In vitro evaluation of CAD/CAM composite materials.

OBJECTIVES: The purpose of this in vitro study was to evaluate the microstructural, elemental and mechanical properties of contemporary computer-aided-design/computer-aided manufacturing (CAD/CAM) resin based composite (RBC) materials. METHODS: Six CAD/CAM RBC materials [Brilliant CRIOS (Coltene Whaledent AG), Cerasmart (GC), Lava Ultimate (3M ESPE), Tetric CAD (Ivoclar Vivadent), Shofu Block HC (Shofu), Grandio Blocs (VOCO GmbH)] were tested. Ten rectangular blocks (14 Χ 12 Χ 18 mm) for each material, after metallographic grinding and polishing, were subjected to Instrumented Indentation Testing (ΙIT). Martens Hardness (HM), Indentation Elastic Modulus (EIT), Elastic (ηIT) and Creep indices (CIT) were determined according to formulas provided by ISO 14577. The diagonal length of each indentation was measured and HV was determined. The results of HM, EIT, ηΙΤ, HV, and CIT were statistically analyzed by one-way ANOVA and Tukey post hoc test employing the material as a discriminating variable (a = 0.05), while the possible correlations were determined by Spearman's correlation test. One specimen from each group was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). RESULTS: Backscattered Electron images and EDX analysis demonstrated differences in size, shape and type of fillers along with elemental composition among materials tested. Statistical significant differences were identified for all mechanical properties tested. Grandio Blocs had the significantly higher HM (953±7 N/mm2), HV (136±1) and EIT (23±1 GPa) followed by Lava Ultimate (ΗM=674±25 N/mm2, HV=105±2, EIT=15±1 GPa). Elastic index ranged from 41% to 52%, with Shofu Block demonstrating the significantly highest ηIT (52 ± 1%) values. Cerasmart had significantly higher CIT value (8.4 ± 0.1%) than all other materials tested, while Grandio Blocs and Lava Ultimate had the lowest ones. Spearman's correlation revealed that all mechanical properties tested exhibited correlations with each other, apart from ηΙΤ. CONCLUSIONS: The results showed that the CAD/CAM materials tested have differences in their microstructure, elemental composition and mechanical properties. CLINICAL SIGNIFICANCE: The RBCs tested showed significant differences in mechanical properties and thus differences in clinical performance are anticipated. RBCs with increased filler loading had the most favorable combination of hardness, elastic modulus and creep index indicating that these materials may have better clinical performance under intraoral loading conditions.

Effect of aging on color, gloss and surface roughness of CAD/CAM composite materials.

OBJECTIVES: To assess the effect of aging procedures on color, gloss and surface roughness of CAD/CAM composite materials. METHODS: 6 CAD/CAM composite materials (Brilliant CRIOS, Cerasmart, Lava Ultimate, Tetric CAD, Shofu Block HC, Grandio Blocs) were tested. 10 CAD/CAM fabricated specimens of each material polished according to manufacturers' recommendations, were subjected to one of the following aging procedures; immersion in coffee (30 days, 37οC), water thermocycling (5000 cycles, 5-55 °C) and photoaging (150,000 kJ/m2). Color, gloss and surface roughness measurements were performed before and after aging and the respective changes were calculated. Kruskal-Wallis tests, paired t-tests, one-way ANOVA and Bonferroni post-hoc tests were used for statistical analysis (a = 0.05). RESULTS: Color changes ranged from 3.03 to 4.13 after coffee immersion, from 1.33 to 2.55 after thermocycling and from 1.02 to 2.75 after photoaging. No statistically significant differences for ΔE*ab were found among materials after coffee immersion and thermocycling (p>0.05). Gloss changes ranged from -5.7 to -1.6 GU after coffee immersion, from -2.3 to 0.1 GU after thermocycling and from -4.4 to 0.5 GU after photoaging. No significant differences in gloss changes were found among materials after aging (p>0.05). Tetric CAD demonstrated the significantly lower gloss and the higher surface roughness after polishing. Except for gloss after thermocycling, aging procedures caused significant alteration of gloss and surface roughness parameters from baseline levels. CONCLUSIONS: Aging procedures caused perceptible but acceptable color changes and small but visible gloss changes, while surface roughness parameters of the tested CAD/CAM composite materials were significantly affected by aging. CLINICAL SIGNIFICANCE: Aging procedures affected CAD/CAM composite materials indicating that these materials may be prone to color and surface alterations in the oral environment that could compromise the esthetics and the performance of the restorations. Clinical studies are needed to investigate the long-term behavior of the newly introduced CAD/CAM materials.

