An evaluation of root resorption incident to orthodontic intrusion

A 3D finite element analysis of biomechanical effects on teeth and bone during true intrusion of anteriors using miniscrews

PURPOSE

The primary objective of this study was to investigate the biomechanical effects and stresses on bone, periodontal ligament (PDL), cementum and displacement along X-, Y- and Z-axis during true intrusion of incisors using mini-implants with Finite Element Analysis; the secondary objective of the study was to find out the best method for anterior intrusion in clinical practice to treat anterior deep bite malocclusions.

MATERIALS AND METHODS

A 3D finite element method was used to simulate true anterior intrusion with sliding mechanics using mini-implants. Two groups were modelled with mini-implants placed distal to lateral incisors for Model 1, and below the anterior nasal spine (ANS) for Model 2, to achieve intrusion. von Mises stress, principal stress on PDL and alveolar bone, displacements in all 3 planes were determined.

RESULTS

Amongst the modalities compared in the present study, the stresses on bone and PDL were showing best behavior for mini-implants placed distal to lateral incisors (Model 1). The teeth showed controlled tooth movement in Model 1.

CONCLUSION

Maximum stress was found in the cortical bone and in the PDL. Nature of the stress changed from compressive to tensile from cervical area to root apex, concentrating mainly at the apical area. Amongst the modalities compared, the best controlled tooth movements for anterior intrusion to treat anterior deep bite malocclusions, was for mini-implants placed distal to lateral incisors (Model 1).

Factors affecting external apical root resorption of maxillary incisors associated with microimplant-assisted rapid palatal expansion

Objective

To measure and compare the extent of root resorption in the maxillary incisors following microimplant-assisted rapid palatal expansion (MARPE) and to identify risk factors of root resorption after expansion.

Methods

Cone-beam computed tomography images were obtained from a total of 60 patients both before expansion (T1) and 3 to 6 months after expansion (T2). Measurements taken included tooth length, root length, crown length and center of resistance. Resorption length (RL) and resorption length percentage (RLp), resorption volume (RV) and resorption volume percentage (RVp) and the amount of expansion were calculated.

Results

A significant difference in tooth length and volume was observed in both the central and lateral incisors before and after expansion. The resorption index (RL, RLp, RV, RVp) was significantly higher in the central incisors than in the lateral incisor. There was a significant correlation between several factors: age and RLp of the central incisors, the amount of expansion and RVp of the central incisors, tooth length of the central incisors and RL, RLp of the central incisors, root/crown ratio of the central incisors and RL of the central incisors, as well as tooth length of the lateral incisors and the RL of the lateral incisors.

Conclusions

Significant root resorption occurs in maxillary incisors following MARPE, with central incisors root resorption being significantly higher than lateral incisors. Key risk factors for root resorption after MARPE include advanced age, a larger amount of expansion, initial tooth length, and a root/crown ratio.

Factors that may increase the risk of external apical root resorption during orthodontic treatment : Retrospective clinical investigation

PURPOSE

To determine the correlation between external apical root resorption and malocclusion-related variables in patients treated with fixed orthodontic appliances.

METHODS

In all, 103 patients aged 12-15 years and treated with edge-wise appliances either without extractions or with four premolar extractions were included in this retrospective cohort study. External apical root resorption was assessed in the pre- and posttreatment panoramic radiographs of these patients for incisors, canines, premolars, and first molars. A total of 2332 teeth were evaluated in 206 panoramic radiographs obtained from 103 patients. The gender of the patients, duration of orthodontic treatments, presence of premolar extractions, Angle classification, overbite, overjet and amount of crowding were assessed. Wilcoxon signed-rank test, Mann-Whitney U test, and Kruskal-Wallis test were used for statistical analysis of the data.

RESULTS

Statistically significant (p < 0.001) root resorption occurred in all examined teeth during orthodontic treatment. The degree of root resorption observed in the premolars was significantly greater in premolar extraction cases than in nonextraction cases. Statistically significant negative correlations were found between the degree of root resorption of the maxillary lateral teeth and between the maxillary first premolar teeth and the amount of maxillary crowding.

CONCLUSIONS

The orthodontic treatment protocols and the amount of tooth movements achieved were shown to be dependent on the severity of dental malocclusions and they have an influence on the amount of external apical root resorption that occurs during the course of orthodontic treatment.

Periodontal considerations during orthodontic intrusion and extrusion in healthy and reduced periodontium

In patients with advanced periodontal disease, pathological tooth migration may occur, which may require subsequent orthodontic treatment for both aesthetic and functional purposes. When planning orthodontic treatment mechanics, intrusive or extrusive forces are frequently indicated. Understanding tissue reactions during these movements is essential for clinicians when devising a comprehensive orthodontic-periodontal treatment plan. This knowledge enables clinicians to be fully aware of and account for the potential effects on the surrounding tissues. The majority of our understanding regarding the behavior of periodontal tissues in both healthy and compromised periodontal conditions is derived from animal studies. These studies offer the advantage of conducting histological and other assessments that would not be feasible in human research. Human studies are nevertheless invaluable in being able to understand the clinically relevant response elicited by the periodontal tissues following orthodontic tooth movement. Animal and human data show that in dentitions with reduced periodontal support, orthodontic intrusion of the teeth does not induce periodontal damage, provided the periodontal tissues do not have inflammation and plaque control with excellent oral hygiene is maintained. On the contrary, when inflammation is not fully controlled, orthodontic intrusion may accelerate the progression of periodontal destruction, with bacterial plaque remnants being displaced subgingivally, leading to further loss of attachment. Orthodontic extrusion, on the other hand, does not seem to cause further periodontal breakdown in dentitions with reduced periodontal support, even in cases with deficient plaque control. This is attributed to the nature of the tooth movement, which directs any plaque remnants coronally (supragingivally), reducing the risk of adverse effects on the periodontal tissues. This specific type of tooth movement can be leveraged to benefit periodontal conditions by facilitating the regeneration of lost hard and soft periodontal tissues in a coronal direction. As a result, orthodontic extrusion can be employed in implant site development, offering an advantageous alternative to more invasive surgical procedures like bone grafting. Regardless of the tooth movement prescribed, when periodontal involvement is present, it is essential to prioritize periodontal therapy before commencing orthodontic treatment. Adequate plaque control is also imperative for successful outcomes. Additionally, utilizing light orthodontic forces is advisable to achieve efficient tooth movement while minimizing the risk of adverse effects, notably root resorption. By adhering to these principles, a more favorable and effective combined orthodontic-periodontal approach can be ensured. The present article describes indications, mechanisms, side effects, and histological and clinical evidence supporting orthodontic extrusion and intrusion in intact and reduced periodontal conditions.

A 3D Finite Element Analysis of biomechanical effects on teeth and bone during true intrusion of posteriors using miniscrews

OBJECTIVE

The primary objective of this study was to investigate the biomechanical effects and stresses on bone, PDL, cementum and displacement along X-,Y- and Z-axis during true intrusion of molars using mini-implants with finite element analysis; the secondary objective of the study was to find out the best method for posterior intrusion in clinical practice.

MATERIAL AND METHODS

A 3D finite element method was used to simulate true molar intrusion using sliding mechanics. Two groups were made, with mini-implants placed on buccal side and palatal side with a cap splint for MODEL1, and a single mini-implant placed buccally with transpalatal arch (TPA) for MODEL2. The material characteristics which include the Young's modulus and Poison's ratio were assigned. von Mises stress, principal stress on PDL and alveolar bone, displacements in all the 3 planes were determined.

