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PubMed1981

Auxiliary retention for complete crowns provided by cement keys.

1. Cement keys were an effective means of increasing the retention of complete cast gold crowns to preparations in extracted teeth. 2. Single grooves placed in either the dentin or in the crown alone were not effective in increasing retention in 30-degree crowns. In 7-degree crowns, a single groove in the crown gave better retention than a single groove in the dentin. 3. Crowns with a 7-degree taper had greater retentive strengths than 30-degree crowns treated identically. The retentive strength of 7-degree crowns with cement keys approached the tensile strength of zinc phosphate cement.

Crowns↗

PubMed1983

Retentive properties of some simplified dowel-core systems to cast gold dowel and core.

The retentive capacity of three groups of dowel and core systems was compared by subjecting them to tensile loading. The following conclusions were made. Retentive values for Parapost dowels were significantly higher than those of both cast-gold and reinforced composite resin dowels and cores. Surface configuration of dowels appeared to be an important factor in retention. No significant differences were observed in the retentive values between cast-gold and obturator-reinforced composite resin dowels and cores. Retentive failure of the obturator-reinforced composite resin system always occurred in the composite resin-dentin interface.

Cementation↗

PubMed1984

Comparison of retentive properties of dowel forms after application of intermittent torsional forces.

Four different forms of cast-gold dowels (round parallel-sided, round parallel-sided with antirotational keyways, tapered, and ovoid parallel-sided) were subjected to intermittent horizontal and vertical rotational forces prior to tensile testing. The results of this experiment indicated that ovoid parallel-sided dowels were the most retentive. Tapered dowels were found to be the least retentive. The addition of antirotational features to the round parallel-sided dowel did not improve the retentive values. The retentive properties of the round parallel-sided dowels, with or without antirotational features, were not statistically different from the ovoid parallel-sided dowels. Sandblasting the finished castings prior to cementation increased retention.

Crowns↗

PubMed1987

Effects of various cementation methods on the retention of prefabricated posts.

Para-Post dowels were cemented by using combinations of cement, cleansing agents, and dentinal treatments. The comparative retentive strengths were as follows: 1. Para-Post posts cemented with composite into mechanically corrugated post spaces recorded the greatest retention. 2. The retention of the posts cemented with composite into post spaces rinsed with 1 ml of 17% EDTA with a pH of 7.5 and followed immediately by 1 ml of 5.25% NaOCl was lowest. 3. The retention of the posts secured with zinc phosphate into mechanically corrugated post spaces was significantly higher than with untapped post spaces. 4. The retentive strength of the posts placed with glass-ionomer cement into post spaces, irrigated with 1 ml of 40% polyacrylic acid solution, and rinsed with distilled water was comparable to that of posts secured with zinc phosphate cement without roughened post spaces.

Cementation↗

PubMed1990

Effect of prolonged ultrasonic instrumentation on the retention of cemented cast crowns.

Occasionally the need arises to remove restorations that have been cemented. Several ultrasonic tips have been developed to aid in removing cemented restorations. Earlier studies of the effects of ultrasonic vibration reveal detrimental effects on amalgam surface and marginal integrity and, at short instrumentation periods (2.5 minutes) in vitro, no significant effect on the retention of cemented cast crowns. Twenty identically machined metal dies had nonprecious crowns waxed, cast, and fitted. Each casting was cemented twice with glass ionomer and zinc phosphate cement. Each cement was tested for the effects of vibration on retention. The cements were mixed according to manufacturer's specifications, placed under 5 kg load, then placed in 37 degrees C water and contained in a humidor. Retention was tested with a 4202 Instron machine to determine the forces needed to overcome retention. Retention ranged from a high of 125.36 kg for glass ionomer without vibration to a low of 19.11 kg for zinc phosphate vibrated for 12 minutes. The use of vibration is considered an advantageous adjunct to other cast restoration removal devices.

Cementation↗

PubMed1991

Tensile strength of five types of retention for resin-bonded prostheses.

The tensile bond strengths of five retention techniques for bonded cast restorations were tested. The retentive methods were the electrolytic etch, Rochette's perforations, retention beads, the recessed surface, and soldered orthodontic mesh. The electrolytic etch and recessed surface methods gave the highest values of bond strength, followed by retention beads. Rochette's perforations and the soldered orthodontic mesh failed to surpass the bond strength of the control group (no additional retention) after 1 hour and provided the lowest bond strength after 24 hours.

