Bone quantity in patients with agenesis of the lower second premolar evaluated in CT scans

• Background Agenesis of a permanent tooth has in Europe a prevalence of 2.6 up to 11.3% and the lower second premolar and the upper lateral incisor are most often affected (except for wisdom teeth). Treatment options are maintenance of the deciduous teeth, implant placement, tooth transplantation, orthodontic treatment for space closure or prosthetic tooth replacement. Especially in the case of agenesis of the lower premolars sand-glass like forms of the mandibular bone are described, which might preclude implant placement without previous augmentation procedures. However, to the best of our knowledge, so far no study is available assessing in detail the mandibular bone quantity in case of agenesis of the lower second premolar compared to a matched control group with regular erupted second premolars. Aim The primary aim was to compare mandibular bone quantity in case of agenesis of the lower second premolar with the deciduous tooth in situ to a matched control group with regularly erupted lower second premolars. Secondly, bone quantity in the region of the mesial and distal adjacent teeth was assessed to receive an overview of the neighbouring bone quantity. Thirdly, the test- and control-group in the region of the second premolar was evaluated on the possibility to place a standard implant. Materials and methods The present study included mandibular CT scans of 100 patients. The test group included 50 patients missing one lower second premolar due to agenesis with the deciduous tooth still in situ. Further, the first premolar and first molar were in situ and regularly erupted. The control group was matched according to age, sex, and tooth’s quadrant and presented regularly erupted first and second premolars and first molars. The dental reconstructions slices in the centre of the first molar and first and second premolar of each participant were used to assess the following parameters: width of the mandibular bone (measured each millimetre starting from the buccal alveolar crest), height and area of the mandibular bone. In the dental reconstruction slices the bony contours were manually retraced, the buccal alveolar crest and the inferior alveolar nerve manually assigned, and the tooth/implant axes indicated. Afterwards, a program for automated image analysis was used for standardised measurements. Further, the possibility of implant placement (4.3mm diameter, 10mm length, 1mm space to the buccal and lingual aspects, 2mm distance to the inferior alveolar nerve) was evaluated. Normal distribution of the data was proven graphically and differences between test and control groups were assessed by independent t-test. The false discovery rate was controlled by applying the Benjamini-Hochberg method and p-values <0.05 were considered as statistically significant. Results Mean width and area of the mandibular bone of the test group were significantly reduced in the region of the first and second premolar compared to the control group. No differences were noticed for the region of the first molar as well as for height measurements. The mean width in the upper third (1-10mm) was not reduced in all three regions. Yet, the mean width of the middle (11-20mm) and of the lower third (>20mm) was significantly reduced in the test group in the region of the first and second premolar, but not of the first molar. In the test group in 42 out of 50 cases (84%) the placement of an implant would have been possible compared to 100% in the control group. Manual linings were performed by a single examiner. This examiner and a second examiner repeated 25% of the whole sample and intra- and inter-examiner observations presented high reliability, with an intra-class correlation coefficient > 0.95. Conclusions and clinical implications In patients with agenesis of the lower second premolar, but deciduous tooth in situ, bone quantity is reduced in the region of the agenesis and at the mesial adjacent tooth. However, bone width is reduced only in an area below the first 10mm, which allows the placement of a standard implant in a high percentage of the cases. In an on-going study these data will be compared to agenesis patients with the deciduous tooth missing to test whether primary tooth maintenance preserves bone quantity.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Odontologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Dentistry (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)