The current state of computer assisted orthognathic surgery: A narrative review.

OBJECTIVES: Since cone beam computed tomography (CBCT) became available, research in the field of computer assisted orthognathic surgery (CAOS) is constantly on the rising. It is the purpose of the present paper to describe the use of the available digital technology in the workflow of CAOS and to provide insight on the advantages and limitations arising from the use of both hardware and software. STUDY SELECTION, DATA AND SOURCES: Systematic reviews, randomised controlled trials, prospective and retrospective clinical studies, case series and reports were consulted with search terms having been entered into PubMed, Google Scholar and the Cochrane database. RESULTS: There is evidence that supports the use of CAOS, which is based on the lack of time-consuming preparatory steps, more accurate treatment planning and overall, better surgical results. On the contrary, there is also evidence of increased need for training and of higher costs. CONCLUSIONS: The workflow of CAOS involves the acquisition of data which are manipulated to provide the virtual patient, the treatment planning with the appropriate software and the actual preparations for surgery. In case of a non-dynamically guided procedure, it also includes the 3d printing of surgical wafers, osteotomy guides and templates. Even though the native environment for any given surgical treatment planning is three-dimensional, several hurdles seem to impede the universal acceptance of CAOS amongst clinicians. CLINICAL SIGNIFICANCE: CAOS is a much desired yet sparsely employed practice for the correction of congenital, developmental or acquired pathologies in the dentomaxillofacial region. This paper addresses the small details in CAOS workflow towards an effective practice, and describes the advantages and limitations of the software and hardware currently in use.

Effect of Staining Solutions on Color Stability, Gloss and Surface Roughness of Removable Partial Dental Prosthetic Polymers.

PURPOSE: To assess the effect of commonly used solutions on color stability, gloss, and surface roughness of removable partial dental prostheses polymers. MATERIALS AND METHODS: Discs (n = 112) were made of a poly(etheretherketone) (PEEK) polymer, a polyamide, an acetal resin and a heat-cured poly(methylmethacrylate) PMMA acrylic resin polished according to manufacturers' instructions. Seven specimens of each material were immersed in coffee, red wine, coca cola and distilled water for 30 days at 37ο C. Changes of color (ΔΕ*) and color coordinates L*α*b* after immersion were calculated with a colorimeter. Changes in the values of gloss and surface roughness parameters (Sa, Sz, Str, Sdr, Sci, Svi) were also measured. Two-way ANOVA and pairwise comparisons were used to evaluate the effect of material and staining solution on parameter value alterations (α = 0.05). RESULTS: The two-way ANOVA revealed that the interaction between material and staining solution significantly affected color changes after immersion [F(9,96) = 44.67, p < 0.001]. PEEK presented the lowest color change (ΔΕ* = 3.83 ± 2) while polyamide had the highest color change overall (ΔΕ* = 14.59 ± 8.65) (p < 0.001). Coffee caused the highest color (ΔΕ* = 13.08 ± 6.98) and gloss changes (ΔG = -6.36 ± 19.2 GU) among different solutions (p < 0.001). PEEK showed the highest alteration of gloss (ΔG = -11.31 ± 15.49 GU), with significant difference with the other three materials (p < 0.001). Insignificant interaction of material and immersing solution was found for surface roughness parameters (p > 0.05). CONCLUSIONS: Among the materials tested, PEEK seemed to be the most stable material when subjected to common, everyday staining solutions. Therefore, PEEK could be a viable solution for an RPDP framework fabrication, expanding the material list of prosthetic options. Further research and clinical trials are required to confirm the above statement.

The direct digital workflow in fixed implant prosthodontics: a narrative review.

