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Turkkahraman H, Yuan X, Salmon B, Chen CH, Brunski JB, Helms JA. Root resorption and ensuing cementum repair by Wnt/β-catenin dependent mechanism. Am J Orthod Dentofacial Orthop 2020; 158:16-27. [DOI: 10.1016/j.ajodo.2019.06.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 06/01/2019] [Accepted: 06/01/2019] [Indexed: 02/02/2023]
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Baxter SJ, Sydorak I, Ma PX, Hatch NE. Impact of pharmacologic inhibition of tooth movement on periodontal and tooth root tissues during orthodontic force application. Orthod Craniofac Res 2019; 23:35-43. [PMID: 31593373 DOI: 10.1111/ocr.12350] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 09/17/2019] [Accepted: 10/03/2019] [Indexed: 12/21/2022]
Abstract
OBJECTIVE The goal of this study was to investigate potential negative sequelae of orthodontic force application ±delivery of an osteoclast inhibitor, recombinant osteoprotegerin protein (OPG-Fc), on periodontal tissues. SETTING AND SAMPLE POPULATION Sprague Dawley rats from a commercial supplier were investigated in a laboratory setting. MATERIALS AND METHODS Rats were randomly divided into four groups (n = 7 each): one group with no orthodontic appliances and injected once prior to the experimental period with empty polymer microspheres, one group with orthodontic appliances and injected once with empty microspheres, one group with orthodontic appliances and injected once with polymer microspheres containing 1 mg/kg of OPG-Fc, and one group with orthodontic appliances and injected with non-encapsulated 5 mg/kg of OPG-Fc every 3 days during the experimental period. The animals were euthanized after 28 days of tooth movement for histomorphometric analyses. RESULTS Root resorption, PDL area and widths were similar in animals without appliances and animals with appliances plus high-dose OPG-Fc. PDL blood vessels were compressed and decreased in number in all animals that received orthodontic appliances, regardless of OPG-Fc. Hyalinization was significantly increased only in animals with orthodontic appliances plus multiple injections of 5 mg/kg non-encapsulated OPG-Fc when compared to animals without appliances. CONCLUSIONS Results of this study indicate that while pharmacological modulation of tooth movement through osteoclast inhibition is feasible when delivered in a locally controlled low-dose manner, high-dose levels that completely prevent tooth movement through bone may decrease local blood flow and increase the incidence of hyalinization.
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Affiliation(s)
- Sarah J Baxter
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Inna Sydorak
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Peter X Ma
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Nan E Hatch
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
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Chan E, Dalci O, Petocz P, Papadopoulou AK, Darendeliler MA. Physical properties of root cementum: Part 26. Effects of micro-osteoperforations on orthodontic root resorption: A microcomputed tomography study. Am J Orthod Dentofacial Orthop 2018; 153:204-213. [PMID: 29407497 DOI: 10.1016/j.ajodo.2017.05.036] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/01/2017] [Accepted: 05/01/2017] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Studies have demonstrated the potential efficacy of micro-osteoperforations in accelerating tooth movement by amplifying the expression of inflammatory markers. The aim of this investigation was to examine the effects of micro-osteoperforations on orthodontic root resorption with microcomputed tomography. METHODS This prospective controlled clinical trial involved 20 subjects requiring extraction of the maxillary first premolars as part of their orthodontic treatment. A buccal tipping force of 150 g was applied to both premolars. Using the Propel appliance (Propel Orthodontics, San Jose, Calif), micro-osteoperforations were applied at a depth of 5 mm on the mesial and distal aspects in the midroot region of the experimental side of the first premolar root; the contralateral side served as the control. After 28 days, both premolars were extracted. The teeth were scanned under microcomputed tomography, and the volumes of root resorption craters were calculated and compared. RESULTS Premolars treated with micro-osteoperforation exhibited significantly greater average total amounts of root resorption than did the control teeth (0.576 vs 0.406 mm3). The total average volumetric root loss of premolars treated with micro-osteoperforation was 42% greater than that of the control teeth. CONCLUSIONS This 28-day trial showed that micro-osteoperforations resulted in greater orthodontic root resorption. However, these results should be verified in patients who are undergoing full-length orthodontic treatment.
