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Objective: To describe the submucosal microbial profiles of peri-implantitis and healthy implants, and to explore bacteria that might be correlated with clinical parameters., Methods: In the present cross-sectional study, 49 patients were recruited. Each patient contributed with one implant, submucosal biofilms were collected from 20 healthy implants and 29 implants with peri-implantitis. DNA was extracted and bacterial 16S ribosomal RNA (16S rRNA) genes were amplified. Submucosal biofilms were analyzed using 16S rRNA sequencing at Illumina MiSeq platform. Differences between the groups were determined by analyzing α diversity, microbial component and microbial structure. The potential correlation between the bacteria with pocket probing depth (PPD) of peri-implant calculated by Spearman correlation analysis., Results: The α diversity of submucosal microbial of health group was significantly lower than that in peri-implantitis group (Chao1 index: 236.85±66.13 vs. 150.54±57.43, P < 0.001; Shannon index: 3.42±0.48 vs . 3.02±0.65, P =0.032). Principal coordinated analysis showed that the submucosal microbial structure had significant difference between healthy and peri-implantitis groups [ R 2 =0.243, P =0.001, analysis of similarities (ANOSIM)]. Compared with healthy implants, relative abundance of periodontal pathogens were higher in peri-implantitis, including members of the red complex ( Porphyromonas gingivalis , Tannerella forsythia , Treponema denticola ) and some members of orange complex ( Precotella intermedia , Eubacterium nodatum , Parvimonas micra ), as well as some new periodontal pathogens, such as Fillifactor alocis , Fretibacterium fastidiosum , Desulfobulbus sp.&#95;HMT&#95;041 , and Porphyromonas endodontalis. Spearman correlation analysis revealed that the relative abundance of Treponema denticola ( r =0.686, P < 0.001), Tannerella forsythia ( r =0.675, P < 0.001), Fretibacterium sp. ( r =0.671, P < 0.001), Desulfobulbus sp.&#95;HMT&#95;041 ( r =0.664, P < 0.001), Filifactor alocis ( r =0.642, P < 0.001), Fretibacterium fastidiosum ( r =0.604, P < 0.001), Porphyromonas gingivalis ( r =0.597, P < 0.001), Porphyromonas endodontalis ( r =0.573, P < 0.001) were positive correlated with PPD. While the relative abundance of Rothia aeria ( r =-0.615, P < 0.001) showed negatively correlation with PPD., Conclusion: Marked differences were observed in the microbial profiles of healthy implants and peri-implantitis. The members of red and orange complex as well as some new periodontal pathogens seem to play an important role in peri-implant disease. Compared with healthy implants, the submucosal microbial of peri-implantitis were characterized by high species richness and diversity.

Objective: To evaluate the type of wound healing following modified crown lengthening surgery in dog model to provide a biological basis for its clinical application., Methods: Flap surgery, traditional crown lengthening procedure and modified crown lengthening procedure were performed on the right maxillary central incisor, the left maxillary central incisor and the left maxillary first lateral incisor respectively of five male beagle dogs. The right maxillary first lateral incisors with no surgical intervention were used as controls. Thirty-six weeks after the experimental procedure, tissue blocks were harvested and prepared for histological examination and analysis., Results: Histometric examination of buccolingual sections stained with hematoxylin-eosin demonstrated that the type of wound healing in the flap surgery group was re-attachment, similar to the control group. For the traditional crown lengthening surgery group, all of the five beagle dogs had lamellar cementum defects on root surface, the wound healing of four beagle dogs was new attachment accompanied by new cementum formation at cementum defect areas and the suprac-restal connective tissue was functionally oriented perpendicular to the new cementum. The wound healing of the other beagle dog was long junctional epithelial attachment, in which the junctional epithelium extended to the apical terminus of the cementum defect. In the modified crown lengthening surgery group, four beagle dogs had cementum defects on root surface (two lamellar cementum defects and two shallow platform-like cementum defects), the wound healing of three beagle dogs was new attachment, however, the supracrestal connective tissue was parallel to the root surface. The type of wound healing of another one beagle dog was long junctional epithelial attachment. Wound healing of one beagle dog in this group could not be characterized due to incomplete dissection., Conclusion: Wound healing in the modified crown lengthening surgery group was similar to the traditional crown lengthening surgery group, and two types of wound healing were observed: new attachment and long junctional epithelium attachment. Neither type of root treatment procedure (root planing or root reshaping) nor root surface defect pattern (the lamellar cementum defect or shallow platform-like cementum defect) influenced the observed type of wound healing.

