Substance P immunoreactivity in periodontal tissues during orthodontic tooth movement

Biological and psychological factors affecting the sensory and jaw motor responses to orthodontic tooth movement

Orthodontic tooth movement (OTM) is associated with an inflammatory response, tooth pain (i.e. orthodontic pain) and changes in dental occlusion. Clinical realms and research evidence suggest that the sensory and jaw motor responses to OTM vary significantly among individuals. While some adjust well to orthodontic procedures, others may not and can experience significant pain or not adjust to occlusal changes. This is of concern, as clinicians cannot anticipate an individual's sensorimotor response to OTM. Converging evidence shows that some psychological states and traits significantly affect the sensorimotor response to OTM and may considerably affect an individual's adaptation to orthodontic or other dental procedures. We performed a topical review to synthesize the available knowledge about the behavioural mechanisms regulating the sensorimotor response to OTM, with the intent of informing orthodontic practitioners and researchers about specific psychological states and traits that should be considered while planning orthodontic treatment. We report on studies focusing on the role of anxiety, pain catastrophising, and somatosensory amplification (i.e. bodily hypervigilance), on sensory and jaw motor responses. Psychological states and traits can significantly affect sensory and jaw motor responses and a patient's adaptation to orthodontic procedures, although large interindividual variability exists. Clinicians can use validated instruments (checklists or questionnaires) to collect information about patients' psychological traits, which can assist in identifying those individuals who may not adjust well to orthodontic procedures. The information included in this manuscript also assists researchers investigating the effect of orthodontic procedures and or/appliances on orthodontic pain.

Effects of Low-Level Laser Therapy on Dentin Hypersensitivity in Periodontally Compromised Patients Undergoing Orthodontic Treatment: A Randomised Controlled Trial

OBJECTIVES

This study aimed to assess the effects of low-level laser therapy (LLLT) on dentin hypersensitivity (DH) in periodontally compromised patients undergoing orthodontic treatment.

METHODS

This triple-blinded randomised controlled trial included 143 teeth with DH from 23 periodontally compromised patients. Teeth on one side of the dental arch were randomly assigned to the LLLT group (LG), while those on the contralateral side were allocated to the non-LLLT group (NG). After orthodontic treatment commenced, patients' orthodontic pain (OP) perceptions were documented in pain diaries. DH was assessed chairside by a visual analogue scale (VASDH) at fifteen timepoints across the orthodontic treatment and retention. VASDH scores were compared among timepoints by the Friedman test, among patients with varying OP perceptions using the Kruskal-Wallis tests, and between the LG and NG with the Mann-Whitney U test.

RESULTS

DH generally decreased over the observation (p < 0.001). The VASDH scores differed among patients with varying OP perceptions at multiple timepoints (p < 0.05). The generalized estimating equation model showed teeth in the LG had a significantly lower VASDH score than the NG at the 3rd month of treatment (p = 0.011).

CONCLUSION

LLLT could be potentially beneficial in managing DH in periodontally compromised patients undergoing orthodontic treatment.

The Effect of Treatment With Clear Aligners Versus Fixed Appliances on Oral Health-Related Quality of Life in Patients With Severe Crowding: A One-Year Follow-Up Randomized Controlled Clinical Trial

Objective

To compare the level of oral health-related quality of life (OHRQoL) between patients receiving clear aligners or fixed appliances within one year of follow-up using Oral Health Impact Profile 14 (OHIP-14), a validated self-administered questionnaire.

Materials and methods

A single-centered, two-arm parallel-group randomized controlled clinical trial was conducted on 36 adult patients (19 females, 17 males; age range: 18 to 25 years) who had severe crowding and require orthodontic treatment with first premolars extraction. The patients were equally and randomly divided into two groups: The clear aligners (CA) group and the fixed appliances (FA) group. OHRQoL was assessed using the OHIP-14 tool at various times during comprehensive orthodontic therapy: baseline (T0), one week (T1), two weeks (T2), one month (T3), 6 months (T4), and 12 months (T5) after starting the active orthodontic treatment. Mann-Whitney U test or Friedman test were used to detect significant differences. The level of significance was set at 5%. 

Results

All of the selected patients entered the statistical analysis stage. There were no significant differences between the CA and FA groups for the psychological discomfort, psychological disability, social disability, and handicap (P˃0.05) at almost all assessment times. For the functional limitation, physical pain, physical disability, and the overall score, there were significant differences between the studied groups (P˂0.05), with the FA group having higher mean scores than the CA group in all of the assessment times.

Conclusion

Patients' treatment with clear aligners has less impact on OHRQoL than those treated using conventional fixed appliances during the first year of treatment.

