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At least 217 records · Page 12Linked to original sources

PubMed2005

Is lumbar spondylosis a cause of urinary retention in elderly women?

OBJECTIVES: Lumbar spondylosis (LS) is a common spinal degenerative disorder which causes various types of lower urinary tract dysfunction (LUTD). However, it is not certain whether LS may cause urinary retention in elderly women. METHODS: In a period covering the past 3 years, we retrospectively reviewed: a) urodynamic case records of women with urinary retention (post-void residuals, PVR > 100 ml), b) the records of women with LUTD due to LS (cauda equina syndrome and spinal canal narrowing by MRI), and c) uro-neurological features of women who belonged to both a) and b). RESULTS: a) One-hundred women with a mean age of 58 years had urinary retention. The most common underlying disease was multiple system atrophy [19], followed by multiple sclerosis [13] and cervical/thoracic tumours [8]. LS was the fourth most common [5], with the highest age (71 years) of all diseases. b) Nineteen women with LUTD had LS (12, canal narrowing of 50-70%; 7 > 70 %), with a mean PVR volume of 60 ml. A fourth [5] of them had urinary retention, with severe spinal canal narrowing (all 5 > 70%). c) Thus, 5 women belonged to both a) and b). In 4 of these women, LUTD followed or occurred together with typical cauda equina syndrome symptoms such as sciatica and saddle anesthesia. However, one elderly woman presented with painless urinary retention, and absent ankle reflexes were the sole neurological abnormality. The urodynamic abnormalities underlying urinary retention included an underactive detrusor in all 5, bladder sensory impairment in 3, an unrelaxing sphincter in 2, a low compliance detrusor in one, neurogenic sphincter motor unit potentials in 2 of 4 studied, and cholinergic supersensitivity of the detrusor in one of 3 studied. Surgical decompression ameliorated urinary retention in 1 of 2 women who had surgery. CONCLUSIONS: In our series, only 5 percent of the women with urinary retention had LS, but LS poses a potential risk for retention, particularly in elderly women with severe spinal canal narrowing. Preganglionic somato-autonomic dysfunctions underlie this condition. It may appear as the sole initial complaint in cases in which no other obvious neurological abnormalities are found.

Aged↗

PubMed1982

Effects of cement on crown retention.

This study indicates that the frequent clinical technique of permanently cementing a crown without removing all traces of a temporary ZOE cement from the tooth has no adverse effect on retention. Circumferential grooving of the tooth preparation did not significantly increase retention. In contrast, cutting a shallow groove in the crown significantly improved retention. Therefore, it would appear that the grooving of the gold casting might be advantageous in conditions where the crown restoration has minimal retention. Significant improvement in retention with grooving of the restorations was accompanied by a change in the location of the cement film. The cement was retained in the crown coronal to the groove rather than on the tooth. This finding was interesting, since previous retention studies showed that adhesive failure occurred at the metal-cement interface. From this data it appears that a primary factor of crown retention is the adhesion or mechanical interlocking of the cement to the crown. This would explain why small variations in cement film thickness, such as those due to the use of die relief, have little effect on retention. In view of these findings, the current concepts on cement retention and cement adhesiveness should be reevaluated.

Crowns↗

PubMed1982

Post-training amygdaloid lesions impair retention of an inhibitory avoidance response.

The study examined the effect of pre- and post-training bilateral amygdaloid lesions on retention of a one-trial inhibitory avoidance response. Groups of rats, including unimplanted controls and implanted controls, were trained and tested for retention at 4, 7 or 12 days following training. The lesions were made at one of several intervals before or after training: 2 days before, immediately after, or 2, 5 or 10 days after. At all retention intervals the retention of implanted controls was poorer than that of unimplanted controls and, in comparison with both control groups, the retention of animals lesioned before training was impaired. Retention was also impaired by the post-training lesions. The degree of impairment varied with the interval between the training and the lesion: lesions made within 2 days following training impaired retention, while lesions made 10 days following training had no impairing effect. These findings suggest that post-training lesions of the amygdala affect retention by impairing time-dependent processes involved in memory storage. With a sufficiently long training-lesion interval (10 days) an intact amygdala is not essential for retention.

Amygdala↗

PubMed2006

Effect of surface treatment on retention of glass-fiber endodontic posts.

