of Science) and the gray literature (Google Scholar, OpenGrey, and ProQuest) until April 2021. According to the PICOS criteria, randomized clinical trials and observational studies that evaluated clinical or radiographic findings compatible with dental pulp changes due to orthodontic force were included. Studies in open apex or traumatized teeth, case series or reports, and laboratory-based or animal studies were excluded. The Newcastle-Ottawa Scale and Cochrane Risk of Bias 2.0 tool were used to determine the risk of bias assessment. The overall certainty level was evaluated with the Grading of Recommendations, Assessment, Development and Evaluations tool.

RESULTS

Twenty-six studies were included. Among the clinical findings, orthodontic force promoted an increased pulp sensibility response and decreased pulp blood flow. Changes in pulp cavity volume and increased incidence of pulp stones were the radiographic findings observed. The studies presented a moderate risk of bias for most of the domains. The certainty of the evidence was considered very low.

CONCLUSIONS

Orthodontic force promoted changes in the dental pulp, generating clinical and radiographic findings. It is crucial to know these changes so that orthodontic mechanics can be safely performed. The clinician has effective noninvasive methods to assess the health and possible pulp changes during orthodontic treatment.

Pulp sensitivity changes during orthodontic treatment at different time periods: a prospective study

Objective

The purpose of this investigation was to recognize pulp sensitivity changes in teeth receiving orthodontic treatment by means of an electric pulp tester (Vitality Scanner Model 2006; Kerr Corporation, Brea CA, USA).

Materials and methods

An electric stimulus response threshold of eight teeth in 22 patients was measured prior to positioning orthodontic attachments, immediately before ligation of a nickel titanium archwire, immediately after ligation of a stainless steel archwire and 9 to 15 months after having achieved the clinical purposes established with the nickel titanium archwires. The first measurement served as baseline.

Results

All teeth responded to an electrical stimulus at all times. No statistical differences were observed between the response thresholds obtained at different treatment times. The mean response threshold of the second measurement showed a decreasing response threshold tendency when compared with those of the baseline measurement. The mean response threshold of the third measurement showed an increasing tendency when compared with those of the baseline measurement. The first maxillary incisor and canine showed the lowest decreasing response threshold after the second measurement and the highest increasing response threshold after the third measurement. Less noticeable, but similar decreasing and increasing response threshold tendencies were observed in all other teeth after the second and third measurements, respectively.

Conclusions

The results obtained in this investigation suggest that pulp sensitivity can be monitored during orthodontic treatment by means of an electric pulp tester.

Clinical relevance

The importance of monitoring the pulp status during orthodontic treatment.

Changes in human pulp blood flow during canine retraction

AIM

To evaluate the effects of maxillary canine retraction on pulpal blood flow (PBF) in humans as recorded by laser Doppler flowmetry (LDF).

METHODS

Maxillary canines of 24 participants were divided into two groups (n = 12 each). Teeth in the study group underwent maxillary canine retraction using mini-implants as anchorage for approximately 4 months, with 100 g of force applied via coil springs. Subjects in the control group received no orthodontic treatment. LDF measurements were recorded at baseline (T0); during retraction, at 24 hours (T1), 3 days (T2), 7 days (T3) and 1 month (T4); and at the end of retraction (T5) in the study group and at similar time-points in control subjects. Data were analyzed using the Friedman, Wilcoxon signed rank and Mann-Whitney U tests, with the significance level set at 0.05.

RESULTS

No significant changes in PBF perfusion units (PU) were observed in the control group over the course of the study. However, PBF in the study group increased significantly from T0 (3.6 ± 0.2 PU) to T1 (3.7 ± 0.2 PU, p < 0.001) and decreased severely from T1 to T2 (3.3 ± 0.1, p < 0.001). PBF in the study group was still significantly lower at T3 (3.4 ± 0.1 PU, p < 0.001) in comparison to T0; however, at T4 and T5, PBF was found to have returned to pre-retraction levels.

