Premolar Extraction Research Articles

Effect of Collagen Plug and Bone Graft on Bone Formation in Rabbit Extraction Model

1. Purpose : This study aimed to investigate the differences in bone regeneration capacity following extraction between a control group without biomaterial placement and experimental groups where biomaterials were inserted (including xenograft, synthetic bone-containing collagen plugs, and collagen plugs).2. Materials and Methods : Bilateral extraction of maxillary first premolars or second premolars was performed, dividing the rabbits into four groups [① Group 1 :no bone graft or collagen plug inserted, ② Group 2: collagen plug inserted after extraction, ③ Group 3: collagen plug containing synthetic bone inserted after extraction, ④ Group 4: xenograft material inserted after extraction]. After euthanized the rabbit, Four and eight weeks postoperatively, the extent of bone formation were evaluated histologically and radiographically.3 Results : The degree of new bone formation using histological analysis showed higher results in both the control groups at weeks 4 and 8, although not statistically significant. Across all groups, higher bone formation was observed at 8 weeks compared to 4 weeks. In radiological analysis using micro CT, Bone Mineral Density (BMD) and Bone Volume/Tissue Volume(BV/TV) were highest in Group 4. Trabecular bone thickness(Tb.Th) was highest in the control group, but not statistically significant.4. Conclusion : In all groups, the degree of new bone formation at 4 and 8 weeks did not show statistically significant differences histologically and radiologically.

Osteoinductively Functionalized 3D-Printed Scaffold for Vertical Bone Augmentation in Beagle Dogs.

To evaluate the efficacy of 3D-printed scaffolds that were osteoinductively functionalized with a bone morphogenetic protein 2 (BMP-2)-incorporated biomimetic calcium phosphate particles (BMP-2-inc. BpNcCaP)/hyaluronic acid (HA) composite gel in vertical bone augmentation in beagle dogs. Four Beagle dogs were used in this study. Three months after the extraction of 1st, 2nd, 3rd, and 4th premolars at both sides of the lower jaws of Beagle dogs, one or two critical-size vertical bone defects (4 mm vertical bone defect without buccal and lingual bone) on each sidewere surgically created. The defects were randomly subjected to the following groups: (1) Control (without bone-defect-filling materials); (2) 3D scaffold; (3) BMP2-inc. BpNcCaP/HA-functionalized 3D scaffold. Six weeks post-surgery, samples were harvested and subjected to micro-CT and histomorphometric analyses. The struts of the BMP2-inc. BpNcCaP/HA-func. 3D scaffold were covered by a thick layer of cemented irregular particles with an average pore size at 327 ± 27 μm. The BpNcCaP/HA-func. 3D scaffold group bore significantly higher bone volume, bone volume fraction, trabecular number, trabecular thickness, bone mineral density, connectivity density, and bone volumes in three directions (mesiodistal, buccolingual, and apicocoronal) when compared with the groups of Control and 3D scaffold. Moreover, the BMP2-inc. BpNcCaP/HA-func. 3D scaffold group bore significantly lower trabecular separation and exhibited significantly higher bone-to-scaffold contact percentage and newly formed bone area percentage within pores in comparison with 3D scaffold. BMP2-inc. BpNcCaP/HA-func. 3D scaffold dramatically enhanced vertical alveolar bone augmentation, which suggests a promising application potential of BMP2-inc. BpNcCaP/HA-func. 3D scaffold in dental clinic.

Favourable dentoalveolar changes after lower premolar extractions for Class III camouflage with completely customized lingual appliances

