Pin Opening Research Articles

Does the available interocclusal space influence the accuracy of the maxillomandibular relationship captured with an intraoral scanner?

Statement of problemThe accuracy of a maxillomandibular relationship acquired by intraoral scanners (IOSs) has been previously analyzed; however, the impact of the interocclusal space on the accuracy of the maxillomandibular relationship remains unknown. PurposeThe purpose of this in vitro investigation was to evaluate the influence of the interocclusal space (0, 1, 2, 3, or 4 degrees of incisal opening in the articulator) on the accuracy of the maxillomandibular relationship captured with an IOS. Material and methodsMarkers were attached to the first molars and canines of maxillary and mandibular diagnostic casts, which were mounted on a semi-adjustable articulator, and digital scans were acquired (TRIOS 4). Both digital scans were duplicated 100 times and distributed into 5 groups depending on the incisal pin opening in the articulator (n=20): 0 (Group 0), 1 (Group 1), 2 (Group 2), 3 (Group 3), and 4 degrees (Group 4). In Group 0 (control), the casts were maintained in maximum intercuspation (MIP) with the incisal pin of the articulator set at 0 degrees. Then, a bilateral virtual occlusal record was acquired and automatically processed by using the IOS software program. A laboratory scanner (Medit T500) was used to digitize the mounted casts. The same procedures were completed in Groups 1, 2, 3, and 4 but with the incisal pin set at 1, 2, 3, and 4 degrees respectively. The interlandmark distances were used to calculate the discrepancies between the control and groups tested. One-way analysis of variance (ANOVA) and pairwise comparison Tukey HSD tests were used to inspect the data (α=.05). ResultsThe interocclusal space available when capturing the occlusal records affected the trueness of the maxillomandibular virtual relationship measured (P<.001). Group 0 (135 μm) obtained the highest distortion, while Group 3 (73 μm) and Group 4 (71 μm) showed the lowest distortion. Additionally, the interocclusal space available (P<.001) impacted the precision of the maxillomandibular virtual relationship measured. Group 0 (111 μm) obtained the highest distortion, while Group 4 (precision mean value of 59 μm) had the lowest distortion among the groups tested. ConclusionsThe interocclusal space available when acquiring virtual bilateral occlusal records using the IOS tested impacted the accuracy of the maxillomandibular relationship. The smallest available interocclusal space tested (maximum intercuspation) showed the worst trueness and precision mean values, while the group with the largest interocclusal space available had the highest trueness and precision mean values among the groups studied.

Complementary-FET (CFET) Standard Cell Synthesis Framework for Design and System Technology Co-Optimization Using SMT

With the relentless scaling of technology nodes, design technology co-optimization (DTCO) for the conventional (Conv.) cell structure is starting to reach its limitations due to limited routing resources, lateral p-n separations, and performance requirements. As a result, system technology co-optimization (STCO) has been proposed to exploit the benefits of 3-D architectures. Complementary-FET (CFET) technology, which stacks p-FET on n-FET or vice versa, can release the restriction of p-n separation and reduce in-cell routing congestion by enabling p-n direct connections. However, CFET standard cell (SDC) synthesis demands holistic considerations to maximize the area benefit of scaling at the block level due to the extremely limited routability that comes from the stacked structure and reduced cell height. In this article, we propose a satisfiability modulo theory (SMT)-based CFET SDC synthesis framework that simultaneously solves place-and-route to generate optimized layouts. We first demonstrate that the CFET structure achieves 10.94% and 21.27% reduction on average cell area and metal length, respectively, and 15.10% smaller block-level area compared to Conv. structure as scaling down to 3.5T architecture. For routability, the proposed constraint-based minimum pin length/minimum pin opening and objective-based edge-based pin-separation/M2 track use reduce up to 48% #DRVs at the block level compared to the previous work. Then, through extensive DTCO explorations on ground design rules and #BEOLs, 3.5T CFET SDCs achieve up to 6.50% smaller block-level areas than 4.5T CFET SDCs. Finally, with the assistance of STCO and DTCO, 3.5T CFET SDCs achieve 21.0% on average reduced block-level areas compared to 4.5T Conv. SDCs.

Attempts to Minimizing Incisal Pin Opening During Processing of Complete Dentures

Background and objectives: Dimensional changes associated with the processing of complete dentures is one of most important problems of acrylic resin denture base materials, these changes lead to series of problems clinically. The aim of this study was to try new attempts to minimizing the post processing dimensional changes. Methods: Forty-two identical maxillary waxed dentures prepared, each of them mounted on an articulator. The initial dimension was measured between the upper and lower members of the articulator before processing, after processing and remounting of the dentures the measurements recorded after deflasking and decasting, comparing these measurements with the initial measurement determined the incisal pin opening (IPO). Two new attempts for decreasing IPO have been tested by modifying the conventional waxed dentures, in the first attempt five wax sprues added to the flanges while in the second attempt four wax sprues added to the palatal surfaces of the waxed dentures. The waxed dentures processed in two types of heat curing acrylic resins. Results: The results showed that both new attempts caused decreasing in the dimensional changes and IPO at both times after deflasking and decasting.Conclusion: It had been concluded that the addition of four waxed sprues will significantly decrease the IPO.

