Laboratory validation of a new gas-enhanced dentine liquid permeation evaluation system

Aim: To validate a new automated dentine permeability testing platform based on pressure change measurements. Methodology: A split chamber was designed allowing for concomitant measurement of fluid permeation and pressure difference. In a first test, system reliability was assessed by interposing a solid metal disk, embedded composite resin disks, or teeth by consecutively measuring eight times under standardized conditions. Secondly, the repeatability and applicability of the method was tested in a dentine wound model by using intact third molars: Class I (2 × 5mm) and a full occlusal preparation as well a ceramic restoration were consecutively performed and repeatedly measured eight times each. In the last test, the system detection limit as well correlation between gas pressure difference and liquid permeation were evaluated: Again, third molars were used and occlusal preparations of increasing size (2 × 5, 3 × 5, 4 × 5, and 5 × 5mm and full occlusal preparations, respectively) were made. Data was analyzed for the linearity of measurement, and R 2 values were calculated. Results: The embedding procedure allowed for perfect separation of the two chambers, and no significant variation in repeated measurements of evaluated samples for the respective treatments (p = 0.05) was found. The detection was 0.002hPa/min for the pressure slope and 0.0225μl/min for the fluid infiltration, respectively. The saline volume was highly correlating to the gas pressure changes (R 2 = 0.996, p < 0.0001). Conclusions: The presented method is a reliable and exact tool to assess dentine permeability by nondestructive and repeatable measurements. Clinical relevance: This method is suitable for measurements and comparison of the effectiveness of dentine wounds sealing materials

