[Comparison of three methods for establishing rat peri-implantitis model].

OBJECTIVE: To compare the efficiency and effect of establishing rat peri-implantitis model by traditional cotton thread ligation and local injection of Porphyromonas gingivalis lipopolysaccharide (LPS) around the implant, as well as the combination of the two methods. METHODS: Left side maxillary first molars of 39 male SD rats were extracted, and titanium implants were implanted after four weeks of healing. After 4 weeks of implant osseointegration, 39 rats were randomly divided into 4 groups. Cotton thread ligation (n=12), local injection of LPS around the implant (n=12), and the two methods combined (n=12) were used to induce peri-implantitis, the rest 3 rats were untreated as control group. All procedures were conducted under 5% isoflurane inhalation anesthesia. The rats were sacrificed 2 weeks and 4 weeks after induction through carbon dioxide asphyxiation method. The maxilla of the rats in the test groups were collected and marginal bone loss was observed by micro-CT. The gingival tissues around the implants were collected for further real time quantitative PCR (RT-qPCR) analysis, specifically the expression of tumor necrosis factor-alpha (TNF-α) as well as interleukin-1ß (IL-1ß). The probing depth (PD), bleeding on probing (BOP) and gingival index (GI) of each rat in the experimental group were recorded before induction of inflammation and before death. RESULTS: After 4 weeks of implantation, the osseointegration of implants were confirmed. All the three test groups showed red and swollen gums, obvious marginal bone loss around implants. After 2 weeks and 4 weeks of inflammation induction, PD, GI and BOP of the three test groups increased compared with those before induction, but only BOP was statistically significant among the three test groups (P < 0.05). At the end of 2 weeks of inflammation induction, marginal bone loss was observed at each site in the cotton thread ligation group and the combined group. At each site, the bone resorption in the combined group was greater than that in the cotton thread ligation group, but the difference was not statistically significant (P > 0.05), bone resorption was observed at some sites of some implants in LPS local injection group. At the end of 4 weeks of inflammation induction, marginal bone loss was observed at all sites in each group. The marginal bone loss in the cotton thread ligation group and the combined group was greater than that in the LPS local injection group, and the difference was statistically significant (P < 0.05). At the end of 2 weeks and 4 weeks of induction, the expression of TNF-α and IL-1ß in the test groups were higher than those in the control group (P < 0.05). CONCLUSION: Compared with local injection of LPS around the implant, cotton thread ligature and the two methods combined can induce peri-implantitis in rats better and faster.

[Evaluation of clinical efficacy of a kind of digital complete denture].

OBJECTIVE: To compare the clinical efficacy of a kind of complete dentures fabricated using computer aided design/computer aided manufacturing (CAD/CAM) workflow with that of the complete denture fabricated using conventional workflow. METHODS: Twenty edentulous patients were included in this prospective, single-blind, self-controlled clinical trial. Two pairs of complete dentures were fabricated for each participant: one using the functional suitable denture (FSD) system with CAD/CAM, and the other using conventional fabrication workflow. In the final delivery appointment, the conventional dentures worn by the participant for 3 months at first. Then the participant swapped to wear digital denture for another 3 months. The patients' satisfaction and oral health related quality of life (OHRQoL) were measured using the visual analogue scale (VAS) and oral health impact profile (OHIP-20E) at baseline, 2 weeks, 1 month, 2 months, and 3 months following denture delivery. In addition, the masticatory efficiency of each pair of dentures was measured after three months adaptation period for each type of dentures. RESULTS: The VAS scores of the twenty patients in FSD denture group on general satisfaction, ease of cleaning, ability to speak, esthetics, stability and oral health status on these six domains were higher than that of conventional denture group 3 months after delivery. While the VAS cores in FSD denture group on comfort, ability to chew and ability to chew up were the same as those of conventional denture group. But there was no significant difference (P>0.05). The VAS score on each domain in FSD denture group was higher than that of conventional denture group 3 months after delivery, three domains of which reached statistical significance (P < 0.05), involving functional limitation, psychological discomfort and total. The masticatory performance of the FSD denture (1.20±0.54) was slightly higher than that for the conventional denture (1.16±0.53), but the difference did not reach statistical significance (P=0.691). CONCLUSIONS: The clinical efficacy of the FSD complete denture is comparable to that of the conventional complete denture. As for patient satisfaction and oral health related quality of life, FSD dentures received comparable scores as conventional complete dentures did.

