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This thesis constitutes a summary of the following series of studies: I Autoradiographic studies on the distribution of zinc-65 in mice. In collaboration with Rune Söremark. The Journal of Nutrition 94,6, 1968. II Comparative study of distribution of injected zinc 65 in the mandibularcondyle and other tissues in rat as determined by gammascintillation. Acta Radiologica, Therapy Physics Biology 1970. Preprint. III Concentration of zinc in some hard and soft tissues of rat determinedby neutron activation analysis. Acta Radiologica, TherapyPhysics Biology 1970. Preprint. IV The distribution of 65Zn in the endochondral growth sites of themandibular condyle and the proximal end of the tibia in youngrats.—An autoradiographic and gamma scintillation study. OdontologiskRevy, 1970. Preprint. V Morphologic and autoradiographic observations on the effect ofzinc deficiency on endochondral growth sites in the white rat. Incollaboration with Ulf Friberg, Stefan Lohmander and TorstenÖberg. Odontologisk Revy, 1970. Preprint. VI The zinc concentration in hard and soft tissues of the rat. Theinfluence of zinc deficient feeding. Acta odontologica Scandinavica,1970. Preprint. These studies will be referred to in the following by the appropriate Roman numerals. / digitalisering@umu.se

digitalisering@umu.se

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Summary Importance of communication from a cultural and linguistic perspective in dental care -A literature review The aim of this literary review was to describe dental care situations where communication difficulties arise due to various cultural and linguistic aspects. This was investigated by the following questions: – What cultural aspects need to be taken into account in order to achieve satisfactory communication in healthcare/dental care? –How is healthcare/dental care affected by the use of verbal and non-verbal communication? – What evidence is there of the usage of alternative methods of communication when language barriers exist in dental care situations? Method was screened in the literary study, and was done as a literary review. Scientific articles have been sought out according to a three-step selection process to search for answers to the research questions. The results showed that the availability of a qualified interpreter ensures the establishment of good communication with dental care patients that have language problems. There is evidence of a significant difference in the use of a qualified interpreter and an interpreter without formal training. The creation of good dialogues and true communication is only possible when cultural and language barriers are broken by using a professional interpreter. In summary, dental care staff needs to meet every individual patient with interest and empathy, regardless of background or communicative ability.Keywords: Cultural Barriers, Dental Care, Foreign Background, Non-Verbal Communication.

