牙科激光焊钛固定桥适合性的研究

目的:比较整体铸造钛固定桥与分部铸造后激光焊接钛固定桥的适合性。方法:机械加工2个标准金属全冠模型,用硅橡胶制取阴模并灌注13个超硬石膏模型。浸蜡压塑成形法完成统一规格的蜡型,桥体用同一规格的塑料棒代替。共分为3组,即单冠铸钛组、分部铸钛焊接组、整体铸钛组。铸件完成后分别置于各自的石膏代型上,用环氧树脂包埋、片切,在HitachiS-2700扫描电子显微镜下观察颈缘特定位置铸件与代型之间的间隙。结果:整体铸钛组颈缘间隙明显大于分部铸钛焊接组和单冠铸钛组(P<0.05),分部铸钛焊接组和单冠铸钛组的颈缘间隙无明显区别。结论:分部铸钛焊接组的适合性优于整体铸钛组。3单位整体铸钛组的颈缘间隙小于100μm,也符合临床要求。     

The seating of one-piece and soldered fixed partial dentures

This laboratory study compared the seating of one-piece castings with that of soldered fixed partial dentures. Two investments were investigated, five American Dental Association type III and five metal ceramic alloy fixed partial dentures were made by using the conventional indirect technique. The investing and casting protocol was designed to produce an ideal fit of the individual complete crown abutments, not the fixed partial denture. Independent seating of each retainer provided a baseline measurement for complete seating and was compared with fixed partial denture seating. Fixed partial dentures were then sectioned and reassembled by soldering twice, using a low- and high-expansion investment. Statistical evaluation identified significant differences between the metals and the techniques. Marginal discrepancies with one-piece casting and lower (0.6%) thermal-expansion soldering were clinically unacceptable. A clinically acceptable fit was obtained with the higher (1%) thermal-expansion soldering investment.     

Comparative accuracy of fixed partial dentures made as one-piece castings or joined by solder.

Four-unit fixed partial dentures were fabricated as a one-piece casting or as two-piece castings joined by soldering prior to the addition of porcelain. The accuracy of the two techniques was compared and evaluated using an anatomic cast-metal master model. All procedures, including SEM measurements, were performed directly on the master model. The cast one-piece units had smaller vertical marginal openings than did the soldered units. The rigid nature of the abutments evokes the problems occurring with osseointegrated implants.     

Tensile strength analysis of midpontic soldering

A total of 120 three-unit fixed partial dentures were made by using a latex mold to produce uniform wax patterns. Four groups were used to compare the tensile strength of connectors with interproximal solder, midpontic vertical solder, midpontic diagonal solder, and a control of one-piece castings. Three different metals were tested and the tensile load required to fracture the samples as well as the fracture sites were recorded. The following was found: Soldering the interproximal connector area produced the weakest solder joints, regardless of metal tested, at p less than .001. There was no significant difference in the fracture loads between midpontic vertical soldering and midpontic diagonal soldering with all three metals at p less than .01. There was no significant difference in fracture loads between midpontic soldering and unit casting with all three metals at p less than .01. The extreme variations in fracture loads when soldering nickel-chrome-beryllium confirms the technique sensitivity of presoldering this alloy.     

Are sectioning and soldering of short-span implant-supported prostheses necessary procedures?

The aim of this study was to evaluate the fit between dental abutments and the metal framework of a 3-unit fixed prosthesis screwed to two implants to determine whether sectioning and soldering of the framework are in fact necessary procedures. The study was based on a model of a metal framework of a 3-unit prosthesis screwed to two implants. A total of 18 metal frameworks were constructed and divided into 3 groups: (1) NS group - each framework was cast in one piece and not sectioned; (2) CS group - the components of each sectioned framework were joined by conventional soldering; and (3) LW group - the components of each sectioned framework were joined by laser welding. The control group consisted of six silver-palladium alloy copings that were not cast together. Two analyses were mperformed: in the first analysis, the framework was screwed only to the first abutment, and in the second analysis, the framework was screwed to both abutments. The prosthetic fit was assessed at a single point using a measuring microscope (Measurescope, Nikon, Japan) and the marginal gap was measured in micrometers. Statistical analysis was performed using analysis of variance (ANOVA), Scheffe's test, Student's t-test, and Mann-Whitney U test. The NS group had larger marginal gaps than the other groups (p<0.01), while the CS and LW groups had a similar degree of misfit with no significant difference between them. The results revealed that, in the case of short-span 3-unit fixed prostheses, the framework should be sectioned and soldered or welded to prevent or reduce marginal gaps between the metal framework and dental abutments.     

