The cantilever fixed partial denture--a literature review.

The cantilever fixed partial denture (FPD) is a restoration with one or more abutments at one end and unsupported at the other end. Forces transmitted through the cantilevered pontics can cause tilting and rotational movements of the abutments. In a cross-arch unilateral cantilever FPD, the distal cantilevered unit is subjected to comparatively less force than the contralateral posterior abutment. The unilateral lack of terminal abutments causes lateral bending forces activate peripheral inhibitory feedback reactions from the periodontal and/or temporomandibular mechanoreceptors. The greatest strain in distal cantilevered FPDs is recorded mesial to the most distal retainer because most fractures occur in this location. To improve the prognosis of the FPD cantilever, the number of abutments should be increased and the number of pontics decreased. The abutment teeth need long roots and acceptable alveolar support. Prepared abutments require adequate length and parallel axial walls. An equilibrated and harmonious occlusion is necessary, as well as exemplary oral hygiene. A cantilevered FPD with adequate periodontal support can replace any tooth in the dental arch, but is especially useful as an alternative to a removable partial denture. The cantilevered FPD requires at least two abutment teeth. The only documented exception permitting a single abutment is the replacement of a maxillary lateral incisor with the canine as an abutment. An alternative to the cantilevered FPD is the osseointegrated implant. As osseointegrated implants become more popular, the need for the tooth-supported cantilevered FPD may decline, but it will remain an alternative treatment modality.     

Cantilever bridges--a cross-sectional study

Life expectancy and functional performance of the cantilever bridges is determined by the length of the cantilever pontic(s) and by the number and localisation of the abutment teeth. No overall epidemiological survey covering this topic was found in the literature. 529 distally cantilevered bridges were evaluated by the authors. There were 310 upper and lower cases. The following parameters were recorded: length of the cantilever part (number of units), the relationship of the cantilevered pontics and the bridge, and the position of the fixed restoration in the dental arch. Previously the cantilevered bridge design was not accepted in Hungary but in spite of this fact a large number of distally cantilevered bridges were made in the country. Most of the examined cantilever bridges are properly designed: two abutments are supporting one pontic (342 cases, 65.56%). However some of the solutions are too risky: one abutment, one cantilevered pontic (110 cases, 20.45%), or two abutments, two cantilevered pontics (53 cases, 9.85%).     

Some characteristics of distal cantilever bridges on the basis of two representative studies (in Hungary)

In Hungary a dental epidemiological study was performed by a team of calibrated dentists of the Department of Prosthetic Dentistry (Semmelweis University, Budapest) in 1985-89 for the first and in 2003-2004 for the second time. Probands were selected randomly from the population attending the compulsory lung screening examinations. Oral inspection was done under artificial light. Data were immediately entered into computer on the spot. In the first epidemiological study after the examination of 9991 people we have found 1625 cantilever bridges, in the second study we examined 4606 people, and we have found 878 cantilever bridges. In 1989 66.9% of the cantilever bridges replaced missing tooth on the mesial and 33.1% on the distal end. In 2004 44.5% of the cantilever bridges replaced missing tooth on the mesial and 55.5% on the distal end. In both investigations one pontic distal cantilevers were the majority of restorations. In the study of 1989 we have found the highest number of the bridges with one distal pontic supported by two abutments. In the 2004 study the most frequently found one pontic distal cantilever bridges were supported by more then two abutments. Both investigations found the most distal cantilever bridges in the upper jaw replacing the first molar (32%, 38%), then the second molar (20%, 28%), and first premolar (18%, 20%). On the lower jaw distal cantilever pontics were replacing first molars in most of the cases (61%, 59%), then second premolars (19%, 24%) and first premolars (8%, 9%). In both investigations most frequently free end saddle (74%, 83%), remaining teeth (19%, 16%), crowns and artificial teeth distally from the cantilever pontic have been found.     

