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.

Dentine hypersensitivity--guidelines for the management of a common oral health problem.

UNLABELLED: Dentine hypersensitivity (DHS) remains a worldwide under-reported and under-managed problem, despite making some dental treatments more stressful than necessary and having a negative impact on the patient's quality of life. This article is designed to build dental professionals' confidence and remove any confusion regarding the diagnosis, prevention and treatment of sensitive teeth caused by dentine hypersensitivity in those patients known to be at risk. There is a need for simple guidelines, which can be readily applied in general practice. However, it is also obvious that one strategy cannot suit all patients. This review describes a DHS management scheme for dental professionals that is linked to management strategies targeted at three different groups of patient. These patient groups are: 1) patients with gingival recession; 2) treatment patients with toothwear lesions; and 3) patients with periodontal disease and those receiving periodontal treatment. The authors also acknowledge the role of industry as well as dental professionals in a continuing role in educating the public on the topic of sensitive teeth. It is therefore important that educational activities and materials for both dental professionals and consumers use common terminology in order to reduce the possibility for confusion. CLINICAL RELEVANCE: This review article provides practical, evidence-based guidance on the management of dentine hypersensitivity for dental professionals covering diagnosis, prevention and treatment. Sensitivity associated with gingival recession, toothwear and periodontal disease and periodontal treatment are specifically addressed in the article.

Qualitative assessment of surface topography of XeCl laser etched Ni-Cr alloy.

OBJECTIVES: The aims of this study were to compare the mode of debonding (adhesive or cohesive) of laser-etched Ni-Cr alloy (Wiron 99) to a standard sandblasting technique, and to a combination of sandblasting and laser etching. The etched surfaces were examined using optical and electron microscopy techniques. METHODS: Five groups of randomly allocated Ni-Cr cylinders were prepared: Group I-sandblasted; Groups II-IV-laser etched at three fluences (3.0, 4.0 and 4.9 J/cm2), Group V-combination sandblasting and laser etching (4.0 J/cm2). Within groups specimens were bonded into pairs (N=8) with composite luting cement (Panavia 21) prior to tensile debonding. Optical and scanning electron microscopy were performed both prior to and following debonding. RESULTS: An oxide layer was observed on sample surfaces before surface preparation by lasing or abrasion. Sandblasting removed the oxidation layer, which low and medium laser fluences alone failed to fully ablate. The highest (4.9 J/cm2) laser fluence melted the surface of the Ni-Cr alloy, covering the oxidation layer. A combination of sandblasting and lasing at 4.0 J/cm2 allowed full removal of the surface oxidation layer due to abrasion, followed by roughening of the surface with the laser. This resulted in greater mean tensile debonding strengths [Murray, A, Attrill, D, Dickinson, M. Dent Mater, 2004, In press] and a tendency for cohesive rather than adhesive interface failures. Groups I-IV underwent partial adhesive failure at both surfaces. Group V, in the main, underwent cohesive failure with a layer of adhesive remaining on both surfaces. SIGNIFICANCE: Laser etching of Ni-Cr alloy in combination with sandblasting optimises bonding to composite luting agents, resulting in a high proportion of cohesive failures when compared to sandblasting or lasing alone.

The effects of XeCl laser etching of Ni-Cr alloy on bond strengths to composite resin: a comparison with sandblasting procedures.

OBJECTIVES: The aim of this study was to determine the effect of laser surface treatment of Ni-Cr alloy on the tensile bond strength of a proprietary composite resin (Panavia 21) in comparison with a conventional sandblasting technique. METHODS: Eighty cylinders of Ni-Cr were randomly allocated into the following groups: Group I-sandblasting only; Group II-low laser fluence (3.0 J/cm(2)); Group III-medium laser fluence (4.0 J/cm(2)); Group IV-high laser fluence (4.9 J/cm(2)); Group V-sandblasting in combination with medium laser fluence (4.0 J/cm(2)). Specimens within groups were bonded into pairs with resin cement as per manufacturer's instructions. They were then de-bonded using a tensile test. RESULTS: The mean de-bond strengths (SD) were: Group I-13.1 (4.2)MPa; Group II-17.6 (5.8)MPa; Group III-25.7 (11.8)MPa; Group IV-22.6 (6.6)MPa; Group V-41.8 (13.2)MPa. A statistically significant improvement (Bonferroni, p<0.05) in bond strength was found for the specimens which had been both lased and sandblasted (Group V) compared to all other groups, including those which were only sandblasted. SIGNIFICANCE: Laser pre-treatment of Ni-Cr alloy increases bond strength to composite resin compared with sandblasting; laser pre-treatment in combination with sandblasting further increases the de-bond strengths.