RESULTS

Bone stress patterns showed compressive stresses on the buccal aspect and tensile stresses on the palatal aspect for both MODELS. Stresses in the PDL and cementum were mainly concentrated in the apex region, with a more uniform distribution of stresses for MODEL 1. Tooth displacement showed true intrusion for both MODELS, i.e. the Z axis, and a more controlled buccal tipping for MODEL 1.

CONCLUSION

Of the modalities compared, the best controlled tooth movements for posterior intrusion in the treatment of open bite were obtained with mini-implants placed with a cap splint (MODEL 1).

Root resorption of maxillary incisors after en masse intrusion and retraction with controlled tipping versus bodily movement in adults

INTRODUCTION

The purpose of this study was to evaluate and compare the incidence of orthodontically induced inflammatory root resorption (OIIRR) after en masse maxillary incisors intrusion and retraction with controlled tipping versus bodily movement using cone beam computed tomography (CBCT).

MATERIAL AND METHODS

This study is a retrospective study performed on CBCT scans of 36 adult females who had their maxillary first premolars extracted followed by en masse anterior retraction and intrusion using labial biocreative therapy type II. Subjects were divided into two groups of 18 subjects each based on the type of tooth movement required during en masse retraction: Group I; the controlled tipping group, and Group II; the bodily movement group. The amount of intrusion, crown and root retraction, change in incisor inclination, and difference in tooth length was measured from the CBCT scans. Independent t tests were used to compare the measurements between the two groups. Pearson rank correlation analysis was applied to identify the relationship between the mean dental changes and the mean changes in tooth length for all four upper incisors.

RESULTS

OIIRR was found in all four maxillary incisors in both groups. No significant differences were found between the two groups. OIIRR was positively correlated to the amount of root apex retraction and negatively correlated to the change in incisor inclination.

CONCLUSIONS

Anterior retraction and intrusion lead to obvious root resorption affecting all maxillary incisors. No significant differences were found between the two groups. Careful clinical monitoring is needed for patients requiring anterior retraction with intrusion with maximum anchorage.

RANKL+ senescent cells under mechanical stress: a therapeutic target for orthodontic root resorption using senolytics

In dentistry, orthodontic root resorption is a long-lasting issue with no effective treatment strategy, and its mechanisms, especially those related to senescent cells, remain largely unknown. Here, we used an orthodontic intrusion tooth movement model with an L-loop in rats to demonstrate that mechanical stress-induced senescent cells aggravate apical root resorption, which was prevented by administering senolytics (a dasatinib and quercetin cocktail). Our results indicated that cementoblasts and periodontal ligament cells underwent cellular senescence (p21⁺ or p16⁺) and strongly expressed receptor activator of nuclear factor-kappa B (RANKL) from day three, subsequently inducing tartrate-resistant acid phosphatase (TRAP)-positive odontoclasts and provoking apical root resorption. More p21⁺ senescent cells expressed RANKL than p16⁺ senescent cells. We observed only minor changes in the number of RANKL⁺ non-senescent cells, whereas RANKL⁺ senescent cells markedly increased from day seven. Intriguingly, we also found cathepsin K⁺p21⁺p16⁺ cells in the root resorption fossa, suggesting senescent odontoclasts. Oral administration of dasatinib and quercetin markedly reduced these senescent cells and TRAP⁺ cells, eventually alleviating root resorption. Altogether, these results unveil those aberrant stimuli in orthodontic intrusive tooth movement induced RANKL⁺ early senescent cells, which have a pivotal role in odontoclastogenesis and subsequent root resorption. These findings offer a new therapeutic target to prevent root resorption during orthodontic tooth movement.

Orofacial findings and orthodontic treatment conditions in patients with down syndrome - a retrospective investigation

INTRODUCTION

The most common chromosomal anomaly is Down syndrome/Trisomy 21, which can be associated with varying degrees of intellectual disability and physical malformation. Specific orofacial characteristics regarding orthodontic treatment options and features are described on the basis of a patient collective from the Witten/Herdecke University, Germany.

METHODS

Data of 20 patients (14 boys and 6 girls, mean age: 11.69 ± 3.94 years) who underwent orthodontic treatment between July 2011 and May 2022 were analyzed. Baseline skeletal and dental conditions were assessed, as well as the presence of hypodontia, displacements, and treatment-related root resorptions. The treatment need was evaluated based on the main findings according to the German KIG classification. In addition, treatment success was determined in relation to patient compliance.

RESULTS

The patient group was characterized predominantly by a class III relationship (ΔANB: -2.07 ± 3.90°; ΔWITS: -3.91 ± 4.33 mm) and a brachyfacial cranial configuration (ΔML-NL: -4.38 ± 7.05°, ΔArGoMe: - 8.45 ± 10.06°). The transversal discrepancy of the dental arch width from maxilla to mandible was -0.91 ± 3.44 mm anteriorly and -4.4 ± 4.12 mm posteriorly. Considering the orthodontic indication groups, the most frequent initial finding and treatment indication represented hypodontia (85%), followed by frontal (75%) and unilateral lateral (35%) crossbite. In 55% of the cases, the teeth had a regular shape, but in 35% a generalized and in 15% an isolated hypoplasia. Only 25% of the patients could be treated with a fixed multiband appliance due to sufficient cooperation. In each of these patients, varying degrees of root resorptions were detected during treatment, and 45% of all treatments had to be terminated prematurely due to a lack of cooperation by patients or parents.

CONCLUSION

The extent of dental and skeletal malformations and the high rate of findings requiring treatment in patients with Down syndrome represent a significant indication for orthodontic therapy, which can be well illustrated by the KIG classification. However, this is in contrast to the eventually increased risk of root resorption, with significantly reduced patient cooperation. A compromised treatment outcome and process must be expected. Consequently, the orthodontic treatment must be simple and realistic to achieve fast and therapeutically satisfactory treatment result.

Biomechanical factors in the open gingival embrasure region during the intrusion of mandibular incisors: A new model through finite element analysis

Introduction: Open gingival embrasure (OGE) is a common complication in adults following clear aligner therapy and the influence of gingival or alveolar bone biotype on OGE is of great concern. Unfortunately, due to the limited number of patients with clearaligner therapy and the clinical methods to distinguish the gingival biotype of patients being invasive, it is difficult to carry out clinical studies on the gingival or alveolar bone biotype of the OGE. In the meanwhile, the detailed biomechanics of the occurrence of OGE remains unknown. The goal of this study was to establish a new model to simulate the virtual space region, namely, the OGE region, to investigate the relationship between alveolar bone biotype and the occurrence of OGE, and explore potential biomechanical factors related to OGE.

Methods: The OGE region in the interproximal space was established using a filler with a very low modulus of elasticity (1 × 10−6 MPa). To illustrate the biomechanics of OGE more exhaustively, a line was created at the top of the alveolar crest along the proximal tooth root. FEA was then used to analyze the biomechanics of the surrounding tissues, the OGE region and the line at the top of the alveolar crest along the proximal tooth root of the central incisor under two different labial bone thicknesses (thick and thin) with an axial inclination of 80°, 90° and 100°.

Results: During intrusion of the incisors in clear aligner therapy, as inclination increased or bone tissue became thinner, the stress in the surrounding tissues [tooth root, alveolar crest, and periodontal ligament (PDL)] was greater. In the OGE region and interproximal alveolar crest, the strain increased with increasing inclination and labial bone thinning. The results from the line at the top of the alveolar crest along the proximal tooth root showed more detailed biomechanics: In all groups, stress and strain were focused on the mesial-labial alveolar crest. Interestingly, our results also demonstrated that when OGE occurs, other complications may arise, including root resorption and bone dehiscence.

