Premolar Extraction Research Articles

Comparison of canine retraction in maxillary arch using self-ligating brackets and conventional brackets: An in vivo study

: In sliding mechanics, a considerable amount of applied force is lost to frictional resistance which places undue stress on the anchor unit. Therefore, for a clinical success with maximal efficiency for canine retraction with sliding mechanics, reduction of the resistance due to friction between brackets and arch wires is important. Self-ligating brackets are claimed to reduce the sliding resistance.: Aim of the study was to compare the clinical outcome of canine retraction using Self ligating brackets and Conventional Brackets during canine retraction. Objectives of the study were to compare the amount of canine retraction using Self ligating brackets and Conventional Brackets and to compare the amount of anchorage loss during canine retraction (CR) using Self ligating brackets and Conventional Brackets.: The study comprised a total of 20 patients aged between 13 and 22 years. Bilateral extraction of the first premolars in maxilla and separate canine retraction was done. A split mouth study design was conducted in which maxillary canines randomly bonded with self-ligating and conventional brackets. Study models were used for the measurement of canine retraction, anchorage loss and canine rotation. Statistical analysis was done. Self-ligating and conventional brackets produced similar amount of canine retraction and anchorage loss of the maxillary molars. Self-ligating brackets gave better rotation control of maxillary canines than conventional brackets. Self-ligating and conventional brackets gave similar results for the amount of canine retraction and anchorage loss. Self-ligating brackets give better rotational control.

Three dimensional assessment of soft tissue facial changes following premolars extraction using laser scanner. A prospective clinical trial

Three dimensional assessment of soft tissue facial changes following premolars extraction using laser scanner. A prospective clinical trial

Inter-septal bone reduction: Impact on space closure, root resorption and canine angulation during en-masse retraction - a randomised controlled trial.

To compare the space closure, root resorption and canine angulation during en-masse retraction of the labial segment after extraction of first premolars with or without interseptal bone reduction distal to the maxillary canines. A single-centre, parallel randomised control trial included 16 participants with a mean age of 21.5 years. Participants were allocated into treatment groups using blocked randomisation, and blinding was employed for outcome assessors and data analysts. The control group consisted of eight participants who underwent therapeutic extraction of maxillary first premolars, while the experimental group included eight participants who underwent interseptal bone reduction immediately after premolar extraction. En-masse retraction was performed using conventional friction mechanics with absolute anchorage in both groups. Measurements of space closure were conducted over 3 consecutive months during retraction. The time taken for total space closure was recorded. Cone-beam computed tomography scans were taken before and 3 months after retraction to assess root resorption and canine angulation. The experimental group demonstrated a significant increase in the rate of en-masse retraction compared to the control group over 3 months (mean difference [MD] = 1.09 mm, 95% confidence interval [CI] = 0.78-1.40), with an overall space closure rate of MD 0.26 mm/month (95% CI = 0.17-0.34). However, these changes were of minimal clinical significance. The change in canine angulation (MD = 4.50°, 95% CI = -1.61-10.61) did not exhibit statistical significance. Substantial root resorption was observed in six maxillary anterior teeth, with no difference between the groups. Interseptal bone reduction is a minimally invasive surgical technique, resulting in a notably accelerated rate of en-masse retraction in the experimental group over 3 months. However, despite the statistical significance, the clinical impact on overall space closure was minimal, with a difference of only 0.26 mm/month observed between the groups. Interseptal bone reduction did not affect the change in canine angulation and root resorption.

Evaluation of post-extraction healing after atraumatic extraction in gutka chewers and non-gutka chewers using the modified inflammation proliferation remodeling scale

