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At least 1,765 records · Page 98Linked to original sources
PubMed2002

Critical assessment of a device to measure incisor crown inclination.

The aims of this study were to critically assess the use of a disposable device--the tooth inclination protractor (TIP)--to record incisor crown inclination and to compare its reliability and validity with that of traditional cephalometric radiographic analysis. The sample comprised 30 dental students with lateral cephalometric radiographs and dental casts. Four examiners were trained and calibrated to digitize radiographs and to use intraoral (on patients and dental casts) and extraoral (on dental casts) TIPs. The following angles were measured on the radiographs: maxillary incisor to maxillary plane, mandibular incisor to mandibular plane, maxillary incisor to occlusal plane, and mandibular incisor to occlusal plane. Measurements were also made with the TIP: maxillary incisor to occlusal plane and mandibular incisor to occlusal plane. All techniques were reliable between examiners. There were statistically significant systematic differences between the TIP and the radiographic assessments. The following differences were found. The TIP tended to record maxillary incisor crown inclination an average of 14 degrees less than maxillary incisor to maxillary plane. The TIP tended to record mandibular incisor crown inclination as similar to mandibular incisor to mandibular plane. The TIP recorded mandibular crown inclination 19 degrees less than mandibular incisor to occlusal plane. The disposable TIP was shown to be a simple, inexpensive, reliable, and valid method of assessing incisor inclination.

Cephalometry↗
PubMed2000

Prefabricated acrylic resin bars for splinting implant transfer copings.

Splinting of implant transfer copings with acrylic resin during impression procedures is performed to accurately transfer the spatial relationships of implants to the master cast. However, distortion may occur during the splinting procedure because of resin polymerization shrinkage. This article describes a simple technique for minimizing this effect by fabrication of resin bars.

Acrylic Resins↗
PubMed2000

Diagnostic management of interdental spacing.

It is a challenge to restore function and esthetics for patients with excessive interdental spacing. This article describes an alternative diagnostic procedure to permit clear communication of the intended outcome among the restorative dentist, orthodontist, and patient. This procedure uses fabrication of multiple duplicated casts, sectioned stone teeth, repositioned stone teeth, full-contour diagnostic wax-ups, and occlusal putty impressions. This procedure can be used as proposed or for various situations in which complex restorative treatment is needed.

Communication↗
PubMed2002

Verification jig for implant-supported prostheses: A comparison of standard impressions with verification jigs made of different materials.

STATEMENT OF PROBLEM: Implant verification jigs are routinely used during the fabrication of implant-supported prostheses. The dimensional accuracy of these jigs is unknown. PURPOSE: The purposes of this study were to (1) compare the dimensional accuracy of verification jigs with that of conventional impression procedures and (2) measure the dimensional accuracy of 3 resin materials used to fabricate verification jigs. MATERIALS AND METHODS: Thirty verification jigs and 20 impressions were made of 3 externally hexed Steri-Oss implants in a master stone base according to the following groups (n = 10 per group): (Group 1) Jig: GC pattern resin; (Group 2) Jig: Duralay resin; (Group 3) Jig: Triad gel resin; (Group 4) Impression: closed-tray impression copings; and (Group 5) Impression: open-tray impression copings. A stone base was fabricated for each experimental jig and impression. Master stone base and experimental stone bases were measured with the following methods: X and Y coordinates of each implant center were obtained with a traveling microscope by averaging the X and Y coordinates of the implant external hex corners. The origins of the coordinates during measurement of each base were arbitrary. Distances between implant center points were calculated by use of the Pythagorean theorem. Vertical measurements (Z-plane) were obtained with a digital caliper at the 2 terminal-implant locations. Interimplant distances and vertical measurements were subtracted from those of the master base, and the resultant distortion values were analyzed with analysis of variance and Tukey Studentized range tests. Statistical significance was set at P<.05. RESULTS: Verification jigs were not significantly more accurate than standard impression procedures. Open-tray impressions showed a significantly greater vertical distortion (Z-R location: 262 +/- 158 microm; P=.0001; Z-L location 333 +/- 189; P=.0001) compared with the other groups. Triad gel jigs showed a significantly greater distortion in one interimplant distance (C-L) than closed-tray impressions (P=.04), whereas Duralay jigs exhibited significant greater distortion than closed-tray and open-tray impressions in the interimplant distance R-C (P=.006). Although not significantly different from other groups, the closed-tray group showed the lowest mean distortion values in all measurements. CONCLUSION: Within the limitations of this study, the accuracy provided by verification jigs was not significantly superior to standard impression procedures. The results suggest that jig fabrication does not improve the dimensional accuracy of stone casts. Open-tray impressions showed a significantly greater inaccuracy in the vertical plane.