Acid Etching, Dental↗

PubMed1992

The degree of zinc phosphate cement coverage of complete crown preparations and its effect on crown retention.

This investigation examined the amount of retentive area covered by cement under complete coverage crowns and its effect on retention. Sixty crowns of self-cured acrylic resin were prepared on 60 identical brass dies and were divided into six groups of 10 crowns each according to different cement applications. The results showed that retention was dependent on the amount of retentive area covered by the cement. The amount of cement in the occlusal part of the cementation space did not affect retention.

Acrylic Resins↗

PubMed1992

Salivary secretion and denture retention.

Correlations between the retention of complete dentures and flow rates of the palatal and parotid glands were studied in 86 patients. The determination of secretion rates and forces of the forward leverage leading to a dislocation of the dentures showed a narrow correlation between the secretion of palatal glands and the retention of maxillary dentures. The retention of mandibular complete dentures is adversely influenced by the secretion rate of minor salivary glands. However, there is no correlation between the flow rate of parotid saliva and the retention of either denture. In addition, the medicinal stimulation of salivation showed that an increase of mucus secretion induced an improved retention of maxillary complete dentures.

Aged↗

PubMed1992

Retention properties of a split-shaft threaded post: cut at different apical lengths.

The retention of the post to the root of an endodontically treated tooth is critical for a successful restoration. Modification of the post length to accommodate a specific clinical situation is common. This study compared the retention of No. 1 and No. 2 Flexi-Post restorations shortened apically from 1 to 5 mm with that reported for full-length control No. 1 and No. 2 Flexi-Post dowels. The experimental material was divided into 10 groups with 10 samples in each group. Retentive values were recorded in pounds with a universal testing machine. Analysis of variance with a Tukey-Student range, multiple-comparison test showed no statistical differences from apical reductions of 1, 2, 3, and 5 mm including the full-length control Flexi-Post No. 1 system. With 4 mm of apical shortening statistically greater retention was recorded. No statistical differences resulted with apical reductions of 1 to 4 mm or with the full-length control Flexi-Post No. 2 system, but 5 mm of apical shortening caused significantly less retention.

Cementation↗

PubMed1992

Retentive properties of threaded split-shaft posts with titanium-reinforced composite cement.

The retention of posts in tooth roots is vital to the success of the restoration. This study compared the retention of posts of various sizes and diameters cemented with a titanium-reinforced composite cement with that of posts previously reported cemented with zinc phosphate cement. Four groups made up of 10 samples each were used and retention values were compared using a universal testing machine. Two-way analysis of variance and the Newman-Keuls multiple range comparison test were performed. Larger diameter posts cemented with titanium cement had better retention than similar posts cemented with zinc phosphate cement. The statistical increase in retention for the larger size posts is probably the result of the deeper channels (threads) in the dentin and the higher cohesive strength for the titanium-reinforced composite resin.

Composite Resins↗

PubMed1993

Retentive properties of a threaded split post with attachment sleeves cemented with various luting agents.

This study determined the retention, in pounds, of Nos. 1 through 3 stainless steel attachment sleeves for the threaded split post system cemented with various cements. Post heads and matching sleeves were also sandblasted and compared with attachments not sandblasted. Four luting agents were selected, zinc oxyphosphate cement (ZOP), and three brands of composite resin cement (CRC). The experiment was divided into two parts; in part 1, samples were not treated, and in part 2, samples were sandblasted. Retentive values were recorded with a universal testing machine. A 2 x 3 x 4 factorial three-way analysis of variance was used to compute the effects sandblasting, sleeve and post type, and the luting agent. No statistical differences were recorded for sleeves not sandblasted, Nos. 1 and 2, regardless of the luting agent. The nonsandblasted No. 3 sleeve cemented with Panavia CRC had significantly greater retention than All-Bond CRC or ZOP. There were no statistical differences in retention of sandblasted sleeves for the No. 1 sleeve despite the type of luting agent. For sandblasted sleeves Nos. 2 and 3, ZOP and Panavia CRC recorded significantly greater retention than All-Bond CRC. However, there was no difference between sandblasting and not sandblasting for the No. 1 sleeve. Mean loads for Nos. 2 and 3 sleeves were substantially greater for sandblasted compared with attachments not sandblasted.