Changes in Lower Facial Height and Facial Esthetics with Incremental Increases in Occlusal Vertical Dimension in Dentate Subjects.

To determine if there are objective changes in lower facial height and subjective changes in facial esthetics with incremental increases in occlusal vertical dimension in dentate subjects. Twenty subjects of four different races and both sexes with a Class I dental occlusion had custom diagnostic occlusal prostheses (mandibular overlays) fabricated on casts mounted on a semi-adjustable articulator. The overlays were fabricated at 2-mm, 3-mm, 4-mm, and 5-mm openings of the anterior guide pin of a semi-adjustable articulator. Direct facial measurements were made between pronasale and menton on each subject while wearing the four different overlays. Thereafter, two digital photographs (frontal and profile) were taken for each subject at maximum intercuspation (baseline) and wearing each of the four mandibular overlays. The photographs of eight subjects were standardized and displayed in a random order to 60 judges comprising 30 laypeople, 15 general dentists, and 15 prosthodontists. Using a visual analog scale, each judge was asked to rate the facial esthetics twice for each of the 80 images. For objective changes, although an anterior guide pin-lower facial height relationship of 1:0.63 mm was observed, the findings were not correlated (P>.20). For subjective changes, the visual analog scale ratings of judges were uncorrelated with increases in anterior guide pin opening up to 5 mm, irrespective of the judge's background status or the sexes of the judges or the subjects (P>.80). Incremental increases in anterior guide pin opening up to 5 mm did not correlate to similar increases in lower facial height. Additionally, it made no difference in a judge's evaluation of facial esthetics irrespective of the judge's background status (layperson, general dentist, or prosthodontist) or sex.

Influence of the Fast-processing Technique on the Number of the Occlusal Contacts and Occlusal Vertical Dimension of Complete Dentures

Occlusal errors during acryl processing affect the retention and stability of complete dentures. The aim of the present study was to assess the influence of a short curing technique on the number of occlusal contacts and the occlusal vertical dimension (OVD) of complete dentures. Complete dentures were prepared. The number of occlusal contacts was recorded in centric relation (CR) using 60 µ articulation paper. The OVD was recorded with the waxed trial denture in place. Dentures were then invested and processed with compression molding and short cure water bath technique. The number of occlusal contacts was recorded again. The amount of pin opening was measured for all of the complete dentures on the articulator. Data were analyzed with paired t-test to determine the alterations. The mean number of occlusal contacts before and after processing was 10.9 ± 2.4 and 6.3 ± 3.1 respectively (4.7 ± 1.9 decrease; p < 0.001). A 2 mm mean increase in OVD was observed in 47.7% of the dentures with < 6 occlusal contact changes and 88.9% of the dentures with ≥ 6 occlusal contact changes (p < 0.003). A significant change in the number of occlusal contacts was associated with an OVD increased up to two times. The short curing technique seems to be related to the decreased occlusal contacts and increased OVD. CLINICAL SIGNIFICANCES: More time is needed to adjust the occlusal errors of this method, because it has a negative effect on the morphologic pattern of artificial teeth of complete dentures and thus should be used carefully.

Experimental study of damage propagation in Over-height Compact Tension tests

This paper describes an experimental investigation into progressive damage development in notched fibre-reinforced composites laminates. The Over-height Compact Tension (OCT) test captures the behaviour of laminates typical of large structures and permits the stable formation of a process zone ahead of the crack tip. This allows a study of the influence of sub-critical damage on progression of fibre failure. A range of lay-ups have been tested using dispersed and blocked plies in the thickness direction. The load vs. pin opening displacement (POD) curve is used to characterise the progressive failure of specimens. A number of interrupted tests were performed for each lay-up to capture the sub-critical damage process before the onset of fibre fracture. Results show that dispersed plies promote fibre failure and crack growth whilst blocked plies promote a larger amount of splitting and delamination which in turn causes a larger process zone and ultimately a tougher laminate.

Comparison of accuracy between compression- and injection-molded complete dentures

Statement of problem. A clinically significant incisal pin opening may occur after processing complete dentures if a compression molding technique is used. To recover the proper vertical dimension of occlusion, a time-consuming occlusal adjustment is necessary that often destroys the anatomy of the artificial teeth. A new injection molding process claims to produce dentures that require few, if any, occlusal adjustments in the laboratory after processing. Purpose. This laboratory study compared incisal pin opening, dimensional accuracy, and laboratory working time for dentures fabricated by this new injection system with dentures constructed by the conventional compression molding technique. Material and methods. Two groups of 6 maxillary and 6 mandibular dentures were evaluated as follows: group 1 (control), Lucitone 199, compression molded with a long cure cycle; and group 2, Lucitone 199, injection molded with a long cure. Incisal pin opening was measured with a micrometer immediately after deflasking. A computerized coordinate measuring machine was used to measure dimensional accuracy of 3-dimensional variations in selected positions of artificial teeth in 4 stages of denture fabrication. Analysis of variance (ANOVA) and t tests were performed to compare the groups. Results. A significant difference was found in pin opening between groups ( t test). Horizontal dimensional changes evaluated with repeated measures ANOVA revealed no significant differences between groups. However, analysis of vertical dimensional changes disclosed significant differences between the groups. There was no appreciable difference in laboratory working time for flasking and molding denture bases between the injection and compression molding techniques when polymethyl methacrylate resin was used. Conclusion. The injection molding method produced a significantly smaller incisal pin opening over the standard compression molding technique. The injection molding technique, using polymethyl methacrylate, was a more accurate method for processing dentures. There were no appreciable differences in laboratory working time between the injection and compression molding techniques. (J Prosthet Dent 1999;82:291-300.)