Comparison of pain levels in patients treated with 3 different orthodontic appliances - a randomized trial

Background and aims

To compare pain levels experienced during initial alignment with three different orthodontic appliance types and to correlate pain with male and female differences, if any.

Methods

A prospective, randomized 3-arm parallel trial allocated 36 adult orthodontic patients into three appliance groups: MBT 0.022" slot (Mini Twin, Ormco, Glendora, USA), self ligating 0.022" slot Damon 3MX (Ormco, Glendora, USA) and clear aligners (Smile align, Mumbai, India). The level of discomfort was assessed through a questionnaire based on the visual analogue scale at four hours, twenty four hours, third and seventh day after appliance placement.

Results

Patients treated with clear aligners reported less pain than patients treated with conventional and self ligating fixed appliances. Patients treated with MBT conventional appliances showed greater pain levels than Damon appliances. A significantly higher visual analogue scale score was observed at 24 hours and the least visual analogue scale scores on the seventh day post appliance placement.

Conclusion

During the first week of orthodontic treatment, patients treated with clear aligners reported lower pain than those treated with conventional and self-ligating appliances.

Effect of systemic delivery of Substance P on experimental tooth movement in rats

INTRODUCTION

The purpose of this study was to investigate the effect of systemic delivery of Substance P (SP) on experimental tooth movement.

METHODS

Forty-eight adult Sprague-Dawley rats were randomly divided into 2 groups and their maxillary first molars were mesially moved with the use of closed-coil springs. The experiment group received systemic injection of SP and the control group received phosphate-buffered saline solution. Transportation distances of first molars were measured. Hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and immunohistochemistry staining were performed to evaluate alveolar bone remodeling. Then the interferon (IFN) γ and tumor necrosis factor (TNF) α concentrations in peripheral blood and local periodontal tissue were measured. Finally, the effects of SP on bone marrow-derived stem cell (BMSC) proliferation and migration were tested in vitro.

RESULTS

Systemic delivery of SP significantly increased the distance of tooth movement and stimulated both osteoclast and osteoblast activities. The concentrations of IFN-γ and TNF-α increased in peripheral blood at early phases of the experiment and decreased in periodontal tissue at late phases. In vitro, the proliferation and migration of BMSCs were promoted by SP.

CONCLUSIONS

Systemic delivery of SP can accelerate orthodontic tooth movement and promote alveolar bone remodeling potentially through immunomodulation and mobilizing endogenous mesenchymal stem cells.

Discomfort associated with Invisalign and traditional brackets: A randomized, prospective trial

OBJECTIVE

To evaluate differences in discomfort levels between patients treated with aligners and traditional fixed orthodontic appliances.

MATERIALS AND METHODS

This blinded, prospective, randomized equivalence two-arm parallel trial allocated 41 adult Class I nonextraction patients to either traditional fixed appliance (6 males and 12 females) or aligner (11 males and 12 females) treatment. Patients completed daily discomfort diaries following their initial treatment appointment, after 1 month and after 2 months. They recorded their levels of discomfort at rest, while chewing, and while biting, as well as their analgesic consumption and sleep disturbances.

RESULTS

Both treatment modalities demonstrated similar levels of initial discomfort. There were no significant sex differences. Patients in the traditional fixed appliances group reported significantly (P < .05) greater discomfort than patients in the aligner group during the first week of active treatment. There was significantly more discomfort while chewing than when at rest. Traditional patients also reported significantly more discomfort than aligner patients after the first and second monthly adjustment appointments. Discomfort after the subsequent adjustments was consistently lower than after the initial bonding or aligner delivery appointments. A higher percentage of patients in the fixed-appliance group reported taking analgesics during the first week for dental pain, but only the difference on day 2 was statistically significant.

CONCLUSIONS

Patients treated with traditional fixed appliances reported greater discomfort and consumed more analgesics than patients treated with aligners. This trial was not registered.

Insight into orthodontic appliance induced pain: Mechanism, duration and management

Most of the orthodontic patients experience pain during treatment and this significantly influences their attitudes and the approach towards treatment. A number of factors that influence pain response include age, gender, personal pain threshold, mood and stress level of the person, cultural differences and types of orthodontic treatment. Pain is a often overlooked subject by orthodontists, it is nevertheless important to understand the source and mechanism of the pain that occurs during treatment, as well as the methods for managing and controlling this pain. This review attempts to overview the mechanism, duration and current management strategies of orthodontic treatment.

Expression of substance P, calcitonin gene-related peptide, β-endorphin and methionine-enkephalin in human dental pulp tissue after orthodontic intrusion: A pilot study

Objective:

To determine the levels of two sensory neuropeptides (substance P [SP] and calcitonin gene-related peptide [CGRP]) and two endogenous opioids (methionine-enkephalin [Met-Enk] and β-endorphin [β-End]) in dental pulp tissue samples subjected to controlled orthodontic intrusive forces.

