The effects of off-axial loading on peri-

implant marginal bone loss in a single

implant: A 1-year retrospective study

after loading

Dong-Won Lee

Department of Dentistry

The Graduate School, Yonsei University

The effects of off-axial loading on peri-

implant marginal bone loss in a single

implant: A 1-year retrospective study

after loading

Dong-Won Lee

Department of Dentistry

The Graduate School, Yonsei University

The effects of off-axial loading on peri-

implant marginal bone loss in a single

implant: A 1-year retrospective study

after loading

Directed by Professor Ik-Sang Moon

The Master’s Thesis

submitted to the Department of Dentistry

and the Graduate School of Yonsei University

in partial fulfillment of the requirements for the degree of

Master of Dental Science

Dong-Won Lee

June 2011

This certifies that the Master’s Thesis of Dong-Won Lee is approved.

___________________________

Thesis Supervisor: Ik-Sang Moon

__________________________ Kwang-Ho Park

___________________________ Dong-Won Lee

The Graduate School Yonsei University

June 2011

감사의 글

부족한 저를 지도해주신 교수님들의 훌륭한 가르침이 있었기에 이

논문이 있을 수 있었습니다. 논문이 완성될 때까지 지속적인 관심과

도움을 주셨던 문익상 교수님, 박광호 교수님, 이동원 교수님께 깊은

감사의 말씀을 먼저 올립니다.

또한 관심과 배려로 저를 이끌어 주시고 학업, 진료, 논문작성에 있어서

항상 귀감이 되어주신 김태형, 김정주, 송동욱, 강영일, 이은경 선생님께도

이 자리를 빌어 감사를 드립니다. 그리고 의국 생활을 함께하며 힘이

되어준 치주과 의국원 남대호, 모덕경, 손선보, 이청운, 어연호 선생님

고맙습니다. 특히 4 년간 함께 동고동락하며 힘든 일, 어려운 일 항상 함께

했던 남대호 선생님에게 큰 고마움을 전하고 싶습니다

지금의 제가 있도록 아낌없는 사랑을 주셨던 아버지, 어머니, 여동생

정현 우리 가족 모두 고맙습니다. 사랑합니다. 그리고 저의 예비신부

의향에게도 곁에 있어주어서 든든하고 행복하다는 말을 전합니다.

논문 교정에 큰 도움을 친구 종훈, 소현 부부에게도 고마운 마음을

전하고 싶습니다

마지막으로 미처 언급하지는 못했지만 제 곁에 계시는 모든 분들께

고마움과 사랑의 마음을 올립니다. 감사합니다.

2011 년 6 월

이 동 원

i

TABLE OF CONTENTS

LEGENDS OF FIGURES, TABLES ··············································· іі ABSTRACT (ENGLISH) ························································ ііі

I. INTRODUCTION ····························································· 1

II. MATERIALS AND METHODS ··········································· 4

1. Pat ien ts · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 4 2. Implant f ix ture · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 4 3. Trea tment procedure · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 6 4. Radiographic examination and evaluation ·························· 6 5. Follow up parameter ················································ 8 6. Sta t i s t i ca l ana lys i s · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 9

III. RESULTS ···································································· 11

1. Clinical examination ·························································· 11 2. Correlation between crown width/fixture width ratio and peri-implant

marginal bone loss ·················· ··················· ············ 11

3. Evaluation of peri-implants soft tissue ······································ 16

IV. DISCUSSION ······························································ 17

V. CONCLUSION ···························································· 21

VI. REFERENCES ····························································· 22

ABSTRACT (KOREAN) ······················································ 30

ii

LEGEND OF FIGURES

Figure 1. Periapical radiographs taken (A) immediately after

prosthesis delivery; (B) after 1 year ·························7

Figure 2. Linear measurement between landmarks························ 8

Figure 3. Scattergrams of correlation between Cr/I ratio and peri-

implant marginal bone loss ········································· 12

Figure 4. Distribution of implants according to crown width

/implant width ratio ····················································· 13

LEGEND OF TABLES

Table 1. Distribution of the installed implants································ 5

