Monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic crowns.

OBJECTIVES: The objective of this study is to compare monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic single-tooth crowns. MATERIALS AND METHODS: Twenty subjects in need of an implant-borne restoration were randomly assigned to receive either a cement-retained (CRR) or a screw-retained (SRR) implant-supported monolithic lithium disilicate (LS2 ) reconstruction. Each patient received a titanium implant with in internal conic connection. After osseointegration and second-stage surgery, healing abutments were placed for about 10 days. The type of restoration (CRR vs. SRR) was randomly assigned, and the restorations were manufactured of monolithic LS2 . Both types of restorations, CRR and SRR, were based on a titanium component (Ti-base) that was bonded to the abutment (CRR) or the crown (SRR). The follow-up period for all restoration was 36 months. Clinical outcome was evaluated according to Functional Implant Prosthetic Score (FIPS). Quality of live (OHIP) and patient's satisfaction were assessed using patient-reported outcome measures (PROMs). Primary endpoint was loss of restoration for any reason. Kaplan-Meier curves were constructed and log-rank testing was performed (p < .05). RESULTS: One restoration of group CRR failed after 6 months due to loss of adhesion between Ti-base and individual abutment. No further biological or technical failures occurred. Kaplan-Meier analysis showed no significant difference between both treatment options (p = .317). There was no statistically significant difference between both types of restoration, neither for FIPS, OHIP, treatment time nor patient satisfaction (p > .05). CONCLUSION: Monolithic hybrid abutment crowns (screw-retained) and monolithic hybrid abutment with adhesively cemented monolithic crowns using lithium disilicate showed no statistically significant difference for implant-based reconstructions in this pilot RCT setting.

Survival and success of veneered zirconia crowns.

AIM: The aim of the present study was to evaluate the long-term clinical survival and success rate of veneered zirconia crowns with a modified anatomical framework design after 10 years in function. MATERIALS AND METHODS: In total, 36 zirconia crowns were fabricated for 28 patients. An anatomically modified framework design was developed. Crowns were inserted between 2008 and 2009. A follow-up of 19 patients with 28 crowns was conducted in 2020 to document mechanical and biologic parameters. Additionally, a modified version of the pink esthetic score (PES) was documented. Patient satisfaction was assessed using United States Public Health Service (USPHS) criteria. The success and survival rates were calculated using the Kaplan-Meier analysis. RESULTS: After more than 10 years of clinical service, the survival rate of the zirconia crowns was 92.9%. Biologic complications occurred in 12% of the examined crowns, whereas technical complications occurred in 54%. Mostly, chippings (50%) and insufficient marginal gaps (50%) were observed. Most crowns were positively evaluated for more than one technical complication. Periodontal conditions with probing depths of up to 3 mm were comparable with measured values before crown delivery (73% to 75%). Most of the crowns had modified PES values of 10 or higher. Patient satisfaction was high. CONCLUSIONS: The modified framework design led to a high survival rate of the crowns but a relatively low success rate. High patient satisfaction and inconspicuous periodontal conditions were demonstrated. Biologic complications occurred far less frequently than technical complications.

Digital versus conventional complete dentures: A randomized, controlled, blinded study.