Materials and Methods:

Sixteen healthy premolars were selected from eight patients who were undergoing extraction for orthodontic purposes. Eight were randomly used as controls, and the other eight were assigned to an experimental group (controlled orthodontic intrusive forces applied for 24 hours). After this period, teeth were extracted, and pulp samples were obtained. All samples were processed to quantify the expression levels of SP, CGRP, Met-Enk, and β-End using commercial radioimmunoassay kits.

Results:

All samples exhibited basal levels of both neuropeptides and endogenous opioids. After 24 hours of the intrusive stimulus, all patients reported a tolerable discomfort localized at the involved premolar. Only SP was significantly increased (P &lt; .05). For the other molecules, no statistically significant differences were observed (P &gt; .05); however, they expressed important increasing trends.

Conclusions:

The expression levels of SP and CGRP in dental pulp samples from the experimental group support the positive correlation between the symptomatic clinical scenario and increased expression levels of neuropeptides, clarifying the role of neurogenic inflammation in early injury response.

Changes of myelinated nerve and myelin basic protein expression in rats' periodontal ligaments after experimental tooth movement

INTRODUCTION

Information about the effect of tooth movement on the myelinated nerve in the periodontal ligament is limited. In this study, we aimed to investigate what responses of the periodontal myelinated nerve can be evoked during experimental tooth movement.

METHODS

In experimental-I group, the maxillary left and mandibular right third molars were moved distally. In experimental-II group, the maxillary left third molar but not the right one was moved, and the bilateral mandibular third molars were extracted. The ultrastructures of the myelinated nerve in the periodontal ligament of the bilateral maxillary third molars were observed under a transmission electron microscope. The expression of myelin basic protein was evaluated by immunohistochemistry.

RESULTS

Degenerative ultrastructural changes of the myelinated nerve in the periodontal ligament were noticed mainly in the myelin sheath; these were observed earlier and were recoverable in the experimental-I group. In contrast, the ultrastructural changes of the myelinated nerve occurred mainly in the axons, were observed later, and were unrecoverable in the experimental-II group. A concomitant decrease of myelin basic protein expression was observed in both groups.

CONCLUSIONS

Both experimental tooth movement and occlusal changes accompanying it caused changes of the myelinated nerve in the periodontal ligament.

Effect of neonatal capsaicin treatment on orthodontic tooth movement in male Sprague-Dawley rats

INTRODUCTION

In this study, we examined the effect of neonatal administration of capsaicin on the magnitude of orthodontic tooth movement in rats.

METHODS

Twelve timed pregnant Sprague-Dawley rats were randomized between the capsaicin group and the vehicle group. The pups received treatment with either capsaicin or vehicle on day 2 of life. Capsaicin treatment has been shown to produce a selective destruction of fine myelinated and unmyelinated Aδ and C sensory nerve fibers, causing an inhibition of the effects from neurogenic inflammation. Tooth-movement experiments began at 12 weeks of age. A mesial tipping force was applied to the maxillary first molar by using a 3-mm length of Sentalloy closed-coil spring (Dentsply GAC Intl, Bohemia, NY) activated from a bonded molar cleat to the maxillary incisors; this appliance delivers a constant tipping force of 50 g. Diastema measurements between the first and second molars were made at 2 and 4 weeks after appliance placement. Measurements were made indirectly from stone models by using a charge-coupled device microscope camera and Optimas 5.2 measurement software (Media Cybernetics, Bethesda, Md). Two-way repeated-measures analysis of variance (ANOVA) was used to analyze the differences between the groups.

RESULTS

The capsaicin-treated rats and the controls did not differ in the amount of tooth movement at the collected time points (P >0.05). Similarly, the magnitude of change of tooth movement from 2 to 4 weeks did not differ between the groups (P >0.05). An increase in average diastema size was observed between 2 and 4 weeks after appliance activation in both treatment groups (P <0.0001).

CONCLUSIONS

These results suggest that neonatal capsaicin desensitization in the rat does not affect the rate of orthodontic tooth movement after the application of a 50-g tipping force to the maxillary first molar. This might be due in part to the development of compensatory mechanisms in the chronically desensitized rat. Further studies are necessary to determine the reproducibility and histologic characteristics of this treatment.

Effects of CO2 laser irradiation of the gingiva during tooth movement

Patients often feel pain or discomfort in response to orthodontic force. It was hypothesized that CO(2) laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos-immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evaluated. Two hrs after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO(2) laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. The maximum temperature below the mucosa during CO(2) laser irradiation was less than 40 degrees C. It was suggested that CO(2) laser irradiation reduced the early responses to nociceptive stimuli during tooth movement and might not have adverse effects on periodontal tissue.

