Abutment margin levels and residual cement occurrence in cement-retained implant restorations: An observational study.

OBJECTIVES: To evaluate the association between different vertical levels of the abutment margin and residual cement prevalence in cement-retained implant restorations with customized abutments. METHODS: One hundred and nine single-unit cement-retained implant restorations with a screw-access channel were included. The crowns were intraorally cemented on the abutments, and excess cement was removed. The abutment-crown complex was unscrewed, and the abutment-crown complex and peri-implant tissue were photographed. Residual cement presence was recorded by dividing the abutment-crown complex and peri-implant tissue into four quadrants: mesial, distal, buccal, and lingual. The prevalence of residual cement was compared according to the height of the custom abutment margin of the corresponding quadrant. A multilevel model was used for statistical analysis (α = .05). RESULTS: Cement remnants were discovered on 72.48% of the dental implants. When the restoration quadrants were compared, cement remnants were present on 51.38%, 39.45%, 20.18%, and 17.43% of the mesial, distal, buccal, and lingual surfaces, respectively (p < .01). Regarding the abutment margin level, cement residues were found in 60.22% and 61.4% of the 0.5 mm subgingival and ≥1 mm subgingival margin groups, respectively, which were significantly more than those in the supragingival (23.65%) and equigingival (26.59%) margin groups (p < .01). After adjustment for confounding factors, the adjusted odds ratio (with 95% confidence interval) for residual cement in the subgingival margin groups was 3.664 (1.71, 7.852) when compared to the supragingival and equigingival margin groups. CONCLUSIONS: The risk of residual cement occurrence was 3.66-fold higher with a subgingival abutment margin than with supragingival and equigingival abutment margins.

Color and surface stainability of additively and subtractively manufactured interim restorative materials against mouth rinses.

STATEMENT OF PROBLEM: Interim restorations are often used along with mouth rinses during the healing period following surgical procedures. However, evidence regarding the color and surface properties of digitally fabricated interim restorations after oral rinsing is lacking. PURPOSE: The purpose of this in vitro study was to evaluate whether different mouth rinses could affect the color and surface roughness of milled and printed interim restorations after simulated oral rinsing. MATERIAL AND METHODS: Disk-shaped specimens (Ø15×2 mm; N=180) were fabricated by using conventional (Jet Tooth Shade), milled (Yamahachi PMMA Disk), and printed (NextDent C&B) resin materials. All resin specimens were divided into 3 different groups according to the rinsing material: distilled water, whitening mouth rinse (Listerine Healthy White), and conventional mouth rinse (Listerine Cool Mint). The specimens were further allocated into short- and long-term subgroups, and oral rinsing simulation was performed (n=10). Short-term rinsing simulated the conditions in a usual interim restoration period, and long-term rinsing was performed to evaluate the properties of the interim materials. The color differences (CIEDE2000, ΔE00) between the baseline and each time point were determined by using a spectrophotometer. The surface roughness of the tested specimens was measured by using a confocal laser scanning microscope. Kruskal-Wallis and Friedman tests with nonparametric pairwise comparisons were used to analyze the data (α=.05). RESULTS: On simulation of a 6-month use of the mouth rinse, the color change in the milled resin did not differ from that in the conventional resin (P>.334), but the printed resin showed a significantly greater color change than the other resins (P<.007). The greatest color change with the printed resin was observed when a conventional mouth rinse was used. However, all color changes were below a perceptible threshold of 1.30. When daily rinsing for 14 years was simulated, all resin groups showed a perceptible color change when conventional mouth rinse was used, and the printed resin showed the greatest median ±interquartile range ΔE00 (2.24 ±0.2). In both short- and long-term simulations, the printed resin rinsed with the conventional mouth rinse showed significantly greater roughness than that rinsed with distilled water (P<.009). CONCLUSIONS: The printed resin showed higher stainability than the conventional resin, and the color change was greatest with the conventional mouth rinse. However, in 6 months of daily mouth rinse simulation, all the tested resin materials exhibited imperceptible color change and clinically acceptable surface roughness.

Effect of phytochemical-filled microcapsules with antifungal activity on material properties and dimensional accuracy of denture base resin for three-dimensional printing.

