University of Groningen
Restorative dentistry done digitally
Schepke, Ulf
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2018
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Schepke, U. (2018). Restorative dentistry done digitally: Implementation and evaluation of some digital
tools in contemporary implant dentistry. Rijksuniversiteit Groningen.
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Dentistry is a field-specific domain, and technological innovations from other domains have to be adopted prior to clinical use and applications. For instance, “rapid prototyping” production processes have to be adapted for manufacturing permanent restorations instead of prototypes, which is a challenge for both restorative dentists and dental technicians. These experiences from the dental field can then be transferred to other domains, since individualization of all kinds of final products will most likely become increasingly important in the future. 3D printing, for instance, offers easy personalization in nearly every line of industry that manufactures products.
After analyzing some digital tools in contemporary clinical dental practice, it is not surprising that the decision about whether to be an early adopter of technological innovation or to favor a more conservative approach remains complex. The innovation itself needs to be analyzed by the restorative dentist in detail, prior to investing time, money, and effort. As painfully demonstrated in the clinical study, the risk of clinical failure can be minimized, at best, but never fully excluded beforehand.
Risk assessment, combined with the expected increase in quality of dental care, should always take center stage in the decision-making process. This thesis highlights the fact that complex choices for technological innovations in restorative dentistry should not solely depend on economic requirements. The restorative dentist needs the freedom to make such complex decisions based on his/her professional autonomy along with all the (often insufficient) evidence available, while bearing in mind that, in the end, he/she is the one responsible for the outcome. Here, the dentist must protect the interests of his patients.
Some final, general remarks: A non-scientific understanding of innovation processes might well involve becoming familiar with the “hype cycle” theory, which in turn could help restorative dentists choose the right moment to invest in new technology innovations. According to Fenn and Raskino (2008), technological innovations generally run through five phases: technological trigger, peak of inflated expectations, trough of disillusionment, slope of enlightenment, and finally the plateau of productivity
(figure 1).
For example, current topics of dental technology innovation feature 3D-printed permanent restorations: short-term expectations are high, while midterm results are still lacking. New hype cycles are emerging at a staggering pace.
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Figure 1
Thy hype cycle according to Jackie Fenn and Mark Raskino. Mastering the hype cycle: How to choose the right innovation at the right time. Harvard Business Press. ISBN 978-1-4221-2110-8, 2008.
The restorative dentist has to deal with a dilemma: He/she not only needs to keep up with modern technology in order to be able to offer state-of-the-art care but also needs to identify which tools are unnecessary among the vast range of novelties offered by the industry. This PhD thesis focuses on some aspects of restorative dentistry related to digital production and treatment execution, more specifically to the field of oral implantology, for which the following research questions are posed and answered in this brief summary:
Can zirconia implant single-tooth replacements perform comparably with the gold standard (titanium implants) in terms of bone to implant contact (chapter 2a)?
Do zirconia implant abutments exhibit bulk and/or surface degradation after one year of clinical service (chapters 2b and 2c)?
Do zirconia implant abutments show a decrease in strength after one year of clinical service (chapter 2c)?
Is the standard procedure for bonding Lava Ultimate crowns to zirconia implant abutments efficient (chapter 3a)?
Does the restorative material have an influence on the debonding rate of crowns bonded to zirconia abutments (chapters 3b and 3c)?
Is there a difference in patient appreciation and chair time between digital and conventional impression-taking in implant dentistry (chapter 4)?
Do customized zirconia implant abutments perform better than zirconia stock abutments after one year of clinical service (chapter 5)?
Zirconia implants are relatively new to the dental implant market, while titanium implants are considered the “gold standard.” In chapter 2a, histological and histomorphometrical features of a retrieved, functional zirconia endosseous implant in a human subject were studied. The findings were related to information available from the literature on osseointegration in other explanted zirconia and titanium implants in humans.
A maxillary zirconia implant in a 52-year old male patient (Zv3, Wolfratshausen, Germany) was retrieved and prepared for light microscopic evaluation. It had functioned successfully without objective or subjective concerns for approximately two years. Histological examination demonstrated that most of the screw threads were filled with bone, showing a uniform color, which was in close contact with the zirconia surface. No intervening fibrous tissue layer was observed between the implant and the surrounding bone. In the calcified tissue, many large, rounded osteoblasts and osteocytes were visible. Bone contact measurements measuring from the most coronal aspect until
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the lowest thread revealed a mean percentage of bone to implant contact of 55.8% (SD 3.8%). This is comparable to findings regarding retrieved implants in the literature, although these show a wide range. The histological data were coherent with a well osseointegrated zirconia implant after two years of functional loading. This provides further evidence of the potential of zirconia to osseointegrate
to a more or less similar degree as titanium implants in humans.
Clinical loading and degradation of yttria-stabilized zirconia due to the tetragonal to monoclinic phase transformation is of clinical concern. This may give rise to impaired long-term service of zirconia implant abutments. This was studied in detail in chapter 2b by means of microstructural characterization using Electron Back Scattering Diffraction (EBSD), in turn using zirconia implants abutments that had functioned clinically for a year. The amount and distribution of the monoclinic phase, the grain-size distribution, and crystallographic orientations between tetragonal and monoclinic crystals in 3 mol.% yttria-stabilized polycrystalline zirconia (3Y-TZP) were determined in two different types of nano-crystalline dental abutments, even for grains smaller than 400 nm. An important and novel conclusion is that no substantial bulk degradation of 3Y-TZP dental implant abutments was detected after one year of clinical use. This is a comforting thought, given the millions of zirconia abutments that have been provided in dental offices worldwide.
The results presented in chapter 2c provide additional relief: 23 stock and 23 CAD/CAM customized zirconia implant abutments (ZirDesignTM and AtlantisTM, Dentsply Sirona implants, Mölndal, Sweden)
were retrieved after one year of clinical service. The conical connections were visually inspected and the abutments were compared with excact pristine copies with respect to the surface fraction of monoclinic phase using Raman spectroscopy. Subsequently, their fracture load on static loading was measured by means of a single load-to fracture test ex vivo. Failure analysis was performed using optical and SEM microscopy.