STATEMENT OF PROBLEM: Several manufacturers have developed a digital workflow for removable prosthodontics. The Baltic Denture System is a 2-visit procedure for the digital production of complete dentures, but clinical studies comparing the system with conventional methods are lacking. PURPOSE: The purpose of this randomized, controlled, blinded crossover trial was to evaluate the impact of the digital versus conventional production of complete dentures on oral health-related quality of life (OHRQoL) measures. MATERIAL AND METHODS: Sixteen participants received 2 sets of new complete dentures produced with a digital (2 visits) and conventional (5 visits) workflow. Each complete denture was in clinical service for an observation period of 3 months. The order of the dentures was randomized, starting with digital or conventional followed by changing the set of dentures after 3 months. The primary outcome was the time-dependent change in the OHRQoL, assessed by using the Oral Health Impact Profile, German version (OHIP-G49), comparing the digital with the conventional workflow. The secondary outcome was the time needed for the fabrication process. The median values of OHIP-G49 total sum scores and OHIP-G49 dimensions were calculated for baseline and 14 days and 3 months after insertion of the dentures. Changes of sum scores over time and differences between the workflows were analyzed by using the Wilcoxon signed-rank test (α=.05). RESULTS: The data of 16 participants (11 men and 5 women; 66 ±8.5 years) were evaluated. The median values of the total OHIP-G49 sum scores and the sum scores of OHIP-G49 dimensions did not differ between workflows (P>.05). With digital dentures, more physical pain was observed after 2 weeks (P=.039). Participants with conventional dentures had less functional limitation after 14 days and felt less handicapped after 3 months (P=.036). Digital dentures were fabricated within 4 hours, whereas fabrication of conventional dentures took 10.5 hours for dentists and dental laboratory technicians. CONCLUSIONS: From the perspective of the participants, the fabrication method of the complete dentures had no significant influence on OHRQoL. However, digital dentures needed only 2 visits, 1 hour less chair time, and 5 hours less time for the dental laboratory technicians.

Digital versus conventional complete dentures: A randomized, controlled, double-blinded crossover trial.

STATEMENT OF PROBLEM: The Baltic Denture System provides a digital way to fabricate complete dentures in 2 visits. Conventional dentures using injection or compression molding require additional visits and complex laboratory procedures. However, how the fabrication method affects clinical outcomes is unclear. PURPOSE: The purpose of this clinical, randomized, controlled, double-blinded crossover trial was to evaluate the impact of the fabrication method (digital versus conventional production) of complete dentures on clinical outcomes. MATERIAL AND METHODS: Sixteen participants received 2 pairs of new complete dentures, produced in a digital and a conventional workflow. Each complete denture was worn for an observation period of 3 months. The order of the dentures was randomized. The primary outcome was the clinical assessment of the dentures by a blinded examiner, including peripheral extension, cutout for buccal and labial frenula, denture extension, and denture thickness. Denture esthetics were evaluated by the midline, position of anterior teeth, buccal corridor, and smile arc, and occlusal relationships were evaluated by the vertical dimension, sagittal relation, the Camper plane, and occlusion. In addition, the retention of maxillary and mandibular dentures and phonetics was evaluated. Differences between the prostheses were statistically analyzed with the McNemar test (α=.05). RESULTS: The borders of the digital dentures were significantly more often overextended at the time of insertion (P=.021), reducing the retention of the digital dentures, especially the maxillary dentures (P=.016). The borders of the dentures could be corrected so that after 2 weeks and 3 months, no significant differences could be seen between digital dentures and conventional dentures. CONCLUSIONS: The fabrication method has a significant influence only on the dimension of the denture border. It was significantly more often overextended in digital dentures and impaired retention, especially of the maxillary dentures, at the time of insertion. As this parameter is correctable, no significant clinical differences could be observed over the observation time of 3 months between digital dentures and conventional dentures.

Impact of endodontic post material on longitudinal changes in interproximal bone level: a randomized controlled pilot trial.

OBJECTIVES: Aim was to evaluate the impact of glass fiber versus titanium endodontic posts on the interproximal bone level around severely damaged endodontically treated teeth. MATERIALS AND METHODS: Thirty-eight participants of a randomized controlled trial on glass fiber (n = 18) and titanium post-endodontic restorations (n = 20) received radiographs at two different times after post placement (T0 = <12 months and T1 = 36-72 months after post placement). A total of 76 radiographs were analyzed with an image-editing software. Medians of changes in mesial and distal interproximal bone level (∆MBL, ∆DBL) were calculated and tested for statistical significance with respect to post material using Mann-Whitney U test (p < 0.05). Impact of post material on bone level changes was assessed in multilevel mixed-effect linear regression models. RESULTS: The mean observation period was 54 months for glass fiber and 50 months for titanium posts. Interproximal bone loss was small in both groups during the study period with no significant differences between groups (glass-fiber group, ∆MBL = - 0.03 mm and ∆DBL = - 0.06 mm; titanium group, ∆MBL = - 0.07 mm and ∆DBL = - 0.17 mm; both p > 0.05). Overall, impact of post material on bone loss was almost negligible with a nonsignificant difference between materials of 0.10 mm during the entire study period. CONCLUSION: The rigidity of endodontic post material has no impact on the level of alveolar bone support of severely damaged endodontically treated teeth. CLINICAL RELEVANCE: Post-endodontic restorations of severely damaged teeth can achieve steady levels of periodontal bone support as a parameter of periodontal health, irrespective of post material.

