All-ceramic Fixed Partial Denture. Studies on aluminum oxide- and zirconium dioxide-based

Keramiska material har länge använts inom tandvården för framställning av tandersättningar. Keramer har många goda egenskaper som gör dem särskilt lämpliga att använda i munnen. Viktigast är kanske att de är biokompatibla, det vill säga att de inte skadar omgivande vävnader, att de inte ger upphov till allergier eller utgör någon risk för förgiftning och att de inte bryts ner i den miljö i vilken de är tänkta att fungera. Särskilt intressanta bland keramerna är porslin som förutom nämnda fördelar har optiska egenskaper som liknar tandemaljens. Detta har bidragit till att dentalt porslin sedan många år används för att ge olika typer av tandersättningar ett ytskikt med tandliknade utseende. Broar är fastsittande tandersättningar som används när man behöver ersätta förlorade tänder. Det idag mest använda materialet för framställning av tandbroar är så kallad "metallkeramik", en kombination av en metallegering, ofta högädel, och ett porslin. Den viktigaste rollen som metallegeringen spelar är att förstärka porslinet så att det motstår de belastningar som förekommer i munnen. Metallegeringar har emellertid flera nackdelar. Dels finns det en risk att patienten är allergisk mot någon av legeringsmetallerna om de läcker ut. Metallers optiska egenskaper begränsar dessutom möjligheterna att få tandersättningarna så tandlika som man många gånger önskar, vilket försvårar förutsättningarna att framställa tandersättningar med gott estetiskt resultat. Sedan mer än 40 år har forskning pågått för att utveckla helkeramiska material som har egenskaper som tillåter framställning av broar utan metallunderstöd. Olika metoder och material har testats, men resultaten har många gånger varit nedslående; broar har spruckit efter en allt för kort tid i funktion. Inte förrän 1985 kom ett material som verkade kunna fungera och som hade teoretiska hållfasthetsvärden långt över de traditionella keramernas. Nittonhundranittiotvå presenterades flera laboratoriestudier med samma slutsats - nu fanns ett material som verkade vara tillräckligt starkt för att kunna användas till broframställning; glasinfiltrerad aluminiumoxid. Man betonade dock att kliniska långtidsstudier behövdes innan materialet kunde rekommenderas för allmänt bruk. Föreliggande arbete består av 5 delarbeten, samtliga rörande helkeramiska broar eller material som används i broarna. Delarbete 1, 3 och 5 är laboratoriestudier medan delarbete 2 och 4 är kliniska studier. I delarbete 1 undersöktes dels vilken inprovningsmetod som ger högst hållfasthet hos porslin (göra bron helt färdig på laboratoriet alternativt att prova den i munnen som halvfabrikat innan bron färdigställs), dels vilken typ av tillslipning man bör göra av tänderna som skall bära bron för att få högst brohållfasthet (s.k. skulderpreparation alternativt chamferpreparation (hålkälsprofil). Delarbete 2 är en klinisk 5-årsuppföljning av broar framställda i glasinfiltrerad aluminiumoxid och delarbete 3 jämför hållfastheten hos 2 olika bromaterial (aluminiumoxid och zirkoniumdioxid). Delarbete 4 är en klinisk 2- årsuppföljning av broar framställda i zirkoniumdioxid och slutligen delarbete 5 jämför helkeramiska broars hållfasthet beroende på om de är förankrade med tänder eller tandimplantat. Utöver dessa delarbeten finns en sammanställning av kliniska resultat från delarbete 2 och 4 efter 11±1 år (glasinfiltrerad aluminiumoxid) respektive 3 år (zirkoniumdioxid). Slutsatserna från avhandlingen är att små broar baserade på aluminiumoxid kan framställas med acceptabelt kliniskt resultat, men att hållfastheten över tid inte är lika bra som för motsvarande broar i metallkeramik. Zirkoniumdioxidbaserade broar med storlek upp till 5 tänder uppvisar lyckandefrekvenser motsvarande metallkeramik inom ramen för den tid föreliggande studie pågått. Laboratorieavsnitten i avhandlingen ger följande slutsatser: Inprovning av porslin i mun på patient bör inte göras innan glansbränning av porslinet gjorts. Vidare bör skulderpreparation väljas framför chamferpreparation för att motstå höga belastningar i bettet. Zirkoniumdioxid är starkare än aluminiumoxid, särskilt efter förbelastning, men ytporslinet på en zirkoniumoxidkrona spricker vid ungefär samma belastning som en aluminiuoxidkrona spricker genom båda skikten (både kärna och ytporslin). Slutligen antyder resultaten i delarbete 5 att helkeramiska broar bör kunna göras på implantat med minst lika bra hållfasthet som på naturliga tänder. Resultaten från laboratoriestudierna behöver emellertid bekräftas i kliniska studier innan metoden kan rekommenderas för allmänt bruk.Background: The development of refined, tougher, and stronger ceramic core materials in recent years has led to the wider use of new, strong all-ceramic systems based on oxide ceramics. Results from in-vitro studies investigating the use of oxide ceramics in shorter all-ceramic fixed partial dentures (FPDs) have been positive, but clinical studies and additional in-vitro studies are needed to confirm the advisability of such procedures. Aims: One aim of this thesis was to investigate whether aluminabased and zirconia-based material systems are adequate for use in shorter (≤ fiveunit) FPDs and to evaluate the clinical results. Additional aims were to investigate how to achieve optimal fracture strength in an all-ceramic FPD by varying the try-in procedure, the cervical shape of the abutments, and the support of the FPD (abutment teeth or dental implants). The final aim was to compare the strength of a zirconia material system with that of an alumina equivalent with known long-term clinical performance. Materials and Methods: Two clinical studies investigating one aluminabased and one zirconia-based material system were performed. Twenty posterior, three-unit FPDs (glass-infiltrated alumina) were followed for 5 years and 20 three–fiveunit FPDs (HIP zirconia) for 2 years. Long-term follow-ups were made after 11+/-1 (glass-infiltrated alumina) and 3 years (HIP zirconia). In three in-vitro studies, the following variables were investigated: 1a) the flexural strength of porcelain specimens depending on whether they were exposed to saliva before the glaze firing (n=20) or first after the glaze firing (n=20), 1b) the fracture strength of three-unit all-ceramic FPDs (glass-infiltrated alumina) supported by abutments prepared with cervical shoulder preparations (n=9) and abutments with cervical chamfer preparations (n=9), 2) the fracture strength of crowns (n=30) made of a zirconia material system (densely sintered zirconia) and of crowns (n=30) of an alumina material system (densely sintered alumina) that had undergone three different pre-treatment modalities (water storage only; water storage and cyclic pre-loading; water storage, cyclic pre-loading, and thermocycling), 3) the fracture strength of all-ceramic FPDs (densely sintered alumina) supported by simulated teeth (n=12) or by dental implants (n=12). Results: The success rate of the clinical alumina study was 90% after 5 years. Six (+/-1) years later (after a total of 11+/-1 years), the success/survival rate was 65%. In the second clinical study, the success rates of the 2- and 3-year follow-ups were 100%. In the three in-vitro studies, the following results were found: 1a) the mean flexural strength of the specimens in the group that was exposed to saliva first after glazing was significantly higher (P < 0.001) than that of the specimens in the group that was exposed to saliva before glazing, 1b) the FPDs luted on shoulder preparations resisted higher loads than the FPDs luted on chamfer preparations (P = 0.051), 2) total fractures were more frequent in the alumina than in the zirconia group (P < 0.001), 3) FPDs loaded on implants resisted higher loads (mean = 604 N, SD=184 N ) than FPDs loaded on abutment teeth (mean= 378 N, SD=152 N, P = 0.003). Conclusions: This thesis justifies the use of shorter alumina- (≤ three-unit) and zirconia-based (≤ five-unit) FPDs as the clinical results are acceptable. The clinical performance of alumina is, however, not as good as that of comparable high-gold alloy based porcelain-fused-to-metal FPDs concerning fracture resistance. Within the limitations of the in-vitro studies: Saliva exposure of porcelain before glaze firing should be avoided to optimize the strength of the porcelain. Shoulder preparations can be beneficial for the strength of all-ceramic FPDs compared to chamfer preparations, as can support by dental implants compared to abutment teeth. The fracture mode of alumina crowns (total fractures) differs from that of zirconia crowns (veneer fractures), suggesting that the zirconia core is stronger than the alumina core