Comparison of the dimensional stability of two waxes and two acrylic resin processing techniques in the production of complete dentures

Two base plate waxes and two denture processing techniques were independently compared for dimensional stability. Occlusion rims were constructed from extra hard and medium soft base plate waxes and teeth were set. Acrylic resin bases were processed by a trial packing technique, and a continuous injection system. Tooth movement was measured in the horizontal and vertical planes to assess wax and denture base dimensional changes at various steps in the process, and after 1, 3, and 8 weeks of denture base immersion in water at room temperature. Posterior palatal border adaptation, incisal pin opening and loss of centric occlusion contacts, were also measured. Results showed there were no significant differences between the two waxes as determined by tooth movement in the horizontal and vertical planes. In comparison to the trial packing technique, the continuous injection system showed significantly smaller changes for incisal pin opening and loss of centric occlusion, and better adaptation of the posterior palatal border to the cast. Measurement of tooth movement in the horizontal and vertical planes showed no significant differences between the two processing techniques for times prior to immersion in water, whereas after 8 weeks immersion the continuous injection technique showed smaller dimensional changes, relative to the original dimensions at the time of investing.

Comparison of changes in vertical dimension between compression and injection molded complete dentures

Complete dentures were made for 30 patients. Fifteen sets were processed by conventional compression molding and 15 sets were processed by using the SR-Ivocap injection system. Changes in vertical dimension between the waxed and processed dentures were measured at the incisal guide pin by using a dial indicator. The difference between the two methods was highly significant on the basis of t-statistics. Whereas the processing changes noted with the conventional pack-and-press method were similar to previous studies, the injection method produced little or no pin opening. The superiority of the injection method before decasting was indisputable, and the results suggest that the laboratory remount procedure may be unnecessary when this system is used.

A mathematical method for calculating the compensating anterior stop pin setting of a semiadjustable arcon articulator

The geometry of a semiadjustable arcon articulator and development of mathematical formulae to calculate the setting of the anterior stop pin that compensates for the thickness of the interocclusal centric relation record are discussed. Measurements of the facebow mounted maxillary cast and interocclusal centric relation record are used in these formulae. Testing on 30 diagnostic mountings indicated that the formulae can reliably predict the amount of anterior stop pin opening necessary to allow near parallelism of the maxillary and mandibular bows of the articulator when the interocclusal centric relation record is removed and the mounted casts are brought into occlusion. The vertical component of dental malocclusion is identified as a source of variability in the setting of the anterior stop pin and therefore in the geometry of the articulator; it is defined as a need for further study.

Minimizing incisal pin opening during complete denture processing

Minimizing incisal pin opening during complete denture processing

Evaluation of incisal guide calibrations

The incisal guide calibrations of three adjustable articulators were investigated and compared to determine the significance of the different incremental markings of each. A method to use vertical changes in the anterior incisal guide of these three articulators accurately to measure jaw and tooth separation was proposed. The relationship between pin opening and incisor opening was evaluated by direct measurement and calculation. Twenty sets of diagnostically mounted casts were examined to evaluate the accuracy of the radius that generates each curved pin in relation to incisor position. Considering the as-manufactured incisal guide markings, casts mounted in a Denar D5A or TMJ articulator will bear a closer relationship between pin opening and incisor separation than casts mounted in a Stuart gnathological computer. To approximate linear incisor separation per calibration mark for each instrument, a table of values was presented for casts mounted at various positions.

Geometric study of incisal guide pin opening

A newly made gold crown on a second molar may open the incisal guide pin of the articulator when placed on its die in the master cast. If the incisal pin opening is 1.5 mm, the amount of occlusal adjustment required on this second molar crown is less than 1.5 mm. The purpose of this geometric study was to determine the opening at the second molar and the incisal edges with a given opening at the incisal guide table.

Processing changes in complete dentures: Posterior tooth contacts and pin opening

Dentures were constructed for 50 patients. The centric relation contacts were marked and photographed before removing the finished trial dentures from the articulator and again on the same articulator and same stone mountings after processing. The amount of incisal pin opening was measured and recorded after processing. An attempt was made to analyze the patterns of centric relation contacts after processing and to determine if there was a correlation of pin opening and tooth contacts. It was found that there was a definite shift of the tooth contacts to the more posterior teeth after processing but that the amount of pin opening did not seem to be related to the number or location of the tooth contacts. The magnitude of pin opening seems to depend upon the amount of shift rather than the direction.