In vitro pilot study comparing a novel implantoplasty sonic instrumentation protocol with a conventional protocol using burs.

BACKGROUND AND OBJECTIVES: The aim of implantoplasty (IP) is to remove titanium implant layers that have been contaminated and to smoothen the implant surfaces so they retain less plaque. However, existing IP methods are very invasive and reduce implant wall thickness. AIM: To investigate the suitability of novel sonic tips in IP and to compare this novel protocol with conventional abrasive procedures. MATERIALS AND METHODS: Thirty dental implants (Ø 4.1 mm, 10 mm length) were distributed in three groups and investigated according to the protocol of Sivolella et al., with modifications to the instrument's feed rate, the applied contact force, and the speed of implant rotations per minute. The upper third of the implant was processed with a diamond-coated bur (BUR) or novel non-diamond-coated sonic tips (AIRSCALER). After standardized IP, the surfaces were analyzed by tactile profilometry and scanning electron microscopy (SEM). Changes in implant weight, implant material loss, and implant fracture strength were assessed. RESULTS: The mean roughness (Ra , Sa ), implant material loss, and change in implant weight were significantly lower in the AIRSCALER group than in the BUR group, whereas the mean compression resistance values were significantly higher in the AIRSCALER group than in the BUR group. CONCLUSIONS: IP with uncoated sonic tips smoothes the surfaces and reduces structural loss of the implant in the area of microthreads. This new IP method could be of great clinical importance, especially for implants with microthreads and reduced diameter or wall thickness.

Immediate loading of dental implants in edentulous mandibles using Locator attachments or Dolder bars: A 9-year prospective randomized clinical study.

AIM: To evaluate the long-term survival, incidence of prosthetic/technical and biological complications and the oral-health-related quality of life in patients with an edentulous mandible who were fitted with overdentures on two immediately loaded implants in the symphyseal area. MATERIALS AND METHODS: Forty-six patients with edentulous mandibles received two immediately loaded implant-retained dentures with either two Locator attachments or egg-shaped bar attachments. Implant outcomes were recorded after a period of observation of 9 years and included prosthetic complications, modified gingiva index (mGI), modified plaque index (mPI), oral health impact profile (OHIP-G) and radiographic estimation of bone loss. RESULTS: In 2020/2021, 27 patients with 54 implants were still available for follow-up. In total, nine implants in six patients were lost. Survival was 89.1% in the bar group and 91.3% in the Locator group. Implant success was 84.6% in the Locator group and 76.9% in the bar group. The mPI values were significantly higher in the bar group than in the Locator group, whereas no difference was seen in the mGI values. During the observation period, 152 prosthetic complications occurred, but the OHIP-G score did not differ significantly. CONCLUSIONS: There was no difference in implant survival between Locator or joint bar attachments over a 9-year observation period. Joint bar attachments were associated with slightly more complications, while patients in the Locator group were able to maintain better oral hygiene. The study was registered in the German Register of Clinical (Trials DRKS00004245).

Survival and success of tooth-implant-supported and solely implant-supported double-crown-retained overdentures: A prospective study over a period of up to 11 years.

OBJECTIVES: To investigate the long-term performance, over a period of up to 11 years, of tooth-implant-supported and solely implant-supported double-crown-retained overdentures (DCRDs) for complete restoration of the jaw. MATERIALS AND METHODS: Between 2002 and 2015, patients were consecutively enrolled in the study at Heidelberg University Hospital's Department of Prosthodontics. Scheduled and unscheduled visits were both documented on standardized forms. Kaplan-Meier curves were used to evaluate survival and success of the DCRDs. Mixed effects Cox regression was used to identify the potential effects of age, sex, jaw, location of implants, and the number of abutment teeth on the success of the DCRDs. RESULTS: One hundred and thirty-nine DCRDs were placed in 126 participants (mean age: 65.6 ± 9.1 years; 76 [60.3%] men). The mean follow-up period was 4.2 years. Fifty-three (38%) DCRDs were solely implant-supported (213 implants) and 86 (62%) were tooth-implant-supported (239 teeth and 199 implants). Cumulative five-year survival was 96.2% in the implant-supported group and 97.7% in the tooth-implant-supported group. Simultaneous consideration of failures and severe complications revealed cumulative five-year success of 88.2% for implant-supported DCRDs and 81.9% for tooth-implant-supported DCRDs, with no significant difference between the two types of restoration. Cox regression analysis revealed a greater risk of major complications (hazard ratio: 4.87, p = .04) for maxillary DCRDs than for mandibular DCRDs. CONCLUSIONS: Although the study design has limitations, the results show that tooth-implant-supported and solely implant-supported DCRDs are both recommendable treatment options. After a mean follow-up of 4.2 years, survival and success were high. However, minor complications were common and required much aftercare. CLINICAL TRIAL REGISTRATION: This study started in 2005 and was approved by the local review board of the University of Heidelberg. In 2005, clinical trial registration was not yet common. For this reason, the study was not registered.

