Keywords
Cone-beam computed tomography - gingival phenotype - implant surgery - Schneiderin
membrane perforation - Schneiderin membrane thickness
Introduction
Dental implants are one of the most acceptable treatments for occlusion and mastication
rehabilitation.[[1]][[2]] Low bone density, a large pneumatized maxillary sinus, and atrophic maxillary alveolar
bone pose a compromised challenge toward the success of implant placement in posterior
maxillary ridge.[[3]
[4]
[5]] To overcome the above limitation and to regenerate adequate bone, sinus lift procedure
has been introduced through which the Schneiderian membrane (SM) is elevated gently,
and bone substitutes are deposited.[[1]
[6]] This procedure is considered to be safe due to low complication rate.[[2]] However, its most common complication is SM perforation (SMP) which leads to acute
or chronic sinusitis, bacterial invasion, swelling, bleeding, and wound dehiscence
and also affects the success and survival rate of dental implants.[[2]
[5]
[7]] The occurrence of this complication varies from 19.5% to 58.3%.[[8]] It is, therefore, important to estimate its occurrence possibility before the operation
and provide additional consideration if needed.[[3]
[9]] SM thickness (SMT) can be determined through biopsy and three-dimensional radiography;
however, the application of these methods in dental offices may be difficult for requiring
special equipment.[[8]] Therefore, attempts to find an anatomic factor that predicts SMT are essential.[[10]] Aimetti et al. obtained mucosa biopsy of maxillary sinus endoscopically and reported a direct relation
between SMT and gingival phenotype (GP).[[11]] GP is characterized as the scalloped and thin gingiva or the flat and thick gingiva
and is determined using histological examination and transgingival probing.[[9]
[10]] Histopathologic examination is an accurate but unrealistic measure in clinical
studies for requiring biopsy, being invasive, time-consuming, and interrupting the
healing process.[[6]
[12]
GPs may assist the clinician in addressing the features of the SM. Therefore, the
aim of this study was to evaluate the relationship between SMT and GP, respectively,
measured by radiography and probing to suggest a reliable and practical predictor
of SMT and to prevent from SMP through sinus lift surgery.
Materials and Methods
This study was an analytic observational cross-sectional study with the aim of evaluating
the relation between the GP and SMT of patients referring to dental faculty of Guilan
University of Medical Sciences. Three hundred and ten patients were chosen based on
the following inclusion and exclusion criteria.
Patients undergoing implant surgery in the first or second molar region of maxilla
or both, with probing depth of 3 mm or less, firm gingiva and without traumatic occlusion,
history of periapical infection, and gingival recession, were included in the study.
Patients with following criteria were excluded from the study: untreated periodontal
disease, previous periodontal surgery and previous sinus surgery, history of previous
orthodontic treatment, consumption of drugs with gingival enlargement side effect,
pregnancy, tobacco smoking, overerupted mandibular molars, and severe bone loss in
the maxillary molar region.
All patients were informed of the study and signed a consent form. Prescription of
cone-beam computed tomography (CBCT) radiography is essential as part of the dental
implant surgery process, and patients did not receive additional radiation for this
study. CBCT was obtained by NewTom VG/Verona/Italy, voxel 0.2–0.24 mm, and field of
view 10 × 10. Radiographic imaging was performed by an oral and maxillofacial radiologist.
Buccolingual cross-sectional images (with the orientation of perpendicular to axial
plan) with 1 mm thickness and 2 mm apart from each other were reconstructed. SMT was
measured in three sequential cuts, in the first and second molar region, and the mean
of SMT in these three cuts was recorded. All measurements were taken in millimeters
using the ruler contained in the NNT Viewer software (NNT 2.21; Image Works, Verona,
Italy).
An expert examiner determined GP clinically before the dental implant surgery. The
GP was assessed by inserting a calibrated standard periodontal probe (UNC-15 Hu-Friedy)
into the gingival sulcus at the midfacial aspect of both central maxillary incisors
(Kan 2003).[[13]] If the outline of the underlying periodontal probe could be seen through the gingival,
it was categorized as thin; if not, it was recorded as thick. Intraexaminer reliability
was assessed in twenty patients. GP and SMT were measured at the baseline and remeasured
after 1 week. The intraclass correlation for SMT and GP ranged from 0.96 to 1.00 which
was defined as excellent reproducibility, according to Gwet (2008).
All the statistical analyses were performed using IBM ® SPSS ® Statistics Version
24 software (IBM, Armonk and North Castle, NY, USA). Frequency and percentage were
used to describe the qualitative data, and mean and standard deviation were used to
describe the quantitative data. To analyze the statistical data, independent samples
test, Pearson's correlation, and linear regression were used. The level of significance
was set at P = 0.05.
Results
This study was carried out to evaluate the relation of SMT with age, gender, and GP.
The average age of patients was 52.59 ± 7.61. The youngest patient was 36 and the
oldest was 67. Age had no statistically significant relation with SMT and GP (P = 0.666 and P = 0.842, respectively). The mean age of patients with thin GP was 52.73 ± 7.76 and
with thick GP was 52.46 ± 7.53.
