©2010 Association for Dental Sciences of the Republic of China

CASE REPORT

J Dent Sci 2010;5(2):114−120

*Corresponding author. Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan.E-mail: yimin@kmu.edu.tw

Introduction

There are four positional parameters that con-tribute to the success of implant restorations: the angulation of the implant, and the buccolingual, mesiodistal and apicocoronal positions relative to the implant platform. It is often difficult to posi-tion a single standard-diameter implant in a nar-row space in an ideal manner. In addition, it is also difficult to esthetically restore a small-sized tooth and install a standard-diameter implant on a narrow

alveolar ridge without performing a guided bone regeneration (GBR) procedure. Narrow-diameter im-plants were recently developed and are now available as therapeutic options for cases with space limita-tions such as the one we present here. Numerous experimental studies confirmed that osseointegra-tion of narrow-diameter implants can be achieved1−6 and maintained.1,2,7−9 For lower anterior teeth, the limited space is always an issue for implant treatment. This report presents the treatment of a case with inadequate space distribution, and after

This report presents a case of inadequate space distribution after orthodontic treat-ment, when a narrow-diameter implant was placed in a limited mandibular ante-rior space (ridge and prosthetic). A 26-year-old female patient presented with a purulent discharge from the mandibular right posterior area. Radiographic and clini-cal evaluations revealed a four-unit bridge spanning teeth 42 to 43 and acute apical periodontitis with root resorption around tooth 42. After careful evaluation, tooth 42 was extracted, and orthodontic treatment was performed to align the posterior teeth and create a dimensionally appropriate space between teeth 41 and 43. A 3i MicroMiniplant with dimensions of 3.25 mm (diameter) ̃ 11.5 mm was implanted in the edentulous area of tooth 42 because of the small size of tooth 42. Autogenous bone particles were placed on the buccal crestal defect, and a healing abutment was attached. After an 8-month healing phase, a final impression was made and an all-ceramic crown was delivered. This case demonstrates that osseous sites with significant dimensional space limitations can be successfully utilized to receive and integrate a narrow-diameter implant that will satisfy esthetic, phonetic and func-tional requirements.

Received: Feb 25, 2010Accepted: May 2, 2010

KEY WORDS:limited space;

lower anterior implant;

narrow-diameter implant

Application of a narrow-diameter implant in a limited space

Chia-Yun Tsai,1 Ching-Fang Tsai,1 Yu-Chuan Tseng,1 Jung-Chang Kung,1 Yi-Min Wu1,2*

1Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan2Faculty of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan

Narrow-diameter implant 115

orthodontic treatment, a narrow diameter implant was placed in a site with limited space (ridge and prosthetic) in the anterior mandible.

Case presentation

Clinical and radiographic evaluations

A 26-year-old female patient was suffering from a purulent discharge in the mandibular right ante-rior area, which was attributed to acute apico-periodontitis and root resorption of tooth 42. The patient was informed that her restorative options included a removable partial denture, a fixed bridge, and a fixed implant restoration. In order to avoid damaging the adjacent teeth, a fixed implant res-toration was selected by the patient. The patient denied having any systemic or inherited diseases.

Radiographic and clinical evaluations revealed no obvious signs or symptoms of an active infection ex-cept for the acute apico-periodontitis and root re-sorption of tooth 42. A four-unit bridge (spanning teeth 42 to 43) with an improperly distributed space was noted (Fig. 1). The patient’s skeletal pattern was Class I, and the facial pattern was orthodiver-gent. A model analysis showed a right canine Class I relationship and left canine Class II relationship, in-cluding the spacing and rotation. The mandibular dental midline had shifted 4.7 mm to the left. The long axes of teeth 31 and 32 were in distoversion, and the long axis of 41 was in mesioversion. The hor-izontal overlap was 2.1 mm, and the vertical overlap was 1.5 mm. The Bolton anterior ratio was 79.7 (77.1 ± 0.2) (Fig. 2A−G). According to the diagnostic wax-up, adequate space distribution for a mini-implant placement and an ideal occlusion was obtained after orthodontic treatment.

According to the above evaluation, orthodontic treatment and then a narrow-diameter implant placement were suggested in this situation.