Table 2. Distribution of the installed implants according to

fixture length and site ······················································ 5

Table 3. Pearson correlation analysis with respect to crown width/

implant width ratio and 1 year bone level change···········11

Table 4. Peri-implant marginal bone level change ·······················14

Table 5. In cantilever group, marginal bone loss comparison

between surface distant and adjacent to the cantilever····15

Table 6. Modified plaque index(mPI) and modified sulcus

bleeding index(mSBI) ···················································· 16

iii

ABSTRACT

The effects of off-axial loading on peri-implant marginal bone loss in

a single implant: A 1-year retrospective study after loading

Dong-Won Lee, D.D.S.

Department of Dental Science

The Graduate School, Yonsei University

(Directed by Professor Ik-Sang Moon, D.D.S., M.S.D., Ph.D.)

The aim of this study was to evaluate the influence of crown width/fixture width ratio

on crestal bone loss around Astra single dental implants placed in the first molar area.

Forty-four subjects (19 males and 25 females; age range: 25 to 75 years; mean age: 54

years) were selected from patients who were treated with single-tooth implants between

March 2001 and December 2009 at the Department of Periodontology, Gangnam

Severance Dental Hospital.

The marginal bone level change and gingival parameters (modified plaque index and

modified sulcus bleeding index) of the peri-implant soft tissue were assessed one year

after functional loading. The perpendicular distances from the center of each fixture to

the most distal (dW) and most mesial (mW) were measured in the periapical radiographic

iv

view (Cr = mW + dW, Cr’ = mW or dW , I=fixture width, I’=fixture width/2).

Pearson correlation analysis was used to determine the correlation between crown

width/fixture width ratio and crestal bone loss; no statistically significant relationship

was found between crown width/fixture width ratio and 1-year bone level change

(p=0.156).

No statistically significant differences in marginal bone level change were found

between axial and non-axial loading implants (Mann-Whitney U-test ; p=0.57).

The bone level change at the surface adjacent and distant to the cantilever were

compared to determine the cantilever effect on the marginal bone loss. Bone level change

for the surface adjacent and distant to the cantilever was not statistically significant

(Wilcoxon’s signed rank test; p=0.08).

Peri-implant soft tissues were clinically healthy and revealed low modified plaque index

(mPI) and modified sulcus bleeding index (mSBI).

From this study, it may be concluded that off-axial loading resulting from a high crown

width/fixture width ratio does not increase the risk for peri-implant marginal bone loss

during functional loading.

Key words: off-axial loading, marginal bone loss, single implant

- 1 -

The effects of off-axial loading on peri-implant marginal bone loss in

a single implant: A 1-year retrospective study after loading

Dong-Won Lee, D.D.S.

Department of Dentistry

The Graduate School, Yonsei University

(Directed by Professor Ik-Sang Moon, D.D.S., M.S.D., Ph.D.)

I. INTRODUCTION

The first molar is the widest tooth and main area of occlusion (Kato et al. 1996;

Nakatsuka et al. 2010). Of all teeth, the first molar is lost most frequently (Müller et al.

2007). Possible treatment options for replacement of missing first molars include use of

conventional fixed partial dentures and implant restoration. The desire to preserve the

adjacent natural teeth has led to an increase in the use of single implants to replace

individual missing teeth.

The use of single implants has been shown to be an effective and predictable treatment

modality for the replacement of single molars, and several studies have suggested

favorable long-term results (Scholander 1999; Pjetursson and Lang 2008; Misch 2008).

To restore an edentulous space, the clinician must frequently use a crown that is

substantially wider than the implant that supports it. This is due to the dimensions and a

- 2 -

shape of implants being different from those of the roots of natural teeth. The greater the

width of the crown in a mesiodistal direction relative to the diameter of an implant, the

greater is the potential for off-axial loading. Rangert et al.(1995) suggested that off-axial

loading due to a discrepancy between crown width and implant width was considered to

contribute to potential bending overload. Such a discrepancy could be induced by the

decreased horizontal bone volume due to tooth extraction.

