Tooth preservation vs. extraction and implant placement in periodontally compromised patients: A systematic review and analysis of studies.

PURPOSE: The aim of this systematic review was to identify studies with a minimum of 5-years follow-up, reporting on the management of periodontally compromised teeth with either extraction and subsequent implant placement or teeth preservation with conventional periodontal treatment and application of regenerative procedures. The outcomes of these two approaches, based on clinical and radiographic data and the incidence of tooth- and implant-loss, were also investigated. MATERIAL AND METHODS: A systematic search for studies reporting on clinical and radiographic outcomes of periodontal treatment or replacement of periodontally compromised teeth with implants was conducted in 3 electronic databases, followed by a hand-search in 8 journals. Only randomized controlled trials (RCTs), cohort studies, and case series with prospective design were included. RESULTS: The initial search resulted in 1080 papers. After the first two screenings, 24 publications were selected for inclusion in this systematic review. The treatment protocols for the teeth preservation group contained nonsurgical and/or surgical periodontal treatment with or without regeneration procedures. The implant studies included extraction of periodontally involved teeth and implant placement with or without bone and soft tissue augmentation, followed by restoration with fixed dental prostheses (FDPs). Survival rates ranged between 81.8% and 100% in the tooth retention group, and between 94.8% and 100% in the implant group. In the extraction group, no complications were reported for 76.09% of the implants. Similarly, no complications were reported for 86.83% of the tooth retention group. The lack of standardized comparable studies prohibited conduction of a metaanalysis. CONCLUSION: Both treatment approaches, treatment of periodontally compromised teeth, or tooth extraction followed by implant placement, present high survival rates. The application of bone regeneration techniques improves the long-term prognosis of periodontally involved teeth. Hence, treatment of periodontally involved teeth with subsequent application of a rigorous maintenance protocol can be a viable alternative for a number of years, before proceeding to extraction and replacement with dental implants. More well-designed randomized controlled trials are needed in order to draw definite conclusions on the subject.

A 3D printing replication technique for fabricating digital dentures.

Digitally fabricated dentures allow clinicians to provide new prostheses for edentulous patients in an efficient manner. One approach uses a replication technique where a prosthesis in need of minor alterations is used as a basis for the definitive prosthesis. Compared with conventional duplication techniques, this method allows for the predictable fabrication of accurate dentures in less time and with increased quality. In this clinical report, interim treatment dentures were scanned and 3D printed to make a replication denture for fabrication of a digital prosthesis with the replication technique.

Association Between Increased Concavity of Maxillary Labial Alveolar Bone and Decreased Labial Cortical Bone Thickness: A Cone Beam Computed Tomography Aided Retrospective Cohort Study.

PURPOSE: To assess whether an increased concavity of maxillary labial alveolar bone is related to labial thickness of cortical bone in that area and to the presence of extraoral manifestations in the philtrum. MATERIALS AND METHODS: Cone beam computed tomography images along with intra- and extraoral photographic images of 50 Caucasian female patients, age range 18 to 65 years (mean: 37 years), previously evaluated for implant treatment were assessed by three experienced prosthodontists. Patients were divided into two groups (A and B), according to the presence or absence of a horizontal groove at the philtrum area. Mann-Whitney U test (α = 0.05) was performed to reveal any statistical differences regarding the angle of the maxillary labial concavity and the labial thickness of the alveolar cortical bone between the two groups. RESULTS: The mean angle of the maxillary concavity in group A was 127.76° while in group B it was 137.12°. The mean thickness of the labial cortical wall of the dental, interdental, and edentulous areas of the 8 anterior teeth for group A were: 0.41 mm, 0.61 mm, and 0.46 mm, respectively; and for group B were: 0.52 mm, 0.72 mm, and 0.56 mm, respectively. The Mann-Whitney U test (α = 0.05) revealed a statistically significant difference for both the angle (p = 0.008) but not for the thickness of the bone (p = 0.062). CONCLUSIONS: According to the results of this study an increased maxillary labial concavity was associated with reduced thickness of the labial cortical wall and the presence of a horizontal groove at the philtrum area.

