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PubMed2005

CSF-1 regulation of osteoclastogenesis for tooth eruption.

The dental follicle regulates the alveolar bone resorption needed for tooth eruption. In the rat first mandibular molar, a decrease in the expression of osteoprotegerin (OPG) in the dental follicle at day 3 enables the osteoclastogenesis needed for eruption to occur. Because colony-stimulating factor-1 (CSF-1) is maximally expressed in the dental follicle at day 3, it was hypothesized that CSF-1 down-regulates OPG gene expression in the dental follicle in vivo. To test this, we compared the expression of OPG in osteopetrotic toothless (tl/tl) rats deficient in CSF-1 with expression in their normal littermates for given ages. OPG gene expression was found to be higher in the dental follicle of the tl/tl mutants than in normals. Transfecting short interfering RNA specific for CSF-1 mRNA into dental follicle cells resulted in an up-regulation of OPG expression. Thus, these studies support our hypothesis that the down-regulation of OPG needed for tooth eruption is mediated by CSF-1.

Animals↗
PubMed2000

Root resorption after orthodontic treatment in high- and low-risk patients: analysis of allergy as a possible predisposing factor.

The development of excessive root resorption during orthodontic tooth movement is an adverse side-effect, which is of great concern. The aim of this investigation was to analyse factors that might be associated with orthodontically induced root resorption. After buccal movement of maxillary premolars in 96 adolescents, the experimental teeth were extracted and subjected to histological analysis and measurement of resorbed root area. Fifty individuals, 18 boys and 32 girls, mean age 13.4 years, were selected and divided into two equal groups: the high-risk group based on measurements of the most severe root resorptions, and the low-risk group on measurements of mild or no root resorptions. After a preliminary screening of possible risk factors regarding root resorption, i.e. root morphology, gingivitis, allergy, nail-biting, medication, etc., only those subjects with allergy showed an increased risk of root resorption, but this was not statistically significant.

Adolescent↗
PubMed1998

Directions of orthodontic tooth movements associated with external apical root resorption of the maxillary central incisor.

External apical root resorption is a multifactorial problem encountered in all disciplines of dentistry, but it is most commonly seen in cases treated orthodontically. Specific tooth movements that are most likely to exacerbate external apical root resorption are poorly understood. Purpose of the present investigation was twofold: (1) to quantify apical and incisal movements of the maxillary central incisor in the sagittal and vertical planes from cephalograms and (2) to use stepwise multivariate linear regression analyses to see which tooth movements and skeletodental relationships are most predictive of external apical root resorption. The sample consisted of 110 adolescents with similar pretreatment malocclusions (Class I crowded or bimaxillary protrusive) and treatment planned similarly (extraction of four first premolars) by experienced private practitioners. Each of three practitioners used a different orthodontic appliance; the sample was divided proportionately into cases treated with Tweed standard edgewise technique, Begg lightwire technique, and Roth-prescription straightwire technique. Lateral cephalograms were analyzed at the start, middle, and end of treatment. There was no statistical difference in average external apical root resorption between sexes or among techniques. Measures of tooth movement were highly predictive, explaining up to 90% of the variation in root resorption. Apical and incisal vertical movements and increase in incisor proclination were the strong predictors of external apical root resorption for each regression model. Incisor intrusion with increase in lingual root torque together were the strongest predictors of external apical root resorption. In contrast, distal bodily retraction, extrusion, or lingual crown tipping had no discernible effect.

Adolescent↗
PubMed2005

Expression of mRNA for osteoprotegerin and receptor activator of nuclear factor kappa beta ligand (RANKL) during root resorption induced by the application of heavy orthodontic forces on rat molars.

INTRODUCTION: Receptor activator of nuclear factor kappa beta ligand (RANKL) activates osteoclast differentiation, whereas this activity is blocked by osteoprotegrin (OPG), so that the relative expression of these 2 proteins might contribute to bone and root resorption during orthodontic tooth movement. We describe experiments with RANKL and OPG mRNA expression in rats subjected to orthodontic forces. It was hypothesized that the ratios of RANKL to OPG expression would increase during root resorption processes. METHODS: Fixed Sentalloy (GAC, Bohemia, NY) closed-coil springs capable of delivering approximately 100 g of force were applied for mesial movement of the mandibular left first molar in 9 male, 7-week-old Wistar rats; the right mandibular molar was used as an internal control for each animal. After 14 days, the rats were killed; tissues from 2 rats were examined by paraffin histology, and high-quality messenger ribonucleic acid (mRNA) was extracted from 4-mm widths of the mesial bony tissues in the remaining animals. RESULTS: Paraffin sections showed osteoclastic resorption of roots on the mesial surfaces of teeth subjected to orthodontic forces. The integrity of mRNA was confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) for the housekeeping gene GAPDH, and that of primers specific for OPG and RANKL was determined by RT-PCR for these genes in material isolated from the UM106 rat cell line known to express both proteins. Densitometric analysis of the RT-PCR OPG product showed an increase in background levels of OPG mRNA in bony tissues subjected to orthodontic forces in all animals studied (P < .05). In contrast, low levels of mRNA for RANKL were detected in only 5 animals and only in association with orthodontic forces. CONCLUSIONS: Data are consistent with changes in levels of OPG and RANKL in tissues subjected to orthodontic forces and experiencing root resorption.