Patients' self-report on post-retained restoration is more valuable than expected! Explorative analysis of an 11-year follow-up.

Objective: Assessment of long-term clinical data regarding post-endodontic restorations is essential for the evaluation of different post-and-core concepts. The aim of the present study was to assess the diagnostic accuracy of patient self-reporting on post-endodontic restorations after 11 years of clinical service.Materials and methods: Twenty-nine patients (61 ± 15 years old) with endodontic glass-fibre and titanium post-endodontic restorations were examined within the 11-year follow-up of a randomized controlled trial. Restorations were assessed by self-reports during a telephone interview (one item), the completion of a four-item questionnaire and clinical and radiographic examination. A gold standard for restoration in situ or 'failure' was defined by clinical and radiographic examination. Diagnostic accuracy of patients' self-reports was evaluated by calculating the sensitivity, specificity, and positive (PPV) and negative predictive values (NPV).Results: After a mean observation time of 137 months (min/max: 125/154 months), 25 (86.2%) restorations were in situ and 4 (13.8%) failures were detected. Self-report during a telephone interview and the four-item questionnaire correctly identified all in situ restorations (specificity = both 100%, NPV = 92.6%/96.2%). Self-report during a telephone interview identified two out of four failures (sensitivity = 50%, PPV = 100%), and self-report on the four-item questionnaire identified three out of four failures (sensitivity = 75%, PPV = 100%).Conclusions: When the clinical examination is not feasible, patients' self-report shows valuable diagnostic potential in the identification of the post-endodontic failure.

Failure loads of all-ceramic cantilever fixed dental prostheses on post-restored abutment teeth: influence of the post presence and post position.

The influence of a fiber post-restored abutment tooth on the load capability of a three-unit zirconia framework cantilever fixed dental prosthesis (cFDP) was evaluated after simulated clinical function. Human lower sound premolars (n = 64) were distributed, in equal numbers, to four experimental groups: two vital abutment teeth (group I; control); mesial abutment tooth post-restored (group II); distal abutment tooth post-restored (group III); and mesial and distal abutment teeth post-restored (group IV). All specimens received an adhesively luted three-unit cFDP of veneered zirconia. Simulated clinical function was performed by two subsequent sequences of thermal-cycling (2 × 3,000 cycles) and mechanical loading (1.2 × 106 load cycles from 0 to 50 N) (TCML). Four specimens failed during TCML (one in each of groups I and IV and two in group II). The maximum load capability ranged from 365 to 538 N and was not significantly different between groups. Specimens with post-restored abutments failed mainly because of abutment tooth fracture of the distal abutment. The presence or position of post-restored abutment teeth has no significant impact on load capability of all-ceramic three-unit cFDPs. The risk of tooth fracture of the distal abutment teeth of a cFDP was significantly increased when one abutment tooth, irrespective of its position, was post-and-core restored.

Direct or Indirect Restoration of Endodontically Treated Maxillary Central Incisors with Class III Defects? Composite vs Veneer or Crown Restoration.

