Jeffrey E. Rubenstein

Measuring fit at the implant prosthodontic interface

Four centers in the United States and Sweden have been working for 2 years to develop systems and methods for measuring fit at the prosthodontic interface. Two systems are based on stylus contact techniques, one system uses a laser as its reader source, and one system is photogrammetric. All the systems are capable of providing data as three-dimensional x, y, and z axes coordinate values that can be transformed into linear and angular data that characterize the bearing surfaces of abutments or abutment replicas and their mating components in the prosthesis framework. The centroid, a single point computed from the collected data, was the measurement unit, derived for these bearing surfaces, that was used to compare the systems. All four methods can most likely detect misfits that are relevant in the clinical setting; however, only one system can be used intraorally. When any measurement system is assessed, the data should always be examined for repeatability to establish the reliability of the system. This investigation made comparisons among the measurement methods used at the four centers. It was apparent from this study that comparisons of data from measurement systems should be rounded to the nearest 10 microns. The SDs determined in the comparisons were larger than 5 microns and therefore misfits should be calculated in terms smaller than 10 microns. This final point is important to the clinician who relies on research reports about precision of fit when selecting treatment approaches in caring for the implant prosthodontic needs of their patients.

Stereo laser-welded titanium implant frameworks: Clinical and laboratory procedures with a summary of 1-year clinical trials

A new technology for implant framework fabrication (Procera) has been introduced to North America after initial clinical trials in Sweden. This technique is unique because it eliminates the conventional approach to framework fabrication with the lost wax casting technique. Clinical and laboratory procedures associated with the Procera technique are described in this article, as are the most recent developments in this rapidly emerging technology. A report of 1-year results of the first 10 patients treated with the Procera technique at the University of Washington is described. Treatment outcome has been favorable, with no clinical evidence of prosthodonic or soft-tissue complications noted. All 50 of the implants placed in the 10 patients remain integrated after 1 year of service. The Procera technology offers an alternative to current conventional framework fabrication techniques. Continued follow-up of this patient series is pursued to explore the treatment outcome for a longer interval of time.

In vitro assessment of three types of zirconia implant abutments under static load

STATEMENT OF PROBLEM Although various zirconia abutments have been introduced, insufficient data exist regarding the maximum load capacity of internal tri-channel connection zirconia implant abutments with various implant-abutment interfaces. PURPOSE The purpose of this in vitro study was to compare the maximum load capacity of 3 different types of internal tri-channel connection zirconia abutments and to assess their mode of failure. MATERIAL AND METHODS The study investigated 3 groups (n=20) of zirconia implant abutments with different implant-abutment interfaces. Group AllZr consisted entirely of zirconia (Aadva CAD/CAM Zirconia Abutment), group FrZr of a titanium insert friction-fitted to the zirconia abutment component (NobelProcera Abutment Zirconia), and group BondZr of a titanium insert bonded to the zirconia abutment component (Lava Zirconia abutment). All the abutments were thermal cycled for 20 000 cycles between 5°C and 55°C. Sixty test implants made of titanium (Dummy NobelReplace) were embedded in autopolymerizing acrylic resin, and 60 zirconia copings (Lava Zirconia) with a uniform thickness of 2.0 mm were fabricated and bonded to the abutments. A universal testing machine was used to statically load all the specimens at a crosshead speed of 1 mm/min. The maximum load was recorded and used as the failure load. The fractured specimens were collected and representative specimens were studied with a stereomicroscope and scanning electron microscope (SEM). One-way ANOVA and post hoc comparisons with the Tukey HSD tests were used for statistical analysis (α=.05). RESULTS The mean (SD) maximum load capacity was 484.6 (56.6) N for NobelProcera, 503.9 (46.3) N for Aadva, and 729.2 (35.9) N for Lava abutments. The maximum load capacity of Lava abutments was significantly higher than that of Aadva or NobelProcera (P< 05). No significant difference between Aadva and NobelProcera abutments was noted. The mode of failure among the Aadva, NobelProcera, and Lava abutments was different. CONCLUSIONS With standard diameter internal tri-channel connection implants, the maximum load capacity of the Lava abutment was significantly higher than that of the Aadva or NobelProcera abutment. No significant difference in maximum load capacity was noted between Aadva and NobelProcera abutments. However, the fracture behavior of all 3 abutments was different.