Magister Scientiae Dentium - MSc(Dent) / Crowns have been used since the 5th century AD to improve both the form and function of teeth in the mouth. A great proportion of the total expenditure on dental care is spent on the provision and replacement of crowns and bridges and the number is increasing every year. A full coverage crown is a restoration placed over a single prepared tooth or it acts as an abutment in a bridge for the restoration of a missing tooth or teeth. Crowns are considered successful only when they meet both the aesthetic and functional requirements of the patient. For these to be met, certain principles for the preparation of the abutment tooth must be adhered to; such principles include features that are incorporated in the tooth preparation that enable it to withstand the forces of dislodgement that the tooth is exposed to both at rest and function. These features are described as the retention and resistance form of the preparation and the important aspect of these is taper. The taper of a tooth preparation is inversely proportional to the retention provided by the preparation. Volumes have been written on the difficulties encountered in making crowns with an adequate taper. Training, experience and operating conditions are among the many determinants of taper obtained by clinicians. Taper values of 2º to 5º were recommended initially for successful crown restorations but over time it was realized that these values were difficult to achieve under clinical conditions without creating undercuts in the preparation. Besides it was shown that even higher taper values might provide adequate retention for crowns. In addition, extra-retentive features such as axial grooves and boxes have been shown to improve retention of crowns. Many of the new luting cements also have adhesive properties that contribute to better retention of crowns and bridges. Various studies have established the prevalent taper obtained by dental students, general practice dentists, residents and prosthodontists while some of these studies have compared the prevalent taper among the different categories of clinicians. None of the studies so far reported has shown the prevalent taper in this environment; all without exception have investigated conditions in Europe, North America and Asia. Aim: This study therefore investigated the prevalent taper obtained routinely under clinical conditions by dental students, general dental practitioners and prosthodontists in two African countries and compared them with the recommended range of 10º to 22º.Method: 432 dies of teeth prepared by students, general practice dentists, resident and practicing prosthodontists were collected and analysed for taper using the double silicone technique. This involved making silicone replicas of the dies, sectioning these at various points and using photographs of the sections to measure their taper. Comparisons of the tapers obtained were carried out between the students, general practitioners and prosthodontists as well as between taper obtained on the different tooth types. Results: Taper ranging from 2º to 100º was obtained on the various tooth types. A mean mesio-distal (MD) and bucco-lingual (BL) taper of 22.5º (SD 11.2) and 26.2º (SD 11.1) respectively and a mean overall taper of 24.3º (SD 9.2) were obtained. Prosthodontists obtained the lowest taper (MD = 20.5º (SD 10.6)), BL = 24. 5º (SD 10.1) and a mean overall taper of 22.5º (SD 8.4). Students were second with a mean MD taper of 23.8º (SD 10.1), BL taper of 26.1º (SD 10.9) and a mean overall taper of 25.0º (SD 8.4). The general practice dentists obtained a mean MD and BL taper of 24.5º (SD 12.4) and 29.1º (SD 12.1) respectively and a mean overall taper of 26.8º (SD 10.6). The lowest taper was seen on premolars while the highest was on molars. Conclusion and recommendation: Most of the preparations analysed had a taper outside the recommended range of 10º to 22º. However, these tapers were similar to those found in other studies. Routinely incorporating extra-retentive features into crown preparation designs will improve success of crown restorations and adhesive cements should be used whenever conditions that allow for adequate retention are not met. The importance of taper should be emphasized more in dental schools and tooth preparation support systems should be used for teaching wherever possible. The need for regular refresher courses for practicing dentists and prosthodontists cannot be over-emphasized. / South Africa

ABSTRACT Background: The ability to identify individual risk factors for development of caries areimportant parts in the perspective of being able to control and limit caries disease. One suchcomponent is to establish, cut-off values for normal versus not normal values of known andputative risk factors. Aim: The aim was to analyze if individual variations of the amount of stimulated salivasecretion, pH-level and buffer capacity as well as content of S. mutans and A.actinomycetemcomitans could be used to form an alternative method to reach cut-off valuesbased on the natural variation in a population of dental students. Methods: This study was conducted by collecting saliva from 71 dental students at Umeåuniversity. The saliva was collected three times over a period of five weeks. The collection ofsaliva was conducted pair vice by the students themselves. The saliva was analyzed regardingsaliva secretion rate, buffer capacity, pH-level and quantity of S. mutans and A.actinomycetemcomitans. Measured factors were plotted graphically to show their stabilityover time among the participants. Results: Saliva secretion (and buffering, pH) showed a normal distribution that rangedwidely but with stable intra-individual values, the bacterial factors showed a non-parametricdistribution ranging from negative to positive values that varied largely. Conclusions: The normal distribution of salivatory properties makes it possible to calculatecut-off values based on standard deviation. The non-parametric distribution of the microbialfactors suggests cut-off values based on infected versus non-infected and intra-individuallyhigh numerical counts of bacteria on repeated analysis.