Mechanisms of tooth eruption and orthodontic tooth movement

Teeth move through alveolar bone, whether through the normal process of tooth eruption or by strains generated by orthodontic appliances. Both eruption and orthodontics accomplish this feat through similar fundamental biological processes, osteoclastogenesis and osteogenesis, but there are differences that make their mechanisms unique. A better appreciation of the molecular and cellular events that regulate osteoclastogenesis and osteogenesis in eruption and orthodontics is not only central to our understanding of how these processes occur, but also is needed for ultimate development of the means to control them. Possible future studies in these areas are also discussed, with particular emphasis on translation of fundamental knowledge to improve dental treatments.

Effect of surgical denervation on orthodontic tooth movement in rats

INTRODUCTION

Tooth movement through bone depends on local inflammatory reactions of the dentoalveolar tissues. Mechanical signals cause sensory afferent nerves to liberate inflammatory peptides around the teeth, creating local inflammation. Relationships between neurogenic inflammation and tooth movement are poorly understood. The objective of this study was to measure the differences in orthodontic tooth movement between rats treated with and without surgical transection of the maxillary nerve.

METHODS

Forty-two Sprague-Dawley rats were divided into 3 groups: (1) those with surgical transection of the maxillary nerve, (2) those with sham surgeries, and (3) those without surgery. After a 2-week healing period, a closed-coil spring appliance was activated to produce a 50 g mesial tipping force on the maxillary first molar. Diastema sizes distal to the first molar were measured in triplicate by using vinyl polysiloxane impression material and stone model pour-ups at 14 and 28 days of tooth movement. Images were captured and measured with a charge coupled device (CCD) microscope camera (Leeds Precision, Minneapolis, Minn) and Optimas measurement software (Media Cybernetics, Newburyport, Mass), respectively. Two-way repeated-measures ANOVA was used for statistical analysis.

RESULTS

Both weight and diastema size increased for all animals throughout the study. Although there were no significant differences between groups at any time point (log diastema, P = .43), the maxillary nerve transection surgery group had a significantly smaller increase in log diastema from 14 to 28 days than either the sham surgery or the nonsurgery group (P = .045).

CONCLUSIONS

This study suggests that surgical denervation causes little net effect on orthodontic tooth movement at these force levels.

Pain Discomfort and Crevicular Fluid Changes Induced by Orthodontic Elastic Separators in Children

The objective of the present investigation was to study the experience of pain after placement of orthodontic elastic separators and the possible associations with the gingival crevicular fluid (GCF) composition changes at the level of interleukin 1-beta (IL-1beta), substance P (SP), and prostaglandin-E2 (PGE2). Eighteen children (mean age 10.8 yrs) in the beginning of the orthodontic treatment were included. Molar elastic separators were inserted mesially to 2 first upper or lower molars. One of the antagonist molars served as control. The GCF was collected from the distobuccal and distopalatal sites from each molar, before (day -7, day 0) and after the placement of separators (1 h, day 1, and day 7). Pain intensity was recorded using a visual analog scale (VAS). The contents of IL-1beta, SP, and PGE2 were determined by enzyme-linked immunosorbent assay. Pain intensity increased after 1 h (VAS = 11) and remained high on day 1 (VAS = 13). On day 7, no significant pain was reported. After 1 h, 1 day, and 7 days, mean GCF IL-1beta levels were significantly elevated at treatment teeth compared to control teeth (highest day 1). The GCF levels of SP and PGE2 for the treatment teeth were significantly higher at day 1 and day 7 than the control teeth. All 3 mediators remained at baseline levels throughout the experiment for the control teeth. The intensity of pain at 1 h was associated to PGE2 levels (R2 = 0.38; P < .05), whereas at day 1, the intensity of pain was associated to IL-1beta levels (R2 = 0.63, P < .0001). Thus, we report a rapid release of biochemical markers (1 h) that peaked after 1 day and partially decreased 7 days later. The intensity of pain followed a similar pattern. Associations were found between the experience of pain intensity and the GCF mediator levels.

PERSPECTIVE

The study may help to detect, in an initial stage, individuals prone to perceive higher level of pain during orthodontic treatment. This may help in the development of methods that will better control and/or alleviate the discomfort of pain during tooth movement.