BACKGROUND: Studies on the material properties and dimensional accuracy of three-dimensionally (3D) printed denture base containing microcapsules with antifungal phytochemicals are lacking. METHODS: Two types of phytochemicals (phytoncide A and B) with antifungal activity were microencapsulated. The 3D-printed denture base specimens with minimum and maximum effective concentrations of microcapsules (6 and 8 wt% for phytoncide A; 15 and 25 wt% for phytoncide B) were prepared. The morphological changes of C. albicans on 3D-printed denture base with microcapsules was microscopically observed. The degree of conversion of 3D-printed denture base with microcapsules investigated. The microhardness and flexural strength values were also measured to evaluate the mechanical properties of 3D-printed denture bases. The dimensional accuracy (trueness) of the specimens with microcapsules was measured as root-mean-square values (RMS) for the whole, upper, and side surfaces of the specimens as well as their total height. For the degree of conversion, microhardness, and flexural strength values, the Kruskal-Wallis analysis and a post-hoc comparison using Mann-Whitney U test was performed. For the analysis of trueness (RMS), the one-way analysis of variance and a post-hoc comparison using Tukey's method was conducted (α = 0.05). RESULTS: At both maximum and minimum effective concentrations of microcapsules, cell surface disruption or membrane breakdown of fungal cells were observed in the specimens. The groups with microcapsules (both phytoncide A- and B-filled) showed significantly lower microhardness and elastic modulus values than the control group (all, P = 0.001). For the trueness, all the RMS values of the whole, upper, and side surfaces of the specimens with microcapsules were less than 100 µm, although significantly higher than those without (all, P = 0.001). The mean flexural strength values of the groups with phytoncide A-filled microcapsule were higher than 65 MPa, not statistically different from that of the control group (all, P > 0.05). However, the groups with phytoncide B-filled microcapsules showed significantly lower values than the control (all, P = 0.001). CONCLUSIONS: Within the limitations of this in-vitro study, the 3D-printed denture base containing 6 wt% of phytoncide A-filled microcapsules was clinically acceptable in terms of antifungal activity, dimensional accuracy, and flexural strength.

Colour stability and surface properties of high-translucency restorative materials for digital dentistry after simulated oral rinsing.

High-translucency restorative materials are commonly used in the restoration of anterior teeth where aesthetics is a critical factor. In this in vitro study, the impact of mouthwash on the colour stability and surface characteristics of high-translucency computer-aided design and computer-aided manufacturing (CAD-CAM) dental restorative materials was evaluated. Two-hundred specimens were fabricated from five high-translucency CAD-CAM materials: a resin nano ceramic; a polymer-infiltrated ceramic network; a feldspathic ceramic; a lithium disilicate glass ceramic; and high-translucency zirconia. Each group of ceramic specimens was then divided into four subgroups: conventional mouthwash (LISTERINE); whitening mouthwash (LISTERINE Healthy White); chlorhexidine gluconate; and distilled water. Oral rinsing was simulated at 100 rpm for 180 h, representing 15 yr of clinical simulation. The specimens were then evaluated for colour, translucency, gloss, roughness, and surface morphology. Two-way ANOVA and linear mixed models were used for intergroup comparisons (α = 0.05). The polymer-infiltrated ceramic network and feldspathic ceramic became brighter, more opaque, less glossy, and rougher after rinsing with the whitening mouthwash. The long-term use of specific mouthwashes can cause deterioration of the optical and surface properties of high-translucency CAD-CAM dental restorations.

Relationship between oral health behaviour and handgrip strength: a cross-sectional study with 7589 Korean adults.

Objective: This cross-sectional study investigated the relationship between handgrip strength and oral health behaviours among Koreans.Methods: The data of 7589 individuals (3384 men and 4205 women) aged ≥19 years who participated in the Korea National Health and Nutrition Examination Survey 2014-2015 were analyzed. Oral health behaviour was assessed based on the number of daily toothbrushing sessions and the use of secondary oral-care products. The association between oral-health behaviour and handgrip strength was investigated adjusting for confounders. Multivariable logistic regression analysis was performed (α = 0.05).Results: The proportion of participants diagnosed with sarcopenia was significantly higher in the group with poor oral-health behaviours. After adjusting for confounders including age, the adjusted odds ratios and 95% confidence intervals of female participants with low handgrip strength in groups toothbrushing thrice or more per day, twice per day, and once or less per day were 1 (reference), 1.18 (0.99-1.4), and 1.24 (0.89-1.71), respectively. There were significantly more participants with low handgrip strength in the group that did not use secondary oral products for both sexes.Conclusions: Oral health behaviour is associated with handgrip strength among adults. Poor oral self-care habits may constitute a risk indicator for low muscle strength.

