OBJECTIVE: To evaluate the clinical and radiographic efficacy of micro crestal flap-alveolar ridge preservation following extraction of mandibular molars with severe periodontitis compared with natural healing, and to preliminarily propose the surgical indication. METHODS: A retrospective analysis was conducted on clinical data from patients with mandibular molars with severe periodontitis either receiving micro crestal flap-alveolar ridge preservation (MCF-ARP group) or undergoing natural healing in department of periodontology, Peking University School and Hospital of Stomatology from September 2013 to June 2021. Cone-beam computed tomography scannings performed before/immediately after extraction (as baseline) and repeated before implantation (after the extraction socket healing) were used to measure the ridge width, height and volumetric changes of the sockets, and the proportion of guided bone regeneration (GBR) during implant therapy were compared between the two groups. RESULTS: Between baseline and healing, significant differences in changes of MCF-ARP group [(8.34±2.81) mm] and natural healing group [(3.82±3.58) mm] in the distances from mandibular canal to center of the tooth socket were recorded (P < 0.001). The ridge width at 1 mm below the most coronal aspect of the crest increased by (3.50±4.88) mm in the MCF-ARP group but decreased by (0.16±5.70) mm in the natural healing group, respectively (P=0.019). After healing, the MCF-ARP group showed the distances from mandibular canal to center of the tooth socket >8 mm in all the cases, with 97.1% exceeding 10 mm. Natural healing group displayed 23.1% of the cases with center bone height < 8 mm and 61.5% exceeding 10 mm. Volume changes at the buccal and lingual aspect as well as the total socket were significantly greater in the MCF-ARP group compared with natural healing group (P < 0.001).At the time of implantation, GBR was performed in 5 out of 68 subjects (8.3%) in the MCF-ARP group, whereas 8 out of 26 subjects (30.8%) in the natural healing group required GBR, reflecting significant difference (P=0.003). CONCLUSION In the sites of mandibular molars with severe periodontitis, when the distances from mandibular canal to center of the tooth socket was not enough (less than 7 mm), clinicians could consider performing the micro crestal flap-alveolar ridge preservation to achieve augmentation for alveolar ridge and reduce the proportion of guided bone regeneration during implant therapy to reduce the difficulty and risk of injuries during implant therapy.
Humans ; Tooth Extraction ; Retrospective Studies ; Surgical Flaps ; Molar/surgery* ; Mandible/surgery* ; Female ; Periodontitis/surgery* ; Male ; Adult ; Middle Aged ; Cone-Beam Computed Tomography ; Alveolar Ridge Augmentation/methods* ; Alveolar Process/surgery* ; Tooth Socket/diagnostic imaging* ; Dental Implantation, Endosseous/methods*

OBJECTIVE: To evaluate the clinical efficacy of clear aligner therapy in patients with severe periodontitis accompanied by pathological tooth displacement in the anterior region. METHODS: This retrospective study analyzed patients diagnosed with severe periodontitis and pathological displacement in the anterior region, who visited both the Periodontics and Orthodontics Departments at Peking University School and Hospital of Stomatology between 2019 and 2022. A total of 26 eligible cases were included in this study. All the patients underwent regular periodontal maintenance throughout the treatment process, and clear aligners were used for orthodontic treatment. Intraoral scans were analyzed by dedicated software to measure and compare occlusal distribution and proximal contact scores before and after orthodontic treatment. Periodontal clinical indicators were assessed at three key time points: before periodontal treatment (T0), before orthodontic treatment (T1), and after orthodontic treatment (T2). All the cases were treated with clear aligner. RESULTS: A total of 217 pathologically displaced anterior teeth from 26 patients were analyzed. Among these, 105 teeth exhibited periodontal pockets [probing depth (PD) ≥5 mm] before periodontal treatment. After clear aligner therapy, the occlusal score improved significantly from 10.35±8.61 to 23.62±9.73 (P < 0.001), and the proximal contact score increased from 13.62±4.73 to 31.62±10.37 (P < 0.001). The median PD decreased significantly from 3.33 mm [interquartile range (IQR)=0.92] at T0 to 2.50 mm (IQR=0.67, P < 0.001) at T1 and remained stable at 2.50 mm (IQR=0.50) after treatment (T2). A significant reduction in PD was observed between T0 and T2 (P < 0.001), but no significant difference was found between T1 and T2 (P=0.948). CONCLUSION Clear aligner therapy demonstrates favorable clinical efficacy in patients with severe periodontitis and pathological anterior tooth displacement. It effectively improves occlusal distribution and proximal contact while maintaining periodontal health in these patients. However, further large-scale prospective controlled studies are needed to verify its long-term clinical outcomes.