Objective: To compare the clinical efficacy of combined application of glycine powder air-polishing and mechanical submucosal debridement in non-surgical treatment of peri-implant diseases., Methods: A randomized controlled clinical study was carried out on patients diagnosed with peri-implant diseases in the Department of Periodontology, Peking University School and Hospital of Stomatology, between May of 2020 and June of 2021.Twenty-eight patients with totally sixty-two implants were enrolled.The patients were randomly divided into the test group and control group. The patients in the test group (13 subjects/32 implants) received mechanical submucosal debridement using titanium curettes combined with application of glycine powder air-polishing, while the control group (15 subjects/30 implants) received mechanical submucosal debridement using titanium only. Clinical parameters, such as plaque index (PLI), pocket probing depth (PPD), bleeding index (BI) and the percentage of suppuration on probing on implants' level (SoP%) were measured at baseline and 8 weeks after non-surgical intervention. Changes and group differences of clinical parameters of the implants before and 8 weeks after non-surgical intervention were compared., Results: Mean PLI, PPD, BI of both the test group and control group significantly reduced 8 weeks after non-surgical intervention ( P < 0.05). Compared with the control group, the test group achieved lower BI (2.7±0.8 vs . 2.2±0.7, P < 0.05), more reduction of BI (0.6±0.7 vs . 1.1±0.6, P < 0.01) and more reduction of SoP% (21.9% vs . 10%, P < 0.05) after non-surgical intervention. Both the control and test groups exhibited comparable PLI and PPD reductions ( P >0.05). For the implants diagnosed with peri-implant mucositis, the test group revealed more signi-ficant reduction in BI and SoP% than the control group (1.0±0.7 vs . 0.4±0.7, P =0.02; 6.3% vs . 0, P =0.012). There was no significant difference existing in PLI and PD improvement between the control group and test group ( P >0.05). For the implants diagnosed with peri-implantitis, there was no significant difference existing in PLI, PPD, BI and SoP% improvement values between the test and control groups ( P >0.05). No complications or discomforts were reported during the study., Conclusion: Both treatment procedures could relieve the inflammation of peri-implant soft tissue. Non-surgical mechanical submucosal debridement combined application of glycine powder air-polishing is associated with significant reduction of soft tissue bleeding and suppuration on probing especially in the implants diagnosed with peri-implant mucositis.

Objective: To measure the three-dimensional morphology of the labial supraosseous gingiva (SOG) and the thickness of related labial bone in maxillary anterior teeth of periodontally healthy Han nationality youth using soft tissue indirect imaging cone-beam computed tomography (CBCT)., Methods: Twenty-five periodontally healthy subjects (11 males and 14 females) with 150 maxillary anterior teeth were involved in this study. A special impression with radiopaque material including the maxillary teeth was made, then a CBCT scan with the elastomeric matrix in position was taken for each subject. The imaging data were generated and transferred to a volumetric imaging software in which three-dimensional reconstruction was conducted and the image analyses were carried out. Measurements were made at the site of labial center of the maxillary anterior teeth. The height of the SOG, the distance between cemento-enamel junction (CEJ) and bone crest, the gingival thickness at the CEJ, and the thickness of bone 2 mm below the labial bone crest were measured and the correlation analysis between the parameters was made. All the data analyses were performed using SPSS 22.0. The data were analyzed with ANVOA and Pearson correlation tests with the significance level at α =0.05., Results: The mean SOG values were (3.49±0.70) mm, (3.48±0.81) mm, and (3.54±0.67) mm for central incisors, lateral incisors and canines, respectively. There were no statistically significant differences among the different sites ( P > 0.05). The mean gingival thickness values were (1.45±0.23) mm, (1.13±0.24) mm, (1.14±0.22) mm for central incisors, lateral incisors and canines, respectively. The gingival thickness of the central incisors was the largest among the maxillary anterior teeth with statistically significant difference ( P < 0.05). No correlation was found between the SOG and gingival thickness among the maxillary anterior teeth ( P > 0.05)., Conclusion: The gingival thickness of central incisors was the largest and the supraosseous gingival height had no correlation with gingival thickness among the periodontally healthy maxillary anterior teeth.