Tachykinins and tachykinin receptors in bone

Tachykinins are neuropeptides that are widely distributed in the body and function as neurotransmitters and neuromodulators. Five tachykinin subtypes: substance P (SP), neurokinin A, neurokinin B, neuropeptide K, and neuropeptide gamma; and three receptor subtypes: neurokinin-1, -2, and -3 receptors, have been identified. SP was the first peptide of the tachykinin family to be identified. It is considered to be an important neuropeptide, and to function in the nervous system and intestine. However, recent advances in the analysis of SP receptors, particularly neurokinin-1 receptors (NK(1)-Rs) that have high affinity for SP, have demonstrated that NK(1)-Rs are distributed not only in neurons and immune cells, but also in other peripheral cells, including bone cells. This article reviews the current understanding of the distribution of SP and other tachykinins in bone, and the function of tachykinins, through neurokinin receptors. The distribution of tachykinin-immunoreactive axons and neurokinin receptors suggests that tachykinins may directly modulate bone metabolism through neurokinin receptors.

Temporal changes in the distribution and number of macrophage-lineage cells in the periodontal membrane of the rat molar in response to experimental tooth movement

In order to evaluate the possible role of macrophages in the remodelling of periodontal tissue in response to tooth movement, temporal changes in the number and distribution of macrophage-lineage cells in the periodontal membrane of the rat molar tooth after experimental tooth movement were examined immunohistochemically using four anti-rat monoclonal antibodies: ED1 (anti-monocyte/macrophage-lineage cells and dendritic cells), ED2 (anti-resident macrophages), KI-M2R (anti-tissue macrophages), and OX6 (anti-class II molecules). The right maxillary first molar tooth of Wistar rats was moved mesially by a closed-coil spring for 1, 3, 5, or 7 days. Sham-treated rats wearing an inactivated appliance for each experimental period and entirely untreated rats were used as controls. Alternate horizontal serial cryostat sections were cut and incubated with antibodies to ED1, ED2, KI-M2R, and OX6. In addition, cells immunopositive for each monoclonal antibody in the periodontal membrane during tooth movement were analysed on the tension and pressure sides. In the control rats, large numbers of cells positively stained with each monoclonal antibody were distributed throughout the periodontal membrane surrounding the distobuccal root. At 1 day after experimental tooth movement, the number of immunopositive cells obtained with all four monoclonal antibodies decreased as compared with those of the control on the mesial/pressure side. During the later experimental time periods, ED1- and OX6-positive cells in the periodontal membrane of this side were significantly increased in number compared with controls, whereas the density and distribution pattern of cells positive with ED2 or KI-M2R remained unchanged. On the mesial/pressure side, which underwent hyalinization, a marked accumulation of OX6- and ED1-reactive cells, but not of ED2- or KI-M2R-reactive cells, was frequently observed in the area of the hyalinized tissue at 5-7 days after the start of tooth movement. On the distal/tension side, no particular change in the distribution of immunopositive cells obtained with any antibody was detected throughout the experimental periods, with the exception that there was a significant increase in the number of ED1-positive cells and in of OX6-positive cells at 1 and 7 days, respectively, after the start of tooth movement. These results suggest that after the start of tooth movement OX6- and ED1-positive cells, which are mostly exudative macrophages, but not ED2- and KI-M2R-positive cells, i.e., resident macrophages, may be actively engaged in bone resorption and the remodelling of tissues on the pressure side of the periodontal membrane.

Pain in orthodontics. A review and discussion of the literature

This literature review focuses on previous studies of pain and pain perception in dentistry with special emphasis on orthodontic treatment. The prevalence of pain and background factors such as age, gender and culture/society, in addition to pain physiology and the influence of concomitant emotional and cognitive factors, is examined. Pain during orthodontic tooth movement is reported from the point of view of its physiology and character and different assessment methods. These aspects are described both generally and specifically in relation to the type of orthodontic forces and to the experience of discomfort other than pain. Since the orthodontic treatment may cause some degree of suffering for the patients, it is important for orthodontists to handle this situation in the best possible way. Some ideas about the possibilities of avoiding, reducing or alleviating pain in orthodontics are discussed.

Endodontic-orthodontic relationships: a review of integrated treatment planning challenges