Humans ; Retrospective Studies ; Periodontitis/therapy* ; Female ; Male ; Adult ; Tooth Migration/therapy* ; Tooth Movement Techniques/methods* ; Treatment Outcome ; Middle Aged ; Young Adult ; Orthodontic Appliances, Removable

OBJECTIVE: To evaluate the wound healing of recipient and donor sites following keratinized mucosa augmentation (KMA) around implants in reconstructed jaw areas and to compare these outcomes with gingival grafts in native jawbone, so as to provide clinical guidance for postoperative maintenance, and to investigate the impact of clinical experience on the evaluation of KMA postoperative healing through subgroup comparisons. METHODS: This study included patients who underwent resection of maxillofacial tumors, fibular or iliac flap reconstruction, and implant placement at Peking University Dental Hospital from October 2020 to April 2023. Three months post-implant placement, the patients were referred for KMA procedures. Clinical photographs of the reconstructed area were taken preoperatively, immediately postoperatively, and 3 weeks and 3 months post-surgery. Additionally, photographs of the palatal donor site were obtained preoperatively and 3 weeks later. Wound healing was assessed by four junior and three senior clinicians utilizing the early healing index (EHI), early wound healing score (EHS), and pink esthetic score (PES).And senior clinicians evaluated the healing effect compared with gingival transplantation on natural jawbone using a 10-point scale. RESULTS: A total of 26 patients with jawbone reconstruction were included, with an average age of (34.2±10.2) years, 11 males (42.3%) and 15 females (57.7%). Among them, 13 cases (50.0%) underwent fibula flap reconstruction, and 13 cases (50.0%) underwent iliac flap reconstruction. The average number of implants per patient was 3.2±0.7. In the recipient area, 3 weeks postoperatively, the EHS was 7.0 (4.0, 9.0), with sub-item scores as follows: Clinical signs of re-epithelialization (CSR) 6.0 (3.0, 6.0), clinical signs of haemostasis (CSH) 1.5 (1.0, 2.0), and clinical signs of inflammation (CSI) 1.0 (0.0, 1.0), indicating that the average appearance of the wound in the recipient area was characterized by generally well-approximated wound edges with minimal fibrin lines and mild erythema and swelling. The EHI for the recipient area was 2.0 (1.5, 2.5), suggesting that the incision was mostly closed with some fibrin lines 3 weeks postoperatively. The long-term healing evaluation system, PES, was 2.5 (2.0, 3.0), with sub-scores for color [1.0 (1.0, 1.5)] and texture [1.5 (1.0, 2.0)], which were slightly different from the reference values.In the palatal donor area, 3 weeks postoperatively, the EHI score was lower at 1.3 (1.0, 2.5), while the EHS score was higher at 8.5 (6.0, 10.0), indicating better soft tissue healing in the donor area compared with the recipient area. Among the clinicians with different levels of experience, the assessment of wound healing revealed that except for the CSI sub-item, where the junior group scored higher than the senior group, all other sub-items showed significantly higher scores in the senior group compared with the junior group. In the EHS evaluation system, the CSH sub-item demonstrated no significant differences between the groups with varying levels of experience. Experienced clinicians' evaluation outcomes of healing effect compared with gum graft on natural alveolar bone was 8.5 (7.5, 9.5), showing high consistency [intraclass correlation coefficient (ICC): 0.892; 95% confidence interval (CI): 0.791－0.949], suggesting slightly suboptimal healing results after KMA surgery. CONCLUSION The healing process following KMA in the context of jawbone reconstruction is relatively protracted, emphasizing the necessity for comprehensive postoperative management. Moreover, clinician experience plays a significant role in the assessment of wound healing outcomes for KMA in maxillofacial reconstruction.