BACKGROUND: The purpose of this narrative review was to examine the applicability of IOS procedures regarding single and multiple fixed implant restorations. Clinical outcomes for monolithic zirconia and lithium disilicate restorations produced through a direct digital workflow were reported. METHODS: A MEDLINE (Pubmed) search of the relevant English-language literature spanning from January 1st 2015 until March 31st 2020 was conducted. In vitro studies comparing digital implant impression accuracy by different IOS devices or in vitro studies examining differences in accuracy between digital and conventional impression procedures were included. Also, RCTs, clinical trials and case series on the success and/or survival of monolithic zirconia and lithium disilicate restorations on implants, manufactured completely digitally were included. In vitro and in vivo studies reporting on restorations produced through an indirect digital workflow, case reports and non-English language articles were excluded. The aim was to investigate the accuracy of IOS for single and multiple fixed implant restorations compared to the conventional impression methods and report on the variables that influence it. Finally, this study aimed to report on the survival and success of fixed implant-retained restorations fabricated using the direct digital workflow. RESULTS: For the single and short-span implant sites, IOS accuracy was high and the deviations in the position of the virtual implant fell within the acceptable clinical limits. In the complete edentulous arch with multiple implants, no consensus regarding the superiority of the conventional, splinted, custom tray impression procedure compared to the IOS impression was identified. Moreover, complete-arch IOS impressions were more accurate than conventional, non-splinted, open or close tray impressions. Factors related to scanbody design as well as scanner generation, scanning range and interimplant distance were found to influence complete-arch scanning accuracy. Single implant-retained monolithic restorations exhibited high success and survival rates and minor complications for short to medium follow-up periods. CONCLUSIONS: The vast majority of identified studies were in vitro and this limited their clinical significance. Nevertheless, intraoral scanning exhibited high accuracy both for single and multiple implant restorations. Available literature on single-implant monolithic restorations manufactured through a complete digital workflow shows promising results for a follow-up of 3-5 years.

Clinical and Patient-Reported Outcomes of Single Posterior Implant-Supported Restorations Completed by Predoctoral Students: A Retrospective Study with Up to 10 Years of Follow Up.

PURPOSE: To assess clinical outcomes of screw-retained implant-supported restorations as well as patient satisfaction and Oral Health-related Quality of Life (OHQoL), when treatment is performed in an academic setting by supervised predoctoral students. MATERIALS AND METHODS: Ninety patients (n = 129 restorations) consented to participate in the study. The mean follow-up period was 4.2 years (range: 4 months to 10.6 years) after crown insertion. All patients filled out a modified Oral Health Impact Profile questionnaire, consisting of 14 questions (OHIP-14). A comprehensive examination of the implant-supported restoration was completed and restorative complications were recorded. Statistical analysis was performed using SPSS (IBM SPSS Statistics, v25; IBM Corp). Restoration survival rates were calculated using Kaplan-Meier survival analysis. RESULTS: The most frequent complication was loss of the mesial interproximal contact (32.2%). The overall restoration survival and success rates were 93.8% and 74.4%, respectively. The majority of patients (95.6%) reported high satisfaction with their decision to get implant treatment in the predoctoral clinic. CONCLUSIONS: In the context of this study, clinical and patient-based outcomes of implant treatment rendered in an academic setting are favorable and comparable to those reported in the literature for restorations completed by experienced dentists.

3D printed complete removable dental prostheses: a narrative review.

BACKGROUND: The purpose of this paper is to review the available literature on three-dimensionally printed complete dentures in terms of novel biomaterials, fabrication techniques and workflow, clinical performance and patient satisfaction. METHODS: The methodology included applying a search strategy, defining inclusion and exclusion criteria, selecting studies and forming tables to summarize the results. Searches of PubMed, Scopus, and Embase databases were performed independently by two reviewers to gather literature published between 2010 and 2020. RESULTS: A total of 126 titles were obtained from the electronic database, and the application of exclusion criteria resulted in the identification of 21 articles pertaining to printed technology for complete dentures. Current innovations and developments in digital dentistry have successfully led to the fabrication of removable dental prostheses using CAD/CAM technologies. Milled dentures have been studied more than 3D printed ones in the currently available literature. The limited number of clinical studies, mainly case reports, suggest current indications of 3D printing in denture fabrication process to be custom tray, record bases, trial, interim or immediate dentures but not definitive prostheses fabrication. Limitations include poor esthetics and retention, inability to balance occlusion and low printer resolution. CONCLUSIONS: Initial studies on digital dentures have shown promising short-term clinical performance, positive patient-related results and reasonable cost-effectiveness. 3D printing has potential to modernize and streamline the denture fabrication techniques, materials and workflows. However, more research is required on the existing and developing materials and printers to allow for advancement and increase its application in removable prosthodontics.

