There is a constant development towards a more aesthetically oriented dentistry. New techniques and new materials are introduced to improve and optimise treatment results and shorten treatment time. This development can be favourable for both the dentist and the patient. If missing one or more teeth due to congenital reason or an incident (dental trauma), it is often challenging to already at an early stage choose the best and most optimal treatment for the particular clinical situation and individual. This thesis presents an overview of the basic biological factor of importance for a succesful treatment outcome: the relation between craniofacial height and alveolar bone height and width (morphology). The idea is to not just focus on the area of the missing tooth, but to incorporate other important factors, such as craniofacial height, sex, and age, in a broader context.
The overall aim of this thesis is to investigate the relation between craniofacial height and alveolar bone morphology (height and width of the maxilla and mandible) as a support and tool in therapy planning of individuals in need of tooth replacement through orthodontic treatment and/or dental implant treatment.
Paper I reports results of an investigation regarding the relation between the craniofacial height and height and width of the maxilla and mandible. The craniofacial height of the patients is divided into three groups: low, normal, and high angle. A radiographic profile image was used to establish the craniofacial height. Two separate lines are traced between anatomical structures on the radiographic 11image. The angle formed between these two lines is used for the classification of craniofacial height (low < 27°, normal 27-37°, high >37°).
The alveolar bone is measured in millimeter with a digital caliper on radiographs obtained in three planes. The measurements of the jaws are performed both in the maxilla and in the mandible, between the teeth in the front (midline), between the premolars, and between the molars, on the right and left side respectively. An association between the craniofacial height and the height and width of the alveolar bone (morphology) was found. The greatest differences between the three craniofacial groups were seen in the anterior region, both in the maxilla and in the mandible. This means that an individual from the high-angle group displays a higher alveolar bone which also is more narrow in the anterior region, especially in the mandible. The opposite pattern is displayed in the low-angle group where the subjects present a low and wide alveolar bone.
In paper II, the measurement technique for the maxilla and mandible was evaluated. Five raters with different experiences within the field of dentistry repeats the same measurements, independent of each other. The results show strong reliability of the measurement technique.
In paper III, new measurements of the alveolar bone were presented, however this time focus was on the anterior part of the maxilla, which is a more aesthetically challenging area. The results from this study strengthen the association previously reported between the craniofacial height and height and width of the maxilla measured on cross-sectional images.
Paper IV is a systematic review of the scientific literature, evaluating risk factors for a maxillary anterior tooth to end up in infraposition over time and to not follow the growth pattern of the adjacent teeth. Infraposition occurs when a tooth or dental implant does not continue to erupt and follow the anticipated growth pattern of the individual. This results in a growth cessation of the topical area and a dental implant still remain in the same place as immediately following treatment, whereas the surrounding teeth continue to erupt as the jaw grows. Dental infraposition can be a disadvantage from both an aesthetic and a functional perspective. An individual with a high angle (high craniofacial height), who presents with a thinner and longer alveolar bone, especially in the anterior part of the jaw, seems to be at a greater risk of developing infraposition of a traumatised tooth or a dental implant since growth seems to continue for longer (both as measured in mm and in years) compared to individuals with a low craniofacial height. The different risk factors investigated were age, sex, and craniofacial height. According to the findings in our systematic review, there is a lack of new scientific papers of high quality and the topic needs to be explored further in order for any conclusions to be drawn.
In conclusion, the results of the present thesis show that craniofacial height should be considered in therapy planning in order to achieve the best long-term treatment results for the patients. This seems to be especially relevant in young individuals where continued growth is expected.