Objective: To explore the preliminary application of "biocopy function" in digital technology of temporary crown in severe tooth attrition, so as to reduce the difficulty of final restoration adjustment in severe tooth wear cases, and save clinical time., Methods: Twelve patients aged between 40 and 65 years with severe tooth attrition were recruited in this study. The experimental group (6 cases, 3 females and 3 males) used the method of digital copy of temporary restoration shape when making the final restoration, and the control group (6 cases, 3 females and 3 males) used the traditional method to make the final restoration. The mean time of central occlusal adjustment and protrusive and lateral occlusal adjustment of each crown, the number of follow-up visits of the patients were recorded and statistically analyzed. The occlusal comfort of the first and the third months after wearing the prosthesis was evaluated by the patients, and the difference of the occlusal comfort of the final prosthesis made by the two methods was compared (the full score was 10 points). The occlusal adjustment time and occlusal comfort score were used as measurement data. Single sample t test was used. The number of follow-up visits was count data. Rank sum test was used for non-normal continuous variables., Results: The mean occlusal time of each crown adjustment in the experimental group was significantly lower than that in the control group ( P < 0.01), and the median number of follow-up visits in the experimental group was lower than that in the control group ( P < 0.01). The average occlusal comfort score of the experimental group was higher than that of the control group at the first time ( P < 0.01). After three months of crown wearing, the median occlusal comfort score of the experimental group was higher than that of the control group ( P < 0.05)., Conclusion: In the case of severe tooth attrition, it is feasible to use the "biocopy function" in the design software to design the final prosthesis, which is conducive to reduce the difficulty of adjustment and achieve predictable functional and aesthetic effects, which is of great significance to save clinical time and improve the accuracy of restoration.

Objective: To compare the clinical effects of ultrasonic subgingival debridement and ultrasonic subgingival debridement combined with manual root planing on severe periodontitis and then to investigate the necessity and significance of manual root planing., Methods: Twenty-three patients with severe periodontitis participated in this split-mouth randomized-controlled clinical trial. Baseline examination and randomization were performed after supragingival scaling: each of the upper and lower jaws had a quadrant as the test group treated with ultrasonic subgingival debridement combined with manual root planing, whereas the other two quadrants were the control group treated with ultrasonic subgingival debridement. Treatment of each patient was at intervals of one week and completed in two visits. Clinical indicators concerning probing depth (PD), clinical attachment loss (CAL) and bleeding index (BI) were recorded at baseline and 1 month, 3 months, 6 months after treatment., Results: There was no significant difference of periodontal indicators between the test group and the control group at baseline. Both the test group and control group resulted in significant improvement of PD, CAL and BI. One and three months after treatment, reduction of PD in the test group was higher than that in the control group [1 month: (2.13±1.31) mm vs. (1.79±1.33) mm, P<0.01; 3 months: (2.46±1.33) mm vs. (2.17±1.38) mm, P<0.01] and reduction of CAL in the test group was higher than that in the control group [1 month: (1.89±2.03) mm vs. (1.65±1.93) mm, P<0.01; 3 months: (2.03±2.05) mm vs. (1.83±1.97) mm, P<0.05]. Six months after treatment, PD in the test group and the control group decreased by (2.52±1.40) mm and (2.35±1.37) mm respectively, and the improvement in the test group was significantly better than that in the control group (P<0.01). CAL in the test group and the control group decreased by (1.89±2.14) mm and (1.77±2.00) mm respectively, and there was no statistical difference between the groups. There was no significant difference in the changes of BI between the two groups 1, 3 and 6 months after treatment., Conclusion: Ultrasonic subgingival debridement combined with manual root planing has more reduction in PD and CAL compared with ultrasonic subgingival debridement. Therefore, it is still necessary to use manual instruments for root planing following ultrasonic subgingival debridement.

Objective: To evaluate and to compare dimensional alterations of hard and soft tissues in molar extraction sites with irregular deficiency of bone plates due to advanced periodontitis receiving two different procedures, namely the flapped and flapless techniques with Bio-Gide membrane covering the Bio-Oss material for ridge preservation., Methods: Twenty-three patients with 24 infected-molar extraction sites received ridge preservation procedure, the first consecutive 12 sites belonged to the flap group (a full thickness mucoperiosteal flap and primary soft tissue closure) and the following 12 sites belonged to the flapless group (minimal flap with a collagen sponge and a secondary soft tissue closure). Width of keratinized tissue was evaluated before tooth extraction and after 6-month healing. Parallel periapical radiographs were taken immediately and 6 months after extraction to evaluate vertical bone changes. The width of the ridge was measured in the center of the ridge at the time of tooth extraction and after 6 months at implant placement., Results: After 6 months, width of keratinized tissue decreased (1.6±1.5) mm in the flap group (P=0.004) when compared with (0.3±1.6) mm in the flapless group (P>0.05). Both groups showed increases in ridge height from the central aspect, (5.53±4.20) mm for flap group and (7.70±4.35) mm for flapless group. These differences between the groups were not statistically significant (P=0.226). The ridge widths were (9.5±2.2) mm for flap group and (9.3±1.0) mm for flapless group at the time of implant insertion, and no statistical significance was observed between the flap and flapless groups., Conclusion: The study points out that both ridge preservation techniques were effective in increasing ridge height and minimizing ridge resorption after tooth extraction, and the ridge width allowed the placement of implants 6 months after ridge preservation. The flapless technique gave positive outcome in terms of the keratinized gingival width than that of the flap technique.