CONCLUSION

The fact that PBF values returned to initial levels within one month of the initiation of retraction despite short-term, hyperaemic, regressive changes demonstrates that the changes observed in PBF during canine retraction are reversible.

Age-related changes of dental pulp tissue after experimental tooth movement in rats

It is generally accepted that the effect of orthodontic tooth movement on the dental pulp in adolescents is reversible and that it has no long-lasting effect on pulpal physiology. However, it is not clear yet if the same conclusion is also valid for adult subjects. Thus, in two groups of rats, aged 6 and 40 weeks respectively, 3 molars at one side of the maxilla were moved together in a mesial direction with a standardized orthodontic appliance delivering a force of 10 cN. The contralateral side served as a control. Parasagittal histological sections were prepared after tooth movement for 1, 2, 4, 8, and 12 weeks. The pulp tissue was characterized for the different groups, with special emphasis on cell density, inflammatory cells, vascularity, and odontoblasts. Dimensions of dentin and the pulpal horns was determined and related with the duration of orthodontic force application and age ware evaluated. We found that neither in young nor in adult rats, force application led to long-lasting or irreversible changes in pulpal tissues. Dimensional variables showed significant age-related changes. In conclusion, orthodontic tooth movement per se has no long-lasting or irreversible effect on pulpal tissues, neither in the young nor in the adult animals.

Influence of orthodontic forces on human dental pulp: a systematic review

AIM

The aim of the present study was to systematically review the influence of orthodontic force on human dental pulp.

METHODS AND RESULTS

The addressed focused question was "Do orthodontic forces affect the human dental pulp?" which was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a specific question was constructed according to the PICO (Participants, Interventions, Control, Outcomes) principle. Databases were explored from 1952 up to and including August 2014 using different combinations of the following keywords: "orthodontic force"; "dental pulp"; "reaction" and "tooth movement". Literature reviews, letters to the editor, commentaries and case-reports were excluded. Thirty studies were included. Six studies assessed the effect of orthodontic forces on pulpal blood flow and 20 studies investigated the pulpal cellular responses to orthodontic forces. In 4 studies, pulpal responses to orthodontic forces were compared between previously traumatized- and non-traumatized teeth.

CONCLUSIONS

There is insufficient scientific validation regarding the association between orthodontic forces and human dental pulp. However, a history of dental trauma maybe considered a risk factor for loss of pulp vitality during orthodontic treatment.

Changes in maxillary incisor dental pulp blood flow during intrusion by mini-implants

AIM

The aim of this clinical study was to identify changes in pulpal blood flow (PBF) in human central incisors resulting from short- and long-term intrusive orthodontic forces from mini-implants.

MATERIALS AND METHODS

A total of 40 sound upper central and lateral incisors in 20 patients scheduled for intrusion for orthodontic reasons were divided into two groups. From each group, 20 teeth were subjected to intrusive force from mini-implants (Group 1 = Light Force: 40 g; Group 2 = Heavy Force: 120 g), whereas the remaining 20 contralateral teeth were not subjected to forces from mini-implants and served as controls. Laser-Doppler flowmetry (LDF) measurements were recorded at baseline and at 3 days and 3 weeks following intrusion.

RESULTS

PBF decreased significantly at 3 days (Light Force Group: 7.72 ± 0.50; Heavy Force Group: 7.72 ± 0.52) and then increased towards baseline at 3 weeks (Light Force Group: 10.37 ± 0.58; Heavy Force Group: 10.31 ± 0.45) following intrusion.

CONCLUSIONS

In other words, despite slight regressive changes in pulpal tissue in the short-term, PBF improved after 3 weeks following intrusion by mini-implants, indicating that the changes observed in PBF is reversible, even following radical incisor intrusion.