Tissue surface adaptation of CAD-CAM maxillary and mandibular complete denture bases manufactured by digital light processing: A clinical study.

STATEMENT OF PROBLEM: Clinical studies evaluating the tissue surface adaptation of complete denture bases fabricated by digital light processing (DLP) are lacking. PURPOSE: The purpose of this clinical study was to assess the tissue surface adaptation of complete denture bases generated by the DLP technique and to compare the adaptation with that of denture bases manufactured by 5-axis milling (MIL) and pack-and-press (PAP) method. MATERIAL AND METHODS: A total of 9 participants with 12 edentulous arches (7 maxillary and 5 mandibular) were included in this study. For each edentulous arch, the complete denture bases with occlusion rims were prepared by 3 different techniques (PAP, MIL, and DLP). A virtual denture base with occlusion rim was designed by means of a digital subtraction tool and served to fabricate the DLP and MIL denture bases. The complete denture bases were placed intraorally with an indicator applied to the intaglio surfaces. The thickness of the indicator was measured within the denture-bearing areas and anatomic landmarks of the edentulous arch to obtain the absolute tissue surface adaptation (ATA) value. The relative tissue surface adaptation (RTA) value was calculated from the differences between the ATA values of DLP or MIL techniques and those of the PAP technique. The Kruskal-Wallis test and the McNemar test were used for statistical analysis (α=.05). RESULTS: No statistically significant differences were found among the 3 denture base fabrication techniques with respect to the ATA values of either arch (P>.05). In terms of the RTA values for the maxillary arch, the DLP base was significantly different from the MIL base in the RC and P areas (both P<.05). The DLP base exhibited a higher frequency of negative RTA values than the MIL base. Regarding the RTA values for the mandibular arch, no significant differences were detected between the DLP and MIL denture bases (P>.05). CONCLUSIONS: The DLP and MIL denture bases demonstrated clinically acceptable tissue surface adaptation to both edentulous the maxilla and mandible. The DLP denture base was likely to exhibit intimate tissue adaptation in the stress-bearing areas of maxillary arches compared with the PAP denture base. The maxillary MIL denture base was likely to exhibit small gaps between the supporting tissue and denture base. Both DLP and MIL mandibular denture bases were likely to show intimate adaptation on the lingual slope compared with the PAP base.

The effect of build angle on the tissue surface adaptation of maxillary and mandibular complete denture bases manufactured by digital light processing.

STATEMENT OF PROBLEM: The effect of different build angles on the tissue surface adaptation of complete denture bases manufactured by digital light processing (DLP) is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of build angle on the tissue surface adaptation of DLP-printed complete denture bases. MATERIAL AND METHODS: Both maxillary and mandibular denture bases were virtually designed based on reference casts and fabricated by the DLP technique. For each arch, a total of 40 denture bases were fabricated with 4 different build angle conditions (90, 100, 135, and 150 degrees) and divided into 4 groups (90D, 100D, 135D, and 150D; 10 denture bases per group). The scanned intaglio surface of each DLP denture base was superimposed on the scanned edentulous area of the reference cast to compare the degree of tissue surface adaptation. Root-mean-square estimate, positive average deviation, and negative average deviation values were measured and displayed with a color deviation map. The Mann-Whitney test and Kruskal-Wallis analysis of variance were used for statistical analyses (α=.05). RESULTS: No statistically significant differences were found for root-mean-square estimate values among any build angle groups in either the maxillary or mandibular arch. With the increase of build angles, the area of positive deviation in the maxillary arch moved from the palatal region to the posterior palatal seal area, and negative deviation became pronounced at the posterior tuberosity. In the maxillary arch, the 135D group showed favorable color distribution of surface deviation. In the mandibular arch, a positive deviation was detected at the labial slope to the crest of the ridge, whereas a negative deviation was observed at the buccal shelf and the retromolar pad. The 100D group showed favorable distribution of surface deviation in the mandible. CONCLUSIONS: In both arches, the difference of overall tissue surface adaptation was not statistically significant in the 4 different build angles. However, the color deviation map revealed that the 135-degree build angle may be appropriate in the maxillary DLP-printed denture base and the 100-degree angle, in the mandibular denture base.