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Affiliation(s)
- Emmanuel Chan
- Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney Local Health District, Surry Hills, New South Wales, Australia.
| | - Oyku Dalci
- Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney Local Health District, Surry Hills, New South Wales, Australia
| | - Peter Petocz
- Department of Statistics, Macquarie University, Sydney, New South Wales, Australia
| | - Alexandra K Papadopoulou
- Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney Local Health District, Surry Hills, New South Wales, Australia
| | - M Ali Darendeliler
- Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Sydney Local Health District, Surry Hills, New South Wales, Australia
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Apical External Root Resorption and Repair in Orthodontic Tooth Movement: Biological Events. BIOMED RESEARCH INTERNATIONAL 2016; 2016:4864195. [PMID: 27119080 PMCID: PMC4828521 DOI: 10.1155/2016/4864195] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 03/08/2016] [Indexed: 12/20/2022]
Abstract
Some degree of external root resorption is a frequent, unpredictable, and unavoidable consequence of orthodontic tooth movement mediated by odontoclasts/cementoclasts originating from circulating precursor cells in the periodontal ligament. Its pathogenesis involves mechanical forces initiating complex interactions between signalling pathways activated by various biological agents. Resorption of cementum is regulated by mechanisms similar to those controlling osteoclastogenesis and bone resorption. Following root resorption there is repair by cellular cementum, but factors mediating the transition from resorption to repair are not clear. In this paper we review some of the biological events associated with orthodontically induced external root resorption.
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Pavone C, Perussi LR, de Oliveira GJPL, Scardueli CR, Cirelli JA, Cerri PS, Junior EM, Spolidorio LC, Marcantonio RAC. Effect of Er,Cr:YSGG laser application in the treatment of experimental periodontitis. Lasers Med Sci 2014; 30:993-9. [PMID: 24477391 DOI: 10.1007/s10103-014-1526-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 01/13/2014] [Indexed: 11/24/2022]
Abstract
The purpose of this study was to evaluate the influence of an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser in the absence or presence of manual scaling and root planning (SRP) for the treatment of induced periodontitis in rats. Ligatures were placed in the subgingival region of the maxillary first molar. After a 7-day period, the ligatures were removed, and 40 rats were randomly divided into four groups (G), as follows: (GI) no treatment, (GII) scaling and root planning (SRP) with curettes, (GIII) Er,Cr:YSGG laser irradiation and (GIV) SRP with curettes followed by Er,Cr:YSGG laser irradiation. Seven and 30 days after the treatment, the animals were sacrificed and histologic, histometric and immunohistochemistry analyses were performed. All groups showed similar histopathological characteristics during the evaluation period. The histometric analysis was confirmed using Bonferroni and paired t tests. At 7 and 30 days, groups II, III and IV exhibited greater bone formation in the furcation area when compared to group I (p < 0.0001; p < 0.05). During the 7-day period, the groups irradiated with the laser (III and IV) showed a statistically larger new bone area than the group treated with SRP (II) (p < 0.01). Immunohistochemistry analysis revealed that the control group exhibited a higher expression of tartrate-resistant acid phosphatase (TRAP) and the receptor activator of nuclear factor κΒ ligand (RANKL) when compared to groups II, III and IV (p < 0.05). All treatments were able to reduce the inflammatory processes, consequently enabling the repair of periodontal tissues. The results achieved with the application of the Er,Cr:YSGG laser suggest that this laser can stimulate greater bone formation, especially over a shorter period of time.
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Affiliation(s)
- Chaine Pavone
- Araraquara Dental School-São Paulo State University "Júlio de Mesquita Filho", Araraquara, São Paulo, Brazil
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Chan HL, Giannobile WV, Eber RM, Simmer JP, Hu JC. Characterization of periodontal structures of enamelin-null mice. J Periodontol 2013; 85:195-203. [PMID: 23646854 DOI: 10.1902/jop.2013.120651] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Enamelin-null (ENAM(-/-)) mice have no enamel. When characterizing ENAM(-/-) mice, alveolar bone height reduction was observed, and it was hypothesized that enamel defects combined with diet are associated with the periodontal changes of ENAM(-/-)mice. The aim of the present study is to compare the dimension of interradicular bone of ENAM(-/-) (knock-out [KO]) with wild-type (WT) mice, maintained on hard (HC) or soft (SC) chow. METHODS A total of 100 animals divided into four groups were studied at 3, 8, and 24 weeks of age: 1) KO/HC; 2) KO/SC; 3) WT/HC; and 4) WT/SC. Microcomputed tomography was performed, and the following measurements were made between mandibular first (M1) and second (M2) molars: relative alveolar bone height (RBH), crestal bone width (CBW), bone volume (BV), bone mineral content (BMC), and bone mineral density (BMD). The position of M1 and M2 in relation to the inferior border of the mandible was also determined at 24 weeks. All variables were analyzed by one-way analysis of variance and Dunnett test for pairwise comparisons. Morphologic analyses were conducted on hematoxylin and eosin-stained sections. RESULTS Radiographically, the enamel layer was absent in ENAM(-/-) mice. Interproximal open contacts were observed exclusively in ENAM(-/-) mice, and the prevalence decreased over time, suggesting that a shifting of tooth position had occurred. Additionally, in the two ENAM(-/-) groups, RBH was significantly lower at 8 and 24 weeks (P <0.02); CBW, BV, and BMC were significantly less (P <0.05) at 24 weeks. No differences in BMD were found among the four groups. The molars migrated to a more coronal position in ENAM(-/-) mice and mice on HC. Histologic findings were consistent with radiographic observations. After eruption, the junctional epithelium was less organized in ENAM(-/-) mice. CONCLUSION The interdental bone density was not affected in the absence of enamelin, but its volume was, which is likely a consequence of alternations in tooth position.