Stock abutments appear to have a better fit. No monoclinic ZrO2volume percentages beyond the detection threshold of 5% were observed in any of the samples. Nevertheless, mean relative fracture loads were 78.8% (SD 29.5%) for stock abutments and 103.9% (SD 15.1%) for CAD/CAM abutments after one year of clinical function. The difference in fracture strength for stock zirconia abutments was statistically significant (P<0.05). So, after one year of clinical service, no substantial tetragonal to monoclinic transformation was observed on the surface of these zirconia abutments. The CAD/CAM customized zirconia implant abutments studied were as strong as their pristine copies, whereas the stock zirconia abutments demonstrated a considerable reduction in fracture strength.
New dental materials are introduced and promoted in the field without extensive clinical testing. Using these materials in a clinical setting might result in unacceptable early failure rates. The purpose of the research presented in chapter 3a was to analyze the bonding of a new dental restorative material to zirconia abutments. Fifty participants seeking single implant treatment were included in a prospective study. Lava Ultimate (LU) (3M ESPE, Seefeld, Germany) crowns were digitally manufactured and extra-orally bonded to either a stock or a customized zirconia abutment by means of a resin composite cement (RelyX Ultimate in combination with Scotchbond Universal, 3M ESPE, Seefeld, Germany), strictly following the manufacturers recommendations. The final restorations were screw-retained to the implants and followed for twelve months. The uncompromised survival
rate of the LU crowns bonded to zirconia abutments after one year of clinical service was only 14% (n=7). Catastrophic failure occurred in 3 cases (6%), whereas debonding failure between LU crowns and zirconia abutments occurred in 80% of the cases (n=40) within the first year of service. LU crowns luted to stock or customized zirconia implant abutments have a poor prognosis, regardless of the abutment type used. In chapter 3b, it was shown that the cement performed well in combination with an alternative restoration material.
Why LU crowns perform so poorly has been a worldwide topic of debate. Most of the crowns described in chapter 3a had loosened, while some had fractured (possibly following loosening). The fragments of three fractured crowns were examined more closely in chapter 3c. The aim of this case series was to identify failure reasons for this CAD/CAM polymer material via fractographic examinations.
The findings underline the debonding of the resin-based crowns from the zirconia implant abutments as being the central reason for fracture. The adhesive interface was identified as the weakest link. Additionally, the hydrolytic stress released from swelling of the resin-based crown and transfer to the luting interface further added to the interfacial stress and most probably contributed to the debonding failure.
Digital impression-making is yet another technological innovation in dental practice. It is supposedly more patient-friendly and less time-consuming than analog techniques, but evidence is lacking to substantiate this assumption. An in vivo, within-subject comparison study was undertaken to examine patient perception and time consumption for two complete-arch impression-making methods: a digital and an analog technique (chapter 4). Fifty participants with a single missing premolar were included. Treatment consisted of implant therapy. Three months after implant placement, complete-arch digital (Cerec Omnicam; Sirona) and analog impressions (individual tray, Impregum; 3M ESPE) were made, and the participant’s opinion was evaluated with a standard questionnaire addressing several domains (inconvenience, shortness of breath, fear of repeating the impression, and feelings of helplessness during the procedure). All participants were asked which procedure they preferred. Operating time was measured with a stopwatch. The differences between impressions made for maxillary and mandibular implants were also compared. The data were analyzed with paired and independent sample t tests, and effect sizes were calculated. Statistically significant differences were found in favor of the digital procedure regarding all subjective domains (P<0.001), with medium to large effect sizes. Digital impression-making for the
restoration of a single implant crown takes less time than analog impression-making. Furthermore, participants preferred the digital scan and reported less inconvenience, less shortness of breath, less fear of repeating the impression, and less of a feeling of helplessness during the procedure.
Finally, in a randomized controlled clinical trial, the potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient-based outcome measurements were studied and presented in chapter 5. Fifty participants with a missing premolar were included and randomly assigned to standard or CAD/CAM customized zirconia abutment therapy.
Statistically significant differences between stock and CAD/CAM customized zirconia abutments
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could not be demonstrated for any of the operationalized variables. The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar was not associated with improvement in clinical performance or patient satisfaction when compared to the use of a stock zirconia abutment. All findings are discussed in chapter 6, the general discussion.
De restauratieve tandarts staat voor een dilemma. Hij/zij moet namelijk op de hoogte zijn van de nieuwste ontwikkelingen om moderne zorg te kunnen bieden, maar moet ook kunnen herkennen welke van de vele innovaties overbodig zijn. In dit proefschrift staat de rol van digitale productie en behandelingen binnen de restauratieve tandheelkunde, en met name de orale implantologie, centraal. In deze korte samenvatting worden de volgende onderzoeksvragen belicht:
Maken zirkonia-implantaten net zo goed botcontact als titanium-implantaten (de gouden standaard) bij enkelvoudige tandvervangingen (hoofdstuk 2a)?
Vertonen zirkonia-implantaat abutments een jaar na plaatsing veroudering in het bulkmateriaal of aan de oppervlakte (hoofdstuk 2b en 2c)?
Nemen zirkonia-implantaat abutments een jaar na plaatsing af in sterkte (hoofdstuk 2c)?
Is de standaardprocedure voor het bevestigen van Lava Ultimate kronen op zirkonia-implantaat abutments effectief (hoofdstuk 3a)?
Is het restauratief materiaal van invloed op de snelheid waarmee kronen, die op zirkonia abutments zijn bevestigd, losraken (hoofdstuk 3b en 3c)?
Is er een verschil in patiëntwaardering en stoeltijd tussen digitale en conventionele afdruknames in de tandheelkundige implantologie (hoofdstuk 4)?
Presteren op maat gemaakte zirkonia-implantaat abutments een jaar na plaatsing beter dan standaard zirkonia-abutments (hoofdstuk 5)?
Het plaatsen van zirkonia-implantaten is een betrekkelijk nieuwe tandheelkundige techniek. Titanium-implantaten worden beschouwd als de gouden standaard. In hoofdstuk 2a worden de histologische en histomorfometrische eigenschappen van een functioneel enossaal zirkonia-implantaat bestudeerd. De resultaten worden vergeleken met literatuurgegevens over osseointegratie van zirkonia- en titanium-implantaten die zijn verwijderd bij mensen.