Maxillary implant overdentures on two or four implants. A prospective randomized cross-over clinical trial of implant and denture success and survival.

OBJECTIVES: To determine implant survival and success of four conventionally but initially asynchronously loaded implants in implant-supported overdentures for the edentulous maxilla, in participants with opposing mandibular two-implant overdentures. MATERIAL AND METHODS: Twenty-six participants received four implants in the region of the maxillary canines and molars. After healing, 24 of these participants (mean age: 68.3 years) were randomly allocated to one of two treatment groups, and the adapted overdenture was attached to two unsplinted cylindrical attachments. The other two matrixes remained unattached to the implants for 3 months. After this period, the other two implants were loaded for 3 months (cross-over design). Then, all four implants were loaded for another 3 months. Kaplan-Meier curves were used to evaluate survival and success of implants and dentures. RESULTS: During the active prosthetic study phase, three participants lost one implant. Two participants lost three implants during the recall period. Implant survival after loading was 93.8% after a mean observation period of 3.1 years. Denture survival was 100%, but denture success was 95.8%, due to major prosthetic complications. Most participants preferred four implants to two. CONCLUSIONS: Within the limitations of the study, it can be concluded that maxillary implant overdentures on two or four implants are both recommendable treatment options. Two posterior implants are not superior to two anterior implants under overdentures retained by unsplinted cylindrical attachments. Implant and prosthetic complications and aftercare measures are common but are mostly easy to handle. However, 23 of the 24 participants preferred the 4-implant maxillary overdenture.

Effect of bone quality and quantity on the primary stability of dental implants in a simulated bicortical placement.

OBJECTIVES: Conventional dental implants inserted in the molar region of the maxilla will reach into the sinus maxillaris when alveolar ridge height is limited. When surgery is performed without prior augmentation of the sinus floor, primary stability of the implant is important for successful osseointegration. This study aimed at identifying the impact of bone quality and quantity at the implantation site on primary implant stability of a simulated bicortical placement. MATERIALS AND METHODS: In our in vitro measurements, bone mineral density, total bone thickness and overall cortical bone thickness were assessed by micro-computed tomography (µCT) of pig scapulae, which resembled well the bicortical situation found in human patients. Dental implants were inserted, and micromotion between bone and implant was measured while loading the implant with an axial torque. RESULTS: The main findings were that primary implant stability did not depend on total bone thickness but tended to increase with either increasing bone mineral density or overall cortical bone thickness. CLINICAL RELEVANCE: Limited bone height in the maxilla is a major problem when planning dental implants. To overcome this problem, several approaches, e.g. external or internal sinus floor elevation, have been established. When planning the insertion of a dental implant an important aspect is the primary stability which can be expected. With other factors, the dimensions of the cortical bone might be relevant in this context. It would, therefore, be helpful to define the minimum thickness of cortical bone required to achieve sufficient primary stability, thus avoiding additional surgical intervention.

Long-term chipping and failure rates of implant-supported and combined tooth-implant-supported metal-ceramic and ceramic fixed dental prostheses: A cohort study.

