The effect of conventional surgery and piezoelectric surgery bone harvesting techniques on the donor site morbidity of the mandibular ramus and symphysis

Abstract

The aim of this study was to evaluate the morbidity following bone harvesting at two different intraoral donor sites, mandibular symphysis and ramus, and to determine the effects of piezoelectric and conventional surgical graft harvesting techniques on donor site morbidity. Intraoral block bone grafts were harvested from the symphysis ( n = 44) and ramus ( n = 31). The two donor site groups were divided into two subgroups according to the surgical graft harvesting method used (conventional or piezoelectric surgery). Intraoperative and postoperative pain was assessed using a visual analogue scale (VAS). Donor site morbidity and the harvesting techniques were compared statistically. Of 290 teeth evaluated in the symphysis group, four needed root canal treatment after surgery. The incidence of transient paresthesia in the mucosa was significantly higher in the symphysis group than in the ramus group ( P = 0.004). In the symphysis group, the incidence of temporary skin and mucosa paresthesia was lower in the piezoelectric surgery subgroup than in the conventional surgery subgroup ( P = 0.006 and P = 0.001, respectively). No permanent anaesthesia of any region of the skin was reported in either donor site group. VAS scores did not differ between the ramus and symphysis harvesting groups, or between the piezoelectric and conventional surgery subgroups. When the symphysis was chosen as the donor site, minor sensory disturbances of the mucosa and teeth were recorded. The use of piezoelectric surgery during intraoral harvesting of bone blocks, especially from the symphysis, can reduce these complications.

Bone grafting techniques for pre-prosthetic alveolar reconstruction, with varying degrees of success, are well documented in the literature. A variety of allografts and alloplastic grafts have been used, however the vast majority of authors have reported the superiority of autogenous bone for alveolar reconstruction. Autogenous bone is considered the gold standard for osseous reconstruction because it does not produce immunological reactions and contains osteoinductive components.

Although the iliac crest is most often used in jaw reconstruction, there is a significant risk of resorption with iliac block bone grafts. This disadvantage, and the fact that dental implants do not require a large amount of bone, has led to the increasing use of autogenous block bone grafts from intraoral sources, particularly from the mandibular symphysis and ramus.

In the repair of localized alveolar defects, bone grafts from the symphysis and the ramus offer several benefits: (1) conventional surgical access; (2) the proximity of donor and recipient sites reduces the length of the operation and the time spent under anaesthesia, making intraoral bone grafts ideal for outpatient implant surgery; and (3) minimal discomfort reported by patients because of the lack of a cutaneous scar and less morbidity as compared with extraoral locations. Despite these advantages, several complications are mentioned in the literature related to bone graft harvesting from the symphysis and the ramus. These include tooth numbness, neurosensory disturbances, alterations of mucosa and skin sensitivity, postoperative discomfort (limited mouth opening, bleeding, swelling, and pain), and aesthetic problems (changes in the contour of the donor area or soft tissue recession).

An advantage of the ramus donor site over the symphysis site is fewer complaints of postoperative discomfort. The disadvantages of the ramus area include the limited surgical access, limited graft volume, and potential hazard of damage to the mandibular neurovascular bundle. Although these features appear to indicate the mandibular symphysis as the graft donor site of choice, both mandibular symphysis and ramus bone grafts are commonly preferred in clinical practice.

The use of ultrasonic vibrations to cut bone was first introduced two decades ago to overcome the limitations of traditional instrumentation in oral bone surgery; this was done by modifying and improving conventional ultrasound technology. Piezoelectric surgery is a minimally invasive technique that reduces the risk of damage to the surrounding soft tissues and important structures, such as nerves, vessels, and mucosa, and produces less collateral tissue damage, resulting in better healing. This surgery also reduces damage to osteocytes during the bone harvesting procedure. Furthermore, piezoelectric surgery minimizes patient psychological stress and fear during osteotomy under local anaesthesia. It is believed that the use of piezoelectric surgery for autogenous alveolar bone harvesting may reduce the risk of sensory disturbance and other donor site morbidities.

A few reports in the literature describing long-term follow-up studies, claim that the mandibular ramus and the retromolar areas are associated with less donor site morbidity than the parasymphyseal region. However, there is still a lack of information regarding any differences in donor site morbidity between the mandibular ramus and the symphysis, especially when early postoperative results are considered. The aims of this study were as follows: (1) to evaluate and compare the morbidity of the mandibular symphysis and ramus donor sites; and (2) to compare the effects of different bone harvesting methods (conventional or piezoelectric surgery) on donor site morbidity.