Bij een 52-jarige mannelijke patiënt werd een maxillair zirkonia-implantaat verwijderd (ZV3, Wolfratshausen, Duitsland) en geprepareerd voor lichtmicroscopisch onderzoek. Het implantaat had circa twee jaar goed gefunctioneerd zonder subjectieve of objectieve problemen. Uit histologisch onderzoek bleek dat in de meeste schroefdraden bot was gegroeid. Het bot had een homogene kleur en maakte goed contact met het zirkonia-oppervlak. Tussen het implantaat en het omringende bot werd geen bindweefsellaag waargenomen. In het gecalcificeerde weefsel waren veel grote, ronde osteoblasten en osteocyten zichtbaar. Uit botcontactmetingen vanaf het bovenste gedeelte tot de onderste schroefdraad bleek dat het gemiddelde percentage bot-implantaatcontact 55.8% bedroeg (SD 3.8%). Dit percentage kwam overeen met de literatuurgegevens over verwijderde
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implantaten, al lopen de waarden in de literatuur uiteen. De histologische gegevens pasten bij een zirkonia- implantaat dat goed geosseointegreerd was na twee jaar functionele belasting. Deze
bevinding ondersteunt de conclusie dat zirkonia-implantaten bij mensen ongeveer dezelfde mate van osseointegratie vertonen als titanium-implantaten.
In de praktijk kan klinische belasting en veroudering van Yttria-gestabiliseerde zirkonia als gevolg van transformatie van de tetragonale naar de monokliene fase een probleem vormen. Dit resulteert mogelijk in een verkorte levensduur van zirkonia-implantaat abutments. Dit onderwerp werd uitgebreid onderzocht in hoofdstuk 2b aan de hand van microstructurele karakterisatie met Electron Backscatter Diffraction (EBSD). Er werd gebruikgemaakt van zirkonia-implantaat abutments die gedurende een jaar klinisch hadden gefunctioneerd. De omvang en verdeling van de monokliene fase, de korrelgrootteverdeling en de kristallografische oriëntatie tussen de tetragonale en monokliene kristallen in 3 mol % Yttria-gestabiliseerde zirkonia-polykristal (3Y-TZP) werden bepaald in twee verschillende typen abutments. Hierbij werd ook rekening gehouden met korrels kleiner dan 400 nm. Er kan geconcludeerd worden dat 3Y-TZP implantaat abutments een jaar
na plaatsing geen aanmerkelijke veroudering in het bulkmateriaal vertonen. Dit is een geruststellende
gedachte, aangezien tandartsen wereldwijd miljoenen zirkonia abutments hebben geplaatst. De resultaten uit hoofdstuk 2c zijn eveneens geruststellend. Een jaar na plaatsing werden 23 standaard en 23 op maat gemaakte CAD/CAM zirkonia-implantaat abutments (ZirDesignTM en
AtlantisTM, Dentsply Sirona implants, Mölndal, Zweden) verwijderd. De conische verbindingen
werden met het oog geïnspecteerd, en de hoeveelheid monoklien zirkonia op de oppervlakte van de abutments werd vergeleken met ongebruikte en identieke exemplaren. Hierbij werd gebruikgemaakt van Raman spectroscopie. Vervolgens werd hun breukbelasting op statische belasting ex vivo gemeten met behulp van een enkelvoudige breuk-op-belasting test. Met behulp van optische microscopie en Scanning Elektronen Microscopie (SEM) werd een foutenanalyse uitgevoerd.
Standaard abutments blijken beter te passen. In geen enkel exemplaar werden monokliene ZrO2 volumepercentages hoger dan de detectiedrempel van 5% gevonden. Toch bedroeg een jaar na plaatsing de gemiddelde relatieve breukbelasting 78.8% (SD 29.5%) voor de standaard abutments en 103.9% (SD 15.1%) voor de CAD/CAM abutments. Het verschil in breuksterkte van standaard zirkonia abutments was statistisch significant (P <0.05). Een jaar na plaatsing werd geen wezenlijke transformatie van de tetragonale naar de monokliene fase waargenomen aan het oppervlak van de zirkonia abutments. De op maat gemaakte CAD/CAM zirkonia-implantaat abutments waren een jaar na plaatsing net zo sterk als de ongebruikte exemplaren, daar waar de standaard zirkonia abutments een aanzienlijke afname in breuksterkte vertoonden.
Nieuwe tandheelkundige materialen worden geïntroduceerd en gepromoot zonder dat ze vooraf uitgebreid klinisch getest zijn. Wanneer deze materialen in een klinische setting worden gebruikt, kan een onacceptabel aantal voortijdige defecten optreden. Het doel van het onderzoek dat in hoofdstuk 3a wordt gepresenteerd was de hechting van nieuw restauratief tandheelkundig materiaal aan zirkonia abutments te analyseren. Vijftig deelnemers die een enkelvoudig implantaat wilden laten plaatsen werden opgenomen in een prospectieve studie. Kronen van het type Lava
Ultimate (LU) (3M ESPE, Seefeld, Duitsland) werden digitaal vervaardigd en extraoraal bevestigd op een standaard of op een op maat gemaakt zirkonia abutment met composietcement (RelyX Ultimate + Scotchbond Universal, 3M ESPE, Seefeld, Duitsland). De aanbevelingen van de fabrikanten werden strikt opgevolgd. De uiteindelijke restauraties waren met schroeven op de implantaten bevestigd en werden gedurende twaalf maanden gevolgd. Slechts zeven (14%) LU kronen die op zirkonia abutments waren bevestigd, waren een jaar na plaatsing in functie (n=7). In drie gevallen (6%) traden ernstige defecten op. In veertig gevallen (80%) waren de LU kronen binnen een jaar na plaatsing losgeraakt van de zirkonia abutments. LU kronen die zijn verlijmd op standaard of op maat gemaakte zirkonia-implantaat abutments hebben een slechte prognose, ongeacht het type abutment. Uit hoofdstuk 3b blijkt dat goede resultaten worden behaald wanneer het cement met een alternatief restauratiemateriaal wordt gecombineerd.
Waarom LU kronen zo slecht presteren is wereldwijd onderwerp van discussie. De meeste van de kronen uit hoofdstuk 3a raakten los, en sommigen braken (mogelijk nadat ze waren losgeraakt). In
hoofdstuk 3c werden de brokstukken van drie gebroken kronen nader onderzocht. Het doel van
deze caseserie was om aan de hand van fractografisch onderzoek te achterhalen waarom defecten optreden in het CAD/CAM polymeermateriaal.
Uit de resultaten komt naar voren dat breuken voornamelijk optreden doordat de kronen op resin-basis losraken van de zirkonia-implantaat abutments. Het adhesief raakvlak bleek de zwakste schakel te zijn. Daarnaast veroorzaakte het hydrolytische opzwellen van de kroon mogelijk stress op het lijmraakvlak. Dit droeg er hoogstwaarschijnlijk aan bij dat de kroon losraakte.
