Marginal fit of 3-unit implant-supported fixed partial dentures: Influence of pattern fabrication method and repeated porcelain firings.

BACKGROUND: Marginal fit significantly impacts the long-term success of dental restorations. Different pattern fabrication methods, including hand-waxing, milling, or 3D printing, may affect restorations accuracy. The effect of porcelain firing cycles on the marginal fit of metal-ceramic restorations remains controversial, with conflicting findings across studies. PURPOSE: The aim was to evaluate the potential effects of multiple porcelain firings (3, 5, 7 cycles) as well as pattern fabrication method (conventional hand-waxing, milling, and 3D printing) on the marginal adaptation of 3-unit implant-supported metal-ceramic fixed partial dentures. It was hypothesized that neither the wax pattern fabrication method nor repeated ceramic firings would significantly affect the marginal adaptation of metal-ceramic crowns. METHODS: In this in-vitro study, 30 Cobalt-Chromium alloy frameworks were fabricated based on pattern made through three techniques: conventional hand-waxing, CAD-CAM milling, and CAD-CAM 3D printing (n = 10 per group). Sixteen locations were marked on each abutment to measure the vertical marginal gap at four stages: before porcelain veneering and after 3, 5, and 7 firing cycles. The vertical marginal gap was measured using direct microscopic technique at ×80 magnification. Mean vertical marginal gap values were calculated and two-way ANOVA and Tukey's post hoc tests were used for inter-group comparisons (α = 0.05). RESULTS: The 3D printing group showed significantly lower (P<0.001) mean vertical marginal gaps (60-76 µm) compared to the milling (77-115 µm) and conventional hand-waxing (102-110 µm) groups. The milling group exhibited a significant vertical gap increase after 3 firing cycles (P<0.001); while the conventional (P = 0.429) and 3D printing groups (P = 0.501) showed no significant changes after 7 firing cycles. Notably, the vertical marginal gap in all groups remained below the clinically acceptable threshold of 120 µm. CONCLUSION: CAD-CAM 3D printing provided superior marginal fit compared to CAD-CAM milling and conventional hand-wax pattern fabrication methods. The impact of porcelain firing on the mean marginal gap was significant only in the milling group. All three fabrication techniques yielded clinically acceptable vertical marginal adaptation after repeated firings. Additive manufacturing holds promise to produce precise implant-supported prostheses.

Comparative Accuracy of Intraoral and Extraoral Digital Workflows for Short Span Implant Supported Fixed Partial Denture Fabrication: An In Vitro Study.

BACKGROUND The advent of digital impressions using computer-aided design and manufacturing technology (CAD/CAM) has simplified and improved the fabrication of implant prostheses in dentistry. The conventional impression has several drawbacks, including tray selection, material type, impression technique, impression disinfection, and cast model storage. The inaccuracies caused by distortion and contraction of impression material can be minimized with digital impressions. This study aimed to compare digital dental impressions of 10 working casts made using the Pindex laser removable die system to fabricate parallel drill channels vs 10 working casts made using the Di-Lok plastic tray removable die system. MATERIAL AND METHODS An implant master die with 2 dental implant analogs was fabricated. Ten working casts using the Pindex laser removable die system with parallel drill channels and 10 working casts using the Di-Lok plastic tray removable die system were fabricated. The working casts were scanned using an extra-oral laboratory scanner and the implant master model was scanned with an intra-oral scanner. RESULTS The properties of the casts made using the 2 systems were evaluated and analyzed with ANOVA and post hoc Tukey test. The mean horizontal linear distances between A1B1 (P<0.021), A2B2 (P<0.018), C1D1 (P<0.026), C2D2 (P<0.03), B1C1 (P<0.01), and mean vertical distances between B1A2 (P<0.015), C1D2 (P<0.001), B1B2 (P<0.028), and C1C2 (P<0.001) were significantly different between the Pindex system and Di-Lok tray system as compared to intra-oral scans. CONCLUSIONS Complete digital workflow with intra-oral scans were more than the partial digital workflow with extra-oral scans for the Pindex system and Di-Lok tray systems.

Does the Build Orientation Parameter Affect the Fit of Fixed Partial Dentures Fabricated by Additive Manufacturing?

PURPOSE: This in vitro study evaluated the adaptation of cobalt-chromium (Co-Cr) fixed dental prostheses (FDPs) fabricated by selective laser melting (SLM) with different build angles. MATERIALS AND METHODS: Maxillary right first premolars and first molars from a typodont were prepared with 1-mm chamfer, 2-mm occlusal reduction, and total taper of 8 degrees to receive three-unit FDPs. After framework design, data were sent to a laser machine, and 30 specimens were fabricated from Co-Cr metal powder by SLM. Specimens were assigned to three groups (n = 10 per group) with different build angles of 0 (A0), 30 (A30), and 45 (A45) degrees. Marginal and internal fit were evaluated. Results were compared among build orientation groups and abutments. Data were analyzed using the Levene test, t test, and analysis of variance (α = .05). RESULTS: A statistical difference was found between different angle groups (P = .015). At the abutment level, a significant difference was found in the gap values between build orientation groups for the molars (P = .048). Group A0 reported the smallest mean discrepancy values, and group A45 the highest. Statistical differences were found between group A45 and groups A0 (P < .001) and A30 (P < .024). CONCLUSIONS: The fit of printed metal FDPs was affected by the build orientation but remained clinically acceptable.