The positive correlation between peri-implant bone loss and over loading has been

observed in both animal studies (Miyata et al. 1997, 1998, 2000), and clinical studies

(Lindquist et al. 1988; Quirynen et al. 1992; Shackleton et al. 1994; Rangert et al. 1995;

Wyatt and Zarb 2002; Baron et al. 2005). These studies indicated that high stress on the

supporting bone around the implant may exert a negative effect on the marginal bone

level.

Finite element analysis (FEA) demonstrated that high stress concentration occurs at the

marginal part of the implant (Borchers and Reichart 1983; Rieger et al. 1990; Bidez and

Misch 1992; Clelland et al. 1993, 1995; Papavasiliou et al. 1996; Holmes and Loftus 1997;

Kitamura et al. 2004).

The discrepancy between crown width and implant width induces a high risk of over

loading and may create the potential for a cantilever effect with high bending moments.

The negative consequences of this size discrepancy are more likely in the molar region,

especially the first molar, because of the greater tooth size and occlusal force in this

region.

FEA was used to test this hypothesis (O’Mahony et al. 2000). A 490-N load was applied

at 0, 2, 4, and 6 mm from the vertical axis of the implant. Off-axial loading resulted in

- 3 -

greatly increased compressive stresses within the crestal cortical bone on the side at

which the load was applied and similarly increased tensile stresses on the side opposite

the load. These stresses increased considerably with each mm distant from the axis of the

applied load. Additionally, the compressive stresses were larger than the tensile stresses

when off-axial load was applied. Similarly, previous FEA studies demonstrated higher

stresses for implant surface adjacent as compared to surface distant cantilevers (Barbier et

al. 1997).

To date, few clinical trials have been conducted to evaluate the potential influence of

off-axial loading in relation to the crown width/fixture width ratio on peri-implant bone

stability.

The aim of this study was to evaluate the influence of the crown width/fixture width

ratio on the crestal bone loss around Astra single dental implants placed in the first molar

region.

- 4 -

II. MATERIALS AND METHODS

1. Patients

This study was approved by the Institutional Review Board of Yonsei University.

Patients were informed in detail about the study procedures and all signed an informed

consent form.

Forty four subjects (19 males and 25 females; age range: 25 to 75 years; mean age: 54

years) were selected from patients who were treated with single implants for replacement

of missing first molars at the Department of Periodontology, Gangnam Severance Dental

Hospital between March 2001 and December 2009.

Criteria for exclusion included untreated active periodontitis, bruxism/parafunction, poor

oral hygiene (mPI>2 - Mombelli et al. 1987), bone grafting in conjunction with implant

placement, uncontrolled compromised systemic disease and the patients with missing

second molars.

2. Implant fixture

Forty four internal-hexed implants (33 AstraTech OsseospeedTM, 11 AstraTech STTM ,

Astra Techs Dental Implant System; Astra Tech AB, Mölndal, Sweden) were used to

replace missing first molars. All implants had diameters of either 4 mm or 5 mm; implant

length varied between 8 mm and 13 mm. Distribution of the installed implants is detailed

in Tables 1 and 2.

- 5 -

Table 1. Distribution of the installed implants

AstraTech OsseospeedTM AstraTech STTM

Straight shape (4mm diameter) 14 6

Conical neck shape (5mm diameter) 19 5

Table 2. Distribution of the installed implants according to fixture length and site

Maxilla Mandible Total

8mm 1 1 2

9mm 8 9 17

11mm 8 13 21

13mm 3 1 4

Total 20 24 44

- 6 -

3. Treatment procedure

A two-stage surgical protocol was used. The second surgery was performed six and three

months later for maxillary and mandibular implants, respectively. Prostheses were

delivered three weeks after the second surgery. Patients were recalled every six months

for professional plaque control, and oral hygiene evaluation.