Complications and survival rates of inlays and onlays vs complete coverage restorations: A systematic review and analysis of studies.

OBJECTIVE: The aim of this study was to identify if different types of indirect restorations used for single teeth had different biological and technical complications, as well as survival rates. METHOD: An electronic search was performed in various electronic databases to identify articles, published between 1980 and 2017. The search terms were categorised into 4 groups: inlay, onlay, inlay/onlay and crown. Manual searches of published full-text articles and related reviews were also performed. RESULTS: A total number of 2849 papers were retrieved initially. After a detailed assessment for eligibility, 9 studies were selected for inclusion. The heterogeneity of the studies did allow neither a meta-analysis nor any meaningful comparison between types of restorations or materials. Only some pooling was performed for representative reasons. The mean survival rate of inlays was 90.89%, while for onlays and crowns it was 93.50% and 95.38%, respectively. For the fourth study group, consisting of both inlays and onlays, the survival rate was found to be 99.43%. Statistical analysis demonstrated caries to be the main biological complication for all types of restorations, followed by a root and/or tooth fracture incidence (11.34%) and endodontic incidence. Ceramic fractures represented the most common technical complication, followed by loss of retention and porcelain chipping. CONCLUSION: The 5-year survival rate for crowns and inlays/onlays is very high, exceeding 90%. An association between the kind of complications and different types of restorations could not be established. Nevertheless, a relatively high failure rate due to caries and ceramic fractures was noted.

[Metastatic Brain Tumor from Lung Adenocarcinoma Presenting a Unique Radiographic Pattern during Afatinib Treatment:A Case Report].

Epidermal growth factor receptor-tyrosine kinase inhibitors(EGFR-TKIs)are used as first-line treatment for patients with EGFR-mutated non-small cell lung cancer(NSCLC). Afatinib, a second-generation EGFR-TKI, is also effective against central nervous system(CNS)metastasis of NSCLC. However, patients treated with EGFR-TKI for many months may be at an increased risk of CNS metastasis due to the development of resistance in tumor cells to EGFR-TKI. The average period for development of resistance to EGFR-TKI is 8 to 10 months after the initiation of treatment. In the case presented herein, NSCLC showed a good clinical course in the 10 months following the initiation of afatinib;however, CNS metastasis progressed and presented unique findings on MR images. The lesions consisted of multiple cyst-like masses without gadolinium enhancement in the cerebellum and brain stem. The patient died within 2 months of the diagnosis of CNS metastasis. The resistance of tumor cells to afatinib may have occurred in the 10 months following the initiation of the treatment. Thus, CNS metastasis of NSCLC treated with afatinib may develop over a period of many months, exhibiting unique MRI findings, and deteriorate rapidly in some cases.

Full-arch implant fixed prostheses: a comparative study on the effect of connection type and impression technique on accuracy of fit.

PURPOSE: The aim of this study was to assess the effect of connection type and impression technique on the accuracy of fit of implant-supported fixed complete-arch dental prostheses (IFCDPs). MATERIALS AND METHODS: An edentulous mandibular cast with five implants was fabricated to serve as master cast (control) for both implant- and abutment-level baselines. A titanium one-piece framework for an IFCDP was milled at abutment level and used for accuracy of fit measurements. Polyether impressions were made using a splinted and non-splinted technique at the implant and abutment level leading to four test groups, n = 10 each. Hence, four groups of test casts were generated. The impression accuracy was evaluated indirectly by assessing the fit of the IFCDP framework on the generated casts of the test groups, clinically and radiographically. Additionally, the control and all test casts were digitized with a high-resolution reference scanner (IScan D103i, Imetric, Courgenay, Switzerland) and standard tessellation language datasets were generated and superimposed. Potential correlations between the clinical accuracy of fit data and the data from the digital scanning were investigated. To compare the accuracy of casts of the test groups versus the control at the implant and abutment level, Fisher's exact test was used. RESULTS: Of the 10 casts of test group I (implant-level splint), all 10 presented with accurate clinical fit when the framework was seated on its respective cast, while only five of 10 casts of test group II (implant-level non-splint) showed adequate fit. All casts of group III (abutment-level splint) presented with accurate fit, whereas nine of 10 of the casts of test group IV (abutment-level non-splint) were accurate. Significant 3D deviations (P < 0.05) were found between group II and the control. No statistically significant differences were found between groups I, III, and IV compared with the control. Implant connection type (implant level vs. abutment level) and impression technique did affect the 3D accuracy of implant impressions only with the non-splint technique (P < 0.05). CONCLUSION: For one-piece IFCDPs, the implant-level splinted impression technique showed to be more accurate than the non-splinted approach, whereas at the abutment-level, no difference in the accuracy was found.