Animals↗
PubMed1990

[Root resorption of vital and endodontically treated teeth in orthodontic movement].

Orthodontic tooth movement frequently induces the resorption of the tooth root, although valuable information concerning the relationship between the root resorption and force magnitude, duration and types of tooth movement and the condition of periodontium obtained. However, it is incompletely known that the situation of candidated tooth itself of orthodontic movement in which pulpectomized non-vital condition influence the process of root resorption and subsequent repairing. Thus, the study was conducted to clarify the effect by the pulpectomy accompanied with tooth movement on the process of root resorption and regeneration of periodontium. A hundred and fifty Wistar rats, weight 180-200 g, 6 weeks old, were used as experimental animals. Prior to experimental tooth movement, first molars of 50 rats were received pulpectomy on both sides followed by filling of root canal (first group) and those of another 50 rats on single side (second group). Maxillary first molars of the other 50 rats were saved as a vital dental pulp control (third group). The first and the third groups of animals were then subjected to experimental tooth movement with the interproximal insertion of elastic rubber as described by Waldo (1953) for 3 days, 1, 2, 3 and 4 weeks. After tooth movement was terminated, animals were sacrificed by ether inhalation or by perfusion of glutaraldehyde fixation solution. The upper jaw from each rat was dissected and prepared specimens for non-decalcified section and light microscopic section. Root resorption and regeneration of cementum were evaluated quantitatively using the modular system for semiautomatic quantitative evaluation of images on the light microscopic section. Occurrence of external root resorption with multinucleated odontoclast associated with experimental tooth movement in pulpectomized tooth were lesser and later than those of vital teeth. These findings suggest that the dental pulp plays an important role in the processes of root resorption and remodeling of cementum associated with orthodontic tooth movement.

Animals↗
PubMed2004

[Expression of cathepsin K and IL-6 mRNA in root-resorbing tissue during tooth movement in rats].

OBJECTIVE: To investigate the expression and the localization of Cathepsin K and IL-6 mRNA in root-resorbing tissue and to elucidate the molecular changes and mechanism of root resorption induced by tooth movement. METHODS: Rats were subject to experimental tooth movement to induce root resorption. In situ hybridization was performed to identify the cells in root-resorbing tissue that produced Cathepsin K or IL-6 the difference of CK mRNA or IL-6 mRNA expression between root resorption group and control group was calculated by t-test. RESULTS: Cathepsin K mRNA was highly and selectively expressed in multinuclear odontoclast and IL-6 mRNA expressed in fibroblast, osteoblast, osteocyte and cementoblast. The expression of Cathepsin K mRNA and IL-6 mRNA in root-resorbing tissue increased evidently compared with the normal periodontium. CONCLUSIONS: Odontoclast in the root-resorbing tissue expresses Cathepsin K mRNA that participates in proteolysis during root resorption. IL-6 plays a very important role in the root resorption as a multifunctional cytokine.

Animals↗
PubMed2003

Root resorption related to hypofunctional periodontium in experimental tooth movement.

Orthodontic movement of non-occluding teeth may result in undesirable apical root resorption. These teeth present with a histologically altered periodontium and are considered to be hypofunctional. The purpose of this study was to compare the amount of root resorption associated with a normal and a hypofunctional periodontium in rats during experimental tooth movement caused by heavy continuous force. The mandibular first molar was induced into a non-occluding condition in the hypofunctional periodontium group. Mesial orthodontic force was applied by means of 50-gram-force closed-coil springs for 15 days in both groups. The active root-resorption lacunae from histological sections, identified by tartrate-resistant acid phosphatase, were measured in terms of length, depth, and area. The results showed that the amount of root resorption was significantly greater in teeth with a hypofunctional periodontium than in those with a normal periodontium (p < 0.05). These results suggest that orthodontic movement of non-occluding teeth should be performed with caution.