[Comparison of the registration methods for the three-dimensional facial scans applied to the design of full-arch implant supported restoration].

OBJECTIVE: To compare the registration accuracy of three-dimensional (3D) facial scans for the design of full-arch implant supported restoration by five methods and to explore the suitable registration method. METHODS: According to the criteria, ten patients with maxillary edentulous jaw or end-stage dentition requiring implant supported restorations were enrolled in this study. A special rim with individual feature marks reflected appropriate occlusal relationship and esthetic characteristics was made for each patient. Both 3D facial scan data of natural laughter and with opener traction to expose the teeth or occlusal rim of each patient were acquired by facial scan and input to the digital analysis software Geomagic Qualify 2012. The dataset was superimposed by five different methods: seven facial anatomical landmark points alignment, facial immobile area alignment (forehead and nasal area), facial anatomical landmark points and immobile area combining alignment, facial feature points alignment, facial and intraoral feature points alignment with the same local coordinate system. The three-dimensional deviation of the same selected area was calculated, the smaller the deviation, the higher the registration accuracy. The 3D deviation was compared among the three registration methods of facial anatomical landmark points, facial immobile area alignment and the combination of the above two methods. Friedman test was performed to analyze the difference among the three methods (α=0.05). The effect of the aid of the facial and intraoral feature points were evaluated. Paired t test were performed to analyze the difference (P<0.05). RESULTS: The average three-dimensional deviation of the selected area after alignment with the facial anatomical landmarks was (1.501 2±0.406 1) mm, significantly larger than that of the facial immobile area best-fit alignment [(0.629 1±0.150 6) mm] and the combination of the two methods[(0.629 1±0.150 6) mm] (P < 0.001). The aid of the facial feature points could significantly reduce the deviation (t=1.001 3, P < 0.001). There was no significant statistical difference in the remaining groups. CONCLUSION: The forehead area of the 3D facial scan can be exposed as much as possible. The establishment of facial characteristic landmark points and the use of the invariant area alignment can improve the accuracy of registration. It should be clinically feasible to apply three-dimensional facial scan to the design of full-arch implant supported restoration with the registration of the immobile area on the face especially the forehead area.

[A novel tray for recording maxillomandibular relationship of edentulous patients based on dimensional surveying of complete dentures].

OBJECTIVE: To measure the dimensional data of complete dentures and to design a novel tray for recording maxillomandibular relationship of edentulous patients. METHODS: For the measurement, 100 pairs of complete dentures from the clinic were surveyed for the following parameters: a1, the distance between the middle fossa of the upper left and right first molars; a2, the anterior-posterior distance between the middle fossa of the upper first molars and the incisal edge; a3, the width of the upper denture; a4, the anterior-posterior length of the upper denture; a51, the height from the mesio-lingual cusp of the right upper first molar to the saddle surface; a52, the height from the central fossa of the right lower first molar to the saddle surface; a6, the height from the notch of the upper lip frenulum to the upper central incisor edge; a7, the least thickness of the labial saddle base in the upper central incisor region. Based on the data, the trays with different sizes were designed and fabricated, and the key parameters were: b1, the distance between the foramina of screw posts, b2, the anterior-posterior distance between the foramina of the screw posts and the incisal edge; b3, the width of the tray; b4, the anterior-posterior length of the tray; b51, the height of the posterior platform with the screw nut; b52, the height of the screw post; b6, the height of the anterior tray handle; b7, the thickness of the anterior tray handle. RESULTS: The minimum, average and maximum data for each parameter were (in millimeter): a1: 37.1, 44.5, and 59.6; a2: 22.6, 29.0, and 38.1; a3: 48.5, 58.2, and 76.6; a4: 37.4, 50.8, and 61.0; a51: 5.6, 9.5, and 14.7; a52: 3.8, 9.9, and 18.8; a6: 8.9, 16.6, and 24.7; a7: 1.2, 2.8, and 5.9. Based on the data, the trays in small, medium and large sizes were designed and fabricated. In clinical application, the putty silicone rubber impression material was used to reline the tray, meanwhile the posterior platform and anterior tray handle were set as the occlusal plane, then the screw posts were added and adjusted till the proper vertical dimension, after that, the putty silicone rubber impression material was added around the screw posts to record the horizontal maxillomandibular relationship, finally, the anterior surface of the tray handle was used to record the midline of the face and lower edge of the upper lip at rest and with smile. CONCLUSION: The dimensional data offered reference for the analysis of restoration space in edentulous patients. The tray designed and fabricated in this study may serve as a new tool for recording the maxillomandibular relationship.