STATEMENT OF PROBLEM: The effects of surface treatment on the retention of prefabricated fiber-reinforced epoxy resin posts are not well understood because most studies measure retention shortly after cementation, without artificial aging. PURPOSE: The purpose of this study was to evaluate the effect of surface treatment on the retention of glass-fiber endodontic posts luted with resin cement and subjected to artificial aging. MATERIAL AND METHODS: Thirty-two single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. Specimens were then divided into 4 groups (n = 8). Post spaces were prepared to a depth of 10 mm by using ISO 90 rotary instruments. The tapered posts received 1 of 4 surface treatments: cleaning with alcohol (Alc), cleaning with alcohol and conditioning with ED-Primer material (Alc-ED), airborne-particle abrasion (Air), or airborne-particle abrasion and conditioning with ED-Primer material (Air-ED). All posts were luted with a composite resin luting agent (Panavia F) after conditioning the canal dentin with autopolymerizing dentin primer (ED-Primer) and without acid etching of the canal dentin. After cementation, the specimens were stored in water at 37 degrees C for 30 days and subjected to simulated aging conditions consisting of 7500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Retention (N) of the posts was measured with a universal testing machine with a crosshead speed of 2 mm/min. The data were analyzed using 1-way ANOVA and the Tukey HSD test (alpha = .05). The dislodged posts were also examined microscopically at x8 and x20 magnification to evaluate the mode of failure. RESULTS: The mean retentive values (N) and SDs of the test groups were as follows: Alc, 375.9 +/- 85.0; Alc-ED, 421.2 +/- 46.8; Air, 534.8 +/- 65.8; and Air-ED, 555.8 +/- 86.9. Airborne-particle-abraded posts had significantly higher retention compared with nonabraded posts (P < .001). Treating the post's surface with ED-Primer material prior to cementation had no significant effect on retention. The failure mode was purely adhesive at the resin cement-post interface for all nonabraded posts. A mixed failure mode, adhesive at the resin cement-dentin interface, at the resin cement-post interface, and cohesive in the resin cement, was observed for airborne-particle-abraded posts. CONCLUSION: Treating the surface of the posts with ED-Primer material before cementation with Panavia F cement produced no significant improvement in the retention of the posts. Airborne-particle abrasion of the surface of the post significantly improved the retention.

Air Abrasion, Dental↗

PubMed2000

Effect of dentin desensitizers and cementing agents on retention of full crowns using standardized crown preparations.

STATEMENT OF PROBLEM: Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. PURPOSE: This research controlled crown preparation surface area and evaluated the effect of various dentin desensitizers and conventional cementing agents on the in vitro retentive strength of cast crowns. METHODS AND MATERIAL: Freshly extracted human molars were prepared for a standardized crown preparation (26 degrees total convergence, 4 mm axial height) with a custom-made pantograph. Dentin desensitizers included none (control), a polymerizable material (All-Bond 2), and a nonpolymerizable desensitizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck's), glass ionomer (Ketac-Cem), resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test condition (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative humidity using a universal testing machine at a crosshead speed of 1.27 mm/min. The proportion of cement retained on the tooth and casting after debonding was quantified according to treatment. Statistical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05.Results. Resin cement exhibited the highest retentive strength and all dentin treatments resulted in significantly different retentive values (All-Bond 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma (4.12 +/- 0.37 MPa)). Retention of resin-modified glass ionomer was between the resin cement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.81 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer values were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0. 20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 MPa). Zinc phosphate had the lowest retention values: control (1.68 +/- 0. 08 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The majority of cement was retained on the debonded tooth surface versus the casting, with the exception of zinc phosphate when used with dentin pretreatments. CONCLUSION: Controlled crown surface areas reduced the variation in strength values permitting high discrimination among retention values of desensitizer/cement combinations. In all but 1 combination, Gluma desensitizer significantly decreased crown retention. With resin cement and resin-modified glass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.

Analysis of Variance↗

PubMed1998

Retention of three endodontic posts cemented with five dental cements.