Saumavuodon kontrolli hammaslääketieteessä – onnistumisen edellytys

Saumavuodon kontrolli hammaslääketieteessä – onnistumisen edellytys Hammaslääketieteen kaikessa korjaavassa hoidossa yhdistetään eri materiaaleja toisiinsa esim. hammaspaikka hampaan kiilteeseen ja hammasluuhun eli dentiiniin tai hammasimplantin kyseessä ollen eri metalliset osat toisiinsa. Materiaalien saumakohdat muodostavat heikon kohdan korjaavan hoidon pitkäiskestolle ja tarjoavat bakteereille kiinnittymiskohdan. Tämän vuoksi mahdollisimman hyvän saumatiiviyden saavuttaminen on olennaisen tärkeä kaikissa hammaslääketieteessä käytetyissä materiaaleissa. Käsillä olevan väitöstutkimuksen tarkoituksena oli kehittää saumavuotoa testaava menetelmä, jota voitaisiin soveltaa hammaslääketieteellisessä materiaalitutkimuksessa. Menetelmän kehitys ja testaustyö on toteutettu Zurichin yliopiston hammaslääketieteen laitoksella. Uuden testausmenetelmän perusideana on mitata paine-eroa kahden kammion välillä, kun testattava näyte on asetettu kammioiden väliin. Materiaalin täydellisen saumatiiviyden ollessa kyseessä kammioiden välisen paine-eron tulisi säilyä muuttumattomana. Samanaikaisesti näytteen läpi kulkevan nesteen tilavuus mittaus kertoo näytteen saumatiiviydestä. Täydellisen tiiviyden ollessa kyseessä nesteen virtausta ei tapahdu. Ensimmäisen tutkimuksen tarkoituksena oli tutkia uuden menetelmän mittausten toistettavuutta, havaintotarkkuutta sekä nestemäärän ja paineen muutosten välistä yhteyttä ajan funktiona. Näytteinä käytettiin hampaita, joihin oli tehty erisuuruisia dentiiniin ulottuvia hammaspaikkoja. Toisessa tutkimuksessa käytettiin testausmateriaalina poistettuja viisauden-hampaita, joihin tehtiin standardoitujen kokoiset paikat ja jotka täytettiin eri paikkausmateriaaleilla ja -menetelmillä. Saumatiiviyden tutkimuksessa uutta menetelmää verrattiin pyyhkäisy-elektronimikroskoopilla (SEM) sekä fuksiini-värin imeytymisellä saataviin tulosiin. Juurihoitotutkimuksessa käytettiin saumatiiviyden tutkimisessa joko yksi- tai monijuurisia hampaita. Hampaisiin tehtiin juurentäytteet ja näitä verrattiin juurikanavan tilavuuteen. Kahdessa viimeisessä tutkimuksessa tutkimusmateriaalina käytettiin kolmen eri valmistajan hammasimplantteja, jotka olivat kooltaan lähes samanlaisia, mutta poikkesivat rakenteeltaan. Implantin ja sen päällysrakenteen saumatiiviyttä tutkittiin uuden menetelmän lisäksi kemiallisella ja bakteeritestillä sekä altistamalla implantit lämmölle ja mekaaniselle rasitukselle. Kehitetyn menetelmän havaittiin tuottavan samat tulokset toistomittauksissa, olevan havaintotarkkuudeltaan hyvä sekä havaitsevan nestemäärän ja paineen muutosten välisen yhteyden ajan funktiona luotettavasti. Tulokset osoittivat myös, että testausmateriaalien kiinnitys oli luotettava ja mittausten toistaminen tuotti lähes identtiset tulokset. Sidostamisen tärkeys estää sauman vuotamista tuli selvästi esille tutkittaessa eri paikkausmateriaaleja ja -menetelmiä. Tiiviin juurikanavan täytön merkitys etenkin monijuurisissa hampaissa tuli selvästi esille yhteytenä juurikanavan täytön laadun ja sauman vuodon välillä. Eri valmistajien implanttijärjestelmät osoittivat toimivan samalla tavalla molemmilla menetelmillä tutkittaessa ja sekä staattisessa että dynaamisessa testissä. Yhteenvetona voidaan todeta, että väitöskirjatyössä kehitetty saumatiiviyttä testaava menetelmä on luotettava ja korreloi hyvin aikaisemmin käytettyjen menetelmien kanssa.In dentistry, the rehabilitation treatment utilizing different materials, results in combination of different materials with each other e.g. Different filling material placed in a tooth to substitute a missing part in contact enamel and dentin, or in the case of a dental implants were two parts joined together. Where the materials joint, the possibility to create an interface where the bacteria can attach or goes through in an uncleansable area is high. It is therefore important and essential to achieve a tight seal whenever dental materials are applied. The present doctoral thesis was aimed to develop a microleakage-testing method that could be applied to dental materials research. Development and validation of the method has been implemented at the University of Zurich, Institute of Dentistry. The new testing method basic idea is to measure the difference in pressure between two chambers where the test sample is held in between the chambers. If the sample is completely tight, the pressure difference between the chambers should remain unchanged. At the same time the fluid volume passing through the sample indicates the sample tightness. In case the sample is tight, the liquid flow does not occur. The purpose of the first study was to validate the new testing method by means of reproducibility, detection accuracy as well as the relationship between the pressure change and the permeated fluid volume over time. Teeth samples were used, in which a different exposed dentin surface areas had been established. In another study, the test samples used were wisdom-teeth with standardized preparation size and location. Teeth were restored with different restoration materials and techniques and then were tested for their tightness with the new method. In this study, the new method was compared with a Scanning electron microscope (SEM) and fuchsin dye penetration tests. Root canal leakage study either in single- or multi-rooted teeth was tested for in the third study. The root canal filling sealability was compared to the remaining unfilled root canal volume. The last two studies utilized implants from three different manufacturers. The implants were almost identical in size, but differed in design. The implants and their corresponding abutments were examined in addition to the new method with molecular and bacterial leakage tests to establish a comparison with traditional known tests. In the second implants leakage study, the implants were exposed to thermo-mechanical stress, simulating intra-oral conditions. The developed method was found to produce the same results for repeated measurements of the same sample. A good correlation between the measured pressure change and the detected penetrating fluid volume amount of fluid over time could be established. The importance of bonding to prevent leakage was clearly revealed through testing various repair materials and techniques. Significance of the root canal filling quality, especially in multi-rooted teeth, was clearly revealed once correlating the root filling quality of the root filling to the leakage detected. Different manufacturers Implant demonstrated to perform in the same way for both testing methods applied in the investigation (namely, the new method and the bacterial leakge test), and for both under static as well dynamic conditions. In summary, the developed method for testing leakage, is reliable and correlates well with the methods previously used

Three root canals in the mesiobuccal root of maxillary molars: case reports and literature review