STATEMENT OF PROBLEM: Combined tooth-implant-supported fixed dental prostheses have been associated with an increased risk of long-term failure. Furthermore, high chipping rates have been reported for ceramic fixed dental prostheses. However, clinical data are sparse. PURPOSE: The purpose of this observational cohort study was to evaluate the chipping and failure rates of metal-ceramic and ceramic implant-supported and combined tooth-implant-supported fixed dental prostheses. MATERIAL AND METHODS: Four hundred thirty-four fixed dental prostheses placed in 324 patients (mean age: 60.8 years) were selected from a prospective clinical long-term study comprising 213 implant-supported fixed dental prostheses, 66 implant-supported cantilever fixed dental prostheses, and 155 tooth-implant-supported fixed dental prostheses. Metal-ceramic fixed dental prostheses (n=260) were fabricated with a high noble metal alloy (n=225) or Co-Cr base metal alloy (n=35) frameworks. Ceramic fixed dental prostheses (n=174) were all zirconia based and had monolithic (n=68), completely veneered (n=43), or partially veneered frameworks (n=63). Kaplan-Meier curves were used to estimate the survival probability and the chipping-free survival rate of the fixed dental prostheses. RESULTS: During the observation period of 0.5 to 12.6 years (mean: 4.26 years), 17 fixed dental prostheses failed because of implant failure (n=6), tooth loss (n=5), major chipping (n=5), or abutment screw loosening (n=1). Survival probability was 96% after 5 years and 91% after 10 years. Cox regression analysis showed that age, sex, fixed dental prosthesis location, type of fixed dental prosthesis support, and fixed dental prosthesis material had no significant effect on fixed dental prosthesis failure. Chipping (n=61) was significantly affected by the framework material and type of veneer (P=.001). After 5 years, the greatest incidence of chipping (39%) was observed for zirconia fixed dental prostheses with a complete veneer compared with an 18% incidence of chipping for metal-ceramic fixed dental prostheses with a high noble metal framework. A lower incidence of chipping was observed for zirconia fixed dental prostheses with a partial veneer or monolithic design. CONCLUSIONS: Implant-implant-supported and combined tooth-implant-supported fixed dental prostheses have promising long-term survival rates. Chipping seems to occur less frequently in monolithic or partially veneered fixed dental prostheses than in fixed dental prostheses with complete veneers.

The effect of transcrestal sinus-floor elevation without graft on the long-term prognosis of maxillary implants.

AIM: To evaluate the effects of (a) transcrestal sinus-floor elevation (TSFE) and (b) residual bone height on long-term implant survival. MATERIALS AND METHODS: Chi-squared and t tests were used for descriptive comparison of the groups. Kaplan-Meier survival curves and corresponding log-rank tests were used to investigate implant survival over time. Multivariable Cox regressions were performed for the total population and experimental group. RESULTS: A total of 634 patients received 648 implants with TSFE, while 674 implants without TSFE served as controls. Thirty implant failures occurred in the experimental group and 28 in the control group. Ten-year Kaplan-Meier survival curves for the 157 implants (24.3%) still under observation showed a probability of survival of 93.7% for the implants with TSFE and 92.9% for the 72 implants without TSFE (p = .678). The probability of 10-year survival of all implants in the experimental group decreased to 77.4% for implants placed in residual bone heights of 1-3 mm, compared with 95.7% for implant sites with bone heights of 4-6 mm and 97.6% for bone heights of >6 mm. CONCLUSIONS: Transcrestal sinus-floor elevation has no negative effect on the long-term implant survival. Membrane perforation or negligible bone height, however, reduces the probability of 10-year survival.

The up-to-11-year survival and success of implants and abutment teeth under solely implant-supported and combined tooth-implant-supported double crown-retained removable dentures.

OBJECTIVE: This retrospective analysis was designed to compare the survival and success of dental implants in solely implant-supported, double crown-retained removable dentures (DCRDs) and combined tooth-implant-supported DCRDs, due to a lack of data on the latter. MATERIAL AND METHODS: From 2002, patients were consecutively admitted for treatment at the Department of Prosthodontics, University of Heidelberg. Surgical and prosthodontic treatment and scheduled and unscheduled visits were recorded on standardized documentation forms. Kaplan-Meier analysis was used to estimate success (survival without major complications). Cox regression was applied to assess risk factors. RESULTS: From this clinical study, 139 DCRDs on 412 implants and 239 teeth met the inclusion criteria. Fifty-three dentures were implant-supported (213 implants). Eighty-six were supported by teeth and implants. The DCRDs were placed in 126 patients. After an observation period of up to 11.2 years (median: 4.2 years), total implant survival was 99.5% for tooth-implant-supported DCRDs and 93.4% for implant-supported ones. The estimated cumulative success was 97.2% (standard error/SE ± 1.2%) and 85.9% (SE ± 2.4%) at five years, respectively. Complications included implant or tooth loss, peri-implantitis, apical periodontitis and tooth fracture. In terms of abutments, results from multiple Cox regression revealed lower failure rates in tooth-implant-supported dentures (p = .04). No other risk factors were identified. CONCLUSIONS: Within the limitations of this study, survival and success are high for both treatment options. Combining teeth and implants in one DCRD might have a positive effect on the prognosis of the implant and the survival of remaining teeth.