Objective: To explore the accuracy of periapical film in evaluating the infrabone root surface area of single-root teeth with different types of resorption of the alveolar bone., Methods: In this study, the medical records and imaging data of patients in Department of Periodontology of Peking University Hospital of Stomatology from January 2014 to December 2016 were retrospectively analysed. The involved teeth were divided into two groups: horizontal bone loss group and vertical bone loss group. Digital three-dimensional models of teeth were segmented from cone beam computed tomography (CBCT) data, and the percentage of the infrabone root surface area was measured. While the percentage of the residual alveolar bone was measured on the periapical films. The correlation of the two percentages were analyzed, and the differences between the two percentages of each group were compared., Results: Thirty-two patients and 79 single-root teeth were involved totally, in whom there were 25 men and 7 women, aged 26-60 years, and of which there were 41 teeth in the horizontal bone loss group and 38 teeth in the vertical bone loss group. The remaining alveolar bone height percentages were 45.13%-90.39% on the periapical films, and at the same time, the infrabone root surface area percentages were 36.27%-93.03% on CBCT. The residual alveolar bone height percentage of the horizontal bone loss group was not subject to normal distribution, so the residual alveolar bone height percentage and the infrabone root surface area percentage were analyzed by Wilcoxon matched pair rank test (P=0.382), and the result showed no statistically significant difference. The mean value of difference value of the two measurements was 0, and the consistency limit of 95 % was -9.7%-9.8%, between the clinical consistency limit (-15%-15%).The residual alveolar bone height percentage and the infrabone root surface area percentage of the vertical bone loss group were analyzed by paired T test (P< 0.001), and the result showed statistically significant difference. The mean value of difference value of the two measurements was 7.2 %, and the consistency limit of 95% was -13.1%-27.5%, beyond clinical consistency limit (-15%-15%)., Conclusion: For the teeth with horizontal bone loss, the proximal residual alveo-lar bone height reflected on the periapical films could show the infrabone root surface area relatively accurately. For the teeth with vertical bone loss, the periapical films could not show the degree of periodontal tissue loss accurately, and it would underestimate the extent of bone destruction usually, so CBCT might be taken to show the bone destruction condition of this type of teeth if necessary.

Objective: To develop a digital workflow of orthodontic-prosthodontic multidisciplinary treatment plan which can be applied in complicated anterior teeth esthetic rehabilitation, in order to enhance the efficiency of communication between dentists and patients, and improve the predictability of treatment outcome., Methods: Twenty patients with the potential needs of orthodontic-prosthodontic multidisciplinary treatment to solve their complicated esthetic problems in anterior teeth were recruited in this study. Digital models of patients' both dental arches and soft tissues were captured using intra oral scanner. Direct prosthodontic (DP) treatment plan and orthodontic-prosthodontic (OP) treatment plan were carried out for each patient. For DP treatment plans, digital wax-up models were directly designed on original digital models using prosthodontic design system. For OP treatment plans, virtual-setups were performed using orthodontic analyze system according to orthodontic and esthetic criteria and imported to prosthodontic design system to finalize the digital wax-up models. These two treatment plans were shown to the patients and demonstrated elaborately. Each patient rated two treatment plans using visual analogue scales and the medians of scores of two treatment plans were analyzed using signed Wilcoxon test. Having taken into consideration various related factors, including time, costs of treatment, each patient chose a specific treatment plan. For the patients chose DP treatment plans, digital wax-up models were exported and printed into resin diagnostic models which would be utilized in the prosthodontic treatment process. For the patients chose OP treatment plans, virtual-setups were used to fabricate aligners or indirect bonding templates and digital wax-up models were also exported and printed into resin diagnostic models for prosthodontic treatment after orthodontic treatment completed., Results: The medians of scores of DP treatment plan and OP treatment plan were calculated and analyzed by IBM SPSS 20. The median of scores of DP treatment plan was 8.4, the minimum value was 6.9 and the maximum value was 9.3. The median of scores of OP treatment plan was 9.0, the minimum value was 7.9 and the maximum value was 9.6. The median of scores of OP was significantly higher than that of DP (Z=-3.23, P<0.01). Finally, 12 patients chose OP treatment plans and 8 patients chose DP treatment plans., Conclusion: For cases with complex esthetic problems in anterior teeth, a digital workflow can demonstrate final treatment outcome and help patients make suitable treatment decisions. In our study, the orthodontic-prosthodontic multidisciplinary treatment plan is feasible which can provide predictions of treatment outcome and improve esthetic outcome with patients' satisfaction.

