To assess if the baseline situations of the patients in the two treatment groups were comparable and well balanced, the distribution of gender, age, and the initial ridge measurements were compared. There were three women and four men in each group. The median age for the test and control group was 50 and 62 years old, respectively (Table 1). The initial alveolar mean ridge widths before lateral augmentation in the test and control group were 3.6 ± 1.0 and 3.4 ± 1.2 mm, respectively (Table 2). Therefore, the baseline situation of the two groups was comparable (p > 0.05).

No infection, discomfort, or suppuration was reported for neither of the two groups throughout the study, and all surgical sites did heal uneventfully. The initial mean ridge width before lateral augmentation of the control group increased from 3.4 ± 1.2 to 6.0 ± 1.1 mm at the 4-month re-entry (Table 2). The initial mean ridge width before lateral augmentation increased from 3.6 ± 1.0 to 5.0 ± 1.4 mm at the 4-month re-entry in the test group (Table 2). This led to an alveolar mean ridge gain of 1.4 ± 1.0 mm in the test group and 2.6 ± 1.0 mm in the control group. Both groups did show a statistically significant (p < 0.05) ridge width gain between baseline and at the 4-month re-entry (Table 2). However, the results showed that early exposure (test group) resulted in significant (p < 0.05) less gain of the alveolar ridge width than when the membrane was not exposed (Table 2).

Furthermore, the reduction of the augmented ridge width right after the lateral augmentation (baseline) to implant placement (after 4 months) was assessed in each subjects. The mean ridge width after lateral ridge augmentation procedure was 9.7 ± 0.9 mm for the test group and 9.1 ± 0.8 mm for the control group (Table 3). The difference between the groups were not statically significant (Table 3). Therefore, baseline situations of the two groups were comparable. Regardless the membrane exposure, there was a significant (p > 0.05) reduction of the initial later ridge augmentation in the both groups after the 4-month healing time. However, the augmented ridge width reduction of 4.7 ± 1.4 mm in the test group was significantly higher (p < 0.05) than the 3.1 ± 0.9 mm assessed for the control group (Table 3). The percentage of ridge width reduction was 48 ± 13% in the test group compared to 33 ± 10% in the control group. Therefore, early membrane exposure resulted in higher reduction of the augmented ridge.