The International journal of prosthodontics最新文献

Purpose: To update data on the transfer accuracy of digital implant impressions by using a coordinate-based analysis, latest intraoral scanners (IOSs) were investigated in an established clinical close model set-up.

Materials and methods: An implant master model (IMM) of the maxilla with four implants in the posterior area (#14/#24 and #16/#26) and a reference cube was scanned with four different IOS (i700 (Medit), Primescan (Dentsply Sirona), Trios 4 and Trios 5 (3Shape) ten times each. Datasets were compared with a reference dataset of IMM that was generated with x-ray computed tomography in advance. 3D deviations for the implant-abutment-interface points (IAIPs) were calculated. Statistical analysis was performed by multifactorial ANOVA (p < .05).

Results: Overall deviations for trueness (mean) ± precision (SD) of the IAIPs ranged from 88±47 μm for the Primescan, followed by 112±57 μm for the i700, 121±42 μm for the Trios 4 and 124±43 μm for the Trios 5 with decreasing accuracy along the scan path. For trueness, one significant difference between the Primescan and the T4 was detected for one implant position. For precision, no significant differences were noticed.

Conclusions: Although the latest IOS showed a significant improvement in transfer accuracy, the accumulating deviation along the scan path is not yet resolved. Considering the Trios system, the innovation seems to be limited as no improvement could be detected between Trios 4 and 5.

Purpose: To evaluate the effect of cheek retractors on the accuracy of capturing peripheral borders in totally edentulous digital scans by comparing the conventional impression technique to digital scans made using two different cheek retractors.

Material and methods: Sixteen edentulous maxillary impressions were made using three techniques: the conventional impression technique, using modeling thermoplastic compound and zinc oxide eugenol paste; the digital intraoral scanning technique using the DIO scan retractor (DIO); and using the Br.nemark lip retractor (BRAN). The control impressions of each patient were poured, scanned using a desktop scanner, then transferred into a three-dimensional analysis software. DIO and BRAN groups were scanned using an intraoral scanner, imported, and superimposed using best fit algorithm on the corresponding control. The root mean square for the whole surface and for particular interest regions were calculated to assess the degree of trueness. The patients' perceptions of the impression techniques were the secondary outcomes. Statistical analyses were performed using the one sample T-test and Wilcoxon test (α=.05).

Results: Significant discrepancies were found for BRAN and DIO compared to the control. No significant discrepancies were found when comparing RMS of BRAN and DIO at different regions. Scan retractors had a significant impact on patient satisfaction, with patients preferring DIO.

Conclusions: Edentulous intraoral scans made using cheek retractors had similar deviations when compared to each other but diverged from the conventional impression in edentulous maxilla. Patient preferences for intraoral scans over conventional impressions were confirmed.

Clinical implications: The use of different retracting methods during intraoral scanning of totally edentulous maxillary arches does not affect the peripheral border registration.

Purpose: To evaluate the adherence of three types of bacteria [Staphylococcus (S) aureus, Escherichia (E) coli, Pseudomonas (Ps) aeruginosa] and the size of the microgap of three different implant systems (JD, ORA, and Ankylos) under four different screw torque values.

Materials and methods: Ten samples for each tested implant system were used under different torques to determine the width of the gaps. The abutments were connected to the fixtures using a universal digital wrench. A torque value of 10 N/cm was applied for all samples. After the assessment of the microgap, the fixture was repositioned into the Bench Vice, and the torque was increased to 20, 30, and, finally, 40 N/cm. The microgap assessment was done using a Scanning Electron Microscope. Before the torque increased to 40, eleven samples for each tested implant system were used under 30 N/cm torque to determine the leakage in the tested implants for S. aureus, E. coli, and Ps. aeruginosa. Data were analyzed with multiple one-way ANOVA, Post Hoc, and chi-square tests.

Results: The Ankylos system showed the widest gap under all torques (p < 0.005), whereas the JD system demonstrated the lowest (p < 0.005). Regarding the bacteria leakage, JD showed the highest adherence to the bacteria, and the adherence was mainly to the Ps. Aeruginosa, while the Ankylos system showed the lowest (p < 0.005).

Conclusion: Within limits, the higher torque provides a higher fit to the IAI, offering more stability. Ankylos implant showed the widest gap, while JD showed the narrowest. Regarding the bacteria leakage, JD showed the highest adherence to Ps. Aeruginosa, while the ORA system showed the highest adherence to E. coli.

Purpose: To compare the fracture load of two framework materials, zirconia and a new fiber-reinforced composite (FRC), for full-arch implant-supported rehabilitations using various cross- sections.

