Sönke Harder

Four-year clinical results of fixed dental prostheses with zirconia substructures (Cercon): end abutments vs. cantilever design.

The purpose of this prospective study was to evaluate the clinical outcome of three- to four-unit posterior all-ceramic fixed dental prostheses (FDPs) made of yttria-stabilized tetragonal zirconia-polycrystal ceramic frameworks (CerconBase; Degudent). Fifty-eight restorations were placed in 48 patients. Twenty-four FDPs had an end abutment design (EAD) replacing 3 premolars and 21 molars. Thirty-four FDPs had a cantilever design (CD) replacing 11 premolars and 23 molars. The frameworks had a minimum proximal connector dimension of 3 x 3 mm. The fixed dental prostheses were cemented with glass-ionomer cement after air-abrading the inner crown surfaces. Three FDPs were defined as drop-outs. The mean observation period was 48 +/- 7 months for the EAD (21 patients/24 FDPs) and 50 +/- 14 months for the CD (25 patients/31 FDPs). The 4-yr survival rate, according to the Kaplan-Meier analyses, was 96% for the EAD and 92% for the CD. The technical complication rate was 13% for the EAD and 12% for the CD, and the biological complication rate was 21% for the EAD and 15% for the CD. For none of the analyses were significant differences found between both groups. After 4 yr the clinical outcome of three- to four-unit posterior FDPs with EAD and CD was promising.

Three-year clinical outcome of single implant-retained mandibular overdentures—Results of preliminary prospective study

OBJECTIVES The aim of this preliminary prospective study was to evaluate the clinical outcome, the oral health-related quality of life (OHRQoL), and the subjective chewing ability of patients with mandibular complete dentures retained by a single implant placed in the mandible midline. METHODS Patients wearing complete dentures were treated with a single implant in the mandible, followed by relining of the dentures and incorporation of ball attachments for implant retention. Implant outcome, prosthodontic maintenance, subjective chewing ability, and the oral health impact profile of the patients were assessed at baseline and at four weeks after connecting the denture and implant. RESULTS Eleven patients were enrolled in this investigation, and the mean observation period was 43.4 months (minimum period: 35, maximum period: 52 months). No implants were lost during observation period, but four dentures needed repair because of the fracture of the denture base in the midline area. A significant improvement was observed in the OHRQoL of the patients after the attachment of the mandibular dentures with a single midline implant. Furthermore, the subjective chewing ability of the patients was significantly improved after implant connection. CONCLUSIONS Within the limitations of this preliminary prospective clinical study, single implant-supported mandibular overdentures were a successful treatment option for older edentulous patients who showed improvements in their OHRQoL and chewing ability.

Influence of the drill material and method of cooling on the development of intrabony temperature during preparation of the site of an implant

Our aim was to evaluate the intrabony friction heat produced by implant drills, using different drill materials and methods of cooling. Four pilot drills and 4 form drills were used. The following combinations of drill material and cooling supply were tested: steel and external cooling; steel and internal cooling; steel coated with zirconium nitride and external cooling; and zirconium oxide and external cooling. The handpiece that supported the drill was fixed in a lifting device. Specimens of bovine ribs were fixed below the handpiece, and the drill speed was set to 1200 rpm. The vertical force was adjusted to 1 kg for pilot drills and 0.5 kg for implant drills. Intrabony temperature during drilling was measured at depths of 4, 8, and 12 mm parallel to the drill, and the depth was limited to 13 mm. There were no significant differences in heat generation between the drill materials (p>.05), but the differences between groups with internal or external cooling supplies were significant (p≤.05). The method of cooling affected the development of the intrabony temperature during preparation of the site of the implant, but the drill material seemed to play no particular role.

Eight-year outcome of posterior inlay-retained all-ceramic fixed dental prostheses

AIM The main goal of this prospective clinical study was to evaluate the outcome of inlay-retained fixed dental prostheses (FDPs) made from heat-pressed lithium-disilicate glass-ceramic. METHODS Forty-five FDPs were placed in 42 patients (21 women, mean age 36.1 years and 21 men, mean age 42.0 years). The FDPs replaced 4 premolars and 19 molars in the maxilla and 4 premolars and 18 molars in the mandible. Preparations were performed in accordance with general principles for ceramic inlay restorations. Five of the 45 FDPs were hybrid-retained restorations, i.e. one abutment tooth with an inlay retainer and one with a full crown retainer. All FDPs were pressed in one piece using lithium-disilicate ceramic (IPS e.max Press, Ivoclar Vivadent). The minimum dimensions for the proximal connector were 4mm in height and 4mm in width (16 mm(2)) with a minimum occlusal ceramic thickness of 1.5mm. The surfaces of the inlay retainer were conditioned by etching with hydrofluoric acid 5% and silane application. Standard adhesive luting techniques were performed using a dentin adhesive (Syntac Classic, Ivoclar Vivadent) and a resin composite (Variolink II, Ivoclar Vivadent). Clinical follow-up examinations were performed annually. RESULTS The mean observation periods were 70 months (minimum 4, maximum 123 months). Twenty-seven FDPs (60%) failed during the observation period and had to be replaced. The Kaplan-Meier survival rate for inlay-retained FDPs was 57% after 5 years and 38% after 8 years, while for hybrid-retained FDPs it was 100% after 5 and 60% after 8 years. CONCLUSIONS Inlay-retained FDPs made from lithium-disilicate ceramic present a high clinical failure rate and therefore cannot be recommended.

