Effect of Material Properties and Variability of Mannitol on Tablet Formulation Development.

PURPOSE: Using a high level of mannitol as a diluent in oral formulations can potentially result in tablet defects (e.g., chipping, cracking) during compression. This work aims to scrutinize the linkage between the mechanical properties and material attributes of mannitol and also uncover how variations between vendors and lots can lead to significant changes in the compaction performance of tablet formulations containing mannitol. METHODS: The mechanical properties (Poisson's ratio, fracture energy) and mechanical performance (ejection force, pressure transmission ratio, residual radial die-wall stress, and tensile strength) of mannitol compacts were assessed on a compaction simulator for four lots of mannitol from two different vendors. The variation of material attributes of each lot, including particle size distribution (PSD), crystal form, primary crystal size and morphology, specific surface area (SSA), powder flow, and moisture absorption were investigated. RESULTS: The variability of material attributes in mannitol lots, especially primary crystal size and SSA, can result in significant changes in mechanical properties and mechanical performance such as ejection force and residual radial die-wall stresses, which potentially led to chipping during compression. CONCLUSION: The study elucidated the linkage between fundamental material attributes and mechanical properties of mannitol, highlighting their impact on tablet defects and compaction performance in compression. A comprehensive understanding of the variability in mannitol properties between vendors and lots is crucial for successful formulation development, particularly when high percentages of mannitol are included as a brittle excipient.

A multicenter randomized controlled clinical pilot study of buccally micro-veneered lithium-disilicate and zirconia crowns supported by titanium base abutments: 1-year outcomes.

OBJECTIVES: To investigate survival rates, technical and biologic outcomes of buccally micro-veneered all-ceramic single implant crowns. MATERIAL AND METHODS: Sixty subjects randomly received immediately or early placed implants. Crowns out of lithium-disilicate (n = 30) and zirconia-ceramic (n = 30) were bonded to titanium-base-abutments. Restorations were inspected at baseline (BL) and during follow-up visits (6, 12 months). Technical and biologic parameters were recorded. Data were analysed descriptively. Differences between groups were tested with Student's t-test. Paired T-test was used when comparing data from the same implant or tooth over time. Linear model repeated measures were used to test differences between materials over time. Differences in counts were evaluated using Pearson Chi-square test. The level of significance was at p < .05. RESULTS: After a mean observation time of 13.2 ± 2.4 months, 54 restorations were re-examined. The implant survival rate was 98.3%, and the restoration survival rate was 100%. One early implant failure occurred. Two minor chippings occurred in lithium-disilicate restorations. No chippings or fractures occurred in any zirconia restorations at 1 year (0%). The technical complication rate was 3.7%, with 7.7% complications among the lithium-disilicate restorations and no differences between the two materials (p = .558). At 1-year follow-up, mean Bleeding on Probing (BOP) was higher at implants (0.27 ± 0.3) than adjacent teeth (0.17 ± 0.18) (p = .046) with no differences between materials (p = .36). Differences in pocket probing depth (PPD) between implants and adjacent teeth were significant (p < .01). Jemt Index improved significantly from BL to 1-y-follow-up (p < .001). CONCLUSIONS: Preliminary results were good, suggesting that the ceramic type does not impact technical and biologic parameters.

Survival and success of veneered zirconia crowns.

AIM: The aim of the present study was to evaluate the long-term clinical survival and success rate of veneered zirconia crowns with a modified anatomical framework design after 10 years in function. MATERIALS AND METHODS: In total, 36 zirconia crowns were fabricated for 28 patients. An anatomically modified framework design was developed. Crowns were inserted between 2008 and 2009. A follow-up of 19 patients with 28 crowns was conducted in 2020 to document mechanical and biologic parameters. Additionally, a modified version of the pink esthetic score (PES) was documented. Patient satisfaction was assessed using United States Public Health Service (USPHS) criteria. The success and survival rates were calculated using the Kaplan-Meier analysis. RESULTS: After more than 10 years of clinical service, the survival rate of the zirconia crowns was 92.9%. Biologic complications occurred in 12% of the examined crowns, whereas technical complications occurred in 54%. Mostly, chippings (50%) and insufficient marginal gaps (50%) were observed. Most crowns were positively evaluated for more than one technical complication. Periodontal conditions with probing depths of up to 3 mm were comparable with measured values before crown delivery (73% to 75%). Most of the crowns had modified PES values of 10 or higher. Patient satisfaction was high. CONCLUSIONS: The modified framework design led to a high survival rate of the crowns but a relatively low success rate. High patient satisfaction and inconspicuous periodontal conditions were demonstrated. Biologic complications occurred far less frequently than technical complications.