Een andere technologische innovatie in de tandheelkundige praktijk is de digitale afdrukname. Deze techniek zou patiëntvriendelijker en minder tijdrovend zijn dan analoge technieken, maar bewijs voor deze stellingname ontbreekt. In hoofdstuk 4 worden de uitkomsten besproken van een in vivo studie onder vijftig deelnemers bij wie één premolaar ontbrak en die een indicatie voor een implantologische enkeltandsvervanging hadden. Drie maanden na plaatsing van de implantaten werden bij iedere patiënt digitale (Cerec Omnicam, Sirona) én analoge (individuele afdruklepel, Impregum; 3M ESPE) afdrukken van de complete tandboog gemaakt.
De meningen van de patiënten werden geïnventariseerd aan de hand van een standaard vragenlijst met verschillende categorieën (ongemak, kortademigheid, angst voor herhaling van de afdrukname en gevoelens van machteloosheid tijdens de procedure). De deelnemers werd gevraagd aan welke procedure ze de voorkeur gaven. De duur van de procedure werd bijgehouden met een stopwatch. Daarnaast werden de resultaten van de afdruknames voor maxillaire en mandibulaire implantaten met elkaar vergeleken. De gegevens werden geanalyseerd aan de hand van gepaarde en onafhankelijke t-testen, en de omvang van de effecten werd berekend.
Statistisch significante verschillen werden gevonden tussen alle subjectieve categorieën (P <0.001) in het voordeel van de digitale procedure. De omvang van de effecten was gemiddeld tot groot.
Digitale afdrukname voor restauraties van een kroon op een implantaat neemt minder tijd in beslag dan analoge afdrukname. De deelnemers gaven de voorkeur aan een digitale afdrukname, en rapporteerden minder ongemak, minder kortademigheid, minder angst voor herhaling van de afdrukname en minder gevoelens van machteloosheid tijdens de procedure.
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Hoofdstuk 5 presenteert onderzoeksresultaten van een gerandomiseerde gecontroleerde klinischestudie met als doel te onderzoeken of individualisering van zirkonia-implantaat abutments leidt tot een beter behoud van het marginale botniveau. Daarnaast werden diverse klinische en patiëntgerelateerde uitkomstmaten onderzocht. Vijftig deelnemers bij wie een premolaar ontbrak en met een indicatie voor een implantologische enkeltandsvervanging werden in de studie opgenomen. Na de implantologische behandeling werden bij hen op gerandomiseerde wijze standaard dan wel op maat gemaakte CAD/CAM zirkonia abutments geplaatst.
Er konden geen statistisch significant verschillen worden aangetoond tussen de standaard en op maat gemaakte CAD/CAM zirkonia abutments wat betreft de geoperationaliseerde variabelen. Het gebruik van een op maat gemaakte CAD/CAM zirkonia abutment bij een enkelvoudige premolaarvervanging was niet geassocieerd met een verbeterde klinische prestatie of toegenomen patiënttevredenheid vergeleken met het gebruik van een standaard zirkonia abutment.
Tot slot worden in de algemene beschouwing (hoofdstuk 6) alle resultaten besproken. Samenvatting
Der restaurativ tätige Zahnarzt steht vor einem Dilemma. Er oder sie muss sich nicht nur aktiv über neue Entwicklungen und technologischen Fortschritt informieren, um die Patienten am medizinischen Fortschritt teilhaben lassen zu können, sondern er muss auch eine sinnvolle Auswahl treffen, welche der vielen Angebote in der Praxis noch nicht angewendet werden können. In dieser Dissertation wird der Wert einiger digitaler Produktionsverfahren und Behandlungsmöglichkeiten in der restaurativen Zahnheilkunde erörtert, zugespitzt auf die zahnärztliche Implantologie. Es werden die folgenden Fragen diskutiert:
Zeigen Einzelzahnimplantate aus Zirkoniumdioxid im Vergleich zum Goldstandard aus Titanium gleichwertigen Knochenkontakt (Kapitel 2a)?
Sind bei Implantatabutments aus Zirkoniumdioxid nach einem Jahr klinischer Nutzung Alterserscheinungen im Inneren oder an der Oberfläche des Abutmentkörpers messbar (Kapitel
2b und 2c)?
Sind Zirkoniumdioxidabutments nach einem Jahr klinischer Nutzung weniger belastbar als ungebrauchte Kopien (Kapitel 2c)?
Funktioniert die gebräuchliche Verklebung von Lava Ultimate Kronen auch mit Zirkoniumdioxidabutments (Kapitel 3a)?
Hat die Wahl des Restaurationsmaterials einen Einfluss auf die Haltbarkeit der Klebeverbindung dieser mit einem Zirkoniumdioxidabutment (Kapitel 3b und 3c)?
Ist die digitale Abformung in der dentalen Implantologie weniger zeitaufwendig und patientenfreundlicher als die konventionelle Abformung (Kapitel 4)?
Haben individuell gefertigte Zirkoniumdioxidabutments ein Jahr nach Eingliederung einen nachweislichen Vorteil gegenüber Standardabutments aus Zirkoniumdioxid (Kapitel 5)?
Der Gebrauch von Zahnwurzelimplantaten aus Zirkoniumdioxid stellt nach wie vor eine neue Technik dar, Implantate aus Titanium gelten bis heute als Goldstandard. In Kapitel 2a werden die histologischen und histomorphometrischen Eigenschaften eines humanen enossalen Zir-koniumdioxidimplantates untersucht. Die Resultate werden mit Ergebnissen aus anderen humanhistologischen Studien an Titanium- und Zirkoniumdioxidimplantaten verglichen.