Effect of different dental ceramic systems on the wear of human enamel: An in vitro study.

STATEMENT OF PROBLEM: The wear of tooth structure opposing different advanced dental ceramic systems requires investigation. PURPOSE: The purpose of this in vitro study was to compare the wear of advanced ceramic systems against human enamel antagonists. MATERIAL AND METHODS: Four ceramic systems (IPS e.max Press, IPS e.max CAD, Noritake Super Porcelain EX-3, and LAVA Plus Zirconia) and 1 control group containing human enamel specimens were used in this study (n = 12). All specimens were fabricated as disks 11 mm in diameter and 3 mm thick. The mesiopalatal cusps of the maxillary third molars were prepared to serve as the enamel styluses. All specimens were embedded individually in 25 mm(3) autopolymerizing acrylic resin blocks. Wear was measured with a cyclic loading machine and a newly designed wear simulator. All enamel styluses (cusps) were scanned using the Activity 880 digital scanner (SmartOptics). Data from the base line and follow-up scans were collected and compared with Qualify 2012 3-dimensional (3D) and 2D digital inspection software (Geomagic), which aligned the models and detected the geometric changes and the wear caused by the antagonist specimen. One-way ANOVA was used to analyze the collected data. RESULTS: After 125,000 bidirectional loading cycles, the mean loss of opposing enamel volume for the enamel disks in the control group was 37.08 µm(3), the lowest mean value for IPS e.max Press system was 39.75 µm(3); 40.58 µm(3) for IPS e.max CAD; 45.08 µm(3) for Noritake Super Porcelain EX-3 system; and 48.66 µm(3) for the Lava Plus Zirconia system. No statically significant differences were found among the groups in opposing enamel volume loss (P=.225) or opposing enamel height loss (P=.149). In terms of opposing enamel height loss, Lava Plus Zirconia system showed the lowest mean value of 27.5 µm. The mean value for the IPS e.max CAD system was 27.91 µm; 29.08 µm for the control enamel; 33.25 µm for the IPS e.max Press system; and 34.75 µm for the Noritake Super Porcelain EX-3 system. CONCLUSIONS: Within the limitations of this in vitro study, no differences were found in the linear and volumetric reduction of enamel cusps abraded against enamel disks and all other ceramic specimens. All ceramic systems exhibited high durability and were wear-friendly to opposing enamel.

A new cell-free bandage-type artificial skin for cutaneous wounds.

Engineered skin substitutes are widely used in skin wound management. However, no currently available products satisfy all the criteria of usability in emergency situations, easy handling, and minimal scar formation. To overcome these shortcomings, we designed a cell-free bandage-type artificial skin, named "VitriBand" (VB), using adhesive film dressing, silicone-coated polyethylene terephthalate film, and collagen xerogel membrane defined as a dried collagen vitrigel membrane without free water. We analyzed its advantages over in-line products by comparing VB with hydrocolloid dressing and collagen sponge. For evaluation, mice inflicted with full-thickness skin defects were treated with VB, hydrocolloid dressing, and collagen sponge. A plastic film group treated only with adhesive film dressing and silicone-coated polyethylene terephthalate film, and a no treatment group were also compared. VB promoted epithelization while inhibiting the emergence of myofibroblasts and inflammation in the regenerating tissue more effectively than the plastic film, hydrocolloid dressing, and collagen sponge products. We have succeeded in establishing a cell-free bandage-type artificial skin that could serve as a promising first-line medical biomaterial for emergency treatment of skin injuries in various medical situations.

Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique.

STATEMENT OF PROBLEM: The accuracy of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) restorations is questionable, and the effect of the die spacer settings is not well stated in the literature. PURPOSE: The purpose of the study was to evaluate the marginal and internal adaptation of E4D crowns fabricated with different spacer thicknesses and to compare these crowns with those fabricated with the heat-press technique. MATERIAL AND METHODS: The E4D system was used to fabricate 30 crowns for the first 3 groups, with different spacer thickness settings: 30 µm, 60 µm, and 100 µm. In the fourth group, 10 lithium disilicate crowns were fabricated with the heat-press technique. The occlusal gap, axial gap, vertical marginal gap, and absolute marginal discrepancy were evaluated by x-ray microtomography. Statistical significance was assessed with the Kruskal-Wallis test (α=.05). For post hoc analyses, the Mann-Whitney U test was used alongside the Bonferroni correction for multiple comparisons (α=.008). RESULTS: Within the CAD/CAM groups, the 30-µm spacer thickness resulted in the lowest median axial gap (90.04 µm), whereas the 60-µm spacer thickness resulted in the lowest median occlusal gap (152.39 µm). The median marginal gap values of the CAD/CAM-60 group (49.35 µm) and CAD/CAM-100 group (46.65 µm) were lower than those of the CAD/CAM-30 group (55.18 µm). No significant differences among the CAD/CAM groups were observed for absolute marginal discrepancy. The heat-press group had significantly different values than those of the CAD/CAM groups. CONCLUSION: The spacer thickness and fabrication technique affected the adaptation of ceramic crowns. The heat-press group yielded the best marginal and internal crown adaptation results. The 30- or 60-µm spacer settings are recommended for the E4D CAD/CAM system.

Conversion of an existing metal ceramic crown to an interim restoration and nonfunctional loading of a single implant in the maxillary esthetic zone: A clinical report.

Implant placement and immediate placement of an interim restoration can be a safe therapeutic approach with high survival rates. The technique is often used in the anterior esthetic area because of the better preservation of the periimplant soft tissue contours. Traditionally this procedure involves the fabrication of an acrylic resin implant-supported interim restoration. This clinical report describes the modification of an existing metal ceramic crown to be used as an implant-supported interim restoration for immediate nonfunctional loading to achieve an improved esthetic result and optimal support of the adjacent soft tissues.

Marginal adaptation of four inlay casting waxes on stone, titanium, and zirconia dies.

STATEMENT OF PROBLEM: Different inlay casting waxes do not produce copings with satisfactory marginal accuracy when used on different die materials. PURPOSE: The purpose of this study was to evaluate the marginal accuracy of 4 inlay casting waxes on stone dies and titanium and zirconia abutments and to correlate the findings with the degree of wetting between the die specimens and the inlay casting waxes. MATERIAL AND METHODS: The inlay casting waxes tested were Starwax (Dentaurum), Unterziehwachs (Bredent), SU Esthetic wax (Schuler), and Sculpturing wax (Renfert). The marginal opening of the waxes was measured with a stereomicroscope on high-strength stone dies and on titanium and zirconia abutments. Photographic images were obtained, and the mean marginal opening for each specimen was calculated. A total of 1440 measurements were made. Wetting between die materials and waxes was determined after fabricating stone, titanium, and zirconia rectangular specimens. A calibrated pipette was used to place a drop of molten wax onto each specimen. The contact angle was calculated with software after an image of each specimen had been made with a digital camera. Collected data were subjected to a 2-way analysis of variance (α=.05). Any association between marginal accuracy and wetting of different materials was found by using the Pearson correlation. RESULTS: The wax factor had a statistically significant effect both on the marginal discrepancy (F=158.31, P<.001) and contact angle values (F=68.09, P<.001). A statistically significant effect of the die material factor both on the marginal adaptation (F=503.47, P<.001) and contact angle values (F=585.02, P<.001) was detected. A significant correlation between the marginal accuracy and the contact angle values (Pearson=0.881, P=.01) was also found. CONCLUSIONS: Stone dies provided wax copings with the best marginal integrity, followed by titanium and zirconia abutments. Unterziehwachs (Bredent), wax produced the best marginal adaptation on different die materials. A significant correlation was found between the marginal accuracy and the contact angle values. As the contact angle value became smaller, the marginal accuracy improved. All combinations of waxes and stone and titanium dies presented a high wettability.

