Biomedical subjects

Saul Weiner

Publications and source records attributed to Saul Weiner.

7 recordsLinked to original sources

PubMed2006

Long-term effects of storage and thermal cycling on the marginal adaptation of provisional resin crowns: a pilot study.

STATEMENT OF PROBLEM: Provisional resin crowns may be used for an extended period while complex treatments are completed. The crowns function intraorally; therefore, moisture absorption and thermal cycling may affect the physical properties of acrylic resin, causing a change in marginal gap size. PURPOSE: The purpose of this pilot study was to examine the effect of long-term water absorption and thermal cycling on marginal gap size of polymethyl methacrylate copolymer and bis-acrylic composite resin crowns. MATERIAL AND METHODS: Specimens (n = 10) were fabricated from 2 acrylic resins: a polymethyl methacrylate (Alike) and a bis-acrylic composite resin (Provitec). Specimens were first fabricated on a metal master die. Custom die stems were fabricated for each specimen from a low-fusing alloy (Cerroblend) to eliminate the factor of polymerization shrinkage. Specimens were then fitted to assure a standardized, pre-experimental marginal gap range of < or = 25 microm. Specimens were stored in a humidor at 37 degrees C and 97% relative humidity for 1 year and subsequently thermal cycled (5 degrees C to 60 degrees C, 6-second dwell time, for 8000 cycles). Measurements in micrometers of the marginal gap were recorded using a microscope equipped with a digital video camera and image analysis software before and after treatment. A 2-way analysis of variance with a split design was performed for factors of materials and treatment (alpha = .05). RESULTS: For the factor of material, there was no significant difference; however, there was a significant difference between treatments, with a significantly greater increase in marginal gap size after thermal cycling (P < .002). CONCLUSION: Provisional crowns made from either a bis-acrylic resin composite or a polymethyl methacrylate copolymer demonstrated loss of marginal adaptation during a simulated long-term period of service.

Acrylic Resins↗

PubMed2006

An in vitro analysis of implant screw torque loss with external hex and internal connection implant systems.

PURPOSE: The purpose of this study was to examine, in a controlled environment, effects of connection design upon screw stability. Implant fixtures have 2 types of connections to the abutment: internal connection and external hex. Four implant systems were tested: Bio-Lok (external hex; Bio-Lok International, Inc., Deerfield Beach, FL); Zimmer (internal connection; Zimmer Dental, Carlsbad, CA); Nobel Biocare (external hex; Nobel Biocare USA, Inc., Yorba Linda, CA); and Astra Tech (internal connection; Astra Tech Inc., Waltham, MA). MATERIALS AND METHODS: Ten samples of each system, including base, implant, abutment, and molar crown, were loaded to 200 N for 1 x 10(6) cycles. Screws were tightened to manufacturers' recommendations,and torque audits done at 2.5 x 10(5), 5 x 10(5), 7.5 x 10(5), and 1 x 10(6) cycles. RESULTS: The Bio-Lok samples lost an average of 10% of the original torque values, the Astra Tech group lost almost all of the torque and loosened, while the Zimmer and Nobel Biocare samples lost an average of 50% of the torque but did not loosen (P <or= 0.05). CONCLUSIONS: It may be concluded from this study that although internal connections are clinically favored, this study did not show any advantage relative to screw loosening. However, screw design may be a significant factor in loosening of the joint.

Crowns↗

PubMed2005

Analysis of changes in implant screws subject to occlusal loading: a preliminary analysis.

