The fracture strength and the failure mode of lithium disilicate or resin nano ceramics as a crown, overlay, or endocrown restoration on endodontically treated teeth.

INTRODUCTION: Different materials and restorative concepts have been proposed over the years to restore endodontically treated teeth (ETT). Monolithic ceramic and composite restoration can be lute to the tooh, without the use of a post. However, little is known how the material stiffness and presence of a composite core will affect the survival and failure mode. The objective of this in-vitro study was to evaluate the fracture strength and failure mode of endodontically treated molars, restored with ceramic or hybrid composite monolithic restoration, in the presence of absence of a composite core. MATERIALS AND METHODS: Sixty depulped molars were restored with a lithium-disilicate (e.max CAD) or hybrid composite (Cerasmart) restoration. Both materials were used in a monolithic approach, but with 3 different designs: (a) monolithic endocrown, (b) crown with a separate composite core, and (c) overlay without core buildup or pulpal extension. Ten sound teeth were used as control group. All groups were thermocycled (10,000 cycles), subsequently loaded in a chewing simulator (100,000 cycles) and finally loaded until fracture. RESULTS: Peak fracture loads and failure modes were registered. No significant differences were seen between the groups in terms of fracture load. Failure modes were statistically significantly different among groups with significant correlation between restoration type and material. (p < 0.001 and p = 0.033, respectively). No group presented significantly higher fracture resistance. Although ceramic crowns and overlays presented the highest repairability, all restored ETT were within the range of the intact tooth' fracture strength. CONCLUSION: No restoration presented significant different fracture loads. However, the type of restoration and material choice were correlated to the fracture mode.

An innovative interprofessional dental clinical learning environment using entrustable professional activities.

INTRODUCTION: Changes in society, new public demands for dental care and contemporary educational insights have influenced dental education worldwide and demand a renewed perspective. Following this perspective, an innovative interprofessional dental Master curriculum was developed at Radboud University Nijmegen in the Netherlands. EDUCATIONAL PRINCIPLES: The curriculum is based on five contemporary educational principles and the core of the curriculum consists of a Student Run Dental Clinic that is fully run by students under professional supervision. THE NEW CURRICULUM: In the Student Run Dental Clinic, Master dental students and Bachelor oral hygiene students are responsible for the care of approximately 750 patients. The students work within the same clinic for 3 years and patients receive oral health care from the same students over a long period. The clinic is a longitudinal cross-disciplinary clinic with different dental subdisciplines. Entrustable professional activities (also known as EPAs), to our knowledge not yet widely used in dental education, were introduced to facilitate learning and assessment. Fourteen EPAs have been developed to stimulate interprofessional education and learning. Of these, five EPAs are identical for the dental and oral hygiene curriculum, leading to extended interprofessional education and learning in the Student Run Dental Clinic. DISCUSSION: Preliminary results show that EPAs are generally well received by supervisors and students. CONCLUSION: To monitor and investigate the exact effect of the interventions and underlying mechanisms, a research programme on interprofessional learning, practice-based learning and EPAs and entrustment in dental education was recently set up.

Defining dental operative skills curricula: An ADEE consensus paper.

This paper reports on the recent activity of the pan-European consensus of the ADEE Special Interest Group for Pre-Clinical Operative Skills. Following the previous recommendations from the group, and in order to support teachers and to harmonise the delivery of skills training across Europe, a more formal curriculum relating to pre-clinical operative skills needs to be created. This paper reports European consensus surrounding the categorisation (level of importance, and difficulty) of basic operative dental clinical skills within the undergraduate curriculum and provides recommendations relating to session structure and timing of curricular elements for basic operative dental clinical skills teaching.

Single crown vs. composite for glass fiber post-retained restorations: An 8-year randomized clinical trial.