ALL-CERAMIC AND PORCELAIN-FUSED-TO-METAL FIXED PARTIAL DENTURES: A COMPARATIVE STUDY BY 2D FINITE ELEMENT ANALYSES

All-ceramic fixed partial dentures (FPDs) have an esthetic approach for oral rehabilitation. However, metal-ceramic FPDs are best indicated in the posterior area where the follow-up studies found a lower failure rate. This 2D finite element study compared the stress distribution on 3-unit all-ceramic and metal-ceramic FPDs and identified the areas of major risk of failure. Three FPD models were designed: (1) metal-ceramic FPD; (2) All-ceramic FPD with the veneering porcelain on the occlusal and cervical surface of the abutment tooth; (3) All-ceramic FPD with the veneering porcelain only on the occlusal surface. A 100 N load was applied in an area of 0.5 mm² on the working cusps, following these simulations: (1) on the abutment teeth and the pontic; (2) only on the abutment teeth; and (3) only on the pontic. Relative to the maximum stress values found for the physiological load, all-ceramic FPD with only occlusal veneering porcelain produced the lowest stress value (220 MPa), followed by all-ceramic FPD with cervical veneering porcelain (322 MPa) and metal-ceramic FPD (387 MPa). The stress distribution of the load applied on the abutments was significantly better compared to the other two load simulations. The highest principal stress values were low and limited in a small area for the three types of models under this load. When the load was applied on the pontic, the highest stress values appeared on the connector areas between the abutments and pontic. In conclusion, the best stress values and distribution were found for the all-ceramic FPD with the veneering porcelain only on the occlusal surface. However, in under clinical conditions, fatigue conditions and restoration defects must be considered.     

The effect of pontic occlusal form on abutment tooth displacement]

The three-dimensional displacements of abutment teeth in fixed partial dentures (FPDs) during mastication were measured while changing the pontic occlusal design, for comparison against those of natural teeth. The purpose of this study was to clarify the influence of pontic occlusal form on the displacements of the abutment teeth, and to decide the optimum pontic occlusal design. Three subjects, who each had a single missing tooth (upper first molar or second premolar), were chosen. After 3-unit FPDs were cemented, abutment tooth displacement during mastication was measured using a three-dimensional tooth displacement transducer Type M-3. The functional or non-functional cusp inclination of the pontic was changed gradually. The flatter the inclination of the functional cusp of pontic became, the more the abutment teeth displaced in the buccal direction. The flatter the inclination of pontic non-functional cusp became, the less the abutment teeth displaced in the buccal direction, and the more the abutment teeth mostly displaced in the palatal direction. If the inclination of the functional cusp of pontic becomes excessively flatter, or the inclination of pontic non-functional cusps becomes as steep as the natural teeth, non-physiological distortion may occur in periodontal tissues of the abutment teeth.     

Technical failures and some related clinical complications in extensive fixed prosthodontics. An epidemiological study of long-term clinical quality

Three hundred and sixteen fixed partial dentures made in 1975-1976 by 112 general practitioners in Malm?, Sweden, were selected for a questionnaire study of the technical failure rates after 6-7 years. Cariologic, periodontal, endodontic, and esthetic complications were also identified, as were those appearing in the stomatognathic system. The total material consisted of three groups with an approximately equal number of reconstructions. One group consisted of fixed partial dentures with distal abutment teeth, another was formed of fixed prostheses with single cantilever pontic/pontics, and a third consisted of double cantilever pontics. Excluding the 26 reconstructions, which had been made for patients who died (24) or emigrated (2) during the observation period, data was obtained for 97% of the selected restorations. The results showed high rates of cariologic (18-31%), endodontic (5-23%), periodontal (7-12%), esthetic (10-16%), and technical (8-34%) complications. Differences were noted between the groups. For all types of technical failures (fractures and loss of retention) higher frequencies were related to the extent of cantilevering. Direct relationships were found between the technical failure rate and the time in service, the sum of all cantilever extension pontics in the reconstructions, and the state of the pulps of the distal abutments. No relationship was found between the technical failure rate and the status of the dentition in the opposing jaw. The clinical significance of the results obtained is discussed.     