Acrylic Resins↗
PubMed2000

Initial cleft size does not correlate with outcome in unilateral cleft lip and palate.

Clinical outcomes in children born with a cleft lip and palate (CLP) have been an area of interest for orthodontists for a number of years. Whilst tools for measurement of these outcomes are available, there is no widely accepted measure of initial cleft severity and no known quantitative indices. Therefore, the potential influence of initial severity remains unmeasured and largely ignored. The aim of this investigation was to determine the importance of initial cleft severity in determining patient outcome. The longitudinal records of 49 children born with a unilateral cleft lip and palate (UCLP), and treated in a single centre were examined. An index of initial cleft severity was developed that categorizes the cleft area as a percentage of the total palate area. The dental arch relationships of the same patients at 6 years of age were also determined. The nature of the association between these was investigated for agreement and correlation by calculation of weighted Kappa and Spearman's correlation coefficient, respectively. No evidence was found in this sample that the initial cleft area had any bearing on the quality of outcome at 6 years of age.

Adolescent↗
PubMed1992

A surgical guide for insertion of implant fixtures.

Successful prosthodontic rehabilitation of edentulous ridges with implants is dependent upon the alignment of multiple fixtures. A simple technique for fabricating a surgical guide is presented in this article.

Dental Implantation, Endosseous↗
PubMedDate not supplied

Transfer of CT scan data to diagnostic casts.

A technique for the transfer of diagnostic information from transaxial CT scans to diagnostic casts is presented. A duplicate of the patient's existing prosthesis is utilized as a custom tray and an impression of the edentulous arch is made. The data from the transaxial radiographs are transferred to the diagnostic cast using anatomical landmarks as reference points. The marked cast can be used by the surgeon and the restorative dentist for optimal implant placement.

Dental Implantation, Endosseous↗
PubMed1999

Three-dimensional guidance system for implant insertion: Part II. Dual axes table--problem solving.

The three-dimensional guidance system for implant insertion is a technique for placing a radiopaque vertical orientation pin over the crest of the alveolar ridge on the stone cast during fabrication of the radiographic guide. The cross-sectional and panoramic reformatted images were reproduced on a Polaroid or 35-mm print. The true vertical orientation pin facilitates (1) identification and the exact planned location of each implant in the reformatted images of the CT scan, (2) establishment of the internal starting point for the osteotomy on a photographic print, (3) optimum implant orientation, and (4) measurement of the angulation between the true vertical orientation line and optimum implant orientation. With the aid of a newly developed dual-axes base and transfer of the internal starting point of each implant to the stone cast, the buccolingual and mesiodistal implant inclinations for each implant were transferred to a surgical guide in the form of surgical steel drill guide tubes. The resulting pilot osteotomy transfers to the alveolar bone the exact starting point and the buccolingual and mesiodistal inclination for each implant. The technique provides a three-dimensional guidance system for implant insertion that is extremely accurate and yet practical.

Anatomy, Cross-Sectional↗
PubMed2005

Shaping ability of RaCe rotary nickel-titanium instruments in simulated root canals.