Objective: To explore a new method of whole-process digital esthetic prosthodontic rehabilitation combined with periodontic surgery for complicated anterior teeth esthetic defects accompanied by soft tissue morphology, to provide an alternative choice for solving this problem under the guidance of three-dimensional (3D) printing digital dental model and surgical guide, thus completing periodontic surgery and digital esthetic rehabilitation of anterior teeth., Methods: In this study, 12 patients with complicated esthetic problems accompanied by soft tissue morphology in their anterior teeth were included. The dentition and facial images were obtained by intra-oral scanning and three-dimensional (3D) facial scanning and then calibrated. Two esthetic designs and prosthodontic outcome predictions were created by computer aided design /computer aided manufacturing (CAD/CAM) software combined with digital photography, including consideration of white esthetics and comprehensive consideration of pink-white esthetics. The predictive design of prostheses and the facial appearances of the two designs were evaluated by the patients. If the patients chose the design of comprehensive consideration of pink-white esthetics, they would choose whether they would receive periodontic surgery before esthetic rehabilitation. The dentition design cast of those who chose periodontic surgery would be 3D printed for the guide of periodontic surgery accordingly., Results: In light of the two digital designs based on intra-oral scanning, facing scanning and digital photography, the satisfaction rate of the patients was significantly higher for the comprehensive consideration of pink-white esthetic design (P<0.05) and more patients tended to choose priodontic surgery before esthetic rehabilitation. The 3D printed digital dental model and surgical guide provided significant instructions for periodontic surgery, and achieved success transfer from digital design to clinical application. The prostheses were fabricated by CAD/CAM, thus realizing the whole-process digital esthetic rehabilitation., Conclusion: The new method for esthetic rehabilitation of complicated anterior teeth esthetic defects accompanied by soft tissue morphology, including patient-involved digital esthetic analysis, design, esthetic outcome prediction, 3D printing surgical guide for periodontic surgery and digital fabrication is a practical technology. This method is useful for improvement of clinical communication efficiency between doctor-patient, doctor-technician and doctors from different departments, and is conducive to multidisciplinary treatment of this complicated anterior teeth esthetic problem.

Objective: To evaluate bone formation in human extraction sockets with absorbed surrounding walls augmented with Bio-Oss and Bio-Gide after a 6-month healing period by histologic and histomorphometric analyses., Methods: Six fresh molar tooth extraction sockets in 6 patients who required periodontally compromised moral tooth extraction were included in this study. The six fresh extraction sockets were grafted with Bio-Oss particle covered with Bio-Gide. The 2.8 mm×6.0 mm cylindric bone specimens were taken from the graft sites with aid of stent 6 months after the surgery. Histologic and histomorphometric analyses were performed., Results: The histological results showed Bio-Oss particles were easily distinguished from the newly formed bone, small amounts of new bone were formed among the Bio-Oss particles, large amounts of connective tissue were found. Intimate contact between the newly formed bone and the small part of Bio-Oss particles was present. All the biopsy cylinders measurement demonstrated a high inter-individual variability in the percentage of the bone, connective tissues and Bio-Oss particles. The new bone occupied 11.54% (0-28.40%) of the total area; the connective tissues were 53.42% (34.08%-74.59%) and the Bio-Oss particles were 35.04% (13.92%-50.87%). The percentage of the particles, which were in contact with bone tissues, amounted to 20.13% (0-48.50%)., Conclusion: Sites grafted with Bio-Oss particles covered with Bio-Gide were comprised of connective tissues and small amounts of newly formed bone surrounding the graft particles.

For ideal implant rehabilitation, an adequate bone volume, optical implant position, and stable and healthy soft tissue are required. The reduction of alveolar bone and changes in its morphology subsequent to tooth extraction will result in insufficient amount of bone and adversely affect the ability to optimally place dental implants in edentulous sites. Preservation of alveolar bone volume through ridge preservation has been demonstrated to reduce the vertical and horizontal contraction of the alveolar bone crest after tooth extraction and reduce the need for additional bone augmentation procedures during implant placement. In this case, a patient presented with a mandible molar of severe periodontal disease, the tooth was removed as atraumatically as possible and the graft material of Bio-Oss was loosely placed in the alveolar socket without condensation and covered with Bio-Gide to reconstruct the defects of the alveolar ridge. Six months later, there were sufficient height and width of the alveolar ridge for the dental implant, avoiding the need of additional bone augmentation and reducing the complexity and unpredictability of the implant surgery. Soft tissue defects, such as gingival and connective tissue, played crucial roles in long-term implant success. Peri-implant plastic surgery facilitated development of healthy peri-implant structure able to withstand occlusal forces and mucogingival stress. Six months after the implant surgery, the keratinized gingiva was absent in the buccal of the implant and the vestibular groove was a little shallow. The free gingival graft technique was used to solve the vestibulum oris groove supersulcus and the absence of keratinized gingiva around the implant. The deepening of vestibular groove and broadening of keratinized gingiva were conducive to the long-term health and stability of the tissue surrounding the implant. Implant installation and prosthetic restoration showed favorable outcome after six months.