The use of PEEK in digital prosthodontics: A narrative review.

BACKGROUND: Advanced computer-aided design and computer-aided manufacturing (CAD-CAM) technology led to the introduction of an increasing number of machinable materials suitable for dental prostheses. One of these materials is polyetheretherketone (PEEK), a high performance polymer recently used in dentistry with favorable physical, mechanical and chemical properties. The purpose of this study was to review the current published literature on the use of PEEK for the fabrication of dental prostheses with CAD-CAM techniques. METHODS: Electronic database searches were performed using the terms "PEEK", "CAD-CAM", "dental", "dentistry" to identify studies related to the use of PEEK for the fabrication of CAD-CAM prostheses. The search period spanned from January 1990 through February 2020. Both in vivo and in vitro studies in English were eligible. Review articles and the references of the included publications were searched to identify relevant articles. RESULTS: A great number of in vitro studies are available in the current literature pointing out the noticeable properties of PEEK. The use of PEEK has been recommended for a wide range of CAD-CAM fabricated fixed and removable dental prostheses. PEEK was additionally recommended for occlusal splints, intra-radicular posts, implant abutments, customized healing abutments and provisional restorations. However, only a few clinical studies were identified. CONCLUSIONS: PEEK could be considered as a viable alternative for CAD-CAM fixed and removable dental prostheses to well-established dental materials. Due to the scarcity of clinical data, clinical trials are needed to assess the long-term performance of PEEK prostheses.

Immediate loading of occluding definitive partial fixed prostheses vs non-occluding provisional restorations - 3-year post-loading results from a pragmatic multicentre randomised controlled trial.

PURPOSE: To compare the clinical outcome of dental implants restored with definitive occluding partial fixed prostheses within 1 week after implant placement with immediate non-occluding provisional restorations to be replaced by definitive prostheses after 4 months. MATERIALS AND METHODS: Forty partially edentulous patients treated with one to three dental implants, at least 8.5 mm long and 4.0 mm wide, inserted with a torque of at least 35 Ncm, were randomised in two groups of 20 patients each, to be immediately loaded with partial fixed prostheses. Patients in one group received one definitive screw-retained, metal-ceramic prosthesis in occlusion within 1 week after placement. Patients in the other group received one non-occluding provisional acrylic reinforced prosthesis within 24 h of implant placement. Provisional prostheses were replaced by definitive ones after 4 months. The follow-up for all patients was 3 years post-loading. Outcome measures were prosthesis and implant failures, any complications, peri-implant marginal bone level changes, aesthetic evaluation by a dental practitioner, patient satisfaction, chair time and number of visits at the dental office from implant placement to delivery of definitive restorations. RESULTS: Three patients dropped out, one from the non-occlusal group and two from the occlusal group. Two immediately occlusally loaded implants with their related definitive prostheses failed early (difference in proportions = 0.10; 95% CI = -0.03 to 0.23; P = 0.488). Five patients from the occlusally loaded group were affected by six complications vs three patients (three complications) in the non-occlusally loaded group. The difference in proportions was not statistically significant (difference in proportions = 0.08; 95% CI = -0.17 to 0.34; P = 0.697). Three years after loading, patients subjected to occlusal loading lost an average of 1.13 mm of peri-implant bone vs 1.03 mm of patients restored with non-occluding definitive partial fixed prostheses. There were no statistically significant differences for marginal bone level changes between the two groups (mean difference = 0.10 mm; 95% CI -0.62 to 0.82; P = 0.779). No significant were the differences for pink aesthetic scores (7.09 vs 6.90; P = 0.873); for aesthetics evaluated by patients (Mann-Whitney U test P = 0.799) and function satisfaction (Mann-Whitney U test P = 0.578). Significantly less chair time (mean difference -38.00; 95% CI -58.96 to -17.04; P = 0.001) and number of visits (mean difference -2.15; 95% CI -2.77 to -1.53; P < 0.001) were required for the immediate definitive prosthesis group. CONCLUSIONS: This study did not provide a conclusive answer, but suggests that immediate occlusal loading by manufacturing immediate definitive partial fixed prostheses decreases chair time and number of visits.