Acid Phosphatase↗
PubMed2006

Root resorption and immune system factors in the Japanese.

The objective of this study was to determine whether there is an association between excessive root resorption and immune system factors in a sample of Japanese orthodontic patients. The records of 60 orthodontic patients (18 males, age 17.7 +/- 5.7 years; 42 females, age 16.4 +/- 6.0 years) and 60 pair-matched controls (18 males, age 15.9 +/- 4.5 years; 42 females, age 18.5 +/- 5.2 years) based on age, sex, treatment duration, and the type of malocclusion were reviewed retrospectively. The validity of our hypothesis was tested using the logistic regression analysis. The pretreatment records revealed that the incidence of allergy and root morphology abnormality was significantly higher in the root resorption group (P = .030 and .001), with a mean odds ratio of 2.794 and 6.317 and 95% confidence interval of 1.107-7.053 and 2.043-19.537, respectively. The incidence of asthma also tended to be higher in the root resorption group. From these results, we concluded that allergy, root morphology abnormality, and asthma may be high-risk factors for the development of excessive root resorption during orthodontic tooth movement in Japanese patients.

Adolescent↗
PubMed1997

External resorption presenting as an intracoronal radiolucent lesion in a pre-eruptive tooth.

A large intracoronal radiolucent lesion in an unerupted permanent molar was found during the routine assessment of a young male Caucasian prior to orthodontic treatment. The tooth was extracted. Histological examination indicated the lesion was caused by external resorption. The defect extended widely into the enamel and dentine, and was repaired in part by bone. The pulp chamber was not involved. The aetiology of these lesions is often obscure but in this case it appeared to have originated in the floor of two developmental pits on the occlusal surface of the tooth.

Child↗
PubMed2000

Application of bone remodeling theories in the simulation of orthodontic tooth movements.

A numerical model that calculates bone apposition and resorption around a tooth root on the basis of bone remodeling theories was developed to simulate orthodontic tooth movements. The model was used to calculate different kinds of orthodontic tooth movements, that were then compared with the expected movements based on clinical experience. For simulation of the movements the root of a canine was modeled in an idealized way in the form of an elliptical paraboloid and was processed with a finite element program. The finite element model was loaded with defined force systems. Two model assumptions were used to calculate the bone remodeling process. The mechanical loads firstly in the periodontal ligament and secondly in the alveolar bone were taken to simulate the following tooth movements: 1. mesial tipping around the center of resistance (force system at the bracket: isolated torque MY = 5 Nmm), 2. rotation around the long axis of the tooth (MZ = 5 Nmm), 3. uncontrolled tipping around the root tip (FX = 1 N, MZ = 5 Nmm), 4. canine retraction (FX = 1 N, MY = -9.5 Nmm, MZ = 5 Nmm), 5. and 6. extrusion/intrusion (FZ = +/- 0.5 N, MX = +/- 2.5 Nmm). Comparison with clinical experience was performed by calculating the orthodontic tooth movements based on the assumption of a fixed position of the center of resistance. It could be demonstrated that the numerical model of orthodontic bone remodeling can be used to calculate orthodontic tooth movements. However, the results are strongly dependent on the model assumptions. The model simulating the bone remodeling on the basis of the loading of the periodontal ligament delivers results that are in very good accordance with the biomechanical assumptions of the position of the center of resistance. However, marked side effects occurred with the second model, especially in the simulations of uncontrolled tipping, translation and intrusion/extrusion. Clinically, these side effects cannot be observed.

Bone Remodeling↗
PubMed1996

[Experimental study on the healing of immediate replanted tooth after using exogenous fibronectin].

The purpose of this article is to study the effect on the healing of immediate replanted teeth after the biological characters of roots were changed by using exogenous fibronectin (Fn). Two adult rhesus monkeys were chosen in the experiment. Upper-incisors of each monkey were extracted. The teeth of experimental group were extracted the roots treated by 0.5 mg/ml Fn solution and replanted immediately. The roots of another animal were used as controls. After operations, the experimental specimens of 4 weeks and 8 weeks were examed histologically by light microscope and studied quantitatively by computer image analysis system. The results reveal that Fn can enhance periodontal healing by improving periodontal reattachment and reducing root resorption of replanted tooth. Fn has also the function to reduce inflammatory reactions significantly during the healing process.

Animals↗
PubMed1989

Calcium hydroxide in the treatment of external root resorption.