Material and methods: A cobalt-chromium metal model simulating the all-on-four concept and including 2 anterior straight and 2 posterior 45- degree angled multi-unit digital implant analogs was manufactured. 4 straight multi-unit abutments were screwed onto the implant analogs. The metallic model was scanned, and 18 frameworks were fabricated, consisting of 9 made of zirconia and 9 made of fiber-reinforced composite (FRC). The frameworks were then divided into 6 groups, with each group consisting of 3 frameworks (n=3). Group division was based on material type (Zirconia or FRC Trilor) and framework cross-section: 3.5 x 6 mm2, 5.5 x 6 mm2, or 7.5 x 6 mm2. All specimens underwent thermocycling in 2 baths (5 ͦ c- 55 ͦ c for 2350 cycles). Subsequently, the frameworks were cemented to the abutments of the metal model and subjected to a load-to-failure bending test at 3 different points using a universal testing machine (crosshead speed: 1 mm/min) until complete fracture occurred (according to ISO/TS 11405:2015). Descriptive statistics were used to present quantitative variables as means ± standard deviations. To compare two means, Student's t-test or Mann-Whitney test was utilized, and for three means, ANOVA test was used.

Results: The FRC group with a 7.5 x 6 mm2 cross-section exhibited the highest load-to-failure values (ranging from 1020 N to 2994N) , while the zirconia group with a 3.5 x 6 mm2 cross-section recorded the lowest values (ranging from 212 N to 1287 N). The material type and framework cross-section significantly affected the mean load-to-fracture values (p< 0.05). Regardless of the framework cross-section, the FRC group exhibited higher fracture loads than the zirconia group. In both materials, fracture load values were increased with larger framework cross-sectional areas, with the highest values observed at the inter-implant midpoint.

Conclusion: The FRC Trilor demonstrated a fracture load that make it a suitable alternative to zirconia for all-on-four implant prosthetic frameworks.

Purpose: The aim of this study was to determine and compare color differences of pressed lithium disilicate ceramic specimens after repeated firing cycles. An additional objective was to determine and evaluate correlation of CIEDE2000 values analyzed by X-Rite Color i5 Spectrophotometer, VITA EasyShade Advance 4.0 and Adobe Photoshop.

Material and methods: Tile specimens (N=36) with 8 x 10 x 1.5mm dimensions were prepared by IPS e.max Press lithium disilicate MT Monochromatic ingots and IPS e.max Multi Press lithium disilicate Multichromatic ingots. Specimens were exposed to 7 repeated firing cycles. Color analysis was performed after the 1st, 2nd, 3rd, 5th, and 7th firing cycles. CIE L*a*b* values were measured by X-Rite Color i5 Spectrophotometer, VITA EasyShade Advance 4.0 and Adobe Photoshop. CIE DE*2000 (ΔE*00) was calculated to estimate color differences.

Results: Linear regression and multiple comparison analysis (Tukey's HSD test) showed a statistically significant (p<.001) color difference ΔE*00 after multiple firing cycles. Statistically significant differences (p<.05) were also noted in different shade groups and between different instruments used for shade evaluation. Moreover, significant differences (p<.05) were found in interactive effects between different shades tested by different instrument, different shades tested after multiple firing cycles and different instruments after multiple firing cycles.

Conclusions: Lithium disilicate material shows significant color differences after repeated firing cycles tested by three color analysis instruments. Measuring instruments used to evaluate CIE L*a*b* color values showed significant differences in color values analysis, which may lead to altered level of interpretation, particularly to determine perceptibility and clinical acceptability thresholds.

Purpose: The aim of this study was to evaluate the influence of restoration bonding and type of preparation on load bearing capacity of a tooth restored with indirect glass ceramic or hybrid ceramic occlusal veneer restoration.

Materials and methods: Occlusal surfaces of extracted human molar teeth were prepared for indirect occlusal veneers with or without circumferential chamfer. The occlusal veneers were milled either from CAD/CAM hybrid ceramic (HC) Cerasmart (GC), or lithium-disilicate glass ceramic (LDGC) IPS e.max CAD (Ivoclar Vivadent) blocks. Finalized veneers were bonded to teeth following manufacturers' instructions or according to the technique for the intended deteriorated bonding using n-hexane wax solution preconditioning on restorations (n=8/group). The ultimate fracture load was recorded, and fracture types were analyzed and classified visually. Statistical analysis was performed using one-way ANOVA.

Results: The highest fracture load was recorded in teeth with bonded LDGC veneer (p≤0.0007). The bonded HC veneers had only marginally higher fracture load compared to non-bonded veneers. In all groups with deteriorated bonding, veneers loosened without tooth fracture whereas in the bonded veneer groups tooth fractures were observed, especially in teeth restored with LDGC material.

Conclusions: Bonded LDGC occlusal veneers have high load bearing capacity which exceeds the fracture resistance of tooth structure. Circumferential chamfer preparation for an occlusal veneer has no influence on fracture load of a restored tooth.

Purpose: The purpose of this work is to observe the effect of the cavity design of the direct composite restoration on a real case of the patient's tooth structures after applying his mandibular kinematics with finite element analysis.

