Root Resorption of Maxillary Posterior Teeth after Rapid Maxillary Expansion: A Comprehensive Review of the Current Evidence from in-vitro and in-vivo Studies



The application of heavy forces to the dentition, as those produced during a Rapid Maxillary Expansion (RME), has been associated in the literature with the development of root resorption of maxillary posterior teeth.


The aim of the present manuscript was to report the available data from in-vitro and in-vivo studies that can elucidate the biological processes of resorption and repair of radicular cementum after RME.


Studies evaluating the occurrence of root resorption after RME by means of histological and radiographic methodology were included. We detailed the changes of the radicular anatomy after RME and provided a synthesis of the most valuable scientific evidence showing the biological processes behind the potential modifications of radicular anatomy. Results. Loss of cementum material and reduction of radicular volumes were seen after rapid maxillary expansion. A small radicular volumetric recovery of anchored teeth occurred after the retention period; this reparative phenomenon was caused by cementum deposition without the reattachment of periodontal fibers, supporting the detrimental effects associated with RR.


Retention period and the timing of radiographic examination could influence the extension of radicular resorption detected after RME since root resorption and cementum repair may occur at the same time at this stage.

Keywords: Rapid maxillary expansion, Maxillary expansion, Orthodontic treatment, Root resorption, Dental root, External root resorption.


Root Resorption (RR) is defined as the dissolution of cementum and dentin of dental roots, in the form of both a physiologic or pathologic condition [1]. RR is also an inevitable sequela of the orthodontic treatment, being dependent on patients’ predisposition and orthodontic mechanics used as etiological factors [2]. Nevertheless, when orthodontic treatment causes RR, it generally does not interfere with the physiologic function of the involved teeth, despite that definitive conclusion cannot be drawn [3].

Among different orthodontic therapies, Rapid Maxillary Expansion (RME) is the treatment of choice for the correction of transversal maxillary deficiency and associated crossbite [4, 5] in growing subjects. During RME, heavy forces are transmitted to the maxilla by the anchored teeth. Those forces cause the hyalinization of the periodontal ligament, preventing dental movement and favoring skeletal expansion [6]. However, skeletal expansion is reached before orthopedic forces are completely dissipated and, consequently, the residual forces stored in the appliance start to move the anchored teeth. At this stage, the side effects related to the orthodontic movement and the sequelae of periodontal ligament hyalinization may occur, namely, buccal bone plate reduction and RR [7-9]. Considering the high prevalence of crossbite among children and youngsters [10], clinicians must be deeply aware of the potential side-effects of RME protocol on the dento-alveolar complex and of the underlying biological phenomena.

In the present paper, we describe in detail the changes in the radicular anatomy that can occur after the RME protocol. In particular, the aim of the present study was to provide a synthesis of the most valuable scientific evidence explaining the biological processes behind the occurrence of resorption and repair phenomena of radicular cementum after RME.


The information as well as the data discussed in the present review were obtained from the most relevant studies addressing the evaluation of root resorption from clinical assessment, histological materials and radiographic investigation (Cone-beam computed tomography). Table 1 shows the most relevant studies assessing the occurrence of Root resorption (RR) after Rapid Maxillary Expansion (RME).

2.1. Clinical Assessment of Root Resorption

The clinical assessment of RR is difficult to achieve due to the lack of clinical pathognomonic symptoms referred by patients. For instance, clinicians generally notice signs of RR through routine examinations such as panoramic or periapical radiographs [11]. However, conventional 2-D radiography shows large inaccuracies in detecting RR, especially when it is located at the buccal or lingual root surface [12], as it may occur after RME. In this respect, literature provides reliable data of root resorption after RME obtained from in-vitro studies using histological material or from in-vivo studies using CBCT-derived volumetric data of dental root [13-26].

2.2. Data of Root Resorption after RME from Histological Material

Barber and Sims [13] examined the roots of extracted premolars, used as anchorage units during RME, by Scanning Electron Microscope (SEM) and found that all specimens Exhibited External Root Resorption (ERR). Most root resorption occurs on the buccal surface of the roots [14-16] in the form of small irregularly shaped lacunae. This can be attributed to the direction of the heavy forces generated by RME protocol that is orientated towards the buccal side of the dentoalveolar arch, thus causing the compression of the periodontal ligament and, consequently, hyalinization on the buccal side of the roots [7, 17]. The area of resorption is mostly located at the buccal radicular surface but to some extent on the mesial, distal, and apical portions of the roots. Similarly, Odenrick et al. [16] reported large areas of resorption on the premolars extracted soon after the end of expansion, as assessed by light microscopy. In both studies [13, 16], the histological data disagreed with radiographic examinations that revealed no signs of ERR on the same premolars. Despite that the reliability of histological evaluation of ERR has been questioned [18] due to the destruction and loss of material during preparation [19], this discordance between histological and radiographic findings suggested that ERR likely was partially undetected or underestimated in the 2D radiographic studies [9].

