Current challenges for 3D printing complete dentures: experiences from a multi-centre clinical trial.

Aims To develop an optimal clinical and laboratory protocol for the fabrication of 3D printing dentures.Design A prospective feasibility study across three UK dental schools.Material and methods Each patient received one conventional and one 3D-printed denture. Both dentures were constructed using the same impression, jaw registration and wax trial denture. Variables investigated included methods of digitisation of the impression and optional use of a 3D-printed baseplate for jaw registration.Results Clinicians strongly preferred 3D-printed baseplates. Patients felt that conventional and printed dentures were similar in retention and stability. More patients favoured conventional dentures over 3D-printed dentures in terms of comfort.Discussion It is feasible to combine conventional clinical work with digital techniques to produce 3D-printed dentures. 3D-printed baseplates offer a cost-effective alternative to conventional bases at the jaw registration stage. Challenges were faced in tooth positioning and managing occlusion, particularly where roots required adjustment.Conclusion 3D printing is suitable for producing baseplates for jaw registration blocks and wax trial insertions. It is feasible to produce 3D-printed dentures using conventional clinical techniques for impressions, jaw registration and wax trial insertion. The workflow used in this study for 3D-printed dentures is not superior to conventional dentures. Further work is required.

Deformation and retentive force following in vitro cyclic fatigue of cobalt-chrome and aryl ketone polymer (AKP) clasps.

OBJECTIVE: To compare the retention force of individual clasps made from cobalt chromium (CoCr) or new aryl ketone polymer (AKP) material, Ultaire™ AKP, following prolonged fatigue testing along ideal and non-ideal paths of removal and to assess 3D deformation of the active and passive clasp tips. METHODS: CoCr and AKP clasps were manufactured in their standard, respective processes, digitally scanned prior to testing, then cycled 15,000 times over an e.max analogue crown in artificial saliva. Retentive load was measured in situ, as a function of cycles. Clasps were rescanned to assess deformation and along with their antagonists subjected to SEM to assess localised wear. RESULTS: Distortion of the CoCr clasps was consistently larger than Ultaire™ AKP clasps, irrespective of removal path. CoCr clasps had significantly higher retentive forces than AKP clasps, for both removal paths. Ultaire™ AKP clasps showed a lower but relatively constant retentive force. The non-ideal path of removal affected retentive forces for both clasp materials. SEM showed localised removal of glaze for e.max crowns used with CoCr clasps. SIGNIFICANCE: Ultaire™ AKP clasps showed significantly less permanent deformation and lower retentive force than CoCr clasps. Unlike CoCr, the Ultaire™ AKP clasps did not work harden, nor had as large a reduction in retentive force and accompanying permanent deformation; the retentive force for the Ultaire™ AKP clasps was consistent over 15,000 cycles of fatigue mimicking prolonged clinical use. The AKP material was more robust; showing minimal deformation even in non-ideal paths of removal, as many patients would routinely use.

Removable partial dentures: The clinical need for innovation.

STATEMENT OF PROBLEM: The number of partially dentate adults is increasing, and many patients will require replacement of missing teeth. Although current treatment options also include fixed partial dentures and implants, removable partial dentures (RPDs) can have advantages and are widely used in clinical practice. However, a significant need exists to advance materials and fabrication technologies because of the unwanted health consequences associated with current RPDs. PURPOSE: The purpose of this review was to assess the current state of and future need for prosthetics such as RPDs for patients with partial edentulism, highlight areas of weakness, and outline possible solutions to issues that affect patient satisfaction and the use of RPDs. MATERIAL AND METHODS: The data on treatment for partial edentulism were reviewed and summarized with a focus on currently available and future RPD designs, materials, means of production, and impact on oral health. Data on patient satisfaction and compliance with RPD treatment were also reviewed to assess patient-centered care. RESULTS: Design, materials, ease of repair, patient education, and follow-up for RPD treatment all had a significant impact on treatment success. Almost 40% of patients no longer use their RPD within 5 years because of factors such as sociodemographics, pain, and esthetics. Research on RPD-based treatment for partial edentulism for both disease-oriented and patient-centered outcomes is lacking. CONCLUSIONS: Future trials should evaluate new RPD materials and design technologies and include both long-term follow-up and health-related and patient-reported outcomes. Advances in materials and digital design/production along with patient education promise to further the application of RPDs and improve the quality of life for patients requiring RPDs.

Dentures for Randomised Controlled Trials.

Making complete dentures for dental research is difficult. The difficulty is not in the construction of dentures, but making sure the clinician is blind to the randomizations, and avoiding confounding variables. For research purposes it is essential that two sets of dentures are similar in every way, apart from the area to be investigated. A previous article showed how to duplicate a lower denture when it was articulated against a single upper denture. This paper describes the additional duplication of upper dentures. These additional problems presented the clinical and technical teams at the Leeds Dental Institute some challenges.