Fracture strength of 3-units fixed partial dentures fabricated with metal-ceramic, graphene doped PMMA and PMMA before and after ageing: An in-vitro study.

OBJECTIVES: To evaluate the fracture strength and linear elongation at break of three-units fixed partial dentures (FPDs) fabricated with traditional and new materials for fixed prosthodontics before and after ageing. METHODS: Sixty models of three-units FPDs were fabricated and cemented onto a Co-Cr model simulating the replacement of a maxillary second premolar. The samples were randomly divided into 3 groups: metal-ceramic (MCR), graphene-doped polymethylmethacrylate (PMMA-GR) and polymethylmethacrylate (PMMA). Half of the samples were directly subjected to fracture test, while the remaining half underwent an ageing process and then a fracture loading test using an electrodynamic testing machine. Fracture load and elongation at break values were taken and statistically analysed. RESULTS: Significant differences were detected between the different materials (p<0.05). All groups showed a reduction of the fracture load and elongation at break values after ageing, but not statistically significant, except for PMMA group (p = 2.012e-19) (p = 3.8e-11). CONCLUSIONS: MCR and PMMA-GR three-units FPDs showed higher fracture strength and lower elongation at break compared to PMMA. MCR and PMMA-GR had higher resistance to ageing processes compared to PMMA. CLINICAL SIGNIFICANCE: PMMA-GR could be considered a material for long-term provisional restorations as its mechanical behaviour and ageing resistance are more like MCR than PMMA.

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures.

OBJECTIVES: The aim of this study was to compare failure load and initial damage in monolithic, partially veneered, and completely veneered (translucent) zirconia cantilevered fixed partial dentures (CFPDs), as well as completely veneered metal-ceramic CFPDs under different support and loading configurations. MATERIALS AND METHODS: Eight test groups with anatomically congruent CFPDs (n = 8/group) were fabricated, differing in CFPD material/support structure/loading direction (load applied via steel ball (Ø 6 mm) 3 mm from the distal end of the pontic for axial loading with a 2-point contact on the inner cusp ridges of the buccal and oral cusps and 1.3 mm below the oral cusp tip for 30° oblique loading): (1) monolithic zirconia/CoCr abutment teeth/axial, (2) monolithic zirconia/CoCr abutment teeth/oblique, (3) partially veneered zirconia/CoCr abutment teeth/axial, (4) partially veneered zirconia/CoCr abutment teeth/oblique, (5) completely veneered zirconia/CoCr abutment teeth/axial, (6) completely veneered CoCr/CoCr abutment teeth/axial (control group), (7) partially veneered zirconia/implants/axial, and (8) partially veneered zirconia/natural teeth/axial. Restorations were artificially aged before failure testing. Statistical analysis was conducted using one-way ANOVA and Tukey post hoc tests. RESULTS: Mean failure loads ranged from 392 N (group 8) to 1181 N (group 1). Axially loaded monolithic zirconia CFPDs (group 1) and controls (group 6) showed significantly higher failure loads. Oblique loading significantly reduced failure loads for monolithic zirconia CFPDs (group 2). Initial damage was observed in all groups except monolithic zirconia groups, and fractography revealed design flaws (sharp edges at the occlusal boundary of the veneering window) in partially veneered zirconia CFPDs. CONCLUSIONS: Monolithic zirconia CFPDs might be a viable alternative to completely veneered CoCr CFPDs in terms of fracture load. However, oblique loading of monolithic zirconia CFPDs should be avoided in clinical scenarios. Design improvements are required for partially veneered zirconia CFPDs to enhance their load-bearing capacity. CLINICAL RELEVANCE: Monolithic zirconia may represent a viable all-ceramic alternative to the established metal-ceramic option for CFPD fabrication. However, in daily clinical practice, careful occlusal adjustment and regular monitoring should ensure that oblique loading of the cantilever is avoided.

Biofilm accumulation on complete arch subperiosteal implant-supported prostheses: Effect of pontic type.

