OBJECTIVES: This study aimed to evaluate the stability of prosthetic screws from three types of craniofacial prostheses retention systems (bar-clip, ball/O-ring, and magnet) when submitted to mechanical cycling. MATERIALS AND METHODS: Twelve models of acrylic resin were used with implants placed 20 mm from each other and separated into three groups: (1) bar-clip (Sistema INP, São Paulo, Brazil), (2) ball/O-ring (Sistema INP), and (3) magnet (Metalmag, São Paulo, Brazil), with four samples in each group. Each sample underwent a mechanical cycling removal and insertion test (f=0.5 Hz) to determine the torque and the detorque values of the retention screws. A servo-hydraulic MTS machine (810-Flextest 40; MTS Systems, Eden Prairie, MN, USA) was used to perform the cycling with 2.5 mm and a displacement of 10 mm/s. The screws of the retention systems received an initial torque of 30 Ncm and the torque values required for loosening the screw values were obtained in three cycles (1,080, 2,160, and 3,240). The screws were retorqued to 30 Ncm before each new cycle. RESULTS: The sample was composed of 24 screws grouped as follows: bar-clip (n=8), ball/O-ring (n=8), and magnet (n=8). There were significant differences between the groups, with greater detorque values observed in the ball/O-ring group when compared to the bar-clip and magnet groups for the first cycle. However, the detorque value was greater in the bar-clip group for the second cycle. CONCLUSION: The results of this study indicate that all prosthetic screws will loosen slightly after an initial tightening torque, also the bar-clip retention system demonstrated greater loosening of the screws when compared with ball/O-ring and magnet retention systems.
Grassland ; Maxillofacial Prosthesis ; Prostheses and Implants* ; Prosthesis Failure ; Prosthesis Retention ; Torque

The purposes of this study were to investigate the satisfaction of use of removable denture elated to general, functional and esthetic factors among dental patients in national sorokdo hospital, and to establish the structure relationships of dental treatment satisfaction. Two hundred fifty hansen`s patients who consented with this survey were selected and examined their oral status. Satisfaction degree was estimated by means of self-developed questionarires, filled out by face-to-face interview. Collected data were analyzed by t-tast The obtained results were as follow : 1. The satisfaction degree of four subscales was highest in esthetic actor (3.17+/-0.36), denture retention factor(3.10+/-0.60), general treatment satisfaction factor(2.94+/-0.56), and masticatory function factor (2.90+/-0.68) in descending order. It was appeared that patients was generally satisfied with all four factor. 2. On the comparison between proportion of denture satisfaction and satisfactio 02n of subscales, as the satisfaction of general treatment, masticatory function and denture retention were increased, the proportion of denture satisfaction of esthetic function and proportion of denture satisfaction. 3. The masticatiory function factor, denture retention factor and genernal satisfaction of treatment factor were directly affected on the denture satisfaction, but esthetic factor was affected indirectly on the denture satisfaction as a result of path analysis
Dental Prosthesis* ; Denture Retention ; Dentures ; Humans

OBJECTIVETo show the trend of the retention change during the circulation of the clasp dislodging and inserting, and to discuss the proper depth of the undercut for a specific clasp. It is also a basic study for the best designing of RPD.

METHODSThe Chatillon force measuring instrument was used to record the variation of the retention of Co-Cr alloy casting Akers clasp when they were dislodging from undercuts of different depths (0.25 mm, 0.50 mm, 0.75 mm) on bicuspid and molar.

RESULTSThe data was analysed of Correlation and Regression by SPSS 10.0 statistic software. The variations of the retention in the circulation are obvious from the different teeth and different undercut depths. It shows an attenuation trend in circulation (P < 0.01). After 400 times dislodging, in bicuspid group, the retention of the clasp used in 0.50 mm undercut became less than the one used in 0.25 mm undercut. While the retention of the clasp used in 0.75 mm decreases most obviously, it values 0.7670 kg. In molar group, the attenuations of the retention at different depths of undercut are similar, the retentions of the clasp still rank as, from great to less, 0.75 mm, 0.50 mm and 0.25 mm, in the depth of undercut.

