[Evaluation of the 5-year clinical restoration effect of implants retained complete overdentures with Locator attachments in 48 patients].

PURPOSE: To observe the long-term clinical effect of implants retained complete overdentures with Locator attachments. METHODS: A total of 48 patients with edentulous jaws treated with implants retained complete overdentures with Locator attachments were selected from the Outpatient Department of Peking University School and Hospital of Stomatology from 2016 to 2017. Among them, 21 patients underwent double-maxillary complete overdentures restoration and 27 patients underwent single-maxillary restoration. A total of 230 implants were implanted. The clinical observation indicators included the implant survival rate, peri-implant mucosal bleeding on probing(BOP), the change in the vertical height of alveolar bone absorption around the implants, overdenture base fracture rate, artificial tooth fall off and fracture rate and other complications. The change of the locator attachment retention force of the implant-supported overdentures was evaluated. SPSS 13.0 software package was used for data analysis. RESULTS: During the five-years clinical observation period, 5 implants fell off, 1 narrow dimeter implant in the anterior zone was broken, and 12 implants were lost to follow-up. The implant survival rate was 97.25%. One year after the restoration therapy finished, peri-implant mucosal bleeding on probing (BOP+) was detected in 48 (21.4%) implants. The average BI was 0.21±0.42, which was higher in the anterior zone than that in the posterior zone. The vertical alveolar bone absorption height around the implants was (0.21±0.35) mm, 2 implants-supported complete overdenture bases were broken. After 5 years of restoration, 163(76.89%) implants had peri-implant mucosal bleeding on probing(BOP+). The average BI was 1.00±0.70, and the vertical alveolar bone absorption height around the implants was (0.58±0.85) mm. There was no significant difference between males and females. There was no significant difference in the peri-implant mucosal bleeding index and the alveolar bone vertical absorption height between the anterior zone and the posterior zone(P＞0.05). The mean BI of peri-implant mucosa and the vertical absorption height of peri-implant alveolar bone were significantly different between the 1-year observation period and the 5-year observation period respectively(P＜0.01). There were 17(26.15%) cases with overdenture bases fracture, and the fracture rate of artificial teeth was 16.92%. Most of them occurred in the midline area of the anterior zone and the location of the overdenture base on the locator attachments. The average first replacement time of the locator attachment nylon retainer washer was 34.2±10.3 months. CONCLUSIONS: Implants retained complete overdentures with Locator attachments are effective in long term clinical observation. Complications are mainly found in peri-implant mucosal bleeding on probing and vertical alveolar bone absorption, and tended to increase gradually over time. The fracture of the implant retains complete overdenture bases and the fall off or fracture of the artificial teeth are the second serious complications. Overdenture base with metal frame at the location of the Locator abutment and the midline of the anterior area should be strengthened, and narrow diameter implants should be avoided as far as possible in the anterior zone.

[Change of ion precipitation and surface roughness of three dental alloys coexisting].

PURPOSE: To study the change of ion precipitation and surface roughness of three dental alloys'coexisting in standard electrolyte solution, in order to provide a reference for the selection of clinical alloy materials. METHODS: Standard samples of Ni-Cr alloy, Co-Cr alloy and Au-Ag-Pd alloy were prepared and divided into 5 groups: Ni-Cr alloy(group N), Co-Cr alloy(group C), Au-Ag-Pd alloy(Group A), Ni-Cr alloy contact with Au-Ag-Pd alloy(group NA), Ni-Cr alloy contact with Co-Cr alloy(group NC). All groups of alloys were soaked in standard electrolyte solution (T=37 ℃, pH=2.31) for 7 days. Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the amount of ions released from each group. The surface morphology of each group was observed and the surface roughness(Ra) was measured using atomic force microscope（AFM）. SPSS 18.0 software package was used for statistical analysis. RESULTS: The amount of nickel ions released from group N, NA, NC was (1.32±0.03) µg/cm2, (2.13±0.07) µg/cm2, (1.53±0.08) µg/cm2, respectively. Nickel ions of group NA and NC was significantly more than that of group N(P<0.05), nickel ions of group NA was significantly more than that of group NC(P<0.05). The amount of chromium ions released from group N, NA, NC was (0.06±0.01) µg/cm2, (0.08±0.01) µg/cm2, (0.05±0.01) µg/cm2, respectively, the amount of chromium ions of group NA was significantly more than that of group NC(P<0.05). The surface roughness of Ni-Cr alloy in group N, NA, NC was (4.60±0.16) nm, (5.37±0.08) nm, (5.04±0.15) nm, respectively. The surface roughness of Ni-Cr alloy in group NA and group NC was significantly larger than that in group N (P<0.05). When contact with Au-Ag-Pd alloy or Co-Cr alloy, the amount of nickel ions released and the surface roughness of Ni-Cr alloy both significantly increased. Compared with Co-Cr alloy, Au-Ag-Pd alloy caused Ni-Cr alloy to release more nickel, chromium ions and formed a rougher surface.