STATEMENT OF PROBLEM: The retention of a post is believed to be a major factor in restoration survival. Therefore the cement with the greatest in vitro retention property should give the best performance for a restoration. PURPOSE: This study compared retentive values of three posts (Flexi-Post, AccessPost, and ParaPost) cemented with five cements (Flexi-Flow, zinc phosphate, Advance, Duet, and Ketac-Cem) plus a control group that consisted of a Flexi-Post No. 2 dowel without cement. MATERIAL AND METHODS: A total of 160 recently extracted human single-rooted teeth with crowns removed at the cementoenamel junction were divided into 16 groups of 10 samples. Post holes were prepared according to manufacturers' instructions. Posts were then cemented with one of the five cements. Each sample was placed into a specialized jig and on a tensile testing machine with crosshead speed of 0.638 cm/minute, applied until failure. A two-way analysis of variance and Newman-Keuls multiple range comparison tests were performed for all cemented groups. A one-way analysis of variance and a Student-Newman-Keuls multiple range comparison test were performed only for the groups with the Flexi-Post dowel, this included the no cement condition, with significant results if p < 0.05. RESULTS: Flexi-Post dowel with Flexi-Flow Natural cement obtained the highest retentive value (303.91 pounds). ParaPost dowel with Duet cement exhibited the lowest retention value (21.23 pounds). The Flexi-Post dowel demonstrated higher mean retention than AccessPost or ParaPost dowels, AccessPost dowel was higher than ParaPost dowel. Flexi-Flow cement had the highest overall mean retention followed, in decreasing order, by zinc phosphate, Advance, Ketac-Cem, and Duet cements. CONCLUSIONS: Flexi-Post dowel was the most retentive post studied with values ranging from 303.91 pounds with Flexi-Flow Natural cements to 150.93 pounds without cement. Flexi-Flow cements had a higher overall mean retention than other cements studied.

Analysis of Variance↗

PubMed1990

An in vitro study of the effect endodontic access preparation and amalgam restoration have upon incisor crown retention.

Endodontic access preparation leads to a significant reduction in crown retention. This study sought to determine whether this retention can be regained after access. Eighteen extracted human maxillary incisors had PFM crowns fabricated. Crowns were cemented, retention measured, recemented, access preparations cut, and retention once again measured. Then, crowns were recemented and accesses restored with dental amalgam and new retention measured. This format allowed each crown to be used as a control of itself. For crowns cemented with zinc phosphate cement and restored with amalgam, a 126% increase over original retention was measured. For crowns cemented with polycarboxylate cement and restored with amalgam, a 237% increase over original retention was measured. For crowns cemented with polycarboxylate cement and restored with amalgam, a 237% increase over original retention was measured. These results suggest that recementing crowns secondary to endodontic access and restoring the access with amalgam regains and even surpasses the original retention.

Cementation↗

PubMed1989

Comparison of retention performance between young rats with fimbria-fornix lesions and aged rats in a 14-unit T-maze.

Young (3-months) and aged (24-months) male F-344 rats were pretrained in one-way active avoidance in a straight runway for 3 days. Then two 10-trial daily sessions were given in a 14-unit T-maze in which the response requirement was to negotiate each of 5 maze segments within 10 s to avoid footshock. One day or one week after acquisition, bilateral electrolytic lesions were made in the fimbria-fornix of young rats (1-day lesion or 1-week lesion). Corresponding sham operations were made for remaining young rats (1-day sham or 1-week sham). Aged animals did not receive any surgical treatment. One week after surgery, a 10-trial retention test was conducted to assess the lesion effects on retention and to manipulate the interval between acquisition and lesions. Aged animals were tested in the maze 1 week after acquisition. Results revealed that rats with fimbria-fornix lesions exhibited significant impairment compared to sham-operated groups on all retention performance measures including errors, runtime, number of shocks, duration of shock, and alternation errors. The number of errors and alternation errors of lesioned animals were still higher than those of sham-operated animals at the second half of the retention test, whereas other non-cognitive measures for lesioned animals recovered to control levels. The interval between acquisition training and lesions had no influence on retention performance. Although performance of aged rats during acquisition and retention trials was significantly worse than that of young controls and lesioned animals, a similar recovery pattern during retention testing was found for young rats with fimbria-fornix lesions and aged rats, i.e. both groups showed significant declines in non-cognitive measures with less decline in cognitive measures. These results suggest that the fimbria-fornix is partially involved in retention of 14-unit T-maze performance and that the age-related retention deficit observed in this task may be related to impaired transmission through this pathway.

Aging↗

PubMed1995

[Effects of anesthesia on postoperative micturition and urinary retention].

