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PubMed2004

Effect of multi-adhesive layering on retention of extraoral maxillofacial silicone prostheses in vivo.

STATEMENT OF PROBLEM: Loss of retention of maxillofacial prostheses often makes the margin visible or the prosthesis dislodge. Using several medical adhesives in combination may improve retention. PURPOSE: The purpose of this study was to investigate the effect of single- and multi-adhesive layering of 2 adhesives on the retention of maxillofacial silicone elastomer strips adhered to the skin of human forearms using a peel test. MATERIAL AND METHODS: Power analysis from a previous study and a pilot trial specified at least 20 subjects. Eight Silastic Adhesive A/MDX4-4210 silicone rubber strips (N=240) were applied in a predetermined random order to the left and right ventral forearms of 30 IRB-approved human subjects. Skin-Prep Protective Dressing was applied. Secure 2 Medical Adhesive (SMA) and Epithane-3 (E3) adhesive were used alone or as SMA/E3 or E3/SMA sandwiches (from skin to prosthesis) to adhere strips. Strips were peeled 6 hours later in a universal testing machine at 10 cm/min and data reported in N/m. Paired t tests were used to evaluate left and right arm differences. A Friedman test for nonparametric correlated data with within-subject design was performed, determining differences between both adhesives singly and in combination (alpha=.05). RESULTS: Tests of left-right differences were insignificant ( P =0.43), so the data from both arms were combined. Many strips with E3 did not adhere before testing and were counted as 0 adhesion. Median peel strengths (and 25th and 75th percentiles) in N/m were: SMA = 76.1 (47.1-107), E3 = 6.75 (0.0-25.9), SMA/E3 = 107 (78.0-132), and E3/SMA= 19.6 (6.99-42.4). All 4 variables were significantly different ( P <.0005). CONCLUSION: The multi-adhesive combination of SMA/E3 had the highest adhesion, followed, in order, by SMA alone, E3/ SMA, and E3 alone. Both E3 groups left a difficult-to-remove residue on the skin. SMA/E3 left a halo-like residue on the skin at the periphery of the strips from the E3 leaking around the SMA. SMA remained adherent to the prosthetic material.

Adhesives↗
PubMed1998

An alternative technique for mandibular advancement prosthesis fabrication.

One of the conservative and successful modalities of treatment for obstructive sleep apnea is the mandibular advancement prosthesis. This prosthesis engages teeth on both dental arches for retention and stability. This article describes a technique that allows the fabrication of such a prosthesis in one piece and in a single laboratory step. This may be beneficial in reducing the laboratory time required for fabrication of such a prosthesis.

Dental Prosthesis Design↗
PubMed2004

Cantilever fixed prostheses utilizing dental implants: a 10-year retrospective analysis.

OBJECTIVE: The dental literature has been unclear about long-term success of fixed cantilever prostheses supported by dental implants. The disappointing results reported when cantilever fixed partial dentures (FPDs) are supported with natural teeth are not directly applicable to implant cantilever FPDs. This article reports on 10 years of implant-retained fixed prostheses primarily in the maxillary arch using the ITI dental implant system. METHOD AND MATERIALS: Sixty cantilever prostheses using 115 ITI dental implants on 36 patients were placed and monitored over a 10-year period. RESULTS: No implant fractures, abutment fractures, porcelain fractures, prosthesis fractures, soft tissue recession, or radiographic bone loss were recorded. All 60 cantilevered prostheses remain in satisfactory function. CONCLUSION: Positive, long-term results, using implant-retained cantilever FPDs can be achieved by: (1) using a rough surface implant of 4.1 mm or greater; (2) using an implant/abutment design that reduces stacked moving parts and reduces the implant-to-crowns ratio; and (3) using a cementable prosthesis design that eliminates the need for occlusal screw retention.

Adult↗
PubMedDate not supplied

A prospective study on the maintenance of implant prostheses in private practice.