Materials and methods

This prospective study was conducted on patients undergoing an onlay bone grafting procedure, performed by the same surgeon in the Department of Oral and Maxillofacial Surgery of Baskent University, between January 2011 and January 2013. Intraoral grafts were harvested consecutively from the mandibular ramus or symphysis; harvesting procedures were performed consecutively by either conventional or piezoelectric surgery. Patients who were able to attend the clinic for follow-up appointments at 1 and 6 months postoperative were included in the study.

The following patients were excluded: those who smoked, patients on medication, patients with periodontal disease, patients with any systemic disorder, such as hypertension, diabetes, rheumatic disease, or a neurological disease, and patients who required revision for an onlay bone grafting procedure.

Surgical procedures

The recipient area was first prepared. Midcrestal and vertical mucosal incisions were made along the recipient area, depending on the graft localization. A mucoperiosteal flap was reflected, and bone defects were revealed. Next, the donor sites were exposed surgically, and a block bone graft was obtained by means of a conventional bone harvesting procedure or using piezoelectric surgical equipment (VarioSurg 50/60 Hz; NSK, Nakanishi Inc., Kanuma, Tochigi, Japan).

To harvest the bone graft from the mandibular ramus, the mucosal incision was performed medial to the external oblique ridge and extended anteriorly to the buccal sulcus of the molar teeth and posteriorly to the retromolar region. A mucoperiosteal flap was reflected, exposing the lateral aspect of the ramus and the third molar area. An anterior vertical bone cut was performed (the length of the bone block depended on the size of the bone graft required), and a posterior vertical bone cut was made on the lateral aspect of the ramus. Following the superior horizontal bone cut, an inferior horizontal bone cut was performed to avoid an unfavourable fracture. Osteotomy lines were elevated with a thin chisel along the entire length of the osteotomy, and the bone block was separated gently to avoid disturbance of the inferior alveolar nerve.

To harvest the bone graft from the symphysis, a full thickness horizontal mucosal incision was performed in the vestibular area of the lower incisor teeth from the right canine to the left canine, and a mucoperiosteal flap was created. The superior horizontal bone cut was performed at least 5 mm below the apices of the incisor teeth and the inferior horizontal bone cut was performed at least 5 mm above the lower border of the mandible. The size of the bone graft was determined by considering the size of the bone defect at the recipient site. The vertical osseous cuts were made under copious irrigation with saline. After removing the corticocancellous bone block with a bone chisel, additional bone was harvested from the caudal site with gauges and curettes. Sharp osseous edges and irregularities were reduced to minimize postoperative discomfort. A gelatin sponge was applied as a haemostatic dressing to the donor area.

The bone blocks were all monocortical bone grafts. The lingual cortex was left intact at the donor site. The block bone graft was adapted and immediately positioned over the recipient area. This graft was fixed to the recipient site with two titanium miniscrews that were 1.5 mm wide and 10 mm long (Synthes GmbH, Oberdorf, Switzerland), and were removed during implant placement. Any sharp angles of the bone block that could perforate the overlying mucosa were removed with a round bur. The periosteum of the buccal flap at the recipient site was incised to allow the adaptation of the wound margins to be as tension-free as possible. Both the donor and the recipient sites were sutured with resorbable sutures, and the sutures were removed 1 week later.

Assessments

Clinical symptoms such as excessive intraoperative bleeding and a prolonged period of healing at the donor site were recorded for all graft harvesting procedures. A visual analogue scale (VAS) was used to assess both intraoperative and postoperative pain.

Parameters of sensory disturbance were evaluated by the same clinician (NA) on both the oral mucosa and adjacent skin ( Fig. 1 ) at 1 and 6 months postoperative. The superficial sensory function of the oral mucosa and adjacent skin was assessed by means of the pointed–blunt test (cotton pellets were used to lightly touch the mucosa and skin for the evaluation of tactile sensitivity). The superficial sensory function of the oral mucosa and adjacent skin was also assessed by two-point discrimination test. Patients were asked to differentiate the number of contacts on the mucosa and skin with their eyes closed. The results were classified into three groups: distance <7 mm indicating no alteration, distance 7–11 mm indicating a slight alteration, and distance >11 mm indicating impaired sensitivity.

Fig. 1
(A) The region of oral mucosa evaluated for the symphysis group; (B) the region of oral mucosa evaluated for the ramus group; (C) the region of skin evaluated for the symphysis group; (D) the region of skin evaluated for the ramus group.

The vitality of the teeth adjacent to the harvesting sites was evaluated using an electric pulp test (Pulp Vitality Tester 9V; Parkell Inc., Edgewood, NY, USA) and the necessity for root canal treatment was evaluated at 6 months postoperative.