The effect of different implant-abutment connections on screw joint stability.

Dental implants with an internal connection have been designed to establish a better stress distribution when lateral external forces act on the prosthesis and minimize the forces transmitted to the fastening screw. In the present study, 10 externally and 10 internally hexed implants were tested with a compressive force applied with an Instron Universal machine. Four cycles of loading-unloading were applied to each specimen to achieve displacements of 0.5, 1, 2, and 2.5 mm. The mean loads for the first cycle were 256.70 N for the external connection and 256 N for the internal connection implants. The independent t test did not reveal any significant differences among the 2 tested groups (P = .780). For the second cycle, the mean loads needed for a displacement of 1 mm were 818.19 N and 780.20 N for the external connection and the internal connection implants, respectively. The independent t test revealed significant differences among the 2 tested groups (P < .001). In the third cycle, the mean load values for a 2-mm displacement were 1394.10 N and 1225.00 N. The independent t test revealed significant differences among the 2 tested groups (P < .001). The mean loads for the fourth cycle were 1488.00 N for the external connection and 1029.00 N for the internal connection implants. These loads were required for a displacement of 2.5 mm. The independent t test revealed significant differences among the 2 tested groups (P < .001). The results of this in vitro study suggest that the internal connection design of the examined implant system could not prevent screw loosening during overloading. No implant or prosthesis failure was noticed in either group.

Effects of surface treatments and cement types on the bond strength of porcelain-to-porcelain repair.

PURPOSE: The purpose of this in vitro study was to evaluate the effects of four surface treatments and two resin cements on the repair bond strength of a ceramic primer. MATERIALS AND METHODS: Eighty-eight pairs of disks (10 and 5 mm in diameter, 3 mm thickness) were prepared from heat-pressed feldspar ceramics (GC Initial IQ). After being stored in mucin-artificial saliva for 2 weeks, the 10-mm disks were divided into four surface treatment groups (n = 22) and then treated as follows: (1) no treatment (control); (2) 40% phosphoric acid; (3) 5% hydrofluoric acid + acid neutralizer + 40% phosphoric acid; (4) silica coating (CoJet-sand) + 40% phosphoric acid. The 5-mm disks were treated with 5% hydrofluoric acid + 40% phosphoric acid. The two sizes of porcelain disks, excluding the control group, were primed with Clearfil Ceramic Primer. The specimens in each group were further divided into two subgroups of 11 each, and bonded with Clearfil Esthetic Cement (CEC) or Panavia F 2.0 Cement (PFC). The specimens were stored in distilled water at 37°C for 24 hours, thermocycled for 3000 cycles at 5 to 55°C, and stored at 37°C for an additional 7 days. Shear bond strength (SBS) was measured with a universal testing machine at a 0.5 mm/min crosshead speed until fracture. Statistical analysis of the results was carried out with a two-way ANOVA and Tukey HSD test (α = 0.05). Debonded specimen surfaces were examined under an optical microscope to determine the mode of failure. RESULTS: The statistical analysis showed that the SBS was significantly affected by surface treatment and resin cement (p < 0.05). For treatment groups bonded with CEC, the SBS (MPa) values were (1) 2.64 ± 1.1, (2) 13.31 ± 3.6, (3) 18.88 ± 2.6, (4) 14.27 ± 2.7, while for treatment groups cemented with PFC, the SBS (MPa) values were (1) 3.04 ± 1.1, (2) 16.44 ± 3.3, (3) 20.52 ± 2.2, and (4) 16.24 ± 2.9. All control specimens exhibited adhesive failures, while mixed types of failures were observed in phosphoric acid-treated groups. The other groups revealed mainly cohesive and mixed failures. CONCLUSIONS: Combined surface treatment of etching with hydrofluoric acid and phosphoric acid provides the highest bond strengths to porcelain. Also, PFC exhibited higher SBS than CEC did.