Background: Filifactor alocis is a gram positive, obligate anaerobic rod bacterium that has shown correlation to pathogenic events that may be linked to periodontitis. Previous studies have proved the presence of so-called “rtx” toxins in F. alocis that are similar to the leukotoxin of A. actinomycetemcomitans. The relevance of this gene in periodontitis is however unknown. Aim: The primary aim of the study was thereby to investigate whether the occurrence of Filifactor alocis carrying the rtx-gene affects the pathological progression of periodontitis or not. The secondary aim was to observe an eventual correlation between high loads F.alocis and attachment loss. Methods: Altogether 99 clinical samples taken from the gingival pockets of Ghanaian adolescents between the age of 10-19 were scanned by using PCR and gel electrophoresis. Thereafter the correlations were analyzed mainly from the point of view of progression by using Excel and MedCalc. Results: The highest significant value was shown in the group where correlation between the rtx- gene occurrence and clinical attachment loss progression existed (44%, p<0.05). No statistically significant values between the high loads of F.alocis and attachment loss were found. Conclusion: Our findings suggested the possible existence of a correlation between the rtx- gene occurrence and clinical attachment loss progression and thus supported our hypothesis. Thereby the primary null hypothesis was rejected. However, no correlation could be seen between F.alocis and attachment loss, which in turn did not support our secondary hypothesis.

ABSTRACT Background. Three-dimensional (3D) printing is a manufacturing technique, based on building objects layer by layer. It has received more attention lately especially in the medical and dental fields.   Aim: To investigate two mechanical properties of three-dimensionally printed polymer-based materials and compare them with conventionally cured polymer-based material.  Methods: Samples of four 3D-printed polymer-based materials (NextDent C&B MFH; NextDent Denture 3D+; NextDent Ortho Rigid and Freeprint® temp) and a conventionally cured and hand-mixed polymer-based provisional material (Luxatemp star) were investigated. Flexural strength and Vickers hardness were analyzed. Before the tests were carried out, all samples were placed in water in 37°C for at least 24 hours.   Results: The flexural strength results showed that there was statistically significant difference between Luxatemp star, NextDent C&B MFH and Freeprint®temp. Both 3D printed materials had a higher flexural strength than the conventionally cured material (Luxatemp star). At the same time, there was no statistically significant difference between Luxatemp star, NextDent Denture 3D+ and NextDent Ortho Rigid. The hardness values showed no statistically significant difference between the conventionally cured material (Luxatemp star) and the 3D printed materials. Furthermore, no statistically significant differences could be seen between the different 3D printed materials.  Conclusions: NextDent C&B MFH and Freeprint®temp had higher flexural strength than the conventionally cured material. NextDent Ortho Rigid and NextDent Denture 3D+ had a flexural strength comparable to the conventionally cured polymer-based material. 3D printed materials had a hardness comparable to the conventionally cured ones.

ABSTRACT  Background: Three-dimensional (3D) printing is a manufacturing technique, based on building objects layer by layer. It has received more attention lately especially in the medical and dental fields.   Aim: To investigate two mechanical properties of three-dimensionally printed polymer-based materials and compare them with conventionally cured polymer-based material.  Methods: Samples of four 3D-printed polymer-based materials (NextDent C&B MFH; NextDent Denture 3D+; NextDent Ortho Rigid and Freeprint® temp) and a conventionally cured and hand-mixed polymer-based provisional material (Luxatemp star) were investigated. Flexural strength and Vickers hardness were analyzed. Before the tests were carried out, all samples were placed in water in 37°C for at least 24 hours.   Results: The flexural strength results showed that there was statistically significant difference between Luxatemp star, NextDent C&B MFH and Freeprint®temp. Both 3D printed materials had a higher flexural strength than the conventionally cured material (Luxatemp star). At the same time, there was no statistically significant difference between Luxatemp star, NextDent Denture 3D+ and NextDent Ortho Rigid. The hardness values showed no statistically significant difference between the conventionally cured material (Luxatemp star) and the 3D printed materials. Furthermore, no statistically significant differences could be seen between the different 3D printed materials.  Conclusions: NextDent C&B MFH and Freeprint®temp had higher flexural strength than the conventionally cured material. NextDent Ortho Rigid and NextDent Denture 3D+ had a flexural strength comparable to the conventionally cured polymer-based material. 3D printed materials had a hardness comparable to the conventionally cured ones.