Reevaluation during orthodontic treatment

Twenty-seven months after orthodontic treatment, a reevaluation was performed in anticipation of a future implant procedure. Radiographic and clini-cal evaluations demonstrated no evidence of re-markable gingivitis or periodontitis. In the space between teeth 41 and 43, tooth 41 was distally tipped and tooth 43 was mesially tipped (Fig. 3). Model analysis showed that the patient now had a bilateral Class I canine relationship, and the lower dental midline was now located 1.1 mm to the left of the maxillary midline. The space between teeth 41 and 43 was 6.4 mm in the mesiodistal dimension and 6.9 mm in the buccolingual dimension (mea-sured from the center of the edentulous space in the mesiodistal aspect). Assuming the buccal and lingual mucosal thickness to be about 1.5 mm,10,11 the bone width should be approximately 3.9 mm. The horizontal overlap was 1.1 mm (the measure-ment was reduced because of spaces in the max-illa and mandible being closed by orthodontic treatment), and the vertical overlap was 1.5 mm (Fig. 4). A diagnostic wax-up (Fig. 5) showed that adequate space existed for an implant-supported prosthesis.

Surgical procedures

Following administration of local anesthesia, cre-stal and sulcular incisions around teeth 41 and 43 were made, and a mucoperiosteal flap was ele-vated for direct visualization of the bone topogra-phy. An external hex 3i MicroMiniplant (3i System Implant Innovations, Palm Beach Gardens, FL, USA; 3.25 mm [diameter] ̃ 11.5 mm; platform diameter, 3.4 mm) was installed at the prepared site. Primary implant stability was achieved. Then, a healing abutment 4.0 mm in diameter and 4 mm in height was tightened onto the implant. Autogenous bone

A B

Fig. 1 (A, B) Preoperative radiographs.

116 C.Y. Tsai et al

particles were taken from the right torus man-dibularis to increase the thickness of the buccal crestal margin (without the combined membrane) (Fig. 6).

Postoperative instructions

The patient was placed on a regimen of 500 mg of amoxicillin and 250 mg of mefenamic acid, four

Fig. 2 (A−G) Clinical examination and model analysis.

A B

Fig. 3 (A, B) Radiographic reevaluation after orthodontic treatment.

A B

D

C

E

GF

0.9mm

1.3mm1.4mm0.8mm

1.9mm

2.6mm

4.1mm5.5mm

1.0mm1.2mm

1.3mm

Narrow-diameter implant 117

A B C

D E

Fig. 4 (A−E) Clinical reevaluation after orthodontic treatment.

times a day for 7 days. The patient was instructed in oral hygiene care and asked to rinse with 0.12% chlorhexidine until the sutures were removed 14 days postoperatively.

Provisional prostheses

Two months after surgery, a provisional crown (Tempron; GC Co., Tokyo, Japan) was fabricated and left out of occlusion. Once the provisional crown was in place, the orthodontist made the final alignment adjustments (Fig. 7).

Definitive prostheses

After 3 years of orthodontic treatment (approxi-mately 8 months after surgery), a final impression was made with a polyether impression material (Impregum F; 3M ESPE, St. Paul, Minnesota, USA). An all-ceramic crown (Lava All-Ceramic System; 3M ESPE) was fabricated. Following occlusal adjust-ment, the all-ceramic crown was cemented with resin cement (Maxcem Elite; Kerr Corp., Orange,

CA, USA) (Fig. 8). The peri-implant tissue appeared to be stable at a 6-month follow-up examination. (Fig. 9).

Discussion

The buccolingual, mesiodistal and apicocoronal po-sitions relative to the implant platform and the angulation of the implant are the four positional parameters that contribute to the success of im-plant restorations.12,13

For the buccolingual position, the buccal wall needs to have a thickness of at least 1 mm to pre-vent recession and improve esthetics. According to Spray et al.,14 if the thickness of the facial mar-ginal bone is < 1.8 mm, the chance of bone loss is increased; if the thickness of the facial marginal bone is ≥ 1.8 mm, the chance of either no change in the bone or bone gain is increased. When the bone thickness is ≥ 2.0 mm, only 2.5% of the implants failed. In our case, we used a 3i MicroMiniplant be-cause of buccolingual space and tooth size limita-tions. The implant diameter was 3.25 mm, and the buccolingual bone width was 3.9 mm. Since buccal bony dehiscence was noted when drilling the ridge, the implant procedure combined with a GBR pro-cedure was required. Dahlin et al.15 showed that there was a significant increase in the percentage bone gain for GBR implants compared with un-treated implants.

