A Comprehensive Assessment of Bone Losses in the Postoperative Phase of Single Implant Placed in Mandibular First Molar Regions: A Cone-Beam Computed Tomography-Based Clinical Study.

BACKGROUND AND AIM: Bone loss surrounding dental implant is an unavoidable phenomenon that occasionally leads to implant failure. Implant-related bone loss exhibits different patterns and rate as per oral milieu and hygiene habits. This study was aimed to clinically assess the crestal bone losses in the postoperative phase of single implant placed in mandibular first molar regions.
MATERIALS AND METHODS: The present in vivo study was planned and completed on the patients selected from the Department of Prosthodontics of the institute. A total of twenty patients were selected randomly in which right mandibular first molar was rehabilitated by dental implants. All radiographic analysis was attempted by cone-beam computed tomography (CBCT). All twenty implants were placed by standard clinical protocols. CBCT analysis was attempted to measure existing bone levels on all four surfaces of implant. These measurements were completed at three different postoperative phases. Informed consent was obtained from all participating patients. STATISTICAL ANALYSIS AND
RESULTS: Statistical analysis was completed by statistical software Statistical Package for the Social Sciences. P <0.05 was taken as statistically significant. Among all 20 patients, males were 14 and females were 6 in the age range of 25-45 years. Mean bone losses were in the range of 0.226-0.737 for Group I. Intergroup comparison by two-sample t-test showed a significant difference (0.01) for mesial surfaces. All mean values were maximum for mesial surfaces and minimum for lingual surfaces.
CONCLUSION: The mean crestal bone loss at four implant surfaces evaluated at different postoperative phases was nonsignificant. However, there were significant differences in mean crestal bone loss at four surfaces of all studied implants in a particular group. Copyright:

INTRODUCTION

Alveolar bone loss is one of the major clinical causes of failure in fixed prosthesis including dental implants. Literature has shown different patterns of crestal or peri-implant bone losses around single and multiple implants.[1] Predominantly bacterial activities have been demonstrated to trigger this phenomenon, however, few subjective factors also play a crucial role in these regards. Many of the workers have revealed smoking as one of the most harmful habits for overall implant success.[23] Poorly maintained oral hygiene and periodontal diseases also induce active bone loss. A very obvious shifting trend has been noticed in the patients as far as the prosthetic work is concerned. Dental implant-related rehabilitations have emerged as the first choice for single and multiple missing situations. The ultimate criteria of long-term implant success are restricted and time-dependent crestal bone loss, clinical absence of mobility, and absence of pain.[4] Several design-related modifications have been suggested over the years for reducing peri-implant bone losses. Platform switching is one modification which potentially restricts microbial encroachments near implant-abutment junction. However, alveolar bone loss is usually considered as multifactorial in origin. As we all know that implant loading procedures are primarily involved in initiation process of bone loss coupled with microbiological activities. Periodontal diseases typically play their major role in initiation of bone loss around implant. Clinically acceptable crown with precisely designed occlusal plane also imparts significantly in the longevity of prosthesis.[5] Few of the pioneer workers have evidenced that most of the osseointegrated titanium implants show only 0.5–1.5 mm crestal bone loss by the end of the 1st year and only 0.06–0.14 mm bone loss after the 1st year.[16] Hence, the resorption plot is declining sharply after the 1st year of service, however, it is not true for all clinical circumstances. Crestal bone loss in the proximity of osseointegrated titanium implants typically exhibits a different rate at all four surfaces. Moreover, this rate of loss of crestal bone crucially depends on implant number, thread designing, surface treatments, interimplant distance, implant–tooth distance, and occlusal load. Literature is overwhelmed with the studies related to peri-implant bone loss in variety of clinical situations. However, only a few of them have actually focused on single-implant rehabilitations and their course of bone loss on all four surfaces. As the crestal bone loss increases almost immediately after placement of prosthesis, special care must be taken by the patients to avoid any disused fate. In the present study, the authors have endeavored to clinically assess the crestal bone losses in the postoperative phase of single implant placed in mandibular right first molar regions.