Adaptation to new complete dentures-is the neuromuscular system outcome-oriented or effort-oriented?

OBJECTIVE: The aim of this study was to observe the adaptation strategy of the stomatognathic system during the adaptation of complete dentures, comprising masticatory parameters and subjective measures. Our hypothesis was that with new dentures, masticatory performance would increase while the effort of the system is kept constant. MATERIAL AND METHODS: Thirty-two patients received standardized new complete dentures. Masticatory performance tests were conducted with old dentures (T1), immediately after incorporation of new dentures (T2) and after an adaptation period of 3 months (T3). Patients habitually chewed the silicone-based artificial test food Optocal. The comminuted test food was analyzed and mean particle sizes (x50) were calculated. Simultaneously, surface EMGs of the anterior temporalis and masseter muscles were recorded. Specific (SMW) and total muscle work (TMW) were determined. Patients filled in the OHIP-49 questionnaire. Test conditions were compared using repeated-measures ANOVA with SPSS 22 (SPSS Inc.) RESULTS: Masticatory performance increased (P = 0.016) between old (x50 = 4.99 ± 0.28) and adapted new dentures (x50 = 4.80 ± 0.33). TMW deteriorated (P = 0.004) at T2 (from TMW1 = 119.77 ± 56.49 to TMW2 = 92.12 46.27), and increased again (P = 0.028) at T3 (TMW3 = 107.66 ± 44.65). OHIP scores decreased significantly in all subscales (P < 0.001…P = 0.046); the total score was reduced (P < 0.001) from 56.24 ± 29.05 (T1) to 34.66 ± 24.74 (T3). CONCLUSION: In complete denture wearers, masticatory performance improves over an adaptation period. Muscle work initially decreased before reaching its original level again after adaptation. Subjective parameters overestimated the functional improvements. CLINICAL SIGNIFICANCE: The subjective evaluation does not adequately reflect functional improvements. The assessment of function requires an adaptation period.

Effect of prosthetic restoration on implant survival and success.

PURPOSE: The objective of this work was to evaluate the effect of prosthetic restoration on the survival of implants and on the incidence of implant-related complications. MATERIAL AND METHODS: From a prospectively documented clinical study, 1569 implants placed in 630 patients (mean age 59.56 years) were evaluated. Selection criteria were a conventional loading protocol, prosthetic restoration with at least one follow-up, and a minimum observation period of 9 months. Implants that failed before prosthetic restoration were excluded. The sample included 1345 tissue-level implants and 104 bone-level implants (Straumann), and 120 Replace implants (Nobel Biocare). The observation period ranged between 9 months and 11 years after prosthetic restoration (mean 4.0 years; SD 2.5). The implants were restored with single crowns (n = 557), fixed dental prostheses (n = 594), or removable dental prostheses (RDP) (n = 418). In the RDP group, 356 implants were restored with telescoping crowns, 22 with bar units 24 with bar joints, and 16 with locator attachments. The incidence of implant-related complications and failures was analyzed by use of Kaplan-Meier survival curves. Cox regression analysis was used to identify possible risk factors. RESULTS: Twenty-seven failures (1.8%; loosened or removed implants) were observed after prosthetic restoration; the incidence of failure was 3% for implants placed in males and 1% for implants placed in females. Other factors had no effect on the incidence of failure. Peri-implantitis (n = 29) and marginal bone loss >2 mm without acute inflammation (n = 6) also resulted in a 4% incidence of severe implant-related complications (62 of 1569; success 96%). Cox regression analysis revealed combined tooth-implant-supported restorations as a significant risk-reducing factor for severe implant-related complications (hazard ratio, HR = 0.34; P = 0.04). There was, furthermore, a tendency toward a greater incidence of complications for implants restored with RDPs than for single crowns (P = 0.08). Other factors, for example location (anterior/posterior, maxilla/mandible), age, sex, or implant placement combined with bone augmentation, had no significant effect on the incidence of implant-related complications (P values ranging between 0.16 and 0.94). CONCLUSIONS: The type of support has a small but significant effect on implant prognosis. For detailed analysis of the effects of loading by different types of prosthetic restoration, larger sample sizes are required.