For the mesiodistal position, a minimum distance of 1.5−2 mm should be maintained between the im-plant and neighboring teeth.16−18 In 2000, Tarnow et al.16 proposed that to minimize vertical bone loss subsequent to implant placement, the adjacent teeth should be 1.5 mm from the implant. In our

Fig. 5 Diagnostic wax-up during orthodontic treatment.

118 C.Y. Tsai et al

case, the mesiodistal distance of the alveolar ridge was 6.4 mm and the implant tooth distance would have been 1.57 mm if we had placed the implant in the middle of the alveolar ridge.

The apicocoronal extension should be as shallow as possible and as deep as necessary. Al-Sabbagh19 suggested 2−3 mm apically to the imaginary line connecting the mid-buccal of the cementoenamel

A

D

G

B

E

H

C

F

I

Fig. 6 (A−I) Surgical procedures.

A B

Fig. 7 (A, B) Provisional prostheses fabricated and left out of occlusion.

Narrow-diameter implant 119

junctions of the adjacent teeth without gingival recession. In our case, the platform was placed level with the mesial crestal bone. The distance to an imaginary line connecting the mid-buccal of ce-mentoenamel junctions of the adjacent teeth was about 2 mm. However, the distance from the inter-proximal contact points to the alveolar crest was 6 mm, so the loss of interdental papillae was antici-pated. A longer contact zone or alteration in teeth alignment was considered.

Although the 3i MicroMiniplant is a narrow-diameter implant by definition, the platform is 3.4 mm, which was wider than the cervical dimen-sion of the patient’s lower incisors (3.12 mm). That was the reason why the result was not identical to the diagnostic wax-up before the treatment. We tried to trick the senses by using implant-supported prostheses to make it appear similar to the adja-cent teeth. An increasing number of studies utilizing the mini-implant system are being reported in the literature.1−6 At the present time, the range of mini-implant diameters is 1.8−2.4 mm, which is signifi-cantly narrower than usual. The results showed that narrow implants were successfully integrated, and patients reported complete satisfaction regarding

Fig. 9 Six-month follow-up after the definitive prostheses were delivered.

A B C

Fig. 8 (A−C) An all-ceramic crown fabricated and cemented with resin cement.

function, esthetics, and phonetics, thereby provid-ing additional therapeutic options for this clinical situation in the future.

The advantage of narrow-diameter implants is that they allow the dental practitioner to perform implant placement without the GBR procedure in spaces with a limited quantity of bone. GBR can be used to cover exposed implant threads in regions of bony dehiscence or horizontal expansion of the re-sidual ridge contour.20−23 Exposed threads of an im-plant can cause persistent gingivitis, fistulae, and/or hyperplasia formation, which in some advanced cases may lead to total implant loss.24 However, per-forming a GBR procedure requires experience and a high degree of surgical skills. In addition, there are drawbacks such as a prolonged time before tooth reconstruction can occur, patient morbidity, and additional expenses.25,26 Side effects of GBR include profound edema, pain, discomfort, and pos-sible risks of nerve and blood vessel injury leading to nerve disturbances and a hematoma. The use of narrow-diameter implants is a significant treat-ment modality when a ridge deficiency problem is encountered. We needed to use a narrow-diameter implant in our case because of the limited amount of prosthetic space; nevertheless, we still encoun-tered ridge deficiency. However, the use of a narrow-diameter implant caused fewer implant threads to be exposed, which diminished the amount of bone graft that was necessary.

From an esthetic point of view, replacing man-dibular incisors with a thin emergence profile is a challenge. When the mesiodistal dimension in the natural dentition is reduced, it is impossible to use a standard-width implant. The use of narrow-diameter implants will be an optimal choice in cases with limited space, and will minimize the need for com-bined GBR procedures. There are several studies that reported high predictability of narrow-diameter implants. Our case demonstrates that a narrow-diameter implant can successfully be integrated and can satisfy the chewing, esthetic, and phonetic func-tions of the patient in a site that has a limited tooth diameter.

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Acknowledgments

This article was supported by the Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. We especially thank Dr John Ebinger for his assistance in the English writing .

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