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Biomedical subjects

M J Edge

Publications and source records attributed to M J Edge.

16 recordsLinked to original sources
PubMed2004

Array geometry for assessment of mandibular implant position using tuned aperture computed tomography (TACT).

OBJECTIVE: To evaluate observer faciolingual depth and vertical depth reading errors when using various X-ray beam array geometries to make basis images for tomosynthetic reconstruction using tuned aperture computed tomography (TACT). MATERIALS AND METHODS: Tissue-equivalent models were constructed to replicate the position of dental implants in relation to simulated mandibular canals. X-ray beam geometries used to acquire the basis images for TACT(TM) integration included horizontal linear, vertical linear, and symmetric and asymmetric conical arrays. Twenty-one dentists trained in the use of TACT acted independently as observers. Tasks included: (1) determination of the relative position of the implant in relation to the simulated canal; and (2) measurement of the vertical depth and faciolingual (lateral) depth dimensions between these two structures. As the study did not involve repeated measures (only one measure was obtained from each observer on each of the two dependent variables), data for faciolingual depth and vertical depth reading errors were analysed using a one-way analysis of variance (ANOVA) with Tukey's honestly significant different (HSD) procedure. RESULTS: Errors in determining the relative position of the implant to the simulated canal were most frequent when the linear horizontal projection geometry was employed for producing basis images (57% error for model #2 where the implant was lingually placed). The mean measurement errors for TACT images constructed using the various different projection arrays depended both on the structural relationship of anatomic features and the employed beam array geometry. CONCLUSION: Conical beam arrays are preferred over linear beam arrays for constructing basis images used with TACT for the purpose of correlating the position of a mandibular dental implant in relation to the mandibular canal. They more consistently allowed the observers to establish a measurement of the faciolingual relationship of the implant to the canal. For vertical depth measurement of the relationship of a mandibular dental implant to the mandibular canal, TACT does not appear to have any advantage over individual simple transmission radiographic images.

Analysis of Variance↗
PubMed1997

The precision of fit at the implant prosthodontic interface.

STATEMENT OF PROBLEM: Percussion, visual observation, and conventional periapical radiographs are the methods most frequently used clinically to evaluate the accuracy of implant component assemblies, whereas methods to measure the precision of fit are limited. PURPOSE: In this study the Periotest instrument was used to evaluate the stability of the interfaces between the implant and the abutment, along with the abutment and the gold cylinder under a series of assembly conditions. The hypothesis tested is that a more negative Periotest value (PTV) would indicate an accurate fit and a more positive value PTV would correlate with an inaccurate fit. MATERIAL AND METHODS: To investigate this hypothesis in vitro, two bovine ribs were used as patient simulation models. Each model contained three self-tapping Brånemark implants placed approximately 7 to 10 mm apart and arranged in a reasonable curvature. A series of component assembly conditions were created as accurate and inaccurate with thickness gauges of 25.4 microns, 50.8 microns, and 101.6 microns. RESULTS: The mean Periotest values and SDs for accurately assembled abutments and gold cylinders were -6.0 +/- 0.32 and -3.4 +/- 0.68, respectively. Periotest value data of the assembly conditions were statistically analyzed with multiple regression analysis. The misfit in the implant to abutment interface resulted in a more negative Periotest value trend (r = 0.54) with increases in gauge thickness. However, the same magnitudes of misfit at the abutment to gold cylinder interface produced a more positive Periotest value trend (r = 0.72). CONCLUSION: The PTV trends were consistent with increased stability at the abutment to implant interface from the increasing magnitude of misfit created with the thickness gauges. In contrast, the measurement trends observed for the abutment to gold cylinder interface were consistent with decreased stability with each increase in gauge thickness inserted at the interface.

Acceleration↗
PubMed1996

Analysis of strain at selected bone sites of a cantilevered implant-supported prosthesis.

Cantilever length of the superstructure of an implant-supported prosthesis can be affected by the location, number, and dimensions of the implants, arch form, opposing dentition, and functionally generated forces. In this study, the effects of cantilever length on load distribution to implants was analyzed. A fresh bovine rib was used to create a clinical simulation in which three implants were used to support an implant prosthesis. The implants were connected by means of a cantilevered superstructure. Six linear strain gauges were placed in strategic locations where it has been reported that stress is concentrated. The model was loaded with an Instron machine and the load was applied at 0, 5, 10, 15, 20 and 25 mm along the cantilever length. Each loading test was repeated five times, and loads of 10 and 20 pounds were applied. Dynamic registration of the strain was recorded at each gauge. Significant differences in the magnitude of strain between the six strain gauge locations were recorded with the 10 and 20 lb loads and at all cantilevered lengths. The results revealed that the greatest maximum strain occurred at the strain gauge positioned on cortical bone over the apex of the most distal implant under both loading conditions.

