[Constructing 3-dimensional colorized digital dental model assisted by digital photography].

OBJECTIVE: To explore a method of constructing universal 3-dimensional (3D) colorized digital dental model which can be displayed and edited in common 3D software (such as Geomagic series), in order to improve the visual effect of digital dental model in 3D software. METHODS: The morphological data of teeth and gingivae were obtained by intra-oral scanning system (3Shape TRIOS), constructing 3D digital dental models. The 3D digital dental models were exported as STL files. Meanwhile, referring to the accredited photography guide of American Academy of Cosmetic Dentistry (AACD), five selected digital photographs of patients'teeth and gingivae were taken by digital single lens reflex camera (DSLR) with the same exposure parameters (except occlusal views) to capture the color data. In Geomagic Studio 2013, after STL file of 3D digital dental model being imported, digital photographs were projected on 3D digital dental model with corresponding position and angle. The junctions of different photos were carefully trimmed to get continuous and natural color transitions. Then the 3D colorized digital dental model was constructed, which was exported as OBJ file or WRP file which was a special file for software of Geomagic series. For the purpose of evaluating the visual effect of the 3D colorized digital model, a rating scale on color simulation effect in views of patients'evaluation was used. Sixteen patients were recruited and their scores on colored and non-colored digital dental models were recorded. The data were analyzed using McNemar-Bowker test in SPSS 20. RESULTS: Universal 3D colorized digital dental model with better color simulation was constructed based on intra-oral scanning and digital photography. For clinical application, the 3D colorized digital dental models, combined with 3D face images, were introduced into 3D smile design of aesthetic rehabilitation, which could improve the patients' cognition for the esthetic digital design and virtual prosthetic effect. CONCLUSION: Universal 3D colorized digital dental model with better color simulation can be constructed assisted by 3D dental scanning system and digital photography. In clinical practice, the communication between dentist and patients could be improved assisted by the better visual perception since the colorized 3D digital dental models with better color simulation effect.

[Influence of carbodiimide-ethanol solution surface treatment on dentin microtensile bond strength].

OBJECTIVE: To evaluate the microtensile bond strength changes and patterns of fractures of the bonding interface after dentine surface treatment with carbodiimide-ethanol solution. METHODS: 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) dissolved in ethanol was diluted into different concentrations of 2, 1, 0.3, 0.1 and 0.01 mol/L EDC-ethanol solutions. Twenty-eight caries-free extracted human third molars were ground metallurgically to prepare flat occlusal mid-coronal dentin surfaces and etched with 35% (mass fraction) phosphoric acid gel. Then they were treated with EDC-ethanol solution for 60 s before the bonding procedure and randomly divided into five experimental groups corresponding to the tested EDC-ethanol concentrations. The ethanol treated and no pre-treated surfaces were used as controls. Single Bond 2 adhesive was applied and resin composite disk was stacked on the treated dentine surface. The teeth with resin composite disks were stored in water at room temperature for 24 h and then sectioned longitudinally to produce stick specimens for microtensile bond strength test. Fracture patterns were observed with a stereomicroscope. RESULTS: The dentin surfaces pre-treated with 2 mol/L [(22.17±13.31) MPa] and 1 mol/L [(45.31±17.80) MPa] EDC-ethanol solutions resulted in statistically significant lower bond strength value (P<0.05). Increasing numbers of fracture pattern at the resin-dentin interface were also found in this two groups with percentages of 81.2% and 41.3% respectively. No significant difference was observed in the groups with 0.3, 0.1, 0.01 mol/L EDC surface treatment (P>0.05). CONCLUSION: No significant difference of immediate bond strengths was found in the 0.3, 0.1, 0.01 mol/L groups compared with the control group. EDC-ethanol solution surface treatment with concentrations of 2 mol/L and 1 mol/L resulted in decreasing of the bonding strength.

[Ectopic osteogenesis of stromal cell-derived factor 1 combined with simvastatin-loaded collagen scaffold in vivo].