BackgroundGutka, a smokeless tobacco mixture containing tobacco and areca nut, is widely consumed in South Asia and impairs wound healing due to vasoconstrictive and cytotoxic effects. Wound healing assessment in oral surgery lacks standardisation, and phase-specific evaluation tools are seldom used. This study aimed to compare post-extraction healing after atraumatic tooth extraction in gutka chewers and non-chewers using the modified Inflammation Proliferation Remodeling (IPR) scale to validate this scale for clinical use.MethodsA prospective cohort study at a dental college in Karachi, Pakistan, included 200 participants aged 18–45 undergoing atraumatic extraction of premolars or molars, divided into gutka chewers (n = 100) and non-chewers (n = 100). The modified IPR scale was developed and validated using content validity assessment by experts, pilot testing, inter-rater reliability (Cohen’s kappa), and internal consistency (Cronbach’s alpha). Wound healing was assessed using the validated modified IPR scale immediately post-extraction (Day 0), at the proliferative phase (Day 7), and the remodelling phase (6 weeks). Statistical analyses included Mann-Whitney U tests, multivariate linear regression, and Spearman’s correlation.ResultsThe modified IPR scale demonstrated good content validity, substantial inter-rater reliability (Cohen’s kappa 0.80–0.86), and good internal consistency (Cronbach’s alpha 0.84). No significant difference in IPR scores was observed between groups during the inflammatory phase (Day 0). Gutka chewers had significantly higher IPR scores during the proliferative phase (mean 5.9 ± 1.6 versus 4.2 ± 1.2; p < 0.001) and the remodelling phase (mean 3.6 ± 1.2 vs. 2.1 ± 0.9; p < 0.001), indicating delayed healing. Gutka use was a significant predictor of delayed healing (B = 1.2, p < 0.001) after adjusting for age and gender. Duration of gutka use positively correlated with higher IPR scores during the proliferative (rho = 0.46, p < 0.001) and remodelling phases (rho = 0.51, p < 0.001), reflecting a dose-dependent effect. The questionnaire was effectively validated with an 80% response rate and a 90.9% completion rate.ConclusionsGutka chewing is significantly associated with delayed post-extraction wound healing, with longer duration correlating with poorer outcomes. The modified IPR scale was effectively validated and proved to be a reliable tool for assessing wound healing progression, demonstrating its utility in clinical practice and research settings. Dental professionals should consider gutka use when planning patient care, and public health initiatives should aim to eliminate gutka consumption to improve oral health outcomes.

Lingual Orthodontic Retreatment of an Adult Patient with Protruded Lips and a Missing Lower Incisor: A Case Report

AbstractOrthodontic retreatment in adult patients presents unique challenges and considerations. Previous dental intervention or even missing teeth may influence treatment planning and pose challenges for bracket bonding.A 23-year-old female patient sought orthodontic retreatment to address her chief complaint of upper lip protrusion. She had previously completed fixed labial orthodontic treatment involving the extraction of a lower central incisor.The diagnosis was a skeletal maxillary protrusion and mandibular dentoalveolar protrusion on dental class I and skeletal class II relationships.A nonsurgical camouflage treatment option was chosen, which involved the removal of the upper first premolars and lower right first premolar. The lower left canine, lateral, and central incisor were substituted with the lower left first premolar, canine, and lateral incisor, respectively. Lingual self-ligating brackets, straight archwires, and temporary anchorage devices were utilized. The treatment was completed after 32 months with an improved facial profile and a stable occlusion.This case report demonstrates the successful retreatment of an adult patient with lip protrusion and relapse of lower arch crowding using straight-wire lingual appliances and premolar extractions. This approach achieved optimal aesthetics and a stable occlusion, highlighting the effectiveness of lingual appliances in complex adult retreatment cases.

To evaluate the divine proportion on silhouette photographs of skeletal class I bimaxillary protrusion cases treated with first premolar extraction- An in-vitro study