[Three-dimensional finite element analysis of one-piece computer aided design and computer aided manufacture involved zirconia post and core].

OBJECTIVE: To analyze the biomechanics trait of one-piece computer aided design and computer aided manufacture (CAD/CAM) zirconia post and core by the Three-dimensional finite element. METHODS: The Three-dimensional finite element models of three upper central incisors restored with one-piece CAD/CAM zirconia post and core (group 1), refabricated zirconia post and hot-pressed porcelain core (group 2), and cast gold alloy post and core (group 3) were built by geometry method respectively. 100 N vertical loading through the central incisor models long axis and 100 N loading along directing at an angle of 45° with the models long axis were used to imitate the central incisor stress state in biting and mandible physiological protraction movement. RESULTS: Under vertical loading, the restored teeth without dentin ferrule, the maximum Von-Mises stress value of the tooth root in group 1 was the least(11.02 N), which was the largest (13.17 N)in group 2. The stress became weaker from the upper to the lower of the tooth root. The maximum Von-Mises stress value of the tooth root, post and core became smaller while the restored teeth with the 2.0 mm high dentin ferrule. Under directing at an angle of 45° loading, without the design of dentin ferrule in the restored teeth, the maximum Von-Mises stress value of the post and core in group 1 was the greatest(20.45 N), while that stress of post and core in group 3 was the smallest(13.61 N). With 2.0 mm high dentin ferrule design in the restored teeth, the tooth root stress became weaker. The maximum Von-Mises stress value of the tooth root was the greatest (14.10 N) in group 3, but which was the lowest (13.38 N) in group 1. CONCLUSION: The results of the Three-dimensional finite element analysis infers that one-piece zirconia post and core restoration is more beneficial to disperse the bite force than the prefabricated zirconia post and the cast gold alloy post and core. The one-piece of zirconia post and core is good to protect the teeth and keep the restoration intact.

[Fracture resistance of teeth restored with one-piece computer aided design and manufacture zirconia posts and cores: an in vitro study].

OBJECTIVE: To compare the fracture resistance of endodontically-treated teeth restored with prefabricated zirconia posts or one-piece computer aided design and computer aided manufacture (CAD/CAM) zirconia posts and cores, and unrestored endodontically-treated teeth. METHODS: Recently extracted human maxillary central incisors (n = 36) were endodontically treated and divided into three groups (n = 12 each): group 1 was restored with prefabricated zirconia posts (Comospost) and hot pressed ceramic cores; group 2 restored with one-piece CAD/CAM zirconia posts and cores; group 3 not restored. The teeth were fixed in a universal load-testing machine; a compressive load was applied at 135 degrees to the long axis of each tooth at a crosshead speed of 1 mm/min until fracture. One-way analysis of variance (Student-Newman-Keuls) was used to determine the significance of the differences in failure load between the groups. RESULTS: The mean fracture loads were (311.75 ± 70.12) N, (423.83 ± 54.58) N and (736.33 ± 82.91) N, respectively. The unrestored teeth exhibited significantly higher fracture resistance than the two groups of restored teeth. The teeth restored with one-piece CAD/CAM zirconia posts and cores had higher fracture resistance than the teeth restored with prefabricated zirconia posts and hot pressed ceramic cores (P < 0.001). CONCLUSION: Within the limitations of this study, the root canal-treated teeth restored with one-piece CAD/CAM zirconia posts and cores had a significantly higher failure resistance than the teeth restored with prefabricated zirconia posts. one-piece CAD/CAM zirconia posts and cores can offer some advantages for esthetic prosthodontics.

[Finite element analysis of tooth restored with one-piece of computer aided design and computer aided manufacturing zirconia post-core in three different radiuses].

