Heiner Weber

Determination of the minimum number of marginal gap measurements required for practical in-vitro testing.

STATEMENT OF PROBLEM Gap measurements along margins are frequently used to assess the quality of single crowns. However, the number of gap measurements required for clinically relevant results in laboratory studies is not known. PURPOSE This study estimated the minimum number of gap measurements on margins of single crowns to produce relevant results for gap analysis. METHODS AND MATERIAL Ten all-ceramic crowns were fabricated on a master steel die. Gaps along crown margins were investigated in a scanning electron microscope on the master steel die without cementation and on replica dies after conventional cementation. Measurements were made in 100 microm steps according to 3 gap definitions. The initial number of measurements per crown (n = 230) was reduced to smaller subsets using both systematic and random approaches to determine the impact on the quality of results. RESULTS On the data of gap definition 1, reduction from 230 to about 50 measurements caused less than +/-5 microm variability for arithmetic means. Analysis of standard errors showed slowly increasing values smaller than 3 microm, both indicating no relevant impact on the quality of results. Smaller data sizes yielded accelerated increase of standard errors and divergent variabilities of mean. The minimum of 50 measurements did not depend on gap definition or on cementation condition. CONCLUSION Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use.

Plaque retention on teeth restored with full-ceramic crowns: A comparative study

Plaque accumulation was determined by using the plaque index of Silness and Löe on 150 crowns in 19 patients. The plaque indices for individual crowns in a quadrant were compared to the average plaque index of the quadrant in which the crowns were inserted (quadrant plaque index = 100%). This comparative study showed that Cerestore full-ceramic crowns have little soft debris retention (32%). Ceramometal crowns (90%), natural teeth (110%), cast gold restorations (148%), and acrylic resin veneer crowns (152%) have increasing plaque retention. The results indicate that ceramics are easily cleaned and exhibit low plaque retention. Increasing the area of ceramic surfaces on restorations decreases plaque retention.

Spark erosion procedure: a method for extensive combined fixed and removable prosthodontic care.

Restoration that uses a combination of fixed and removable partial dentures, which involves precision attachments and telescopic procedures, represents one of the highest levels of functional and esthetic therapy. In the past, these restorations were mostly made with high gold-content alloys. The dental spark erosion procedure offers a sophisticated method for using base metal alloys for these complex restorations. This procedure combines the functional and esthetic advantages of precision restorations with the advantageous properties of base metal alloys such as low thermal conductivity, high strength, and lower cost.

Additive Manufacturing: A Comparative Analysis of Dimensional Accuracy and Skin Texture Reproduction of Auricular Prostheses Replicas

PURPOSE The use of computer-aided design/computer-aided manufacturing (CAD/CAM) and additive manufacturing in maxillofacial prosthetics has been widely acknowledged. Rapid prototyping can be considered for manufacturing of auricular prostheses. Therefore, so-called prostheses replicas can be fabricated by digital means. The objective of this study was to identify a superior additive manufacturing method to fabricate auricular prosthesis replicas (APRs) within a digital workflow. MATERIALS AND METHODS Auricles of 23 healthy subjects (mean age of 37.8 years) were measured in vivo with respect to an anthropometrical protocol. Landmarks were volumized with fiducial balls for 3D scanning using a handheld structured light scanner. The 3D CAD dataset was postprocessed, and the same anthropometrical measurements were made in the CAD software with the digital lineal. Each CAD dataset was materialized using fused deposition modeling (FDM), selective laser sintering (SLS), and stereolithography (SL), constituting 53 APR samples. All distances between the landmarks were measured on the APRs. After the determination of the measurement error within the five data groups (in vivo, CAD, FDM, SLS, and SL), the mean values were compared using matched pairs method. To this, the in vivo and CAD dataset were set as references. Finally, the surface structure of the APRs was qualitatively evaluated with stereomicroscopy and profilometry to ascertain the level of skin detail reproduction. RESULTS The anthropometrical approach showed drawbacks in measuring the protrusion of the ears helix. The measurement error within all groups of measurements was calculated between 0.20 and 0.28 mm, implying a high reproducibility. The lowest mean differences of 53 produced APRs were found in FDM (0.43%) followed by SLS (0.54%) and SL (0.59%)--compared to in vivo, and again in FDM (0.20%) followed by SL (0.36%) and SLS (0.39%)--compared to CAD. None of these values exceed the threshold of clinical relevance (1.5%); however, the qualitative evaluation revealed slight shortcomings in skin reproduction for all methods: reproduction of skin details exceeding 0.192 mm in depth was feasible. CONCLUSION FDM showed the superior dimensional accuracy and best skin surface reproduction. Moreover, digital acquisition and CAD postprocessing seem to play a more important role in the outcome than the additive manufacturing method used.

A Comparison Of Il-1β, E2 (Pge2), Pai-2 and Tnf-Α Levels in Gingival Crevicular Fluid (Gcf) and Peri-Implant Crevicular Fluid (Picf) from Groups of Patients with Healthy Teeth, Healthy Implants, Periodontitis and Peri-Implantitis

Objectives: The aim of this study was to analyse simultaneously four markers in gingival crevicular fluid (GCF) and peri-implant crevicular fluid (PICF) from 41 patients in four different groups over a period of six months in order to establish profiles indicating quantitative ratio and potential correlations. Material and Methods: We compared levels of interleukin-1 beta (IL-1s), prostaglandin E2 (PGE2), specific plasminogen activator inhibitor 2 (PAI-2) and tumor necrosis factor-alpha (TNF-α) in GCF and PICF from four groups of patients: healthy teeth (n=10), healthy implants (n=10), periodontitis (n=11) and peri-implantitis (n=10). Clinical parameters including bacterial flora were quantified by PCR-analysis. The concentration in GCF/PICF of IL-1β, PAI-2, E2 (PGE2) was determined by ELISA, TNF-α by Western blot analysis. Results: Healthy teeth showed significantly higher levels of IL-1β than healthy implants. The mean level of E2 (PGE2) for healthy teeth was twice as high as for healthy implants. Periodontitis and peri-implantitis sites showed highly increased secretion of IL-1s and E2 (PGE2) resulting in significantly higher levels of IL-1s in periodontits than in peri-implantitis. Highest TNF-α levels showed in the peri-implantitis group, lowest in healthy teeth. Lowest concentrations of PAI-2 appeared in peri-implantitis, highest in healthy implants. Conclusions: Within the limits of the study it could be hypothesized that the significantly higher levels of IL-1s and E2 (PGE2) for healthy teeth than for healthy implants could in part be due to the lack of periodontal ligament cells around implants. Another possible explanation could be the anti-inflammatory property of titanium surfaces of implants.