OBJECTIVES: This study aimed to compare the success and survival rates of metal-ceramic crowns and composite resin restorations applied in root filled teeth that received a glass fiber post. METHODS: A prospective, randomized controlled trial, with equivalent parallel groups was designed. Eighty-two teeth were randomly allocated to the metal-ceramic or composite resin groups. Multivariate Cox regression analysis with shared frailty for patients and Kaplan-Meier curves were performed using success and survival rates (p<0.05). RESULTS: Seventy-five post-retained restorations (34 metal-ceramic crowns and 41 composite restorations) in 62 patients were analyzed. The median follow-up was 8.1 years [IQR 4.0-9.9]. Twenty-seven failures were observed. Twenty-two failures (81.5 %) were observed in the composite resin group, of which six (27.3 %) were not repairable. Five failures (18.5 %) were observed in the metal-ceramic crown group, of which three (66.6 %) were non-repairable. The cumulative success rate at 8 years was 85.0 % for crowns (AFR=1.31 %) and 43.2 % for composite resins (AFR=6.58 %), while the survival rate was 93.8 % for crowns (AFR=0.52 %) and 97.6 % for composite resins (AFR=0.20 %). Considering the success rates, adjusted multivariate Cox regression showed that composite resin had a Hazard Ratio of 5.07 (95 %CI, 1.99-12.89) greater than the metal-ceramic crown. No significant difference in the failure risk was observed when the survival rates were considered (HR=0.38, 95 %CI (0.10 - 1.44), p = 0.156). Co-variables did not affect the success and survival rates (p>0.05). CONCLUSIONS: Metal-ceramic crowns showed a higher success rate than composite restorations. The survival rates were similar, but composite restorations presented a higher need for repairs. CLINICAL SIGNIFICANCE: Post-retained composite restorations may need more reinterventions during the lifecycle, although more preservation of sound tooth structure is expected with a large restoration of resin post-and-core. These aspects have to be discussed with the patient for decision-making planning.

Biomechanical properties of different endocrown designs on endodontically treated teeth.

OBJECTIVE: To compare the biomechanical properties of different endocrown designs on endodontically treated teeth with an extensive defect in the mesial wall using a three-dimensional finite element method (3D FEM). METHODS: Four finite element analysis models were designed and built up based on different endocrown configurations in a mandibular molar. One model was designed as a butt joint preparation with 2 mm occlusal thickness(control), the other three models were butt joint designs with different distances between the bottom of the mesial wall preparation and the cemento-enamel junction (CEJ): 2 mm, 1 mm and 0 mm respectively. A vertical load parallel with the longitudinal axis of the tooth and an oblique load with a 45°angle to the longitudinal axis were applied to the occlusal surfaces. The maximum Von Misses (VM) stresses and stress distribution patterns were calculated and compared. Weibull risk-of-rupture analysis was used to analyze the survival probability of the restorations and tooth in the different models. RESULTS: For the restoration, the model with a mesial wall destruction at the level of CEJ showed much higher risk of failure than other models. Overall, none of the four models showed failure. Under oblique loading, VM stress in the cement layer of the models with a mesial wall defect was higher than in the control model. In the dentin, the highest VM stresses were found in the peri-cervical dentin. Under the oblique loading, the model with the mesial wall destruction at the level of CEJ restored by endocrown showed the highest risk of failure. CONCLUSION: Under the oblique loading, with the increase of the simulated defect in the mesial wall, the peak VM stress values in the cement layer increased accordingly. In the model with a mesial wall defect up to the level of CEJ risk of failure was highest in the cervical dentin.

Up to 17-year controlled clinical study on post-and-cores and covering crowns.

OBJECTIVE: The aim of this long-term follow-up was to collect up to 17-year survival data of different metal post-and-core restorations with a covering crown. METHODS: At initiation of the study, a controlled clinical trial, single tooth was provided with an artificial covering crown, by 18 operators. Restorations under investigation were the post-and-core restorations: cast post-and-core restorations, prefabricated metal post and resin composite core restorations, and post-free all-composite core restorations. Before treatment allocation, the recipient tooth was categorized according to the expected dentin height after tooth preparation. A tooth was assessed to have "substantial dentin height" (Trial 1) or "minimal dentin height" (Trial 2). The study sample consisted of 257 patients that received 307 core restorations. The performance of the restorations was based on data collected from the files of the current dentists monitoring the oral health of the patients. The survival probability was analyzed at different levels: on the restoration level (S(R)), and on the level of the tooth carrying the restoration (S(T)). Kaplan Meier analyses were used to compare survival probabilities. RESULTS: "Type of post-and-core restoration" showed no influence on the survival probability (at both levels) in both trials (P-value>0.05). The 17-year survival rates at restoration level varied from 71% to 80%, and at tooth level from 83% to 92%. CONCLUSIONS: The results of this study showed no difference in survival probabilities among different core restorations under a covering crown of endodontically treated teeth. The preservation of substantial remaining coronal tooth structure seems to be critical to the long-term survival of endodontically treated crowned teeth.

Clinical Fit of Partial Removable Dental Prostheses Based on Alginate or Polyvinyl Siloxane Impressions.