This study examined the adjustments, repairs, time, and costs required to maintain 69 implant prostheses in private prosthodontic practice for an average of 22 months after placement. For the removable prosthesis design, the most common adjustment was contouring the prosthesis and the most common repair was retentive component replacement. Screw tightening or fracture repair were the most frequently needed modifications for fixed implant prostheses. Each removable implant prosthesis averaged four times as many postplacement adjustments and almost twice as many repairs as did each fixed implant prosthesis, and the mean length of each maintenance appointment was also longer for removable prostheses. Mean repair costs were approximately 60% higher for the removable design.

Adult↗
PubMed1980

A flexible moulage for the fabrication of an orbital prosthesis.

A technique is disucssed by which a flexible three-piece moulage may be fabricated. This procedure is a useful aid in the modeling of an orbital prosthesis. It permits the continued transfer of a wax pattern from the moulage to the patient utilizing the tissue undercuts for the retention and stabilization of the pattern. The critical task of properly positioning the ocular prosthesis is simplified by the increased stability of the entire pattern. This is of the utmost importance since even a slight error in the alignment of the eye can entirely negate the effect of an otherwise accurate prosthesis. In addition, the retention of the wax pattern simplifies the carving procedure, and accurate detail is easily secured. The acrylic resin surface on which the final silicone prosthesis is cured has proven to be accurate. Well-adapted, thin margins of the facial prosthesis have been consistently obtained.

Acrylic Resins↗
PubMed1978

Obturator prosthesis design for acquired maxillary defects.

Fabrication of obturator prostheses does not require a special ability to fabricate a prosthesis extension into a defect or an arbitrary extension of a prosthesis into a defect. Fabrication of an obturator prosthesis depends on the application of basic prosthodontic principles that are used in the treatment of patients without maxillary defects. Some principles must be modified because of the defect and the character and position of the remaining structures. The defect, in conjunction with the remaining structures, must be used to provide support, retention, and stability of an obturator prosthesis. If basic prosthodontic principles are applied the size and extension of the obturator will be determined, and the extensive variation so commonly seen in obturators will be minimized. Acceptable prosthodontic care for the patient with the acquired maxillary defect should include cautious prosthesis design combined with routine maintenance care to provide comfort, function, cosmetics, and minimal change to the compromised remaining structures.

Alveolar Process↗
PubMed2001

Practical application of polyurethane and Velcro in maxillofacial prosthetics.

A procedure is described for the fabrication of an extraoral prosthesis with an acrylic resin substructure that retains a magnet sealed from the environment by a polyurethane liner. Velcro is used to enhance the bond of the acrylic substructure to the silicone prosthesis. This procedure results in improved retention of the acrylic resin substructure and protection of the magnet with an encapsulating polyurethane liner.

Acrylic Resins↗
PubMed1999

Fabrication and use of a surgical template for placing implants to retain an auricular prosthesis.

A procedure is described for the fabrication of a 3-dimensional surgical template to guide the placement of implants to retain an auricular prosthesis. This procedure requires a diagnostic wax pattern that is checked while on the patient to ensure it is positioned correctly and is also the correct size. The wax pattern is processed into a clear, methyl methacrylate resin, 3-dimensional surgical template. The most effective type of surgical template for planning implant placement is a 3-dimensional acrylic template that closely resembles the final prosthesis. This template will direct the implant placement where the retentive elements are most easily concealed, under the thickest areas of the prosthesis, which are the antihelix and antitragus. This location allows the best esthetic and functional results. An additional advantage of this technique is that it allows the retrieval of the diagnostic wax pattern of the auricle so that it can be used to fabricate the definitive prosthesis.

Ear, External↗
PubMed1994

Comminution of food with mandibular implant-retained overdentures.

When complete-denture wearers are treated with from four to six implants and mandibular implant-borne prostheses, masticatory performance improves. No significant improvement has been observed with two implants and implant-mucosa-borne overdentures, suggesting that the masticatory performance of edentulous subjects depends on the degree of support for their mandibular prostheses by implants or alveolar mucosa. To verify this hypothesis, we studied, in a randomized clinical trial, the comminution of an artificial test food during mastication. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture, a mandibular overdenture retained by two permucosal cylindric implants through a single bar-clip attachment, or a mandibular overdenture retained by a transmandibular implant through five clips on a triple-bar construction with cantilever extensions. In comparison with the subjects wearing mandibular implant-retained overdentures, the subjects with conventional complete dentures needed between 1.5 and 3.6 times more chewing strokes to achieve an equivalent reduction in particle size. No differences in masticatory performance and efficiency were found between the subjects who had received two permucosal cylindric implants and those who had received a transmandibular implant. The results suggest that the increased retention and stability of the mandibular denture, rather than the degree of support by implants or alveolar mucosa, determine the wearer's ability to comminute food during mastication.