Osseointegration of Dental Implants in a Patient with Hajdu-cheney Syndrome.

BACKGROUND: Hajdu-Cheney Syndrome (HCS) is a rare hereditary bone metabolism disorder characterized by acro-osteolysis, short stature, craniofacial changes, periodontitis and premature tooth loss. Extensive search of the current literature revealed no reports of implant placement in patients with HCS. CASE REPORT: A 22-year old woman with osteoporosis, generalized advanced chronic periodontitis and premature tooth loss was referred to the Postgraduate Clinic of Periodontology, University of Athens-Greece. The patient was diagnosed in 2001 with HCS. The patient received non-surgical periodontal treatment and several teeth were extracted due to extensive alveolar bone loss. After careful consideration of the possible implications deriving from the patient's condition and having taken her young age into account, initially, a dental implant was placed in the upper right first premolar region. Specific protocols such as longer healing periods were implemented, so five years after placement and successful osseointegration of this implant, four additional dental implants were placed in the posterior regions of the maxilla and the mandible. Prosthetic rehabilitation followed 6 months after implant placement. Upon completion of periodontal treatment, the patient was enrolled in a periodontal maintenance program. RESULTS: Clinical and radiographic examination of the patient during the periodontal maintenance program after implant placement revealed no abnormalities in the implant region. CONCLUSION: Patients with HCS suffer from periodontitis, bone destruction and premature tooth loss. This case indicates the successful osseointegration of dental implants in patients with HCS. However, further research is required in order to determine the predictability of dental implant placement in those patients.

Immediate occluding definitive partial fixed prosthesis versus non-occluding provisional restorations - 4-month post-loading results from a pragmatic multicenter randomised controlled trial.

PURPOSE: To compare the clinical outcome of dental implants restored with definitive occluding partial fixed prostheses within 1 week, after implant placement with immediate non-occluding provisional restorations, which were to be replaced by definitive prostheses after 4 months. MATERIALS AND METHODS: Fifty partially edentulous patients treated with one to three dental implants, at least 8.5 mm long and 4.0 mm wide inserted with a torque of at least 35 Ncm, were randomised in two groups of 25 patients each, to be immediately loaded with partial fixed prostheses. Patients of one group received one definitive screw-retained metal-ceramic prosthesis in occlusion within 1 week after placement. Patients of the other group received one non-occluding provisional acrylic reinforced prosthesis within 24 h after implant placement. Provisional prostheses were replaced after 4 months by definitive ones. The follow-up for all patients was 4-months post-loading. Outcome measures were prosthesis and implant failures, any complications, peri-implant marginal bone level changes, aesthetic evaluation by a clinician, patient satisfaction, chair time and number of visits at the dental office from implant placement to delivery of definitive restorations. RESULTS: No patient dropped out. Two immediately occlusally loaded implants with their related definitive prostheses (8%) failed early (difference in proportions = 0.08; 95% CI: -0.03 to 0.19; P = 0.490). Four complications occurred in the occlusal group versus one in the non-occlusal group; (difference in proportions = 0.12; 95% CI: -0.04 to 0.28; P = 0.349). Four months after loading, patients subjected to non-occlusal loading lost an average of 0.72 mm of peri-implant bone versus 0.99 mm of patients restored with occluding definitive partial fixed prostheses. There were no statistically significant differences for marginal bone level changes between the two groups (mean difference = -0.27 mm; 95% CI: -0.84 to 0.30; P = 0.349). The differences for aesthetic scores showed no statistical significance (8.26 versus 7.58; P = 0.445); the same was seen for aesthetics evaluated by patients (Mann-Whitney U test: P = 0.618). Patients in the non-occlusal group were significantly more satisfied with the function of their implant-supported prostheses (Mann-Whitney U test: P = 0.039). Significantly less chair time (mean difference = -28.4 min; 95% CI: -48.82 to -7.99; P = 0.007) and the number of visits (mean difference = -1.88; 95% CI: -2.43 to -1.33; P < 0.001) were required for the immediate definitive prosthesis group. CONCLUSION: This study did not provide a conclusive answer but may suggest that provisional prostheses non-occlusally immediately loaded may increase patient functional satisfaction, chair time and the number of visits, with respect to definitive prostheses immediately loaded in functional occlusion.