PURPOSE: The aim of this ex-vivo study was to evaluate the load capacity of direct or indirect endodontically restored maxillary central incisors with Class III defects, with or without glass-fiber posts. MATERIALS AND METHODS: Seventy-two extracted human maxillary central incisors were endodontically treated and bi-proximal Class III cavities were prepared. Specimens were randomly allocated to six groups (n = 12): direct restoration with composite (C); direct restoration with composite and additional glass-fiber post (CP); ceramic veneer restoration (V), ceramic veneer restoration and additional glass-fiber post (VP), ceramic crown restoration (Cr), ceramic crown restoration and additional glass-fiber post (CrP). Specimens were exposed to thermomechanical loading (TML: 1.2 million cycles, 1 to 50 N; 6000 thermal cycles between 5°C and 55°C for 1 min each), and subsequently linearly loaded until failure (Fmax [N]) at an angle of 135 degrees 3 mm below the incisal edge on the palatal side. Statistical tests were performed using the Kruskall-Wallis and Mann-Whitney U-Test. RESULTS: During dynamic loading by TML, one early failure occurred in group C, CP, and CrP. Subsequent linear loading resulted in mean fracture load values [N] of C = 483 ± 219, CP = 536 ± 281, V = 908 ± 293, VP = 775 ± 333, Cr = 549 ± 258, CrP = 593 ± 259. The Kruskal-Wallis test showed significant differences of load capacity between groups (p < 0.05). Mann-Whitney U-test revealed significantly lower maximum fracture load values of group C compared to group V (p = 0.014), after Bonferroni-Holm correction. Non-restorable root fracture was the most frequent type of failure. CONCLUSION: Endodontically treated maxillary central incisors with Class III defects directly restored with composite are as loadable as indirect crown restorations. Compared to full-coverage restorations, less invasive veneers appear to be more beneficial. Additional placement of glass-fiber posts shows no positive effect.

Influence of a face-bow on oral health-related quality of life after changing the vertical dimension in the articulator: a randomized controlled trial. Part II.

OBJECTIVES: In a double-blind randomized controlled clinical trial, the impact of face-bow registration for remounting complete dentures (CDs) on oral health-related quality of life (OHRQoL) was evaluated. MATERIALS AND METHODS: New CDs of 32 subjects were clinically remounted using intraoral pin registration. CDs were transferred into a semi-adjustable articulator corresponding to group #1: mean settings with Bonwill triangle and Balkwill angle, and group #2: arbitrary hinge axis with a face-bow registration. After occlusal adjustment, subjects were followed up after 3 (T1) and 84 (T2) days. The primary outcome was the change of OHRQoL by OHIP-G49, while as secondary outcome, mucosal alterations were evaluated over time. Mean values of OHIP-G49 total sum scores and OHIP-dimensions were calculated for baseline (T0) and days 3 (T1) and 84 (T2) after intervention. Based on bootstrapping methods (changes of total OHIP sum score) and the Wilcoxon test (changes of sum scores of OHIP dimensions), analyses of between-group differences were performed. RESULTS: Mean values (MV) of OHIP-G49 sum scores decreased in both groups from T0 (#1 48.56; #2 45.46) to T1 (#1 31.43 (p = 0.012); #2 43.20) and to T2 (#1 29.06; #2 29.40), which represents an improvement in OHRQoL. MV of OHIP-dimension sum scores decreased from T0 to T1 in both groups (#1 seven dimensions; #2 four dimensions); the decrease of sum scores was tested as not statistically significant (p > 0.05). CONCLUSIONS: From the patient's perspective, mean-value-based remounting methods are of value. The use of a face-bow was not perceived as superior. CLINICAL RELEVANCE: From the patient's perspective, remounting of CDs will be positively perceived, irrespective of the use of a face-bow.

Does a face-bow lead to better occlusion in complete dentures? A randomized controlled trial: part I.

