Cordless digital workflow for scanning implant-supported prostheses at the abutment level: A dental technique.

A custom abutment produced from a digital scan can be used to develop an implant-supported prosthesis with ideal contours. A scan body is used to obtain information about the location of the implant fixture, and the scan body has a special scan region that facilitates superimposition. This dental technique indirectly obtains the margin of the definitive prosthesis by designing the special scan region on a custom abutment and superimposing prescanned abutment data onto intraoral scanned data.

Efficacy of plasma treatment for surface cleansing and osseointegration of sandblasted and acid-etched titanium implants.

PURPOSE: This study was conducted to evaluate the effects of plasma treatment of sandblasted and acid-etched (SLA) titanium implants on surface cleansing and osseointegration in a beagle model. MATERIALS AND METHODS: For morphological analysis and XPS analysis, scanning electron microscope and x-ray photoelectron spectroscopy were used to analyze the surface topography and chemical compositions of implant before and after plasma treatment. For this animal experiment, twelve SLA titanium implants were divided into two groups: a control group (untreated implants) and a plasma group (implants treated with plasma). Each group was randomly located in the mandibular bone of the beagle dog (n = 6). After 8 weeks, the beagle dogs were sacrificed, and volumetric analysis and histometric analysis were performed within the region of interest. RESULTS: In morphological analysis, plasma treatment did not alter the implant surface topography or cause any physical damage. In XPS analysis, the atomic percentage of carbon at the inspection point before the plasma treatment was 34.09%. After the plasma treatment, it was reduced to 18.74%, indicating a 45% reduction in carbon. In volumetric analysis and histometric analysis, the plasma group exhibited relatively higher mean values for new bone volume (NBV), bone to implant contact (BIC), and inter-thread bone density (ITBD) compared to the control group. However, there was no significant difference between the two groups (P > .05). CONCLUSION: Within the limits of this study, plasma treatment effectively eliminated hydrocarbons without changing the implant surface.

The oral microbiome of implant-abutment screw holes compared with the peri-implant sulcus and natural supragingival plaque in healthy individuals.

PURPOSE: An implant-supported prosthesis consists of an implant fixture, an abutment, an internal screw that connects the abutment to the implant fixture, and the upper prosthesis. Numerous studies have investigated the microorganisms present on the implant surface, surrounding tissues, and the subgingival microflora associated with peri-implantitis. However, there is limited information regarding the microbiome within the internal screw space. In this study, microbial samples were collected from the supragingival surfaces of natural teeth, the peri-implant sulcus, and the implant-abutment screw hole, in order to characterize the microbiome of the internal screw space in healthy subjects. METHODS: Samples were obtained from the supragingival region of natural teeth, the peri-implant sulcus, and the implant screw hole in 20 healthy subjects. DNA was extracted, and the V3-V4 region of the 16S ribosomal RNA was sequenced for microbiome analysis. Alpha diversity, beta diversity, linear discriminant analysis effect size (LEfSe), and network analysis were employed to compare the characteristics of the microbiomes. RESULTS: We observed significant differences in beta diversity among the samples. Upon analyzing the significant taxa using LEfSe, the microbial composition of the implant-abutment screw hole's microbiome was found to be similar to that of the other sampling sites' microbiomes. Moreover, the microbiome network analysis revealed a unique network complexity in samples obtained from the implant screw hole compared to those from the other sampling sites. CONCLUSIONS: The bacterial composition of the biofilm collected from the implant-abutment screw hole exhibited significant differences compared to the supra-structure of the implant. Therefore, long-term monitoring and management of not only the peri-implant tissue but also the implant screw are necessary.

Comparison of fit and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems.

PURPOSE: This study aims to clinically compare the fitness and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems. MATERIALS AND METHODS: Total of 40 patients were enrolled in this study, and 9 different zirconia crowns were prepared per patient. Each crown was made through the cross-application of 3 different design software (EZIS VR, 3Shape Dental System, Exocad) with 3 different processing devices (Aegis HM, Trione Z, Motion 2). The marginal gap, absolute marginal discrepancy, internal gap(axial, line angle, occlusal) by a silicone replica technique were measured to compare the fit of the crown. The scanned inner and outer surfaces of the crowns were compared to CAD data using 3D metrology software to evaluate trueness. RESULTS: There were significant differences in the marginal gap, absolute marginal discrepancy, axial and line angle internal gap among the groups (P < .05) in the comparison of fit. There was no statistically significant difference among the groups in terms of occlusal internal gap. The trueness ranged from 36.19 to 43.78 µm but there was no statistically significant difference within the groups (P > .05). CONCLUSION: All 9 groups showed clinically acceptable level of marginal gaps ranging from 74.26 to 112.20 µm in terms of fit comparison. In the comparison of trueness, no significant difference within each group was spotted. Within the limitation of this study, open CAD-CAM systems used in this study can be assembled properly to fabricate zirconia crown.

Evaluation of Clinical Accuracy of Implant Abutment-Level Impression Technique Using Digital Superimposition of Customized Abutment.