Previous histologic evidences [13, 16] have suggested that the formation of resorption lacunae is not permanent and that the resorption cavities can be filled by subsequent deposition of hard tissue. However, these studies failed to identify the reattachment of periodontal fibers in the areas of reparative cementum deposition. Accordingly, Langford and Sims [8] showed that the cellular cementum obtained by repair deposition was constituted of scarce and inconsistent Sharpey’s fibres and, thus, it was different from that of normal cellular cementum. These findings would suggest that the cementum repair of a root defect could not be associated with the reattachment of principal periodontal fibers, supporting the detrimental effects associated with RR.

Table 1.
Most relevant studies assessing the occurrence of Root Resorption (RR) after Rapid Maxillary Expansion (RME).
Study Design Study Sample Maxillary
Assessment of RR
Assessment of RR
Barber and Sims 1981 Clinical Trial 9 subjects No RR assessed via
periapical radiograph
Extended RR
assessed via SEM
Odenrick et al. 1991 Clinical Trial 9 subjects Haas and Hyrax
No RR assessed via
periapical radiograph
Extended RR
assessed via LM
Langford and Sims 1982 Clinical Trial 18 subjects Hyrax expander - Extended RR assessed via SEM and subsequent repair deposition of cementum without Sharpey’s fibres and periodontal fibers reattachment
Baysal et al. 2012 Retrospective 25 subjects Hyrax expander Reduced radicular volume
after RME assessed via CBCT. No significant differences in the percentage of volume loss
Dindaroğlu and Doğan 2016 Clinical Trial 33 subjects Haas and Hyrax
Significant root volume loss was observed in both the Hyrax and the Haas appliances, assessed via CBCT. The repair was observed in resorption cavities after 6 months of retention -
SEM = Scanning Electron Microscope; LM = Light Microscopy; CBCT = Cone-beam Computed Tomography

2.3. Data of Root Resorption after RME from CBCT Studies

In the last decade, the usage of Cone-Beam Computed Tomography (CBCT) has been widespread in dentistry [20-22]. In this regard, CBCT scans provide 3-D images of dentoalveolar structures without projection errors, also showing less artifacts compared to conventional CT [21]. Concerning the development of radicular resorption cavities, CBCT has shown greater accuracy in detecting in-vitro simulated RR compared to conventional periapical radiographs [11]. Besides, CBCT allows for the detection of radicular volume changes which is of great relevance for recording RR, since this phenomenon can provoke dental volume loss and be underestimated if assessed via bidimensional analysis of root length [23].

Previous CBCT studies have compared the radicular volumes before and after RME and have suggested that skeletal maxillary expansion induces radicular volume loss of posterior teeth [14, 24, 25]. In these studies, maxillary first molars were the teeth most affected by radicular resorption ranging from 83.12 mm3 to 37.4 mm3. First premolars and second premolars were affected by radicular volume loss ranging from 40.86 mm3 to 13.12 mm3 from 37.64 mm3 to 13.93 mm3, respectively. According to the findings of Baysal [24] and Dindaroğlu [25], maxillary first molars loosed up to 6.87% of total volume [25] or from 10.50% to 13.70% of the volume for each root [24]. Also, first and second premolars showed a total volume reduction respectively from 5.58% to 7.21% and from 5.77% to 6.47% [24, 25]. Such volumetric loss was found immediately after the active treatment phase [24-26]and after almost five months of retention [14].


Given the above-mentioned findings, it can be assumed that root development is disrupted by the application of heavy forces, as those produced by rapid maxillary expansion. However, the retention period and the timing of radiographic examination can influence the extension of radicular resorption detected after RME. Histological findings revealed that RR is sustained long after termination of the active phase of RME and suggested that the cumulated forces stored in the appliance may support the radicular resorption even during the retention period [3, 15, 27, 28]. According to Barber and Sims [13], it could be possible that even the relapse forces extending later into treatment (up to 9 months) may additionally contribute to forces on the dentition with the expansion devices operating as retainers.