4. Radiographic examination and evaluation

Radiographs were taken with an extension cone paralleling (XCP) device (Extension

Cone Paralleling Kit, Rinn, Elgin, IL, USA.) using the parallel cone technique (70 kV, 8

mA, 0.250 s). A 5.5 mm spherical metal bearing was placed to aid length measurement.

All films were developed using the same automatic processor (Periomat, Durr Dental,

Bietigheim-Bissingen, Germany.) according to the manufacturer's instructions. Films

were digitized using a digital scanner (EPSON GT-12000, EPSON, Nagano, Japan.) at an

input resolution of 2400 dpi with 256 gray scale. Periapical radiographs (Kodak Insight,

film speed F, Rochester, NY, USA.) were taken one day after implant placement,

immediately before the second surgery, immediately after prosthesis delivery, and one

year after functional loading.

Measurements were taken to the nearest 0.01 mm using computer software (Image J

1.43u, Wayne Rasband, National Institutes of Health, USA); calibration was performed

using the known distance of the spherical metal bearing (5.5mm). Peri-implant marginal

bone level change was measured by comparing radiographs taken immediately after

prosthesis delivery to those taken one year after functional loading (Figure 1). Reference

points were defined as the border between the polished surface and the rough surface of

- 7 -

the fixture. Marginal bone levels at the mesial and distal implant surfaces were assessed

by measuring the distance between the reference point and the most apical point of the

bone level; these values were then averaged.

The following linear measurements between landmarks were taken(Figure 2). dW=

perpendicular distance from the center of the fixture to the most distal aspect of the

crown , mW=perpendicular distance from the center of the fixture to the most mesial

aspect of the crown. Cr = mW + dW, Cr’ = mW or dW , I = fixture width, I’= fixture

width/2.

Figure 1. Periapical radiographs taken (a) immediately after prosthesis delivery; (b)

after 1 year.

- 8 -

Figure 2. Linear measurement between landmarks. dW= perpendicular distance from the

center of the fixture to the most distal aspect of the crown, mW=perpendicular

distance from the center of the fixture to the most mesial aspect of the crown,

Cr = mW + dW, Cr’ = mW or dW, I = fixture width, I’= fixture width/2.

5. Follow up parameter

At the 1-year follow up visit, patients were evaluated for pain, discomfort and implant

related infection. To rule out the possible influence of inflammation of the peri-implant

soft tissues on the surrounding marginal bone, the modified plaque index (mPI) and

modified sulcus bleeding index (mSBI) were measured at four aspects around each

implant (Mombelli et al. 1987). Averages of the four measured plaque and sulcus

bleeding index values were calculated.

- 9 -

6. Statistical analysis

The pilot study with 8 patients indicated 41 samples would be needed to determine

correlation between implant/crown width ratio and peri-implant marginal bone loss.

The D’Agostino–Pearson test was used to test the normality of the distribution. The

outcome variables exhibited non-normal distribution except Cr/I ratio.

The hypothesis to be tested was as follows

i. There is a correlation between the Cr/I ratio and the crestal bone loss.

Pearson correlation analysis was used to analyze the correlation between

crown width/fixture width ratio and crestal bone loss.

ii. Non-axial loading (high Cr/I ratio) has an effect on the peri-implant marginal

bone loss.

To compare axial and non-axial loading, the two end quartiles of the

distribution of the implants with regard to the crown width/implant width

ratio were chosen to represent axial-loading implants and non axial-loading

implants. Axial loading and non-axial loading were compared using the Mann

- Whitney U-test.

iii. In each implant, compressive stress may induce more peri-implant marginal

bone loss than tensile stress when off-axial loading is applied

A “cantilever group” was defined as implants having a Cr’/I’ mesial-distal

difference>0.57(0.57= median). At each implant, bone level changes for the

surface adjacent (compressive stress) and distant to the cantilever (tensile

stress) were compared using the Wilcoxon’s signed-rank test.

The peri-implants soft tissue indices between axial loading and non-axial loading were

- 10 -

compared using the Mann - Whitney U-test.

Statistical software (SPSS for windows, release 17.0, SPSS Inc., Chicago, IL, USA) was

used to process all data.

