A systematic review and meta-analysis of 3-unit fixed dental prostheses: Are the results of 2 abutment implants comparable to the results of 2 abutment teeth?

Mechanical strength of stock and custom abutments as original and aftermarket components after thermomechanical aging

OBJECTIVES

The study aimed to assess the impact on the mechanical strength and failure patterns of implant-abutment complexes of choosing different abutment types, designs and manufacturers, aiding in selecting the optimal restorative solution. Stock and custom abutments from original and aftermarket suppliers were subjected to thermomechanical aging.

MATERIAL AND METHODS

Stock and custom abutments from the implant manufacturer (original) and a aftermarket supplier (nonoriginal) were connected to identical implants with internal connection. Custom abutments were designed in a typical molar and premolar design, manufactured using the workflow from the respective suppliers. A total of 90 implants (4 mm diameter, 3.4 mm platform, 13 mm length) equally divided across 6 groups (three designs, two manufacturers) underwent thermo-mechanical aging according to three different regimes, simulating five (n = 30) or 10 years (n = 30) of clinical function, or unaged control (n = 30). Subsequently, all samples were tested to failure.

RESULTS

During aging, no failures occurred. The mean strength at failure was 1009N ± 171, showing significant differences between original and nonoriginal abutments overall (-230N ± 27.1, p < .001), and within each abutment type (p = .000), favoring original abutments. Aging did not significantly affect the failure load, while the type of abutment and manufacturer did, favoring original and custom-designed abutments. The most common failure was implant bending or deformation, significantly differing between original and nonoriginal abutments and screws. All failure tests resulted in clinically unsalvageable implants and abutments.

CONCLUSIONS

Within the limitations of this study, original abutments exhibited a higher mechanical strength compared to the nonoriginal alternative, regardless of the amount of simulated clinical use. Similarly, custom abutments showed higher mechanical strength compared to stock abutments. However, mechanical strength in all abutments tested was higher than average chewing forces reported in literature, thus components tested in this study can be expected to perform equally well in clinical situations without excessive force.

Should compromised first permanent molar teeth in children be routinely removed? A health economics analysis

OBJECTIVE

To evaluate the cost-effectiveness of retaining one or more compromised first permanent molars (cFPMs) affected by dental caries or enamel hypomineralization, compared to timely extraction, in children aged 8 years.

METHODS

A Markov model was developed to simulate the lifetime of a cFPM. Two management strategies were compared: extraction facilitating spontaneous space closure or maintenance of teeth with restorations. Ten health states were utilized to capture long-term outcomes including various tooth restorations, prostheses or a retained gap at the cFPM site. Outcomes were expressed as Quality Adjusted Tooth-Years (QATYs). The model was informed by survey data on patient preferences for treatment outcomes and UK data on costs. Discounted costs and QATYs were calculated over 62 years.

RESULTS

Regardless of the number of cFPMs, retaining cFPMs was more effective than early removal, generating an additional 2.3 QATYs per cFPM. Early removal of one or two cFPM under general anaesthetic (GA) was more expensive than retention and hence never cost-effective. Retaining a cFPM was more expensive than early removal under local anaesthesia or where four cFPMs were extracted under GA. In these cases, retaining cFPMs was cost-effective if a QATY was valued at £100 or £35, respectively. Results were robust to sensitivity analysis.

CONCLUSION

Preserving a cFPM was more cost-effective than the early loss of one, or two cFPMs under GA. Preservation of four cFPMs was cost-effective if sufficient value was placed on a QATY. These findings can guide clinical practice on management of cFPMs alongside patient/payer values on maintaining teeth.

Prospective evaluation of implants-supported, tooth-implant supported, and teeth-supported 3-unit posterior monolithic zirconia fixed restorations: Bite force and patient satisfaction

OBJECTIVES

This study aimed to evaluate the maximum bite force (MBF) and satisfaction of patients restored with implants, combined tooth-implants, and teeth-supported monolithic zirconia fixed dental prostheses (FDPs).