Survival and complications of computer aided‐designing and computer‐aided manufacturing vs. conventionally fabricated implant‐supported reconstructions: a systematic review

OBJECTIVES The aim of this systematic review was to assess the internationally published survival and complication rates of implant-supported computer-aided designing (CAD) and computer-aided manufacturing (CAM)-fabricated restorations and to compare them with those of conventionally fabricated implant-supported restorations. METHODS An electronic MEDLINE search was conducted to identify prospective and retrospective cohort studies on CAD-CAM fabricated implant-supported restorations with a mean follow-up time of at least 1 year. Failure and complication rates were evaluated and descriptive statistics were performed. RESULTS An electronic MEDLINE search revealed four studies reporting on implant-supported CAD-CAM fabricated restorations. The cumulative 5-year survival rate of implants supporting full-arch-fixed dental prostheses (FDPs) ranged from 81.4% to 95.6%. Reported survival rates of implants supporting all-ceramic single crowns (SCs) were 100% [95% confidence interval (CI): 92.4-100]. The cumulative 5-year survival rate for full-arch FDPs ranged from 72.2% to 100%. Reported cumulative 5-year survival rates for all-ceramic SCs were 100% (95% CI: 92.4-100%). Technical complications were reported in two of the four selected studies and the estimated annual failure rate for chipping/fracture of the veneering material was 0.43 (95% CI: 0.06-3.06) for implant-supported all-ceramic SCs and 3.61 (95% CI: 2.05-6.36) for implant-supported FDPs. CONCLUSIONS Only a small number of clinical studies reporting on implant-supported CAD-CAM fabricated restorations exists which makes a scientifically valid comparison with conventionally fabricated restorations impossible.

Influence of cement film thickness on the retention of implant-retained crowns.

PURPOSE The main goal of this study was to establish a new, high precision procedure to evaluate the influence of cement film thickness on the retention of cemented implant-retained crowns. MATERIALS AND METHODS Ninety-six tapered titanium abutments (6° taper, 4.3 mm diameter, Camlog) were shortened to 4 mm. Computer-aided design was used to design the crowns, and selective laser sintering, using a cobalt-chromium alloy, was used to produce the crowns. This method used a focused high-energy laser beam to fuse a localized region of metal powder to build up the crowns gradually. Before cementing, preset cement film thicknesses of 15, 50, 80, or 110 μm were established. Glass ionomer, polycarboxylate, or resin cements were used for cementation. After 3 days storage in demineralized water, the retention of the crowns was measured in tension using a universal testing machine. RESULTS The cement film thicknesses could be achieved with a high level of precision. Interactions between the factors cement and cement film thickness could be found (p ≤ 0.001). For all cements, crown retention decreased significantly between a cement film thickness of 15 and 50 μm (p ≤ 0.001). At 15 μm cement film thickness, the resin cement was the most retentive cement, followed by the polycarboxylate and then the glass ionomer cement (p ≤ 0.05). CONCLUSIONS The results suggest that cement film thickness has an influence on the retentive strength of cemented implant-retained crowns.

Dental implants stimulate expression of Interleukin-8 and its receptor in human blood—An in vitro approach†

Interleukin (IL)-8 secreted from osteoblasts and peripheral blood monocytes increases in patients with aseptic hip-implant loss and in patients with mucositis after dental implant insertion. We explored in vitro the possibility of an IL-8-mediated inflammatory response as a consequence of contact between different dental implant surfaces and human blood. Titanium and zirconia implants were incubated in human blood. Nonstimulated blood served as negative, while blood stimulated with bacterial lipopolysaccharides (LPS) served as positive control. After depyrogenization, to examine the possible role of LPS, implants were again submerged in blood. Gene-expression of IL-8 and its receptor was measured by real-time quantitative polymerase chain reaction. In a receptor mediated, but LPS-independent manner, titanium implants led to a more pronounced increase in IL-8 gene expression when compared with zirconia implants. Depyrogenization resulted after 24 h in zirconia implants in decreased IL-8 gene expression. Altered IL-8 expression could indicate aseptic, at least LPS-independent implant loss, which may be an additional feature in the manifestation of peri-implantitis, possibly triggered by microscopically small implant-particles. Hence, opening a new field of investigations to further understand the possible mechanism underlying the manifestation of implant failure.