A Randomised Controlled Study Comparing the Anterior Mandibular Labio-Lingual Neutral Zone Position in Edentulous Subjects With and Without Their Maxillary Denture In-Situ.

Opinion is divided as to whether the neutral zone impression to determine the labio-lingual position of mandibular complete dentures requires the maxillary denture to remain in-situ or not. Two such neutral zone impressions were recorded for each of the 12 participants of this randomised controlled study. The presence of the maxillary denture made no statistically significant mean difference in labio-lingual position of the mandibular neutralzone. Within the confines of this research protocol there was no evidence that the shift in the labio-linguial position of the anterior mandibular neutral zone was consistently affected by the presence of a maxillary appliance.

IMPROVDENT: improving dentures for patient benefit. A crossover randomised clinical trial comparing impression materials for complete dentures.

BACKGROUND: According to the UK Adult Dental Health Survey (2009) 15% of adults aged 65-74, 30% aged 75-84 and 47% aged >85 years are edentulous and require complete dentures. Patients' quality of life and nutrition status are affected by poor dentures. The quality of the dental impression is the most important issue for improving the fit and comfort of new dentures. There is paucity of RCT evidence for which impression material is best for complete dentures construction. This study aims to compare two impression materials for effectiveness and cost effectiveness. METHODS/DESIGN: IMPROVDENT is a double-blind crossover trial comparing the use of alginate and silicone, two commonly used denture impression materials, in terms of patient preference and cost-effectiveness. Eighty five edentulous patients will be recruited and provided with two sets of dentures, similar in all aspects except for the impression material used (alginate or silicone). Patients will try both sets of dentures for a two-week period, unadjusted, to become accustomed to the feel of the new dentures (habituation period). Patients will then wear each set of dentures for a period of 8 weeks (in random order) during which time the dentures will be adjusted for optimum comfort. Finally, patients will be given both sets of dentures for a further two weeks to wear whichever denture they prefer (confirmation period).Patients will be asked about quality of life and to rate dentures on function and comfort at the end of each trial period and asked which set they prefer at the end of the habituation period (unadjusted denture preference) and confirmation period (adjusted denture preference). A health economic evaluation will estimate incremental cost-effectiveness ratios of producing dentures from the two materials. A qualitative study will investigate the impact of dentures on behaviour and quality of life. FUNDING: IMPROVDENT is funded by NIHR RfPB (PB-PG-0408-16300). DISCUSSION: This trial aims to provide evidence on the costs and quality of dentures cast from two different commonly used impression materials; the intention is to significantly impact on the quality of denture production within NHS dentistry. TRIAL REGISTRATION: ISRCTN Register: ISRCTN01528038 UKCRN Portfolio ID: 8305.

Providing support for the pontic of natural tooth adhesive bridges: a clinical report.

Resin bonded bridges have become established as a treatment option for replacing missing teeth. Their development can be traced to the work of Rochette who used a macro mechanically bonded metal framework to stabilize mobile teeth. Adaptations of Rochette's concept, using natural teeth as pontics, have been presented. The use of a natural tooth has aesthetic and psychological advantages for the patient. The high failure rate of natural tooth pontics may be explained by a lack of support for the tooth on the metal framework. A clinical report is presented to illustrate a previously unreported technique to improve pontic support.

The effect of seating velocity on pressure within impressions.

STATEMENT OF PROBLEM: Oral mucosa can distort under impressions. To reduce or control mucosal distortion, modern impression techniques aim to reduce or control the impression pressure. If changing seating velocity significantly changes pressure, then this effect should be considered for clinical impressions of mucosa. PURPOSE: The purpose of this study was to investigate the relationship between seating velocity and pressure generation during simulated impressions. MATERIAL AND METHODS: Vinyl polysiloxane impression material (Express) was placed between 2 approximating discs in a universal testing machine. The velocity at which the discs approximated was varied. The 7 selected seating velocities were 0.75 mm/s, 1 mm/s, 1.25 mm/s, 1.5 mm/s, 2 mm/s, 2.5 mm/s, and 3 mm/s. The pressure generated at the center of the disk was recorded. Five separate recordings were made for each velocity. One-way ANOVA and post hoc tests (Tukey B and Dunnett T3) (alpha=.05) were used to evaluate peak pressure data at each velocity. RESULTS: The mean (SD) of the recorded pressures for each velocity were 239 (6.67) KPa, 273 (14.89) KPa, 347 (11.97) KPa, 425 (19.73) KPa, 487 (17.84) KPa, 547 (21.25) KPa, and 624 (32.60) KPa, respectively. As the velocity increased, there was a significant (P<.001) concurrent increase in peak pressure. CONCLUSIONS: In this in vitro experiment, changing the velocity of seating had a significant effect on the peak pressure produced during simulated impressions.

Case report: differential pressure impressions for complete dentures.

A method of producing a differential pressure, secondary impression of a lower arch with a sharp bony ridge is described. The use of this technique allows the clinician to dictate where the load is to be borne by the mucosa.