Objective: To explore a crown form classification method for upper central incisor which is more objective and scientific than traditional classification method based on the standardized photography technique. To analyze the relationship between crown form of upper central incisors and papilla filling in periodontally healthy Chinese Han-nationality youth., Methods: In the study, 180 periodontally healthy Chinese youth ( 75 males, and 105 females ) aged 20-30 (24.3±4.5) years were included. With the standardized upper central incisor photography technique, pictures of 360 upper central incisors were obtained. Each tooth was classified as triangular, ovoid or square by 13 experienced specialist majors in prothodontics independently and the final classification result was decided by most evaluators in order to ensure objectivity. The standardized digital photo was also used to evaluate the gingival papilla filling situation. The papilla filling result was recorded as present or absent according to naked eye observation. The papilla filling rates of different crown forms were analyzed. Statistical analyses were performed with SPSS 19.0., Results: The proportions of triangle, ovoid and square forms of upper central incisor in Chinese Han-nationality youth were 31.4% (113/360), 37.2% (134/360) and 31.4% (113/360 ), respectively, and no statistical difference was found between the males and females. Average κ value between each two evaluators was 0.381. Average κ value was raised up to 0.563 when compared with the final classification result. In the study, 24 upper central incisors without contact were excluded, and the papilla filling rates of triangle, ovoid and square crown were 56.4% (62/110), 69.6% (87/125), 76.2% (77/101) separately. The papilla filling rate of square form was higher (P=0.007)., Conclusion: The proportion of clinical crown form of upper central incisor in Chinese Han-nationality youth is obtained. Compared with triangle form, square form is found to favor a gingival papilla that fills the interproximal embrasure space. The consistency of the present classification method for upper central incisor is not satisfying, which indicates that a new classification method, more scientific and objective than the present one, is to be found.

Objective: To investigate the changes of the vertical height and width of the alveolar bone six months after the alveolar ridge preservation in periodontal compromised molar sites of severe alveolar bone defects with clinical direct measurement, parallel periapical radiographs, and cone-beam computed tomography (CBCT), and to analyze the effect of the three different methods of measurement., Methods: In this study, 20 subjects requiring tooth extraction on account of periodontal disease with a total of 23 extracted molars were enrolled. Extractions were performed atraumatically and patients were received alveolar ridge preservation procedure with Bio-Oss and Bio-Gide. Clinical direct measurements were taken after tooth extraction and during the implant surgery 6 months later, CBCT scans and parallel periapical radiographs were taken immediately after ridge preservation and 6 months later. The changes of alveolar ridge width and vertical height after six months were measured and analyzed through the above-mentioned three methods and the similarities and differences of the measured effect were compared., Results: There were no significant difference of alveolar vertical height in the center of the extraction sites, the center of distal aspect, and distobuccal aspect between the clinical direct measurements and the CBCT measurements (P>0.05), alveolar vertical height in other points and alveolar width measurements were statically significant (P<0.05). After 6 months, 10 sites of 10 subjects were received a flap and re-entered to perform dental implants surgery. The vertical height in the center of alveolar increased significantly and the changes of alveolar vertical height of clinical direct and CBCT measurement were (6.15 ± 1.73) mm and (6.59 ± 2.53) mm, respectively. The measurements of the width of the alveolar bone were (8.45 ± 1.18) mm and (8.52 ± 1.27) mm, respectively. The measurements of the two methods were not statistically significant (P>0.05). The change of the alveolar height in the center of the extraction socket after six months measured by parallel periapical was (5.84 ± 4.28) mm, which was closed to the clinical direct measurement and the CBCT measurement., Conclusion: Clinical direct measurement and CBCT measurement were largely consistent in the evaluation of the alveolar bone height and width after the alveolar ridge preservation using deproteinized boving bone mineral (DBBM, Bio-Oss) and bioabsorbable collagen membrane (Bio-Gide) in periodontal compromised molar sites of severe bone defects.