Association between Diabetes and the Use of Removable Dental Prostheses among the Korean Population.

BACKGROUND: A balanced nutrient intake is important for patients with diabetes. Even if individuals have the same number of residual natural teeth, there are large differences in the masticatory performance between edentulous sites restored with a fixed dental prosthesis, including dental implants, and those restored with a removable dental prosthesis. This study assessed whether the prevalence and control of diabetes differed based on the use of removable dental prostheses through an analysis of nationally representative data. METHODS: Overall, 8,155 individuals (3,525 men and 4,630 women) aged ≥ 50 years were included in this study and were classified into the following 3 groups: group 1, did not use any removable dental prostheses (NF); group 2, used removable partial dentures (RPD); and group 3, used removable complete dentures on at least 1 jaw (CD). The characterization of diabetic patients and glycemic control were analyzed and compared among groups. To determine the relationship between diabetes and the use of dental prostheses, multivariable logistic regression analysis was performed (P < 0.05). RESULTS: The adjusted odds ratios and 95% confidence intervals for diabetes in men participants in groups NF, RPD, and CD were 1 (reference), 1.165 (0.878-1.544), and 1.491 (1.034-2.151), respectively, after adjusting for confounding factors. Diabetes and glycemic control were significantly associated with the use of removable dental prostheses among men. CONCLUSION: The use of removable dental prostheses is a potential risk indicator for uncontrolled diabetes in Korean men adults, suggesting the need for a comprehensive approach to minimize the complications of diabetes mellitus.

Augmented reality in dentistry: a current perspective.

Augmentation reality technology offers virtual information in addition to that of the real environment and thus opens new possibilities in various fields. The medical applications of augmentation reality are generally concentrated on surgery types, including neurosurgery, laparoscopic surgery and plastic surgery. Augmentation reality technology is also widely used in medical education and training. In dentistry, oral and maxillofacial surgery is the primary area of use, where dental implant placement and orthognathic surgery are the most frequent applications. Recent technological advancements are enabling new applications of restorative dentistry, orthodontics and endodontics. This review briefly summarizes the history, definitions, features, and components of augmented reality technology and discusses its applications and future perspectives in dentistry.

Evaluation of the trueness and tissue surface adaptation of CAD-CAM mandibular denture bases manufactured using digital light processing.

STATEMENT OF PROBLEM: Studies assessing the trueness and tissue surface adaptation of computer-aided design and computer-aided manufacturing (CAD-CAM) mandibular complete denture bases fabricated using digital light processing (DLP) are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the trueness of DLP-generated denture bases and to compare the tissue surface adaptation of DLP with milling and pack and press. MATERIAL AND METHODS: The mandibular denture bases were virtually designed on a reference cast and were fabricated using DLP. Their intaglio surfaces were scanned and superimposed on the reference CAD denture base to evaluate the trueness. The reference cast was duplicated to create 10 identical master casts that were scanned to design 10 virtual denture bases. Twenty denture bases were fabricated with DLP and milling (10 specimens per technique). In addition, 10 denture bases were fabricated with the pack and press technique. The intaglio surfaces of the denture bases were scanned and superimposed on the corresponding master casts to compare tissue surface adaptation among the 3 techniques. The Mann-Whitney test and Kruskal-Wallis analysis of variance (α=.05) were used for statistical analyses. RESULTS: For trueness, the milled denture base was better than the DLP denture base (P<.001). However, no statistically significant difference was detected with respect to tissue surface adaptation of the denture base, regardless of the fabrication technique (P>.05). The DLP denture base showed comparable tissue surface adaptation with the milled base, one with a small interquartile range. CONCLUSIONS: The intaglio surfaces of DLP and milled denture bases corresponded within a 100-µm accuracy compared with the master cast. Although the DLP denture base exhibited tissue compression on the ridge crest, it showed comparable tissue adaptation to the milled denture base.