Literature review There is a paucity of information on the concise relationship between endodontics and orthodontics during treatment planning decisions. This relationship ranges from effects on the pulp from orthodontic treatment and the potential for resorption during tooth movement, to the clinical management of teeth requiring integrated endodontic and orthodontic treatment. This paper reviews the literature based on the definition of endodontics and the scope of endodontic practice as they relate to common orthodontic-endodontic treatment planning challenges. Literature data bases were accessed with a focus on orthodontic tooth movement and its impact on the viability of the dental pulp; its impact on root resorption in teeth with vital pulps and teeth with previous root canal treatment; the ability to move orthodontically teeth that were endodontically treated versus nonendodontically treated; the role of previous tooth trauma; the ability to move teeth orthodontically that have been subjected to endodontic surgery; the role of orthodontic treatment in the provision for and prognosis of endodontic treatment; and, the integrated role of orthodontics and endodontics in treatment planning tooth retention. Orthodontic tooth movement can cause degenerative and/or inflammatory responses in the dental pulp of teeth with completed apical formation. The impact of the tooth movement on the pulp is focused primarily on the neurovascular system, in which the release of specific neurotransmitters (neuropeptides) can influence both blood flow and cellular metabolism. The responses induced in these pulps may impact on the initiation and perpetuation of apical root remodelling or resorption during tooth movement. The incidence and severity of these changes may be influenced by previous or ongoing insults to the dental pulp, such as trauma or caries. Pulps in teeth with incomplete apical foramen, whilst not immune to adverse sequelae during tooth movement, have a reduced risk for these responses. Teeth with previous root canal treatment exhibit less propensity for apical root resorption during orthodontic tooth movement. Minimal resorptive/remodelling changes occur apically in teeth that are being moved orthodontically and that are well cleaned, shaped, and three-dimensionally obturated. This outcome would depend on the absence of coronal leakage or other avenues for bacterial ingress. A traumatized tooth can be moved orthodontically with minimal risk of resorption, provided the pulp has not been severely compromised (infected or necrotic). If there is evidence of pulpal demise, appropriate endodontic management is necessary prior to orthodontic treatment. If a previously traumatized tooth exhibits resorption, there is a greater chance that orthodontic tooth movement will enhance the resorptive process. If a tooth has been severely traumatized (intrusive luxation/avulsion) there may be a greater incidence of resorption with tooth movement. This can occur with or without previous endodontic treatment. Very little is known about the ability to move successfully teeth that have undergone periradicular surgical procedures. Likewise, little is known about the potential risks or sequelae involved in moving teeth that have had previous surgical intervention. Especially absent is the long-term prognosis of this type of treatment. During orthodontic tooth movement, the provision of endodontic treatment may be influenced by a number of factors, including but not limited to radiographic interpretation, accuracy of pulp testing, patient signs and symptoms, tooth isolation, access to the root canal, working length determination, and apical position of the canal obturation. Adjunctive orthodontic root extrusion and root separation are essential clinical procedures that will enhance the integrated treatment planning process of tooth retention in endodontic-orthodontic related cases.

Delayed recruitment of immunocompetent cells in denervated rat periodontal ligament following experimental tooth movement

It has previously been shown that the number of mononuclear phagocytic cells in the periodontal ligament (PDL) of orthodontically moved rat molars is significantly increased (p < or = 0.05) at 3, 7, and 14 days compared with the controls. Since these changes coincide with increased density of peptidergic nerve fibers, it was of particular interest to investigate a possible relation between the immunocompetent cells and sensory nerve fibers in the PDL of experimentally moved and denervated rat molars. Twenty-two young animals had the first right mandibular molar moved mesially, 7, 14, and 21 days after ipsilateral inferior alveolar nerve axotomy. The left side served as unoperated control. An immunohistochemical procedure was carried out on alternate, serial, cryostat sections with antibodies against CDllb (macrophages, dendritic cells) and class II major histocompatibility complex (MHC) molecules (RT1B). At 7 and 14 days, the number of CD11b+- and RT1B-expressing cells in the denervated PDL showed no significant difference compared with the contralateral side. However, at 21 days, when periodontal tissue re-innervation is established, the number of the investigated immunocompetent cells in the PDL of the denervated and experimentally moved mandibular molars demonstrated a significant difference compared with the contralateral and control molars (p < or = 0.05). It can be concluded that axotomy of the inferior alveolar nerve delays the recruitment of macrophage-like and class II MHC molecule-expressing cells in the PDL of orthodontically moved rat molars. The results further indicate that sensory nerve fibers interact with immunocompetent cells and participate in their mobilization to locally inflamed tissues.

Immunocompetent cells in rat periodontal ligament and their recruitment incident to experimental orthodontic tooth movement