Composition, phase analysis, biaxial flexural strength, and fatigue of unshaded versus shaded Procera zirconia ceramic.

STATEMENT OF THE PROBLEM: Recent interest in shaded zirconia has raised questions about the relative stability of the tetragonal phase after colorant oxide additions. PURPOSE: The purpose of this in vitro study was to evaluate the effects of fatigue cycling on the stability of a commercially available dental zirconia (Procera) in both unshaded and shaded compositions by measuring the change in biaxial flexural strength (BFS) after 500 000 cycles at 80-N loads and in phase composition as detected by x-ray diffraction (XRD). MATERIAL AND METHODS: Partially stabilized zirconia disks (NobelProcera) were fabricated in unshaded and shaded forms (12 mm diameter × 0.8 mm thick). Specimens were analyzed by energy-dispersive x-ray spectroscopy (EDS) and by wavelength-dispersive x-ray spectroscopy (WDS) for oxide compositions which indicated the presence of small amounts of Fe-O (0.13 ±0.10 wt %) in the shaded specimens. XRD focused on the tetragonal (T) and monoclinic (M) peaks in the 20 to 40 degrees 2θ range. The disks were polished on 1 side, cyclically loaded (80N, 500 000 cycles, custom 4-station fatigue test machine), and tested for residual BFS after cycling. Unshaded (U) and shaded groups (S) were compared before (U1, S1) and after (U2, S2) load cycling with XRD and residual BFS. RESULTS: Residual BFS (MPa) for specimens before (U1=856 ±99 versus S1= 842 ±40) and after fatigue (U2=772 ±65 versus S2= 718 ±68) were statistically different (U1 versus U2; S1 versus S2; U2 versus S2, P<.05). The XRD of U1 and S1 specimens revealed tetragonal and cubic zirconia. U2 and S2 specimens contained tetragonal zirconia, with the initial appearance of small amounts of monoclinic zirconia after fatigue cycling. Monoclinic detection was measured on the tension side of the tested specimens and varied between tests at the center and radially at 4 mm. CONCLUSIONS: The results indicated shaded materials more readily transform the tetragonal to the monoclinic phase during load cycling than unshaded ones. However, extrapolating the effects of any shortening of the service life of zirconia compositions is difficult. The potential mitigating effects of other factors such as the thermal postprocessing of porcelain veneers, stains on zirconia, or effects of water have yet to be investigated.

Cyclic Loading Effect on Color Stability of Unshaded versus Shaded Zirconia.

STATEMENT OF PROBLEM: Shaded versions of dental zirconia may improve initial color matching to teeth, but might change color with cyclic mechanical loading. PURPOSE: The purpose of this study was to measure the color of unshaded and shaded zirconia dental ceramic before and after cyclic mechanical loading and calculate color differences (ΔE). MATERIAL AND METHODS: Disk-shaped specimens (N = 30, Nobel Procera, 0.8 mm thick, 12 mm diameter) of unshaded or shaded zirconia (intrinsically shaded by small oxide modifications) were fabricated by the Nobel Biocare using standard CAD-CAM processing. Milled surfaces were polished. CIE L*a*b* values were measured (Konica Minolta spectrophotometer) before and after mechanical cycling (custom modified Leinfelder test machine, biaxial flexure loading, load = 80 N × 500,000 cycles, dry), and L*a*b* individual differences and ΔE color differences were calculated and compared (ANOVA, p < 0.05). RESULTS: Mean L*a*b* values for the unshaded group before (U1 = 86.165, -0.887, 0.372) and after (U2 = 84.860, -0.805, 0.097) cyclic loading were compared to the shaded group before (S1 = 75.281, -0.679, 23.251) and after (S2 = 74.961, -1.233, 22.439) cyclic loading. All color variables for both unshaded and shaded groups were significantly different between before and after cyclic loading (p < .004) except for the L* value of the shaded group. The ΔE for unshaded (1.441 ± 0.495) versus shaded (1.252 ± 0.363) were statistically different but clinically the change would not be detectable at this point. CONCLUSIONS: The color of the unshaded and shaded zirconia specimens was influenced by cyclic loading (p < 0.05). Color changes were detectable but small at levels up to 500,000 cycles, and remained clinically acceptable at that point. CLINICAL SIGNIFICANCE: It is important to acknowledge any possible color changes that might occur in zirconia restorations, especially in the esthetic zone. Minor color changes that are individually imperceptible to the human eye within different restorative components may be compounded to produce clinically significant color change that is not aesthetically acceptable.