Analysis of Variance↗
PubMed1996

The influence of occlusal design on simulated masticatory forces transferred to implant-retained prostheses and supporting bone.

The influence of occlusal surface design on the longitudinal success of implant treatment is believed to be significant, but it is not well understood. It has been suggested that limiting lateral forces by reducing cuspal inclination is beneficial in the maintenance and preservation of osseointegration. This study used a method to apply quantified vertical forces to a food substance and record the forces and strain transmitted through cusped 33-degree and cuspless 0-degree occlusal design specimens to a simulated implant-retained prosthesis and the supporting bone. A series of five masticatory cycles were applied to each of the specimens with a universal testing machine. The data were analyzed to compare (1) forces required to cause initial breakage of the food, (2) maximum breakage forces applied before cycle termination, and (3) maximum strain registered by strain gauges at the bone level. Initial breakage forces for the cuspless specimen were 50% less than for the cusped specimen (p = 0.006). No significant differences were found between maximum breakage forces and maximum strain (p values 0.744 and 0.315, respectively). The results of this pilot study indicated that the occlusal configuration and cusp angulation of implant-retained prostheses play a significant role in force transmission and the stress-strain relationship in bone.

Animals↗
PubMed1996

The Periotest method: implant-supported framework precision of fit evaluation.

PURPOSE: In this study, the Periotest instrument was used to measure the precision of fit between cast high noble-metal frameworks and the supporting implants in a patient-simulation model. Three framework conditions and three implant-location variables were used to evaluate the rigidity of the assembly as measured by the Periotest method. The framework variables were (1) one-piece castings (OPC); (2) sectioned-soldered inaccurate castings (SSIC); and (3) sectioned-soldered accurate castings (SSAC). The implant-location variables were right anterior (RA), center (C), and left anterior (LA). MATERIALS AND METHODS: The patient simulation model used consisted of three self-tapping Branemark implants in a reasonable arch curvature in bovine bone. Three working casts were fabricated from the patient-simulation model using polyvinyl siloxane and tapered impression copings. From the working casts, three sets of three frameworks were fabricated as OPCs, SSICs, and SSACs using type 3 high noble alloy. The SSICs were fabricated with a quantitative misfit of 101.6 microns at the facial surface, between the abutment-to-gold cylinder interface at the C implant location. Periotest value (PTV) measurements were made at the midfacial surface of the frameworks directly above each abutment-to-gold cylinder interface. Three measurements were made for each test condition. The data were analyzed to compare framework condition(s) and implant location(s) using ANOVA and Fisher's Protected Least Significant Difference Comparison Test. RESULTS: The ANOVA showed that significant differences exist between the mean PTV data for framework condition and for implant location (p < .01). Significant differences were shown between the mean PTV data for the SSAC assemblies and the OPC and SSIC assemblies. The SSICs displayed a more positive (+) mean PTV than the OPCs. The OPC assemblies had a more positive mean PTV than the SSAC assemblies. The mean PTV data for the SSAC assemblies had a significantly different PTV (p < .01) than the other two framework condition assemblies. The OPC and the SSIC assemblies had PTVs that were not significantly different. The C implant location was significantly different from the RA and the LA implant locations (p < .01). The RA and the LA implant locations were not significantly different from each other. The C implant location always demonstrated the most positive mean PTV regardless of the framework condition being tested. CONCLUSIONS: The Periotest instrument quantified differences in the precision of fit between three framework conditions. The SSAC assemblies were significantly more rigid than the OPC and SSIC assemblies. The OPC and SSIC assemblies' mean PTVs were not significantly different. The mean PTVs for the C implant location and the RA and LA implant locations were significantly different (p < .01). The mean PTVs of the RA and LA implant locations were not significantly different. The implant-location PTVs followed the same rank order for all three framework conditions. The procedures used to fabricate a more precise fit between the framework and the supporting implants is influenced by the skill of the clinician and technician.

Analysis of Variance↗
PubMed1994

Surface cracking identified in polished and self-glazed dental porcelain.

