Comparison of the marginal fit of lithium disilicate crowns fabricated with CAD/CAM technology by using conventional impressions and two intraoral digital scanners.

STATEMENT OF PROBLEM: Conventional impression materials and techniques have been used successfully to fabricate fixed restorations. Recently, digital pathways have been developed, but insufficient data are available regarding their marginal accuracy. PURPOSE: The purpose of this in vitro study was to compare the marginal gap discrepancy of lithium disilicate single crowns fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by using both conventional and 2 digital impression techniques. MATERIAL AND METHODS: One typodont maxillary right central incisor was prepared for a ceramic crown. Ten impressions were made by using each method: conventional with polyvinyl siloxane impression material, Lava COS (3M ESPE), and iTero (Cadent) intraoral scanning devices. Lithium disilicate (e.max CAD) crowns were fabricated with CAD/CAM technology, and the marginal gap was measured for each specimen at 4 points under magnification with a stereomicroscope. The mean measurement for each location and overall mean gap size by group were calculated. Statistically significant differences among the impression techniques were tested with F and t tests (α=.05). RESULTS: The average (±SD) gap for the conventional impression group was 112.3 (±35.3) µm. The digital impression groups had similar average gap sizes; the Lava group was 89.8 (±25.4) µm, and the iTero group was 89.6 (±30.1) µm. No statistically significant difference was found in the effects among impression techniques (P=.185) CONCLUSIONS: Within the limitations of this study, digital and conventional impressions were found to produce crowns with similar marginal accuracy.

Effect of implant divergence on the accuracy of definitive casts created from traditional and digital implant-level impressions: an in vitro comparative study.

PURPOSE: The purpose of this research was to compare the accuracy of definitive casts created with digital and conventional methods for implants with internal-octagon connections placed parallel or at different angles (15, 30, or 45 degrees). MATERIALS AND METHODS: Four customized epoxy resin master casts were fabricated with two-implant analogs placed in the posterior mandible with different degrees of divergence. For the conventional (control) group, 10 traditional impressions were taken on each master cast with custom trays, open-tray impression copings, and polyvinyl siloxane; definitive stone casts were poured with type IV dental stone. For the digital group, 10 digital impressions were taken on each master cast with two-piece scannable impression copings and an intraoral digital scanner; definitive milled polyurethane casts were fabricated by the manufacturer. All four master casts and 80 control and test casts were scanned and digitized, and the data sets were compared. Any deviations in measurements between the definitive and corresponding master casts were analyzed statistically. RESULTS: The amount of divergence between implants did not affect the accuracy of the stone casts created conventionally; however, it significantly affected the accuracy of the milled casts created digitally. A decreasing linear trend in deviations for both distance and angle measurements suggested that the digital technique was more accurate when the implants diverged more. At 0 and 15 degrees of divergence, the digital method resulted in highly significantly less accurate definitive casts. At 30 and 45 degrees of divergence, however, the milled casts showed either no difference or marginal differences with casts created conventionally. CONCLUSION: The digital pathway produced less accurate definitive casts than the conventional pathway with the tested two-implant scenarios. To ensure passive fit of definitive prostheses, verification devices and casts may be used when materials are produced digitally.

Complete oral rehabilitation of a patient with hereditary gingival fibromatosis: a clinical report.

Hereditary gingival fibromatosis is a rare disease that has several debilitating oral and psychological manifestations, especially with young children and adolescents. The complexity of the treatment as well as the timing relative to the growth and maturation of the patient present a challenge. Few treatment options have been reported in the literature. This clinical report presents a multidisciplinary approach to treating a young patient with hereditary gingival fibromatosis by using implant-supported prostheses. The treatment steps and its outcome are discussed.

The influence of digital fabrication options on the accuracy of dental implant-based single units and complete-arch frameworks.