BackgroundThe aim of the investigation was to evaluate if the inclination of the lower anterior teeth can be controlled reliably after lower premolar extraction for Class III camouflage treatment with completely customized lingual appliances (CCLAs). Treatment outcome was tested against the null hypothesis that lower premolar extractions for non-surgical camouflage treatment of a Class III malocclusion will lead to further compensation by retroclining mandibular incisors during CCLA treatment.MethodsThis retrospective study included 25 patients (f/m 12/13; mean age 20.7 years, SD 9.5 years) with uni- or bilateral Class III molar relationship and a Wits value of ≤ -2 mm. In all consecutively debonded patients, lower premolars were extracted to correct the sagittal relationship with a non-surgical camouflage approach. Lateral head films prior to (T1) and at the end of lingual orthodontic treatment (T2) were used to evaluate skeletal and dentoalveolar effects. A paired t-test with alpha = 5% was used to define differences between the endpoints. The linear correlation between the inclination of the mandibular incisors at T1 and the achieved correction was measured with the Pearson correlation coefficient (PCC). A Schuirmann’s TOST equivalence test was used to check if the final lower incisor inclination was within the defined norms.ResultsThe null hypothesis was rejected as the mean lower incisor inclination was improved by 1.8° despite lower premolar extractions (T1: 86.8°/ T2: 88.6°). There was a strong correlation (-0.75) between the lower incisor inclination at T1 and the achieved correction indicating a controlled correction towards the norm regardless of the initial incisor position. At T2, the interincisal angle as well as the lower incisor inclination were within the norm.ConclusionLower premolar extractions for non-surgical camouflage treatment of a Class III malocclusion will not lead to undesired retroclining of mandibular incisors during CCLA treatment even in severe cases.

Anchorage loss of the posterior teeth under different extraction patterns in maxillary and mandibular arches using clear aligner: a finite element study

BackgroundExtracting the premolars is an effective strategy for patients with bimaxillary dentoalveolar protrusion. Clear aligners (CAs) close the extraction spaces through shortening the length of aligners. The contraction force generated by the terminal of aligners makes the posterior teeth tip mesially, which is known as the roller coaster effect. This phenomenon is even worse in the 2nd premolar extraction cases. Posterior anchorage preparation is commonly used to protect the angulation of molars, taking the form of presetting distal tipping value. However, the distal tipping design aggravates the anchorage loss of anterior teeth simultaneously. This study aimed to explore the different anchorage loss of the posterior teeth when the 1st or 2nd premolars were extracted using CAs, respectively in maxillary and mandibular arches, further providing guidance for anchorage preparation design in clinical practice.MethodsTwo bimaxillary finite element models with different extraction patterns were established to simulate the anterior en-masse retraction process of the CAs. In Model 1, the maxillary and mandibular 1st premolars were extracted, while in Model 2, the 2nd premolars were extracted. Finite element analysis methods were utilized to analyze the tipping angle of the anterior and posterior teeth.ResultsCompared between two models, the anterior teeth exhibited a greater lingual inclination tendency and the posterior teeth exhibited a slighter mesial tipping tendency in Model 1 regarding individual tooth. The closer to the extraction spaces, the greater the tip, and the distal tipping tendency of the 1st premolars was more evident than the mesial tipping tendency of the 1st molars in Model 2. Compared between the maxillary and mandibular arches, the mesial tipping tendency of individual posterior tooth was more evident in the maxilla. In addition, the highest hydrostatic stress of the periodontal ligaments was concentrated on the cervical and apical parts directly adjacent to the extraction spaces, and it exhibited relatively uniform distribution in Model 1.ConclusionsThe individual posterior tooth showed the same mesial tipping direction but to different degree when the 1st or the 2nd premolars were extracted during clear aligner treatment. Presetting anchorage preparation design for the posterior teeth is essential to alleviate the roller coaster effect, especially in the 2nd premolar extraction cases. Furthermore, larger anchorage preparation value should be proposed for the maxillary posterior teeth.

Assessing position changes of impacted third molars in treatment of class II malocclusion with premolars extraction.