Development of a tooth movement model of root resorption during intrusive orthodontic treatment

There is a high risk of external apical root resorption (EARR) following the application of intrusive orthodontic forces to the apical root. However, there is a lack of suitable animal models to study this phenomenon in depth. This study compared the usability of three different types of loops, namely, vertical helical loop, box loop, and L loop, for preparing a rat model of orthodontic tooth movement with invasive forces. Results showed a significant downward movement in the first molar of the rat after L loop placement for 14 days. Three-dimensional reconstructed images showed root resorption and length shortening on the apical root and decreased bone volume and trabecular thickness in the alveolar bone under compression. Histological staining revealed odontoclasts on the root resorption fossa. This study showed that orthodontic tooth movement using the L loop provides an effective experimental animal model of EARR.

Comparative cone-beam computed tomographic evaluation of maxillary incisor intrusion and associated root resorption: Intrusion arch vs mini-implants

INTRODUCTION

Various literature has verified that apical root resorption is a common adverse effect of orthodontic treatment, particularly intrusion. Conventional radiographic techniques underestimated root lengths and overestimated tooth lengths. Cone-beam computed tomography (CBCT) is a useful diagnostic tool to detect orthodontically induced external apical root resorption. This prospective study aimed to compare maxillary incisor intrusion and associated root resorption via CBCT.

METHODS

Thirty patients aged 16-23 years, having a deepbite of 6-8 mm and excessive gingival display on smiling, were divided into 2 groups: group 1, with 15 patients who were treated with Burstone intrusion arch, and group 2 with 15 patients who were treated with mini-implants applying 100 g of intrusive force for 4 months with activation done every 4 weeks. During this 4-month study period, no treatment was performed other than the intrusion of incisors. CBCT scans were obtained before and after the intrusion phase of treatment to compare the amount of intrusion and associated root resorption among both groups.

RESULTS

No significant difference was found in mean incisor intrusion between groups 1 and 2 (P = 0.772), with slightly more proclination of incisors in group 1, resulting in a significant (P = 0.018) increase in the vertical change of incisal edge in group 1. A statistically significant difference was found in root resorption among both groups (P = 0.004), with more root resorption in group 2.

CONCLUSIONS

The results of this study indicate intrusion with both the intrusion systems using appropriate intrusive forces is effective in opening the bite with slightly more external apical root resorption in the mini-implant group.

Are asthma and allergy associated with increased root resorption following orthodontic treatment? A meta-analysis

OBJECTIVE

The aim of this study is to systematically investigate the available evidence from human studies regarding the association of asthma and/or allergy with EARR.

MATERIALS AND METHODS

Unrestricted searches in 6 databases and manual searching were performed up to May 2022. We looked for data on EARR after orthodontic treatment in patients with/without asthma or allergy. Relevant data were extracted, and the risk of bias was assessed. An exploratory synthesis was carried out using the random effects model, and the overall quality of the evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation.

RESULTS

From the initially retrieved records, nine studies met the inclusion criteria (three cohort and six case-control). Overall, increased EARR was observed in the individuals with allergies in their medical history (Standardised Mean Difference [SMD]: 0.42, 95% Confidence Interval [CI]: 0.19 to 0.64). No difference in EARR development was observed among individuals with or without a medical history of asthma (SMD: 0.20, 95% CI: -0.06 to 0.46). The quality of available evidence, excluding studies at high risk, was rated as moderate for the exposure to allergy, and low for the exposure to asthma.

CONCLUSION

Increased EARR was noted in individuals with allergies compared to the control group, while no difference was observed for individuals with asthma. Until more data become available, good practice would suggest that it is important to identify patients with asthma or allergy and consider the possible implications.

Efficacy of lower arch leveling, lower incisors' root resorption, and pain associated with the correction of curve of Spee using different orthodontic archwires: a randomized clinical trial

OBJECTIVES

To compare between 3 archwires (AWs) for leveling curve of Spee (COS) in terms of efficacy of reduction, external apical root resorption (EARR), pain experienced, and the lower arch dimensional changes during COS leveling.

TRIAL DESIGN

Randomized clinical trial.

SETTING

Jordan University of Science and Technology Postgraduate dental clinics.

MATERIAL AND METHODS

Fifty-three subjects with COS > 5 mm were included in this study. The subjects were randomly divided into three groups based on the AW used: group 1, 0.017 × 0.025-inch stainless-steel (SS) AW; group 2, 0.019 × 0.025-inch SS AW; and group 3, 0.021 × 0.025-inch β-titanium (TMA) AW. The intervention was randomly allocated using the permuted random block size of 3 with a 1:1:1 allocation ratio. In the three groups, a 5-mm depth reverse COS was placed in the AWs. The following time points were defined for COS assessment: T1, before interventional leveling AW placement; and T2-T7, 1-6 months after interventional leveling AW placement. Records consisted of dental study models and periapical (PA) radiographs. Pain scores were recorded using visual analogue scale. Patients were followed up on a monthly basis until COS < 1.5 mm.

MAIN OUTCOME MEASURES

COS depth reduction, lower incisors' EARR, pain scores, and arch dimensional changes.

RESULTS

An overall reduction of 3.82 mm, 4.47 mm, and 3.85 mm of the depth of COS was achieved in groups 1, 2, and 3, respectively. The mean differences of 0.65 mm between groups 1 and 2 and 0.62 mm between groups 2 and 3 were significant at P < 0.05. Lower incisors' EARR during leveling COS ranged from 0.68 to 0.72 mm, from 0.63 to 0.82 mm, and from 0.53 to 0.88 mm in groups 1, 2, and 3, respectively (P > 0.05). Higher pain scores were reported by group 2 subjects during the first 24 h. Arch length and width increased significantly in groups 2 and 3 (P < 0.05). In all groups, COS leveling was achieved by lower incisor intrusion and proclination and lower molar extrusion.

CONCLUSIONS

All investigated AWs were effective in leveling COS with minimal lower incisors' EARR (< 1 mm). COS was leveled by lower incisors' intrusion and proclination and lower molar extrusion. Pain scores were the highest in group 2 during the first 24 h.

CLINICAL RELEVANCE

The 3 investigated leveling AWs were effective for the leveling COS and at the same time safe on the roots of the lower anterior teeth.

Dynamics, Efficacies, and Adverse Effects of Maxillary Full-Arch Intrusion Using Temporary Anchorage Devices (Miniscrews): A Finite Element Analysis

Introduction

Absolute anchorages obtained from temporary anchorage devices (TADs, miniscrews) considerably facilitate dental movements and make some very difficult movements such as full-arch intrusions possible. Despite the significance of assessing strategies to fully intrude the arch using mini-implants, there is no study in this regard except a few case reports. Therefore, we simulated/tested 4 scenarios.

Methods

Four maxilla models were created with different miniscrews/appliances: (1) two miniscrews were placed distal to laterals and one in the mid sagittal region. (2) Two mini-implants were inserted in mesial of canines and 2 others between bilateral first and second molars, plus another TAD in the midpalatal area, plus a transpalatal arch (TPA). (3) Two mini-implants were inserted between bilateral canines and first premolars and 2 others between bilateral first and second molars + TPA. (4) Two mini-implants were installed between lateral-and-canine and 2 miniscrews between second premolars and first molars + TPA. Intrusive forces (80 g anterior, 150 g posterior) were exerted using stainless-steel coil springs. Stresses/displacements were measured. Risk of external root resorption was evaluated.