Mechanical properties of bone tissues surrounding dental implant systems with different treatments and healing periods.

OBJECTIVES: The objective of the current study was to examine whether the nanoindentation parameters can assess the alteration of bone quality resulting from different degrees of bone remodeling between bone tissue ages around the dental implant interface with different treatments and healing periods. MATERIALS AND METHODS: Dental implants were placed in mandibles of six male dogs. Treatment groups included: resorbable blast media-treated titanium (Ti) implants, alumina-blasted zirconia implants (ATZ), alumina-blasted zirconia implants applied with demineralized bone matrix (ATZ-D), and alumina-blasted zirconia implants applied with rhBMP-2 (ATZ-B). Nanoindentation modulus (E), hardness (H), viscosity (η), and viscoelastic creep (Creep/P max) were measured for new and old bone tissues adjacent to the implants at 3 and 6 weeks of post-implantation. A total of 945 indentations were conducted for 32 implant systems. RESULTS: Significantly lower E, H, and η but higher Creep/P max were measured for new bone tissues than old bone tissues, independent of treatments at both healing periods (p < 0.001). All nanoindentation parameters were not significantly different between healing periods (p > 0.568). ATZ-D and ATZ-B implants had the stiffer slope of correlation between E and Creep/P max of the new bone tissue than Ti implant (p < 0.039). CONCLUSIONS: Current results indicated that, in addition to elastic modulus and plastic hardness, measurement of viscoelastic properties of bone tissue surrounding the implant can provide more detailed information to understand mechanical behavior of an implant system. CLINICAL RELEVANCE: Ability of energy absorption in the interfacial bone tissue can play a significant role in the long-term success of a dental implant system.

Prosthetic rehabilitation with an implant-supported fixed prosthesis using computer-aided design and computer-aided manufacturing dental technology for a patient with a mandibulectomy: A clinical report.

The fabrication of dental prostheses with computer-aided design and computer-aided manufacturing shows acceptable marginal fits and favorable treatment outcomes. This clinical report describes the management of a patient who had undergone a mandibulectomy and received an implant-supported fixed prosthesis by using additive manufacturing for the framework and subtractive manufacturing for the monolithic zirconia restorations.

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

OBJECTIVES: The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. MATERIALS AND METHODS: The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. RESULTS: The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface. CONCLUSIONS: A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

Effects of hydrophilicity and fluoride surface modifications to titanium dental implants on early osseointegration: an in vivo study.

PURPOSE: The purpose of this study was to investigate in vivo histomorphometric differences in initial bone response to modified sand-blasted, large-grit, acid-etched (modSLA), and fluoride-modified (F-mod) implant surfaces in rabbit tibia models. MATERIALS AND METHODS: Field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and x-ray photoelectron spectroscopy (XPS) were used to determine surface characteristics. Each of 3 live New Zealand white rabbits received an F-mod implant in one tibia and a modSLA implant in the other. After 1 week, the rabbits were killed, and the undecalcified histologic slides were prepared. Bone-to-implant contact (BIC) ratio and bone area (BA) were calculated in a defined area under a light microscope. RESULTS: FE-SEM, CLSM, and XPS showed that the modSLA surface was significantly rougher than the F-mod, and that the F-mod surface had a very small amount of fluoride. However, despite these surface variances, histomorphometric analyses revealed no significant differences in either BIC or BA. CONCLUSIONS: Our results suggest that the in vivo effects of increased hydrophilicity, when added to a titanium dental implant surface, on early bone response may be similar to the effects of surface fluoride treatment.

Comparison of the osteogenic potential of titanium- and modified zirconia-based bioceramics.