STATEMENT OF PROBLEM: Complete arch subperiosteal implant-supported prostheses present challenges in terms of effective cleaning, leading to the accumulation of biofilm on their intaglio surfaces. The association between different intaglio surface morphologies and biofilm accumulation on complete arch subperiosteal implant-supported prostheses is unclear. PURPOSE: The purpose of this in vitro study was to investigate the correlation between the intaglio surface of complete arch subperiosteal implant-supported prostheses and biofilm accumulation. MATERIAL AND METHODS: Sixty-eight complete arch subperiosteal implant-supported prostheses were fabricated with varying interimplant distances and pontic morphologies. Four different types of pontic morphologies were included: saddle, flat, scalloped, and ovate. To simulate biofilm accumulation, a green aerosol was sprayed onto the intaglio surface. Dental floss was used to clean the colored spray from the intaglio surface. The intaglio surfaces of prostheses were then scanned with an intraoral scanner. The biofilm areas were identified and calculated by using a 3-dimensional macroscopical quantification method. The distances between adjacent implants and transmucosal height were measured. The correlation between interimplant distances and biofilm areas, and the correlation between the biofilm areas and transmucosal height, were analyzed using the Spearman test. Furthermore, a generalized estimating equation (GEE) was employed to examine the relationship between pontic morphology and biofilm area, adjusting for location, cantilever, implant distance, and transmucosal height (α=.05). RESULTS: A significant correlation was found between the biofilm area and transmucosal height (correlation coefficient=0.208, P<.001). A significant increase in biofilm accumulation was observed in the saddle group compared with the 3 groups in GEE Models I and II. CONCLUSIONS: Flat pontics and ovate pontics have significantly lower biofilm retention. Moreover, transmucosal height plays a significant role in biofilm accumulation in the pontic area.

Perio-prosthodontic pontic site management, part II: Pontic site reconstruction strategies to enhance the esthetic and biological outcomes.

OBJECTIVE: Ridge deformities are present in most patients after tooth extraction; these defects make the management of future implant and pontic sites challenging to deal with. The restorative team should be able to diagnose and treat these deformities to allow for successful outcomes. Many approaches have been described to reconstruct pontic sites, each with specific indications. This article describes the different approaches to reconstructing pontic sites and their indications to allow for a proper esthetic and biological environment for future restorations. CLINICAL CONSIDERATIONS: Depending on the severity of the defect, location, and the esthetic necessity, pontic site enhancement can be done through different approaches, some requiring soft tissue grafting, hard tissue grafting, or both. Understanding the indications of the treatment options is essential to allow the clinician to make the right therapeutic decision and achieve the best possible perio-prosthodontic outcomes. CONCLUSIONS: An adequate balance between the soft tissue and prosthetics is essential to achieve successful results on implant-supported or tooth-supported fixed dental prostheses (FDPs). Selecting the right approach to treat ridge deformities is necessary to increase treatment success, reduce over-treatment, and create a biologically sound environment for restorations. CLINICAL SIGNIFICANCE: Pontic site enhancement through reconstructive surgery will allow for esthetically pleasing and biologically stable results, allowing restorations to emulate natural structures lost after tooth extraction.

Digital workflow for monolithic and veneered zirconia and metal-ceramic posterior fixed partial dentures: A five-year prospective randomized clinical trial.

Purpose To evaluate and compare the survival, success rates, and biological and technical complications of three-unit posterior monolithic and veneered zirconia and metal-ceramic (MC) posterior fixed partial dentures (FPDs) fabricated using a digital workflow and computer-aided design and computer-aided manufacturing (CAD/CAM) over a 5-year follow-up.Methods Ninety patients in need of three-unit posterior FPDs were randomized to receive monolithic zirconia (MZ), veneered zirconia (VZ), and MC restorations (n = 30 each). Teeth preparations were scanned using an intraoral scanner, and restorations were milled and cemented with resin cement. Clinical performance and periodontal parameters were assessed at baseline and yearly up to 5 years after insertion. Data analysis was performed using the Kaplan-Meier method, Friedman test, and Wilcoxon signed-rank test with Bonferroni correction and Mann-Whitney U test.Results The 5-year survival rates of the MZ, VZ, and MC FPDs were 87%, 97%, and 100%, respectively (P = 0.04). Most complications were biological in nature. Only one MZ FPD fractured 58 months after placement. All the restorations were assessed as satisfactory at each recall. Differences were found in the gingival index score over time in the VZ and MC groups. The margin index remained stable throughout the follow-up period in both zirconia groups.Conclusions The results of this study suggest that using a digital workflow to fabricate posterior FPDs is an adequate treatment option and that monolithic zirconia could be a viable alternative to metal-ceramic or veneered zirconia. However, further long-term studies are necessary to provide stronger evidence in patients with bruxism.

Long-term clinical outcome of three-unit fixed-fixed posterior zirconia ceramic inlay-retained FDPs with a modified design.