Third molars (M3) remaining impacted in Class II malocclusion characterised with sagittal mandibular deficiency is a high probability. The null hypothesis of this study is that mesioangular M3s changes position through the eruption way inClass II malocclusion treatmentrequiring moderate anchoragewith four first premolars extraction.The aim of this study is to reconsider the decision to surgically extract impacted third molars in four premolars extraction treatment of Class II malocclusion. The materials consisted of the pre-treatment and post-treatment lateral cephalograms and orthopantomographs of 30 individuals with skeletal and dental Class II malocclusion with a mean chronological age of 13.48 years, who were treated by the same clinician (H.G.) with four first premolar extractions via the straight wire technique at the Ankara University Faculty of Dentistry Department of Orthodontics, Ankara, Turkey. The sagittal position of the upper and lower incisors and molars, M3position and M3space were evaluated with the paired-t test; the relationship between the sagittal position of the upper and lower incisors and molars and the change in M3position were evaluated with correlation analysis. Results: The study found the retroclination and mesial movement of the upper incisors and molars, and an increase in the M3space by the fixed orthodontictreatment. An insignificant steepening of both the upper right M3position and the lower right M3position was found. A statistically significant increase in the lower right and left side M3spaces was found. Positive correlations between lower right M3angulation and the sagittal position of the lower incisors and first molars were found. Improvement in the mesioangulation of the M3s and an increase in the M3space were achieved in this study. Based on the findings, it is useful to review the decision for prophylactic surgical extraction of the M3s before orthodontic treatment in such cases, taking into account the risks of postoperative complications.

Periodontal Ligament Reactions to Orthodontic Force: A Transcriptomic Study on Maxillary and Mandibular Human Premolars.

Orthodontic force (OF) induces a variety of reactions in the periodontal ligament (PDL) that could potentially account for individual variability regarding orthodontic tooth movement (OTM). This study investigates the transcriptomic profile of human PDL tissue subjected to OF invivo for 7 and 28 days, additionally comparing the differences between maxillary and mandibular PDL. Healthy patients requiring orthodontic premolar extractions were randomly assigned to one of three groups: control (CG) where no OF was applied, 7 days and 28 days, where premolars were extracted either 7 or 28 days after the application of a 50-100 g OF. Total RNA was extracted from the PDL tissue and analyzed via RNA-seq. Differentially expressed genes (DEGs) were identified using a false discovery rate and fold change threshold of < 0.05 and ≥ 1.5 respectively. Functional and Protein-Protein Interaction analysis were performed. After 7 days of OF, the reaction of PDL to OF is characterized by cell responses to stress, increased bone resorption, inflammation and immune response, and decreased bone formation. In contrast, after 28 days, bone regeneration is more prominent, and processes of bone homeostasis, immune response, and cell migration are present. The response of maxillary and mandibular PDL was different. Bone resorption was observed in the maxilla at 7 and 28 days, while in the mandible expression of cell proliferation and transcriptional activity were predominant after 28 days of OF. The early reaction of the PDL to OF corresponds with increased bone resorption and decreased bone formation. After 28 days, bone formation became more prominent. The maxillary and mandibular PDL present asynchronous responses during OTM. These findings enhance our comprehension of the mechanisms underlying the origin-specific responses of PDL to different lengths of OF, which is potentially relevant in the development of personalized therapeutic strategies.

Three-dimensional assessment of alveolar bone changes and root resorption in extraction patients after fixed orthodontic treatment: A prospective study

The aim of this study was to evaluate the alveolar crestal bone height, alveolar bone thickness, and root resorption in mandibular incisors after fixed orthodontic treatment. A total of 35 patients (mean age 17.02 ± 3.24 years) with moderate to severe mandibular anterior crowding requiring first premolar extraction were included. Cone beam computed tomography scans of the mandibular anterior region were obtained from the patients before and after orthodontic treatment. The alveolar crestal bone height, cortical bone thickness (CBT) (at apex and midroot level), labial and lingual alveolar bone thickness, and root resorption were assessed for all mandibular incisors. Paired Student's t test was used to compare pretreatment and post-treatment alveolar bone changes and root resorption. A significant decrease in lingual crestal bone height was observed in all mandibular incisors after orthodontic treatment (P < 0.001). Lingual CBT decreased at the midroot level significantly for all mandibular incisors after completion of orthodontic treatment (P < 0.001). A significant decrease in total lingual bone thickness was observed in all mandibular incisors (P < 0.001). Root lengths of mandibular incisors decreased significantly in the sagittal and coronal sections after orthodontic treatment (P < 0.001). Fixed orthodontic treatment with premolar extraction results in a significant reduction of alveolar crestal bone height, CBT (at midroot level), and alveolar bone thickness on the lingual aspect of mandibular incisors. Significant orthodontically induced inflammatory root resorption was observed in all mandibular incisors after orthodontic treatment.