OBJECTIVES: In a double-blinded randomized controlled clinical trial, the impact of face-bow registration for remounting complete dentures (CDs) on the occlusal parameters (part I) was evaluated. MATERIALS AND METHODS: New CDs of 32 patients were duplicated and mounted after intraoral pin registration according to mean settings (group 1) and (group 2) using a face-bow (arbitrary hinge axis). The vertical dimension was reduced to the first occlusal contact point, and a bite record was fabricated in the articulator. The number of contacts and the number of teeth in contact were evaluated by a computer program (laboratory result). After randomization, half of the CDs were adjusted according to protocol of group 1 and group 2 and delivered to the patients. After 3 days (T1) and 84 days (T2), clinical static contact points and teeth in contact were counted. Contact points and teeth in contact of both groups (laboratory results) and at different moments (clinical results) were analyzed statistically with the F test and bootstrapping. RESULTS: Laboratory: No. 2 (face-bow) showed more occlusal contact points than no. 1 (mean setting), p > 0.05. The number of teeth with at least one occlusal contact was significantly higher in no. 2 (p = 0.027). Clinic: The mean number of teeth with at least one clinical contact point was significantly higher in no. 1 (no. 1 = 7.13, no. 2 = 5.31; p = 0.042). Extent of the vertical shift poorly correlated with number of laboratory occlusal contact points (R 2 = 0.017). CONCLUSIONS: Considering the complex multistep study design, a limited number of participants, and referring to one specific arbitrary face-bow, the following conclusion could be drawn: no substantial difference by the use of the arbitrary face-bow compared to a mean setting could be determined, when changing the vertical dimension in the articulator within a remounting procedure of complete dentures. CLINICAL RELEVANCE: Further research is necessary to determine the effects of different arbitrary face-bows on the fabrication and adaptation of removable dentures.

Effect of Final Irrigation Protocol and Etching Mode on Bond Strength of a Multimode Adhesive in the Root Canal.

PURPOSE: To analyze the effects of ethanol for final post space irrigation and etching mode on the bond strength of fiber posts luted with a mild multimode adhesive (pH 2.3) as compared with a reference group using a self-adhesive resin cement (SAR). MATERIALS AND METHODS: Human anterior teeth were endodontically treated. After post space preparation, the root canals were irrigated using 1% sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation, followed by either distilled water (control) or distilled water and ethanol 99% as final post space irrigation. Fiber posts were luted using Futurabond U in self-etch mode (FU-SE), Futurabond U in etch-and-rinse mode (FU-ER), or Futurabond DC (SE) in combination with a dual-curing core buildup material (Grandio Core, all VOCO); alternatively, posts were inserted using a self-adhesive composite cement (RelyX Unicem 2, 3M ESPE). Bond strengths were evaluated using push-out tests following thermocycling (TC) and storage in 0.9% NaCl for 3 months. RESULTS: Mean push-out bond strengths (MPa) were significantly affected by the luting system (p < 0.0005) but not by the irrigation protocol (p = 0.068; ANOVA), although a significant interaction between the factors "luting agent" and "pre-treatment" was observed. FU E&R (21.28 [4.34]) and RX (20.12 [7.32]) revealed significantly higher bond strengths compared to FU SE (15.9 [6.02]), whereas F DC (18.8 [6.9]) did not differ significantly from all other groups. Ethanol pre-treatment increased bond strength in the apical part of the root canal for all materials, with the exception of FU E&R. CONCLUSION: Mild multimode adhesives exhibit comparable mean bond strengths to a SAR cement within the root canal for luting fiber posts if applied in an etch-and-rinse mode. Using this approach, ethanol application has no positive effects on bond strength.

Are self-adhesive resin cements suitable as core build-up materials? Analyses of maximum load capability, margin integrity, and physical properties.

OBJECTIVES: The aim of the present study was to test a self-adhesive resin cement used as core build-up material in comparison to two commercially available core build-up materials. MATERIALS AND METHODS: Forty human anterior teeth were endodontically treated and fiber post insertion (RelyX Fiber posts) and core build-ups were performed using two core build-up materials applied with an etch-and-rinse adhesive approach (Luxacore Dual-LC and Clearfil Core-CC) and an experimental self-adhesive resin cement (SAR) in two application modes (SAR Handmix and SAR Automix). Samples were subjected to thermo-mechanical loading. Margin integrity was determined using scanning electron microscopy (SEM), and maximum load capability (Fmax) was evaluated. Physical properties of the tested materials were also examined. RESULTS: Fmax was significantly affected by the core build-up material (p < 0.0005; one-way ANOVA). CC [481 (158) N] revealed significantly higher Fmax compared to LC [226 (80) N], SAR Hand [205 (115), and SAR Automix [197 (134) N] (p < 0.05; Tukey-B). The percentage of margin quality "continuous margin" in enamel after thermo-mechanical loading (TML) differed significantly among groups (p < 0.0005; Kruskal-Wallis); CC demonstrated a significantly higher percentage of margin quality "continuous margin" compared to the other groups. Physical properties were significantly affected by the different core materials (p < 0.0005; ANOVA); CC and LC demonstrated significantly higher flexural strength compared to both SAR groups as well as significantly higher water sorption of both SAR groups compared to CC and LC. CONCLUSION: Within the limitations of the present in vitro study, we conclude that the investigated experimental self-adhesive resin cement is not suitable as a core build-up material due to the lower maximum load capability, low margin quality, and the data of the mechanical properties. CLINICAL RELEVANCE: The investigated experimental self-adhesive resin cement cannot be recommended as a core build-up material.