OBJECTIVES: To assess the long-term clinical outcome of posterior inlay-retained fixed dental prostheses (IRFDPs) with a modified design made from zirconia ceramic. METHODS: In 30 patients thirty 3-unit IRFDPs were placed to replace 7 premolars (4 in the maxilla, 3 in the mandible), and 23 first molars (15 in the maxilla, 8 in the mandible). Preparations were accomplished in agreement with the general principles for ceramic inlay restorations and modified with a short retainer-wing bevel preparation within the enamel at the buccal and oral sides. The frameworks were milled from 3Y-TZP ceramic, and the pontics were veneered with feldspathic ceramic. All IRFDPs were bonded with a phosphate monomer containing luting resin after air-abrasion of the intaglio surfaces. The patients were recalled 6-12 months after placement, and then annually. Kaplan-Meier analysis was used to calculate the survival and complication rates of the IRFDPs. RESULTS: The mean observation time was 10.6 ± 1.5 years. The 10-year cumulative survival rate was 89% with 4 failures, two of them were due to deep secondary caries with loss of retention, one due to repeated debonding with enamel fractures, and one due to generalized progressive periodontitis. The most common complication was chipping of the veneering ceramic (20.1%). Eighteen IRFDPs were free of any type of complication up to 15.4 years, which corresponds to a 10-year cumulative success rate of 70.4%. CONCLUSION: The long-term clinical performance of modified IRFDPs made of veneered zirconia ceramics was favorable after 10 years, therefore, they represent a treatment alternative to replace posterior single missing teeth. CLINICAL SIGNIFICANCE: Zirconia-based IRFDPs fabricated in the modified design may represent a substance-preserving alternative to conventional posterior FDPs to replace posterior single missing teeth, particularly in cases where implants cannot be placed, and when the adjacent teeth already have small restorations or defects.

The effect of pre-ceramic soldering on marginal and internal fit of 4-unit zirconia frameworks and monolithic zirconia fixed dental prostheses.

The aim of this study is to evaluate the effect of pre-ceramic soldering on the marginal and internal fit of 4-unit zirconia fixed dental prostheses (FPDs) that have two abutments and two pontics. 4-unit zirconia frameworks (Zirkonzahn ICE Translucent) (Z Group) and monolithic zirconia (Zirkonzahn Prettau) (M Group) FPDs were manufactured. Groups were divided into two groups (n = 10) control (ZC and MC) and soldering (ZS and MS). Samples of ZS and MS groups were cut into two pieces under cooling water and soldered with a bonding material (DCM Zircon HotBond). The marginal and internal fit of the restorations were measured from 36 points of each sample and cement space volume was calculated using reverse engineering software (Geomagic Design X). The mean and standard deviations were submitted to Generalized Linear Mixed Model (GLMM) analysis (α = 0.05). Statistical differences between groups before and after pre-ceramic soldering on point measurements were found. In total cement spacing measurements, a significant difference was found amongst all groups (P < 0.05). However, in premolars, a statistically significant difference was found between ZC and ZS groups and MC and MS groups (P < 0.05). All discrepancies after pre-ceramic soldering were found to be lower than before.

Survival of fixed prosthetic restorations on vital and nonvital teeth: A systematic review.

PURPOSE: To evaluate the survival rate of full-coverage tooth-supported fixed prosthetic restorations, single crowns (SCs), and fixed dental prostheses (FDPs), taking into consideration the potential influence of tooth-vitality, presence and type of post, and type of prosthetic restoration material. MATERIALS AND METHODS: In October 2022, two authors independently conducted a search in PubMed, Web of Science, and Scopus electronic databases as well as a hand search to identify clinical human studies on full-coverage SCs and FDPs supported by vital and/or non-vital abutments and/or a combination of both, with a minimum observation period of 24 months. RESULTS: Out of 4198 studies identified through the database search and 22 through hand searching, 26 studies fulfilled the inclusion criteria and were included in the analysis of the present systematic review. Included studies scored six points and more according to Newcastle-Ottawa Scale (NOS). The highest estimated 5-year survival rate was observed for (metal-ceramic and all-ceramic) SCs on vital teeth (98.3%; 95% CI [98.1, 98.6%]) and all ceramic SCs on non-vital teeth with fiber post (95.0%; 95% CI [94.5-95.4%]). Metal-ceramic SCs on vital teeth (97.1%; 95% CI [95.6-98.7%]) showed a statistically significant higher estimated 5-year survival rate compared to metal-ceramic SCs with cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001), fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001) and without post (85.7%; 95% CI [80.7, 90.6%], P < 0.032). All-ceramic SCs with fiber post had a statistically significant higher estimated 5-year survival rate (95.0%; 95% CI [94.5-95.4%]) compared to metal-ceramic SCs on non-vital teeth with fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001). SCs (all-ceramic and metal-ceramic) with fiber post had a statistically significantly higher estimated 5-year survival rate of (92.7%; 95% CI [92.4-92.9%]) than SCs made of metal-ceramic and retained by cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001). For FDPs, the 5-year survival rate was significantly higher for FDPs on vital abutments (84.9%; 95% CI [75.9, 93.9%]) compared to FDPs retained by non-vital abutment/s (81.3%; 95% CI [80.3, 82.2%], P = 0.049) irrespective to presence, type of post, and FDPs material. The results are limited by the limited number of studies and the presence of uncontrolled confounding clinical variables. CONCLUSIONS: Within the limitations of the study, tooth vitality is suggested to contribute positively to the survival of SCs and FDPs.