OBJECTIVE: To construct and evaluate a novel tissue-engineered bone composed of murine stromal cell-derived factor 1(mSDF-1), simvastatin (SIM) and collagen scaffold (Bio-Oss®), serving as a cell-homing approach for bone formation. METHODS: In the study, 32 ICR mice were randomly divided into 4 groups,each group including 8 mice. The drug-loaded collagen scaffolds were implanted subcutaneously onto the cranium of each mouse according to the groups: (1) 1:50 (volume ratio) dimethyl sulfoxide (DMSO)/phosphate-buffered saline (PBS) solution + collagen scaffold (blank control group); (2) 10⁻³ mol/L SIM solution + collagen scaffold (SIM group); (3) 200 mg/L mSDF-1 solution + collagen scaffold (mSDF-1 group); and (4) 10® mol/L SIM +200 mg/L mSDF-1 solution + collagen scaffold (SIM + mSDF-1 group). One week after implantation, the mice were treated by injecting the same drug solution mentioned above around the scaffold once a day for two days. The specimens were harvested 6 weeks after implantation and the bone formation was evaluated by soft X-ray analysis, HE staining and immunohistochemical staining. Angiogenesis of each group was checked by calculation of vessels in each tissue section. RESULTS: Six weeks after implantation, the collagen scaffolds were retrieved. The value of gray scale for the SIM+mSDF-1 group [(421 836.5 ± 65 425.7)pixels] was significantly higher than that of the blank control group[(153 345.6 ± 45 222.2) pixels, P<0.01], the SIM group [(158 119.2 ± 100 284.2)pixels, P<0.01], and the mSDF-1 group[(255 529.5 ± 152 142.4)pixels, P<0.05]; HE staining analysis revealed that significant bone formation was achieved in the SIM + mSDF-1 group; The immunohistochemical staining showed the existence of osteopontin and osteocalcin in the SIM + mSDF-1 group; There were more vessels in the SIM+mSDF-1 group[(46 ± 8)vessels/mm²] than in the blank control group [(23 ± 7) vessels/mm2, P<0.01], and the SIM group[(24 ± 6) vessels/mm2, P<0.01]. CONCLUSION: The novel tissue-engineered bone composed of mSDF-1, SIM and collagen scaffolds has the potential to form bone subcutaneously in vivo. It represents a novel method of in vivo bone re-generation without seed cell delivery.

[Application of patient-participated digital design in esthetic rehabilitation of anterior teeth].

OBJECTIVE: To explore a new method of patient-involved digital design, esthetic outcome prediction and fabrication for the esthetic rehabilitation of anterior teeth, and to provide an alternative choice for the restoration of anterior teeth. METHODS: In this study, 32 patients with esthetic problems in their anterior teeth were included and divided into two groups randomly: the experimental group (16 patients) and control group (16 patients). In the experimental group, the dentition and facial images were obtained by intra-oral scanning and Three-dimensional (3D) facial scanning and then calibrated. The design of the rehabilitation and the esthetic outcome prediction were created by computer-aided design (CAD) software. After morphologic modification according to the patients' opinions, prostheses were fabricated according to the final design by computer-aided manufacturing (CAM) equipment. As for the control group, the regular design method was applied to restore their anterior teeth. The time consuming in the first insertion of each restoration in both groups was recorded. The quality of the prostheses was assessed by another prosthedontist. The satisfaction to prostheses and the facial appearance were evaluated by the patients. RESULTS: The process of the patient-involved digital design and outcome anticipation was successfully established. The patients were satisfied with the esthetic effects of the anterior restoration made by the digital technique. The acceptance rate of the patients on the digital rehabilitation in the experimental group was 100%. There was no significant difference of the quality of the prostheses between the two groups. The satisfaction rate of the patients on prostheses and facial appearance was significantly higher in the experimental group than in the control group (P < 0.05). In addition, the time consuming in the first insertion of the experimental group was much shorter than that in the control group (P < 0.01). CONCLUSION: The new method of the patient-involved digital design, esthetic outcome prediction and fabrication for the esthetic rehabilitation of anterior teeth is a practical technique. This method is useful in shortening the time consuming of the restoration of anterior teeth and improving the patient satisfaction with the esthetic outcome.