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Affiliation(s)
- Hsun-Liang Chan
- Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI
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Rodrigues LV, Vasconcelos AC, Campos PA, Brant JMC. Apoptosis in pulp elimination during physiological root resorption in human primary teeth. Braz Dent J 2009; 20:179-85. [PMID: 19784460 DOI: 10.1590/s0103-64402009000300001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulp samples of 50 healthy human teeth with indication for extraction were examined to evaluate the role of apoptosis in pulp elimination during physiological root resorption. Two groups were formed: a test group (n=30) composed of pulp samples of primary teeth with physiological root resorption and a control group (n=20) composed of pulp samples of permanent maxillary third molars. Morphological evidence of apoptosis as well as in situ detection of cellular DNA fragmentation by TUNEL assay and detection of internucleosomal pattern of fragmentation of the genomic DNA by electrophoresis were observed. The apoptotic index of the primary tooth group was significantly higher than that of the permanent tooth group (51.01 +/- 0.52 versus 25.32 +/- 0.68) (p<0.001). TUNEL reaction showed intense and diffuse labeling in the pulp samples of primary teeth, which were discrete in the controls. Intense DNA internucleosomal fragmentation, a specific pattern for apoptosis, was observed in primary tooth pulps DNA by electrophoresis, in the permanent tooth pulps this pattern fragmentation of the genomic DNA for apoptosis were not present. These results seem to indicate a role of apoptosis in pulp elimination during the physiological root resorption of human primary teeth.
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Affiliation(s)
- Luciana Villela Rodrigues
- Department of General Pathology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
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Physical properties of root cementum: part 12. The incidence of physiologic root resorption on unerupted third molars and its comparison with orthodontically treated premolars: a microcomputed-tomography study. Am J Orthod Dentofacial Orthop 2009; 136:148.e1-9; discussion 148-9. [PMID: 19651333 DOI: 10.1016/j.ajodo.2009.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2007] [Revised: 05/30/2009] [Accepted: 05/30/2009] [Indexed: 11/21/2022]
Abstract
UNLABELLED INTRODUCTION Root resorption can occur as a physiologic or a pathologic process, and it is an unwanted side effect of orthodontic treatment. No baseline studies have assessed this phenomenon in the absence of force variables such as mastication, parafunction, and soft-tissue pressure. In this study, we investigated the incidence and quantitative value of root resorption on unerupted third molars with normal development using microcomputed tomography. METHODS Nine unerupted, nonimpacted maxillary third molars were collected from 6 patients (ages, 19.47 plus /minus 1.89 years). The teeth were examined with microcomputed tomography and compared with teeth from other studies. (The other teeth had been treated with buccally directed light [25 g] or heavy [225 g] forces applied for 28 days, or light [25 g] or heavy [225 g] intrusion forces for 28 days.) RESULTS Imaging and volumetric analyses showed resorption craters in many locations and with various magnitudes. Analysis of variance was completed by position (P = 0.04), surface (P = 0.07), height (P = 0.045), left or right side of the mouth (P = 0.85), and subject (P = 0.70). The midroot region on the mesial surfaces of the third molars, near the root structure of adjacent erupted second molars, had the greatest statistical significance. When compared with crater volumes of fully erupted first premolars, we found that the unerupted third molar sample had a slightly greater cube root volume per tooth than the erupted first premolars not subjected to orthodontic force and a similar cube root volume per tooth as did first premolars subjected to light (25 g) buccal and intrusive orthodontic forces. CONCLUSIONS Root resorption as a consequence of orthodontic treatment might be added to a baseline level of root resorption. The elevated results suggest that resorption might occur as part of hard-tissue remodeling and turnover, eruption, or transmission of masticatory forces through the dentition to the alveolar bone.