Worn denture teeth of a full-arch implant-supported fixed dental prosthesis: A technique to restore.

Worn denture teeth continue to be a significant complication with implant-supported prostheses. This article discusses a case report that used an intraoral scanning system to restore an existing maxillary implant-supported prosthesis with significant posterior occlusal wear.  IPS e.max (Ivoclar Vivadent, Schaan, Liechtenstein) restorations were fabricated and cemented to the prepared posterior denture teeth to re-establish the occlusal vertical dimension and to help prevent further wear of the occlusal surfaces.

Sobrevivência em fadiga de coroas bioinspiradas bilaminadas: estudo in vitro / Fatigue survival rate of bioinspired bilaminar crowns: in vitro study

O objetivo deste estudo foi avaliar o comportamento biomecânico através da resistência à fadiga e análise por elementos finitos de coroas bioinspiradas bilaminadas com infraestruturas modificadas na superfície vestibular (Estudo A) e utilizando diferentes materiais cerâmicos com módulos elásticos distintos (Estudo B). Para isso, foram confeccionados 90 preparos para coroa total em resina epóxi G10, sobre os quais foram preparadas coroas bioinspiradas de acordo com os seguintes grupos: Estudo A - IC (infraestrutura convencional), IME (infraestrutura modificada estratificada) e IMC (infraestrutura modificada cimentada), todas confeccionadas em dissilicato de lítio (infraestrutura) + porcelana (recobrimento); Estudo B ­ DL+LEU (dissilicato de lítio + leucita), LEU+DL (leucita + dissilicato de lítio), CH+DL (cerâmica híbrida + dissilicato de lítio) e CH+LEU (cerâmica híbrida + leucita). Para o Estudo A, todas as infraestruturas foram usinadas; os recobrimentos dos grupos IC e IME foram confeccionados através da estratificação, e os recobrimentos do grupo IMC foram usinados. Já para o Estudo B, todas as peças foram usinadas, de acordo com o material cerâmico de cada grupo. Em seguida, foi realizada a cimentação adesiva dos recobrimentos sobre as infraestruturas (a depender do grupo) e das coroas sobre os preparos utilizando cimento resinoso fotopolimerizável (Variolink Esthetic LC). Após a cimentação, os espécimes foram submetidos ao teste de fadiga cíclica (10.000 ciclos, 20Hz), e como desfecho foram considerados dois eventos, em que o primeiro foi a ocorrência de trinca e/ou lascamento (evento 1) e o segundo foi a falha catastrófica do conjunto (evento 2). Os valores de carga e número de ciclos para falha em que foram observados os eventos 1 e 2 foram utilizados para realizar a análise de sobrevivência de acordo com Kaplan-Meier e Log-Rank (Mantel-Cox; 95%). As marcas de fratura e o modo de falha das coroas foram avaliados e classificados por estereomicroscópio óptico e microscópio eletrônico de varredura. Por fim, foi realizada análise por elementos finitos (FEA) para ambos os estudos, a fim de avaliar a distribuição de tensões sobre as coroas e interface adesiva. Para o Estudo A, os resultados do teste de fadiga mostraram que, considerando o evento 1 (trinca/lascamento), os grupos IC e IMC apresentaram médias de carga fadiga estatisticamente significantes entre si (733,33 N e 913,33 N, respectivamente), enquanto o grupo IME apresentou média superior (1.020 N). O mesmo foi observado para o número de ciclos em fadiga para todos os grupos. Ao considerar o evento 2 (falha catastrófica), os três grupos apresentaram médias estatisticamente semelhantes entre si (~1.028 N). Os resultados de FEA mostraram que o grupo IC concentrou maior tensão de tração do que os grupos IME e IMC. Para o Estudo B, no teste de fadiga, o grupo DL+LEU apresentou a maior média de resistência à fadiga (evento 1: 913,33 N e evento 2: 1033,33 N), enquanto todas as outras combinações de materiais cerâmicos analisadas foram estatisticamente semelhantes entre si, considerando carga e número de ciclos. Com relação ao FEA, os grupos com cerâmica híbrida (CH+DL e CH+LEU) apresentaram menores picos de concentração de tensão na infraestrutura do que os grupos com cerâmicas vítreas (DL+LEU e LEU+DL), porém, em contrapartida, concentraram maior tensão na interface adesiva. Com isso, conclui-se que a utilização da infraestrutura modificada é uma alternativa viável e promissora para tratamentos reabilitadores, apresentando sobrevivência em fadiga e distribuição de tensões satisfatórias. Além disso, a combinação entre uma infraestrutura de dissilicato de lítio e recobrimento de cerâmica a base de leucita corresponde a melhor abordagem considerando a infraestrutura modificada.(AU)