Humans ; Wound Healing ; Adult ; Male ; Female ; Gingiva/transplantation* ; Plastic Surgery Procedures/methods* ; Middle Aged ; Surgical Flaps ; Keratins

OBJECTIVE: To compare the influence of different emergence profile of implants in mandibular molar on the peri-implant soft tissue. METHODS: Forty-four implants were divided into two equal groups by mucosal thickness, ≥2 mm (group A) or < 2 mm (group B), and were randomly included in the test group and the control group. In the control group, the patients were treated by a prosthesis with no transmucosal modifications (subgroups A1 and B1). In groups A1 and B1, the prostheses maintained the original emergence profile of the healing abutment. In the test group, the prostheses were designed based on a width-to-height ratio (W/H) of 1.3 ∶ 1 (subgroups A2 and B2). In group A2, the buccal transmucosal configuration design was slightly concave, and in group B2, the prostheses were designed with convex buccal transmucosal configuration. Assessments were made before delivery of the definitive restoration (T0), one month (T1) and 12 months (T2) after loading. The soft tissue and prosthesis information were obtained by intraoral scan and were converted to digital models. The digital models of different time were superimposed together. Buccal mucosal W/H, emergence angle (EA) and buccal mucosal margin recession (ΔGM) were measured. RESULTS: One year after loading, the buccal mucosal margin recession in the test group (groups A2 and B2) was significantly lower than that in the control group (groups A1 and B1). The ΔGM in group A2 was significantly lower than that in group A1 (P=0.033), but in groups B1 and B2, it was not significantly different. The W/H in group A2 increased significantly one month after loading, but remained stable at one year. In the A1 group, the W/H changed little from initial to one month, but increased significantly at one year after loading. The W/H in group B2 remained stable from the beginning to one year, while in group B1, it changed little one month after loading, but increased significantly by one year. CONCLUSION When the initial mucosal thickness was ≥2 mm, the slightly concave prosthesis designed based on the biological W/H significantly maintained the level of buccal mucosa. When the mucosal thickness was < 2 mm, the slightly convex prosthesis design maintained a more stable W/H over one year.
Humans ; Mandible/surgery* ; Molar/surgery* ; Male ; Female ; Adult ; Middle Aged ; Dental Prosthesis Design ; Dental Implants ; Dental Implantation, Endosseous/methods*

OBJECTIVE: To evaluate the clinical outcomes and define the indications for a one-stage mandibular reconstruction technique that combines iliac bone flaps with immediate implant-based dentures, and to assess both the accuracy of surgical planning and the long-term success of the procedure. METHODS: A total of ten patients underwent the procedure at Peking University Hospital of Stomatology between June 2020 and August 2023. The preoperative biopsy pathology of all the patients confirmed a benign tumor. In this technique, iliac bone flaps were used for mandibular reconstruction, and immediate implant-based dentures were placed during the same surgical session. Various outcome measures were evaluated, including the accuracy of the surgical reconstruction, implant placement deviations (entry point, apical point, depth, and angle), and long-term outcomes, such as cervical bone resorption, implant survival, and the cumulative survival rate. RESULTS: Thirty-eight implants were successfully inserted into the iliac flaps of the ten patients. The median follow-up duration was 23.5 months, and no significant complications occurred during the follow-up period, such as infections, titanium plate exposure, implant loosening, or damage to the implants and dentures. The accuracy of preoperative virtual surgical planning (VSP) was highly reliable. The repeatability of the VSP model compared to the postoperative reconstructed mandible was as follows: 67.82% ±10.16% within 1 mm, 82.14% ±6.58% within 2 mm, and 90.61% ±4.62% within 3 mm. The average maximum deviation from the plan was (6.10±0.89) mm, with an average overall deviation of (1.14±0.31) mm. For the implants, deviations in critical parameters were as follows: entry point deviation was (2.02±0.58) mm, apical point deviation was (2.25± 0.66) mm, depth deviation was (1.26±0.51) mm, and angular deviation was 1.84°±1.10°. The implant survival rate remained 100% during the follow-up, with a cumulative survival rate of 97.37% from 1 to 4 years. Average cervical bone resorption was 0.94 mm. CONCLUSION The combination of iliac bone flaps with immediate implant-based dentures for one-stage mandibular reconstruction demonstrated pro-mising clinical outcomes, including high implant survival and minimal complications. This technique proved to be safe and reliable for mandibular reconstruction. However, further studies with larger sample sizes and longer follow-up periods are necessary to confirm the long-term efficacy and optimal indications for this procedure.