[Independent innovation research of functionally suitable denture digital system].

Fabrication of conventional complete dentures involves a complex restoration method, requiring significant time and typically involving primary impressions, definitive impressions, jaw relation records, clinic try-in, and complete denture placement, which has been used for nearly a century without change. A novel digital system named Functionally Suitable Denture (FSD) was researched and developed so as to reduce clinical steps, operation difficulties and errors of complete denture restoration. It pioneered a unique diagnostic complete denture aided by computer aided design (CAD) & 3D printing, by which, the functional impression, jaw relation, and try-in (3 steps) were simplified to 1 step, thus the number of visits to the dentist was reduced by 2 times. Moreover, for the first time, it put forward a CAD software of template matching based on the expert design, which was an efficient and intelligent design scheme, and the excellent denture experts' experience and skills could be inherited and iterated. The system included the 3D scanner with appropriate accuracy and high efficiency, the CAD software, the special 3D printer and process software, and the innovative clinical operation process. The Patent Cooperation Treaty (PCT) patent international search report showed that all the 15 claims of the technology were of novelty, creativity and industrial utility. All the digital products were independently developed and made by Peking University School and Hospital of Stomatology, China. The design and manufacture process of denture prosthesis was fast, simple and accurate. At the same time, personalized functional and aesthetic matching of the patients after wearing prosthesis was realized. It effectively solved the global problems of "slow, difficult and inaccurate" of the traditional manual technology of complete denture, and brought good news to edentulous patients. Compared with the traditional complete denture treatment, FSD system has a wide range of applications for different types of edentulous patients, including those with severe resorption of the alveolar ridge or a high occlusal force. Furthermore, the low-cost of 3D printers, compared with expensive milling machines, may make the approach more accessible. This review describes that our research is related to the development of the FSD system, including multi-source data acquisition technology, three generations of complete denture design software, 3D printing systems of individual tray and complete denture pattern, the clinical and laboratory operation process of the FSD system.

[Oral hygiene maintenance of locator attachments implant overdentures in edentulous population: A longitudinal study].

OBJECTIVE: To investigate the oral hygiene status of edentulous patients with locator attachments implant overdentures (IOD) and to analyze the relationship among daily hygiene behavior, oral hygiene status and peri-implant diseases. METHODS: Edentulous patients who received IOD treatment with locator attachments from January 2012 to May 2016 were recruited. Clinical and radiographic examinations were conducted to assess the peri-implant tissue status. Modified plaque index (mPLI), sulcus bleeding index (SBI), gingival index (GI), and probing depth (PD) were recorded and peri-implant marginal bone loss (MBL) was measured using paralleling projection technique. Patients' peri-implant oral hygiene maintainence habits were investigated. The correlation between peri-implant diseases and oral hygiene status and behaviors was analyzed. RESULTS: Fifty patients (125 implants) with an average follow-up time of 22 months (6-54 months) were enrolled. The mean values of mPLI, SBI, and GI were 1.4±1.2, 0.8±0.7, and 0.7± 0.6, respectively. Average PD was (2.2±0.7) mm. Mesial and distal maginal bone resorptions were (1.1±1.1) mm and (0.9±0.9) mm, respectively. The prevalance of mucositis and peri-implantitis of the implants were 49.6% and 0. The prevelance of mucositis in the patients with poor oral hygiene (mPLI≥2) was 11.9 times as much as that of those with adequate oral hygiene (mPLI<1). The patients who performed oral hygiene procedure on attachments at least twice a day achieved much lower mPLI scores than those who cleaned less than twice a day. CONCLUSION: Oral hygiene condition in the group of patients with implant overdentures was poor, and it contributed to increased risk of peri-implant mucositis. The prevelance of musositis of the paitients with poor oral hygiene was 11.9 times as much as that of those with proper oral hygiene. Patients wearing IOD should pay more attention to the hygiene of the attachments.

