Clinical performance of cantilevered fixed dental prostheses abutments in the shortened dental arch

Objectives

This article is part of a randomized clinical trial on different treatments in the shortened dental arch (SDA). It focused on the abutment tooth prognosis with cantilevered fixed dental prostheses (CFDPs).

Methods

Sixty-two patients with a bilaterally SDA up to the first or second premolar in the mandible or maxilla were evaluated. In 57 of 124 quadrants, second premolars were replaced by a CFDP (cantilever group). In the remaining 67 quadrants, a natural second premolar was present and thus no need for a CFDP was given (non-cantilever group). Patients were recalled annually up to 5 years.

Results

The mean observation period was 56.3 months (min. 3.0, max. 76.2, SD 16.1). Kaplan–Meier survival rates concerning tooth loss and tooth fracture were 93.9%/94.0% in the cantilever group and 91.9%/92.8% in the non-cantilever group. Differences between both groups were not significant. The survival rate concerning loss of retention of CFDP retainers was 92.1% in the cantilever group.

Conclusion

After 5 years of clinical service, CFDPs for the replacement of the second premolar showed no negative impact on the abutment tooth prognosis.

Clinical significance

Cantilevered fixed dental prostheses present a viable treatment option in the shortened dental arch without compromising the medium-term abutment tooth prognosis.     

Survival of anterior cantilevered all-ceramic resin-bonded fixed dental prostheses made from zirconia ceramic

Objectives

This study evaluated the clinical outcome of all-ceramic resin-bonded fixed dental prostheses (RBFDPs) with a cantilevered single-retainer design made from zirconia ceramic.

Methods

Forty-two anterior RBFDPs with a cantilevered single-retainer design were made from yttrium oxide-stabilized zirconium oxide ceramic. RBFDPs were inserted using Panavia 21 TC as luting agent after air-abrasion of the ceramic bonding surface.

Results

During a mean observation time of 61.8 months two debondings occurred. Both RBFDPs were rebonded using Panavia 21 TC and are still in function. A caries lesion was detected at one abutment tooth during recall and was treated with a composite filling. Therefore, the overall six-year failure-free rate according to Kaplan–Meier was 91.1%. If only debonding was defined as failure the survival rate increased to 95.2%. Since all RBFDPs are still in function the overall survival rate was 100% after six years.

Conclusions

Cantilevered zirconia ceramic RBFDPs showed promising results within the observation period.

Clinical Significance

Single-retainer resin-bonded fixed dental prostheses made from zirconia ceramic show very good mid-term clinical survival rates. They should therefore be considered as a viable treatment alternative for the replacement of single missing anterior teeth especially as compared to an implant therapy.     

Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium disilicate ceramic

BackgroundThe authors conducted a prospective study to evaluate the long-term outcome of crown-retained fixed dental prostheses (FDPs) made from monolithic lithium disilicate ceramic (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein).MethodsFaculty dentists at the Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany, placed 36 three-unit FDPs in 28 patients to replace six anterior and 30 posterior teeth. The proximal connector size (height and width) was 4 × 3 millimeters for anterior FDPs and 4 × 4 mm for posterior FDPs. FDPs were cemented either conventionally with glass ionomer cement (n = 19) or adhesively with resin-based composite (n = 17). Patients made annual recall visits.ResultsThe mean (standard deviation) observation period was 121 (12.8) months. FDPs' survival rate (survival being defined as remaining in place either with or without complications) was 100 percent after five years and 87.9 percent after 10 years, and their success rate (success being defined as remaining unchanged and free of complications) was 91.1 percent after five years and 69.8 percent after 10 years. The cementation method did not affect the outcome.ConclusionThree-unit FDPs made from monolithic lithium disilicate ceramic showed five- and 10-year survival and success rates that were similar to those of conventional metal-ceramic FDPs.Clinical ImplicationsIf the manufacturer's recommendations are followed, three-unit FDPs made from monolithic lithium disilicate ceramic may be a safe alternative to metal-ceramic FDPs regardless of the cementation method used.     