While a direct correlation between the total area of resorption and the timing retention period was not found, data from histological materials [8, 13, 16] showed an increase in cementum repair with longer periods of retention. In this respect, Cheng [29] postulated that the cementum reparative process could start when the orthodontic forces are below a certain level. Accordingly, Dindaroğlu et al. [25] found, in their CBCT study, a small radicular volumetric recovery of anchored teeth after the retention period of RME protocol. The values of volumetric gain found in this study ranged from 4.43 mm3 for first premolars to 25.14 mm3 for first molars and reflected the amount of reparative cementum that occurred at this stage. Thus, it can be assumed that both RR and cementum repair may occur at the same time during the retention period, with the former process prevailing to an amount that is influenced by several variables such as age, skeletal maturity, biological response and type of maxillary expansion. Therefore, sequential radiographic monitoring should be required to detect the maximum extension of RR. However, this is not possible considering the ethical limitation related to the patients’ radiation exposure [30-32]. For the same reason, CBCT examination taken at 6 months of retention may be insufficient to appreciate the full extension of radicular volumetric recovery, which suggests tissue repair. In this regard, volumetric assessment of radicular hard tissue could not provide an accurate appraisal of functional surface area with periodontal fibers attachment [9, 33-36]. Despite the fact that the radicular volumetric recovery (repair process) obtained during retention can mitigate the total volumetric damage occurred after RME, the alternation between resorption and later reparative processes could significantly and irremediably affect the periodontal ligament support in the interested areas, according to the histological findings available.

Further investigation is warranted both from a histological and an in vivo 3D radiographic approach. More studies involving the 3D evaluation of root resorption comparing various appliance designs and retention periods are also required in order to further elucidate the aspects related to the RR after RME [37].

3.1. The Alternative Treatment Approach to Reduce the Risk of Root Resorption after RME

Skeletal anchorage has been proposed to increase the skeletal effect of RME, limiting dentoalveolar issues and the associated side-effects [38-40]. Recent comparative findings suggest that bone-borne RME induces greater opening of the mid-palatal suture reducing the excessive load caused by conventional appliances onto the buccal periodontal ligament of teeth to which they are anchored [41-43]. With this notion in mind, it has been speculated that skeletal anchorage could potentially alleviate the development of side-effects caused by RME on premolars and molars used as anchorage with conventional tooth-borne expander [43]. As a consequence, miniscrew-supported palatal expander may be a possible treatment alternative to reduce the risk of root resorption of maxillary posterior teeth. However, the management of RME supported by skeletal anchorage could be more arduous than conventional system (toot-borne) since miniscrews could undergo fracture under excessive load or when smaller diameters are used [44, 45]; additionally, infections of the insertion site is another complication that can occur with the usage of miniscrews [46].

Considering the prevalence of transverse maxillary deficiency among children and adolescents [10], the awareness of the risks associated with the use of a tooth-borne and a bone-borne RME appears clinically relevant and future studies including subjects treated with tooth-borne and bone-borne maxillary expander are required to compare the risk of root resorption between the two groups.


The present review focused on the adaptive phenomena occurring in the radicular portion of maxillary posterior teeth after the application of heavy forces as those produced by RME protocol. Previous evidence suggests that both root resorption and cementum repair are involved in RME. However, the retention period and the timing of radiographic examination can influence the extension of radicular resorption detected after RME, since root resorption and cementum repair may occur at the same time at this stage. A sequential radiographic monitoring should be required to detect the maximum extension of RR. However, this is not possible considering the ethical limitation related to the patients’ radiation exposure.


Not applicable.




The authors declare no conflict of interest, financial or otherwise.


V. R. research strategy, F.C. writing, G. F. co-writing, O. B. investigation, C. C. revision, A. L.G. supervision and conceptualization.


