[Comparison of soft and hard tissue stability between immediate implant and delayed implant in maxillary anterior region after loading 2 years].

OBJECTIVE: To compare the peri-implant tissue stability between immediate implant and delayed implant in maxillary anterior region after loading 2 years. METHODS: In the study, 38 patients with single anterior tooth loss in the Second Clinical Division of Peking University School and Hospital of Stomatology from October 2010 to December 2011 were enrolled, and 43 implants were inserted. The gingival contour was induced using implant-supported temporary crowns prior to restoration till permanent prostheses delivered. The gingival papilla height, labial gingival margin level and peri-implant bone level were measured immediately after the permanent restoration and 2 years later. RESULTS: In the study, 16 patients were treated by immediate implant for 17 implants; 22 patients were treated by delayed implant for 26 implants. The implant stability quotient (ISQ) value of the 2 groups showed no significant difference before permanent restoration (P>0.05). In all the cases after loading 2 years, the average mesial gingival papilla height in the implant area of the immediate group and delayed group increased by (0.15 ± 0.42) mm and (0.06 ± 0.65) mm, respectively; the distal gingival papilla height increased by (0.06 ± 0.50) mm and (0.02 ± 0.57) mm respectively; while the labial gingival margin level shrinkages were (0.15 ± 0.23) mm and (0.15 ± 0.46) mm, respectively. The peri-implant bone losses in the mesial side were (0.67 ± 0.35) mm and (0.6 9 ± 0.49) mm, respectively, while in the distal side were (0.73 ± 0.31) mm and (0.75 ± 0.48) mm, respectively. All these indicators showed no significant difference between the 2 groups (P>0.05). CONCLUSION: Both the cases obtained optimizer results after loading 2 years, and the soft and hard tissues around the implant were very stable, which means that both the protocols can achieve reliable therapeutic effects. If we can handle the indications, immediate implant for anterior teeth shows similar efficacy with delayed implant in the short term. But immediate implant in terms of shortening the course of treatment is clearly superior to delayed implant.

[Evaluation of short-term clinical therapeutic efficiency of computer aided design and manufacturing titanium-ceramic-fixed partial dentures for implant-supported restoration in posterior region].

OBJECTIVE: To evaluate the clinical results of computer aided design and computer aided manufacturing (CAD/CAM) titanium-ceramic-fixed partial dentures for implant-supported restoration in posterior region. METHODS: In the study, 90 patients (47 males, 43 females, and the mean age of 48.7 years ranging from 30-62 years) with posterior tooth missing underwent implant-supported porcelain fuse mental prostheses with CAD/CAM titanium-base. A total of 135 prostheses (159 prosthetic units) were fabricated, and 152 implants were placed. The evaluators examined the integrity of restoration, gingival health, color match and marginal adaptation. The mean follow-up time was 51.9 months (24-80 months). RESULTS: No implant was lost during the loading time. All the patients were satisfied at the end of their treatment. The chipping rate of porcelain fuse mental prostheses with CAD/CAM titanium-base was 13.2%(21/159 prosthetic units), No fracture of titanium-base was observed, and 7.4% (10/135) prostheses were found loosening. The authors rated 97.8% (132/135) prosthesis as good or better in regard to color match, 100% (152/152) implants had excellent marginal adaptation. CONCLUSION: The implant-supported titanium-based porcelain fuse mental prostheses with CAD/CAM show good marginal integrity and shade stability, with a clinically acceptable chipping rate, and these restorations can achieve success in the case of posterior tooth missing. Further study is needed to determine the long-term results.

[Clinical effects of ridge augmentation with the half-columnar shaped mandibular bone block for the placement of dental implants].

OBJECTIVE: To evaluate the treatment effects of the half-columnar shaped mandibular block bone onlay grafting technique for augmentation of the resorbed maxillary anterior alveolar ridge after single tooth missing. METHODS: A total of 15 sites of 14 patients received ridge augmentation surgeries. The recipient sites were prepared with trephines, the half-columnar shaped bone blocks were harvested from the ramus and external oblique ridges with trephines according to diameters of the recipient sites. The bone blocks were placed as lateral onlay grafts on recipient beds and secured by means of titanium screws. Particulate bone was added and absorbable membranes were used to stabilize and protect the grafts. After a mean interval of 4.5 months of healing the flaps were re-opened, the screws were removed and non-submerged implants were placed. The width and height of the alveolar ridges were recorded. After 3 months, implant-supported crowns were provided to the patients. One year later, the peri-impant condition and the marginal bone resorption on the proximal sites were observed. RESULTS: Mean lateral augmentation obtained at the time of bone grafting was (3.8 + or - 0.8) mm, 5 out of 15 sites exhibited a mean of 3 mm of vertical augmentation. The mean healing time was 4.5 months, the mean percentage of horizontal and vertical bone resorption in the mean time were 8% and 7% respectively. No major complications were recorded at donor sites. No implant was lost during the study period. Clinical parameters and probing depth (< or = 4 mm) demonstrated the presence of a healthy peri-implant mucosa after 1 year of prosthetic reconstruction. The clinical and radiographic bone observations showed no more than 1.2 mm of resorption after bone graft and implant placement. CONCLUSION: The half-columnar shaped mandibular bone graft (from the ramus and external oblique ridge) is a promising technique for bone augmentation in localized alveolar ridge defects after single tooth missing. This procedure offers easy access, good bone quantity for localized repair, low morbidity, decreased complaints of postoperative sensory disturbances or discomfort, minimal graft resorption, and a shorter healing time as compared with other methods for bone repair.