Do chlorhexidine and ethanol improve bond strength and durability of adhesion of fiber posts inside the root canal?

OBJECTIVES: The aim was to investigate the effects of chlorhexidine and ethanol pretreatment of the root canal on push-out bond strengths and durability of adhesion of fiber posts luted with two different adhesive strategies. MATERIALS AND METHODS: One hundred twenty human anterior teeth were endodontically treated. After post space preparation, the root canals were irrigated using 1 % sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation followed by distilled water (control). In pretreatment (PT) group, chlorhexidine (CHX) root canals were irrigated using 2 % chlorhexidine; and in the PT group, 99 % ethanol was used prior application of the luting agent. Two different post-and-luting systems with an etch-and-rinse (CX) adhesive approach (n = 60) and a self-adhesive resin cement (RX; n = 60) were inserted into the root canals. Bond strengths were evaluated initially and after thermocycling and storage for 6 months using push-out tests. RESULTS: Bond strength was significantly affected by the adhesive strategy (p < 0.0005), the pretreatment (p < 0.0005) and the location inside the root canal (p < 0.0005; repeated measurement ANOVA). Ethanol significantly increased bond strengths irrespective of the luting agent used compared to the control and CHX group (p < 0.05; Tukey's B). CONCLUSION: Ethanol significantly increased bond strength of the CX and the RX system inside the root canal and could be recommended as a final rinse for luting fiber posts using an ethanol-based etch-and-rinse adhesive system or self-adhesive resin cement. CLINICAL RELEVANCE: PT of the root canal using ethanol seems to facilitate adhesive luting of fiber posts with the tested adhesive system and luting cements.

Various irrigation protocols for final rinse to improve bond strengths of fiber posts inside the root canal.

Irrigation after post space preparation and its effects on the bond strength of different adhesive strategies are still an issue of interest. The aim of the present study was to investigate the effects of various irrigation protocols (IPs) on the push-out bond strengths of fiber posts. One-hundred and fifty extracted human anterior teeth were divided into three groups (n = 50 each) and endodontically treated. The post space was irrigated before post placement using the following five IPs in each group: IP1 (control): 5 ml of distilled water; IP2: 5.25% sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation (PUI); IP3: 1% NaOCl applied with PUI; IP4: 18% ethylenediaminetetracetic acid (EDTA) followed by 5.25% NaOCl; and IP5: 2% chlorhexidine (CHX). Fiber posts placement in each group was performed using three different adhesive strategies. A self-etch adhesive system revealed higher bond strength (16.2 ± 6.9 MPa) compared with an etch-and-rinse adhesive (8.5 ± 4.2 MPa) and a self-adhesive resin cement (9.2 ± 4.7 MPa). The use of 18% EDTA/5.25% NaOCl increased the bond strength of the self-adhesive resin cement. Conversely, this IP decreased the bond strength for the etch-and-rinse adhesive system, whilst 1% NaOCl enhanced the bond strength for the same system. Consequently, each adhesive strategy may need to be adapted to a specific IP.

Evaluating the prospective crown-root ratio after extrusion and crown lengthening procedures in vitro.