Functional adaptation of the masticatory system to implant-supported mandibular overdentures.

OBJECTIVES: The purpose of this study was to investigate the adaptation behavior of the stomatognathic system after immediate loading (24 to 72 h after surgery) of two implants supporting mandibular overdentures, assessed on insertion and three months later. The study hypothesis was that insertion of the overdentures would significantly change masticatory performance and muscle activity at both times. MATERIAL AND METHODS: Thirty subjects (nine female, mean age 69.64 ± 11.81 years; 21 male, mean age 68.67 ± 7.41 years) who participated in a randomized clinical trial were included in the study. Each patient was examined three times: (i) at baseline, after already having worn new dentures for three months (T1); (ii) immediately after insertion of the overdentures on the implants (T2); and (iii) after an adaptation period of three months (T3). Examination comprised assessment of masticatory performance with artificial test food (Optocal), and simultaneous bilateral surface EMG recording of the masseter and anterior temporalis muscles. Particle-size distribution (representative value X50 ), maximum muscle contraction (MVC), and total muscle work (TMW; area under the curve) were compared by use of repeated-measures analysis of variance (ANOVA). RESULTS: At T3, all measured variables (i.e., masticatory performance and muscle activity) were significantly different from those at T1. At T2, no significant changes were observed. The study hypothesis had to be rejected for T2 but accepted for T3. CONCLUSION: Functional rehabilitation (in terms of masticatory performance and masticatory muscle activity) does not occur immediately after immediate loading of two implants with mandibular overdentures, but requires a significant time for functional improvement.

Spatially resolved analysis of plutonium isotopic signatures in environmental particle samples by laser ablation-MC-ICP-MS.

Laser ablation-multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was optimized and investigated with respect to its performance for determining spatially resolved Pu isotopic signatures within radioactive fuel particle clusters. Fuel particles had been emitted from the Chernobyl nuclear power plant (ChNPP) where the 1986 accident occurred and were deposited in the surrounding soil, where weathering processes caused their transformation into radioactive clusters, so-called micro-samples. The size of the investigated micro-samples, which showed surface alpha activities below 40 mBq, ranged from about 200 to 1000 µm. Direct single static point ablations allowed to identify variations of Pu isotopic signatures not only between distinct fuel particle clusters but also within individual clusters. The resolution was limited to 100 to 120 µm as a result of the applied laser ablation spot sizes and the resolving power of the nuclear track radiography methodology that was applied for particle pre-selection. The determined (242)Pu/(239)Pu and (240)Pu/(239)Pu isotope ratios showed a variation from low to high Pu isotope ratios, ranging from 0.007(2) to 0.047(8) for (242)Pu/(239)Pu and from 0.183(13) to 0.577(40) for (240)Pu/(239)Pu. In contrast to other studies, the applied methodology allowed for the first time to display the Pu isotopic distribution in the Chernobyl fallout, which reflects the differences in the spent fuel composition over the reactor core. The measured Pu isotopic signatures are in good agreement with the expected Pu isotopic composition distribution that is typical for a RBMK-1000 reactor, indicating that the analyzed samples are originating from the ill-fated Chernobyl reactor. The average Pu isotope ratios [(240)Pu/(239)Pu = 0.388(86), (242)Pu/(239)Pu = 0.028(11)] that were calculated from all investigated samples (n = 48) correspond well to previously published results of Pu analyses in contaminated samples from the vicinity of the Chernobyl NPP [e.g. (240)Pu/(239)Pu = 0.394(2) and (242)Pu/(239)Pu = 0.027(1); Nunnemann et al. (J Alloys Compd 271-273:45-48, 1998)].

Undetected residual cement on standard or individualized all-ceramic abutments with cemented zirconia single crowns - a prospective randomized pilot trial.