Reliability and aging behavior of three different zirconia grades used for monolithic four-unit fixed dental prostheses

ObjectiveTo investigate the fracture resistance and phase composition of tooth supported four-unit fixed dental prostheses (FDPs) made from three different zirconia grades after loading and aging.MethodsSeventy-two FDPs were fabricated from 3Y-TZP, 4Y-PSZ and 5Y-PSZ. This resulted in 24 FDPs per grade, subdivided into three groups (n = 8): a control group (C), a hydrothermally aged (H₂O, 85 °C, 90 days) group (A) and a group subjected to loading (2.5M cycles, 98N) with simultaneous thermal cycling (H₂O, 5–55 °C) subsequent to treatment A (AL). Subsequently, FDPs were statically loaded to fracture. Phase composition was quantified by X-ray diffraction (XRD) and μ-Raman spectroscopy. Focused ion beam (FIB) - Scanning electron microscopy (SEM) was used for visualization in-depth.ResultsCompared to 3Y-C FDPs (1233 ± 165N), reduced fracture load was found for 5Y-C FDPs (889 ± 80 N; p < .001). This did not apply for 4Y-C samples (1065 ± 111N). Treatments (A, AL) did not negatively affect the fracture load for the three grades of zirconia (p > .645). Both A and AL increased monoclinic phase content for 3Y and 4Y FDPs, whereas FIB-SEM suggests no transformability of 5Y-PSZ. 5Y-AL FDPs showed cracks and fractures at the abutment walls and restoration margins after dynamic loading. Reduced fracture load of 5Y samples as compared to 3Y and 4Y was associated with deficient transformability in the fracture zone.SignificanceAging and loading did not negatively affect the fracture resistance of monolithic four-unit FDPs made from three grades of zirconia. Due to cracks after dynamic loading, 5Y-PSZ cannot be recommended for the clinical application of four-unit FDPs.     

The fit of metal-ceramic crowns, a clinical study

The fit of two series of metal-ceramic crowns, made by students at the Dental Faculties in Oslo and Gothenburg, was measured by means of a replica technique and compared. Measurements were performed both for the crown, die and the crown-tooth situation. The measurements showed a mean film thickness of about 100 μm between crown and tooth along the axial walls. A statistically significant difference in mean film thickness was found between the two series of crowns with the best fit in the Oslo-series. In both series, the mean film thickness between crown and die was about 80% of that between crown and tooth.     

Residual stress of porcelain-fused to zirconia 3-unit fixed dental prostheses measured by nanoindentation

Objective

To evaluate the residual stress (nanoindentation based on hardness) of fatigued porcelain-fused to zirconia 3-unit fixed dental prostheses (FDP) with different framework designs.

Complication and failure rates of fixed dental prostheses in patients treated for periodontal disease

Objectives: To evaluate the biological and technical complication rates of fixed dental prostheses (FDP) with end abutments or cantilever extensions on teeth (FDP‐tt/cFDP‐tt) on implants (FDP‐ii/cFDP‐ii) and tooth‐implant‐supported (FDP‐ti/cFDP‐ti) in patients treated for chronic periodontitis. Material and methods: From a cohort of 392 patients treated between 1978 and 2002 by graduate students, 199 were re‐examined in 2005. Of these, 84 patients had received ceramo‐metal FDPs (six groups). Results: At the re‐evaluation, the mean age of the patients was 62 years (36.2–83.4). One hundred and seventy‐five FDPs were seated (82 FDP‐tt, 9 FDP‐ii, 20 FDP‐ti, 39 cFDP‐tt, 15 cFDP‐ii, 10 cFDP‐ti). The mean observation time was 11.3 years; 21 FDPs were lost, and 46 technical and 50 biological complications occurred. Chances for the survival of the three groups of FDPs with end abutments were very high (risk for failure 2.8%, 0%, 5.6%). The probability to remain without complications and/or failure was 70.3%, 88.9% and 74.7% in FDPs with end abutments, but 49.8–25% only in FDPs with extensions at 10 years. Conclusions: In patients treated for chronic periodontitis and provided with ceramo‐metal FDPs, high survival rates, especially for FDPs with end abutments, can be expected. The incidence rates of any negative events were increased drastically in the three groups with extension cFDPs (tt, ii, ti). Strategic decisions in the choice of a particular FDP design and the choice of teeth/implants as abutments appear to influence the risks for complications to be expected with fixed reconstruction. If possible, extensions on tooth abutments should be avoided or used only after a cautious clinical evaluation of all options. To cite this article:
Brägger U, Hirt‐Steiner S, Schnell N, Schmidlin K, Salvi GE, Pjetursson B, Matuliene G, Zwahlen M, Lang NP. Complication and failure rates of fixed dental prostheses in patients treated for periodontal disease.
Clin. Oral Impl. Res. 22 , 2011; 70–77.
doi: 10.1111/j.1600‐0501.2010.02095.x     

Survival and failure modes: platform‐switching for internal and external hexagon cemented fixed dental prostheses