Three-year clinical evaluation of fiber-reinforced composite fixed partial dentures using prefabricated pontics

PURPOSE: The purpose of this study was to evaluate the clinical performance of surface-retained adhesive composite fixed partial dentures reinforced by an ultra-high molecular weight polyethylene (UHMWP) fiber (Ribbond THM). MATERIALS AND METHODS: Twenty-three surface-retained fiber reinforced composite (FRC) fixed partial dentures (FPD) were placed by two operators in 23 patients, each with a single missing tooth. The restorations included prefabricated composite resin pontics, and no preparations were done on the lingual surfaces of the abutment teeth. The patients were recalled for examinations every year for up to 3 years. Restorations were evaluated directly using the modified Ryge criteria. The minimum observation period was 1 year and the maximum observation period was 3 years. RESULTS: At baseline, 23 restorations were graded as Alpha for all parameters. At one year and two years (n = 21), three Bravos for wear resistance and surface texture/gingival inflammation and two Bravos for color match were observed. Twenty-one of 23 restorations were retained at the end of two years (91.3%) and 78.3% were retained after a maximum of 3 years. CONCLUSION: The results of this clinical study suggestthat UHMWP FRC FPDs are quite acceptable at least forthree years. However, further clinical investigations are still needed for improved long-term clinical performance.     

Prosthetic epidemiology

The need for an epidemiological method which focuses upon the problems of missing teeth, tooth spaces and prosthetic treatment is emphasized. From the prosthetic viewpoint the distinction between missing teeth and tooth spaces must be made and examples are given to show that up to 20 per cent of missing teeth do not give rise to tooth space. The presentation of the prosthetic parameters per tooth is recommended using the six alternatives: tooth present; tooth missing (open space); tooth missing (closed space); tooth replaced by pontic in fixed bridge, by removable partial denture, or by complete denture. In the presentation of the mean number of existing teeth, fixed bridge pontics should be included as they serve as natural teeth both aesthetically and functionally. Data on removable dentures, or edentulism without denture wearing, should be presented in such a way that comparisons at jaw level as well as at person level can be made. A system for this is described. The method may be used in industrialized countries where there is much prosthetic treatment as well as in developing countries with few health services. Comparisons will still be meaningful.     

Resin-bonded prostheses for posterior teeth.

This study evaluated fixed partial dentures bonded with resin to dentin on posterior teeth with minimal tooth preparation. The patients included were missing at least one premolar or first molar. The abutment teeth next to the modification spaces were moderately restored with MOD or class II restorations on most of the teeth. A total of 20 patients with 23 fixed partial dentures were included in the study. After removal of existing restorations, the abutment teeth were prepared to eliminate undercuts on the perimeter of the preparations. Undercut areas within the preparation were not filled but were blocked out later in the laboratory. The fixed partial dentures employed inlays as retainers for a metal ceramic pontic. The metal framework was cast in a high noble gold alloy. The areas of the retainers to be bonded were treated with the Kulzer Silicoater method. Immediately before cementation, enamel was etched and exposed dentin was treated with Gluma. Kerr's resin bonded bridge cement was used for cementation. Patients were recalled after periods of 1 week, 1 month, 6 months, 1 year, 2 years, and 4 years for evaluation. None of the restorations lost retention and no major adverse effects were observed in the 4-year follow-up period.     

下颌第二磨牙缺失单端固定义齿修复的临床观察

目的：观察下颌第二磨牙缺失单端固定义齿修复的临床效果。方法：对以下颌第二前磨牙和第一磨牙为基牙，以单端固定义齿修复下颌第二磨牙缺失的25例患者进行临床和放射检查。结果：所修复的25例病例中有2例失败于固位力不足，1例失败于基牙折裂。其它均使用良好。结论：只要桥体设计合理，基牙牙体及牙周状况好，可以单端固定义齿的形式修复缺失的下颌第二磨牙。     

Clinico-statistical observation of various prosthetic restorations at the Prosthetic Department, Asahi University Hospital. 4. Circumstances concerning prosthetic method for missing teeth for the duration from April 1986 to March 1987