Indirect repair of saliva-contaminated materials using veneering ceramics.

PURPOSE: To analyze the in vitro efficacy of a surface conditioning liquid facilitating ceramic repairs of saliva-contaminated metal-ceramic and all-ceramic restorations. MATERIALS AND METHODS: Specimens constructed from nonprecious alloy (NPA), precious alloy (PA), lithium-disilicate (LD), zirconia (ZI), veneering ceramics for zirconia (VZI), veneering ceramics for lithium-disilicate (VLD), and veneering ceramics for metal alloys (VM) were manufactured (total: n = 168; each material n = 24). Veneering ceramic cylinders (thickness: 2 mm) were hand-layered on top of the specimens. Shear bond strength (SBS) tests were performed, measuring the maximum bond strength (MBS) of the cylinders on the specimens. Following this, the specimens were artificially aged and stored in artificial saliva for 30 days at 37°C. After physical cleaning using aluminum oxide air abrasion, a new surface conditioning liquid was applied (test, n = 84) or not (control, n = 84). New ceramic cylinders were hand-layered followed by a second SBS test. Descriptive statistics, linear regression analyses, and a one-sample t-test (α = 0.05) were used to ascertain the differences within (prerepair vs. postrepair) and between the groups. RESULTS: All specimens in the test group could be repaired, whereas 18 repairs in the control group failed. After the repairs, an MBS decrease was observed for the NPA specimens of the control group (-15.5 MPa, p = 0.004) but not among any of the test groups. Comparing the change in MBS between the test and control groups, the reduction was significantly higher in the repaired NPA specimens of the control group (mean difference 11.8 MPa, p = 0.017). CONCLUSIONS: Using the analyzed surface conditioning liquid, metal-ceramic and all-ceramic materials can be repaired, while some repairs failed without the liquid. The initial bond strengths between core and veneering materials could be restored in all specimens when the new surface conditioning liquid was applied.

Clinical protocol for intraoral repair of a chipped all-ceramic crown: a case report.

Ceramic chipping occurs frequently in veneered all-ceramic crowns, and the decision to repair or replace them depends on many factors. The least invasive method is the intraoral repair. This case report describes a conservative restorative treatment performed on a chipped dental crown. A 59-year-old patient fractured her all-ceramic crown, revealing chipping and debonding of the feldspathic ceramic veneer and exposure of the zirconia framework. The fractured fragment was brought to the dental office. Due to the patient's esthetic concerns about prolonged treatment, it was decided to use the fragment to repair the crown intraorally. The result exceeded the patient's expectations. The intraoral repair of a chipped all-ceramic crown is a conservative and low-cost alternative that allows for immediate restoration of the function and esthetics. It is essential to establish protocols that can support clinician decision-making about the most appropriate clinical treatment, seeking the longevity of the restoration and the dental structure.

Tooth chipping prevalence and patterns in extant primates.

