Dental cone beam CT : An updated review

Cone beam computed tomography (CBCT) is a diverse 3D x-ray imaging technique that has gained significant popularity in dental radiology in the last two decades. CBCT overcomes the limitations of traditional twodimensional dental imaging and enables accurate depiction of multiplanar details of maxillofacial bony structures and surrounding soft tissues. In this review article, we provide an updated status on dental CBCT imaging and summarise the technical features of currently used CBCT scanner models, extending to recent developments in scanner technology, clinical aspects, and regulatory perspectives on dose optimisation, dosimetry, and diagnostic reference levels. We also consider the outlook of potential techniques along with issues that should be resolved in providing clinically more effective CBCT examinations that are optimised for the benefit of the patient.Peer reviewe

Minimum size and positioning of imaging field for CBCT scans of impacted maxillary canines

Objectives In children and adolescents, cone-beam computed tomography (CBCT) is frequently used for localization of unerupted or impacted teeth in the anterior maxilla. CBCT causes a higher radiation dose than conventional intraoral and panoramic imaging. The objective was to analyze the location of impacted canines in a three-dimensional coordinate and thereby optimize the CBCT field-of-view (FOV), for radiation dose reduction. Materials and methods Location of 50 impacted maxillary canines of children under 17 years was retrospectively evaluated from CBCT scans. The minimum and maximum distances of any part of the right- and left-side canines to three anatomic reference planes were measured to assess the adequate size and position of a cylindrical image volume. Results A cylinder sized 39.0 (diameter)x33.2 (height) mm, with its top situated 13.8 mm above the hard palate, its medial edge 8.4 mm across the midline, and anterior edge 2.5 mm in front of the labial surface of maxillary central incisors fitted all the analyzed canines. Conclusions In this sample, the FOV required for imaging maxillary impacted canines was smaller than the smallest FOV offered by common CBCT devices. We encourage development of indication-specific CBCT imaging programs and aids to facilitate optimum patient positioning.Peer reviewe

Minimum size and positioning of imaging field for CBCT-scans of impacted lower third molars : a retrospective study

Background Cone-beam Computed Tomography (CBCT) is widely used for preoperative 3D imaging of lower third molars. Hence, for this imaging indication, the present study aimed to define the minimum field-of-view (FOV) size and its optimum placement, to decrease radiation exposure, and highlight the need of computer-assisted FOV centering technique for dental CBCT devices. To facilitate proper placement of image field, lower second molar was chosen as reference. Methods The retrospective study included 50 CBCT-scans of 46 patients with mean age of 34 years. Based on the lower second molar, a three-dimensional coordinate was formed and the location of mandibular canal (MC) and the dimensions and locations of the lower third molars, and possible associated pathological findings were assessed. Accordingly, the FOV size and position for third-molar imaging were optimized, while ensuring encompassment of all relevant structures. Results The minimum cylindrical volume, covering lower third molars and MC, was 32.1 (diameter) x 31.6 (height) mm, placed in relation to the second molar crown, top 2.2 mm above cusp tips, anterior edge 6.7 mm in the front of the most distal point of the crown, and lingual edge 7.9 mm on the medial side of the lingual wall. Conclusions The optimized FOV for lower third molars was smaller than common standard small FOVs. We recommend using FOV volume 3.5 null x 3.5 cm for third molars without associated pathology. Accurate FOV protocols are essential for development of new CBCT-devices with computer-assisted and indication-specific FOV placement.Peer reviewe

Jäljitettävyyttä ja vastuullisuutta palvelevan elinkaaripohjaisen ympäristötiedon hallintamallin määrittely ja käytön kehittäminen elintarvikeketjussa

HierarchyNet -loppuraportt

Timing of dental development in osteogenesis imperfecta patients with and without bisphosphonate treatment

Peer reviewe

Minimum size and positioning of imaging field for CBCT-scans of impacted lower third molars: a retrospective study

Background: Cone-beam Computed Tomography (CBCT) is widely used for preoperative 3D imaging of lower third molars. Hence, for this imaging indication, the present study aimed to define the minimum field-of-view (FOV) size and its optimum placement, to decrease radiation exposure, and highlight the need of computer-assisted FOV centering technique for dental CBCT devices. To facilitate proper placement of image field, lower second molar was chosen as reference.Methods: The retrospective study included 50 CBCT-scans of 46 patients with mean age of 34 years. Based on the lower second molar, a three-dimensional coordinate was formed and the location of mandibular canal (MC) and the dimensions and locations of the lower third molars, and possible associated pathological findings were assessed. Accordingly, the FOV size and position for third-molar imaging were optimized, while ensuring encompassment of all relevant structures.Results: The minimum cylindrical volume, covering lower third molars and MC, was 32.1 (diameter) × 31.6 (height) mm, placed in relation to the second molar crown, top 2.2 mm above cusp tips, anterior edge 6.7 mm in the front of the most distal point of the crown, and lingual edge 7.9 mm on the medial side of the lingual wall.Conclusions: The optimized FOV for lower third molars was smaller than common standard small FOVs. We recommend using FOV volume 3.5∅ × 3.5 cm for third molars without associated pathology. Accurate FOV protocols are essential for development of new CBCT-devices with computer-assisted and indication-specific FOV placement.</p