Bond strength between different bonding systems and densely sintered alumina with sandblasted surfaces or as produced

The traditional zinc phosphate cementation technique for crowns and fixed partial dentures (FPDs) is based on mechanical retention where the geometry of the prepared tooth provides retention for the restoration. In clinical situations where mechanical retention is compromised or regarded insufficient, a bonding system can be used to provide retention. This study investigates whether bond strengths of different bonding systems to densely sintered high-strength alumina ceramics are sufficient. One hundred twenty pairs of industrially manufactured specimens--one block and one cylinder-shaped disc of densely sintered alumina--were used. The cementation surfaces of the blocks were sandblasted with 110-microm aluminium oxide while the cementation surfaces of the discs were left untreated, as produced. The pairs were then bonded with one of six different bonding systems. Each bonding group of 20 samples was randomly divided into thermocycled and non-thermocycled subgroups (n=10). Both subgroups were stored 1 week in distilled water (37 degrees C). During this week, the thermocycled subgroup underwent 5000 thermocycles (5 degrees C-55 degrees C). Following pre-treatment, the specimens were loaded until fracture in a universal testing machine to determine shear bond strength. Data were analysed using student's t-test and a one-way ANOVA. Fractured interfaces were examined under a light microscope to classify the failure mode of the debonded area as adhesive, cohesive, or a combination of the two. The highest bond strengths, achieved with two of the bonding systems, were significantly higher than the remaining bonding systems, irrespective of pretreatment--(p>0.001). The predominant failure mode for both treated and untreated surfaces was adhesive. Two of the six tested bonding systems achieved sufficient shear bond strength to densely sintered alumina. Furthermore, recommendations on whether to use surface-treated or as produced densely sintered alumina must be based on which bonding system is being used