For restoration of extensively damaged teeth preprosthetic treatment measures are necessary. Crown lengthening and extrusion affect the prospective crown-root ratio (CRR). The subject of this in vitro study was to compute CRRs for both treatment approaches. 120 human maxillary central extracted incisors were measured. Measurements were calculated for five treatment groups: C (control), E-2 mm (extrusion of 2 mm), E-4 mm (extrusion of 4 mm), CL-2 mm (crown lengthening of 2 mm), and CL-4 mm (crown lengthening of 4 mm). Tooth (TL), root (RL), and crown lengths (CL) were measured from mesial (m) and facial (f) cemento-enamel junction (CEJ), and respective anatomic (CRR) and effective crown-root ratios (eCRR) were calculated. Following CRR values were computed for C: CRR-m = 0.4 ± 0.1, CRR-f = 0.7 ± 0.1. All crown-root ratios were lower (more favourable) for extrusion compared to crown lengthening (p < 0.001). ECRRs were higher than anatomic CRRs. CRR at mesial CEJ was significantly lower than CRR with facial CEJ as reference (p < 0.001). Mesial measurement-based calculations of CRR typically based on radiographic images should be interpreted with caution as they underestimate the eCRR. CRR can be expected as lower, i.e. more favourable, when teeth are extruded than crown lengthened.

Fiber post placement with core build-up materials or resin cements-an evaluation of different adhesive approaches.

OBJECTIVE: To compare push-out bond strength of fiber-posts luted with different adhesive approaches to root canal dentin. MATERIALS AND METHODS: Forty maxillary first incisors were decoronated and endodontically treated. Specimens were randomly distributed into five groups (n = 8) and fiber-posts (DentinPost coated, Komet) were inserted using five different luting materials: etch-and-rinse adhesive systems and corresponding core-and-post material in groups 1 (DentinBond/DentinBuild, Komet) and 2 (XP Bond + SCA/Core-X flow, Densply), self-adhesive resin cements in groups 3 (RelyX Unicem, 3M Espe) and 4 (SmartCem 2, Dentsply) and a self-etch adhesive/resin cement in group 5 (ED-Primer II/Panavia F 2.0, Kuraray). The roots were sectioned into eight 1 mm thick serial slices and within 48 h push-out bond strength was investigated. Statistical analyses were performed using non-parametrical Kruskal-Wallis H-test and Mann-Whitney U-test for differences between experimental groups at p < 0.05. The failure modes were analyzed using Chi square test. RESULTS: The bond strength [MPa] (mean/min-max) for groups 3 (12.35/3.60-32.44), 4 (13.52/4.48-30.69) and 2 (11.15/5.23-35.58) were significantly higher (p < 0.001) compared to groups 1 (6.66/2.34-24.89) and 5 (7.41/0.28-34.18). Adhesive failure between dentin and luting agent was the most frequent failure mode. CONCLUSIONS: Bond strength of fiber-posts adhesively luted to root canal dentin was significantly higher when self-adhesive resin cements were used. One (group 2) of the tested core-and-post materials/etch-and-rinse adhesive achieved comparable bond strength values.

Long-term Survival of Adhesively Luted Post-endodontic Restorations.

INTRODUCTION: The objective of this prospective clinical study was to investigate survival for endodontically treated teeth restored with adhesively luted prefabricated dentinlike or rigid posts. METHODS: Data were recorded for glass-fiber posts (GFPs) and compared with historical controls evaluating glass-fiber (GFP I) and titanium posts (TPs) for 128 patients. Three groups were defined based on the type of post system used: group 1, GFP I (n = 41); group 2, GFP II (n = 41); and group 3, TP (n = 46). Posts were adhesively luted with self-adhesive resin, adhesive composite core buildups were performed, and all teeth were restored with full-coverage restorations. The primary end point was restoration survival at recall. Outcome was assessed after 6, 12, 24 and up to 178 months clinically and radiographically. Data were analyzed by the Kaplan-Meier log-rank test and Cox regression analysis. RESULTS: After up to 178 months of observation, 26 restorations failed (GFP I: 10, GFP II: 9, and TP: 7) and 49 (GFP I: 18, GFP II: 12, and TP: 19) were in situ. Cumulative survival probabilities were 57.1% for the GFP I, 56.5% for the GFP II, and 71.8% for the TP groups. In bivariate Cox regression, the factors tooth type and grade of abrasion were significantly assfociated with failure. In multivariate Cox regression, none of the investigated factors were significantly associated with failure. The post system had no significant impact on tooth survival (P > .05). CONCLUSIONS: Comparing GFPs and TPs, the post system had no impact on tooth survival up to 15 years. This study indicates that the effect size of post material on survival is low.