The effect of variations in translucency and background on color differences in CAD/CAM lithium disilicate glass ceramics.

PURPOSE: The purpose of this study was to compare the effect of variations in translucency and background on color differences (ΔE) for different shades of computer-aided design and computer-aided manufacturing (CAD/CAM) lithium disilicate glass ceramics. MATERIALS AND METHODS: A pilot study suggested n = 10 as an appropriate sample size for the number of lithium disilicate glass ceramic cylinders per group. High-transparency (HT) and low-transparency (LT) cylinders (diameter, 12 mm; length, 13 mm) were fabricated in three ceramic shades (BL1, A2, C3) using CAD/CAM technology and were cut into specimen disks (thickness, 1.2 mm; diameter, 12 mm) for placement on Natural Die (ND1 and ND4) backgrounds. Four combinations of translucency and background color were evaluated in terms of color differences for the three ceramic shades: group 1 (HT ND1, reference), group 2 (HT ND4), group 3 (LT ND1), and group 4 (LT ND4). A spectrophotometer was used to measure the color differences. Nonparametric tests (Kruskal-Wallis tests) were used to evaluate the color differences among the tested groups, and Mann-Whitney U tests with Bonferroni correction were used as post hoc tests. Furthermore, for each ceramic shade, the HT groups were compared to the LT groups using the Mann-Whitney U test. RESULTS: Significant differences were present among the tested groups of the same ceramic shade (p < 0.001). The highest ΔE values were observed in the HT ND4 group for BL1, while the lowest ΔE values were found in the LT ND1 group for both A2 and C3. Further, the HT groups and the groups with a darker background (ND4) showed increased ΔE values compared with the other groups (p < 0.001). CONCLUSIONS: Within the limitations of this study, the results suggested that the translucency and background color significantly influenced the lithium disilicate glass ceramic color among the BL1, A2, and C3 ceramic shades. Changing the underlying color from a lighter background to a darker background resulted in increased color differences.

To Preserve or Extract? A Scoping Review and a Prognostic Decision Tool using Multispecialty Indicators.

As implant-supported restorations have become very popular, there is a tendency to extract teeth and replace them with implants. However, the first goal of dentistry should always be the preservation of natural teeth, given the prerequisite that these can be maintained with the application of appropriate treatment modalities. Therefore, individual tooth risk assessment and prognosis are very important in the treatment plan process. Four important factors influencing the dentist's decision on whether to save or extract a compromised tooth have been identified, and an extensive search of the related English language literature has been performed. Additionally, hand-search in related journals was implemented, and classical textbooks were consulted. Identified articles on patient-related, periodontal, endodontic, and restorative factors were thoroughly analyzed, focusing on diagnosis and tooth prognosis. Fifty-two selected references have been carefully selected and reviewed. Available information was used to develop a color-coded prognostic decision chart with four different factors and up to fourteen crucial parameters. All factors and parameters were analyzed in an effort to help the restorative dentist make a prognostic decision. The proposed color-coded prognostic decision chart can be helpful when a treatment plan is made, and predictable restorative care is planned. This comprehensive prognostic decision chart can aid dentists in providing clinical care of high quality and establishing a consensus on available restorative options. It can additionally establish appropriate communication with patients and third-party individuals in the restorative care process, effectively manage risk factors, and provide a framework for quality assessment in restorative treatment.