Bei einem 52-jährigen Mann wurde ein Zirkoniumdioxidimplantat (ZV3, Wolfratshausen, Deutschland) zusammen mit einer dünnen, zylinderförmigen Schicht des Umgebungsknochens aus dem Oberkiefer entfernt und für die lichtmikroskopische Analyse vorbereitet. Das Implantat hatte zuvor ca. zwei Jahre normal funktioniert, ohne subjektive oder objektive Probleme verursacht zu haben. Im histologischen Bild ergab sich, dass in den meisten Implantatwindungen
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Knocheneinwuchs stattgefunden hat. Der Knochen stellte sich als farblich homogen dar und vermied den Kontakt zur Implantatoberfläche nicht. Bindegewebige Einwucherungen konnten nicht festgestellt werden. In dem kalzifizierten Gewebe wurden viele große, runde Osteoblasten und Osteozyten angetroffen. Der mittlere Knochen-Implantatkontakt (bone to implant contact) am Implantatrand betrug 55,8% (SD 3,8%). Dieser Wert spiegelt in etwa die in der Literatur genannten Werte an explantierten Implantaten wider, obwohl man beobachten kann, dass diese Werte weit auseinanderliegen. Die histologische Analyse passt gut zu einem zwei Jahre lang erfolgreich osseointegrierten Zirkoniumdioxidimplantat. Dieser Befund unterstützt die These, dass Zirkoniumdi-oxidimplantate beim Menschen erfolgreich osseointegrieren.
In der zahnärztlichen Praxis gibt es allerdings Zweifel an der Eignung von Yttria-stabilisiertem Zirkoniumdioxid als Biomaterial aufgrund möglicher Degradation während klinischer Belastung durch kristalline Veränderungen (der sogenannten tetragonal-monoklinen Transformation). Dieser Vorgang könnte möglicherweise für eine verkürzte Lebensdauer von Implantatabutments aus Zirkoniumdioxid sorgen. Dieser Fragestellung widmet sich eine mittels Electron Back Scatter Diffraction (EBSD) durchgeführte mikrostrukturelle Analyse (Kapitel 2b). Die Abutments wurden ein Jahr lang klinisch gebraucht, anschließend aus dem Patientenmund entfernt und analysiert. Untersucht wurden Verteilung und Konzentration der monoklinen Phase, die Verteilung der Kristallgrößen und die kristallographische Orientierung zwischen der tetragonalen und monoklinen Phase in zwei verschiedenartig hergestellten Abutments aus 3 mol.% yttria-stabilized polycrystalline zirconia (3Y-TZP). Interessant und neu ist, dass keine nennenswerte Degradation von 3Y-TZP nach einem Jahr klinischer Nutzung im Inneren des Materials festgestellt werden konnte. Angesichts mehrerer Millionen benutzter Implantatabutments aus Zirkoniumdioxid weltweit ist dies ein beruhigendes Ergebnis.
Auch die Resultate aus Kapitel 2c sorgen für weitere Entspannung: 23 Standardabutments und 23 individuell hergestellte Abutments aus Zirkoniumdioxid (ZirDesignTM und AtlantisTM, Dentsply
Sirona implants, Mölndal, Schweden) wurden nach einem Jahr wieder aus dem Patientenmund entfernt. Die konische Verbindung der Abutments wurde visuell begutachtet und der Anteil monokliner Phase auf der Oberfläche anschließend mittels RAMAN Spektroskopie mit dem einer identischen, unbenutzten Kopie des Abutments verglichen. Anschließend wurde der Unterschied der maximalen Frakturbelastung für jedes Abutmentpaar bei statischer Belastung ex vivo gemessen. Die Schadensanalyse wurde mittels Elektronen- und optischer Mikroskopie durchgeführt. Augenscheinlich ist die Passung von Standardabutments homogener. Auf keinem Abutment wurde monoklines Zirkoniumdioxid oberhalb der Detektionsgrenze von 5% gefunden. Dennoch wurde ein mittlerer Unterschied der maximalen Frakturbelastung vor und nach einem Gebrauchsjahr von 78,8% (SD 29,5%) bei Standardabutments gegenüber 103,9% (SD 15,1%) bei individuell hergestellten Abutments gefunden. Der Unterschied der maximalen Frakturbelastung bei den Standardabutments war statistisch signifikant (P<0,05). Bei keinem der verschiedenen Zirko-niumdioxiabutmenttypen ist substanzielle t-m Transformation an der Oberfläche aufgetreten und die individuell hergestellten Abutments waren ebenso belastbar wie deren ungebrauchten Kopien. Dagegen zeigten die gebrauchten Standardabutments einen beträchtlichen Rückgang der Belastbarkeit im
Vergleich mit den ungebrauchten.
Neue dentale Restaurationsmaterialien können auf dem Markt gelangen, ohne vorher eine ausgiebige klinische Testphase durchlaufen zu haben. Der Gebrauch dieser Materialien kann dann unter Umständen zu unakzeptablen Ausfallquoten führen. In Kapitel 3a wurde das Klebeverhalten von einem neuen Restaurationsmaterial auf Zirkoniumdioxidabutments analysiert. Fünfzig Patienten mit Indikation zur implantologischen Einzelzahnversorgung im Prämolarbereich wurden in einer prospektiven Studie inkludiert. Lava Ultimate Kronen (LU, 3M ESPE, Seefeld, Deutschland) wurden digital hergestellt und gemäß Herstellerangaben extraoral mit entweder Standard- oder individuell hergestellten Zirkoniumdioxidabutments verklebt (RelyX Ultimate und Scotchbond Universal, 3M ESPE, Seefeld, Deutschland).
Die definitiven Abutmentkronen wurden mit dem Implantat verschraubt und zwölf Monate lang klinisch gefolgt. Nur 7 der 50 Abutmentkronen (14%) zeigten noch nach einem Jahr adhäsiven Verbund. 3 Kronen (6%) präsentierten sich während dieser Periode mit einem irreparablen Versagen und 40 Kronen (80%) hatten sich vom Abutment gelöst. An Zirkoniumdioxidabutments geklebte LU Kronen haben eine schlechte Prognose, unabhängig vom gewählten Abutmentdesign.
In Kapitel 3b konnte gezeigt werden, dass der verwendete Adhäsivzement in Kombination mit einem anderen Restaurationsmaterial problemlos funktioniert hat.