Lip and incisor changes in patients with different ethnicities treated with extraction versus nonextraction: A cone-beam computed tomography study

This study used cone-beam computed tomography (CBCT) via voxel-based superimposition to evaluate lip and incisor changes after orthodontic treatment with four premolar extractions (Ext) versus nonextraction (Non-Ext) among African American (AA) and White (W) patients. A total of 240 CBCTs of 120 adolescent orthodontic patients with Class I skeletal/dental relationships were included. Patients were initially divided according to treatment, and then each group was subdivided according to patients' ethnicity (Ext/W = 30, Ext/AA = 30, Non-Ext/W = 30, and Non-Ext/AA = 30). CBCTs were imported into Invivo6 for voxel-based superimposition. Lip and incisor measurements were recorded. Independent t tests and two-way ANOVA were used for statistical assessment. The Non-Ext/W group had a greater increase in all outcome variables compared with the Non-Ext/AA group, with a significant change in volume and position of upper (UL) and lower lips (LL), inclination of upper (U1) and lower incisors (L1), and position of U1. The Ext/AA group had a greater decrease in all measured outcomes compared with the Ext/W group, with significant change in inclination of U1 and L1, and position and volume of LL. W patients had more crowding than AA patients in both treatment approaches. Retraction ratios of 6.5:1 and 2.1:1 were recorded between the U1 and UL positions, and L1 and LL positions, respectively. There were no direct interaction effects between ethnicity and treatment, nor were there any significant effects of ethnicity after controlling for the covariates. Ethnicity alone has no impact on incisor and lip position after treatment. However, ethnicity in the form of initial presentation of malocclusion can have a significant influence.

A Cephalometric Study Of Vertical Skeletal Changes After Extraction And Non-Extraction Fixed Orthodontic Treatment Of Class I Malocclusion In North Indian Population

Background: Orthodontic treatments frequently involve tooth extractions to address crowding and protrusion, but the effects of these extractions on vertical skeletal changes are still debated. Research has extensively covered aspects like soft tissue response and smile aesthetics, yet there is no consensus on their impact on vertical dimensions. This issue is particularly pertinent for hyperdivergent individuals, who make up about 22% of orthodontic patients. A proposed technique for such cases includes counterclockwise rotation of the lower jaw and advancement of posterior teeth to manage open bites or excessive vertical facial height. This study aims to compare vertical skeletal changes in Class I malocclusion patients undergoing extraction versus non-extraction fixed orthodontic treatments. Material and Methods: We analysed pre- and post-treatment lateral cephalometric radiographs from 60 Class I crowding patients, evenly split into extraction and non-extraction groups. Eight vertical skeletal parameters were assessed and compared statistically between the two groups. Superimposition analysis of radiograph tracings was used to explore vertical changes related to molar mesialization, particularly in the extraction group. Results: The extraction group demonstrated significant reductions in vertical skeletal dimensions compared to the non-extraction group. Measurements including FMA, SN-GoGn, Y-axis, SN-PP, and PP-MP showed significant differences, with reductions in the extraction group (P = 0.001). Procrustes superimposition indicated effective molar mesialization in the extraction group, which was not observed in the non-extraction group. Conclusion: Extraction of first premolars in fixed orthodontic treatment leads to a notable decrease in vertical skeletal dimensions, in contrast to the slight increase seen with non-extraction treatments. This reduction is largely due to molar mesialization, which enhances vertical skeletal dimensions and treatment stability in Class I crowding cases.

Effects of Attachment Design and Aligner Material on Mandibular Canine Distal Bodily Movement in Aligner Treatment