Blake M, Woodside DG, Pharoah MJ. A radiographic comparison of apical root resorption after orthodontic treatment with the edgewise and speed appliances. Am J Orthod Dentofacial Orthop 1995; 108(1): 76-84.
Brezniak N, Wasserstein A. Root resorption after orthodontic treatment: Part 2. Literature review. Am J Orthod Dentofacial Orthop 1993; 103(2): 138-46.
Weltman B, Vig KW, Fields HW, Shanker S, Kaizar EE. Root resorption associated with orthodontic tooth movement: a systematic review. Am J Orthod Dentofacial Orthop 2010; 137(4): 462-76.
Liu S, Xu T, Zou W. Effects of rapid maxillary expansion on the midpalatal suture: a systematic review. Eur J Orthod 2015; 37(6): 651-5.
Lo Giudice A, Fastuca R, Portelli M, et al. Effects of rapid vs slow maxillary expansion on nasal cavity dimensions in growing subjects: a methodological and reproducibility study. Eur J Paediatr Dent 2017; 18(4): 299-304.
Zhou Y, Long H, Ye N, et al. The effectiveness of non-surgical maxillary expansion: a meta-analysis. Eur J Orthod 2014; 36(2): 233-42.
Lo Giudice A, Barbato E, Cosentino L, Ferraro CM, Leonardi R. Alveolar bone changes after rapid maxillary expansion with tooth-born appliances: a systematic review. Eur J Orthod 2018; 40(3): 296-303.
Langford SR, Sims MR. Root surface resorption, repair, and periodontal attachment following rapid maxillary expansion in man. Am J Orthod 1982; 81(2): 108-15.
Forst D, Nijjar S, Khaled Y, Lagravere M, Flores-Mir C. Radiographic assessment of external root resorption associated with jackscrew-based maxillary expansion therapies: a systematic review. Eur J Orthod 2014; 36(5): 576-85.
da Silva Filho OG, Santamaria M Jr, Capelozza Filho L. Epidemiology of posterior crossbite in the primary dentition. J Clin Pediatr Dent 2007; 32(1): 73-8.
Yi J, Sun Y, Li Y, Li C, Li X, Zhao Z. Cone-beam computed tomography versus periapical radiograph for diagnosing external root resorption: A systematic review and meta-analysis. Angle Orthod 2017; 87(2): 328-37.
Westphalen VP, Gomes de Moraes I, Westphalen FH, Martins WD, Souza PH. Conventional and digital radiographic methods in the detection of simulated external root resorptions: a comparative study. Dentomaxillofac Radiol 2004; 33(4): 233-5.
Barber AF, Sims MR. Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study. Am J Orthod 1981; 79(6): 630-52.
Akyalcin S, Alexander SP, Silva RM, English JD. Evaluation of three-dimensional root surface changes and resorption following rapid maxillary expansion: a cone beam computed tomography investigation. Orthod Craniofac Res 2015; 18(Suppl. 1): 117-26.
Langford SR. Root resorption extremes resulting from clinical RME. Am J Orthod 1982; 81(5): 371-7.
Odenrick L, Karlander EL, Pierce A, Kretschmar U. Surface resorption following two forms of rapid maxillary expansion. Eur J Orthod 1991; 13(4): 264-70.
Leonardi R, Lo Giudice A, Rugeri M, Muraglie S, Cordasco G, Barbato E. Three-dimensional evaluation on digital casts of maxillary palatal size and morphology in patients with functional posterior crossbite. Eur J Orthod 2018; 40(5): 556-62.
Chan EK, Darendeliler MA. Exploring the third dimension in root resorption. Orthod Craniofac Res 2004; 7(2): 64-70.
Amano M, Agematsu H, Abe S, et al. Three-dimensional analysis of pulp chambers in maxillary second deciduous molars. J Dent 2006; 34(7): 503-8.
Lo Giudice A, Rustico L, Caprioglio A, Migliorati M, Nucera R. Evaluation of condylar cortical bone thickness in patient groups with different vertical facial dimensions using cone-beam computed tomography. Odontology 2020; 108(4): 669-75. Epub ahead of print
Scarfe WC, Farman AG, Sukovic P. Clinical applications of cone-beam computed tomography in dental practice. J Can Dent Assoc 2006; 72(1): 75-80.
Guerrero ME, Jacobs R, Loubele M, Schutyser F, Suetens P, van Steenberghe D. State-of-the-art on cone beam CT imaging for preoperative planning of implant placement. Clin Oral Investig 2006; 10(1): 1-7.
Wang Y, He S, Guo Y, Wang S, Chen S. Accuracy of volumetric measurement of simulated root resorption lacunas based on cone beam computed tomography. Orthod Craniofac Res 2013; 16(3): 169-76.
Baysal A, Karadede I, Hekimoglu S, et al. Evaluation of root resorption following rapid maxillary expansion using cone-beam computed tomography. Angle Orthod 2012; 82(3): 488-94.
Dindaroğlu F, Doğan S. Evaluation and comparison of root resorption between tooth-borne and tooth-tissue borne rapid maxillary expansion appliances: A CBCT study. Angle Orthod 2016; 86(1): 46-52.