Improvement of the detection of human pulpal blood flow using a laser Doppler flowmeter modified for low flow velocity

OBJECTIVE

Human pulpal blood flow (PBF) signals as measured by laser Doppler flowmeter (LDF) decrease with age. Although this decrease is considered to be due in part to slow blood flow, information regarding this velocity in humans has been lacking. The aims of the present study were to estimate the blood flow velocity in human dental pulp and to evaluate the validity of LDF modified for the measurement of slow blood flow.

DESIGN

Mean blood flow velocities at the upper central incisor, gingiva, fingertip and forearm of 28 volunteers (mean age: 38.6 years old) were estimated using LDF with a frequency analyser. Blood flow signals at these measurement areas were recorded using two different LDFs: (a) one with a standard blood flow range; and (b) one modified for low blood flow velocity.

RESULTS

The frequency range of the Doppler shift measured at the teeth with an opaque rubber dam was the narrowest (median: 4.3kHz) among all of the measurement areas. The estimated mean blood flow velocity was the slowest at the teeth with a dam (median: 0.18mm/s). LDF for low blood flow velocity detected larger and clearer pulsatile blood flow signals from the teeth with dams than did standard LDF.

CONCLUSIONS

The present results indicate that the velocity of PBF in humans is very low and that LDF modified for the measurement of slow blood flow is appropriate for PBF measurement in humans.

Laser Doppler Blood-Flow Signals from Human Teeth during an Alignment and Leveling Movement Using a Superelastic Archwire

Objective. The purpose of this study was to examine alterations in blood-flow signals (BFS) from human teeth during an alignment and leveling phase (superelastic wire 0.014′′) in a clinical orthodontic treatment using laser doppler flowmetry (LDF). Materials and Methods. Recordings were made in 12 maxillary left central incisors. The basal value of the BFS from each tooth (without orthodontic forces) was compared with the corresponding values of BFS during four periods of observation: 20 minutes, 48 hours, 72 hours, and one month after the activation of the orthodontic appliance. Results. Statistically significant decrease of BFS was observed at 20 minutes, 48 hours, and 72 hours (P < 0.05). No differences were found comparing BFS on day 30 and the corresponding basal values. Conclusion. Under real clinical conditions, a significant decrease in BFS was verified during the initial phase of the treatment, followed by a recovery on day 30.

Doppler flowmetry as a tool of predictive, preventive and personalised dentistry

Periodontal lesions are considered a major problem in the global burden of oral diseases due to their high frequency and negative impact on quality of life. Periodontal inflammation is accomplished by a breakdown of microcirculatory function. Early detection of gingival microvessel dysfunction helps diagnose and prevent the progression of initial periodontal pathology. Doppler flowmetry is a useful tool in the diagnosis, monitoring, prognosis and management of periodontal patients which allows access not only of gingival blood flow but also of pulpal microcirculation. Doppler flowmeters might help to realise the ultimate target of predictive, preventive and personalised periodontology tailored with respect to the particular patient. This article highlights the main working principles of laser Doppler flowmeters and the ultrasonic Doppler flowmeters. The advances in blood flow measurement by ultrasonic flowmetry are discussed.

Effect of low level laser therapy on dental pulp during orthodontic movement

AIM: To validate the protocol described here to be used in future clinical trials related to the effect of laser therapy on dental pulp.

METHODS: Histologically treated samples from eight human healthy premolar teeth obtained from the middle root level were distributed in four groups: group 1 (G1) absolute control; group 2 (G2) only laser irradiation; group 3 (G3) exposed only to orthodontics; and group 4 (G4) treated with orthodontics and laser. Laser treatment was performed at 830 nm wavelength, 100 mW (energy 80 J/cm², 2.2 J), for 22 s in the vestibular surface and 22 s in the palatal surface, 1 mm away from the dental root mucosa. Three staining methods were performed: hematoxylin-eosin (HE), Masson’s Trichrome method and Gomori’s method.