This study assessed the shaping ability of RaCe rotary nickel-titanium instruments in simulated root canals. Forty simulated root canals consisting of four different shapes were prepared with RaCe rotary nickel-titanium instruments in a crowndown approach. Preoperative images were taken at the outset and postoperative images at various stages of preparation including at the conclusion of the shaping procedure. The combined images enabled assessment of aberrations and resin removal at various positions along the canal length. Overall, mean preparation time to size 40, .02 taper was 1.36 min. Thirty-three canals (83%) maintained the working length, three instruments deformed and no zips, perforations, or ledges were created. Under the conditions of this study RaCe rotary nickel-titanium instruments prepared simulated canals rapidly and successfully, with little change in working length and with few aberrations or instrument deformities.

Dental Alloys↗
PubMed2005

A comparison of torque required to fracture rotary files with tips bound in simulated curved canal.

The purpose of this study was to compare torque force and rotation needed to fracture three types of nickel titanium alloy rotary instruments in a simulated curved root canal space that were bound at the file tip. Files of similar size tips were studied. The files studied were ProFiles with 0.04 taper diameters of 15, 20, 25, 30, 35, 40, 45; 0.04 ProFile GT sizes 20, 30, 40; and ProTaper files sizes S1, S2, F1, F2, and F3. All files were 25 mm in length. Unwinding was defined as the rotation in degrees it took for a file to fracture after the first evidence of permanent deformation. All files exhibited permanent deformation before breaking, with the ProFile GT files demonstrating the greatest unwinding. The #45 0.04 ProFile withstood the most force while the #20 ProFile GT required the least amount of force before beginning to exhibit permanent deformation. The S1 and S2 ProTaper files fractured with so little rotation that no extended data were recorded. Generally, as the file diameter increased, the force needed to begin unwinding also increased. Also, as the file diameter increased, the force needed to fracture also increased.

Analysis of Variance↗
PubMed1995

Three-dimensional distortion of gold alloy castings and welded titanium frameworks. Measurements of the precision of fit between completed implant prostheses and the master casts in routine edentulous situations.

Thirty routine patients, provided with fixed prostheses supported by osseointegrated Brånemark implants in edentulous lower jaws, were arranged into three different groups with regard to design of the metal framework. Ten patients received cast gold alloy frames and the other two groups were provided with two different designs of welded titanium frames. The fit of the completed prostheses was measured in three dimensions (3-D) in relation to the master cast, by means of a photogrammetric technique, prior to insertion. Mean 3-D distortion of the centre point of the gold cylinder was 42 (s.d. 8) microns for the cast framework. The corresponding mean distortion for the two designs of titanium frameworks was 43 (s.d. 16) and 36 (s.d. 10) microns, respectively. Least distortion was observed in vertical direction for all three designs. None of the different designs of metal frames showed a significantly better fit (P > 0.05), but the cast and oldest titanium framework design presented a much wider range of distortion. This indicated a higher risk of sectioning and resoldering during the fabrication of the prostheses as compared to the more consistently fabricated prostheses, with a new titanium framework design.

Dental Casting Technique↗
PubMed1998

Die stone disinfection: incorporation of sodium hypochlorite.

PURPOSE: Previous research has shown that dental gypsum casts may be effectively disinfected by the substitution of 10% of the gauging water with 5.25% solution of sodium hypochlorite. The purpose of this investigation was to determine the properties of gypsum produced from such a solution as opposed to tap water alone. MATERIALS AND METHODS: Tests included setting time, compressive strength, rigidity, diametral tensile strength, setting expansion, hardness, and detail reproduction. RESULTS: The addition of sodium hypochlorite to the gauging water resulted in a statistically significant increase in the compressive strength and rigidity, and a decrease in setting time (p < or = .5). All other properties remained unchanged. CONCLUSIONS: This substitution may be an effective and convenient method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties.

Calcium Sulfate↗
PubMed2005

Dimensional accuracy of 7 die materials.