[Influence of implants prepared by selective laser melting on early bone healing].

OBJECTIVE: To evaluate the influence of the rough surface of dental implants prepared by selective laser melting (SLM) on early bone healing around titanium implants. METHODS: A total of sixteen titanium implants were involved in our research, of which eight implants were prepared by SLM (TIXOS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex) and the other eight were sandblasted, large-grit and acid-etched (SLA) implants (IMPLUS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex). All of the dental implants were inserted into the healed extraction sockets of the mandible of two adult male Beagle dogs. Half of the dental implants were designed to be healed beneath the mucosa and the other half were intended to be healed transgingivally and were immediately loaded by acrylic resin bridge restoration. Three types of tetracycline fluorescent labels, namely calcein blue, alizarin complexone and calcein, were administered into the veins of the Beagle dogs 2, 4, and 8 weeks after implant placement respectively for fluorescent evaluation of newly formed bone peri-implant. Both Beagle dogs were euthanized 12 weeks after implant insertion and the mandible block specimens containing the titanium implants and surrounding bone and soft tissue of each dog were carefully sectioned and dissected. A total of 16 hard tissue slices were obtained and stained with toluidine blue for microscopic examination and histomorphometric measurements. Histological observation was made for each slice under light microscope and laser scanning confocal microscope (LSCM). Comparison on new bone formation around titanium implants of each group was made and mineral apposition rate (MAR) was calculated for each group. RESULTS: Dental implants prepared by selective laser melting had achieved satisfying osseointegration to surrounding bone tissue after the healing period of 12 weeks. Newly formed bone tissue was observed creeping on the highly porous surface of the SLM implant and growing into the pores of surface structure. Higher MAR values were shown for SLM implants compared with SLA implants (P<0.01). CONCLUSION: Dental implants prepared by selective laser melting could promote early bone healing and improve mineral apposition rate.

[Evaluation of the fabrication deviation of a kind of milling digital implant surgical guides].

OBJECTIVE: To evaluate the deviation of digital implant surgical guides during fabrication process in the Organical Dental Implant (ODI) system. METHODS: This study included two parts. The first part was the in vitro study. A resin block with a diagnostic template was used for the planning. After cone beam computed tomography (CBCT) scanning, a surgical guide with eight implants was virtually designed using the ODI system. The guide was milled by a 5-axial numerical controlled milling machine, and an optical scanning was taken to digitalize the guide to a standard tessellation language (STL) form. The STL data were then imported into an ODI software and registered with the original design. The deviation of the sleeves between the design and the STL was measured in the ODI software and set as the golden standard. Then the ODI examination table was used to measure the deviation of the guide during fabrication. Examiners A and B measured 10 times separately. The reliability and the validity of the examination table was calculated. The second part was the in vivo study: The deviation during fabrication of 12 guides designed and fabricated by the ODI system were measured using the examination table. RESULTS: The standard deviation of the deviation measured using the examination table by examiners A and B were all below 0.40 mm (for the shell reference points) and 0.71 degree (for the angles). No significant difference was found between the two examiners for any implant sites. The result of the examination table was larger than that of the software for the shell reference point (t-test, P<0.05), but no significant difference was found for the angle deviation (t-test, P>0.05). The 45 implants positions in the 12 guides for the in vivo study were examined using the examination table. The deviations at the shell reference points were (1.06±0.29) mm (0.42-1.75 mm), and at the implant tip were (1.12±0.48) mm (0.41-2.44 mm). The angle deviations were (1.42±0.70) degree (0.29-2.96 degree). CONCLUSION: Deviation is unavoidable during the fabrication process of the guides. The examination table of the ODI system is a reliable and valid tool to measure the deviation during fabrication of the ODI guides. More studies should be designed to research the relationship between the fabrication deviation and the implant insertion deviation.