RESULTS: The pulp histology parameters were evaluated and the results classified in to 3 parts: an inflammatory response, soft tissue response (dental pulp) and hard tissue response (dentin and predentin). There was no inflammation (chronic or acute) in any of the evaluated groups. The zones of pulp necrosis were found in one premolar of G3 and in one of G4; in groups G2 and G4 there was higher angiogenesis than in the other two groups. G4 group presented the highest level of vascularization. A reduced nerve density was observed in G3. A G2 specimen showed increased nerve density. A higher rate of calcification was observed in G1 compared to G2. Denticles, either real or false, were observed in G1, G2 and G3. Sclerosis of dentin and focal dentin loss was observed among all the groups. Secondary dentin was present in one sample in G1 and G2. A necrosis zone was found in one sample of G3 and G4. No differences between groups were observed in the odontoblast irregularity layer but the layer was wider in the group treated with laser only. A notable difference was detected in reduction of the cell-free layer between the groups G1 and G4. The findings in pulp tissue favor its adaptative response against dental movement induced by orthodontics. No definitive conclusions may be derived as this is a pilot study.

CONCLUSION: The protocol described here was shown to be an effective method to evaluate changes in dental pulp submitted to low level laser in teeth under orthodontic movement.

Changes in gingival blood flow during orthodontic treatment

The aim of the study was to investigate the changes in gingival blood flow due to orthodontic forces. Eleven volunteers, with the maxillary canine in an ectopic position were tested. A Laser Doppler Flowmeter (LDF) with a gingival probe was used, registering both the blood flow and temperature of the gingivae. After baseline measurement, a fixed orthodontic appliance was bonded. Measurements were repeated monthly, after activation of the appliance. The study lasted 6 months. The baseline value was 338.7 ± 201.56 P.U. [Perfusion Unit (mean ± S.D.)] which decreased to 218.9 ± 74.83 P.U. (p < 0.05) after two months and the final value of 363.9 ± 194.86 P.U was not significantly different from that initially (p > 0.5). The results showed that application of a force of 75 g resulted in a decrease in gingival blood flow up to 50%, but this returned to previous values after a few months. The study supports this measurement technique as a useful tool for monitoring gingival blood flow in long-term studies as well.

Change in dental pulp parameters in response to different modes of orthodontic force application

OBJECTIVES

(1) To evaluate dental pulp sensitivity by electrical pulp testing and measure aspartate aminotransferase activity in the pulp after 14 days of orthodontic intrusion, and (2) to compare those measurements with measurements obtained in teeth after 7 days of intrusion and 7 days of rest.

MATERIALS AND METHODS

The study sample included 13 subjects (mean age = 16.5 +/- 2.7 years). For every subject, before extraction, two contralateral premolars were included in a spring and loaded by a force. Two study groups were formed: Group A, teeth with 14 days of mechanical load, and Group B, teeth with 7 days of mechanical load plus 7 days of rest. Electrical pulp testing and aspartate aminotransferase activity measurements were performed after 14 days in all tested teeth. After extraction, aspartate aminotransferase activity in the pulp was determined spectrophotometrically at 20 degrees C.

RESULTS

Mean aspartate aminotransferase activity values were 0.21 U/mg (SD = 0.15) in Group A and 0.27 U/mg (SD = 0.17) in Group B. Mean electrical pulp testing readings were 38.92 microA (SD = 24.61) in Group A and 36.77 microA (SD = 26.84) in Group B. Mean values of the intrusive force magnitude did not differ in both groups.

CONCLUSIONS

Different durations of orthodontic intrusion, defined as 14 days of load and 7 days of load followed by 7 resting days, were not reflected by electrical pulp testing or by aspartate aminotransferase activity levels in the pulp of the affected teeth. However, the response threshold to electrical pulp stimulation was elevated in all tested teeth.

Pulpal blood flow changes due to rapid maxillary expansion

OBJECTIVE

To determine the pulpal blood flow (PBF) changes in anchorage teeth associated with the high forces of a rapid maxillary expansion (RME) appliance.