OBJECTIVE: To assess the frequency and amount of residual cement after attachment of monolithic zirconia crowns to standard and individualized ceramic abutments. MATERIAL AND METHODS: Twenty patients (mean age 58.9 years at inclusion in the study; 30% male) were randomized to receive either a standard or an individualized abutment on a bone-level implant. Monolithic zirconia single crowns were attached to abutments by use of permanent glass-ionomer cement. Crowns were fabricated with an occlusal hole to enable unscrewing of the abutment-crown complex. Immediately after cementation, superstructures were removed and both the peri-implant soft tissue and the abutment-crown complex were photographed in a standardized manner, to detect residual cement. Photographs were analyzed using Corel Photo Paint X7, and residual cement-to-total abutment and residual cement-to-peri-implant soft tissue area ratios were calculated. RESULTS: Residual cement was observed for 9 of 10 (90%) individualized abutments, compared with 4 of 10 (40%) standard abutments (OR = 13.5, P = 0.049). Twenty-seven of 40 (68%) individualized abutment surfaces were affected, compared with 12 of 40 (30%) standard abutment surfaces. The probability of observing residual cement was approximately five times higher for the surfaces of individualized abutments than for those of standard abutments (P = 0.005). The mean amount of sulcus surface covered by cement was 1.17% (SD 2.85) for the individualized abutments and 3.78% (SD 7.40) for the standard abutments. The position of the margin significantly affected the amount of residual cement. CONCLUSION: Both individualized and standard all-ceramic abutments result in small amounts of subgingival residual cement on abutment and sulcus surfaces. However, use of individualized abutments does not guarantee complete avoidance of undetected cement rests. Undetected residual cement might be avoided by use of all-ceramic abutments with visible abutment shoulders.

Particle size distributions determined by optical scanning and by sieving in the assessment of masticatory performance of complete denture wearers.

OBJECTIVES: Standard procedure for the measurement of masticatory performance is the fractionated sieving of fragmented test food, which is substantially time consuming. The aim of this study was to introduce a less laborious, comparable, and valid technique based on scanning. METHODS: Fifty-six Optocal chewing samples were minced by wearers of complete dentures with 15 and 40 chewing strokes and analyzed by both a sieving and a scanning method. The sieving procedure was carried out using ten sieves (5.6, 4.0, 2.8, 2.0, 1.4, 1.0, 0.71, 0.5, 0.355, and 0.25 mm) and measuring the weight of the specific fractions. Scanning was performed with a flatbed scanner (Epson Expression1600Pro, Seiko Epson Corporation, Japan, 1,200 dpi). Scanned images underwent image analysis (ImageJ 1.42q, NIH, USA), which yielded descriptive parameters for each particle. Out of the 2D image, a volume was estimated for each particle. In order to receive a discrete particle size distribution, area-volume-conversion factors were determined. The cumulated weights yielded by either method were curve fitted with the Rosin-Rammler distribution (MATLAB, The MathWorks, Inc., Natick, USA) to determine the median particle size X 50. RESULTS: The Rosin-Rammler distributions for sieving and scanning resembled each other and showed an excellent correlation in 15/40 chewing strokes (r = 0.995/r = 0.971, P < 0.01, Pearson's correlation coefficient). The median particle sizes varied between 4.77/3.04 and 5.36/5.28 mm (mean 5.07/4.67) for scanning and 4.69/2.39 and 5.23/5.43 mm (mean 5.03/4.57) for sieving. On average, scanning overestimated the X 50 values by 1/2.4 %. The scanning method took 10 min per sample in contrast to 50 min for sieving. CONCLUSION: Optical scanning is a valid method comparable to sieving. CLINICAL RELEVANCE: The described method is feasible and appropriate for the measurement of masticatory performance of denture wearers.

Evaluation of the operating parameters of the liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source for elemental mass spectrometry.

The liquid sampling-atmospheric pressure glow discharge (LS-APGD) has been assessed as an ionization source for elemental analysis with an interdependent, parametric evaluation regarding sheath/cooling gas flow rate, discharge current, liquid flow rate, and the distance between the plasma and the sampling cone of the mass spectrometer. In order to better understand plasma processes (and different from previous reports), no form of collision/reaction processing was performed to remove molecular interferents. The evaluation was performed employing five test elements: cesium, silver, lead, lanthanum and nickel (10(-4) mol L(-1) in 1 mol L(-1) HNO3). The intensity of the atomic ions, levels of spectral background, the signal-to-background ratios, and the atomic-to-oxide/hydroxide adduct ratios were monitored in order to obtain fundamental understanding with regards to not only how each parameter effects the performance of this LS-APGD source, but also the inter-parametric effects. The results indicate that the discharge current and the liquid sampling flow rates are the key aspects that control the spectral composition. A compromise set of operating conditions was determined: sheath gas flow rate = 0.9 L min(-1), discharge current = 10 mA, solution flow rate = 10 µL min(-1), and sampling distance = 1 cm. Limits of detection (LODs) were calculated using the SBR-RSDB (signal-to-background ratio/relative standard deviation of the background) approach under the optimized condition. The LODs for the test elementals ranged from 15 to 400 ng mL(-1) for 10 µL injections, with absolute mass values from 0.2 to 4 ng.