Objective: To construct the finite element models of maxillary central incisor and the simulations with crown lengthening surgery and post-core restoration in management of different crown-root fracture types, to investigate the stress intensity and distributions of these models mentioned above, and to analyze the indications of crown lengthening from the point of view of mechanics., Methods: An extracted maxillary central incisor and alveolar bone plaster model were scanned by Micro-CT and dental impression scanner (3shape D700) respectively. Then the 3D finite element models of the maxillary central incisor and 9 simulations with crown lengthening surgery and post-core restoration were constructed by Mimics 10.0, Geomagic studio 9.0 and ANSYS 14.0 software. The oblique static force (100 N) was applied to the palatal surface (the junctional area of the incisal 1/3 and middle 1/3), at 45 degrees to the longitudinal axis, then the von Mises stress of dentin, periodontal ligament, alveolar bone, post and core, as well as the periodontal ligament area, were calculated., Results: A total of 10 high-precision three-dimensional finite element models of maxillary central incisor were established. The von Mises stress of models: post>dentin>alveolar bone>core>periodontal ligament, and the von Mises stress increased linearly with the augmentation of fracture degree (besides the core). The periodontal ligament area of the crown lengthening was reduced by 12% to 33%. The von Mises stress of periodontal ligament of the B2L2c, B2L3c, B3L1c, B3L2c, B3L3c models exceeded their threshold limit value, respectively., Conclusion: The maxillary central incisors with the labial fracture greater than three-quarter crown length and the palatal fracture deeper than 1 mm below the alveolar crest are not the ideal indications of the crown lengthening surgery.

In this article, different methods to deal with teeth fractures were discussed by presenting a case of traumatic crown-root fracture in the anterior esthetic zone. The traumatic crown-root fracture is a common problem in clinic. When a fracture line locates in close proximity to or below the alveolar bone crest, the fracture most likely involve the junctional epithelium and the connective tissue attachment. This type of fracture becomes a challenge for restorative dentists because it involves biologic, functional, and esthetic considerations, especially when the fracture occurs in an esthetic area. In this case, a young patient presented with two fractured upper anterior teeth to the Department of Periodontics, Peking University School and Hospital of Stomatology. After the comprehensive clinical evaluation, the right central incisor was decided to extract for implant therapy and the right lateral incisor was decided to retain by one modified crown lengthening surgery. The most common technique applied to save a retained root is a clinical crown lengthening procedure. However, the aggressive alveolar bone resection of both target and adjacent teeth to reestablish the bone width and periodontal health may compromise functional and esthetic outcomes. To reduce loss of excessive osseous tissue during osteotomy procedure, the modified crown lengthening of the right lateral incisor was performed, including minor bone resection and root reshaping. Regarding the right central incisor, the retained root was all located below the alveolar bone crest. The extraction and implant procedure, combined with guided bone graft were performed to avoid the damage to neighbor teeth during traditional restorative therapy and to reshape a preferable buccal contour. At the last visit, the patient was recalled with healthy periodontium, normal tooth function and favorable esthetic results.

Objective: To compare the bone dimensional changes following tooth extraction alone with extraction plus ridge preservation (using deproteinized boving bone mineral Bio-Oss® and bioresorbable collagen mambrane Bio-Gide®) in periodontal compromised extraction sockets., Methods: Eighteen molars of sixteen subjects requiring tooth extraction because of periodontal destruction were enrolled in this study. The subjects were assigned to the control group (extraction alone, EXT) or to the test group (ridge-preservation procedure with Bio-Oss® and Bio-Gide, RP). Parallel periapical X-rays and cone-beam computed tomography (CBCT) scans were taken immediately after tooth extraction alone or plus ridge-preservation (baseline) and 6 months later. The changes of horizontal ridge width and vertical ridge height were assessed., Results: At the central buccal aspect, the ridge height increased 2.9 mm in RP group, and reduced 1.0 mm in EXT group. At the distal buccal aspect, the ridge height increased 1.45 mm in RP group, and reduced 1.45 mm in EXT group. The differences between the groups reached statistical significance (P<0.05). The mean ridge width increased at the 1 mm below the crest (the horizontal ridge width was measured with grafting material at three levels at 1 mm below the most coronal aspect of the crest,HW1), which amounted to 3.40 to 5.80 mm in RP group, and 1.45 to 2.90 mm in EXT group. The mean ridge increased at the 4 mm below the crest (the horizontal ridge width was measured with grafting material at three levels at 4 mm below the most coronal aspect of the crest,HW4), which amounted to 0.40 to 3.50 mm in RP group, and reduced 0.10 to increased 0.15 mm in EXT group. The test group and the control group were not significantly different (P>0.05)., Conclusion: The ridge-preservation approach using Bio-Oss® in combination with Bio-Gide® can significantly increase vertical ridge height and horizontal ridge width after tooth extraction compared with extraction alone in periodontal compromised molars.