Abstract Purpose Dental crowding is a result of a mismatch between tooth size and arch dimensions, which leads to malocclusion; treatment often involves premolar extraction before orthodontic alignment. Clear aligners are limited in their ability to achieve canine distal bodily movement, a common orthodontic maneuver. This study investigated the impacts of attachment design and aligner material on the efficacy of canine distal bodily movement. Methods A finite element analysis was conducted to examine the impact of various attachment designs and two aligner materials, thermoplastic polyurethanes/polycarbonate (TPU/PC) and polyethylene terephthalate glycol-modified (PETG), on mandibular canine distal bodily movement. The investigation focused on the biomechanical responses in the periodontal ligament (PDL) and surrounding alveolar bone. Results Attachment configuration exerted a strong influence on mandibular canine movement. Vertically oriented attachment pairs positioned mesially (mesial occlusal–mesial cervical) resulted in the most effective canine distal bodily movement, followed by a rectangular attachment. TPU/PC aligners induced slightly higher principal stresses in the PDL and von Mises stress and strain in the surrounding alveolar bone compared with PETG aligners; however, the difference was negligible, amounting to less than 6%. Conclusion Attachment design, specifically vertically oriented pairs positioned mesially (mesial occlusal–mesial cervical), was determined to be the crucial factor influencing the efficacy of canine distal bodily movement. The choice of aligner material (TPU/PC or PETG) has minimal impact on this orthodontic procedure.

Evaluation Of Lateral Root Resorption In Maxillary Teeth Among First Premolar Extraction Cases After Space Closure- A CBCT Study

Background: Orthodontic treatment usually involves usage of light continuous forces but when heavy forces are used it leads to apical root resorption. External apical root resorption refers to reduction in root structure involving the apices. This resorption is of transient inflammatory type. 2D images are commonly used for diagnostic purposes in orthodontics but it cannot detect root resorption on lingual or buccal surfaces thus cannot measure the volume of root loss. Cone beam computed tomography which can provide 3D images was introduced in late 1990s. Images provided by CBCT are more more accurate than panoramic and periapical radiographs . Therefore in this study , CBCT is used to evaluate lateral root resorption in maxillary teeth after after space closure among first premolar extraction cases . Materials and Methods: CBCTs of 20 patients fulfilling inclusion and exclusion criteria were taken before the start of orthodontic treatment and after space closure. Post treatment root width was substracted from the pre treatment root width at three levels from CEJ (3mm,6mm,9mm). The normality test (Shapiro-Wilk Test) was performed to analyze the data, and the results were expressed as frequency with percentage and mean with standard deviation. Difference between means were assessed using paired t test for before and after the procedure. All the statistical analyses were carried out at a 5% level of significance, and results with a P value &lt; 0.05 were considered statistically significant. Results: Considering all the three levels the least tooth resorption was observed in the case of central incisor (0.1750 ± 0.0444, p &lt;0.001) and highest in the canine tooth (5.900± 0.0000, p &lt;0.001) . Conclusion: When root resorption is detected, it is recommended to pause the treatment for about 6 months to allow for root repair. Intermittent forces, which provide rest periods between applications, are more tissuefriendly and can help reduce the risk of further resorption

Does enamel deproteinisation with 10% papain affect shear bond strength of orthodontic adhesives: a randomised controlled trial.

To evaluate the effect of 10% papain as an enamel deproteinising agent on the shear bond strength (SBS) of three orthodontic adhesives: Transbond XT, resin-modified glass ionomer cement (RMGIC) and Biofix. Single-centre, double-blinded, split-mouth randomised controlled trial. Department of Orthodontics and Dentofacial Orthopaedics, Nair Hospital Dental College, Mumbai, India. A total of 20 participants requiring bilateral premolar extraction for fixed orthodontic treatment in both the maxillary and mandibular arches were included in this study. In total, 80 premolars from the above-mentioned participants were divided into four groups as follows: group A: Transbond XT deproteinised with 10% papain gel; group B: Biofix deproteinised with 10% papain gel; group C: RMGIC deproteinised with 10% papain gel; and group D: Transbond XT without enamel deproteinisation as a control group-bonded as instructed by the manufacturer. After deproteinisation, brackets were bonded and after a follow-up period of 28 days, the teeth were extracted. The SBS was then measured using the Universal Testing Machine. The force needed to shear the bracket was documented, and bond strengths were subsequently calculated in megapascals (MPa). The obtained results were subjected to statistical analysis and one-way ANOVA was performed to compare the mean SBS between the groups. Subsequently, pairwise comparisons were conducted using Tukey's post hoc test. There was a statistically significant difference in SBS among all groups (P = 0.002). The SBS of TransXT with deproteinisation increased significantly compared with TransXT without deproteinisation (P = 0.03). There was no statistically significant difference between the SBS of TransXT without deproteinisation and RMGIC (P = 0.47) and Biofix (P = 0.39), both with deproteinisation. The use of 10% papain for deproteinising enamel improved the SBS of all materials. Deproteinising improved the SBS of RMGIC and Biofix to the level of TransXT without deproteinisation.