[Esthetic evaluation of Cerec 3D anterior crowns].

OBJECTIVE: To observe the short-term effect of clinical application of Cerec 3D anterior crowns. METHODS: A total of 16 patients were restored with 31 Cerec 3D anterior crowns. All restorations were stained before cementation. The evaluation started 1 week after luting. The restorations were examined in accordance with the modified US Public Health Service (USPHS) criteria at baseline and every 6 - 12 months. RESULTS: The observation period of 31 Cerec 3D anterior crowns varied from 8 to 33 months. The mean observation period was 22 months. All restorations scored A or B by modified USPHS standard. And 22 out of 31 restorations scored A for all criteria while 8 restorations scored B in color matching. Slight differences of translucency and chroma could be observed. Between baseline and follow-up examinations, insignificant shift from A-to B-rating occurred. CONCLUSION: Cerec 3D anterior crowns may achieve favorable short-term esthetic effects.

Quality of life in patients with cancer-related Brown IIb maxillary defect: A comparison between conventional obturation rehabilitation and submental flap reconstruction.

OBJECTIVES: The purpose of this retrospective study was to compare the differences in quality of life (QOL) outcomes between the conventional obturator prostheses (COP) and the pedicled submental artery island flap (SAIF) in the reconstruction of Brown IIb maxillary defects. MATERIALS AND METHODS: The QOL of 116 eligible patients who had a lapse ≥ 12 months after the cancer-related maxilla ablation was evaluated by the University of Washington quality of life scale (UW-QOL), Performance Status Scale for Head and Neck (PSS-HN), and Obturator Functioning Scale (OFS). RESULTS: Patients in the SAIF group reported statistically and clinically significant higher overall QOL scores but lower chewing scores in the UW-QOL scale when compared with those in the COP group (P < 0.05). Clinically significantly higher scores were also observed in the recreation and anxiety domains in the UW-QOL scale for the SAIF group, but there was no statistical significances. The COP group reported more complaints about the nasal leakage when swallowing and the shape of the upper lip, and had a stronger willingness to avoid family or social events in the OFS (P < 0.05). CONCLUSIONS: For patients with Brown IIb defects, SAIF reconstruction can achieve reduced nasal leakage when swallowing, improved upper-lip contour, increased social activity, and superior overall QOL than COP. The inferior chewing function in the SAIF group indicated the need for dental rehabilitation with a conventional denture or osseointegrated implants.

[Denture-like applicators with radioactive seeds for treatment of palatal malignant tumors].

OBJECTIVE: To design and make denture-like applicators containing radioactive seeds for treatment of malignant tumors in the hard palate where only thin layers of soft tissues are available. METHODS: Forty-two patients were treated with denture-like applicators containing (125)I radioactive seeds after local resection of malignant salivary gland tumors the hard palate. Sixteen patients were male, and 26 patients were female. The average age was 37.6 years old (18-74 years old). The denture-like applicators were consisted of three parts: resin layer (about 1.0 mm in thickness) which contacted with surgical area and contained radioactive seeds; the cobalt-chromium alloy layer (about 1.0 mm in thickness) which protected surrounding normal tissues; the clasps which acted as retainers for applicators. The resin layer and the alloy layer were connected together mechanically. Artificial teeth were applied on the applicators to restore the masticatory function when partially edentulous upper jaws were available. All these patients were followed up for 12-72 months. The complications in target areas and adjacent normal tissues were observed. The stability of radioactive seeds, the recurrence of the tumor was also observed during the follow-up. RESULTS: No patients complained about hurt or burning of adjacent normal tissues. 8/42 patients felt some uncomfortable, such as gagging, more saliva on the first one or two days. No radioactive seeds were lost and dislocated during the treatment. The surgical wounds healed perfectly. No mucosal ulcer, no recurrence of tumor, and no other complications for the target areas were observed. The living standard of the patients was improved. CONCLUSION: The denture-like applicator containing (125)I radioactive seeds is a feasible, effective, and convenient way to treat malignant tumors around the hard palate, where there is no enough room to implant radioactive seeds. This method can effectively irradiate the target areas when treating the malignant tumors in the palate.

