Peter Pospiech

Zirconium Dioxide Implant Abutments for Posterior Single-Tooth Replacement: First Results

BACKGROUND Prefabricated implant abutments made of zirconium dioxide (yttria-stabilized polycrystalline tetragonal zirconia; Y-TZP) have proved to be useful in the esthetically demanding anterior region and may also be useful for premolar and molar replacement because of their obvious positive impact on the health of peri-implant soft tissues. METHODS Forty screw implants were inserted in the posterior region of 24 patients and provided with prefabricated all-ceramic abutments made of zirconium dioxide Y-TZP. Zirconia-based crowns were used as superstructures. The following parameters were used to document the state of soft tissue: the modified plaque index (mPI), sulcus fluid flow rate (SFFR), modified sulcus bleeding index (mSBI), and probing depth (PD). Additionally, implant stability was measured using an electronic mobility testing device. RESULTS All implants (N = 40) followed up after 6 months in function were osseointegrated and showed good stability. In the presence of good oral hygiene (mPI: 0.3), the parameters SFFR (16) and mSBI (0.7) were indicative of stable and healthy soft tissue. The mean PD was highest at the distal points of measurement (2.4 mm) and was generally at a low level. Neither implant loss nor crown fractures occurred. Chipping of parts of the veneering ceramic was registered in three cases (7.5%). CONCLUSIONS After 6 months in function, no mechanical failure was registered in any of the all-ceramic abutments. On clinical investigation, the peri-implant soft tissues were largely healthy and devoid of inflammation.

All-ceramic crowns: bonding or cementing?

Despite the wide variety of all-ceramic systems available today, the majority of dental practitioners hesitate to recommend and insert all-ceramic crowns. This article regards the nature of the ceramic materials, the principles of bonding and adhesion, and the clinical problems of the acid-etch technique for crowns. Advantages and disadvantages are discussed, and the influences of different factors on the strength of all-ceramic crowns are presented. Finally, the conclusion is drawn that conventional cementing of all-ceramic crowns is possible when the specific properties of the ceramics are taken into consideration.

Prefabricated zirconium dioxide implant abutments for single‐tooth replacement in the posterior region: evaluation of peri‐implant tissues and superstructures after 12 months of function

AIM In the present study, prefabricated abutments made of zirconium dioxide Y-TZP (tetragonal zirconia polycrystals) were inserted into the posterior region under controlled clinical conditions. The aim was to test whether abutments made of zirconium dioxide are suitable for this indication. Investigation parameters included reactions of peri-implant tissue and the structural integrity of the all-ceramic superstructures on the implants. Results after 12 months in function are reported in this article. MATERIAL AND METHODS Forty implants of the XiVE S plus screw-type implants (DENTSPLY Friadent) were inserted into the posterior region of 24 patients. After the healing period, the implants were provided with all-ceramic abutments made of zirconium dioxide Y-TZP (FRIADENT CERCON Abutment; DENTSPLY Friadent). All-ceramic crowns (CERCON smart ceramics; DENTSPLY DeguDent) were used as superstructures and cemented using the conventional method. The following parameters were used to document the state of soft tissue: modified plaque index (mPI), sulcus fluid flow rate (SFFR, Periotron; Oraflow Inc), modified sulcus bleeding index (mSBI) and pocket depth (ST). Mesial and distal bone levels were determined on radiographs during the prosthetic treatment and at the 12-month recall. The Periotest (Medizintechnik Gulden) was used to determine implant stability. RESULTS All implants could be followed up after 12 months in function. In the presence of good oral hygiene (mPI: 0.5), the parameters SFFR (18) and mSBI (0.5) were indicative of stable and healthy soft tissue. ST was highest at the distal points of measurement (2.3 mm) and was generally at a low level. Compared with the baseline situation, proximal bone defects were reduced from -1.1 to -1 mm during the 12-month period of functioning. The mean Periost values at the 12-month recall were -1.9 in the maxilla and -3.8 in the mandible. Neither implant loss nor crown fractures occurred. Chipping of parts of the veneering ceramic was registered in four cases (10%). CONCLUSION After 12 months of wear, no mechanical failure was registered in any of the all-ceramic abutments. On clinical investigation, the peri-implant hard and soft tissues were largely healthy and devoid of inflammation.