PURPOSE: The aim of this study was to analyze the clinical fit of metal-frame partial removable dental prostheses (PRDPs) based on custom trays used with alginate or polyvinyl siloxane impression material. MATERIALS AND METHODS: Fifth-year students of the Nijmegen Dental School made 25 correct impressions for 23 PRDPs for 21 patients using alginate, and 31 correct impressions for 30 PRDPs for 28 patients using polyvinyl siloxane. Clinical fit of the framework as a whole and of each retainer separately were evaluated by calibrated supervisors during framework try-in before (first evaluation) and after (second evaluation) possible adjustments (score 0 = poor fit, up to score 3 = good fit). Framework fit and fit of the denture base were evaluated at delivery (third evaluation). Finally, postinsertion sessions were evaluated and total number of sessions needed, sore spots, adjustments to the denture base, and reported food-impaction were recorded. RESULTS: No significant differences in clinical fit (of the framework as a whole, for the retainers, or for the denture base) were found between the groups in the three evaluation sessions. Differences were not found for postinsertion sessions with one exception: in the alginate group, four subjects reported food impaction, versus none in the polyvinyl siloxane group. CONCLUSION: Clinical fit of metal-frame PRDPs based on impressions with custom trays combined with alginate or polyvinyl siloxane was similar.

Fracture behavior of structurally compromised non-vital maxillary premolars restored using experimental fiber reinforced composite crowns.

PURPOSE: To study the fracture behavior of direct resin composite crowns with or without experimental fiber reinforcement. METHODS: Clinical crowns of single-rooted maxillary premolars were cut off at the cemento-enamel junction. Canals were prepared with Gates Glidden drills up to size 4. No additional post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardized (depth 2 mm, diameter 1.75 mm). Three groups of 14 samples were treated as follows: (1) custom-made glass FRC post (EverStick Post); fibers 5 mm deep in the canal, (2) similar post-system as (1) with incorporation of a new type of glass fiber fabric, (3) no fiber reinforcement (control). Posts were cemented with resin cement (Panavia F). Resin composite crowns (Filtek Z250) were made using an anatomically formed mold. Static load until fracture was applied using a universal loading device with a cylindrical bar (diameter 2 mm) with a crosshead speed of 5 mm/minute (loading angle: 30 degrees to the tooth long-axis). Failure modes were categorized as favorable and unfavorable failures. RESULTS: There was no significant difference in mean failure loads among the four groups (P > 0.05). Favorable failures occurred significantly more often in Group 2 than in the other groups (P < 0.05). The results suggest that an incorporated glass fiber fabric does not affect the load-bearing capacity of resin composite complete crowns on structurally compromised and non-vital premolars. Incorporation of a glass fiber fabric, however, has a beneficial effect on the failure mode.

Impression Procedures for Metal Frame Removable Partial Dentures as Applied by General Dental Practitioners.

This pilot study analyzed impression procedures for conventional metal frame removable partial dentures (RPDs). Heads of RPD departments of three dental laboratories were asked to record features of all incoming impressions for RPDs during a 2-month period. Records included: (1) impression procedure, tray type (stock/custom), impression material (elastomer/alginate), use of border-molding material (yes/no); and (2) RPD type requested (distal-extension/tooth-bounded/combination). Of the 132 total RPD impressions, 111 (84%) involved custom trays, of which 73 (55%) were combined with an elastomer. Impression border-molding material was used in 4% of the cases. Associations between impression procedure and RPD type or dentists' year/university of graduation were not found.

Composite resin core-crown reconstructions: an up to 17-year follow-up of a controlled clinical trial.

PURPOSE: The aim of this long-term follow-up study was to collect up to 17 years of survival data of endodontically treated single teeth with or without a prefabricated metal post. MATERIALS AND METHODS: Single teeth were provided with direct composite resin core-crown reconstructions with or without posts by 15 operators. Restorations consisted of either a prefabricated metal post and a composite core-crown reconstruction or a post-free direct composite reconstruction. Allocation of either restoration was performed by balanced drawing. These restorations were not covered by an artificial crown. The study sample consisted of 87 patients who received 98 core-crown reconstructions. The performance of the restorations was evaluated based on data collected from the files of the clinicians currently monitoring the oral health of the patients. The survival probability was analyzed at different levels: on the restoration level and on the level of the tooth carrying the restoration. Kaplan-Meier analysis was used to compare survival probabilities. RESULTS: Post placement showed no influence on the survival probability at either level (P > .05). The estimated overall survival rate at 17 years was 53% +/- 14% at the restoration level and 79% +/- 11% at the tooth level. CONCLUSION: The results of this long-term follow-up study showed no difference in survival probabilities between different direct composite resin core-crown reconstructions of endodontically treated single teeth (with or without a post).