Results

The highest amounts of incisor/molar intrusion were seen in model 1. Model 2 had fewer intrusions, but its control over undesired movements was greater. Model 4 drastically reduced molar intrusion and considerably increased premolar intrusion. Overall amounts of intrusion were highest in the first 2 models, marking them as proper candidates for cases needing greater intrusion extents. Model 2 may be useful when miniscrew loosening/failure is a concern, while model 1 is recommended when fewer miniscrews are allowed. Overall, the highest and lowest root resorptions might occur in models 1 and 4, respectively.

Conclusions

Each model showed certain efficacies/drawbacks and thus is recommended for a particular set of cases. Therefore, depending on the diagnosis and treatment plan, one or more of these scenarios might be desirable.

Effects on root axes and resorption of simultaneous intrusion and retraction of maxillary central and lateral incisors using mini-implant supported three-piece burstone base arch: A prospective observational study

OBJECTIVE

Prospective morphometric evaluation of the positional changes and root resorption of maxillary central and lateral incisors undergoing simultaneous intrusion and retraction (SIR) using mini-implant supported 3-piece Burstone base arch.

MATERIALS AND METHODS

Bracket head type mini-implants were inserted between the maxillary second premolar and first permanent molar. After maxillary canine retraction, SIR of maxillary incisors was begun using mini-implant supported 3-piece Burstone arch. A segmental CBCT was taken before and after SIR of the maxillary four incisors. Data collected were analysed using Paired t test, ANOVA test, independent sample t test and Pearson's correlation test.

RESULTS

Sixteen patients of 17.9±1.94 years mean age with class II division 1 malocclusion, deep bite≥4mm and overjet 5-8mm were selected. All mini-implants showed good stability during treatment with no looseness. Increasing the vertical end of the anterior segment up to 10mm led to controlled tipping and partial bodily retraction of the maxillary central and lateral incisors. The centre of resistance (CRe) of the four maxillary incisors was retracted 2.38±0.77mm and intruded 2.76±1.0mm with a mean change in axial inclination of 9.76±3.45°. The mean amount of root resorption of the four incisors was 1.29±0.59mm over a mean period of 6.2 months.

CONCLUSIONS

The mini-implant supported 3-piece Burstone base arch had a pronounced effect on SIR of flared maxillary incisors with clinically insignificant amount of root resorption.

Root resorption associated with maxillary buccal segment intrusion using variable force magnitudes

OBJECTIVES

To compare the root resorption resulting from miniscrew-supported maxillary posterior dentoalveolar intrusion using two different force magnitudes.

MATERIALS AND METHODS

Adult patients with skeletal open bite, indicated for maxillary posterior dentoalveolar intrusion, were recruited and randomly assigned to the comparison or intervention groups. The comparison group involved applying 200 g of intrusive force per segment, which measured 20 g per root, while this force was 400 g per segment in the intervention group, measuring 40 g per root.

RESULTS

Twenty participants were included in the final analysis after 2 patients dropped out, 1 in each group, to end up with 10 subjects (200 roots) per group. There was statistically significant root resorption of 0.84 ± 0.96 mm and 0.93 ± 1.00 mm in the comparison and the intervention groups, respectively. However, there was no statistically significant difference between the groups.

CONCLUSIONS

Root resorption inevitably took place in association with orthodontic intrusion. However, increasing the magnitude of the intrusive force did not increase the amount of root resorption, either statistically or clinically.

An Assessment of the Effects of Orthodontic Treatment after Apexification of Traumatized Immature Permanent Teeth: A Retrospective Study

INTRODUCTION

Root resorption may occur in traumatized necrotic teeth that have undergone apexification after orthodontic treatment. This study examined the effects of orthodontic treatment on the outcome of apexification.

METHODS

This retrospective study included 36 children presenting with anterior permanent traumatized teeth with immature roots who were treated by apexification and root canal treatment. The orthodontic group consisted of 17 children with 24 teeth that were subjected to orthodontic treatment after apexification. The control group consisted of 19 children with 21 teeth that underwent only apexification without orthodontic treatment. Almost half of the teeth in both groups underwent apexification with calcium hydroxide, whereas the other half were treated with mineral trioxide aggregate. The effects of sex, stage of root development, and apexification material on the outcomes of apexification were analyzed and compared between the 2 groups.

RESULTS

Apexification was successful in 88% of cases after at least 5 years of follow-up. Neither apexification technique nor sex had a significant effect on treatment outcome. The stage of root development had a positive effect on outcome, although it was not statistically significant. Some root resorption (average = 0.3 mm) was observed after orthodontic treatment, whereas teeth that underwent apexification without orthodontic treatment exhibited some root elongation (average = 0.1 mm). This difference was highly significant.

CONCLUSIONS

Minor root resorption was observed in the orthodontic group compared with a minor increase in root length in the control group. Orthodontic movement of immature traumatized teeth after apexification appears to be safe.

Mini-Implant Assisted Gummy Smile and Deep Bite Correction

This article demonstrates the noninvasive means of correction of gummy smile and deep bite by using mini-implants in a relapsed patient. Intrusion of the maxillary arch was achieved by using mini-implants in the anterior and posterior region. Significant reduction in the gingival and incisal display was seen with improved smile esthetics and ideal overbite and overjet by the end of the treatment. The aim of the article is to present a case where gummy smile was effectively treated by mini-implants without undergoing invasive surgical procedures.

Intrusion of posterior teeth using miniplates: intrusive mechanics is not the same as intrusion force

Objective:

Biologically explain some of the bone mechanisms involved in the intrusion, or intrusive effect, of teeth submitted to skeletal open bite correction using four miniplates.

Methods:

The results of dental intrusion were measured and compared in 3D reconstructions of cone beam computed tomography scans taken before and after treatment of 20 patients with skeletal open bite, aged between 18 and 59 years.

Results:

The results allow deducing that the compression and traction forces biologically promoted deformation or deflection of the osteocyte network that controls bone design, and these effects involved the external and internal surfaces of the bone, with the formation of new layers, including the cervical portion of the alveolar bone crest. This helps understanding how dental intrusion occurs in intrusive mechanics, whose forces are of inclination rather than intrusion. The root resorptions caused by the use of miniplates were insignificant, due to the more homogeneous distribution of forces in the several teeth simultaneously involved.

Conclusion:

Imaging studies in CT scans tend to capture in details the subperiosteal and endosteal phenomena of dental intrusion - before and after the application of intrusive mechanics -, in the form of a set of modifications called dental intrusion or intrusive effect .

Evaluation of root resorption following orthodontic intrusion: a systematic review and meta-analysis

BACKGROUND/OBJECTIVE

To quantify the expected amount of orthodontically induced root resorption (OIRR) after orthodontic intrusion and assess the treatment-related factors.

SEARCH METHODS AND ELIGIBILITY CRITERIA

Six electronic databases and partial grey literature were searched without limitations regarding language or publication year until April 2020. Randomized clinical trials and non-randomized prospective and retrospective studies evaluating root resorption after orthodontic intrusion were included.

DATA COLLECTION AND ANALYSIS

Risk of bias (RoB) assessment was performed with the Cochrane Collaboration's RoB Tool 2.0 and ROBINS-I tool for the randomized and non-randomized studies, respectively. The data were combined into two random-effects meta-analyses estimating OIRR following orthodontic intrusion. One evaluated OIRR in the anterior region, while the other assessed OIRR in the posterior region. Sub-group analyses regarding the type of mechanics applied, duration of intrusion, amount of force, and sensitivity analysis of the study design and imaging examinations were also performed. The certainty of the evidence was assessed through the Grade of Recommendation, Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

The qualitative analysis included 14 studies; however, the meta-analysis was performed with 7 records. The random-effects model assumes that 0.72 mm [95% confidence interval (CI): 0.16 to 1.28] and 0.41 mm (95% CI: -0.24 to 1.07) of OIRR should be expected in the incisors and the molars, respectively. Sub-group analyses showed that the assessed treatment-related factors presented minimum impact in OIRR after orthodontic intrusion. The GRADE resulted in moderate and low certainty regarding the meta-analysis.