The objective of this study was to evaluate the biomechanical behavior through fatigue resistance and finite element analysis of bilaminar bioinspired crowns with modified infrastructures on the buccal surface (Study A) and using different ceramic materials with different elastic moduli (Study B). For this, 90 preparations were made for a full crown in G10 epoxy resin, on which bioinspired crowns were prepared according to the following groups: Study A - CI (conventional infrastructure), SMI (stratified modified infrastructure) and CMI (cemented modified infrastructure ), all made of lithium disilicate (infrastructure) + porcelain (veneer); Study B ­ LD+LEU (lithium disilicate + leucite), LEU+LD (leucite + lithium disilicate), HC+LD (hybrid ceramic + lithium disilicate) and HC+LEU (hybrid ceramic + leucite). For Study A, all infrastructures were machined; the coverings of the CI and SMI groups were made through stratification technique, and the veneers of the SMI group were machined. For Study B, all pieces were machined, according to the ceramic material of each group. Then, the veneers were cemented into their infrastructures (depending on the group) and crowns were cemented into preparations using light-cured resin cement (Variolink Esthetic LC). After cementing, the specimens were subjected to the cyclic fatigue test (10,000 cycles, 20Hz), and as an outcome two events were considered: the occurrence of cracking and/or chipping (event 1) and catastrophic failure (event 2). The load (N) and number of cycles to failure in which events 1 and 2 were observed were used to perform the survival analysis according to Kaplan-Meier and Log-Rank (Mantel- Cox; 95%). The fracture marks and failure mode of the crowns were evaluated and classified by optical stereomicroscope and scanning electron microscope. Finally, finite element analysis (FEA) was performed for both studies in order to evaluate the stress distribution over the crowns and adhesive interface. For Study A, the results of the fatigue test showed that, considering event 1 (cracking/chipping), the CI and CMI groups presented average to failure that were statistically significant compared to each other (733.33 N and 913.33 N, respectively), while the SMI group showed higher averages (1,020 N). Same pattern was observed for the number of cycles under fatigue for both groups. When considering event 2 (catastrophic failure), the three groups presented statistically similar means (~1,028 N). The FEA results showed that the CI group concentrated greater tensile stress than the CMI and SMI groups. For Study B, in the fatigue test, the LC+LEU group presented the highest average fatigue resistance (event 1: 913.33 N and event 2: 1033.33 N), while all other combinations of ceramic materials analyzed were statistically similar to each other, considering load and number of cycles. Regarding FEA, the groups with hybrid ceramics (HC+LC and HC+LEU) showed lower stress concentration peaks in the infrastructure than the groups with glass ceramics (LC+LEU and LEU+LC), however, on the other hand, concentrated greater tension at the adhesive interface. With this, it is concluded that the use of modified infrastructure is a viable and promising alternative for oral rehabilitation treatments, presenting satisfactory fatigue survival and adequate stress distribution. Furthermore, the combination of a lithium disilicate infrastructure and a leucite-based ceramic coating corresponds to the best approach considering the modified infrastructure.(AU)

[Long-term clinical evaluation of different types of resin-bonded fixed partial denture to replace lost anterior teeth].

Objective: To evaluate the clinical survival rates and influence factors of different types of resin-bonded fixed partial dentures (RBFPD) used in anterior missing teeth restoration. Methods: Ninety-three RBFPD were delivered to 92 patients [92 patients,43 males and 49 females, average age (46.1±12.8) years] who visited Peking University School and Hospital of Stomatology from January 2006 to December 2021 for restoration of 1 or 2 anterior missing teeth. Altogether 32 cases of glass fiber reinforced RBFPD, 39 cases of glass-based ceramic RBFPD and 22 cases of porcelain-fused-to-metal RBFPD were retrospectively analyzed. The complete survival rate, functional survival rate, patients' satisfaction and color matching of the restorations were recorded and evaluated every year since the replacement with RBFPD. The Kaplan-Meier survival curve method was used for survival analysis, and the Log-rank analysis was used to compare the effect of the number of missing teeth, position (maxillary or mandibular), cantilever or non-cantilever and gender on the survival rate of the restorations. Results: The overall survival time for the 93 RBFPD was 13.7 years (95%CI: 12.3-15.1 years). There was a decreasing trend in complete survival and functional survival for all three material RBFPD from year to year, but complete and functional survival rates exceeded 90% at year 5 and exceeded 80% at year 10. The complete survival rate of the glass-ceramic RBFPD was higher than the other two during the follow-up period, with a complete survival rate of 90% (35/39) at year 15. The porcelain-fused-to-metal RBFPD had a higher functional survival rate in years 1-8, but the complete and functional survival rates showed a substantial decrease after year 9. The single-factor Log-rank analysis showed that the success rate of porcelain-fused-to-metal RBFPD was significantly higher than that of glass fiber reinforced RBFPD (χ²=7.33, P=0.007), and the success rate of RBFPD with 1 missing tooth restored was significantly higher than that of RBFPD with 2 missing teeth restored (χ²=3.23, P=0.072). The differences in success rates between different restoration positions (maxillary and mandibular), cantilever or non-cantilever, and gender factors were not statistically significant (χ²=2.26, P=0.133; χ²=0.68, P=0.411; χ²=1.07, P=0.300). Conclusions: For the restoration of individual missing anterior teeth, both porcelain-fused-to-metal RBFPD and glass-based ceramic RBFPD achieve a high long-term clinical success rate, with glass-based ceramic RBFPD being more able to ensure long-term restorative result.