OBJECTIVES: A tooth chip occurs when a hard object forcefully contacts the surface of the tooth, typically removing enamel from the occlusal edge. In this study, chipping patterns in extant primates were compared, and hard-object-feeding assessed alongside other factors (e.g., grit mastication and dental properties), to elucidate dietary and behavioral inferences in archeological and paleontological samples. MATERIALS AND METHODS: Thirteen species of extant primates were studied, including eight species within the Cercopithecidae, two within the Ceboidea, and three within the Hominoidea. Four additional species were also incorporated from the literature for some of the analyses. The severity (Grade 1-3), position (buccal, lingual, mesial, and distal) and number of tooth fractures were recorded for each specimen. RESULTS: Species considered hard-object-feeding specialists presented higher rates of chipping, with sakis, mandrills, sooty mangabeys and Raffles' banded langurs having high chipping rates (28.3%, 36.7%, 48.4%, and 34.7% of teeth, respectively). Species that seasonally eat harder foods had intermediate chipping frequencies (e.g., brown woolly monkeys: 18.5%), and those that less commonly consume hard food items had the lowest chipping frequencies (e.g., Kloss gibbon: 7.3%; chimpanzees: 4.4%). DISCUSSION: The results suggest hard food mastication influences differences in chipping prevalence among the species studied. Although Homo fossil samples show high rates of chipping comparable to hard-object-feeding extant primates, they display a different pattern of chipping, supporting the hypothesis that these fractures are mostly non-food related (e.g., grit mastication in Homo naledi; non-masticatory tooth use in Neanderthals).

Current-Season Infection With Ordinary and Recombinant Strains of Potato virus Y Has Detrimental Effects on Chipping Potato Yield and Tuber Quality.

Potato virus Y (PVY) is the most economically important virus infecting potatoes worldwide. Current-season spread of PVY occurs when aphids transmit the virus from infected to noninfected plants during the growing season. The impact of current-season PVY infection on yield and quality of chip processing potatoes is not well documented. In a replicated, greenhouse experiment conducted over 2 years, we measured the effect of current-season infection with four PVY strains (PVYO, PVYN-Wi, PVYNTN, and PVYN:O) on chip processing varieties Atlantic, Lamoka, and Snowden. PVY infection decreased yield and tuber specific gravity for some combinations of potato variety and virus strain but did not affect the appearance of chips including the prevalence of stem-end chip defects. This work suggests that current-season infection of chipping potatoes imposes a cost on producers and emphasizes the need for continued investment in seed certification and development of PVY-resistant cultivars.

Nondestructive Detection of Magnetic Contaminant in Aluminum Casting Using Thin Film Magnetic Sensor.

The thin film magneto-impedance sensor is useful for detecting a magnetic material nondestructively. The sensor made by single layer uniaxial amorphous thin film has a tolerance against surface normal magnetic field because of its demagnetizing force in the thickness direction. Our previous study proposed the sensitive driving circuit using 400 MHz high frequency current running through the sensor to detect the logarithmic amplifier. We also confirmed the sensitivity of the sensor within 0.3 T static normal magnetic field, which resulted in detection of 5 × 10-8 T of 5 Hz signal. This paper proposes a nondestructive inspection system for how detecting a contaminant of small tool steel chipping in aluminum casting specimen would be carried out. Three channel array sensors installed in the 30 mT static field detecting area were fabricated and experimentally showed a detection of low remanence magnetic contaminant in a bulk aluminum casing specimen.

Enamel chipping in Taï Forest cercopithecids: Implications for diet reconstruction in paleoanthropological contexts.

Antemortem enamel chipping in living and fossil primates is often interpreted as evidence of hard-object feeding (i.e., 'durophagy'). Laboratory analyses of tooth fracture have modeled the theoretical diets and loading conditions that may produce such chips. Previous chipping studies of nonhuman primates tend to combine populations into species samples, despite the fact that species can vary significantly in diet across their ranges. Chipping is yet to be analyzed across population-specific species samples for which long-term dietary data are available. Here, we test the association between enamel chipping and diet in a community of cercopithecid primates inhabiting the Taï Forest, Ivory Coast. We examined fourth premolars and first molars (n = 867) from naturally deceased specimens of Cercocebus atys, Colobus polykomos, Piliocolobus badius,Procolobus verus, and three species of Cercopithecus. We found little support for a predictive relationship between enamel chipping and diet across the entire Taï monkey community. Cercocebus atys, a dedicated hard-object feeder, exhibited the highest frequencies of (1) chipped teeth and (2) chips of large size; however, the other monkey with a significant degree of granivory, Co. polykomos, exhibited the lowest chip frequency. In addition, primates with little evidence of mechanically challenging or hard-food diets-such as Cercopithecus spp., Pi. badius, and Pr. verus-evinced higher chipping frequencies than expected. The equivocal and stochastic nature of enamel chipping in the Taï monkeys suggests nondietary factors contribute significantly to chipping. A negative association between canopy preference and chipping suggests a role of exogenous particles in chip formation, whereby taxa foraging closer to the forest floor encounter more errant particulates during feeding than species foraging in higher strata. We conclude that current enamel chipping models may provide insight into the diets of fossil primates, but only in cases of extreme durophagy. Given the role of nondietary factors in chip formation, our ability to reliably reconstruct a range of diets from a gradient of chipping in fossil taxa is likely weak.