Hardness Changes of Tissue Conditioners in Various Storage Media: An in Vitro Study.

The aim of the present study was to evaluate the effects of storage media on the longitudinal hardness changes of tissue conditioning materials. Four tissue-conditioning materials were used for fabrication of 80 disc-shaped specimens and divided in four groups, stored in four storage media. The specimens underwent artificial ageing corresponding to 30 nights of extra-oral storage. Hardness measurements were obtained at nine intervals between 8 and 240 hours after specimen fabrication. To test the effects of storage media on hardness we employed multivariate modelling (Bonferroni correction; α = 0.05). The materials exhibited varying hardness changes, most pronounced when stored in ambient air.

Matching repeatability and interdevice agreement of 2 intraoral spectrophotometers.

STATEMENT OF PROBLEM: The visual determination of tooth color with standard shade guides is a subjective method of color communication, depending on variables such as the light source, the operator, and the tooth. The assessment of tooth color may be improved by the use of special devices such as colorimeters or spectrophotometers. However, the repeatability and the interdevice agreement of these devices have not been thoroughly investigated. PURPOSE: The purpose of this study was to evaluate the effect of different illuminants (natural daylight, dental unit lamp, and daylight lamp) on the matching repeatability of 2 intraoral spectrophotometers (Easyshade and SpectroShade). MATERIAL AND METHODS: The maxillary right central incisor and canine and the mandibular left central incisor of each of 10 dental students were measured by a single operator using both devices. The color of each tooth was assessed 3 times with each device under each of the 3 different illuminants (natural daylight, a dental unit lamp, and a daylight lamp). The device readings were expressed in Vitapan 3D-Master shade codes. Statistical analysis was performed and the level of agreement was assessed with the Spearman Correlation Coefficient. RESULTS: A particularly high to moderate level of agreement among the readings made under natural daylight, a dental unit lamp, and a daylight lamp was observed for both devices (P<.01), suggesting that their matching repeatability was not completely satisfactory for clinical practice. A moderate and a moderate to high level of agreement was found among Easyshade readings when the 3 different illuminants were used. The level of agreement for the respective SpectroShade readings was particularly high to high (P<.001). A particularly low level of agreement was found among the respective Easyshade and SpectroShade readings performed under any of the illuminants tested (P<.05), suggesting poor interdevice reliability. CONCLUSIONS: The matching repeatability of both devices under natural daylight, a dental unit lamp, and a daylight lamp was not completely satisfactory for clinical practice. The effects of different illuminants seem to be more pronounced for Spectroshade than for Easyshade. The interdevice agreement between the 2 devices tested was poor, suggesting that the 2 devices were not compatible.

Presentation of two cases of immediate restoration of implants in the esthetic region, using facilitate software and guides with stereolithographic model surgery prior to patient surgery.