MATERIALS AND METHODS

Thirty partially edentulous patients in need of three units of FDPs in their mandibular posterior region were divided into three equal groups (n = 10) as follows: Group-1 patients received two implants for each at the second premolar and second molar regions, Group-2 patients received one implant for each at the second molar region, and Group-3 patients with missing lower first molar. All the restorations were constructed from monolithic zirconia. Patients were evaluated 1 week after placement of restorations (baseline) and then after 6, 12, and 24-month intervals for MBF using force transducer occlusal force meter and satisfaction (function, esthetic, and overall satisfaction) using a visual analog scale.

RESULTS

The mean MBF for Group 1 was higher than Group 2 (p = .044) but not that of Group 3 (p = .923). Additionally, Group 3 displayed a higher MBF than Group 2, although this difference was not statistically significant (p = .096). Concerning patient satisfaction, all study groups reported high levels of satisfaction across all satisfaction elements, and no significant differences were observed between the groups.

CONCLUSION

Within the limitations of this study, it can be concluded that Group 1 gives comparable anticipated treatment outcomes as Group 3 concerning biting force and patient satisfaction. However, Group 2 gives comparable satisfaction results with biting force value within the normal range; thus, it might be used as a treatment option in a specific situation.

Mechanical comparison of milled fiber-reinforced resin composite and Co-Cr frameworks with different connector cross-sectional geometries: An in vitro study

This study compared the effect of using milled fiber-reinforced resin composite and Co-Cr (milled wax and lost-wax technique) frameworks for 4-unit implant-supported partial fixed dental prostheses; and also, evaluated the influence of the connector's cross-sectional geometries on the mechanical behavior. Three groups of milled fiber-reinforced resin composite (TRINIA) for 4-unit implant-supported frameworks (n = 10) with three connectors geometries (round, square, or trapezoid), and three groups of Co-Cr alloy frameworks manufactured by milled wax/lost wax and casting technique, were analyzed. The marginal adaptation was measured before cementation using an optical microscope. Then, the samples were cemented, thermomechanical cycled (load of 100 N/2 Hz, 10⁶ cycles; 5, 37, and 55 ᵒC, a total of 926 cycles at each one), and cementation and flexure strength (maximum force) analyzed. Analysis of stress distribution in framework veneered considering resin and ceramic properties for fiber-reinforced and Co-Cr frameworks, respectively, implant, and bone was by finite element analysis under three contact points (100 N) on the central region. ANOVA and Multiple paired test-t with Bonferroni adjustment (α = 0.05) were used for data analysis. Fiber-reinforced frameworks showed better vertical adaptation (mean ranged from 26.24 to 81.48 μm) compared to the Co-Cr frameworks (mean ranged from 64.11 to 98.12 μm), contrary to horizontal adaptation (respectively, means ranged from 281.94 to 305.38 μm; and from 150.70 to 174.82 μm). There were no failures during the thermomechanical test. Cementation strength showed three times higher for Co-Cr compared to fiber-reinforced framework, as well as flexural strength (P < .001). Regarding stress distribution, fiber-reinforced had a pattern of concentration in the implant-abutment complex. There were no significant differences in stress values or changes observed among the different connector geometries or framework materials. Trapezoid connector geometry had a worse performance for marginal adaptation, cementation (fiber-reinforced 132.41 N; Co-Cr 255.68 N) and flexural strength (fiber-reinforced 222.57 N; Co-Cr 614.27 N). Although the fiber-reinforced framework showed lower cementation and flexural strength, considering the stress distribution values and absence of failures in the thermomechanical cycling test, it can be considered for use as a framework for 4-unit implant-supported partial fixed dental prostheses in the posterior mandible. Besides, results suggest that trapezoid connectors mechanical behavior did not perform well compared to round or square geometries.