In vitro fracture behavior of maxillary premolars with metal crowns and several post-and-core systems.

The in vitro fracture behavior of severely damaged premolars, restored with metal crowns with limited ferrule and several post-and-core systems, was investigated. Crowns of maxillary premolars were removed and canals were prepared with Gates Glidden drills and with Parapost drills. Groups of 11 samples were each treated with cast post-and-cores (Parapost XP, Wironium Plus) (group 1), prefabricated metal posts (Parapost XH) (group 2), prefabricated glass fiber posts (Parapost FiberWhite) (group 3), and custom-made glass fiber posts (EverStick Post) (group 4). Posts and composite cores and metal crowns in groups 2, 3, and 4 were adhesively cemented. Post-and-cores and crowns in group 1 were cemented with phosphate cement. Thermocycling was performed (6,000x, 5-55 degrees C). Two static load tests (30 degrees ) were applied. During the first load test (preloading) no failures occurred. Failure modes from the second load test were categorized into favorable and unfavorable failures. Mean failure loads among the four groups (group 1, 1,845 N; group 2, 1,718 N; group 3, 1,812 N; and group 4, 1,514 N) were not significantly different. Unfavorable failures were root fractures and favorable failures were postcrown displacements. No differences in frequencies of unfavorable/favorable failures were seen among the groups. The results suggest that different post-and-core systems have no influence on the fracture behavior of severely damaged premolars restored with metal crowns with limited ferrule.

5-year follow-up of a prospective clinical study on various types of core restorations.

PURPOSE: This study tested whether: (1) the survival rate of cast post-and-core restorations is better than the survival of direct post-and-core restorations and post-free all-composite cores; and (2)the survival of these buildup restorations is influenced by the remaining dentin height after preparation. MATERIALS AND METHODS: In a clinical trial, 18 operators made 319 core restorations in 249 patients. The restorations involved were: (1) cast post-and-core restorations; (2) direct post and composite core restorations; and (3) post-free all-composite cores. All restorations were made under single porcelain-fused-to-metal crowns. Treatments were allocated after dentin height assessment using balanced drawing. Failures were registered during a 5-year period. RESULTS: Fifteen restorations failed during the follow-up period. Five failures occurred during the first month; they were considered to be independent from clinical aging and excluded from further survival assessments. The overall survival was 96%+/-2%. No difference was found between the survivals of the different types of restorations. The factor "remaining dentin height" appeared to have a significant effect on the survival of post-and-core restorations (98%+/-2% survival for "substantial dentin height" vs 93%+/-3% for "minimal dentin height"). CONCLUSION: The type of post and core was not relevant with respect to survival. The amount of remaining dentin height after preparation influenced the longevity of a post-and-core restoration.

A structured analysis of in vitro failure loads and failure modes of fiber, metal, and ceramic post-and-core systems.

PURPOSE: This study sought to aggregate literature data on in vitro failure loads and failure modes of prefabricated fiber-reinforced composite (FRC) post systems and to compare them to those of prefabricated metal, custom-cast, and ceramic post systems. MATERIALS AND METHODS: The literature was searched using MEDLINE from 1984 to 2003 for dental articles in English. Keywords used were (post or core or buildup or dowel) and (teeth or tooth). Additional inclusion/exclusion steps were conducted, each step by two independent readers: (1) Abstracts describing post-and-core techniques to reconstruct endodontically treated teeth and their mechanical and physical characteristics were included (descriptive studies or reviews were excluded); (2) articles that included FRC post systems were selected; (3) in vitro studies, single-rooted human teeth, prefabricated FRC posts, and composite as the core material were the selection criteria; and (4) failure loads and modes were extracted from the selected papers, and failure modes were dichotomized (distinction was made between "favorable failures," defined as reparable failures, and "unfavorable failures,"defined as irreparable [root] fractures). RESULTS: The literature search revealed 1,984 abstracts. Included were 244, 42, and 12 articles in the first, second, and third selection steps, respectively. Custom-cast post systems showed higher failure loads than prefabricated FRC post systems, whereas ceramic showed lower failure loads. Significantly more favorable failures occurred with prefabricated FRC post systems than with prefabricated and custom-cast metal post systems. CONCLUSION: The variable "post system" had a significant effect on mean failure loads. FRC post systems more frequently showed favorable failure modes than did metal post systems.