[Influence of the interforaminal arch form of edentulous mandibles on design of "All-on-4": preliminary research based on conebeam computed tomography].

OBJECTIVE: To classify the interforaminal arch form of edentulous mandibles by measuring the anterior-posterior distance (A-P distance) of implants planned to be inserted in "All-on-4" protocol using conebeam computed tomography (CBCT) data, and to investigate the influence of the arch form on the "All-on-4" distally tilted implants. METHODS: Seventy-four CBCT images of edentulous mandibles were collected, including 35 males and 39 females respectively. "All-on-4"implant supported fixed prostheses were designed for these patients based on the CBCT data. The A-P distance was measured in the plane which crossed bilateral mental foramens and was parallel to the occlusal plane. The interforaminal arch form of edentulous mandibles were classified according to the A-P distance. The radian of the jaw arch 7.5 mm mesially to the mental foramen was measured bilaterally, and its correlation with the A-P distance was studied. RESULTS: The average A-P distance of implant supported fixed prostheses planned in the interforaminal region was (8.5±1.5) mm (minimum 4.5 mm, maximum 11.8 mm). In the study, 12.2% of the subjects' mandibles were classified as square arch form with A-P distances ≤7 mm, 54.0% were classified as ovoid with A-P distances >7 mm and ≤9 mm, 33.8% were classified as tapered with A-P distances >9 mm. Bilaterally, 148 results of the radian of the jaw arch 7.5 mm mesially to the mental foramen were obtained, and the average radian was 15.9°±5.5° (minimum 5.6°, maximum 35.2°). The radian and the A-P distance showed a negative correlation with statistical significance. CONCLUSION: In this research, the ovoid arch form was the most common type in edentulous mandibles, followed by tapered arch form. The square arch form showed the lowest percentage. As the arch form went squarer, the A-P distance became shorter, the radian of the jaw arch mesially to the mental foramen went greater, and the bone width that distally tilted implants need became bigger. The interforaminal arch form of the edentulous mandible should be analyzed before an implant supported fixed restoration is designed in the interforaminal region. The angle of inclination of distal implants should be reasonable. The bone width of the distal implant site must be adequate. The square arch form contributes negatively to the structure of implant supported fixed prostheses with distal cantilever design.

[Evaluation of production and clinical working time of computer-aided design/computer-aided manufacturing (CAD/CAM) custom trays for complete denture].

OBJECTIVE: To compare the technician fabrication time and clinical working time of custom trays fabricated using two different methods, the three-dimensional printing custom trays and the conventional custom trays, and to prove the feasibility of the computer-aided design/computer-aided manufacturing (CAD/CAM) custom trays in clinical use from the perspective of clinical time cost. METHODS: Twenty edentulous patients were recruited into this study, which was prospective, single blind, randomized self-control clinical trials. Two custom trays were fabricated for each participant. One of the custom trays was fabricated using functional suitable denture (FSD) system through CAD/CAM process, and the other was manually fabricated using conventional methods. Then the final impressions were taken using both the custom trays, followed by utilizing the final impression to fabricate complete dentures respectively. The technician production time of the custom trays and the clinical working time of taking the final impression was recorded. RESULTS: The average time spent on fabricating the three-dimensional printing custom trays using FSD system and fabricating the conventional custom trays manually were (28.6±2.9) min and (31.1±5.7) min, respectively. The average time spent on making the final impression with the three-dimensional printing custom trays using FSD system and the conventional custom trays fabricated manually were (23.4±11.5) min and (25.4±13.0) min, respectively. There was significant difference in the technician fabrication time and the clinical working time between the three-dimensional printing custom trays using FSD system and the conventional custom trays fabricated manually (P<0.05). CONCLUSION: The average time spent on fabricating three-dimensional printing custom trays using FSD system and making the final impression with the trays are less than those of the conventional custom trays fabricated manually, which reveals that the FSD three-dimensional printing custom trays is less time-consuming both in the clinical and laboratory process than the conventional custom trays. In addition, when we manufacture custom trays by three-dimensional printing method, there is no need to pour preliminary cast after taking the primary impression, therefore, it can save the impression material and model material. As to completing denture restoration, manufacturing custom trays using FSD system is worth being popularized.