Ten-Year Follow-Up of Implant-Supported All-Ceramic Fixed Dental Prostheses : A Randomized, Prospective Clinical Trial

PURPOSE: The aim of this study was to evaluate the long-term clinical performance of and patient satisfaction with implant-supported all-ceramic fixed dental prostheses (FDPs) and to compare two different all-ceramic systems, Denzir (DZ) and In-Ceram Zirconia (InZ). MATERIALS AND METHODS: A total of 18 patients received 25 partial FDPs; 13 DZ, and 12 InZ. RESULTS: Of these patients, 17 attended the 10-year follow-up. None of the restorations had fractured. Fractures of the veneering porcelain were observed in nine patients; two from the InZ group and seven from the DZ group. All FDPs were in use, and all patients were fully satisfied with the treatment. CONCLUSION: Results from this long-term follow-up suggest that implant-supported all-ceramic FDPs are an acceptable treatment alternative

Implant-supported full-arch zirconia-based mandibular fixed dental prostheses. Eight-year results from a clinical pilot study.

Abstract Objective. The purpose of this pilot study was to evaluate the long-term clinical performance of implant-supported full-arch zirconia-based fixed dental prostheses (FDPs). Materials and methods. Ten patients received full-arch zirconia-based (Cercon) mandibular FDPs supported by four implants (Astra Tech). Nine patients received 10-unit FDPs and one patient received a 9-unit FDP. The FDPs were cemented onto individually prepared titanium abutments and were evaluated at baseline and after 12, 24, 36 and 96 months. Results. Nine patients attended the 8-year follow-up. None of the restorations showed bulk fracture, all FDPs were in use. Fractures of the veneering porcelain were, however, observed in eight patients. A total of 36 out of 89 units (40%) showed such fractures. Patient satisfaction was excellent despite the veneering material fractures. Conclusion. Results from this 8-year pilot study suggest that implant-supported full-arch zirconia-based FDPs can be an acceptable treatment alternative

Five-year follow-up of implant-supported all-ceramic FDPs. A randomized clinical trial

Objectives: The purpose of this study was to evaluate the clinical performance of two- to five-unit implant-supported all-ceramic restorations and to compare the results of two different all-ceramic systems, Denzir® (DZ) and In-Ceram Zirconia® (InZ). Methods: Eighteen patients were treated with a total of 25 two- to five-unit implant-supported fixed dental prostheses. Nine patients were given restorations of the DZ system and the other nine were given restorations of the InZ system. The restorations were cemented with zinc phosphate cement onto customized titanium abutments and were evaluated after one, three and five years. Results: At the five-year follow-up, all restorations were in function; none had fractured. Superficial cohesive (chip-off) fractures were, however, observed in 9 of the 18 patients (11 of 25 restorations). Sixteen units in the DZ group (9 of 13 restorations) and 3 in the InZ group (2 of 12 restorations) had chip-off fractures. The difference between the two groups regarding frequency of chip-off fractures was statistically significant (P<0.05 at FDP level and P<0.001 at unit level). Conclusion: The results suggest that all-ceramic implant-supported fixed dental prostheses of two- to five-units may be considered a treatment alternative. The DZ system as used in this study, however, exhibits an unacceptable amount of veneering porcelain fractures and thus cannot be recommended for the type of treatment evaluated in this trial. Poor compatibility or problems with the bond mechanisms between veneer and framework could not explain the chip-off fractures. Factors concerning veneering porcelain need to be further evaluated

All-ceramic multi-unit implant-supported fixed dental prostheses : A prospective clinical study