In-vitro simulation of tooth mobility for static and dynamic load tests: a pilot study.

OBJECTIVE: Simulation of tooth mobility in vitro with or without reduced bone support is an aspect of particular interest from the clinical perspective. To elucidate adequate simulation of the periodontal ligament in terms of tooth mobility, three materials were investigated. METHODS: Human lower sound premolars were selected and randomly assigned to six groups (n = 5) and stored at 37°C in a 0.5%-chloramine solution. For tooth mobility simulation, roots were covered with a thin layer of three types of material: (i) polyurethane elastomeric material, (ii) polyether impression material and (iii) A-polysiloxane soft cushion material. Teeth were embedded in an acrylic resin block simulating no and 50% bone loss, respectively. Specimens were statically subjected up to a maximum load of 30 N perpendicular to tooth axis (crosshead speed = 1 mm/min) in a universal material testing machine. Load-deflexion curves and periotest values were recorded. Statistical analysis was performed using 2-way Anova and post-hoc Bonferroni Test (p = 0.05). The Pearson's correlation coefficient between deflexion and periotest values was calculated. RESULTS: Median horizontal deflexion values (µm) of specimen crowns with no bone loss were significant higher for polysiloxane (210) compared to polyurethan (24) (p < 0.001). The tooth deflexion, e.g. tooth mobility, increased significantly as the bone level decreased only when specimens were embedded in polysiloxane (iii) (1150) (p = 0.045). All specimens with reduced bone support layered with polyether were dislocated. Deflexion was significantly positive correlated with periotest values (p = 0.01). CONCLUSION: Using A-polysiloxane soft cushion material combined with autopolymerizing acrylic resin may be suitable to simulate increased tooth mobility in vitro.

Interface analysis after fatigue loading of adhesively luted bundled fiber posts to human root canal dentin.

OBJECTIVES: The aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-core interface. METHOD: Crowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (µCT) was used to exemplary compare pre and post TML geometries. RESULTS: Static load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids. CONCLUSION: Fracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-Ct analyses after TML, lead to the assumption that applied forces result in alterations in the regions of voids.

Bond strength of conventional, subtractive, and additive manufactured denture bases to soft and hard relining materials.

OBJECTIVE: To investigate the tensile and flexural strength of poured, subtractive, and additive manufactured denture base methacrylates bonded to soft and hard relining materials after hydrothermal cycling and microwave irradiation. METHODS: This study included a conventional (CB), subtractive (SB), and additive (AB) base material as well as a soft (SCR) and hard (HCR) chairside and one hard laboratory-side (HLR) relining material. Reference bodies of the base materials and bonded specimens to the relining materials were produced with a rectangular cross-section. The specimens were either pre-treated by water storage (50 h, 37 °C), hydrothermal cycling (5000 cycles, 5 °C and 55 °C, 30 s each), or microwave irradiation (6 cycles, 640 W, 3 min, wet). A tensile and four-point bending test were performed for a total of 504 specimens. Data were analysed using multivariate analysis of variance (MANOVA) with post-hoc Tukey tests (α = 0.05). RESULTS: In comparison with the other reference groups SB showed marginally higher tensile and flexural strength (p < 0.047). Bond strength to SCR was affected neither by the base material nor by the pre-treatment (p > 0.085). HCR demonstrated twice the bond strength to AB compared with SB and CB (p ≤ 0.001). HLR showed the highest bond strength to CB (p ≤ 0.001). There was no difference between the specimens after hydrothermally cycling and microwave irradiation (p > 0.318). SIGNIFICANCE: The bond strength of hard relining materials to subtractive and additive manufactured denture bases differ compared with conventional pouring.