Antimicrobial filling of implant cavities.

The Journal of Prosthetic Dentistry Kern and Harder Jung and Bashutski 3. Design the outline of the template and the guidance indentations for screws so that a tripod is formed between 2 bone screws (Stryker Instruments, Kalamazoo, Mich) positioned through the guidance indentations of the template on the labial surface of the maxillary anterior alveolar ridge area and a palatal extension of the template in the midpalatal area (Fig. 1). 4. Apply a thin coat of separating agent (Model Release Agent; Dentsply Trubyte) (MRA) to the cast. Then, adapt a sheet of visible light-polymerized urethane dimethyl methacrylate (Triad Denture Base Material, Regular Pink Fibered; Dentsply Trubyte) to the cast over the area outlined previously, using finger pressure. Apply the bulk of the sheet on the palatal extension and trifurcation area of the template to increase the strength in that area, and then trim as desired with a knife (Buffalo Dental Mfg Co, Syosset, NY). Place the cast and base material in a light-polymerization unit (Triad 2000 curing unit; Dentsply Intl) and polymerize for 4 minutes. Trim and polish the surgical template with a tungsten carbide bur (SS White Burs, Inc; Lakewood, NJ), an Arbor band (Faskut Super Band Arbor Bands; Denstply Trubyte), and a slurry of pumice and lathe polishing wheel. 5. Position the template on the maxillary edentulous ridge. Place two 2.0 x 16-mm bone screws (Stryker Instruments) in the alveolar bone through the guidance indentations of the template after drilling with a 1.6-mm-diameter drill bit (Stryker Instruments) under saline irrigation. Secure the template manually in place by using 2 bone screws in the anterior maxilla region. Using the surgical template as a guide, make crestal incisions over the maxillary posterior edentulous residual ridges and tuberosities using a #15 blade (Bard-Parker Stainless Steel Surgical Blade, Becton, Dickinson and Co, Franklin Lakes, NJ). 6. Excise excess soft tissue and then reflect a full-thickness mucoperiosteal flap on the buccal and palatal to gain access to the entire tuberosity area (Fig. 2). Using the template as a guide again, outline the bony ridge to be removed using a tapered fissure bur (14-C0608; Brasseler USA, Savannah, Ga) in an air-driven handpiece (Hall Surgairtome Two; Zimmer, Inc, Warsaw, Ind). Remove the template and proceed to remove the outlined area of bone using a mallet and chisel. Smooth the remaining bone using an oval osteotomy bur (14-C0905; Brasseler USA) and a bone file (KLS Martin LP, Jacksonville, Fla). Irrigate the site with copious amounts of saline and close the wound with tension-free closure using absorbable 3-0 chromic gut suture material (Ethicon, Inc, Somerville, NJ). 7. Finally, remove the mini-screws.

Changes in human mandibular bone morphology after heat application

PURPOSE Intraosseous heat development is always a problem during bone surgery performed using rotary burs and ultrasound devices. However, only few data exist regarding the morphological effects of applied heat on bone surfaces. METHODS We used 24 human mandibular bone specimens of the mental region from six body donators. Three body donators were fixed in ethanol and the others were stored frozen. Heat application to the bone surfaces at temperatures of 40 degrees C, 50 degrees C, 60 degrees C and 100 degrees C for 1 min respectively, was performed under controlled conditions using an iron heater, and followed by examination using (i) scanning electron microscopy (SEM), (ii) demineralized paraffin sections, and (iii) cryostat sections (both HE staining). RESULTS There was no difference in the morphology or histology between fixed or unfixed bone specimens. The bone surface was smooth in both groups at 40 degrees C and 50 degrees C of heat application. Applications of 60 degrees C and 100 degrees C induced a rough-textured surface with small cavities visible with SEM and demineralized HE staining. The bone appeared to be unaffected at lower planes. The frozen HE histology could not be evaluated. Although useful in other studies, here the sections were broken and displaced on the glass slide. Therefore, this technique is not recommended by the authors. CONCLUSION Our findings suggest the applicability of SEM for bone surface morphology and demineralized paraffin sections (HE staining) for frontal plane evaluation. Fixed and non-fixed bone specimens seem to be equal in their morphology and can both be used in these kinds of studies.

Prosthodontics in digital times: a case report.

Dentistry has not been exempt from changes in this era of technology-driven revolution. Entire workflows are already digitalized, and restorations are designed and manufactured using computer-aided solutions. This case report describes the reconstruction of 24 teeth using digital techniques.