Accuracy of computer-guided implant surgery by a CAD/CAM and laser scanning technique.

OBJECTIVES: To explore the method of manufacturing an implant surgery template with a computer-aided design/computer-aided manufacturing (CAD/CAM) technique and evaluate its precision in clinical cases. METHODS: Patients referred to the 2nd Dental Center of Peking University who were partially edentulous, were enrolled and scanned with cone beam computed tomography (CBCT). Diagnostic casts were laser scanned to record the configuration of the patients' dentition and mucosae. CBCT and laser scanning data were subsequently loaded into Simplant software. Implant positions were planned in the software with a computer-aided design technique, and surgical templates were fabricated with a rapid prototyping technique. These templates were used to guide implant placement surgery. RESULTS: The mean value of linear deviation was 1.00 mm (range 0 to 2.16 mm) for implant shoulder and 1.26 mm (range 0.51 to 2.86 mm) for the implant apex. The mean angular deviation was 4.74 degress (0.37 to 10.28 degrees). Deviations were higher in the posterior region than anterior. The tooth-supported template provided higher precision than did the tooth/ mucosa-supported template, but no statistically significant difference was found. CONCLUSION: Computer-guided implant surgery with the CAD/CAM technique provides dentists with a good platform for preoperative planning, precise implant insertion, and ideal rehabilitation. The protocol of this three-dimensional laser scanning technique can provide precision comparable to that of double-scanning.

Evaluation of the therapeutic efficiency of mandibular anterior implant-supported fixed bridges with cantilevers.

BACKGROUND: Dental implant technology has developed rapidly in recent years. However, the use of implant-supported fixed bridges with cantilevers has been controversial. The purpose of this study was to evaluate the clinical results of the mandibular anterior implant-supported fixed bridges with a cantilever. Method Thirty-three patients (15 males, 18 females; mean age, 42.6 years; range 20-54 years) with two missing anterior mandibular teeth had single implant-supported fixed bridges with a cantilever. Clinical examination was recorded and radiographs were taken. The mean duration of follow-up was 30 months (15-44 months). RESULTS: All implants survived. Loosening or fracture of the prosthesis was not observed. All patients were satisfied with the treatment. The mean bone resorption values after 12, 24, and 36 months of implant loading were 0.94, 1.18 and 1.35 mm respectively. The changes of gingival papilla height ranged from 0 to 0.5 mm. There was significant difference between 1-year and 2 or 3 years restoration groups regarding the average gingival height changes (P < 0.05). CONCLUSION: After careful and precise selection of patients, restoration with a single implant-supported fixed bridge with a cantilever can be recommended if two anterior mandibular teeth are missing.

Reduced brain-derived neurotrophic factor expression in cortex and hippocampus involved in the learning and memory deficit in molarless SAMP8 mice.

BACKGROUND: The molarless condition has been reported to compromise learning and memory functions. However, it remains unclear how the molarless condition directly affects the central nervous system, and the functional consequences on the brain cortex and hippocampus have not been described in detail. The aim of this study was to find the molecular mechanism related with learning and memory deficit after a bilateral molarless condition having been surgically induced in senescence-accelerated mice/prone 8 (SAMP8) mice, which may ultimately provide an experimental basis for clinical prevention of senile dementia. METHODS: Mice were either sham-operated or subjected to complete molar removal. The animals' body weights were monitored every day. Learning ability and memory were measured in a water maze test at the end of the 1st, 2nd, and 3rd months after surgery. As soon as significantly prolonged escape latency in the molarless group was detected, the locomotor activity was examined in an open field test. Subsequently, the animals were decapitated and the cortex and hippocampus were dissected for Western blotting to measure the expression levels of brain-derived neurotrophic factor (BDNF) and the tropomyosin related kinase B (TrkB), the high affinity receptor of BDNF. RESULTS: Slightly lower weights were consistently observed in the molarless group, but there was no significant difference in weights between the two groups (P > 0.05). Compared with the sham group, the molarless group exhibited lengthened escape latency in the water maze test three months after surgery, whereas no difference in locomotor activity was observed. Meanwhile, in the cortex and hippocampus, BDNF levels were significantly decreased in the molarless group (P < 0.05); but the expression of its receptor, TrkB, was not significantly affected. CONCLUSION: These results suggested that the molarless condition impaired learning and memory abilities in SAMP8 mice three months after teeth extraction, and this effect was accompanied by significantly reduced BDNF expression in the cortex and hippocampus.