LIMITATIONS

The major limitation of the present meta-analysis is that OIRR can be affected by several factors, some of which are assessed in this review.

CONCLUSIONS

Orthodontic intrusion, evaluated as an isolated mechanic, caused less than 1 mm of OIRR, which is within the acceptable limits for clinical implication. Treatment-related factors did not show a significant influence on OIRR.

REGISTRATION

This review was registered in PROSPERO, protocol number CRD42018098495.

One versus two anterior miniscrews for correcting upper incisor overbite and angulation: a retrospective comparative study

Background

Miniscrews are effective devices for performing upper incisor intrusion. Different mechanics can be applied depending on the treatment objectives. This study aimed to evaluate the efficacy of one or two anterior miniscrews for upper incisor correction in cases of overbite and angulation in adult patients.

Methods

Forty-four adults with deep overbite were divided into two groups: group 1 was treated with one miniscrew between upper central incisors and group 2 with two miniscrews between upper lateral incisors and canines. Incisor intrusion and length were measured from lateral cephalograms before treatment, after treatment and at least 12 months into retention (T0, T1 and T2). Forces were applied (90 g) from the miniscrews to the archwire using elastomeric chains. ANOVA analysis was used to determine whether differences between evaluation times were statistically significant.

Results

Mean root resorption was 2.15 ± 0.85 mm, which ceased after active treatment. Overbite mean correction was − 3.23 ± 1.73 mm with no statistically significant relapse. Overbite correction and incisor intrusion were significantly greater in group 2 (− 3.80 ± 1.43 versus − 2.75 ± 1.63 for OB and 8.19 ± 3.66 versus 5.69 ± 2.66 for intrusion). Resorption and overbite correction were positively related. No counterclockwise rotation of the mandibular plane was observed.

Conclusions

Overbite correction can be performed by means of upper incisor intrusion without rotation of the mandibular plane. Correction of upper incisor intrusion and overbite is greater in patients treated with two miniscrews. The increase in upper incisor buccal angulation is greater with one miniscrew. Root resorption is positively related to the extent of intrusion. Stability is satisfactory regardless of whether one or two miniscrews are used.

Pure Mandibular Incisor Intrusion: A Finite Element Study to Evaluate the Segmented Arch Technique

Leveling the curve of Spee is a commonly-used strategy to correct deep bites. Although several techniques have been proposed to intrude mandibular incisors (MI), flaring of these teeth is often observed and in many instances undesired. A three-dimensional (3D) finite element model (FEM) was used to locate the ideal point of force application (PFA) to achieve pure MI intrusion with the three-piece arches' technique. It comprised (1) a 0.021 × 0.025 in. stainless steel (SS) wire that passively filled the slots of the canine and premolar brackets and the first and second molar tubes, bilaterally; (2) a 0.0215 × 0.0275 in. SS intrusion base arch (IBA) inserted into the MI brackets, that presented a step down distal to the lateral incisors brackets and a posterior extension arm; (3) titanium-molybdenum tip-back springs designed to apply the intrusion force, fitted inside the first molar gingival tube. Four PFA on the IBA were simulated (FEM 1, 2, 3, and 4). FEM 3 resulted in pure MI and was considered the ideal PFA. FEM1 and 2 showed intrusion and buccal crown flaring of the MI, whereas FEM4 resulted in intrusion and lingual crown flaring of those teeth. Clinicians may consider three-piece arch mechanics to achieve pure MI intrusion. However, they must be aware that when force was applied anteriorly or posteriorly to the ideal PFA, the incisors would incline labially or lingually, respectively.

Comparison of orthodontic root resorption of root-filled and vital teeth using micro-computed tomography

OBJECTIVE

To evaluate the difference in orthodontic root resorption between root-filled and vital teeth.

MATERIAL AND METHODS

Sixteen individuals who required bilateral premolar tooth extraction due to orthodontic treatment and had a previously root-filled premolar tooth on one side were included in the study. The experimental group consisted of root-filled premolar teeth, and the control group consisted of contralateral vital premolar teeth. A 150-g buccally directed force was applied to these teeth using 0.017 × 0.025-inch TMA cantilever springs. The premolars were extracted 8 weeks after the application of force. Images were obtained using micro-computed tomography. Resorption measurements were obtained using the Image J program.

RESULTS

The mean values for resorption were 0.08869 mm³ for the root-filled teeth and 0.14077 mm³ for the contralateral teeth, indicating significantly less resorption for the root-filled teeth compared with the contralateral teeth after the application of orthodontic force (P = .003). In both groups, the most resorption was seen on the cervical-buccal and apical-lingual surfaces. The mean resorption value of the cervical region was 0.06305 mm³ in the control group and 0.0291 mm³ in the experimental group, and the difference was statistically significant (P = .002).

CONCLUSIONS

Root-filled teeth showed significantly less orthodontic root resorption than vital teeth.

Extruded upper first molar intrusion: Comparison between unilateral and bilateral miniscrew anchorage

Objective:

The aim of his study was to evaluate the stress on tooth and alveolar bone caused by orthodontic intrusion forces in a supraerupted upper molar, by using a three-dimensional Finite Element Method (FEM).

Methods:

A superior maxillary segment was modeled in the software SolidWorks 2010 (SolidWorks Corporation, Waltham, MA, USA) containing: cortical and cancellous bone, supraerupted first molar, periodontal tissue and orthodontic components. A finite element model has simulated intrusion forces of 4N onto a tooth, directed to different mini-screw locations. Three different intrusion mechanics vectors were simulated: anchoring on a buccal mini-implant; anchoring on a palatal mini-implant and the association of both anchorage systems. All analyses were performed considering the minimum principal stress and total deformation. Qualitative analyses exhibited stress distribution by color maps. Quantitative analysis was performed with a specific software for reading and solving numerical equations (ANSYS Workbench 14, Ansys, Canonsburg, Pennsylvania, USA).

Results:

Intrusion forces applied from both sides (buccal and palatal) resulted in a more homogeneous stress distribution; no high peak of stress was detected and it has allowed a vertical resultant movement. Buccal or palatal single-sided forces resulted in concentrated stress zones with higher values and tooth tipping to respective force side.

Conclusion:

Unilateral forces promoted higher stress in root apex and higher dental tipping. The bilateral forces promoted better distribution without evidence of dental tipping. Bilateral intrusion technique suggested lower probability of root apex resorption.

Effect of the application of high-frequency mechanical vibration on tooth length concurrent with orthodontic treatment using clear aligners: A retrospective study

OBJECTIVES:

To evaluate the possible change in teeth lengths as an indicator of orthodontically induced tooth root resorption (OITRR) after high-frequency mechanical vibration (HFV) treatment concurrent with Invisalign Smart Track® aligners as evaluated by cone beam computed tomography (CBCT).

MATERIALS AND METHODS:

The sample, composed of 30 patients with an average age of 26 ± 11 years and Class I malocclusion with an initial anterior crowding ranging from 3 to 5 mm, was divided equally into two groups; Group I received adjunctive high-frequency mechanical vibration (HFV); Group II, the control, did not receive adjunctive mechanical treatment. The maxillary incisor's teeth lengths were measured using Mimics software before (T1) and after (T2) treatment. All data were analyzed using Student's t-test. Reliability testing was completed by randomly selecting 10 patients’ CBCTs, and their teeth lengths were measured twice by the same investigator over a 15-day interval and compared confirming intra-operator accuracy.