Changes in the curvature of upper and lower lips following the first premolar extraction in Class I bimaxillary protrusion - A cephalometric study

Bimaxillary dentoalveolar protrusion is a condition characterized by protrusion of the maxillary and mandibular incisors with increased procumbency of the lips. The treatment of choice for these patients is fixed orthodontic treatment after extraction of four first premolars. This treatment would result in the retraction of anterior teeth with a resultant decrease in soft tissue convexity. Objective of the study is to find out how the curvature of upper and lower lip change following fixed appliance therapy in patients with class I Bimaxillary protrusion following extraction of first premolars. A total of 32 subjects, 13 males and 19 females in the age group of 13-21 years diagnosed with BMP were included in the study. Pre-treatment and post-treatment cephalograms were obtained from subjects satisfying the inclusion and exclusion criteria. Cephalometric landmarks, lines used in the study were marked and analysed. The soft tissue parameters were measured and compared using paired t test and Pearson’s correlation coefficient. The overall effect of orthodontic correction of bimaxillary protrusion from subjects were analysed by evaluating the soft tissue changes between pre-treatment and post treatment cephalometric radiographs. There is a statistically significant difference with decrease in ULST, B`-PM line, B`-LiPog`, A`-PM line, LLIT, LLVT, Pog-Pog` and no statistically significant difference in A`-NtLs and ULVT. The results showed a reduction in lip procumbency. Among the soft tissue parameter studied, there is a statistically significant decrease observed for ULST, B`-PM line, B`-LiPog`, A`-PM line, LLIT, LLVT and Pog-Pog`.

Improved stability of open bite deformities: taking control of the transverse width using digital technology and robotic archwire bending

Many factors need to be considered when selecting the treatment protocol for the surgical correction of skeletal open bite deformities. In order to achieve stable long-term results, it is essential to explore the origin of the open bite, including any dysfunction of the temporomandibular joint or tongue and compromised nasal breathing, in addition to the skeletal deformity. Recurrence of a skeletal open bite is associated with relapse of the expanded transverse width. Three-dimensional virtual planning allows different treatment options to be explored and final decisions to be made together with the orthodontist who also designs the patient’s digital occlusion. This study presents a treatment protocol for predictable and stable widening of the maxillary transverse width over the long term, involving premolar extraction and rounding and shortening of the upper dental arch by advancing the molar segments. The stability of inter-canine, inter-premolar, and inter-molar distances, as well as overjet and overbite, were measured in 16 patients treated with this technique; measurements were obtained pre- and post-surgery, and the mean follow-up was 43 months. Orthodontic treatment was designed digitally and finished with robotically bent wires (SureSmile), which allowed exact planning of the overall treatment until debonding, thus making orthognathic surgery more predictable for the patient. The changes in transverse width were significant and stable over time.

The effect of single versus multiple piezocisions on the rate of canine retraction: a randomized controlled trial