ATPase activity of human ABCG1 is stimulated by cholesterol and sphingomyelin.

ATP-binding cassette protein G1 (ABCG1) is important for the formation of HDL. However, the biochemical properties of ABCG1 have not been reported, and the mechanism of how ABCG1 is involved in HDL formation remains unclear. We established a procedure to express and purify human ABCG1 using the suspension-adapted human cell FreeStyle293-F. ABCG1, fused at the C terminus with green fluorescent protein and Flag-peptide, was solubilized with n-dodecyl-ß-D-maltoside and purified via a single round of Flag-M2 antibody affinity chromatography. The purified ABCG1 was reconstituted in liposome of various lipid compositions, and the ATPase activity was analyzed. ABCG1 reconstituted in egg lecithin showed ATPase activity (150 nmol/min/mg), which was inhibited by beryllium fluoride. The ATPase activity of ABCG1, reconstituted in phosphatidylserine liposome, was stimulated by cholesterol and choline phospholipids (especially sphingomyelin), and the affinity for cholesterol was increased by the addition of sphingomyelin. These results suggest that ABCG1 is an active lipid transporter and possesses different binding sites for cholesterol and sphingomyelin, which may be synergistically coupled.

An in vitro comparison of the accuracy of implant impressions with coded healing abutments and different implant angulations.

STATEMENT OF PROBLEM: Fabricating implant definitive casts with CAD/CAM technology (Robocasts) from coded healing abutment impressions represents a simpler and innovative alternative to conventional implant impression techniques. However, information about the accuracy of the impressions and the resultant definitive casts is limited. PURPOSE: The purpose of the study was to evaluate the accuracy of the Robocasts and compare them to those definitive casts fabricated with conventional implant impression techniques (open tray with splinted impression copings technique). MATERIAL AND METHODS: A reference epoxy resin cast was fabricated and shaped to simulate a dental arch. Two regular platform implant replicas (Biomet 3i Certain, 4.1 mm diameter and 15 mm length) with internal connections were placed 10 mm apart with a 10-degree convergence for one side of the reference resin cast and a 30-degree convergence for the other. Coded healing abutments (Encode) were placed at 3 different heights above the level of the soft tissue replication material (approximately 1, 2, and 4 mm) and served as test groups (E1, E2, and E4), and open trays with splinted impression copings (OTSC) served as a control group. The control group was compared to the impressions of the coded healing abutments by using a standardized measurement protocol. Impressions were made for each group (n=18) and poured with vacuum mixed (100 g powder/20 mL water) Type IV dental stone. The vertical discrepancy (Z axis) between 2 prefabricated passively fitting titanium reference frameworks and the platforms of the implant replicas was measured with an optical comparator applying the 1 screw test. Data were analyzed with Kruskal-Wallis and post-hoc Mann-Whitney U tests, as well as the Wilcoxon signed-rank tests. The Bonferroni correction was used to account for multiple comparisons. The significance level (α) used in a given set of tests was equal to .05 divided by the number of tests performed in that set. RESULTS: The median vertical discrepancy of each coded healing abutment impression group was higher than the corresponding median of the control group (OTSC) for every combination of angulation and position. Kruskal-Wallis tests indicated a statistically significant difference (P<.001) between groups for each angulation/position combination. All post hoc Mann-Whitney U tests indicated statistically significant differences (all P≤.002) between OTSC and the other groups. Differences between the angulations and positions were not statistically significant when accounting for multiple comparisons. CONCLUSIONS: The implant definitive casts fabricated from the coded healing abutment impressions were found to be less accurate than those fabricated from the open tray with splinted impression copings technique for restoring 2 paired (10 or 30 degrees) convergent internal connection implants with nonengaging screw-retained splinted 2-unit implant restorations. Accuracy of fit was not influenced by the implant angulation or position for either impression technique or by the Encode healing abutment height for the Encode impression technique.