Materials and methods: Four complex maxillomandibular models of teeth 17 and 47 were constructed from the patient's cone-beam acquisition and the patient's kinematic data recorded with Modjaw® were added. Different shapes and sizes of mesio-occluso-distal (M.O.D.) composite restorations were simulated, including the polymerization shrinkage of this material. Finite element analyses were used to observe the Von Mises stresses occurring during polymerization and mastication.

Results: The stresses were observed at the cavity margin and the amplitude of the stresses was higher when the enamel volume was lower. The reduction in occlusal enamel volume with the open-angle vestibular and palatal walls resulted in a greater increase in stresses observed on the structures.

Conclusions: The occlusal enamel is the area that bears the maximum masticatory stress, the loss of this enamel volume generates a much greater concentration of stress on the underlying structures. It is important to preserve as much enamel tissue as possible when designing a cavity for a direct composite restoration.

Purpose: To determine the frequency of insert changes for combined maxillary and mandibular implant overdentures (IOD) using the Locator Legacy system. A secondary objective was to assess the survival of dental implants with IODs.

Materials and methods: This retrospective audit reviewed clinical records with up to 12 years follow up from 785 patients who received IODs using the Locator system at a dental hospital. From these, 151 had a combined maxillary opposed by a mandibular IOD and from this, 37 had data retrieved using a minimum data set. The frequency of insert change was recorded and descriptive analysis was provided by means and standard deviations for continuous variables. Frequencies of categorical values were reported as percentages.

Results: 222 implants were placed on 21 men, 16 women with a mean age 67.5 years (SD 8.8). All patients were reviewed at least once. Maxillary and mandibular IODs experienced 1.9 (SD 2.0) and 1.2 (SD 1.2) mean insert changes per patient, respectively. The mean time (SD) between initial and first insert change for maxillary and mandibular IODs was 3.4 months (SD 3.2) and 6.4 months (SD 7.2) and between the first and second insert change was 9.9 months (SD 9.0) and 10.0 months (SD 8.3), respectively. Implant failure was 21.6% and 2.7% in the maxilla and mandible respectively.

Conclusions: Clinicians should anticipate the first insert change around 3 months for maxillary IOD and 6 months for mandibular IOD. Subsequently, the second insert change to be around 10 months for both maxillary and mandibular IODs.

Purpose: To investigate the medium-term survival of Dalbo-Rotex retention elements, identify potential risk factors for complication or loss, and to consider economic factors.

Materials and methods: Patients treated with Dalbo-Rotex retention elements in a university setting were retrospectively identified and examined. Clinical data comprised assessments of the dental, periodontal, endodontic, and prosthetic situation, including radiographic analysis. Patient satisfaction was quantified with visual analog scale questionnaires. Five-year Kaplan-Meier plots for relative survival and success rates were calculated.

Results: The 45 included patients had a total of 76 Dalbo-Rotex retention elements. Twelve Dalbo-Rotex elements failed and complications occurred in 42.1% of elements, equating to a survival rate of 84.2% and a success rate of 47.4% after a mean observation period of 49.2 months (SD 52.4, range 6-219 months). The 5-year cumulative survival and success rate was 62.4% (95% CI 44.0-88.4%) and 35.6% (95% CI 23.8-53.2%), respectively. Patients' self-assessment of prostheses retention was rated at 82 (IQR 40-92.2) with low pain perception at 4.5 (IQR 0-30). Probing pocket depth levels were significantly reduced in patients adhering to a regular recall interval compared with those with longer intervals.

Conclusions: Chairside Dalbo-Rotex retention elements are a straightforward chairside method for prostheses retention that achieve good survival over medium-term follow up with high patient satisfaction. This technique is therefore a viable alternative to cast post copings that may be particularly valuable for patients with limited financial resources.

Background: Maxillary premolars have a unique anatomical location. This is an CBCT based study where the suitability of maxillary premolars for immediate implant placement (IIP) is evaluated. Based on prosthetically driven treatment treatment planning a simple classification system is put forth.

Materials and methods: 150 CBCTs of maxillary first premolars were analysed in BlueskyBio software. The topographic position of the tooth was determined by analysing the dimensions of the buccal and lingual cortical plates, the distance between the bucco-lingual plates and the residual bone height from the root apex to the floor of the sinus. Virtual placement of an implant was carried out such that the implant would be positioned 1 mm apical to the buccal bone crest, would engage 3 mm of bone apical to the root apex, and would have a trajectory so that the abutment access was from the central fossa. Four categories were identified and the classification was proposed.

Results: It was observed that 74% of cases had buccal bone<1mm,26% had buccal bone >1mm. 79% cases had an average distance >3mm between root apex and maxillary sinus, 21% had an average distance of root apex and maxillary sinus <3mm. The categorizations of implant placement were as follows -Type 1- 24%, Type 2- 56.6%, Type 3-43.3%, Type 4- 0%.

Conclusions: In majority of maxillary 1st premolars an IIP is possible with the implants to be placed in the palatal sockets or the furcation area. In cases were the buccal plate thickness is inadequate, simultaneous grafting should be considered between the implant position and buccal plate.