Three-year clinical performance of monolithic and partially veneered zirconia ceramic fixed partial dentures.

OBJECTIVE: To compare the 3-year survival and success rates of monolithic (M) and partially veneered (PV) zirconia-fixed partial dentures (FPDs). MATERIALS AND METHODS: Sixty-seven FPDs (n = 33 M-FPDs; n = 34 PV-FPDs) were placed in 51 patients (n = 23 males; mean age 61.5 years) and clinically followed up 1 week, 6 months, and then yearly after placement. One hundred per cent (100%) of M-FPDs and 70% of PV-FPDs were located in the posterior region. Ninety-two per cent (92%) of M-FPDs had three units, whereas 50% of PV-FPDs had more than three units. A facial veneer was present in 73% of the PV-FPDs units. Survival and success were calculated using the Kaplan-Meier method and compared using the log-rank test (α = .05). RESULTS: The mean observation period was 3.5 years for M-FPDs and 3.1 years for PV-FPDs. Most complications associated with FPDs were biological in nature. Ceramic defects occurred exclusively among PV-FPDs. Three-year survival was 96.7% for M-FPDs and 93.8% for PV-FPDs (P = .064). Three-year success was 93.8% for M-FPDs and 81.7% for PV-FPDs (P = .039). CONCLUSIONS: The use of both M-FPDs and PV-FPDs yielded clinically successful results over a mean period of 3 years. CLINICAL SIGNIFICANCE: By using monolithic or facially veneered zirconia, ceramic FPDs could be fabricated which showed only a minimum of technical complications over the period of investigation without sacrificing adequate esthetics.

Effect of Potassium Nitrate and Boric Acid on the Bond Strength of Veneering Ceramics to Zirconia.

In this study, the effects of boric acid addition to the veneer ceramics and treatment of the ceramic cores immersed in potassium nitrate solution were evaluated to reduce the micro cracks that may occur in the internal structure of the ceramic, increase the mechanical properties and improve the chemical bonding strength of core ceramics. In the data obtained after the experiment, the average MPa values showed statistically significant differences according to the groups (p⟨0.001). The average value in the control group (C) was lower than the others. There was no statistically significant between the mean values of the boric acid application in the veneer ceramic (IB) group and zirconia core immersed in the potassium nitrate solution (IN) group. The highest mean values were observed between the veneer ceramic and the zirconia core by application of boric acid and potassium nitrate (IBN) group. As a result potassium nitrate and boric acid application affects the bond strength between zirconia core and veneer ceramic and increases mechanical properties of ceramics.

Chipping of veneering ceramic on a lithium disilicate anterior single crown: Description of repair method and a fractographic failure analysis.