Influence of coping design on the cervical color of ceramic crowns.

STATEMENT OF PROBLEM: The replication of natural teeth, especially with single-tooth restorations, represents a challenge. Similar to metal ceramic crowns, different designs of zirconia substructures have been suggested to improve the esthetic results of zirconia ceramic crowns. PURPOSE OF STUDY: The purpose of the study was to analyze the color of the cervical portion of single zirconia ceramic crowns fabricated with different zirconia coping designs. MATERIAL AND METHODS: The color, measured on the CIELAB color scale, of 3 different groups of restorations (n=10) fabricated with zirconia coping (Lava) and feldspathic porcelain (Noritake Super Porcelain) was analyzed with a spectrophotometer. Conventional zirconia crowns with zirconia facial margins were compared with ceramic crowns with porcelain facial margins and either a horizontal reduction of the zirconia coping (1.0 mm reduction) or an additional vertical reduction (1.0 mm additional reduction). The 3 groups, each with a different coping extension, were examined with a 1-way ANOVA and the Fisher exact test, and the differences of the groups were evaluated by applying ΔE thresholds (α=.05). RESULTS: The mean color difference among all the groups was not clinically significant (ΔE<3.7). Reduced color differences were present between the 2 porcelain butt margin groups of crowns (ΔE=1.06, between group H and V). Increased differences were present between the zirconia margin group and the porcelain butt margin group (ΔE=2.54 between group C and H; ΔE=2.41 between group C and V). Lab* values were examined in all the groups of crowns to determine the clinical implications. CONCLUSIONS: Within the limitation of the study, no significant differences were present among the tested groups of crowns. Nevertheless, although some differences were present between the zirconia margin group and the porcelain butt margin group, reduced differences were present between the 2 different cutback designs.

Delayed linear dimensional changes of five high strength gypsum products used for the fabrication of definitive casts.

STATEMENT OF PROBLEM: Prolonged storage of definitive casts made from Type IV and Type V gypsum products, especially in an environment of increased temperature and low humidity, may result in contraction. PURPOSE: The purpose of this study was to evaluate the linear dimensional changes of 5 different high strength stones after exposing them to 2 different storage conditions over a period of 3 weeks. MATERIAL AND METHODS: Three Type IV dental stones (Fujirock, Vel-Mix, Suprastone) and 2 Type V dental stones (Hard Rock, Jade Stone) were tested in this study. A circular conical stainless steel die with a diameter of 66 mm and a height of 10 mm was made. Two V-shaped grooves, 38 mm apart, were scribed on the surface of the die for the purposes of measurement. A conical stainless steel ring with a bottom inner diameter of 68 mm and a top inner diameter of 65 mm was also fabricated to fit precisely around the stainless steel die. The dental stone was mixed with water under vacuum and poured under vibration onto the stainless steel die, which was surrounded by the ring. The specimens (n=20) were separated from the stainless steel die 1 hour after pouring. Half of these specimens (control) were stored in a room at 22 ±1°C with relative humidity of 50 ±5%, while the rest of the specimens were placed in a temperature regulating incubator at 40 ±1°C and relative humidity of <20%. The linear dimensional changes were recorded at designated time intervals with a traveling microscope over a 3 week period. Collected data were subjected to a 2-way repeated-measures analysis of variance (ANOVA) (α=.05). RESULTS: The highest expansion values for the specimens in the control group were recorded between 72 and 96 hours. A contraction was noticed thereafter for all specimens, in both groups. No difference in the measurements was registered between the second and third week. ANOVA revealed significant differences (P<.001) among different Type IV and V dental stone products, time, and storage conditions. CONCLUSIONS: The highest expansion values for all specimens in the control group were recorded between 72 and 96 hours. The highest expansion values for all specimens in the experimental group were recorded at 24 hours. For all specimens, contraction was noticed up to the 2-week measurements. All factors examined (dental stone, time, storage condition) significantly affected the linear dimensional changes.