Clinical comparison of metal ceramic resin-bonded fixed dental prostheses with a conventional and a mixed retainer design.

STATEMENT OF PROBLEM: Little is known about the clinical performance of fixed dental prostheses that rigidly connect adhesive retainers and crowns. PURPOSE: The purpose of this retrospective analysis was to assess and compare the clinical performance of resin-bonded fixed dental prostheses with a conventional and a mixed retainer design. MATERIAL AND METHODS: Included as participants were all patients of the hospital since 2004 with regular clinical follow-up who were treated with 3-unit or 4-unit metal ceramic resin-bonded fixed dental prostheses with a conventional 2-adhesive retainer design (conventional group) or with a mixed type combining an adhesive retainer with a crown or a partial crown retainer (mixed group). The analysis included 84 participants with a total of 57 (64%) prostheses in the conventional group and 32 (36%) prostheses in the mixed group. Treatment and data collection were standardized. Cumulative survival without failure (defined as a restoration in need of replacement), chipping, and debonding were estimated by the Kaplan-Meier method and compared for the groups (log-rank test) (α=.05). RESULTS: During a mean observation period of 4.1 years (SD, 2.5 years; minimum, 0.4 years; maximum, 9.4 years), 12 complications occurred in 10 restorations. Defects of the ceramic veneer (n=6) were observed most frequently. The estimated 5-year failure-free survival rate was 97.4% (standard error, .025) in the conventional group and 95% (standard error, .049) in the mixed group (log-rank, P=.32). The 5-year cumulative survival rate without chipping was 90.7% (standard error, .064) for the conventional group and 93.8% (standard error, .061) for the mixed group (log-rank, P=.44). The 5-year cumulative survival rate without debonding was 95.1% (standard error, .034) for the conventional group and 91.5% (standard error, .058) for the mixed group (log-rank, P=.54). CONCLUSIONS: Limited by a small sample size and a short follow-up period, the findings of this retrospective analysis indicate that the clinical performance, in terms of survival and the incidence of complications, is comparable for conventional resin-bonded fixed dental prostheses and those that rigidly connect an adhesive wing and a partial or complete crown. Acceptable 5-year survival and complication rates imply that the medium-term prognosis for resin-bonded restorations with a retentive preparation design is comparable with that for conventional fixed dental prostheses.

Resistance to Fracture in Fixed Dental Prostheses Over Cemented and Screw-Retained Implant-Supported Zirconia Cantilevers in the Anterior Region: An In Vitro Study.

PURPOSE: To evaluate the resistance to fracture in cantilevered fixed dental prostheses (cFDPs) of single implant-supported zirconia cantilevers in the anterior region. MATERIALS AND METHODS: Thirty-two cemented and solely screw-retained cFDPs consisting of an implant-supported crown replacing the central incisor and an attached cantilever unit in the position of the lateral incisor in the maxilla were constructed by computer-aided design (CAD) and machined by computer-aided manufacturing (CAM). For the cemented solution, a cFDP was designed on top of a customized abutment luted to an adhesive base. For screw-retained cFDPs, abutment, cement gap, and restoration of the cementable design were combined. All cFDPs were veneered manually on the facial side. Half of the samples underwent artificial aging (thermocycling and chewing simulation) before fracture tests were conducted with loads applied to the pontic either parallel to the implant axis (axial loading on the pontic) or tilted lingually by α = 45 degrees (oblique loading on the pontic). Thus, there were eight groups differing in cFDP design, artificial aging, and load application (n = 8/group). If fracture (Fu,total) occurred within the implant components, the adhesive base was replaced by a cast CoCr base, and the cFDP's fracture resistance (Fu,cFDP) was also determined. Using statistical analyses (SPSS 24, IBM), factors affecting fracture resistance were identified. RESULTS: Fu,total was mainly correlated to screw fractures and therefore not affected by cFDP design. Oblique loading on the pontic (Fu,total = 231 N - 352 N), however, led to a significant (P < .001) decrease in ultimate load compared with axial loading on the pontic (Fu,total = 611 N - 815 N). In relation to Fu,total, Fu,cFDP was approximately twice as high for both loading conditions. CONCLUSION: When relating the results to maximum occlusal forces exerted in the maxillary anterior region, single implant-supported cFDPs can be a viable restorative treatment option.