Values were deemed statistically significant if the p-value was lower than 0.05.

- 11 -

III. RESULT

1. Clinical examination

No specific complications were found during the observation period. All of the implants

functioned normally. No subjects complained of pain or mobility of the implants. No

inflammation was observed in any of the implants.

2. Correlation between crown width/fixture width ratio and peri-

implant marginal bone loss

A. Correlation between crown width/implant width ratio and 1 year bone level change.

A weak positive correlation was found between crown width/implant width ratio and 1

year bone level change (Figure 3). But Pearson’s correlation analysis did not revealed a

statistically significant between crown width/implant width ratio and 1 year bone level

change (Table 3).

Table 3. Pearson correlation analysis with respect to crown width/implant width

ratio and 1 year bone level change

Coefficient p-value

Cr/I r = 0.217 0.156

- 12 -

Figure 3. Scattergrams of correlation between Cr/I ratio and peri-implant marginal bone

loss

- 13 -

B. Axial loading and Non-axial loading

The frequency distribution of implants with regard to the crown width/implant width

ratio is given in Figure 4.

No statistically significant differences in marginal bone change were found between

axial and non-axial-loading implants. (Table 4)

Figure 4. Distribution of implants according to crown width/implant width ratio.

- 14 -

Table 4. Peri-implant marginal bone level change (mm)

Axial loading Non axial loading

N 11 11

Mean marginal bone loss 0.05 0.06

Standard deviation 0.06 0.09

Median 0.04 0.02

95% CI for the median 0-0.08 0-0.10

p-value 0.57

The two tail quartiles were selected to represent axial loading (n=11 ;mean1.83 ;range 1.55-

2.03) and non-axial loading(n=11 ; mean2.72 ;range 2.52-3.07)

- 15 -

C. Marginal bone loss (mm) comparison between surface distant and adjacent to the

cantilever

More bone loss tended to occur on the surface adjacent to the cantilever. However, bone

level changes for the surfaces adjacent and distant to the cantilever showed no statistically

significant difference (Table 5).

Table 5. In cantilever group, marginal bone loss (mm) comparison between

surface distant and adjacent to the cantilever

Surface distant to the cantilever

Surface adjacent to the cantilever

N 22 22

Mean marginal bone loss 0.03 0.07

Standard deviation 0.06 0.11

Median 0 0

95% CI for the median 0-0.06 0-0.02

p-value 0.08

Cantilever group: Cr’/I’ mesial-distal difference>0.57(0.57=median)

- 16 -

3. Evaluation of peri-implants soft tissue

The peri-implant soft tissues were found to be clinically healthy. The average mPI and

the average mSBI was 0.32 and 0.17 respectively. The average mPI of the axial loading

group was 0.45, and that of the non-axial group was 0.25. The average mSBI was 0.18 for

the axial loading group and 0.15 for the non-axial loading group. No significant

differences were found between the two groups for the mPI (p = 0.24) and mSBI (p =

0.93) (Table 6).

Table 6. Modified plaque index (mPI) and modified sulcus bleeding index (mSBI)

All patients Axial Non axial

mPI(mean/median/standard deviation) 0.32/0.25/0.43

0.45/0.38/0.40 0.25/0.125/0.39

p= 0.24

mSBI(mean/median/standard deviation) 0.17/0.00/0.33

0.18/0.00/0.33 0.15/0.00/0.32

p=0.93

- 17 -

IV. DISCUSSION

Marginal bone level alteration around implants is frequently used to assess the outcome

in longitudinal studies that evaluate implant therapy. Although many factors are

considered, occlusal loading and inflammation due to biofilm formation are frequently

cited as the most important factors affecting the peri-implant marginal bone level change.