Objectives: The aim of the study is to assess the divine proportion of soft tissues seen in bimaxillary protrusion cases and compare this proportion on pre-treatment and post-treatment Silhouette photographs of skeletal (Sk) Class I bimaxillary protrusion patients treated by premolars extraction. Material and Methods: This research was conducted on 50 samples of pre-treatment along with post-treatment outline form photographs of Sk Class I bimaxillary protrusion patients aged 18–30 years in an orthodontics and dentofacial orthopedics department. The samples had an equal distribution with 25 males and females. All profile photos with Class I bimaxillary protrusion were converted into silhouette form. To assess the divine proportion in patient profiles, each silhouette photograph was marked by five anatomic landmarks, which were as follows: Soft-tissue nasion (N), trichion (Tr), subnasale (Sn), stomion (St), and a soft-tissue menton (Me) which was followed by the measurement of six linear dimensions; ratios were measured as R1, R2, R3, R4, and R5. These ratios of the patient’s profile, both before and after the treatment, were then compared to find out the soft-tissue alterations that have taken place in patients having Class I bimaxillary protrusion corrected by the first four premolars extraction. Results: The findings indicate that all post-treatment proportions in males indicated highly noticeable changes in contrast to pre-treatment ratios. However, females revealed highly noticeable differences in R1, R2, and R4 ratios, statistically evident differences were shown by R3 and R5 ratios in contrast to ratios before the treatment. Thus, the proportions appeared to be closer to the divine proportion. Conclusion: The results showed that all the ratios were found to be closer to divine proportion, and thus, premolars extraction in cases with convex facial form does help us to achieve esthetically pleasing faces.

Sensors: future tools for detecting young patient's stress during a dental invasive versus a non-invasive dental treatment-a pilot study.

A reliable tool to visualise children's early stress signs to prevent dental fear development is needed. The aim was to evaluate the commercially available, CE marked, Shimmer3 GSR + unit's ability to indicate for stress as a reaction of fear or pain for a non-invasive dental treatment (NI) and an invasive dental treatment (I). Patients 14-16years old were invited to undergo an oral check-up (NI) or an orthodontic premolar extraction (I), respectively. Digital data, measured via electrodes and optical pulse probe, placed on the wrist and fingers, monitored by the Shimmer3 GSR + unit, was transferred via Bluetooth to the HP-laptop. The observed digital parameters were: heart rate based on photoplethysmography (PPG), galvanic skin response (GSR), and 3-axis gyroscope and accelerometer signals for hand movements. Protocols for patient self-report scales were used: coloured analogue scale for pain intensity, facial analogue scale for the mood, and a dental fear scale. Descriptive statistics was performed. The NI-group: 20 patients, (14.6 ± 0.5years), underwent 20 oral check-ups. The I-group: 14 patients, (15.3 ± 0.5years), underwent 28 premolar extractions. All patients tolerated the Shimmer3 GSR + unit well. The GSR signal increased significantly, at start and during the oral injection, in the I-group. The GSR amplitudes persisted throughout and post the dental injection. No general uniform pattern or high GSR amplitudes were produced regarding NI-group. Considering the limitations of this study, the following conclusions can be made: the invasive treatment resulted in a specific unison GSR pattern, while the non-invasive procedure showed individually scattered GSR reactions. The commercially available CE-marked Shimmer3 GSR + device indicated the patient's stress response triggered by the invasive anaesthetic procedure.

Perception of facial esthetics and cephalometric correlations in Class II patients: a comparison between two-phase and one-phase treatments

An effective orthodontic treatment should not only aim for satisfactory occlusal outcomes but also consider its impact on facial esthetics. The study aims to evaluate and compare the perception of profile esthetics of skeletal Class II patients treated with two orthodontic modalities: (1) Two-phase approach involving functional appliances followed by fixed appliances with premolar extractions, or (2) One-phase approach using fixed appliances with premolar extractions. Additionally, the study aims to evaluate the correlation between the perceived esthetics and the corresponding cephalometric measurements. The study included 40 skeletal Class II adolescents who underwent either two-phase (n = 20, mean age = 12.38 ± 1.18) or one-phase (n = 20, mean age = 12.53 ± 0.79) orthodontic treatments. Eighty profile silhouettes (pre- and post-treatment) were assessed by 64 raters, including 23 orthodontists, 21 general dental practitioners, and 20 laypersons. The raters used a visual analog scale (VAS) to access profiles, upper and lower lips, and chin esthetics. At pre-treatment, all three groups of raters gave significantly lower scores to the profile silhouettes of the two-phase group compared to the one-phase group (P < 0.01); however, after treatment, they rated the two-phase group significantly higher (P ≤ 0.001). The two-phase group exhibited greater improvements in profile and upper and lower lip esthetics as perceived by all raters (P ≤ 0.001). Furthermore, cephalometric results revealed greater reductions in SNA, ANB, Wits appraisal, and G’-Sn-Pog’ in the two-phase group compared to the one-phase group (P < 0.05). Five cephalometric parameters (SNB, SNPog, overjet, overbite, and UL-SnPog’) demonstrated significant correlations with VAS scores given by orthodontists (P < 0.05). In conclusion, the two-phase group showed greater subjective and objective improvements in facial esthetics than the one-phase group. Additionally, the anteroposterior mandibular position and upper lip protrusion may be the primary cephalometric parameters correlated with subjective facial profile perceptions.

