The objective of this study was to investigate alveolar crest dimensional changes following extraction and unassisted healing of maxillary molars. Cone beam computed tomography (CBCT) images taken before and after extraction of maxillary first or second molars were examined and linear measurements performed to evaluate the changes in alveolar bone crest. Mean horizontal resorption was found to be 6.6 + 3.7 mm in the horizontal dimension and and 2.4 + 1.4 mm in the vertical dimension. The analyses revealed statistically significant correlations between: distance between bone to CEJ on the palate aspect and vertical palatal resorption (R2=0.586, P=0.01); palatal alveolar crest thickness and mean horizontal resorption (R2=-0.422, P=-0.01); and mean horizontal resorption and mid-crestal vertical resorption (R2=0.435, P=0.0001). This study concluded that extraction of maxillary molar teeth without intervention led to extensive atrophy of the alveolar crest.
It has been clearly demonstrated in multiple animal models and clinical investigations that the alveolar ridge undergoes marked dimensional changes following tooth extraction. While multiple clinical studies have investigated post-extraction dimensional alterations of the alveolar bone, these studies have either not isolated molars as their own group, not reported on maxillary molars, or excluded molar entirely. This investigation therefore aimed to fill that gap in the literature by evaluating alveolar dimensional change post-extraction of maxillary molars.
Materials and Methods
The population of patients who had presented to the Ostrow School of Dentistry of USC for extraction of maxillary first or second molars between March of 2009 and June of 2015 were quarried. Inclusion criteria consisted of the availability of CBCT taken at both before and after extraction. Exclusion criteria consisted of ridge preservation grafting. Twenty-two patients were identified that had required a total of twenty-four teeth to be extracted. Linear measurements were performed on CBCT images using SIMPLANT PRO 6.0 software. The buccal and palatal plate thickness, horizontal width at 1, 2, 3 and 5 mm apical to the crest, as well as ridge height at buccal, middle of crest and palatal were measured on pre-operative images. The distance from bone crest to CEJ on buccal and palatal aspects of roots were also measured. Standardized reference points were used to repeat the measurements on the ridge width and height at same positions.
Quantitative analysis of CBCT images demonstrated a mean horizontal resorption of6.6 + 3.7 mm in the horizontal dimension and 2.4 + 1.4 mm in the vertical dimension. Furthermore, the mean horizontal thickness of the alveolar bone in the maxillary molar area was found to be 9.8 + 4.9, 12.2 + 4.2, 13.0 + 3.4, 13.5 + 1.7 mm at 1, 2, 3 and 5 mm apical to the alveolar crest, respectively. Following a healing period of 10.9 + 11.5 months, percent resorption was found to be 87.8% + 26.3, 71.9% + 30.4, 56.0% + 31.7 and 28.7% + 33.2% at 1, 2, 3 and 5mm apical to the alveolar crest, retrospectively. The alveolar crest also underwent 2.4 + 1.4mm of vertical bone loss. Statistically significant correlations were found between: distance between bone to CEJ on the palate aspect and vertical palatal resorption (R2=0.586, P=0.01); palatal alveolar crest thickness and mean horizontal resorption (R2=-0.422, P=-0.01); and mean horizontal resorption and mid-crestal vertical resorption (R2=0.435, P=0.0001).
Extraction of maxillary molar teeth without additional intervention led to extensive horizontal and vertical bone atrophy that extended at least up to 5mm apical to the original crest. The extensive loss of alveolar bone can potentially compromise implant therapy, requiring additional augmentation procedures.