Assessment of marginal bone loss using full thickness versus partial thickness flaps for alveolar ridge splitting and immediate implant placement in the anterior maxilla

Abstract

The aim of this study was to evaluate the effectiveness of maintaining the periosteal attachment of the facial and palatal cortical plates on crestal bone loss that occurs at the margin of dental implants placed immediately in split anterior maxillary alveolar ridges. This was a prospective randomized comparative clinical trial. The study population included 22 patients with edentulous anterior maxillary alveolar ridges who presented for treatment during the period March 2012 to September 2013. The selected patients were divided randomly into two equal groups. All patients underwent a maxillary ridge splitting technique; a total of 43 implants were placed immediately. A full thickness mucoperiosteal flap was performed in the control group patients, while a split thickness mucosal flap was done in the study group patients. Assessments included measurements of the linear changes in the marginal bone surrounding the implants immediately postoperative and after 6 months. Measurements were taken from cross-sectional and longitudinal cone beam computed tomography images using special software. The partial thickness flap used in the study group decreased the percentage of bone loss by 9.5% for the labial bone plate, 7.9% for the palatal bone plate, and 3.5% for the mesiodistal bone plate.

Introduction

One of the most important factors for successful implant placement is the horizontal dimension of the available bone at the desired implant location. Based on clinical experience, the minimum required dimensions of bone include a ridge width of 6 mm, allowing for a minimum thickness of 1–1.5 mm of bone on the facial and lingual aspects of the implant, and a vertical bone height of 10 mm.

A limitation in the alveolar ridge width constitutes a major problem for the successful placement of dental implants due to the discrepancy between the diameter of the implant and the horizontal dimension of the alveolar ridge. Several surgical procedures have been used successfully for augmentation of the deficient alveolar ridge, such as guided bone regeneration, cortical autogenous onlay block grafting, ridge expansion, and distraction osteogenesis. These have drawbacks, such as greater financial cost, an increase in the overall treatment period, and possible donor site morbidity.

As an alternative to these approaches, a variety of alveolar ridge splitting techniques have been introduced for the treatment of horizontal ridge deficiencies. Ridge splitting techniques have proved to be successful for the horizontal augmentation of alveolar ridges, especially in the maxilla due to the resilience and softness of the bone. However, crestal bone loss that occurs secondary to ridge splitting techniques presents a serious obstacle to the success of implant placement in the aesthetic zone and has become a critical and challenging feature of that procedure.

Previous trials have been performed in order to overcome this complication by making a modification to the flap design, using either full thickness flaps and placing membranes, or split thickness flaps leaving the periosteal attachment on the split surfaces intact.

The purpose of this study was to compare partial thickness to full thickness flaps in reducing crestal bone loss at the margin of dental implants.

Materials and methods

The investigators designed and implemented a single-institution, double-blind, randomized comparative clinical study. A total of 22 patients suffering missing single or multiple maxillary anterior teeth were selected. After obtaining approval from the ethics and research committee, all patients were informed of the procedures and consented to be followed throughout the study.

To be included in the study sample, patients had to fulfil the following inclusion criteria: (1) A partially edentulous anterior maxillary ridge. (2) Criteria of the edentulous ridge, including (a) an anterior maxillary vertical dimension of ≥10 mm measured from the alveolar crest to the basal bone of the maxilla (i.e. alveolar ridge had no vertical inadequacy); (b) horizontal alveolar dimension ranging from 3 to 5 mm at the crest and 6 to 8 mm at the basal part of the ridge, measured from the labial to the lingual cortex.

Patients were excluded as study subjects if they fell into the following criteria: (1) any systemic disease directly affecting bone metabolism and healing; (2) local disease that may interfere with bone healing; (3) a history of any grafting procedure at the designated edentulous ridge.

The patients were divided randomly into two equal groups: (1) those who underwent the ridge-splitting technique using a full thickness mucoperiosteal flap (control group), and (2) those who underwent the ridge-splitting technique using a partial thickness mucosal flap (study group).

Materials and methods

The investigators designed and implemented a single-institution, double-blind, randomized comparative clinical study. A total of 22 patients suffering missing single or multiple maxillary anterior teeth were selected. After obtaining approval from the ethics and research committee, all patients were informed of the procedures and consented to be followed throughout the study.

To be included in the study sample, patients had to fulfil the following inclusion criteria: (1) A partially edentulous anterior maxillary ridge. (2) Criteria of the edentulous ridge, including (a) an anterior maxillary vertical dimension of ≥10 mm measured from the alveolar crest to the basal bone of the maxilla (i.e. alveolar ridge had no vertical inadequacy); (b) horizontal alveolar dimension ranging from 3 to 5 mm at the crest and 6 to 8 mm at the basal part of the ridge, measured from the labial to the lingual cortex.

Patients were excluded as study subjects if they fell into the following criteria: (1) any systemic disease directly affecting bone metabolism and healing; (2) local disease that may interfere with bone healing; (3) a history of any grafting procedure at the designated edentulous ridge.