Humans ; Mandibular Reconstruction/methods* ; Male ; Ilium/surgery* ; Female ; Middle Aged ; Surgical Flaps ; Adult ; Mandible/surgery* ; Aged ; Dental Implantation, Endosseous/methods* ; Immediate Dental Implant Loading/methods* ; Bone Transplantation/methods* ; Dental Implants

OBJECTIVE: Dynamic navigation approaches are widely employed in the context of implant placement surgery. Implant surgery can be divided into immediate and delayed surgery according to the time of implantation. This retrospective study was developed to compare the accuracy of dynamic navigation system for immediate and delayed implantations. METHODS: In the study, medical records from all patients that had undergone implant surgery between August 2019 and June 2021 in the First Clinical Division of the Peking University School and Hospital of Stomatology were retrospectively reviewed. There were 97 patients [53 males and 44 females, average age (47.14±11.99) years] and 97 implants (delayed group: 51; immediate group: 46) that met with study inclusion criteria and were included. Implant placement accuracy was measured by the superposition of the planned implant position in the preoperative cone beam computed tomography (CBCT) image and the actual implant position in the postoperative CBCT image. The 3-dimensional (3D) entry deviation (3D deviation in the coronal aspect of the alveolar ridge), 3D apex deviation (3D deviation in the apical area of the implant) and angular deviation were analyzed as the main observation index when comparing these two groups. The 2-dimensional (2D) horizontal deviation of the entry point and apex point, and the deviation of entry point depth and apex point depth were the secondary observation index. RESULTS: The overall implant restoration survival rate was 100%, and no mechanical or biological complications were reported. The implantation success rate was 100%. The 3D entry deviation, 3D apex deviation and angular deviation of all analyzed implants were (1.146±0.458) mm, (1.276±0.526) mm, 3.022°±1.566°, respectively; while in the delayed group these respective values were (1.157±0.478) mm, (1.285±0.481) mm and 2.936°±1.470° as compared with (1.134±0.440) mm, (1.265±0.780) mm, 3.117°±1.677° in the immediate group. No significant differences (P=0.809, P=0.850, P=0.575) in accuracy were observed when comparing these two groups. CONCLUSION Dynamic computer-assisted implant surgery system promotes accurate implantation, and both the immediate and delayed implantations exhibit similar levels of accuracy under dynamic navigation system that meets the clinical demands. Dynamic navigation system is feasible for immediate implantation.
Humans ; Male ; Female ; Retrospective Studies ; Middle Aged ; Cone-Beam Computed Tomography ; Dental Implantation, Endosseous/methods* ; Surgery, Computer-Assisted/methods* ; Dental Implants ; Adult ; Surgical Navigation Systems ; Immediate Dental Implant Loading/methods* ; Imaging, Three-Dimensional

OBJECTIVE: The triply periodic minimal surface (TPMS) Gyroid porous scaffolds were built with identical porosity while varying pore sizes were used by fluid mechanics finite element analysis (FEA) to simulate the in vivo microenvironment. The effects of scaffolds with different pore sizes on cell adhesion, proliferation, and osteogenic differentiation were evaluated through calculating fluid velocity, wall shear stress, and permeability in the scaffolds. METHODS: Three types of gyroid porous scaffolds, with pore sizes of 400, 600 and 800 μm, were established by nTopology software. Each scaffold had dimensions of 10 mm × 10 mm × 10 mm and isotropic internal structures. The models were imported to the ANSYS 2022R1 software, and meshed into over 3 million unstructured tetrahedral elements. Boun- dary conditions were set with inlet flow velocities of 0.01, 0.1, and 1 mm/s, and outlet pressure of 0 Pa. Pressure, velocity, and wall shear stress were calculated as fluid flowed through the scaffolds using the Navier-Stokes equations. At the same time, permeability was determined based on Darcy' s law. The compressive strength of scaffolds with different pore sizes was evaluated by ANSYS 2022R1 Static structural analysis. RESULTS: A linear relationship was observed between the wall shear stress and fluid velocity at inlet flow rates of 0.01, 0.1 and 1 mm/s, with increasing velocity leading to higher wall shear stress. At the flow velocity of 0.1 mm/s, the initial pressures of scaffolds with pore sizes of 400, 600 and 800 μm were 0.272, 0.083 and 0.079 Pa, respectively. The fluid pressures were gradually decreased across the scaffolds. The average flow velocities were 0.093, 0.078 and 0.070 mm/s, the average wall shear stresses 2.955, 1.343 and 1.706 mPa, permeabilities values 0.54×10^-8 1.80×10^-8 and 1.89×10^-8 m² in the scaffolds with pore sizes of 400, 600 and 800 μm. The scaffold surface area proportions according with optimal wall shear stress range for cell growth and osteogenic differentiation were calcula-ted, which was highest in the 600 μm scaffold (27.65%), followed by the 800 μm scaffold (17.30%) and the 400 μm scaffold (1.95%). The compressive strengths of the scaffolds were 23, 26 and 34 MPa for the 400, 600 and 800 μm pore sizes. CONCLUSION The uniform stress distributions appeared in all gyroid scaffold types under compressive stress. The permeabilities of scaffolds with pore sizes of 600 and 800 μm were significantly higher than the 400 μm. The average wall shear stress in the scaffold of 600 μm was the lowest, and the scaffold surface area proportion for cell growth and osteogenic differentiation the largest, indicating that it might be the most favorable design for supporting these cellular activities.