Oral and Periodontal Risk Factors of Prosthetic Success for 3-Unit Natural Tooth-Supported Bridges versus Implant-Supported Fixed Dental Prostheses

The goals of this research are: (1) to compare the survival and prosthetic success of metal-ceramic 3-unit tooth- versus implant-supported fixed dental prostheses; (2) to evaluate the influence of several risk factors on the prosthetic success of tooth- and implant-supported fixed dental prostheses (FPDs). A total of 68 patients with posterior short edentulous spaces (mean age 61.00 ± 1.325 years), were divided into two groups: 3-unit tooth-supported FPDs (40 patients; 52 FPD; mean follow-up 10.27 ± 0.496 years) and 3-unit implant-supported FPDs (28 patients; 32 FPD; mean follow-up 8.656 ± 0.718 years). Pearson-chi tests were used to highlight the risk factors for the prosthetic success of tooth- and implant-supported FPDs and multivariate analysis was used to determine significant risk predictors for the prosthetic success of the tooth-supported FPDs. The survival rates of 3-unit tooth- versus implant-supported FPDs were 100% and 87.5%, respectively, while the prosthetic success was 69.25% and 68.75%, respectively. The prosthetic success of tooth-supported FPDs was significantly higher for patients older than 60 years (83.3%) vs. 40-60 years old (57.1%) (p = 0.041). Periodontal disease history decreased the prosthetic success of tooth- versus implant-supported FPDs when compared with the absence of periodontal history (45.5% vs. 86.7%, p = 0.001; 33.3% vs. 90%, p = 0.002). The prosthetic success of 3-unit tooth- vs. implant-supported FPDs was not significantly influenced by gender, location, smoking, or oral hygiene in our study. In conclusion, similar rates of prosthetic success were recorded for both types of FPDs. In our study, prosthetic success of tooth- versus implant-supported FPDs was not significantly influenced by gender, location, smoking, or oral hygiene; however, history of periodontal disease is a significant negative predictor of success in both groups when compared with patients without periodontal history.

Survival Rate of 3-unit Fixed Partial Dentures Replacing First Molars: A Retrospective Cohort Study

Fixed partial dentures (FPDs) made of 12% Au-Pd alloy are covered under Japan's national health insurance system. The survival rate of such 3-unit fixed FPDs remains unknown, however. The purpose of this retrospective study was to assess their survival rate in the replacement of first molars. A total of 140 FPDs were included, and the endpoint was removal of an FPD. During the observation period, 43 FPDs were removed. The FPD survival rate was 70.2% at 10 yr, 58.2% at 15 yr, and 42.1% at 20 yr according to the Kaplan-Meier method. The estimated mean survival period was 19.4 yr. The main reasons for FPD loss were dental caries (27.9%), separation from the abutment tooth (18.6%), and pulpitis (18.6%). Single factor analysis using the log-rank test showed that two factors influenced FPD survival: a smaller gonial angle and deep pockets around the abutment teeth. This effect was not statistically significant in either case, however (p>0.05). The present results suggest that the prevention of caries and of the separation of the dentures from the abutment teeth are important factors in the long-term survival of FPDs.

Three-unit fixed dental prostheses supported by either two abutment implants or two abutment teeth: A comparative retrospective cohort study

OBJECTIVES

In general, similar restorative constructions are made on natural teeth and on dental implants. The assumption is made that implants and their restoration perform the same as natural roots and their prosthetic restoration. Evaluating cohorts of three-unit bridges on teeth and on implants, this retrospective clinical study aimed to compare implants and teeth as supporting units, including the reconstructions, in terms of survival, success, clinical, radiographic, and patient-reported outcomes.

MATERIAL AND METHODS

From an 8-year period, all patients treated with a posterior three-unit fixed reconstruction on either implants or teeth, with a follow-up of at least 2 years, were identified. For each implant-supported reconstruction, a comparable tooth-supported reconstruction was selected, based on the length of follow-up, the material of the reconstruction, and the location in either the maxilla or mandible.