消极吻合技术在下颌前牙种植修复中的应用

目的：探讨种植修复消极吻合的重要性。方法：32例下颌前牙缺失骨量不足患者种植85颗种植体,取模,制作金属基底冠桥,分开其连接处,试戴就位,分开处在口内以成型塑料连接,重新二次印模,激光焊接,再试基底冠桥,检查其颈部密合性和翘动情况,制作烤瓷牙,粘固固位种植修复体,定期牙周维护。分别于种植修复后3、6、12月临床检查修复体稳定性与牙龈情况,X线检查种植体-骨界面与牙槽嵴情况。结果：种植修复成功31例,失败1例。结论：消极吻合是保证口腔种植修复成功的要素之一。     

Distortion of Three-Unit Implant Frameworks During Casting, Soldering, and Simulated Porcelain Firings

PURPOSE: The aim of this study was to assess distortion inherent in casting, soldering, and simulated porcelain firings of screw-retained, implant-supported three-unit fixed partial dentures (FPDs). MATERIALS AND METHODS: Ten wax patterns were fabricated on a die-stone cast containing two implants, 20 mm apart from center to center. Five specimens were cast in a high-palladium alloy, exposed to simulated porcelain firings, sectioned, and then soldered with low-fusing solder. Five specimens were cast, sectioned, soldered with high-fusing solder, and then exposed to simulated porcelain firings. For each specimen, two horizontal and six vertical distances between appropriately scribed reference points were measured with a traveling microscope. Comparisons were made among the various measurements taken after wax-pattern fabrication, casting, high- and low-fusing soldering, and each porcelain firing. Data were analyzed using a repeated-measures factorial ANOVA (alpha = 0.05). RESULTS: Significant difference was detected in the amount of horizontal distortion during casting (53 +/- 24 microns) and high-fusing soldering (-49 +/- 50 microns), as well as in the amount of horizontal distortion during high-fusing soldering (-49 +/- 50 microns) and low-fusing soldering (17 +/- 26 microns). However, no clinically significant difference was found in the amount of horizontal distortion during casting, low-fusing, and high-fusing soldering. The greatest amount of distortion during the simulated porcelain firings took place during the oxidizing cycle. CONCLUSIONS: Soldering did not improve the casting misfit of a three-unit implant-retained FPD model. Metal-ceramic implant frameworks should be oxidized before intraoral fit evaluation.     

Prosthetic and orthodontic rehabilitation of a patient with missing maxillary lateral incisors: a case report.

IPS Empress 2 materials can be used for fabrication of short-span fixed partial dentures in the anterior region as well as single crowns. This clinical report describes the prosthodontic treatment of a 16-year-old male patient with missing permanent maxillary left and right incisors with IPS Empress 2 fixed partial dentures following orthodontic treatment.     

Oral rehabilitation for a patient with oligodontia and maxillary hypoplasia

An 18 year old female with oligodontia and maxillary hypoplasia was treated using an interdisciplinary team approach involving orthodontists, maxillofacial surgeons and prosthodontists. Full mouth one-piece fixed partial dentures were the final restoration. The fixed partial dentures fabricated for the maxilla and mandible using the concept of a shortened dental arch resulted in improved esthetics and the masticatory function. This paper describes the treatment procedures for an oligodontia patient with alveolar bone hypoplasia.     

A comparison of impression materials for complete-arch fixed partial dentures

This study compared the marginal fit of complete-arch fixed prostheses under simulated clinical conditions. Prostheses were made on casts constructed from three commonly used impression materials; polyether, polyvinyl siloxane (medium-viscosity and putty-wash), and reversible hydrocolloid. A maxillary dentoform with four abutment teeth was used as the master cast and six impressions were made with each material. Individual castings for each abutment were made on the stone casts. The abutment castings were luted together on the casts to provide a complete-arch fixed partial denture using a ticonium framework and acrylic resin. The marginal fit of the abutment castings was measured on the master cast before and after the prostheses were luted together. The polyether and both addition silicone impression materials were significantly more accurate than the reversible hydrocolloid in both situations. All of the single castings were clinically acceptable, but the luted restorations made from reversible hydrocolloids were not.     

Nonprecious cast-metal alloys in dentistry.

This review of selected articles from October 1989 to October 1990 is divided into two sections: a review of clinical studies and a review of laboratory studies for nonprecious cast metals. The clinical articles are centered on biological compatibility issues, such as taste anomalies (dysgeusia) attributed to cast metals and allergy correlation to base metals, and on technique and longevity evaluations involving resin-bonded fixed partial dentures. Laboratory articles are mainly devoted to metal preparation before bonding of etched or resin-bonded fixed partial dentures and the estimated bond strengths of the metal castings. Other selected articles are based on studies of physical properties and physical testing of nonprecious alloys, such as modulus of rupture, to determine ceramic compatibility, castibility testing, marginal fit of fixed partial dentures, and flexure testing of of traditional and experimental designs for cast major connectors. Additionally, a low-cost method of titanium casting is reviewed.     