A young lady with unsatisfied restorations of upper anterior teeth and swollen gum wanted to improve aesthetics. Oral examination showed that 12-22 were provisional crowns with normal occlusion, poorly gingival contour and gummy smile. The gingiva was red, light swollen and bleeding on probing. X-ray showed the roots of 11, 21 were short and the alveolar bone absorbed. After the periodontal initial treatment, an ideal location of gingival margin was determined. Then, an esthetic periodontal surgery was performed to recover the biology width and the gingival margin was fitted with the anterior teeth. The temporary restorations were made twice to guide the gingiva growth by changing the shape of the restorations and moving up the contact points of the restorations. The ceramic crowns were completed 3 months after the operation. The gummy smile disappeared and the gingival margin was filled well with the upper anterior ceramic crowns. The 14-month follow-up presented a satisfied effect. Crown lengthening surgery combined restorative therapy could lead papilla to grow well. This process is beneficial for the future treatment plan and clinical esthetic evaluation.

Objective: To establish the relationship of the gingival crest, the gingival curve characteristic point (inflection point, IP) and the contact points and to use it as reference to design the location of contact area in anterior teeth restoration to form the natural papillae., Methods: Two-dimensional gingival curve morphology analysis based on standardized digital images was done to measure the value of different points in the upper anterior teeth for 120 young Chinese., Results: In the maxillary anterior teeth, the average mesial papilla heights(MPH) of central incisors(CI), lateral incisors(LI), canines(CA) were (4.49 ± 0.86) mm, (3.64 ± 0.77) mm and (4.12 ± 0.92) mm; the average distal gingival papilla heights(DPH) were (4.09 ± 0.72) mm, (3.48 ± 0.83) mm and (4.13 ± 0.94) mm . The relationship of the gingival curve inflection points of maxillary anterior teeth with the gingival zenith and the contact points were determined in horizontal and vertical ways. In the CI, the mesial IP in X and Y axis were 0.61±0.10 and 0.26±0.07, in distal were 0.57±0.10 and 0.25±0.07. In the LI, the mesial IP in X and Y axis were 0.50±0.10 and 0.23±0.08, in distal were 0.56±0.11 and 0.26±0.08. In the CA, the mesial IP in X and Y axis were 0.52±0.09 and 0.23±0.07, the distal IP were 0.60±0.12 and 0.26±0.08., Conclusion: The upper anterior teeth papillae shapes of the different teeth and gingival curves are determined with certain characteristics, and the gingival curve inflection points have some mathematical relationship with the gingival crest and the contact points.

Objective: To develop a novel method for obtaining the clear visualization of the gingival profile by cone-beam computed tomography (CBCT) that consistently allows the measurements of gingival thickness and use it to explore the relationship between the gingival thickness and gingival biotype, and the gingival thickness and underlying alveolar bone thickness in the maxillary anterior region., Methods: In this study, 15 volunteers with healthy gingiva in the maxillary anterior teeth were involved, and a special preparation was done before CBCT scans including making impression with the contrast agent. The tissue biotypes were assessed clinically with the probe, The thickness of both gingiva and bone and the gingival thickness of the cemento-enamel junction (CEJ) were measured radiographically with cone-beam computed tomography scans. All data analyses were performed using SPSS 16.0., Results: The CBCT image showed clear visualization of the gingival profile. The average gingival thickness of the CEJ was (1.22±0.32) mm. A correlation was observed between the tissue biotypes and the gingival thickness (r=0.449,P<0.05). The labial gingival thickness was negative associated with the underlying bone thickness measured with CBCT in the maxillary anterior region (r=-0.31, P=0.021)., Conclusion: A method was established for measuring gingival thickness based on cone-beam computed tomography. The gingival biotypes had a positive correlation with gingival thickness of the CEJ.

Objective: To present a modified option to surgical crown lengthening for repair of biologic width loss., Methods: The alternative to the traditional method involves reshaping the fractured root surface in combination with conservative removal of the supporting alveolar bone to rebuild the biological width. Although these teeth were considered as not suitable for the traditional methods, 7 teeth from 7 patients with fracture surface located lower than alveolar bone crest were treated by this modified method of surgical crown lengthening. Restoration was accomplished on these teeth two month later. Periodontal index such as tooth mobility, plaque index, probing depth and bleeding index were recorded and followed up., Results: The mean follow-up period was 17 months (ranged from 10 to 31 months). Result of surgery and restoration of these 7 teeth was satisfactory. The gingival tissue remained healthy and esthetic with good function., Conclusion: This modified surgical crown lengthening can be used as an alternative to the traditional method to save more fractured teeth.