This study evaluated the probability of survival (reliability) of platform‐switched fixed dental prostheses (FDPs) cemented on different implant–abutment connection designs. Eighty‐four‐three‐unit FDPs (molar pontic) were cemented on abutments connected to two implants of external or internal hexagon connection. Four groups (n = 21 each) were established: external hexagon connection and regular platform (ERC); external hexagon connection and switched platform (ESC); internal hexagon and regular platform (IRC); and internal hexagon and switched platform (ISC). Prostheses were subjected to step‐stress accelerated life testing in water. Weibull curves and probability of survival for a mission of 100,000 cycles at 400 N (two‐sided 90% CI) were calculated. The beta values of 0.22, 0.48, 0.50, and 1.25 for groups ERC, ESC, IRC, and ISC, respectively, indicated a limited role of fatigue in damage accumulation, except for group ISC. Survival decreased for both platform‐switched groups (ESC: 74%, and ISC: 59%) compared with the regular matching platform counterparts (ERC: 95%, and IRC: 98%). Characteristic strength was higher only for ERC compared with ESC, but not different between internal connections. Failures chiefly involved the abutment screw. Platform switching decreased the probability of survival of FDPs on both external and internal connections. The absence in loss of characteristic strength observed in internal hexagon connections favor their use compared with platform‐switched external hexagon connections.     

Accuracy of additively manufactured zirconia four-unit fixed dental prostheses fabricated by stereolithography,digital light processing and material jetting compared with subtractive manufacturing

ObjectiveTo evaluate the manufacturing accuracy of zirconia four-unit fixed dental prostheses (FDPs) fabricated by three different additive manufacturing technologies compared with subtractive manufacturing.MethodsA total of 79 zirconia FDPs were produced by three different manufacturing technologies, representing additive (one stereolithography [aSLA] and one material jetting [aMJ] device, two digital light processing [aDLP1/aDLP2] devices) and subtractive manufacturing (two devices [s1/s2]), the latter serving as references. After printing, additively manufactured FDPs were debound and finally sintered. Subsequently, samples were circumferentially digitized and acquired surface areas were split in three Regions Of Interest (ROIs: inner/outer shell, margin). Design and acquired data were compared for accuracy using an inspection software. Statistical evaluation was performed using the root mean square error (RMSE) and nonparametric Kruskal-Wallis method with post hoc Wilcoxon-Mann-Whitney U tests. Bonferroni correction was applied in case of multiple testing.ResultsRegardless the ROI, significant differences were observed between manufacturing technologies (P < 0.001). Subtractive manufacturing was the most accurate with no significant difference regarding the material/device (s1/s2, P > 0.054). Likewise, no statistical difference regarding accurary was found when comparing s2 with aMJ and aSLA in most ROIs (P > 0.085). In general, mean surface deviation was< 50 µm for s1/s2 and aMJ and< 100 µm for aSLA and aDLP2. aDLP1 showed surface deviations> 100 µm and was the least accurate compared to the other additive/subtractive technologies.SignificanceAdditive manufacturing represents a promising set of technologies for the manufacturing of zirconia FDPs, but not yet as accurate as subtractive manufacturing. Methodological impact on accuracy within and in between different additive technologies needs to be further investigated.     

牙科用氧化锆增韧纳米复相铝瓷粉体的制备与性能研究

目的 研制牙科用氧化锆增韧纳米复相铝瓷粉体并测试其理化性能，探讨影响铝瓷粉体性能的制备工艺。方法 表面诱导沉淀法制备纳米复相铝瓷粉体，记录分散剂加入量及pH值对氧化铝悬浮液沉降物体积的影响；观察超声时间对粉体团聚的影响；X射线衍射分析添加稳定剂前后粉体晶相的组成，扫描电子显微镜下观察其形貌。结果 pH=9、分散剂加入量wt=0．2％～0．3％时，悬浮液分散性好；超声处理后粉体粒径下降；稳定剂处理后复相铝瓷粉体含有单斜相和四方相氧化锆。在原始颗粒较大的氧化铝表面均匀分布着直径约80～100nm的氧化锆细颗粒。结论 控制制备工艺，采用表面诱导沉淀法可得到粒度细、分散好的氧化锆增韧纳米复相铝瓷粉体；经稳定剂处理后，复相铝瓷中的氧化锆成为部分稳定氧化锆。     

Survival and debonding resistance of posterior cantilever resin-bonded fixed dental prostheses for moderately and severely worn dentition during thermomechanical loading