MATERIALS AND METHODS

The study was performed with 14 girls and 7 boys for a total of 21 patients between 10 and 15 years of age (mean, 13.1 +/- 1.39 years). A modified acrylic bonded RME appliance was used as an expansion appliance. Laser Doppler flowmetry was used for the pulpal perfusion measurements. Records were taken from 42 upper central incisors, 28 canines, and 42 first molars at the following time intervals: just before expansion (T1); at the first week of expansion (T2); at the end of the expansion process (T3); and at the third (T4), seventh (T5), and 12th weeks of retention (T6). The data gained were statistically evaluated by parametric tests.

RESULTS

PBF values of the anchorage teeth were doubled at the first week of expansion; however, these values began to decrease because of separation of the median palatal suture. PBF values tended to reach their initial values during the retention period. Pulpal perfusion changes of all examined anchorage teeth were similar to each other from the beginning to the end of the evaluation.

CONCLUSION

PBF changes that occur with RME are reversible.

Parameters influencing increase in pulp chamber temperature with light-curing devices: curing lights and pulpal flow rates

This laboratory study examined the effects of curing lights with different light intensities and changing flow rate on the increase in pulpal temperature during the light curing process and the rate of the subsequent decrease in temperature after the termination of light curing. The tip of a temperature sensor was positioned on the pulpal dentinal wall of the buccal side of the maxillary premolar. Metal tubes were inserted in the palatal and buccal root of the tooth, one for water inflow and the other for water outflow. The tubes were connected to a pump to control the flow rate. The water flow rate was set to 4.2 microl/minute, 28 microl/minute or 70 microl/minute. At each flow rate, the unprepared tooth was light cured from the buccal side 1 mm from the buccalsurface, using four different curing lights. The temperature data were recorded and stored on a computer every second for three minutes. The curing lights that were used were: Astralis 10 (QTH(high), Ivoclar Vivadent), Bluephase 16i (LED(conv), Ivoclar Vivadent) and two experimental LED-curing lights (LED(exp2000), LED(exp3000), Ivoclar Vivadent). The power densities were 1200 mW/cm2, 1600 mW/cm2, 2000 mW/cm2 and 3000 mW/cm2, respectively. The curing lights, LED(conv), LED(exp2000) and LED(exp3000) were activated for 60 seconds, and the QTH(high) was activated for 30 sec- onds. The maximum intrapulpal temperature (TM) and rate of temperature change at 30 seconds after turning off the light (S(30LO)) were analyzed by two-way ANOVA with a post-hoc Tukey test (p < 0.05). The influencing factors were the flow rates and curing lights.

RESULTS

The T(MAX) ranged from 41.0 degrees C to 53.5 degrees C. There was a difference between the curing lights (p < 0.05), with LED(exp3000) > LED(exp2000) > LED(conv) > QTH(high). There was no difference in T(MAX) between the different flow rates (p > 0.05). Both the curing lights and flow rates affected the SE(30LO) (p < 0.05). The S(30LO) was LED(exp3000) < LED(exp2000) > LEDon, , QTH(high) (p < 0.05). The S(30LO) at 70 microl/minutes was higher than at 4.2 pd/minutes and 28 microl/minutes (p < 0.05).

CLINICAL IMPLICATION

Because the increase in temperature is directly related to the light intensity and exposure time, curing devices with high power density (> 1200 mW/cm2) should only be activated for a short period of time (< 15 seconds) even in teeth without cavity preparation. The flow rate had only a negligible effect on the temperature increase.