PURPOSE: The purpose of this study was to compare the linear dimensional accuracy and the handling characteristics of 7 die materials. MATERIALS AND METHODS: A master die analogous to a complete veneer crown preparation was machined from medical grade stainless steel, and 3 measurements (1: vertical; 2 and 3: horizontal) were made from 3 scribed reference lines. Individual polyvinylsiloxane impressions were made (n = 10) for each of the specimens. The fabricated dies were measured (50x) to the nearest 0.0001 mm. Data were subject to ANOVA/Duncan tests at significance level 0.05 and pairwise comparisons. RESULTS: Type IV resin-impregnated dental stone and copper-plated dies most closely approximated the dimensions of the master die, and were not significantly different from each other in any of the pairwise comparisons. Conventional Types IV and V dental stone dies exhibited setting expansion within the range appropriate for gypsum. Epoxy resin die materials demonstrated shrinkage comparable to the expansion of the Types IV and V dies. Polyurethane dies displayed a combination of linear expansion and shrinkage. Bis-acryl composite resin dies had excessive shrinkage. CONCLUSIONS: Type IV resin-impregnated dental stone and copper-plated dies were more dimensionally accurate than the other die materials tested.

Calcium Sulfate↗
PubMedDate not supplied

Pressure generated on a simulated mandibular oral analog by impression materials in custom trays of different design.

PURPOSE: The purpose was to measure the pressure exerted under a simulated mandibular edentulous impression at different locations using commonly used impression materials and four impression tray configurations. MATERIALS AND METHODS: This study was performed using an oral analog that simulated an edentulous mandibular arch. Three pressure transducers were embedded in the oral analog-one pressure transducer in the anterior ridge area, and the other two in the right and left buccal shelves. Four configurations of custom trays were fabricated: trays with no relief, with and without holes; and trays with relief, with and without holes. The impression materials tested were light body polysulfide, light body vinyl polysiloxane, medium body vinyl polysiloxane, and irreversible hydrocolloid. The custom tray and the oral analog were mounted using a reline jig, and a Satec universal testing machine was used to apply a constant pressure of 1 kg/cm(2) over a period of 5 minutes on the loaded custom tray. Eighty impressions for the 16 groups (n = 5) were made, and pressures were recorded every 10 seconds. Factorial ANOVA and Tukey Multiple Comparison Test were used to analyze the results (p < 0.05). RESULTS: A significant difference was found in the pressure produced using different impression materials. Irreversible hydrocolloid and medium body vinyl polysiloxane produced significantly higher pressure than light body polysulfide and light body vinyl polysiloxane impression materials. The presence of holes and/or relief significantly altered the magnitude of pressure produced by irreversible hydrocolloid and medium body vinyl polysiloxane but not light body polysulfide and light body vinyl polysiloxane. CONCLUSION: All impression materials produced pressure during simulated mandibular edentulous impression making. For making mandibular edentulous impressions, low-viscosity impression materials-light body polysulfide and light body vinyl polysiloxane-are recommended. Tray modification was not important in changing the amount of pressure produced for the low-viscosity impression materials.

Analysis of Variance↗
PubMed2004

Temporary crowns: repositioning key as a new technical approach in the clinical relining phase.

UNLABELLED: To accomplish prosthetic rehabilitation, a series of important procedures must be followed to achieve the correct final prosthetic outcome. The protocol presented in this article proposes a different approach that involves relining the temporary crowns during the provisional phase by means of a repositioning key. This approach is especially useful for therapeutic provisional restoration in patients with temporomandibular joint disorders. CLINICAL SIGNIFICANCE: The methodology presented allows the exclusion of arbitrary repositioning in the three-dimensional space of the provisional restoration, considering it as a fixed starting point. Our results tend to emphasize this technique not only for the ease of use, but also for the shorter time required for the occlusal fitting procedures in the final finishing phases.

Crowns↗