Topic: Basic research
Presented at the 23
rdAnnual Scientific Meeting of the European Association for Osseointegration
25-27 September 2014, Rome, Italy
References
Conclusions and Clinical Implications
Aim
Bone quantity in patients with agenesis
of the lower second premolar evaluated in CT scans
Kristina Bertl1,2, Maria Burt1, Michael Bertl3, Patrick Heimel4,5,6, André Gahleitner7, Werner Zechner1, Christian Ulm1
1 Division of Oral Surgery, Bernhard Gottlieb School of Dentistry, Medical University of Vienna, Austria 2 Department of Periodontology, Faculty of Odontology, University of Malmö, Sweden
3 Division of Orthodontics, Bernhard Gottlieb School of Dentistry, Medical University of Vienna, Austria
4 Karl Donath Laboratory for Hard Tissue and Biomaterial Research, Division of Oral Surgery, Medical University of Vienna, Austria 5 Austrian Cluster for Tissue Regeneration, Vienna, Austria
6 Ludwig Boltzmann Institute for Clinical and Experimental Traumatology, Vienna, Austria
7 Department of Diagnostic Radiology, Division of Osteoradiology, General Hospital, Medical University of Vienna, Austria
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Larmour, C.J., P.A. Mossey, B.S. Thind, A.H. Forgie & D.R. Stirrups (2005) Hypodontia--a retrospective review of prevalence and etiology. Part I. Quintessence Int 36, 263-270.
Ostler, M.S. & V.G. Kokich (1994) Alveolar ridge chnages in patients congenitally missing mandibular second premolars. The Journal of
Prosthetic Dentistry 71(2), 144-149. The primary aim was to assess radiographically mandibular bone quantity and
dimension in patients with agenesis of the lower second premolar but the primary tooth still in situ and to compare to a matched control group with regularly erupted lower second premolars. Second, the mandibular bone quantity and dimension in the area of the neighbouring teeth were assessed. Third, the region of the second premolar was evaluated as implant site for standard implant placement.
In Europe agenesis of a permanent tooth has a prevalence of 2.6 - 11.3%. The lower second premolar and the upper lateral incisor are most often affected (except for wisdom teeth) (Larmour 2005). Among others implant placement is a frequent treatment option to replace the missing tooth. Yet, as the alveolar bone is a tooth depending structure, tooth agenesis might be accompanied by a reduced amount of bone. Ostler & Kokich (1994) presented approximately 25% alveolar ridge width loss within 3 years after lower primary molar extraction measured on casts, which are representing the soft and hard tissue. Yet, tooth agenesis might cause a reduced amount of alveolar bone already with the primary tooth still in situ.
Background
Results
Materials and Methods
Altogether, 100 mandibular CT scans were included; 50 patients with agenesis of a second premolar but the primary tooth in situ and the first premolar and molar regularly erupted (test group) and 50 patients matched according to age, sex, and tooth’s quadrant and regularly erupted first and second premolars and first molars (control group). The dental reconstructions slices in the centre of the first and second premolar and of the first molar were assessed on the following parameters: width (measured each millimetre starting from the buccal alveolar crest), height, and area of the mandibular bone. The region of the second premolar was evaluated as possible implant site (Figure 1).
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 and for height measurements (Table 1). The mean width in the upper third of the mandibular bone (1 to 10mm) was not reduced in all three regions. Yet, the mean width of the middle (11 to 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 (Table 1, Figure 2 and 3). 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.
In patients with agenesis of the lower second premolar, but the primary tooth
still in situ, mandibular 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 is not impairing the placement of a
standard implant in a high percentage of the cases. In order to test, whether
the primary tooth is able to preserve the bone quantity in the upper third of
the mandibular bone, these data will be compared in an on-going study to a
group of agenesis patients with the primary tooth already missing.
Figure 1. Evaluation of the region
of the second premolar as implant s i t e f o r s t a n d a r d i m p l a n t placement. The available space for an implant with 4.3mm diameter and 10mm length with 1mm distance to the buccal and lingual aspects and 2mm to the inferior alveolar nerve (resulting in a rectangle of 12x6.3mm displayed in light blue) was tested. The red parts are indicating, where the implant bed is too small and the orange point is indicating the inferior alveolar nerve.
Figure 2. Example of an agenesis patient with 75 still in situ (b) and with a reduced
amount of mandibular bone in the middle and lower third especially in the region of the first (a) and second (b) premolar; (c) region of the first molar of the same patient.
Figure 3. Visualisation of each mm of the mandibular bone width confronting the
agenesis and the control group. The asterisk (*) is indicating a statistically significant reduced width in the agenesis group (p<0.05; independent t-test).
Table&1.&Comparison*of*the*assessed*parameters*between*agenesis*and*control*group*in*all*3*assessed*regions*
(independent*t8test*with*controlling*the*false*discovery*rate*by*applying*the*Benjamini8Hochberg*method).*
parameters& group&
region&
1st&premolar& 2nd&premolar& 1st&molar&
mean&±&S.D.& p, value& mean&±&S.D.& p, value& mean&±&S.D.& p, value& wi dt h& (m m )&
mean& agenesis& 9,12*±*1,25* 0,04& 9,24*±*1,11* 0,02& 10,41*±*1,20* 0,08*
control& 9,71*±*1,81* 9,79*±*1,01* 10,80*±*0,87* upper& third& agenesis& 8,99*±*1,53* 0,10* 9,53*±*1,46* 0,11* 11,61*±*1,57* 0,23* control& 9,47*±*1,36* 9,96*±*1,19* 11,93*±*0,99* middle& third& agenesis& 9,51*±*1,58* 0,04& 9,64*±*1,38* 0,02& 10,00*±*1,40* 0,08* control& 10,24*±*1,72* 10,40*±*1,48* 10,69*±*1,32* lower& third& agenesis& 8,77*±*1,37* 0,04& 7,99*±*1,21* 0,01& 8,20*±*1,36* 0,08* control& 9,42*±*1,20* 8,81*±*0,98* 8,71*±*0,90*
area&(mm2)& agenesis& 251,09*±*49,22* 0,03& 246,05*±*48,21* 0,02& 254,41*±*49,46* 0,08*
control& 278,13*±*44,62* 271,58*±*41,49* 274,45**±39,18*
height&(mm)& agenesis& 27,84*±*3,44* 0,06* 27,06*±*3,56* 0,06* 25,18*±*3,19* 0,08*
control& 29,04*±*2,51* 28,28*±*2,58* 26,29*±*2,55*
Significant&values&(p<0.05)&are&presented&in&bold.&S.D.&standard&deviation.&
