Critical appraisal: horizontal ridge augmentation with GBR, with or without autogenous block grafts

Paper appraised: Mendoza-Azpur G, de la Fuente A, Chavez E, Valdivia E, Khouly I. Horizontal ridge augmentation with guided bone regeneration using particulate xenogenic bone substitutes with or without autogenous block grafts: A randomized controlled trial. Clin Implant Dent Relat Res. 2019;21(4):521–530. doi:10.1111/cid.12740

The PICO question

In adults needing an implant-supported restoration with at least one site of horizontal bone defect of less than 4 mm, does horizontal ridge augmentation with an intraoral autogenous block graft (ABG) combined with particulate xenograft under a resorbable membrane, compared with particulate xenograft under a resorbable membrane alone (GBR), differ in horizontal bone width gained, implant failure, surgical complications and the need for regrafting?

Patient selection

42 patients with 65 implant sites were recruited from the Periodontal Postgraduate Clinic, Faculty of Dentistry, Científica del Sur University, Lima (Peru).

• Included: adults over 18 with at least one site of horizontal bone defect under 4 mm needing an implant-supported restoration, good oral hygiene, and no previous augmentation at the site.
• Excluded: poor oral hygiene, untreated periodontitis, uncontrolled systemic disease, head-and-neck irradiation, immunocompromise, intravenous amino-bisphosphonates, parafunction, pregnancy or lactation, drug or alcohol abuse, psychiatric disorders, heavy smoking, infection at the site, or extraction sites with less than 3 months of healing.

Patients were randomized to the intervention (22 patients, 31 implants) or comparator group (20 patients, 34 implants).

Data collection and analysis

CBCT scans at baseline, 6 and 18 months measured horizontal dimensional change; a 1 mm difference in resorption between groups was taken as the clinically relevant difference. Outcomes were compared with the chi-square test (P < 0.05).

Results

• 6 months: horizontal bone width (HBW) was 8.6 ± 1.35 mm (GBR) and 7.9 ± 0.87 mm (ABG) — not significant (P = 0.26).
• 18 months: 8.6 ± 1.75 mm (GBR) and 7.6 ± 0.79 mm (ABG) — not significant (P = 0.11).
• 6 → 18 months: HBW change of 0.0 mm (P = 0.1) for GBR and −0.3 mm (P = 0.08) for ABG.
• No implant failures at 12 months after loading and no regrafting in either group.
• Haematoma and sensory disturbance were significantly more frequent with ABG than with GBR.

Authors' conclusion: within the limits of the study, guided bone regeneration with or without an autogenous block graft can be an effective way to augment horizontally deficient mandibular or maxillary ridges before implant placement.

Commentary

Implant survival keeps improving, but proper implant-site development remains essential. Bone loss after extraction complicates implant placement, especially when a long time has passed since the extraction, and most alveolar resorption happens in width rather than height.1 It can be managed by reducing implant diameter or by augmenting the ridge. Narrower implants have limited indications and can compromise stress distribution and aesthetics,2 so guided bone regeneration is often the more practical choice: a barrier combined with a graft gives satisfactory hard- and soft-tissue augmentation and high implant survival.3 Autogenous bone is regarded as the gold standard but is available only in limited quantities, so it is often combined with another graft.4 This trial therefore compared autogenous block plus particulate xenograft under a membrane with particulate xenograft under a membrane alone.

Risk of bias

• Randomization: a computer random generator, operated by an investigator not otherwise involved — but the allocation ratio was not reported, and the groups ended up unequal in size.
• Allocation concealment: adequate (opaque envelopes).
• Consent: participants were informed in detail about the procedures and complications.
• Blinding: the radiographic assessor was blinded, but the operating surgeon and the participants knew the allocation.
• Attrition and reporting: all outcomes were reported for all participants, drop-outs were described, and a per-protocol analysis was used.

Overall, the lack of blinding of the operating surgeon puts the study at high risk of bias.

Validity and applicability

The high risk of bias limits external validity. The difference in horizontal bone width between groups at 6 and 18 months was neither statistically nor clinically significant — about 0.3 mm. Of the complications, haematoma and sensory disturbance were significantly more frequent with ABG, and they matter clinically to patients. Confidence intervals were not reported. Given the adequate sample size and complete outcome reporting, the results can still be considered applicable.

Bottom line: for horizontal defects under 4 mm, particulate xenograft GBR alone achieved similar bone width to GBR plus an autogenous block, with fewer complications for the patient.

References

1. Schropp L, Wenzel A, Kostopoulos L, et al. Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent. 2003;23:313–23.
2. Le B, Nielsen B. Esthetic implant site development. Oral Maxillofac Surg Clin North Am. 2015;27(2):283–311. doi:10.1016/j.coms.2015.01.009
3. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants. 2007;22 Suppl:49–70.
4. Khoury F, Antoun H, Missika P. Bone Augmentation in Oral Implantology. Berlin: Quintessence; 2007.