Das adhäsive Versagen von LU Kronen hat eine weltweite Debatte ausgelöst. Die Mehrzahl der in Kapitel 3a beschriebenen Kronen hat sich vom Abutment gelöst, während einige Kronen frakturiert waren (möglicherweise nachdem sie sich gelöst hatten). Diese Fragmente wurden eingehend untersucht in Kapitel 3c. Der Zweck dieser Fallserienstudie war via fraktographischer Analyseverfahren mögliche Fehlerursachen aufzuspüren. Die Ergebnisse lassen die Ablösung der Kunststoffkronen vom Abutment als Ursache für die Frakturen vermuten. Der Klebeverbund wurde als Schwachstelle identifiziert. Möglicherweise hat die im Restaurationsmaterial auftretende Volumenzunahme durch hydrolytische Schwellung für den nötigen Stress am Klebeverbund gesorgt. Die digitale Kieferabformung ist eine weitere Innovation in der Zahnarztpraxis. Man unterstellt dieser Technologie mehr Patientenfreundlichkeit und Zeitersparnis verglichen mit der konventionellen Methode, aber bisher ist wenig Literatur zu diesem Thema verfügbar. In Kapitel 4 werden in einer in vivo Studie bei fünfzig Patienten mit Indikation zur implantologischen Einzelzahnversorgung im Prämolarbereich beide Methoden zur Ganzkieferabdrucknahme im selben Patienten miteinander verglichen. Drei Monate nach erfolgreicher Implantation wurden sowohl digitale (Cerec Omnicam, Sirona) als auch analoge Abformungen (Impregum, 3M ESPE) erstellt und die Patienten mittels eines standardisierten Fragebogens befragt zu den Themen Ungemach, Kurzatmigkeit, Angst vor wiederholter Abdrucknahme und Gefühlen von Machtlosigkeit während des Geschehens. Alle Teilnehmer wurden außerdem gefragt, welche Form der Abdrucknahme sie bevorzugten. Die benötigte Zeit für beide Methoden wurde mit einer Stoppuhr gemessen. Unterschiede zwischen Ober- und Unterkiefer wurden ebenfalls analysiert. Die statistische Auswertung geschah mithilfe eines gepaarten, unabhängigen t Tests, außerdem wurde die Effektstärke bestimmt. Für alle Variablen wurden statistisch signifikante Unterschiede zwischen den beiden Modalitäten gefunden mit mittleren bis großen Effektstärken (P<0,001). Die digitale Ganzkieferabdrucknahme zur
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Herstellung von implantatgetragenen Einzelzahnkronen ist weniger zeitaufwändig als die konventionelle Abdrucknahme. Des Weiteren bevorzugten die Patienten die digitale Abformung und berichteten über weniger Ungemach, weniger Kurzatmigkeit, weniger Angst vor Wiederholung und weniger Hilflosigkeit verglichen mit der konventionellen Methode.
Schließlich wird im Kapitel 5 in einer randomisierten und kontrollierten klinischen Studie untersucht, ob die Verwendung von individuell hergestellten Zirkoniumdioxidabutments im Vergleich zu Standardabutments Auswirkungen auf den marginalen Knochenerhalt hat. Zusätzlich wurden mehrere sekundäre klinische Variablen mituntersucht, sowie ein Patientenfragebogen ausgewertet. Fünfzig Patienten mit Indikation zur implantologischen Einzelzahnversorgung im Prämolarbereich wurden zu diesem Zweck inkludiert. Die Behandlungsmodalität (individuell hergestellte Abutments oder Standardabutments) wurde zufällig zugewiesen. Bei der Auswertung konnten keinerlei statistisch signifikante Unterschiede festgestellt werden. Die Verwendung von individuell hergestellten Zirkoniumdioxidabutments zeigte weder klinische Überlegenheit noch waren Patienten zufriedener verglichen mit Standardabutments aus Zirkoniumdioxid. Das Kapitel 6 beinhaltet eine allgemeine Diskussion der gefunden Resultate.
This thesis is the result of the collaboration of many people. Without their help, this book would never have been finished. Some of them were directly involved in the process, and some helped me to focus on this thesis throughout the past 5 years.
I would like to address my special gratefulness to prof. dr. Marco Cune, whose support and energy for the project was never-ending. Beste Marco, there was not a single moment in my whole PhD trajectory when I would have felt under-supervised or left behind. It all started with a fancy drink on a beautiful beach somewhere on the south coast of Portugal, and I am happy that our teamwork will not end with the defense of my PhD thesis. You ask a lot from yourself and this alone was enough motivation for me to go on during difficult periods which I also had to encounter. Thank you very much for being my supervisor and for teaching me much more than conducting and reporting on research. I am extraordinary impressed by your work style and leadership qualities.
I would also like to address my sincere gratitude to all my patients, who were willing to participate in our clinical study. Most of you experienced more inconveniences during the trial than I had foreseen. Thank you very much for your patience. Without you, there would be nothing left but theory in this project, and that is the least thing a dentist would like.
For the financial support that made our research possible I would first of all like to thank the Centre for Dentistry and Dental Hygiene, namely prof. dr. Frank Abbas (former head), dr. Luc van de Sluis (current head), Hans Schulten (finance director) and Henri Lohr (Chef de Clinique). Also, I would like to thank our two main sponsors for the project, Dentsply Implants (now Dentsply Sirona) and
3M. I believe that this thesis is a good example that collaboration between industry and academia
can be successful for both parties, even though short-term interests might differ.
I am especially glad with my second and third promotor, the dream team. Prof. dr. Henny Meijer, beste Henny, thank you very much for being my second promotor. You are a very experienced researcher and you were always willing to help when I had those “very unique” questions. No need to worry – you had seen them before. Problems appeared to be smaller after sessions with you. The same counts for my third promotor, prof. dr. Gerry Raghoebar. Beste Gerry, thank you for your prompt and encouraging feedback and your excellent performance in setting up the clinical study. Thanks to your important impulses we got the project going. It would be an honor for me to continue working together with the dream team.
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I feel honored to have prof. dr. Hugo de Bruyn, prof. dr. Arie Jan van Winkelhoff and prof. dr.
Gert Meijer as members of the Reading Committee. Beste Hugo, Arie Jan, Gert: I know that all of
you are very busy people. Thank you very much for taking the time to review this book and for being part of the corona.
Dear prof. dr. Albert Feilzer, dr. Ralph van Brakel, dr. Joerd van der Meer: Beste Albert, thank you very much for sharing your expertise with me. It is an honor to have you in the corona. Beste Ralph, thank you for coming to Groningen. It feels safe when you and Marco are around, especially when I am lost somewhere in the mountains. Beste Joerd, your attitude towards technology and your deep understanding have been a source of inspiration for me throughout the whole project. Actually it was you who encouraged me to write and publish my first case report.
I would like to thank prof. dr. Jan Wilschut for being the Chair of the Committee of Deans. We met more or less exactly when I started my PhD trajectory and we have had vivid intellectual exchange since then. Thank you, Jan, for your open mind and fresh view in our conversations. Sometimes I am afraid you are half a dentist by now.