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Jäger A, Kunert D, Friesen T, Zhang D, Lossdörfer S, Götz W. Cellular and extracellular factors in early root resorption repair in the rat. Eur J Orthod 2008; 30:336-45. [PMID: 18632841 DOI: 10.1093/ejo/cjn012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The aim of this study was to investigate the role of extracellular matrix components, such as collagen type I, fibronectin, and osteopontin (OPN) during cementum repair following experimentally induced tooth movement, and to characterize the cells taking part in the regenerative process. The upper right first molars were moved mesially in 21 three-month-old male Wistar rats using a coil spring with a force of 0.5 N. After 9 days, the appliance was removed and the animals were killed in groups of three immediately after withdrawal of the force and 5, 7, 10, 12, 14, and 17 days later. Three rats served as non-experimental control animals. The maxillae were prepared and processed for histological analysis. Together with the disappearance of the multinucleated odontoclasts from the resorption lacunae, signs of repair were visible 5 days after the release of the orthodontic force. The first signs of cementum repair were seen on day 10. The newly produced cementum was of the acellular extrinsic fibre type (AEFC) and reattachment was achieved with the principal periodontal ligament (PDL) fibres orientated almost perpendicular to the root surface. The initial interface formed between the old and new cementum, as well as the new AEFC, was characterized by a strong immunoreaction with OPN and collagen I antibody, but only a weak immunoreaction with the fibronectin antibody. Only a small number of mononuclear cells, which were involved in the repair process, showed a positive immunoreaction with the osteoblastic lineage markers runt-related transcription factor 2 and osteocalcin. These same cells stained sparsely with muscle segment homeobox homologue 2, but not with the E11 antibody. Thus, most of the cells associated with this reparative activity on the surface of the lacunae were differentiated PDL cells of the fibroblastic phenotype. Cells with a defined osteoblastic phenotype seemed to be of minor importance in this repair process.
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Affiliation(s)
- Andreas Jäger
- Department of Orthodontics, University of Bonn, Bonn, Germany.
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Ren Y, Maltha JC, Liem RSB, Stokroos I, Marie Kuijpers-Jagtman A. Age-dependent external root resorption during tooth movement in rats. Acta Odontol Scand 2008; 66:93-8. [PMID: 18446550 DOI: 10.1080/00016350801982522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
OBJECTIVE To investigate the effect of age on root resorption and distribution along different parts of the root during prolonged light force application. MATERIAL AND METHODS Orthodontic appliances were placed in two groups of 30 rats (one group 6 weeks old, the other 9-12 months old), with contralateral sides as controls. Groups of animals were killed at 1, 2, 4, 8, and 12 weeks. At the study site, incidence was counted as either 1 (with resorption) or 0 (without); severity was measured as the summed length of all resorption lacunae as a percentage of study total root length. RESULTS Young and adult rats had the same incidence of root resorption in the early phase (<4 weeks), and both increased in the late phase (4-12 weeks) to the same level. Severity of resorption increased with prolonged tooth movement only in adult rats. However, there was no age-related difference in either the early or the late phase. In both groups, the middle part of the root had the highest incidence of resorption; the most severe resorption occurred exclusively at this part. CONCLUSION Orthodontic intervention even with light forces increased both the incidence and severity of root resorption, the more so in the middle part of the root. Adult rats had increased incidence and severity with prolonged tooth movement.