Postoperative micturition difficulties, considered as minor complications, have a high incidence. Acute urinary retention can follow all types of anaesthetics or operations. Surgical trauma to the pelvic nerves or to the bladder, postoperative oedema around the bladder neck, and pain-induced reflex spasm of the external and internal urethral sphincters may play a role in the development of urinary retention. Acute urinary retention is the most common complication of surgery for benign anorectal disease. The incidence of urinary retention is more likely to occur in old male patients. Preoperative urinary symptoms are not a prerequisite for developing postoperative urinary retention, although they are considered to be a risk factor. The type of anaesthetic, postoperative pain and its management may have little effect on the occurrence of postoperative urinary dysfunction. Studies on the urodynamic effects of various anaesthetic agents are rare. The parasympatholytic drugs increase bladder capacity, decrease the rate of bladder contractions and cause downward trends in urethral resistance. The barbiturates and halothane produce similar effects on urethral resistance. The anaesthetic agents decrease the intrabladder pressure and inhibit the micturition reflex. Halothane decreases bladder contractions and increases its capacity measured by the cystometrogram. Urinary retention is a side effect of opioids, particularly after intrathecal or epidural administration. Epidural morphine relaxes the detrusor muscle with a corresponding increase in the maximal bladder capacity. Spinal opioids influence the function of the lower urinary tract, by direct spinal action on the sacral nociceptive neurons and autonomic fibres, as well as by an effect on supraspinal centres. Naloxone increases detrusor pressure, decreases bladder capacity, and causes a need to void. Urinary retention is less common after a short-acting (lidocaine 5%) than after a long-acting agent (bupivacaine 0.5%). After spinal anaesthesia, detrusor strength and the ability to void restarts with the return of sacral sensation to pinprick. A single episode of bladder overdistention can result in significant morbidity. Overfilling of the bladder can stretch and damage the detrusor muscle, leading to atony of the bladder wall, so that recovery of micturition may not occur when the bladder is emptied. On the other hand, the excessive use of an indwelling catheter can lead to urinary tract infection, urethral stricture and prolonged hospital stay. Short-term prophylactic catheterisation is recommended in patients with obstructive symptoms. Patients at risk for urinary retention should be stimulated to void and provided a quiet environment in which to do so. They should be encouraged to seat, stand or ambulate as early as possible. The alpha 1 adrenergic receptor blocking agents have been used for treatment of organic or functional urinary retention. It is essential to make sure the bladder empties regularly in the postoperative period, especially in day-case surgery or in patients receiving opioid analgesia or after epidural anaesthesia.

Analgesics, Opioid↗

PubMed2006

Urinary retention after haemorrhoidectomy: Impact of stapled haemorrhoidectomy.

OBJECTIVE: Urinary retention is a common complication following haemorrhoidectomy. Stapled haemorrhoidectomy (SH) is associated with less postoperative pain, but whether or not this can reduce the incidence of urinary retention has not been evaluated. This study aimed to compare the incidence of urinary retention in patients treated with SH with those treated with conventional haemorrhoidectomy (CH). METHODS: Charts of patients who underwent haemorrhoidectomy between May 2000 and March 2003 were reviewed. Data on demographics of patients, operative procedures, modes of anaesthesia, postoperative hospital stay and morbidities including urinary retention were collected. Factors that might affect the incidence of urinary retention were analysed by univariate and multivariate analyses. RESULTS: During the study period, 204 patients (100 men and 104 women; mean age, 49 years; age range, 20-82 years) underwent haemorrhoidectomy. SH was performed in 90 (44.1%) patients while the other 114 (55.9%) had CH. Seventy patients (34.3%) were operated on as day cases. One hundred and seventeen (57.4%) patients underwent surgery under general anaesthesia and 87 (42.6%) were operated on under spinal anaesthesia. Urinary retention occurred in 31 patients (seven with SH and 24 with CH, p = 0.009). Logistic regression showed that general anaesthesia (p = 0.044; odds ratio [OR], 2.43; 95% confidence interval [CI], 1.02-5.97) and SH (p = 0.046; OR, 2.66; 95% CI, 1.02-7.00) were independent factors associated with a lower incidence of urinary retention. CONCLUSION: The incidence of urinary retention following haemorrhoidectomy was 15.2%. General anaesthesia and SH were independent significant factors associated with a lower incidence of urinary retention.