ObjectivesThe purpose of this study was to investigate the survival rate, the debonding resistance, and the failure modes of different occlusal veneer designs when used as a retainer for posterior cantilever, resin-bonded fixed dental prostheses (RBFDPs) at two tooth wear levels.MethodsFour test groups were assigned: two groups with occlusal-proximal preparation (PT1 and PT2 for grade 2 and 3 wear), and two groups for occlusal-proximal and lingual preparation (PLT1 and PLT2 for grade 2 and 3 wear) Monolithic zirconia ceramic (3Y-TZP) RBFDPs were luted with an adhesive bonding system (Panavia V5). The specimens underwent a chewing simulation for 1.200.000 cycles with a load of 5 kg and thermocycling for 7500 cycles between 5 °C and 55 °C. The surviving restorations were debonded under quasi-static conditions. The results were analyzed with ANOVA.ResultsThe specimens exhibited a 100 % survival rate after thermomechanical fatigue loading. The debonding resistance was statistically significant higher for group PLT1 than for group PT1 (P = 0.004), and higher for group PT2 than group PT1 (P ≤ 0.001). However, the debonding resistance showed no statistically significant difference between groups PT2 and PLT2 (P = 0.343), and groups PLT1 and PLT2 (P = 0.222). Groups PT1 and PT2 showed favorable failure modes in 62.5 % and 0.00 % of the specimens, respectively. While groups PLT1 and PLT2 presented 25 % favorable failure modes.SignificanceOcclusal veneers showed promising results as a retainer for cantilever RBFDPs. The lingual extension might increase debonding resistance. Nevertheless, conservative designs with lingual and proximal bevels are to be recommended, irrespective of the level of tooth wear.     

微创全瓷贴面修复临床应用初探

目的 通过分析微创全瓷修复体的美学效果和成功率,初步评价该修复形式的临床应用价值.方法 对30例前牙美学缺陷患者的44颗患牙进行0.5 mm厚度以内的牙体预备或不进行牙体预备,采取长石质陶瓷材料制作全瓷修复体,应用树脂粘接剂粘接.修复后患者采用视觉模拟评分法(visual analogue scales,VAS)评价美学效果满意度;同时,3名修复专业医师对修复后照片进行美学效果评价(边缘美观效果、颜色、形态、半透明度).修复后6、12、24个月复查评价成功率.结果 修复后患者对修复体美学效果的满意度为9.2±0.4;医师美学效果评价中修复体的边缘美观效果、颜色、形态、半透明度优秀率分别为89％(39/44)、91％(40/44)、98％ (43/44)和93％(41/44).修复后6、12、24个月成功率分别为100％(44/44)、98％(43/44)和91％(40/44).结论 微创全瓷贴面修复体具有优秀的美学效果和满意的成功率,在严格掌握适应证的前提下,牙科美学治疗中可采用这种治疗方式.     

Reliability and failure modes of implant-supported zirconium-oxide fixed dental prostheses related to veneering techniques

Objectives

To compare fatigue failure modes and reliability of hand-veneered and over-pressed implant-supported three-unit zirconium-oxide fixed-dental-prostheses(FDPs).

Methods

Sixty-four custom-made zirconium-oxide abutments (n = 32/group) and thirty-two zirconium-oxide FDP-frameworks were CAD/CAM manufactured. Frameworks were veneered with hand-built up or over-pressed porcelain (n = 16/group). Step-stress-accelerated-life-testing (SSALT) was performed in water applying a distributed contact load at the buccal cusp-pontic-area. Post failure examinations were carried out using optical (polarized-reflected-light) and scanning electron microscopy (SEM) to visualize crack propagation and failure modes. Reliability was compared using cumulative-damage step-stress analysis (Alta-7-Pro, Reliasoft).

Results

Crack propagation was observed in the veneering porcelain during fatigue. The majority of zirconium-oxide FDPs demonstrated porcelain chipping as the dominant failure mode. Nevertheless, fracture of the zirconium-oxide frameworks was also observed. Over-pressed FDPs failed earlier at a mean failure load of 696 ± 149 N relative to hand-veneered at 882 ± 61 N (profile I). Weibull-stress-number of cycles-unreliability-curves were generated. The reliability (2-sided at 90% confidence bounds) for a 400 N load at 100 K cycles indicated values of 0.84 (0.98-0.24) for the hand-veneered FDPs and 0.50 (0.82-0.09) for their over-pressed counterparts.