OBJECTIVE: This article presents a retrospective analysis of an anterior single crown that showed chipping of the veneering ceramic, the clinical stages of intraoral repair made in composite resin, and fractographic analysis of the causes of failure. CLINICAL CONSIDERATIONS: The ceramic chipping occurred in the incisal and labial surfaces of the crown, 1 year after installation. Clinical examination revealed the presence of occlusal interference, which was probably responsible for chipping. Vinyl-polysiloxane impression was made from the patient, and epoxy replica was produced. The replica was gold coated and inspected under the optical microscopy and scanning electron microscope (SEM) for descriptive fractography. Optical microscopy and SEM images showed that chipping initiated at the incisal edge, where it is possible to note an area of damage accumulation. At the labial surface, multiple arrest lines with their convex sides facing the incisal edge were observed. The fractured area was repaired intraorally with composite resin, and the patient's occlusion was checked and monitored. CONCLUSION: According to the fractographic analysis, occlusal interference was related to ceramic chipping in the incisal edge. Intraoral repair technique with composite resin was indicated for this moderate chipping. CLINICAL SIGNIFICANCE: Retrieval analysis of chipping ceramic delivers better understanding of the failure origin and could prevent future failures. Intraoral repair is a practical and conservative technique and may be performed in a single clinical session without requiring the removal of prosthesis.

Influence of Core-Veneer Thickness Ratio on the Fracture Load and Failure Mode of Zirconia Crowns.

PURPOSE: To evaluate the influence of different core-veneer thickness (CVT) ratios on fracture loads and failure modes of zirconia crowns with or without thermomechanical cycling (TC). MATERIALS AND METHODS: Forty yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) cores were veneered with a pressable ceramic and divided into four groups (n = 10): group 1 - 1:3 CVT ratio (0.5-mm core, 1.5-mm veneer); group 2 - 1:1 CVT ratio (1.0-mm core, 1.0-mm veneer); groups 3 and 4 - identical to groups 1 and 2, respectively, except that they underwent TC (1,000,000 cycles with an 84-N load applied at a 4-Hz frequency, temperature cycling at 4°C, 37°C, and 55°C - 30 seconds each). Loads were applied axially to the central fossa of the crowns with a 1 mm/min crosshead speed at 200 N until failure. RESULTS: Two-way ANOVA showed that the crowns with a 1:3 CVT ratio had a lower mean fracture load than crowns with a 1:1 CVT ratio (group 1 = 1666.4 ± 466.4 N; group 2 = 2156.6 ± 472.3 N). TC had no effect on the fracture load for crowns with the same CVT ratio. The failures observed for the crowns in groups 1, 3, and 4 were fractures within the veneering ceramic, which exposed the core. The failure severity of fractures for group 2 was less extensive, characterized by chipping within the ceramic veneer. CONCLUSION: Crowns with a 1:1 CVT ratio had higher fracture load values and more conservative failures. TC had no effect on the fracture load of the ceramic crowns.

A Randomized Clinical Trial Comparing Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Partial Dentures: A 5-Year Follow-Up.

PURPOSE: To compare the survival, success rates, and biological/technical complications of posterior metal-ceramic (MC) and zirconia fixed partial dentures (FPDs). MATERIALS AND METHODS: A total of 40 patients requiring 40 posterior FPDs were randomly assigned to receive 20 zirconia and 20 MC restorations. The restorations were examined 1 week (baseline) and 1, 3, and 5 years after the end of treatment. Technical and biological outcomes were compared. Data were statistically analyzed using the Wilcoxon signed-rank and Mann-Whitney U tests. RESULTS: The survival rates of both groups were 100%, and the success rates were 80% (zirconia) and 100% (MC). No biological complications were observed. Minor chipping was found in 20% of the zirconia restorations. No differences in periodontal parameters were observed between groups. CONCLUSIONS: Zirconia FPDs exhibited the same survival rate (100%) as MC FPDs after 5 years; however, the success rate was 80%, because an increased rate of chipping was observed in zirconia restorations.

Tooth fractures in the Krapina Neandertals.