Adult↗
PubMed2005

Retention versus sacrifice of the posterior cruciate ligament in total knee replacement for treatment of osteoarthritis and rheumatoid arthritis.

BACKGROUND: The functional and clinical results to support the choice whether or not to retain the posterior cruciate ligament (PCL) during total knee arthroplasty have not been gathered and analysed so far. There are at least some trials showing no difference. OBJECTIVES: To identify the difference in functional, clinical, and radiological outcome between retention and sacrifice of the PCL in total knee arthroplasty in patients with osteoarthrosis and other non-traumatic diseases. SEARCH STRATEGY: A search was conducted in MEDLINE(Through PubMed; 1966 - March 2004), EMBASE (1980 - March 2004), Cochrane Central Register of Controlled Trials (CENTRAL Issue 2004 - 1), and Current Contents (1996 - March 2004). Also, references of selected articles were checked and citation tracking on the articles selected was performed. SELECTION CRITERIA: Randomised controlled trials comparing retention to sacrifice of the PCL during total knee arthroplasty with regard to functional, radiological and clinical outcome in patients with osteoarthritis and other non-traumatic diseases were selected by two independent reviewers. DATA COLLECTION AND ANALYSIS: Methodological quality was assessed with the checklist by van Tulder and the Jadad list. Data was collected with a predeveloped form. Meta-analysis was performed with subgroup analyses on age, gender, disease severity, and follow-up time, if allowed by adequate power. MAIN RESULTS: Eight randomised controlled trials were found. Two treatment options were compared against PCL retention: PCL sacrifice without additional stabilisation (post and cam mechanism) (2 studies), and PCL sacrifice with posterior stabilized design (5 studies). One study included all three options. Range of motion was found to be 8.1 degrees higher in the posterior stabilized group compared to the PCL retention group (p=0.01, 95% confidence interval [1.7, 14.5]), although the heterogeneity was high (I(2 )= 66.3%). PCL resection without substituting the PCL with a posterior stabilised prosthesis showed no difference compared to PCL retention (p=0.31, I(2) = 83.2%). On clinical scores, only Hospital for Special Surgery score revealed a significant difference of 1.6 points (p=0.03, 95% confidence interval [-3.1, -0.1]) between PCL retention versus PCL sacrifice and substitution combined favouring the latter group. The necessary subgroup analyses could not be performed for the clinical scores. AUTHORS' CONCLUSIONS: These results should be interpreted with caution as the methodological quality of the studies was highly variable. We conclude that there is, so far, no solid base for the decision to either retain or sacrifice the PCL with or without use of a posterior stabilized design during total knee arthroplasty. The technique of PCL retention is difficult because the normal configuration and tension need to be reproduced with ligament tensioners. Knowledge of the technique needs to be improved before it can yield superior results compared to the more straightforward techniques of PCL sacrifice or use of a posterior stabilized design. Also, studies evaluating the effect of both techniques should address the right outcome parameters such as range of motion, contact position, and anterior-posterior stability. Suggestions are given to improve future research on this specific topic of knee arthroplasty.

Arthritis, Rheumatoid↗
PubMed2004

In vitro effect of microwave irradiation on the retentive force of magnets.