Nearly 51.5% (67) of patients were female and 48.5% (63) were male. The average of
SMT in male patients was 1.68 ± 4.3 mm, and in female patients was 1.59 ± 3.41 mm.
However, the difference of SMT among males and females was not statistically significant
(P = 0.196). In terms of GP, males and females were statistically significantly different
such that females had thin GP more frequently compared to males (P = 0.003) [[Table 1]].
Table 1:
Distribution of gingival phenotype based on gender
|
Gender
|
Gingival phenotype
|
|
Thin
|
Thick
|
|
Female, % (n)
|
61.2 (41)
|
38.8 (26)
|
|
Male, % (n)
|
34.9 (22)
|
65.1 (41)
|
|
Total, % (n)
|
48.5 (63)
|
51.5 (67)
|
According to the statistical analysis, 48.5% (63) of patients had thin GP and 51.5%
(67) had thick GP. The mean of SMT was 1.47 ± 3.13 mm in patients with thin GP and
was 1.79 ± 3.88 mm in patients with thick GP. SMT and GP were positively associated
such that SMT was statistically significantly thinner in patients with thin GP compared
to those with thick GP (P ≤ 0.001).
Discussion
It is important to attempt to find an anatomic factor that predicts SMT preoperatively
to prevent from SMP. This study was designed to evaluate the relation between SMT
and GP in patients requiring dental implant in the posterior region of maxilla.
SMT varies in different studies as a result of variations in geographic population
and inclusion criteria such as having periodontal disease or not and racial and ethnical
differences. In the current study, SMT was 1.47 ± 3.13 mm in patients with thin GP
and was 1.79 ± 3.88 mm in patients with thick GP, while Aimetti et al. reported 0.45–0.85 mm and 0.95–1.40 mm, respectively.[[11]] Pommer et al. reported 0.02–0.35 mm and Kalyvas et al. stated 0.4–2.8 mm as the mean of SMT.[[1]
[2]] In Janner et al. and Wen et al. studies, SMTs >2 mm were more frequent in patients.[[3]
[14]] As opposed, in Shanbhag et al.'s study, the most frequently SMT found was thickness of <2 mm.[[15]] Insua et al. state that periodontal diseases, apical periodontitis, and tooth extraction thicken
the SMT.[[16]] By contrast, Janner et al. consider endodontic, periodontal, and periapical condition to have no significant
influence on SMT.[[3]] Furthermore, there are controversies over the effect of smoking and allergy on
SMT due to their dependence on individuals' usage and sensitivity.[[2]
[5]
[8]
[16]]
Some studies come in accordance with current findings that age has no influence on
SMT and sinus abnormalities,[[2]
[17]] which are in contrast with findings of Lathiya et al., Goller-Bulut et al., Çam et al., and Vallo et al.[[5]
[18]
[19]
[20]] The aforementioned differences attribute to the age of patients attempting the
studies. The mean age of patients in studies in line with the current study is 50–60,
while in the rest of researches is 30–40 years old.
Khorramdel et al. found no significant relation between gender and GP and SMT, while other studies
and the current study stated that male patients tend to have thicker SMT.[[2]
[3]
[8]
[11]
[19]] Manjunath et al. stated that GP changes as female patients' age, but this trend was not found in the
male patient.[[21]]
The results claim the relationship between GP and SMT to be significant. Patients
with thick GP have thicker SMT, and patients with thin GP have thinner SMTs which
correspond with the following studies.[[9]
[11]
[22]]
Aimetti et al. evaluated GP and SMT, respectively, by probing and excising a biopsy of sinus mucosa.[[11]] Studies state that differences in the location of the biopsy and amount of inflammatory
infiltrate can lower the accuracy of this method and require specific equipment.[[16]] In another study, Yilmaz et al. recorded GP and SMT using CBCT.[[9]] Assessment of GP in radiographic images is not accurate due to the superimposition
of anatomic features and difficult visualizing.[[8]] Similar to the current study, Chaturvedi et al. assessed GP using probe transparency and measured SMT in CBCTs of patients. They
concluded that the GP can provide information about SMT preoperatively.[[22]] Similarly, the results of the current study show that probing, as the simplest
method of determining GP, can be easily used before sinus lift surgery to predict
the SMT and prevent SMP. The limitation of Chaturvedi et al.'s study was that they did not assess the relation of SMT and gender.[[22]] While, in the current study, the relation was assessed so that SMT tends to be
thicker in male patients. Limitations of the current study were small sample size
and performing the study in the Iranian population. The SMT and GP may vary in different
races and ethnicity. Further studies are required to study the relation of SMT and
GP in larger sample size and in different study population.
Conclusion
From the findings of this study, it can be concluded that SMT was thinner in patients
with thin GP and was thicker in patients with thick GP. Within the limitations of
the current study, it may be suggested that GP is an important clinical predictor
for SMT, particularly if CBCT evaluations or histological examinations are not possible.