One of my favorite moments of my research was when prof. dr.-ing. Ulrich Lohbauer from Erlangen University contacted me unexpectedly and offered a collaboration. I was positively surprised that there are people out there who do not only read what we have published but are actually even interested in it. Dear Uli, meanwhile we have published two papers together, even though we have not (really) met yet. Hopefully this will change soon. The impact of this collaboration is a lot more meaningful than however calculated ranking points.
I would like to thank dr. Václav Ocelík for the collaboration and help with the EBSD part of the thesis. Vasek, you have been the driving force behind that project and the way you supervised Hamid at the Department of Applied Physics at Zernike serves as an excellent example of cooperation between faculties. I would also like to thank dr. David Vainchtein for his valuable ideas. David, it was always very pleasant to have you in the team. I would like to address my special thanks also to prof. dr. Jeff
de Hosson for making this collaboration possible.
I am very grateful to prof. dr. Wesley Browne and dr. Shaghayegh Abdolahzadeh. Dear Wesley and Shaya, it was a pleasure to work with you on the RAMAN project. I am very impressed by the efficient way of working in the Stratingh Institute for Chemistry. I hope you will appreciate further collaboration.
I would like to thank prof. dr. Thomas Palstra and dr. Jacob Baas for their help in finding my way through the Zernike complex and for their help with the X-ray diffraction.
awesome crew 205, I unfortunately do not see you anymore on a regular basis. I miss our sessions where you showed me your freshest and most exciting photo-material. Let’s continue to support each other, because nobody has time to do everything alone. One of the coolest things about research is that it gets bigger by sharing.
Wouter, unfortunately you do not work at the CTM anymore, but luckily people always meet twice.
Or more often in our case. Thank you for your considerable help with this thesis. I am looking forward to realizing all the other ideas we have together.
Charlotte and Wim, I would like to thank you for performing the implant therapy for this project at
“our” location. Both of you have been role models and helped me with uncountable tips and tricks on how to finish a PhD.
Linda & Linda, you are surely not the same person, but you work perfectly together. Thank you,
Linda, for maintaining my research agenda and thoroughly doing the patient administration. I am really happy that you took over this important part. And I would like to thank you, Linda, for organizing the logistics around the implant therapy.
Patrick, Bernd, Alette and Rudi, together Elysee Dental Groningen. Thank you so much not only
for the secure production of all 3 original sets of restorations for our 50 patients but also for your patience and willingness to fabricate an extra set and performing all reparations during the clinical trial.
I would like to thank Tally and her colleagues for the perfect assistance at the Maxillofacial Surgery Department. I am really impressed by your professional way of working and the fine atmosphere that was abundantly present every time I had the pleasure to work with you.
Team Learn & Earn: Jitske and Michelle, you have been the research assistants from the first hour.
Thank you for your creativity in dealing with my compulsion to control everything and for your valuable ideas. Thies & Joey, we had so much fun together that you decided to go on unpaid. I hope that you never (really) regretted that decision. Thank you for your contribution to this thesis.
Phillip and Jantien, you have not yet graduated, but that will happen sooner than you can imagine
(from a retrospective point of view of course). I would be happy to be able to continue working with you and I would like to thank you both for your various support with my research. Hamid, your extraordinary talent made you one of the few with a publication by the time of your graduation. It was a pleasure to work with you. I would also like to thank Eva, Nicole, Matthijs and Karel for helping me with this research project.
Petra and Tiny, thank you so much for supporting me with all kinds of different questions and
requests I had. Without you, our department would not be such a pleasant place to work.
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I would like to address my special thanks to Jeroen and the whole ICT team of sector F. I am hopefully not your best client, am I? There are two unsolved mysteries regarding my two working laptops: A) things don’t work when I try to solve them by myself; B) they do work when you fixed them at your place but they do not work downstairs. Thank you for your enormous patience with me.
Gladine, Manon and Grietje, thank you very much for all the time that you have been part of the
treatment team. You know my working style better than I do sometimes.
I would like to thank Thea, Steven and his crew, Erwin and his crew, especially Dennis and Peter for many helping hands during the past couple of years.
Teatske and Tineke, thank you for always being there for us when we have a question or need
anything.
The concept of this thesis became a manuscript during the first week of August in 2017 on Schiermonnikoog. I would like to thank you, Tatjana, for your hospitality and the valuable input for this thesis, including the title.
Nikos, thank you for introducing me to the CTM and for the critical discussions about the society we
had back then. It was you who first got me to the idea of obtaining a PhD.
Berend, you know that I appreciate your skills and your way of accurate working, but I would like to
emphasize that I am happy to have you as a person in our team. I am looking forward to the coming projects with you.
To all members of the former Department of Fixed and Removable Prosthodontics and Biomaterials, thank you for the pleasant cooperation during the last couple of years. I think we can
proudly say that we stopped at the top.
Martijn, do you need some interesting literature about that?
Special thanks for support and collaboration to dr. Hans vP, dr. Jan T, Rolf dR, Peter dB, Edzard,
Dick P, dr. Geerten-Has T, dr. DJ Hunter, dr. Menke S, Riemer and Enne during the past 5 years.
Many thanks to the whole Skillslab crew, namely Alie, Renate, Alex, Siem and Rina. It’s a pleasure to work with you in a team. I am looking very forward to our goal to make the Skillslab great again (it has never been small by the way).
RCS crew, thank you for the opportunity to exchange thoughts on restorative dentistry with you.
It’s interesting to realize how differently one can plan a treatment with the same goals in mind. The discussions kept me reflecting on my own decision-making.
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Praktijkteam dr. James Huddleston Slater, it’s a pleasure to work with you. Thank you for adopting
me within no-time. It already feels a bit like a family.
Menno, thank you for your solution-minded way of thinking. It’s always a great pleasure to discuss
the technical aspects of the treatment plan with you, and beside your profound knowledge of digital processes in restorative dentistry you are a fantastic person. Let’s continue our collaboration. Thanks to the whole GTL team.
I would like to thank some of my teachers whose answers taught me asking questions: Ingo
Thalmann, dr. Stefan Wentaschek, dr. Hengstenberg, dr. Dietrich, prof. dr. Scheller and dr. Alfons Kreissl.
Boudewijn, thank you for your help and creative input for various smaller and bigger issues that
came up during the project. You have a very intensive way of listening. Now I would like to listen to you again. You are a very special person.