The Randomized Shortened Dental Arch Study Tooth Loss

The evidence concerning the management of shortened dental arch (SDA) cases is sparse. This multi-center study was aimed at generating data on outcomes and survival rates for two common treatments, removable dental prostheses (RDP) for molar replacement or no replacement (SDA). The hypothesis was that the treatments lead to different incidences of tooth loss. We included 215 patients with complete molar loss in one jaw. Molars were either replaced by RDP or not replaced, according to the SDA concept. First tooth loss after treatment was the primary outcome measure. This event occurred in 13 patients in the RDP group and nine patients in the SDA group. The respective Kaplan-Meier survival rates at 38 months were 0.83 (95% CI: 0.74-0.91) in the RDP group and 0.86 (95% CI: 0.78-0.95) in the SDA group, the difference being non-significant.

The fracture behavior of premolar teeth with class II cavities restored by both direct composite restorations and endodontic post systems

PURPOSE The aim of the study was to evaluate the influence of different posts on the fracture load and fracture mode of endodontically treated premolars with class II cavities and direct composite restorations in an ex vivo setting. METHODS Forty-eight single-rooted human premolars were endodontically treated and prepared with standardized MO (mesio-occlusal) cavities. Eight teeth each received either no posts or were restored with titanium screws (BKS), glass fiber posts (DentinPost), or quartz fiber posts (DT Light SL). Sixteen teeth were restored with zirconium dioxide posts (CeraPost). BKS-screws and eight zirconium dioxide posts were cemented conventionally with glass ionomer cement; Panavia F resin cement was used for all others. The specimens were restored with direct composite restorations. Eight sound premolars served as the controls. After thermomechanical fatigue testing, the samples were loaded until fracture occurred at an angle of 45 degrees . All specimens were evaluated for fracture lines. RESULTS The sound teeth showed the significant highest fracture load (792.50+/-210.01 N). The group restored with quartz fiber posts differed not significantly from the control. In the groups with fiber posts and titanium screws significant higher fracture load values occurred as in the group with direct composite restorations without posts. The groups with fiber posts did not show a more favorable fracture mode than the other groups. CLINICAL SIGNIFICANCE The use of an intraradicular post in premolars with class II cavities can significantly increase the resistance towards extra-axial forces.

The Randomized Shortened Dental Arch Study 5-year Maintenance

The scientific evidence concerning prosthodontic care for the shortened dental arch (SDA) is sparse. This randomized multicenter study aimed to compare two common treatment options: removable partial dental prostheses (RPDPs) for molar replacement vs. no replacement (SDA). One of the hypotheses was that the follow-up treatment differs between patients with RPDPs and patients with SDAs during the 5-year follow-up period. Two hundred and fifteen patients with complete molar loss in one jaw were included in the study. Molars were either replaced by RPDPs or not replaced according to the SDA concept. A mean number of 4.2 (RPDP) and 2.8 (SDA) treatments for biological or technical reasons occurred during the 5-year observation time per patient. Concerning the biological aspect, no significant differences between the groups could be shown, whereas treatment arising from technical reasons was significantly more frequent for the RPDP group. When the severity of treatment was analyzed, a change over time was evident. When, at baseline, only follow-up treatment with minimal effort is required, over time there is a continuous increase to moderate and extensive effort observed for both groups (Controlled-trials.com number ISRCTN97265367).