The symphysis ( n = 44) and ramus ( n = 31) groups were divided into subgroups according to the surgical graft harvesting method used: conventional surgery or piezoelectric surgery. First, the parameters for donor site morbidity of the ramus and symphysis groups were compared, and then the subgroups of each group were compared.

Statistical analysis

The data analysis was performed using SPSS for Windows version 11.5 (SPSS Inc., Chicago, IL, USA). Ordinal data were recorded as the median (minimum–maximum); the number of cases and percentage were recorded for nominal data. The Wilcoxon signed rank test was used to determine whether differences in median VAS scores between groups were statistically significant. Nominal data were analyzed using Pearson’s χ 2 , continuity corrected χ 2 , or Fisher’s exact test, as applicable. A P -value of less than 0.05 was considered statistically significant. For all possible multiple comparisons, the Bonferroni correction was applied to control type I error.

Results

Out of 105 consecutive patients, 64 (16 males and 48 females) were included in this study after applying the inclusion and exclusion criteria. These 64 patients underwent 75 bone grafting operations. They ranged in age from 17 to 71 years (mean age 44.8 years).

Forty-four bone harvests were from the mandibular symphysis (symphysis group) and 31 were from the mandibular ramus (ramus group). In the symphysis group, 13 bone harvests were done by conventional surgery and 31 by piezoelectric surgery. In the ramus group, 15 bone harvests were done by conventional surgery and 16 by piezoelectric surgery.

No sign of major sensory disturbance, permanent paresthesia (anaesthesia), hyperesthesia, or hypoesthesia of the oral mucosa or the adjacent skin was detected in either the symphysis group or the ramus group at 6 months postoperative. However, different incidences of minor sensory disturbance (temporary paresthesia) were observed in the symphysis and ramus groups at 1 month postoperative.

There was no statistical difference between the symphysis and ramus groups with respect to the incidences of excessive intraoperative bleeding and a prolonged healing period. Excessive intraoperative bleeding was seen in three cases in the ramus group (9.7%), whereas it was not seen in any case in the symphysis group. A prolonged healing period was detected in five cases in the ramus group (16.1%) and in four cases in the symphysis group (9.1%).

When temporary paresthesia of the skin was assessed in the patients in the ramus and symphysis groups by pointed–blunt test, no statistically significant difference was found between the two groups. However, temporary paresthesia of the oral mucosa, as assessed by the pointed–blunt test, was significantly higher in the symphysis group ( P = 0.004) ( Table 1 ). When temporary paresthesia of the skin and mucosa was assessed in patients in the ramus and symphysis groups by two-point discrimination test, there was no statistically significant difference between the two groups ( Table 2 ).

Table 1
Results of the pointed–blunt test for the ramus and symphysis groups.
Parameters Ramus group ( n = 31) Symphysis group ( n = 44) P -value a
Skin 1.000 b
Normal 27 (87.1%) 38 (86.4%)
Temporary paresthesia 4 (12.9%) 6 (13.6%)
Mucosa 0.004 c
Normal 28 (90.3%) 25 (56.8%)
Temporary paresthesia 3 (9.7%) 19 (43.2%)

a According to the Bonferroni correction, P < 0.025 was considered statistically significant.

b Fisher’s exact test.

c Continuity corrected χ 2 test.

Table 2
Results of the two-point discrimination test for the ramus and symphysis groups.
Parameters Ramus group ( n = 31) Symphysis group ( n = 44) P -value a
Skin 0.039 b
<7 mm 31 (100.0%) 38 (86.4%)
7–11 mm 0 (0.0%) 6 (13.6%)
Mucosa 0.142 c
<7 mm 26 (83.9%) 29 (65.9%)
7–11 mm 5 (16.1%) 15 (34.1%)

a According to the Bonferroni correction, P < 0.025 was considered statistically significant.

b Fisher’s exact test.

c Continuity corrected χ 2 test.

There was no statistically significant difference between the symphysis and ramus groups for intraoperative and postoperative VAS scores, the necessity for root canal treatment to the adjacent tooth, or for a negative vitality test result. The intraoperative and postoperative median VAS pain scores were similar in the ramus and symphysis groups ( Table 3 ). Sixty teeth related to the bone graft harvesting site were evaluated in the ramus group and 290 teeth were evaluated in the symphysis group. Root canal treatment was not required in the ramus group; in the symphysis group, however, four root canal treatments of an adjacent tooth were needed ( Table 3 ).

Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on The effect of conventional surgery and piezoelectric surgery bone harvesting techniques on the donor site morbidity of the mandibular ramus and symphysis
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