Tawse‐Smith 2002.

Methods	Trial design: randomised, parallel group trial Location: Dunedin, New Zealand Number of centres: one (university dental clinic of the University of Otago, Dunedin, New Zealand) Recruitment period: not stated Funding source: not stated
Participants	Inclusion criteria: patients with edentulous mandibles having 13 to 15 mm of residual anterior bone height Exclusion criteria: patients with type IV bone quality (very soft bone) according to the Lekholm and Zarb classification detected at implant insertion (none), previously bone‐grafted or irradiated jaws, history of bruxism, any evidence of current or previous smoking and any systemic diseases likely to compromise implant surgery Age at baseline: range 55‐80 years Gender: not reported Number randomised: 48 (4 groups, 2 groups evaluated each implant system) Number evaluated: 48 (no withdrawals at 1 year)
Interventions	Comparison: Early versus conventional loading Gp A (n = 12) Early loading: 2 unsplinted implants with ball attachments loaded at 6 weeks Gp B (n = 12) Conventional loading: 2 unsplinted implants with ball attachments supporting an overdenture loaded at 12 weeks Patients in groups A&B used Steri‐Oss® (Steri‐Oss, Yorba Linda, California, USA) non‐submerged acid‐etched titanium screws HL series, 3.8 mm in diameter Gp C (n = 12) Early loading: 2 unsplinted implants with ball attachments loaded at 6 weeks Gp D (n = 12) Conventional loading: 2 unsplinted implants with ball attachments supporting an overdenture loaded at 12 weeks Patients in groups C&D used Southern (Southern Implants Ltd, Irene, South Africa) non‐submerged sand‐blasted acid‐etched titanium screws Duration of follow‐up: 2 years
Outcomes	Prosthesis/implant failures, Periotest, marginal bone level changes on standardised intraoral radiographs, plaque accumulation, modified sulcus bleeding index, probing pocket depth, width of the keratinised mucosa 1‐year data used
Notes	Sample size calculation: not reported Most of the failed implants were placed by a surgeon who placed only Steri‐Oss implants
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Reported in the article: "Participants were randomly allocated to either the Sterioss system or the Southern Implant system on a one‐by‐one basis. For each system, participants were further allocated with maximum concealment into 2 subgroups (12 participants), in whom mandibular implant overdentures and their respective matrices were inserted following the standard 12‐week healing period, or the test group (12 participants), in whom a 6‐week healing period was followed by loading in a similar manner" Author replied that "Table of random numbers were used to randomly allocated participants"
Allocation concealment (selection bias)	Unclear risk	Reported in the article: "participants were randomly allocated to either the Sterioss system or the Southern Implant system on a one‐by‐one basis. For each system, participants were further allocated with maximum concealment into 2 subgroups (12 participants), in whom mandibular implant overdentures and their respective matrices were inserted following the standard 12‐week healing period, or the test group (12 participants), in whom a 6‐week healing period was followed by loading in a similar manner" No clarifying reply to letter
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Nothing reported in the article Author replied that "measurements were made by calibrated blinded outcome assessors"
Incomplete outcome data (attrition bias) All outcomes	Low risk	All data presented
Selective reporting (reporting bias)	Low risk	All outcomes appear to be presented
Other bias	High risk	It appears that implants were not placed in a balanced way by different operators but that one inexperienced operator, placing preferentially one type of implants, might have biased the success rates