Tissue Scaffolds/chemistry* ; Porosity ; Finite Element Analysis ; Osteogenesis ; Cell Differentiation ; Cell Proliferation ; Tissue Engineering/methods* ; Hydrodynamics ; Humans ; Stress, Mechanical ; Cell Adhesion

OBJECTIVE: To investigate the clinical application effect of the along-axis extraction method in the extraction of impacted mandibular third molars (IMTM) and to compare the biomechanical characteristics of different root extraction techniques through three-dimensional finite element analysis. METHODS: A total of 68 patients requiring IMTM extraction were enrolled and randomly divided into two groups: the experimental group underwent the along-axis extraction method, while the control group underwent the traditional buccal bone removal and root extraction method. The duration of the procedure, intraoperative and postoperative complications were recorded. Three-dimensional finite element analysis further revealed the stress distribution in the tooth root, jawbone, periodontal ligament, and mandibular canal during different root extraction methods. RESULTS: The duration of root extraction, pain score and swelling on the first postoperative day in the control group were (7.87±3.90) min, 4.62±1.90 and (11.37±5.12) mm, respectively, which were significantly higher than those in the experimental group [(5.74±2.37) min, 3.87±1.19 and (7.22±3.39) mm, respectively]. The root fracture rate and lingual bone plate fracture rate in the control group were significantly higher than those in the experimental group (P < 0.05). The results of finite element analysis showed that the control group ' s lingual al-veolar bone had the higher peak equivalent stress, and lingual bone plate fracture was prone to occur. The periodontal ligament of the experimental group had the higher equivalent stress value, making it more likely to rip and more likely to cause root displacement. When subjected to force, the experimental group' s instantaneous root displacement was higher, but the control group ' s root displacement was more pronounced in the lingual direction. CONCLUSION This study suggests that the along-axis extraction me-thod can not only effectively shorten the operative time but also reduce postoperative complications after extraction of impacted mandibular third molars, and enhance the safety of the operation and the patient' s comfort. Three-dimensional finite element analysis shows the biomechanical characteristics of various root extraction techniques visually, serves as a valuable guide for choosing and refining clinical surgical techniques, and confirms that extracting a tooth' s root along its long axis yields better clinical results.