INTRODUCTION The knowledge of root canal anatomy is essential to ensure a successful outcome of surgical and nonsurgical root canal treatment. The aims of this article were to present 2 cases of maxillary molars with 3 mesiobuccal root canals and to review the available literature on this anatomic variation. METHODS The first case described a nonsurgical root canal treatment of tooth #16 in a 29-year-old man with the aid of a dental operating microscope. In the second case, an extracted maxillary right first molar was scanned by a micro-computed tomographic system and reconstructed 3-dimensionally using modeling software. RESULTS In both cases, the mesiobuccal root had 3 canals (type 3-2 in case I and type 3-3 in case II), whereas the distobuccal and palatal roots had a single canal. The literature review showed that the overall incidence of 3-canaled mesiobuccal roots in maxillary molars ranged from 1.3%-2.4% and that the most common root canal configuration was type 3-2. CONCLUSIONS Clinicians should always anticipate the presence of extra canals in maxillary molars and use all the available tools to locate and treat these

Impact of dynamic loading on the implant-abutment interface using a gas-enhanced permeation test in vitro

Purpose: To assess implant leakage under static conditions as well as during and after dynamic loading. Materials and methods: Implants (Astra Tech (A), Biomet 3i (B) and Nobel Biocare (C)) were evaluated for leakage (n=8/group). Testing to assess the gas pressure change over time (hPa/min) and infiltrated fluid volume, was performed in a Gas Enhanced Permeation Test (GEPT) to qualify embedding. Implant apexes were then drilled, abutments were mounted and resin build-ups were fabricated. GEPT was reassessed. Samples were afterward mounted in a computer-controlled masticator while tested to bacterial leakage, they were daily observed for turbidity. Samples were then reassessed using GEPT. Dunnett's and Fisher's exact tests were utilized to compare implant and to analyze bacterial leakage. Results: Significant differences in GEPT values were shown after loading (p=0.034). Leakage resistance was best for B when compared to C (p=0.023). Samples with higher GEPT values demonstrated earlier bacterial leakage, occurring after 1 or 2 days (A=4, B=0, C=6) and showing favorability for implant system B (p=0.009). Conclusion: Implants leaking under static conditions had increased potential for bacterial leakage under dynamic conditions. As strongly correlating to sophisticated analytical methods, GEPT is a promising technique for assessing the overall implant system leakage resistance

Laboratory validation of a new gas-enhanced dentine liquid permeation evaluation system

AIM: To validate a new automated dentine permeability testing platform based on pressure change measurements. METHODOLOGY: A split chamber was designed allowing for concomitant measurement of fluid permeation and pressure difference. In a first test, system reliability was assessed by interposing a solid metal disk, embedded composite resin disks, or teeth by consecutively measuring eight times under standardized conditions. Secondly, the repeatability and applicability of the method was tested in a dentine wound model by using intact third molars: Class I (2 × 5 mm) and a full occlusal preparation as well a ceramic restoration were consecutively performed and repeatedly measured eight times each. In the last test, the system detection limit as well correlation between gas pressure difference and liquid permeation were evaluated: Again, third molars were used and occlusal preparations of increasing size (2 × 5, 3 × 5, 4 × 5, and 5 × 5 mm and full occlusal preparations, respectively) were made. Data was analyzed for the linearity of measurement, and R (2) values were calculated. RESULTS: The embedding procedure allowed for perfect separation of the two chambers, and no significant variation in repeated measurements of evaluated samples for the respective treatments (p = 0.05) was found. The detection was 0.002 hPa/min for the pressure slope and 0.0225 μl/min for the fluid infiltration, respectively. The saline volume was highly correlating to the gas pressure changes (R (2) = 0.996, p < 0.0001). CONCLUSIONS: The presented method is a reliable and exact tool to assess dentine permeability by nondestructive and repeatable measurements. CLINICAL RELEVANCE: This method is suitable for measurements and comparison of the effectiveness of dentine wounds sealing materials

Influence of the internal anatomy on the leakage of root canals filled with thermoplastic technique

OBJECTIVES: The aim of this paper is to evaluate the influence of the internal anatomy on the leakage of root canals filled with the thermoplastic technique. MATERIALS AND METHODS: The upper central incisors (UCI) and mesial roots of the lower molars (MRLM) (n = 12 each) were tested regarding leakage using the gas-enhanced permeation test (GEPT) after root filling. The quality of the root fillings was assessed using micro-computed tomography (μCT) by superimposing scans before and after treatment to calculate unfilled volume. The calculated void volume was compared between the groups and correlated to the measured leakage values. Data were analyzed using t test and Pearson's correlation tests (p < 0.05). RESULTS: The mean void volume did not differ between UCI and MRLM (13.7 ± 6.2% vs. 14.2 ± 6.8%, respectively). However, significantly more leakage was evident in the MRLM (p < 0.001). While the leakage correlated highly to the void volume in the MRLM group (R = 0.981, p < 0.001), no correlation was found in UCI (R = 0.467, p = 0.126). CONCLUSION: MRLM showed higher leakage values, which correlated to the void volume in the root canal fillings. CLINICAL RELEVANCE: Care should always be taken while doing root canal treatments, but attention to teeth with known/expected complex root canal anatomy should be considered