Several studies have indicated that periodontally compromised patients showed a higher

rate of peri-implant bone loss than patients without periodontitis (Hardt et al. 2002;

Karoussis et al. 2003; Matarasso et al. 2010). In order to prevent peri-implant marginal

bone loss due to bacterial biofilm formation and consequent inflammation, we ensured

that the patients in this current study maintained a high level of infection control

throughout the follow-up period, This is evident from the low mPI and mSBI scores

obtained. It should be noted that patients with poor oral hygiene were excluded from this

study. Periodontally compromised subjects received complete periodontal treatment

before the second surgery. Therefore it can be assumed that any marginal bone loss we

observed may be attributed to factors other than inflammation caused by biofilm

formation.

The aim of this study was to evaluate the influence of off-axial loading, based upon the

crown width/fixture width ratio, on the crestal bone loss following replacement of missing

first molars. Off-axial loading is considered to contribute to bending overload(Rangert et

al. 1995).

The overall crestal bone loss was very small. Mean values for all groups were well

- 18 -

below accepted levels of bone loss for implants at 1 year of function (Albrektsson et al.

1986).

Our results demonstrated that there is no correlation between crown width/fixture width

ratio and crestal bone loss over a 1-year period of functional loading of a single implant

replacing missing first molar in patients who maintain a high standard of oral hygiene. No

statistically significant differences in marginal bone change were found between axially

and non-axially loaded implants that were categorized according to crown width/implant

width ratio(p = 0.57). Bone level changes for the surface adjacent and distant to the

cantilever created by loading the implant were compared. The results revealed that no

statistically significant differences in mean marginal bone loss between the two areas

(p=0.08).

These results differ from those found in prior FEA studies. Because It seems that the

stress level of the implants with the off-axial loading is within the load bearing capacity

of the surrounding bone. Frost (1992, 2004) suggested the theory that apposition of the

bone around an oral implant is the biological response to a mechanical stress below a

certain threshold, whereas loss of marginal bone may be the result of mechanical stress

beyond this threshold. In dog studies, it was shown that mechanical stress leads to bone

remodeling and thickening (Ogiso et al. 1994; Barbier et al. 1997). In a study by Melsen

and Lang (2001), bone apposition was most frequently found when strain varied between

3400 and 6600 microstrain. On the other hand, when the strain exceeded 6700 microstrain,

the bone induced a bone loss.

To date, the magnitude of the force necessary to cause peri-implant marginal bone loss

in a normal clinical environment has not been established. Controlled randomized clinical

- 19 -

trials are necessary to identify this force; however, due to ethical concerns, it is of course

impossible to deliver prosthetics that deliberately induce over load in patients. When

interpreting the results of this study, it should be noted that the crown width/implant

width ratio was based solely on measurements taken from the mesial-distal direction. We

recognize that off-axial loading in the buccal-lingual direction is of equal importance;

however, this type of loading could not be included in the study due to unfeasibility of

measuring buccal-lingual crown width on the periapical radiographic view.

It is worth mentioning that individual bite force and bone mechanical properties may

affect the results when investigating the effects of loading on marginal bone loss.

Previous studies have shown that occlusal force and bone property vary from person to

person. Age and gender influence the maximal bite force (Ikebe et al. 2005; Palinkas et al.

2010). When load is applied, the strain on the bone is dependent upon the mechanical

properties of the bone; the same amount of stress can result in different amounts of strain

in bones that posses different mechanical properties. In a prospective human study, Manz

(1997) observed that the amount of radiographic marginal bone loss around implants was

related to the density of bone as observed during surgery. These factors may explain the

discrepancy between FEA studies and clinical studies.

Several animal experiments examined the influences of overloading on peri-implants

marginal bone loss. (Isidor 1996, 1997; Miyata et al. 1997, 1998, 2000; Duyck et al. 2001;

Heitz-Mayfield et al. 2004; Kozlovsky et al. 2007). These studies were designed to

evaluate excessive loading conditions that may not be comparable with loading conditions

during normal function in humans. In spite of the extreme conditions, in most of the

studies, it was found that the loading did not induce peri-implant marginal bone loss.