BackgroundPiezocision is a minimally invasive surgical method aiming to accelerate tooth movement. However, its effect was found to be transient, appertaining to the regional acceleratory phenomenon (RAP). Hence, the aim of the study was to evaluate the effect of single and multiple piezocisions on the rate of orthodontic tooth movement (OTM). Moreover, the impact of both protocols on canine tipping and orthodontically induced inflammatory root resorption (OIIRR) has been assessed.MethodsThirty indicated patients for the therapeutic extraction of maxillary first premolars were enlisted in this split-mouth study, and they were randomly split into two equal groups, each including 15 subjects. In the Single Application Group (SAG), one side of the maxillary arch arbitrarily received a single piezocision before the onset of canine retraction, whereas in the Multiple Application Group (MAG), piezocisions were randomly performed on one side, three times on a monthly basis, over the 12-week study period. The contralateral sides of both groups served as the controls. Canine retraction was carried out bilaterally using nickel-titanium closed-coil springs, delivering 150 g of force, and the rate of tooth movement, as well as canine tipping were evaluated on a monthly basis, over a 3-month period. Cone-bean computed tomography scans were also conducted pre- and post- canine retraction, and OIIRR was assessed using Malmgren Index.ResultsThe reported outcomes revealed a significant increase in the amount of canine retraction, canine tipping, as well as root resorption scores on the experimental sides in both groups SAG and MAG post-retraction (p < 0.001). However, upon comparing the experimental sides in both groups, non-significant differences have been observed between them regarding all the assessed outcomes (p > 0.05).ConclusionsSingle and multiple piezocisions effectively accelerate OTM in comparison to conventional orthodontic treatment, with relative outcomes reported by both intervention frequencies. Accordingly, single piezocision is recommended as an adjunct to OTM. Furthermore, significant tooth tipping as well as a significantly higher root resorption risk accompanies both single and multiple piezocision applications in conjunction with OTM.Name of the RegistryClinicaltrials.govTrial Registration NumberNCT05782088Date of Registration23/03/2023 “Retrospectively registered”.URLhttps://clinicaltrials.gov/ct2/show/NCT05782088

Analysis of the Forces and Moments in Canine Bodily Movement with Different Clear Aligners’ Extraction Space Designs

This study aimed to optimize space closure efficiency by comparing the forces and moments exerted by different designs of clear aligners (CAs) during the movement of maxillary canines into the premolar extraction space. The forces and moments were measured using a multi-axis force/moment transducer on the maxillary right canine. The CAs were fabricated from thermoformed polyethylene terephthalate glycol. The following four edentulous space designs were tested: the edentulous space was left intact (Group 1); the edentulous space was replaced with a premolar pontic (Group 2); the edentulous space was replaced with a half-sized premolar pontic (Group 3); and the edentulous space was replaced with a rectangular column beam (Group 4). The maxillary right canine was moved 0.25 mm distally. All groups experienced buccodistal and intrusive forces; compared with the other groups, Group 1 showed significantly greater intrusive and smaller distal forces, and Group 4 showed significantly greater distal forces. All groups experienced distal tilting, lingual inclination, and mesial rotational moments. These findings suggest that modifying the thickness and extent of the adjacent teeth in the edentulous area of the CA can improve local stiffness, thereby reducing the tipping of the teeth into the edentulous space. This study emphasizes the importance of the CA design in controlling forces and moments for effective orthodontic treatment.

Three-dimensional assessment of low-level laser therapy on orthodontic miniscrew displacement using CBCT: a retrospective study

BackgroundThis study aimed to assess the effect of Low-Level Laser Therapy (LLLT) on sagittal, transverse and vertical Orthodontic miniscrew displacement.Materials and methodsThe study included CBCTs from the records of 12 adult patients who underwent upper first premolar extraction and canine retraction with orthodontic miniscrews for maximum anchorage. The miniscrews on one side received LLL, while the other side served as a control. The Low-Level Laser was applied to assess its effect on the displacement of the miniscrews. The used CBCTs have been taken at two-time points: immediately after miniscrew insertion (T0) and four months after the start of canine retraction (T1) with a total of 24 CBCTs. Miniscrew displacement was assessed by measuring head (HMS) and tail (TMS) displacement to the axial, coronal and mid-sagittal planes on the CBCT at the two time points. Miniscrews displacement (T1-T0) was compared between LLL side and control side. Comparisons were performed using paired samples t-test. The significance level was set at p-value < 0.05. The reproducibility of measurements was assessed by intraclass correlation coefficient (ICC).ResultsAfter four months of canine retraction, HMS and TMS from both laser and control sides showed significant three-dimensional displacement at p < 0.05. No significant difference in mean displacement in the vertical, sagittal, nor transverse planes between both sides was elicited.ConclusionLLL application in the used protocol does not affect the amount of miniscrew displacement in any of the three planes of space. Miniscrew displacement was significant in both groups.

Three-Dimensional Evaluation of Condylar Position and Joint Spaces Following Orthodontic Treatment With Quadruple Premolar Extractions.