Signature of circulating small non-coding RNAs during early fracture healing in mice

Fracture healing is a complex process with multiple overlapping metabolic and differentiation phases. Small non-coding RNAs are involved in the regulation of fracture healing and their presence in circulation is under current interest due to their obvious value as potential biomarkers. Circulating microRNAs (miRNAs) have been characterized to some extent but the current knowledge on tRNA-derived small RNA fragments (tsRNAs) is relatively scarce, especially in circulation.In this study, the spectrum of circulating miRNAs and tsRNAs was analysed by next generation sequencing to show their differential expression during fracture healing in vivo. Analysed tsRNA fragments included stress-induced translation interfering tRNA fragments (tiRNAs or tRNA halves) and internal tRNA fragments (i-tRF), within the size range of 28–36 bp. To unveil the expression of these non-coding RNAs, genome-wide analysis was performed on two months old C57BL/6 mice on days 1, 5, 7, 10, and 14 (D1, D5, D7, D10, and D14) after a closed tibial fracture.Valine isoacceptor tRNA-derived Val-AAC 5′end and Val-CAC 5′end fragments were the major types of 5′end tiRNAs in circulation, comprising about 65 % of the total counts. Their expression was not affected by fracture. After a fracture, the levels of two 5′end tiRNAs Lys-TTT 5′ and Lys-CTT 5′ were decreased and His-GTG 5′ was increased through D1-D14. The level of miR-451a was decreased on the first post-fracture day (D1), whereas miR-328-3p, miR-133a-3p, miR-375-3p, miR-423-5p, and miR-150-5p were increased post-fracture. These data provide evidence on how fracture healing could provoke systemic metabolic effects and further pinpoint the potential of small non-coding RNAs as biomarkers for tissue regeneration.</p

Multiple targets identified with genome wide profiling of small RNA and mRNA expression are linked to fracture healing in mice

Long-bone fracture is a common injury and its healing process at the fracture site involves several overlapping phases, including inflammation, migration of mesenchymal progenitors into the fracture site, endochondral ossification, angiogenesis and finally bone remodelling. Increasing evidence shows that small noncoding RNAs are important regulators of chondrogenesis, osteogenesis and fracture healing. MicroRNAs are small single-stranded, non-coding RNA-molecules intervening in most physiological and biological processes, including fracture healing. Angiogenin-cleaved 5' tRNA halves, also called as tiRNAs (stress-induced RNAs) have been shown to repress protein translation. In order to gain further understanding on the role of small noncoding RNAs in fracture healing, genome wide expression profiles of tiRNAs, miRNAs and mRNAs were followed up to 14 days after fracture in callus tissue of an in vivo mouse model with closed tibial fracture and, compared to intact bone and articular cartilage at 2 months of age. Total tiRNA expression level in cartilage was only approximately one third of that observed in control D0 bone. In callus tissue, 11 mature 5'end tiRNAs out of 191 tiRNAs were highly expressed, and seven of them were differentially expressed during fracture healing. When comparing the control tissues, 25 miRNAs characteristic to bone and 29 miRNAs characteristic to cartilage tissue homeostasis were identified. Further, a total of 54 out of 806 miRNAs and 5420 out of 18,700 mRNAs were differentially expressed (DE) in callus tissue during fracture healing and, in comparison to control bone. They were associated to gene ontology processes related to mesenchymal tissue development and differentiation. A total of 581 miRNA-mRNA interactions were identified for these 54 DE miRNAs by literature searches in PubMed, thereby linking by Spearman correlation analysis 14 downregulated and 28 upregulated miRNAs to 164 negatively correlating and 168 positively correlating miRNA-mRNA pairs with chondrogenic and osteogenic phases of fracture healing. These data indicated that tiRNAs and miRNAs were differentially expressed in fracture callus tissue, suggesting them important physiological functions during fracture healing. Hence, the data provided by this study may contribute to future clinical applications, such as potential use as biomarkers or as tools in the development of novel therapeutic approaches for fracture healing.</p

Evaluation of the Biocompatibility of Poly (ortho ester), Copolymer of ε-caprolactone/D,L-lactide and the Composite of Copolymer of ε-caprolactone/D,L-lactide and Tricalciumphosphate as Bone Filling Material