OBJECTIVE: To compare the stress distribution of teeth restored with one-piece of computer aided design and computer aided manufacturing (CAD/CAM) zirconia post-cores in three different radiuses. METHODS: Constructing the 2D finite element models of the standard maxillary central incisal restored by one-piece of CAD/CAM zirconia post-cores and all ceramic crowns, the radius of post was 1.5 mm, 2.0 mm and 2.5 mm respectively. Two tooth root types with or without the ferrule were constructed and there were 6 models in general. Group 1:100 N force loading to the restored teeth through the long axle of teeth and veritical the incisal edge. Group 2: 100 N inclined force loading beneath the incisal edge 2.0 mm by 45° cross the long axle of teeth in the palate side. The stress distribution characteristic of post-cores and teeth roots were analysed. RESULTS: In veritical loading, the stress distribution of one-piece of CAD/CAM zirconia post-core with 2.0 mm radius was better distributed than the two others, The stress concentration of teeth roots locate at the root canal wall where the end of the post exists, which increased with the wider radius of the post-core. In 45° inclined loading, the maximum stress of the zirconia post-core and the teeth root was more than three times of which in vertical loading. In post-cores, the stress concentration was in the labia middle 1/3 of the post. In teeth roots, the stress concentration located at the lateral wall in the post end and the area of the apical foramen. The stress of the post-cores and teeth roots was decreasing in the teeth root with a 2.0 mm ferrule. CONCLUSION: 2.0 mm radicus of the one-piece of CAD/CAM zirconia post-core is a better choice in clinic. There should be a conical degree in the teeth roots preparing for one-piece of CAD/CAM zirconia post-core restoration. The force of protrusive movement has a greater influence on the post-core and teeth roots. The area of apical may be apt to break in overloading.

[All-ceramic resin bonded fixed partial denture made of IPS hot-pressed casting porcelain restore anterior missing teeth: a three years clinical observation].

OBJECTIVE: To clinic observation of IPS Empress2 and IPS e.max all ceramic resin bonded fixed partial dentures used in one anterior teeth lost in upper jaw or less than two anterior tooth lost in lower jaw. METHODS: 22 patients, 26 restorations had been made, which included 16 single-retainer all ceramic resin bonded fixed partial dentures and 10 two-retainers all ceramic resin bonded fixed partial dentures. Secondary caries of the abutments, shade in the margin of the retainers and the integrity of the restorations had been observed at 3 months, 6 months, 1 year, 2 years and 3 years after all ceramic resin bonded fixed partial dentures having been bonded. RESULTS: In the 3 years of clinic observation of the anterior all ceramic resin bonded fixed partial dentures, 1 two-retainers restoration lost bond after it had been made for 3 months, a retainer of one two-retainers restoration was broken after 6 months, but they are still used after modified as one-retainer all ceramic resin bonded fixed partial dentures, 1 two-retainers restoration lost bond two year later, It was integrity and re-bonded again that was still stable. No secondary carries and no shade in margin of the retainers had been found. Their color matches with the nature teeth excellently. The success rate was 88.5%. CONCLUSION: IPS Empress 2 and IPS e.max all ceramic resin bonded fixed partial dentures should be a good selection in one or two teeth lose in anterior jaws.

[Two years clinical observation of anterior all zirconia ceramic resin bonded fixed partial dentures].

OBJECTIVE: To observe the restoration effect of anterior all zirconia ceramic resin bonded fixed partial dentures, and to find a new fixed restorative method for restoring one or two missing anterior teeth. METHODS: Twenty-nine missing anterior teeth from twenty-three patients were restored with all zirconia ceramic resin bonded fixed partial dentures, and restorations were devided in to two groups according to the number of retainers, i.e. the single-retainer group and the two-retainer group. The integrity, secondary caries, marginal shade and color match of the restorations were evaluated with the standard of American Public Health Association (APHA). The average period of observation was 22 months. RESULTS: One restoration from the two-retainer group failed, two restorations from the single-retainer group failed. The shade of two restorations were evaluated as discernable whiter compared to adjacent teeth. There was no secondary caries and marginal shade. The two year success rate of anterior all zirconia ceramic resin bonded fixed partial dentures was 90% (26/29). CONCLUSIONS: All zirconia ceramic resin bonded fixed partial dentures used for less than two anterior missing teeth can achieved definite aesthetic effect and physiologic function. It was a new type of fixed restoration for anterior missing teeth. However, to determine long-term result of this restoration more data are needed.

[Three-dimensional finite element analysis of two different framework designs of compound galvano-ceramic bridges].