Forst DD. External root resorption associated with maxillary expansion therapies as evaluated via cone beam computed tomography: A retrospective randomized clinical trial. Canada: University of Alberta. Master Thesis, Edmonton 2015.2015.
Isola G, Anastasi GP, Matarese G, et al. Functional and molecular outcomes of the human masticatory muscles. Oral Dis 2018; 24(8): 1428-41.
Isola G, Polizzi A, Iorio-Siciliano V, Alibrandi A, Ramaglia L, Leonardi R. Effectiveness of a nutraceutical agent in the non-surgical periodontal therapy: a randomized, controlled clinical trial. Clin Oral Investig 2020.
Cheng LL, Türk T, Elekdağ-Türk S, Jones AS, Petocz P, Darendeliler MA. Physical properties of root cementum: Part13. Repair of root resorption 4 and 8 weeks after the application of continuous light and heavy forces for 4 weeks: a microcomputed-tomography study Am J OrthodDentofacialOrthop 2009; 136, 320: e1-e10.
Cordasco G, Portelli M, Militi A, et al. Low-dose protocol of the spiral CT in orthodontics: comparative evaluation of entrance skin dose with traditional X-ray techniques. Prog Orthod 2013; 14: 24.
Leonardi R. Cone-beam Computed Tomography and Three-Dimensional Orthodontics. J Orthod 2019; 46(1): 45-8.
Leonardi RM, Aboulazm K, Giudice AL, et al. Evaluation of mandibular changes after rapid maxillary expansion: a CBCT study in youngsters with unilateral posterior crossbite using a surface-to-surface matching technique. Clin Oral Investig 2020. [published online ahead of print, 2020 Aug 2].
Isola G, Alibrandi A, Rapisarda E, Matarese G, Williams RC, Leonardi R. Association of vitamin D in patients with periodontitis: A cross-sectional study. J Periodontal Res 2020; 55(5): 602-12. [published online ahead of print, 2020 Mar 16].
Isola G, Giudice AL, Polizzi A, Alibrandi A, Patini R, Ferlito S. Periodontitis and tooth loss have negative systemic impact on circulating progenitor cell levels: A clinical study. Genes (Basel) 2019; 10(12): 1022.
Isola G, Alibrandi A, Currò M, et al. Evaluation of salivary and serum ADMA levels in patients with periodontal and cardiovascular disease as subclinical marker of cardiovascular risk. J Periodontol 2020. [published online ahead of print, 2020 Jan 7].
Isola G, Polizzi A, Santonocito S, Alibrandi A, Ferlito S. Expression of salivary and serum malondialdehyde and lipid profile of patients with periodontitis and coronary heart disease. Int J Mol Sci 2019; 20(23): 6061.
Lo Giudice A, Galletti C, Gay-Escoda C. CBCT assessment of radicular volume loss after rapid maxillary expansion: A systematic review J ClinExp Dent 2018; 1, 10(5): e484-94.
Krüsi M, Eliades T, Papageorgiou SN. Are there benefits from using bone-borne maxillary expansion instead of tooth-borne maxillary expansion? A systematic review with meta-analysis. Prog Orthod 2019; 20(1): 9.
Lo Giudice A, Quinzi V, Ronsivalle V, Martina S, Bennici O, Isola G. Description of a digital work-flow for CBCT-guided construction of micro-implant supported maxillary skeletal expander. Materials (Basel) 2020; 13(8): 1815.
Lo Giudice A, Ronsivalle V, Lagravere M, Leonardi R, Martina S, Isola G. Transverse dentoalveolar response of mandibular arch after rapid maxillary expansion (RME) with tooth-borne and bone-borne appliances:A CBCT retrospective study. Angle Orthod in press
Celenk-Koca T, Erdinc AE, Hazar S, Harris L, English JD, Akyalcin S. Evaluation of miniscrew-supported rapid maxillary expansion in adolescents: A prospective randomized clinical trial. Angle Orthod 2018; 88(6): 702-9.
Akyalcin S, McIver HP, English JD, Ontiveros JC, Gallerano RL. Effects of repeated sterilization cycles on primary stability of orthodontic mini-screws. Angle Orthod 2013; 83(4): 674-9.
Lo Giudice A, Leonardi R, Ronsivalle V, et al. Evaluation of pulp cavity/chamber changes after tooth-borne and bone-borne rapid maxillary expansions: a CBCT study using surface-based superimposition and deviation analysis. Clin Oral Investig in press
Scribante A, Montasser MA, Radwan ES, et al. Reliability of Orthodontic Miniscrews: Bending and Maximum Load of Different Ti6Al-4V Titanium and Stainless Steel Temporary Anchorage Devices (TADs). Materials (Basel) 2018; 5; 11(7): 1138.
Sfondrini MF, Gandini P, Alcozer R, Vallittu PK, Scribante A. Failure load and stress analysis of orthodontic miniscrews with different transmucosal collar diameter. J Mech Behav Biomed Mater 2018; 87: 132-7.
Andrucioli MCD, Matsumoto MAN, Fukada SY, et al. Quantification of pro-inflammatory cytokines and osteoclastogenesis markers in successful and failed orthodontic mini-implants. J Appl Oral Sci 2019; 7, 27: e20180476.