Lara, you made me move to Groningen a long time ago. That you designed this book is simply
beautiful. Thank you.
Beste Eric, you are not my first paranymph, you are in first place a very special and true friend to me. I will never forget and always be grateful for the day we met in front of the skillslab in Mainz, during the summer course of 2000. Thanks, by the way, for being my personal career manager, among so many other things.
Beste Sjoerd, my second paranymph: you promised me some 5 years ago to stay at the CTM till at least the day that I have obtained my PhD. Since then our collaboration grew continually and today I seek your advice whenever I can. All of a sudden we ended up more as friends than colleagues. I admire your enthusiasm while giving lectures and your warm wisdom in looking at people. I should reconsider the date of my defense.
Awesome crew 205, you guys helped me with not getting lost in my research activity. Even though
we are by now quite a research-minded group I would not want to miss the diverse and controversial discussions about all the other stuff that exists. Thank you, Dik, for changing my perspective on a regular basis. Empirical evidence is certainly not enough to understand the whole world. I am very impressed by the depths of knowledge you have. Frits, you are such a fine person, your hugs are more team-forming than any staff-day can be. You always cheer me up when I am down, I am happy you are there. Carline, can you miss someone who never existed? I am sure I would if you weren’t part of the 205 crew. Even when you are grumpy (yes, sometimes even Carline can be grumpy) I am sure the rest of us agrees with me that it’s still pleasant to have you around. Not to mention the other 99% of the time. Maurits, thank you for your sincere enthusiasm for research and the discussions we
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Acknowledgements
had on various topics. I believe that you are incredibly talented not only in performing research, but also with your skilled hands. You have already convinced me that some of those “hopeless” molars can be enduringly saved. Christiaan, I appreciate a lot the relaxed and sincere way of your work. You don’t seem to stress yourself, therefore you search for a sustainable solution that enables you to work more efficiently in the future. And you absolutely do not keep those solutions for yourself. Thank you very much for really being so generous.
Know your neighbors: Selma, you already spread your talented wings two years ago to fly away
from the RUG and I felt very honored to be your paranymph. Now I realize what a lousy one I was. Thanks for forgiving me. Luckily we’ll go snowboarding soon, maybe I can pay you back in Jägermeister. Anne, I am happy to have talked to you at a fire evacuation exercise in the summer of 2013. Most certainly you don’t remember that day, but after that we became friends. Luckily you came back from your London experience to beautiful Groningen. You helped me a lot during the final stage of my PhD, every time I needed good advice from an “out of dentistry” perspective you were there. Thank you! Sigrid, you are the coolest researcher I know. I really like your topic (even though I don’t understand a word) and when I listen to you I sometimes think science can be really fun. I am looking forward to pushing you through the PhD like you did with me. Don’t forget to bring swimwear!
I would also like to thank the Becker family as well as Lilli and Floris for always giving me a good feeling when being in Berlin. Johannes G, thank you for being such a wonderful person.
Homies: nothing can beat homies and you know that. Thank you for your continuous support. If
anyone made half a Dutchman out of me it’s you. I am grateful for every single one of you, be sure! I had a great time in Boschlust with you guys and you always knew how to balance my work-life ratio. That also counts for Spanish dentists living there by the way. Special thanks to Peter, Hannah and Wytse.
Dear Kusum, I would like to thank you for helping me through the sometimes stressful times with your positive thoughts and your very valuable point of view. Can’t wait for the next mind-wellness session with you.
I would like to thank some of my oldest friends form Buchholz where I grew up. Inga, Beedle, Freed,
Sven, Steffi, Ösen, Soeren, Susanne, thank you for being there.
And I want to thank my friends that I made during my study time in Mainz: Johannes, Michi and
Anne P, Stephan, Simon, Nelly, Paddy, Julia, Eric’s brother Hanno, Johannes D, Dennis, Steffi & Andi, Sandra, Anja S, Barbara, Moritz & Kathrin, the neighbors and many more.
Finally I learned to drill in Frankfurt, we had so much fun there. Thank you Ayça, Tina and Esther for still being an important part of my life.
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I would like to address my special thanks to you, Lena, and to your many fantastic friends, that I would love to take over if you wouldn’t need them.
The good thing about family is that they will always stay your family, regardless what you do or don’t do. Thank you very much, Arne, for being “our” big brother. The opportunity to make use of your Kiez-castle literally every time we wanted to has been priceless to Anu and me. Next time we come for fun only: parts of this thesis were written at your place by the way. Karen, unfortunately Stuttgart is at quite a distance from Groningen, but that makes your visits even more special to me. Thank you for still being my big supporting sister. Dorit, you have been a very good listener and your advice is worth a lot. You are a person full of spirit. Thank you for sharing that. Bengt, you have always been the anchor of my life. Our long relationship has been incredibly dynamic, and there is no human being that knows me better than you do. I would also like to thank Elizabeth, Hannah &
Joel for welcoming Anu and me any time in Gothenburg. It always feels a bit like home.
Mama (†) and Papa, everything I have I got from you in a way. You were always there for me. For you
AKD BU (not the boat of course) is everything, and it always feels that way. Thank you so much. You are the best dad on the planet.
Anu, your support has been uncountable. Thank you for all your patience with me during the past
years. Luckily for me you had all the understanding for the situation due to your own dissertation a year ago. I would like to thank you especially for this last year. You really pampered me all day long and it might not be easy for me to get used to normality. Your smiles make me happy when you catch me doing other things instead of working towards my deadlines. But let’s not care about normality. I am so much looking forward to spending more time with you, the whole world is open for us. And please don’t ever stop with writing those post-its for me Y.
Curriculum Vitae
Ulf Schepke was born on February 12th 1979 in Kiel, Germany. In 2005 he graduated as a dentist at the Johannes Gutenberg University (JGU) in Mainz, Germany and one year later defended his doctoral thesis titled: “The discoloring effects of food on the color stability of esthetic brackets” at the Department of Orthodontics at the JGU. Subsequently, he worked full time as an assistant dentist for two years in Frankfurt/Main in Germany in the private clinic of dr. med. dent. Alfons Kreissl. Since 2008 he works at the University Medical Center Groningen, the Netherlands as a teacher and researcher at the Center for Dentistry and Oral Health. Currently he holds the position of the Head of Preclinic, next to his clinical activities in the private office of dr. Huddleston Slater.