Dental fractures can be produced during life or post-mortem. Ante-mortem chipping may be indicative of different uses of the dentition in masticatory and non-masticatory activities related to variable diets and behaviors. The Krapina collection (Croatia, 130,000 years BP), thanks to the large number of teeth (293 teeth and tooth fragments) within it, offers an excellent sample to investigate dental fractures systematically. Recorded were the distribution, position and severity of the ante-mortem fractures according to standardized methods. High frequencies of teeth with chipping in both Krapina adults and subadults suggest that the permanent and deciduous dentition were heavily subjected to mechanical stress. This is particularly evident when the frequencies of chipping are compared with those in modern humans (Upper Paleolithic and historic samples) that we analysed using the same methods. The distribution of chipping in the Krapina sample (anterior teeth are more affected) and its position (labial) suggest a systematic use of the anterior teeth for non-masticatory tasks.

Fracture behavior of all-ceramic, implant-supported, and tooth-implant-supported fixed dental prostheses.

OBJECTIVES: In vitro investigation of the effects of fixed dental prosthesis (FDP) support and loading conditions on the fracture behavior of all-ceramic, zirconia-based FDP veneered with computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured lithium disilicate ceramic. MATERIALS AND METHODS: Based on a model for a 3-unit FDP in the molar region (tooth in region 15, implant in region 17), 16 identical zirconia frameworks were fabricated and veneered with milled lithium disilicate ceramic. Another 16 FDPs were manufactured similarly, using a model in which the tooth was replaced by an implant. The specimens underwent 10,000 thermal cycles between 6.5 and 60 °C and 1,200,000 chewing cycles with a force magnitude of 100 N. All were then subsequently loaded until fracture in a universal testing device. Half of the FDPs were subjected to centric and axial loading on the pontic, the others to eccentric and oblique loading on one cusp of the pontic. RESULTS: No failures were observed after artificial aging. Fracture loads of tooth-implant-supported restorations were 1636 ± 158 and 1086 ± 156 N for axial and oblique loading, respectively; implant-supported FDPs fractured at 1789 ± 202 and 1200 ± 68 N, respectively. Differences were significant for load application (P < 0.001) and support type (P = 0.020). For the two types of load application, fracture mode differed substantially: complete fracture was observed for centric and axial loading whereas mixed cohesive/adhesive failure was observed for many FDPs loaded eccentrically and obliquely. CONCLUSIONS: The high incidence of chipping of manually veneered implant-supported all-ceramics restorations might be reduced by use of CAD/CAM-manufactured lithium disilicate veneers. CLINICAL RELEVANCE: FDPs veneered with lithium disilicate resist occlusal forces of 500 N, irrespective of load application and support type. The fracture resistance of implant-supported FDPs was, however, higher than that of combined tooth-implant-supported FDPs. Their clinical use seems to be justified.

Suppression of the vacuolar invertase gene delays senescent sweetening in chipping potatoes.

BACKGROUND: Potato chip processors require potato tubers that meet quality specifications for fried chip color, and color depends largely upon tuber sugar contents. At later times in storage, potatoes accumulate sucrose, glucose, and fructose. This developmental process, senescent sweetening, manifests as a blush of color near the center of the fried chip, becomes more severe with time, and limits the storage period. Vacuolar invertase (VInv) converts sucrose to glucose and fructose and is hypothesized to play a role in senescent sweetening. To test this hypothesis, senescent sweetening was quantified in multiple lines of potato with reduced VInv expression. RESULTS: Chip darkening from senescent sweetening was delayed by about 4 weeks for tubers with reduced VInv expression. A strong positive correlation between frequency of dark chips and tuber hexose content was observed. Tubers with reduced VInv expression had lower hexose to sucrose ratios than controls. CONCLUSION: VInv activity contributes to reducing sugar accumulation during senescent sweetening. Sucrose breakdown during frying may contribute to chip darkening. Suppressing VInv expression increases the storage period of the chipping potato crop, which is an important consideration, as potatoes with reduced VInv expression are entering commercial production in the USA. © 2017 Society of Chemical Industry.

Retrospective 2- to 7-Year Follow-Up Study of 20 Double Full-Arch Implant-Supported Monolithic Zirconia Fixed Prostheses: Measurements and Recommendations for Optimal Design.