RESULTS:

The control group showed a statistically significant decrease in tooth lengths compared to the HFV group which showed nonstatistically significant change of tooth lengths.

CONCLUSION:

Patients treated with HFV showed minimum tooth length changes after treatment, which may indicate that HFV can reduce OITRR with treatment using clear aligners.

Volumetric evaluation of root resorption on the upper incisors using cone beam computed tomography after 1 year of orthodontic treatment in adult patients with marginal bone loss

OBJECTIVES:

To determine upper incisor root resorption, volume loss, and the relationship between root volume loss and tooth movement after 1 year of orthodontic treatment in patients with marginal bone loss.

MATERIALS AND METHODS:

A total of 30 women (46.3 ± 5.4 years old) with moderate upper incisor bone loss who required intrusion during orthodontic treatment were recruited. Pre- and post-treatment cone beam computed tomography images were reconstructed. Upper incisors at pre- and post-treatment were superimposed; labio- and palato-apical, middle, and coronal third root volumes were assessed. Tooth movement and alveolar bone height were measured from lateral cephalometric radiographs and cone beam computed tomography. Changes in root volume/alveolar bone height were compared using paired-sample t-tests, percentage root volume loss for each tooth/segment was evaluated by one-way analysis of variance, and the relationship between percentage root loss and degree of tooth movement was assessed by linear regression.

RESULTS:

Mean root volume significantly decreased on the labio- and palato-apical aspects of 12 and labio-apical aspects of 21 and 22 ( P ≤ .024). Palato-apical segment volume loss was greater on lateral than central incisors ( P ≤ .016). Two-dimensional root length and cementoenamel junction-bone crest distance did not change between T0 and T1, with no significant relationship between tooth movement amount and percentage root volume loss.

CONCLUSIONS:

Delivery of 40 g intrusive force to the four upper incisors using a T-loop and the leveling phase lead to more apical root volume loss on lateral than central incisors. There was no relationship between extent of tooth movement and upper incisor root volume loss.

Evaluation of the load system produced by a single intrusion bend in a maxillary lateral incisor bracket with different alloys

OBJECTIVES

To evaluate if a 0.5-mm vertical bend applied on an incisor bracket produces movements in other planes and if different wires influence these effects.

MATERIALS AND METHODS

An acrylic model of a treated patient with brackets passively bonded was attached to an Orthodontic Force Tester, and a load cell was attached to the left lateral incisor. Thirty 0.019 × 0.025-inch archwires were divided into three groups according to their alloy: SS (stainless steel), B-Ti (beta-titanium), and MF (beta-titanium wire coated with nickel-titanium). Step-bends of 0.5 mm high were placed on the lateral incisor bracket using a universal plier, and the forces and moments in three dimensions were statistically analyzed by analysis of variance and Tukey post hoc test.

RESULTS

SS produced a larger force (3.4 N) than the B-Ti (1.41 N) and the MF (0.53 N; P < .001). Lingual forces were produced by the SS (0.82 N) and B-Ti (0.31 N) groups, while in the MF group, the force was insignificant. SS produced a mesial force of 0.24 N, while the B-Ti force was insignificant and MF produced 0.09 N. Groups produced different crown-distal tipping moments (SS = 31.48 N-mm, B-Ti = 11.7 N-mm, and MF = 4.55 N-mm) and different crown-buccal tipping moments. SS produced larger moments (3.63 N-mm) than B-Ti (1.02 N-mm) and MF (0.36 N-mm) wires. A mesial-out rotational moment was observed in all groups (SS = 7.17 N-mm, B-Ti = 3.46 N-mm, and MF = 0.86 N-mm).

CONCLUSIONS

A 0.5-mm intrusion bend produced lingual and mesial side effects. In addition to the distal and buccal crown-tipping moments, there was a mesial-out moment. Compared with SS, B-Ti and MF wires produced lower forces. These more flexible wires showed side effects with lesser intensity.

A comparative study of the effect of the intrusion arch and straight wire mechanics on incisor root resorption: A randomized, controlled trial

OBJECTIVE

To analyze and compare external apical root resorption (EARR) of maxillary incisors treated by intrusion arch or continuous archwire mechanics.

MATERIALS AND METHODS

This cone-beam computed tomography (CBCT) study analyzed 28 deep bite patients in the permanent dentition who were randomly divided into two groups: Group 1, 12 patients with initial mean age of 15.1 ± 1.6 years and mean overbite of 4.6 ± 1.2 mm treated with the Connecticut intrusion arch (CIA) in the upper arch (Ortho Organizers, Carlsbad, Calif) for a mean period of 5.8 ± 1.27 months. Group 2, 16 patients with initial mean age of 22.1 ± 5.7 years and mean overbite of 4.1 ± 1.1 mm treated with conventional leveling and alignment using continuous archwire mechanics for 6.1 ± 0.81 months. The degree of EARR was detected in 112 maxillary incisors by using CBCT scans and a three-dimensional program (Dolphin 11.7, Dolphin Imaging & Management Solutions, Chatsworth, Calif). The CBCT scans were obtained before (T1) and 6 months after initiation of treatment (T2). Differences between and within groups were assessed by nonpaired and paired t-tests, respectively, with a 5% significance level.

RESULTS

Significant differences were found for both groups between T1 and T2 ( P < .05) indicating that EARR occurred in both groups. However, there were no significant differences when EARR was compared between group 1 (-0.76 mm) and group 2 (-0.59 mm).

CONCLUSIONS

The Connecticut intrusion arch did not lead to greater EARR of maxillary incisors when compared with conventional orthodontic mechanics.

Cone-beam computed tomography for the assessment of root-crown ratios of the maxillary and mandibular incisors in a Korean population

Objective

This retrospective, cross-sectional study aimed to establish reference data for normal crown and root lengths and the root–crown ratios (R/C ratios) for the mature maxillary and mandibular incisors in a Korean population by using cone-beam computed tomography (CBCT).

Methods

We included 672 Korean patients (141 men and 531 women; mean age, 27.2 ± 7.7 years) who underwent CBCT examinations during various dental treatments. Crown and root lengths and the R/C ratios of the maxillary and mandibular incisors were measured using CBCT data, which were analyzed to detect significant differences between demographic factors as well as sagittal and vertical skeletal or occlusal relationships.

Results

Teeth of the same type in each half-arch were symmetrical. The mean R/C ratios varied from 1.1 to 1.2 for the maxillary incisors and from 1.3 to 1.4 for the mandibular incisors. Crown and root lengths were greater in men than in women, regardless of tooth type. Root lengths and R/C ratios for the mandibular incisors were significantly greater in patients with skeletal Class II malocclusion or an excessive overjet than in the other patients. The R/C ratios for the mandibular incisors were lower in patients with an open bite than in those with a normal or deep bite. Moreover, the R/C ratios for the mandibular incisors increased with age.

Conclusions

The data obtained in our study can serve as reference values for crown and root lengths and the R/C ratios for the maxillary and mandibular incisors in the Korean population.

[A perspective on the use of bone anchorage as opposed to other types of anchorage techniques]

INTRODUCTION

To convert our objectives into the desired treatment results, we need to control our mechanics and thus the anchorage used by avoiding any unwanted movements. It now seems unthinkable, at the dawn of the 21^st century, to ignore the useful contribution of orthodontic screw-borne anchorage. Nevertheless, we are entitled to raise a number of legitimate questions. Do these forms of anchorage offer an alternative to all types of mechanics? Will they permit us to manage clinical situations which are beyond the scope of a more classical approach? Can they enhance the quality of our treatments?