RESULTS

For the Implant-group, 24 patients could be matched with 24 best matching patients with tooth-supported fixed dental prostheses (FPDs). Supporting implants and implant-supported reconstructions were all in function with a mean follow-up of 52 ± 23 months. Two tooth-supported reconstructions had been replaced (91.7% survival) (mean follow-up: 52 ± 19 months). Radiographic bone levels and soft tissue conditions were favorable in both groups with minor differences. There was no significant difference in overall patient satisfaction. The modified USPHS-score revealed an 87.5% overall success in the Implant-group and 91.7% in the Tooth-group.

CONCLUSIONS

Implant-supported three-unit FDPs are a reliable treatment option with survival and success rates not significantly different from the results of tooth-supported three-unit FDPs.

Clinical outcomes of single implant supported crowns versus 3-unit implant-supported fixed dental prostheses in Dubai Health Authority: a retrospective study

Background

This study assessed retrospectively the clinical outcomes of single implant-supported crowns and implant-supported fixed dental prostheses (FDPs).

Methods

This case series compared biological and technical complications in single implant-supported crowns and implant-supported bridges in a time framed sample of all patients who received dental implants between 2009 and 2016 in Dubai Health Authority. Only 3-unit implant-supported prostheses (FDPs) with one intervening pontic and an implant each end were included for comparison to single crown supported implants. Cantilevered implants, implant-supported dentures and cases involving bone grafts or sinus lifts were excluded. The primary outcome measure was marginal bone loss, measured on digital radiographs taken after prosthesis placement at baseline and one year after implant loading, whilst peri-implantitis and technical complications were secondary outcomes. Mixed regression models adjusted for clustering of implants within patients was used for patient and implant factor associations.

Results

A total of 454 patients (152 males; 302 females) had 1673 implants. The mean age of males (53.7 years, SD 14.6) was significantly greater than females (49.3 years, SD 12.9, p < 0.001). Mean mesial bone loss on the FDPs was significantly greater at 1 year (1.14 mm, SD 0.63) compared with the mesial surface of single implant-supported crowns (0.30 mm, SD 0.43, p < 0.001). Mean distal bone loss was also significantly greater at 1 year on the distal surfaces of implants supporting bridgework (1.29 mm, SD 0.71) compared with distal surfaces on single implant-supported crowns (0.36 mm, SD 0.54, p < 0.001). Mean marginal bone loss mesially and distally around implants placed in the lower anterior sextant was significantly greater compared to all other sites (p < 0.001). Bone loss by gender, patient’s age and medical condition was not different between the 2 implant groups. Screw loosening was the main technical complication (11.5%) whilst peri-implantitis occurred rarely (0.5%). The 66 cement retained implants had significantly more complications compared to the 1607 screw retained implants (p < 0.001).

Conclusions

Mean marginal bone loss around the supporting implants of FDPs (3-unit fixed bridgework) was greater than on single implant-supported crowns at one year after implant loading. Position in the mouth was associated with bone loss. Biological and technical complications occurred rarely.

Critical review about two myths in fixed dental prostheses: Full-Coverage vs. Resin-Bonded, non-Cantilever vs. Cantilever

The purpose of this review was to assess the literature regarding four types of fixed dental prostheses (FDPs)/resin-bonded FDPs (RBFDPs) to provide clinicians with a comparative overview of two myths: “RBFDPs are easy to debond in patients’ mouths” and “cantilever RBFDPs still have some clinical problems, especially in terms of overloading the abutment teeth and being easy to debond”. A total of 782 papers were identified, 753 of which were judged unsuitable and thus excluded, leaving a total of 29 articles for inclusion in this review. The results indicated that 1) Two-retainer RBFDPs achieve clinical results comparable to full-coverage three-unit FDPs; 2) Cantilever RBFDPs show excellent long-term clinical outcomes (especially in incisor teeth) compared with other FDPs; 3) RBFDPs typically show less catastrophic failure than conventional FDPs, rebonding should be considered when debonding occurs; and 4) Cantilever RBFDPs can be recommended as defect replacement prostheses for maxillary lateral incisors and mandibular incisor teeth.

Scientific field: Prosthodontics, Adhesive dentistry, Esthetic dentistry