Improvements in both implant microsurfaces and placement techniques have reduced healing time and increased survival rates. CAD/CAM technology and improved ceramic materials allow for achievement of improved esthetics at the implant restoration level. Two clinical procedures have the capacity to decrease patient postoperative discomfort and improve esthetics. Flapless surgery reduces surgical trauma and postoperative problems. Placement of the final prosthetic abutment at the time of implant placement stabilizes soft tissue adhesion and position to the implant. Both results require careful presurgical planning with precise implant and abutment placement. This is a clinical report of two cases that are part of a larger ongoing clinical trial of 20 patients. The inclusion criterion was that patients should be missing a single tooth in the esthetic zone. Facilitate™ software was used in conjunction with dicom files transferred from CT scans for diagnosis. Stereolithographic models and surgical guides were fabricated from the digital information. Surgical guides were used preoperatively so implant replicas could be placed in stereolithographic models as simulated surgery. A ZirDesign™ ceramic abutment was adapted on the model, and a provisional crown was fabricated. At the time of actual implant surgery, the same surgical guide was used with a flapless approach. The previously modified ceramic abutment was screw-retained and torqued to place into the implant. The provisional crown was then cemented after blocking out the screw access hole. A final restoration was fabricated from all-ceramic material after several months. Success requires careful patient selection and attention to each step of the technique. Preliminary outcomes from the ongoing clinical trial are promising.

Prosthodontic treatment of a class IV ACP PDI patient, with Langerhans cell histiocytosis (LCH).

Langerhans cell histiocytosis (LCH) is a disease of unknown etiology with a frustrating and unpredictable course. Surviving adult patients suffering from the multisystem type of the disease present with problems in most organs. This article presents the oral rehabilitation of a 28-year-old patient, with multisystem sequelae that included the oral cavity, classifying him as a Class IV American College of Prosthodontists Prosthodontic Diagnostic Index patient. A 5-year course of treatment is analyzed, starting from merely replacing missing teeth with a removable partial denture. The second stage of prosthetic rehabilitation included replacement of the removable prosthesis with fixed partial dentures. The final and most important aspect of treatment was the 2-year follow-up, when the patient presented with no problems or adverse effects. The purpose of this presentation is to offer an insight to prosthodontic treatment possibilities for patients suffering from multisystem LCH and to show the value of a "team approach" to achieving a positive outcome.

Fabrication of a fixed provisional implant restoration. A report of three cases.

A clinical problem for patients with posterior partial edentulism who are going to be treated with dental implants is provisionalization during the period of soft and hard tissues preparation, the period of osseointegration and construction of the final restoration. Up to now, the available solutions were either the construction of a removable prosthesis or immediate loading of implants. The purpose of this article is to present an alternative technique for fabricating a fixed provisional restoration in patients with posterior partial edentulism. It is referred to as a teeth-tissue supported restoration which retention and support is provided from prepared or unprepared teeth while support also is gained from the maxillary tubercles or the retromolar pads of the upper and lower jaws.

Intrasurgical implant position transfer and interim restoration placement.

In the esthetic zone, the placement of an interim prosthesis is an important stage in implant treatment for gingival contouring. This article presents a simple procedure for making an intraoperative implant position transfer to construct an interim prosthesis with optimal shape and emergence profile. This prosthesis, inserted at stage II surgery, guides soft tissue healing and aids in the fabrication of a definitive prosthesis with optimal gingival contours.

Three-dimensional computerized stress analysis of commercially pure titanium and yttrium-partially stabilized zirconia implants.

PURPOSE: The purpose of this study was to use three-dimensional finite element analysis to analyze stress distribution patterns in Re-Implant implants made of commercially pure titanium (cpTi) and yttrium-partially stabilized zirconia (YPSZ). MATERIALS AND METHODS: Two three-dimensional finite element analysis models of a maxillary incisor with Re-Implant implants were made, surrounded by cortical and cancellous bone. A porcelain-fused-to-metal crown for the cpTi implant and a ceramic crown for the YPSZ implant were modeled. Stress levels were calculated according to the von Mises criteria. RESULTS: Higher stresses were observed at the area where the implant entered the bone. Stresses were higher at the facial and lingual surfaces than the proximal ones. In cortical bone and at the junction of cortical and cancellous bone, stress distribution presented a pattern of alternating higher (4.0 to 5.0 MPa) and lower (1.3 to 2.0 MPa) stress areas. Higher stresses were found at the apical third of the implant-to-bone junction as well. CONCLUSION: Re-Implant implants presented a pattern of low, well-distributed stresses along the entire implant-to-bone interface. YPSZ implants had very similar stress distribution to cpTi implants and may be viable esthetic alternatives, especially in maxillary anterior regions.