Clinical application and research progress of digital complete denture.

Digital technologies use high-precision three-dimensional scanning, intelligence-aided design software, and multi-axis numerical control milling or 3D printing, which can produce restorations with reliable precision and suitable function. However, the development of digital technologies in the field of complete denture restoration has been slow due to the complexity of prosthesis. This review article introduces the current research status and clinical applications of digital complete dentures in prosthodontic clinics and dental laboratories to provide beneficial references to prosthodontists and dental technicians.

Clinical Evaluation of 532-nm Green Laser on Dentin Hypersensitivity: A Randomized Double-Blind Clinical Trial.

Objective: The aim of this study was to evaluate the therapies of low-level green laser and chemical desensitizer in the treatment of dentin hypersensitivity (DH). Methods: Forty-eight patients with 96 sensitive teeth were invited to participate in this clinical trial and were randomly divided into three groups. One group was treated with low-level green laser, the second group was treated with desensitizer [sodium fluoride (NaF)], and the third group acted as the placebo group and was treated with distilled water and placebo laser. The wavelength of green laser was 532 nm and the irradiance was 15 J/cm2 per treatment site. Hypersensitivity was assessed by visual analogue scale (VAS) according to cold test and probing at baseline. Immediately, 2 weeks, and 3 months after the application of green laser, NaF, and placebo, the participants' sensitivity level was accessed by new VAS analysis. Results: Forty-five patients with 90 teeth (n = 15 patients/group; 30 teeth/group) were followed up for 2 weeks and 3 months after treatment. There were significant differences in VAS scores between the placebo group and intervention group (green laser group and NaF group; analysis of variance, p < 0.05) at all three time points. The mean pain scores in DH reduced significantly immediately after treatment in the green laser group and NaF group when stimulated by cold and probing, whereas no significant difference was observed with these two therapies after 2 weeks (p > 0.05). After 3 months, mean VAS scores of the NaF group were higher than those of the green laser group (p < 0.01). Conclusions: Therefore, the green laser displayed similar effectiveness as NaF in treatment of DH and could be a promising new therapy to reduce DH.

Preventive and Control Measures for the Coronavirus Pandemic in Clinical Dentistry.

A severe public health crisis has been declared worldwide since coronavirus disease 2019 (COVID-19) was classified as a pandemic of acute respiratory infectious disease by the World Health Organisation (WHO). China has taken strict measures to curb the spread of the disease to save lives, and has managed to control the outbreak. COVID-19 is mainly transmitted through respiratory droplets and close physical contact, so it is challenging to prevent nosocomial infection and possible spread during dental treatment. Since the initial phase of the COVID-19 outbreak, a disease prevention and control strategy based on the new concept of population risk classification and rational use of personal protective equipment has been implemented by the Peking University Hospital of Stomatology. Nosocomial infection prevention and control concepts and measures relating to dental diagnosis and treatment are critically checked in the hospital. Our experiences in handling this situation are shared here and may have wide-ranging implications for infection prevention and control (IPC) for COVID-19 in dental practices worldwide.

Clinical Efficiency and Patient Preference of Immediate Digital Impression after Implant Placement for Single Implant-Supported Crown.