CONCLUSIONthe proper depth of the undercut for bicuspid is 0.25 mm, and 0.50 mm for molar.

Dental Clasps ; Dental Prosthesis Retention ; Humans

OBJECTIVETo evaluate the effect of different auxiliary resistance forms on the resistance and marginal fitness of complete crowns for short molar preparations.

METHODSA total of 70 Nissin resin teeth were prepared with 20° total occlusal convergence, 2.5 mm of occlusocervical height, and a shallow finish line on a milling machine. The milled preparations were then randomly assigned to 7 groups of 10. The first group was used as the control group. A total of 30 dies were modified by preparing interproximal grooves with angles of 0°, 6°, and 20° centered on the mesial and distal surfaces of the dies. The rest of the teeth were prepared with occlusal holes in the center of the occlusal surface milled with the same burs to form 0°, 6°, and 20° holes. Cobalt-chromium copings were fabricated for all specimens. The marginal gap of specific points on the axial surface was measured before and after cementation. The resistance of each specimen was evaluated by applying an external force at an angle of 45° to the long axis of the die by using a universal testing machine in a lingual to buccal direction. The maximum force applied before crown dislodgement was measured. Data were analyzed using the SAS 9.2 software.

RESULTSThe results showed that the 0° groove, 0° hole, and 6° hole were effective in improving the resistance of the complete crowns (P<0.05). The 0° groove, 6° groove, 0° hole, 6° hole, and 20° hole had significant difference with the control group in terms of marginal discrepancies (P<0.05).

CONCLUSIONAuxiliary resistance forms with less degree indicate greater resistance force but worse marginal fitness. In clinical practice, if the resistance of a preparation is enough, the auxiliary resistance forms should be avoided from being used.

Cementation ; Crowns ; Dental Prosthesis Design ; Dental Prosthesis Retention ; Humans ; Molar ; Tooth Crown

PURPOSE: The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. MATERIALS AND METHODS: Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 106 cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). RESULTS: The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). CONCLUSION: The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.
Crowns ; Dental Implants, Single-Tooth ; Dental Prosthesis Retention ; Dental Prosthesis, Implant-Supported ; Diamond ; Prosthesis Failure ; Titanium ; Torque*

OBJECTIVETo investigate the manufacture method and the effects of Cosmopost ceramic posts, to summarize the indications of Cosmopost ceramic post in clinic.

METHODS228 pieces Cosmopost ceramic posts and cores were made for 96 patients. 2l7 pieces full ceramic crowns and 8 pieces full ceramic bridgs for Cosmopost ceramic posts and cores were made. The fitness of Cosmopost ceramic post were checked, and the color of all full ceramic crowns and full ceramic bridgs were checked in clinic. The amount of loosening and broken in all restorations were checked every year in clinic. follow up 2 - 3 years.

RESULTS1 Cosmopost ceramic post was fracture about 1.5 mm before the full ceramic crown was worn. 227 pieces Cosmopost ceramic posts were perfect. All of the full ceramic crowns and bridgs for full ceramic posts were excellent in color. No loosening and broken cases were checked in 0.5 - 3 years. But the indications of Cosmopost ceramic posts were strict in clinic.

CONCLUSIONCosmopost ceramic post has natural aesthetic effect and good strength. it can be used in clinic.

Adolescent ; Adult ; Color ; Dental Porcelain ; Dental Prosthesis Design ; Dental Prosthesis Retention ; Female ; Humans ; Male ; Middle Aged ; Post and Core Technique

This case study was to report the possible increase in the denture retention and psychological relief using the implant-supported fixed prostheses in a completely edentulous patient. The implants were placed in the anterior portion of the mandible in a patient who had completely edentulous state following the extraction of residual abutment teeth, and consequently a distal extension removable partial denture was fabricated. The patient's adaptation and satisfaction to the new prosthesis was monitored and confirmed in terms of masticatory function and esthetics, by restoring the oral condition similar to initial status before the residual teeth extraction. After 6 months, radiographic examination confirmed that both the abutment teeth and the implants were stable and well maintained. Considering the relatively short clinical follow-up period, however, continuous long-term monitoring was required.
Dental Prosthesis, Implant-Supported ; Denture Retention ; Denture, Partial, Removable ; Esthetics ; Follow-Up Studies ; Humans ; Mandible ; Mandibular Prosthesis ; Prostheses and Implants ; Tooth