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Rapid tooth movement through distraction osteogenesis of the periodontal ligament in dogs. Chin Med J (Engl) 2008. [DOI: 10.1097/00029330-200803010-00017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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Tsuchiya M, Akiba Y, Takahashi I, Sasano Y, Kashiwazaki J, Tsuchiya S, Watanabe M. Comparison of expression patterns of cathepsin K and MMP-9 in odontoclasts and osteoclasts in physiological root resorption in the rat molar. ACTA ACUST UNITED AC 2008; 71:89-100. [DOI: 10.1679/aohc.71.89] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Masahiro Tsuchiya
- Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry
| | | | - Ichiro Takahashi
- Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry
| | - Yasuyuki Sasano
- Division of Craniofacial Development and Regeneration, Tohoku University Graduate School of Dentistry
| | - Jun Kashiwazaki
- Division of Craniofacial Development and Regeneration, Tohoku University Graduate School of Dentistry
| | - Shinobu Tsuchiya
- Division of Oral Dysfunction Science, Tohoku University Graduate School of Dentistry
| | - Makoto Watanabe
- Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry
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Foo M, Jones A, Darendeliler MA. Physical properties of root cementum: Part 9. Effect of systemic fluoride intake on root resorption in rats. Am J Orthod Dentofacial Orthop 2007; 131:34-43. [PMID: 17208104 DOI: 10.1016/j.ajodo.2005.02.030] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Revised: 01/31/2005] [Accepted: 02/15/2005] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Orthodontically induced inflammatory root resorption is a common complication in orthodontic treatment. Fluoride has been reported to have a beneficial effect against root resorption in dental traumatology. The effect of fluoride on orthodontically induced inflammatory root resorption has not been investigated. This study was undertaken to investigate the effect of fluoride on the incidence of root resorption. METHODS Thirty-two female 8-week-old Wistar rats were separated into 4 groups. Two groups (6 rats per group) were controls; they did not undergo orthodontic tooth movement. The other 2 groups (10 rats per group) had orthodontic tooth movement consisting of activated 100-g closing nickel-titanium coils (NiTi 10-000-06, GAC International, Bohemia, NY) connecting the mandibular first molar to the incisors. Fluoridated water (100 ppm) was given ad libitum to 1 control and 1 experimental group. The other 2 groups received deionized water. After 2 weeks, the animals were killed, and the samples were harvested. Resorption craters were scanned with a Micro CT (SkyScan 1072, Aartselaar, Belgium). Software analysis of the scanned samples provided a volumetric measurement of the resorption craters on the mandibular molar cementum surface. RESULTS Resorption sites were found in the control samples, especially on the distal surfaces; this could be attributed to normal physiological tooth drift. Resorption sites were significantly (P <.05) increased in the groups receiving orthodontic tooth movement. CONCLUSIONS Fluoride reduces the size of resorption craters, but the effect is variable and not statistically significant (P >.05).
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Affiliation(s)
- Matthew Foo
- Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney, Australia
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Roberts WE, Roberts JA, Epker BN, Burr DB, Hartsfield JK. Remodeling of Mineralized Tissues, Part I: The Frost Legacy. Semin Orthod 2006. [DOI: 10.1053/j.sodo.2006.08.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Sahara N, Ozawa H. Cementum-like tissue deposition on the resorbed enamel surface of human deciduous teeth prior to shedding. ACTA ACUST UNITED AC 2004; 279:779-91. [PMID: 15278949 DOI: 10.1002/ar.a.20069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Prior to the shedding of human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentin, and this resorption occasionally extends coronally from the dentinoenamel junction into the enamel. After the end of resorption, however, the resorbed enamel surface is repaired by the deposition of a cementum-like tissue. Using this phenomenon as an observation model, in this study we examined the sequence of cellular and extracellular/matrix events involved in the enamel resorption repair by light and electron microscopy. As the odontoclast terminated its resorption activity, it detached from the resorbed enamel surface; thereafter, numerous mononuclear cells were observed along the resorbed enamel surface. Most of these mononuclear cells made close contact with the resorbed enamel surface, and coated pits or patches were observed on their plasma membrane facing this surface. Furthermore, they frequently contained thin needle- or plate-like enamel crystals in their cytoplasmic vacuoles as well as secondary lysozomes. Following the disappearance of these monononuclear cells, the resorbed enamel surface now displayed a thin coat of organic matrix. Ultrastructurally, this organic layer was composed of a reticular and/or granular organic matrix, but contained no collagen fibrils. Energy-dispersive X-ray microanalysis of this thin organic layer in undecalcified sections revealed small spectral peaks of Ca and P. Cementum-like tissue initially formed along this thin organic layer, increased in width, and appeared to undergo mineralization as time progressed. The results of our observations demonstrate that regardless of type of matrix of dental hard tissues, tooth repair may be coupled to tooth resorption, and suggest that mononuclear cells and an organic thin layer found on the previously resorbed enamel surface may play an important role in the repair process initiated after resorption of the enamel.
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Affiliation(s)
- Noriyuki Sahara
- Department of Oral Histology and Institute for Oral Science, Matsumoto Dental University, Nagano 399-0781, Japan.
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