The development of high-strength oxide ceramic materials has led to increased interest in all-ceramic fixed dental prostheses (FDPs). Success rates reported in clinical studies on such reconstructions are close to those of porcelain fused to metal (PFM) FDPs. These reconstructions however, are still of limited size and have so far only concerned FDPs supported by natural teeth. Objectives: The purpose of this study was to evaluate the clinical performance of mutli-unit all-ceramic FDPs supported by dental implants. Methods: Ten patients received all-ceramic FDPs designed according to the Cercon® technique and supported by four AstraTech implants in the lower jaw. Nine patients received ten-unit prostheses and one patient received a nine-unit FDP. The FDPs were cemented with Panavia F2.0 onto preparable titanium abutments. The FDPs were evaluated at baseline, twelve, twenty-four and thirty-six months. The surface and marginal integrity were rated according to the California Dental Association (CDA) quality assessment system. Results: At the three-year follow up all FDPs were in use and all patients reported that they were fully satisfied with the treatment. None of the reconstructions had fractured. Superficial cohesive, chip-off, fractures of the veneering porcelain were, however, observed in nine patients. A total of 34 of 99 units (34%) showed such chip-off fractures. Corresponding results for the twelve-month and twenty-four month follow-ups were 14% and 19% respectively. Most patients were unaware of the fractures, some fractures were adjusted by polishing but no FDPs were in need of replacement. Conclusion: Results from this three-year study suggest that multi-unit all-ceramic implant-supported FDPs designed according to the Cercon® technique may be considered a treatment alternative. Better understanding of the factors behind chip-off fractures is necessary togehter with long-term follow-up studies before the material and technique can be recommended for general use

A prospective study of implant-supported full-arch yttria-stabilized tetragonal zirconia polycrystal mandibular fixed dental prostheses : three-year results

PURPOSE: The development of high-strength oxide ceramic materials has led to increased interest in all-ceramic fixed dental prostheses (FDPs). Success rates reported in clinical studies for all-ceramic FDPs based on high-strength oxide ceramic materials reportedly approach those of porcelain-fused-to-metal FDPs. These reconstructions, however, are still of limited size and have mainly concerned FDPs supported by natural teeth. The purpose of this study was to evaluate the clinical performance of multiunit all-ceramic FDPs supported by dental implants. MATERIALS AND METHODS: Ten patients received mandibular yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) FDPs manufactured according to the Cercon technique and supported by four Astra Tech implants. Nine patients received 10-unit FDPs and one patient received a 9-unit FDP. The FDPs were cemented with Panavia F 2.0 onto individually prepared titanium abutments. The FDPs were evaluated at baseline and after 12, 24, and 36 months. RESULTS: At the 3-year follow-up, all FDPs were in use, and all patients were fully satisfied with their treatment. None of the reconstructions had fractured. Superficial chip-off fractures of the veneering porcelain were, however, observed in nine patients (34 of 99 units, 34%). CONCLUSION: Results from this 3-year study suggest that implant-supported full-arch Y-TZP FDPs manufactured according to the Cercon technique should be viewed as a treatment alternative cautiously. A better understanding of the factors resulting in chip-off fractures is needed, together with longer follow-up studies involving larger numbers of patients, before the material and technique can be recommended for general use

Use of Abutment-teeth vs. Dental Implants to Support All-ceramic Fixed Partial Dentures : An In-vitro Study on Fracture Strength

The aim of the present in-vitro study was to compare the fracture strength of all-ceramic Fixed Partial Dentures supported by tooth-analogues and periodontal membrane with the same supported by dental implants. As ceramics are highly brittle, they cannot withstand deformations of more than 0.1% without fracturing. Hence, when planning an all-ceramic FPD, it is essential to evaluate abutment sup-port, as the fracture strength of all-ceramic constructions depends on the stability of the support to reduce strain in the beam of the prosthe-sis. The support provided by implants differs, however, from the sup-port provided by natural teeth as the implants are anchored directly in the bone with no intermediate tissue. One question that arises is whether strain and stress in the prosthesis are lower when the prosthe-sis is loaded on implants compared to natural teeth and hence if all-ceramic FPDs benefit from implant support. Twenty-four three-unit all-ceramic FPDs-12 supported by two dental implants and 12 by two tooth-analogues serving as end abutments-were made. All FPDs were subjected to preloading in a preloading procedure and subsequently subjected to load until fracture occurred. Load at fracture were regis-tered and comparisons between the two groups were made. The loads at fracture were statistically significant higher in the group supported by implants compared to the group supported by tooth-analogues (p = 0.003). Within the limitations of this in-vitro study, the following con-clusions can be drawn: All-ceramic fixed partial dentures can be used in combination with dental implants. The solid support gained from implants might thus be beneficial for the outcome of such treatment due to decreased strain and stress levels in the prosthesis when loaded on implants compared to when loaded on natural teeth. Clinical stud-ies are, however, needed to confirm these findings as there are more factors that influence the final clinical outcome

15 Years of Clinical Experience with Procera® Alumina

This paper reviews the long history and background development of technical, laboratory and clinical applications of Procera® technology for the fabrication of restorations on teeth and implants. Current clinical practice is considered and long-term results presented