STATEMENT OF PROBLEM: Few studies have addressed the possible effect(s) of microwave irradiation on the magnetic properties of "permanent" magnets during the fabrication of dental and maxillofacial prostheses. PURPOSE: The objective of this study was to investigate the influence of microwave irradiation energy on the retentive force of a magnetic attachment system used in maxillofacial prosthetic rehabilitation. MATERIAL AND METHODS: A heat-polymerized PMMA disk (6 cm in diameter) was fabricated. Seven magnets were placed around the wafer in a circumferential fashion: 1 in the center and 6 surrounding it. The 7 magnets were spaced 2 cm from their respective centers. Seven heat-polymerized PMMA cylinders were also used, and a magnet (counter-magnet) was placed in the center of each even with the cylinder's surface. Once the investment had set (45 minutes after mixing), the 7 counter-magnets in the cylinders were placed against the 7 magnets in the acrylic wafer. A second mixture of investment material was added. The flasks were separated, and the acrylic wafer was removed to accommodate the 7 counter-magnets in the base mold in the same geometric configuration and to serve as a "spacer" for the silicone material. A 1:1 mixture of medical grade elastomer (MDX4-4210) and medical adhesive silicone (type A) was packed and compressed, the molds were reclamped, and the excess silicone was removed. The elastomer/silicone wafer was packed and compressed into the test and base molds, the molds were reclamped, and excess silicone was removed. The first group of magnets, designated Group A, received microwave irradiation for 5 minutes at low power (112 W). This procedure was repeated for each group of magnets at the following polymerizing times (n=14): Group B, 10 minutes; Group C, 15 minutes; Group D, 20 minutes; Group E, 25 minutes; Group F, 30 minutes; and Group G, 35 minutes. Measurements of retentive force (N) at 10 mm/min ramp rate of speed of separation was conducted. The specimen rate read 5.0 points/second. Data were analyzed using a 1-way analysis of variance (alpha=.05); individual mean values were compared using the Tukey test (alpha=.05). RESULTS: There were no statistical differences in retentive force between groups D, E, and F (20, 25, and 30 minutes, respectively) or between groups A, B, C, D, F, and G (5, 10, 15, 20, 30, and 35 minutes, respectively). When the microwave-irradiated groups A through G were compared with the control group, there was a significant difference (P<.05) in retentive force (N). Group E (25 minutes) showed the largest reduction of retentive force (0.3 N, a reduction of 12%). CONCLUSION: If a prosthesis is processed using a microwave and contains samarium cobalt magnets, the retentive force may be reduced up to 12% under specific conditions.

Cobalt↗
PubMed2001

Effect of adhesive retention of maxillofacial prostheses. Part 2: Time and reapplication effects.

STATEMENT OF PROBLEM: The success of most non-implant-retained extraoral prostheses depends on retention derived from skin adhesives. Part 1 of this study found that Skin-Prep Protective Dressing improved the retentive properties of adhesives and that Secure(2) Medical Adhesive was stronger than Epithane-3. Part 2 investigates the application of a second layer of adhesive to the prosthesis, which was earlier noted to improve retention at later time periods. PURPOSE: This study measured the force needed to remove silicone elastomer strips with Secure(2) Medical Adhesive from the skin of human subjects. Testing was performed before and after the removal of the strips and reapplication of the adhesive. MATERIAL AND METHODS: Secure(2) Medical Adhesive was painted on silicone rubber strips and placed in a nonsequential random order of the 3 variables to 3 sites on the ventral forearms of 21 human subjects and tested over an 8-hour period. The bond strength was measured at 0, 4, and 8 hours. After a reapplication of adhesive over the existing adhesive, additional bond strength measurements were made at 4 and 8 hours. Testing was at 10 cm/min in an Instron. All subjects had Skin-Prep coating applied before adhesive application. RESULTS: Bond strengths for both single applications and reapplications of the adhesive were greater at 0 hours and became significantly weaker after the 4- and 8-hour periods. The second application of the adhesive produced the strongest bonds when measured at 4 hours (110 N/m). Bonding was significantly higher at 8 hours if a second application of adhesive was applied at 0 or 4 hours. CONCLUSION: The results of this study indicate that the bond strength of silicone elastomer to skin decreased over an 8-hour interval. After removal of the silicone rubber strip and reapplication of Secure(2) Medical Adhesive over the existing adhesive, bond strengths increased.

Adhesiveness↗
PubMed1994

Prosthetic restoration of a nasal defect--a case report.

Restoration of facial defect makes very special demands on the maxillofacial prosthodontist. The key to successful rehabilitation includes good cosmetic result, proper selection of materials and excellent retention qualities. This case report presents a face disfigured by cancer which is restored with a silicone nasal prosthesis. Steps of the clinical and technical procedures of how a light-weight hollow prosthesis is fabricated are described. This special feature enhances retention and by incorporating a polyurethane lining, both aesthetics and retention are further improved, rehabilitating the patient and improving the quality of life. The basic requirements necessary for a successful facial prosthesis are also discussed.