Zirconia is now favored over titanium for use in dental implant materials because of its superior aesthetic qualities. However, zirconia is susceptible to degradation at lower temperatures. In order to address this issue, we have developed modified zirconia implants that contain tantalum oxide or niobium oxide. Cells attached as efficiently to the zirconia implants as to titanium-based materials, irrespective of surface roughness. Cell proliferation on the polished surface was higher than that on the rough surfaces, but the converse was true for the osteogenic response. Cells on yttrium (Y)/tantalum (Ta)- and yttrium (Y)/niobium (Nb)-stabilized tetragonal zirconia polycrystals (TZP) discs ((Y, Ta)-TZP and (Y, Nb)-TZP, respectively) had a similar proliferative potential as those grown on anodized titanium. The osteogenic potential of MC3T3-E1 pre-osteoblast cells on (Y, Ta)-TZP and (Y, Nb)-TZP was similar to that of cells grown on rough-surface titanium. These data demonstrate that improved zirconia implants, which are resistant to temperature-induced degradation, retain the desirable clinical properties of structural stability and support of an osteogenic response.

Topographical and crystalline change on surface by sandblasting improve flexural and shear bond strength of niobia-modified yttria-stabilized tetragonal zirconia polycrystal.

This study aimed to investigate the effects of sandblasting on the physical properties and bond strength of two types of translucent zirconia: niobium-oxide-containing yttria-stabilized tetragonal zirconia polycrystals ((Y, Nb)-TZP) and 5 mol% yttria-partially stabilized zirconia (5Y-PSZ). Fully sintered disc specimens were either sandblasted with 125 µm alumina particles or left as-sintered. Surface roughness, crystal phase compositions, and surface morphology were explored. Biaxial flexural strength (n=10) and shear bond strength (SBS) (n=12) were evaluated, including thermocycling conditions. Results indicated a decrease in flexural strength of 5Y-PSZ from 601 to 303 MPa upon sandblasting, while (Y, Nb)-TZP improved from 458 to 544 MPa. Both materials significantly increased SBS after sandblasting (p<0.001). After thermocycling, (Y, Nb)-TZP maintained superior SBS (14.3 MPa) compared to 5Y-PSZ (11.3 MPa) (p<0.001). The study concludes that (Y, Nb)-TZP is preferable for sandblasting applications, particularly for achieving durable bonding without compromising flexural strength.

Bone formation around zirconia implants combined with rhBMP-2 gel in the canine mandible.

OBJECTIVE: The aim of this study was to estimate the effects of zirconia implants and recombinant human bone morphogenetic protein-2 (rhBMP-2) gel on the acceleration of local bone formation and osseointegration in the canine mandible. MATERIALS AND METHODS: Four groups of 48 implants with identical geometry were installed in the mandibles of beagle dogs: alumina-blasted zirconia implants applied with rhBMP-2, alumina-blasted zirconia implants applied with demineralized bone matrix (DBM), alumina-blasted zirconia implants, and resorbable blast media-treated titanium (Ti) implants. For the first two groups, zirconia implants were inserted after the surgical sites were filled with rhBMP-2 or DBM gel. For the other two groups, zirconia or Ti implants were installed with no adjunctive treatment. Fluorescent bone markers were administered to monitor bone remodeling at weeks 2, 4, and 5 postimplantation. After healing periods of 3 weeks and 6 weeks, the animals were sacrificed, and fluorescent microscopy, histology, and histomorphometric analyses were performed. RESULTS: Fluorescent microscopy showed that bone formation around the zirconia implants installed with rhBMP-2 gel was the most prominent at 2 weeks postimplantation, while the Ti implants acquired bone apposition mainly at week 5. No significant differences were found in bone area among the groups (P > 0.05). The zirconia implants showed similar bone-to-implant contact to the Ti implants. There were no significant differences in bone-to-implant contact between the zirconia implants with rhBMP-2 gel and those with DBM (P > 0.05). CONCLUSIONS: The zirconia implants with alumina-blasted surfaces may achieve osseointegration in much the same manner as the well-established Ti implants. The area influenced by rhBMP-2 gel, including the alveolar crest, may cause active remodeling and early bone formation.

Clinical use of alumina-toughened zirconia abutments for implant-supported restoration: prospective cohort study of survival analysis.