Conclusions

Both zirconium-oxide FDP systems were resistant under accelerated-life-time-testing. Over-pressed specimens were more susceptible to fatigue loading with earlier veneer chipping.     

Fracture behaviour of zirconia ceramic cantilever fixed dental prostheses in vitro

Objective. Evaluation of the fracture resistance of all-ceramic cantilever fixed dental prostheses (FDPs) manufactured from zirconia frameworks and veneered with a press ceramic. Material and Methods. Two mandibular premolars were prepared either with a box inlay cavity or with a full crown chamfer preparation and then duplicated. 40-three-unit cantilever FDPs replacing one premolar, with a group size of eight for each design, were manufactured. In group i-i the cantilever FDPs were retained by two inlays, in group i-c by an inlay–crown combination, and in group c-c by two crowns. The frameworks in groups i-c-R and c-c-R were reinforced by an additional shoulder on the oral side of the zirconia frameworks. All FDPs were subjected to thermal cycling (TC) and 600,000 cycles of mechanical loading (ML) with 50 N. The load to fracture was measured and fracture sites were evaluated. Results. The mean fracture values ranged from 172 N to 792 N. Fracture-strength values were significantly lower for the i-i retained FDPs than for the i-c and c-c combinations. There was no significant effect of the reinforcing shoulder in groups i-c-R and c-c-R. For FDPs with a crown on the terminal tooth, fractures were usually within the distal wall of the distal crown. Conclusions. Inlay–inlay retained cantilever FDPs cannot withstand the mastication forces expected. Fracture load values for inlay–crown and crown–crown-retained FDPs encourage further clinical investigation. The mode of fracture indicates that reinforcement of the distal crown wall might enhance fracture resistance.     

Application of titanium and titanium alloys to fixed dental prostheses

PurposeTitanium and titanium alloys are one of the main metallic materials in the medical and dental fields because of their biocompatibility. In this review, the application of titanium and its alloys as the substitute materials for Ag–Pd–Au alloy in the casting of fixed dental prostheses was examined.Study selectionA reference search was performed through PubMed based on the keywords titanium, titanium alloy, and dental casting. Other relevant references were obtained from the citation in the articles.ResultsThe dental casting technology for titanium has already been developed for clinical use, which enables the use of appropriate casting machines and investment materials for titanium and its alloys available commercially. The mechanical properties, castability, and corrosion resistance of titanium and titanium alloys were reported to be comparable or superior to the conventional dental alloys. Clinical researches reported that titanium and Ti-6Al-7Nb alloy casings showed suitable quality for clinical application.ConclusionTitanium and its alloys can be the substitute materials for Ag–Pd–Au alloy, and should be considered worthy of qualifying for the dental insurance coverage.     

Fracture load of tooth-implant-retained zirconia ceramic fixed dental prostheses: effect of span length and preparation design

Objectives: Evaluation of the effect of different span length and preparation designs on the fracture load of tooth–implant‐supported fixed dental prostheses (TIFDPs) manufactured from yttrium‐stabilized zirconia frameworks. Material and methods: Forty‐eight TIFDPs were manufactured using a CAD/CAM system and veneered with a press ceramic. Rigidly mounted implants (SLA, diameter 4.1 mm, length 10 mm) in the molar region with a titanium abutment were embedded in PMMA bases pairwise with premolars. All premolars were covered with heat‐shrink tubing to simulate physiological tooth mobility. Six different test groups were prepared (a) differing in the preparation design of the premolar (inlay [i]; crown [c]), (b) the material of the premolar (metal [m]; natural human [h]) and (c) the length of the TIFDPs (3‐unit [3]; 4‐unit [4]). All TIFDPs underwent thermomechanical loading (TCML) (10,000 × 6.5°/60°; 6 × 10⁵× 50 N). The load to fracture (N) was measured and fracture sites were evaluated macroscopically. Results: None of the restorations failed during TCML. The mean fracture loads (standard deviations) were 1,522 N (249) for the 3‐unit, inlay‐retained TIFDPs on a metal abutment tooth (3‐im), 1,910 N (165) for the 3‐cm group, 1,049 N (183) for group 4‐im, 1,274 N (282) for group 4‐cm, 1,229 N (174) for group 4‐ih and 911 N (205) for group 4‐ch. Initial damages within the veneering ceramic occurred before the final failure of the restoration. The corresponding loads were 24–52% lower than the fracture load values. Conclusions: All restorations tested could withstand the mastication forces expected. Fracture‐load values for 3‐ and 4‐unit inlay–crown and crown–crown‐retained TIFDPs should spur further clinical investigation.