Aged↗
PubMed1993

Adapting a dental surveyor to function in two planes.

Many bilateral distal extension removable partial dentures possess insufficient guidance to control their dislodgement. When such a situation is observed, the tips of retentive clasps must be located in both an occlusogingival and mesiodistal (away from the denture base area) undercut. The specific location can be identified with a dental surveyor that has been adapted to function in two planes. Details of the adaptation process and use of the surveyor are described.

Dental Clasps↗
PubMed1999

Laparoscopic repair of large hiatal hernia with polytetrafluoroethylene.

BACKGROUND: Several studies have shown that large hiatal hernias are associated with a high recurrence rate. Despite the problem of recurrence, the technique of hiatal herniorrhaphy has not changed appreciably since its inception. In this 3-year study we have evaluated laparoscopic hiatal hernia repair in individuals with a hernia defect greater than 8 cm in diameter. METHODS: A series of 35 patients with sliding or paraesophageal hiatal hernias was prospectively randomized to hiatal hernia repair with (n = 17) or without (n = 18) polytetrafluoroethylene (PTFE). All patients had an endoscopic and radiographic diagnosis of large hiatal hernia. Both repairs were performed by using interrupted stitches to approximate the crurae. In the group randomized to repair with prosthesis, PTFE mesh with a 3-cm "keyhole" was positioned around the gastroesophageal junction with the esophagus through the keyhole. The PTFE was stapled to the diaphragm and crura with a hernia stapler. RESULTS: Patients were followed with EGD and esophagogram at 3 months postoperatively, and with esophagogram every 6 months thereafter. Individuals with PTFE had a longer operation time, but the 2-day hospital stay was the same in both groups. The cost of the repair was $1050 +/- $135 more in the group with the prosthesis. There were two complications (1 pneumonia, 1 urinary retention) in the group repaired with PTFE and one complication (pneumothorax) in the group without prosthesis. The group without PTFE was notable for three (16.7%) recurrences within the first 6 months of surgery. CONCLUSION: On the basis of these preliminary results it appears that repair with PTFE may confer an advantage, with lower rates of recurrence in patients with large hiatal hernia defects.

Adult↗
PubMed2001

Analysis of stiffness and stress in I-bar clasps.

An I-bar clasp is one of the most popular direct retainers for distal-extension removable partial dentures. However, no adequate information is available on the shape associated with biomechanics. This study aimed (1) to establish a three-dimensional (3D) finite-element modelling method of I-bar clasps, and (2) to clarify the effect of the shape on the stress and stiffness of I-bar clasps. 3D computer models of I-bar clasps were created with vertical and horizontal straight sections connected with a curved section with six parameters: thickness of the clasp tip (T), width of the clasp tip (W), radius of the curvature (R), horizontal distance between the base and the vertical axis (H), vertical dimension between the tip and the horizontal axis (V), taper (change of width per unit length along the axis)(Tp). Stress decreased as T, W, R and Tp increased, and as V decreased. Stiffness (which is proportional to retention) increased as T, W, R and Tp increased, and as H and V decreased. In both stress and stiffness, the effects of T and Tp were especially large. From the results, a systematic formula between the clasp shape and the stiffness was derived.

Computer Simulation↗
PubMed2000

Design principles for cantilevered resin-bonded fixed partial dentures.

Recent clinical studies show 2-unit cantilevered resin-bonded fixed partial dentures to be as retentive or more retentive than their fixed-fixed counterparts. The fact that the 2-unit prosthesis is successful adds value to the clinical use of resin-bonded fixed partial dentures because the single-abutment prosthesis is even simpler and more cost effective than fixed-fixed designs. However, there is no evidence-based information relating to design principles for abutment preparation and framework design for the single-abutment, single-retainer prosthesis. The aim of this report is to suggest principles of design for the 2-unit cantilevered fixed partial denture, based on information gained from studies on fixed-fixed designs.

Cost-Benefit Analysis↗