OBJECTIVES: The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates. MATERIAL AND METHODS: From May 1998 to September 2010, 213 patients aged 18 years or older were recruited. The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments. During the follow-up, each restoration was coded as a dental event, which included loosening or fracture of abutment screws, and abutment fracture. From the coded data, the effects of the investigated clinical variables-restored area (anterior/posterior), number of prosthodontic units (one/two units or over), prosthesis type (single-unit/multiunit without pontic/multiunit with pontic), implant system, and patient gender-on the survival of the abutments were evaluated. Survival analysis using Kaplan-Meier method and Cox proportional hazard model was applied. The 5-year survival and complication rates of the abutments were assessed. RESULTS: The number of prosthodontic units and the type of prosthesis had a significant association with complication rates (P < 0.05). Kaplan-Meier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7%. Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9% and 3.8%, respectively. The 5-year survival rate of the abutments was more than 95%, regardless of the type of prosthesis. CONCLUSIONS: Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations. Single tooth replacement with the abutment at the molar region may require special care and extra attention.

Effect of translucency of CAD-CAM ceramic restorative materials and scanning aid conditions on the accuracy of intraoral scans.

Background/purpose: Subsurface scattering from translucent material would affect the digital scans. This study aimed to evaluate the effect of translucency of ceramic restorative materials and scanning aid conditions on the accuracy of intraoral scans. Materials and methods: Identical anatomic contour crowns with ten ceramic restorative materials were fabricated: five zirconia, three lithium disilicate glass-ceramic, and two leucite reinforced glass-ceramic. The models with ceramic crowns were digitized with an intraoral scanner (IOS) and analyzed for accuracy (n = 10) with and without a scanning aid. Scan time efficiency was recorded. Square-shaped specimens with 1.0-mm thickness were fabricated with the same materials, and translucency parameter (TP) values were measured. One-way ANOVA, Welch ANOVA, and a post-hoc pairwise comparison or independent t-test were used for trueness and time analysis, and the F-test was used to examine the precision (α = 0.05). Pearson correlation test was conducted. Results: Significant differences were revealed for trueness with no scanning aid condition and for TP values (P < 0.05). In contrast, no statistically significant differences were observed for trueness with a scanning aid. A strong correlation (r = 0.854, P < 0.01) between TP value and trueness with no scanning aid was revealed. By applying a scanning aid, trueness was improved and scan time efficiency significantly increased (P < 0.05). Conclusion: The translucency of ceramic restorative materials negatively affects the accuracy of IOS scan without a scanning aid; however, the scan accuracy and time efficiency of IOS scanning for ceramic restorations can be improved by applying scanning aid, and prostheses with high quality without unnecessary labor can be produced.

Reliability of digital repeated-scan superimposition and single-scan techniques for wear volume loss assessment on flat surfaces.

OBJECTIVES: Evidence on the reliability of digital techniques for wear volume assessment using three-dimensional (3D) scan datasets is scarce. This study evaluated the reliability of a repeated-scan superimposition technique and two single-scan techniques in assessing wear volume loss on flat surfaces of 3D-printed resin specimens. METHODS: Cuboid-shaped (15×10×10 mm) resin specimens were 3D-printed (n = 14) and scanned before and after 200,000 cycles of masticatory simulation. For the repeated-scan superimposition technique, digital 3D models of specimens before and after masticatory simulation were superimposed, and the volume loss was determined. The first single-scan technique utilized a computer-aided design freeware program, while the second one employed a 3D-metrology software program. In the freeware program, the worn area of 3D objects was edited directly to obtain a flat surface. In the 3D-metrology software program, the worn area was deleted first and then filled to the flat surface. The volume differences before and after editing were calculated in each software program. Agreement between the three measurement techniques was determined through intraclass correlation coefficients (ICCs). One-way analysis of variance was performed to compare the wear volume loss assessed by the three techniques (α = 0.05). RESULTS: High inter-technique reliability was observed between the three assessment techniques (ICC = 0.998, p < .001). On pair-wise comparisons of two of the three techniques, all pairs showed high consistency (ICC ≥ 0.999, p < .001). No significant difference was found in the wear volume loss assessed using the three techniques (p = .996). CONCLUSIONS: Digital repeated-scan superimposition and two single-scan techniques demonstrated high reliability in assessing wear volume loss on flat surfaces. CLINICAL SIGNIFICANCE: The repeated-scan superimposition technique can be effectively utilized to assess wear volume loss of anatomically shaped specimens and flat surfaces. This study indicates that the single-scan techniques may serve as a suitable alternative to the repeated-scan superimposition technique when evaluating wear volume loss of flat surfaces.