Radicular Intracanal Splitting Forces and Cutting Efficiency of NiTi Rotary Versus Reciprocating Systems: A Comparative In Vitro Study

This study aimed to compare the intracanal lateral force and cutting efficiency associated with two engine-driven nickel-titanium (NiTi) systems during root canal shaping. Bovine single-rooted teeth models were assembled to a custom-made splitting force measuring platform while being endodontically treated with rotary (ProTaper Gold [PTG]) or reciprocal systems (WaveOne Gold [WOG]) by two clinicians. The cutting efficiency test was run for each group by a free-falling endomotor on dentin discs for 3 min. The resulting force, files, and stroke force peaks were recorded. Data were analyzed by the Shapiro-Wilk test and ANOVA. Statistical significance was set at alpha = 0.05. Intracanal lateral forces (p &lt; 0.01), cutting efficiency (p &lt; 0.01), and time efficiency (p &lt; 0.01) were significantly different between the NiTi groups. The maximum lateral splitting force was detected using the PTG shaping full-length file (S1) and during the WOG final stroke. Thus, caution is advised when reciprocating single-file systems approach the apical third or when using a large taper and wide-diameter rotatory instruments. The WOG had significantly less maximum horizontal splitting force and significantly greater cutting efficiency but less time efficiency than the PTG system

Acoustic hypochlorite activation in simulated curved canals

INTRODUCTION: It was the goal of this study to compare different NaOCl activation schemes regarding a desired and an untoward outcome. Ultrasonic tips and a currently marketed sonic system were used in conjunction with a 2.5% sodium hypochlorite solution. Necrotic pulp tissue dissolution in simulated accessory canals and transportation of the main canal were assessed. METHODS: Epoxy resin models (10 per group) with a curved simulated main root canal and two simulated accessory canals filled with necrotic bovine pulp tissue were irrigated passively with one of three ultrasonic setups (straight stainless steel files, prebent stainless steel files, or nickel-titanium tips) or a sonic device in conjunction with a plastic tip. Activation was performed four times for 30 seconds with replenishment of the NaOCl solution in between. All the files/tips had a 2% taper and a 0.15-mm tip diameter according to the manufacturer. Data from superimposing and analyzing digital photos before and after treatment were statistically analyzed using one-way analysis of variance followed by Bonferroni's correction for multiple comparisons (alpha < 0.05). RESULTS: Passive ultrasonic irrigation (PUI) in all the groups dissolved significantly more tissue than sonic activation (p < 0.05). No detectable canal transportation with sonic activation was observed. The difference in this outcome was not significant compared with ultrasonically activated nickel-titanium tips, whereas the straight stainless steel files caused significantly more ledging compared with these setups (p < 0.05). CONCLUSION: Under the current conditions, PUI with a nickel-titanium tip promoted superior tissue-dissolving effects over sonic irrigant activation while maintaining simulated canal anatomy

Radicular Intracanal Splitting Forces and Cutting Efficiency of NiTi Rotary Versus Reciprocating Systems: A Comparative In Vitro Study

This study aimed to compare the intracanal lateral force and cutting efficiency associated with two engine-driven nickel-titanium (NiTi) systems during root canal shaping. Bovine single-rooted teeth models were assembled to a custom-made splitting force measuring platform while being endodontically treated with rotary (ProTaper Gold [PTG]) or reciprocal systems (WaveOne Gold [WOG]) by two clinicians. The cutting efficiency test was run for each group by a free-falling endomotor on dentin discs for 3 min. The resulting force, files, and stroke force peaks were recorded. Data were analyzed by the Shapiro-Wilk test and ANOVA. Statistical significance was set at alpha = 0.05. Intracanal lateral forces (p p p < 0.01) were significantly different between the NiTi groups. The maximum lateral splitting force was detected using the PTG shaping full-length file (S1) and during the WOG final stroke. Thus, caution is advised when reciprocating single-file systems approach the apical third or when using a large taper and wide-diameter rotatory instruments. The WOG had significantly less maximum horizontal splitting force and significantly greater cutting efficiency but less time efficiency than the PTG system