The statistics for prosthetic restorations used for missing teeth at the Prosthetic Department of Asahi University Hospital from April 1986 to March 1987 were compared with those obtained for an earlier period (April 1983 to March 1984). Fixed bridges and removable partial dentures constituted the majority of the prosthetic restorations for posterior teeth. Fixed bridges were twice more frequently used for anterior teeth during this period than during the previous period. For a single missing tooth, fixed bridges amounted to 90% and removable partial dentures to 10%, as they did in the previous period. For two or more missing teeth, the use of fixed bridges was some what increased compared to the previous period. As in the previous report, the use of so-called one-tooth denture was most frequent for missing lower first molar. For bridges, the average number of missing teeth and that of abutment teeth were 1.3 and 2.4 respectively. Bridges for one missing tooth with two abutment teeth were most frequently used. For removable partial dentures, the average number of missing teeth and that of abutment teeth were 6.1 and 2.8 respectively. Removable partial dentures for two missing teeth with two abutment teeth were most frequently used. Full cast crowns were most frequently used for bridge retainers, followed by facing crowns. Facing crowns were used more than twice as frequently during this period as they were during the previous period.(ABSTRACT TRUNCATED AT 250 WORDS)     

The capacity of reduced periodontal tissues to support fixed bridgework

The total area of periodontal ligament around the abutment teeth in 60 fixed bridges, inserted in patients treated for advanced periodontal disease, was calculated and compared with the total "periodontal ligament area" of the teeth replaced by pontics. The calculations revealed that only in 8% of the bridge restorations did the periodontal ligament area of the abutment teeth equal or exceed that of the replaced teeth. In 57% of the bridge material the periodontal ligament area of the abutments was less than 50% of the anticipated normal ligament area of the pontics. Despite the fact that the periodontal support for the restorations was dramatically reduced, all bridges have functioned properly for 8-11 years and the periodontal tissues around the abutment teeth have not suffered further loss of attachment during the period of maintenance care.     

不同直径种植体与天然牙联合支持固定桥的应力分析

目的:通过三维有限元方法研究种植体直径对天然牙种植体联合固定桥周围骨组织应力的影响。方法:CT扫描获得志愿者DICOM数据,通过Mimics软件、Imageware逆向工程软件及ANSYS软件处理,先建立左侧下颌第二前磨牙和第二磨牙支持的天然牙固定桥三维有限元模型,用不同直径种植体替换下颌第二磨牙得到一系列种植体-天然牙联合支持式固定桥的三维有限元模型。分别在垂直向和斜向45°集中加载下,对比分析天然牙及种植体周围的应力分布情况。结果:相同加载条件下,不同模型的第二前磨牙(天然牙)颈部应力无明显区别。对联合支持式固定桥,当种植体直径由3.5 mm增加为4.3 mm时,种植体颈部和基台的应力明显降低(近1/2);随种植体直径增加,2处应力也继续降低,但降低的幅度明显放缓。结论:随着种植体直径的增大,种植体颈缘处骨组织及基台的von Mises应力逐渐减小,但对天然牙周围的应力影响较小。斜向载荷时,天然牙、种植体周围骨组织及基台受到的von Mises应力显著增大,更易导致固定桥修复的失败。     

An analysis of stress around abutment teeth and periodontium in three-unit fixed partial dentures--photoelastic analysis with simulated periodontal ligament

The mechanical characteristics of zirconia, hybrid hard resin and dental metal for crowns and fixed partial dentures (FPD) have been researched for clinical applications. However, for these kinds of restorations, the distribution of mechanical stress around the abutment teeth and periodontium during function has not been sufficiently assessed. The aim of this study was to clarify the influence of these materials upon abutment teeth and periodontium through a two-dimensional photoelastic method. Two-dimensional simulation models of three-unit FPDs were constructed from these materials. By applying a force of 400 N vertically to these FPDs, the stress distribution around the abutment teeth and alveolar bone was analyzed and the fringe orders were recorded with a transmission polariscope. As a result, the fringe order values at the root dentin around the marginal area of the pontic joint were the highest in zirconia, and the smallest in hybrid hard resin. The spread of internal stress around the marginal area was larger in the hybrid hard resin model and dental metal model than in the zirconia model. This study suggested that differences in stress distribution within the abutment teeth and around the alveolar bone were related to differences in elastic coefficients of the materials used in FPDs.     