OBJECTIVE: To analyze stress distribution of two framework designs in compound galvano-ceramic bridges made with three-dimensional finite element models. METHODS: Three-dimensional finite element models were developed for compound galvano-ceramic bridges with two designed retainers of Ni-Cr frameworks which ringed or partially covered the electroformed gold caps. The models were vertically loaded 200 N on the center of the occlusal surface of the pontic and loaded 400 N on the center of buccoclusal marginal ridge from buccal aspect to lingual aspect at a 30 degree angle with the occlusion plane respectively. The stress distributions and the level of stress concentration in the two models were analyzed by the FEA software. RESULTS: Stress distributing in two designed framework of compound galvano-ceramic bridges were similar. The highest von Mises stress of compound galvano-ceramic bridges was concentrated in the distal connector of the pontic and retainer. Under the vertical loading, the von Mises stress was 24.17 MPa for the partial cover retainer of the Ni-Cr framework and 24.85 MPa for the circular retainer. Under the lateral loading, the corresponding figures were 42.83 MPa and 42.69 MPa. No matter vertical or lateral loading, the margin of electroformed cap was the concentration area of the von Miese stress. CONCLUSIONS: In this study, the stress concentration area of compound galvano-ceramic bridges with Ni-Cr framework and electroformed gold caps was the connector and the margin of electroformed cap was the insubstantial area.

[The 6-year clinical comparison of compound galvano-ceramic bridges with gold alloy and Ni-Cr alloy ceramic bridges].

OBJECTIVE: To evaluate and compare effects of compound galvano-ceramic bridges with Ni-Cr alloy ceramic bridges and gold alloy ceramic bridges in clinic. METHODS: A total of 105 bridges were made for 103 patients. Of them, 35 were compound galvano-ceramic bridges, 35 Ni-Cr alloy ceramic bridges, and 35 gold alloy ceramic bridges respectively. The marginal fitness and fracture of ceramic bridges were checked and caries or second caries of all abutments were also examined in clinic at 6 years after cementation. RESULTS: The marginal fitness of compound galvano-ceramic bridges was evaluated as good in 100% of the bridges, which was better than the fitness of gold alloy ceramic bridges (91%) and Ni-Cr alloy ceramic bridges (77%) (P < 0.01). There was no difference in fracture of ceramic layer among compound galvano-ceramic, gold alloy ceramic, and Ni-Cr alloy ceramic bridges at 6 years (P > 0.05). None of compound galvano-ceramic bridge was found out caries or second caries of abutments. Two of 35 (6%) gold alloy ceramic bridges was found out second caries of abutments and five of 35 (14%) Ni-Cr alloy ceramic bridges were found out caries or second caries of abutments at 6 years. None of frameworks of all bridges was loose or broken. CONCLUSIONS: The 6-year clinical study on compound galvano-ceramic bridges presents good results in marginal fitness and fracture resistance, which indicates the compound galvano-ceramic bridge can be used in clinic.

[Experimental mechanics analysis of posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps].

OBJECTIVE: To measure the fracture strength of the posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive and to provide reference data for clinical application. METHODS: A standard low dental cast was achieved with 46 missing. Five posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps, with abutments being 47 and 45. The low dental cast was fixed on the panel of the universal testing machine, vertical load given on the central of the pontic as the velocity of 2 mm/min. RESULTS: The fracture strength of the posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps was (877.00+/-126.53) N, the fracture strength of the metal frame was (1,448.94+/-51.02) N. CONCLUSION: Posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps could endure the normal human occlusal force.

[A three-year clinical evaluation of galvano-ceramic bridges made by Ni-Cr pontic bonding galvano caps].

OBJECTIVE: To evaluate the clinical effect of galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive based on three-year clinical trials. METHODS: A total of 29 galvano-ceramic bridges made by Ni-Cr pontic fired bonding on the galvano caps were used for 26 patients. Abutment teeth plaque indices (PI) were compared according to Silness and Löe standards and their papillary bleeding indices (PBI) according to Mazza standards before restoration and after 36 months' restoration. At the same time, the integrity and marginal fitness of galvano-ceramic bridges were observed. RESULTS: The PBI at abutment teeth were higher than those before restoration, Wilcoxon test revealed significant difference. Their PI were lower than those before restoration, Wilcoxon test revealed significant difference. All the galvano-ceramic bridges were perfect in marginal fitness and color. The rate of integrity was 89.7% in the period of observation. CONCLUSION: Galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive hold out good prospects for clinical use in fixed restoration.