A case is presented in which calcium hydroxide was used in endodontic treatment of external root resorption in a tooth with a necrotic pulp, during active orthodontic movement. A calcified deposit formed, filling a defect, and the tooth was subsequently obturated with gutta-percha. Thus, both types of therapy--endodontic and orthodontic--were performed simultaneously.

Adolescent↗
PubMed1990

[The study of root resorption of human deciduous teeth. I. Histological observation by light microscope].

Sixty-four human non-carious deciduous teeth were used to observe the root resorption of deciduous teeth by means of light microscope. The extent of root resorption was classified into 6 grades: Res. O, Res. i, Res. 1/4, Res. 1/2, Res. 3/4, Res. Co. In the physiological root resorption of deciduous tooth, there are numerous, large multinucleated odontoclasts and mononuclear fibroblasts or macrophages residing at the Howship's lacunae. The odontoclasts resorbed hard dental tissues, including cementum, dentin. A characteristic of active or "resorbing" odontoclasts, but not in free or inactive odontoclasts is cytoplasmic projections, or brush borders, which were found near the underlying hard dental tissues. The deciduous root resorption was found to be most advanced in the apical areas. Because of the different eruption path of the permanent successors, the position of deciduous root resorption varied. Generally, the lingual surface was resorbed more extensively than the labial surface in the deciduous anterior teeth; the resorption of the furcal area and interradicular cementum surface of the roots were more advanced in the deciduous molars. Predentin can be resorbed by odontoclasts, too. However, it seems more resistant to resorption than dentin. Resorption lacunae could be observed in the root canal and pulp chamber. This means that the internal root resorption probably occur simultaneously. Periodontal fiber attachment was observed in some Howship's lacunae of the root surface. Inflammatory changes occurred in the pulp of deciduous teeth during the shedding process, especially when the deciduous root was resorbed more than one half way. The appearance of the repairing cellular cementum and periodontal fiber attachment was clearly observed in some deciduous roots.

Child↗
PubMed2001

Predicting and preventing root resorption: Part II. Treatment factors.

The main objective of this study was to determine which treatment factors are most clearly identified with external apical root resorption that is detectable on periapical radiographs at the end of orthodontic treatment. The records of 868 patients who completed fixed, edgewise treatment from experienced clinicians in private practice were examined. The horizontal and vertical displacement of the root apex of the maxillary central incisor was measured on cephalometric radiographs. Patients who underwent first premolar extraction therapy had more resorption than those patients who had no extractions or had only maxillary first premolars removed. Duration of treatment and the horizontal (but not vertical) displacement of the incisor apices were significantly associated with root resorption. No differences were found for slot size, archwire type, use of elastics, and types of expansion. However, there was considerable variation among the 6 offices that were surveyed; 1 office averaged nearly a full millimeter more of resorption per anterior tooth than the office with the least amount of root resorption. We conclude that the clinician should exercise caution with those patients in whom extraction therapy is planned for overjet correction that requires above average treatment time. Finally, each clinician should be aware that the root resorption seen in one practice may be different from the root resorption found in another practice.

Adolescent↗
PubMed1976

Root resorption by ameloblastomas and cysts of the jaws.

Radiographs of 122 cases of a series of nonmalignant simple jaw cysts and ameloblastomas were examined and the frequency of resorption of adjacent tooth roots compared. The ameloblastomas proved to have a root resorptive potential far greater than the cystic lesions considered. Certain statistically significant differences were observed in the root resorption related to the cystic lesions. The dentigerous cyst showed a tendency to resorb roots (55%), whereas in this study no resorption was observed in primordial cysts. These differences may aid the clinician in the preoperative differential diagnosis. It is suggested that the capacity of the dentigerous cyst for root resorption may be the result of its origin from the dental follicle, which is associated with resorption of the roots of primary teeth during normal tooth succession.

Ameloblastoma↗
PubMed2005

Auto-transplantation in the restorative management of traumatized anterior teeth: a case report.

UNLABELLED: Auto-transplantation can be used to replace missing anterior teeth following traumatic injuries. This technique has the advantage (over other forms of treatment) of maintaining alveolar bone height which allows orthodontic and further restorative intervention by way of implants later in life. Careful restorative management of transplanted teeth is vital to their long-term survival as inadequate maintenance post transplant may result in root resorption and eventual tooth loss. This paper describes the restorative management of two cases following transplantation. CLINICAL RELEVANCE: Dental practitioners should be aware of the option to auto-transplant teeth as part of an overall treatment plan and the subsequent interventions often required.

Adolescent↗