James Dudley

Retention of cast crown copings cemented to implant abutments

BACKGROUND The cementation of crowns to dental implant abutments is an accepted form of crown retention that requires consideration of the properties of available cements within the applied clinical context. Dental luting agents are exposed to a number of stressors that may reduce crown retention in vivo, not the least of which is occlusal loading. This study investigated the influence of compressive cyclic loading on the physical retention of cast crown copings cemented to implant abutments. METHODS Cast crown copings were cemented to Straumann synOcta titanium implant abutments with three different readily used and available cements. Specimens were placed in a humidifier, thermocycled and subjected to one of four quantities of compressive cyclic loading. The uniaxial tensile force required to remove the cast crown copings was then recorded. RESULTS The mean retention values for crown copings cemented with Panavia-F cement were statistically significantly greater than both KetacCem and TempBond non-eugenol cements at each compressive cyclic loading quantity. KetacCem and TempBond non-eugenol cements produced relatively low mean retention values that were not statistically significantly different at each quantity of compressive cyclic loading. Compressive cyclic loading had a statistically significant effect on Panavia-F specimens alone, but increased loading quantities produced no further statistically significant difference in mean retention. CONCLUSIONS Within the limitations of the current in vitro conditions employed in this study, the retention of cast crown copings cemented to Straumann synOcta implant abutments with a resin, glass ionomer and temporary cement was significantly affected by cement type but not compressive cyclic loading. Resin cement is the cement of choice for the definitive non-retrievable cementation of cast crown copings to Straumann synOcta implant abutments out of the three cements tested.

Maxillary implant overdentures: current controversies

Mandibular implant overdentures have established and predictable benefits over traditional mucosa-borne mandibular dentures and now form part of mainstream dentistry. Maxillary implant overdentures present a number of different challenges. This selective review highlights the paucity of evidence and inconsistent findings in the maxillary implant overdenture literature.

Implants for the ageing population

Dental implant treatment has established benefits over traditional alternatives. Age-related changes in systemic and oral health in conjunction with social, economic and resource considerations often introduce complexities into dental implant treatment of ageing patients. When time, opportunity, discomfort and maintenance costs are coupled with cost-benefit and quality of life predictions, otherwise simple treatment decisions can become more difficult. Implants for different types of prostheses in both arches and the different types of prostheses themselves present a variety of treatment challenges, risks, benefits and maintenance requirements. This narrative review discusses selective literature pertinent to the provision of dental implant treatment in the ageing population.

The 2-implant maxillary overdenture: a clinical report.

Maxillary implant overdentures present a number of different challenges in comparison to the established and predictable benefits of mandibular implant overdentures. This report highlights the lack of evidence and conflicting findings in the maxillary implant overdenture literature and presents a clinical treatment of a 2-implant and subsequently 1-implant maxillary overdenture with reduced palatal coverage.

Accuracy of Milled Titanium Frameworks Constructed with Direct Scanning and Splinted Impression Techniques

PURPOSE To compare vertical microgaps of milled titanium implant frameworks constructed using (1) direct model scanning (DMS) and (2) splinted impression (SIM) techniques. MATERIALS AND METHODS Three BioHorizon external hex implants were embedded in an epoxy resin model, and convenience samples of four identical frameworks in the DMS group and five in the SIM group were constructed. Implant-framework interfaces were scanned with a microcomputed tomography (CT) scanner, and the vertical microgap measured with one-screw and two-screw tests using CT analyzer (CTAn) software. RESULTS The mean maximum vertical microgap measured using the one-screw test was 13.25 μm in the DMS group and 72.40 μm in the SIM group (P < .0001). The mean maximum vertical microgap measured using the two-screw test was 10.5 μm in the DMS group and 36.2 μm in the SIM group (P = .0002). CONCLUSION The milled titanium frameworks produced from direct scanning of implants had a smaller vertical microgap than frameworks produced from splinted impressions and master models.