OBJECTIVE: To evaluate the time efficiency and patient preference of three impression techniques by comparing immediate digital impression performed directly after implantation with regular digital impression and conventional implant impression performed 3 months after implantation. METHODS: Twenty consecutive patients with a missing single molar or premolar who received implant treatment were recruited into this prospective self-controlled clinical trial. Three different impression techniques were performed after implant surgery on all the participants: An intraoral scanning (IOS) impression performed immediately after implant placement (immediate digital impression) was compared with a regular digital impression and a classic polyether impression (conventional implant impression) performed 3 months after implant surgery. The operating time of each impression technique was recorded. Patients were asked to complete a visual analogue scale (VAS) questionnaire on their perception of the three techniques to describe their satisfaction and preference. Statistical analyses were performed with the Wilcoxon signed rank test. RESULTS: The clinical time of the immediate digital impression (10.97 ± 2.1 min) was significantly shorter than that of the conventional implant impression (14.45 ± 3.0 min) (P < 0.05). The mean time of the immediate digital impression (10.97 ± 2.1 min) was statistically the same as that of the regular digital impression (10.23 ± 2.7 min) (P > 0.05). Participants' subjective evaluation indicated higher satisfaction with the immediate digital impression than with the regular digital impression and the conventional implant impression. CONCLUSION: The immediate digital impression was more efficient than the conventional implant impression and had the same efficiency as the regular digital impression. Among the three impression techniques, the participants showed higher satisfaction with the immediate digital impression.

Origin and Clinical Applications of Neural Crest-Derived Dental Stem Cells.

Over the past few decades, scientific research into neural crest-derived stem cells has progressed rapidly. The migration and differentiation of neural crest-derived stem cells has been an interesting area of research. Stem cells within teeth originating from the embryonic neural crest have attracted increasing attention in clinical and scientific research because they are easy to obtain and have superb stemness. The stem cells within the teeth include dental pulp stem cells (DPSCs), dental follicle stem cells (DFSCs), stem cells from apical papilla (SCAPs), stem cells from human exfoliated deciduous teeth (SHEDs), and periodontal ligament stem cells (PDLSCs). To date, there have been several interesting studies focusing on dental pulp regeneration, neural regeneration and the revascularization for therapeutic applications.

[Biocompatibility test of polymethylmethacrylate denture base resin containing silver-supported antimicrobial agent STR-1 at nanometer level].

OBJECTIVE: To evaluate the biocompatibility of polymethylmethacrylate(PMMA) denture base resin containing silver-supported antimicrobial agent STR-1 of nanometer level in vitro. METHODS: According to the national standards for biological evaluation of dental materials, the cytotoxicity of denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was examined by molecular filtrating method, and the hemolysis of STR-1, denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was also surveyed. RESULTS: The control denture base resin without containing STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were not cytotoxic to L929 cells. Two hours and 24 hours after cell culturing, the filter membranes of the control and experimental groups were stained evenly with blue color. The staining intensity was not decreased and the fading areas were 0 mm2 during the culturing. The cytotoxicity grades were 0. The hemolysis rates of the antimicrobial agent STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were 1.7%, 3.5% and 3.7% respectively. They were less than the national guild standard 5% which represent no hemolysis. CONCLUSION: The PMMA denture base resins containing silver-supported antimicrobial agents STR-1 of nanometer level at concentrations of 5 g/L and 10 g/L exhibit good biocompatibility.

[A pilot study on the effects of Mini-SG F attachments on periodontal health of the abutment teeth used in free-end partial removable dentures].

OBJECTIVE: To investigate the effects of Mini-SG F attachment on periodontal health of the abutment teeth in restoring free-end removable partial dentures (RPDs). METHODS: The periodontal status of the abutments in restoring free-end RPDs was longitudinally observed with periodontal indices commonly used in clinics, and a group comparison was made using a one-way analysis of variance (ANOVA). RESULTS: The stability and retention of free-end RPDs retained by Mini-SG F attachments were excellent during the whole observation course. Compared with the periodontal status of the first and the second abutments before restoration respectively, no significant differences in gingival indices, plaque indices, periodontal probing depth, alveolar bone resorption levels of those were shown 6 months after restoration. The mobility of the abutments was significantly reduced when they were splinted together. CONCLUSION: Mini-SG F attachments used in free-end RPDs have no evident adverse effect on periodontal health of the abutment teeth, and the way of splinting the abutments is advantageous to their long-term health and stability.

Inflatable hollow obturator prostheses for patients undergoing an extensive maxillectomy: a case report.