PURPOSE: To measure the extension of cantilever lengths, thicknesses, and heights of zirconia prostheses in the lingual and facial areas of the distal screw access openings, and to evaluate the clinical performance regarding chipping or fracture of the distal cantilevered sections of double full-arch CAD/CAM screw-retained, stained, monolithic zirconia, gingival-colored ceramic implant-supported fixed prostheses (MZ-FPs). MATERIALS AND METHODS: Ten edentulous patients were provided with a total of 20 CAD/CAM double full-arch MZ-FPs. The zirconia thicknesses around distal screw access openings at three different levels (crown height space, screw access opening lengths, and dimensions of the cantilevered segments) were measured in the resin prototypes. Patients were evaluated clinically (visually) without magnification, with intraoral digital photography, and radiologically by the author, approximately every 6 months. Ten patients with 20 MZ-FPs were evaluated. Twenty resin prototypes with 35 cantilevered segments (15 maxillary, 20 mandibular) were measured. The lingual and facial thicknesses of the resin frameworks and the crown height spaces of 35 distal access openings were measured. RESULTS: The average extension of the maxillary cantilever segments was 7.72 mm; the mandibular cantilever average was 13.72 mm. The average crown height space for maxillary prostheses was 13.27 mm, for the mandibular prostheses it was 11.89 mm. Zirconia thickness around distal screw access openings at the middle of the crowns, margins and middle of the gingival areas (buccal side of maxillary prostheses) was 4.29, 3.79, and 3.87 mm, respectively. On the lingual sides the thicknesses were 3.13, 2.85, and 3.15 mm, respectively. For mandibular prostheses the thicknesses were 3.56, 3.08, and 3.15 mm, respectively, on the buccal sides, and 2.07, 2.00, and 2.99 mm, respectively, on the lingual sides. No implant failure or changes in the occlusal surface, chipping of the cuspid or incisal edges, or prosthesis distal extension fractures were observed during follow-up periods ranging from 2 to 7 years. The survival rate was 100% for implants and prostheses. In one of the patients, chipping of the pink ceramic was noted in the maxillary prosthesis 36 months after placement. CONCLUSIONS: The results of this study indicated that full-arch MZ-FPs without cutback, or with partial digital cutback and veneering ceramic, were a therapeutic option. Recommendations regarding the thickness of zirconia at the level of the distal screw access openings, the crown height spaces, and the lengths of the cantilever segments were recorded. Additional in vitro and clinical studies will be required for more scientific analysis of the criteria for design of this type of prosthesis to minimize prosthetic complications. Long-term and multicenter studies are needed to corroborate the findings discussed in this report.

Influence of misfit on the occurrence of veneering porcelain fractures (chipping) in implant-supported metal-ceramic fixed dental prostheses: an in vitro pilot trial.

OBJECTIVE: Technical complications such as veneer fractures are more common in implant-supported than tooth-supported restorations. The underlying causes have not been fully identified. The aim of this study was to evaluate whether misfit between the restoration and the implant may affect the risk of veneer fractures. MATERIALS AND METHODS: Twenty standardized five-unit implant-supported metal-ceramic fixed dental prostheses (FDP)s were manufactured and fixed in acrylic blocks. The test group consisted of ten FDPs fixed with a 150-µm misfit at the distal abutment. The remaining ten FDPs were fixed without misfit and acted as a control group. All FDPS underwent cyclic loading for a total of 100,000 cycles at 30-300 N. The FDPs were checked for cracks or chip-off fractures regularly. After cyclic load, the retorque value of all abutment screws was checked. RESULTS: Cracks within the veneering porcelain were noted in nine FDPs in the test group and one FDP in the control group. This difference was statistically significant (P < 0.001). Fractures of the veneering porcelain occurred in three FDPs in the test group. No fractures occurred in the control group. This difference was not statistically significant. There were no significant differences in retorque values neither between the groups nor between different abutment positions in the FDPs. CONCLUSIONS: Within the limitations of this in vitro pilot trial, it is suggested that misfit between a restoration and the supporting implant may increase the risk of cracking and/or chipping of the veneering porcelain for metal-ceramic FDPs.