The aims of this study were to evaluate the number and distribution of immunocompetent cells in normal rat periodontal ligament (PDL) and to quantify their recruitment incident to experimental tooth movement. 27 young animals had the 1st right maxillary molar moved mesially by an orthodontic appliance for 1, 3, 7 and 14 days, respectively. 4 animals served as untreated controls. An immunohistochemical procedure was carried out on alternate serial cryostat sections, and monoclonal antibodies against CD11b (macrophages, dendritic cells), CD43 (lymphocytes, polymorphs), CD4 (helper T-lymphocytes), and class II MHC molecules were used. Mean counts of the immunolabeled cells in the control group showed the highest number of CD11b+ and class II molecule expressing cells, while CD4+ and CD43+ cells were scarcely found. Significant increase in the number of CD11b+, CD43+ cells and class II molecules was found in the PDL of the experimentally moved 1st molars compared with the contralateral side and the control group, while CD4+ cells showed no significant increase. CD11b+ and cells expressing class II molecules were found around hyalinized tissue, between dentin and cellular cementum and close to Malassez' epithelial cells. In conclusion, normal rat PDL has high number of macrophage and dendritic-like cells, but few lymphocytes and granulocytes. Furthermore, experimental tooth movement leads to significant recruitment of cells belonging to the mononuclear phagocytic system, but has no significant effect on the number of lymphocytes and granulocytes in the rat PDL.

Neurogenic substance P stimulates osteogenesis in vitro

Previous studies have shown that there is colocalization of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive nerve fibers in bone, periosteum and bone marrow. Because SP may also possibly play a role in bone formation, we decided to test whether it has an osteogenic stimulating effect on developing bone in vitro. To this end, 0.4, 4 and 40 micrograms/ml of SP in BGJb medium was added daily to 3 million light density (LD) bone marrow white cells which were separated by Ficoll-Paque density gradient separation then seeded onto a previously prepared fibroblast feeder layer in Petri dishes. Seven days after adding SP, in the control without SP there were 2 bone colonies; with 0.4 micrograms of SP there were 3 colonies; with 4 micrograms there were 5 colonies; with 40 micrograms there were 7 colonies. In addition, there was an increase in the size of bone colonies in the SP-added group. The results indicated that SP had a dose-related osteogenic stimulating effect. The increase in the number and size of bone colonies by SP was probably caused by stimulating stem cell mitosis, osteoprogenitor cell differentiation or osteoblastic activity.

Angiogenesis in human dental pulp following orthodontic tooth movement

The pulpal response to orthodontic force is thought to involve cell damage, inflammation, and wound healing. These situations are likely to be associated with the release of angiogenic growth factors. We therefore investigated human dental pulps to determine if angiogenic changes could be detected after orthodontic force application. Fifteen premolar teeth were treated with straight-wire fixed orthodontic appliances for two weeks, and comparisons were made with 15 untreated control premolar teeth from the same subjects. The teeth were extracted and sectioned. The pulps were removed, divided into 1-mm sections, embedded in collagen, and cultured in growth media for up to four weeks. Cultures were examined daily, by light microscopy, for growth and number of microvessels. Apparent microvessels were observed within five days. Confirmation of microvessel identification was by electron microscopy for endothelial cell morphology. There were significantly greater numbers of microvessels at day five and day ten of culture in the pulp explants from orthodontically treated teeth compared with those from the pulps of control teeth. These results are consistent with the hypothesis that there is an increase in angiogenic growth factors in the pulp of orthodontically moved teeth.

A histological study on the effect of different periods of orthodontic force on the innervation and dimensions of the cat periodontal ligament

Using light microscopy, the numbers of myelinated axons in the periodontal ligament of the cat mandibular canine were counted after orthodontic forces had been applied for either 3 days or 12 weeks, and also 8 weeks after removal of a force that had been applied for the previous 12 weeks. After 3 days no significant changes in axon number were recorded, but after 12 weeks there were significantly fewer myelinated axons in the periodontal ligament of the experimental teeth than in the control teeth. This reduction was not reversed after an 8 week recovery period. The width of the ligament was measured in an attempt to correlate regions of nerve fibre degeneration with areas of compression or tension, and the tooth root circumference was measured to assess the extent of any root resorption. It appeared that axon degeneration occurred both in areas of compression and tension. Root resorption had occurred after 12 weeks of applied force and there was no significant change after the 8 week recovery period. These findings support the view that nerve injury occurs as a result of orthodontic force and may possibly be permanent.