The presence of a large palatal or maxillary defect after partial or total maxillectomy for tumor, trauma or congenital deformation poses a challenge to prosthodontists, particularly when the use of an implant cannot be considered. This case report described the use of an air valve in a hollow silicone obturator to manufacture an inflatable obturator that could be extended further into undercut area to retain itself. The inflatable obturator exhibited adequate retention, stability and border sealing, thereby improving the masticatory,pronunciation and swallowing functions of patients. It may be a suitable alternative treatment option to an implant-retained obturator.

[The related factors of bruxism in children].

OBJECTIVE: To investigate the related factors of children bruxism. METHODS: Data of 117 children with primary and mixed dentition of 4-10 years of age were collected in the present study. There were 59 children in bruxism group and 58 children in control group. Oral and temporomandibular joint examinations were carried out on each child, and the parents were asked to fill the questionnaires. The data were statistically analyzed, and the relationship between the factors and the occurrence of bruxism was examined. RESULTS: The odd ratio (OR) for psychology factor, occlusal factor, specific sleep posture, parents heredity and relatives heredity were 1.074, 1.528, 4.472, 11.164 and 8.757, respectively. CONCLUSIONS: Psychology factor, occlusal factor, specific sleep posture and heredity factor are the related factors of children bruxism.

[Repair of high-voltage electric burn in jaw and neck region with insular pectoralis major myocutaneous flap].

OBJECTIVE: To evaluate the effect of insular pectoralis major myocutaneous flap on repair of jaw and neck tissue defect as a result of high-voltage electric burn. METHODS: Eighteen patients with large area tissue defect in jaw and neck caused by high-voltage electric burn hospitalized from August 2001 to December 2007 were repaired with insular pectoralis major myocutaneous flap. The flaps (from 12 cm x 10 cm to 16 cm x 13 cm) was transplanted in 8 patients after early wound debridement, and in 10 patients on infected wounds. RESULTS: All flaps survived wells except in 4 patients necrotic area (length 2-5 cm, width 1-2 cm) appeared in the distal wound edge, localized dehiscence of wound edge in 2 cases, which were healed after dressing change or secondary suturing. Patients were followed up from 6 months to 3 years, and the appearance and function were satisfactory. CONCLUSIONS: Pectoralis major muscle island myocutaneous flap has the advantage of large tissue mass, with thin and flat muscle belly, and rich blood supply, which is suitable for repair of large deep tissue defect in jaw and neck.

[Silver-ion release and particle distribution of denture base resin containing nanometer-sized silver-supported antimicrobial agent].

OBJECTIVE: To investigate the distribution of antimicrobial agent STR-1 of nanometer level which was incorporated with ball-grinding method in the polymethylmethacrylate (PMMA) denture base, and to study the release mode of silver ions from the base. METHODS: The distribution of the antimicrobial agent in the PMMA denture base containing STR-1 at concentrations of 0 g/L, 5 g/L, and 10 g/L was examined with scanning electronic microscopy. Then, PMMA resin bases containing STR-1 at the three concentrations were respectively immersed in artificial saliva at 37 degrees C for 54 days. The release of silver ions from the resin bases was surveyed with inductively coupled plasma-mass spectroscopy (ICP-MS) every 24 hours. RESULTS: The antimicrobial agent incorporated by ball-grinding method was even-distributed with individual particles of nanometer level in the PMMA resin base. The release of silver ions from the PMMA resin with antimicrobial agent was extremely slow during the test, a very small fraction of the silver ions released. At the beginning of the test, the release speed was extremely slow, the speed increased rapidly in the middle of the test, and at the end of the test, the speed returned to slow and steady. The cumulative release curve of silver ions was of "S" type. CONCLUSIONS: STR-1 can be even-distributed in the denture base, and the silver ions release from the base with extremely slow speed. It also indicates that biological safety and long-term antimicrobial efficacy of denture base containing silver-supported antimicrobial agents of nanometer level are possibly obtained based on their slow release of silver ions.