Analysis of stress distribution in a screw-retained implant prosthesis

Four types of implant superstructures were screwed onto implant bodies, and the strains created around the implant bodies were compared and analyzed within the IMZ Implant System. Three IMZ implants were embedded in the center of a polyurethane block (30 x 40 x 30 mm), and a total of 16 superstructures was fabricated by 4 methods: 1-piece cast, 1-piece cast/split soldering, soldering, and passive fit. Six strain gauges were placed on the surface of the block 1 mm apart. Three embedded implants were numbered, and a fixed partial denture was placed on these implants and screwed by a torque wrench using 14.5 Ncm torque. This procedure was repeated 7 times for each fixed partial denture, and each created strain was measured when the last screw was tightened. In all fixed partial dentures, strains were produced around the implant bodies when screws retaining the prosthesis were tightened, and the strain was relieved with unscrewing. The magnitude of strain was greater with the 1-piece cast method or the section/solder method than with the soldering and passive-fit methods. Of the 2 soldering methods, when the screw on the middle implant was tightened before those on the terminal 2 implants, the magnitude of strain was lower with the soldering method than with the 1-piece cast/split soldering method. When the order of screw tightening was changed, there were significant differences in the magnitude of strain at each gauge with the soldering method. With the passive-fit method, no differences in the magnitude of strain attributable to the order of screw tightening could be detected. The magnitude of strain produced around a screw-retained implant prosthesis was significantly lower with the passive-fit method when compared to the other 3 fabricating methods. Furthermore, the implants prepared by the passive-fit method were not affected by the order of screw tightening.     

Effect of Core Material and Restoration Design on Strength of Endodontically Treated Bovine Teeth: A Laboratory Study

Purpose: The purpose of this study was to evaluate the fracture resistance of bovine teeth restored with one-piece cast core/crowns and no ferrule, compared to teeth restored with amalgam cores and full coverage crowns, with and without a dentine ferrule.
Materials and Method: Thirty bovine incisors were selected and modified to ensure all teeth had axial dentine walls of similar size. The teeth were then randomly allocated to one of the three groups: control group restored with amalgam core and cast crown without ferrule; ferrule group restored with amalgam core and cast crown with a 2-mm dentine ferrule; one-piece group restored with one-piece cast core/crown without ferrule. Each tooth was loaded to the point of fracture.
Results: The mean load resisted by the control group, the ferrule group, and the one-piece group were 1092.5, 1843.5, and 1463.1 N, respectively. The mean load resisted by the ferrule group was significantly greater than the control group ( p < 0.001) and the one-piece cast core/crown group ( p = 0.04). The mean load resisted by the one-piece cast core/crown group was significantly greater than the control group ( p = 0.04).
Conclusions: The maximum load resistance was significantly enhanced by a 2-mm ferrule compared with teeth with no ferrule and teeth restored with one-piece cast core/crowns. Teeth restored with one-piece cast core/crowns were significantly more resistant to loading than teeth restored with amalgam cores and crowns without a ferrule.     

Influence of finish-line form on crown cementation.

Studies reporting the influence of finish-line configuration on the fit of cemented crowns have had conflicting conclusions. This study examined the effect of finish-line configuration on the fit of cemented complete crowns. Three identical tooth preparations were made, each with a different facial finish line: shoulder, shoulder-bevel, and chamber. The prepared teeth were replicated to produce 45 epoxy resin teeth, 15 for each finish-line design. Thirty cast crowns were fabricated and seated on their respective epoxy resin teeth--fifteen without cement and fifteen with zinc phosphate cement. An additional set of fifteen castings, seated on their working dies, was used for control measurements. All specimens were embedded, sectioned, and measured at predetermined sites. Results showed that finish-line form does not affect the fit of cemented crowns.     

Fixed Rehabilitation of an ACP PDI Class III Patient

This clinical report documents the treatment of a 63-year-old Caucasian female Prosthodontic Diagnostic Index Class III patient using dental implants and a fixed prosthetic reconstruction. The treatment involved the fabrication of single crowns and fixed partial dentures retained by natural teeth in the maxillary arch. The posterior segments of the mandibular arch were rehabilitated with fixed partial dentures retained by endosseous implants.     

Clinical outcome of glass-fiber-reinforced crowns and fixed partial dentures: a three-year retrospective study.