Long-term performance of implant-supported metal-ceramic and all-ceramic single crowns.

PURPOSE: To evaluate failure rates and incidence of chipping for metal-ceramic and all-ceramic implant-supported single crowns (SCs). METHODS: Six hundred and fifty-two implant-supported SCs placed in 404 patients (mean age: 57.8 years; 193 male; mean SCs per patient: 1.6) were evaluated up to 12.8 years. The frameworks of the SCs were made from Au alloys (n = 319), CoCr (n = 37), zirconia (n = 286), or lithium disilicate (n = 10). Full-coverage ceramic veneers were placed on 319 Au SCs, 34 CoCr SCs, and 92 zirconia SCs. One hundred and fifty-two monolithic zirconia SCs were not veneered. A partial veneer was placed on the buccal surface only of a further 42 zirconia SCs. RESULTS: A total of 26 failures were caused by loss of implants (n = 6), ceramic fractures and chipping (n = 15), loosening of the abutment (n = 4), or swallowing of a de-cemented SC (n = 1). Kaplan-Meier analysis revealed a probability of survival of 96% after five years and 92% after 10 years. A greater incidence of failure was observed for lithium disilicate and zirconia SCs than for metal-ceramic SCs (p < .05). Separate analysis of the most frequent complication, chipping (n = 61), revealed that zirconia and lithium disilicate frameworks were significant risk factors for chipping (p < 0.05). Furthermore, a significantly greater incidence of chipping was observed for SCs with full-coverage veneers than for monolithic zirconia SCs and for SCs with partial veneers (p < .05). CONCLUSION: Avoidance of full-coverage veneers significantly improves the clinical performance of implant-supported crowns, primarily reduces the incidence of chipping.

Cemented Single Crown Retention on Dental Implants: An In Vitro Study.

PURPOSE: The aim of this study was to determine the influence of selected cements, abutment heights, and aging on the retention of zirconia crowns on zirconia abutments. MATERIALS AND METHODS: Zirconia crowns and abutments (height: 4.0 or 5.5 mm) were sandblasted and retained using five different cements. Axial pull-off tests were performed after thermocycling or 3 days of water storage. RESULTS: An increase in abutment height was associated with an increase in decementation force when permanent cementation was tested. The aging protocol showed that temporarily cemented crowns showed a significant retention decrease, while use of a permanent cement led to a moderate increase. CONCLUSION: Only use of permanent cements ensures clinically adequate decementation forces.

Effects of Cement, Abutment Surface Pretreatment, and Artificial Aging on the Force Required to Detach Cantilever Fixed Dental Prostheses from Dental Implants.

PURPOSE: To examine the in vitro effects of different cements, abutment surface preconditioning, and artificial aging on the maximum tensile force needed to detach cantilever fixed dental prostheses (FDPs) from dental implants with titanium abutments. MATERIALS AND METHODS: A total of 32 tissue-level implants were combined with standardized titanium abutments. For each test group, eight cantilever FDPs were fabricated using selective laser melting (cobalt-chromium [CoCr] alloy). The inner surfaces of the cantilever FDPs and half of the abutments were sandblasted and then joined by use of four different cements (two permanent and two semi-permanent) in two different amounts per cement. Subgroups were tested after either artificial aging (thermocycling and chewing simulation) or 3 days of water storage. Finally, axial pull off-tests were performed for each abutment separately. RESULTS: Cement type and surface pretreatment significantly affected decementation behavior. The highest retention forces (approximately 1,200 N) were associated with sandblasted abutments and permanent cements. With unconditioned abutments, temporary cements (Fu < 100 N), as well as glass-ionomer cement (Fu ≈ 100 N), resulted in rather low retention forces. Zinc phosphate cement guaranteed high retention forces. After aging, retention was sufficient only for cementation with zinc phosphate cement and for the combination of sandblasted abutments and glass-ionomer cement. CONCLUSIONS: When glass-ionomer cement is used to fix cantilever FDPs on implants, sandblasting of standard titanium abutments may help prevent loss of retention. Retention forces were still high for FDPs fixed with zinc phosphate cement, even when the abutments were not pretreated. Use of permanent cements only, however, is recommended to prevent unwanted loosening of cantilever FDPs.