Loosening of the abutment screw can present a problem for the stability of the implant-supported crown or prosthesis. The purpose of this study was to understand the parameters of screw loosening, using an in vitro model, including loss of torque, screw head rotation, changes in screw dimension, and distortion of the implant-abutment joint. Implants (4 x 10 mm) were potted in autopolymerizing blocks. Abutments were placed with screws tightened with a 35-Ncm torque and standardized crowns fabricated. There were 3 implant systems used: Nobel Biocare USA, Inc. (Yorba Linda, CA), 3i Implant Innovations, Inc. (Palm Beach Gardens, FL), and Bio-Lok International, Inc. (Deerfield Beach, FL). Seven samples were tested for each system. Samples were loaded with 300-N loads for 50,000 cycles at 1 Hz. Torque turn audits were performed at 10,000, 25,000, and 50,000 cycles. At the conclusion of the loading, counterclockwise rotation of the abutment screw was measured. The screws were retrieved and measurements made compared with the controls. Finally, 1 sample from each group was embedded in resin, sectioned longitudinally, and examined under the standard error of the mean. The Nobel Biocare system showed a 9.4-Ncm loss of torque from the loading protocol. This result was accompanied by a counterclockwise rotation of 7 degrees and a 200-ìm elongation of the screw. Finally, there was compression and distortion of the longitudinally sectioned joint architecture observed with the standard error of the mean. From the 3i and Bio-Lok International groups, no loss of torque, counterclockwise rotation, or lengthening of the screws was observed. Intimate adaptation of the joint without distortion was seen in the longitudinal sections. Screw loosening appears to follow specific parameters that include counterclockwise rotation, lengthening of the screw, and distortion of the screw joint. This process is likely associated with both the physical properties of the screw as well as its configuration.

Bone Screws↗

PubMed2004

Resistance to crown displacement on a hexagonal implant abutment.

The purpose of this study was to evaluate the resistance and retention of a hexagonal abutment to crown displacement with varying crown heights (10, 12, and 14 mm) and axis of load. Implants were embedded in resin blocks at a 30 degree angle to the vertical. Crowns were made at heights of 10, 12, and 14 mm. Groups of 5 crowns for each of the 3 crown heights were loaded (200 N) both under the long axis and off axis. The marginal gaps were measured using standardized periapical radiographs before and after loading. The gaps were statistically compared using a 3-way analysis of variance with factors of load, crown height, and point of load. Crowns were loaded to 10 cycles or point of failure. The 10-mm crowns did not show any displacement. The 12-mm and 14-mm groups only showed displacement of the off axis-loaded crowns. The average marginal displacement was 193.56 micro (standard deviation [SD] +/- 138.62 micro) at point of failure (320,717 cycles) and 400.18 micro (SD +/- 644.31) at point of failure (134,278 cycles), respectively. A 1-piece implant with a standardized abutment design can provide sufficient resistance and retention form for crowns of varying dimension if loads are centered over the long axis of the crown.

Crowns↗

PubMedDate not supplied

The effect of gingival retraction procedures on periodontal indices and crevicular fluid cytokine levels: a pilot study.

PURPOSE: The purpose of this study was to examine the effects of placement of retraction cord subgingivally upon periodontal indices including plaque index (PI), gingival index (GI), pocket depth (PD), bleeding on probing (BOP), and attachment level (AL), as well as gingival crevicular fluid (GCF) and TNF-alpha levels. METHODS: Ten teeth in 6 patients who were periodontally healthy were selected. These teeth had pocket depths of 3 mm or less, no evidence of significant loss of attachment, BOP, or plaque accumulation. The patients each received an oral prophylaxis. The following week, baseline measurements of periodontal indices and TNF-alpha were taken and the retraction cord was placed for 15 minutes. Following removal, the patients were dismissed. The periodontal indices measured included PI, GI, PD, BOP, and AL. In addition, the levels of TNF-alpha in GCF, were investigated. These measurements were made before gingival retraction as a baseline and on the 1st, 3rd, 7th, 14th, and 28th days post retraction. RESULTS: A repeated measures ANOVA showed that TNF-alpha levels in GCF were significantly increased at all five intervals after gingival retraction compared to the baseline. The mean TNF-alpha level peaked at Day 1 (0.90 +/- 0.62), then declined at Days 3 (0.53 +/- 0.16), 7 (0.43 +/- 0.08), 14 (0.47 +/- 0.10), and 28 (0.43 +/- 0.08) but was still elevated 54% above baseline at Day 28, p < 0.01. The GI was significantly elevated at Day 1 (0.9 +/- 0.49), p < 0.01; Day 3 (0.53 +/- 0.32); and Day 7 (0.33 +/- 0.33), p < 0.05. Unlike TNF-alpha, GI recovered to the baseline by day 14. Other periodontal parameters, PI, PD, BOP, and AL were not significantly altered by the gingival retraction procedure. CONCLUSION: This pilot study supports the previous research that gingival retraction causes an acute injury that heals clinically in 2 weeks as is indicated by the GI. It also provides the first evidence that gingival retraction results in an elevation of the proinflammatory cytokine, TNF-alpha, in GCF.