Teeth and tooth nerves

(1) Although our knowledge on teeth and tooth nerves has increased substantially during the past 25 years, several important issues remain to be fully elucidated. As a result of the work now going on at many laboratories over the world, we can expect exciting new findings and major break-throughs in these and other areas in a near future. (2) Dentin-like and enamel-like hard tissues evolved as components of the exoskeletal bony armor of early vertebrates, 500 million years ago, long before the first appearance of teeth. It is possible that teeth developed from tubercles (odontodes) in the bony armor. The presence of a canal system in the bony plates, of tubular dentin, of external pores in the enamel layer and of a link to the lateral line system promoted hypotheses that the bony plates and tooth precursors may have had a sensory function. The evolution of an efficient brain, of a head with paired sense organs and of toothed jaws concurred with a shift from a sessile filter-feeding life to active prey hunting. (3) The wide spectrum of feeding behaviors exhibited by modern vertebrates is reflected by a variety of dentition types. While the teeth are continuously renewed in toothed non-mammalian vertebrates, tooth turnover is highly restricted in mammals. As a rule, one set of primary teeth is replaced by one set of permanent teeth. Since teeth are richly innervated, the turnover necessitates a local neural plasticity. Another factor calling for a local plasticity is the relatively frequent occurrence of age-related and pathological dental changes. (4) Tooth development is initiated through interactions between the oral epithelium and underlying neural crest-derived mesenchymal cells. The interactions are mediated by cell surface molecules, extracellular matrix molecules and soluble molecules. The possibility that the initiating events might involve a neural component has been much discussed. With respect to mammals, the experimental evidence available does not support this hypothesis. In the teleost Tilapia mariae, on the other hand, tooth germ formation is interrupted, and tooth turnover ceases after local denervation. (5) Prospective dental nerves enter the jaws well before onset of tooth development. When a dental lamina has formed, a plexus of nerve branches is seen in the subepithelial mesenchyme. Shortly thereafter, specific branches to individual tooth primordia can be distinguished. In bud stage tooth germs, axon terminals surround the condensed mesenchyme and in cap stage primordia axons grow into the dental follicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Alteration of nerve growth factor-receptor expression in the periodontal ligament of the rat during experimental tooth movement

This pilot study deals with the initial responses of neural elements showing nerve growth factor-receptor (NGFR) immunoreactivity in the periodontal ligament of rats to orthodontic forces. The animals were killed at intervals of 1, 2, 6, 12 h and 1, 3, 5, 7 days after the insertion of elastic bands between the maxillary first and second molars. Serial frozen sections, prepared from each animal, were processed immunohistochemically to demonstrate NGFR, after which the periodontal ligament of the mesial root of the maxillary second molar was examined microscopically. In control sections, NGFR-positive neural elements were predominantly distributed at the apex of the bony socket on the distal side of the periodontal ligament. After 1 h of tooth movement, NGFR positively-stained nerve fibres tended to disappear slightly in both the intermediate and coronal regions of the distal periodontal ligament. By the third day of tooth movement, the periodontal ligament nerve fibres showed more intense NGFR-immunoreactivity; thick, positively stained nerve fibres were recognized on the distal side in which active bone remodelling was occurring, and a few of these fibres were densely distributed around blood vessels or near Howship's lacunae. The distribution of NGFR-positive neural elements on the mesial side increased at 5 days of tooth movement. Finally, at 7 days of tooth movement, staining intensity for NGFR appeared to decrease. These findings demonstrate that an alteration in the distribution and the intensity of immunoreactive staining for NGFR in the periodontal ligament is associated with the bone remodelling induced by orthodontic tooth movement.

Effects of hormones and cytokines on stimulation of adenylate cyclase and intracellular calcium concentration in human and canine periodontal-ligament fibroblasts

Adenylate cyclase was stimulated by prostaglandin E2 (PGE2) and parathyroid hormone-related protein (PTHrP) in both these types of fibroblast and by calcitonin gene-related protein (CGRP) in the human fibroblasts in vitro. PGE2 (1 microM), CGRP (1 microM), and PTHrP (1 microM) stimulated adenylate cyclase up to 50-fold, 10-fold and 9-fold, respectively. Calcitonin (CT), substance P (SP), interleukin-1 beta (IL-1 beta), and transforming growth factor-beta 1 (TGF beta 1) had no effect on adenylate cyclase in either fibroblast. Intracellular Ca2+ (iCa2+) was measured in individual fibroblasts from the periodontal ligament using Indo-1 and an adherent cell analysis and sorting interactive laser cytometer. Ionomycin (3 microM) caused a transient rise of iCa2+ in all human and canine fibroblasts tested. The mean percentage increase in iCa2+ in response to ionomycin was 820 and 840% for human and canine fibroblasts, respectively. The human fibroblasts responded to PGE2 (1 microM) by an increased iCa2+ concentration; the mean percentage increase in iCa2+ was 187%. SP caused a less pronounced increase in iCa2+ in the human fibroblasts (56%). CGRP and SP caused a similar response in the canine fibroblasts. The mean percentage increase in iCa2+ in response to SP and CGRP was 95 and 78%, respectively. PTH, PTHrP, platelet-activating factor, CT, and IL-1 beta had no effect on iCa2+ in either type of fibroblast. The data indicate that cAMP and calcium have roles as intracellular secondary messengers in the action of PGE2, SP, CGRP, and PTHrP in fibroblasts of human and canine periodontal ligament.