MATERIALS AND METHODS

Each of the authors describes clinical situations using screw-borne anchorage and compares with a conventional approach in order to make a non-exhaustive analysis of the mechanics applied, in their own office, and then highlights the most effective technique.

RESULTS

With 15 years experience in the use of miniscrews, orthodontists have now adopted them with their many advantages as an integral item in their therapeutic armamentarium. However, treatment plans must be coherent. Our mechanics must be well thought-out and represent a cogent entity under the control of the practitioner. Creating screw-borne anchorage demands total control over anchorage stability.

Comparison of anterior and posterior mini-implant-assisted maxillary incisor intrusion: Root resorption and treatment efficiency

OBJECTIVE

To compare, through cone-beam computed tomography (CBCT), the root resorption and treatment efficiency of two different mini-implant-assisted modalities in intruding the maxillary incisors.

MATERIALS AND METHODS

Thirty-two adults who had deep bite and elongated maxillary incisors were randomly allocated to two groups: anterior mini-implant group (AMG) and posterior mini-implant group (PMG). In the AMG, approximately 40 g of force was applied per side with elastic chains from mini-implants placed between the lateral incisors and canines and in the PMG, with beta-titanium wires from mini-implants placed between the second premolars and first molars. This study was conducted on CBCT scans taken before intrusion and after 4 months of intrusion. Data were analyzed by means of a paired t-test, independent t-test, and Pearson's correlation test.

RESULTS

One patient was excluded from the AMG due to mini-implant loosening. While the incisors showed a significant reduction in length and volume, this amount was greater in the AMG, especially in the central incisors (P < .05). Together with the mean intrusion rates of 0.62 and 0.39 mm/mo in the AMG and PMG respectively, the center of resistance of the incisors showed distal movement with labial tipping; these changes were greater in the PMG (P < .001). Volumetric root resorption was correlated with the amount of intrusion (P < .05).

CONCLUSIONS

Intrusion anchoring from posterior mini-implants is preferred in cases of upright incisors, as the use of such mechanics directs the roots into the spongiosa where they undergo less root resorption and more labial tipping.

[Indirect usage of miniscrew anchorage to intrude overerupted mandibular incisors in a Class II patient with a deep overbite]

Vertical dentoalveolar discrepancies are a common problem in orthodontic patients but are often difficult to treat with traditional mechanics. This case report illustrates the successful treatment of overerupted mandibular incisors via the indirect use of miniscrew anchorage. A woman (age, 22 years 9 months) had chief complaints of maxillary incisor protrusion and crooked teeth. An excessive curve of Spee caused by elongation of the mandibular incisors was also found. The patient was diagnosed with a severe Class II Division 1 malocclusion and a deep overbite. After extraction of the mandibular first premolars and the subsequent leveling phase, the elongated incisors were intruded with a novel method, which involved the combined use of sectional archwires and miniscrews placed in the premolar areas. After the procedure, the mandibular incisors had been intruded by 6.5 mm with no undesirable side effects. The total active treatment period was 42 months. The resultant occlusion and satisfactory facial profile were maintained after 30 months of retention. Our novel intrusion approach shows potential for correcting a deep overbite.

Orthodontic intrusion of maxillary incisors: a 3D finite element method study

Objective:

In orthodontic treatment, intrusion movement of maxillary incisors is often necessary. Therefore, the objective of this investigation is to evaluate the initial distribution patterns and magnitude of compressive stress in the periodontal ligament (PDL) in a simulation of orthodontic intrusion of maxillary incisors, considering the points of force application.

Methods:

Anatomic 3D models reconstructed from cone-beam computed tomography scans were used to simulate maxillary incisors intrusion loading. The points of force application selected were: centered between central incisors brackets (LOAD 1); bilaterally between the brackets of central and lateral incisors (LOAD 2); bilaterally distal to the brackets of lateral incisors (LOAD 3); bilaterally 7 mm distal to the center of brackets of lateral incisors (LOAD 4).

Results and Conclusions:

Stress concentrated at the PDL apex region, irrespective of the point of orthodontic force application. The four load models showed distinct contour plots and compressive stress values over the midsagittal reference line. The contour plots of central and lateral incisors were not similar in the same load model. LOAD 3 resulted in more balanced compressive stress distribution.

Curve of Spee - from orthodontic perspective

The presence of a curve of Spee (COS) of variable depth is common finding in the occlusal arrangement and is sixth key of occlusion The understanding of COS in the field of orthodontics is very important as orthodontists deal with it in virtually every patient they treat. An excessive COS is a common form of malocclusion that may be addressed in many ways, including posterior extrusion, anterior intrusion, and incisor proclination. The specific approach to leveling of COS should be selected based on each patient's needs. Soft tissue, crown–gingival relations, occlusal plane, and skeletofacial concerns are among the special considerations for treatment planning for leveling of COS.

Association of orthodontic force system and root resorption: A systematic review

INTRODUCTION

In this systematic review, we assessed the literature to determine which evidence level supports the association of orthodontic force system and root resorption.

METHODS

PubMed, Cochrane, and Embase databases were searched with no restrictions on year, publication status, or language. Selection criteria included human studies conducted with fixed orthodontic appliances or aligners, with at least 10 patients and the force system well described.

RESULTS

A total of 259 articles were retrieved in the initial search. After the review process, 21 full-text articles met the inclusion criteria. Sample sizes ranged from 10 to 73 patients. Most articles were classified as having high evidence levels and low risks of bias.

CONCLUSIONS

Although a meta-analysis was not performed, from the available literature, it seems that positive correlations exist between increased force levels and increased root resorption, as well as between increased treatment time and increased root resorption. Moreover, a pause in tooth movement seems to be beneficial in reducing root resorption because it allows the resorbed cementum to heal. The absence of a control group, selection criteria of patients, and adequate examinations before and after treatment are the most common methodology flaws.

Iatrogenic Damage to the Periodontium Caused by Orthodontic Treatment Procedures: An Overview

In orthodontic treatment, teeth are moved in to new positions and relationships and the soft tissue and underlying bone are altered to accommodate changes in esthetics and function. Function is more important than esthetics. The speciality of orthodontics has in addition to its benefits, complications as well as risks associated with its procedures. However the benefits outweigh the risks & complications in most of the treatment cases. Few of the unwanted side effects associated with treatment are tooth discolorations, enamel decalcification, periodontal complications like open gingival embrasures, root resorption, allergic reactions to nickel & chromium as well as treatment failure in the form of relapse.

The effect of central incisor's root proximity to the cortical plate and apical root resorption in extraction and non-extraction treatment

Aims:

The present study was conducted to investigate the relevance of cortical plate proximity of maxillary central incisor root, maxillary alveolar bone width, and the apical root resorption in extraction and non-extraction orthodontically treated cases. Further, the correlation between the apical root resorption and the various parameters was investigated.

Materials and Methods:

A total of 80 lateral head cephalographs, 40 pre-treatment and 40 post-treatment, of orthodontic subjects with a mean age of 15 years treated with fixed standard edgewise appliance were obtained. All subjects were divided into two groups as extraction and non-extraction cases. Twelve linear and three angular parameters were measured and evaluated. The paired “t”-test, Pearson's correlation coefficient, and the stepwise regression analysis were done to test the relationship between the apical root resorption and the various parameters.