[Distribution and content of transforming growth factor-ß1 and vascular endothelial growth factor in each layer of concentrated growth factors].

OBJECTIVE: To investigate the distribution and content of transforming growth factor-ß1 (TGF-ß1) and vascular endothelial growth factor (VEGF) in concentrated growth factors (CGF) gel, and to clarify the difference among different layers of CGF. METHODS: Venous blood samples were collected from 6 healthy volunteers to prepare CGF. The distribution, integrated optical density (IOD) and average optical density (AOD) of TGF-ß1 and VEGF in CGF gel and red blood cell (RBC) layer were measured using immunohistochemistry. The concentrations of TGF-ß1 and VEGF in the supernatant serum at baseline and the CGF releasate after 1 day were evaluated with enzyme-linked immunosorbent assays. RESULTS: Abundant TGF-ß1 and VEGF were concentrated in CGF gel. However, only a little could be found in polykaryocytes and sporadic platelets in RBC layer. Platelets and leukocytes were concentrated in between the two layers with high expression of TGF-ß1. The concentrations of TGF-ß1 and VEGF in the CGF releasate(55 236.78±3 686.34), (610.99±148.81) ng/L were significantly higher than those in the supernatant serum (20 710.20±4 523.14), (335.20±51.69) ng/L (P<0.001). CONCLUSION: CGF contains high quantities of TGF-ß1 that can promote new bone formation and tissue healing. We suggest that CGF gel should be used right after being prepared. Supernatant serum and the area between CGF gel and RBC layer could also be mixed with bone substitute materials.

[Clinical outcome of single posterior implant-supported monolithic zirconia crowns fabricated using full digital workflow and conventional workflow: a 3-year follow-up].

Objective: To compare the clinical performance of posterior single implant-supported monolithic zirconia crowns fabricated by full digital workflow and that of those fabricated by conventional workflow. Methods: This is prospective clinical research. Thirty-five patients who participated in a previous study during August 2017 to October 2018 at Department of Prosthodontics, Peking University School and Hospital of Stomatology were included in this 3-year follow-up study. The 35 patients, 17 females and 18 males, aged (49.0±15.4) years (24-86 years old), was allocated into two groups. In the full digital workflow group, intraoral scanning was taken immediately after implant placement, and a full zirconia implant crown was fabricated using model-free computer aided design/computer aided manufacturing (CAD/CAM) procedure (n=14). In the conventional group, a conventional impression was taken 3 months after implant placement and the stone model was produced. A full zirconia implant crown was fabricated using conventional model-based procedure (n=21). Three years following crown delivery, all the prostheses were evaluated in the aspect of color, surface roughness, contour and marginal integrity using modified US Public Health Service criteria (MUSPHS criteria). The soft and hard tissue around implant was evaluated using modified plaque index, probing depth (PD), number of implants with bleeding on probing, marginal bone loss (MBL). The biological and mechanical complication were also recorded. Statistical analysis was performed using independent samples t test, Mann-Whitney U test and Fisher's exact test. Results: The total survival rate of prosthesis and implant was 100% (35/35). No significant difference in MUSPHS criteria ratings on color, surface roughness, contour and marginal integrity of these crowns were found between the full digital workflow group and the conventional group (P>0.05). Sixteen out of the 35 crowns had a contour score of B due to loss of interproximal contact. Ten out of the 35 crowns had the screw hole sealing resin sinking or falling off, four in the full digital workflow group and six in the conventional group. There was no significant difference in the rate of prostheses mechanical complications between the two groups (P=1.000). For all the implants, there was no significant difference in MBL, PD, the modified plaque index, and number of implants with bleeding on probing between the two groups (U=119.50,133.00,142.50, t=-0.53, P>0.05). Conclusions: The clinical performance of implant-supported posterior single monolithic zirconia crowns fabricated by full digital workflow was stable. There was no significant difference in the clinical performance of the single implant crowns between the full digital workflow group and the conventional group.

[Treatment planning and key points in clinical procedure of implant overdenture for edentulous patients].