MATERIALS AND METHODS

The present study was designed and executed in the Department of Prosthodontics of the college wherein twenty single-tooth implants were studied for surrounding crestal bone loss. Initially, patients were screened in which dental implants were planned to be placed for missing right mandibular first molar. Therefore, the authors analyzed a total of twenty implants efficiently. Exclusion criterion included lack of soft-tissue defect and absence of any severe pathology related with jaws. Both male and female patients were included in the study having an age range of 25–45 years. Preoperative and postoperative radiographic analysis was completed by cone-beam computed tomography (CBCT). CBCT also assisted operators in perfect selection of implant as per available bone density, bone height, and bone width. All twenty osseointegrated dental implants were placed by standard osteotomy procedures. Stage 2 surgeries were attempted approximately 3 months after initial implant placement. Nonplatform-switched standard-sized abutments were placed for all twenty cases (screw retained only). CBCT analysis was done to determine existing bone levels on all four sides (lingual, buccal, mesial, and distal) of implant [Figure 1]. These measurements were attempted at three different postoperative phases (30 days, 90 days, and 180 days). The authors have not analyzed the effects of implant loading, particularly on surrounding bone. Crestal bone losses were figured out by comparing CBCT radiographs of bone heights at various time intervals. Moreover, radiographs made instantly after implant osteotomy (control group) were compared with CBCT made later at three different time intervals. All willing patients were asked to submit signed informed consent. On the basis of timing, all studied single implants were segregated into three study groups. Groups I, II, and III included bone loss assessments done in posttreatment phases at 30 days, 90 days, and 180 days, respectively. Master data were entered into spreadsheet to prepare master sheet which was later sent for basic statistical analysis. P <0.05 was considered statistically significant (P < 0.05).

Figure 1

Cone-beam computed tomography-assisted dimensional analysis of implant (pretreatment) and evaluation of bone levels (posttreatment)

Statistical analysis and results

Statistical analysis was completed by statistical software Statistical Package for the Social Sciences (SPSS, IBM Incorporation, NY City, USA) version 21.0. The ultimate endeavor was to calculate P values, mean, standard deviation, Chi-square test, standard error, and 95% confidence interval. In all 20 studied patients, males were 14 and females were 6 in the age range of 25–45 years. Mean bone losses were in the range of 0.226–0.737 for Group I. Statistically significant difference was identified for lingual surface (0.02). In Group II, minimum mean bone loss was 0.239 and maximum was 0.712 recognized at lingual and mesial surfaces. A statistically significant difference was recognized for lingual surface (0.01). It is therefore very clear that maximum bone losses were noticed at mesial surfaces while minimum bone losses were identified at lingual surfaces of all studied implants in all groups [Tables 1–3]. In addition, there were very negligible differences between mean bone losses on all surfaces between groups. Furthermore, it indicated that changes in mean bone loss were comparatively insignificant in the first 6 months after osteotomy procedures. These inferences were in contrast to several other studies conducted on crestal bone loss assessment. Assessment of mean bone losses among the three study groups using one-way ANOVA [assessed in contrast with control group; Table 4] showed a very significant P value (0.002). Intergroup comparison (for all three study groups) by two-sample t-test showed significant difference (0.01) for mesial surfaces [Graph 1 and Table 5].

Table 1

Basic statistical illustration (for Group I: Evaluated and compared with control group after 30 days of posttreatment phases)

Studied implant sides	n	Mean bone loss	SD	SE	95% CI	Pearson Chi-square assessment	P
Buccal	20	0.480	0.029	0.128	1.96	2.837	0.09
Lingual	20	0.226	0.038	0.963	1.69	2.033	0.02*
Mesial	20	0.737	0.102	0.169	1.44	1.627	0.50
Distal	20	0.578	0.239	0.163	1.78	1.836	0.20

*P<0.05 significant. SD: Standard deviation, SE: Standard error, CI: Confidence interval

Table 3

Basic statistical illustration (for Group III: Evaluated and compared with control group after 180 days of posttreatment phases)

Studied implant sides	n	Mean bone loss	SD	SE	95% CI	Pearson Chi-square assessment	P
Buccal	20	0.382	0.536	0.235	1.42	1.637	0.10
Lingual	20	0.242	0.073	0.174	1.06	2.902	0.08
Mesial	20	0.723	0.425	0.094	1.62	1.683	0.01*
Distal	20	0.580	0.938	0.038	1.96	2.028	0.20

*P<0.05 significant. SD: Standard deviation, SE: Standard error, CI: Confidence interval

Table 4

Assessment of mean bone losses among the three study groups using one-way ANOVA (assessed in contrast with control group)

Factors	Degree of freedom	Sum of squares ∑	Sum of squares mean ∑	F	P
Among groups	3	2.748	0.353	1.034	0.002*
Inside groups	28	7.733	0.021	-
Collective	32.17	9.536	-

*P<0.05 significant

Graph 1

Two-sample t-test for evaluation of actual bone losses between Group I, Group II, and Group III