The impact of digitization and conventional techniques on the fit of fixed partial dentures FPDs: systematic review and Meta-analysis.

PURPOSE OF THE STUDY: The goal behind this study is to answer the question "In tooth-supported fixed partial dentures (FPDs), does the digital impression techniques compared to fabrications using conventional impression methods improve the marginal and internal fit? BACKGROUND: The incorporation of digital technology in the fabrication of fixed partial dentures (FPDs) has accelerated over the past decade. This study is directed at evaluating the marginal and internal fit of FPDs manufactured using digital approaches compared to conventional techniques. The need for updated data has encouraged this review. MATERIALS AND METHODS: An electronic search was conducted in PubMed, Scopus, Web of Science, and the Grey Database to identify relevant studies. The Modified Methodological Index for Non-Randomized Studies (MINORS) was used to assess the risk of bias in in vitro experiments. The key results of this meta-analysis were the standard mean differences (SMDs) and 95% confidence intervals (CI) of each main variance, marginal fit, and internal fit between the digital and conventional techniques. Additional analyses were performed to assess the significance of three subgroup parameters: method of digitalization, cement spacer thickness, and span length, and their influence on the fit of the FPDs. RESULTS: Based on predefined criteria, of the seven articles included in this systematic review, only five were selected for the quantitative data analysis. The marginal fit results were (P = 0.06; SMD: -1.88; 95% CI: - 3.88, 0.11) (P > 0.05) and the internal fit results were (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.10) (P < 0.05). Regarding the subgroup analyses, the method of digitalization subgroup results were (P = 0.35; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.80; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively. The span length results were (P = 0.10; SMD: -1.89; 95% CI: - 3.89, 0.11) for marginal fit and (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.11) for internal fit. The cement spacer thickness (P = 0.01; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.04; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively. CONCLUSION: Tooth-retained fixed partial dentures FPDs produced by digital scanning and computer-aided design/computer-aided manufacturing (CAD/CAM) systems can significantly enhance the internal fit compared with those manufactured by traditional methods. Intraoral scanners can replace conventional impressions for the fabrication of FPDs because they minimize the operating time and reduce patient pain. Further clinical studies are required to obtain more conclusive results. SYSTEMATIC REVIEW REGISTRATION: This systematic review and meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42021261397.

Comparative Mechanical Testing for Digitally Produced Provisional Fixed Partial Dentures vs the Conventional Method: An In Vitro Study

PURPOSE: To examine and compare the fracture strength of implant-cemented fixed partial denture (FPD) prostheses fabricated with digital vs conventional chairside methods. MATERIALS AND METHODS: Three groups of seven specimens each were produced: group A (3D printing); group B (milling); and group C (conventional chairside manufacturing), which served as a control. All groups were cemented to standard implant abutments placed in artificial bone blocks. Fracture strength testing was performed using a universal testing machine. Statistical analysis of the resultant maximum forces was performed using SPSS version 25 software (Mann- Whitney U test, P < .05). RESULTS: The mean fracture load value of the group A FPDs was 260.14 N ± 28.88, for group B was 663.57 N ± 140.55, and for group C was 266.65 N ± 63.66. CONCLUSIONS: Milled provisional FPDs showed a higher fracture resistance compared to 3D-printed and control groups. However, no such difference could be detected between the 3D-printed and control groups.

Successful complete oral rehabilitation of a patient with osteopetrosis with extensive pre-treatments, bone grafts, dental implants and fixed bridges: a multidisciplinary case report.

BACKGROUND: Osteopetrosis comprises a group of inherited disorders that are rare and result in abnormal bone structure. Bone remodeling is extremely inhibited because osteoclasts are nonfunctional or lacking. This condition causes overgrowth of bone with disappearance of the bone marrow, leading to aplastic anemia; obstruction of nerve passages in the skull leads to blindness and often hearing impairment. In most cases, osteopetrosis results in oral complications such as tooth deformation, hypomineralization, and delayed or absent tooth eruption. The only curative treatment is hematopoietic stem cell transplantation (HSCT). The main treatment of the oral complications during childhood and adolescence consists in protecting the erupted teeth against caries disease through prophylactic treatment aimed at optimal oral hygiene through frequent regular dental visits throughout life. Many patients with osteopetrosis require major oral rehabilitation to treat complications of the disease. Improved results of HSCT increase the likelihood that dental professionals will encounter patients with osteopetrosis. CASE PRESENTATION: In this case report, we show that individuals with osteopetrosis who have severe oral complications can be treated successfully if they are treated for osteopetrosis at an early age. The boy had his dental care in pedodontics, and regular multidisciplinary meetings were held for future treatment planning. At the age of 15, he was then referred for rehabilitation. The initial evaluations revealed no further growth in the alveolar bone. The rehabilitation was done stepwise, with extraction of malformed and malpositioned teeth. Initially, the patient received a removable partial denture followed by reconstruction of the width of the alveolar process, titanium implants, temporary fixed bridges, and finally screw-retained titanium-ceramic bridges with titanium frames for the upper and lower jaws. CONCLUSIONS: The three-year follow-up after loading indicated a stable marginal bone level and optimal oral hygiene as a result of frequent professional oral hygiene care. The patient showed no signs of symptoms from the temporomandibular joint and has adapted to the new jaw relation without any functional or phonetical issues.