PURPOSE: To compare the accuracy and reproducibility of digital versus conventional dental impressions and fabrication techniques for single units and full-arch implant frameworks. MATERIALS AND METHODS: A total of 24 samples, divided into four groups, were created using conventional and digital implant impression/fabrication techniques: group 1 (conventional single implant), group 2 (digital single implant), group 3 (conventional complete arch), and group 4 (digital complete arch). All impressions were made at the abutment level. Marginal fit measurements were made using an optical microscope at two points (buccal and lingual) for each sample. Statistical analysis was performed using F and t tests (α = .05). RESULTS: For single implants, the conventional impression/fabrication pathway resulted in a mean marginal discrepancy of 24.1 µm compared to 61.43 µm for the digital impression/fabrication pathway. For full-arch frameworks, the conventional impression/fabrication pathway resulted in a mean marginal discrepancy of 135.1 µm compared to 63.14 µm for the digital technique. CONCLUSION: The conventional pathway resulted in a smaller marginal discrepancy for single-implant frameworks. In contrast, the digital pathway resulted in a smaller marginal discrepancy for full-arch implant frameworks.

Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces.

STATEMENT OF THE PROBLEM: Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available. PURPOSE: To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces. MATERIAL AND METHODS: Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05). RESULTS: Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit. CONCLUSION: Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness.

A direct technique to fabricate an intraoral shield for unilateral head and neck radiation.

A radiation oncologist may ask the prosthodontist to fabricate an intraoral shield when ipsilateral fields are used for patients with head and neck cancer. A technique for its fabrication is described that can be accomplished with materials and equipment that are readily available in the dental office. Baseplate wax is used intraorally to fabricate a pattern, which is duplicated with irreversible hydrocolloid material. Autopolymerizing acrylic resin is then used to make the shield. This simple technique can be completed in a single visit.

Implementation of a laboratory quality assurance program: the Louisville experience.

Remakes, or the refabrication of dental prostheses, can occur as a result of inherent inaccuracies in both clinical and laboratory procedures. Because dental schools manage large numbers of predoctoral dental students with limited familiarity and expertise as related to clinical prosthodontic techniques, it is likely these schools will experience an elevated incidence of laboratory remakes and their ramifications. The University of Louisville School of Dentistry, not unlike other dental schools, has experienced remakes associated with both fixed and removable prosthodontic procedures. Limitations in faculty standardization and variable enforcement of established preclinical protocols have been identified as variables associated with the high percentage of remakes documented. The purpose of this study was to introduce the implementation of a new multidepartmental quality assurance program designed to increase consistency and quality in both information provided to commercial dental laboratories and the prostheses returned. The program has shown to be advantageous in terms of cost-effectiveness and treatment outcomes. A statistically significant decrease in remake percentages has been recorded from inception of this program in December 2010 until December 2012. Furthermore, this program has resulted in more consistent communication between the dental school and commercial dental laboratories, among faculty members, and between faculty and students.

Fabrication of a fixed multipurpose template retained by existing dental implants.

This report describes the use of a multipurpose template stabilized with existing implants to provide accurate information for immediate implant placement, to facilitate impression making, and to record maxillomandibular relationships for the fabrication of an interim immediate implant-supported fixed prosthesis.

Oral rehabilitation of an edentulous patient using two-segment le fort I repositioning and implant-supported fixed prostheses.

Anteroposterior (AP) deficiencies present a restorative treatment challenge. Complex, multidisciplinary planning is necessary for the success of the treatment. This clinical report describes an approach to managing a complex complete oral rehabilitation of an edentulous patient with skeletal transverse and AP deficiencies with a history of facial trauma to the left zygomaticomaxillary complex. This was further complicated by a hopeless remaining dentition and pneumatization of the maxillary sinuses. Treatment included initial bony augmentation of the vertically and horizontally deficient maxilla, dental implant placement, provisional restoration in a Class III malocclusion with bilateral posterior crossbite, and Le Fort I osteotomy with transverse widening and advancement to correct the skeletal deficiency. Definitive restoration was accomplished with implant-supported fixed prostheses that provided ideal facial balance and occlusion.