Many randomized controlled clinical trials have reported that implant overdentures provided edentulous people with better retention, stability, and masticatory performance than conventional complete dentures did. The design of implant overdentures for edentulous jaws should be based on comprehensive consideration of factors such as anatomic structure, alveolar bone resorption, inter-arch distance, choice of implant number/distribution and suprastructure. During the clinical procedure, timing of attachment connection, choice of impression technique, methods of maxilla-mandibular relationship registration, wax-up try-in, and prostheses delivery should be determined according to the type of implant overdentures. The appropriate choices and conduction of the above-mentioned procedures can guarantee the long-term success of the prostheses. This review elaborates on the clinical significance, treatment design, key steps in clinical procedure of implant overdenture, and summarizes follow-up and maintenance following denture delivery.

[Surveillance of filariasis in some vulnerable areas in Guangxi after filariasis elimination].

OBJECTIVE: To explore the measures for continuing surveillance of filariasis. METHODS: Selecting some vulnerable spots for focal surveillance, double-slide biood sampling for microfilaria examination, dissecting vectors for detecting the mosquitoes infected with filarial larva, using IFAT for detecting antifilarial antibody. RESULTS: 27,938 persons were examined for microfilaria and 4,454 mosquitoes were dissected for filaria larva, all were negative. 3,606 serum samples were examined for antifilarial antibody average positive rate was 1.35%(0.39-4.97%). CONCLUSION: The results of surveillance showed that the achievement of filariasis control in Guangxi after filariasis elimination is consolidated.

[On the transmission role of residual microfilaremia cases in the area with filariasis virtually eradicated].

The transmission role of the residual microfilaremia cases was studied in Pingle Village, Liangqing Township, Yongning County where bancroftian filariasis had been virtually eradicated during 1984-1988. The results indicated that after the microfilarial rate of the human population met the criterion of elimination of filariasis, namely below 1% of the total population in all the administrative villages, and the average density of microfilaria being around 5 per 60 microliters peripheral blood, subsequent control measures might be no longer instituted while the microfilaria rate and its density could continue to decline. Some residual microfilaremiae cases having higher microfilarial density turned negative gradually, so did the natural infection rate of Culex quinquefasciatus with filaria larvae and its density year by year. No filaria larvae were found in vector mosquitoes in 1987-1988. The authors deemed that the filariasis transmission in this area has been interrupted.

[Long-term surveillance after basic elimination of bancroftian filariasis].

The longitudinal and cross-sectional systemic surveillance have been conducted for 9-11 consecutive years in six counties (cities) of Guangxi Zhuang Autonomous Region after basic elimination of bancroftian filariasis. The two different control regimens had been used with DEC selective treatment followed by mass treatment of all persons and selective treatment followed by taking DEC medicated salt. During the former 6 years, residual microfilaremia cases could still be detected; whereas during the latter 5 years, no microfilaremia cases could be detected at all. The natural infection of vector mosquitoes showed negative. The positive rate of antibody in the populations was reduced to 1.4-5.5% detected by IFAT, reaching to the level of local non-endemic areas. The result indicated that the transmission of filariasis in these areas has been blocked. The authors suggested that a period of 10 years might be appropriate for surveillance after basic elimination of bancroftian filariasis.

Evaluation of permethrin-impregnated mosquito-nets against mosquitoes in China.

In Yishan County, Guangxi Province, China, where malaria and Brugian filariasis are transmitted by vectors belonging to the Anopheles hyrcanus Pallas group, a study was conducted from June to November 1986 to evaluate the effectiveness of permethrin-impregnated mosquito bednets to reduce man/vector contact. In three experimental villages a total of 246 mosquito nets were treated with permethrin EC at a dosage of 0.5 g/m2. Control bioassays (1 h exposure) of treated nets gave up to 100% mortality of Armigeres subalbatus (Coquillett), Anopheles sinensis Wiedemann and Culex tritaeniorhynchus Giles for up to 19 weeks. During 5 months evaluation in the villages, permethrin-impregnated mosquito-nets reduced the number of mosquitoes found inside nets by 99.3% for Culex quinquefasciatus Say, by 94.4% for Anopheles sinensis Wiedemann and by 75% for Anopheles lesteri anthropophagus Xu & Feng. This measure could thus be considered an appropriate means of controlling vectors in villages.