PURPOSE: We describe our experience with the Permacol graft in anophthalmic socket reconstruction, and compare it to the autologous buccal mucosal graft, emphasizing the postoperative vascularization and contraction of each graft. METHODS: This was a retrospective comparative study. We measured the time necessary for the graft surface to be completely vascularized, as well as the fornix depth of the conjunctival sac in anophthalmic patients. RESULTS: Ten patients underwent Permacol graft reconstruction, with 44 undergoing buccal mucosal graft reconstruction. Seven eyelids (70%) in the Permacol group had a good outcome, with improvement in lower eyelid position and prosthesis retention. Nine out of 10 eyelids (90%) in this group showed complete vascularization of the graft at 2.6 ± 1.9 months postoperatively, while the grafted buccal mucosa was fully vascularized at 1.1 ± 0.3 months postoperatively (p < 0.01). Postoperative fornix depth in the Permacol group was 9.1 ± 2.2 mm, compared to 14.9 ± 4.5 mm in the buccal mucosal graft group (p < 0.01). Mean increases in fornix depth were 33.1% and 67.9% of the mean vertical length of the implanted graft. CONCLUSIONS: The Permacol graft can be useful as spacer graft material in anophthalmic socket patients. It takes longer to vascularize, and undergoes greater graft shrinkage with time, compared to the buccal mucosal graft.
Acellular Dermis* ; Anophthalmos ; Eyelids ; Humans ; Lacrimal Apparatus ; Mouth Mucosa* ; Prosthesis Retention ; Retrospective Studies ; Transplants*

OBJECTIVETo determine ITI implants stability in different bone types using RFA and to provide evidence for feasibility of early loading.

METHODSA total of 104 ITI sand-blasted large-grit acid-etched (SLA) implants in 50 patients were classified into 3 groups according to bone type. Resonance frequency analysis was conducted at 0, 1, 4, 6, 8 and 12 weeks after installation.

RESULTSThe survival rate was 100%. Primary stability was affected by bone type (P < 0.001). The implant stability quotient (ISQ) was significantly higher in type I bone than in type IV bone. At 12 weeks, there was no significant difference among the 3 groups. Comparison of ISQ was made between 6 th week and 12 th week for all bone types, there was no significant difference for type I and III (P > 0.05) while there was for type IV (P < 0.001).

CONCLUSIONSEarly loading with ITI SLA implants placed in type I, III bone were highly predictable.

Bone Density ; Dental Implantation, Endosseous ; Dental Implants ; Dental Prosthesis Retention ; Humans

OBJECTIVETo analyze effects of different thread helix angles and densities on the primary stability of immediately loaded implants using the three-dimensional finite element model analysis.

METHODSFive models of three-dimensional finite element (0.8 mm, 1.6 mm, 2.4 mm, double-threaded, and triple-threaded) were created using the commercial codes of Pro/E software, Hypermesh software, and ABAQUS software. In conditions of horizontal and vertical loading, the micro-motion of the finite element models with different thread helix angles and densities were computed with ABAQUS software.

RESULTSConcerning different thread helix angles, the micro-motion of single-threaded implant was the minimum and that of the triple-threaded was the maximum with vertical and horizontal loading. The micro-motion of doubled-threaded implant was the minimum compared with thread pitch 1.6 mm and the micro-motion of triple-threaded implant was the minimum compared with thread pitch 2.4 mm with vertical and horizontal loading.

CONCLUSIONSThe thread helix angle and density of implants can greatly affect the vertical interfacial micro-motion. With increasing thread pitchs, the resistance of implant to vertical load is weakened; with increasing thread helix angle, the resistance of implant to vertical load is weakened; with increasing thread density, the resistance of implant to the vertical load is weakened.

Dental Implants ; Dental Prosthesis Design ; Dental Stress Analysis ; Denture Retention ; Finite Element Analysis