This study aimed to assess the alterations in the temporomandibular joint among adult patients undergoing orthodontic treatment involving the extraction of four premolars. A cohort of 44 adults, with a mean age of 24.2 years, underwent orthodontic therapy that included quadruple premolar extractions. Cone-beam computed tomography scans were performed before and after the treatment to evaluate the temporomandibular joints. The three-dimensional assessment focused on the condylar position relative to the cranial base and the articular fossa, the axial condylar rotation, and the joint spaces. Notably, a significant posterior shift of the condyle was detected (P≤0.01), averaging a 0.41mm retraction. The posterior joint space narrowed by 0.32mm post-treatment. Additionally, a medial tilt of 0.62° in the condyle's long axis was observed in the frontal plane. No significant changes were recorded for the other condylar positions, rotations, or joint space dimensions. The findings suggest that orthodontic treatment with four premolar extractions may instigate condylar repositioning and rotation. These insights can inform refinements in treatment protocols.

Assessment of mini-aesthetics in Class I malocclusion subjects who underwent orthodontic treatment with or without extraction of four premolars – A prospective study

Smile and facial attractiveness are strongly correlatedThis study aimed to assess the effect of extraction or non-extraction orthodontic treatment on mini-aesthetics in patients with Class I malocclusion by measurement of the smile variables.A total of 56 subjects were selected and grouped as Group 1- treated non-extraction, Group 2A-treated with extraction of first premolars and groups 2B- treated with extraction of second premolar teeth. Each subject was photographed with a posed smile and NHP using DSLR camera. The images were then imported into a computer software and the following smile parameters were assessed: gingival display, smile index, maxillary incisor display on smile and buccal corridor ratio.The mean measured maxillary incisor display was 1.39±0.34, 2.31±0.50 and 0.90±0.19mm in Group 1, Group 2A and Group 2B. The mean measured gingival display on smiling was 0.07±0.07, 0.38±0.65 and 0.07±0.15mm in Group 1, Group 2A and Group 2B. The mean measured smile index was 0.15±0.68, 1.20±0.22 and 0.95±0.41 in Group 1, Group 2A and Group 2B. The mean measured buccal corridor ratio was 0.83±0.39, 1.59±0.26 and 1.26±0.31 in Group 1, Group 2A and Group 2B. There was an increase in maxillary incisor display after fixed Orthodontic treatment in the non-extraction group and a decrease in first premolar extraction group while second premolar extraction group showed no changes. Smile index was increased post-treatment in first premolar and second premolar extraction group while non-extraction group showed no significant difference. Buccal corridor ratio decreased in first premolar and second premolar extraction groups while non-extraction group showed no changes.

How accurate is predicted root movement achieved in four first-premolar extraction cases with Invisalign?

This study aims to compare the achieved and predicted root movements in adults after four first-premolar extractions and Invisalign treatment. Thirty-three consecutive adults (22 Class I, 9 Cusp-to-cusp Class II and 2 Cusp-to-cusp Class III) from a single clinical division who completed the first series of aligners after premolar extractions were included in this retrospective study. A pretreatment cone-beam computed tomography model was registered onto the pretreatment surface-scanned dental model (SSDM) to locate the pretreatment root apices of the whole dentition. These were copied and transferred to the predicted and achieved post-treatment SSDMs to acquire the locations of the predicted and achieved post-treatment root apices. The differences between predicted and achieved root movements (DPARMs) were tested using the paired t-test or Wilcoxon signed rank test. In the anteroposterior direction, posterior root movements of maxillary and mandibular anterior teeth were poorly achieved (3.24-5.74 mm DPARMs, p < .05). In the vertical direction, roots of maxillary anterior teeth achieved greater intrusion (0.70-0.93 mm DPARMs, p < .05), while those of mandibular incisors achieved less intrusion (0.57-0.65 mm DPARMs, p < .05) than predicted. In the mediolateral direction, lateral incisor roots did not move distally (-0.65 to -0.96 mm DPARMs, p < .05), while those of canines did not move buccally, compared with the prediction (-0.75 mm DPARMs, p < .05). In the four first-premolar extraction treatments with Invisalign, root movements were not achieved as predicted, particularly for anterior teeth in the anteroposterior direction.