Closure of buccosinusal communication with rotation of a palatal flap: case report

An buccosinusal communication is an abnormal pathway between the oral cavity and the maxillary sinus. It is usually caused by surgical procedures such as the extraction of premolars and maxillary molars, due to the proximity of the roots to the floor of the maxillary sinus. The aim of this study is to report a surgical treatment for the closure of an buccosinusal communication with the advancement of a palatal flap. The patient was a 45-year-old female adult with no systemic comorbidities and no allergies. She reported pain in the left cheek and nasal discharge. Intraoral examination revealed an area of fistula in the region of element 26 measuring approximately 4-5mm. The CT scan showed a hyperdense image in the left maxillary sinus suggestive of sinus infection and a hypodense image in the region corresponding to the alveolus of element 26, suggestive of an buccosinusal communication. Initially, preoperative laboratory tests were requested and antibiotic therapy was prescribed. Intra- and extra-oral antisepsis, infiltration anesthesia were performed, fistulectomy, demarcation of the palatal flap, incision and full-thickness mucoperiosteal detachment, rotation of the palatal flap to obliterate the fistula and stabilization of the fistula using single-stitch sutures in the raw donor region with fibrin sponges under the suture, for later installation of surgical cement to help protect the wound. The patient is well, with complete closure of the communication and no evidence of post-operative complications.

Clinical Efficacy of CBCT and 3D-Printed Replicas in Molar Autotransplantation: A Controlled Clinical Trial.

To evaluate the efficacy of the combined cone-beam (CBCT)/3D-replicas protocol on the clinical and radiographic outcomes of autotransplanted molars. Controlled clinical trial registered ISRCTN13563091 from August 2019 to September 2022. Patients aged 13-22 years requiring permanent premolar extraction and having at least one non-erupted third molar were enrolled at the Institute of Stomatology, Stradins University, Riga, Latvia. Patients in the 3D-replicas (n = 30) underwent maxillary CBCT scans and had 3D-printed replicas of the third molar fabricated, while the control group (n = 28) did not. The clinical outcomes included tooth mobility, bleeding on probing, and periodontal pocket depth assessed at 3, 6, and 12 months. The radiographic outcomes included root development, obliteration, periapical status, and crown changes at 12 months. Of the 55 patients assigned to interventions, 46 completed the study. No significant differences in survival and radiographic outcomes were found between the control (n = 22) and 3D-replica group (n = 24): root development (p = 0.3), root resorption (p = 0.057), periapical status (p = 0.7), and crown/root ratio change (p = 0.4). Logistic regression showed no significant associations between radiologic predictors (root resorption: p = 0.4; periapical status: p > 0.9; root development: p = 0.8). Significant clinical outcome predictors included total operative time (β = 0.0043, p = 0.049), Moorrees' stage (stage 4: β = -0.31, p < 0.001; stage 5: β = -0.39, p < 0.001), and four donor placement times (β = 0.93, p < 0.001), but group assignment was not a significant predictor. The CBCT/3D-replica protocol showed no significant differences in the clinical or radiological outcomes. The high success rates in both groups suggest that the protocol is valuable primarily for optimizing surgical efficiency and as a training tool for clinicians.