The randomized shortened dental arch study (RaSDA): design and protocol

BackgroundVarious treatment options for the prosthetic treatment of jaws where all molars are lost are under discussion. Besides the placement of implants, two main treatment types can be distinguished: replacement of the missing molars with removable dental prostheses and non-replacement of the molars, i.e. preservation of the shortened dental arch. Evidence is lacking regarding the long-term outcome and the clinical performance of these approaches. High treatment costs and the long time required for the treatment impede respective clinical trials.Methods/designThis 14-center randomized controlled investigator-initiated trial is ongoing. Last patient out will be in 2010. Patients over 35 years of age with all molars missing in one jaw and with at least both canines and one premolar left on each side were eligible. One group received a treatment with removable dental prostheses for molar replacement (treatment A). The other group received a treatment limited to the replacement of all missing anterior and premolar teeth using fixed bridges (treatment B). A pilot trial with 32 patients was carried out. Two hundred and fifteen patients were enrolled in the main trial where 109 patients were randomized for treatment A and 106 for treatment B. The primary outcome measure is further tooth loss during the 5-year follow-up. The secondary outcome measures encompassed clinical, technical and subjective variables. The study is funded by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG WA 831/2-1, 2-2, 2-3, 2-4, 2-5).DiscussionThe particular value of this trial is the adaptation of common design components to the very specific features of complex dental prosthetic treatments. The pilot trial proved to be indispensable because it led to a number of adjustments in the study protocol that considerably improved the practicability. The expected results are of high clinical relevance and will show the efficacy of two common treatment approaches in terms of oral health. An array of secondary outcome measures will deliver valuable supplementary information. If the results can be implemented in the clinical practice, the daily dental care should strongly profit thereof.Trial registrationThe trial is registered at ClinicalTrials.gov under ISRCTN68590603 (pilot trial) and ISRCTN97265367 (main trial).

Influence of the preparation design and artificial aging on the fracture resistance of monolithic zirconia crowns

PURPOSE The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. MATERIALS AND METHODS An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃–55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. RESULTS The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. CONCLUSION The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.