The patients were divided randomly into two equal groups: (1) those who underwent the ridge-splitting technique using a full thickness mucoperiosteal flap (control group), and (2) those who underwent the ridge-splitting technique using a partial thickness mucosal flap (study group).

Preoperative preparation

Clinical evaluation

A thorough medical and dental history, followed by clinical examination was carried out for all patients. Clinical labio-palatal measurements were done using a calliper to ensure the patients met our initial inclusion criteria prior to further investigations. Impressions were taken and a diagnostic wax-up was performed on the study cast to fabricate a vacuum-formed stent in order to locate the proposed osteotomy sites during surgery.

Radiographic evaluation

A cone beam computed tomography (CBCT) scan was done as a final investigation for the assessment of the labio-palatal width of the edentulous alveolar ridge. The width of each implant site was measured accurately on the reformatted cross-sectional images at 3 points (at 3 mm, 6 mm, and 9 mm) ( Fig. 1 ).

Fig. 1
Reformatted cross-sectional CBCT showing the calculation of the horizontal dimension of the ridge at three points 3, 6, and 9 mm from the crest (preoperative view).

Surgical procedures

All patients underwent surgery under local anaesthesia using mepivacaine hydrochloride 2% and levonordefrin (Scandonest; Septodont, France). Povidone–iodine surgical scrub was applied to the patient. A three-line pyramidal flap was raised in which the crestal incision was carried out rather palatally in order to compensate for the increase in ridge width following the ridge splitting. Oblique releasing incisions were made 2 mm away from the papillae of the teeth enclosing the edentulous area (papilla preservation incision).

Reflection of the labial and palatal mucoperiosteal flap was done: a full thickness flap in the control group ( Fig. 2 ) and a split thickness flap in the study group ( Fig. 3 ). A midcrestal bony cut was done using a tungsten carbide disc of 1.5-mm thickness. Cuts were performed transperiosteally in the study group. Two vertical stop cuts were made at the distal ends of the midcrestal bony cut on the facial surface of the alveolar ridge, extending 5 mm apically from the crest of the ridge ( Fig. 2 ).

Fig. 2
Bone cuts (top view); the single arrows indicate two vertical stop cuts and the double arrows indicate the midcrestal cut (control group).

Fig. 3
Labial and palatal split thickness flap reflection (study group).

Ridge splitting osteotomes of sequential widths (2 and 3 mm) were used to revise the bony cuts. Ridge splitting osteotomes were gradually malleted to a depth of 5–7 mm creating a channel at the designated implant site along the crest of the bone. Expanders (osteotomes) of sequential diameters (2.3, 2.8, 3.4, and 4.1 mm) were introduced through their corresponding guides in the stent ( Figs. 4 and 5 ).

Fig. 4
Final horizontal dimension of the alveolar ridge (bone flap); arrows show the prepared osteotomy sites.

Fig. 5
Ridge expansion osteotomes introduced through the split ridge (study group).

The final drill was introduced for threading the osteotomy sites, followed by implant insertion using a torque-wrench in a self-tapping fashion, engaging the basal bone for primary stability ( Fig. 6 ).

Fig. 6
Placement of the final implant in the split ridge.

Alloplastic bone material, silicon-substituted hydroxyapatite (Si-HA) 60% and β-tricalcium phosphate (β-TCP) 40% (Bone Medik DM Bone; Meta BioMed Co. Ltd, Oksan, Korea), was mixed with saline and packed into the interpositional space ( Figs. 7 and 8 ). Finally, the under surface of the flap was scored and tension free closure was performed using 3–0 Vicryl sutures ( Figs. 9 and 10 ).

Fig. 7
Application of alloplastic bone material in the inter-cortical gaps (control group).

Fig. 8
Application of the alloplastic bone material to fill the inter-cortical gaps (study group).

Fig. 9
Wound closure with 3–0 Vicryl sutures (control group).

Fig. 10
Wound closure with 3–0 Vicryl sutures (study group).

Postoperative care included a cold compress over the upper lip applied for 20 min every hour for 6 h postoperatively. The patient was kept on a clear fluid diet for the first 24 h, then a soft diet was maintained for the following day. The patient was advised to use a warm saline oral rinse three times daily for 1 week.

CBCT assessment

For the calculation of marginal bone loss (MBL), the implant was used as a reference by adjusting the cross-sectional and panoramic long axis in the centre of the implant and bisecting it (showing the buccolingual and mesiodistal dimensions). On the cross-sectional view, a line was drawn just parallel to the implant, starting at the crest of the labial plate of bone and ending at the apical level of the implant; height was recorded in millimetres. The same process was repeated from the palatal direction ( Figs. 11 and 12 ). The panoramic view (longitudinal cut) was utilized to calculate the mesial and distal bone heights in millimetres ( Figs. 13 and 14 ).

Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Assessment of marginal bone loss using full thickness versus partial thickness flaps for alveolar ridge splitting and immediate implant placement in the anterior maxilla
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