Adhesives↗

PubMed1985

Naloxone influences retention behaviour depending on the degree of novelty inherent to the training situation.

The effects of immediate posttraining subcutaneous administration of naloxone (0.25, 1 or 5 mg/kg) on retention behaviour of rats trained in an inhibitory avoidance task, subjected or not to familiarization with the training situation prior to the training trial (pretraining) have been investigated. Naloxone did not influence performance of pretrained rats not subjected to footshock at training. The drug did not significantly modify retention latencies of pretrained rats subjected to a weak footshock. However, administration of naloxone facilitated retention behaviour of non-pretrained rats subjected to a weak footshock. Likewise, naloxone significantly increases retention latencies of pretrained rats subjected to a high footshock at the training trial. These data indicate that naloxone influences retention behaviour depending on the degree of novelty linked to the training situation: a facilitatory effect of the drug is observed when the training trial becomes associated with a clear novel situation for the animals (high footshock in pretrained rats or a weak footshock in non-pretrained animals).

Animals↗

PubMed1988

The effect of a calcium antagonist on the retention of simple associational learning.

Using a newly developed training paradigm, rats were trained to associate a spatial location and a black interior with mild footshock and another adjacent location with white interior with the absence of footshock in three independent experiments. Retention of these associations was measured 24 and 48 hr after training in situation in which the animals could move freely between the black and white locations over a 90 sec test. Other rats were subjected to a control procedure in which shock was received on both the black and the white sides of the apparatus. In each of the experiments, half of the animals in the experimental and the control groups were trained following the administration of the calcium slow channel blocking agent, nimodipine (5 mg/kg), and the other half after saline administration. In experiment 1, the injections were given 15 min before training. In experiment 2, the injections were given chronically, over a 6 day period before training. In experiment 3, the animals were given a single injection 7 days before training. In all cases, retention was examined both 24 and 48 hr after training. The results were that the experimental procedures produce a strong aversion to the black portion of the apparatus. The greatest amount of retention was found in animals that had received the chronic injections, whether they were of saline or of nimodipine. In every aspect of retention in which the saline-treated rats were less than perfect in retention, the nimodipine animals exhibited superior performance.

Animals↗

PubMed1996

Effects of beta-CCE on retention of aversively- and appetitively-motivated tasks in rats.

Beta-carboline-3-carboxylic acid ethyl ester (beta-CCE; 1.0 or 5.0 mg/kg, i.p.) or vehicle control was administered to male Sprague-Dawley rats immediately after training in an aversively- or appetitively-motivated task. Aversively-motivated training consisted of a one-trial step-though inhibitory (passive) avoidance task with a 0.6 mA, 1.0 s foot shock. Retention was tested 21 days after training. The 5.0 mg/kg dose of beta-CCE significantly enhanced retention performance in the inhibitory avoidance task compared to the vehicle control. For appetitive training, the animals learned a T-maze for water reward. Retention was tested 48 h later, and neither dose of beta-CCE was found to affect retention performance. These results suggest that beta-CCE, when administered immediately after training, may alter retention performance of an aversively-motivated task but not an appetitive task.

Animals↗

PubMed1991

Naloxone eliminates passive avoidance retention deficits produced by pretest exposure to novelty in rats.

Pretest exposure to novelty or injections of beta-endorphin can enhance passive avoidance (PA) retention (e.g., Izquierdo & McGaugh, 1985). Enhanced retention may result from a "state-dependent" match between the CNS state during test and the novelty-induced beta-endorphin state that is obtained during training in a novel apparatus. Our Experiment 1 suggests that, unlike PA, Pavlovian fear conditioning in a conditioned lick suppression (CLS) paradigm may be beta-endorphin "state-independent." Rats were given one tone-shock pairing in a novel environment. Baseline lick rates and CLS tested 48 h later in a familiar environment were not affected by pretest exposure to novelty and/or injections of 3.33 mg/kg naloxone HCl. In Experiment 2, the same rats were PA trained/tested in a new apparatus. Saline or naloxone injections and various exposure (novel, familiar, none) conditions preceded (1h) the 24-h retention test. Pretest exposure to novelty reduced retention and naloxone eliminated that deficit. In Experiment 3, naive rats given pretest exposure to novelty also showed a PA retention deficit. The results of Experiments 2 and 3 may complement rather than contradict previous findings. Pretest induction of a beta-endorphin state by novelty may either enhance state-dependent retrieval of a "weak" memory trace or make a "strong/well consolidated" training memory more vulnerable to retroactive interference from "new learning" during the pretest exposure period.