Taking a conventional implant abutment-level impression with the gingival retraction technique can cause side effects such as gingival recession and bleeding. In order to overcome these problems, an impression technique using digital superimposition of the customized abutment is newly introduced. In this technique, digital impression data and pre-scanned abutment data are superimposed to reproduce the abutment's location and shape on computer-aided design software. The present investigation was conducted to evaluate the clinical accuracy of the newly adapted digital superimposition impression technique by assessing the fit of fabricated prostheses. The results showed clinical efficacy of this technique, satisfying both convenience and clinically acceptable marginal and internal fit.

Effects of Gamma Radiation-Induced Crosslinking of Collagen Type I Coated Dental Titanium Implants on Osseointegration and Bone Regeneration.

This study aimed to compare two methods of crosslinking collagen type I on implanted titanium surfaces, that is, using glutaraldehyde (GA) or gamma-rays (GRs), in a beagle dog model. For in vivo experiments, implants were allocated to three groups and applied to mandibular bone defects in beagle dogs; Group SLA; non-treated Sandblasted, large grit, acid-etched (SLA) implants, Group GA; SLA implants coated with GA crosslinked collagen type I, Group GR; SLA surface implants coated with collagen type I and crosslinked using 25 kGy of 60Co gamma radiation. New bone µCT volumes were obtained, and histologic and histometric analyses were performed in regions of interest. The GR group had significantly better new bone areas (NBAs) and bone to implant contact (BIC) results than the SLA group (p < 0.05), but the GA and GR groups were similar in this respect. New bone volumes and inter-thread bone densities (ITBD) were non-significantly different in the three groups (p > 0.05). Within the limits of this study, gamma-ray collagen crosslinking on titanium implants can be considered a substitute for glutaraldehyde crosslinking.

Retrospective Clinical Study of a Freely Removable Implant-Supported Fixed Dental Prosthesis by a Microlocking System.

This retrospective clinical study was conducted to evaluate the clinical usefulness of a freely removable microlocking implant prosthesis (MLP) that was developed to overcome the problems with conventional implant prostheses. A total of 54 patients (male: 31, female: 23) and 100 implant prostheses were included. Patients were divided into three groups such as 6-12 months, 12-18 months, and 18-24 months according to the used period after implant prosthesis delivery, and the patients in each group were recalled for examinations of survival rate, marginal bone resorption, peri-implant soft tissue indices, and complications. The prosthetic complications were analysed by combining the recorded chart data during the periodic checks including the last call for this study. During a 2-year observation period, all the implants showed a 100% survival rate without clinical mobility and functional problems. There was no significant difference in marginal bone resorption, plaque index, and bleeding index over the observation period after implant prosthesis delivery. Probing depth of the 18-24 months group (1.5 ± 0.19 mm) was significantly lower than that of the 6-12 months group (p < 0.05). The main complication was abutment loosening (4%), followed by implant prosthesis fracture (2%) and food impaction (2%) which were recorded. Within the limits of the present study, the implant prostheses with MLP are considered to be an applicable and predictable treatment method.

Evaluation of 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide Cross-Linked Collagen Membranes for Guided Bone Regeneration in Beagle Dogs.

The purpose of this study was to evaluate the bone regeneration efficacy of an 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-cross-linked collagen membrane for guided bone regeneration (GBR). A non-cross-linked collagen membrane (Control group), and an EDC-cross-linked collagen membrane (Test group) were used in this study. In vitro, mechanical, and degradation testing and cell studies were performed. In the animal study, 36 artificial bone defects were formed in the mandibles of six beagles. Implants were inserted at the time of bone grafting, and membranes were assigned randomly. Eight weeks later, animals were sacrificed, micro-computed tomography was performed, and hematoxylin-eosin stained specimens were prepared. Physical properties (tensile strength and enzymatic degradation rate) were better in the Test group than in the Control group. No inflammation or membrane collapse was observed in either group, and bone volumes (%) in defects around implants were similar in the two groups (p > 0.05). The results of new bone areas (%) analysis also showed similar values in the two groups (p > 0.05). Therefore, it can be concluded that cross-linking the collagen membranes with EDC is the method of enhancing the physical properties (tensile strength and enzymatic degradation) of the collagen membranes without risk of toxicity.

Wear Characteristics of Dental Ceramic CAD/CAM Materials Opposing Various Dental Composite Resins.

The aim of this study was to evaluate the wear properties of opposed dental ceramic restorative CAD/CAM materials and several posterior direct restorative composite resins. Three kinds of dental ceramics CAD/CAM materials (monolithic zirconia, lithium disilicate, leucite) and four dental composite resins-that is, MI Gracefil, Gradia Direct P, Estelite Σ Quick, and Filtek Supreme Ultra-were used in this study. For each of the 12 groups (three ceramics × four composite resins), five each of a canine-shaped ceramic specimen and a cuboidal shape opposing composite resin were prepared. All of the specimens were tested in a thermomechanical loading machine (50 N, 100,000 cycles, 5/55 °C). Wear losses of ceramic specimens and composite resin specimens were evaluated using a three-dimensional profiling system and an electronic scale, respectively. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni's correction. Zirconia showed significantly less volumetric loss than lithium disilicate or leucite regardless of composite resin type (p > 0.05/3 = 0.017), and that Estelite Σ Quick showed significantly more weight loss than Filtek Supreme Ultra, MI Gracefil, or Gradia Direct P regardless of ceramic type (p > 0.05/6 = 0.083). Zirconia showed less volumetric loss than lithium disilicate or leucite. Some composite resins opposing ceramics showed considerable weight loss.