The purpose of this series of studies was to evaluate the biocompatibility of poly (ortho) ester (POE), copolymer of ε-caprolactone and D,L-lactide [P (ε-CL/DL-LA)] and the composite of P(ε-CL/DL-LA) and tricalciumphosphate (TCP) as bone filling material in bone defects. Tissue reactions and resorption times of two solid POE-implants (POE 140 and POE 46) with different methods of sterilization (gamma- and ethylene oxide sterilization), P(ε-CL/DL-LA)(40/60 w/w) in paste form and 50/50 w/w composite of 40/60 w/w P(ε-CL/DL-LA) and TCP and 27/73 w/w composite of 60/40 w/w P(ε-CL/DL-LA) and TCP were examined in experimental animals. The follow-up times were from one week to 52 weeks. The bone samples were evaluated histologically and the soft tissue samples histologically, immunohistochemically and electronmicroscopically. The results showed that the resorption time of gamma sterilized POE 140 was eight weeks and ethylene oxide sterilized POE 140 13 weeks in bone. The resorption time of POE 46 was more than 24 weeks. The gamma sterilized rods started to erode from the surface faster than ethylene oxide sterilized rods for both POEs. Inflammation in bone was from slight to moderate with POE 140 and moderate with POE 46. No highly fluorescent layer of tenascin or fibronectin was found in the soft tissue. Bone healing at the sites of implantation was slower than at control sites with the copolymer in small bone defects. The resorption time for the copolymer was over one year. Inflammation in bone was mostly moderate. Bone healing at the sites of implantation was also slower than at the control sites with the composite in small and large mandibular bone defects. Bone formation had ceased at both sites by the end of follow-up in large mandibular bone defects. The ultrastructure of the connective tissue was normal during the period of observation. It can be concluded that the method of sterilization influenced the resorption time of both POEs. Gamma sterilized POE 140 could have been suitable material for filling small bone defects, whereas the degradation times of solid EO-sterilized POE 140 and POE 46 were too slow to be considered as bone filling material. Solid material is difficult to contour, which can be considered as a disadvantage. The composites were excellent to handle, but the degradation time of the polymer and the composites were too slow. Therefore, the copolymer and the composite can not be recommended as bone filling material.Tutkimuksen tausta Kasvojen ja leukojen alueella luupuutoksia voi syntyä trauman, tulehdusten ja synnynnäisten epämuodostumien seurauksena. Kasvainten poiston jälkeen tarvitaan myös luuta korvaamaan menetettyä kudosta. Luuta voidaan menettää myös hampaiden kiinnityskudossairauksissa sekä hampaiden poistojen seurauksena. Nykyisin luupuutosten korvaamiseen käytetään potilaan omaa luuta, toisesta henkilöstä saatua luuta tai erilaisia luuta korvaavia materiaaleja. Suu- ja leukakirurgiassa käytetään useimmiten potilaan omaa luuta korvaamaan kudospuutosta. Luusiirteitä voidaan ottaa luuston eri kohdista mm. suoliluusta, kylkiluusta, sääriluusta sekä ala- tai yläleuasta. Lisäksi voidaan käyttää erilaisia vieraan henkilön luusta valmistettuja luuvalmisteita sekä kalsiumfosfaattiyhdisteitä, bioaktiivista lasia sekä erilaisia polymeerejä. Henkilön omaa luuta käytettäessä vaatii kirurginen toimenpide enemmän aikaa ja saattaa aiheuttaa luovutuskohdan kipua. Seurauksena voi olla myös hermovaurio. Luusiirteen koko saattaa myös pienentyä merkittävästi asettamisen jälkeen. Kalsiumfosfaattiyhdisteiden, bioaktiivisen lasin ja erilaisten polymeerien käsiteltävyys on joskus hankalaa eivätkä ne ole yhtä hyviä luuta korvaavina materiaaleina kuin potilaan oma luu. Tämän vuoksi on luuta korvaavien materiaalien kehittäminen tärkeää. Näillä on tiettyjä etuja verrattuna henkilön omaan luusiirteeseen. Materiaalin saatavuus ei ole rajoitettu, valmiste on heti käyttövalmiina ja potilas välttää toisen leikkauskohdan kivun ja epämukavuuden. Tällä tavoin saavutetaan myös kustannussäästöjä. Elimistössä hajoavia polymeerejä on kehitetty jo yli 30 vuoden ajan. Niitä voidaan käyttää silloin, kun elimistössä tarvitaan väliaikaisesti