Table 5

Intergroup comparison by two-sample t-test for evaluation of parameters (actual bone losses) between Group I, Group II, and Group III

Implant sides	Groups						P
	I		II		III
	Mean	SD	Mean	SD	Mean	SD
Buccal	0.480	0.029	0.393	0.738	0.382	0.536	0.20
Lingual	0.226	0.038	0.239	0.039	0.242	0.073	0.08
Mesial	0.737	0.102	0.712	0.526	0.723	0.425	0.01*
Distal	0.578	0.239	0.608	0.293	0.580	0.938	0.40

*P<0.05 significant. SD: Standard deviation

DISCUSSION

Rehabilitation of complete or partial edentulous situations with implant has become very popular clinical practice in this modern era. Many of the researchers believed that implant undergoes multiple remodeling phases once they installed in the jaw bone. These transformations are principally physiological and typically induced by defense system of the body. Crestal bone loss more than 0.1 mm per year is considered alarming for implant long-term sustainability.[12] Saminsky et al. have shown an increased peri-implant bone loss in patients with smoking habits and osteoporosis.[7] These inferences should be mandatorily included while case selection and history recording. Klinge described peri-implant bone loss around implants and tissue-related complications. They did not find any concrete correlation between implant bone loss and surrounding infections. Their inferences were not exactly as per ours as they only studied transmucosal implants.[8] Literature is overwhelmed with the long-term studies showing high survival rate in spite of surrounding bone loss. Early crestal bone loss is principally seen before implant loading whereas late bone loss is noticed after crown placement up to 1 year. Apart from peri-implant infections, there are few other factors also that lead to it such as surgical trauma, existence of microspace, and excess occlusal pressure. Qian et al. had attempted a web-based search in the literature to estimate possible etiologies for peri-implant bone loss over 10 years. They concluded that this phenomenon is multifactorial in origin.[9] Merin has shown the effects of occlusal corrections on bone regeneration in peri-implant area. He strongly recommended comprehensive examination and periodic maintenance sessions.[10] Aloy-Prósper et al. showed management strategies of implant-induced bone loss. They stated that guided bone regeneration methodology can be successfully utilized to treat advanced bony defects. Like our study, they also attempted to quantify bone losses at all surfaces of implant at different time intervals. Their study conclusions and inferences were highly comparable to our implications.[11] Uslu et al. have demonstrated a correlation of diabetes on crestal bone loss around implant. They concluded that individuals with controlled diabetes usually exhibit a similar bone loss pattern as a nondiabetic person. However, these recommendations were drawn after 3 years of implant positioning in upper arch with 96% of success rate.[12] Hashim and Cionca reviewed general risk factors related with implantitis. They confirmed that there is nothing like “high-risk implant” which is prone to develop future bone loss. Similarly, “high-risk patient” is also extremely misused term by dental professionals in Asian countries. Nevertheless, we must be aware of any possibility of future complication induced by peri-implant bone loss.[13] Salim et al. have explored peri-implant bony changes by traditional radiography. They concluded that orthopantomograph is an average radiographic tool as it does not allow an operator to quantify different bone levels at different sections.[14] However, with the latest three-dimensional radiographies like CBCT, these issues have been largely resolved. In our study, the authors studied precise crestal bone losses at different time intervals by CBCT. Actual calculations were attempted by the software itself by comparing sectional images made at different timings. The inferences were very contrasting and comparable with the study conducted by Jung et al.[15]

CONCLUSION

Within the limitations of the study, the authors have witnessed visible bone losses at all studied surfaces in all implants. The mean crestal bone loss at four surfaces calculated at three postoperative phases was nonsignificant. On the other hand, there were significant differences in mean crestal bone loss at four surfaces of all studied implants in a particular group. In addition, these crestal bone losses were apparently stagnant in the first 6 months of implant loading. Our study outcomes have clearly shown crestal bone loss patterns at different surfaces at different timings; however, clinical applicability of these inferences must be supported with other subjective factors also.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Table 2

Basic statistical illustration (for Group II: Evaluated and compared with control group after 90 days of posttreatment phases)

Studied implant sides	n	Mean bone loss	SD	SE	95% CI	Pearson Chi-square assessment	P
Buccal	20	0.393	0.738	0.280	1.92	1.738	0.40
Lingual	20	0.239	0.039	0.827	1.02	1.938	0.01*
Mesial	20	0.712	0.526	0.426	1.38	1.342	0.90
Distal	20	0.608	0.293	0.894	1.53	1.838	0.10

*P<0.05 significant. SD: Standard deviation, SE: Standard error, CI: Confidence interval