PURPOSE: Polishing and glazing porcelain surfaces of restorations is thought to help reduce the wear on the opposing occlusion because of reduced roughness. MATERIALS AND METHODS: To test this theory, samples of a variety of dental porcelains were prepared and subjected to various polishing and self-glazing treatments commonly used in dentistry and then viewed using scanning electron microscope (SEM). Fine cracks were discovered in the surface of the samples that had been polished and then self-glazed. These cracks were typically greater than 50 microns in length with submicron surface openings and crack depths less than 20 microns. To establish the treatments responsible for the formation of these cracks, a more controlled study was performed. Samples of Vita VMK 68 no. 559 incisal porcelain (Vita Zahnfabrik, Bad Såchingen, Germany) were prepared and subjected to six treatments (sample size = 3): treatment no. 1, as-fired condition; treatment no. 2, self-glazed (32 degrees C per minute to 960 degrees C, then cooled); treatments no. 3 and 4, wet ground followed by 1 micron diamond polish (no. 4 was then self-glazed); treatments no. 5 and 6, ground and polished using a Shofu porcelain adjustment kit (Shofu Inc, Kyoto, Japan) (no. 6 was then self-glazed). The samples were observed using SEM. RESULTS: Treatments no. 1, 2, 3, and 5 showed no cracking; however, treatments no. 4 and 6 showed cracking in all specimens (approximate levels 5,100 microns/mm2 and 3,600 microns/mm2, respectively). CONCLUSIONS: Polishing followed by self-glazing produces fine surface cracks. The rougher surface resulting from the surface cracks and subsequent porcelain chipping may cause wear of opposing occlusal surfaces.

Dental Alloys↗
PubMed1993

The effect of selective die spacer placement techniques on the seatability of castings.

It has been reported in the literature that impingement of the casting at the axial-occlusal line angle of the tooth preparation may be a major cause of incomplete seating following cementation. It has been suggested that an additional coat of spacer applied to these areas on the laboratory die before the fabrication of the casting may alleviate this discrepancy. This study evaluated the effect of three die spacer placement techniques on the seatability of cemented castings. Results showed no statistical difference in seating between castings made with conventional relief and those made with additional relief at the axial-occlusal line angles. Castings relieved exclusively at the axial-occlusal line angles exhibited significant post-cementation marginal openings.

Analysis of Variance↗
PubMed1993

The potential for bonding titanium restorations.

PURPOSE: The use of titanium for implants has shown the biological acceptance of the metal. Recently, methods of using titanium for restorations, crowns, and bridges have been introduced using both cast and spark erosion systems for fabrication. A potential also exists for using titanium for bonded (Maryland) bridges. MATERIALS AND METHODS: In this study, the potential for bonding titanium was investigated by cementing with various adhesives: (A) metal to metal, (B) metal to enamel, and (C) comparing with a known procedure of bonding nickel-chromium. Truncated cones of pure titanium were fabricated with a 5-mm circular face for bonding to a larger titanium disc embedded in a plastic ring. A special jig was used to pull the bonded cone from the disc on an Instron tensile testing machine (Instron Corporation, Canton, MA). The resin-metal adhesives used were: (1) Infinity, (2) Metabond, (3) All-Bond 2, and (4) Panavia. These were compared with (5) nickel-chromium cones sandblasted and bonded to nickel-chromium with Panavia. Titanium cones were also bonded to human enamel with (6) Panavia and (7) Metabond. The 10 samples in each group were subjected to tensile force, and point of fracture was recorded. The data were subjected to an analysis of variance with a Scheffe F test at the 95% level of significance. RESULTS: The results of tensile forces in MPa were (1) Infinity, 28.1 +/- 3.6; (2) Metabond, 28.1 +/- 1; (3) All-Bond 2, 49.5 +/- 4.3; (4) Panavia, 57.9 +/- 3.1; (5) Panavia to nickel-chromium, 42.9 +/- 6.6; (6) Panavia to enamel, 18.5 +/- 4.7; and (7) Metabond to enamel, 19.3 +/- 3.5. Titanium was most effectively bonded with All-Bond 2 and Panavia, with Panavia samples significantly better than Panavia to nickel-chromium samples. CONCLUSIONS: It was concluded that titanium bonded restorations with certain adhesive cements were a definite possibility.

Analysis of Variance↗
PubMed1987

An alternate method for establishing porcelain margins.

The technique described is simple, safe, and requires no special training or expertise in its application. Hi-Temp special liquid is readily available and has an indefinite shelf life. The technique enables easy fabrication of ceramometal crowns with porcelain margins with fewer problems and greater accuracy.

Crowns↗
PubMed1987

Surgical placement guide for use with osseointegrated implants.

The fabrication and use of the implant surgical guide allows two dentists to treat a patient with minimal communication loss and achieve a result desired by both. It also greatly facilitates planning and actual treatment for the same dentist by assuring that implants are surgically placed where originally planned (Fig. 6).

Acrylic Resins↗