Humans ; Finite Element Analysis ; Tooth, Impacted/surgery* ; Tooth Extraction/methods* ; Molar, Third/surgery* ; Mandible/surgery* ; Imaging, Three-Dimensional ; Female ; Adult ; Biomechanical Phenomena ; Male ; Tooth Root/surgery* ; Young Adult ; Adolescent

OBJECTIVE: To develop an original-mirror alignment associated deep learning algorithm for intelligent registration of three-dimensional maxillofacial point cloud data, by utilizing a dynamic graph-based registration network model (maxillofacial dynamic graph registration network, MDGR-Net), and to provide a valuable reference for digital design and analysis in clinical dental applications. METHODS: Four hundred clinical patients without significant deformities were recruited from Peking University School of Stomatology from October 2018 to October 2022. Through data augmentation, a total of 2 000 three-dimensional maxillofacial datasets were generated for training and testing the MDGR-Net algorithm. These were divided into a training set (1 400 cases), a validation set (200 cases), and an internal test set (200 cases). The MDGR-Net model constructed feature vectors for key points in both original and mirror point clouds (X, Y), established correspondences between key points in the X and Y point clouds based on these feature vectors, and calculated rotation and translation matrices using singular value decomposition (SVD). Utilizing the MDGR-Net model, intelligent registration of the original and mirror point clouds were achieved, resulting in a combined point cloud. The principal component analysis (PCA) algorithm was applied to this combined point cloud to obtain the symmetry reference plane associated with the MDGR-Net methodology. Model evaluation for the translation and rotation matrices on the test set was performed using the coefficient of determination (R²). Angle error evaluations for the three-dimensional maxillofacial symmetry reference planes were constructed using the MDGR-Net-associated method and the "ground truth" iterative closest point (ICP)-associated method were conducted on 200 cases in the internal test set and 40 cases in an external test set. RESULTS: Based on testing with the three-dimensional maxillofacial data from the 200-case internal test set, the MDGR-Net model achieved an R² value of 0.91 for the rotation matrix and 0.98 for the translation matrix. The average angle error on the internal and external test sets were 0.84°±0.55° and 0.58°±0.43°, respectively. The construction of the three-dimensional maxillofacial symmetry reference plane for 40 clinical cases took only 3 seconds, with the model performing optimally in the patients with skeletal Class Ⅲ malocclusion, high angle cases, and Angle Class Ⅲ orthodontic patients. CONCLUSION This study proposed the MDGR-Net association method based on intelligent point cloud registration as a novel solution for constructing three-dimensional maxillofacial symmetry reference planes in clinical dental applications, which can significantly enhance diagnostic and therapeutic efficiency and outcomes, while reduce expert dependence.
Humans ; Deep Learning ; Algorithms ; Imaging, Three-Dimensional/methods* ; Male ; Female ; Maxilla/diagnostic imaging* ; Adult

OBJECTIVE: To quantitatively evaluate the accuracy of data obtained from liquid-interference surfaces using an intraoral 3D scanner (IOS) integrated with a compressed airflow system, so as to provide clinical proof of accuracy for the application of the compressed airflow system-based scanning head in improving data quality on liquid-interference surfaces. METHODS: The study selected a standard model as the scanning object, adhering to the "YY/T 1818-2022 Dental Science Intraoral Digital Impression Scanner" guidelines, a standard that defined parameters for intraoral scanning. To establish a baseline for accuracy, the ATOS Q 12M scanner, known for its high precision, was used to generate true reference values. These true values served as the benchmark for evaluating the IOS performance. Building on the design of an existing scanner, a new scanning head was developed to integrate with a compressed airflow system. This new design aimed to help the IOS capture high-precision data on surfaces where liquid-interference, such as saliva, might otherwise degrade scanning accuracy. The traditional scanning method, without airflow assistance, was employed as a control group for comparison. The study included five groups in total, one control group and four experimental groups, to investigate the effects of scanning lens obstruction, airflow presence, liquid media, and the use of the new scanning head on scanning process and accuracy. Each group underwent 15 scans, generating ample data for a robust statistical comparison. By evaluating trueness and precision in each group, the study assessed the impact of the compressed airflow system on the accuracy of IOS data collected from liquid-interference surfaces. Additionally, we selected Elite and Primescan scanners as references for numerical accuracy values. RESULTS: The scanning accuracy on liquid-interference surfaces was significantly reduced in terms of both trueness and precision [Trueness: 18.5 (6.5) vs. 38.0 (6.7), P < 0.05; Precision: 19.1 (8.5) vs. 31.7 (15.0), P < 0.05]. The use of the new scanning head assisted by the compressed airflow system significantly improved the scanning accuracy [Trueness: 22.3(7.6) vs. 38.0 (6.7), P < 0.05; Precision: 25.8 (9.6) vs. 31.7 (15.0), P < 0.05]. CONCLUSION The scanning head based on the compressed airflow system can assist in improving the accuracy of data obtained from liquid-interference surfaces by the IOS.
Imaging, Three-Dimensional/methods* ; Humans ; Dental Impression Technique/instrumentation*