OBJECTIVE: Glass-fiber-reinforced resin composites for the fabrication of esthetic single crowns and fixed partial dentures have been developed recently. However, little data on the clinical outcome of such restorations have been published. The purpose of this retrospective study was to evaluate the clinical outcome of crowns and fixed partial dentures made from the glass-fiber-reinforced resin composite material Targis/Vectris. METHOD AND MATERIALS: Between 1995 and 1997, 39 patients were treated with 67 single crowns and 83 fixed partial dentures. Twenty-five crowns and 28 fixed partial dentures were cemented with temporary cement, while 42 crowns and 55 fixed partial dentures were cemented with either zinc-phosphate cement or glass-ionomer cement. RESULTS: In September 2001, 57 restorations in 17 patients were still in function. The three-year survival rate calculated according to the Kaplan-Meier method was 58.8% for all restorations. However, after this time, it was 37.5% for crowns and 59.9% for fixed partial dentures cemented with temporary cement, and 55.1% for crowns and 67.9% for fixed partial dentures cemented with zinc phosphate or glass ionomer. The differences between the restoration groups were not statistically significant. CONCLUSION: Glass-fiber-reinforced crowns and fixed partial dentures made with the glass-fiber-reinforced resin composite material Targis/Vectris showed a lower survival rate than that published for metal-ceramic crowns and fixed partial dentures. Therefore, the use of this material for the fabrication of single crowns or fixed partial dentures as permanent restorations cannot be recommended.     

Marginal and internal adaptation of commercially pure titanium and titanium-aluminum-vanadium alloy cast restorations

AIM: The purpose of this in vitro study was to investigate the marginal accuracy and internal fit of complete cast crowns and three-unit fixed partial dentures (FPDs) cast with commercially pure titanium (CPTi) and Titanium-Aluminum-Vanadium alloy (Ti-6Al-4V). METHODS AND MATERIALS: CPTi and Ti-6Al-4V alloy were used to cast twelve single crowns and twelve three-unit FPDs. A traveling microscope was used to measure marginal gap and discrepancies in internal fit. Two and one-way analysis of variance (ANOVA) analyses were used to determine the effects of the marginal and internal fit discrepancies. RESULTS: The Ti-6Al-4V alloy demonstrated a significantly smaller marginal gap than CPTi (P<0.0001). The recorded marginal discrepancies for both metals were within a clinically accepted range (<100 microm). The single crown fit discrepancy was significantly smaller than the three-unit FPD for both the CPTi and the Ti-6Al-4V alloy (P<0.0001). For the internal fit discrepancy, the occlusal surface showed the greatest gaps. CONCLUSIONS: The Ti-6Al-4V alloy demonstrated a better fit than CPTi. Single crowns showed an improved fit when compared with the three-unit FPD. Mid-occlusal internal gap demonstrated greater values than the axial internal gap. CLINICAL IMPLICATIONS: This in vitro study suggested marginal fit of complete crowns and three-unit FPDs cast by CPTi or Ti-6Al-4V alloy were within the range of what is clinically acceptable for longevity of restorations.     

Frequency and location of artificial crowns and fixed partial dentures constructed at a dental school

The material consists of patients who received single crowns and fixed partial dentures at the Department of Prosthetics, Dental Faculty, University of Oslo in the period 1967-73. Two-thirds of the patients were women, and about two-thirds of the restorations were made in the maxilla. A total of 3275 crowns were received by 2145 patients. On average, maxillary teeth were crowned 7 years earlier than mandibular teeth. A total of 1393 fixed partial dentures, consisting of 6835 units, were made for 1368 patients.     

Measurement of distortions in fixed partial dentures resulting from degassing.

1. During the degassing phase, fixed partial dentures removed immediately when the temperature reached 1,900 degrees F (1,038 degrees C) with soldered connectors do not distort more than those with cast connectors. While not tested, heat-soaking could be expected to cause a greater amount of distortion, especially for fixed and supported partial dentures having soldered connectors. 2. Use of custom-made sagger trays giving support to long-span fixed partial dentures at the ends and within the span is desirable for both degassing and porcelain firing, regardless of whether or not the connectors are cast or soldered. 3. The accumulative amount of possible distortion resulting from soldering, degassing, and porcelain firing may be clinically significant if precautions are not affected.     

CAD/CAM一体化玻璃纤维桩核抗折力的体外实验研究

目的比较CAD/CAM一体化玻璃纤维桩核与预成纤维桩和铸造金合金桩核修复体的抗折力。方法27颗离体上中切牙截冠根充后随机分为3组,分别采用一体化玻璃纤维桩核、预成纤维桩和铸造金合金桩核加铸造金属冠进行修复。使用万能力学试验机测试样本的抗折力并观察损坏模式。结果一体化玻璃纤维桩核组的抗折力为246.9±43.8N,显著高于预成玻璃纤维桩组（174.89±37.5N）,而与铸造金合金桩核组（290.1±84.2N）无显著差异。各组样本的损坏模式主要为牙颈部的损伤。结论CAD/CAM一体化玻璃纤维桩核修复上中切牙的抗折力与铸造金合金桩核近似,高于预成玻璃纤维桩。