Comparison Change of Pre and Post-Treatment in Vermilion Height and Lip Area in Adult Class II Division I Malocclusion Treated with Premolar Extraction

Aim: This study aimed to evaluate the alterations in vermilion height and lip area before and after fixed orthodontic treatment in adult patients with Class II Division I malocclusion who underwent premolar extractions. Assessments were conducted using frontal photographs and measurements from lateral cephalograms focusing on dentoalveolar and soft tissue parameters. Methods: Twenty-three adult patients with Class II skeletal malocclusion were selected from the records of the Department of Orthodontics and Dentofacial Orthopedics at AJ Institute of Dental Sciences, Mangalore. Pre-treatment and post-treatment lateral cephalograms and frontal photographs were obtained. Cephalograms were captured using a standardized KODAK 8000c digital cephalostat (69 kVp, 12 mA, 2 s), ensuring accurate patient positioning. The same investigator manually traced the cephalograms to minimize observer variability. Measurements were computed both manually and digitally for comparison purposes. Results: The study found a significant increase in the thickness from the cervical portion of the upper incisors to the upper lip after treatment (mean post-treatment: 15.77±2.28 mm; pre-treatment: 14.95±1.90 mm; P=0.006). Conversely, the thickness from the lower incisors to the upper lip decreased significantly post-treatment (mean post-treatment: 15.46±2.72 mm; pre-treatment: 17.26±2.19 mm; P&lt;0.001). Additionally, there was a significant increase in vermilion height (St-Me) and lower facial height (N-Me) after treatment, with mean differences of 3.58 mm (P&lt;0.001) and 1.18 mm (P=0.04), respectively. Conclusion: Orthodontic treatment involving premolar extractions in Class II Division I malocclusion patients led to significant soft tissue changes, particularly in lip thickness and vermilion height. Other parameters did not exhibit statistically significant differences.

Orthodontic Camouflage For Class II Malocclusion: A Case Study Using Miniscrew Implants And Strategic Extractions

This case report describes the orthodontic treatment of a 21-year-old Caucasian female patient with a Class III incisor relationship on a Class II skeletal base and increased vertical proportions. The patient presented with severe crowding in both upper and lower arches, gingivitis, molar incisors hypomineralization, and extensive caries in the LL6 tooth. She also exhibited decreased overjet, a complete overbite, and a significant shift in upper and lower dental midlines. The primary objective of treatment was to correct the malocclusion through orthodontic camouflage, which involved the extraction of upper and lower first premolars on the right side and first molars on the left. Miniscrew implants were utilized to enhance anchorage. Fixed appliances with a preadjusted MBT prescription were employed for alignment and leveling of both arches. The treatment resulted in improved occlusion, correction of midlines, and resolution of the patient’s aesthetic concerns. The case underscores the efficacy of orthodontic camouflage in managing complex malocclusion cases in adults while avoiding surgical intervention.

Evaluation of Rate of Space Closure Between Platelet Rich Plasma (Prp) Injection and Piezocision in Bimaxillary Protrusion Cases

Aim: Reducing orthodontic treatment duration is a significant concern for both patients and clinicians, as prolonged treatments can lead to complications like dental caries, root resorption, and decreased patient compliance. This study aims to compare the effectiveness of two minimally invasive techniques—Piezocision and platelet-rich plasma (PRP) injection—in accelerating orthodontic tooth movement during space closure in patients with bimaxillary protrusion. Methods: Sixteen patients diagnosed with Angle's Class I bimaxillary protrusion requiring extraction of first premolars were randomly assigned to two groups. Group A (n = 8) underwent Piezocision-assisted orthodontic treatment, while Group B (n = 8) received submucosal PRP injections. In both groups, one side of the maxillary arch served as the experimental side, and the contralateral side served as the control. Measurements of space closure were taken at the initiation of retraction (T₀) and after 90 days (T₁). Results: Both Piezocision and PRP significantly enhanced the rate of space closure compared to their control sides. However, Piezocision demonstrated a statistically faster rate of tooth movement than PRP injection. The mean difference in space closure between the Piezocision and PRP groups at T₁ was significant (p &lt; 0.001). Conclusion: While both Piezocision and PRP injections effectively accelerated orthodontic tooth movement, Piezocision proved to be more efficient in reducing treatment time. Clinicians may consider Piezocision as a preferred method for patients seeking expedited orthodontic treatment.

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.

Orthodontic camouflage with extractions of premolars in Class III Malocclusion. Case report

Orthodontic camouflage with extractions of premolars in Class III Malocclusion. Case report

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.