Animals↗

PubMed1993

The central amygdala is involved in conditioning but not in retention of active and passive shock avoidance in male rats.

The present study was designed to further characterize the involvement of the central amygdaloid nucleus (CEA) in the conditioning and the retention of both active and passive stress-related behaviors. Active shock avoidance was investigated in a shuttle-box. CEA-lesioned and sham-operated animals received 30 trials on 2 consecutive days. During the first day of conditioning, the CEA-lesioned animals failed to learn to avoid, but on the second day these rats showed avoidance behavior that was comparable to the sham-lesioned ones. When lesioned animals received a total of 60 trials on 1 day, they failed to show avoidance, suggesting deficits in acquisition performance but presence of latent learning following CEA lesioning. However, the retention response, which was studied by lesioning the CEA between a 2-day avoidance training and a retention test, was unaffected. Stress-related learning was also studied in a test of passive avoidance of a previously received single, inescapable electric footshock. When the lesion was placed before the single learning trial, the retention of the response was absent. However, CEA-lesioning after the learning trial revealed no differences between the CEA-lesioned and sham-lesioned animals. In conclusion, these results demonstrate that the CEA is involved in the conditioning rather than retention of both active and passive shock avoidance responses.

Amygdala↗

PubMed1993

Nicotinic receptor agonists facilitate retention of avoidance training: participation of dopaminergic mechanisms.

The effect of nicotinic receptor agonists on retention of the inhibitory avoidance (IA) response were investigated in mice. Animals received intraperitoneal drug injections before training, and retention was evaluated 24 h later. Nicotine and cytisine, but not lobeline, significantly increased retention of the IA training. Cotinine, the main metabolite of nicotine, was inactive in the same test. Retention was not affected by the injection of the D1-D2 receptor antagonist cis-flupentixol, but the preadministration of cis-flupentixol significantly blocked the facilitatory effect of nicotine and cytisine on memory. These results demonstrate that the nicotinic receptor agonists nicotine and cytisine facilitate the retention of avoidance responses and suggest that this effect is mediated through central dopaminergic pathways.

Alkaloids↗

PubMed1990

Effects of peripherally administered arginine-vasopressin on learning, retention and forgetting in mice.

The effects of peripheral injections of (Arg)-vasopressin were investigated on different stages of memory processes using an appetitive visual discrimination task and a one-trial passive avoidance conditioning in mice. The peptide was administered at one of two doses: 50 micrograms/kg or 25 micrograms/kg. The main effects of vasopressin were observed only for the higher dose. Concerning pre-session vasopressin administration in the visual discrimination task, the effect of the peptide seemed to depend on the level of learning reached at the time of treatment. Indeed, we observed a deleterious effect of vasopressin on learning capacities when the peptide was administered before the first learning session, a bimodal effect (either an improvement or an impairment) on performance when the peptide was administered before the second learning session and an important enhancement of retention performance when the peptide was administered before the retention session, performed 24 days after training. When post-session vasopressin administration was assessed, an improvement of performance was observed indicating a facilitatory effect of vasopressin on consolidation processes. When passive avoidance conditioning was used, an enhancement of retention performance was registered only when the peptide was injected before the retention session at the 50 micrograms/kg dose. No facilitation was observed for the 25 micrograms/kg dose whatever the experimental condition was, i.e. post-learning or pre-retention injection. In order to test eventual non-specific effects of vasopressin, the influence of the peptide on locomotor activity was assessed before the two doses. The results show an important reduction of locomotor activity with the 50 micrograms/kg dose, during 4 h following vasopressin injection. No effect was observed with the 25 micrograms/kg dose. The whole results suggest that vasopressin-induced hypoactivity can directly influence the subsequent learning performance when the treatment was performed in pre-session situations. However, when the level of information is sufficient and beyond the direct effect of the drug, a memory effect may be considered with the 50 micrograms/kg dose independently from the locomotor effect, when the treatment was delivered during consolidation period (post-session) or in long-term retrieval situation (pre-session).

Animals↗