Exposition gegenüber Nanopartikeln und neuen Materialien in der Zahnheilkunde

ZusammenfassungZahnmedizin und Zahntechnik zeichnen sich durch ein vielfältiges Tätigkeits- und demzufolge heterogenes Expositions-Spektrum der Beschäftigten aus. Mögliche Gesundheitsrisiken sind neben einem dermalen Kontakt zu den unterschiedlichsten Arbeitsstoffen und Sekundärprodukten vor allem durch die Inhalation von Aerosolen, ultrafeinen Stäuben bzw. Nanopartikeln gegeben.Eine orientierende Analyse der Partikelanzahlkonzentrationen in den Behandlungsräumen und dem Dentallabor der Universitäts-Zahnklinik erfolgte mit dem tragbaren Kondensationspartikelzähler (CPC 3007, TSI), der die Gesamtpartikelanzahl in einem Größenbereich von 10 bis 1 000 nm in einem Konzentrationsbereich von bis zu 105 pt/cm3 bestimmt.Bei zahnärztlichen Routine-Tätigkeiten zeigten sich im Allgemeinen keine signifikanten Spitzenkonzentrationen. Demgegenüber fanden sich kurzzeitige, über Sekunden anhaltende Maxima bei der Anwendung von Propan- und Butanhaltigem Kältespray zur Sensibilitätsprüfung, bei intraoraler Applikation von Druckluft oder im Rahmen von Wurzelkanalbehandlungen, bei denen am Behandlungsstuhl offene Flammen Verwendung fanden.Konzentrationen > 400 000 pt/cm3 wurden bei der Bearbeitung von PMMA-haltigen Materialien z.B. im Rahmen der prothetischen Versorgung dokumentiert, die durch eine lokale Absaugung auf 1/20 der initialen Konzentration reduziert werden konnten. Eine gleichzeitige Flüssigkeitskühlung führte ebenfalls zu einer signifikanten Verminderung der Partikelspitzenkonzentration von 167 000 auf 5 700 pt/cm3 beim Fräsen von Glaskeramik bzw. von 45 000 auf 7 000 pt/cm3 bei der Verarbeitung von Zirkoniumdioxid-Keramik.Während repräsentativer Tätigkeiten wurden gleichzeitig Partikelproben aus der Raumluft gewonnen, die durch moderne Bildgebungsverfahren (REM) einschließlich gekoppelter Elementanalyse (EDX) visualisiert und u.a. als Zirkonium-, Gold- und Titanium-Partikel im Nanomaßstab verifiziert wurden.Die lediglich bei speziellen und verhältnismäßig selten ausgeführten Tätigkeitsabläufen in Zahnklinik und Dentallabor dokumentierten signifikanten Partikelspitzenkonzentrationen bedürfen — insbesondere vor dem Hintergrund eines toxischen Potentials einiger Arbeitsstoffe wie Zirkonium und (Poly-)Methylmethacrylate — adäquater organisatorischer, technischer und personenbezogener Schutzmaßnahmen am Arbeitsplatz zur Prävention berufsbedingter Erkrankungen der Atemwege und der Haut.AbstractDentists and dental technicians are subjected to a various and heterogeneous spectrum of activities and related exposures. Not only dermal contact to different working substances and secondary products but also inhalation of aerosols, ultrafine and nano particles are relevant to potential health effects.The measurement of number concentrations of ultrafine particles in the dental office and laboratory of the university dental clinic was carried out using the handheld condensation particle counter (CPC 3007, TSI). This model is capable to count single particles at concentrations as high as 105 pt/cm3 and the lower detection limit is 10 nm.No significant particle concentrations were found during routine dental activities. Short time maxima were detected while using ice spray to prove the sensitivity of the teeth, intraoral application of compressed air and endodontic treatment performed by using open flames.Concentrations of > 400.000 pt/cm3 were documented during working with polymethacrylates associated with dental prosthesis, reduced to 1/20 by local suction. Liquid cooling during drilling procedures of glass ceramic resulted in a reduction of 167.000 to 5.700 pt/cm3 and of 45.000 to 7.000 pt/cm3 while drilling of Zirconium oxide ceramics.During representative activities, particle samples were collected and visualized by SEM and identified as nano particles of Zirconium, Gold and Titanium by EDX-analysis.Significant peak particle concentrations detectable just during special and infrequent activities of dentists and dental technicians require adequate organizational, technical and personal protective measures at the working place in order to prevent occupational diseases of the respiratory system or skin. A potential toxicity of different occupational substances esp. Zirconium and polymethacrylates has to be observed.

Management of shortened dental arches and periodontal health: 5-year results of a randomised trial.

In a multicentre randomised trial (German Research Association, grants DFG WA 831/2-1 to 2-6, WO 677/2-1.1 to 2-2.1.; controlled-trials.com ISRCTN97265367), patients with complete molar loss in one jaw received either a partial removable dental prosthesis (PRDP) with precision attachments or treatment according to the SDA concept aiming at pre-molar occlusion. The objective of this current analysis was to evaluate the influence of different treatments on periodontal health. Linear mixed regression models were fitted to quantify the differences between the treatment groups. The assessment at 5 years encompassed 59 patients (PRDP group) and 46 patients (SDA group). For the distal measuring sites of the posterior-most teeth of the study jaw, significant differences were found for the plaque index according to Silness and Löe, vertical clinical attachment loss (CAL-V), probing pocket depth (PPD) and bleeding on probing. These differences were small and showed a slightly more unfavourable course in the PRDP group. With CAL-V and PPD, significant differences were also found for the study jaw as a whole. For CAL-V, the estimated group differences over 5 years amounted to 0.27 mm (95% CI 0.05; 0.48; P = 0.016) for the study jaw and 0.25 mm (95% CI 0.05; 0.45; P = 0.014) for the distal sites of the posterior-most teeth. The respective values for PPD were 0.22 mm (95% CI 0.03; 0.41; P = 0.023) and 0.32 mm (95% CI 0.13; 0.5; P = 0.001). It can be concluded that even in a well-maintained.patient group statistically significant although minor detrimental effects of PRDPs on periodontal health are measurable.