Adult↗

PubMed1994

Long-term retention of skilled visual search: do young adults retain more than old adults?

Young and old Ss received extensive consistent-mapping visual search practice (3,000 trials). The Ss returned to the laboratory following a 16-month retention interval. Retention of skilled visual search was assessed using the trained stimuli (assessment of retention of stimulus-specific learning) and using new stimuli (assessment of retention of task-specific learning). All Ss, regardless of age group, demonstrated impressive retention. However, age-related retention differences favoring the young were observed when retention of stimulus-specific learning was assessed. No age-related retention differences were observed when task-specific learning was assessed. The data suggest that age-related retention capabilities depend on the type of learning assessed.

Adult↗

PubMed1998

Transballoon cystometry: a new technique to assess detrusor function after urinary retention.

OBJECTIVE: To validate a new urodynamic technique to assess detrusor function in patients presenting with acute urinary retention, using the balloon channel of their Foley catheter (transballoon cystometry), and to use the technique to assess patients presenting in acute retention. PATIENTS AND METHODS: The technique of transballoon cystometry is described and validated in vitro using a specially constructed water manometer, and in vivo on five patients who had a suprapubic catheter in addition to the urethral Foley catheter. Fifty-two patients presenting in acute retention underwent transballoon cystometry one week after catheterization; they were divided according to their clinical presentation into uncomplicated acute retention (41 patients) and acute-on-chronic retention (11 patients). The results from transballoon cystometry were compared between these groups. RESULTS: The pressure recorded through the balloon channel was equal to that recorded through the lumen of the catheter, both in vitro and in vivo. Patients with acute-on-chronic retention had a larger volume at first sensation, a larger maximum cystometric capacity, higher end-filling pressure and lower maximum detrusor pressure during isometric contraction than patients in uncomplicated retention. CONCLUSION: Transballoon cystometry is accurate and easy to perform. The clinical distinction between uncomplicated acute retention and acute-on-chronic retention was supported by the urodynamic data. This test could be used before surgery to identify patients with detrusor failure.

Acute Disease↗

PubMed2004

Parameters affecting retentive force of conus crowns.

The aim of this study was to determine the values of the retentive forces of the telescopic crowns. At the first step of the study, the samples having different heights and angles were compared in relation to retentive force. At the second step, the samples were subjected to removal procedures having a pre-determined speed, force and number. The obtained retention values were compared. Ninety dies were prepared in order to measure the retention of the conus crowns. The removal tests were performed with the insertion/separation device. The speed of the test device was 100 cm min(-1) providing the placement of the pieces with 5 kgf in 100, 200, 300, 500, 1000, 5000 and 10 000 cycles. The mean of the retention values of the changes of the angles were found to be statistically different (P < 0.01). According to the results of the variant analysis, the differences in the changes of the height were statistically significant (P < 0.01). The differences between the changes of the number of procedures of all groups were statistically significant (P < 0.01). The number of procedures, height and angle interactions were statistically insignificant (P = 0.758). According to the results of this study, the effect of the angle and height factors in terms of retention among the groups were not independent of each other. In equal angles, as the height increased, increased retention measurements were obtained. In more acute angles, the increase in retention was more obvious. It was also found that an accessory device was necessary to maintain retention capabilities after a long-term use.

Crowns↗

PubMed1993

Adding retentive features in the rebonding of cast metal resin-bonded prostheses.

Many methods have been used to improve retention in resin-retained fixed prostheses, such as electrolytic etching of the retainer, the labial wrap design, proximal grooves, cast pin retention, and the use of improved adhesive resins such as Panavia EX (Kuraray Co, Osaka, Japan). Insufficient retentive features often lead to debonding of resin-retained fixed prostheses. Debonded prostheses may occasionally be recemented and successfully retained by the addition of retentive features to the prosthesis and abutment teeth. When recementing a debonded prosthesis with questionable retention, additional retention may be added to the retentive wings of the prosthesis by using a Rochette retentive hole in combination with pin retention or enamel/dentinal slots in the abutment teeth.

Dental Pins↗

PubMed2003

[The measurement of retentive forces in mandibular complete overdenture with Magfit magnetic attachments].