Effect of different sintering protocols on the fracture strength of 3-unit monolithic gradient zirconia fixed partial dentures: An in vitro study.

STATEMENT OF PROBLEM: Strength-gradient zirconia combining 3 zirconia formulations with different flexural strengths has been reported to have outstanding mechanical properties. However, data concerning the effect of different sintering protocols on the fracture strength of 3-unit monolithic gradient zirconia fixed partial dentures (FPDs) are sparse. PURPOSE: The purpose of this in vitro study was to test the effect of different sintering protocols on the fracture strength of 3-unit monolithic gradient zirconia FPDs. MATERIAL AND METHODS: Two custom-made stainless-steel master dies were designed to replicate a mandibular right second premolar and second molar prepared to receive a 3-unit monolithic zirconia FPD. Thirty monolithic zirconia FPDs were milled from gradient zirconia blanks and allocated to 3 groups (n=10) according to the sintering protocols: high-speed sintering, speed sintering, and conventional sintering. The FPDs were cemented onto the corresponding dies with traditional glass ionomer cement. All FPDs were cyclic loaded (600 000 cycles/49 N/1.7 Hz) in a mastication simulator. Fracture load measurements for each FPD were determined by using a universal testing machine. Scanning electron microscopy (SEM) at ×80 magnification was used to examine a fractured FPD from each group. A representative specimen from each group was examined with SEM at ×30 000 magnification to determine the grain size. One-way ANOVA, pair-wise Tukey honestly significant difference (HSD), and Pearson correlation tests were used for statistical analysis of the data (α=.05). RESULTS: The high-speed sintered FPDs recorded the highest statistically significant fracture load mean ±standard deviation value (2526 ±300 N), followed by the speed sintered FPDs (2136 ±127 N), while the lowest statistically significant fracture load mean value was recorded with the conventionally sintered FPDs (1361 ±181 N) (P<.001). In addition, the mean ±standard deviation grain size values were 488 ±272 nm for the high-speed sintered specimen, 578 ±409 nm for the speed sintered specimen, and 832 ±551 nm for the conventionally sintered specimen (P<.001). A significant negative correlation was found between fracture strength and grain size among the 3 groups. CONCLUSIONS: The fracture strength of 3-unit monolithic gradient zirconia FPDs sintered by using a high-speed protocol was significantly higher than that of speed and conventionally sintered FPDs (P<.001). The high-speed sintering protocol reduced the mean grain size of gradient zirconia FPDs compared with that of both speed and conventional sintering protocols.

Three-Year Follow-up of a Randomized Clinical Trial on Screw-Retained Monolithic Zirconia Restorations on Ti-Base Abutments Based on Digital or Conventional Impression Techniques.

PURPOSE: To report on the follow-up of two previously published RCTs on the performance of screw-retained monolithic zirconia restorations on titanium (ti)-base abutments based on either digital scans through intraoral optical scanning (IOS) or conventional impressions. MATERIALS AND METHODS: A total of 54 patients receiving 89 restorations (44 solitary crowns [SC], 21 splinted crowns [2-FDP], and 24 three-unit fixed partial dentures [3-FDP]) were included for the 1- to 3-year follow-up period. Restoration survival and technical complications were documented. RESULTS: In total, 50 patients with 84 restorations completed the 3-year follow-up. One 3-FDP from the digital group was lost. This resulted in a survival rate of 97.9% for the digital group and 100% for the conventional group and an overall survival rate of 98.8% for screw-retained monolithic zirconia restorations on implants after 3 years. There was no statistically significant survival difference between the digital and conventional restorations (P = .362). When evaluated separately, a 100% survival rate of SCs and 97.7% for 2-FDPs could be reported. One decementation and three screw loosenings occurred in the 1- to 3-year follow-up. The multiple-implant restorations showed higher (23.3%) complication rates at the restoration level than the SCs (4.9%) after 3 years of function (P = .026). CONCLUSIONS: Screw-retained monolithic zirconia restorations on ti-base abutments show promising survival rates after 3 years of function. Restorative complications in screw-retained monolithic zirconia restorations on Ti-base abutments are more likely to happen in the first year of function and are more common in multiple-implant restorations than SCs. The impression type (digital or conventional) does not seem to influence these results.