Porciani 2006.

Methods	Title: whitening effect by stain inhibition from a chewing gum with sodium hexametaphosphate in a controlled 12‐week single‐blinded trial Trial design: randomised, single‐blinded, cross‐over trial Location: University of Siena, Dental School, Siena, Italy Language: English Number of centres: 1 Recruitment period: not reported Funding source: Perfetti Van Melle
Participants	Participants: mean age 30.6 years Total number: 54 Inclusion criteria: subjects had to present with 8 incisors without any fillings, crowns, or fixed orthodontic appliances Exclusion criteria: exhibit no oral or facial pain or disease more than 3 cups of tea and/or coffee Number randomised: 54 Method of randomisation: not reported Method of allocation concealment: not reported Method of blinding: not reported Number evaluated: 54
Interventions	Total number of intervention groups: 2 4% sodium hexametaphosphate Placebo Duration of treatment: 12 weeks
Outcomes	Reduction in stain (0 = no stain, 1 = light stain, 2 = moderate stain, 3 = heavy stain) Stain area (0 = no stain, 1 = stain covering up to 1/3 of the region, 2 = stain covering from 1/3 to 2/3 of the region, and 3 = stain covering greater than 2/3 of the region) Stain intensity Smoker versus non‐smokers
Notes	Sample size calculation: not reported Adverse effects: not reported Health‐related quality of life: not reported Key conclusions of the study authors: "The results indicated that chewing gum containing sodium hexametaphosphate reduced induced stain formation by 33% compared to no gum treatment" Correspondence required: no Contact: Francesco Porciani, piercateadsl@libero.it
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "were randomly assigned to the test gum or no‐gum group.." However, method of randomisation is not reported
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "the teeth were scored for stain deposits by the same examiner who was blinded to the product assignments"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "All 54 subjects (27 females and 27 males) initially enrolled in the study completed it"
Selective reporting (reporting bias)	Low risk	All outcomes described were reported. Conclusions are in accordance with the results
Other bias	Low risk	None