Shear Bond Strength of Denture Teeth to Heat- and Light-Polymerized Denture Base Resin

PURPOSE To evaluate the shear bond strengths of highly cross-linked denture teeth bonded to heat-polymerized poly(methyl methacrylate) (PMMA) or a light-polymerized urethane dimethacrylate (UDMA) denture base resin with or without a diatoric and with or without an acrylate bonding agent. MATERIALS AND METHODS The denture base resins tested were Lucitone 199 (heat-polymerized PMMA) and Eclipse (light-polymerized UDMA). One hundred sixty mandibular central incisor denture teeth were divided into four groups (n = 40): group 1: ground surface as control; group 2: ground surface with diatoric; group 3: ground surface with bonding agent; group 4: ground surface with bonding agent and diatoric. Half of each group (n = 20) was processed with either heat- or light-polymerized resin. All specimens were treated with thermocycling for 1000 cycles, alternating between 5 and 55 °C with a dwell time of 30 seconds. Half the specimens in each group were treated with cyclic loading at 22 N for 14,400 cycles at 1.5 Hz. All specimens were tested with shear load to failure. Data were analyzed with students t-test, 2- and 3-way ANOVA, and Dunnetts T3 method (p < 0.05). RESULTS Statistical analysis demonstrated no significant effect on shear bond strength from cyclic loading. For the Lucitone 199 (L) specimens, mean shear bond strengths and standard deviations were (N) 66.5 ± 28.4, 72.7 ± 31.5, 80.6 ± 17.1, and 76.9 ± 21.9 for groups 1L, 2L, 3L, and 4L, respectively. For the Eclipse (E) specimens, mean shear bond strengths and standard deviations were (N) 3.7 ± 1.2, 7.3 ± 3.3, 90.0 ± 20.7, and 94.2 ± 17.8 for groups 1E, 2E, 3E, and 4E, respectively. No statistically significant differences in shear bond strengths were noted for the Lucitone 199 groups (p = 0.11). Eclipse shear bond strengths were significantly higher in groups 3E and 4E than in groups 1E and 2E (p ≤ 0.05). In a 3-way ANOVA for groups 3 and 4, the shear bond strengths for the Eclipse specimens were significantly higher than the Lucitone 199 specimens (p = 0.01). CONCLUSIONS When evaluating the shear bond strength of IPN denture teeth to denture base resins, specimens using an acrylate bonding agent with the Eclipse (light-polymerized) resin yielded significantly higher shear bond strengths than all of the Lucitone 199 groups and the Eclipse resin groups without a bonding agent.

An in vitro comparison of photogrammetric and conventional complete-arch implant impression techniques.

STATEMENT OF PROBLEM Conventional impression techniques for recording the location and orientation of implant-supported, complete-arch prostheses are time consuming and prone to error. The direct optical recording of the location and orientation of implants, without the need for intermediate transfer steps, could reduce or eliminate those disadvantages. PURPOSE The objective of this study was to assess the feasibility of using a photogrammetric technique to record the location and orientation of multiple implants and to compare the results with those of a conventional complete-arch impression technique. MATERIAL AND METHODS A stone cast of an edentulous mandibular arch containing 5 implant analogs was fabricated to create a master model. The 3-dimensional (3D) spatial orientations of implant analogs on the master model were measured with a coordinate measuring machine (CMM) (control). Five definitive casts were made from the master model with a splinted impression technique. The positions of the implant analogs on the 5 casts were measured with a NobelProcera scanner (conventional method). Prototype optical targets were attached to the master model implant analogs, and 5 sets of images were recorded with a digital camera and a standardized image capture protocol. Dimensional data were imported into commercially available photogrammetry software (photogrammetric method). The precision and accuracy of the 2 methods were compared with a 2-sample t test (α=.05) and a 95% confidence interval. RESULTS The location precision (standard error of measurement) for CMM was 3.9 µm (95% CI 2.7 to 7.1), for photogrammetry, 5.6 µm (95% CI 3.4 to 16.1), and for the conventional method, 17.2 µm (95% CI 10.3 to 49.4). The average measurement error was 26.2 µm (95% CI 15.9 to 36.6) for the conventional method and 28.8 µm (95% CI 24.8 to 32.9) for the photogrammetric method. The overall measurement accuracy was not significantly different when comparing the conventional to the photogrammetric method (mean difference = -2.6 µm, 95% CI -12.8 to 7.6). CONCLUSIONS The precision of the photogrammetric method was similar to CMM, but lower for the conventional method as compared to CMM and the photogrammetric method. However, the overall measurement accuracy of the photogrammetric and conventional methods was similar.