keinotekoista materiaalia korvaamaan, lisäämään tai tukemaan omaa kudosta. Kudoksen parantuessa hajoaa elimistölle vieras materiaali ja korvautuu vähitellen omalla kudoksella. Elimistölle vieras materiaali aiheuttaa kuitenkin aina kudosreaktion, joka tulisi tarkasti määrittää ennen materiaalin käyttämistä luun korvikkeena. Tutkimuksen tavoite Tutkimuksen tavoitteena oli arvioida kahden elimistössä hajoavan polymeerin sopivuutta luupuutosten täyttömateriaaliksi. Tehdyssä työssä tutkittiin näiden polymeerien aiheuttamia kudosreaktioita ja hajoamisaikaa. Menetelmät Koemateriaaleina käytettiin kahta erilaista polymeeria. Ensimmäinen polymeeri oli kiinteä poly (orto esteri) (POE 140 ja POE 46), joka oli steriloitu kahdella eri menetelmällä (gamma- ja etyleenioksidisterilointi). Toinen polymeeri oli tahnamainen ε-kaprolaktoni/laktidi-kopolymeeri, joko sellaisenaan tai seostettuna trikalsiumfosfaatilla (komposiitti). Komposiitissa A oli kopolymeerin ja trikalsiumfosfaatin suhde 50:50 ja komposiitissa B 27:73. Tutkimus suoritettiin koe-eläinmalleilla. Luunäytteet tutkittiin histologisesti ja radiologisesti ja pehmytkudosnäytteet histologisesti, immunohistokemiallisesti sekä elektronimikroskooppisesti. Tulokset POE 140 aiheutti lievästä kohtalaiseen tulehdusreaktion luussa ja sen hajoamisaika oli kahdeksan viikkoa gammasteriloiduilla polymeerilla ja 13 viikkoa etyleenioksidisteriloidulla polymeerilla. POE 46 aiheutti kohtalaisen tulehdusreaktion luussa ja sen hajoamisaika oli yli 24 viikkoa. Gammasteriloitu POE hajosi nopeammin kuin etyleenioksidisteriloitu POE. Kopolymeeri ja komposiitit aiheuttivat kohtalaisen tulehduksen luukudoksessa. Kopolymeerin ja komposiitti B:n hajoamisaika oli yli vuoden ja komposiitti A:n hajoamisaika oli yli neljä kuukautta. Kaikki tutkitut polymeerit ja komposiitit aiheuttivat ns. vierasesinereaktion. Solunulkopuolisten glykoproteiinien, tenaskiinin ja fibronektiinin esiintyvyys todettiin suhteellisen alhaiseksi. Elektonimikroskooppisesti arvioituna oli sidekudoksen rakenne normaali. Johtopäätökset Kiinteä gammasteriloitu POE 140 voisi sopia luudefektien täyttömateriaaliksi lyhyen hajoamisajan ja sen aiheuttaman lievän/kohtalaisen tulehdusreaktion vuoksi. Kiinteä materiaali oli kuitenkin hankala käsitellä ja asettaa luupuutosalueelle. Kopolymeerin hajoamisaika oli liian pitkä ja käsiteltävyys huono. Molemmat komposiitit olivat helppoja käsitellä. Niiden hajoamisaika oli kuitenkin liian pitkä sekä luussa että pehmytkudoksessa. Komposiitit aiheuttivat kohtalaisen tulehdusreaktion luussa. Kopolymeeriä tai komposiitteja ei voi suositella luupuutosten täyttömateriaaleiksi.Tulevaisuudessa elimistössä hajoavien ja ei-hajoavien polymeerien kehittyminen sekä kantasoluhoidot avaavat täysin uusia mahdollisuuksia leukojen alueen luupuutosten hoitoon

Is dental panoramic tomography appropriate for all young adults because of third molars?

Objective:The purpose of this study was to determine, if a dental panoramic tomograph (DPT) is appropriate for every young adult due to third molars. Materials and methods:The study sample consisted of 217 university students (20% men and 80% women; mean age 20.7 years; SD +/- 0.6 years) and included a questionnaire about symptoms caused by third molars, clinical oral examination of third molars, and a DPT. Subjects were divided into the following groups: subjects with a clinical indication for a DPT and subjects without such indication. The DPTs were then examined for findings regarding third molars. Results:Clinical indication for a DPT was observed in 64% of the subjects. Radiography revealed an additional 1.4% of the subjects with >= 1 radiographic signs of disease in relation to their third molars. Also, an additional 27% of the subjects had >= 1 other radiographic findings in relation to third molars that may have affected the clinical decision making. Conclusions:In our study population, clinically undetectable pathology cannot be considered as an indication for a DPT. However, if prevailing clinical practice supports preventive removals and detecting or monitoring of unerupted third molars, a referral to DPT can be considered as good clinical practice.Peer reviewe