Preoperative Intraoral Evaluation of Planned Fixed Partial Denture Pontics Using Silicone Putty

A preoperative visualization and evaluation of fixed partial denture (FPD) pontics in the anterior dentition is necessary for both the patient and the dentist. Such an evaluation allows patients to decide whether the esthetic and functional parameters of the restoration meet their requirements and expectations. To facilitate such an assessment, a method that allows stable intraoral positioning of the pontics is required. This article describes a technique to achieve this in a simple and effective way before the abutments are prepared. In addition, it also allows the operator to modify the pontics intraorally for esthetics and later incorporate the same pontics into the interim prosthesis. The integration of this pretreatment pontic evaluation procedure into FPD restorations assures better results and patient satisfaction.     

First two-year complications of fixed partial dentures,eight units or more. Swedish Guarantee Insurance claims

This study is an analysis of fixed partial dentures (FPDs), 8 units or more, that failed or suffered severe complications within the first 2 years after cementation. The material consists of claims to the Swedish Gurantee Insurance for Fixed Prosthodontics. Claim reports, radiographs, etc. were available. Over a 6-month period, 36 FPDs were sampled, 34 of which were made by general practitioners. The sampling resulted in 41 complications in 26 maxillary and 10 mandibular FPDs, 29 of which were made in metal-ceramics. The mean extension was 10.9 units, with an abutment/pontic ratio of 1.4; 40.6% of the abutments were root-canal treated and supplied with root posts. The complications were: metal framework fractures 41%, loss of retention 24%, porcelain fractures 17%, tooth/root fractures 10%, and miscellaneous 7%. The high proportion of metal framework fractures is not in accordance with other studies of FPD complications. No factor that could explain this high frequency could be identified. The fact that the selection of FPD complications applied to the first 2 years only, that the FPDs had been constructed by general practitioners, and that there were many root-canal-treated abutments and distal extension cantilever pontics, might be factors of importance.     

First two-year complications of fixed partial dentures, eight units or more. Swedish Guarantee Insurance claims

This study is an analysis of fixed partial dentures (FPDs), 8 units or more, that failed or suffered severe complications within the first 2 years after cementation. The material consists of claims to the Swedish Guarantee Insurance for Fixed Prosthodontics. Claim reports, radiographs, etc. were available. Over a 6-month period, 36 FPDs were sampled, 34 of which were made by general practitioners. The sampling resulted in 41 complications in 26 maxillary and 10 mandibular FPDs, 29 of which were made in metal-ceramics. The mean extension was 10.9 units, with an abutment/pontic ratio of 1.4; 40.6% of the abutments were root-canal treated and supplied with root posts. The complications were: metal framework fractures 41%, loss of retention 24%, porcelain fractures 17%, tooth/root fractures 10%, and miscellaneous 7%. The high proportion of metal framework fractures is not in accordance with other studies of FPD complications. No factor that could explain this high frequency could be identified. The fact that the selection of FPD complications applied to the first 2 years only, that the FPDs had been constructed by general practitioners, and that there were many root-canal-treated abutments and distal extension cantilever pontics, might be factors of importance.     

Changes over time in the clientele and restoration pattern in a dental school prosthodontic department

The clientele and the production of single artificial crowns and fixed partial dentures in the Department of Prosthodontics were compared from 1964/68-1982/87. In the first period 65 per cent of the single crowns were made for women versus 55 per cent in the second. In the first period 69 per cent of the crowns were placed in the upper jaw as against 60 per cent in the second period. On average 1.6 crowns were made per female patient in the first period versus 1.4 per male patient. In the second period both sexes averaged 1.8 units. In both jaws the percentage of root-filled crowned teeth had increased in the second period to 60 per cent from 48 per cent in the upper jaw and 46 per cent in the lower jaw. In both sexes maxillary and mandibular teeth were crowned on average 13 years later in the second period than in the first. Sixty per cent of the fixed partial dentures were made for women in the first period versus 55 per cent in the second. In the first period 74 per cent of the bridges were made for the upper jaw as against 70 per cent in the second period. The mean pontic to abutment ratio was 0.7 in both periods. The maximum number of bridges in the first period were made for patients 40-59 years of age versus 50-69 years in the second period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of two preparation designs and pontic distance on bending and fracture strength of fiber-reinforced composite inlay fixed partial dentures