Results and Conclusions:

The study revealed slightly greater amount of apical root resorption in extraction subjects as compared to non-extraction subjects. However, no statistically significant difference was found between the two treatment modalities. In extraction subjects, the apical root resorption was directly proportional to the pre-treatment length of maxillary central incisor and inversely proportional to the root width in apical one-third region, though there was a weak correlation. In non-extraction subjects, the pre-treatment anteroposterior position of the root apex of maxillary central incisor in the alveolar bone, in combination with its root width in the apical one-third region formed the predictive factors for the variance in the amount of the apical root resorption, though there was a weak correlation. Furthermore, the changes in the alveolar widths at the root apex and mid-root region were considered as predictive factors for the amount of apical root resorption during extraction and non-extraction treatment, respectively.

Predisposing factors to severe external root resorption associated to orthodontic treatment

OBJECTIVE

The aim of this study was to evaluate predisposing factors among patients who developed moderate or severe external root resorption (Malmgren's grades 3 and 4), on the maxillary incisors, during fixed orthodontic treatment in the permanent dentition.

METHODS

Ninety-nine patients who underwent orthodontic treatment with fixed edgewise appliances were selected. Patients were divided into two groups: G1 - 50 patients with no root resorption or presenting only apical irregularities (Malmgren's grades 0 and 1) at the end of the treatment, with mean initial age of 16.79 years and mean treatment time of 3.21 years; G2 - 49 patients presenting moderate or severe root resorption (Malmgren's grades 3 and 4) at the end of treatment on the maxillary incisors, with mean initial age of 19.92 years and mean treatment time of 3.98 years. Periapical radiographs and lateral cephalograms were evaluated. Factors that could influence the occurrence of severe root resorption were also recorded. Statistical analysis included chi-square tests, Fisher's exact test and independent t tests.

RESULTS

The results demonstrated significant difference between the groups for the variables: Extractions, initial degree of root resorption, root length and crown/root ratio at the beginning, and cortical thickness of the alveolar bone.

CONCLUSION

It can be concluded that: Presence of root resorption before the beginning of treatment, extractions, reduced root length, decreased crown/root ratio and thin alveolar bone represent risk factors for severe root resorption in maxillary incisors during orthodontic treatment.

Apical root resorption in maxillary incisors when employing micro-implant and J-hook headgear anchorage: a 4-month radiographic study

This study evaluated, over a 4-month study period, the amount of apical root resorption occurring in maxillary central incisors following their retraction when employing either micro-implant or J-hook headgear anchorage. The prospective randomised clinical trial was conducted in Orthodontic Clinic, College of Stomatology, China from 2008-2009. Subjects are patients requiring fixed appliances on waiting list (n=20). In female Han Chinese patients aged from 16-26 years, standardized periapical radiographs from 10 randomly assigned patients with maxillary protrusions comprising the micro-implant group, and from 10 similar patients comprising the J-hook headgear group, were assessed for maxillary central incisor apical root resorption. Measurements before and after orthodontic therapy were also obtained from lateral cephalometric radiographs to calculate incisor horizontal retraction and vertical intrusion distances. Estimated retraction force vectors were calculated in horizontal and vertical directions for both treatment groups. Data analysis employed t-tests and the Pearson correlation test, with α=0.05 for statistical significance. The results showed that when compared with the J-hook group, significantly more apical root resorption shortening of the maxillary central incisors was observed in the micro-implant group (1.27 mm difference, 95% CI=0.70-1.84, P<0.001), which was associated with a significantly larger retraction distance (P=0.004) and a smaller vertical force component (P<0.0001). We are led to conclude that continuous activation of the nickel-titanium coil springs used in the micro-implant group resulted in significantly more apical root resorption shortening and maxillary central incisor retraction than when intermittent J-hook retraction was employed. The employment of continuous duration orthodontic forces presents a risk for increased apical root resorption that requires careful radiographic monitoring.

Significance of curve of Spee: An orthodontic review

Exaggerated curve of Spee is frequently observed in dental malocclusions with deep overbites. Such excessive curve of Spee alters the muscle imbalance, ultimately leading to the improper functional occlusion. It has been proposed that an imbalance between the anterior and the posterior components of occlusal force can cause the lower incisors to overerupt, the premolars to infraerupt, and the lower molars to be mesially inclined. This altered condition requires specialized skills for the practitioner. It would be useful if we have a thorough knowledge of how and when this curve of Spee develops, so that it will aid us in our treatment. The understanding of why the curve of Spee develops is limited in literature. The purpose of this article is to increase our knowledge regarding the development and its effect on dentition and its treatment in exaggerated cases.

Mecânica intrusiva gera forças de inclinação e estímulos ortopédicos com reposicionamento dentário e remodelação óssea simultâneos OU Na mecânica intrusiva não se aplica forças de intrusão, mas obtém-se o efeito intrusivo

As agressões de baixa intensidade e longa duração no periósteo induzem a formação de novas camadas e podem aumentar o volume do osso e mudar sua forma. Nas mecânicas intrusivas, a inclinação natural das raízes propicia que os movimentos dentários sejam de inclinação. Ao mesmo tempo que promove forças de compressão do ligamento periodontal dos dentes submetidos a esse tipo de mecânica, em outras áreas ocorrem forças de tensão com deflexão. Esses efeitos também envolvem as superfícies externas, visto que a espessura do osso no processo alveolar é pequena e pode levar à formação de novas camadas, incluindo a parte mais cervical da crista óssea alveolar. Nas mecânicas intrusivas, ocorre uma remodelação alveolar de natureza ortodôntica associada a uma modificação da estrutura óssea interna e externa, atendendo a demandas de forças com características ortopédicas. O efeito intrusivo nas mecânicas ditas intrusivas pode ser o resultado da remodelação alveolar induzida pelas forças de inclinação e da modificação do volume ósseo decorrente da formação óssea subperiosteal na parte externa do processo alveolar. Provavelmente, estudos imaginológicos apurados, com tomografias computadorizadas de alta precisão, poderão captar esses fenômenos subperiosteais em futuros trabalhos envolvendo pacientes antes e depois da aplicação das mecânicas intrusivas.

Severe external apical root resorption--local cause or genetic predisposition?

BACKGROUND

Current data suggest that a large extent of the variation in orthodontic root resorption may be explained by differences in individual genetic predisposition. This would imply, however, a similar root resorption reaction in all teeth.

OBJECTIVE

To determine the incidence and extent of severe external apical root resorptions (SEARR) in maxillary incisors during multibracket (MB) appliance treatment.

PATIENTS AND METHODS

Of the whole sample of patients having completed MB treatment at the University of Giessen between 1991 and 2010 (P(Total)=3198), all subjects exhibiting severe root resorptions on at least one maxillary incisor were selected. SEARR were defined according to Malmgren et al. [39] (grade-IV RR=resorption >1/3 root length). Evaluation was performed using orthopantomograms from before and after MB treatment. The crown and root length of the affected teeth were measured. The extent of SEARR was assessed taking pretreatment crown length into consideration.

RESULTS

SEARR was detected in 16 patients. Thus, the incidence of SEARR on maxillary incisors during MB treatment totalled 0.5%. The median of SEARR of the affected incisors was 38.6% of the initial root length (minimum=33.4%, maximum=61.0%). Most subjects exhibited only single affected teeth. Only two subjects (0.06% absolute/12.5% relative) presented four maxillary incisors with SEARR.

CONCLUSIONS

The incidence of SEARR on maxillary incisors during MB treatment (0.5%) was very low compared to the literature. With only 12.5% of SEARR patients presenting four affected teeth, local rather than systemic/genetic factors seem to have predisposed the present subjects to SEARR.