OBJECTIVE: To evaluate the in vivo retentive forces of mandibular complete overdenture with Magfit attachments, as well as the relation between the location of magnetic attachments and the retentive forces of the denture. METHODS: 5 patients were selected and treated with mandibular complete overdentures retained by Magfit EX600 and MD800 attachments. A strainometer was used to measure the retentive forces in anterior, central and posterior parts of the overdenture before and after magnets were set. The vertical and anterior-upper 60 degrees retentive forces of the overdenture were measured one month later. RESULTS: The retentive forces of the overdentures after setting magnets were significantly greater than that before magnets were set (P < 0.05). There was no significant difference in retentive forces between the different parts (P > 0.05). The retentive force in vertical direction was greater than that in anterior-upper 60 degrees direction (P < 0.025). CONCLUSION: Magnetic attachments can significantly improve the retention of mandibular complete overdenture. The location of magnetic attachments greatly influences the retentive force of the overdenture.

Aged↗

PubMed2004

Comparative study of retentive anchor systems for overdentures.

OBJECTIVES: This study aimed to evaluate the retention on two or four implants of eight resilient and nonresilient retentive anchors used in overdentures. METHOD AND MATERIALS: Eight groups of retentive anchors were used: Dyna and Shiner (magnets); Dalla Bona and O-Ring (balls); Ceka Revax and Zaag attachments (studs); the cast bar (Dolder type) system with plastic clips; and the milled bars system. These specimens with their respective overdentures were prepared on two similar acrylic resin models with four implants (3.75 x 13 mm). Ten tensile strength tests (Instron) were performed on each group at a speed of 3 mm per minute. The statistical analysis (one-way analysis of variance, Tukey's HSD test) was considered significant. RESULTS: The pull force values ranged between 0.400 and 3.800 daN (International System of Units). There was a significant difference in retention in favor of the milled bars in comparison with the Ceka Revax, Hader bars, Zaag attachments, O-Ring, and Dyna groups, and a marginally significant difference compared with the Dalla Bona group. There was a highly significant difference with the Shiner magnets. CONCLUSION: The milled bar system was the most retentive anchor, with the Dalla Bona, Ceka Revax, Hader Bar, Zaag attachment, and O-Ring groups being the second most retentive. The least retentive groups were the Shiner and Dyna magnets. Proper abutment placement in the mandible and the correct selection of the retentive anchor will improve overdenture retention.

Analysis of Variance↗

PubMed1990

Clasping system with rotational path of insertion. 2. Relation between mesio-distal distance of edentulous space and retentive force.

The rotational path of insertion differs substantially from the conventional path or perpendicular path of insertion. With a rotational path, one segment of the partial denture is seated first, then the remainder of it is rotated into position. One segment of this system is the rigid retentive component with a long occlusal rest and the other is the conventional clasp. This study examined the influence of mesio-distal distance of the edentulous space, the point of the displacing force, the undercut of rigid retentive component and the inclination of the abutment tooth on the retention of this system. The following results were obtained: 1) Retention of the denture was the lowest when a displacing force was applied at the conventional clasp part under the conditions of mesio-distal distances with edentulous spaces of 10, 20 and 30 mm, respectively. 3) Retention showed a tendency to decrease progressively as the proximal undercut on the rigid retentive component was changed to 2.0, 1.5, 1.0 and 0.5 mm, respectively. The values of the decreasing ratio of retentive forces were almost the same regardless of the mesio-distal distance of the edentulous space. 4) Retention of the denture was improved when a tilted tooth was used as an abutment tooth on the rigid retentive component side.

Dental Clasps↗

PubMedDate not supplied

[Influence of impressions' border formation on retention of lower complete dentures].

Examinations of the retention of lower individual trays without formation of borders and with borders shaped of wax for impressions have been carried out in 32 patients with toothless mandible. The retention of impressions and lower complete dentures has also been examined. The examinations have been demonstrated that formation of lower individual impression trays' borders increases the retention of lower complete denture. The formation of borders in the anterior region of sublingual fovea influences the retention of lower complete dentures most. Simultaneous formation of borders in the anterior regions of sublingual salcus and oral cavity vestibule ensures the greatest retention of the dentures. The retention of lower complete dentures shows positive correlations with the retentions of impression trays and impressions and that is why the estimation of the impression's retention of the toothless mandible should be done each time to determine the recommendations for the end of the procedure or performance of suitable corrections. Carrying lower complete dentures for 1-4 weeks doesn't influence the retention force of these dentures.

Dental Impression Technique↗