STATEMENT OF PROBLEM: Joint fractures observed in Targis/Vectris inlay adhesive fixed restorations may be related to the preparation design. PURPOSE: This in vitro study investigated the effects of the proximal tooth preparation design and the pontic distance on the fracture strength and the amount of bending of fiber-reinforced inlay adhesive fixed partial dentures. MATERIALS AND METHODS: Forty extracted premolars and 40 molars were embedded in a PMMA resin to represent a premolar and molar mesiodistal separation distance of 7 mm and 11 mm, respectively. Two preparation designs were used (proximal box and tub-shaped). The sample size was 10 for each group. Fiber-reinforced inlay adhesive fixed partial dentures were fabricated by use of the Targis/Vectris system and luted adhesively to the teeth with Variolink luting agent. A vertical force was loaded to the center of the fixed partial dentures at a crosshead speed of 1 mm/min. The initial bending (mm) prior to fracture was evaluated by measuring the distance the test rod moved from a 10 N preload to fracture. The differences in the mean fracture strength and the average amount of bending as a function of the preparation designs and pontic distances were compared by use of a 2-way analysis of variance (alpha=.05). The specimens were examined optically for the type of failure with a stereomicroscope. The fracture surface of the specimens was examined by scanning electron microscopy, and radiography was used to investigate the surface morphological features at the failure sites and to determine the fracture mode. A chi-square test was used to identify the differences in the debonding rates between the types of preparation designs and the pontic distance (alpha=.05). RESULTS: The mean fracture strength and the standard deviation of the fiber-reinforced inlay retained adhesive fixed partial denture group was 1368+/-212 N for the 7-mm tub group, 885+/-109 N for the 11-mm tub group, 1779+/-317 N for the 7-mm box group, and 1336+/-281 N for the 11-mm box group. The fracture strength was significantly higher in the 7-mm pontic distance (P<.001) and for the box-shaped tooth preparation (P<.001). The amount of bending was significantly greater in the 7-mm pontic distance (P=.025) and the box-shaped tooth preparation (P=.002). Debonding was observed only in premolar teeth and tub-shaped design groups. CONCLUSION: The box-shaped tooth preparation may be considered for restoration of a missing single posterior tooth with fiber-reinforced inlay adhesive fixed partial dentures.     

Biomechanical interactions in tooth-implant-supported fixed partial dentures with variations in the number of splinted teeth and connector type: a finite element analysis.

OBJECTIVE: The aim of this study was to investigate the biomechanical interactions in tooth-implant-supported fixed partial dentures (FPDs) under several loading conditions with different numbers of splinted teeth and connector types (rigid and non-rigid) by adopting the three-dimensional (3D) non-linear finite element (FE) approach. MATERIAL AND METHODS: A 3D FE FPD model was constructed containing one Frialit-2 implant in the mandibular second-molar region splinted to the first and second premolars. Frictional contact elements were used to simulate realistic interface conditions within the implant system and the non-rigid connector function. The main effects for each level of the three investigated factors (loading condition, number of splinted teeth and connector type) in terms of the stress values and dissimilar mobility of the natural teeth and implant were computed for all models. RESULTS: The results indicated that load condition was the main factor affecting the stress developed in the implant, bone and prosthesis when comparing the type of connector and the number of splinted teeth. The stress values were significantly reduced in centric or lateral contact situations once the occlusal forces on the pontic were decreased. However, the prosthesis stress for the non-rigid connections was increased more than 3.4-fold relative to the rigid connections. Moreover, the average tooth-to-implant displacement ratios (R(TID)) with a non-rigid connection were obviously larger than those for rigid connections under axial loading forces. Adding an extra tooth to support a three-unit tooth-implant FPD only exploited its function when the prosthesis withstood lateral occlusal forces. CONCLUSIONS: The load condition is the main factor affecting stress distribution in different components (bone, prosthesis and implant) of tooth-implant-supported FPDs. Minimizing the occlusal loading force on the pontic area through selective grinding procedures could reduce the stress values obviously. A non-rigid connector may more efficiently compensate for the dissimilar mobility between the implant and natural teeth under axial loading forces but with the risk of increasing unfavorable stresses in the prosthesis.