A Comparison of Marginal Gaps of All-Ceramic Crowns Constructed from Scanned Impressions and Models

PURPOSE This study compared the marginal gaps of computer-aided design/computer-aided manufacture (CAD/CAM)-fabricated all-ceramic crowns constructed from scanned impressions and models and with two different occlusal reduction designs. MATERIALS AND METHODS Two typodont mandibular first molars were prepared to receive CAD/CAM-fabricated all-ceramic crowns. Both molars were prepared to ideal crown reduction, the first with anatomical occlusal reduction (AOR) and the second with completely flat occlusal reduction (FOR). Nine polyvinyl siloxane impressions (PVS) were taken, and nine stone replicas fabricated for each preparation. All impressions and stone models were scanned using a laser scanner (Planmeca Planscan, E4D technologies), and 36 lithium disilicate (IPS e.max CAD) crowns were milled. The marginal gap was measured in four locations using a light stereomicroscope. RESULTS Crowns constructed from preparations with both occlusal reduction designs demonstrated similar marginal gaps (FOR = 97.98; AOR = 89.12; P = .739). However, all crowns constructed from scanned impressions presented significantly larger marginal gaps than the crowns fabricated from scanned models (impressions = 109.26; models = 77.84; P = .002). CONCLUSION Scanning stone models produced all-ceramic crowns with significantly smaller marginal gaps than scanning impressions, irrespective of the occlusal reduction design.

Comparison of Coronal Tooth Reductions Resulting from Different Crown Preparations

PURPOSE The aim of this study was to quantify the coronal tooth structure reductions (CTSRs) resulting from a variety of different types of crown preparations performed by undergraduate dental students in a simulation clinic teaching program. MATERIALS AND METHODS A total of 76 students each submitted 21 different crown preparations completed on typodont teeth, which were individually weighed and analyzed in relation to whole and sectioned reference teeth to calculate the CTSR resulting from each preparation. RESULTS The largest CTSR resulted from preparations for porcelain bonded to zirconia crowns (50.6%), followed by those for porcelain bonded to metal (PBM) crowns (44.3%), PBM fixed partial dentures (32.8%), shell crowns (32.5%), and full gold crowns (24.6%). CONCLUSION A wide range of CTSRs resulted from the different types of crown preparations investigated in this study. The crown preparations performed by the undergraduate students produced more conservative coronal reductions than comparable crown preparations generated under controlled in vitro conditions.

Prosthodontic management of maxillofacial cases: a case series

Maxillofacial prosthetics is an important and recognized sub-discipline of prosthodontics that forms a key component of postgraduate training programmes. General dentists have a role to play in the management of maxillofacial defect patients even though treatment usually requires a multidisciplinary approach in an institutional environment. Maxillofacial prosthetic cases frequently present with complex histories but simple patient goals. The conservatively managed implant-retained auricular prosthesis, speech aid prosthesis and orbital prosthesis cases described in this report were completed in a postgraduate clinical residency program and highlight the intrinsic complexities, challenges and ultimately satisfaction related to cases of this nature.

Twenty-year analysis of implant treatment in an Australian public dental clinic

BACKGROUND This retrospective cohort study reviewed dental implant treatment completed at the Adelaide Dental Hospital over a 20-year period. METHODS The database of implant treatment completed between 1996 and 2015 was analysed for patient, implant, prosthesis and operator specifics together with known implant status. RESULTS Three hundred and twenty patients (mean age, 51.50 years) were treated with 527 implants. One hundred and eighty-four female patients received 296 implants and 136 males received 231 implants. Three hundred implants were restored with single crowns, 147 implants were restored with 63 mandibular implant overdentures, five implants were restored with two maxillary implant overdentures and 67 implants were restored with 20 full-arch fixed prostheses. The overall known implant survival rate was 87.67%. Mandibular implant overdentures had a risk of implant failure four times that of single implant-retained crowns that was statistically significant (P = 0.0100). CONCLUSIONS Implant treatment completed in this public sector clinic using finite resources and a defined system of patient and restorative selection criteria demonstrated a high known implant survival rate. Utilizing a structured and maintained patient recall protocol, it would be ideal to investigate further parameters of interest, particularly those that could improve treatment delivery and longevity.

All-ceramic crown preparations - an alternative technique.

BACKGROUND The aim of this study was to compare the crown preparation dimensions produced from two different techniques of preparation for posterior all-ceramic crowns. METHODS Twenty-four fourth year dental students undertook a course of advanced simulation training involving education in an alternative technique of preparation for a 36 all-ceramic crown. Crown preparations performed using the traditional technique were compared with an alternative technique for total occlusal convergence (TOC) and reduction difference (RD) using digital scanning and comparative software. RESULTS Groups that spent the most time performing the alternative technique produced crown preparations with significantly lower buccolingual (BL) TOC. The training resulted in crown preparations that were closer to ideal TOC and RD measurements. CONCLUSIONS The alternative technique of crown preparation for a posterior all-ceramic crown showed initial promise in creating a less buccolingually tapered and more ideally occlusally reduced crown preparation.