Analysis of the dentin-pulp complex in teeth submitted to orthodontic movement in rats

In order to microscopically analyze the pulpal effects of orthodontic movement, 49 maxillary first molars of rats were submitted to orthodontic appliance composed of a closed coil spring anchored to the maxillary incisors, placed for the achievement of mesial movement. Material and Methods: Ten animals were used as the control group and were not submitted to orthodontic force; the other animals were divided into groups according to the study period of tooth movement, namely 1, 2, 3, 4, 5, 6 and 7 days. The investigation of pulp and periodontal changes included hyalinization, fibrosis, reactive dentin and vascular congestion. Statistical evaluation was performed between control and experimental groups and between periods of observation using non-parametric chi-square, Kruskal-Wallis and Dunn tests. Results: There was no statistically significant difference concerning pulpal changes between control and experimental groups nor between periods of observation. The control group, at 3 and 5 days, revealed greater hyalinization of the periodontal ligament (p<0.05), whereas root resorption was significantly greater at 5 and 7 days (p<0.05). Conclusion: No morphological change from the effect of induced tooth movement could be found in the dentin-pulp complex. In addition, no inflammatory or pulp degeneration, detectable in optical microscopy, was found in experimental groups.

Morphologic and hemodynamic analysis of dental pulp in dogs after molar intrusion with the skeletal anchorage system

INTRODUCTION

We have successfully treated skeletal open bite by intruding posterior teeth with the skeletal anchorage system. Our aim in this study was to morphologically and hemodynamically evaluate the changes in pulp tissues when molars are radically intruded.

METHODS

The mandibular fourth premolars of 9 adult beagle dogs were divided into 3 groups: a sham operated group (n = 6, 3 dogs), 4-month intrusion group (n = 6, 3 dogs), and a further 4-month retention group (n = 6, 3 dogs). We evaluated the morphological changes of the pulp and dentin-the amount of vacuolar degeneration in the odontoblast layer, the predentin width and nervous continuity in the pulp tissue, and the pulpal blood-flow response evoked by electrical stimulation in the dental pulp.

RESULTS

Extreme molar intrusion with the skeletal anchorage system caused slight degenerative changes in the pulp tissue, followed by recovery after the orthodontic force was released. Circulatory system and nervous functions were basically maintained during the intrusion, although a certain level of downregulation was observed. These morphologic and functional regressive changes in the pulp tissue after molar intrusion improved during the retention period.

CONCLUSIONS

Histologic changes and changes in pulpal blood flow and function are reversible, even during radical intrusion of molars.

Alkaline phosphatase activity in dental pulp of orthodontically treated teeth

INTRODUCTION

The aim of this study was to examine alkaline phosphatase (ALP) activity in the dental pulp of orthodontically treated teeth.

METHODS

Sixteen healthy subjects (mean age 17.0 +/-1.6 years) who required extraction of 4 first premolars for orthodontic reasons participated. One maxillary first premolar subjected to orthodontic force was the test tooth. The contralateral first premolar, bracketed but not subjected to mechanical stress, was the control tooth. After a week of treatment, the first premolars were extracted and the dental pulp removed from the teeth. ALP activity was determined spectrophotometrically and the results expressed as units/liter per milligram of pulp tissue [U/(L x mg)].

RESULTS

ALP activity was 89 +/- 26 U/(L x mg) in the test teeth and 142 +/- 33 U/(L x mg) in the control teeth. The difference between the groups was statistically significant (P < .01).

CONCLUSIONS

Orthodontic treatment can lead to significant early-phase reduction in ALP activity in human dental pulp tissue.

Aspartate aminotransferase activity in pulp of orthodontically treated teeth

This study examines the aspartate aminotransferase activity in the pulp of orthodontically treated teeth. Seventeen healthy male and female subjects (ages: 14.5-19.6; mean 16.8 +/- 1.6 years) who needed extraction of the maxillary first premolars for orthodontic reasons were enrolled in the study. One randomly chosen maxillary first premolar, included in a straight-wire fixed orthodontic appliance and supporting orthodontic force, was considered as the test tooth. The contralateral first premolar, included in the orthodontic appliance but not subjected to mechanical stress, was used as the control tooth. After a week of treatment, the dental pulp tissues were extracted from both experimental teeth. Aspartate aminotransferase activity was significantly elevated in the test teeth as compared with the control teeth. These results demonstrate that in the early phases of treatment, orthodontic force application to the teeth can lead to significant metabolic changes in the pulp of these teeth.