Adult↗

PubMedDate not supplied

Sensory responses from loading of implants: a pilot study.

PURPOSE: Osseointegrated implants lack a periodontal ligament. Nevertheless, masticatory function in subjects with implant-supported restorations appears similar to function in those with natural dentition. It is not clear how the neurophysiologic mechanisms that modulate jaw movement are associated with osseointegrated implants. This study examined the output from the inferior alveolar nerve during implant loading. MATERIALS AND METHODS: In 3 dogs, 3 premolars were extracted in the mandible and 2 endosseous titanium implants were placed, allowed to osseointegrate for 3 months, and loaded with vibration force at the threshold response for tooth vibration, at 2x threshold, and at 3x threshold. Neurophysiologic recordings were made from the inferior alveolar nerve during loading of both implants and the adjacent molar and canine. The response magnitude in action potentials in the 50- ms poststimulus period and latency of inferior alveolar afferents in milliseconds were compared following implant loading. RESULTS: Detectable inferior alveolar nerve responses were recorded following loading from both the implants and the teeth at 2x and 3x threshold. However, the response magnitude of teeth (canine, 2.38 +/- 0.18 at 2x, 2.78 +/- 0.2 at 3x; molar, 2.2 +/- 0.16 at 2x, 2.5 +/- 0.21 at 3x) was twice that of the implants (anterior, 1.3 +/- 0.12 at 2x, 1.68 +/- 0.13 at 3x; posterior, 0.8 +/- 0.1 at 2x, 1.53 +/- 0.15 at 3x). The differences in response magnitude between the teeth and implants were significant (P < .05). The latency of response was similar. DISCUSSION: Management of the occlusion for implant-supported restorations has been empirically developed. An underlying assumption has been that implant-guided jaw function lacks significant proprioception to modulate mastication and related jaw movements. This animal study provides preliminary evidence that force application to implants does elicit a proprioceptive response. CONCLUSION: Loading of implants does elicit a sensory response that can be observed in the inferior alveolar nerve. The implications are that during occlusal function, information from regions associated with the implant can provide knowledge that could potentially modulate jaw activity in a manner similar to natural teeth.

Action Potentials↗

PubMedDate not supplied

Marginal integrity of direct and indirect castings for implant abutments.

PURPOSE: Current implant systems with screw-retained abutments permit direct laboratory fabrication of castings. Computer aided drafting systems further enhance the fabrication of computer-milled abutments (CMAs) and castings. The purpose of this study was to compare marginal accuracy, as measured by gap size, of castings made directly on CMAs with those made indirectly on epoxy and stone dies. MATERIALS AND METHODS: Castings were made directly for 10 CMAs. Marginal gap measurements were made with the castings seated on the abutments (group A). Castings were also made indirectly on stone and epoxy dies obtained from impressions of the abutments. Marginal gap measurements were made with these indirectly made castings seated on their CMAs (groups B and E). In addition, the directly made castings were transferred between CMAs and marginal gap measurements made (group D). Marginal gap measurements of the groups were compared with analysis of variance (ANOVA) and pair-wise comparisons (Scheffé test). RESULTS: Groups A and D had marginal gaps of less than 100 microm. These marginal gaps were significantly smaller (P < .05) than the gaps of groups B and E, made on dies, which were approximately 200 to 500 microm. DISCUSSION AND CONCLUSIONS: With CMAs, it is possible to make an exact duplicate of the abutment. This permits the laboratory to make castings on duplicate abutments with greater precision than can be obtained using the indirect technique. Direct fabrication of castings resulted in smaller marginal gaps, which in turn allows a better marginal seal and improved retention of castings.

Dental Abutments↗