- 20 -

Peri-implant marginal bone response to excessive off-axial loading has been studied in

clinical studies. Koutouzis et al (2007) indicated that off-axial loading due to tilted

implant position did not increase the risk of bone loss in a 5-year study. Other publication

support these findings (Krekmanov et al. 2000; Aparico et al. 2001; Calandriello and

Tomatis 2005). Additionally, several clinical studies have shown no significant

differences in radiographic bone height between cantilever and non cantilever sides of

each implant (Wennström et al. 2004; Palmer et al. 2011). That results observed in vitro

may not be the same as clinical results which has been corroborated by our findings.

In this study, it was demonstrated that off-axial loading of implants with large crown

width/implant width ratios did not induce peri-implant marginal bone loss. There, the

clinical outcome of replacement of large teeth such as the first molar with a single implant

can be predictable in terms of maintaining the marginal bone level. However, given that

off-axial loading may raise prosthetic complications such as screw looseness, screw

fracture, porcelain fracture, and fixture fracture, further clinical study is necessary to

thoroughly evaluate the influence of the crown width/fixture width ratio.

- 21 -

V. Conclusion

Within the limitations of this study, we conclude that non-axial load resulting from

crown width/fixture width ratio does not increase the risk for peri-implant marginal bone

loss after 1-year functional loading

- 22 -

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국문요약

Off-axial loading이 단일 임플란트 주위 변연골 소실에 미치는

영향에 대한 후향적 연구

<지도교수: 문 익 상, D.D.S., M.S.D., Ph.D.>

연세대학교 대학원 치의학과

이 동 원, D.D.S

이 연구의 목적은 제 1 대구치에서 임플란트로 수복하는 경우 임플란트 폭경에

대한 보철물의 폭경의 비율이 임플란트 주변 변연골에 미치는 영향을 평가하는

것이다.

연구를 위해 제 1 대구치에 단일 임플란트(33 AstraTech OsseospeedTM, 11

AstraTech STTM , Astra Techs Dental Implant System; Astra Tech AB,

Mölndal, Sweden)를 식립한 44 명의 환자를 선정하였다. 임플란트의 직경은

4mm 와 5mm 였으며 길이는 8 에서 13mm 로 다양하였다. 상부 보철물

연결시의 방사선 사진과 기능적 부하를 가하고 1 년 후의 방사선 사진 사이의

- 31 -

임플란트 변연골 흡수량을 비교 분석하였다. 또한 연조직의 염증이 임플란트 주변

변연골에 미치는 영향을 최소화하기 위해 구강 위생 교육과 관리를 정기적으로

시행하였고 정기 검진 시 치태지수와 점막지수를 측정하였다.

임플란트 폭경에 대한 보철물의 폭경의 비율 과 임플란트 주변 변연골 사이의

상관 관계를 알기 위해 Pearson correlation analysis 를 이용하여 분석한

결과 통계적으로 유의한 결과가 나타나지 않았다(p=0.156).

임플란트 폭경에 대한 보철물의 폭경의 비율의 분포에서 4 분위 수를 구하여

양끝에 해당하는 그룹을 axial loading 그룹 과 non axial loading 그룹으로

정하고 두 그룹 사이의 임플란트 변연골 사이 변화량을 분석한 결과 두 그룹

사이에서 골 흡수량은 유의한 차이를 보이지 않았다(p=0.57). 각각의

임플란트에서 보철물의 폭경과 임플란트 직경 사이의 차이에 의해 발생할 수

있는 외팔보 효과를 조사하기 위해 외팔보에 가까운 쪽과 먼 쪽의 골 흡수량을

비교한 결과 두 그룹 사이에 통계적으로 유의한 차이를 보이지 않았다(p=0.08).

또한 보철물 연결 1 년 후의 치태 지수와 점막지수는 환자들에서 양호하게

나타났다.(평균치태지수=0.32, 평균점막지수=0.17)

이 번 연구 결과, 임플란트 폭경에 대한 보철물의 폭경의 비율은 임플란트 주변

변연골의 흡수를 야기하지 않는 것으로 나타났다.

핵심 단어: off-axial loading, 단일 임플란트, 변연골 흡수