Complete arch implant impression technique

When making a definitive impression for an arch containing multiple implants, there are many reported techniques for splinting impression copings. This article introduces a splint technique that uses the shim method, which has been demonstrated to reduce laboratory and patient chair time, the number of impression copings and laboratory analogs needed, and the ultimate cost.

The use of computer-aided manufacturing during the treatment of the edentulous mandible in an oral radiation therapy patient: clinical report

This clinical report describes the treatment of an edentulous patient with previous radiation therapy to the base of the tongue. A computer-aided manufactured titanium framework was used to fabricate the implant-supported fixed complete denture and meet the functional and psychosocial needs of the patient.

Effect of simulated intraoral variables on the accuracy of a photogrammetric imaging technique for complete-arch implant prostheses

Statement of problem. Conventional impression techniques to obtain a definitive cast for a complete‐arch implant‐supported prosthesis are technique‐sensitive and time‐consuming. Direct optical recording with a camera could offer an alternative to conventional impression making. Purpose. The purpose of this in vitro study was to test a novel intraoral image capture protocol to obtain 3‐dimensional (3D) implant spatial measurement data under simulated oral conditions of vertical opening and lip retraction. Material and methods. A mannequin was assembled simulating the intraoral conditions of a patient having an edentulous mandible with 5 interforaminal implants. Simulated mouth openings with 2 interincisal openings (35 mm and 55 mm) and 3 lip retractions (55 mm, 75 mm, and 85 mm) were evaluated to record the implant positions. The 3D spatial orientations of implant replicas embedded in the reference model were measured using a coordinate measuring machine (CMM) (control). Five definitive casts were made with a splinted conventional impression technique of the reference model. The positions of the implant replicas for each of the 5 casts were measured with a Nobel Procera Scanner (conventional digital method). For the prototype, optical targets were secured to the implant replicas, and 3 sets of 12 images each were recorded for the photogrammetric process of 6 groups of retractions and openings using a digital camera and a standardized image capture protocol. Dimensional data were imported into photogrammetry software (photogrammetry method). The calculated and/or measured precision and accuracy of the implant positions in 3D space for the 6 groups were compared with 1‐way ANOVA with an F‐test (&agr;=.05). Results. The precision (standard error [SE] of measurement) for CMM was 3.9 &mgr;m (95% confidence interval [CI] 2.7 to 7.1 &mgr;m). For the conventional impression method, the SE of measurement was 17.2 &mgr;m (95% CI 10.3 to 49.4 &mgr;m). For photogrammetry, a grand mean was calculated for groups MinR‐AvgO, MinR‐MaxO, AvgR‐AvgO, and MaxR‐AvgO obtaining a value of 26.8 &mgr;m (95% CI 18.1 to 51.4 &mgr;m). The overall linear measurement error for accurately locating the top center points (TCP) followed a similar pattern as for precision. CMM (coordinate measurement machine) measurement represents the nonclinical gold standard, with an average error TCP distance of 4.6 &mgr;m (95% CI 3.5 to 6 &mgr;m). All photogrammetry groups presented an accuracy that ranged from 63 &mgr;m (SD 17.6) to 47 &mgr;m (SD 9.2). The grand mean of accuracy was calculated as 55.2 &mgr;m (95% CI 8.8 to 130.8 &mgr;m). Conclusions. The CMM group (control) demonstrated the highest levels of accuracy and precision. Most of the groups with the photogrammetric method were statistically similar to the conventional group except for groups AvgR‐MaxO and MaxR‐MaxO, which represented maximum opening with average retraction and maximum opening with maximum retraction.